WO2023100866A1

WO2023100866A1 - Adhesive sheet and method for manufacturing adhesive sheet

Info

Publication number: WO2023100866A1
Application number: PCT/JP2022/043965
Authority: WO
Inventors: 裕貴福島
Original assignee: リンテック株式会社
Priority date: 2021-12-03
Filing date: 2022-11-29
Publication date: 2023-06-08
Also published as: JPWO2023100866A1; TW202330832A; CN118215717A; KR20240117527A

Abstract

Provided is an adhesive sheet 1 having at least an adhesive layer 11, wherein the transmittance of the adhesive layer 11 at a wave number of 1105-1125 cm-1 in IR transmittance measurement is 50% or greater, and the stress at 200% elongation when a tensile test elongating the adhesive layer 11 at a speed of testing of 200 mm/minute is 6.15×104 N/m2 to 1.0×107 N/m2. The adhesive sheet 1 has excellent weather resistance and blister resistance.

Description

Adhesive sheet and method for producing adhesive sheet

The present invention relates to an adhesive sheet and its manufacturing method.

In the displays of various electronic devices, especially in mobile electronic devices and in-vehicle displays, a protective panel is provided on the surface side of the display module. The protective panel is usually adhered to a display module or the like via an adhesive layer.

As a pressure-sensitive adhesive composition for the pressure-sensitive adhesive layer used in the above applications, Patent Document 1 describes urethane (meth)acrylate (X), (meth ) discloses an ultraviolet curable pressure-sensitive adhesive composition containing an acrylic monomer (Y) and a photopolymerization initiator (Z).

JP 2017-222757 A

Here, the above-mentioned displays, especially displays for vehicles and displays for outdoor use, are often exposed to ultraviolet rays from sunlight for a long period of time or placed in a high temperature or high temperature and high humidity environment. sex is required. However, the pressure-sensitive adhesive composition of Patent Document 1 is inferior in weather resistance because it discolors under the above conditions.

By the way, as the protective panel, a plastic plate is sometimes used from the viewpoint of weight reduction and safety. However, unlike glass plates, plastic plates generate outgassing and permeate water vapor under high-temperature and high-humidity conditions. As a result, blisters such as air bubbles, floating, and peeling may occur between the plastic plate and the adhesive layer. Therefore, the pressure-sensitive adhesive layer is also required to have blister resistance.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a pressure-sensitive adhesive sheet excellent in weather resistance and blister resistance, and a method for producing the same.

To achieve the above objects, firstly, the present invention provides a pressure-sensitive adhesive sheet having at least a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer has a transmittance of 50% at a wave number of 1105 to 1125 cm ^-1 in IR transmittance measurement. Above, a tensile test was performed in which the pressure-sensitive adhesive layer was elongated at a tensile speed of 200 mm/min, and the stress when elongated by 200% was 6.15 × 10 ⁴ N/m ² or more and 1.0 × 10 ⁷ Provided is a pressure-sensitive adhesive sheet characterized by having a density of N/m ² or less (Invention 1).

In the above invention (Invention 1), the transmittance at wave numbers of 1105 to 1125 cm ⁻¹ in IR transmittance measurement is large as described above, so that the amount of ether bonds derived from polyethers such as polyethylene glycol is small. The pressure-sensitive adhesive is resistant to discoloration even when exposed to ultraviolet light for a long period of time, and has excellent weather resistance. Further, when the stress at 200% elongation is within the above range, the blister resistance is excellent.

In the above invention (Invention 1), the thickness of the adhesive layer is preferably 60 μm or more and 10000 μm or less (Invention 2).

In the above inventions (inventions 1 and 2), the adhesive constituting the adhesive layer is preferably a solventless acrylic adhesive (invention 3).

In the above inventions (inventions 1 to 3), the pressure-sensitive adhesive preferably contains a (meth)acrylic acid ester polymer or a crosslinked product thereof and a cured product of an active energy ray-curable component (invention 4). .

In the above inventions (Inventions 1 to 4), two release sheets are provided, and the pressure-sensitive adhesive layer is sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets. Preferred (invention 5).

The second aspect of the present invention is a method for producing the adhesive sheet (inventions 1 to 5), comprising an acrylic syrup (A) containing an acrylic polymer (a1) and an acrylic monomer (a2), and an active energy ray-curable A method for producing a pressure-sensitive adhesive sheet, comprising: curing a pressure-sensitive adhesive composition containing the component (B) (excluding the component of the acrylic syrup (A)) with an active energy ray to form the pressure-sensitive adhesive layer. (Invention 6).

The third aspect of the present invention is a method for producing the adhesive sheet (inventions 1 to 5), comprising an acrylic syrup (A) containing an acrylic polymer (a1) and an acrylic monomer (a2), and an active energy ray-curable An adhesive composition containing component (B) (excluding the acrylic syrup (A) component) and a thermal cross-linking agent (C) is cured with active energy rays and thermally cross-linked to form the adhesive layer. (Invention 7).

The adhesive sheet according to the present invention has excellent weather resistance and blister resistance.

1 is a cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention; FIG. It is a sectional view of a layered product concerning one embodiment of the present invention.

Embodiments of the present invention will be described below.
[Adhesive sheet]
A pressure-sensitive adhesive sheet according to one embodiment of the present invention has at least a pressure-sensitive adhesive layer. The transmittance at a wave number of 1105 to 1125 cm ⁻¹ in the IR transmittance measurement of the pressure-sensitive adhesive layer is preferably 50% or more, and a tensile test is performed to stretch the pressure-sensitive adhesive layer at a tensile speed of 200 mm / min. The stress when elongated (stress at 200% elongation) is preferably 6.15×10 ⁴ N/m ² or more and 1.0×10 ⁷ N/m ² or less. The above transmittance is a value measured by infrared absorption spectroscopy, and the specific measurement method is as shown in the test examples described later. Further, the details of the tensile test are also as shown in the test examples described later.

A wave number of 1105 to 1125 cm ⁻¹ is a wave number region showing strong absorption derived from C—O—C antisymmetric stretching of an aliphatic ether bond. Ether bonds of polyethers such as polyethylene glycol are easily cut by irradiation with ultraviolet rays, and the pressure-sensitive adhesive tends to be discolored (yellowing). In the pressure-sensitive adhesive sheet according to the present embodiment, since the transmittance at the wave number of 1105 to 1125 cm ⁻¹ is large as described above, the amount of polyether such as polyethylene glycol is small, and therefore, the adhesive sheet can be adhered even when irradiated with ultraviolet rays for a long time. The agent is resistant to discoloration and has excellent weather resistance. Moreover, in the pressure-sensitive adhesive sheet according to the present embodiment, since the stress at 200% elongation is within the above range, the pressure-sensitive adhesive sheet is excellent in blister resistance. That is, even if the adherend (particularly a plastic plate) generates outgassing under high temperature and high humidity conditions, the pressure-sensitive adhesive layer confines the outgassing to the adherend, causing air bubbles at the interface between the pressure-sensitive adhesive layer and the adherend. The occurrence of floating, peeling, etc. is suppressed.

From the viewpoint of weather resistance, the transmittance is preferably 50% or more, more preferably 52% or more, particularly preferably 54% or more, and further preferably 58% or more. preferable. Although the upper limit of the transmittance is not particularly limited, it is usually preferably 99% or less, more preferably 90% or less, particularly preferably 80% or less, and further preferably 70% or less. is preferred.

From the viewpoint of blister resistance, the stress at 200% elongation is preferably 6.15×10 ⁴ N/m ² or more, more preferably 7.00×10 ⁴ N/m ² or more. , particularly preferably 8.00×10 ⁴ N/m ² or more, more preferably 9.00×10 ⁴ N/m ² or more. Further, from the viewpoint of ensuring good adhesiveness, the stress at 200% elongation is preferably 1.00 × 10 ⁷ N/m ² or less, and is 1.00 × 10 ⁶ N/m ² or less. It is more preferably 5.00×10 ⁵ N/m ² or less, particularly preferably 3.00×10 ⁵ N/m ² or less.

