CN116042128A

CN116042128A - Optical adhesive sheet with release liner

Info

Publication number: CN116042128A
Application number: CN202211334572.4A
Authority: CN
Inventors: 山本真也; 野田美菜子; 永田拓也
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2021-10-28
Filing date: 2022-10-28
Publication date: 2023-05-02
Also published as: KR20230061258A; TW202323025A; JP2023065821A

Abstract

Provided is a release liner-attached optical adhesive sheet suitable for achieving good release liner releasability. The release liner-equipped adhesive sheet (X) is provided with an adhesive sheet (10) and release liners (20, 30). The release liner (20) is in releasable contact with the 1 st face (11) of the adhesive sheet (10). The release liner (30) is in releasable contact with the 2 nd face (12) of the adhesive sheet (10). The adhesive sheet (10) has a shear storage modulus of 10MPa or less in the range of-40 ℃ to 100 ℃. The ratio of the release force F2 for releasing the release liner (30) from the adhesive sheet (10) to the release force F1 for releasing the release liner (20) from the adhesive sheet (10) is 0.1 to 0.6.

Description

Optical adhesive sheet with release liner

Technical Field

The present invention relates to an optical adhesive sheet with a release liner.

Background

The display panel has a laminated structure including elements such as a pixel panel, a polarizing plate, a touch panel, and a cover film. In the manufacturing process of such a display panel, for example, an optically transparent adhesive sheet (optical adhesive sheet) is used in order to join elements included in the laminated structure to each other. The optical adhesive sheet is produced as a release liner-coated optical adhesive sheet having both surfaces covered with a release liner.

On the other hand, for example, for a smart phone and a tablet terminal, a display panel that can be repeatedly folded (folded) has been developed. The foldable display panel is particularly capable of being repeatedly deformed between a curved shape and a flat non-curved shape. In such a folding display panel, each element in the laminated structure is made to be bendable repeatedly, and a thin optical adhesive sheet is used for bonding between the elements. An optical pressure-sensitive adhesive sheet for flexible devices such as a folding display panel is described in patent document 1 below, for example.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2018-111754

Disclosure of Invention

Problems to be solved by the invention

An optical pressure-sensitive adhesive sheet for flexible devices is required to be highly soft in order to have sufficient follow-up property for an adherend when the device is deformed and excellent stress relaxation property. However, in the release liner-attached optical adhesive sheet, the softer the optical adhesive sheet, the more likely the occurrence of defects at the time of release of the release liner. The adverse conditions include excessive deformation and defects in the optical adhesive sheet. The adverse conditions also include an undesired peeling of one release liner from the other release liner when the other release liner is peeled from the optical adhesive sheet.

The present invention provides a release liner-attached optical adhesive sheet suitable for achieving good release liner releasability.

Solution for solving the problem

The present invention [1] includes an optical adhesive sheet with a release liner, comprising: an optical adhesive sheet having a 1 st surface and a 2 nd surface on the opposite side of the 1 st surface; a 1 st release liner in releasable contact with the 1 st surface; and a 2 nd release liner in releasable contact with the 2 nd surface, wherein the optical adhesive sheet has a shear storage modulus of 10MPa or less in a range of-40 ℃ to 100 ℃, and a ratio of a release force F2 for releasing the 2 nd release liner from the optical adhesive sheet to a release force F1 for releasing the 1 st release liner from the optical adhesive sheet is 0.1 to 0.6.

The invention [2] includes the release liner-equipped optical adhesive sheet according to [1], wherein the 1 st release liner has a 1 st base film and a 1 st release layer, the 1 st release layer is disposed on the 1 st base film side of the optical adhesive sheet and is in contact with the optical adhesive sheet, the 2 nd release liner has a 2 nd base film and a 2 nd release layer, the 2 nd release layer is disposed on the 2 nd base film side of the optical adhesive sheet and is in contact with the optical adhesive sheet, and a ratio of a thickness of the 2 nd release layer to a thickness of the 1 st release layer is 0.16 or more and 15 or less.

The invention [3] includes the release liner-equipped optical adhesive sheet according to [2], wherein the 1 st release layer and/or the 2 nd release layer is a silicone release layer.

The invention [4] includes the release liner-equipped optical adhesive sheet according to any one of the above [1] to [3], wherein the optical adhesive sheet has a shear storage modulus of 1MPa or less at 25 ℃.

The invention [5] includes the release liner-equipped optical adhesive sheet according to any one of [1] to [4], wherein the optical adhesive sheet has a shear storage modulus of 0.005MPa or more in a range of-40℃to 100 ℃.

ADVANTAGEOUS EFFECTS OF INVENTION

In the release liner-equipped optical adhesive sheet of the present invention, as described above, the optical adhesive sheet has a shear storage modulus of 10MPa or less in the range of-40 ℃ to 100 ℃, and the ratio (F2/F1) of the release forces F1 and F2 of the 1 st/2 nd release liners in contact with both surfaces of the soft optical adhesive sheet is 0.1 to 0.6. Such a release liner-attached optical adhesive sheet is suitable for achieving good release liner releasability.

Drawings

Fig. 1 is a schematic cross-sectional view of one embodiment of the release liner-equipped optical adhesive sheet of the present invention.

Description of the reference numerals

X pressure-sensitive adhesive sheet with release liner (optical pressure-sensitive adhesive sheet with release liner)

H thickness direction

10 pressure-sensitive adhesive sheet (optical pressure-sensitive adhesive sheet)

11 st face 1

12 nd surface 2

20 Release liner (Release liner 1)

21 base film (1 st base film)

22 release layer (release layer 1)

30 Release liner (Release liner No. 2)

31 base film (2 nd base film)

32 release layer (release layer 2)

Detailed Description

As shown in fig. 1, a release liner-equipped adhesive sheet X, which is one embodiment of the release liner-equipped optical adhesive sheet of the present invention, includes an adhesive sheet 10, a release liner 20 (release liner 1) and a release liner 30 (release liner 2). The pressure-sensitive adhesive sheet 10 has a 1 st surface 11 and a 2 nd surface 12 on the opposite side of the 1 st surface 11. The release liner 20 is in releasable contact with the 1 st face 11. The release liner 30 is in releasable contact with the 2 nd side 12. That is, the release liner-attached adhesive sheet X includes the release liner 20, the adhesive sheet 10, and the release liner 30 in this order in the thickness direction H. The release liner-attached adhesive sheet X is expanded in a direction (in-plane direction) orthogonal to the thickness direction H.

The adhesive sheet 10 is an optically transparent adhesive sheet (optical adhesive sheet). The adhesive sheet 10 is, for example, an adhesive sheet disposed at a light passing portion in a flexible device. As the flexible device, for example, a flexible display panel can be cited. The flexible display panel has a laminated structure including elements such as a pixel panel, a film-like polarizing plate (polarizing film), a touch panel, and a cover film. The adhesive sheet 10 is used for bonding elements included in a laminated structure to each other, for example, in a process of manufacturing a display panel. The release liner 20 is a release liner having a relatively large release force (heavy release liner), and the release liner 30 is a release liner having a relatively small release force (light release liner). The release liner 30 and the release liner 20 are sequentially peeled from the adhesive sheet 10 when the adhesive sheet 10 is used.

