WO2023074557A1

WO2023074557A1 - Optical pressure-sensitive adhesive sheet

Info

Publication number: WO2023074557A1
Application number: PCT/JP2022/039268
Authority: WO
Inventors: 裕貴小原
Original assignee: 日東電工株式会社
Priority date: 2021-10-27
Filing date: 2022-10-21
Publication date: 2023-05-04
Also published as: TW202328370A

Abstract

This pressure-sensitive adhesive sheet (10) is an optical pressure-sensitive adhesive sheet containing a base polymer. This pressure-sensitive adhesive sheet (10) has a gel percentage G (%) of 90% or less, a shear storage modulus E (MPa) at 25°C, and a product of the gel percentage G and shear storage modulus E of 5 or greater.

Description

optical adhesive sheet

The present invention relates to an optical adhesive sheet.

A display panel has a laminated structure including elements such as a pixel panel, a polarizing film and a cover glass. In the manufacturing process of the display panel, for example, an optically transparent adhesive sheet (optical adhesive sheet) is used for bonding elements included in the laminated structure. The optical adhesive sheet is produced, for example, as an optical adhesive sheet with a double-sided release liner. An optical pressure-sensitive adhesive sheet for use in display panels is described, for example, in Patent Document 1 below.

Japanese Patent Application Laid-Open No. 2020-122140

The laminated structure of the display panel includes elements with surface steps. For example, a decorative or light-shielding printed layer is provided on the edge of the surface of the cover glass on the pixel panel side, and there is a step (printed step) between the surface of the cover glass and the surface of the printed layer. Therefore, an optical pressure-sensitive adhesive sheet for display panel applications is required to have reliability in bonding between adherends as well as softness to the extent that it can follow printing steps (step conformability). Insufficient step followability of the optical adhesive sheet is caused, for example, by air bubbles being formed along the printed layer between the optical adhesive sheet and the cover glass bonded to the surface of the cover glass with the printed layer. cause and is undesirable.

From the viewpoint of conformability to unevenness, it is preferable that the optical adhesive sheet is soft. However, the softer the optical pressure-sensitive adhesive sheet, the more local recesses and streaks (grooves) are formed on the surface of the pressure-sensitive adhesive sheet when multiple sheets of the optical pressure-sensitive adhesive sheet (optical pressure-sensitive adhesive sheet with double-sided release liner) are stacked and stored. (lower storage stability). The formation of recesses and streaks in the optical adhesive sheet is not preferable because it causes unevenness in light transmission in the optical adhesive sheet.

The present invention provides an optical adhesive sheet suitable for achieving both step followability and storage stability.

The present invention [1] is an optical pressure-sensitive adhesive sheet containing a base polymer, having a gel fraction G (%) of 90% or less, a shear storage elasticity E (MPa) at 25°C, and the gel content An optical pressure-sensitive adhesive sheet in which the product of the modulus G and the shear storage modulus E is 5 or more.

The present invention [2] includes the optical adhesive sheet according to [1] above, wherein the gel fraction G is 40% or more.

The present invention [3] includes the optical pressure-sensitive adhesive sheet according to [1] or [2] above, wherein the shear storage modulus E is 0.1 MPa or more.

The present invention [4] includes the optical pressure-sensitive adhesive sheet according to any one of [1] to [3] above, wherein the shear storage modulus E is 0.3 MPa or less.

The present invention [5] includes the optical pressure-sensitive adhesive sheet according to any one of [1] to [4] above, wherein the base polymer has a weight average molecular weight of 300,000 or more.

The present invention [6] includes the optical adhesive sheet according to any one of [1] to [5] above, which is a photocurable adhesive sheet.

The present invention [7] further comprises a first release liner in releasable contact with one side in the thickness direction of the optical adhesive sheet, and a second release liner in releasable contact with the other side in the thickness direction of the optical adhesive sheet. The optical pressure-sensitive adhesive sheet according to any one of [1] to [6] above.

As described above, the optical pressure-sensitive adhesive sheet of the present invention has a gel fraction G (%) of 90% or less, and the product of the gel fraction G and the shear storage elasticity E (MPa) at 25° C. is , 5 or more. Such an optical pressure-sensitive adhesive sheet is suitable for ensuring a good balance between softness for realizing good step conformability and shape retention for realizing good storage stability. Therefore, the optical pressure-sensitive adhesive sheet of the present invention is suitable for achieving both step followability and storage stability.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of one Embodiment of the optical adhesive sheet of this invention. An example of the manufacturing method of the optical adhesive sheet shown in FIG. 1 is represented. 2A represents the process of forming a coating film of the pressure-sensitive adhesive composition, FIG. 2B represents the process of forming a sheet, FIG. 2C represents the process of peeling the light release liner, and FIG. 2D represents the post-addition to the base pressure-sensitive adhesive sheet. Representing the step of supplying the components, FIG. 2E represents the step of laminating another light release liner to the sheet. An example of the usage method of the optical adhesive sheet shown in FIG. 1 is represented. FIG. 3A shows the step of bonding the optical adhesive sheet to the first adherend, and FIG. 3B shows the first adherend and the second adherend via the optical adhesive sheet on the first adherend. represents the step of joining. 1 is a graph plotting measurement results of shear storage modulus E (horizontal axis) and gel fraction G (vertical axis) of optical pressure-sensitive adhesive sheets of Examples and Comparative Examples. 1 shows the positional relationship between a glass plate and an optical adhesive sheet in a joined body used for evaluation of conformability to steps in Examples and Comparative Examples.

A pressure-sensitive adhesive sheet 10 as an embodiment of the present invention has a sheet shape with a predetermined thickness and spreads in a direction perpendicular to the thickness direction H (plane direction), as shown in FIG. The adhesive sheet 10 has an adhesive surface 11 and an adhesive surface 12 opposite to the adhesive surface 11 . FIG. 1 shows a state in which

release liners

21 and 22 are adhered to

adhesive surfaces

11 and 12 of an adhesive sheet 10 . A release liner 21 is placed on the adhesive surface 11 . The release liner 21 is a first release liner releasably in contact with one surface (adhesive surface 11 ) of the adhesive sheet 10 in the thickness direction H. A release liner 22 is disposed on the adhesive surface 12 . The release liner 21 is a second release liner releasably in contact with the other surface (adhesive surface 12 ) of the adhesive sheet 10 in the thickness direction H. Moreover, the adhesive sheet 10 is an optically transparent adhesive sheet (optical adhesive sheet). The adhesive sheet 10 is, for example, an optical adhesive sheet that is arranged at a light passing portion of the display panel. Examples of display panels include liquid crystal panels and organic EL panels. A display panel has a laminated structure including elements such as, for example, a pixel panel, a polarizing film, a touch panel, and a cover glass. The pressure-sensitive adhesive sheet 10 is used, for example, for bonding elements included in a laminated structure in the manufacturing process of a display panel.

The adhesive sheet 10 contains a base polymer. The pressure-sensitive adhesive sheet 10 has a gel fraction G (%) of 90% or less, a shear storage elasticity E (MPa) at 25° C., and a product of the gel fraction G and the shear storage elasticity E (G× E) is 5 or more. Such a pressure-sensitive adhesive sheet 10 is suitable for ensuring a good balance between softness for realizing good step conformability and shape retention for realizing good storage stability. For example, in the pressure-sensitive adhesive sheet 10, even when the gel fraction G is relatively small, the product (G×E) is 5 or more, and the shear storage elastic modulus E is large to such an extent that the gel fraction G is small. can complement In the pressure-sensitive adhesive sheet 10, even when the shear storage elastic modulus E is relatively small, the gel fraction G is so large that the product (G×E) is 5 or more, so that the shear storage elastic modulus E is small. can complement Therefore, the pressure-sensitive adhesive sheet 10 is suitable for achieving both step followability and storage stability. Specifically, it is as shown in Examples and Comparative Examples below. In addition, in the pressure-sensitive adhesive sheet 10, from the viewpoint of ensuring a good balance between softness for realizing good conformability to steps and shape retention for realizing good storage stability, the product (G×E) is It is preferably 7 or more, more preferably 9 or more, still more preferably 10 or more, and is preferably 18 or less, more preferably 16 or less, still more preferably 14 or less.

The gel fraction G is preferably 40% by mass or more, more preferably 45% by mass, from the viewpoint of ensuring high shape restoration properties when local recesses and streaks (grooves) are temporarily generated in the adhesive sheet 10. Above, more preferably 50% by mass or more, still more preferably 55% by mass or more. In the pressure-sensitive adhesive sheet 10, a high shape-restoring property helps to achieve good storage stability. The gel fraction G is set from the viewpoint of reducing the internal stress (repulsive stress generated in the portion forced to deform due to the step) generated in the adhesive sheet 10 when the adhesive sheet 10 is attached to the stepped surface of the adherend. , preferably 85% by mass or less, more preferably 80% by mass or less, still more preferably 75% by mass or less, still more preferably 70% by mass or less, and particularly preferably 65% by mass or less. The fact that the internal stress of the adhesive sheet 10 is small helps to realize good step followability. Methods for adjusting the gel fraction G of the adhesive sheet 10 include, for example, selection of the type of base polymer in the adhesive sheet 10, adjustment of the molecular weight, and adjustment of the compounding amount. Methods for adjusting the gel fraction G of the pressure-sensitive adhesive sheet 10 include selection of the type of cross-linking agent when the base polymer is cross-linked with the cross-linking agent, adjustment of the molecular weight, and adjustment of the compounding amount. Moreover, the method for measuring the gel fraction G is as described later with regard to Examples.