In the pressure-sensitive adhesive sheet according to the present embodiment, a 200 μm pressure-sensitive adhesive layer is laminated to a triacetyl cellulose (TAC) film (thickness: 40 μm, water vapor transmission rate 841 g/(m 24 h)), 40 ° C., 90% The water vapor permeability measured in accordance with JIS Z0208 under RH conditions is preferably 150 g/(m ² ·24 h) or more, more preferably 200 g/(m ² ·24 h) or more, particularly 215 g. /(m ² ·24h) or more is preferable.

Since the water vapor transmission rate of the pressure-sensitive adhesive layer at a thickness of 200 μm is large as described above, the structure (for example, glass plate/adhesive layer/plastic plate) in which the adherend is bonded by the pressure-sensitive adhesive layer is heated to a high temperature. Even when the pressure-sensitive adhesive layer is placed under humid conditions, the water that has entered the pressure-sensitive adhesive layer is easily removed from the pressure-sensitive adhesive layer when the temperature returns to normal temperature and humidity, and the condensation of water is less likely to occur, resulting in the deterioration of the pressure-sensitive adhesive layer. Whitening is suppressed. That is, the pressure-sensitive adhesive layer has excellent resistance to whitening under heat and humidity.

The upper limit of the water vapor permeability of the pressure-sensitive adhesive layer at a thickness of 200 μm is preferably 1000 g/(m ² 24 h) or less, and 800 g/(m ² 24 h) or less, from the viewpoint of blister resistance. is more preferably 500 g/(m ² ·24 h) or less, and more preferably 300 g/(m ² ·24 h) or less. A specific method for measuring the water vapor transmission rate is as shown in the test examples described later.

The shear modulus of the adhesive constituting the adhesive layer in the present embodiment is preferably 0.01 MPa or more, more preferably 0.04 MPa or more, particularly preferably 0.06 MPa or more, Furthermore, it is preferably 0.08 MPa or more. This makes the blister resistance more excellent. In addition, from the viewpoint of ensuring good adhesiveness, the shear modulus is preferably 10 MPa or less, more preferably 5 MPa or less, particularly preferably 1 MPa or less, and further preferably 0.5 MPa or less. is preferred. The shear modulus in this specification is a value measured by a torsional shear method at a measurement frequency of 1 Hz in accordance with JIS K7244-6. Specifically, it is as shown in the test examples described later.

The gel fraction of the adhesive constituting the adhesive layer in the adhesive sheet of the present embodiment is preferably 40% or more, more preferably 60% or more, and particularly preferably 70% or more. Furthermore, it is preferably 74% or more. Further, the gel fraction is preferably 100% or less, more preferably 95% or less, particularly preferably 90% or less, further preferably 88% or less. When the gel fraction of the pressure-sensitive adhesive is within the above range, the pressure-sensitive adhesive will have a predetermined cohesive force, and the blister resistance will be more excellent. In addition, the method for measuring the gel fraction in the present specification is as shown in the test examples described later.

FIG. 1 shows a specific configuration as an example of the pressure-sensitive adhesive sheet according to this embodiment.
As shown in FIG. 1, the adhesive sheet 1 is sandwiched between two

release sheets

12a and 12b and the two

release sheets

12a and 12b so as to be in contact with the release surfaces of the two release sheets 12a and 12b. and an adhesive layer 11 . In this specification, the release surface of the release sheet refers to the surface of the release sheet that has releasability, and includes both the surface that has been subjected to a release treatment and the surface that exhibits releasability without being subjected to a release treatment. .

1. Each element 1-1. Adhesive layer The type of adhesive constituting the adhesive layer 11 of the adhesive sheet 1 according to the present embodiment is not particularly limited, and examples thereof include acrylic adhesives, polyester adhesives, polyurethane adhesives, and rubber adhesives. agent, silicone-based pressure-sensitive adhesive, or the like. Among them, it is preferable to use a solvent-free acrylic pressure-sensitive adhesive that easily satisfies the physical properties described above, does not involve volatilization of an organic solvent, and facilitates thick film coating. The solvent-free acrylic pressure-sensitive adhesive may be a cross-linking type that is cross-linked with a thermal cross-linking agent, or may be a non-cross-linking type.

The adhesive constituting the adhesive layer 11 of the adhesive sheet 1 according to the present embodiment contains at least a (meth)acrylic acid ester polymer or a crosslinked product thereof and a cured product of an active energy ray-curable component. is preferred. Such an adhesive easily satisfies the physical properties described above.

The adhesive constituting the adhesive layer 11 of the adhesive sheet 1 according to the present embodiment is, in particular, an acrylic syrup (A) containing an acrylic polymer (a1) and an acrylic monomer (a2), and an active energy ray-curable component. (B) (excluding the component of acrylic syrup (A)) and an adhesive composition (hereinafter sometimes referred to as "adhesive composition P1") is cured with active energy rays, or acrylic an acrylic syrup (A) containing a system polymer (a1) and an acrylic monomer (a2), an active energy ray-curable component (B) (excluding the acrylic syrup (A) component), and a thermal cross-linking agent (C) The adhesive composition containing (hereinafter sometimes referred to as "adhesive composition P2") is preferably cured with active energy rays and thermally crosslinked. In addition, said "adhesive composition P1" and "adhesive composition P2" are collectively called "adhesive composition P."

(1) Component of adhesive composition (1-1) Acrylic syrup (A)
(1-1-1) acrylic polymer (a1)
The acrylic polymer (a1) contained in the acrylic syrup (A) is preferably a (meth)acrylate polymer. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. In addition, the concept of "copolymer" is also included in "polymer".

The (meth)acrylic acid ester polymer preferably contains a (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer. Thereby, favorable adhesiveness can be expressed. Alkyl groups may be straight or branched.

The (meth)acrylic acid alkyl ester is preferably a (meth)acrylic acid alkyl ester having an alkyl group with 2 to 20 carbon atoms from the viewpoint of adhesiveness. Examples of (meth)acrylic acid alkyl esters having alkyl groups of 2 to 20 carbon atoms include ethyl acrylate, propyl acrylate, n-butyl acrylate, n-pentyl (meth)acrylate, and (meth)acrylic acid. n-hexyl, 2-ethylhexyl (meth)acrylate, n-octyl acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-(meth)acrylate - includes lauryl and the like.

Among the above, from the viewpoint of efficiently imparting adhesive strength, (meth)acrylic acid alkyl esters having an alkyl group having a carbon number of 2 to 12 are more preferable, and acrylic acid alkyl esters having an alkyl group having a carbon number of 4 to 10 are preferable. is particularly preferred. Specifically, n-butyl acrylate, 2-ethylhexyl (meth)acrylate and isooctyl (meth)acrylate are preferred. In particular, n-butyl acrylate is particularly preferred from the viewpoint of achieving both stress at 200% elongation and adhesive strength at a high level.

Moreover, from the viewpoint of comparison with the high Tg monomer described later, the (meth)acrylic acid alkyl ester is preferably a monomer having a low glass transition temperature (Tg). Specifically, the glass transition temperature (Tg) is preferably 0° C. or lower, more preferably -20° C. or lower, and particularly preferably -40° C. or lower. Although the lower limit of the glass transition temperature (Tg) is not particularly limited, it is preferably approximately −90° C. or higher. A monomer with a low glass transition temperature (Tg) greatly contributes to the exertion of adhesive strength and helps to adjust the stress at 200% elongation to a low level.
The (meth)acrylic acid alkyl esters described above may be used alone, or two or more thereof may be used in combination.

From the viewpoint of imparting adhesiveness, the (meth)acrylic acid ester polymer contains 30% by mass or more of a (meth)acrylic acid alkyl ester having an alkyl group having 2 to 20 carbon atoms as a monomer unit constituting the polymer. It is preferably contained, particularly preferably at least 40% by mass, more preferably at least 50% by mass. In addition, from the viewpoint of ensuring the content of other monomers, it is preferable that the (meth)acrylic acid alkyl ester having an alkyl group having 2 to 20 carbon atoms is contained in an amount of 90% by mass or less, particularly 80% by mass or less. is preferable, and it is more preferable to contain 70% by mass or less. Note that the above content does not include the high Tg monomer portion described later.

