WO2016027908A1

WO2016027908A1 - Surface protective film

Info

Publication number: WO2016027908A1
Application number: PCT/JP2015/075804
Authority: WO
Inventors: 克彦堀米; 雄一倉田; 知親富永
Original assignee: リンテック株式会社
Priority date: 2014-08-19
Filing date: 2015-09-11
Publication date: 2016-02-25
Also published as: WO2016027908A8

Abstract

This surface protective film is affixed to an optical member or an electronic member and is used to protect the surface of the optical member or the electronic member, wherein: the surface protective film is provided with a support body having a bending resistance of 5,000-45,000 mN·cm, and an adhesive layer on one surface of the support body; the support body has a buffer layer comprising one or more materials selected from buffer layer formation resin films and buffer layer formation compositions containing an energy-beam-polymerizable compound; and when the buffer layer is indented by the tip of a triangular-pyramid-shaped indenter having a tip curvature radius of 100 nm and an inter-ridge angle of 115° at a speed of 10 μm/min, the indentation depth (Z) required for the compression load to reach 2 mN is 2.5 μm or above.

Description

Surface protection film

The present invention relates to a surface protective film in which a pressure-sensitive adhesive is laminated on one surface of a support, and in particular, a surface that is applied to the surface of various optical members and electronic members and used to protect the surface. It relates to a protective film.

Conventionally, camera lens units, communication / sensor modules, motor units such as vibrators, imaging modules, etc., such as unitized optical and electronic components, prevent surface damage during processing, assembly, inspection, transportation, etc. In order to do this, a surface protective film may be stuck on the exposed surface. The surface protective film is peeled off from the optical member or the electronic member when the surface protection is no longer necessary.

Moreover, as a base material of such a surface protective film, for example, it is known to use a polyethylene terephthalate film from the viewpoint of obtaining transparency and a base material such as polyimide or polyethylene naphthalate from the viewpoint of heat resistance. (See Patent Document 1).

JP 2005-341520 A

In recent years, optical members and electronic members as described above have been reduced in size, and the size of the surface protection film has been reduced accordingly. Therefore, it has become difficult to process the surface protective film into an appropriate size using a punching blade. Therefore, the demand for improving the processing accuracy of the surface protective film is increasing.
Moreover, since attachment and peeling of a surface protective film are normally performed manually, it is calculated | required that workability | operativity of attachment and peeling is made favorable. Specifically, since the film is small in size, misalignment is likely to occur at the time of attachment, and the frequency of reattachment is increased. In order to reduce the frequency of re-sticking, improvement in the ease of sticking has been demanded. In addition, if the surface protective film is difficult to peel from the adherend, an excessive load is applied to the optical member or electronic member that is the adherend, and the delicate member is damaged (distortion, scratches, etc.). there is a possibility. Therefore, it is required to improve the peeling performance of the surface protective film.
However, for example, Patent Document 1 does not discuss workability such as punching process, pasting, and peeling of the surface protective film.

This invention is made | formed in view of the above problem, and the subject of this invention is the optical member or the electronic member excellent in the workability | operativity at the time of the processability at the time of sticking and peeling, and a surface protection film It is to provide a surface protective film.

As a result of intensive studies, the inventors of the present invention have a support body in which the surface protective film has a specific bending resistance, and the support body reaches a compression load of 2 mN when an indenter having a predetermined shape is pushed in. The present inventors have found that the above-mentioned problems can be solved by having a buffer layer having a pressing depth required to achieve a predetermined value or more, and the present invention has been completed.
That is, the present invention provides the following [1] to [12].
[1] A surface protective film that is applied to an optical member or an electronic member and used to protect the surface thereof,
Comprising a support having a bending resistance of 5000 mN · cm or more and 45000 mN · cm or less, and an adhesive layer on one surface of the support,
The support has a buffer layer composed of at least one selected from a buffer layer-forming composition containing an energy beam polymerizable compound and a buffer layer-forming resin film, and has a tip curvature radius of 100 nm and a ridge angle of 115 °. Surface protective film having a pressing depth (Z) of 2.5 μm or more required to reach a compression load of 2 mN when the tip of the triangular pyramid-shaped indenter is pressed into the buffer layer at a speed of 10 μm / min. .
[2] The surface protective film according to [1], wherein the support further has a base material.
[3] The surface protective film according to the above [2], wherein the support is a support further having a resin layer on a surface opposite to the surface on which the buffer layer of the substrate is provided.
[4] The surface protective film according to any one of [1] to [3], wherein the buffer layer is exposed on a surface opposite to the pressure-sensitive adhesive layer.
[5] The surface protective film according to any one of [2] to [4], wherein the substrate is a resin film made of polyethylene terephthalate.
[6] The composition for forming a buffer layer is a polymerizable compound having urethane (meth) acrylate (a1), an alicyclic group having 6 to 20 ring atoms or a heterocyclic group as the energy ray polymerizable compound ( The surface protective film according to any one of [1] to [5] above, comprising a2) and a polymerizable compound (a3) having a functional group.
[7] The surface protective film according to any one of [1] to [6], wherein the buffer layer forming resin film is a polyethylene film.
[8] The surface protective film according to any one of [1] to [7] above, wherein the buffer layer has a thickness of 5 to 100 μm.
[9] The surface protective film according to any one of [1] to [8], wherein the pressure-sensitive adhesive layer is made of an energy ray-curable pressure-sensitive adhesive composition.
[10] The pressure-sensitive adhesive layer comprises an energy ray-curable pressure-sensitive adhesive composition containing an acrylic copolymer,
The acrylic copolymer contains a monomer component containing at least 5 to 50% by mass of an alkyl (meth) acrylate having an alkyl group having 1 or 2 carbon atoms and not containing a carboxyl group-containing monomer or less than 5% by mass. The surface protective film according to any one of [1] to [9] above, which is a copolymer.
[11] A member with a surface protective film, comprising: an optical member or an electronic member; and the surface protective film according to any one of the above [1] to [10] attached to a surface of the optical member or the electronic member.
[12] A method of protecting the surface by applying the surface protective film according to any one of [1] to [10] to the surface of an optical member or an electronic member.

In the present invention, it is possible to provide a surface protective film for an optical member or an electronic member that is excellent in the processability of the surface protective film and the workability at the time of pasting and peeling.

In the description of the present specification, the “energy beam” means, for example, an ultraviolet ray or an electron beam, and an ultraviolet ray or an electron beam is preferable.
In the description of the present specification, the “weight average molecular weight (Mw)” is a value in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method, and specifically described in the examples. It is a value measured based on the method.
In addition, in the description in the present specification, for example, “(meth) acrylate” means both “acrylate” and “methacrylate”, and other similar terms are also the same.

[Surface protection film]
The surface protective film of the present invention is used for affixing to an optical member or an electronic member and protecting the surface thereof, and a support and a pressure-sensitive adhesive layer provided on one surface of the support. Is provided.
Hereinafter, each member of the surface protective film will be described.

<Support>
The support body which the surface protective film of this invention has is a support body which has a buffer layer, Comprising: The bending resistance is 5000 mN * cm or more and 45000 mN * cm or less.
When a support having a bending resistance of less than 5000 mN · cm is used, when the obtained surface protective film is applied to the surface of an optical member or an electronic member, the surface protective film is not strong enough to be applied to the target application position. It becomes difficult to work and the workability is inferior.
In addition, when using a support having a bending resistance exceeding 45000 mN · cm, when the surface protection film attached to the optical member or electronic member surface is peeled off from the surface of the member, the stiffness of the surface protection film is too strong. It becomes difficult to peel off and workability is inferior. Furthermore, when an unnecessary load is applied to the optical member or the electronic member when peeling off, the member may be damaged.
In particular, at the time of manual sticking and peeling work, the above-described work becomes even more difficult because a small-sized surface protective film is handled using a tool such as a finger or tweezers.
From such a viewpoint, the bending resistance of the support is preferably 5500 mN · cm or more, more preferably 6000 mN · cm or more, and preferably 42500 mN · cm or less, more preferably 40000 mN · cm or less. . The bending resistance is a value measured and calculated by a method according to JIS L 1913, specifically, a method described in the examples.
Further, the thickness of the support is not particularly limited as long as the bending resistance of the support is in the above range, but workability when the surface protective film of the present invention is attached to and peeled off from an optical member or an electronic member. From the viewpoint of improving the thickness, it is preferably 30 to 200 μm, more preferably 40 to 200 μm, still more preferably 50 to 150 μm.

(Buffer layer)
The buffer layer of the support has a compressive load of 2 mN when the tip of a triangular pyramid-shaped indenter having a tip radius of curvature of 100 nm and a ridge angle of 115 ° is pushed into the buffer layer at a speed of 10 μm / min. The indentation depth (Z) (hereinafter also simply referred to as “indentation depth (Z)”) required for the above is 2.5 μm or more.
The buffer layer is a layer composed of at least one selected from a buffer layer forming composition containing an energy ray polymerizable compound and a buffer layer forming resin film, and is a buffer layer forming composition containing an energy ray polymerizable compound. It is relatively easy to adjust the indentation depth (Z) of the buffer layer by selecting the composition or selecting the resin film for forming the buffer layer.
Moreover, since a buffer layer is easy to enlarge indentation depth, it is preferable that it is a layer which consists of 1 or more types chosen from the composition for buffer layer formation containing an energy-beam polymeric compound.

