JP7500169B2 - Composite sheet for forming protective film - Google Patents

Description

The present invention relates to a composite sheet for forming a protective film.

2. Description of the Related Art In the process of manufacturing a semiconductor device, a workpiece that needs to be processed to obtain a target product may be protected with a protective film.
For example, in manufacturing a semiconductor device using a mounting method called the face down method, a semiconductor wafer having electrodes such as bumps on its circuit surface is used as a workpiece, and in order to prevent cracks from occurring in the semiconductor wafer or in the semiconductor chips that are its divisions, the back surface of the semiconductor wafer or the semiconductor chip opposite to the circuit surface may be protected with a protective film. Also, in the manufacturing process of the semiconductor device, a semiconductor device panel described later is used as a workpiece, and in order to prevent warping and cracks from occurring in this panel, any part of the panel may be protected with a protective film.

To form such a protective film, for example, a composite sheet for forming a protective film is used, which is configured to include a support sheet, a film for forming a protective film on one side of the support sheet, and the film for forming the protective film.
The film for forming a protective film may function as a protective film by its curing, or may function as a protective film in an uncured state. The support sheet can be used to fix a workpiece having the film for forming a protective film or a cured product thereof. For example, when a semiconductor wafer is used as the workpiece, the support sheet can be used as a dicing sheet required when dividing the semiconductor wafer into semiconductor chips. Examples of the support sheet include a sheet having a substrate and an adhesive layer provided on one side of the substrate; a sheet consisting of only the substrate, etc. When the support sheet has an adhesive layer, the adhesive layer is disposed between the substrate and the film for forming a protective film in the composite sheet for forming a protective film.

When using the above-mentioned composite sheet for forming a protective film, first, the film for forming a protective film in the composite sheet for forming a protective film is attached to the desired location of the workpiece.
Next, the workpiece provided with such a composite sheet for forming a protective film is processed as necessary to obtain a processed workpiece. For example, when a semiconductor wafer is used as the workpiece, after the composite sheet for forming a protective film is attached to the back surface of the workpiece by the film for forming a protective film therein, the formation of a protective film by hardening the film for forming a protective film, the cutting of the film for forming a protective film or the protective film, the division of the semiconductor wafer into semiconductor chips (dicing), and the picking up of the semiconductor chip (semiconductor chip with a film for forming a protective film or semiconductor chip with a protective film) having the film for forming a protective film or the protective film on the back surface after cutting from the support sheet are appropriately performed at appropriate timing. When the semiconductor chip with the film for forming a protective film is picked up, the semiconductor chip with the film for forming a protective film is made into a semiconductor chip with a protective film by hardening the film for forming a protective film, and finally, a semiconductor device is manufactured using the semiconductor chip with the protective film.

Patent Document 1 discloses a dicing tape-integrated film for semiconductor backside, in which a film for flip-chip type semiconductor backside formed of a thermosetting resin component and a thermoplastic resin component with a glass transition temperature of 25°C or higher and 200°C or lower is laminated on a dicing tape having an adhesive laminated on a substrate.

Patent No. 5479991

As such composite sheets for forming protective films, in addition to those that include a support sheet with an adhesive layer that hardens when heated, support sheets that include an adhesive layer that hardens when exposed to energy rays such as ultraviolet rays are used.
Energy ray curable adhesives are usually composed of a photopolymerizable resin and a photopolymerization initiator, and the photopolymerizable resin is crosslinked by the photopolymerization initiator and cured by irradiation with energy rays, but before energy ray curing, there is a problem that the non-crosslinked photopolymerizable resin and the photopolymerization initiator migrate from the adhesive layer to the film for forming a protective film, or the components of the film for forming a protective film migrate to the adhesive layer. If such component migration occurs, the adhesive layer is not cured sufficiently after irradiation with energy rays, or crosslinking occurs between the adhesive layer and the film for forming a protective film, so that when a semiconductor chip (semiconductor chip with protective film) having a cured protective film on the back side is picked up from a support sheet, the semiconductor chip with protective film cannot be peeled off from the support sheet, and peeling may occur between the semiconductor chip and the protective film.

The present invention aims to provide a composite sheet for forming a protective film, which comprises a substrate, and on one surface of the substrate, an energy ray curable adhesive layer and a film for forming a protective film are laminated in this order and in contact with each other, and which enables a semiconductor chip with a protective film to be peeled off from a support sheet without peeling between the semiconductor chip and the protective film when the semiconductor chip with the protective film is picked up from the support sheet.

The present invention provides a composite sheet for forming a protective film, comprising a substrate, and an energy ray-curable pressure-sensitive adhesive layer and a film for forming a protective film laminated in this order and in contact with each other on one surface of the substrate, and the pressure-sensitive adhesive layer has a gel fraction of 80% or more.
The present invention provides a composite sheet for forming a protective film, comprising a substrate, and an energy ray-curable pressure-sensitive adhesive layer and a film for forming a protective film laminated in this order and in contact with each other on one surface of the substrate, wherein the pressure-sensitive adhesive layer has a gel fraction of 20% or more and less than 80%, and the film for forming a protective film has a glass transition temperature (Tg) of 3°C or more.

In the composite sheet for forming a protective film of the present invention, the film for forming a protective film preferably has a loss modulus at 23° C. of 3 MPa or more.
In the composite sheet for forming a protective film of the present invention, it is preferable that the film for forming a protective film contains a filler (D), and that in the film for forming a protective film, the content ratio of the filler (D) to the total mass of the film for forming a protective film is 50 mass% or more.

The present invention provides a composite sheet for forming a protective film, which includes a substrate, and on one surface of the substrate, an energy ray curable adhesive layer and a film for forming a protective film are laminated in this order and in contact with each other, and which enables the semiconductor chip with the protective film to be peeled off from the support sheet without peeling between the semiconductor chip and the protective film when the semiconductor chip with the protective film is picked up from the support sheet.

1 is a cross-sectional view showing a schematic example of a composite sheet for forming a protective film according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a schematic diagram of another example of a composite sheet for forming a protective film according to an embodiment of the present invention. 1A to 1C are cross-sectional views for illustrating an example of a method for producing a semiconductor chip with a protective film when a composite sheet for forming a protective film according to an embodiment of the present invention is used.

◇Composite sheet for forming a protective film The composite sheet for forming a protective film according to the first embodiment of the present invention comprises a substrate, and an energy ray-curable adhesive layer and a film for forming a protective film are laminated in this order and in contact with each other on one surface of the substrate, and the gel fraction of the adhesive layer is 80% or more.
By setting the gel fraction of the energy ray curable adhesive in the adhesive layer of the composite sheet for forming a protective film to be equal to or greater than the lower limit, it is possible to suppress the transfer of components between the energy ray curable adhesive layer before energy ray curing and the film for forming a protective film, and when picking up the semiconductor chip with the protective film from the support sheet, it is possible to peel the semiconductor chip with the protective film from the support sheet without peeling between the semiconductor chip and the protective film.

The composite sheet for forming a protective film according to the second embodiment of the present invention comprises a substrate, and an energy ray curable adhesive layer and a film for forming a protective film are laminated in this order and in contact with each other on one surface of the substrate, the adhesive layer has a gel fraction of 20% or more and less than 80%, and the film for forming a protective film has a glass transition temperature of 3°C or more.
When the glass transition temperature of the protective film forming film is 3°C or higher, even if the gel fraction of the adhesive layer before energy ray curing is 20% or more and less than 80%, the mutual migration of components between the energy ray curable adhesive layer before energy ray curing and the protective film forming film can be suppressed, and when the semiconductor chip with the protective film is picked up from the support sheet, the semiconductor chip with the protective film can be peeled off from the support sheet without peeling between the semiconductor chip and the protective film.

In the composite sheet for forming a protective film of the present invention, the loss modulus E'' of the film for forming a protective film at 23°C is preferably 3 MPa or more, more preferably 5 MPa or more, and even more preferably 10 MPa or more, and may be, for example, any of 17 MPa or more and 45 MPa or more. When the loss modulus of the film for forming a protective film at 23°C is equal to or more than the lower limit, it is possible to suppress migration of low molecular weight components such as the photopolymerizable resin and photopolymerizable initiator of the energy ray curable adhesive to the film for forming a protective film.

The loss modulus E'' of the protective film forming film at 23°C is preferably 100 MPa or less, more preferably 90 MPa or less. When the loss modulus E'' of the protective film forming film at 23°C is equal to or less than the lower limit, the handling of the protective film forming film when applied to a workpiece can be improved.

In the composite sheet for forming a protective film of the present invention, the film for forming a protective film contains a filler (D), and in the film for forming a protective film, the content ratio of the filler (D) to the total mass of the film for forming a protective film is preferably 50 mass% or more, more preferably 53 mass% or more, and even more preferably 55 mass% or more, and may be, for example, 60 mass%. In the film for forming a protective film, the content ratio of the filler (D) to the total mass of the film for forming a protective film is the lower limit value or more, so that the migration of low molecular weight components such as the photopolymerizable resin and photopolymerizable initiator of the energy ray curable adhesive to the film for forming a protective film can be further suppressed.

In the film for forming a protective film, the content ratio of the filler (D) to the total mass of the film for forming a protective film is preferably 90 mass% or less, and more preferably 80 mass% or less. In the film for forming a protective film, the content ratio of the filler (D) to the total mass of the film for forming a protective film is equal to or less than the lower limit, thereby improving the adhesion of the film for forming a protective film to a workpiece.

The film for forming a protective film in the composite sheet for forming a protective film of this embodiment may be curable or non-curable.

In this specification, as long as the laminated structure of the support sheet and the cured product of the film for forming a protective film is maintained even after the film for forming a protective film is cured, this laminated structure is referred to as a "composite sheet for forming a protective film."

In addition, in this specification, the term "adhesive layer" simply means "adhesive layer before curing."

The composite sheet for forming a protective film of this embodiment may have other layers that do not fall under any of the substrate, adhesive layer, film for forming a protective film, and release film, as long as the effects of the present invention are not impaired.
The type of the other layer is not particularly limited and can be arbitrarily selected depending on the purpose.
The position, shape, size, etc. of the other layers can be selected arbitrarily depending on the type of the other layers, and are not particularly limited, but it is preferable that the size of the film for forming a protective film is larger than the workpiece.

The thickness of the workpiece to which the composite sheet for forming a protective film of this embodiment is applied is not particularly limited, but is preferably 30 to 1000 μm, and more preferably 70 to 400 μm, in order to facilitate processing (e.g., dividing) into the workpiece described below.

The composite sheet for forming a protective film in this embodiment is intended to be attached to a workpiece, and a preferred example of the workpiece to which it is to be attached is a semiconductor wafer. The composite sheet for forming a protective film is preferably intended to be attached to the back surface of a semiconductor wafer.

FIG. 1 is a cross-sectional view that illustrates an example of a composite sheet for forming a protective film according to an embodiment of the present invention.
The composite sheet 101 for forming a protective film shown here is composed of a support sheet 10 and a film 13 for forming a protective film provided on one side 10a (sometimes referred to as the "first side" in this specification) of the support sheet 10.
The support sheet 10 is configured to include a substrate 11 and an adhesive layer 12 provided on one surface 11a of the substrate 11. In the composite sheet 101 for forming a protective film, the adhesive layer 12 is disposed between the substrate 11 and a film 13 for forming a protective film.
That is, the composite sheet 101 for forming a protective film is constructed by laminating a substrate 11, a pressure-sensitive adhesive layer 12, and a film 13 for forming a protective film in this order in the thickness direction.
The surface 10a of the support sheet 10 facing the protective film forming film 13 (sometimes referred to as the "first surface" in this specification) is the same as the surface 12a of the adhesive layer 12 opposite the substrate 11 (sometimes referred to as the "first surface" in this specification).

The composite sheet 101 for forming a protective film further includes an adhesive layer 16 for a jig and a release film 15 on the film 13 for forming a protective film.
In the composite sheet 101 for forming a protective film, the film 13 for forming a protective film is laminated over the entire or almost entire surface of the first surface 12a of the adhesive layer 12, and a jig adhesive layer 16 is laminated on a part of the surface 13a (sometimes referred to as the "first surface" in this specification) opposite the adhesive layer 12 side of the film 13 for forming a protective film, i.e., on a region near the periphery. Furthermore, a release film 15 is laminated on the region of the first surface 13a of the film 13 for forming a protective film where the jig adhesive layer 16 is not laminated, and on the surface 16a (sometimes referred to as the "first surface" in this specification) opposite the film 13 for forming a protective film of the jig adhesive layer 16.

Not only in the case of the composite sheet for forming a protective film 101, but also in the composite sheet for forming a protective film of this embodiment, the release film (e.g., release film 15 shown in FIG. 1) is of any configuration, and the composite sheet for forming a protective film of this embodiment may or may not include a release film.

The jig adhesive layer 16 is used to fix the composite sheet for forming a protective film 101 to a jig such as a ring frame.
The jig adhesive layer 16 may have, for example, a single-layer structure containing an adhesive component, or may have a multi-layer structure in which layers containing adhesive components are laminated on both sides of a core sheet.

With the release film 15 removed, the composite sheet 101 for forming a protective film is used by attaching any part of a workpiece (not shown) to the first surface 13a of the film 13 for forming a protective film, and then attaching the first surface 16a of the jig adhesive layer 16 to a jig such as a ring frame.

FIG. 2 is a cross-sectional view that illustrates a schematic diagram of another example of the composite sheet for forming a protective film according to one embodiment of the present invention.
In FIG. 2 and subsequent figures, the same components as those shown in the figures already described are given the same reference numerals as in the figures already described, and detailed description thereof will be omitted.

The composite sheet 102 for forming a protective film shown here is the same as the composite sheet 101 for forming a protective film shown in FIG. 1, except that the shape and size of the film for forming a protective film are different, and the adhesive layer for the jig is laminated on the first surface of the pressure-sensitive adhesive layer, not on the first surface of the film for forming a protective film.

More specifically, in the composite sheet 102 for forming a protective film, the film 23 for forming a protective film is laminated in a partial region of the first surface 12a of the adhesive layer 12, i.e., in the central region in the width direction (left-right direction in FIG. 2) of the adhesive layer 12. Furthermore, the adhesive layer 16 for a jig is laminated in the region of the first surface 12a of the adhesive layer 12 where the film 23 for forming a protective film is not laminated, i.e., in the region near the peripheral portion. A release film 15 is laminated on the surface 23a (sometimes referred to as the "first surface" in this specification) opposite the adhesive layer 12 side of the film 23 for forming a protective film and on the first surface 16a of the adhesive layer 16 for a jig.

So far, the composite sheet for forming a protective film having an adhesive layer for a jig has been shown as composite sheet for forming a protective film 101 shown in FIG. 1 and composite sheet for forming a protective film 102 shown in FIG. 2, but this is an example of another composite sheet for forming a protective film having an adhesive layer for a jig.

The composite sheet for forming a protective film having such a jig adhesive layer is used by attaching the first surface of the jig adhesive layer to a jig such as a ring frame.
In this way, the composite sheet for forming a protective film of this embodiment may be provided with a jig adhesive layer regardless of the form of the support sheet and the film for forming a protective film.

An example of a composite sheet for forming a protective film that does not have a jig adhesive layer is the composite sheet for forming a protective film 102 shown in FIG. 2 that does not have a jig adhesive layer 16. However, this is just one example of another composite sheet for forming a protective film that does not have a jig adhesive layer.

In Figures 1 and 2, a substrate, an adhesive layer, a film for forming a protective film, and a release film are shown as constituting the composite sheet for forming a protective film, but the composite sheet for forming a protective film of this embodiment may also have other layers that do not fall into any of these categories.
When the composite sheet for forming a protective film shown in FIG. 1 and FIG. 2 includes the other layer, the position of the other layer is not particularly limited, except for between the pressure-sensitive adhesive layer and the film for forming a protective film.

In the composite sheet for forming a protective film of this embodiment, the size and shape of each layer can be selected arbitrarily depending on the purpose.
The configuration of the composite sheet for forming a protective film will be described in detail below.

Support Sheet The support sheet according to one embodiment of the present invention can be laminated with a film for forming a protective film, as described below, to form a composite sheet for forming a protective film.

The support sheet of this embodiment can be used to fix a workpiece having a film for forming a protective film or a cured product thereof, which will be described later, at any location.
Examples of the workpiece include a semiconductor wafer, a semiconductor device panel, etc. A semiconductor device panel is something that is handled in the manufacturing process of a semiconductor device, and a specific example thereof is a single circuit board on which a plurality of electronic components are mounted.
In this specification, a processed workpiece is referred to as a “workpiece product.” For example, when the workpiece is a semiconductor wafer, an example of the workpiece product is a semiconductor chip.
For example, when the workpiece is a semiconductor wafer, the support sheet of this embodiment can be used to fix a semiconductor wafer having a protective film-forming film or a cured product thereof on the back surface.

The support sheet may, for example, include a sheet having a substrate and an adhesive layer provided on one side of the substrate. When the support sheet has an adhesive layer, the adhesive layer is disposed between the substrate and the film for forming a protective film in the composite sheet for forming a protective film described below.

When a support sheet having a substrate and an adhesive layer is used, the adhesive strength or adhesion between the support sheet and the film for forming a protective film in the composite sheet for forming a protective film can be easily adjusted.
When a support sheet consisting of only a substrate is used, the composite sheet for forming a protective film can be produced at low cost.
When a support sheet having a substrate and an adhesive layer is used, it is possible to impart new functions to the support sheet or the composite sheet for forming a protective film. In addition, the adhesive strength or adhesion between the support sheet and the film for forming a protective film can be adjusted more easily than in the case of the above-mentioned adhesive layer.

Substrate The substrate is in the form of a sheet or film, and examples of the constituent material of the substrate include various resins.
Examples of the resin include polyolefins such as low-density polyethylene (LDPE) and polypropylene (PP); ethylene-methacrylic acid copolymers (EMAA); polyvinyl chloride (PVC); polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); polyethersulfone, polyacrylic esters; and polycarbonate (PC).