The (meth)acrylic acid ester polymer preferably contains a reactive functional group-containing monomer having a reactive functional group in the molecule as a monomer constituting the polymer. By containing this reactive functional group-containing monomer, it reacts with a thermal cross-linking agent (C) described later via the reactive functional group derived from the reactive functional group-containing monomer, thereby resulting in a crosslinked structure (three-dimensional network structure) is formed, and a pressure-sensitive adhesive having a predetermined cohesive strength is obtained. In addition, even when the thermal cross-linking agent (C) is not used, the reactive functional group derived from the reactive functional group-containing monomer contributes to wet heat whitening resistance.

Examples of the reactive functional group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxy group in the molecule (carboxy group-containing monomer), and a monomer having an amino group in the molecule (amino group-containing monomer). monomer) and the like are preferred. One of these reactive functional group-containing monomers may be used alone, or two or more thereof may be used in combination. Among the above-mentioned reactive functional group-containing monomers, hydroxyl group-containing monomers having excellent reactivity with the thermal cross-linking agent (C) are preferred.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, (meth) ) hydroxyalkyl (meth)acrylates such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth)acrylate; Among them, a hydroxyalkyl group having 1 to 4 carbon atoms in the obtained (meth)acrylic acid ester polymer from the viewpoint of reactivity with the thermal crosslinking agent (C) and copolymerization with other monomers. (Meth)acrylic acid hydroxyalkyl esters having Specifically, for example, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate and the like are preferred, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are particularly preferred. be done. These may be used alone or in combination of two or more.

Examples of carboxy group-containing monomers include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among them, acrylic acid is preferable from the viewpoint of adhesive strength and reactivity with the thermal cross-linking agent (C). These may be used alone or in combination of two or more.

The (meth)acrylic acid ester polymer preferably contains 5% by mass or more, more preferably 10% by mass or more, of a reactive group-containing monomer as a monomer unit constituting the polymer as a lower limit. , In particular, it is preferably contained in an amount of 15% by mass or more, more preferably 20% by mass or more. In addition, the (meth)acrylic acid ester polymer preferably contains 50% by mass or less, and preferably 40% by mass or less, of a reactive group-containing monomer as a monomer unit constituting the polymer. More preferably, the content is particularly preferably 35% by mass or less, and more preferably 30% by mass or less. When the (meth)acrylic acid ester polymer contains the reactive group-containing monomer in the above amount as a monomer unit, a good crosslinked structure is formed in the obtained adhesive, and the mechanical properties described above are easily satisfied.

The (meth)acrylic acid ester polymer preferably does not contain a carboxy group-containing monomer as a monomer unit constituting the polymer. Since the carboxyl group is an acid component, the absence of the carboxyl group-containing monomer prevents the adhesive from being applied to objects to which the acid is attached, such as transparent conductive films such as tin-doped indium oxide (ITO), metal films, and the like. Even if it exists, it is possible to suppress those problems (corrosion, resistance value change, etc.) caused by the acid. However, it is permissible to contain a predetermined amount of the carboxy group-containing monomer to the extent that such problems do not occur. Specifically, the (meth)acrylic acid ester polymer contains 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less of a carboxy group-containing monomer as a monomer unit. It is allowed to contain in the amount of

In addition, the (meth)acrylic acid ester polymer is a monomer having a glass transition temperature (Tg) exceeding 0 ° C. as a homopolymer (hereinafter sometimes referred to as a "high Tg monomer") as a monomer unit constituting the polymer. .) is also preferred. The inclusion of high Tg monomers can increase the stress at 200% elongation. The glass transition temperature (Tg) is more preferably 4° C. or higher, particularly preferably 8° C. or higher. Although the upper limit is not particularly limited, it is about 300°C.

Examples of high Tg monomers include methyl acrylate (Tg 10°C), methyl methacrylate (Tg 105°C), ethyl methacrylate (Tg 65°C), n-butyl methacrylate (Tg 20°C), isobutyl methacrylate (Tg 48°C), t-butyl methacrylate (Tg107°C), n-stearyl acrylate (Tg30°C), n-stearyl methacrylate (Tg38°C), cyclohexyl acrylate (Tg15°C), cyclohexyl methacrylate (Tg66°C), phenoxyethyl acrylate (Tg5°C), phenoxyethyl methacrylate (Tg54°C), benzyl methacrylate (Tg54°C), isobornyl acrylate (Tg94°C), isobornyl methacrylate (Tg180°C), N-acryloylmorpholine (Tg145°C), adamantyl acrylate (Tg 115°C), adamantyl methacrylate (Tg 141°C), dimethylacrylamide (Tg 89°C), acrylamide (Tg 165°C), vinyl acetate (Tg 32°C), styrene (Tg 80°C), and the like. Among the above, acrylic monomers such as methyl acrylate, methyl methacrylate, isobornyl acrylate, and N-acryloylmorpholine are preferred from the viewpoint of increasing stress at 200% elongation without deteriorating optical properties. These may be used alone or in combination of two or more.

When the (meth)acrylic acid ester polymer contains a high Tg monomer as a monomer unit constituting the polymer, from the viewpoint of increasing the stress at 200% elongation to a predetermined range, as the monomer unit constituting the polymer, The content of the high Tg monomer is preferably 1% by mass or more, particularly preferably 10% by mass or more, and more preferably 15% by mass or more. In addition, from the viewpoint of ensuring the content of other monomers, the content of the high Tg monomer is preferably 50% by mass or less, particularly preferably 40% by mass or less, and further preferably 30% by mass or less. is preferred.

The (meth)acrylic acid ester polymer may optionally contain other monomers as monomer units constituting the polymer. As other monomers, monomers containing no reactive functional groups are preferred so as not to inhibit the above-described effects of the reactive functional group-containing monomers. Examples of such monomers include alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

The (meth)acrylic acid ester polymer is preferably polymerized without solvent by bulk polymerization. The polymerization mode of the (meth)acrylic acid ester polymer may be a random copolymer or a block copolymer.

The weight average molecular weight of the acrylic polymer (a1) ((meth)acrylic acid ester polymer) is preferably 200,000 or more, more preferably 400,000 or more, from the viewpoint of increasing the stress at 200% elongation. is preferably 600,000 or more, and more preferably 800,000 or more. Further, from the viewpoint of dispersibility in diluted monomers, the weight average molecular weight is preferably 3 million or less, more preferably 2 million or less, particularly preferably 1,500,000 or less. It is preferably 1,000,000 or less. In addition, the weight average molecular weight in this specification is the value of standard polystyrene conversion measured by the gel permeation chromatography (GPC) method.

The content ratio of the acrylic polymer (a1) in the acrylic syrup (A) is preferably 1% by mass or more, more preferably 5% by mass or more, and particularly preferably 10% by mass or more. Furthermore, it is preferably 15% by mass or more. In addition, the content ratio is preferably 50% by mass or less, more preferably 40% by mass or less, particularly preferably 30% by mass or less, and further preferably 20% by mass or less. . When the content ratio of the acrylic polymer (a1) is within the above range, it becomes easier to obtain a syrup having a uniform and appropriate viscosity.

(1-1-2) acrylic monomer (a2)
The acrylic monomer (a2) contained in the acrylic syrup (A) is preferably the same component as the constituent monomers of the acrylic polymer (a1). The acrylic monomer (a2) may be an unreacted product obtained by polymerizing the acrylic polymer (a1) by a bulk polymerization method, or may be obtained by adding an acrylic monomer to the unreacted product. good. Furthermore, the coating viscosity of the adhesive composition P can be suitably adjusted by adding an acrylic monomer.

The acrylic monomer to be further added is preferably the same component as the constituent monomer of the acrylic polymer (a1), that is, the acrylic monomer (a2). Moreover, the blending ratio of each monomer is preferably the same as the blending ratio of the constituent monomers of the acrylic polymer (a1). Thereby, the polymer obtained by curing the acrylic syrup (A) has a desired monomer composition ratio.

The content ratio of the acrylic monomer (a2) in the acrylic syrup (A) is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, Furthermore, it is preferably 80% by mass or more. In addition, the content ratio is preferably 99% by mass or less, more preferably 95% by mass or less, particularly preferably 90% by mass or less, and further preferably 85% by mass or less. . When the content ratio of the acrylic monomer (a2) is within the above range, the solventless adhesive composition P has a suitable coating viscosity.