Further, the present inventors, in the configuration of the surface protection film, by providing a buffer layer adjusted so that the indentation depth (Z) is 2.5 μm or more at a position in contact with the punching blade during processing, It has been found that the punching accuracy of the surface protective film can be improved and the size of the surface protective film can be accurately controlled.
In the case of a surface protective film having a buffer layer whose indentation depth (Z) is less than 2.5 μm, the buffer layer becomes too hard, making it difficult for the punching blade to enter during the punching process, or protecting the surface against the punching blade. It is difficult to accurately control the size of the surface protective film after the punching process because the film becomes slippery.
On the other hand, in the case of a surface protective film having a buffer layer having an indentation depth (Z) of 30 μm or less, the buffer layer is not excessively soft, so that the buffer layer does not stick to the punching blade even during the punching process. Since the buffer layer is not deformed and the surface protective film is not displaced when the punching blade comes into contact, the size of the surface protective film after the punching process can be easily controlled accurately.
From such a viewpoint, the indentation depth (Z) is preferably 2.5 to 30.0 μm, more preferably 5.0 to 25.0 μm, still more preferably 8.0 to 20.0 μm, and still more. The thickness is preferably 12.0 to 20.0 μm.
In the present invention, the indentation depth (Z) means a value measured by the method described in Examples.
Further, the indentation depth (Z) appropriately changes the type and content of components contained in the composition for forming a buffer layer containing the energy beam polymerizable compound that forms the buffer layer, the degree of curing of the buffer layer, and the like. Thus, it is possible to adjust so as to belong to the above range. Moreover, it can also be adjusted to belong to the said range also by selecting suitably the raw material resin of the resin film for buffer layer formation which forms a buffer layer.
In the surface protective film of the present invention, the buffer layer is preferably exposed on the surface opposite to the adhesive layer described later.

The energy beam polymerizable compound contained in the buffer layer forming composition is not particularly limited as long as it is a compound capable of forming a buffer layer having an indentation depth (Z) in the above range. For example, photocurable Resin or monomer can be used.
However, from the viewpoint of adjusting the indentation depth (Z) to be in the above-mentioned range, the energy ray polymerizable compound is urethane (meth) acrylate (a1), an alicyclic group having 6 to 20 ring atoms or a heterocyclic group. A composition for forming a buffer layer comprising a polymerizable compound (a2) having a cyclic group and a polymerizable compound (a3) having a functional group is preferred.
Moreover, it is preferable that the composition for buffer layer formation contains a photoinitiator, and may contain another additive and a resin component in the range which does not impair the effect of this invention.
Hereinafter, each component contained in the composition for buffer layer formation containing an energy beam polymeric compound is demonstrated.

[Urethane (meth) acrylate (a1)]
The urethane (meth) acrylate (a1) used in the composition for forming a buffer layer containing an energy ray polymerizable compound is a compound having at least a (meth) acryloyl group and a urethane bond, and has a property of being polymerized and cured by irradiation with energy rays. It is what you have.
The urethane (meth) acrylate (a1) may be an oligomer, a high molecular weight product, or a mixture thereof, but a urethane (meth) acrylate oligomer is preferable.

The weight average molecular weight (Mw) of the component (a1) is preferably 1,000 to 100,000, more preferably 2,000 to 60,000, still more preferably 3,000 to 20,000.
Further, the number of (meth) acryloyl groups (hereinafter also referred to as “number of functional groups”) in the component (a1) may be monofunctional, bifunctional, or trifunctional or more, but is preferably monofunctional or bifunctional. .

The component (a1) can be obtained, for example, by reacting a (meth) acrylate having a hydroxyl group with a terminal isocyanate urethane prepolymer obtained by reacting a polyol compound and a polyvalent isocyanate compound.
In addition, you may use a component (a1) individually or in combination of 2 or more types.

The polyol compound used as a raw material for the component (a1) is not particularly limited as long as it is a compound having two or more hydroxy groups.
Specific examples of the polyol compound include alkylene diol, polyether type polyol, polyester type polyol, and polycarbonate type polyol.
Among these, a polyester type polyol is preferable.
The polyol compound may be a bifunctional diol, a trifunctional triol, or a tetrafunctional or higher polyol, but is preferably a bifunctional diol, and more preferably a polyester type diol.

Examples of the polyvalent isocyanate compound include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; isophorone diisocyanate, norbornane diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, dicyclohexylmethane-2 , 4'-diisocyanate, ω, ω'-diisocyanate dimethylcyclohexane, etc .; 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tolidine diisocyanate, tetramethylene xylylene diisocyanate, naphthalene- And aromatic diisocyanates such as 1,5-diisocyanate.
Among these, isophorone diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate are preferable.

Urethane (meth) acrylate (a1) can be obtained by reacting the terminal isocyanate urethane prepolymer obtained by reacting the above-described polyol compound with the polyvalent isocyanate compound with (meth) acrylate having a hydroxy group.
The (meth) acrylate having a hydroxy group is not particularly limited as long as it is a compound having a hydroxy group and a (meth) acryloyl group in at least one molecule.

Specific examples of the (meth) acrylate having a hydroxy group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 4-hydroxycyclohexyl (meth). Acrylate, 5-hydroxycyclooctyl (meth) acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, pentaerythritol tri (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, etc. Hydroxy-alkyl (meth) acrylates; hydroxy-group-containing (meth) acrylamides such as N-methylol (meth) acrylamide; vinyl alcohol, vinyl phenol, bisphenol The reaction product obtained by the diglycidyl ester of Nord A (meth) acrylic acid is reacted, and the like.
Among these, hydroxyalkyl (meth) acrylate is preferable, and 2-hydroxyethyl (meth) acrylate is more preferable.

The conditions for reacting the terminal isocyanate urethane prepolymer and the (meth) acrylate having a hydroxy group are preferably the conditions of reacting at 60 to 100 ° C. for 1 to 4 hours in the presence of a solvent and a catalyst added as necessary. .

The content of the component (a1) in the composition for forming a buffer layer containing the energy beam polymerizable compound is such that the indentation depth (Z) forms a buffer layer having the above-mentioned range. Is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, still more preferably 25 to 55% by mass, and still more preferably 30 to 50% by mass with respect to the total amount (100% by mass).

[Polymerizable compound (a2) having an alicyclic group or heterocyclic group having 6 to 20 ring atoms]
The component (a2) used in the composition for forming a buffer layer containing an energy beam polymerizable compound is a polymerizable compound having an alicyclic group or heterocyclic group having 6 to 20 ring-forming atoms, and at least one (meth) A compound having an acryloyl group is preferred. By using this component (a2), the film formability of the obtained composition for forming a buffer layer can be improved.

The number of ring-forming atoms of the alicyclic group or heterocyclic group contained in the component (a2) is preferably 6 to 20, more preferably 6 to 18, still more preferably 6 to 16, and still more preferably 7 to 12. It is.
Examples of the atoms forming the ring structure of the heterocyclic group include a carbon atom, a nitrogen atom, an oxygen atom, and a sulfur atom.
In the present invention, the number of ring-forming atoms means the number of atoms constituting the ring itself of a compound having a structure in which atoms are bonded in a ring, and is not bonded to an atom (for example, bonded to an atom constituting the ring). Hydrogen atoms) and atoms included in a substituent when the ring is substituted by a substituent are not included in the number of ring-forming atoms.

Specific components (a2) include, for example, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxy (meth) acrylate, cyclohexyl (meth) acrylate, And alicyclic group-containing (meth) acrylates such as adamantane (meth) acrylate; heterocyclic group-containing (meth) acrylates such as tetrahydrofurfuryl (meth) acrylate and morpholine (meth) acrylate;
In addition, you may use a component (a2) individually or in combination of 2 or more types.
Among these, alicyclic group-containing (meth) acrylate is preferable, and isobornyl (meth) acrylate is more preferable.

The content of the component (a2) in the buffer layer forming composition containing the energy beam polymerizable compound is such that the indentation depth (Z) forms a buffer layer having the above-mentioned range, and the obtained buffer layer forming From the viewpoint of improving the film formability of the composition, it is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and still more preferably 25% with respect to the total amount (100% by mass) of the buffer layer forming composition. It is ˜55 mass%, more preferably 30-50 mass%.

[Polymerizable compound having functional group (a3)]
The component (a3) used in the buffer layer-forming composition containing the energy beam polymerizable compound is a polymerizable compound containing a functional group such as a hydroxyl group, an epoxy group, an amide group, or an amino group, and at least one (meth) A compound having an acryloyl group is preferred.
Component (a3) has good compatibility with component (a1), the viscosity of the composition for forming a buffer layer is adjusted to an appropriate range, and the elastic modulus of the buffer layer formed from the composition is also appropriate. It can be a range. Therefore, by using this component (a3), it is possible to form a buffer layer having an indentation depth (Z) in the above range.
Examples of the component (a3) include a hydroxyl group-containing (meth) acrylate, an epoxy group-containing (meth) acrylate, an amide group-containing compound, and an amino group-containing (meth) acrylate.

Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxy Examples include butyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and phenylhydroxypropyl (meth) acrylate.
Examples of the epoxy group-containing (meth) acrylate include glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, and allyl glycidyl ether.
Examples of amide group-containing compounds include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N -Methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide and the like.
Examples of amino group-containing (meth) acrylates include primary amino group-containing (meth) acrylates, secondary amino group-containing (meth) acrylates, and tertiary amino group-containing (meth) acrylates.
Examples of other polymerizable compounds having a functional group include vinyl compounds such as hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylformamide, N-vinylpyrrolidone, and N-vinylcaprolactam.
In addition, you may use a component (a3) individually or in combination of 2 or more types.