The resin constituting the substrate may be one type or two or more types, and if there are two or more types, the combination and ratio of these can be selected arbitrarily.

The substrate may be made of one layer (single layer) or may be made of two or more layers. When made of multiple layers, these layers may be the same or different from each other, and the combination of these layers is not particularly limited.

In this specification, not only in the case of the substrate, "multiple layers may be the same or different from each other" means "all layers may be the same, all layers may be different, or only some layers may be the same", and further, "multiple layers are different from each other" means "at least one of the constituent materials and thickness of each layer is different from each other".

The thickness of the substrate is preferably 50 to 300 μm, more preferably 60 to 140 μm, and particularly preferably 80 to 100 μm. By setting the thickness of the substrate within such a range, the flexibility of the composite sheet for forming a protective film and the attachability to a workpiece or a processed workpiece are further improved.
Here, the "thickness of the substrate" means the thickness of the entire substrate. For example, the thickness of a substrate consisting of multiple layers means the total thickness of all layers constituting the substrate.

It is preferable that the substrate has a high thickness precision, i.e., that the thickness variation is suppressed regardless of the part. Among the above-mentioned constituent materials, examples of materials that can be used to form a substrate with such a high thickness precision include polyolefin, polyethylene terephthalate, etc.

In addition to the main constituent materials such as the resin, the substrate may contain various known additives such as fillers, colorants, antistatic agents, antioxidants, organic lubricants, catalysts, and softeners (plasticizers).

The substrate may be transparent or opaque, and may be colored or have other layers vapor-deposited thereon to the extent that the energy ray curability of the pressure-sensitive adhesive layer is ensured.
For example, when the protective film-forming film has energy ray curing properties, the substrate is preferably one that transmits energy rays.
For example, in order to optically inspect the film for forming a protective film in the composite sheet for forming a protective film through the substrate, it is preferable that the substrate is transparent.

In order to improve adhesion to a layer (e.g., a pressure-sensitive adhesive layer, a film for forming a protective film, etc.) provided thereon, the surface of the substrate may be subjected to a roughening treatment such as sandblasting or solvent treatment, or an oxidation treatment such as corona discharge treatment, electron beam irradiation treatment, plasma treatment, ozone/ultraviolet radiation treatment, flame treatment, chromic acid treatment, or hot air treatment. The surface of the substrate may be treated with a primer.
The substrate may also have an antistatic coating layer; a layer that prevents the substrate from adhering to other sheets or to an adsorption table when the composite sheets for forming a protective film are stacked and stored.

The substrate can be manufactured by a known method. For example, a substrate containing a resin can be manufactured by molding a resin composition containing the resin.

Adhesive Layer The adhesive layer is in the form of a sheet or film and contains an adhesive.
Examples of the adhesive include adhesive resins such as acrylic resins, urethane resins, rubber resins, silicone resins, epoxy resins, polyvinyl ethers, polycarbonates, and ester resins, with acrylic resins being preferred.

In this specification, the term "adhesive resin" includes both resins that are adhesive and resins that are adhesive. For example, the adhesive resins include not only resins that are adhesive themselves, but also resins that become adhesive when used in combination with other components such as additives, and resins that become adhesive in the presence of a trigger such as heat or water.

The adhesive layer may consist of one layer (single layer) or may consist of two or more layers. When it consists of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited.

The thickness of the adhesive layer is preferably 1 to 14 μm, more preferably 2 to 12 μm, and may be, for example, 3 to 8 μm. When the thickness of the adhesive layer is equal to or greater than the lower limit, the effect of providing the adhesive layer is more pronounced. When the thickness of the adhesive layer is equal to or less than the upper limit, printing can be performed more satisfactorily on the film for forming a protective film or its cured product in the composite sheet for forming a protective film. This printing can then be more easily viewed through the support sheet from the outside of the support sheet side of the composite sheet for forming a protective film.
Here, "the thickness of the adhesive layer" means the thickness of the entire adhesive layer. For example, the thickness of an adhesive layer consisting of multiple layers means the total thickness of all layers that make up the adhesive layer.

In this embodiment, the adhesive layer is formed using an energy ray curable adhesive. That is, the adhesive layer is energy ray curable. The physical properties of the energy ray curable adhesive layer before and after curing can be easily adjusted. For example, by curing the energy ray curable adhesive layer before picking up the semiconductor chip with a protective film or the semiconductor chip with a film for forming a protective film, which will be described later, these semiconductor chips can be picked up more easily.

In this specification, the term "energy rays" refers to electromagnetic waves or charged particle beams having an energy quantum, and examples thereof include ultraviolet rays, radiation, electron beams, etc. Ultraviolet rays can be irradiated by using, for example, a high-pressure mercury lamp, a fusion lamp, a xenon lamp, a black light, an LED lamp, etc. as an ultraviolet ray source. Electron beams can be irradiated by generating them using an electron beam accelerator, etc.
In this specification, the term "energy ray curable" means a property of being cured by irradiation with energy rays, and the term "non-energy ray curable" means a property of not being cured even when irradiated with energy rays.

In the composite sheet for forming a protective film of the first embodiment, the gel fraction of the adhesive layer is 80% or more, preferably 85% or more, and more preferably 90% or more. By having the gel fraction of the adhesive layer be 80% or more, it is possible to suppress the mutual transfer of components between the energy ray curable adhesive layer before energy ray curing and the film for forming a protective film, and when picking up the semiconductor chip with the protective film from the support sheet, it is possible to peel the semiconductor chip with the protective film from the support sheet without peeling between the semiconductor chip and the protective film.

In the composite sheet for forming a protective film of the second embodiment, the gel fraction of the pressure-sensitive adhesive layer is 20% or more and less than 80%, preferably 30% or more and less than 80%, more preferably 40% or more and less than 80%. Even if the gel fraction of the pressure-sensitive adhesive layer is less than 80%, the glass transition temperature (Tg) of the film for forming a protective film described later is 3° C. or more, so that the mutual migration of components between the energy ray curable pressure-sensitive adhesive layer before energy ray curing and the film for forming a protective film can be suppressed, and when the semiconductor chip with the protective film is picked up from the support sheet, the semiconductor chip with the protective film can be peeled off from the support sheet without peeling between the semiconductor chip and the protective film.
In the composite sheet for forming a protective film of the second embodiment, when the gel fraction of the adhesive layer is in the above range, the adhesive layer can be easily formed. When the gel fraction is less than 20%, the adhesive layer remains on the film for forming a protective film, and the reliability of the semiconductor chip with the protective film is reduced.

The gel fraction of the pressure-sensitive adhesive layer can be measured by a known method. Specifically, it can be measured by the following method.
A release film is prepared by forming a silicone-based release agent layer on one side of a polyethylene terephthalate base film (thickness 38 μm). Next, a pressure-sensitive adhesive composition is applied to the release-treated surface of the release film and dried to form a pressure-sensitive adhesive layer having a thickness of 20 μm.
Then, the pressure-sensitive adhesive layer is cut into a size of 50 mm x 100 mm to prepare a sample, and wrapped in a nylon mesh sheet (mesh size 200) of 100 mm x 150 mm to prepare a test piece. The mass M1 of the sample alone is weighed with a precision balance, and then the test piece is immersed in ethyl acetate (100 mL) at 25 ° C for 24 hours, and then the test piece is taken out and dried at 120 ° C for 1 hour, and further left under conditions of 23 ° C and relative humidity 50% for 1 hour to adjust the humidity. Next, the mass M2 of the sample alone, excluding the mass of the mesh sheet of the test piece, is weighed with a precision balance. Then, the gel fraction of the sample (i.e., the pressure-sensitive adhesive layer) before energy ray irradiation is calculated by the following formula.
Gel fraction of pressure-sensitive adhesive layer (%)=(M2/M1)×100

<<Adhesive composition>>
The adhesive layer can be formed using an adhesive composition containing an adhesive. For example, the adhesive composition can be applied to a surface on which the adhesive layer is to be formed, and dried as necessary, to form the adhesive layer at a desired location. The ratio of the contents of the components that do not vaporize at room temperature in the adhesive composition is usually the same as the ratio of the contents of the components in the adhesive layer. In this specification, "room temperature" means a temperature that is not particularly cooled or heated, that is, an ordinary temperature, and examples of the temperature include a temperature of 15 to 25°C.

The adhesive composition may be applied by a known method, for example, using various coaters such as an air knife coater, blade coater, bar coater, gravure coater, roll coater, roll knife coater, curtain coater, die coater, knife coater, screen coater, Mayer bar coater, kiss coater, etc.

There are no particular limitations on the drying conditions for the adhesive composition. If the adhesive composition contains a solvent, which will be described later, it is preferable to heat-dry it. For adhesive compositions containing a solvent, it is preferable to dry them, for example, at 70 to 130°C for 10 seconds to 5 minutes.

When providing an adhesive layer on a substrate, for example, an adhesive composition may be applied to the substrate and dried as necessary to laminate the adhesive layer on the substrate. When providing an adhesive layer on a substrate, for example, an adhesive composition may be applied to a release film and dried as necessary to form an adhesive layer on the release film, and the exposed surface of this adhesive layer may be attached to one surface of the substrate to laminate the adhesive layer on the substrate. In this case, the release film may be removed at any time during the manufacturing process or during the use process of the composite sheet for forming a protective film.

In the present invention, the adhesive is energy ray curable. Examples of the energy ray curable adhesive composition include an adhesive composition (I-1) containing a non-energy ray curable adhesive resin (I-1a) (hereinafter sometimes abbreviated as "adhesive resin (I-1a)") and an energy ray curable compound; an adhesive composition (I-2) containing an energy ray curable adhesive resin (I-2a) (hereinafter sometimes abbreviated as "adhesive resin (I-2a)") in which an unsaturated group has been introduced into the side chain of the adhesive resin (I-1a); and an adhesive composition (I-3) containing the adhesive resin (I-2a) and an energy ray curable compound.

[Adhesive resin (I-1a)]
The adhesive resin (I-1a) in the adhesive composition (I-1), adhesive composition (I-2) and adhesive composition (I-3) (hereinafter, these adhesive compositions are collectively abbreviated as "adhesive compositions (I-1) to (I-3)") is preferably an acrylic resin.

The acrylic resin may, for example, be an acrylic polymer having at least a structural unit derived from an alkyl (meth)acrylate ester.
The (meth)acrylic acid alkyl ester may, for example, be one in which the alkyl group constituting the alkyl ester has 1 to 20 carbon atoms, and the alkyl group is preferably linear or branched.

In this specification, "(meth)acrylic acid" is a concept that includes both "acrylic acid" and "methacrylic acid." The same applies to terms similar to (meth)acrylic acid. For example, "(meth)acryloyl group" is a concept that includes both "acryloyl group" and "methacryloyl group," and "(meth)acrylate" is a concept that includes both "acrylate" and "methacrylate."

The acrylic polymer preferably further contains a structural unit derived from a functional group-containing monomer in addition to the structural unit derived from an alkyl (meth)acrylate.
Examples of the functional group-containing monomer include those in which the functional group reacts with a crosslinking agent described below to become a crosslinking starting point, and those in which the functional group reacts with an unsaturated group in an unsaturated group-containing compound described below to enable the introduction of an unsaturated group into a side chain of an acrylic polymer.

Examples of the functional group-containing monomer include hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, and epoxy group-containing monomers.

The acrylic polymer may further contain a structural unit derived from another monomer, in addition to the structural unit derived from the alkyl (meth)acrylate ester and the structural unit derived from the functional group-containing monomer.
The other monomer is not particularly limited as long as it is copolymerizable with the (meth)acrylic acid alkyl ester and the like.
Examples of the other monomers include styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, and acrylamide.

In the pressure-sensitive adhesive compositions (I-1) to (I-3), the structural units contained in the acrylic resin such as the acrylic polymer may be of one type or of two or more types. When there are two or more types, the combination and ratio of the structural units may be selected arbitrarily.

In the acrylic polymer, the content of the structural units derived from functional group-containing monomers is preferably 1 to 35% by mass based on the total amount of structural units.

The adhesive composition (I-1) or the adhesive composition (I-3) may contain only one type of adhesive resin (I-1a), or two or more types. When two or more types are contained, the combination and ratio of the adhesive resins may be selected arbitrarily.

In the adhesive composition (I-1), the content of the adhesive resin (I-1a) relative to the total mass of the adhesive composition (I-1) is preferably 5 to 99 mass %.

[Adhesive resin (I-2a)]
The adhesive resin (I-2a) in the adhesive compositions (I-2) and (I-3) can be obtained, for example, by reacting a functional group in the adhesive resin (I-1a) with an unsaturated group-containing compound having an energy ray-polymerizable unsaturated group.

The unsaturated group-containing compound is a compound having, in addition to the energy ray-polymerizable unsaturated group, a group that can bond to the adhesive resin (I-1a) by reacting with a functional group in the adhesive resin (I-1a).
Examples of the energy ray-polymerizable unsaturated group include a (meth)acryloyl group, a vinyl group (ethenyl group), and an allyl group (2-propenyl group), and the like, with a (meth)acryloyl group being preferred.
Examples of the group capable of bonding to a functional group in the adhesive resin (I-1a) include an isocyanate group and a glycidyl group capable of bonding to a hydroxyl group or an amino group, and a hydroxyl group and an amino group capable of bonding to a carboxy group or an epoxy group.

Examples of the unsaturated group-containing compound include (meth)acryloyloxyethyl isocyanate, (meth)acryloyl isocyanate, and glycidyl (meth)acrylate.

The adhesive composition (I-2) or (I-3) may contain one type of adhesive resin (I-2a) or two or more types. When there are two or more types, the combination and ratio of the adhesive resins can be selected arbitrarily.

In the adhesive composition (I-2) or (I-3), the content of the adhesive resin (I-2a) relative to the total mass of the adhesive composition (I-2) or (I-3) is preferably 5 to 99 mass %.

[Energy ray curable compound]
The energy ray-curable compound in the pressure-sensitive adhesive compositions (I-1) and (I-3) includes a monomer or oligomer that has an energy ray-polymerizable unsaturated group and is curable by irradiation with energy rays.

Of the energy ray-curable compounds, examples of the monomer include polyvalent (meth)acrylates such as trimethylolpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, and 1,6-hexanediol (meth)acrylate; urethane (meth)acrylate; polyester (meth)acrylate; polyether (meth)acrylate; and epoxy (meth)acrylate.
Among the energy ray-curable compounds, examples of the oligomer include oligomers obtained by polymerizing the above-exemplified monomers.

The pressure-sensitive adhesive composition (I-1) or (I-3) may contain one type of energy ray-curable compound or two or more types of compounds. When two or more types of compounds are contained, the combination and ratio of the compounds can be selected arbitrarily.

In the pressure-sensitive adhesive composition (I-1), the content of the energy ray-curable compound is preferably 1 to 95% by mass relative to the total mass of the pressure-sensitive adhesive composition (I-1).
In the pressure-sensitive adhesive composition (I-3), the content of the energy ray-curable compound is preferably 0.01 to 300 parts by mass relative to 100 parts by mass of the pressure-sensitive adhesive resin (I-2a).

[Crosslinking agent]
When the acrylic polymer having a structural unit derived from a functional group-containing monomer in addition to a structural unit derived from a (meth)acrylic acid alkyl ester is used as the pressure-sensitive adhesive resin (I-1a), it is preferable that the pressure-sensitive adhesive composition (I-1) further contains a crosslinking agent.
In addition, when the adhesive resin (I-2a) is, for example, the acrylic polymer having a structural unit derived from a functional group-containing monomer similar to that in the adhesive resin (I-1a), the adhesive composition (I-2) or (I-3) may further contain a crosslinking agent.

The crosslinking agent, for example, reacts with the functional group to crosslink the adhesive resins (I-1a) together or the adhesive resins (I-2a) together.
Examples of the crosslinking agent include isocyanate-based crosslinking agents (crosslinking agents having an isocyanate group) such as tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and adducts of these diisocyanates; epoxy-based crosslinking agents (crosslinking agents having a glycidyl group) such as ethylene glycol glycidyl ether; aziridine-based crosslinking agents (crosslinking agents having an aziridinyl group) such as hexa[1-(2-methyl)-aziridinyl]triphosphatriazine; metal chelate-based crosslinking agents (crosslinking agents having a metal chelate structure) such as aluminum chelate; and isocyanurate-based crosslinking agents (crosslinking agents having an isocyanuric acid skeleton).

The crosslinking agent contained in the pressure-sensitive adhesive composition (I-1) or (I-2) may be one type or two or more types. When two or more types are contained, the combination and ratio of the crosslinking agents can be selected arbitrarily.

In the pressure-sensitive adhesive composition (I-1), the content of the crosslinking agent is preferably 0.01 to 50 parts by mass, and may be, for example, any one of 0.01 to 35 parts by mass and 0.01 to 20 parts by mass, relative to 100 parts by mass of the pressure-sensitive adhesive resin (I-1a).
In the pressure-sensitive adhesive composition (I-2) or (I-3), the content of the crosslinking agent is preferably 0.01 to 50 parts by mass relative to 100 parts by mass of the pressure-sensitive adhesive resin (I-2a), and may be, for example, any one of 0.01 to 35 parts by mass, 0.01 to 20 parts by mass, and 0.01 to 10 parts by mass.

[Photopolymerization initiator]
The pressure-sensitive adhesive compositions (I-1) to (I-3) may further contain a photopolymerization initiator. The pressure-sensitive adhesive compositions (I-1) to (I-3) containing a photopolymerization initiator sufficiently undergo a curing reaction even when irradiated with relatively low-energy energy rays such as ultraviolet rays.