The adhesive sheet 10 has a shear storage modulus of 10MPa or less in the range of-40 ℃ to 100 ℃. That is, the adhesive sheet 10 has a maximum shear storage modulus of 10MPa or less at-40 to 100 ℃. Such a configuration is suitable for ensuring high flexibility required for flexible device application in the adhesive sheet 10. From the viewpoint of ensuring high soft properties, the maximum shear storage modulus is preferably 8MPa or less, more preferably 6MPa or less, still more preferably 5MPa or less, still more preferably 4.7MPa or less, and particularly preferably 4.5MPa or less. The maximum shear storage modulus is preferably 0.005MPa or more, more preferably 0.01MPa or more, still more preferably 0.05MPa or more, still more preferably 0.1MPa or more, and particularly preferably 0.5MPa or more, from the viewpoint of securing cohesive force as a pressure-sensitive adhesive material in the pressure-sensitive adhesive sheet 10. The method for determining the shear storage modulus is as described in the following description of the examples. Examples of the method for adjusting the shear storage modulus of the pressure-sensitive adhesive sheet 10 include selection of the type of the base polymer in the pressure-sensitive adhesive sheet 10, adjustment of the molecular weight, and adjustment of the blending amount. Examples of the method for adjusting the shear storage modulus of the pressure-sensitive adhesive sheet 10 include selection of the type and adjustment of the amount of the functional group in the base polymer.

From the viewpoint of ensuring the soft property of the adhesive sheet 10 in the room temperature region, the shear storage modulus of the adhesive sheet 10 at 25 ℃ is preferably 1MPa or less, more preferably 500kPa or less, still more preferably 300kPa or less, still more preferably 100kPa or less, still more preferably 70kPa or less, and particularly preferably 50kPa or less. From the viewpoint of ensuring cohesive force of the adhesive sheet 10 in the room temperature region, the shear storage modulus of the adhesive sheet 10 at 25 ℃ is preferably 5kPa or more, more preferably 10kPa or more, still more preferably 15kPa or more, and particularly preferably 20kPa or more.

The ratio (F2/F1) of the release force F2 for peeling the release liner 30 from the adhesive sheet 10 to the release force F1 for peeling the release liner 20 from the adhesive sheet 10 is 0.6 or less, preferably 0.5 or less, and more preferably 0.45 or less. The release liner-attached adhesive sheet X having the ratio (F2/F1) of the release forces F1, F2 of the release liners 20, 30 in contact with both sides of the soft adhesive sheet 10 in such a range as described above is suitable for suppressing unexpected peeling of the release liner 20 when the release liner 30 is peeled from the adhesive sheet 10. For example, as shown in the examples described below. The peel forces F1 and F2 are values obtained by performing a peel test for peeling the release liner from the adhesive sheet 10 under conditions of a measurement temperature of 25 ℃, a peel angle of 180 ° and a stretching speed of 300 mm/min, respectively (specifically, as will be described later in the examples). The ratio (F2/F1) of the peeling forces F1, F2 is 0.1 or more, preferably 0.15 or more, more preferably 0.2 or more. The release liner-attached adhesive sheet X having the ratio (F2/F1) of the release forces F1, F2 of the release liners 20, 30 in contact with both sides of the soft adhesive sheet 10 in such a range as described above is suitable for ensuring the ease of release of the release liners 20, 30 from the adhesive sheet 10 in a well-balanced manner. On this basis, the release liner-attached adhesive sheet X having the ratio (F2/F1) of the release forces F1, F2 in the above-described range is suitable for suppressing excessive deformation and defects of the adhesive sheet 10 at the time of peeling of the release liners 20, 30. As described above, the release liner-attached adhesive sheet X is suitable for achieving good release liner peelability.

From the viewpoint of suppressing accidental peeling of the release liner 20 when the release liner 30 is peeled from the adhesive sheet 10, the peeling force F1 is preferably 0.17N/50mm or more, more preferably 0.20N/50mm or more, and still more preferably 0.23N/50mm or more. From the viewpoint of ensuring the release easiness of the release liner 20 from the adhesive sheet 10, the release force F1 is preferably 1N/50mm or less, more preferably 0.8N/50mm or less, still more preferably 0.6N/50mm or less, particularly preferably 0.5N/50mm or less. Examples of the method for adjusting the release force F1 include selection of the type of the release layer 22 (described later) of the release liner 20 and adjustment of the thickness. Examples of the method for adjusting the peeling force F1 include selection of the type of the base polymer in the pressure-sensitive adhesive sheet 10, adjustment of the molecular weight, and adjustment of the blending amount. The method of adjusting the peeling force F1 includes selection of the types of components other than the base polymer in the pressure-sensitive adhesive sheet 10 and adjustment of the blending amount of the components. Examples of the component include a crosslinking agent, a silane coupling agent, and an oligomer. These adjustment methods are also similar to those for the peeling force F2.

From the viewpoint of suppressing accidental peeling of the release liner 30 from the adhesive sheet 10, the peeling force F2 is preferably 0.05N/50mm or more, more preferably 0.06N/50mm or more. From the viewpoint of ensuring the release easiness of the release liner 30 from the adhesive sheet 10, the release force F2 is preferably 0.5N/50mm or less, more preferably 0.4N/50mm or less, still more preferably 0.3N/50mm or less, and particularly preferably 0.2N/50mm or less. Examples of the method for adjusting the release force F2 include selection of the type and adjustment of the thickness of the release layer 32 (described later) of the release liner 30. The method of adjusting the peeling force F2 includes selection of the type of the base polymer, adjustment of the molecular weight and adjustment of the blending amount of the base polymer, selection of the type of the component other than the base polymer, and adjustment of the blending amount of the component in the adhesive sheet 10.

The release liner 20 includes a base film 21 (1 st base film) and a release layer 22 (1 st release layer) in this embodiment. The release layer 22 is disposed on the adhesive sheet 10 side of the base film 21 and contacts the adhesive sheet 10. As a material of the base film 21, for example, a plastic film having flexibility is cited. Examples of the plastic film include polyethylene terephthalate film, polyethylene film, polypropylene film and polyester film. The thickness of the base film 21 is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 200 μm or less, more preferably 150 μm or less. The release layer 22 is a layer formed by subjecting the surface of the base film 21 to a release treatment with a release treatment agent. Examples of the release treatment include silicone release treatment, long-chain alkyl acrylate release treatment, and fluorine release treatment. That is, examples of the release layer 22 include a silicone release layer, a long-chain alkyl acrylate release layer, and a fluorine release layer. The release layer 22 is preferably a silicone release layer from the viewpoint of ease of adjustment of the release force of the adhesive (adhesive sheet 10).

The release liner 30 includes a base film 31 (base film 2) and a release layer 32 (release layer 2) in this embodiment. The release layer 32 is disposed on the adhesive sheet 10 side of the base film 31 and contacts the adhesive sheet 10. The material and thickness of the base film 31 are the same as those described above with respect to the material and thickness of the base film 21. The release layer 32 is a layer formed by subjecting the surface of the base film 31 to a release treatment with a release treatment agent. Examples of the release treatment include silicone release treatment, long-chain alkyl acrylate release treatment, and fluorine release treatment. That is, examples of the release layer 32 include a silicone release layer, a long-chain alkyl acrylate release layer, and a fluorine release layer. The release layer 32 is preferably a silicone release layer from the viewpoint of ease of adjustment of the release force of the adhesive (adhesive sheet 10).

The ratio (H2/H1) of the thickness H2 of the release layer 32 to the thickness H1 of the release layer 22 is preferably 0.16 or more, more preferably 0.18 or more, still more preferably 0.20 or more, and is preferably 15 or less, preferably 10 or less, still more preferably 8 or less, and particularly preferably 6 or less. Such a configuration is preferable for adjusting the ratio (F2/F1) of the peeling forces F1, F2 to 0.1 or more and 0.6 or less.