Among these, from the viewpoint of forming a buffer layer having an indentation depth (Z) in the above range, a hydroxyl group-containing (meth) acrylate is preferable, and a hydroxyl group-containing (meta) having an aromatic ring such as phenylhydroxypropyl (meth) acrylate is preferred. ) Acrylate is more preferred.

The content of the component (a3) in the buffer layer forming composition containing the energy beam polymerizable compound is such that the indentation depth (Z) forms a buffer layer in the above range, and the obtained buffer layer forming From the viewpoint of improving the film formability of the composition, it is preferably 5 to 40% by mass, more preferably 7 to 35% by mass, and still more preferably 10% with respect to the total amount (100% by mass) of the buffer layer forming composition. To 30% by mass, and more preferably 13 to 25% by mass.

The content ratio [(a2) / (a3)] (mass ratio) of (a2) and component (a3) contained in the components in the buffer layer forming composition is preferably 0.5 to 3 0.0, more preferably 1.0 to 3.0, still more preferably 1.3 to 3.0, and still more preferably 1.5 to 2.8.
If the said content ratio is 0.5 or more, the film-forming property of the composition for buffer layer formation obtained can be made favorable. On the other hand, if the content ratio is 3.0 or less, a buffer layer having an indentation depth (Z) in the above range can be formed.

[Polymerizable compounds other than components (a1) to (a3)]
The composition for forming a buffer layer containing the energy beam polymerizable compound may contain other polymerizable compounds other than the components (a1) to (a3) as long as the effects of the present invention are not impaired.
Examples of other polymerizable compounds include alkyl (meth) acrylates having an alkyl group having 1 to 20 carbon atoms; vinyl compounds such as styrene: and the like.
In addition, you may use these other polymeric compounds individually or in combination of 2 or more types.

The content of the other polymerizable compound in the composition for forming a buffer layer containing the energy beam polymerizable compound is preferably 0 to 20% by mass, more preferably 0 to 10% by mass, and still more preferably 0 to 5% by mass. More preferably, it is 0 to 2% by mass.

(Photopolymerization initiator)
When forming the buffer layer, the composition for forming the buffer layer containing the energy ray polymerizable compound may further contain a photopolymerization initiator from the viewpoint of shortening the polymerization time by light irradiation and reducing the light irradiation amount. preferable.
Examples of the photopolymerization initiator include photopolymerization initiators such as benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, and peroxide compounds, and photosensitizers such as amines and quinones. More specifically, for example, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, etc. Can be mentioned.
These photopolymerization initiators can be used alone or in combination of two or more.

The content of the photopolymerization initiator in the composition for forming a buffer layer containing the energy beam polymerizable compound is preferably 0.05 to 15 parts by mass with respect to 100 parts by mass of the total amount of the energy beam polymerizable compound. The amount is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass.

[Other additives and resin components]
Moreover, the composition for buffer layer formation containing the said energy ray polymeric compound may contain another additive and a resin component in the range which does not impair the effect of this invention.
Examples of other additives include antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, antistatic agents, flame retardants, and dyes.
When these additives are blended, the content of each additive in the composition for forming a buffer layer is preferably 0.01 to 6 parts by mass with respect to 100 parts by mass of the total amount of the energy beam polymerizable compound, More preferably, it is 0.1 to 3 parts by mass.

(Resin film for buffer layer formation)
The buffer layer forming resin film (hereinafter also referred to as “buffer layer resin film”) is not particularly limited as long as it is a resin film capable of forming a buffer layer having an indentation depth (Z) in the above range. Absent. For example, when the surface protective film after processing is peeled off using an adhesive tape or a heat seal material, a polyethylene film is used from the viewpoint of improving the adhesive force with the adhesive tape or the heat seal material. Is preferred. Examples of the polyethylene resin that is a raw material for the polyethylene film include high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE).

The thickness of the buffer layer is not particularly limited as long as the bending resistance of the support is within the above range, but the workability when attaching and peeling the surface protective film of the present invention to an optical member or an electronic member is good. In view of the above, it is preferably 5 to 100 μm, more preferably 10 to 80 μm, and still more preferably 15 to 50 μm.

(Base material)
The support preferably further has a substrate. When a base material is provided, the buffer layer is provided on one surface of the base material.
The substrate is not particularly limited as long as the bending resistance of the support is in the above range, but a resin film (hereinafter also referred to as “resin film for substrate”) is preferable from the viewpoint of water resistance and heat resistance. .
Examples of the resin constituting the resin film for a substrate include polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, wholly aromatic polyester, polyamide, polyimide, polyacetal, polycarbonate, modified polyphenylene oxide, polyphenylene sulfide, and polysulfone. , Polyether ketone, biaxially oriented polypropylene and the like.
Among these resins, one or more selected from polyester, polyamide, polyimide, and biaxially stretched polypropylene are preferable, polyester is more preferable, and polyethylene terephthalate is still more preferable.
Further, the substrate may be a single layer film made of one or more or two or more resins selected from the above resins, or may be a film in which two or more of these resin films are laminated.

Further, the base material used in the present invention may contain a filler, a colorant, an antistatic agent, an antioxidant, an organic lubricant, a catalyst, and the like as long as the effects of the present invention are not impaired.
Further, the substrate may be transparent or opaque, and may be colored as desired. For example, when the buffer layer or the pressure-sensitive adhesive layer described later contains an energy beam polymerizable compound, the buffer layer or the pressure-sensitive adhesive layer needs to have transparency to the wavelength of the energy beam used for curing the energy beam polymerizable compound. is there. That is, when ultraviolet rays are used as the energy rays, a light transmissive film is used as the substrate. Moreover, when using an electron beam as an energy beam, the base material does not need to be light-transmitting, and a colored film may be used.
In addition, in order to improve the adhesion with the buffer layer and / or the pressure-sensitive adhesive layer, at least one surface of the base material used in the present invention may be subjected to an adhesion treatment such as a corona treatment, which will be described later. A layer may be provided.
The thickness of the substrate is not particularly limited as long as the bending resistance of the support is in the above range, but is adjusted according to the performance required for the surface protective film, and is preferably 10 to 300 μm. Particularly preferred is 30 to 150 μm.

(Resin layer)
The support may further have a resin layer on the surface opposite to the surface on which the buffer layer of the substrate is provided.
The resin layer is not particularly limited as long as the bending resistance of the support is in the above range. For example, the same resin film as the buffer layer resin film described above can be used. From the viewpoint of improving the adhesion with the pressure-sensitive adhesive layer described later, a polyethylene film is preferable. For example, high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or the like can be used as the resin that is a raw material for the polyethylene film.
The thickness of the resin layer is not particularly limited as long as the bending resistance of the support is within the above range, but the workability when the surface protective film of the present invention is attached to and peeled from an optical member or an electronic member is good. In view of the above, it is preferably 5 to 100 μm, more preferably 10 to 80 μm, and still more preferably 15 to 50 μm.

<Adhesive layer>
Although it does not specifically limit as an adhesive which forms the adhesive layer which the surface protection film of this invention has, For example, an acrylic adhesive, a urethane adhesive, a silicone adhesive, a rubber adhesive, a polyester adhesive Is mentioned.
These pressure-sensitive adhesives may be used alone or in combination of two or more.

In the said adhesive, it is preferable that it is an acrylic adhesive. Moreover, when it is the said acrylic adhesive, it is generally an acrylic adhesive (henceforth an acrylic adhesive composition) containing an acrylic copolymer (A).
The acrylic copolymer (A) usually constitutes a pressure-sensitive adhesive component in the pressure-sensitive adhesive layer, and is hereinafter also referred to as a main polymer.
In the following description, an example in the case of an acrylic pressure-sensitive adhesive will be mainly described, but the same applies to other types of pressure-sensitive adhesives. In this case, the main polymer constituting the pressure-sensitive adhesive component is acrylic. A polymer other than the polymer (A) is used.
The acrylic copolymer (A) is obtained by copolymerizing a monomer component (hereinafter also referred to as “copolymer component”) containing an alkyl (meth) acrylate as a main monomer. Examples of the alkyl (meth) acrylate include those having 1 to 18 carbon atoms in the alkyl group, such as methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, and butyl. (Meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate Etc.
The acrylic copolymer (A) contains an alkyl (meth) acrylate as a copolymer component, preferably 50% by mass or more, more preferably 50 to 99.5% by mass, based on the total amount of the copolymer component. .

The acrylic copolymer (A) contains, as a copolymer component, an alkyl (meth) acrylate having an alkyl group having 1 or 2 carbon atoms out of the alkyl (meth) acrylate, based on the total amount of the copolymer component. The content is preferably 5 to 50% by mass. When the content is 5% by mass or more, the adhesive strength, particularly when the acrylic adhesive is an energy ray curable adhesive, the adhesive strength after irradiation with energy rays becomes too high, and the peeling performance is deteriorated. Can be suppressed. Further, the initial adhesive strength does not become too high, and sufficient reworkability can be obtained. If the content is 50% by mass or less, the adhesive strength is insufficient, and the surface protection film may be unexpectedly peeled off from the electronic member and the optical member during each step to be described later, thereby sufficiently protecting the electronic member and the optical member. It can be prevented from becoming impossible.
From the above viewpoints, the acrylic copolymer (A) contains, as a copolymer component, an alkyl (meth) acrylate having an alkyl group having 1 or 2 carbon atoms in an amount of 10 to More preferably, it is contained in an amount of 40% by mass, more preferably 15-35% by mass.
Examples of the alkyl (meth) acrylate having 1 or 2 carbon atoms in the alkyl group include methyl (meth) acrylate and ethyl (meth) acrylate. Among these, methyl acrylate and methyl methacrylate are preferable.