Examples of the photopolymerization initiator include benzoin compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin methyl benzoate, and benzoin dimethyl ketal; acetophenone compounds such as acetophenone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2,2-dimethoxy-1,2-diphenylethane-1-one, and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one; bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyl Examples of the compound include acylphosphine oxide compounds such as diphenylphosphine oxide; sulfide compounds such as benzyl phenyl sulfide and tetramethylthiuram monosulfide; α-ketol compounds such as 1-hydroxycyclohexyl phenyl ketone; azo compounds such as azobisisobutyronitrile; titanocene compounds such as titanocene; thioxanthone compounds such as thioxanthone; peroxide compounds; diketone compounds such as diacetyl; benzyl; dibenzyl; benzophenone; 2,4-diethylthioxanthone; 1,2-diphenylmethane; 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone; and quinone compounds such as 1-chloroanthraquinone and 2-chloroanthraquinone.
As the photopolymerization initiator, for example, a photosensitizer such as an amine can also be used.

The photopolymerization initiators contained in the pressure-sensitive adhesive compositions (I-1) to (I-3) may be one type or two or more types. When two or more types are contained, the combination and ratio of the photopolymerization initiators can be selected arbitrarily.

In the pressure-sensitive adhesive composition (I-1), the content of the photopolymerization initiator is preferably 0.01 to 20 parts by mass relative to 100 parts by mass of the content of the energy ray-curable compound.
In the pressure-sensitive adhesive composition (I-2), the content of the photopolymerization initiator is preferably 0.01 to 20 parts by mass relative to 100 parts by mass of the pressure-sensitive adhesive resin (I-2a), and may be, for example, any one of 0.01 to 10 parts by mass and 0.01 to 5 parts by mass.
In the pressure-sensitive adhesive composition (I-3), the content of the photopolymerization initiator is preferably 0.01 to 20 parts by mass per 100 parts by mass of the total content of the pressure-sensitive adhesive resin (I-2a) and the energy ray-curable compound.

The gel fraction of the pressure-sensitive adhesive compositions (I-1) to (I-3) can be adjusted by the molecular weight of the polymer that is the material of the pressure-sensitive adhesive composition, the amount of functional groups that serve as crosslinking origins, the amount of crosslinking agent, etc. For example, the gel fraction of the pressure-sensitive adhesive composition can be increased by increasing the amount of crosslinking agent.

[Other additives]
The pressure-sensitive adhesive compositions (I-1) to (I-3) may contain other additives that do not fall under any of the above-mentioned components, within the scope that does not impair the effects of the present invention.
Examples of the other additives include known additives such as antistatic agents, antioxidants, softeners (plasticizers), fillers, rust inhibitors, colorants (pigments, dyes), sensitizers, tackifiers, reaction retarders, and crosslinking accelerators (catalysts).
The reaction retarder is, for example, a retarder that inhibits the progress of unintended crosslinking reactions in the pressure-sensitive adhesive compositions (I-1) to (I-3) during storage due to the action of a catalyst mixed in the pressure-sensitive adhesive compositions (I-1) to (I-3). Examples of the reaction retarder include a retarder that forms a chelate complex by chelating with a catalyst, and more specifically, a retarder that has two or more carbonyl groups (-C(=O)-) in one molecule.

The other additives contained in the pressure-sensitive adhesive compositions (I-1) to (I-3) may be one type or two or more types, and when there are two or more types, the combination and ratio of them can be selected arbitrarily.

The content of other additives in the pressure-sensitive adhesive compositions (I-1) to (I-3) is not particularly limited and may be selected appropriately depending on the type of additive.

[solvent]
The pressure-sensitive adhesive compositions (I-1) to (I-3) may contain a solvent. By containing a solvent, the pressure-sensitive adhesive compositions (I-1) to (I-3) have improved suitability for application to a surface to be coated.
In this specification, unless otherwise specified, the term "solvent" is used as a concept that includes not only a substance that dissolves a target component, but also a dispersion medium that disperses the target component.

The solvent is preferably an organic solvent, and examples of the organic solvent include ketones such as methyl ethyl ketone and acetone; esters (carboxylates) such as ethyl acetate; ethers such as tetrahydrofuran and dioxane; aliphatic hydrocarbons such as cyclohexane and n-hexane; aromatic hydrocarbons such as toluene and xylene; and alcohols such as 1-propanol and 2-propanol.

The adhesive compositions (I-1) to (I-3) may contain one type of solvent or two or more types of solvents. If there are two or more types of solvents, the combination and ratio of the solvents may be selected arbitrarily.

The solvent content of the pressure-sensitive adhesive compositions (I-1) to (I-3) is not particularly limited and may be adjusted as appropriate.

<<Method of producing pressure-sensitive adhesive composition>>
The pressure-sensitive adhesive compositions such as the pressure-sensitive adhesive compositions (I-1) to (I-3) can be obtained by blending the pressure-sensitive adhesive and, if necessary, components other than the pressure-sensitive adhesive, for constituting the pressure-sensitive adhesive composition.
The order of addition of the components is not particularly limited, and two or more components may be added simultaneously.
The method for mixing the components during blending is not particularly limited, and may be appropriately selected from known methods such as a method of mixing by rotating a stirrer or stirring blade, a method of mixing using a mixer, a method of mixing by applying ultrasound, etc.
The temperature and time during addition and mixing of each component are not particularly limited as long as the components do not deteriorate, and may be adjusted appropriately. The temperature is preferably 15 to 30°C.

Protective Film-Forming Film The protective film-forming film can be laminated with a support sheet having a pressure-sensitive adhesive layer, as described below, to form a composite sheet for protective film formation.

The protective film forming film forms a protective film for protecting any part of the workpiece or the workpiece. When the workpiece is a semiconductor wafer, the protective film forming film of this embodiment can be used to form a protective film on the surface opposite to the circuit forming surface of the semiconductor wafer and the semiconductor chip (in this specification, either of these may be referred to as the "back surface"). In this specification, such a workpiece having a protective film may be referred to as a "workpiece having a protective film", and a semiconductor chip having a protective film on its back surface may be referred to as a "semiconductor chip having a protective film".
The protective film forming film is soft and can be easily attached to an object such as a workpiece or a processed workpiece.

The protective film forming film may function as a protective film by being cured, or may function as a protective film in an uncured state. The protective film forming film that functions as a protective film in an uncured state can be considered to have formed a protective film, for example, when it is attached to the desired location of the workpiece.

As described above, the protective film-forming film may be curable or non-curable.
The curable protective film-forming film may be either heat-curable or energy ray-curable, or may have both heat-curable and energy ray-curable properties.
In this specification, the term "non-curable" refers to a property that does not cure by any means, such as heating or irradiation with energy rays.

When a protective film is formed by thermally curing a film for forming a protective film, unlike when the film is cured by irradiation with energy rays, the film for forming a protective film can be sufficiently cured by heating even if it is thick, so that a protective film with high protective performance can be formed. In addition, a large number of films for forming a protective film can be heated and thermally cured all at once by using a normal heating means such as a heating oven.
When the protective film is formed by curing the film for forming a protective film by irradiation with energy rays, unlike the case of thermal curing, the composite sheet for forming a protective film does not need to have heat resistance, and a wide range of composite sheets for forming a protective film can be configured. In addition, the film can be cured in a short time by irradiation with energy rays.
When the protective film-forming film is used as the protective film without being cured, the curing step can be omitted, so that a workpiece with a protective film can be manufactured by a simplified process.

Regardless of whether the film for forming a protective film is curable or non-curable, and if it is curable, regardless of whether it is heat-curable or energy ray-curable, the film for forming a protective film may consist of one layer (single layer) or may consist of two or more layers. When the film for forming a protective film consists of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited.

Regardless of whether the film for forming a protective film is curable or non-curable, and in the case of curable, regardless of whether it is heat curable or energy ray curable, the thickness of the film for forming a protective film is preferably 1 to 100 μm, more preferably 3 to 80 μm, and particularly preferably 5 to 60 μm, and may be, for example, either 5 to 40 μm or 5 to 20 μm. When the thickness of the film for forming a protective film is equal to or greater than the lower limit, a protective film having higher protective ability can be formed. When the thickness of the film for forming a protective film is equal to or less than the upper limit, excessive thickness can be avoided.
Here, "thickness of the film for forming a protective film" means the overall thickness of the film for forming a protective film, and for example, the thickness of a film for forming a protective film consisting of multiple layers means the total thickness of all layers that constitute the film for forming a protective film.

In the composite sheet for forming a protective film of the first embodiment, the glass transition temperature (Tg) of the film for forming a protective film is preferably 3°C or higher, more preferably 5°C or higher, and even more preferably 15°C or higher, for example, 10°C or higher, 20°C or higher. By having the glass transition temperature of the film for forming a protective film be equal to or higher than the lower limit, it is possible to suppress the mutual migration of components between the energy ray curable adhesive layer before energy ray curing and the film for forming a protective film, and when picking up the semiconductor chip with the protective film from the support sheet, the effect of being able to peel the semiconductor chip with the protective film from the support sheet without peeling between the semiconductor chip and the protective film is further improved.

In the composite sheet for forming a protective film of the second embodiment, the glass transition temperature (Tg) of the film for forming a protective film is 3°C or higher, preferably 5°C or higher, more preferably 15°C or higher, and even more preferably 20°C or higher, for example, 10°C or higher. By having the glass transition temperature of the film for forming a protective film be equal to or higher than the lower limit, even if the gel fraction of the adhesive layer before energy ray curing is 20% or more and less than 80%, it is possible to suppress the mutual migration of components between the energy ray curable adhesive layer before energy ray curing and the film for forming a protective film, and when picking up the semiconductor chip with the protective film from the support sheet, it is possible to peel the semiconductor chip with the protective film from the support sheet without peeling between the semiconductor chip and the protective film.

In the composite sheet for forming a protective film of the first embodiment and the composite sheet for forming a protective film of the second embodiment, the loss modulus E'' of the film for forming a protective film at 23°C is preferably 3 MPa or more, more preferably 5 MPa or more, for example, 10 MPa or more, 15 MPa or more, 20 MPa or more, 25 MPa or more, 30 MPa or more, 40 MPa or more, 50 MPa or more, etc.
The upper limit of the loss modulus E'' of the film for forming a protective film at 23° C. is not particularly limited. For example, a film for forming a protective film having a loss modulus of 100 MPa or less can be easily produced.

The glass transition temperature (Tg) and the loss modulus E″ at 23° C. of the film for forming a protective film can be measured by a known method. Specifically, they can be measured by the following method.
The samples are laminated to a thickness of about 200 μm, and the resulting laminate is processed to a size of 4 mm in width and 30 mm in length (distance between chucks) to prepare a test specimen. The tensile loss modulus E″ of this test specimen is measured at 23° C. and a measurement frequency of 1 Hz using an automatic dynamic viscoelasticity tester (manufactured by Orientec Co., Ltd., product name “Rheovibron DDV-0.1FP”), and the peak temperature of tan δ at this time is taken as the glass transition temperature (Tg).

<<Protective Film-Forming Composition>>
The film for forming a protective film can be formed using a composition for forming a protective film containing its constituent materials. For example, the film for forming a protective film can be formed by applying the composition for forming a protective film to the surface to be formed and drying it as necessary. The ratio of the contents of the components that do not vaporize at room temperature in the composition for forming a protective film is usually the same as the ratio of the contents of the components in the film for forming a protective film.
The thermosetting protective film forming film can be formed using a thermosetting protective film forming composition, the energy ray curable protective film forming film can be formed using an energy ray curable protective film forming composition, and the non-curable protective film forming film can be formed using a non-curable protective film forming composition. In this specification, when the protective film forming film has both thermosetting and energy ray curing properties, if the contribution of the thermal curing of the protective film forming film to the formation of the protective film is greater than the contribution of the energy ray curing, the protective film forming film is treated as a thermosetting film. On the other hand, if the contribution of the energy ray curing of the protective film forming film to the formation of the protective film is greater than the contribution of the thermal curing, the protective film forming film is treated as an energy ray curing film.

The protective film-forming composition can be applied, for example, in the same manner as in the application of the pressure-sensitive adhesive composition described above.

Regardless of whether the film for forming a protective film is curable or non-curable, and in the case of curable film, regardless of whether the film is heat-curable or energy ray-curable, the drying conditions of the composition for forming a protective film are not particularly limited. However, when the composition for forming a protective film contains a solvent described below, it is preferable to heat-dry it. And, the composition for forming a protective film containing a solvent is preferably heat-dried, for example, at 70 to 130°C for 10 seconds to 5 minutes. However, it is preferable to heat-dry the thermosetting composition for forming a protective film so that the composition itself and the film for forming a thermosetting protective film formed from this composition are not thermally cured.

The following describes the films for forming thermosetting protective films, energy ray curable protective films, and non-curable protective films.

Film for forming a thermosetting protective film The curing conditions when the film for forming a thermosetting protective film is attached to the desired location of the workpiece and thermally cured to form a protective film are not particularly limited as long as the degree of curing is such that the protective film can fully perform its function, and may be selected appropriately depending on the type of film for forming a thermosetting protective film.
For example, the heating temperature during thermal curing of the thermosetting protective film-forming film is preferably 100 to 200° C., more preferably 110 to 180° C., and particularly preferably 120 to 170° C. The heating time during thermal curing is preferably 0.5 to 5 hours, more preferably 0.5 to 3 hours, and particularly preferably 1 to 2 hours.

Preferred thermosetting protective film-forming films include, for example, those containing a polymer component (A) and a thermosetting component (B). The polymer component (A) is a component that can be considered to be formed by a polymerization reaction of a polymerizable compound. The thermosetting component (B) is a component that can undergo a curing (polymerization) reaction using heat as a reaction trigger. In this specification, polymerization reaction also includes polycondensation reaction.

<Thermosetting protective film-forming composition (III-1)>
A preferred example of a composition for forming a thermosetting protective film includes a composition for forming a thermosetting protective film (III-1) (sometimes abbreviated herein as "composition (III-1)") containing the polymer component (A) and a thermosetting component (B).

[Polymer component (A)]
The polymer component (A) is a component for imparting film-forming properties, flexibility, and the like to the thermosetting protective film-forming film.
The polymer component (A) contained in the composition (III-1) and the thermosetting protective film-forming film may be one type or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily.

Examples of polymer component (A) include acrylic resins, polyesters, urethane resins, acrylic urethane resins, silicone resins, rubber resins, phenoxy resins, thermoplastic polyimides, etc., with acrylic resins being preferred.

The acrylic resin in the polymer component (A) may be any known acrylic polymer.
The weight average molecular weight (Mw) of the acrylic resin is preferably 10,000 to 2,000,000, and more preferably 100,000 to 1,500,000. When the weight average molecular weight of the acrylic resin is equal to or greater than the lower limit, the shape stability (stability over time during storage) of the thermosetting protective film-forming film is improved. In addition, when the weight average molecular weight of the acrylic resin is equal to or less than the upper limit, the thermosetting protective film-forming film is more likely to conform to the uneven surface of the adherend, and the occurrence of voids and the like between the adherend and the thermosetting protective film-forming film is more suppressed.
In this specification, unless otherwise specified, the "weight average molecular weight" is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

The glass transition temperature (Tg) of the acrylic resin is preferably 3°C or higher and 70°C or lower, and more preferably 3°C or higher and 50°C or lower. When the Tg of the acrylic resin is equal to or higher than the lower limit, it is possible to suppress the mutual migration of components between the energy ray curable adhesive and the film for forming a protective film before energy ray curing, and when picking up the semiconductor chip with the protective film from the support sheet, the effect of being able to peel the semiconductor chip with the protective film from the support sheet without peeling between the semiconductor chip and the protective film is further improved. In addition, when the Tg of the acrylic resin is equal to or lower than the upper limit, the adhesive strength of the film for forming a thermosetting protective film and its cured product to the adherend is improved.

Examples of acrylic resins include polymers of one or more (meth)acrylic acid esters; copolymers of two or more monomers selected from (meth)acrylic acid, itaconic acid, vinyl acetate, acrylonitrile, styrene, and N-methylolacrylamide.

Examples of the (meth)acrylic acid ester constituting the acrylic resin include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, and p) (meth)acrylic acid alkyl esters in which the alkyl group constituting the alkyl ester has a chain structure having 1 to 18 carbon atoms, such as isononyl acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (lauryl (meth)acrylate), tridecyl (meth)acrylate, tetradecyl (meth)acrylate (myristyl (meth)acrylate), pentadecyl (meth)acrylate, hexadecyl (meth)acrylate (palmityl (meth)acrylate), heptadecyl (meth)acrylate, and octadecyl (meth)acrylate (stearyl (meth)acrylate);
(meth)acrylic acid cycloalkyl esters such as isobornyl (meth)acrylate and dicyclopentanyl (meth)acrylate;
(Meth)acrylic acid aralkyl esters such as benzyl (meth)acrylate;
(Meth)acrylic acid cycloalkenyl esters such as (meth)acrylic acid dicyclopentenyl ester;
(meth)acrylic acid cycloalkenyloxyalkyl esters such as (meth)acrylic acid dicyclopentenyloxyethyl ester;
(Meth)acrylic acid imide;
glycidyl group-containing (meth)acrylic acid esters such as glycidyl (meth)acrylate;
hydroxyl group-containing (meth)acrylic acid esters such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate;
Examples of such esters include (meth)acrylic acid esters containing a substituted amino group, such as N-methylaminoethyl (meth)acrylate. Here, the term "substituted amino group" refers to a group in which one or two hydrogen atoms of an amino group are substituted with a group other than a hydrogen atom.

The acrylic resin may be, for example, a copolymer of one or more monomers selected from (meth)acrylic acid, itaconic acid, vinyl acetate, acrylonitrile, styrene, N-methylolacrylamide, etc., in addition to the (meth)acrylic acid ester.

The acrylic resin may be made up of one type of monomer or two or more types of monomers, and when two or more types are used, the combination and ratio of these monomers can be selected arbitrarily.

The acrylic resin may have a functional group capable of bonding with other compounds, such as a vinyl group, a (meth)acryloyl group, an amino group, a hydroxyl group, a carboxyl group, or an isocyanate group. The functional group of the acrylic resin may bond with other compounds via a crosslinking agent (F) described below, or may bond directly with other compounds without the crosslinking agent (F). The acrylic resin bonds with other compounds via the functional group, which tends to improve the reliability of the package obtained using the composite sheet for forming a protective film.