From the viewpoint of ensuring the peeling function of the peeling layer 22, the thickness H1 of the peeling layer 22 is preferably 0.01 μm or more, more preferably 0.05 μm or more, and still more preferably 0.1 μm or more. From the viewpoint of suppressing the light peeling of the release liner 20, the thickness H1 is preferably 1 μm or less, more preferably 0.8 μm or less, and still more preferably 0.6 μm or less.

From the viewpoint of ensuring the peeling function of the peeling layer 32, the thickness H2 of the peeling layer 32 is preferably 0.01 μm or more, more preferably 0.05 μm or more, and still more preferably 0.1 μm or more. From the viewpoint of suppressing the light peeling of the release liner 30, the thickness H2 is preferably 1 μm or less, more preferably 0.8 μm or less, and even more preferably 0.6 μm or less.

The adhesive sheet 10 is a sheet-like pressure-sensitive adhesive formed of an adhesive composition. The adhesive sheet 10 (adhesive composition) contains at least a base polymer.

The base polymer is an adhesive component that exhibits adhesiveness in the adhesive sheet 10. Examples of the base polymer include: acrylic polymers, silicone polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyvinyl ether polymers, vinyl acetate/vinyl chloride copolymers, modified polyolefin polymers, epoxy polymers, fluoropolymers, and rubber polymers. The base polymer may be used alone or in combination of two or more. From the viewpoint of ensuring good transparency and adhesion of the adhesive sheet 10, an acrylic polymer is preferably used as the base polymer.

The acrylic polymer is a copolymer containing a monomer component of a (meth) acrylic acid ester in a ratio of 50 mass% or more. "(meth) acrylic" refers to acrylic and/or methacrylic.

As the (meth) acrylic acid ester, an alkyl (meth) acrylate is preferably used, and an alkyl (meth) acrylate having an alkyl group of 1 to 20 carbon atoms is more preferably used. The alkyl (meth) acrylate may have a linear or branched alkyl group, or may have a cyclic alkyl group such as an alicyclic alkyl group.

Examples of the alkyl (meth) acrylate having a linear or branched alkyl group include: methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (i.e., lauryl (meth) acrylate, isotridecyl (meth) acrylate, tetradecyl (meth) acrylate, isotetradecyl (meth) acrylate, pentadecyl (meth) acrylate, cetyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, isooctyl (meth) acrylate, and nonadecyl (meth) acrylate.

Examples of the alkyl (meth) acrylate having an alicyclic alkyl group include: cycloalkyl (meth) acrylate, alicyclic (meth) acrylate having a bicyclic aliphatic hydrocarbon ring, and alicyclic (meth) acrylate having a tricyclic or higher aliphatic hydrocarbon ring. Examples of the cycloalkyl (meth) acrylate include: cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, and cyclooctyl (meth) acrylate. Examples of the (meth) acrylic acid ester having a bicyclic aliphatic hydrocarbon ring include isobornyl (meth) acrylate. Examples of the (meth) acrylate having an aliphatic hydrocarbon ring having three or more rings include: dicyclopentyl (meth) acrylate, dicyclopentyloxyethyl (meth) acrylate, tricyclopentyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, and 2-ethyl-2-adamantyl (meth) acrylate.

As the alkyl (meth) acrylate, an alkyl acrylate having an alkyl group of 3 to 15 carbon atoms is preferably used, and at least one selected from the group consisting of n-butyl acrylate, 2-ethylhexyl acrylate and dodecyl acrylate is more preferably used.

The ratio of the alkyl (meth) acrylate in the monomer component is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, particularly preferably 92% by mass or more, from the viewpoint of appropriately exhibiting basic characteristics such as adhesiveness in the adhesive sheet 10. The ratio is, for example, 99 mass% or less.

The monomer component may contain a copolymerizable monomer copolymerizable with the alkyl (meth) acrylate. Examples of the copolymerizable monomer include monomers having a polar group. Examples of the polar group-containing monomer include a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and a monomer having a nitrogen atom-containing ring. The polar group-containing monomer contributes to modification of the acrylic polymer such as introduction of a crosslinking point into the acrylic polymer and securing of cohesion of the acrylic polymer.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate. As the hydroxyl group-containing monomer, at least one selected from the group consisting of 4-hydroxybutyl acrylate and 2-hydroxyethyl acrylate is preferably used.

The ratio of the hydroxyl group-containing monomer in the monomer component is preferably 1% by mass or more, more preferably 2% by mass or more, and still more preferably 3% by mass or more, from the viewpoint of introducing a crosslinked structure into the acrylic polymer and securing cohesive force of the adhesive sheet. From the viewpoint of adjusting the polarity of the acrylic polymer (regarding the compatibility of various additive components in the adhesive sheet with the acrylic polymer), the ratio is preferably 20 mass% or less, more preferably 10 mass% or less.

Examples of the carboxyl group-containing monomer include: acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

The ratio of the carboxyl group-containing monomer in the monomer component is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, and still more preferably 0.8 mass% or more, from the viewpoints of introducing a crosslinked structure into the acrylic polymer, securing cohesive force of the adhesive sheet, and securing adhesion force to an adherend of the adhesive sheet. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adherend by acid, the ratio is preferably 10 mass% or less, more preferably 5 mass% or less.

Examples of the monomer having a ring containing a nitrogen atom include: n-vinyl-2-pyrrolidone, N-methyl vinyl pyrrolidone, N-vinyl pyridine, N-vinyl piperidone, N-vinyl pyrimidine, N-vinyl piperazine, N-vinyl pyrazine, N-vinyl pyrrole, N-vinyl imidazole, N-vinyl oxazole, N- (meth) acryl-2-pyrrolidone, N- (meth) acryl piperidine, N- (meth) acryl pyrrolidine, N-vinyl morpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1, 3-oxazin-2-one, N-vinyl-3, 5-morpholinedione, N-vinyl pyrazole, N-vinyl isoxazole, N-vinyl thiazole, and N-vinyl isothiazole. As the monomer having a nitrogen atom-containing ring, N-vinyl-2-pyrrolidone is preferably used.

The ratio of the monomer having a ring containing a nitrogen atom in the monomer component is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, and still more preferably 1 mass% or more, from the viewpoint of securing cohesive force of the adhesive sheet and securing adhesion force of the adhesive sheet to an adherend. From the viewpoints of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (regarding the compatibility of various additive components in the adhesive sheet with the acrylic polymer), the ratio is preferably 30 mass% or less, more preferably 20 mass% or less.

The monomer component may comprise other copolymerizable monomers. Examples of the other copolymerizable monomer include: anhydride monomer, sulfonic acid group-containing monomer, phosphoric acid group-containing monomer, epoxy group-containing monomer, cyano group-containing monomer, alkoxy group-containing monomer, and aromatic vinyl compound. These other copolymerizable monomers may be used alone or in combination of two or more.

The base polymer preferably has a crosslinked structure. As a method for introducing a crosslinked structure into a base polymer, there can be mentioned: a method of compounding a base polymer having a functional group capable of reacting with a crosslinking agent and a crosslinking agent in an adhesive composition, and reacting the base polymer with the crosslinking agent in an adhesive sheet (method 1); and a method (method 2) in which a polyfunctional monomer is contained in a monomer component forming a base polymer, and a base polymer having a branched structure (crosslinked structure) introduced into a polymer chain is formed by polymerization of the monomer component. These methods may be used in combination.

Examples of the crosslinking agent used in the method 1 include compounds that react with functional groups (e.g., hydroxyl groups and carboxyl groups) contained in the base polymer. Examples of such a crosslinking agent include: isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, and metal chelate crosslinking agents. The crosslinking agent may be used alone or in combination of two or more. As the crosslinking agent, an isocyanate crosslinking agent, a peroxide crosslinking agent and an epoxy crosslinking agent are preferably used in view of high reactivity with hydroxyl groups and carboxyl groups in the base polymer and easiness of introducing a crosslinked structure.