In addition, the acrylic copolymer (A) contains, as a copolymer component, an alkyl (meth) acrylate having an alkyl group with 3 or more carbon atoms in the alkyl (meth) acrylate, based on the total amount of the copolymer component. The content is preferably 30 to 85% by mass. By making content of the alkyl (meth) acrylate whose carbon number of an alkyl group is 3 or more into such a range, it becomes easy to provide suitable adhesive performance and peeling performance to a surface protection film. From such a viewpoint, the content of the alkyl (meth) acrylate having 3 or more carbon atoms in the alkyl group is more preferably 40 to 80% by mass, and further preferably 45 to 75% by mass.

The alkyl (meth) acrylate having 3 or more carbon atoms in the alkyl group is preferably an alkyl (meth) acrylate in which the alkyl group has 3 to 8 carbon atoms, and the alkyl group has 4 to 8 carbon atoms. Alkyl (meth) acrylates are more preferred, and alkyl acrylates having an alkyl group with 4 to 8 carbon atoms are more preferred. Specifically, n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, and the like are preferable.

The acrylic copolymer (A) preferably contains a polymerizable monomer other than alkyl (meth) acrylate as the copolymer component, and specifically contains a functional group-containing monomer. The functional group-containing monomer provides a functional group necessary for bonding an unsaturated group-containing compound, which will be described later, to the acrylic copolymer (A) and for reaction with a crosslinking agent, which will be described later. The functional group-containing monomer is a monomer having a polymerizable double bond and a functional group such as a hydroxyl group, a carboxyl group, an amino group, a substituted amino group, and an epoxy group in the molecule.

Here, the acrylic copolymer (A) does not contain a carboxyl group-containing monomer as a copolymer component, or even if it contains a carboxyl group-containing monomer, the content thereof is the total amount of the copolymer component. It is preferable that the amount is less than 5% by mass. By not containing a carboxyl group-containing monomer or reducing the content, the pressure-sensitive adhesive layer can suppress an excessive increase in the adhesive strength after irradiation with energy rays and can improve the peelability of the surface protective film. In addition, an excessive increase in initial adhesive force can be suppressed, and reworkability can be improved.
From these viewpoints, the content of the carboxyl group-containing monomer in the copolymer component is preferably less than 3% by mass, more preferably less than 1% by mass, and further, no carboxyl group-containing monomer is contained as a copolymer component. Most preferred. Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, itaconic acid and the like.

As the functional group-containing monomer, a hydroxyl group-containing compound is preferably used, and more preferably, a hydroxyl group-containing (meth) acrylate is used. The acrylic copolymer (A) is preferably obtained by copolymerizing a copolymer component containing 0.2 to 40% by mass of hydroxyl group-containing (meth) acrylate with respect to the total amount of the copolymer component. . When the content of the hydroxyl group-containing (meth) acrylate is within the above range, the acrylic copolymer (A) can be appropriately crosslinked with a crosslinking agent described later.
The content of the hydroxyl group-containing (meth) acrylate is more preferably 0.3 to 30% by mass, and further preferably 0.5 to 30% by mass. When the hydroxyl group-containing (meth) acrylate is 1 to 30% by mass, an unsaturated group-containing compound to be described later can be appropriately introduced into the side chain while ensuring appropriate adhesive performance. It becomes possible to appropriately crosslink the polymer (A).
Specific examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and the like. Can be mentioned.
The above functional group-containing monomers may be used alone or in combination of two or more.

In addition to the above monomers, the acrylic copolymer (A) includes (meth) acrylic acid esters, dialkyl (meth) acrylamides, vinyl formate, vinyl acetate, styrene other than alkyl (meth) acrylate and functional group-containing monomers. , Vinyl acetate or the like may be included as a copolymer component. As (meth) acrylic acid esters other than (meth) acrylic acid alkyl esters and functional group-containing monomers, (meth) acrylic acid alkoxyalkyl esters, (meth) acrylic acid alkyleneoxyalkyl esters, (meth) acrylic acid nonylphenoxy polyethylene Glycol, tetrahydrofuran furfuryl acrylate, diacrylates which are esters of polyether and acrylic acid, and the like may also be used.
As the dialkyl (meth) acrylamide, dimethyl (meth) acrylamide, diethyl (meth) acrylamide and the like are used. Dialkyl (meth) acrylamide is preferably used, for example, when the pressure-sensitive adhesive composition is an energy ray-curable pressure-sensitive adhesive composition and is an XY type described later. By using dialkyl (meth) acrylamide as a constituent monomer, the compatibility of the energy beam curable acrylic copolymer with the energy beam polymerizable compound (B) such as a highly polar urethane acrylate is improved.
The weight average molecular weight of the acrylic copolymer is preferably 100,000 or more, more preferably 100,000 to 1,500,000, and further preferably 150,000 to 1,000,000. The weight average molecular weight of the acrylic polymer here refers to the reaction of the unsaturated group-containing compound when an unsaturated group-containing compound described later is reacted to form an energy ray-curable acrylic polymer. It means the previous acrylic copolymer.

The pressure-sensitive adhesive composition used for the pressure-sensitive adhesive layer may be a non-energy ray-curable pressure-sensitive adhesive composition or an energy-ray-curable pressure-sensitive adhesive composition, An agent composition is preferred.
The energy ray-curable pressure-sensitive adhesive composition is not particularly limited as long as it has energy ray curability, but an X-type one is used as a preferred embodiment. The X-type energy ray-curable pressure-sensitive adhesive composition is one in which the main polymer itself constituting the pressure-sensitive adhesive component of the pressure-sensitive adhesive has energy beam curability. For example, in the case of an acrylic pressure-sensitive adhesive composition, at least a part of the acrylic copolymer obtained by copolymerizing the above-described copolymer component is replaced with an energy ray curable acrylic copolymer having an unsaturated group in the side chain. It is a polymer.
The energy ray curable acrylic copolymer is obtained by reacting the above-mentioned acrylic copolymer with an unsaturated group-containing compound.

The unsaturated group-containing compound has a substituent capable of reacting with a functional group of the functional group-containing monomer constituting the acrylic copolymer (A). This substituent varies depending on the type of functional group possessed by the functional group monomer. For example, when the functional group is a hydroxyl group or a carboxyl group, the substituent is preferably an isocyanate group or an epoxy group. When the functional group is a carboxyl group, the substituent is preferably an isocyanate group or an epoxy group, and the functional group is In the case of an amino group or a substituted amino group, an isocyanate group or the like is preferable as the substituent. When the functional group is an epoxy group, a carboxyl group is preferable as the substituent, and among these, an isocyanate group is preferable. One such substituent is contained in each molecule of the unsaturated group-containing compound.

The unsaturated group-containing compound contains 1 to 5, preferably 1 to 2, energy beam polymerizable carbon-carbon double bonds per molecule. The energy beam polymerizable carbon-carbon double bond is preferably a (meth) acryloyl group. Specific examples of such unsaturated group-containing compounds include (meth) acryloyloxyethyl isocyanate, meta-isopropenyl-α, α-dimethylbenzyl isocyanate, (meth) acryloyl isocyanate, allyl isocyanate, glycidyl (meth) acrylate, Examples include (meth) acrylic acid. Also, an acryloyl monoisocyanate compound obtained by reaction of a diisocyanate compound or polyisocyanate compound with hydroxyethyl (meth) acrylate; obtained by reaction of a diisocyanate compound or polyisocyanate compound, a polyol compound and hydroxyethyl (meth) acrylate. And acryloyl monoisocyanate compounds.

As the unsaturated group-containing compound, a polymerizable group-containing polyalkyleneoxy compound represented by the following formula (1) can also be used.

In the formula, R ¹ is hydrogen or a methyl group, preferably a methyl group, R ² to R ⁵ are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms, preferably hydrogen, and n is 2 It is an integer above, preferably 2-4. A plurality of R ² to R ⁵ may be the same as or different from each other. That is, since n is 2 or more, the polymerizable group-containing polyalkyleneoxy group represented by the formula (1) contains 2 or more R ² . In this case, two or more R ^{2 s} may be the same or different. The same applies to R ³ to R ⁵ . NCO represents an isocyanate group.

The unsaturated group-containing compound is usually about 10 to 100 equivalents with respect to 100 equivalents of the functional group of the acrylic copolymer (A). Since it can be used, it is preferably used in a proportion of about 15 to 95 equivalents, more preferably about 20 to 90 equivalents.
As the unsaturated group-containing compound, a compound having a (meth) acryloyl group and an isocyanate group is preferably used, and specifically, (meth) acryloyloxyethyl isocyanate is preferable.

As the energy beam curable pressure-sensitive adhesive composition, a Y-type energy beam curable pressure-sensitive adhesive composition is used as another preferred embodiment. The Y-type energy ray-curable pressure-sensitive adhesive composition contains an energy ray-polymerizable compound (B) separately from the main polymer constituting the pressure-sensitive adhesive component of the pressure-sensitive adhesive such as the acrylic copolymer (A). The energy beam curability is imparted.