The content of the acrylic syrup (A) in the adhesive composition P according to the present embodiment is preferably 70% by mass or more, particularly preferably 80% by mass or more, and further preferably 90% by mass or more. Preferably. Also, the content of the acrylic syrup (A) is preferably 100% by mass or less, particularly preferably 99% by mass or less. When the content of the acrylic syrup (A) is within the above range, the physical properties described above are easily satisfied.

(1-2) Active energy ray-curable component (B)
The active energy ray-curable component (B) is a component different from the components of the acrylic syrup (A) described above (acrylic polymer (a1) and acrylic monomer (a2)).

In the adhesive obtained by active energy ray curing of the adhesive composition P according to the present embodiment, the active energy ray-curable component (B) gives a branched structure in the linear polymerization of the acrylic monomers (a2). have a role. It is presumed that the pressure-sensitive adhesive thus obtained has a three-dimensional network structure. In addition, the acrylic polymer (a1) described above is presumed to exist in a form incorporated into the three-dimensional network structure, and is thought to play a role of a plasticizer.

The active energy ray-curable component (B) is not particularly limited as long as it is a component that can be cured by irradiation with an active energy ray and the above effects can be obtained. may be a mixture of Among them, polyfunctional acrylate-based monomers, which can provide pressure-sensitive adhesives that easily satisfy the mechanical properties described above, are preferred.

Examples of polyfunctional acrylate monomers include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate. , neopentyl glycol adipate di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphate di( meth)acrylate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, ethoxylated isocyanuric acid di(meth)acrylate, ethoxylated bisphenol A diacrylate, 9,9-bis[4-(2- Bifunctional type such as acryloyloxyethoxy)phenyl]fluorene; trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate , ethoxylated isocyanuric acid tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris-(2-(meth)acryloxyethyl)isocyanurate, ε-caprolactone-modified tris-(2-(meth) acryloxyethyl) isocyanurate; tetrafunctional types such as diglycerin tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; pentafunctional types such as propionic acid-modified dipentaerythritol penta(meth)acrylate; Hexafunctional types such as dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, and the like can be mentioned. These may be used individually by 1 type, and may be used in combination of 2 or more type. Moreover, from the viewpoint of excellent compatibility with the (meth)acrylic acid ester polymer, the polyfunctional acrylate monomer preferably has a molecular weight of less than 1,000.

Among the above, polyfunctional acrylate-based monomers containing an isocyanurate structure in the molecule are particularly preferable from the viewpoint of making it easier to satisfy the mechanical properties of the resulting pressure-sensitive adhesive.

An active energy ray-curable acrylate oligomer can also be used as the active energy ray-curable component (B). Examples of such acrylate oligomers include polyester acrylate, epoxy acrylate, polybutadiene acrylate, silicone acrylate, and the like.

In addition, since the urethane acrylate oligomer has a polyether such as polyethylene glycol for the purpose of imparting flexibility, the use of the urethane acrylate oligomer may not satisfy the transmittance at the wave number of 1105 to 1125 cm ⁻¹ described above. becomes higher. From this point of view, the adhesive composition P preferably does not contain a urethane acrylate oligomer and a urethane acrylate monomer. However, even when it is contained, the content is preferably suppressed to 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less.

The weight average molecular weight of the acrylate oligomer is preferably 50,000 or less, particularly preferably 1,000 to 50,000, and further preferably 3,000 to 40,000. These acrylate-based oligomers may be used singly or in combination of two or more.

The content of the active energy ray-curable component (B) in the adhesive composition P is preferably 0.001 parts by mass or more, and 0.01 parts by mass with respect to 100 parts by mass of the acrylic syrup (A). It is more preferably 0.05 parts by mass or more, particularly preferably 0.10 parts by mass or more. The content is preferably 40 parts by mass or less, more preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and even more preferably 1 part by mass or less. When the content of the active energy ray-curable component (B) is within the above range, the mechanical properties described above are more likely to be satisfied, and the resulting pressure-sensitive adhesive can have more excellent blister resistance. can.

(1-3) Thermal cross-linking agent (C)
The thermal cross-linking agent (C) is an optional component in the adhesive composition P, but is preferably contained in the adhesive composition P. The thermal cross-linking agent (C) cross-links the cured product ((meth)acrylic acid ester polymer) of the acrylic syrup (A) through the cross-linking reaction of the adhesive composition P2, and satisfactorily forms a cross-linked structure of a three-dimensional network structure. It becomes possible to This makes it easier to satisfy the mechanical properties described above.

The thermal cross-linking agent (C) may be any one that reacts with the reactive functional group of the acrylic polymer (a1) ((meth)acrylic acid ester polymer). For example, isocyanate cross-linking agent, epoxy cross-linking agent, amine cross-linking agent, melamine cross-linking agent, aziridine cross-linking agent, hydrazine cross-linking agent, aldehyde cross-linking agent, oxazoline cross-linking agent, metal alkoxide cross-linking agent, metal chelate cross-linking agents, metal salt-based cross-linking agents, ammonium salt-based cross-linking agents, and the like. Among the above, isocyanate-based cross-linking agents having excellent reactivity with hydroxyl groups and carboxy groups are preferred. In addition, a thermal crosslinking agent (C) can be used individually by 1 type or in combination of 2 or more types.

The isocyanate-based cross-linking agent contains at least a polyisocyanate compound. Examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; and alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. , and their biuret, isocyanurate, and adducts which are reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among them, trimethylolpropane-modified aromatic polyisocyanate, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate, are preferable from the viewpoint of reactivity with hydroxyl groups and carboxy groups.

It should be noted that the epoxy-based cross-linking agent requires the acrylic monomer to contain an acid-based monomer, which is disadvantageous when considering application to adherends that are corroded by acids such as metals. From this point of view, the adhesive composition P preferably does not contain an epoxy-based cross-linking agent. However, even when it is contained, the content of the epoxy-based cross-linking agent is preferably suppressed to 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less.

The content of the thermal cross-linking agent (C) in the adhesive composition P2 is preferably 0.01 parts by mass or more, particularly 0.05 parts by mass or more, relative to 100 parts by mass of the acrylic syrup (A). It is preferably 0.1 parts by mass or more. In addition, the content is preferably 1.0 parts by mass or less, particularly preferably 0.8 parts by mass or less, and further preferably 0.5 parts by mass or less. When the content of the thermal cross-linking agent (C) is within the above range, the above mechanical properties are more easily satisfied.

(1-4) Photopolymerization initiator (D)
When ultraviolet rays are used as active energy rays for curing the adhesive composition P, the adhesive composition P preferably further contains a photopolymerization initiator (D). By containing the photopolymerization initiator (D) in this way, the acrylic syrup (A) and the active energy ray-curable component (C) can be efficiently polymerized, and the polymerization curing time and the irradiation of the active energy ray can be reduced. can be reduced.

Examples of such a photopolymerization initiator (D) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy -2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenylketone, 2-methyl-1-[4- (methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylamino Benzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tertiary-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2 , 4-diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoate, oligo[2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone], 2,4 ,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and the like. These may be used alone or in combination of two or more.

The content of the photopolymerization initiator (D) in the adhesive composition P is preferably 0.01 parts by mass or more as a lower limit, particularly 0.1, with respect to 100 parts by mass of the acrylic syrup (A). It is preferably at least 0.2 parts by mass, more preferably at least 0.2 parts by mass. Also, the upper limit is preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and further preferably 1 part by mass or less.

(1-5) Various Additives The adhesive composition P may optionally contain various additives commonly used in acrylic adhesives, such as silane coupling agents, antistatic agents, tackifiers, and antioxidants. , light stabilizers, softeners, fillers, refractive index modifiers, rust inhibitors and the like can be added.

The adhesive composition P preferably further contains a silane coupling agent. As a result, the adhesiveness to the adherend is improved, and the blister resistance is further improved.

As the silane coupling agent, an organosilicon compound having at least one alkoxysilyl group in the molecule, having good compatibility with the (meth)acrylic acid ester polymer, and having optical transparency is preferred.