In the present invention, as the polymer component (A), a thermoplastic resin other than an acrylic resin (hereinafter sometimes simply abbreviated as "thermoplastic resin") may be used alone without using an acrylic resin, or may be used in combination with an acrylic resin. By using the thermoplastic resin, the peelability of the protective film from the support sheet is improved, the thermosetting protective film-forming film can be easily conformed to the uneven surface of the adherend, and the occurrence of voids, etc. between the adherend and the thermosetting protective film-forming film can be further suppressed.

The weight average molecular weight of the thermoplastic resin is preferably 1,000 to 100,000, and more preferably 3,000 to 80,000.

The glass transition temperature (Tg) of the thermoplastic resin is preferably 3°C or higher and 150°C or lower, and more preferably 3°C or higher and 120°C or lower.

Examples of the thermoplastic resin include polyester, polyurethane, phenoxy resin, polybutene, polybutadiene, polystyrene, etc.

The thermoplastic resin contained in composition (III-1) and the film for forming a thermosetting protective film may be one type or two or more types, and when there are two or more types, the combination and ratio thereof can be selected arbitrarily.

In composition (III-1), the ratio of the content of polymer component (A) to the total content of all components other than the solvent (i.e., the ratio of the content of polymer component (A) in the film for forming a thermosetting protective film to the total mass of the film for forming a thermosetting protective film) is preferably 10 to 85 mass%, more preferably 15 to 70 mass%, and even more preferably 20 to 60 mass%, regardless of the type of polymer component (A), and may be, for example, any of 20 to 45 mass% and 20 to 35 mass%, or any of 35 to 60 mass% and 45 to 60 mass%.

The polymer component (A) may also be a thermosetting component (B). In the present invention, when the composition (III-1) contains a component that corresponds to both the polymer component (A) and the thermosetting component (B), the composition (III-1) is considered to contain the polymer component (A) and the thermosetting component (B).

[Thermosetting component (B)]
The thermosetting component (B) is a component for curing the thermosetting protective film-forming film.
The thermosetting component (B) contained in the composition (III-1) and the film for forming a thermosetting protective film may be one type or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily.

Examples of the thermosetting component (B) include epoxy-based thermosetting resins, thermosetting polyimides, polyurethanes, unsaturated polyesters, silicone resins, etc., with epoxy-based thermosetting resins being preferred.

(Epoxy thermosetting resin)
The epoxy thermosetting resin comprises an epoxy resin (B1) and a thermosetting agent (B2).
The epoxy-based thermosetting resin contained in the composition (III-1) and the film for forming a thermosetting protective film may be one type or two or more types. When two or more types are contained, the combination and ratio thereof can be selected arbitrarily.

Epoxy resin (B1)
The epoxy resin (B1) may be any known epoxy resin, such as a polyfunctional epoxy resin, a biphenyl compound, bisphenol A diglycidyl ether and its hydrogenated product, orthocresol novolac epoxy resin, a dicyclopentadiene type epoxy resin, a biphenyl type epoxy resin, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, or a phenylene skeleton type epoxy resin.

As the epoxy resin (B1), an epoxy resin having an unsaturated hydrocarbon group may be used. An epoxy resin having an unsaturated hydrocarbon group has a higher compatibility with acrylic resins than an epoxy resin not having an unsaturated hydrocarbon group. Therefore, by using an epoxy resin having an unsaturated hydrocarbon group, the reliability of the workpiece with a protective film obtained using the composite sheet for forming a protective film is improved.

Examples of epoxy resins having an unsaturated hydrocarbon group include compounds obtained by converting a part of the epoxy groups of a polyfunctional epoxy resin into a group having an unsaturated hydrocarbon group. Such compounds can be obtained, for example, by subjecting the epoxy groups to an addition reaction with (meth)acrylic acid or a derivative thereof.
Furthermore, examples of epoxy resins having an unsaturated hydrocarbon group include compounds in which a group having an unsaturated hydrocarbon group is directly bonded to an aromatic ring or the like constituting the epoxy resin.
The unsaturated hydrocarbon group is a polymerizable unsaturated group, and specific examples thereof include an ethenyl group (vinyl group), a 2-propenyl group (allyl group), a (meth)acryloyl group, and a (meth)acrylamide group, with an acryloyl group being preferred.

The number average molecular weight of the epoxy resin (B1) is not particularly limited, but from the viewpoints of the curability of the thermosetting protective film-forming film and the strength and heat resistance of the protective film that is the cured product thereof, it is preferably 300 to 30,000, more preferably 300 to 10,000, and particularly preferably 300 to 3,000.
The epoxy equivalent of the epoxy resin (B1) is preferably from 100 to 1000 g/eq, and more preferably from 150 to 950 g/eq.

The epoxy resin (B1) may be used alone or in combination of two or more kinds. When two or more kinds are used in combination, the combination and ratio of the two or more kinds can be selected arbitrarily.

Heat curing agent (B2)
The heat curing agent (B2) functions as a curing agent for the epoxy resin (B1).
The heat curing agent (B2) may be, for example, a compound having two or more functional groups capable of reacting with an epoxy group in one molecule. Examples of the functional group include a phenolic hydroxyl group, an alcoholic hydroxyl group, an amino group, a carboxyl group, and an anhydride group of an acid group, and the like. The phenolic hydroxyl group, the amino group, or an anhydride group of an acid group is preferable, and the phenolic hydroxyl group or the amino group is more preferable.

Among the heat curing agents (B2), examples of phenolic curing agents having a phenolic hydroxyl group include polyfunctional phenolic resins, biphenols, novolac-type phenolic resins, dicyclopentadiene-type phenolic resins, and aralkyl-type phenolic resins.
Among the heat curing agents (B2), examples of amine-based curing agents having an amino group include dicyandiamide.

The heat curing agent (B2) may have an unsaturated hydrocarbon group.
Examples of the heat curing agent (B2) having an unsaturated hydrocarbon group include a compound in which a portion of the hydroxyl groups of a phenol resin is substituted with a group having an unsaturated hydrocarbon group, and a compound in which a group having an unsaturated hydrocarbon group is directly bonded to an aromatic ring of a phenol resin.
The unsaturated hydrocarbon group in the heat curing agent (B2) is the same as the unsaturated hydrocarbon group in the above-mentioned epoxy resin having an unsaturated hydrocarbon group.

When a phenol-based curing agent is used as the heat curing agent (B2), it is preferable that the heat curing agent (B2) has a high softening point or glass transition temperature in order to improve the peelability of the protective film from the support sheet.

Of the thermosetting agents (B2), for example, the number average molecular weight of resin components such as polyfunctional phenol resins, novolac type phenol resins, dicyclopentadiene type phenol resins, and aralkyl type phenol resins is preferably 300 to 30,000, more preferably 400 to 10,000, and particularly preferably 500 to 3,000.
Of the thermosetting agent (B2), the molecular weight of the non-resin components, such as biphenol and dicyandiamide, is not particularly limited, but is preferably, for example, 60 to 500.

The heat curing agent (B2) may be used alone or in combination of two or more kinds. When two or more kinds are used in combination, the combination and ratio of the two or more kinds can be selected arbitrarily.

In the composition (III-1) and the film for forming a thermosetting protective film, the content of the thermosetting agent (B2) is preferably 0.1 to 100 parts by mass, more preferably 0.5 to 50 parts by mass, and may be, for example, any of 0.5 to 25 parts by mass, 0.5 to 10 parts by mass, and 0.5 to 5 parts by mass, relative to 100 parts by mass of the epoxy resin (B1). When the content of the thermosetting agent (B2) is equal to or greater than the lower limit, the curing of the film for forming a thermosetting protective film proceeds more easily. When the content of the thermosetting agent (B2) is equal to or less than the upper limit, the moisture absorption rate of the film for forming a thermosetting protective film is reduced, and the reliability of the package obtained using the composite sheet for forming a protective film is further improved.

In the composition (III-1) and the thermosetting film for forming a protective film, the content of the thermosetting component (B) (for example, the total content of the epoxy resin (B1) and the thermosetting agent (B2)) is preferably 5 to 120 parts by mass, more preferably 5 to 80 parts by mass, relative to 100 parts by mass of the content of the polymer component (A). For example, it may be any of 5 to 40 parts by mass, 5 to 20 parts by mass, and 5 to 10 parts by mass, or any of 40 to 80 parts by mass, 50 to 75 parts by mass, and 60 to 75 parts by mass. When the content of the thermosetting component (B) is in such a range, for example, the adhesive force between the cured product of the film for forming a protective film and the support sheet is suppressed, and the peelability of the support sheet is improved.

[Curing Accelerator (C)]
The composition (III-1) and the film for forming a thermosetting protective film may contain a curing accelerator (C). The curing accelerator (C) is a component for adjusting the curing speed of the composition (III-1).
Preferred examples of the curing accelerator (C) include tertiary amines such as triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris(dimethylaminomethyl)phenol; imidazoles such as 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole (imidazoles in which one or more hydrogen atoms are substituted with groups other than hydrogen atoms); organic phosphines such as tributylphosphine, diphenylphosphine, and triphenylphosphine (phosphines in which one or more hydrogen atoms are substituted with organic groups); and tetraphenylboron salts such as tetraphenylphosphonium tetraphenylborate and triphenylphosphine tetraphenylborate.

The curing accelerator (C) contained in the composition (III-1) and the film for forming a thermosetting protective film may be one type or two or more types. When there are two or more types, the combination and ratio of the two or more types can be selected arbitrarily.

When the curing accelerator (C) is used, the content of the curing accelerator (C) in the composition (III-1) and the film for forming a thermosetting protective film is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 7 parts by mass, relative to 100 parts by mass of the content of the thermosetting component (B). When the content of the curing accelerator (C) is equal to or greater than the lower limit, the effect of using the curing accelerator (C) is more pronounced. When the content of the curing accelerator (C) is equal to or less than the upper limit, for example, the effect of suppressing the highly polar curing accelerator (C) from migrating to the adhesive interface with the adherend and segregating in the film for forming a thermosetting protective film under high temperature and high humidity conditions is enhanced. As a result, the reliability of the workpiece with a protective film obtained using the composite sheet for forming a protective film is further improved.

[Filler (D)]
The composition (III-1) and the thermosetting film for forming a protective film may contain a filler (D). By containing the filler (D) in the film for forming a thermosetting protective film, the film for forming a thermosetting protective film and its cured product (i.e., the protective film) can easily adjust the thermal expansion coefficient, and by optimizing this thermal expansion coefficient for the object on which the protective film is formed, the reliability of the workpiece with the protective film obtained using the composite sheet for forming a protective film is further improved. In addition, by containing the filler (D) in the film for forming a thermosetting protective film, the moisture absorption rate of the protective film can be reduced and the heat dissipation can be improved.

The filler (D) may be either an organic filler or an inorganic filler, but is preferably an inorganic filler.
Preferred inorganic fillers include, for example, powders of silica, alumina, talc, calcium carbonate, titanium white, red iron oxide, silicon carbide, boron nitride, and the like; beads obtained by spheronizing these inorganic fillers; surface-modified products of these inorganic fillers; single crystal fibers of these inorganic fillers; glass fibers, and the like.
Among these, the inorganic filler is preferably silica or alumina, and more preferably silica.

The filler (D) contained in the composition (III-1) and the film for forming a thermosetting protective film may be one type or two or more types, and when there are two or more types, the combination and ratio thereof can be selected arbitrarily.

In composition (III-1), the ratio of the content of the filler (D) to the total content of all components other than the solvent (i.e., the ratio of the content of the filler (D) to the total mass of the film for forming a thermosetting protective film in the film for forming a thermosetting protective film) is preferably 50% by mass or more, more preferably 55% by mass or more. The upper limit of the content ratio of the filler (D) is preferably 80% by mass or less, and preferably 70% by mass or less, and may be, for example, 50% by mass or more and 80% by mass or less, 55% by mass or more and 80% by mass or less, 50% by mass or more and 70% by mass or less, or 55% by mass or more and 70% by mass or less. When the ratio is in such a range, it is possible to suppress the mutual migration of components between the energy ray curable adhesive and the film for forming a protective film before energy ray curing.

[Coupling Agent (E)]
The composition (III-1) and the thermosetting film for forming a protective film may contain a coupling agent (E). By using a coupling agent (E) having a functional group capable of reacting with an inorganic compound or an organic compound, the adhesiveness and adhesion of the film for forming a thermosetting protective film to an adherend can be improved. In addition, by using the coupling agent (E), the cured product of the film for forming a thermosetting protective film has improved water resistance without impairing heat resistance.

The coupling agent (E) is preferably a compound having a functional group capable of reacting with the functional groups of the polymer component (A), the thermosetting component (B), etc., and is more preferably a silane coupling agent.
Preferred examples of the silane coupling agent include 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxymethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propylmethyldiethoxysilane, 3-(phenylamino)propyltrimethoxysilane, 3-anilinopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, bis(3-triethoxysilylpropyl)tetrasulfane, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriacetoxysilane, and imidazole silane.

The coupling agent (E) contained in the composition (III-1) and the film for forming a thermosetting protective film may be one type or two or more types. When two or more types are contained, the combination and ratio of the coupling agents can be selected arbitrarily.

When a coupling agent (E) is used, the content of the coupling agent (E) in the composition (III-1) and the film for forming a thermosetting protective film is preferably 0.03 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and particularly preferably 0.1 to 2 parts by mass, relative to 100 parts by mass of the total content of the polymer component (A) and the thermosetting component (B). When the content of the coupling agent (E) is equal to or greater than the lower limit, the effects of using the coupling agent (E), such as improved dispersibility of the filler (D) in the resin and improved adhesion of the film for forming a thermosetting protective film to the adherend, are more significantly obtained. In addition, when the content of the coupling agent (E) is equal to or less than the upper limit, the generation of outgassing is further suppressed.

[Crosslinking agent (F)]
When the polymer component (A) is one having a functional group capable of bonding with other compounds, such as a vinyl group, a (meth)acryloyl group, an amino group, a hydroxyl group, a carboxyl group, or an isocyanate group, such as the above-mentioned acrylic resin, the composition (III-1) and the thermosetting film for forming a protective film may contain a crosslinking agent (F). The crosslinking agent (F) is a component for bonding the functional group in the polymer component (A) with other compounds to form a crosslink, and by crosslinking in this manner, the initial adhesive strength and cohesive strength of the film for forming a thermosetting protective film can be adjusted.

Examples of the crosslinking agent (F) include organic polyvalent isocyanate compounds, organic polyvalent imine compounds, metal chelate crosslinking agents (crosslinking agents having a metal chelate structure), aziridine crosslinking agents (crosslinking agents having an aziridinyl group), etc.

The crosslinking agent (F) contained in the composition (III-1) and the thermosetting protective film-forming film may be one type or two or more types. When there are two or more types, the combination and ratio of the crosslinking agents can be selected arbitrarily.

When a crosslinking agent (F) is used, the content of the crosslinking agent (F) in the composition (III-1) is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and particularly preferably 0.5 to 5 parts by mass, per 100 parts by mass of the polymer component (A). When the content of the crosslinking agent (F) is equal to or greater than the lower limit, the effect of using the crosslinking agent (F) is more pronounced. In addition, when the content of the crosslinking agent (F) is equal to or less than the upper limit, excessive use of the crosslinking agent (F) is suppressed.

[Energy ray curable resin (G)]
The composition (III-1) and the film for forming a thermosetting protective film may contain an energy ray curable resin (G). By containing the energy ray curable resin (G), the film for forming a thermosetting protective film can change its properties by irradiation with energy rays.

The energy ray curable resin (G) is obtained by polymerizing (curing) an energy ray curable compound.
The energy ray-curable compound includes, for example, a compound having at least one polymerizable double bond in the molecule, and is preferably an acrylate-based compound having a (meth)acryloyl group.

Examples of the acrylate-based compounds include (meth)acrylates containing a chain aliphatic skeleton such as trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate; (meth)acrylates containing a cyclic aliphatic skeleton such as dicyclopentanyl di(meth)acrylate; polyalkylene glycol (meth)acrylates such as polyethylene glycol di(meth)acrylate; oligoester (meth)acrylates; urethane (meth)acrylate oligomers; epoxy-modified (meth)acrylates; polyether (meth)acrylates other than the polyalkylene glycol (meth)acrylates; and itaconic acid oligomers.

The weight average molecular weight of the energy ray curable compound is preferably 100 to 30,000, and more preferably 300 to 10,000.

The energy ray curable compound used in the polymerization may be one type or two or more types, and when two or more types are used, the combination and ratio of the compounds may be selected arbitrarily.

The composition (III-1) and the film for forming a thermosetting protective film may contain one type of energy ray curable resin (G), or two or more types. When two or more types are contained, the combination and ratio of these can be selected arbitrarily.

When an energy ray curable resin (G) is used, the content of the energy ray curable resin (G) in the composition (III-1) relative to the total mass of the composition (III-1) is preferably 1 to 95 mass%, more preferably 5 to 90 mass%, and particularly preferably 10 to 85 mass%.

[Photopolymerization initiator (H)]
When the composition (III-1) and the film for forming a thermosetting protective film contain an energy ray curable resin (G), they may contain a photopolymerization initiator (H) in order to efficiently proceed with the polymerization reaction of the energy ray curable resin (G).

The photopolymerization initiator (H) in the composition (III-1) may be, for example, the same as the photopolymerization initiator that may be contained in the above-mentioned pressure-sensitive adhesive composition.

The photopolymerization initiator (H) contained in the composition (III-1) and the thermosetting protective film-forming film may be one type or two or more types. When there are two or more types, the combination and ratio of the photopolymerization initiators can be selected arbitrarily.

When a photopolymerization initiator (H) is used, the content of the photopolymerization initiator (H) in the composition (III-1) is preferably 0.1 to 20 parts by mass, more preferably 1 to 10 parts by mass, and particularly preferably 2 to 5 parts by mass, per 100 parts by mass of the energy ray-curable resin (G).