The shear storage elastic modulus E is preferably 0.1 MPa or more, more preferably 0.12 MPa or more, and still more preferably 0.15 MPa or more from the viewpoint of ensuring high shape retention against the pressing force acting on the adhesive sheet 10. is. In the pressure-sensitive adhesive sheet 10, high shape retention is useful for achieving good storage stability. The shear storage elastic modulus E is preferably 0.3 MPa or less, more preferably 0.3 MPa or less, from the viewpoint of reducing the internal stress generated in the adhesive sheet 10 when and after the adhesive sheet 10 is attached to the stepped surface of the adherend. is 0.25 MPa or less, more preferably 0.22 MPa or less, still more preferably 0.2 MPa or less. The fact that the internal stress of the adhesive sheet 10 is small helps to realize good step followability. Methods for adjusting the shear storage modulus E of the adhesive sheet 10 include, for example, selection of the type of base polymer in the adhesive sheet 10, adjustment of the molecular weight, and adjustment of the compounding amount. Methods for adjusting the shear storage modulus E of the pressure-sensitive adhesive sheet 10 include selection of the type of cross-linking agent when the base polymer is cross-linked with the cross-linking agent, adjustment of the molecular weight, and adjustment of the compounding amount. Moreover, the method for measuring the shear storage modulus E of the pressure-sensitive adhesive sheet 10 at 25° C. is as described later with regard to Examples.

In the adhesive sheet 10, the base polymer is an adhesive component that develops adhesiveness. Base polymers include, for example, 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. From the viewpoint of ensuring good transparency and adhesiveness in the adhesive sheet 10, an acrylic polymer is preferably used as the base polymer.

An acrylic polymer is a copolymer of a monomer component (first monomer component) containing 50% by mass or more of (meth)acrylic acid ester. "(Meth)acrylic" means acrylic and/or methacrylic.

As the (meth)acrylic acid ester, an alkyl (meth)acrylic acid ester is preferably used, and an alkyl (meth)acrylic acid ester in which the alkyl group has 1 to 20 carbon atoms is more preferably used. The (meth)acrylic acid alkyl ester may have a linear or branched alkyl group, or may have an alicyclic alkyl group.

Examples of (meth)acrylic acid alkyl esters having a linear or branched alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, (meth)acryl Isobutyl acid, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, n-hexyl (meth)acrylate , Heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, (meth) Decyl acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (i.e. lauryl (meth)acrylate), isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, (meth)acrylate Pentadecyl acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, isostearyl (meth)acrylate, and nonadecyl (meth)acrylate.

Examples of (meth)acrylic acid alkyl esters having an alicyclic alkyl group include, for example, (meth)acrylic acid cycloalkyl esters, (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring, and tricyclic (Meth)acrylic acid esters having the above aliphatic hydrocarbon rings can be mentioned. Cycloalkyl (meth)acrylates include, for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. Examples of (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring include isobornyl (meth)acrylate. Examples of (meth)acrylic acid esters having a tricyclic or higher aliphatic hydrocarbon ring include, for example, dicyclopentanyl (meth)acrylate, tricyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2- Methyl-2-adamantyl (meth)acrylate and 2-ethyl-2-adamantyl (meth)acrylate.

The (meth)acrylic acid alkyl esters may be used alone, or two or more of them may be used in combination. As the (meth)acrylic acid alkyl ester, an acrylate alkyl ester having an alkyl group having 3 to 18 carbon atoms is preferably used, and more preferably n-butyl acrylate (BA) or cyclohexyl acrylate (CHA). , 2-ethylhexyl acrylate (2EHA), and isostearyl acrylate (ISTA).

The ratio of the (meth)acrylic acid alkyl ester in the monomer component is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably It is 75% by mass or more. The same ratio is, for example, 99% by mass or less.

The monomer component may contain a copolymerizable monomer other than (meth)acrylic acid that is copolymerizable with the (meth)acrylic acid alkyl ester. Such copolymerizable monomers include, for example, monomers having polar groups. Polar group-containing monomers include, for example, nitrogen atom-containing ring-containing monomers, hydroxyl group-containing monomers, and carboxy group-containing monomers. The polar group-containing monomer is useful for modifying the acrylic polymer, such as introducing cross-linking points into the acrylic polymer and securing the cohesive strength of the acrylic polymer.

Examples of monomers having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, (meth)acryloylmorpholine, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinyl Piperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N - vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, Included are N-vinylisoxazole, N-vinylthiazole, and N-vinylisothiazole. As the monomer having a nitrogen atom-containing ring, preferably at least one selected from the group consisting of N-vinyl-2-pyrrolidone (NVP) and acryloylmorpholine (ACMO) is used.

The ratio of the monomer having a nitrogen atom-containing ring in the monomer component is preferably 1% by mass or more, from the viewpoint of ensuring the cohesive force of the adhesive sheet 10 and ensuring the adhesion of the adhesive sheet 10 to the adherend. It is preferably 5% by mass or more, more preferably 8% by mass or more. The same ratio is preferably 30% by mass or less from the viewpoint of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (related to compatibility between various additive components and the acrylic polymer in the adhesive sheet 10). , more preferably 25% by mass or less, and still more preferably 20% by mass or less.

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

The ratio of the hydroxyl group-containing monomer in the monomer component is preferably 1% by mass or more, more preferably 3% 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 ensuring cohesive force in the pressure-sensitive adhesive sheet 10. is 5% by mass or more. The same ratio is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of adjusting the polarity of the acrylic polymer (related to the compatibility between the various additive components and the acrylic polymer in the adhesive sheet 10). is 17% by mass or less.

Carboxy group-containing monomers include, for example, (meth)acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

The proportion of the carboxyl group-containing monomer in the monomer component is preferably 0.00, from the viewpoints of introducing a crosslinked structure into the acrylic polymer, ensuring the cohesive force of the adhesive sheet 10, and ensuring the adhesion of the adhesive sheet 10 to the adherend. 05% by mass or more, more preferably 0.1% by mass or more, and still more preferably 0.5% by mass or more. The same proportion is preferably 5% by mass or less, more preferably 3% by mass or less, from the viewpoints of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of acid corrosion of the adherend.

The monomer component may contain other copolymerizable monomers. Other copolymerizable monomers include, for example, acid anhydride monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, alkoxy group-containing monomers, and aromatic vinyl compounds. be done. These other copolymerizable monomers may be used alone, or two or more of them may be used in combination.

The base polymer preferably has a crosslinked structure. Methods for introducing a crosslinked structure into the base polymer include, for example, the following first method and second method. In the first method, a base polymer having a functional group capable of reacting with a cross-linking agent and a cross-linking agent are blended in a pressure-sensitive adhesive composition, and the base polymer and the cross-linking agent are allowed to react in the pressure-sensitive adhesive sheet. In the second method, the monomer component forming the base polymer contains a polyfunctional compound as a cross-linking agent, and the polymer chain is polymerized to form a base polymer in which a branched structure (cross-linked structure) is introduced. do. These methods may be used in combination.

Examples of the cross-linking agent used in the first method include compounds that react with functional groups (such as hydroxyl groups and carboxy groups) contained in the base polymer. Such crosslinkers include, for example, isocyanate crosslinkers, peroxide crosslinkers, epoxy crosslinkers, oxazoline crosslinkers, aziridine crosslinkers, and carbodiimide crosslinkers. The cross-linking agents in the first method may be used alone, or two or more of them may be used in combination. As the cross-linking agent in the first method, an isocyanate cross-linking agent is preferably used because it has high reactivity with hydroxyl groups and carboxy groups in the base polymer and facilitates the introduction of a cross-linked structure.

Examples of isocyanate cross-linking agents include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, isocyanates, and polymethylene polyphenyl isocyanates. The isocyanate cross-linking agent also includes derivatives of these isocyanates. Examples of the isocyanate derivative include isocyanurate-modified products and polyol-modified products. Commercially available isocyanate cross-linking agents include, for example, Coronate L (trimethylolpropane adduct of tolylene diisocyanate, manufactured by Tosoh), Coronate HL (trimethylolpropane adduct of hexamethylene diisocyanate, manufactured by Tosoh), Coronate HX (hexa isocyanurate of methylene diisocyanate, manufactured by Tosoh), Takenate D110N (trimethylolpropane adduct of xylylene diisocyanate, manufactured by Mitsui Chemicals), and Takenate 600 (1,3-bis(isocyanatomethyl)cyclohexane, manufactured by Mitsui Chemicals) is mentioned.

Peroxide crosslinking agents include dibenzoyl peroxide, di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t- butyl peroxyneodecanoate, t-hexyl peroxypivalate, and t-butyl peroxypivalate.

Examples of epoxy cross-linking agents include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane tri glycidyl ether, diglycidylaniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane. .