Such silane coupling agents include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropyltrimethoxysilane and like silicon compounds containing polymerizable unsaturated groups, 3-glycidoxypropyltrimethoxysilane, 2-( Silicon compounds having an epoxy structure such as 3,4-epoxycyclohexyl)ethyltrimethoxysilane, mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane , 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane and other amino group-containing silicon compounds, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or at least one of these, and an alkyl group-containing silicon compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, etc. and condensates of. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The content of the silane coupling agent in the adhesive composition P is preferably 0.01 parts by mass or more, particularly 0.05 parts by mass or more, relative to 100 parts by mass of the acrylic syrup (A). is preferred, and more preferably 0.1 parts by mass or more. Also, the content is preferably 1 part by mass or less, particularly preferably 0.5 parts by mass or less, and further preferably 0.3 parts by mass or less. When the content of the silane coupling agent is within the above range, the adhesiveness to the adherend is improved, making it easier to develop suitable adhesive strength.

(2) Production of adhesive composition The adhesive composition P is prepared by preparing an acrylic syrup (A), adding an active energy ray-curable component (B) to the obtained acrylic syrup (A), and optionally heat It can be produced by adding a cross-linking agent (C), a photopolymerization initiator (D) and an additive and thoroughly mixing them.

For the preparation of the acrylic syrup (A), it is preferable to first polymerize the acrylic polymer (a1) by a bulk polymerization method. Although the acrylic monomer remains as an unreacted product by this bulk polymerization, an additional acrylic monomer may be added as desired to adjust the viscosity, and the total amount thereof becomes the acrylic monomer (a2). As described above, the acrylic monomer to be further added is preferably the same component as the constituent monomers of the acrylic polymer (a1), and the blending ratio of each monomer is the same as that of the constituent monomers of the acrylic polymer (a1). It is preferably the same as the ratio.

(3) Formation of adhesive layer The adhesive layer 11 is an adhesive obtained by subjecting the adhesive composition P1 to active energy ray curing, or an adhesive obtained by subjecting the adhesive composition P2 to active energy ray curing and thermal crosslinking. It is preferably composed of

When using the adhesive composition P1, it can be preferably formed by applying the adhesive composition P1 to a desired object and then curing the adhesive composition P1 by irradiation with active energy rays. Further, when using the adhesive composition P2, after applying the adhesive composition P2 to a desired object, the adhesive composition P2 is cured by irradiation with active energy rays and thermally crosslinked, preferably can be formed.

Here, active energy rays refer to electromagnetic waves or charged particle rays that have energy quanta, and specifically include ultraviolet rays and electron beams. Among active energy rays, ultraviolet rays are particularly preferable because they are easy to handle.

Ultraviolet irradiation can be performed by a high-pressure mercury lamp, a fusion H lamp, a xenon lamp, ^or the ^like . is more preferable, and 80 to 200 mW/cm ² is particularly preferable. The amount of light is preferably 10 to 10,000 mJ/cm ² , more preferably 100 to 5,000 mJ/cm ² , and particularly preferably 500 to 2,000 mJ/cm ² . On the other hand, electron beam irradiation can be performed by an electron beam accelerator or the like, and the electron beam irradiation dose is preferably about 10 to 1000 krad.

The adhesive composition P in the present embodiment can be cured by high intensity (high illuminance) ultraviolet irradiation, so that the line speed can be increased and the productivity can be improved.

The thermal crosslinking of the adhesive composition P2 may be performed by heat treatment, or may be performed by providing a curing period of about 1 to 2 weeks at room temperature (eg, 23°C, 50% RH).

(4) Thickness of adhesive layer One of the technical features of the adhesive composition P in the present embodiment is that a thick film can be obtained by one coating and the curing time is short. have. Therefore, it has excellent cost competitiveness in technical fields where a thick pressure-sensitive adhesive layer is required. From such a viewpoint, the thickness of the pressure-sensitive adhesive layer 11 is preferably 60 µm or more, more preferably 90 µm or more, particularly preferably 150 µm or more, further preferably 400 µm or more. .

On the other hand, the upper limit of the thickness of the adhesive layer 11 is not particularly limited, but is preferably 10000 μm or less, more preferably 5000 μm or less, particularly preferably 1000 μm or less, and further 800 μm or less. is preferred.

1-2. Release Sheet The

release sheets

12a and 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, and are peeled off when the adhesive sheet 1 (adhesive layer 11) is used. In the adhesive sheet 1 according to this embodiment, one or both of the

release sheets

12a and 12b are not necessarily required.

Examples of the

release sheets

12a and 12b include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, and polybutylene. Terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene/(meth)acrylic acid copolymer film, ethylene/(meth)acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film, fluorine A resin film or the like is used. Crosslinked films of these are also used. Furthermore, a laminated film of these may be used.

The release surfaces of the

release sheets

12a and 12b (especially the surfaces in contact with the adhesive layer 11) are preferably subjected to a release treatment. Examples of release agents used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Of the

release sheets

12a and 12b, it is preferable that one of the release sheets is a heavy release type release sheet with a large release force, and the other release sheet is a light release type release sheet with a small release force.

Although there are no particular restrictions on the thickness of the

release sheets

12a and 12b, it is usually about 20 to 150 μm.

2. Manufacture of Adhesive Sheet As an example of manufacturing the adhesive sheet 1, the adhesive composition P1 is applied to the release surface of one release sheet 12a (or 12b) to form a coating layer, and then the other coating layer is coated on the coating layer. The release surface of the release sheet 12b (or 12a) is overlapped and laminated. Then, the coating layer is cured by irradiating the coating layer with an active energy ray through the release sheet 12a (or 12b) to form the pressure-sensitive adhesive layer 11 .

As another production example of the adhesive sheet 1, the adhesive composition P2 is applied to the release surface of one release sheet 12a (or 12b) to form a coating layer, and then the other release sheet is coated on the coating layer. 12b (or 12a) are laminated with the peeled surfaces overlapping each other. By irradiating the coating layer with active energy rays through the release sheet 12a (or 12b) and thermally cross-linking the coating layer, the coating layer is cured and thermally cross-linked to form the pressure-sensitive adhesive layer 11 .

As a method for applying the adhesive composition P, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used. Since the adhesive composition P is a solvent-free adhesive composition, thick film coating is easy.

3. Physical Properties of Adhesive Sheet (1) Adhesive Strength The adhesive strength of the adhesive sheet 1 of the present embodiment to alkali-free glass is preferably 10 N/25 mm or more, more preferably 20 N/25 mm or more, and particularly 25 N/25 mm. It is preferably 30 N/25 mm or more, more preferably 30 N/25 mm or more. This makes the blister resistance more excellent.

On the other hand, the upper limit of the adhesive strength is not particularly limited, but considering reworkability, it is preferably 100 N/25 mm or less, more preferably 90 N/25 mm or less, and particularly 80 N/25 mm or less. It is preferably 70 N/25 mm or less, most preferably 60 N/25 mm or less.

Here, the adhesive strength in this specification basically refers to the adhesive strength measured by the 180 degree peeling method according to JIS Z0237:2009, but the measurement sample is 25 mm wide and 100 mm long. It is attached to an adherend, pressurized at 0.5 MPa and 50° C. for 20 minutes, then left under normal pressure, 23° C. and 50% RH for 24 hours, and then measured at a peel rate of 300 mm/min. shall be

(2) Haze value The haze value of the adhesive layer 11 of the adhesive sheet 1 according to the present embodiment is preferably 10% or less, particularly preferably 5% or less, and further preferably 1% or less. is preferred. As a result, the transparency is very high, and it is suitable for optical applications (for displays). On the other hand, the lower limit of the haze value of the adhesive layer 11 is not particularly restricted. Although the lower limit value may be 0%, it is usually about 0.1% in consideration of measurement accuracy and the like. Here, the haze value in this specification is a value measured according to JIS K7136:2000.

(3) Total light transmittance The total light transmittance of the adhesive layer 11 of the adhesive sheet 1 according to the present embodiment is preferably 80% or more, more preferably 90% or more, and particularly 95% or more. is preferably 99% or more. As a result, the transparency is very high, and it is suitable for optical applications (for displays). The upper limit of the total light transmittance of the pressure-sensitive adhesive layer is not particularly limited, and may be 100%, or may slightly exceed 100% in relation to measurement. The total light transmittance in this specification is a value measured according to JIS K7361-1:1997.