[Colorant (I)]
The composition (III-1) and the thermosetting film for forming a protective film preferably contain a colorant (I). By using the colorant (I), a film for forming a protective film having a light (266 nm) transmittance of 60% or less can be more easily produced.

Examples of colorants (I) include known ones such as inorganic pigments, organic pigments, and organic dyes.

Examples of the organic pigments and organic dyes include aminium-based dyes, cyanine-based dyes, merocyanine-based dyes, croconium-based dyes, squalium-based dyes, azulenium-based dyes, polymethine-based dyes, naphthoquinone-based dyes, pyrylium-based dyes, phthalocyanine-based dyes, naphthalocyanine-based dyes, naphtholactam-based dyes, azo-based dyes, condensed azo-based dyes, indigo-based dyes, perinone-based dyes, perylene-based dyes, dioxazine-based dyes, quinacridone-based dyes, isoindolinone-based dyes, quinophthalone-based dyes, pyrrole-based dyes, thioindigo-based dyes, metal complex-based dyes (metal complex dyes), dithiol metal complex-based dyes, indolephenol-based dyes, triarylmethane-based dyes, anthraquinone-based dyes, dioxazine-based dyes, naphthol-based dyes, azomethine-based dyes, benzimidazolone-based dyes, pyranthrone-based dyes, and threne-based dyes.

Examples of the inorganic pigments include carbon black, cobalt-based pigments, iron-based pigments, chromium-based pigments, titanium-based pigments, vanadium-based pigments, zirconium-based pigments, molybdenum-based pigments, ruthenium-based pigments, platinum-based pigments, ITO (indium tin oxide)-based pigments, and ATO (antimony tin oxide)-based pigments.

The colorant (I) contained in the composition (III-1) and the thermosetting protective film-forming film may be one type or two or more types, and when there are two or more types, the combination and ratio of these can be selected arbitrarily.

When using the colorant (I), the content of the colorant (I) in the film for forming a thermosetting protective film may be adjusted appropriately according to the purpose. For example, by adjusting the content of the colorant (I) in the film for forming a thermosetting protective film and adjusting the light transmittance of the protective film, the visibility of the print when laser printing is performed on the protective film can be adjusted. In addition, by adjusting the content of the colorant (I) in the film for forming a thermosetting protective film, the design of the protective film can be improved and the grinding marks on the back surface of the semiconductor wafer can be made less visible. In consideration of these points, in the composition (III-1), the ratio of the content of the colorant (I) to the total content of all components other than the solvent (i.e., the ratio of the content of the colorant (I) to the total mass of the film for forming a thermosetting protective film) is preferably 0.1 to 10% by mass, more preferably 0.1 to 7.5% by mass, and particularly preferably 0.1 to 5% by mass. When the ratio is equal to or greater than the lower limit, the effect of using the colorant (I) is more pronounced. Also, when the ratio is equal to or less than the upper limit, excessive decrease in the light transmittance of the thermosetting protective film-forming film is suppressed.

[General-purpose additives (J)]
The composition (III-1) and the thermosetting film for forming a protective film may contain a general-purpose additive (J) within the range that does not impair the effects of the present invention.
The general-purpose additive (J) may be a known one and may be arbitrarily selected depending on the purpose, and is not particularly limited. Preferred examples thereof include plasticizers, antistatic agents, antioxidants, gettering agents, and ultraviolet absorbers.

The general-purpose additive (J) contained in the composition (III-1) and the thermosetting protective film-forming film may be one type or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily.
The content of the composition (III-1) and the general-purpose additive (J) in the thermosetting protective film-forming film is not particularly limited and may be appropriately selected depending on the purpose.

[solvent]
The composition (III-1) preferably further contains a solvent, since the composition (III-1) containing a solvent has good handleability.
The solvent is not particularly limited, but preferred examples thereof include hydrocarbons such as toluene and xylene; alcohols such as methanol, ethanol, 2-propanol, isobutyl alcohol (2-methylpropan-1-ol), and 1-butanol; esters such as ethyl acetate; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran; and amides (compounds having an amide bond) such as dimethylformamide and N-methylpyrrolidone.
The composition (III-1) may contain one kind of solvent or two or more kinds of solvents. When two or more kinds of solvents are contained, the combination and ratio thereof can be selected arbitrarily.

More preferred examples of the solvent contained in composition (III-1) include methyl ethyl ketone, toluene, ethyl acetate, etc., which allow the components contained in composition (III-1) to be mixed more uniformly.

The content of the solvent in composition (III-1) is not particularly limited and may be selected appropriately depending on, for example, the types of components other than the solvent.

<Method for producing a composition for forming a thermosetting protective film>
The thermosetting protective film-forming composition such as composition (III-1) can be obtained by blending the respective components constituting the composition.
The thermosetting protective film-forming composition can be produced, for example, in the same manner as in the case of the pressure-sensitive adhesive composition described above, except that the types of ingredients used are different.

Energy ray-curable film for forming a protective film The curing conditions for forming a protective film by attaching the energy ray-curable film for forming a protective film to a desired location on a workpiece and curing it with energy rays are not particularly limited as long as the protective film has a degree of curing that allows it to fully exhibit its functions, and may be appropriately selected depending on the type of the film for forming an energy ray-curable protective film.
For example, the illuminance of the energy rays during energy ray curing of the energy ray-curable protective film-forming film is preferably 120 to 280 mW/cm ^2. The amount of energy rays during the curing is preferably 100 to 1000 mJ/cm ² .

The energy ray-curable protective film-forming film may, for example, be one containing an energy ray-curable component (a), and preferably one containing an energy ray-curable component (a) and a filler.
In the energy ray-curable protective film-forming film, the energy ray-curable component (a) is preferably uncured and has adhesive properties, and more preferably is uncured and has adhesive properties.

<Energy ray-curable protective film-forming composition (IV-1)>
A preferred example of the energy ray-curable protective film-forming composition is energy ray-curable protective film-forming composition (IV-1) (sometimes simply abbreviated as "composition (IV-1)" in this specification) containing the energy ray-curable component (a).

[Energy ray-curable component (a)]
The energy ray-curable component (a) is a component that is cured by irradiation with energy rays, and imparts film-forming properties, flexibility, and the like to the energy ray-curable protective film-forming film, and is also a component for forming a hard protective film after curing.
Examples of the energy ray-curable component (a) include a polymer (a1) having an energy ray-curable group and a weight average molecular weight of 80,000 to 2,000,000, and a compound (a2) having an energy ray-curable group and a molecular weight of 100 to 80,000. The polymer (a1) may be at least partially crosslinked with a crosslinking agent, or may not be crosslinked.

(Polymer (a1) having an energy ray-curable group and a weight average molecular weight of 80,000 to 2,000,000)
Examples of the polymer (a1) having an energy ray-curable group and a weight average molecular weight of 80,000 to 2,000,000 include an acrylic resin (a1-1) obtained by reacting an acrylic polymer (a11) having a functional group capable of reacting with a group possessed by another compound with an energy ray-curable compound (a12) having a group reactive with the functional group and an energy ray-curable group such as an energy ray-curable double bond.

Examples of the functional group capable of reacting with a group possessed by another compound include a hydroxyl group, a carboxy group, an amino group, a substituted amino group (a group in which one or two hydrogen atoms of an amino group are substituted with a group other than a hydrogen atom), an epoxy group, etc. However, from the viewpoint of preventing corrosion of circuits of a workpiece or a processed workpiece, etc., it is preferable that the functional group is a group other than a carboxy group.
Of these, the functional group is preferably a hydroxyl group.

Acrylic polymer having a functional group (a11)
The acrylic polymer (a11) having a functional group may be, for example, a polymer obtained by copolymerizing an acrylic monomer having the functional group with an acrylic monomer not having the functional group. In addition to these monomers, the acrylic polymer may also be a polymer obtained by copolymerizing a monomer other than the acrylic monomer (a11) with a non-acrylic monomer.
The acrylic polymer (a11) may be a random copolymer or a block copolymer, and a known method can be used for the polymerization method.

Examples of acrylic monomers having the functional group include hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, substituted amino group-containing monomers, and epoxy group-containing monomers.

Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; non-(meth)acrylic unsaturated alcohols (unsaturated alcohols without a (meth)acryloyl skeleton) such as vinyl alcohol and allyl alcohol.

Examples of the carboxy group-containing monomer include ethylenically unsaturated monocarboxylic acids (monocarboxylic acids having an ethylenically unsaturated bond) such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids (dicarboxylic acids having an ethylenically unsaturated bond) such as fumaric acid, itaconic acid, maleic acid, and citraconic acid; anhydrides of the ethylenically unsaturated dicarboxylic acids; and (meth)acrylic acid carboxyalkyl esters such as 2-carboxyethyl methacrylate.

The acrylic monomer having the functional group is preferably a hydroxyl group-containing monomer.

The acrylic monomer having the functional group constituting the acrylic polymer (a11) may be one type or two or more types, and when two or more types are used, the combination and ratio thereof can be selected arbitrarily.

Examples of acrylic monomers not having a functional group include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, and isopropyl (meth)acrylate. Examples of (meth)acrylic acid alkyl esters include those in which the alkyl group constituting the alkyl ester has a chain structure containing 1 to 18 carbon atoms, such as Sononyl, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (lauryl (meth)acrylate), tridecyl (meth)acrylate, tetradecyl (meth)acrylate (myristyl (meth)acrylate), pentadecyl (meth)acrylate, hexadecyl (meth)acrylate (palmityl (meth)acrylate), heptadecyl (meth)acrylate, and octadecyl (meth)acrylate (stearyl (meth)acrylate).

Examples of acrylic monomers that do not have the functional group include alkoxyalkyl group-containing (meth)acrylic acid esters such as methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, and ethoxyethyl (meth)acrylate; aromatic group-containing (meth)acrylic acid esters including aryl (meth)acrylate esters such as phenyl (meth)acrylate; non-crosslinkable (meth)acrylamide and derivatives thereof; non-crosslinkable tertiary amino group-containing (meth)acrylic acid esters such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate.

The acrylic monomer not having a functional group constituting the acrylic polymer (a11) may be one type or two or more types, and when two or more types are used, the combination and ratio thereof can be selected arbitrarily.

Examples of the non-acrylic monomer include olefins such as ethylene and norbornene; vinyl acetate; and styrene.
The non-acrylic monomer constituting the acrylic polymer (a11) may be of only one kind or of two or more kinds. When two or more kinds are used, the combination and ratio thereof can be selected arbitrarily.

In the acrylic polymer (a11), the ratio (content) of the amount of the structural unit derived from the acrylic monomer having the functional group to the total amount of the structural units constituting the acrylic polymer (a11) is preferably 0.1 to 50 mass%, more preferably 1 to 40 mass%, and particularly preferably 3 to 30 mass%. When the ratio is in such a range, the content of the energy ray curable group in the acrylic resin (a1-1) obtained by copolymerization of the acrylic polymer (a11) and the energy ray curable compound (a12) makes it possible to easily adjust the degree of curing of the protective film to a preferred range.

The acrylic polymer (a11) constituting the acrylic resin (a1-1) may be one type or two or more types. When there are two or more types, the combination and ratio thereof can be selected arbitrarily.

In composition (IV-1), the ratio of the content of acrylic resin (a1-1) to the total content of components other than the solvent (i.e., the ratio of the content of acrylic resin (a1-1) to the total mass of the energy ray-curable protective film-forming film) is preferably 1 to 70 mass%, more preferably 5 to 60 mass%, and particularly preferably 10 to 50 mass%.

Energy ray curable compound (a12)
The energy ray curable compound (a12) preferably has one or more groups selected from the group consisting of an isocyanate group, an epoxy group, and a carboxy group as a group capable of reacting with the functional group of the acrylic polymer (a11), and more preferably has an isocyanate group as the group. For example, when the energy ray curable compound (a12) has an isocyanate group as the group, the isocyanate group easily reacts with the hydroxyl group of the acrylic polymer (a11) having a hydroxyl group as the functional group.

The number of the energy ray-curable groups that the energy ray-curable compound (a12) has in one molecule is not particularly limited and can be appropriately selected in consideration of the physical properties, such as the shrinkage rate, required for the intended protective film, for example.
For example, the energy ray-curable compound (a12) preferably has 1 to 5, and more preferably 1 to 3, energy ray-curable groups in one molecule.

Examples of the energy ray-curable compound (a12) include 2-methacryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, and 1,1-(bisacryloyloxymethyl)ethyl isocyanate;
an acryloyl monoisocyanate compound obtained by reacting a diisocyanate compound or a polyisocyanate compound with hydroxyethyl (meth)acrylate;
Examples of the isocyanate include an acryloyl monoisocyanate compound obtained by reacting a diisocyanate compound or a polyisocyanate compound with a polyol compound and hydroxyethyl (meth)acrylate.
Among these, the energy ray-curable compound (a12) is preferably 2-methacryloyloxyethyl isocyanate.

The energy ray curable compound (a12) constituting the acrylic resin (a1-1) may be one type or two or more types, and when there are two or more types, the combination and ratio thereof can be selected arbitrarily.

In the acrylic resin (a1-1), the ratio of the content of the energy ray curable group derived from the energy ray curable compound (a12) to the content of the functional group derived from the acrylic polymer (a11) is preferably 20 to 120 mol%, more preferably 35 to 100 mol%, and particularly preferably 50 to 100 mol%. When the content ratio is in such a range, the adhesive strength of the cured product of the energy ray curable protective film forming film is greater. Note that when the energy ray curable compound (a12) is a monofunctional compound (having one of the groups in one molecule), the upper limit of the content ratio is 100 mol%, but when the energy ray curable compound (a12) is a polyfunctional compound (having two or more of the groups in one molecule), the upper limit of the content ratio may exceed 100 mol%.

The weight average molecular weight (Mw) of the polymer (a1) is preferably 100,000 to 2,000,000, and more preferably 300,000 to 1,500,000.
Here, the "weight average molecular weight" is as explained above.

When the polymer (a1) is at least partially crosslinked by a crosslinking agent, the polymer (a1) may be crosslinked at the group reactive with the crosslinking agent by polymerization of a monomer that does not correspond to any of the above-mentioned monomers described as constituting the acrylic polymer (a11) and has a group reactive with the crosslinking agent, or may be crosslinked at a group reactive with the functional group derived from the energy ray-curable compound (a12).

The polymer (a1) contained in the composition (IV-1) and the energy ray-curable protective film-forming film may be one type or two or more types. When two or more types are contained, the combination and ratio thereof can be selected arbitrarily.

(Compound (a2) having an energy ray-curable group and a molecular weight of 100 to 80,000)
The energy ray-curable group in the compound (a2) having an energy ray-curable group and a molecular weight of 100 to 80,000 includes a group containing an energy ray-curable double bond, and preferred examples thereof include a (meth)acryloyl group and a vinyl group.

The compound (a2) is not particularly limited as long as it satisfies the above conditions, but examples thereof include low molecular weight compounds having energy ray curable groups, epoxy resins having energy ray curable groups, and phenolic resins having energy ray curable groups.

Among the compounds (a2), examples of the low molecular weight compound having an energy ray-curable group include polyfunctional monomers or oligomers, and are preferably acrylate compounds having a (meth)acryloyl group.
Examples of the acrylate-based compound include 2-hydroxy-3-(meth)acryloyloxypropyl methacrylate, polyethylene glycol di(meth)acrylate, propoxylated ethoxylated bisphenol A di(meth)acrylate, 2,2-bis[4-((meth)acryloxypolyethoxy)phenyl]propane, ethoxylated bisphenol A di(meth)acrylate, 2,2-bis[4-((meth)acryloxydiethoxy)phenyl]propane, 9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene, 2,2-bis[4-((meth)acryloxypolypropoxy)phenyl]propane, tricyclodecane dimethanol di(meth)acrylate, 1,10-decane diol di(meth)acrylate, 1,2-dimethylphenyl di(meth)acrylate, 1,3-dimethylphenyl di(meth)acrylate, 1,4-dimethylphenyl di(meth)acrylate, 1,5-dimethylphenyl di(meth)acrylate, 1,6-dimethylphenyl di(meth)acrylate, 1,7-dimethylphenyl di(meth)acrylate, 1,8-dimethylphenyl di(meth)acrylate, 1,9-dimethylphenyl di(meth)acrylate, 1,10-dimethylphenyl di(meth)acrylate, 1,2-dimethylphenyl di(meth)acrylate, 1,3-dimethylphenyl di(meth)acrylate, 1,4-dimethylphenyl di(meth)acrylate, 1,5-dimethylphenyl di(meth)acrylate, 1,6-dimethylphenyl di(meth)acrylate, 1,7-dimethylphenyl di(meth)acrylate, 1,8-dimethylphenyl di(meth)acrylate, 1,9-dimethylphenyl di(meth)acrylate, 1,9-dimethylphenyl di(meth)acrylate, 1,10-dimethylphenyl di(meth)acrylate, 1,2-dimethylphenyl di(meth)acrylate, 1,3-dimethylphenyl di(meth)acrylate, 1,4-dimethylphenyl di(meth)acrylate, 1,5-dimethylphenyl di(meth)acrylate, 1,6-dimethylphenyl bifunctional (meth)acrylates such as 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 2,2-bis[4-((meth)acryloxyethoxy)phenyl]propane, neopentyl glycol di(meth)acrylate, ethoxylated polypropylene glycol di(meth)acrylate, and 2-hydroxy-1,3-di(meth)acryloxypropane;
Polyfunctional (meth)acrylates such as tris(2-(meth)acryloxyethyl)isocyanurate, ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate, ethoxylated glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol poly(meth)acrylate, and dipentaerythritol hexa(meth)acrylate;
Examples of the polyfunctional (meth)acrylate oligomer include urethane (meth)acrylate oligomer.