The amount of the cross-linking agent in the first method is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, per 100 parts by mass of the base polymer, from the viewpoint of ensuring the cohesive force of the adhesive sheet 10. More preferably, it is 0.1 parts by mass or more. From the viewpoint of ensuring good tackiness in the pressure-sensitive adhesive sheet 10, the amount of the cross-linking agent blended with respect to 100 parts by mass of the base polymer is, for example, 5 parts by mass or less, preferably 1 part by mass or less, and more preferably 0.2 parts by mass. is less than

In the second method, the monomer component (including the polyfunctional compound and the monofunctional monomer for introducing the crosslinked structure) may be polymerized at once or in multiple stages. In the multi-stage polymerization method, first, a monofunctional monomer for forming a base polymer is polymerized (prepolymerization), thereby producing a partially polymerized product (a mixture of a polymer with a low degree of polymerization and an unreacted monofunctional monomer). A prepolymer composition is prepared containing Next, after adding a polyfunctional compound as a cross-linking agent to the prepolymer composition, a polymerization reaction is allowed to proceed in a reaction system containing the partially polymerized product and the polyfunctional compound (main polymerization).

Examples of polyfunctional compounds include polyfunctional monomers and polyfunctional oligomers containing two or more ethylenically unsaturated double bonds in one molecule. Polyfunctional monomers include polyfunctional (meth)acrylates.

Polyfunctional (meth)acrylates include bifunctional (meth)acrylates, trifunctional (meth)acrylates, and polyfunctional (meth)acrylates with tetrafunctional or higher functionality.

Examples of bifunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and 1,6-hexanediol. Di(meth)acrylates, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, ethoxylated bisphenol A diacrylate (BPAEODE), and neopentyl glycol di(meth)acrylate.

Examples of trifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tris(acryloyloxyethyl) isocyanurate.

Tetrafunctional or higher polyfunctional (meth)acrylates include, for example, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, alkyl-modified dipentaerythritol penta( meth)acrylates, and dipentaerythritol hexa(meth)acrylates.

As the polyfunctional (meth)acrylate, a tetrafunctional or higher polyfunctional (meth)acrylate is preferably used, and dipentaerythritol hexaacrylate (DPHA) is more preferably used.

Polyfunctional oligomers include, for example, urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, polyether (meth)acrylate oligomers, polyol (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, polyethylene glycol di(meth) Acrylates and polypropylene glycol di(meth)acrylates.

The polyfunctional compound as the cross-linking agent in the second method may be used alone, or two or more of them may be used in combination. As the polyfunctional compound, preferably at least one selected from the group consisting of 1,6-hexanediol diacrylate (HDDA), trimethylolpropane triacrylate (TMPTA), and urethane acrylate oligomer (UAO) is used. .

When a polyfunctional monomer is used as the polyfunctional compound, the amount of the polyfunctional monomer in the monomer component is preferably 0.02 parts by mass or more per 100 parts by mass of the monofunctional monomer, from the viewpoint of ensuring the cohesive force of the adhesive sheet 10. , more preferably 0.05 parts by mass or more, and still more preferably 0.07 parts by mass or more. From the viewpoint of ensuring good tackiness in the adhesive sheet 10, the amount of the polyfunctional monomer is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and still more preferably 1 part by mass per 100 parts by mass of the monofunctional monomer. It is below the department.

When a polyfunctional oligomer is used as the polyfunctional compound, the amount of the polyfunctional oligomer in the monomer component is preferably 0.2 parts by mass or more per 100 parts by mass of the monofunctional monomer from the viewpoint of ensuring the cohesive force of the adhesive sheet 10. , more preferably 0.5 parts by mass or more, and still more preferably 0.7 parts by mass or more. From the viewpoint of ensuring good tackiness in the adhesive sheet 10, the amount of the polyfunctional oligomer is preferably 8 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 3 parts by mass per 100 parts by mass of the monofunctional monomer. It is below the department.

The acrylic polymer (base polymer) can be formed by polymerizing the above monomer components. Polymerization methods include, for example, solution polymerization, emulsion polymerization, and solventless photopolymerization (eg, ultraviolet polymerization). Ethyl acetate and toluene, for example, are used as solvents for solution polymerization. A chain transfer agent may be used in the polymerization. Moreover, as a polymerization initiator, for example, a thermal polymerization initiator and a photopolymerization initiator are used. A polymerization initiator may be used independently and two or more types may be used together. The amount of the polymerization initiator used is preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, and still more preferably 0.07 parts by mass or more per 100 parts by mass of the monomer component. It is 1 part by mass or less, more preferably 0.5 parts by mass or less, and still more preferably 0.3 parts by mass or less.

Thermal polymerization initiators include, for example, azo polymerization initiators and peroxide polymerization initiators. Examples of azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionate)dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2- imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, and 2,2'-azobis(N,N'-dimethyleneisobutyramidine) dihydrochloride mentioned. Peroxide polymerization initiators include, for example, dibenzoyl peroxide, t-butyl permaleate, and lauroyl peroxide.

Examples of photopolymerization initiators include radical photopolymerization initiators, cationic photopolymerization initiators, and anionic photopolymerization initiators.

Examples of radical photopolymerization initiators include acylphosphine oxide photopolymerization initiators, benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators, α-ketol photopolymerization initiators, and aromatic sulfonyl chloride photopolymerization initiators. Polymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators are listed. be done.

Examples of acylphosphine oxide photopolymerization initiators include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenyl Included are phosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide. Examples of benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and 2,2-dimethoxy-1,2-diphenylethan-1-one. mentioned. Acetophenone-based photopolymerization initiators include, for example, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl ) dichloroacetophenone. Examples of α-ketol photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. . Examples of aromatic sulfonyl chloride photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzyl-based photopolymerization initiators include benzyl. Benzophenone photoinitiators include, for example, benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, and polyvinylbenzophenone. Examples of ketal photopolymerization initiators include benzyl dimethyl ketal. Thioxanthone photoinitiators include, for example, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

The weight-average molecular weight (Mw) of the base polymer is preferably 300,000 or more, more preferably 400,000 or more, and even more preferably 600,000 or more, from the viewpoint of securing the cohesive force of the adhesive sheet 10 . The weight-average molecular weight of the base polymer is preferably 1,200,000 or less, more than It is preferably 1,000,000 or less, more preferably 800,000 or less. The weight average molecular weight of the base polymer is measured by gel permeation chromatography (GPC) and calculated by polystyrene conversion. Specifically, the method for measuring the weight average molecular weight of the base polymer is as described later with regard to Examples.

The glass transition temperature (Tg) of the base polymer is preferably 0° C. or lower, more preferably -20° C. or lower, even more preferably -40° C. or lower, and still more preferably -40° C. or lower, from the viewpoint of ensuring sufficient flexibility in the pressure-sensitive adhesive sheet 10. -45°C or less. The glass transition temperature is, for example, −80° C. or higher.

For the glass transition temperature of the base polymer, the glass transition temperature (theoretical value) obtained based on the following Fox formula may be used. The Fox equation is a relational expression between the glass transition temperature Tg of a polymer and the glass transition temperature Tgi of a homopolymer of monomers constituting the polymer. In the Fox formula below, Tg represents the glass transition temperature (° C.) of the polymer, Wi represents the weight fraction of the monomer i constituting the polymer, and Tgi represents the glass transition of the homopolymer formed from the monomer i. Indicates temperature (°C). Literature values can be used for the glass transition temperature of homopolymers. For example, the "Polymer Handbook" (4th edition, John Wiley & Sons, Inc., 1999) lists the glass transition temperatures of various homopolymers. On the other hand, the glass transition temperature of a homopolymer of a monomer can also be determined by the method specifically described in JP-A-2007-51271.

The adhesive sheet 10 may be a photocurable adhesive sheet (photocurable adhesive sheet). The term “photocurability” refers to the property of becoming highly elastic when irradiated with active energy rays such as ultraviolet rays. The photocurable adhesive sheet 10 preferably further contains a photopolymerizable polyfunctional compound and a photopolymerization initiator. The photocurable pressure-sensitive adhesive sheet 10 can be attached to the stepped surface of the adherend in a soft state before being photocured (can be photocured after being attached). Such a pressure-sensitive adhesive sheet 10 is preferable for realizing good step followability in bonding to an adherend having a stepped surface.

Examples of photopolymerizable polyfunctional compounds include polyfunctional monomers and polyfunctional oligomers. The photopolymerizable polyfunctional compound may be used alone, or two or more of them may be used in combination.

Examples of polyfunctional monomers include the polyfunctional monomers described above as polyfunctional compounds for forming the base polymer. At least one selected from the group consisting of ethoxylated bisphenol A diacrylate (BPAEODE), trimethylolpropane triacrylate (TMPTA), and dipentaerythritol hexaacrylate (DPHA) is preferably used as the polyfunctional monomer.

When a polyfunctional monomer is used as the photopolymerizable polyfunctional compound, the content of the polyfunctional monomer in the adhesive sheet 10 is preferably 0.6 parts by mass or more, more preferably 0.9 parts by mass per 100 parts by mass of the base polymer. parts or more, more preferably 1.2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and even more preferably 8 parts by mass or less. Such a configuration is suitable for ensuring good bonding reliability in the adhesive sheet 10 after photocuring.