As the energy ray polymerizable compound (B), energy ray polymerizable oligomers such as epoxy acrylate, urethane acrylate, polyester acrylate, and polyether acrylate, and energy ray polymerizable monomers are used.
As the energy ray polymerizable monomer, a low molecular weight compound having two or more functional groups having at least two photopolymerizable carbon-carbon double bonds in the molecule is used. Specifically, trimethylolpropane tri (meth) is used. Acrylate, tetramethylolmethane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, dipentaerythritol hexa (meth) acrylate or 1,4 -Butylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate and the like are used.

Among these, urethane acrylate oligomers are preferably used. The urethane acrylate oligomer is a compound including an isocyanate unit and a polyol unit and having a (meth) acryloyl group at the terminal. As urethane acrylate oligomers, terminal isocyanate urethane oligomers are produced by reaction of polyols having hydroxyl groups at the ends, such as polyether-type polyols and polyester-type polyols, with polyisocyanates. ) And the like obtained by reacting a compound having an acryloyl group. Such urethane acrylate oligomers have energy ray curability due to the action of the (meth) acryloyl group.

Examples of the polyisocyanate used in the urethane acrylate oligomer include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, and 1,4-xylylene diisocyanate. Diphenylmethane 4,4-diisocyanate, isophorone diisocyanate, 1,3-bis- (isocyanatomethyl) -cyclohexane, 4,4′-dicyclohexylmethane diisocyanate, and the like. Examples of the compound having a (meth) acryloyl group include (meth) acrylates having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and polyethylene glycol (meth) acrylate. Examples of the (meth) acrylate having a hydroxyl group include polyhydric alcohols such as pentaerythritol and partial esters of (meth) acrylic acid.

The urethane acrylate oligomer is preferably a bifunctional or higher functional group having two or more (meth) acryloyl groups in one molecule, but if not used in combination with the X type, a trifunctional or higher functional group is preferred. More than the group is more preferable. By using one having three or more functional groups, it is easy to lower the adhesive strength after irradiation with energy rays, and the peel performance of the surface protective film tends to be good. The urethane acrylate oligomer usually has 12 functional groups or less.
The urethane acrylate oligomer preferably has a weight average molecular weight of 1000 to 15000, more preferably 1500 to 8500.
The energy beam polymerizable compound (B) is usually blended in an amount of 5 to 200 parts by mass with respect to 100 parts by mass of the acrylic copolymer (A) (main polymer). Is preferably 200 parts by mass, more preferably 70 to 150 parts by mass. By keeping the content of the energy beam polymerizable compound (B) in the above range, the adhesive strength of the pressure-sensitive adhesive layer before energy ray irradiation is appropriately maintained, and the adhesive strength is appropriately reduced by curing with energy rays. Can do.

The energy ray-curable pressure-sensitive adhesive composition may be a composition using both X-type and Y-type (hereinafter referred to as XY type). That is, the acrylic pressure-sensitive adhesive contains the energy beam polymerizable compound (B) in addition to the acrylic polymer (A), and at least a part of the acrylic copolymer (A) is not present in the side chain. What is an energy ray curable acrylic copolymer having a saturated group can also be used as a preferred embodiment. By using the XY type, the breaking strength and breaking elongation of the pressure-sensitive adhesive layer are improved, and the adhesive residue on the adherend when the surface protective film is peeled is easily reduced.
For example, the energy ray curable acrylic copolymer used for the XY type is the same as that used for the X type.

Also, the energy ray polymerizable compound (B) used in the XY type is the same as that used in the Y type described above, and is preferably a urethane acrylate oligomer. It is more preferable to use isophorone diisocyanate, 1,3-bis- (isocyanatomethyl) -cyclohexane, 4,4′-dicyclohexylmethane diisocyanate, etc. Moreover, as a polyol which forms the polyol unit in urethane acrylate, it is preferable to use polypropylene glycol (PPG), polyethylene glycol (PEG), polytetramethylene glycol, polycarbonate diol, etc., and the number average molecular weight of these polyols Is preferably 300 to 2000, particularly preferably 500 to 1000.
Further, the polyol preferably contains two or more kinds of polyols in order to improve the breaking stress and breaking elongation of the pressure-sensitive adhesive layer, and the polyol contains PPG and PEG. It is particularly preferred that it consists only of PPG and PEG. The molar ratio of PPG to PEG is preferably 9: 1 to 1: 9, more preferably 9: 1 to 1: 4, and further preferably 4: 1 to 3: 2. Most preferably, the ratio is from 5: 2.5 to 6.5: 3.5.
Further, the urethane acrylate oligomer in the XY type is preferably a bifunctional group having two (meth) acryloyl groups in one molecule. By using a bifunctional group, it becomes easy to increase the breaking strength and breaking elongation while improving the peeling performance and the adhesiveness.
In the XY type, the energy ray polymerizable compound (B) is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer (A) (main polymer). More preferably, it is part by mass.

The pressure-sensitive adhesive layer may have a crosslinked structure in which a main polymer such as an acrylic copolymer (A) is crosslinked. Examples of the crosslinking agent (C) contained in the pressure-sensitive adhesive composition for crosslinking include organic polyvalent isocyanate compounds, organic polyvalent epoxy compounds, and organic polyvalent imine compounds. Among these, organic polyvalent isocyanate compounds are exemplified. Isocyanate compounds (isocyanate-based crosslinking agents) are preferred.

Examples of organic polyvalent isocyanate compounds include aromatic polyvalent isocyanate compounds, aliphatic polyvalent isocyanate compounds, alicyclic polyvalent isocyanate compounds, trimers of these organic polyvalent isocyanate compounds, and these organic polyvalent isocyanate compounds. Examples thereof include terminal isocyanate urethane prepolymers obtained by reacting with a polyol compound.

Specific examples of the organic polyvalent isocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4. '-Diisocyanate, diphenylmethane-2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, tolylene diisocyanate Examples include adducts of trimethylolpropane.

Specific examples of the organic polyvalent epoxy compound include 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, Examples include ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, and diglycidyl amine.

Specific examples of the organic polyvalent imine compound include N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, tetra Mention may be made of methylolmethane-tri-β-aziridinylpropionate and N, N′-toluene-2,4-bis (1-aziridinecarboxyamide) triethylenemelamine.

The content of the crosslinking agent (C) is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, with respect to 100 parts by mass of the acrylic copolymer (A) (main polymer). Particularly preferably, it is used in a ratio of 0.5 to 8 parts by mass. When the content of the crosslinking agent (C) is not more than the above upper limit, the pressure-sensitive adhesive layer is prevented from being excessively crosslinked, and appropriate adhesive force is easily obtained. Moreover, by making the usage-amount of a crosslinking agent more than the said lower limit, it is prevented that an adhesive adheres to an electronic member or an optical member.

Moreover, it is preferable that an energy-beam curable adhesive composition contains a photoinitiator (D).
Examples of photopolymerization initiators include photoinitiators such as benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, and peroxide compounds, and photosensitizers such as amines and quinones. 1-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyldiphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloranthraquinone Examples include 2,4,6-trimethylbenzoyldiphenylphosphine oxide. By mix | blending a photoinitiator (D), the irradiation time and irradiation amount of the energy beam for hardening can be decreased.
The content of the photopolymerization initiator (D) is not particularly limited, but is preferably 0.1 to 10 parts by mass, more preferably 1 with respect to 100 parts by mass of the acrylic copolymer (A) (main polymer). Is 5 parts by mass.

Further, the pressure-sensitive adhesive layer may be colored so that the light transmittance of the surface protective film is less than 50%. Since the visibility of the surface protective film is improved by coloring the pressure-sensitive adhesive layer, for example, the surface protective film is easily peeled from a release sheet described later by hand. The light transmittance of the surface protective film is measured with a spectrophotometer UV-3600 manufactured by Shimadzu Corporation at a wavelength of 600 nm. The light transmittance is preferably about 10 to 40%.
In order to color the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition usually contains a dye and a pigment, and among them, a blue dye and a blue pigment are preferably contained.

In addition, the above-mentioned pressure-sensitive adhesives include antioxidants, softeners (plasticizers), deterioration inhibitors, antistatic agents, flame retardants, rust inhibitors, fillers, silicone compounds, silane coupling agents, chain transfer agents, and the like. Components other than the above components may be contained as appropriate.

When the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer made of an energy ray-curable pressure-sensitive adhesive composition, the surface protective film preferably has a pressure-sensitive adhesive force before irradiation with energy rays of 1000 to 20000 mN / 25 mm. More preferably, it is 16000 mN / 25 m. When the adhesive strength before energy beam irradiation is 1000 mN / 25 m or more, the adhesive strength of the surface protective film to the optical member and the electronic member is increased, and the protective performance is improved. Moreover, it becomes easy to make the adhesive force after energy ray irradiation a desired magnitude | size by setting it as 20000 mN / 25mm or less. The adhesive strength before energy beam irradiation can be adjusted by the type and blending ratio of alkyl (meth) acrylate, the amount of crosslinking agent used, and the like.

The surface protective film preferably has an adhesive strength of 0.1 to 100 mN / 25 mm, more preferably 20 to 90 mN / 25 mm after energy beam irradiation. When the adhesive force after energy beam irradiation falls within such a range, the surface protective film can be easily peeled off from the optical member or the electronic member after energy beam irradiation.
The adhesive strength after energy beam irradiation can be controlled by the type and amount of the energy beam polymerizable compound (B) and the amount of unsaturated groups introduced into the acrylic copolymer.