Of the compounds (a2), examples of the epoxy resins having energy ray-curable groups and the phenolic resins having energy ray-curable groups that can be used include those described in paragraph 0043 of JP 2013-194102 A. Although such resins also fall under the category of resins constituting the thermosetting component described below, in the present invention they are treated as the compounds (a2).

The weight average molecular weight of the compound (a2) is preferably 100 to 30,000, and more preferably 300 to 10,000.

The compound (a2) contained in the composition (IV-1) and the energy ray-curable protective film-forming film may be one type or two or more types. When two or more types are contained, the combination and ratio thereof can be selected arbitrarily.

[Polymer (b) having no energy ray-curable group]
When the composition (IV-1) and the energy ray-curable protective film-forming film contain the compound (a2) as the energy ray-curable component (a), they preferably further contain a polymer (b) having no energy ray-curable group.
The polymer (b) may be at least partially crosslinked with a crosslinking agent, or may not be crosslinked.

Examples of the polymer (b) having no energy ray-curable group include acrylic polymers, phenoxy resins, urethane resins, polyesters, rubber-based resins, and acrylic urethane resins.
Among these, the polymer (b) is preferably an acrylic polymer (hereinafter sometimes abbreviated as "acrylic polymer (b-1)").

The acrylic polymer (b-1) may be a known one, for example, a homopolymer of one type of acrylic monomer, a copolymer of two or more types of acrylic monomers, or a copolymer of one or more types of acrylic monomers and one or more types of monomers other than the acrylic monomers (non-acrylic monomers).

Examples of the acrylic monomer constituting the acrylic polymer (b-1) include (meth)acrylic acid alkyl esters, (meth)acrylic acid esters having a cyclic skeleton, glycidyl group-containing (meth)acrylic acid esters, hydroxyl group-containing (meth)acrylic acid esters, and substituted amino group-containing (meth)acrylic acid esters. Here, the "substituted amino group" is as described above.

The (meth)acrylic acid alkyl ester can be, for example, the same as the acrylic monomer not having a functional group (e.g., (meth)acrylic acid alkyl ester in which the alkyl group constituting the alkyl ester has a chain structure having 1 to 18 carbon atoms) constituting the acrylic polymer (a11) described above.

Examples of the (meth)acrylic acid ester having a cyclic skeleton include cycloalkyl (meth)acrylic acid esters such as isobornyl (meth)acrylate and dicyclopentanyl (meth)acrylate;
(Meth)acrylic acid aralkyl esters such as benzyl (meth)acrylate;
(Meth)acrylic acid cycloalkenyl esters such as (meth)acrylic acid dicyclopentenyl ester;
(Meth)acrylic acid cycloalkenyloxyalkyl esters such as (meth)acrylic acid dicyclopentenyloxyethyl ester are included.

Examples of the glycidyl group-containing (meth)acrylic acid ester include glycidyl (meth)acrylate.
Examples of the hydroxyl group-containing (meth)acrylic acid ester include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.
Examples of the substituted amino group-containing (meth)acrylic acid ester include N-methylaminoethyl (meth)acrylate.

The non-acrylic monomers constituting the acrylic polymer (b-1) include, for example, olefins such as ethylene and norbornene; vinyl acetate; styrene; and the like.

The polymer (b) having no energy ray-curable group and at least a portion of which is crosslinked with a crosslinking agent may be, for example, a polymer in which a reactive functional group in the polymer (b) has reacted with a crosslinking agent.
The reactive functional group may be appropriately selected according to the type of crosslinking agent, and is not particularly limited. For example, when the crosslinking agent is a polyisocyanate compound, the reactive functional group may be a hydroxyl group, a carboxyl group, an amino group, etc., and among these, a hydroxyl group having high reactivity with an isocyanate group is preferred. When the crosslinking agent is an epoxy compound, the reactive functional group may be a carboxyl group, an amino group, an amide group, etc., and among these, a carboxyl group having high reactivity with an epoxy group is preferred. However, in terms of preventing corrosion of the circuit of the workpiece or the workpiece, it is preferred that the reactive functional group is a group other than a carboxyl group.

The polymer (b) having the reactive functional group but not having an energy ray curable group can be, for example, one obtained by polymerizing at least a monomer having the reactive functional group. In the case of the acrylic polymer (b-1), one or both of the acrylic monomers and non-acrylic monomers listed as the monomers constituting the polymer can be one having the reactive functional group. The polymer (b) having a hydroxyl group as a reactive functional group can be, for example, one obtained by polymerizing a hydroxyl group-containing (meth)acrylic acid ester, and also can be one obtained by polymerizing a monomer in which one or more hydrogen atoms in the acrylic monomers or non-acrylic monomers listed above are substituted with the reactive functional group.

In the polymer (b) having a reactive functional group, the ratio (content) of the amount of the structural units derived from the monomer having a reactive functional group to the total amount of the structural units constituting the polymer (b) is preferably 1 to 20 mass%, and more preferably 2 to 10 mass%. When the ratio is in this range, the degree of crosslinking in the polymer (b) is in a more preferable range.

The weight average molecular weight (Mw) of the polymer (b) that does not have an energy ray-curable group is preferably 10,000 to 2,000,000, and more preferably 100,000 to 1,500,000, in order to improve the film-forming properties of the composition (IV-1). Here, the "weight average molecular weight" is as explained above.

The composition (IV-1) and the energy ray-curable protective film-forming film contain only one type of polymer (b) that does not have an energy ray-curable group, or two or more types of polymers. When there are two or more types, the combination and ratio of the polymers can be selected arbitrarily.

The composition (IV-1) may contain either one or both of the polymer (a1) and the compound (a2). When the composition (IV-1) contains the compound (a2), it is preferable that the composition (IV-1) further contains a polymer (b) having no energy ray-curable groups, and in this case, it is also preferable that the composition (IV-1) further contains the (a1). The composition (IV-1) may not contain the compound (a2), but may contain both the polymer (a1) and the polymer (b) having no energy ray-curable groups.

When composition (IV-1) contains the polymer (a1), the compound (a2), and the polymer (b) that does not have an energy ray-curable group, the content of the compound (a2) in composition (IV-1) is preferably 10 to 400 parts by mass, and more preferably 30 to 350 parts by mass, per 100 parts by mass of the total content of the polymer (a1) and the polymer (b) that does not have an energy ray-curable group.

In composition (IV-1), the ratio of the total content of the energy ray curable component (a) and the polymer (b) not having an energy ray curable group to the total content of components other than the solvent (i.e., the ratio of the total content of the energy ray curable component (a) and the polymer (b) not having an energy ray curable group to the total mass of the film in the energy ray curable protective film forming film) is preferably 5 to 90 mass%, more preferably 10 to 80 mass%, and particularly preferably 20 to 70 mass%. When the ratio of the content of the energy ray curable component is in such a range, the energy ray curability of the energy ray curable protective film forming film becomes better.

In addition to the energy ray-curable component, composition (IV-1) may contain one or more selected from the group consisting of a thermosetting component, a filler, a coupling agent, a crosslinking agent, a photopolymerization initiator, a colorant, and a general-purpose additive, depending on the purpose.

The thermosetting component, filler, coupling agent, crosslinking agent, photopolymerization initiator, colorant, and general-purpose additive in composition (IV-1) are the same as the thermosetting component (B), filler (D), coupling agent (E), crosslinking agent (F), photopolymerization initiator (H), colorant (I), and general-purpose additive (J) in composition (III-1).

For example, by using the composition (IV-1) containing the energy ray-curable component and the thermosetting component, the adhesive strength of the energy ray-curable film for forming a protective film formed therefrom to an adherend is improved by heating, and the strength of the protective film formed from this energy ray-curable film for forming a protective film is also improved.
In addition, by using the composition (IV-1) containing the energy ray curable component and the colorant, the energy ray curable film for forming a protective film formed therefrom exhibits the same effects as those in the case where the thermosetting film for forming a protective film described above contains the colorant (I).

In composition (IV-1), the thermosetting component, filler, coupling agent, crosslinking agent, photopolymerization initiator, colorant, and general-purpose additive may each be used alone or in combination of two or more kinds. When two or more kinds are used in combination, the combination and ratio of the two or more kinds can be selected arbitrarily.

The contents of the thermosetting component, coupling agent, crosslinking agent, photopolymerization initiator, colorant, and general-purpose additive in the composition (IV-1) may be appropriately adjusted depending on the purpose, and are not particularly limited.
The content of the filler in composition (IV-1) is preferably 80% by mass or less, and preferably 70% by mass or less, and may be, for example, any of 50% by mass or more and 80% by mass or less, and 55% by mass or more and 80% by mass or less, or may be any of 50% by mass or more and 70% by mass or less, and 55% by mass or more and 70% by mass or less. When the ratio is in such a range, it is possible to suppress the components from migrating between the energy ray-curable pressure-sensitive adhesive and the protective film-forming film before energy ray curing.

Composition (IV-1) preferably further contains a solvent, since dilution improves its handling properties.
The solvent contained in the composition (IV-1) may be, for example, the same as the solvent in the composition (III-1).
The composition (IV-1) may contain only one type of solvent, or two or more types of solvents.
The content of the solvent in the composition (IV-1) is not particularly limited, and may be appropriately selected depending on, for example, the types of components other than the solvent.

<Method of producing energy ray-curable protective film-forming composition>
The energy ray-curable protective film-forming composition such as composition (IV-1) can be obtained by blending the respective components constituting the composition.
The energy ray-curable protective film-forming composition can be produced, for example, in the same manner as in the case of the pressure-sensitive adhesive composition described above, except that the types of blended components are different.

Non-curable Protective Film Formation Film Preferred non-curable protective films include those containing a thermoplastic resin and a filler.

<Non-curable protective film-forming composition (V-1)>
A preferred example of a non-curable protective film-forming composition is a non-curable protective film-forming composition (V-1) (sometimes referred to herein simply as "composition (V-1)") containing the thermoplastic resin and a filler.

[Thermoplastic resin]
The thermoplastic resin is not particularly limited.
More specifically, the thermoplastic resin may be, for example, the same as the non-curable resins such as acrylic resins, polyesters, polyurethanes, phenoxy resins, polybutenes, polybutadienes, and polystyrenes, which are listed as components contained in the above-mentioned composition (III-1).

The thermoplastic resin contained in composition (V-1) and the non-curable protective film-forming film may be one type or two or more types, and when two or more types are contained, the combination and ratio thereof can be selected arbitrarily.

In composition (V-1), the ratio of the content of the thermoplastic resin to the total content of components other than the solvent (i.e., the ratio of the content of the thermoplastic resin in the film for forming a non-curable protective film to the total mass of the film for forming a non-curable protective film) is preferably 25 to 75 mass%.

[Filling material]
The non-curable film for forming a protective film containing a filler exhibits the same effects as the thermosetting film for forming a protective film containing a filler (D).

The filler contained in composition (V-1) and the film for forming a non-curable protective film may be the same as the filler (D) contained in composition (III-1) and the film for forming a thermosetting protective film.

The composition (V-1) and the non-curable protective film-forming film may contain one type of filler or two or more types of fillers. If there are two or more types, the combination and ratio of the fillers can be selected arbitrarily.

In composition (V-1), the ratio of the filler content to the total content of all components other than the solvent (i.e., the ratio of the filler content in the non-curable protective film-forming film to the total mass of the non-curable protective film-forming film) is preferably 50 to 75 mass%. By having the ratio in this range, it becomes easier to adjust the thermal expansion coefficient of the non-curable protective film-forming film (i.e., the protective film), as in the case of using composition (III-1).

The composition (V-1) may contain other components in addition to the thermoplastic resin and filler, depending on the purpose.
The other components are not particularly limited and can be arbitrarily selected depending on the purpose.
For example, by using the composition (V-1) containing the thermoplastic resin and the colorant, the non-curable film for forming a protective film (in other words, a protective film) formed exhibits the same effects as those of the thermosetting film for forming a protective film described above containing the colorant (I).

In composition (V-1), the other components may be used alone or in combination of two or more kinds. When two or more kinds are used in combination, the combination and ratio thereof may be selected arbitrarily.

The content of the other components in composition (V-1) is not particularly limited and may be adjusted appropriately depending on the purpose.

Composition (V-1) preferably further contains a solvent, since dilution improves its handleability.
The solvent contained in the composition (V-1) may be, for example, the same as the solvent in the above-mentioned composition (III-1).
The composition (V-1) may contain only one type of solvent, or two or more types of solvents.
The content of the solvent in the composition (V-1) is not particularly limited, and may be appropriately selected depending on, for example, the types of components other than the solvent.

<Method for producing a composition for forming a non-curable protective film>
A non-curable protective film-forming composition such as composition (V-1) can be obtained by blending the respective components constituting the composition.
The non-curable protective film-forming composition can be produced, for example, in the same manner as in the case of the pressure-sensitive adhesive composition described above, except that the types of ingredients used are different.

The composite sheet for forming a protective film can be produced by laminating the above-mentioned layers so that they are in a corresponding positional relationship, and adjusting the shapes of some or all of the layers as necessary. The method for forming each layer is as described above.

For example, when a pressure-sensitive adhesive layer is laminated on a substrate during the production of a support sheet, the pressure-sensitive adhesive composition may be applied onto the substrate and dried as necessary.
Alternatively, the pressure-sensitive adhesive layer can be laminated on the substrate by coating the pressure-sensitive adhesive composition on a release film, drying it as necessary to form a pressure-sensitive adhesive layer on the release film, and then laminating the exposed surface of the pressure-sensitive adhesive layer to one surface of the substrate. In this case, the pressure-sensitive adhesive composition is preferably coated on the release-treated surface of the release film.
Although the above has been described with reference to an example in which a pressure-sensitive adhesive layer is laminated on a substrate, the above-mentioned method can also be applied to, for example, a case in which the other layer is laminated on a substrate.

On the other hand, for example, when a film for forming a protective film is laminated on an adhesive layer already laminated on a substrate, a composition for forming a protective film can be applied to the adhesive layer to directly form a film for forming a protective film. A layer other than the film for forming a protective film can also be laminated on the adhesive layer in a similar manner using a composition for forming this layer. In this way, when a new layer (hereinafter abbreviated as "second layer") is formed on any layer (hereinafter abbreviated as "first layer") already laminated on a substrate to form a continuous two-layer laminate structure (in other words, a laminate structure of the first layer and the second layer), a method of applying a composition for forming the second layer on the first layer and drying it as necessary can be applied.
However, it is preferable that the second layer is formed in advance on a release film using a composition for forming the second layer, and the exposed surface of the second layer opposite to the side in contact with the release film is bonded to the exposed surface of the first layer to form a continuous two-layer laminate structure. In this case, it is preferable that the composition is applied to the release-treated surface of the release film. The release film may be removed as necessary after the laminate structure is formed.
Here, the case where a film for forming a protective film is laminated on the pressure-sensitive adhesive layer has been taken as an example, but the target laminate structure can be arbitrarily selected, for example, when the other layer is laminated on the pressure-sensitive adhesive layer.

In this way, all layers other than the substrate that make up the composite sheet for forming a protective film can be formed in advance on a release film and laminated by laminating them to the surface of the desired layer, so the composite sheet for forming a protective film can be manufactured by appropriately selecting the layers that will undergo such a process as necessary.

The composite sheet for forming a protective film is usually stored with a release film attached to the surface of the outermost layer (e.g., the film for forming a protective film) opposite the support sheet. Therefore, a composition for forming a layer constituting the outermost layer, such as a composition for forming a protective film, is applied to this release film (preferably its release-treated surface) and dried as necessary to form a layer constituting the outermost layer on the release film, and the remaining layers are laminated by any of the methods described above on the exposed surface opposite the side in contact with the release film of this layer, and the release film is not removed and the laminated state is left as it is, thereby obtaining a composite sheet for forming a protective film with a release film.

◇ Manufacturing method for workpieces with protective film (Method of using composite sheet for forming protective film)
The composite sheet for forming a protective film can be used to manufacture the workpiece having the protective film.
An example of a method for manufacturing a workpiece with a protective film, in which a protective film is provided at any location on the workpiece, includes a bonding step of bonding a film for forming a protective film in the composite sheet for forming a protective film to a desired location on the workpiece to produce a laminate in which the composite sheet for forming a protective film is provided (laminated) on the workpiece, a curing step of curing the film for forming a protective film, which is performed as necessary after the bonding step, a printing step of printing on the film for forming a protective film or its cured product in the composite sheet for forming a protective film in the laminate after the bonding step by irradiating laser light from the outside of the support sheet side of the composite sheet for forming a protective film through the support sheet, and a processing step of processing the workpiece after the printing step to produce a workpiece, in which the film for forming a protective film after bonding to the workpiece is used as a protective film without being cured, or the cured product obtained by curing is used as a protective film.

An example of a method for manufacturing a workpiece with a protective film when the work is a semiconductor wafer, i.e., a semiconductor chip with a protective film, is a method for manufacturing a semiconductor chip with a protective film provided on the back surface of the semiconductor chip, comprising the steps of: a bonding step of bonding a film for forming a protective film in the composite sheet for forming a protective film to the back surface of the semiconductor wafer to produce a laminate in which the composite sheet for forming a protective film is provided on the back surface of the semiconductor wafer; a curing step, which is performed as necessary after the bonding step, of curing the film for forming a protective film; a printing step, which is performed after the bonding step, of printing on the film for forming a protective film or its cured product by irradiating the film for forming a protective film in the composite sheet for forming a protective film in the laminate or its cured product with laser light from the outside of the support sheet side of the composite sheet for forming a protective film through the support sheet; and a dividing/cutting step, which is performed after the printing step, of dividing the semiconductor wafer to produce a semiconductor chip, and further cutting the film for forming a protective film or its cured product. and a pick-up process of separating the semiconductor chip equipped with the cut protective film-forming film or its cured product from the support sheet and picking it up. The protective film-forming film after being attached to the semiconductor wafer is used as a protective film without being cured, or the cured product obtained by curing the film is used as a protective film.

In the above manufacturing method, if the workpiece is a semiconductor wafer, the workpiece can be as described above.