Examples of polyfunctional oligomers include the polyfunctional oligomers described above as polyfunctional compounds for forming the base polymer. At least one selected from the group consisting of urethane acrylate oligomer (UAO) and polypropylene glycol diacrylate (PGDA) is preferably used as the polyfunctional oligomer.

When a polyfunctional oligomer is used as the photopolymerizable polyfunctional compound, the content of the polyfunctional oligomer in the adhesive sheet 10 is preferably 0.6 parts by mass or more, more preferably 0.9 parts by mass per 100 parts by mass of the base polymer. parts or more, more preferably 1.2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and even more preferably 8 parts by mass or less. Such a configuration is suitable for ensuring good bonding reliability in the adhesive sheet 10 after photocuring.

Examples of the photopolymerization initiator (third photopolymerization initiator described later) include the photopolymerization initiators described above as the photopolymerization initiator for base polymer polymerization. The content of the photopolymerization initiator in the adhesive sheet 10 is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and still more preferably 0.03 parts by mass or more per 100 parts by mass of the base polymer. Preferably, it is 0.05 parts by mass or more. Such a configuration is preferable for forming a crosslinked network with a sufficient crosslink density in the adhesive sheet 10 by a photopolymerization reaction when the adhesive sheet 10 is irradiated with light, thereby significantly changing the viscoelasticity of the adhesive sheet 10. . The content of the photopolymerization initiator in the adhesive sheet 10 is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less per 100 parts by mass of the base polymer. Such a configuration is preferable for suppressing excessive generation of the polymerization initiator when the adhesive sheet 10 is irradiated with light and for forming a long-distance and continuous crosslinked network by photopolymerization reaction.

The adhesive sheet 10 may contain an oligomer in addition to the base polymer. The oligomer preferably has a glass transition temperature higher than that of the base polymer. The pressure-sensitive adhesive sheet 10 containing such an oligomer is preferable from the viewpoint of ensuring the adhesive strength of the pressure-sensitive adhesive sheet 10 to the adherend. As for the glass transition temperature of the oligomer, the glass transition temperature (theoretical value) obtained based on the above Fox formula may be used.

When the base polymer of the adhesive sheet 10 is an acrylic polymer, the oligomer is preferably an acrylic oligomer. The acrylic oligomer is a copolymer of a monomer component (second monomer component) containing 50% by mass or more of (meth)acrylic acid alkyl ester.

As the acrylic oligomer, an acrylic oligomer that does not have a polar group is preferable. Such acrylic oligomers are preferably a (meth)acrylic acid alkyl ester having a chain alkyl group (chain alkyl (meth)acrylate) and a (meth)acrylic acid alkyl ester having an alicyclic alkyl group (fatty). It is a copolymer of monomer components containing cyclic alkyl (meth)acrylate). Specific examples of these (meth)acrylic acid alkyl esters include, for example, the (meth)acrylic acid alkyl esters described above with respect to the base polymer.

As the chain alkyl (meth)acrylate, methyl methacrylate is preferable because it has a high glass transition temperature (Tg) and excellent compatibility with the acrylic polymer. As the alicyclic alkyl (meth)acrylate, dicyclopentanyl acrylate, dicyclopentanyl methacrylate (DCPMA), cyclohexyl acrylate, and cyclohexyl methacrylate are preferable from the viewpoint of achieving a high Tg of the acrylic oligomer. That is, the acrylic oligomer is a polymerization of a monomer component containing one or more selected from the group consisting of dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate, and methyl methacrylate. It is preferably an object.

The proportion of the alicyclic alkyl (meth)acrylate in the monomer component of the acrylic oligomer is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and particularly preferably 35% by mass or more. . The same ratio is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. The proportion of chain alkyl (meth)acrylate in the monomer component of the acrylic oligomer is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. The same ratio is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and particularly preferably 35% by mass or more. These constitutions regarding the monomer composition of the acrylic oligomer are preferable from the viewpoint of compatibility between the hydrophobicity and the increase in Tg of the acrylic oligomer.

The acrylic oligomer is obtained by polymerizing the monomer component of the acrylic oligomer. Polymerization methods include, for example, solution polymerization, emulsion polymerization, and active energy ray polymerization (eg, UV polymerization). A polymerization initiator may be used in the polymerization of the acrylic oligomer. A chain transfer agent may be used in the polymerization of the acrylic oligomer.

The weight-average molecular weight of the acrylic oligomer is preferably 2,000 or more, more preferably 3,000 or more, and even more preferably 4,000 or more, from the viewpoint of exhibiting the functions of the acrylic oligomer. The weight-average molecular weight of the acrylic oligomer is preferably 8,000 or less, more preferably 6,500 or less, and even more preferably 6,000, from the viewpoint of securing the mobility of the acrylic oligomer in the adhesive sheet 10 and achieving high concentration distribution on the adhesive surface. It is below.

When the adhesive sheet 10 contains an acrylic oligomer, the content of the acrylic oligomer in the adhesive sheet 10 is preferably 0.05 parts by mass or more per 100 parts by mass of the base polymer in order to sufficiently increase the adhesive strength of the adhesive sheet 10. , more preferably 0.1 parts by mass or more, and still more preferably 0.2 parts by mass or more. From the viewpoint of ensuring the transparency of the adhesive sheet 10, the content of the acrylic oligomer in the adhesive sheet 10 is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass per 100 parts by mass of the base polymer. It is below the department. In the pressure-sensitive adhesive sheet 10, when the content of the acrylic oligomer is too large, the haze tends to increase and the transparency tends to decrease due to the decrease in compatibility of the acrylic oligomer.

The adhesive sheet 10 may contain other components as necessary. Other ingredients include, for example, solvents, UV absorbers, antioxidants, rust inhibitors, silane coupling agents, and antistatic agents. The solvent includes, for example, a polymerization solvent that is optionally used during polymerization of the acrylic polymer, and a solvent that is added to the polymerization reaction solution after polymerization. For example, ethyl acetate and toluene are used as the solvent.

UV absorbers include triazine UV absorbers, benzotriazole UV absorbers, benzophenone UV absorbers, salicylate UV absorbers, and cyanoacrylate UV absorbers. As the ultraviolet absorber, a triazine ultraviolet absorber is preferable because it has high absorbability of ultraviolet rays in the wavelength range of 320 nm to 370 nm and excellent compatibility with the acrylic polymer. The ultraviolet absorbers may be used alone, or two or more of them may be used in combination.

Commercially available triazine UV absorbers include, for example, bisethylhexyloxyphenolmethoxyphenyltriazine (trade name “Tinosorb S”, manufactured by BASF), 2-(4,6-bis(2,4-dimethylphenyl)-1,3 2-(2,4-dihydroxyphenyl)-4, a reaction product of ,5-triazin-2-yl)-5-hydroxyphenyl and [(alkyloxy)methyl]oxirane (product name “TINUVIN400”, manufactured by BASF) ,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidate reaction product (product name "TINUVIN 405", manufactured by BASF), (2, 4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (product name “TINUVIN 460”, manufactured by BASF), 2-(4,6 -diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol (product name "TINUVIN 577", manufactured by BASF), 2-(2-hydroxy-4-[1-octyl) oxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (product name “TINUVIN 479”, manufactured by BASF), and 2-(4,6-diphenyl-1, 3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol (“ADK STAB LA-46”, manufactured by ADEKA).

Commercially available benzotriazole UV absorbers include, for example, 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3- Tetramethylbutyl)phenol (product name “TINUVIN 928”, manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (product name “TINUVIN PS”, manufactured by BASF), 2-(2H -benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (product name "TINUVIN 900", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6 -dodecyl-4-methylphenol (product name "TINUVIN571", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (product name "TINUVIN P", manufactured by BASF), 2-(2H-benzo Triazol-2-yl)-4-6-bis(1-methyl-1-phenylethyl)phenol (product name “TINUVIN 234”, manufactured by BASF), 2-[5-chloro(2H)-benzotriazol-2-yl ]-4-methyl-6-(tert-butyl)phenol (product name “TINUVIN 326”, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (product name "TINUVIN 328", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (product name "TINUVIN 329", manufactured by BASF), and , 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole (product name “Sumisorb 250”, manufactured by Sumitomo Chemical).

The content of the UV absorber in the adhesive sheet 10 is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more per 100 parts by mass of the base polymer, from the viewpoint of ensuring the UV-cutting function of the adhesive sheet 10. and preferably 3 parts by mass or less, more preferably 2 parts by mass or less.

Examples of antioxidants include phenol antioxidants, phosphorus antioxidants, sulfur antioxidants, and amine antioxidants. The antioxidants may be used alone, or two or more of them may be used in combination.

As the antioxidant, a phenolic antioxidant is preferably used, and a hindered phenolic antioxidant is more preferably used. Hindered phenol antioxidants include, for example, pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (product name "Irganox 1010", manufactured by BASF), octadecyl -3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (product name “Irganox 1076”, manufactured by BASF), 4,6-bis(dodecylthiomethyl)-o-cresol (product name “Irga Nox 1726", manufactured by BASF), triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] (product name "Irganox 245", manufactured by BASF), bis(2, 2,6,6-tetramethyl-4-piperidyl) sebacate (product name “TINUVIN770”, manufactured by BASF), and dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidine ethanol (product name "TINUVIN622", manufactured by BASF).