(4) Chromaticity b*
The absolute value of the chromaticity b* defined by the CIE1976L*a*b* color system of the adhesive layer 11 of the adhesive sheet 1 according to the present embodiment is preferably 2.00 or less, and 1.40 or less. is more preferably 0.80 or less, and more preferably 0.50 or less. Accordingly, it can be said that the pressure-sensitive adhesive layer 11 is less colored and has excellent colorless transparency. The chromaticity b* is preferably within the above range even when the adhesive layer 11 is irradiated with ultraviolet light for 1000 hours (irradiance: 75 to 700 W/m ² ).

In the adhesive layer 11 of the adhesive sheet 1 according to the present embodiment, the absolute value of Δb*, which is the difference in chromaticity b* before and after 1000 hours of ultraviolet irradiation (irradiance: 75 to 700 W/m ² ), is It is preferably 1.50 or less, more preferably 0.80 or less, and particularly preferably 0.20 or less. As a result, it can be said that the yellowing due to ultraviolet irradiation is well suppressed and the weather resistance is excellent.

(5) Wet heat whitening resistance The wet heat whitening resistance of the pressure-sensitive adhesive layer 11 in the present embodiment can be quantitatively evaluated by the haze value. Specifically, a laminate obtained by laminating a glass plate (soda lime glass) and a plastic plate (acrylic resin plate, thickness 0.7 mm) with the adhesive layer 11 in this embodiment was heated at 85°C and 85°C. After performing a durability test in which it is stored for 120 hours under moist heat conditions of % RH, the haze value (%) when stored for 24 hours at normal temperature and humidity of 23 ° C. and 50% RH is converted to the haze value before the durability test ( %) is preferably less than 5.0 points, more preferably less than 2.0 points, particularly preferably less than 1.0 points, and further preferably less than 0.5 points. Less than a point is preferred. When the increase in haze value is above, the increase in haze value is small even after being placed under moist heat conditions, and it can be said that the whitening of the pressure-sensitive adhesive is suppressed.

4. Use of Adhesive Sheet The adhesive sheet 1 according to this embodiment can also be suitably used to bond two rigid bodies together. It is more difficult to bond hard bodies together with a pressure-sensitive adhesive layer than to bond films together or a film and a hard body, and the yield at the time of bonding tends to decrease. According to 1, two hard bodies can be satisfactorily bonded.

The term "rigid body" as used herein refers to a member whose structure can be bent at an angle of less than 90° without being irreversibly deformed. The angle is preferably less than 60°, more preferably less than 45°, particularly preferably less than 10° and even more preferably less than 5°. The bendable angle (bending angle) refers to the angle at which a rigid body is placed on a horizontal surface, one end is fixed, and the other end is raised from the horizontal surface. say the angle. The hard body may consist of a single layer or a single member, or may consist of multiple layers or multiple members. In the latter case, it is used as one object consisting of a plurality of layers or a plurality of members at the time of lamination with the adhesive layer, and the object as a whole satisfies the above bending angle. Alternatively, even if the member does not satisfy the above bending angle, the object can be said to be a rigid body.

Specifically, the pressure-sensitive adhesive sheet 1 according to the present embodiment can be suitably used for bonding two rigid members constituting a display body, as described later.

[Laminate]
A laminate according to one embodiment of the present invention includes two display body-constituting members and an adhesive layer sandwiched between the two display body-constituting members. It is formed from the adhesive layer of the adhesive sheet. This laminate is a display (display panel) or a member thereof.

At least one of the display body constituent members preferably includes a plastic plate. Unlike a glass plate, a plastic plate generates outgas and permeates water vapor under high temperature and high humidity conditions. As a result, generally, blisters such as air bubbles, floating, and peeling tend to occur between the plastic plate and the adhesive layer. However, in the laminate according to the present embodiment, by using the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet described above, air bubbles, The occurrence of blisters such as floating and peeling is suppressed.

FIG. 2 shows a specific configuration as an example of the laminate according to this embodiment.
As shown in FIG. 2, the laminated body 2 according to the present embodiment includes a first display body constituting member 21, a second display body constituting member 22, and a first display body constituting member 21 and a second display body constituting member 22 positioned therebetween. It is composed of the member 21 and the pressure-sensitive adhesive layer 11 sandwiched between the second display body-constituting member 22 .

As the laminate 2, for example, it may be a member constituting a part of a display such as a liquid crystal (LCD) display, a light emitting diode (LED) display, an organic electroluminescence (organic EL) display, electronic paper, etc. The display body itself may be used. Note that the display may be a touch panel.

The adhesive layer 11 in the laminate 2 is formed from the adhesive layer 11 of the adhesive sheet 1 described above, and is preferably the adhesive layer 11 itself.

The first display member constituting member 21 and the second display member constituting member 22 are not particularly limited as long as the adhesive layer 11 can be adhered thereto. Further, the first display body constituent member 21 and the second display body constituent member 22 may be made of the same material or may be made of different materials.

Specifically, the first display body constituent member 21 is preferably a protective panel made of a plastic plate or a laminate including a plastic plate. These members are usually rigid bodies.

The plastic plate is not particularly limited, and examples thereof include acrylic resin plates such as a polycarbonate resin (PC) plate and a polymethyl methacrylate resin (PMMA) plate, acrylic resin such as a polymethyl methacrylate resin layer on a polycarbonate resin plate. Examples include a plastic plate having laminated layers. The above-mentioned polycarbonate resin plate may contain a resin other than polycarbonate resin as a constituent material, and the above-mentioned acrylic resin plate may contain a resin other than acrylic resin as a constituent material. may contain.

Although the thickness of the plastic plate is not particularly limited, it is usually 0.2 to 5 mm, preferably 0.4 to 3 mm, particularly preferably 0.6 to 2.5 mm, more preferably 0.5 mm to 0.5 mm. 8 to 2.1 mm.

Various functional layers (transparent conductive film, metal layer, silica layer, hard coat layer, antiglare layer, ultraviolet absorption layer, etc.) may be provided on one or both sides of the plastic plate. Wiring may be formed. Moreover, the transparent conductive film and the metal layer may be patterned.

The second display body constituent member 22 is not particularly limited, but includes a desired optical member, a display body module, a member of the display body module, and the like. A display module is usually a rigid body.

Examples of the optical member include anti-scattering films, polarizing plates (polarizing films), polarizers, retardation plates (retardation films), viewing angle compensation films, brightness enhancement films, contrast enhancement films, liquid crystal polymer films, and diffusion films. , transflective films, transparent conductive films, and the like. Examples of the anti-scattering film include a hard coat film in which a hard coat layer is formed on one side of a base film.

Further, the optical member may be a glass plate or a laminated member including a glass plate. The glass plate is not particularly limited, and examples thereof include chemically strengthened glass, alkali-free glass, quartz glass, soda lime glass, barium-strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, and barium borosilicate glass. etc. These optical members are usually rigid bodies.

The thickness of the glass plate is not particularly limited, but is usually 0.1 to 10 mm, preferably 0.2 to 8 mm, more preferably 0.8 to 4 mm, and particularly preferably 1 to 2 mm. be.

Examples of the display modules include liquid crystal (LCD) modules, light emitting diode (LED) modules, organic electroluminescence (organic EL) modules, and electronic paper. The above-described glass plate, plastic plate, optical member, and the like are usually laminated on these display modules. For example, LCD modules are laminated with polarizers, which form one surface of the LCD module.

In the present embodiment, the first display member forming member 21 may be a liquid crystal cell, and the second display member forming member 22 may be a backlight unit.

In order to manufacture the laminate 2, as an example, one of the release sheets 12a of the adhesive sheet 1 is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 is transferred to one of the first display body constituent members 21. Stick to the surface.

Next, the other release sheet 12b is peeled off from the adhesive layer 11 of the adhesive sheet 1, and the exposed adhesive layer 11 of the adhesive sheet 1 and the second display member constituting member 22 are laminated to obtain a laminate. . As another example, the bonding order of the first display body forming member 21 and the second display body forming member 22 may be changed.

The adhesive layer 11 in the above laminate 2 has excellent blister resistance, so even when the laminate 2 is placed under conditions of, for example, 85 ° C. and 85% RH for 72 hours, the adhesive layer 11 and each display body The occurrence of air bubbles, floating, peeling, etc. at the interfaces with the

constituent members

21 and 22 is suppressed.

The embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiment is meant to include all design changes and equivalents that fall within the technical scope of the present invention.

For example, one of the

release sheets

12a and 12b in the adhesive sheet 1 may be omitted.