Examples of the isocyanate crosslinking agent include: toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanates. Further, as the isocyanate crosslinking agent, derivatives of these isocyanates can be mentioned. Examples of the isocyanate derivative include isocyanurate modified products and polyol modified products. Examples of the commercial products of the isocyanate crosslinking agent include cornate L (trimethylolpropane adduct of toluene diisocyanate, manufactured by eastern corporation), cornate HL (trimethylolpropane adduct of hexamethylene diisocyanate, manufactured by eastern corporation), cornate HX (isocyanurate of hexamethylene diisocyanate, manufactured by eastern corporation), takenate D110N (trimethylolpropane adduct of xylylene diisocyanate, manufactured by tricyclopedia chemical Co., ltd.), and Takenate600 (1, 3-bis (isocyanatomethyl) cyclohexane, manufactured by tricyclopedia chemical Co., ltd.).

The peroxide crosslinking agent may be: dibenzoyl peroxide, di (2-ethylhexyl) peroxydicarbonate, di (4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-hexyl peroxypivalate, and tert-butyl peroxypivalate.

Examples of the epoxy crosslinking agent include bisphenol a, epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol triglycidyl ether, 1, 6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidylamine, N' -tetraglycidyl m-xylylenediamine, and 1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane.

Isocyanate crosslinking agents (particularly difunctional isocyanate crosslinking agents) and peroxide crosslinking agents are preferable from the viewpoint of ensuring the flexibility of the adhesive sheet 10. The isocyanate crosslinking agent (particularly, trifunctional isocyanate crosslinking agent) is preferable from the viewpoint of securing durability of the adhesive sheet 10. In the base polymer, the difunctional isocyanate crosslinker and the peroxide crosslinker form softer two-dimensional crosslinks, while the trifunctional isocyanate crosslinker forms stronger three-dimensional crosslinks. From the viewpoint of having both durability and flexibility of the adhesive sheet 10, it is preferable to use a trifunctional isocyanate crosslinking agent in combination with a peroxide crosslinking agent and/or a difunctional isocyanate crosslinking agent.

From the viewpoint of ensuring cohesive force of the adhesive sheet 10, the blending amount of the crosslinking agent is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass or more, relative to 100 parts by mass of the base polymer. In the pressure-sensitive adhesive sheet 10, the amount of the crosslinking agent blended with respect to 100 parts by mass of the base polymer is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, from the viewpoint of ensuring good tackiness.

In the method 2, the monomer component (including the polyfunctional monomer for introducing a crosslinked structure and other monomers) may be polymerized at one time or may be polymerized in multiple stages. In the multistage polymerization method, first, a monofunctional monomer for forming a base polymer is polymerized (prepolymerized), thereby producing a prepolymer composition containing a part of a polymer (a mixture of a polymer having a low degree of polymerization and an unreacted monomer). Next, after adding a polyfunctional monomer to the prepolymer composition, a part of the polymer and the polyfunctional monomer are polymerized (main polymerization).

Examples of the polyfunctional monomer include polyfunctional (meth) acrylates having 2 or more ethylenically unsaturated double bonds in 1 molecule. The polyfunctional monomer is preferably a polyfunctional acrylate from the viewpoint of being capable of introducing a crosslinked structure by active energy ray polymerization (photopolymerization).

Examples of the polyfunctional (meth) acrylate include: difunctional (meth) acrylates, trifunctional (meth) acrylates, and multifunctional (meth) acrylates of four or more functionalities.

Examples of the difunctional (meth) acrylate include: ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol dimethacrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, glycerol di (meth) acrylate, neopentyl glycol di (meth) acrylate, stearic acid modified pentaerythritol di (meth) acrylate, dicyclopentadiene diacrylate, di (meth) acryl isocyanurate, and alkylene oxide modified bisphenol di (meth) acrylate.

Examples of the trifunctional (meth) acrylate include: trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and tris (acryloxyethyl) isocyanurate.

Examples of the polyfunctional (meth) acrylate having four or more functions include: ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxy penta (meth) acrylate, alkyl modified dipentaerythritol pentaacrylate, and dipentaerythritol hexa (meth) acrylate.

The molecular weight of the polyfunctional monomer is preferably 1500 or less, more preferably 1000 or less. The functional group equivalent (g/eq) of the polyfunctional monomer is preferably 50 or more, more preferably 70 or more, and still more preferably 80 or more. The functional group equivalent is preferably 500 or less, more preferably 300 or less, and further preferably 200 or less. These structures are preferable from the viewpoint of properly adjusting the viscoelasticity (for example, shear storage modulus and loss tangent) by introducing a crosslinked structure into the base polymer.

The acrylic polymer can be formed by polymerizing the monomer components. Examples of the polymerization method include: solution polymerization, solvent-free photopolymerization (e.g., UV polymerization), bulk polymerization, and emulsion polymerization. As the solvent for the solution polymerization, for example, ethyl acetate and toluene can be used. As the initiator for polymerization, for example, a thermal polymerization initiator and a photopolymerization initiator can be used. The amount of the polymerization initiator used is, for example, 0.05 parts by mass or more and 1 part by mass or less based on 100 parts by mass of the monomer component.

Examples of the thermal polymerization initiator include azo polymerization initiators and peroxide polymerization initiators. Examples of the azo polymerization initiator include: 2,2' -azobisisobutyronitrile, 2' -azobis-2-methylbutyronitrile, dimethyl 2,2' -azobis (2-methylpropionate), 4' -azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2' -azobis (2-amidinopropane) dihydrochloride, 2' -azobis [2- (5-methyl-2-imidazolin-2-yl) propane ] dihydrochloride, 2' -azobis (2-methylpropionamidine) disulfate, and 2,2' -azobis (N, N ' -dimethylene isobutyl amidine) dihydrochloride. Examples of the peroxide polymerization initiator include: dibenzoyl peroxide, t-butyl peroxymaleate, and lauroyl peroxide.

Examples of the photopolymerization initiator include: benzoin ether-based photopolymerization initiator, acetophenone-based photopolymerization initiator, α -ketol-based photopolymerization initiator, aromatic sulfonyl chloride-based photopolymerization initiator, photoactive oxime-based photopolymerization initiator, benzoin-based photopolymerization initiator, benzil-based photopolymerization initiator, benzophenone-based photopolymerization initiator, ketal-based photopolymerization initiator, thioxanthone-based photopolymerization initiator, and acylphosphine oxide-based photopolymerization initiator.

In the polymerization, a chain transfer agent and/or a polymerization inhibitor (polymerization retarder) may be used for the purpose of molecular weight adjustment or the like. Examples of the chain transfer agent include α -thioglycerol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid (Mercaptoacetic acid), 2-mercaptoethanol, mercaptoacetic acid (Thioglycolic acid), 2-ethylhexyl thioglycolate, 2, 3-dimercapto-1-propanol, and α -methylstyrene dimer.

The molecular weight of the base polymer can be adjusted by adjusting the kind and/or amount of the polymerization initiator. For example, in radical polymerization, the higher the amount of the polymerization initiator, the higher the radical concentration of the reaction system, and therefore the higher the density of the reaction starting point and the lower the molecular weight of the base polymer to be formed tend to be. On the other hand, the smaller the amount of the polymerization initiator, the lower the density of the reaction initiation point, and therefore, the more easily the polymer chain is elongated and the larger the molecular weight of the base polymer to be formed tends to be.