From the viewpoint of suppressing oxidative deterioration of the adhesive sheet 10, the content of the antioxidant in the adhesive sheet 10 is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more per 100 parts by mass of the base polymer. Also, it is preferably 3 parts by mass or less, more preferably 2 parts by mass or less.

Examples of silane coupling agents include silane coupling agents containing epoxy groups. Epoxy group-containing silane coupling agents include, for example, 3-glycidoxydialkyldialkoxysilanes and 3-glycidoxyalkyltrialkoxysilanes. 3-glycidoxydialkyldialkoxysilanes include, for example, 3-glycidoxypropylmethyldimethoxysilane and 3-glycidoxypropylmethyldiethoxysilane. 3-glycidoxyalkyltrialkoxysilanes include, for example, 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane. As the silane coupling agent, 3-glycidoxyalkyltrialkoxysilane is preferably used, and 3-glycidoxypropyltrimethoxysilane is more preferably used.

The content of the silane coupling agent in the adhesive sheet 10 is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 5 parts by mass or less, per 100 parts by mass of the base polymer. More preferably, it is 3 parts by mass or less.

The thickness of the adhesive sheet 10 is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of ensuring sufficient adhesion to the adherend and from the viewpoint of handling. The thickness of the adhesive sheet 10 is preferably 300 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and even more preferably 120 μm or less, from the viewpoint of thinning the display panel.

The haze of the adhesive sheet 10 is preferably 1% or less, more preferably 0.8% or less, even more preferably 0.6% or less, and particularly preferably 0.4% or less. Such a configuration is preferable for suppressing light scattering in the pressure-sensitive adhesive sheet 10 and ensuring the transparency required for display panel applications. The haze of the adhesive sheet 10 is, for example, 0.01% or more. Haze can be measured using a haze meter in accordance with JIS K7136 (2000). Examples of the haze meter include "NDH2000" manufactured by Nippon Denshoku Industries Co., Ltd. and "HM-150N" manufactured by Murakami Color Research Laboratory. Specifically, the method for measuring haze is as described later with regard to Examples.

The total light transmittance of the adhesive sheet 10 is preferably 80% or higher, more preferably 85% or higher, and even more preferably 90% or higher. The total light transmittance of the adhesive sheet 10 is, for example, 100% or less. The total light transmittance of the adhesive sheet 10 can be measured according to JIS K 7375 (2008). The method for measuring the total light transmittance is specifically described later with regard to Examples.

The adhesive sheet 10 can be manufactured, for example, as follows (solvent-free manufacturing method).

First, a prepolymer composition is prepared by solvent-free photopolymerization. Specifically, first, a mixture (liquid) containing the above-described monofunctional monomer for forming the base polymer and a photopolymerization initiator (first photopolymerization initiator) is prepared. This mixture is solvent-free. Next, by irradiating the mixture with ultraviolet rays, part of the monofunctional monomers in the mixture is photopolymerized to obtain a prepolymer composition (solvent-free prepolymer composition). Light sources for ultraviolet irradiation include, for example, ultraviolet LED lights, black lights, high-pressure mercury lamps, and metal halide lamps. Moreover, in the ultraviolet irradiation, a wavelength cut filter for cutting a part of the wavelength region of the light emitted from the light source may be used as necessary. In the ultraviolet irradiation, the illuminance is, for example, 5 to 200 mW/cm ² , and the integrated irradiation light amount is, for example, 100 to 5000 mJ/cm ² . UV irradiation is preferably continued until the composition has a viscosity of about 15 to 25 Pa·s. This viscosity is a value measured with a Brookfield viscometer under the conditions of rotor No. 5, rotor speed of 10 rpm, and temperature of 30°C. The prepolymer composition contains a photopolymerized monofunctional monomer (photopolymerized polymer) and a monofunctional monomer that has not undergone a polymerization reaction (residual monomer). Also, the prepolymer composition is solvent-free. A photopolymer is a polymer produced by photopolymerization. Photopolymerization is a polymerization method in which the polymerization reaction of polymerizable components proceeds by irradiation with active energy rays such as ultraviolet rays.

Next, a photopolymerizable polyfunctional compound, a photopolymerization initiator (second photopolymerization initiator), and optionally other components are added to the prepolymer composition to prepare a pressure-sensitive adhesive composition. do. Other ingredients include, for example, antioxidants and silane coupling agents. Since the adhesive composition does not contain a solvent, it is a solvent-free adhesive composition.

Next, as shown in FIG. 2A, a coating film 10a is formed between the release liners 21 and 22 (coating film forming step). Specifically, the adhesive composition is applied onto the release liner 21 to form the coating film 10a, and then the release liner 22 is adhered onto the coating film 10a on the release liner 21. For example, release liner 22 is a light release liner with less release force than release liner 21, and release liner 21 is a heavy release liner.

The

release liners

21 and 22 are each, for example, a flexible plastic film. Examples of such plastic films include polyester films such as polyethylene terephthalate films, polyethylene films, and polypropylene films. The thickness of the release liner is, for example, 3 μm or more and, for example, 200 μm or less. The surface of the release liner is preferably release treated.

Examples of methods for applying the adhesive composition include roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, and lip coating. , and die coats.

Next, as shown in FIG. 2B, the coating film 10a between the

release liners

21 and 22 is irradiated with ultraviolet rays to form the adhesive sheet 10 (sheet forming step). When irradiated with ultraviolet rays, a photopolymerization reaction proceeds in the reaction system containing the above-mentioned residual monomer and the photopolymerizable polyfunctional compound in the coating film to form a photopolymerized polymer (base polymer) having a photocrosslinked structure. Thereby, the adhesive sheet 10 having no photocurability is obtained.

In order to manufacture the photocurable pressure-sensitive adhesive sheet 10, as shown in FIG. 2C, the pressure-sensitive adhesive sheet 10 obtained in the sheet forming process is used as a base pressure-sensitive adhesive sheet 10b, and a release liner 22 is formed from the base pressure-sensitive adhesive sheet 10b. is peeled off (peeling step).

Next, as shown in FIG. 2D, the post-additive component is supplied to the base adhesive sheet 10b (post-additive component supply step). For example, a post-additive component solution (not shown) containing a post-additive component and a solvent is applied to the exposed surface of the base adhesive sheet 10b. The post-addition component contains a photopolymerizable polyfunctional compound and a photopolymerization initiator (third photopolymerization initiator), and may contain additives such as ultraviolet absorbers and antioxidants. Next, while permeating the post-addition component from the surface of the base adhesive sheet 10b into the base adhesive sheet 10b, the solvent is vaporized by heating as necessary. Prior to this step, the base polymer already has a crosslinked structure to form the base adhesive sheet 10b. Therefore, the vaporization of the solvent in this step hardly forms the surface of the citrus peel on the base adhesive sheet 10b (it is not substantially formed). Also, the photocurable adhesive sheet 10 is formed by the base adhesive sheet 10b and the post-addition component. The amount of the photopolymerizable polyfunctional compound added in this step is preferably 2.5 parts by mass or more, more preferably 3 parts by mass or more, per 100 parts by mass of the photopolymer polymer formed in the above-described sheeting process. More preferably 3.5 parts by mass or more, preferably 12 parts by mass or less, more preferably 8 parts by mass or less, still more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less. Such a configuration is suitable for ensuring good bonding reliability in the adhesive sheet 10 after photocuring.

Next, as shown in FIG. 2E, another release liner 22 is adhered to the adhesive sheet 10 (lamination step).

As described above, the adhesive sheet 10 whose adhesive surface is covered and protected by the

release liners

21 and 22 can be manufactured. The pressure-sensitive adhesive sheet 10 formed from a solvent-free pressure-sensitive adhesive composition is suitable for reducing environmental loads. Also, the

release liners

21 and 22 are peeled off from the adhesive sheet 10 when the adhesive sheet 10 is used.

The adhesive sheet 10 can also be manufactured by the following method (solvent type manufacturing method).

First, the base polymer is formed by solution polymerization. Thereby, a polymer solution containing the base polymer is obtained.

Next, ingredients other than the base polymer are added to the polymer solution as needed. In order to manufacture the photocurable adhesive sheet 10, a photopolymerizable polyfunctional compound and a photopolymerization initiator are added as other components. A pressure-sensitive adhesive composition is thus obtained.

Next, after the adhesive composition is applied onto the release liner 21 to form a coating film, the coating film is dried. The drying temperature of the coating film is, for example, 50°C to 200°C. The drying time is, for example, 5 seconds to 20 minutes. After that, the release liner 22 is laminated on the adhesive sheet 10 on the release liner 21 .

As described above, the adhesive sheet 10 in which the

adhesive surfaces

11 and 12 are covered and protected by the

release liners

21 and 22 can be manufactured. The

release liners

3A and 3B show an example of how to use the adhesive sheet 10. FIG. The method of using the adhesive sheet 10 is a method of bonding adherends using the adhesive sheet 10 .