In the manufacturing method, by using the composite sheet for forming a protective film of the present embodiment described above, even when the laser light having a short wavelength such as 266 nm is irradiated, the film for forming a protective film in the composite sheet for forming a protective film or its cured product can be printed well. Furthermore, this printing can be clearly seen from the outside of the support sheet side of the composite sheet for forming a protective film, through the support sheet.

The production method is divided into a production method having the curing step (sometimes referred to as "production method (1)" in this specification) and a production method not having the curing step (sometimes referred to as "production method (2)" in this specification).
These manufacturing methods will be explained below in order.

<<Production method (1)>>
The manufacturing method (1) is a manufacturing method of a workpiece with a protective film, which is provided at any location of the workpiece, and includes an attachment step of attaching a film for forming a protective film in the composite sheet for forming a protective film to a desired location of the workpiece to produce a laminate in which the composite sheet for forming a protective film is provided (laminated) on the workpiece; a curing step of curing the film for forming a protective film after the attachment step; a printing step of printing on the film for forming a protective film or its cured product in the composite sheet for forming a protective film in the laminate after the attachment step by irradiating laser light from the outside of the support sheet side of the composite sheet for forming a protective film through the support sheet to print on the film for forming a protective film or its cured product; and a processing step of processing the workpiece after the printing step to produce a workpiece, in which the cured product obtained by curing the film for forming a protective film after being attached to the workpiece is the protective film.

Figure 3 is a cross-sectional view for explaining an example of the manufacturing method (1) when the workpiece is a semiconductor wafer. Here, a manufacturing method is explained when using the composite sheet 101 for forming a protective film shown in Figure 1.

<Attachment process>
In the bonding step, the composite sheet 101 for forming a protective film is used from which the release film 15 has been removed, and as shown in Fig. 3(a), the film 13 for forming a protective film in the composite sheet 101 for forming a protective film is bonded to the rear surface 9b of the semiconductor wafer 9. In this way, a laminate 901 is produced that includes the semiconductor wafer 9 and the composite sheet 101 for forming a protective film provided on the rear surface 9b.

In the attaching step, the protective film-forming film 13 may be softened by heating and then attached to the semiconductor wafer 9 .
In this figure, bumps and the like on the circuit forming surface 9a of the semiconductor wafer 9 are omitted.
Furthermore, the symbol 13b indicates the surface (sometimes referred to as the "second surface" in this specification) opposite the first surface 13a of the protective film-forming film 13 (in other words, the pressure-sensitive adhesive layer 12 side).

The semiconductor wafer 9 may have its back surface ground to obtain a desired thickness. In other words, the back surface 9b of the semiconductor wafer 9 may be a ground surface.

It is preferable that the semiconductor wafer 9 does not have any grooves that run between its circuit formation surface 9a and back surface 9b.

<Curing process>
After the sticking step, in the curing step, the protective film-forming film 13 is cured as shown in FIG. 3(b).
Here, a case is shown in which a curing step is performed before the printing step.
In this embodiment, the protective film-forming film 13 is cured after being attached to the semiconductor wafer 9, and the cured product is used as the protective film, regardless of whether it is cut or not.

By carrying out the curing process, the composite sheet 101 for forming a protective film becomes the composite sheet 1011 for forming a protective film in which the film 13 for forming a protective film has become its cured product 13', and a cured laminate 9011 is obtained which is composed of the semiconductor wafer 9 and the composite sheet 1011 for forming a protective film provided on its back surface 9b.
Symbol 13a' indicates a first surface of the cured material 13' corresponding to the first surface 13a of the film 13 for forming a protective film, and symbol 13b' indicates a second surface of the cured material 13' corresponding to the second surface 13b of the film 13 for forming a protective film.

In the curing step, if the protective film-forming film 13 is thermosetting, the protective film-forming film 13 is heated to form a cured product 13'. If the protective film-forming film 13 is energy ray-curable, the protective film-forming film 13 is irradiated with energy rays through the support sheet 10 to form a cured product 13'.

In the curing process, the curing conditions of the protective film-forming film 13, i.e., the heating temperature and heating time during thermal curing, and the illuminance and light amount of the energy rays during energy ray curing, are as described above.

<Printing process>
3(c), the cured product 13' in the composite sheet 1011 for forming a protective film in the cured laminate 9011 is printed by irradiating the cured product 13' with laser light L from the outside of the composite sheet 10 for forming a protective film through the support sheet 10. Printing (not shown) is performed on a second surface 13b' of the cured product 13'.

By carrying out the printing process, the composite sheet 1011 for forming a protective film becomes the composite sheet 1012 for forming a protective film having the printed cured product 13', and a printed and cured laminate 9012 is obtained that is composed of the semiconductor wafer 9 and the composite sheet 1012 for forming a protective film provided on its back surface 9b.

The wavelength of the laser light L is preferably shorter than that of conventional laser light, and more preferably 266 nm.

<Divide/Cut Process>
After the printing step, in the dividing/cutting step, as shown in FIG. 3(d), the semiconductor wafer 9 is divided to produce semiconductor chips 9', and the cured product 13' is cut.
By carrying out the dividing/cutting step, a plurality of semiconductor chips 91 with protective films are obtained, each of which includes a semiconductor chip 9' and the cured product 130' after cutting provided on a back surface 9b' of the semiconductor chip 9'. All of the plurality of semiconductor chips 91 with protective films are aligned on one support sheet 10, and the semiconductor chips 91 with protective films and the support sheet 10 constitute a group of semiconductor chips with protective films 910.

The symbol 130a' indicates a first surface of the cured material 130' after cutting, which corresponds to the first surface 13a' of the cured material 13', and the symbol 130b' indicates a second surface of the cured material 130' after cutting, which corresponds to the second surface 13b' of the cured material 13'.
Reference numeral 9 a ′ denotes a circuit-forming surface of a semiconductor chip 9 ′, which corresponds to the circuit-forming surface 9 a of the semiconductor wafer 9 .

The semiconductor chips 9' can be produced by dividing the semiconductor wafer 9 (in other words, dicing) using a known method.
Examples of methods for dividing the semiconductor wafer 9 include methods for cutting the semiconductor wafer, such as blade dicing, which uses a blade to dice the semiconductor wafer 9; laser dicing, which dices the semiconductor wafer 9 by irradiating a laser; and water dicing, which dices the semiconductor wafer 9 by spraying water containing an abrasive. The cut may be made up to the adhesive layer 12, or may reach the substrate 11. When the cut is made up to the adhesive layer 12, cutting waste is less likely to be generated. When the cut is made up to the substrate 11, the expandability during expansion is improved.
When these methods are applied, for example, the semiconductor wafer 9 may be divided and the cured material 13' may be cut at the same time, so that the division of the semiconductor wafer 9 and the cutting of the cured material 13' may be performed simultaneously.

As a method for dividing the semiconductor wafer 9, there are methods other than the method of cutting the semiconductor wafer.
That is, in this method, first, a planned division location is set inside the semiconductor wafer 9, and a laser beam is irradiated so as to converge on this location as a focal point, thereby forming a modified layer inside the semiconductor wafer 9. The modified layer of the semiconductor wafer is different from other locations of the semiconductor wafer, and is altered by the irradiation of the laser beam, and has a weak strength. Therefore, when a force is applied to the semiconductor wafer 9, a crack extending in the direction of both sides of the semiconductor wafer 9 occurs in the modified layer inside the semiconductor wafer 9, which becomes the starting point for dividing (cutting) the semiconductor wafer 9. Next, a force is applied to the semiconductor wafer 9 to divide the semiconductor wafer 9 at the site of the modified layer, and semiconductor chips are produced. Such a method of dividing the semiconductor wafer 9 with the formation of a modified layer is called Stealth Dicing (registered trademark).
For example, a semiconductor wafer on which a modified layer is formed can be divided by expanding it in a direction parallel to its surface and applying a force. When applying the method of expanding a semiconductor wafer in this way, the division of the semiconductor wafer 9 and the cutting of the cured product 13' may be performed simultaneously by expanding the cured product 13' of the protective film forming film together with the semiconductor wafer 9 and cutting the cured product 13' at the same time. The cutting of the cured product 13' by expanding is preferably performed at a low temperature such as -20 to 5°C.

If the division of the semiconductor wafer 9 and the cutting of the cured material 13' are not performed simultaneously, the cutting of the cured material 13' can be performed separately by a known method in addition to the division of the semiconductor wafer 9.

<Pickup process>
In the pick-up step after the dividing/cutting step, as shown in Fig. 3(e), the semiconductor chip 9' (semiconductor chip 91 with a protective film) having the cut cured material 130' is picked up by being pulled away from the support sheet 10. Here, the pick-up direction is indicated by arrow I.

The semiconductor chip 91 with the protective film can be picked up by a known method. For example, a vacuum collet or the like can be used as the detachment means 8 for detaching the semiconductor chip 91 with the protective film from the support sheet 10. Note that only the detachment means 8 is not shown in cross section here, and this is the same in the subsequent similar figures.
In this manner, the desired semiconductor chip 91 with a protective film is obtained.

In the semiconductor chips 91 with protective film that were the subject of the printing process, including the one that was picked up, the printing is clearly maintained on the second surface 130b' of the cured product 130' after cutting.

<Timing of Curing Process>
Although the above description has been given of a case where the curing step is performed between the bonding step and the printing step, the timing of performing the curing step in the manufacturing method (1) is not limited to this. For example, in the manufacturing method (1), the curing step may be performed between the printing step and the dividing/cutting step, between the dividing/cutting step and the picking up step, or after the picking up step.

When the curing step is performed after the bonding step and the printing step, in the printing step, the film 13 for forming a protective film in the composite sheet 101 for forming a protective film in the laminate 901 shown in Fig. 3(a) is printed on by irradiating the film 13 for forming a protective film with laser light L from outside the composite sheet 101 for forming a protective film through the support sheet 10 on the support sheet 10 side. Printing (not shown) is performed on the second surface 13b of the film 13 for forming a protective film.
In this case, the printing process can be carried out in the same manner as the printing process described above, except that the target of irradiation with the laser light L is not the cured product 13' of the film 13 for forming a protective film, but the film 13 for forming a protective film.

<Other steps>
The manufacturing method (1) may include, in addition to the steps of the attaching step, the curing step, the printing step, the dividing/cutting step, and the picking up step, other steps not corresponding to any of the steps mentioned above.
The types of the other steps and the timing of carrying them out can be arbitrarily selected depending on the purpose, and are not particularly limited.

<<Production method (2)>>
The manufacturing method (2) is a manufacturing method for a workpiece with a protective film, which is provided at any location on the workpiece, and includes an attachment step of attaching a film for forming a protective film in the composite sheet for forming a protective film to a desired location on the workpiece to produce a laminate in which the composite sheet for forming a protective film is provided (laminated) on the workpiece; a printing step of printing on the film for forming a protective film in the composite sheet for forming a protective film in the laminate by irradiating laser light from outside the support sheet side of the composite sheet for forming a protective film through the support sheet after the attachment step; and a processing step of processing the workpiece to produce a workpiece after the printing step, in which the film for forming a protective film is not hardened after being attached to the workpiece to form a protective film.
Manufacturing method (2) is the same as manufacturing method (1) except that, regardless of the type of workpiece, it does not have the curing process and the film for forming a protective film after being attached to the workpiece serves as the protective film as is, and produces the same effects as manufacturing method (1).

Up to this point, we have mainly explained the method for manufacturing a workpiece with a protective film when using the composite sheet 101 for forming a protective film shown in Figure 1, but the method for manufacturing a workpiece with a protective film in this embodiment is not limited to this.
For example, even if a composite sheet for forming a protective film shown in FIG. 2 or the like other than the composite sheet for forming a protective film 101 shown in FIG. 1 is used, a workpiece with a protective film can be similarly manufactured by the above-mentioned manufacturing method.
When using a composite sheet for forming a protective film of another embodiment, based on the difference in structure between this sheet and the composite sheet for forming a protective film 101, steps may be added, modified, deleted, etc. as appropriate in the above-mentioned manufacturing method to manufacture a workpiece with a protective film.

◇Method of manufacturing a semiconductor device After obtaining a workpiece with a protective film by the above-mentioned manufacturing method, the workpiece with a protective film can be used to manufacture a semiconductor device by a known appropriate method depending on the type of the workpiece. For example, if the workpiece with a protective film is a semiconductor chip with a protective film, the semiconductor chip with the protective film is flip-chip connected to the circuit surface of a substrate, and then the semiconductor chip is made into a semiconductor package, and the semiconductor package can be used to manufacture the desired semiconductor device (not shown).

The present invention will be described in more detail below with reference to specific examples. However, the present invention is not limited to the examples shown below.

<Raw materials for resin production>
The full names of the raw materials for producing the resins, which are abbreviated in the present examples and comparative examples, are shown below.
MA: Methyl acrylate HEA: 2-hydroxyethyl acrylate 2EHA: 2-ethylhexyl acrylate MOI: 2-methacryloyloxyethyl isocyanate BA: n-butyl acrylate GMA: glycidyl methacrylate VAc: vinyl acetate AA: acrylic acid HEMA: 2-hydroxyethyl methacrylate

<Materials for producing the protective film-forming composition>
The raw materials used in the production of the composition for forming a protective film are shown below.
[Polymer component (A)]
(A)-1: Acrylic polymer obtained by copolymerizing MA (85 parts by mass) and HEA (15 parts by mass) (weight average molecular weight: 300,000, glass transition temperature: 6° C.)
(A)-2: Acrylic polymer obtained by copolymerizing BA (55 parts by mass), MA (10 parts by mass), GMA (20 parts by mass) and HEA (15 parts by mass) (weight average molecular weight: 800,000, glass transition temperature: -28°C)
[Thermosetting component (B1)]
(B1)-1: Bisphenol A type epoxy resin ("jER828" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 184 to 194 g/eq)
(B1)-2: Bisphenol A type epoxy resin ("jER1055" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 800 to 900 g/eq)
(B1)-3: Dicyclopentadiene type epoxy resin (DIC Corporation, "Epicron HP-7200HH", epoxy equivalent: 255 to 260 g/eq)
[Thermal curing agent (B2)]
(B2)-1: Heat-activated latent epoxy resin curing agent Dicyandiamide (manufactured by Mitsubishi Chemical Corporation, DICY7, active hydrogen content 21 g/eq)
[Curing Accelerator (C)]
(C)-1: 2-phenyl-4,5-dihydroxymethylimidazole ("Curesol 2PHZ-PW" manufactured by Shikoku Chemical Industry Co., Ltd.)
[Filler (D)]
(D)-1: Silica filler (fused silica filler, average particle size 8 μm)
[Coupling Agent (E)]
(E)-1: Silane coupling agent (KBM503, manufactured by Shin-Etsu Chemical Co., Ltd.)
[Crosslinking agent (F)]
(F)-1: Isocyanate-based crosslinking agent ("Coronate L" manufactured by Tosoh Corporation, an adduct of trimethylolpropane and tolylene diisocyanate trimer)
[Colorant (I)]
(I)-1: A pigment obtained by mixing 32 parts by mass of a phthalocyanine blue pigment (Pigment Blue 15:3), 18 parts by mass of an isoindolinone yellow pigment (Pigment Yellow 139), and 50 parts by mass of an anthraquinone red pigment (Pigment Red 177), and pigmenting the mixture such that the total amount of the three pigments/the amount of styrene acrylic resin was 1/3 (mass ratio).
[Energy ray curable resin (G)]
(G)-1: ε-caprolactone-modified tris-(2-acryloxyethyl)isocyanurate ("A-9300-1CL" manufactured by Shin-Nakamura Chemical Co., Ltd., a trifunctional ultraviolet-curable compound)

[Example 1]
<<Manufacture of Support Sheet>>
<Production of adhesive resin (I-2a)>
The acrylic polymer having a weight average molecular weight of 600,000, which is a copolymer of 2EHA (42 parts by mass), VAc (40 parts by mass), and HEA (18 parts by mass), was added with MOI (in an amount such that the total number of moles of isocyanate groups in the MOI is 0.8 times the total number of moles of hydroxyl groups derived from HEA in the acrylic polymer), and the addition reaction was carried out in an air stream at 50° C. for 48 hours to obtain the desired adhesive resin (I-2a)-1.
Hereinafter, the acrylic polymer may be referred to as "adhesive resin (I-1a)-1."

<Production of Pressure-Sensitive Adhesive Composition (I-2)>
An energy ray curable adhesive composition (I-2)-1 was prepared containing adhesive resin (I-2a)-1 (100 parts by mass), a hexamethylene diisocyanate crosslinking agent (Tosoh's "Coronate L") (0.21 parts by mass), and a photopolymerization initiator (BASF's "Irgacure 127", 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one) (3 parts by mass), and further containing ethyl acetate as a solvent, with the total concentration of all components other than the solvent being 30% by mass. The contents of all components other than ethyl acetate shown here are the contents of the target product not including the solvent.

<Manufacture of Support Sheet>
A release film ("SP-PET381031", manufactured by Lintec Corporation, thickness 38 μm) made of polyethylene terephthalate film, one side of which had been subjected to a release treatment by silicone treatment, was used, and the pressure-sensitive adhesive composition (I-2)-1 obtained above was applied to the release-treated surface, followed by drying by heating at 100° C. for 2 minutes to form an energy ray-curable pressure-sensitive adhesive layer having a thickness of 5 μm. The gel fraction of the pressure-sensitive adhesive layer was 90%. The gel fraction of the pressure-sensitive adhesive layer was a value measured by the method described above. This also applies to the following examples and comparative examples.
Next, a polypropylene film (1) (thickness 80 μm, colorless) was laminated as a substrate to the exposed surface of the adhesive layer to produce a laminated sheet in which the substrate, adhesive layer and release film were laminated in this order in the thickness direction, i.e., a support sheet with a release film.