The weight average molecular weight of the base polymer is preferably 10 ten thousand or more, more preferably 30 ten thousand or more, and still more preferably 50 ten thousand or more from the viewpoint of securing cohesive force of the adhesive sheet 10. The weight average molecular weight of the base polymer was measured by Gel Permeation Chromatography (GPC), and calculated by conversion to polystyrene.

The glass transition temperature (Tg) of the base polymer is preferably 0℃or lower, more preferably-10℃or lower, and still more preferably-20℃or lower. The glass transition temperature is, for example, at least-80 ℃.

As the glass transition temperature (Tg) of the base polymer, a glass transition temperature (theoretical value) obtained based on the following Fox formula can be used. The Fox formula is a relation between the glass transition temperature Tg of the polymer and the glass transition temperature Tgi of the homopolymer of the monomers constituting the polymer. In the following Fox formula, tg represents the glass transition temperature (. Degree. C.) of the polymer, wi represents the weight fraction of the monomer i constituting the polymer, tgi represents the glass transition temperature (. Degree. C.) of the homopolymer formed from the monomer i. As regards the glass transition temperature of the homopolymer, literature values can be used. Glass transition temperatures of the various homopolymers are listed, for example, in Polymer Handbook (4 th edition, john Wiley & Sons, inc., 1999) and in synthetic resin entry for New Polymer library 7 coating (North sentry, proc. Congress, polymer journal, 1995). On the other hand, the glass transition temperature of the homopolymer of the monomer can be obtained by a method specifically described in JP-A2007-51271.

Fox 1/(273+tg) =Σ [ Wi/(273+tgi) ]

The adhesive composition may contain one or two or more oligomers in addition to the base polymer. When an acrylic polymer is used as the base polymer, an acrylic oligomer is preferably used as the oligomer. The acrylic oligomer is a copolymer containing a monomer component of an alkyl (meth) acrylate at a ratio of 50 mass% or more, and has a weight average molecular weight of, for example, 1000 to 30000.

The glass transition temperature of the acrylic oligomer is preferably 60℃or higher, more preferably 80℃or higher, still more preferably 100℃or higher, particularly preferably 110℃or higher. The glass transition temperature of the acrylic oligomer is, for example, 200℃or lower, preferably 180℃or lower, and more preferably 160℃or lower. By using a combination of a low Tg acrylic polymer (base polymer) having a crosslinked structure and a high Tg acrylic oligomer, the adhesive force of the adhesive sheet 10, particularly the adhesive force at high temperature, is improved. The glass transition temperature of the acrylic oligomer is calculated by the above Fox formula.

The acrylic oligomer is obtained by polymerizing the monomer component of the acrylic oligomer. Examples of the polymerization method include: solution polymerization, bulk polymerization, and emulsion polymerization. In the polymerization of the acrylic oligomer, a polymerization initiator may be used, or a chain transfer agent may be used for the purpose of adjusting the molecular weight.

The adhesive composition may contain a silane coupling agent. The content of the silane coupling agent in the adhesive composition is preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, relative to 100 parts by mass of the base polymer. The content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less.

The adhesive composition may contain other components as needed. Examples of the other components include: solvents, tackifiers, plasticizers, softeners, antioxidants, fillers, colorants, ultraviolet absorbers, antioxidants, surfactants, and antistatic agents. Examples of the solvent include a polymerization solvent used when the acrylic polymer is polymerized, if necessary, and a solvent added to the polymerization reaction solution after the polymerization. As the solvent, for example, ethyl acetate and toluene can be used.

The thickness of the pressure-sensitive adhesive sheet 10 is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of securing sufficient adhesion to an adherend. From the viewpoint of the handleability of the adhesive sheet 10, the thickness of the adhesive sheet 10 is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less, particularly preferably 50 μm or less.

The haze of the pressure-sensitive adhesive sheet 10 is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less. The haze of the pressure-sensitive adhesive sheet 10 can be measured by using a haze meter according to JIS K7136 (year 2000). Examples of the haze meter include "NDH2000" manufactured by Nippon electric color industry Co., ltd and "HM-150" manufactured by Toku Kogyo Co., ltd.

The release liner-attached adhesive sheet X can be manufactured as follows, for example.

First, the release liners 20, 30 are prepared. The release liner 20 can be produced by forming the release layer 22 on one side of the base film 21. The release layer 22 can be formed by subjecting the surface of the base film 21 to a release treatment with a release treatment agent. The release liner 30 can be produced by forming a release layer 32 on one side of a base film 31. The release layer 32 can be formed by subjecting the surface of the base film 31 to a release treatment with a release treatment agent.

Next, the adhesive composition is coated on the release liner 20 to form a coating film, and then the coating film is dried. Examples of the method for applying the adhesive composition include: roll coating, roll lick coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating. The drying temperature of the coating film is, for example, 50 to 200 ℃. The drying time is, for example, 5 seconds to 20 minutes.

Next, a release liner 30 is attached to the coating film on the release liner 20. Then, the coating film is cured as needed. The curing temperature is, for example, 20℃to 160 ℃. The curing time is, for example, 1 minute to 21 days. The coating film is irradiated with light as needed. Examples of the light source for light irradiation include: ultraviolet LED lamps, high pressure mercury lamps, and metal halide lamps.

The optical adhesive sheet X with a release liner can be manufactured by operating as described above.

Examples

The present invention will be specifically described with reference to the following examples. However, the present invention is not limited to the examples. The specific numerical values of the compounding amounts (contents), physical property values, parameters, and the like described below may be substituted for the upper limits (numerical values defined as "below", "less than") or the lower limits (numerical values defined as "above", "exceeding") of the compounding amounts (contents), physical property values, parameters, and the like described in the above-described "specific embodiments".

Release liner L ₁₁ Is made of (1)

A stripping treatment solution having an organosilicon solid content of 0.7% was prepared by mixing 90 parts by mass of an organosilicon stripping treatment agent (product name "KE-3703", product name: manufactured by Xinyue Kagaku Co., ltd.) with 0.3 parts by mass of a platinum catalyst for curing organosilicon (product name "CAT-PL-50T", product name: manufactured by Xinyue Kagaku Co., ltd.) and a solvent, each of which was 28.5% by mass of a toluene solution of an addition type organosilicon stripping treatment agent having a hydrosilyl group in its molecule. The solvent is toluene and hexane in a volume ratio of 1: 1.

Next, a biaxially oriented polyester film (product name "Lumiror XD500P", thickness 75 μm, manufactured by Toray Advanced Materials Korea) was peeled off as a base film. Specifically, first, the release treating agent solution is applied to one side of the base film to form a coating film. Bar #9 was used for coating. Then, the coating film on the base film was dried by heating at 130 ℃ for 1 minute using a hot air dryer. Thus, a silicone release layer having a thickness of 0.1 μm was formed on the base film.

Working as described above, a release liner L was produced ₁₁ . Release liner L ₁₁ Has a laminated structure of a base film and a release layer (thickness: 0.1 μm).

Release liner L ₁₂ Is made of (1)

In the preparation of the release treatment agent solution, the silicone solid content concentration was set to 1.5 mass% instead of 0.7 mass%, and the release liner L was used in addition to this ₁₁ Similarly, a release liner L was produced ₁₂ . Release liner L ₁₂ Has a laminated structure of a base film and a release layer (thickness: 0.3 μm).

Release liner L ₁₃ Is made of (1)

In the preparation of the release treatment agent solution, the silicone solid content concentration was set to 2.5 mass% instead of 0.7 mass%, and the release liner L was used in addition to this ₁₁ Similarly, a release liner L was produced ₁₃ . Release liner L ₁₃ Has a laminated structure of a base film and a release layer (thickness: 0.5 μm).