In this method, first, as shown in FIG. 3A, the adhesive sheet 10 is attached to the cover glass 31 (first adherend). The cover glass 31 has a first surface 31a and a second surface 31b opposite to the first surface 31a. A printing layer 32 for decoration or light shielding is formed on the edge of the first surface 31a. The printed layer 32 is provided, for example, over the entire periphery of the edge of the cover glass 31 . The cover glass 31 has a step (printing step) between the first surface 31 a and the surface of the printed layer 32 . That is, the cover glass 31 is a stepped adherend having a stepped surface. Specifically, in this step, the adhesive sheet 10 is attached to the area including the printed layer 32 on the surface 31 a of the cover glass 31 . FIG. 3A exemplarily shows a case where the adhesive sheet 10 is attached to the entire surface 31a of the cover glass 31. FIG.

Next, as shown in FIG. 3B, the cover glass 31 and the member 33 are joined with the adhesive sheet 10 on the cover glass 31 interposed therebetween. The member 33 is, for example, a pixel panel for a display panel, a polarizing film, or a touch panel. Thereby, the joined body W is obtained. In the joined body W, the cover glass 31 and the member 33 are joined with the adhesive sheet 10 .

When the adhesive sheet 10 is photocurable, the adhesive sheet 10 in the joined body W is photocured by ultraviolet irradiation. Due to the ultraviolet irradiation, the photopolymerization reaction of the photopolymerizable polyfunctional compound proceeds in the adhesive sheet 10 to form a photopolymerized product of the photopolymerizable polyfunctional compound. Since the photopolymerization reaction proceeds around the base polymer, a photopolymerized product of the photopolymerizable polyfunctional compound is formed while forming an interpenetrating polymer network (IPN) with the base polymer. Thereby, the pressure-sensitive adhesive sheet 10 becomes highly elastic. Light sources for ultraviolet irradiation include, for example, ultraviolet LED lights, black lights, high-pressure mercury lamps, and metal halide lamps. Moreover, in ultraviolet irradiation, a wavelength cut filter may be used to cut a part of the wavelength region of the light emitted from the light source. In the ultraviolet irradiation, the illuminance is, for example, 5 to 200 mW/cm ² , and the integrated irradiation light amount is, for example, 50 to 10000 mJ/cm ² .

The present invention will be specifically described below with reference to examples. However, the invention is not limited to the examples. In addition, the specific numerical values such as the compounding amount (content), physical property values, parameters, etc. described below are the corresponding compounding amounts ( content), physical properties, parameters, etc., upper limits (values defined as “less than” or “less than”) or lower limits (values defined as “greater than” or “greater than”).

[Example 1]
<Preparation of prepolymer composition>
In a flask, to a monomer mixture of 78 parts by mass of n-butyl acrylate (BA), 16 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 6 parts by mass of 4-hydroxybutyl acrylate (4HBA), After adding a total of 0.07 parts by mass of the two types of first photopolymerization initiators, the mixture is irradiated with ultraviolet rays in a nitrogen atmosphere to polymerize some of the monomer components in the mixture and preform. A polymer composition was obtained. As the first photopolymerization initiator, 0.035 parts by mass of "Omnirad 184" (1-hydroxycyclohexylphenyl ketone) manufactured by IGM Resins, and "Omnirad 651" manufactured by IGM Resins (2,2-dimethoxy-1,2 -diphenylethan-1-one) 0.035 parts by mass. UV irradiation was continued until the viscosity of the composition reached about 20 Pa·s. This viscosity is a value measured with a Brookfield viscometer under the conditions of rotor No. 5, rotor speed of 10 rpm, and temperature of 30° C. (the same applies to viscosity described later). The resulting prepolymer composition is a partially polymerized product containing a photopolymerized product (photopolymerized polymer P1a) and a monomer component (residual monomer) that has not undergone a polymerization reaction.

<Preparation of adhesive composition>
Next, 100 parts by weight of the prepolymer composition, 2 parts by weight of acryloylmorpholine (ACMO) as an additional monomer, 8 parts by weight of 4-hydroxybutyl acrylate (4HBA) as another additional monomer, and 1.2 parts by mass of urethane acrylate oligomer (UAO) (product name “Art Resin UN-350 NDTN001BA”, manufactured by Negami Kogyo Co., Ltd.), 0.4 parts by mass of a second photopolymerization initiator, and an antioxidant (product name “Irga Nox 1010", manufactured by BASF) 0.5 parts by mass, a rust inhibitor (product name "BT-120", benzotriazole, manufactured by Johoku Chemical Industry Co., Ltd.) 0.15 parts by mass, and a silane coupling agent (product name "KBM- 403", 3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed with 0.35 parts by mass to obtain an adhesive composition. As the second photopolymerization initiator, "Omnirad 819" (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) manufactured by IGM Resins was used.

<Preparation of base adhesive sheet>
Next, a pressure-sensitive adhesive composition is applied onto the release-treated surface of the first release liner (product name: "Diafoil MRF", thickness: 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side to form a coating film. bottom. Next, the release-treated surface of the second release liner (product name: "Diafoil MRE", thickness: 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side was laminated onto the coating film on the first release liner. rice field. Next, the coating film between the release liners was irradiated with ultraviolet rays from the second release liner side, and the coating film was photocured to form a pressure-sensitive adhesive layer with a thickness of 100 μm (ultraviolet irradiation step). In the ultraviolet irradiation, a black light (manufactured by Toshiba) was used as a light source, the illuminance was set to 6.5 mW/cm ² , and the irradiation integrated light amount was set to 1500 mJ/cm ² . In the UV irradiation step, the photopolymerization reaction proceeds in the reaction system containing the residual monomer, the additional monomer, and the cross-linking agent in the coating film to form a photopolymerization polymer P1b having a photo-crosslinked structure. Moreover, since the photopolymerization reaction proceeds around the photopolymerization polymer P1a, the photopolymerization polymer P1b is formed around the photopolymerization polymer P1a. The adhesive layer formed in this step contains the photopolymerization polymer P1a and the photopolymerization polymer P1b as base polymers. As described above, a base PSA sheet with a double-sided release liner (first release liner/base PSA sheet (thickness: 100 μm)/second release liner) was produced.

<Preparation of post-addition component solution>
16.1 parts by mass of trimethylolpropane triacrylate (TMPTA) (product name “Viscoat #295”, manufactured by Osaka Organic Chemical Industry Co., Ltd.) as a photopolymerizable polyfunctional compound, and 0.68 parts by mass of a third photopolymerization initiator A post-additive component solution was prepared by mixing 3.5 parts by mass of an ultraviolet absorber (product name “Tinosorb S”, manufactured by BASF) and 39.7 parts by mass of ethyl acetate as a solvent (other than the solvent in the solution is a post-addition ingredient). As the third photopolymerization initiator, "Omnirad819" manufactured by IGM Resins was used. Table 1 shows the composition of the post-addition component solution. In Table 1, the unit of the blending amount of each component is relative "parts by mass".

<Production of optical adhesive sheet>
After peeling off the second release liner from the double-sided release liner-attached base PSA sheet, the exposed surface of the base PSA sheet was coated with a post-additive component solution to a thickness of 20 μm (coating treatment). A bar coater RDS No. 10 manufactured by RD SPECIALTIES was used for coating. Next, it was dried in a dryer at 110° C. for 60 seconds. The post-addition components (photopolymerizable polyfunctional compound, third photopolymerization initiator, ultraviolet absorber) were permeated into the base adhesive sheet and the solvent was vaporized by the coating treatment and the drying treatment. A photocurable pressure-sensitive adhesive sheet S1 was formed by permeation of the post-addition component into the base pressure-sensitive adhesive sheet. The amount of the photopolymerizable polyfunctional compound (TMPTA) added is 5.6 parts by mass per 100 parts by mass of the base polymer (the total of 100 parts by mass of the prepolymer composition, the additional monomer and the cross-linking agent). The amount of 3 photopolymerization initiator (Omnirad 819) added was 0.24 parts by mass (in Table 2, the relative amount of each component is shown in parentheses attached to the component; the same applies to Table 3). Next, on the optical adhesive sheet on the first release liner, the release-treated surface of the third release liner (product name: "Diafoil MRE", thickness: 75 µm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side was pasted. Matched.

As described above, the adhesive sheet S1 with a double-sided release liner (first release liner/adhesive sheet S1 (thickness: 100 μm)/third release liner) of Example 1 was produced. The adhesive sheet S1 is a photocurable optical adhesive sheet containing a base polymer, a photopolymerizable polyfunctional compound, and a third photopolymerization initiator.

[Example 2]
PSA sheet S2 with a double-sided release liner of Example 2 was prepared in the same manner as PSA sheet S1 with a double-sided release liner of Example 1 except for the following.

　In the preparation of the adhesive composition, the amount of the cross-linking agent (UAO) was set to 0.8 parts by mass. In the preparation of the post-additive component solution, the amount of TMPTA (photopolymerizable polyfunctional compound) was 5.7 parts by mass, and another photopolymerizable polyfunctional compound was ethoxylated bisphenol A diacrylate (BPAEODE) (product name “ABE -300", manufactured by Shin-Nakamura Chemical Co., Ltd.) 1.8 parts by mass, the amount of the third photopolymerization initiator (Omnirad 819) is 1.4 parts by mass, and the amount of ethyl acetate is 49.1 parts by mass. part. In this example, the adhesive sheet S2 (a photocurable optical adhesive sheet containing a base polymer, a photopolymerizable polyfunctional compound, and a third photopolymerization initiator) was prepared from such an adhesive composition and a post-additive component solution. ) was formed. In this example, the amount of TMPTA added as the photopolymerizable polyfunctional compound per 100 parts by weight of the base polymer was 2.0 parts by mass, and the amount of BPAEODE added as another photopolymerizable polyfunctional compound was 0. 6 parts by weight, and the amount of the third photoinitiator (Omnirad 819) added is 0.5 parts by weight (shown in Table 2).