Although the present invention will be described in more detail with reference to examples and the like, the scope of the present invention is not limited to these examples and the like.

[Example 1]
1. Preparation of acrylic syrup 55 parts by mass of n-butyl acrylate, 10 parts by mass of isobornyl acrylate, 10 parts by mass of acryloylmorpholine, and 25 parts by mass of 4-hydroxybutyl acrylate are copolymerized by a bulk polymerization method to obtain (meth)acrylic syrup. An acid ester polymer was produced. This state is syrupy and contains the acrylic polymer (meth)acrylic acid ester polymer and the unreacted acrylic monomers. The polymer content in the syrup was 22% by mass. Further, when the molecular weight of the (meth)acrylic acid ester polymer was measured by the following method, the weight average molecular weight (Mw) was 800,000.

To 100 parts by mass of the syrup, 20.4 parts by mass of butyl acrylate, 3.7 parts by mass of isobornyl acrylate, 3.7 parts by mass of acryloylmorpholine, and 9.3 parts by mass of 4-hydroxybutyl acrylate are added to obtain a polymer. The ratio was adjusted to 16% by mass (monomer ratio: 84% by mass), and this was used as acrylic syrup (A).

2. Preparation of adhesive composition 100 parts by mass of the above acrylic syrup (A) and ε-caprolactone-modified tris-(2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd.) as the active energy ray-curable component (B) Product name “NK Ester A-9300-1CL”) 0.15 parts by mass, and a trifunctional isocyanate cross-linking agent (manufactured by Tosoh Corporation, product name “Coronate HXR”) as a thermal cross-linking agent (C) 0.10 parts by mass , 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one 0.30 parts by weight as a photopolymerization initiator (D) and 0.10 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent were mixed and thoroughly stirred to obtain an adhesive composition P.

Here, Table 1 shows each formulation of the adhesive composition when the acrylic syrup (A) is 100 parts by mass (all solid content). Details of abbreviations and the like in Table 1 are as follows.
[(Meth)acrylate polymer]
BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate IBXA: isobornyl acrylate ACMO: N-acryloylmorpholine MA: methyl acrylate 4HBA: 4-hydroxybutyl acrylate

3. Formation of adhesive layer The adhesive composition P is applied to the release-treated surface of a heavy-release release sheet (manufactured by Lintec Co., Ltd., product name "SP-PET752150") in which one side of a polyethylene terephthalate film is release-treated with a silicone-based release agent. , and a knife coater to form a coating layer. A light release release sheet (manufactured by Lintec Corporation, product name "SP-PET381130 ”) was laminated.

Next, the coating layer was irradiated with ultraviolet light under the following conditions through a light release type release sheet to cure the coating layer and form a pressure-sensitive adhesive layer having a thickness of 100 μm. After that, it was cured for 7 days under conditions of 23° C. and 50% RH to obtain an adhesive sheet having a structure of heavy release release sheet/adhesive layer (thickness: 100 μm)/light release release sheet.
<Ultraviolet irradiation conditions>
・Using a high-pressure mercury lamp ・Illuminance 100mW/cm ² , Light quantity 2000mJ/cm ²
・Using “UVPF-A1” manufactured by Eye Graphics Co., Ltd. for UV illuminance and photometer

The thickness of the pressure-sensitive adhesive layer is a value measured using a constant pressure thickness measuring instrument (manufactured by Teclock, product name "PG-02") in accordance with JIS K7130.

[Examples 2 to 8, Comparative Examples 1 to 2, 4]
Composition and weight average molecular weight (Mw) of (meth) acrylic acid ester polymer, polymer ratio/monomer ratio in acrylic syrup (A), amount of active energy ray-curable component (B), amount of cross-linking agent (C) The same procedure as in Example 1 was carried out except that the compounding amount, the photopolymerization initiator (D) compounding amount, the silane coupling agent compounding amount, the ultraviolet irradiation conditions, and the thickness of the pressure-sensitive adhesive layer were changed as shown in Table 1. to produce a pressure-sensitive adhesive sheet.

[Comparative Example 3]
By dehydration condensation of 2-hydroxyethyl acrylate (HEA), isophorone diisocyanate (IPDA), and polypropylene glycol (PPG), isophorone diisocyanate and polyethylene glycol are alternately repeated, and both ends are formed via isophorone diisocyanate. A urethane acrylate oligomer (Mw: 20,000) capped with 2-hydroxyethyl acrylate was obtained.

The resulting urethane acrylate oligomer was diluted with 2-ethylhexyl acrylate, isobornyl acrylate, and 4-hydroxybutyl acrylate to a concentration of 20% by mass to obtain a syrup. To 100 parts by mass of this syrup, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropane-1-as a photopolymerization initiator (D) 0.30 parts by mass of ON and 0.10 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent were mixed and thoroughly stirred to obtain an adhesive composition P.

A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 using the above-described pressure-sensitive adhesive composition P. However, the thickness of the adhesive layer was set to 200 μm.

Here, the weight-average molecular weight (Mw) described above is a polystyrene-equivalent weight-average molecular weight measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement).
<Measurement conditions>
・ GPC measurement device: HLC-8020 manufactured by Tosoh Corporation
・ GPC column (passed in the following order): TSK guard column HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (x2)
TSK gel G2000HXL
・Measurement solvent: tetrahydrofuran ・Measurement temperature: 40°C

[Test Example 1] (Measurement of gel fraction)
The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut into a size of 80 mm × 80 mm, the pressure-sensitive adhesive layer was wrapped in a polyester mesh (mesh size 200), and the mass was weighed with a precision balance. By subtracting the individual mass, the mass of the adhesive alone was calculated. Let the mass at this time be M1.

Next, the adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. After that, the pressure-sensitive adhesive was taken out and air-dried for 24 hours in an environment of 23° C. and 50% relative humidity, and further dried in an oven at 80° C. for 12 hours. After drying, the mass was weighed with a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. Let the mass at this time be M2. A gel fraction (%) is represented by (M2/M1)×100. Table 2 shows the results.

[Test Example 2] (Tensile test)
After laminating a plurality of pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples to a total thickness of 800 μm, a sample of 10 mm width×75 mm length was cut out. The above sample is set in a tensile tester (manufactured by Orientec, product name "Tensilon") so that the sample measurement site is 10 mm wide x 20 mm long (extending direction), and the test is performed in an environment of 23 ° C. and 50% RH. Using a tensile tester, the film was elongated at a tensile speed of 200 mm/min, and the stress (N/m ² ) when elongated by 200% was measured. Table 2 shows the results.

[Test Example 3] (Measurement of shear modulus)
The release sheets were peeled off from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and a plurality of pressure-sensitive adhesive layers were laminated to a thickness of 3 mm. A cylinder with a diameter of 8 mm (height: 3 mm) was punched out from the resulting laminate of pressure-sensitive adhesive layers, and this was used as a sample.

For the above samples, the shear modulus (MPa) was measured according to JIS K7244-6 by the torsional shear method using a viscoelasticity measuring device (manufactured by Physica, product name "MCR300") under the following conditions. Table 2 shows the results.
Measurement frequency: 1Hz
Measurement temperature: 23°C

[Test Example 4] (IR measurement)
The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut into 1-cm squares and used as samples. The light release film was peeled off from the sample, and an IR measuring device (manufactured by PerkinElmer, product name "Spectrum 100 FT-IR Spectrometer") was used to measure the surface of the adhesive layer of the sample by the ATR method using a diamond prism. Transmittance (%) was measured in the range of 4000 cm ⁻¹ . Among them, the transmittance (%) of the peak near 1110 cm ⁻¹ was read. The results are shown in Table 2 together with peak wavenumbers.

[Test Example 5] (Measurement of water vapor permeability)
The pressure-sensitive adhesive layers of the 200 μm-thick pressure-sensitive adhesive sheets obtained in Examples (other than Examples 1 and 3) and Comparative Examples were covered with a triacetyl cellulose (TAC) film (manufactured by Konica Minolta, product name “Konica TAC KC4UAW”, thickness : 40 μm, water vapor transmission rate 841 g/(m 2 ·24 h)), and this was used as a sample. The water vapor permeability (g/(m ² ·24h)) of the sample was measured in accordance with JIS Z0208 under the conditions of 40°C and 90% RH. Table 2 shows the results.