Moreover, it is preferable that the initial stage adhesive force before energy beam irradiation of an adhesive layer is less than 10000 mN / 25mm. By setting the initial adhesive force to such a relatively low value, it becomes easy to re-attach the surface protective film, and the reworkability is improved. The lower limit value of the initial adhesive strength is not particularly limited, but is usually 500 mN / 25 mm or more. The initial adhesive strength is more preferably 3000 to 9500 mN / 25 mm.
The initial adhesive strength can be adjusted by the kind and blending ratio of the alkyl (meth) acrylate, the kind and blending ratio of the functional group-containing monomer, the amount of the crosslinking agent used, and the like.
Moreover, the measuring method of the above-mentioned adhesive force and initial stage adhesive force is the value measured based on the method described below.

〔Adhesive force〕
The surface protective film is cut to a width of 25 mm to form a sample, and is attached to the mirror surface of the silicon wafer as an adherend with a 2 kg roller in an environment of 23 ° C. and 50% relative humidity. After standing for 20 minutes in an environment of 23 ° C. and 50% relative humidity, the adhesive strength when peeled at 180 ° at a tensile speed of 300 mm / min is measured to obtain the adhesive strength before energy beam irradiation.
In addition, the sample attached to the silicon wafer after standing for 20 minutes is irradiated with ultraviolet rays in a nitrogen atmosphere (illuminance: 230 mW / cm ² , using a RAD-2000m / 12 manufactured by Lintec Corporation). Light quantity 190 mJ / cm ² ). Thereafter, the adhesive force when peeled at 180 ° in a tensile rate of 300 mm / min in an environment of 23 ° C. and 50% relative humidity is measured and set as the adhesive strength after irradiation with energy rays.
[Initial adhesive strength]
The surface protective film is cut into a width of 25 mm to obtain a sample, and is attached to a silicon wafer as an adherend with a 2 kg roller in an environment of 23 ° C. and 50% relative humidity. Immediately after the application (within 1 minute), the adhesive strength when peeled at 180 ° in a tensile rate of 300 mm / min in an environment of 23 ° C. and 50% relative humidity is measured, and the adhesive strength is taken as the initial adhesive strength.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is preferably 3 to 50 μm, more preferably 5 to 30 μm. It becomes easy to improve the adhesiveness with respect to a to-be-adhered body because the thickness of an adhesive layer exists in the said range.

Moreover, a surface protection film may provide an adhesive layer partially on a support body, and may form a non-adhesion part with an adhesion part on a support body. In order to create a surface protective film partially provided with an adhesive layer, screen printing or inkjet printing may be performed. The adhesive portion and the non-adhesive portion may be arranged in any pattern selected from a stripe shape, a lattice shape, a dot shape, a shape in which a plurality of wavy lines are arranged, a checkered pattern, and a shape in which various patterns are arranged in a plurality. Other shapes may be preferable.
In addition, when an adhesive layer is partially provided in pattern shape, the pattern is normally provided in the whole surface of a support body.
Further, in each pattern, the pattern pitch (that is, the interval between adjacent adhesive portions or the interval between adjacent non-adhesive portions) is preferably 10 to 500 μm, more preferably 10 to 300 μm, particularly The thickness is preferably 10 to 250 μm.
That is, the width of each stripe and the interval between stripes, the width of each wavy line and the interval between wavy lines, the width of each line forming the lattice, the interval between adjacent lines constituting the lattice, the interval between dots The width and height of the dots, or the height and width of each square constituting the checkered pattern is preferably 10 to 500 μm, more preferably 10 to 300 μm, and particularly preferably 10 to 250 μm.

Further, the surface protective film may be cured in advance by irradiating a part of the pressure-sensitive adhesive layer with energy rays before adhering to the surface of the adherend. When part of the pressure-sensitive adhesive layer is partially cured by irradiation with energy rays, the adhesive surface that adheres to the surface of the adherend of the surface protective film is strongly adhered to the surface without being irradiated with energy rays. Part and an energy ray are irradiated and hardened | cured, and the weak adhesive part whose adhesive force is lower than a strong adhesive part is provided.
The strong adhesive portion and the weak adhesive portion are preferably arranged in a pattern like the above-described adhesive portion and non-adhesive portion. Note that the details of the pattern of the strong adhesive portion and the weak adhesive portion are the same as the pattern of the adhesive portion and the non-adhesive portion described above, and thus the description thereof is omitted.
The partial curing of the pressure-sensitive adhesive layer is not particularly limited, but for example, it is publicly known through a mask having an opening having a shape matching the weakly-adhesive part or a light-shielding member having a light-shielding part having a shape corresponding to the strong adhesive part. It is good to carry out by irradiating an adhesive layer with an energy ray from an irradiation apparatus. The energy ray may be applied to the pressure-sensitive adhesive layer from the support side through the support, or may be applied from the opposite side of the support.
Even when the pressure-sensitive adhesive layer is partially cured, as described later, before the surface protective film is peeled off from the optical member or the electronic member, the surface protective film attached to the adherend is applied to the surface protective film. It is preferable to irradiate energy rays.
Adhesive part and non-adhesive part or strong adhesive part and weak adhesive part are provided on the surface protective film, and the ratio of the area of the adhesive part and non-adhesive part, or the ratio of the area of strong adhesive part and weak adhesive part is adjusted appropriately By doing so, the adhesive force of the surface protective film can be appropriately adjusted.

<Easily adhesive layer>
The said support body may have an easily bonding layer between a base material and a buffer layer, between a base material and a resin layer, or both in order to improve the adhesiveness between the layers of each layer.
Further, in order to improve the adhesion between the support and the pressure-sensitive adhesive layer, the surface is in contact with the surface of the pressure-sensitive adhesive layer (if the support has a resin layer or a substrate, any surface thereof). May have an easy-adhesion layer.
Although it does not specifically limit as a composition for easy-adhesion layer formation which forms an easy-adhesion layer, For example, the composition containing a polyester-type resin, a urethane-type resin, a polyester urethane-type resin, an acrylic resin etc. is mentioned.
The easy-adhesion layer-forming composition contains a crosslinking agent, a photopolymerization initiator, an antioxidant, a softening agent (plasticizer), a filler, a rust inhibitor, a pigment, a dye, and the like as necessary. May be.
The thickness of the easy adhesion layer is preferably 0.01 to 10 μm, more preferably 0.03 to 5 μm.

<Peeling sheet>
The pressure-sensitive adhesive layer side of the surface protective film of the present invention may be protected with a release sheet by attaching a release sheet. A release sheet that has been subjected to a double-sided release treatment, a release sheet that has been subjected to a single-sided release treatment, or the like is used.
As the base for the release sheet, a resin film is preferable, and examples of the resin constituting the resin film include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, polypropylene resin, polyethylene resin, and the like. Polyolefin resin and the like.
Examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long chain alkyl resins, alkyd resins, and fluorine resins.
The thickness of the release sheet is not particularly limited, but is preferably 10 to 200 μm, more preferably 20 to 150 μm.

The film area of the surface protective film is preferably 100 mm ² or less, more preferably about 10 to 80 mm ² . A surface protection film becomes small according to an optical member and an electronic member. Generally, when the film size is reduced, operations such as pasting and peeling become difficult. Since the surface protective film of the present invention has good peeling performance as described above, it is easy to peel off even by manual work. The shape of the surface protective film is not limited, but is processed into, for example, a circular shape, an annular shape, a square shape, a rectangular shape, or the like.
In addition, when processing a surface protection film into a predetermined film area thru | or a predetermined shape, a punching process is usually performed as described later.

<Method for producing surface protective film>
There is no restriction | limiting in particular as a manufacturing method of the surface protection film of this invention, It can manufacture by a well-known method.
For example, the buffer layer provided on the release sheet and the pressure-sensitive adhesive layer provided on the release sheet can be bonded to each side of the substrate. Moreover, a buffer layer can be provided directly on the surface of the substrate to produce a support, and the pressure-sensitive adhesive layer can be provided on the support.
In addition, the buffer layer provided on the release sheet and the pressure-sensitive adhesive layer provided on the release sheet may be bonded to each other.

As a method for forming a buffer layer on a release sheet or substrate, a coating film can be formed by directly applying the buffer layer forming composition on the release sheet or substrate by a known application method. . Moreover, a buffer layer can be formed by drying a coating film and / or irradiating energy rays.
Examples of the coating method include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

Moreover, in order to improve applicability | paintability, an organic solvent may be mix | blended with the raw material of the composition for buffer layer formation, or the resin film for buffer layer formation, and you may apply | coat on a peeling sheet as a solution form.
Examples of the organic solvent to be used include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, isopropanol and the like.
In addition, as for these organic solvents, the organic solvent used at the time of the synthesis | combination of each component contained in a composition may be used as it is, and 1 or more types of other organic solvents may be added.

When the composition for forming a buffer layer for forming the coating film is a composition for forming a buffer layer containing an energy beam polymerizable compound, the coating film is cured by irradiating energy rays to the buffer layer. Can be formed.
The buffer layer may be cured completely at once, or may be cured in multiple steps. In other words, after the coating film on the release sheet is completely cured to form a buffer layer, it may be bonded to the base material, and a semi-cured buffer layer forming film is formed without completely curing the coating film. Then, after the buffer layer forming film is bonded to the base material, the buffer layer may be formed by irradiating energy rays again to be completely cured.
Or, after forming the buffer layer forming film in a semi-cured state without completely curing the coating film directly on the substrate, the buffer layer may be formed by irradiating energy rays again and completely curing Good.