[Example 3]
PSA sheet S3 with a double-sided release liner of Example 3 was produced in the same manner as PSA sheet S1 with a double-sided release liner of Example 1 except for the following.

In the preparation of the pressure-sensitive adhesive composition, the amount of the cross-linking agent (UAO) was set to 1.7 parts by mass. In the preparation of the post-additive component solution, the amount of TMPTA (photopolymerizable polyfunctional compound) was 11.4 parts by mass, the amount of the third photopolymerization initiator (Omnirad 819) was 0.5 parts by mass, and ethyl acetate was 44.6 parts by mass. In this example, the adhesive sheet S3 (a photocurable optical adhesive sheet containing a base polymer, a photopolymerizable polyfunctional compound, and a third photopolymerization initiator) was prepared from such an adhesive composition and a post-additive component solution. ) was formed. In this example, the added amount of the photopolymerizable polyfunctional compound (TMPTA) was 4.0 parts by mass, and the added amount of the third photopolymerization initiator (Omnirad 819) was 0.18 parts per 100 parts by mass of the base polymer. Parts by weight (shown in Table 2).

[Example 4]
<Preparation of base polymer>
64.5 parts by mass of n-butyl acrylate (BA) and 9.6 parts of N-vinyl-2-pyrrolidone (NVP) were placed in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube. parts by mass, 4-hydroxybutyl acrylate (4HBA) 14.9 parts by mass, cyclohexyl acrylate (CHA) 6.0 parts by mass, isostearyl acrylate (ISTA) 5.0 parts by mass, and thermal polymerization initiation 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as an agent, 0.1 parts by mass of α-thioglycerol as a chain transfer agent, and 170 parts by mass of ethyl acetate as a polymerization solvent. The mixture was reacted at 56° C. for 5 hours and then at 70° C. for 3 hours while stirring under a nitrogen atmosphere (polymerization reaction). As a result, a polymer solution containing an acrylic polymer (base polymer) was obtained.

<Preparation of acrylic oligomer>
60 parts by mass of dicyclopentanyl methacrylate (DCPMA), 40 parts by mass of methyl methacrylate (MMA), and a chain transfer agent A mixture containing 3.5 parts by mass of α-thioglycerol as a solvent and 100 parts by mass of toluene as a polymerization solvent was stirred at 70° C. for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by mass of AIBN as a thermal polymerization initiator is added to the mixture to prepare a reaction solution, and the mixture is reacted at 70 ° C. for 2 hours and then at 80 ° C. for 2 hours under a nitrogen atmosphere. (polymerization reaction). Next, by heating the reaction solution at 130° C., the toluene and the chain transfer agent were volatilized and removed. As a result, an acrylic oligomer (solid form) was obtained. The weight average molecular weight of this acrylic oligomer was 5,100.

<Preparation of adhesive composition>
In the above polymer solution, 0.3 parts by mass of the above acrylic oligomer per 100 parts by mass of the base polymer, and polypropylene glycol diacrylate (PGDA) as a photopolymerizable polyfunctional compound (product name "APG-400", Shin-Nakamura Chemical Industry) Co., Ltd.) 6.4 parts by mass, 5.1 parts by mass of dipentaerythritol hexaacrylate (DPHA) as another photopolymerizable polyfunctional compound, and an isocyanate cross-linking agent (product name “Takenate D110N”, xylylene diisocyanate tri methylolpropane adduct, Mitsui Chemicals) 0.1 parts by mass, dibutyltin dilaurate (product name "OL-1", Tokyo Fine Chemicals Co., Ltd.) 0.3 parts by mass as a cross-linking catalyst, and 1 part by mass of acetylacetone as a cross-linking inhibitor. .3 parts by mass, 0.5 parts by mass of a third photopolymerization initiator, and 0.7 parts by mass of a silane coupling agent (product name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) are added and mixed to form an adhesive. A formulation composition was prepared. As the third photopolymerization initiator, "Omnirad 184" manufactured by IGM Resins was used.

<Production of optical adhesive sheet>
The pressure-sensitive adhesive composition was applied to the release-treated surface of the first release liner (product name: "Diafoil MRF", thickness: 75 µm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side to form a coating film. Next, the coating film on the first release liner was dried by heating at 100° C. for 3 minutes to form a pressure-sensitive adhesive layer with a thickness of 100 μm. Next, the release-treated surface of a second release liner (product name: "Diafoil MRE", thickness: 75 µm, manufactured by Mitsubishi Chemical Corporation) whose one side was release-treated was attached to the pressure-sensitive adhesive layer on the first release liner. . After that, an aging treatment was carried out at 25° C. for 3 days, and in the adhesive layer, the cross-linking reaction of the base polymer with the isocyanate cross-linking agent was allowed to proceed, thereby forming a pressure-sensitive adhesive sheet S4.

As described above, the pressure-sensitive adhesive sheet S4 with a double-sided release liner (first release liner/adhesive sheet S4 (thickness: 100 μm)/second release liner) of Example 4 was produced. The adhesive sheet S4 is a photocurable optical adhesive sheet containing a base polymer, a photopolymerizable polyfunctional compound, and a third photopolymerization initiator.

[Example 5]
<Preparation of prepolymer composition>
In a flask, to a monomer mixture of 78 parts by mass of n-butyl acrylate (BA), 16 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 6 parts by mass of 4-hydroxybutyl acrylate (4HBA), After adding a total of 0.07 parts by mass of the first photopolymerization initiator, the mixture is irradiated with ultraviolet rays in a nitrogen atmosphere to polymerize a part of the monomer components in the mixture to form a prepolymer composition. got As the first photopolymerization initiator, 0.035 parts by mass of "Omnirad 184" manufactured by IGM Resins and 0.035 parts by mass of "Omnirad 651" manufactured by IGM Resins were used. UV irradiation was continued until the viscosity of the composition reached about 20 Pa·s. The resulting prepolymer composition is a partially polymerized product containing a photopolymerized product (photopolymerized polymer P1a) and a monomer component (residual monomer) that has not undergone a polymerization reaction.

<Preparation of adhesive composition>
Next, 100 parts by weight of the prepolymer composition, 8 parts by weight of acryloylmorpholine (ACMO) as an additional monomer, and 1.3 parts by weight of N-vinyl-2-pyrrolidone (NVP) as another additional monomer, 1.7 parts by mass of UAO (product name “Artresin UN-350 NDTN001BA”, manufactured by Negami Kogyo Co., Ltd.) as a cross-linking agent, 0.4 parts by mass of a second photopolymerization initiator, and an antioxidant (product name “Irganox 1010 ”, manufactured by BASF), 0.5 parts by mass of an ultraviolet absorber (product name “Tinosorb S” manufactured by BASF), and α-methylstyrene dimer as a chain transfer agent (product name “Nofmer MSD”, Japan Oil) 0.07 parts by mass, rust inhibitor (product name "BT-120", Johoku Chemical Industry Co., Ltd.) 0.15 parts by mass, silane coupling agent (product name "KBM-403", Shin-Etsu Chemical Co., Ltd. (manufactured) was mixed with 0.35 parts by mass to obtain a pressure-sensitive adhesive composition. As the second photopolymerization initiator, "Omnirad819" manufactured by IGM Resins was used.

<Production of optical adhesive sheet>
Next, a pressure-sensitive adhesive composition is applied onto the release-treated surface of the first release liner (product name: "Diafoil MRF", thickness: 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side to form a coating film. bottom. Next, the release-treated surface of the second release liner (product name: "Diafoil MRE", thickness: 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side was laminated onto the coating film on the first release liner. rice field. Next, the coating film between the release liners was irradiated with ultraviolet rays from the second release liner side, and the coating film was photocured to form a pressure-sensitive adhesive layer with a thickness of 100 μm (ultraviolet irradiation step). In the ultraviolet irradiation, a black light (manufactured by Toshiba) was used as a light source, the illuminance was set to 6.5 mW/cm ² , and the irradiation integrated light amount was set to 3000 mJ/cm ² . In the UV irradiation step, the photopolymerization reaction proceeds in the reaction system containing the residual monomers, the additional monomers, and the cross-linking agent in the coating film to form a photopolymerization polymer P1c having a photocrosslinking structure. Further, since the photopolymerization reaction proceeds around the photopolymerization polymer P1a, the photopolymerization polymer P1c is formed around the photopolymerization polymer P1a. The adhesive layer formed in this step contains the photopolymerization polymer P1a and the photopolymerization polymer P1c as base polymers.

As described above, the pressure-sensitive adhesive sheet S5 with a double-sided release liner of Example 5 (first release liner/adhesive sheet S5 (thickness: 100 μm)/second release liner) was produced. The adhesive sheet S5 does not have photocurability.