[Test Example 6] (Measurement of haze value)
The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were attached to glass to prepare measurement samples. After performing background measurement on glass, the haze value (%) was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH5000") according to JIS K7136: 2000 for the measurement sample. It was measured. Table 2 shows the results.

[Test Example 7] (Measurement of total light transmittance)
The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were attached to glass to prepare measurement samples. After performing background measurement with glass, the above measurement sample is measured according to JIS K7361-1: 1997 with a haze meter (manufactured by Nippon Denshoku Industries, product name “NDH5000”). Total light transmittance (%) was measured. Table 2 shows the results.

[Test Example 8] (Measurement of adhesive strength)
The light-release type release sheet was peeled off from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was coated with a polyethylene terephthalate (PET) film having an easy-adhesion layer (manufactured by Toyobo Co., Ltd., product name "PET A4300"). , thickness: 100 μm) to obtain a laminate of heavy release type release sheet/adhesive layer/PET film. The laminate thus obtained was cut into a piece having a width of 25 mm and a length of 100 mm, which was used as a sample.

In an environment of 23 ° C. and 50% RH, the heavy release release sheet was peeled off from the sample, and the exposed adhesive layer was attached to non-alkali glass (manufactured by Corning, product name "Eagle XG"). , pressurized at 0.5 MPa and 50° C. for 20 minutes in an autoclave manufactured by Kurihara Seisakusho. Then, after leaving it for 24 hours under the conditions of 23° C. and 50% RH, using a tensile tester (manufactured by Orientec Co., Ltd., product name “Tensilon”), under the conditions of a peel speed of 300 mm / min and a peel angle of 180 degrees. Adhesive strength (N/25 mm) was measured. Conditions other than those described here were measured according to JIS Z0237:2009. Table 2 shows the results.

[Test Example 9] (Measurement of chromaticity b*)
The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were sandwiched between two soda-lime glass plates (manufactured by Nippon Sheet Glass Co., Ltd., thickness: 0.7 mm), and this was used as a sample. Using a spectrophotometer (manufactured by Shimadzu Corporation, product name "UV-3600"), the chromaticity b* (initial) defined by the CIE1976 L*a*b* color system was measured for the sample. Table 2 shows the results.

Next, in accordance with JIS A1439:2016, the sample was subjected to an ultraviolet fade meter (Fade) (manufactured by Suga Test Instruments Co., Ltd., product name "U48") in an atmosphere of 63 ± 3 ° C (sample temperature) and 50% RH. ) was used to irradiate ultraviolet rays for 1000 hours (irradiance: 500±100 W/m ² ). Subsequent samples were measured for chromaticity b* (after UV) in the same manner as above. Also, Δb*, which is the difference in chromaticity b* before and after the ultraviolet irradiation, was calculated. Table 2 shows the results.

[Test Example 10] (Evaluation of weather resistance)
Based on the absolute value of Δb* obtained in Test Example 9, weather resistance was evaluated according to the following evaluation criteria. Table 2 shows the results.
A: The absolute value of Δb* was 0.20 or less.
Good: The absolute value of Δb* was more than 0.20 and less than 1.50.
x: The absolute value of Δb* was 1.50 or more.

[Test Example 11] (Evaluation of blister resistance)
The light-release type release sheet was peeled off from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was transferred to a plastic plate (Mitsubishi Gas Chemical Co., Ltd. company, product name "Iupilon Sheet MR58U", thickness: 0.7 mm, containing ultraviolet absorber) was attached to the PC board side to obtain a plastic board with an adhesive layer.

The heavy release type release sheet is peeled off from the plastic plate with the adhesive layer obtained above, and the plastic plate is attached to a soda lime glass plate (manufactured by Nippon Sheet Glass Co., Ltd.) with a size of 70 mm × 150 mm through the exposed adhesive layer. , thickness: 0.7 mm). After autoclaving for 30 minutes under conditions of 50° C. and 0.5 MPa, it was allowed to stand at normal pressure, 23° C. and 50% RH for 24 hours, and this was used as a sample.

The obtained sample was stored for 72 hours under high temperature and high humidity conditions of 85° C. and 85% RH. Then, the state of the interface between the pressure-sensitive adhesive layer and the adherend (plastic plate, glass plate) was visually observed, and the blister resistance was evaluated according to the following criteria. Table 2 shows the results.
⊚: There were no air bubbles, floating or peeling.
Good: Bubbles with a diameter of less than 1 mm were generated, but no lifting or peeling occurred.
x: Air bubbles, floating, and peeling occurred on the whole.

[Test Example 12] (Evaluation of wet heat whitening resistance)
The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples are formed of a 1.1 mm-thick alkali-free glass plate (water vapor permeability of 0.0006 g/(m ² · 24 h)) and a 0.7 mm-thick It was sandwiched between plastic plates (manufactured by Mitsubishi Rayon Co., Ltd., product name “Acrylite MR-200”, water vapor transmission rate 44 g/(m ² ·24 h ·100 μm)) to obtain a laminate. The resulting laminate was autoclaved under conditions of 50° C. and 0.5 MPa for 20 minutes, and then allowed to stand at normal pressure, 23° C. and 50% RH for 24 hours, and used as a sample.

For the above samples, the haze value (haze value before durability test; %) was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-5000") according to JIS K7136:2000.

Next, the sample was stored for 120 hours under wet heat conditions of 85°C and 85% RH (durability test), and then left for 24 hours at normal temperature and normal humidity of 23°C and 50% RH. The haze value (haze value after durability test; %) of the sample was measured in the same manner as above.

Based on the measured difference (point) in the haze value before and after the durability test, the wet heat whitening resistance was evaluated according to the following criteria.
A: The difference in haze value is less than 0.5 points.
Good: The difference in haze value is 0.5 points or more and less than 2.0 points.
x: The difference in haze value is 2.0 points or more.

As can be seen from Table 2, the pressure-sensitive adhesive sheets produced in Examples had excellent weather resistance and blister resistance, as well as excellent wet heat whitening resistance.

The pressure-sensitive adhesive sheet according to the present invention can be suitably used, for example, for bonding a protective panel made of a plastic plate and a desired display body constituent member.

DESCRIPTION OF SYMBOLS 1... Adhesive sheet 11...

Adhesive layer

12a, 12b... Release sheet 2... Laminated body 21... First display body component 22... Second display body component

Claims

A pressure-sensitive adhesive sheet having at least a pressure-sensitive adhesive layer,
The transmittance at a wave number of 1105 to 1125 cm −1 in IR transmittance measurement of the adhesive layer is 50% or more,
A tensile test was performed in which the pressure-sensitive adhesive layer was elongated at a tensile speed of 200 mm/min, and the stress when elongated by 200% was 6.15 × 10 4 /m 2 or more and 1.0 × 10 7 N/m 2 or less. An adhesive sheet characterized by:
The pressure-sensitive adhesive sheet according to claim 1, wherein the thickness of the pressure-sensitive adhesive layer is 60 µm or more and 10000 µm or less.
The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is a solvent-free acrylic pressure-sensitive adhesive.
The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive contains a (meth)acrylic acid ester polymer or a crosslinked product thereof, and a cured product of an active energy ray-curable component.
Equipped with two release sheets,
2. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer is sandwiched between the two release sheets so as to be in contact with the release surfaces of the two release sheets.
A method for producing the pressure-sensitive adhesive sheet according to any one of claims 1 to 5,
an acrylic syrup (A) containing an acrylic polymer (a1) and an acrylic monomer (a2);
An adhesive composition containing an active energy ray-curable component (B) (excluding the acrylic syrup (A) component) is cured with an active energy ray to form the adhesive layer. A method for manufacturing an adhesive sheet.
A method for producing the pressure-sensitive adhesive sheet according to any one of claims 1 to 5,
an acrylic syrup (A) containing an acrylic polymer (a1) and an acrylic monomer (a2);
an active energy ray-curable component (B) (excluding the acrylic syrup (A) component);
A method for producing a pressure-sensitive adhesive sheet, comprising subjecting a pressure-sensitive adhesive composition containing a thermal cross-linking agent (C) to active energy ray curing and heat-crosslinking to form the pressure-sensitive adhesive layer.