Release liner L ₁₄ Is made of (1)

In the preparation of the release treatment agent solution, the silicone solid content concentration was set to 3.5 mass% instead of 0.7 mass%, and the release liner L was used in addition to this ₁₁ Similarly, a release liner L was produced ₁₄ . Release liner L ₁₄ Has a laminated structure of a base film and a release layer (thickness: 0.7 μm).

Release liner L ₂₁ Is made of (1)

A stripping treatment solution having a concentration of 0.7% BY mass of a silicone solid content was prepared BY mixing 30 parts BY mass of a silicone-based stripping treatment (product name "LTC761", product name "BY 240-850", product name Dow Corning Toray) containing a 30% BY mass toluene solution of an addition type silicone-based stripping treatment agent having a polyorganosiloxane group in a molecule and a polyorganosiloxane crosslinking agent having a hydrosilyl group in a molecule, product name "SRX 212", product name "Dow Corning Toray") with 0.9 parts BY mass of a silicone dispersion, 2 parts BY mass of a platinum catalyst for curing silicone, and a solvent. The solvent is toluene and hexane in a volume ratio of 1: 1.

Working as described above, a release liner L was produced ₂₁ . Release liner L ₂₁ Has a laminated structure of a base film and a release layer (thickness: 0.1 μm).

Release liner L ₂₂ Is made of (1)

In the preparation of the release treatment agent solution, the silicone solid content concentration was set to 2.5 mass% instead of 0.7 mass%, and the release liner L was used in addition to this ₂₁ Similarly, a release liner L was produced ₂₂ . Release liner L ₂₂ Has a laminated structure of a base film and a release layer (thickness: 0.5 μm).

[ example 1 ]

Preparation of adhesive composition

First, a mixture containing 45 parts by mass of 2-ethylhexyl acrylate (2 EHA), 2 parts by mass of N-Butyl Acrylate (BA), 42 parts by mass of Lauryl Acrylate (LA), 4 parts by mass of 4-hydroxybutyl acrylate (4 HBA), 7 parts by mass of N-vinyl-2-pyrrolidone (NVP) and 0.015 part by mass of a photopolymerization initiator (trade name "Omnirad184", manufactured by IGM Resins) was irradiated with ultraviolet light (polymerization reaction) to obtain a prepolymer composition (polymerization ratio: about 10%) (the prepolymer composition contains a monomer component which was not subjected to polymerization reaction). Next, 100 parts by mass of the prepolymer composition, 0.08 part by mass of dipentaerythritol hexaacrylate (DPHA) as a 1 st crosslinking agent, and 0.3 part by mass of a silane coupling agent (product name "KBM-403", 3-glycidoxypropyl trimethoxysilane, manufactured by Xinyue chemical Co., ltd.) were mixed to obtain an adhesive composition C1.

Formation of adhesive sheet

First, in the release liner L as the 1 st release liner ₁₁ The adhesive composition C1 is applied thereon to form a coating film (coating film forming step). The coating film is formed on the release liner L ₁₁ Is provided on the silicone release layer. Next, the release liner L is used as the 2 nd release liner ₂₁ Is attached to the release liner L on the silicone release layer side ₁₁ The coating film thereon (bonding step). Will release liner L ₂₁ The silicone release layer side of (2) is bonded to the coating film. Next, a release liner L is interposed therebetween ₂₁ The coating film was irradiated with ultraviolet rays, and the coating film was cured by ultraviolet rays to form a transparent 1 st adhesive layer having a thickness of 50. Mu.m. In ultraviolet irradiation, black light was used as an irradiation light source, and the irradiation intensity was set to 5mW/cm ² (the same applies to ultraviolet irradiation described later).

The release liner-attached adhesive sheet of example 1 (release liner L) was produced in the manner described above ₁₁ Optical adhesive sheet (1 st adhesive layer)/release liner L ₂₁ )。

[ example 2 ]

A release liner-equipped adhesive sheet of example 2 was produced in the same manner as the release liner-equipped adhesive sheet of example 1, except for the following. In the coating film forming step, the release liner L is used ₁₂ As the 1 st release liner, in the release liner L ₁₂ A coating film of the adhesive composition C1 was formed on the silicone release layer of (C).

The release liner-equipped adhesive sheet of example 2 has a release liner L ₁₂ Light sourceChemical adhesive sheet (1 st adhesive layer) and release liner L ₂₁ Is a laminated structure of (a).

[ example 3 ]

A release liner-equipped adhesive sheet of example 3 was produced in the same manner as the release liner-equipped adhesive sheet of example 1, except for the following. In the coating film forming step, the release liner L is used ₁₃ As the 1 st release liner, in the release liner L ₁₃ A coating film of the adhesive composition C1 was formed on the silicone release layer of (C).

The release liner-equipped adhesive sheet of example 3 had a release liner L ₁₃ Optical adhesive sheet (1 st adhesive layer) and release liner L ₂₁ Is a laminated structure of (a).

[ example 4 ]

A release liner-equipped adhesive sheet of example 4 was produced in the same manner as the release liner-equipped adhesive sheet of example 1, except for the following. In the bonding step, the release liner L is used ₂₂ As the 2 nd release liner, release liner L ₂₂ Is attached to the release liner L on the silicone release layer side ₁₁ Coating film on the surface.

The release liner-equipped adhesive sheet of example 4 has a release liner L ₁₁ Optical adhesive sheet (1 st adhesive layer) and release liner L ₂₂ Is a laminated structure of (a).

[ example 5 ]

First, a mixture containing 50 parts by mass of 2-ethylhexyl acrylate (2 EHA), 2 parts by mass of N-Butyl Acrylate (BA), 40 parts by mass of Lauryl Acrylate (LA), 6 parts by mass of 4-hydroxybutyl acrylate (4 HBA), 2 parts by mass of N-vinyl-2-pyrrolidone (NVP) and 0.015 part by mass of a photopolymerization initiator (trade name "Omnirad184", manufactured by IGM Resins) was irradiated with ultraviolet light (polymerization reaction), to obtain a prepolymer composition (polymerization rate: about 10%). Next, 100 parts by mass of the prepolymer composition, 0.08 part by mass of dipentaerythritol hexaacrylate (DPHA) as a 1 st crosslinking agent, and 0.3 part by mass of a silane coupling agent (product name "KBM-403", 3-glycidoxypropyl trimethoxysilane, manufactured by Xinyue chemical Co., ltd.) were mixed to obtain an adhesive composition C2. A release liner-equipped adhesive sheet of example 5 was produced in the same manner as the release liner-equipped adhesive sheet of example 1 except that the adhesive composition C2 was used in place of the adhesive composition C1 to form a transparent 2 nd adhesive layer having a thickness of 50 μm.

The release liner-equipped adhesive sheet of example 5 has a release liner L ₁₁ Optical adhesive sheet (2 nd adhesive layer) and release liner L ₂₁ Is a laminated structure of (a).

[ example 6 ]

Preparation of adhesive composition

First, a mixture (solid content concentration 47% by mass) containing 63 parts by mass of 2-ethylhexyl acrylate (2 EHA), 19 parts by mass of n-Butyl Acrylate (BA), 8 parts by mass of Lauryl Acrylate (LA), 10 parts by mass of 4-hydroxybutyl acrylate (4 HBA), 0.1 part by mass of 2,2' -Azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and ethyl acetate as a solvent was stirred at 56 ℃ under a nitrogen atmosphere for 5 hours (polymerization reaction). Thus, a polymer solution containing an acrylic polymer was obtained. To the polymer solution, 0.3 parts by mass of dibenzoyl peroxide (BPO) as a 2 nd crosslinking agent and 0.3 parts by mass of a silane coupling agent (trade name "KBM-403", manufactured by siegesbeck chemical industry co., ltd.) were added and mixed with respect to 100 parts by mass of the acrylic polymer in the polymer solution, to obtain an adhesive composition C3.