<<Production of protective film>>
<Production of protective film-forming composition (III-1)>
Polymer component (A)-1 (25.5 parts by mass), thermosetting component (B1)-1 (10.2 parts by mass), (B1)-2 (1.7 parts by mass), (B1)-3 (5.4 parts by mass), thermosetting agent (B2)-1 (0.4 parts by mass), curing accelerator (C)-1 (0.4 parts by mass), filler (D)-1 (54.1 parts by mass), coupling agent (E)-1 (0.3 parts by mass), and colorant (I)-1 (2.0 parts by mass) were dissolved or dispersed in a mixed solvent of methyl ethyl ketone, toluene and ethyl acetate, and stirred at 23 ° C. to obtain a thermosetting protective film-forming composition (III-1)-1 having a total concentration of 50% by mass of all components other than the solvent. Note that the blending amounts of all components other than the mixed solvent shown here are the blending amounts of the target product not including the solvent.
The content of the filler in the thermosetting composition for forming a protective film excluding the solvent was 54.1 mass %. The Tg of the composition for forming a protective film was 23.5°C.

<Production of protective film>
A release film (second release film, "SP-PET381031" manufactured by Lintec Corporation, thickness 38 μm) made of polyethylene terephthalate film, one side of which was treated for release by silicone treatment, was used, and the protective film-forming composition (III-1)-1 obtained above was applied to the release-treated surface, followed by drying at 100°C for 2 minutes to produce a thermosetting protective film-forming film having a thickness of 25 μm.
The loss modulus E'' of the above protective film-forming film was 51.6 MPa.

Furthermore, a release-treated surface of a release film (first release film, "SP-PET381031" manufactured by Lintec Corporation, thickness 38 μm) was attached to the exposed surface of the obtained film for forming a protective film, the side not provided with the second release film, to obtain a laminated film comprising the film for forming a protective film, the first release film provided on one surface of the film for forming a protective film, and the second release film provided on the other surface of the film for forming a protective film.

<<Production of Composite Sheet for Forming Protective Film>>
The release film was removed from the support sheet obtained above. The first release film was also removed from the laminated film obtained above. The exposed surface of the pressure-sensitive adhesive layer obtained by removing the release film was bonded to the exposed surface of the film for forming a protective film obtained by removing the first release film, thereby producing a composite sheet for forming a protective film in which the base material, the pressure-sensitive adhesive layer, the film for forming a protective film, and the second release film were laminated in this order in the thickness direction.

<<Evaluation of composite sheets for forming protective films>>
The above composite sheet for forming a protective film was used to bond an 8-inch mirror wafer and a protective film-forming film. The obtained laminate of the wafer and the composite sheet for forming a protective film was heated at 130° C. for 2 hours to harden the film for forming a protective film to form a protective film, and then allowed to stand until it reached room temperature.
The wafer surface was then fixed by suction to the suction table, the end of the support sheet was held by an arm, and a peel test was performed at the interface between the protective film and the support sheet at a peel angle of 180° and a peel speed of 300 mm/min. The peelability at the interface between the protective film and the support sheet was evaluated according to the following criteria.
A: The protective film and the support sheet could be peeled off at the interface without any problems.
B: The protective film and the support sheet could be peeled off at their interface, but there was some snagging (zipping) during the peeling.
C: Peeling was not possible at the interface between the protective film and the support sheet, and peeling occurred at the interface between the wafer and the protective film.

<<Production and evaluation of film for forming protective film and composite sheet for forming protective film>>
[Example 2]
A film for forming a protective film and a composite sheet for forming a protective film were produced and evaluated in the same manner as in Example 1, except that 29.6 parts by mass of polymer component (A)-1 and 50 parts by mass of filler (D)-1 were used when producing the composition for forming a protective film.
The loss modulus E'' of the above protective film-forming film was 11.0 MPa.
The content of the filler in the thermosetting composition for forming a protective film excluding the solvent was 50.0 mass %. The Tg of the composition for forming a protective film was 13.0°C.
The results are shown in Table 1.

[Example 3]
A support sheet, a film for forming a protective film, and a composite sheet for forming a protective film were produced and evaluated in the same manner as in Example 1, except that when producing the composition for forming a protective film, polymer component (A)-2 (19.0 parts by mass) was used instead of polymer component (A)-1 (25.5 parts by mass), and 60.6 parts by mass of filler (D)-1 was used.
The loss modulus E'' of the above protective film-forming film was 2.2 MPa.
The content of the filler in the thermosetting composition for forming a protective film excluding the solvent was 60.6 mass %. The Tg of the composition for forming a protective film was 2.2°C.
The results are shown in Table 1.

[Example 4]
A film for forming a protective film and a composite sheet for forming a protective film were produced and evaluated in the same manner as in Example 1, except that when producing the composition for forming a protective film, polymer component (A)-2 (25.5 parts by mass) was used instead of polymer component (A)-1 (25.5 parts by mass), and 54.1 parts by mass of filler (D)-1 was used.
The loss modulus E'' of the above protective film-forming film was 1.3 MPa.
The content of the filler in the thermosetting composition for forming a protective film excluding the solvent was 54.1 mass %. The Tg of the composition for forming a protective film was 1.7°C.
The results are shown in Table 1.

[Example 5]
Polymer component (A)-1 (35.98 parts by mass), thermosetting component (B1)-1 (11.24 parts by mass), (B1)-2 (2.04 parts by mass), (B1)-3 (7.48 parts by mass), thermosetting agent (B2)-1 (0.48 parts by mass), curing accelerator (C)-1 (0.48 parts by mass), filler (D)-1 (40.0 parts by mass), coupling agent (E)-1 (0.3 parts by mass), and colorant (I)-1 (2.0 parts by mass) were dissolved or dispersed in a mixed solvent of methyl ethyl ketone, toluene and ethyl acetate, and stirred at 23 ° C. to obtain a thermosetting protective film-forming composition (III-1)-1 having a total concentration of 50% by mass of all components other than the solvent. Note that the blending amounts of all components other than the mixed solvent shown here are the blending amounts of the target product not including the solvent.
The content of the filler in the thermosetting composition for forming a protective film excluding the solvent was 40.0 mass %. The Tg of the composition for forming a protective film was 16.5°C.
Next, a film for forming a protective film and a composite sheet for forming a protective film were produced using the above composition for forming a protective film in the same manner as in Example 1, and were evaluated.
The loss modulus E'' of the above protective film-forming film was 18.4 MPa.
The results are shown in Table 1.

[Example 6]
A support sheet, a film for forming a protective film, and a composite sheet for forming a protective film were produced and evaluated in the same manner as in Example 1, except that, in the production of the support sheet, energy ray curable adhesive composition (I-2)-2 produced by the method described below was used instead of energy ray curable adhesive composition (I-2)-1, and the thickness of the adhesive layer was changed to 10 μm instead of 5 μm. The gel fraction of the adhesive layer was 50%. In addition, the loss modulus E″ of the film for forming a protective film was 51.6 MPa.
The results are shown in Table 1.

<Production of adhesive resin (I-2a)>
A copolymer of 2EHA (21 parts by mass), VAc (76 parts by mass), AA (1 part by mass), and HEMA (2 parts by mass) was mixed with an acrylic polymer (100 parts by mass) having a weight average molecular weight of 300,000, a mixture of bifunctional and hexafunctional urethane acrylate (72 parts by mass), a hexamethylene diisocyanate crosslinking agent (Tosoh Corporation's "Coronate L") (3 parts by mass), a photopolymerization initiator (BASF Corporation's "Irgacure 127", 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one) (3 parts by mass), and the concentration was adjusted to 30% with ethyl acetate to obtain the desired adhesive resin (I-2a)-2.

<Production of Pressure-Sensitive Adhesive Composition (I-2)-2>
An energy ray curable adhesive composition (I-2)-2 was prepared containing adhesive resin (I-2a)-2 (100 parts by mass), a hexamethylene diisocyanate crosslinking agent (Tosoh's "Coronate L") (3 parts by mass), and a photopolymerization initiator (BASF's "Irgacure 127", 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one) (3 parts by mass), and further containing ethyl acetate as a solvent, with the total concentration of all components other than the solvent being 30% by mass. The contents of all components other than ethyl acetate shown here are the contents of the target product not including the solvent.
The content of the filler in the thermosetting composition for forming a protective film excluding the solvent was 54.1 mass %. The Tg of the composition for forming a protective film was 23.5°C.
The results are shown in Table 1.

[Example 7]
A film for forming a protective film and a composite sheet for forming a protective film were produced and evaluated in the same manner as in Example 6, except that 29.6 parts by mass of polymer component (A)-1 and 50 parts by mass of filler (D)-1 were used when producing the composition for forming a protective film.
The loss modulus E'' of the above protective film-forming film was 11.0 MPa.
The content of the filler in the thermosetting composition for forming a protective film excluding the solvent was 50.0 mass %. The Tg of the composition for forming a protective film was 13.0°C.
The results are shown in Table 1.

[Example 8]
A film for forming a protective film and a composite sheet for forming a protective film were produced and evaluated in the same manner as in Example 5, except that the adhesive composition (I-2)-2 was used instead of the energy ray-curable adhesive composition (I-2)-1 when producing the support sheet.
The loss modulus E'' of the above protective film-forming film was 18.4 MPa.
The content of the filler in the thermosetting composition for forming a protective film excluding the solvent was 40.0 mass %. The Tg of the composition for forming a protective film was 16.5°C.
The results are shown in Table 1.

[Example 9]
<Production of protective film-forming composition (IV-1)>
Polymer component (A)-1 (27.07 parts by mass), energy ray curable resin (G)-1 (10.0 parts by mass), crosslinking agent (F)-1 (0.77 parts by mass), photopolymerization initiator ((BASF "Irgacure 369", 2-(dimethylamino)-1-(4-morpholinophenyl)-2-benzyl-1-butanone) (0.6 parts by mass), filler (D)-1 (56.65 parts by mass), coupling agent (E)-1 (0.4 parts by mass), and colorant (I)-1 (4.5 parts by mass) were dissolved or dispersed in a mixed solvent of methyl ethyl ketone, toluene, and ethyl acetate, and stirred at 23°C to obtain an energy ray curable protective film forming composition (III-1)-1 having a total concentration of all components other than the solvent of 50% by mass. Note that the amounts of components other than the mixed solvent shown here are all amounts of the target product not including the solvent.
The content of the filler in the energy ray-curable composition for forming a protective film excluding the solvent was 56.7% by mass. The Tg of the composition for forming a protective film was 6.2°C.

<Production of protective film>
A release film (second release film, "SP-PET381031" manufactured by Lintec Corporation, thickness 38 μm) made of polyethylene terephthalate film, one side of which was treated for release by silicone treatment, was used, and the protective film-forming composition (III-1)-1 obtained above was applied to the release-treated surface, followed by drying at 100° C. for 2 minutes to produce an energy ray-curable protective film-forming film having a thickness of 25 μm.
The loss modulus E'' of the above protective film-forming film was 5.8 MPa.

Furthermore, a release-treated surface of a release film (first release film, "SP-PET381031" manufactured by Lintec Corporation, thickness 38 μm) was attached to the exposed surface of the obtained film for forming a protective film, the side not provided with the second release film, to obtain a laminated film comprising the film for forming a protective film, the first release film provided on one surface of the film for forming a protective film, and the second release film provided on the other surface of the film for forming a protective film.

<<Production of Composite Sheet for Forming Protective Film>>
The release film was removed from the support sheet obtained in the same manner as in Example 1. The first release film was also removed from the laminated film obtained above. Then, the exposed surface of the pressure-sensitive adhesive layer obtained by removing the release film was bonded to the exposed surface of the film for forming a protective film obtained by removing the first release film, thereby producing a composite sheet for forming a protective film in which the base material, the pressure-sensitive adhesive layer, the film for forming a protective film, and the second release film were laminated in this order in the thickness direction.
Next, the composite sheet for forming a protective film was evaluated in the same manner as in Example 1, except that instead of curing by heating at 130°C for 2 hours, the composite sheet was cured by irradiating light with a wavelength of 365 nm three times under conditions of an illuminance of 215 mW/ ^cm2 and a light quantity of 187 mJ/ ^cm2 .
The results are shown in Table 1.

[Comparative Example 1]
A film for forming a protective film and a composite sheet for forming a protective film were produced and evaluated in the same manner as in Example 6, except that when producing the composition for forming a protective film, polymer component (A)-2 (19.0 parts by mass) was used instead of polymer component (A)-1 (25.5 parts by mass), and 60.6 parts by mass of filler (D)-1 was used.
The loss modulus E'' of the above protective film-forming film was 2.2 MPa.
The content of the filler in the thermosetting composition for forming a protective film excluding the solvent was 60.6 mass %. The Tg of the composition for forming a protective film was 2.2°C.
The results are shown in Table 1.

[Comparative Example 2]
A film for forming a protective film and a composite sheet for forming a protective film were produced and evaluated in the same manner as in Example 6, except that when producing the composition for forming a protective film, polymer component (A)-2 (25.5 parts by mass) was used instead of polymer component (A)-1 (25.5 parts by mass), and 54.1 parts by mass of filler (D)-1 was used.
The loss modulus E'' of the above protective film-forming film was 1.3 MPa.
The content of the filler in the thermosetting composition for forming a protective film excluding the solvent was 54.1 mass %. The Tg of the composition for forming a protective film was 1.7°C.
The results are shown in Table 1.

As is clear from the above results, in all of Examples 1 to 5 and 9, the gel fraction of the adhesive in the support sheet before UV curing was 90%, the composite sheet for forming a protective film was rated A for peelability, and the support sheet and the film for forming a protective film could be peeled off smoothly at the interface.

In all of Examples 6 to 8, the gel fraction of the adhesive of the support sheet before UV curing was 50%, but the Tg of the protective film-forming film was 3°C or higher, and the peelability evaluation of the protective film-forming composite sheet was A or B. In Example 8, the peelability evaluation was slightly poor, but in all of the protective film-forming composite sheets, peeling was possible at the interface between the support sheet and the protective film-forming film.

In contrast, in both of the composite sheets for forming a protective film in Comparative Examples 1 and 2, the gel fraction of the adhesive of the support sheet before UV curing was 50%, and the Tg of the film for forming a protective film was less than 3°C. In addition, the loss modulus E'' of the film for forming a protective film at 23°C was less than 3 MPa. As a result, the peelability evaluation of the composite sheet for forming a protective film was C, and peeling did not occur at the interface between the support sheet and the film for forming a protective film, but occurred at the interface between the film for forming a protective film and the adherend.

The present invention can be used in the manufacture of semiconductor devices.

101, 102: Composite sheet for forming protective film, 1011: Composite sheet for forming protective film with cured film for forming protective film, 1012: Composite sheet for forming protective film with cured and printed film for forming protective film, 10: Support sheet, 10a: One side (first side) of the support sheet, 13, 23: Film for forming protective film, 13': Protective film (cured product of film for forming protective film), 130': Protective film after cutting (cured product of film for forming protective film after cutting), 9: Semiconductor wafer, 9a: Circuit formation surface of semiconductor wafer, 9b: Back surface of semiconductor wafer, 9': Semiconductor chip, L: Laser light

Claims (5)

The present invention provides a method for manufacturing a protective film having an energy ray-curable pressure-sensitive adhesive layer and a protective film-forming film laminated in this order on one surface of the substrate in contact with each other,
The pressure-sensitive adhesive layer contains an acrylic resin,
the protective film-forming film contains a compound having an energy ray-curable group and a weight average molecular weight of 100,000 to 2,000,000, or a compound having an energy ray-curable group and a weight average molecular weight of 100 to 80,000,
A composite sheet for forming a protective film, wherein the pressure-sensitive adhesive layer has a gel fraction of 80% or more and 90% or less,
The film for forming a protective film contains a filler (D),
In the film for forming a protective film, the content ratio of the filler (D) to the total mass of the film for forming a protective film is 40 mass% or more and 80 mass% or less,
the compound having a weight average molecular weight of 100,000 to 2,000,000 and having an energy ray-curable group is an acrylic resin obtained by reacting an acrylic polymer having a functional group capable of reacting with a group possessed by another compound with an energy ray-curable compound having a group reactive with the functional group and an energy ray-curable group,
The compound having an energy ray-curable group and a weight average molecular weight of 100 to 80,000 is an acrylate compound having a (meth)acryloyl group, an epoxy resin having an energy ray-curable group, or a phenol resin having an energy ray-curable group. The present invention provides a method for manufacturing a protective film having an energy ray-curable pressure-sensitive adhesive layer and a protective film-forming film laminated in this order on one surface of the substrate in contact with each other,
The pressure-sensitive adhesive layer contains an acrylic resin,
the protective film-forming film contains a compound having an energy ray-curable group and a weight average molecular weight of 100,000 to 2,000,000 or a compound having an energy ray-curable group and a weight average molecular weight of 100 to 80,000,
The pressure-sensitive adhesive layer has a gel fraction of 20% or more and less than 80%,
A composite sheet for forming a protective film, wherein the glass transition temperature of the film for forming a protective film is 3° C. or higher,
The film for forming a protective film contains a filler (D),
In the film for forming a protective film, the content ratio of the filler (D) to the total mass of the film for forming a protective film is 40 mass% or more and 80 mass% or less,
the compound having a weight average molecular weight of 100,000 to 2,000,000 and having an energy ray-curable group is an acrylic resin obtained by reacting an acrylic polymer having a functional group capable of reacting with a group possessed by another compound with an energy ray-curable compound having a group reactive with the functional group and an energy ray-curable group,
The compound having an energy ray-curable group and a weight average molecular weight of 100 to 80,000 is an acrylate compound having a (meth)acryloyl group, an epoxy resin having an energy ray-curable group, or a phenol resin having an energy ray-curable group. The composite sheet for forming a protective film according to claim 1, wherein the glass transition temperature of the film for forming a protective film is 3°C or higher. The composite sheet for forming a protective film according to any one of claims 1 to 3, wherein the loss modulus of the film for forming a protective film at 23°C is 3 MPa or more. The composite sheet for forming a protective film according to any one of claims 1 to 4, wherein the content ratio of the filler (D) to the total mass of the film for forming a protective film is 50 mass% or more and 80 mass% or less .

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