As an energy ray irradiated by the said hardening process, an ultraviolet-ray is preferable.
The irradiation amount of energy rays is appropriately changed depending on the type of energy rays. For example, when ultraviolet rays are used, the illuminance of the irradiated ultraviolet rays is preferably 50 to 500 mW / cm ² , more preferably 100 to 340 mW / cm ² , and the irradiation amount of ultraviolet rays is preferably 80 to 2500 mJ / cm ² , More preferably, it is 100 to 2000 mJ / cm ² .

Moreover, when using the resin film for buffer layers as a buffer layer, a buffer layer can be formed using a general extrusion laminating process other than said coating method. Moreover, the resin film for buffer layers shape | molded previously can also be bonded together with the resin film for base materials using an adhesive agent.

The method for forming the pressure-sensitive adhesive layer is not particularly limited, but an energy ray-curable pressure-sensitive adhesive composition diluted with an appropriate solvent as necessary is applied on the release sheet so as to have a predetermined dry film thickness, and thereafter After drying to form a pressure-sensitive adhesive layer, a base material or a support may be bonded to the pressure-sensitive adhesive layer. Moreover, the energy ray-curable pressure-sensitive adhesive composition diluted with an appropriate solvent as required may be directly applied to a substrate or a support and then dried to form a pressure-sensitive adhesive layer.

Moreover, when processing a surface protection film into a predetermined film area, the process (punching process) which uses a punching blade may be mainly performed. In this punching process, the punching blade is usually inserted from the surface opposite to the surface on which the pressure-sensitive adhesive layer of the support is provided (that is, the surface on which the buffer layer is provided). By using the surface protective film of the present invention, since the buffer layer is present on the surface of the surface protective film on the side where the punching blade is applied, slippage of the punching blade that occurs during the punching process can be suppressed, and processing accuracy is improved. Can be made. For example, the punching process may be performed on a laminate of the pressure-sensitive adhesive layer and the support formed on the release sheet. By this punching process, the shape of the surface protection film is changed to a predetermined shape such as a circle as described above.
Moreover, you may form an unevenness | corrugation suitably in a surface protection film by stamping etc. at arbitrary timings.

[Optical member or electronic member]
As an optical member or an electronic member protected by the surface protective film of the present invention, an imaging module in which one or more lenses and an imaging sensor such as a CCD or CMOS are housed in a casing or a package; a plurality of lenses is a lens mirror Examples include a lens unit held in a tube and housed in a housing or a package as necessary; a light emitting element unit having a light emitting element such as an LED; a motor unit such as a vibrator; a communication module, a sensor module, and the like. These optical members and electronic members are preferably members that are used by being attached to other members such as a substrate.

The optical member refers to an optical component that receives or emits light, or includes an optical component that transmits light. Among the above, an imaging module, a lens unit, a light emitting element unit, a communication module that transmits or receives an optical signal, An example of the optical member is an optical sensor module. The electronic member usually includes at least a part of an electric circuit and includes an electronic component that transmits or receives an electric signal, an electronic component that processes an electric signal, an electronic component that operates by an electric signal or electric power, and the like. Among them, a motor unit such as an imaging module, a light emitting element unit, and a vibrator, a communication module that transmits or receives an electrical signal, various sensor modules, and the like are specific examples of the electronic member. Note that a communication module, an optical sensor module, an imaging module, a light emitting element unit, and the like that transmit or receive optical signals are members that are both electronic members and optical members.
Moreover, it is preferable that the optical member or the electronic member is, for example, one in which the electronic component or the optical component is housed in a package or a housing or supported by a support member. Moreover, it is preferable that a part of electronic component or optical component is exposed on the surface, and the surface protection film is used, for example, to protect the exposed component.

[Usage of surface protection film]
The surface protective film of this invention is used in order to stick on the surface of an optical member or an electronic member, and to protect the surface. Specifically, an optical member or an electronic member (hereinafter also simply referred to as a member with a surface protective film) to which a surface protective film is attached is processed, attached to another member, inspected, transported, or the like. The surface protective film protects the surface of the optical member or the electronic member in these steps. The surface protective film is peeled off from the optical member or the electronic member after being irradiated with energy rays and reducing the adhesive force when these steps are finished and the surface protection is no longer necessary.
In addition, sticking and peeling of a surface protection film are normally performed manually. At that time, by using the surface protective film of the present invention, it is difficult to cause a shift in the attaching position when attaching to the surface of the optical member or the electronic member, so that the frequency of reattaching is reduced. In addition, since the surface protective film once pasted can be peeled off without applying an excessive load even when peeled off from the adherend, it damages the optical member or electronic member that is the adherend (distortion is distorted). Can be prevented.
In addition, the member with a surface protective film may be heated in steps such as the above-described processing, attachment, inspection, or conveyance. The heating temperature at that time is not particularly limited, but is about 60 to 200 ° C., preferably about 70 to 150 ° C. The pressure-sensitive adhesive layer may become highly adhesive when heated. When the energy ray-curable pressure-sensitive adhesive composition is used for the pressure-sensitive adhesive layer of the surface protective film of the present invention, even if the pressure-sensitive adhesive force is increased by heating, the pressure-sensitive adhesive force is reduced by irradiating energy rays thereafter. Therefore, it is difficult for peeling failure or adhesive residue to occur when the surface protective film is peeled off.

It is preferable that the optical member or the electronic member (the member with the surface protective film) to which the surface protective film is attached is attached to another member such as a substrate with an adhesive, for example. At this time, a thermosetting adhesive is used, and in order to cure the adhesive, the member with a surface protective film is usually at a temperature of 60 to 200 ° C. or higher, preferably about 70 to 150 ° C. as described above. Heating is preferred. Thereafter, when the surface protection is unnecessary, the surface protection film is peeled from the optical member or the electronic member after the surface protection film is irradiated with energy rays and the adhesive force is reduced.

Further, the surface protective film is particularly preferably used as a surface protective film for an imaging module in the above-described optical member or electronic member.
The imaging module is usually provided with a light receiving portion for receiving light from the outside on one surface and guiding the light to the imaging device via a lens inside the module. The light receiving unit is provided on a part (for example, the center) of one surface of the imaging module and is made of glass or transparent resin. The surface protective film is preferably attached to one surface of the imaging module where the light receiving part is provided so as to cover the light receiving part. Since the surface protective film adheres to the surface of the light receiving unit and the casing or package around the light receiving unit with high adhesive force before irradiation with energy rays, the light receiving unit provided on one surface of the imaging module should be appropriately protected. Is possible. Moreover, since the adhesive strength of the surface protective film is reduced after irradiation with energy rays, the surface protective film can be easily peeled off from the imaging module, and it is possible to prevent adhesive residue from being generated in the light receiving portion and the like.
In addition, as above-mentioned, it is preferable that the imaging module with which the surface protective film was stuck is heated for hardening of a thermosetting adhesive, and is attached to other members, such as a board | substrate.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

The measurement method and evaluation method in the present invention are as follows.
[Measuring method]
<Weight average molecular weight of raw material (Mw)>
Using a gel permeation chromatograph, measurement was performed under the following conditions, and values measured in terms of standard polystyrene were used.
(Measurement condition)
Measuring device: Product name “HLC-8220GPC”, manufactured by Tosoh Corporation)
Column: Product name “TSKGel SuperHZM-M” manufactured by Tosoh Corporation)
Developing solvent: Tetrahydrofuran Column temperature: 40 ° C
Flow rate: 1.0 mL / min
<Bending softness of support>
Measurements were performed in the MD direction and TD direction of the support by a method according to JIS L 1913. However, a 45 ° cantilever type tester was used, and the support was cut into 20 mm × 150 mm test pieces. Two test pieces used for the measurement were prepared in each of the MD direction and the TD direction. Here, the test piece in the MD direction means that the longitudinal direction of the test piece is the MD direction of the support.
For each test piece, the bending length (mN · cm) was measured four times in total, twice on the front surface (both ends) and twice on the back surface (both ends). The average value was calculated for the measurement results for the four times. The same measurement was performed for the TD direction.
From the measured value of the bending length of two test pieces in the MD direction and the mass per unit area (g / m ² ) of the test piece used for the measurement, the calculation formula described in JIS L 1913 is used. MD bending resistance was calculated. Similarly, in the TD direction, the TD bending resistance was calculated using the measurement values of the bending lengths of two test pieces.
The calculated values of MD bending resistance and TD bending resistance were averaged to obtain the bending resistance (mN · cm) of the support.
<Measurement of indentation depth (Z) of buffer layer>
A dynamic microhardness meter (manufactured by Shimadzu Corporation, product name “DUH-W201S”) and a triangular pyramid indenter with a tip radius of curvature of 100 nm and a ridge angle of 115 ° are used as an indenter at 23 ° C. and 50% RH. Measurement was performed under an environment of (relative humidity).
Specifically, it is placed on the glass plate of the dynamic microhardness meter so that the buffer layer of the produced surface protective film is exposed, and the tip of the triangular pyramid-shaped indenter is 10 μm / min with respect to the buffer layer. The indentation depth (Z) was measured when the compression load reached 2 mN.

[Method for evaluating surface protective film]
<Punching accuracy>
The surface protective film was punched by inserting a punching blade from the support side. The punching size was a circle with a diameter of 5 mm. About the surface protection film after performing a punching process, the diameter of the X direction and the Y direction orthogonal to X direction was measured, and the following references | standards evaluated.
A: Diameter in X direction and Y direction is within 5 ± 0.1 mm B: Diameter in X direction or Y direction exceeds 5 ± 0.1 mm <Workability>
The surface protective film was processed into a circle having a diameter of 5 mm. This surface protective film was peeled off from the release sheet using tweezers, and was bonded to an imaging module as an adherend. Moreover, the surface protection film was peeled off from the imaging module using tweezers after UV irradiation, and the workability was evaluated according to the following criteria.
A: It was easy to peel off from the release sheet, and the attachment to the imaging module could be easily performed without mistake. Further, peeling after UV irradiation could be easily performed.
B: Although time was required for peeling from the release sheet and time was required for bonding to the imaging module, peeling after UV irradiation was easily performed.
C: The film could be easily peeled off from the release sheet, and could be easily attached to the imaging module without any mistake, but it took time to peel off after UV irradiation.