Formation of adhesive sheet

First, in the release liner L as the 1 st release liner ₁₁ The adhesive composition C3 was applied thereon to form a coating film (coating film forming step). The coating film is formed on the release liner L ₁₁ Is provided on the silicone release layer. Next, the release liner L is used as the 2 nd release liner ₂₁ Is attached to the release liner L on the silicone release layer side ₁₁ The coating film thereon (bonding step). Next, the release liner L is removed ₁₁ 、L ₂₁ The film in between was dried by heating at 100℃for 1 minute and then at 150℃for 3 minutes, to form a transparent 3 rd adhesive layer having a thickness of 50. Mu.m.

The release liner-attached adhesive sheet of example 6 (release liner L) was produced by the procedure described above ₁₁ Optical adhesive sheet(3 rd adhesive layer)/Release liner L ₂₁ )。

Example 7

A release liner-equipped adhesive sheet of example 7 was produced in the same manner as the release liner-equipped adhesive sheet of example 6, except for the following. In the coating film forming step, the release liner L is used ₁₃ As the 1 st release liner, in the release liner L ₁₃ A coating film of the adhesive composition C3 was formed on the silicone release layer of (C).

The release liner-equipped adhesive sheet of example 7 had a release liner L ₁₃ Optical adhesive sheet (3 rd adhesive layer) and release liner L ₂₁ Is a laminated structure of (a).

Comparative example 1

A release liner-equipped adhesive sheet of comparative example 1 was produced in the same manner as the release liner-equipped adhesive sheet of example 1, except for the following. In the coating film forming step, the release liner L is used ₁₄ As the 1 st release liner, in the release liner L ₁₄ A coating film of the adhesive composition C1 was formed on the silicone release layer of (C).

The release liner-equipped adhesive sheet of comparative example 1 has a release liner L ₁₄ Optical adhesive sheet (1 st adhesive layer) and release liner L ₂₁ Is a laminated structure of (a).

Comparative example 2

A release liner-equipped adhesive sheet of comparative example 2 was produced in the same manner as the release liner-equipped adhesive sheet of example 6, except for the following. In the coating film forming step, the release liner L is used ₁₄ As the 1 st release liner, in the release liner L ₁₄ A coating film of the adhesive composition C3 was formed on the silicone release layer of (C).

The release liner-equipped adhesive sheet of comparative example 2 had a release liner L ₁₄ Optical adhesive sheet (3 rd adhesive layer) and release liner L ₂₁ Is a laminated structure of (a).

[ comparative example 3 ]

First, a mixture containing 40 parts by mass of 2-ethylhexyl acrylate (2 EHA), 3 parts by mass of N-Butyl Acrylate (BA), 41 parts by mass of isostearyl acrylate (ISTA), 1 part by mass of 4-hydroxybutyl acrylate (4 HBA), 15 parts by mass of N-vinyl-2-pyrrolidone (NVP) and 0.015 part by mass of a photopolymerization initiator (product name "Omnirad 184", manufactured by IGM Resins Co.) was irradiated with ultraviolet light (polymerization reaction), to obtain a prepolymer composition (polymerization rate: about 10%). Next, 100 parts by mass of the prepolymer composition, 0.02 part by mass of dipentaerythritol hexaacrylate (DPHA) as a 1 st crosslinking agent, and 0.3 part by mass of a silane coupling agent (product name "KBM-403", manufactured by Xinyue chemical Co., ltd.) were mixed to obtain an adhesive composition C4. A release liner-equipped adhesive sheet of comparative example 3 was produced in the same manner as the release liner-equipped adhesive sheet of example 1 except that the adhesive composition C4 was used in place of the adhesive composition C1 to form a transparent 4 th adhesive layer having a thickness of 50 μm.

The release liner-equipped adhesive sheet of comparative example 3 had a release liner L ₁₁ Optical adhesive sheet (4 th adhesive layer) and release liner L ₂₁ Is a laminated structure of (a).

Thickness of release layer

Before the production of the release liner-equipped adhesive sheet, the release liner L used as the 1 st release liner was measured by FE-TEM observation ₁₁ 、L ₁₂ 、L ₁₃ 、L ₁₄ Thickness of each silicone release layer of (2) and release liner L used as release liner of (2) ₂₁ 、L ₂₂ Is used for the thickness of each silicone release layer. Specifically, first, after a protective layer was provided on the surface of the silicone release layer of the release liner, the release layer was flaked by FIB microsampling in a state in which the release liner was cooled, and a sample for cross-section observation was produced. In the FIB microsampling method, an FIB device (trade name "FB2200", hitachi) is used, and the acceleration voltage is set to 30kV. Next, the thickness of the release layer in the sample for cross-section observation was measured by FE-TEM observation. In the FE-TEM observation, an acceleration voltage was set at 200kV using an FE-TEM apparatus (trade name "JEM-2800", manufactured by JEOL). Tables 1 and 2 show the thickness H1 (μm) of the silicone release layer of the 1 st release liner, the thickness H2 (μm) of the silicone release layer of the 2 nd release liner, and the ratio (H2/H1) of the thickness H2 to the thickness H1.

Shear storage modulus

Dynamic viscoelasticity was measured for each of the adhesive sheets of examples 1 to 7 and comparative examples 1 to 3.

First, a measurement sample was prepared for each adhesive sheet. Specifically, first, a plurality of adhesive sheet patches cut out from an adhesive sheet were bonded to each other to prepare a sample sheet having a thickness of about 1.5 mm. Then, the sheet was punched out to obtain columnar pellets (diameter: 7.9 mm) as a sample for measurement.

Then, a dynamic viscoelasticity measurement device (product name "Advanced Rheometric Expansion System (ARES)", manufactured by Rheometric Scientific corporation) was used for the measurement sample, and the dynamic viscoelasticity measurement was performed after being fixed to a jig having a diameter of 7.9mm for a parallel plate. In the present measurement, the measurement mode was set to the shear mode, the measurement temperature range was set to-40℃to 100℃and the temperature rise rate was set to 5℃per minute, and the frequency was set to 1Hz. The shear storage modulus at 25℃and the maximum shear storage modulus in the measured temperature range were read from the measurement results. The values are shown in tables 1 and 2.

Stripping force

The release force for releasing the 1 st release liner from the adhesive sheet was measured for each release liner-carrying adhesive sheets of examples 1 to 7 and comparative examples 1 to 3 (1 st measurement).

In the production of the test piece for measurement 1, first, a sample piece (width 50 mm. Times. Length 100 mm) was cut out from the pressure-sensitive adhesive sheet with a release liner. Then, the 2 nd release liner was peeled off from the sample sheet, and the exposed surface of the adhesive sheet thus exposed was bonded to a glass plate, to obtain a test piece.

Then, after the test piece was left to stand at 23℃for 60 minutes, a peeling test was performed to peel the 1 st release liner in the test piece from the adhesive sheet, and the force required for peeling was measured as the peeling force. In this measurement, a tensile tester (product name "Autograph AG-50NX plus)", manufactured by Shimadzu corporation, was used, the measurement temperature was set at 23 ℃, the peeling angle was set at 180 °, and the tensile speed was set at 300 mm/min (the same applies to the measurement of 2 to be described later). The measured peel force F1 (N/50 mm) is shown in tables 1 and 2.