[Production Example 1]
(Synthesis of urethane acrylate oligomer (UA-1))
A bifunctional urethane acrylate oligomer (UA-1) having a weight average molecular weight (Mw) of 5000 is reacted with a terminal isocyanate urethane prepolymer obtained by reacting a polyester diol and isophorone diisocyanate. Got.

[Example 1]
(1) Preparation of composition for forming buffer layer 40 parts by mass of the urethane acrylate oligomer (UA-1) synthesized in Production Example 1 so that the total amount of the energy ray polymerizable compound is 100 parts by mass (solid content ratio). 40 parts by mass of isobornyl acrylate (IBXA) and 20 parts by mass of phenylhydroxypropyl acrylate (HPPA) were blended, and 1-hydroxycyclohexyl phenyl ketone (product name “Irgacure 184” manufactured by BASF) was used as a photopolymerization initiator. 2.0 parts by mass and 0.2 parts by mass of a phthalocyanine pigment were blended to prepare a composition for forming a buffer layer.

(2) Production of support
The above-mentioned composition for forming a buffer layer on a substrate made of a polyethylene terephthalate film (trade name; Cosmo Shine, product number: A-4100, manufactured by Toyobo Co., Ltd.) having a thickness of 50 μm so that the thickness after curing is 20 μm. The product was applied to form a coating film. And the ultraviolet-ray was irradiated with respect to the said coating film, the said coating film was semi-hardened, and the buffer layer formation film was formed.
The above ultraviolet irradiation uses a belt conveyor type ultraviolet irradiation device (product name “ECS-401GX”, manufactured by I-Graphics) and a high-pressure mercury lamp (H04-L41 manufactured by I-Graphics: H04-L41). The measurement was performed under irradiation conditions of a height of 150 mm, a lamp output of 3 kW (converted output of 120 mW / cm), an illuminance of 120 mW / cm ^{2 with} a light wavelength of 365 nm, and an irradiation amount of 100 mJ / cm ² .
Then, the surface of the formed buffer layer forming film and a release sheet (trade name “SP-PET 381031” manufactured by Lintec Co., Ltd., polyethylene terephthalate (PET) film subjected to silicone release treatment, thickness: 38 μm) are released. The peeled surface was bonded, and ultraviolet rays were irradiated again from the release sheet side on the buffer layer forming film to completely cure the buffer layer forming film, thereby forming a buffer layer having a thickness of 20 μm.
In addition, said ultraviolet irradiation uses the above-mentioned ultraviolet irradiation apparatus and a high pressure mercury lamp, lamp | ramp height 150mm, lamp output 3kW (converted output 120mW / cm), illuminance 160mW / cm < ² > of light wavelength 365nm, irradiation amount 500mJ / Cm ² was performed under irradiation conditions.

(3) Formation of pressure-sensitive adhesive layer 69.5 parts by mass of n-butyl acrylate, 30 parts by mass of methyl acrylate, and 0.5 parts by mass of 2-hydroxyethyl acrylate were polymerized in an ethyl acetate solvent to obtain a weight average molecular weight of 46 Ten thousand acrylic copolymers were obtained. 100 parts by mass (converted to solid content) of an acrylic copolymer diluted with an ethyl acetate solvent, 120 parts by mass of a pentaerythritol 5-9 functional urethane acrylate oligomer having a weight average molecular weight of 2300, and a photopolymerization initiator Energy ray curable pressure-sensitive adhesive by mixing 2.0 parts by mass of Irgacure 184 (manufactured by BASF) and 8 parts by mass of an organic polyvalent isocyanate compound (product name “BHS8515”, manufactured by Toyochem Co., Ltd.) as a crosslinking agent A diluted ethyl acetate solution of the composition (Y type) was obtained. This diluted solution was applied to the substrate side surface of the support so that the thickness after drying was 20 μm, and then dried by heating at 100 ° C. for 1 minute to form an adhesive on the substrate. A layer was formed to obtain a surface protective film.

[Example 2]
A surface protective film was produced in the same manner as in Example 1 except that the thickness of the buffer layer was 50 μm.

[Example 3]
Similar to Example 1 except that a support having a thickness of 75 μm and a low-density polyethylene film (buffer layer) having a thickness of 25 μm bonded to the same base material as in Example 1 with an epoxy resin adhesive was used. Thus, a surface protective film was produced.

[Example 4]
A support having a thickness of 100 μm was prepared by laminating a low-density polyethylene film (buffer layer and resin layer) having a thickness of 25 μm with an epoxy resin adhesive on both surfaces of the same substrate as in Example 1. A pressure-sensitive adhesive layer having a thickness of 20 μm was formed on the resin layer surface in the same manner as in Example 1 to produce a surface protective film.

[Example 5]
A surface protective film was produced in the same manner as in Example 1 except that a polyethylene terephthalate film (trade name: Cosmo Shine, product number: A-4100, manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm was used as the substrate.

[Comparative Example 1]
A surface protective film was produced in the same manner as in Example 1 except that the buffer layer was not formed.

[Comparative Example 2]
A surface protective film was produced in the same manner as in Example 1 except that a low-density polyethylene film having a thickness of 80 μm was used as the substrate.

[Comparative Example 3]
A surface protective film was produced in the same manner as in Example 1 except that a low-density polyethylene film having a thickness of 50 μm was used as the substrate and the thickness of the buffer layer was changed to 50 μm.

[Comparative Example 4]
A surface protective film was produced in the same manner as in Example 1, except that a polyethylene terephthalate film (trade name: Cosmo Shine, product number: A-4100, manufactured by Toyobo Co., Ltd.) having a thickness of 125 μm was used as the substrate.

From Table 1, it can be seen that the surface protective films prepared in Examples 1 to 5 are both excellent in workability and workability.
On the other hand, the surface protective film produced in Comparative Example 1 has excellent workability because the support has good bending resistance, but has no buffer layer, has a shallow depth of pushing into the base material, and has good workability. It became inferior result.
In Comparative Examples 2 and 3, the workability was inferior due to the low bending resistance of the support, and in Comparative Example 4, the workability was inferior because the bending resistance of the support was too high. .

The surface protective film of the present invention is excellent in workability and workability.
Therefore, the surface protective film of the present invention can be suitably used as, for example, a surface protective film that protects the surface of an optical member or an electronic member. It is possible to effectively prevent a reduction in the frequency of reattachment due to the improvement of the sticking property and damage to the adherend during peeling.

Claims

A surface protective film that is applied to an optical member or an electronic member and used to protect the surface thereof,
Comprising a support having a bending resistance of 5000 mN · cm or more and 45000 mN · cm or less, and an adhesive layer on one surface of the support,
The support has a buffer layer composed of at least one selected from a buffer layer-forming composition containing an energy beam polymerizable compound and a buffer layer-forming resin film, and has a tip curvature radius of 100 nm and a ridge angle of 115 °. Surface protective film having a pressing depth (Z) of 2.5 μm or more required to reach a compression load of 2 mN when the tip of the triangular pyramid-shaped indenter is pressed into the buffer layer at a speed of 10 μm / min. .
The surface protective film according to claim 1, wherein the support further has a base material.
The surface protective film according to claim 2, wherein the support is a support further having a resin layer on a surface opposite to a surface on which the buffer layer of the substrate is provided.
The surface protective film according to any one of claims 1 to 3, wherein the buffer layer is exposed on a surface opposite to the pressure-sensitive adhesive layer.
5. The surface protective film according to claim 2, wherein the substrate is a resin film made of polyethylene terephthalate.
The composition for forming a buffer layer is, as the energy ray polymerizable compound, urethane (meth) acrylate (a1), a polymerizable compound (a2) having an alicyclic group or heterocyclic group having 6 to 20 ring-forming atoms, The surface protective film according to any one of claims 1 to 5, comprising a polymerizable compound (a3) having a functional group.
The surface protective film according to any one of claims 1 to 6, wherein the resin film for forming a buffer layer is a polyethylene film.
The surface protective film according to any one of claims 1 to 7, wherein the buffer layer has a thickness of 5 to 100 µm.
The surface protective film according to any one of claims 1 to 8, wherein the pressure-sensitive adhesive layer comprises an energy ray-curable pressure-sensitive adhesive composition.
The pressure-sensitive adhesive layer is made of an energy ray-curable pressure-sensitive adhesive composition containing an acrylic copolymer,
The acrylic copolymer contains a monomer component containing at least 5 to 50% by mass of an alkyl (meth) acrylate having an alkyl group having 1 or 2 carbon atoms and not containing a carboxyl group-containing monomer or less than 5% by mass. The surface protective film according to any one of claims 1 to 9, which is a copolymer.
A member with a surface protective film comprising: an optical member or an electronic member; and the surface protective film according to any one of claims 1 to 10 attached to a surface of the optical member or the electronic member.
A method for protecting a surface of the optical member or electronic member by applying the surface protective film according to any one of claims 1 to 10 to the surface of the optical member or electronic member.