On the other hand, the release force for releasing the release liner 2 from the adhesive sheet was measured for each release liner-carrying adhesive sheets of examples 1 to 7 and comparative examples 1 to 3 (measurement of 2).

In the production of the test piece for measurement 2, first, a sample piece (width 50 mm. Times. Length 100 mm) was cut out from the pressure-sensitive adhesive sheet with a release liner. Next, the 1 st release liner side of the sample piece was bonded to the glass plate using a double-sided strong adhesive tape, to obtain a test piece.

Then, after the test piece was left to stand at 23℃for 60 minutes, a peel test was performed to peel the 2 nd release liner in the test piece from the adhesive sheet, and the force required for peeling was measured as the peel force. The measured peel force F2 (N/50 mm) is shown in tables 1 and 2. The ratio of the peel force F2 to the peel force F1 (F2/F1) is also shown in tables 1 and 2.

Bending test

The release liner-attached adhesive sheets of examples 1 to 7 and comparative examples 1 to 3 were evaluated for adhesion to an adherend in a bending test. Specifically, the following is described.

First, the 2 nd release liner was peeled off from the release liner-attached adhesive sheet, and the exposed surface thus exposed was subjected to plasma treatment. On the other hand, plasma treatment was also performed on both sides (1 st side and 2 nd side) of the polarizing film having a thickness of 51. Mu.m. In addition, the surface of the transparent polyimide film having a thickness of 80 μm and the surface of the polyethylene terephthalate (PET) film having a thickness of 125 μm were also subjected to plasma treatment. In each plasma treatment, a plasma irradiation apparatus (product name "AP-TO5", manufactured by Seattle Ltd.) was used, the voltage was set TO 160V, the frequency was set TO 10kHz, and the treatment speed was set TO 5000 mm/min. Then, the exposed surface of the pressure-sensitive adhesive sheet is bonded to the 1 st surface of the polarizing film. In this bonding, the adhesive sheet with the 1 st release liner was pressure-bonded to the polarizing film by reciprocating a 2kg roller 1 time at 23 ℃. Then, the 1 st release liner was peeled off from the adhesive sheet with a polarizing film, and the transparent polyimide film was attached to the exposed surface of the adhesive sheet thus exposed. Then, the PET film was laminated on the 2 nd side of the polarizing film via a thin adhesive sheet having a thickness of 15. Mu.m. In this bonding, the polarizing film and the PET film were pressure-bonded by reciprocating a 2kg roller 1 time in an environment of 23 ℃. Thus, a laminated film having a laminated structure of a PET film (thickness 125 μm), a thin adhesive sheet (thickness 15 μm), a polarizing film (thickness 51 μm), an adhesive sheet (thickness 50 μm), and a transparent polyimide film (thickness 80 μm) was obtained.

Next, a sample for evaluation was cut out from the laminated film thus prepared. Specifically, a rectangular sample of 35mm×100mm was cut out of the laminated film so that the absorption axis direction of the polarizing film was parallel to the longitudinal direction among the cut samples. Next, the sample was subjected to autoclave treatment at 35℃and 0.50MPa for 15 minutes.

Then, for this sample, a bending test was performed by using a planar body no-load U-shaped expansion and contraction tester (YUASA SYSTEM co., ltd.). In this test, bending jigs were attached to both ends of the sample in the longitudinal direction in a range of 20mm from the edge of the sample, and the sample was fixed to the tester (the region 60mm in the center of the sample in the longitudinal direction was left unfixed). In the present test, the sample was repeatedly deformed (bent) 20 ten thousand times at a bending speed of 60rpm between a bent state in which the surface on the PET film side was inside and a non-bent state in a constant temperature and humidity tank under conditions of a temperature of 60 ℃ and a relative humidity of 95%. Specifically, the bending mode in this test is a mode in which the axial direction of the bending moment acting on the sample is perpendicular to the absorption axis direction of the polarizing film. In this bent form, the bending radius of the sample was set to 1.3mm and the bending angle was set to 180 °. Then, the adhesion of the adhesive sheet to the adherend in such a bending test was evaluated as "good" when no peeling occurred between the adhesive sheet and the adherend (transparent polyimide film, polarizing film), and as "bad" when peeling occurred. The evaluation results are shown in tables 1 and 2.

Peel test

Release liner release properties were evaluated for each of the release liner-attached adhesive sheets of examples 1 to 7 and comparative examples 1 to 3.

In the production of the sample for evaluation, first, a rectangular sample piece (300 mm. Times.200 mm) was cut out from the release liner-attached adhesive sheet. Next, the 1 st release liner side of the sample piece was bonded to the glass plate using a double-sided strong adhesive tape. Next, one end (width 20mm×length 50 mm) of a polyimide tape was attached to a region selected from 4 vertices (1 st vertex) and the vicinity thereof on the 2 nd release liner side exposed surface of the rectangular sample sheet on the glass plate.

Then, the other end portion of the polyimide tape was rapidly stretched (peeling operation of the 2 nd release liner). In this peeling operation, the stretching direction of the polyimide tape was along the direction of the diagonal line passing through the 1 st apex and the 2 nd apex on the opposite side to the 1 st apex in the rectangular sample piece on the glass plate, and the peeling angle based on the 2 nd release liner of the polyimide tape was 180 °. In such a 2 nd release liner release operation, the case where no release occurs between the 1 st release liner and the adhesive sheet was evaluated as "good" in releasability, and the case where release also occurs between the 1 st release liner and the adhesive sheet was evaluated as "poor" in releasability. The evaluation results are shown in tables 1 and 2.

TABLE 1

TABLE 2

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Claims

1. An optical adhesive sheet with a release liner, comprising:

an optical adhesive sheet having a 1 st surface and a 2 nd surface on the opposite side of the 1 st surface;

a 1 st release liner in releasable contact with the 1 st face; and

a 2 nd release liner in releasable contact with said 2 nd face,

the optical adhesive sheet has a shear storage modulus of 10MPa or less in the range of-40 ℃ to 100 ℃,

the ratio of the release force F2 for releasing the 2 nd release liner from the optical adhesive sheet to the release force F1 for releasing the 1 st release liner from the optical adhesive sheet is 0.1 to 0.6.

2. The release liner-equipped optical adhesive sheet according to claim 1, wherein,

the 1 st release liner has a 1 st base film and a 1 st release layer, the 1 st release layer being disposed on the optical adhesive sheet side of the 1 st base film and in contact with the optical adhesive sheet,

the 2 nd release liner has a 2 nd base film and a 2 nd release layer, the 2 nd release layer being disposed on the optical adhesive sheet side of the 2 nd base film and in contact with the optical adhesive sheet,

the ratio of the thickness of the 2 nd release layer to the thickness of the 1 st release layer is 0.16 or more and 15 or less.

3. The release liner-equipped optical adhesive sheet according to claim 2, wherein the 1 st release layer is a silicone release layer.

4. The release liner-equipped optical adhesive sheet according to claim 2, wherein the 2 nd release layer is a silicone release layer.

5. The release liner-equipped optical adhesive sheet according to any one of claims 1 to 4, wherein the optical adhesive sheet has a shear storage modulus of 1MPa or less at 25 ℃.

6. The release liner-equipped optical adhesive sheet according to any one of claims 1 to 4, wherein the optical adhesive sheet has a shear storage modulus of 0.005MPa or more in a range of-40 ℃ to 100 ℃.

7. The release liner-equipped optical adhesive sheet according to claim 5, wherein the optical adhesive sheet has a shear storage modulus of 0.005MPa or more in the range of-40 ℃ to 100 ℃.