[Example 6]
PSA sheet S6 with double-sided release liner of Example 6 was produced in the same manner as PSA sheet S5 with double-sided release liner of Example 5 except for the following.

In the preparation of the adhesive composition, the amount of ACMO as an additional monomer is 3 parts by mass, NVP is not blended, 4HBA 8 parts by mass is blended as another additional monomer, and the amount of the cross-linking agent (UAO) is 2.2 parts by mass, 0.04 parts by mass of TMPTA as another cross-linking agent, 0.35 parts by mass of the second photopolymerization initiator (Omnirad 819), and 0.35 parts by mass of the ultraviolet absorber (Tinosorb S). The blending amount was 0.9 parts by mass, and α-methylstyrene dimer (Nofmer MSD) was not blended as a chain transfer agent. In this example, a pressure-sensitive adhesive sheet S6 was formed from such a pressure-sensitive adhesive composition. The adhesive sheet S6 does not have photocurability.

[Example 7]
PSA sheet S7 with a double-sided release liner of Example 7 was prepared in the same manner as PSA sheet S5 with a double-sided release liner of Example 5 except for the following.

In the preparation of the prepolymer composition, the amount of NVP was set to 18 parts by mass, and 78 parts by mass of 2-ethylhexyl acrylate (2EHA) and 4 parts by mass of 2-hydroxyethyl acrylate (2HEA) were used instead of BA and 4HBA. compounded. In the preparation of the adhesive composition, 17.6 parts by mass of 2HEA was blended as an additional monomer instead of ACMO and NVP, and 1,6-hexanediol diacrylate (HDDA) (product name "A-HD -N", Shin-Nakamura Chemical Co., Ltd.) 0.088 parts by mass, the amount of the second photopolymerization initiator (Omnirad 819) is 0.156 parts by mass, and the amount of the ultraviolet absorber (Tinosorb S) was 0.91 parts by mass, and an antioxidant (Irganox 1010), a chain transfer agent (Nofmar MSD), and a rust inhibitor (BT-120) were not blended. In this example, a pressure-sensitive adhesive sheet S7 was formed from such a pressure-sensitive adhesive composition. The adhesive sheet S7 does not have photocurability.

[Comparative Example 1]
<Preparation of base polymer>
63 parts by weight of 2EHA, 15 parts by weight of NVP, 13 parts by weight of 2HEA, 9 parts by weight of methyl methacrylate (MMA), and 0.2 parts by mass of AIBN as a thermal polymerization initiator and 178.1 parts by mass of ethyl acetate as a polymerization solvent were stirred under a nitrogen atmosphere at 56°C for 5 hours, and then at 70°C for 3 hours. , was reacted (polymerization reaction). As a result, a polymer solution containing an acrylic polymer (base polymer) was obtained.

<Preparation of adhesive composition>
In the above polymer solution, 2.5 parts by mass of PGDA (product name "APG-400", manufactured by Shin-Nakamura Chemical Co., Ltd.) as a photopolymerizable polyfunctional compound per 100 parts by mass of the base polymer, and an isocyanate cross-linking agent (product name " Takenate D110N", manufactured by Mitsui Chemicals) 0.2 parts by mass, 3.0 parts by mass of acetylacetone as a cross-linking inhibitor, 0.2 parts by mass of a third photopolymerization initiator, and a silane coupling agent (product name "KBM- 403", manufactured by Shin-Etsu Chemical Co., Ltd.) was added and mixed to prepare an adhesive composition. As the third photopolymerization initiator, "Omnirad 184" manufactured by IGM Resins was used.

<Production of optical adhesive sheet>
The pressure-sensitive adhesive composition was applied to the release-treated surface of the first release liner (product name: "Diafoil MRF", thickness: 75 µm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side to form a coating film. Next, the coating film on the first release liner was dried by heating at 100° C. for 3 minutes to form a pressure-sensitive adhesive layer with a thickness of 100 μm. Next, the release-treated surface of a second release liner (product name: "Diafoil MRE", thickness: 75 µm, manufactured by Mitsubishi Chemical Corporation) whose one side was release-treated was attached to the pressure-sensitive adhesive layer on the first release liner. . After that, an aging treatment was performed at 25° C. for 3 days to allow the crosslinking reaction of the base polymer with the isocyanate crosslinking agent to proceed in the adhesive layer to form an adhesive sheet S8.

As described above, a pressure-sensitive adhesive sheet S8 with a double-sided release liner (first release liner/adhesive sheet S8 (thickness: 100 μm)/second release liner) of Comparative Example 1 was produced. The adhesive sheet S8 is a photocurable optical adhesive sheet containing a base polymer, a photopolymerizable polyfunctional compound, and a third photopolymerization initiator.

[Comparative Example 2]
PSA sheet S9 with a double-sided release liner of Comparative Example 2 was prepared in the same manner as PSA sheet S5 with a double-sided release liner of Example 5 except for the following.

In the preparation of the prepolymer composition, the amount of NVP was set to 10 parts by mass, the amount of 4HBA was set to 8 parts by mass, 22 parts by mass of 2EHA and 60 parts by mass of lauryl acrylate (LA) were blended instead of BA, and The amount of one photopolymerization initiator (Omnirad 184) was 0.1 parts by mass, and the amount of another first photopolymerization initiator (Omnirad 651) was 0.1 parts by mass. In the preparation of the adhesive composition, 37 parts by weight of 2EHA was added as an additional monomer instead of ACMO and NVP, 0.08 parts by weight of HDDA was added instead of UAO as a cross-linking agent, and "Omnirad 819" was used as a second photopolymerization initiator. Instead of 0.05 parts by mass of "Omnirad 651", the amount of silane coupling agent (KBM-403) is 0.3 parts by mass, an ultraviolet absorber (Tinosorb S), and an antioxidant (Irganox 1010), a chain transfer agent (Nofmar MSD), and a rust inhibitor (BT-120) were not blended. In this example, a pressure-sensitive adhesive sheet S9 (thickness: 100 μm) was formed from such a pressure-sensitive adhesive composition. The adhesive sheet S8 does not have photocurability.

<Total light transmittance, haze>
The optical adhesive sheets of Examples 1 to 7 and Comparative Examples 1 and 2 were measured for total light transmittance and haze as follows.

First, we prepared a sample for measurement. Specifically, after peeling off one release liner from the optical adhesive sheet, the exposed surface of the optical adhesive sheet was attached to non-alkali glass (manufactured by Matsunami Glass Co., Ltd.), and the release liner was peeled off from the optical adhesive sheet on the glass. . A sample for measurement was thus obtained. Next, the total light transmittance and haze of the sample were measured in accordance with JIS K7136 (2000) using a haze meter "HM-150N" manufactured by Murakami Color Research Laboratory. In addition, in this measurement, the measurement result obtained by measuring only the alkali-free glass under the same conditions was used as a baseline. Tables 2 and 3 show the total light transmittance (%) and haze (%) of each optical adhesive sheet.

<Weight average molecular weight>
The weight average molecular weights (Mw) of the base polymers and acrylic oligomers described above in Examples 1 to 7 and Comparative Examples 1 and 2 were measured by gel permeation chromatography (GPC) under the following measurement conditions. Calculated as a converted value. In the measurement, a GPC measurement device (product name "HLC-8120GPC", manufactured by Tosoh) was used. A sample solution was prepared as follows. First, using a base polymer or an acrylic oligomer as a sample, a tetrahydrofuran (THF) solution (containing 10 mM phosphoric acid) having a sample concentration of 0.15% by mass was prepared, and the THF solution was allowed to stand for 20 hours. Next, the THF solution was filtered with a membrane filter having an average pore size of 0.45 μm, and the filtrate was obtained as a sample solution for molecular weight measurement. Tables 2 and 3 show the weight average molecular weight (Mw) of each base polymer in Examples 1 to 7 and Comparative Examples 1 and 2.

[Measurement conditions for GPC]
Column: TSKgel GMH-H (S), manufactured by Tosoh Column temperature: 40 ° C.
Eluent: tetrahydrofuran solution containing phosphoric acid (phosphoric acid concentration 10 mM)
Flow rate: 0.5 mL/min Sample injection volume: 100 μL
Standard sample: Polystyrene Detector: Differential refractometer (RI)
Standard sample: polystyrene (PS)

<Gel fraction>
The gel fraction of each optical adhesive sheet of Examples 1 to 7 and Comparative Examples 1 and 2 was measured. Specifically, it is as follows.

First, the optical adhesive sheet between the release liners was irradiated with ultraviolet rays through the release liners. In the ultraviolet irradiation, a metal halide lamp was used as a light source, the illuminance was set at 300 mW/cm ² , and the irradiation integrated light amount was set at 3000 mJ/cm ² . Next, about 1 g of adhesive sample was taken from the optical adhesive sheet. Next, the mass (W ₁ ) of the adhesive sample was measured. Next, the adhesive sample was immersed in 40 g of ethyl acetate in a container for 7 days. Next, all components insoluble in ethyl acetate (insoluble portion) were collected. The undissolved portion was then dried (removal of ethyl acetate) at 130° C. for 2 hours. Next, the mass (W ₂ ) of the undissolved portion was measured. Then, the gel fraction G (% by mass) of the optical adhesive sheet after photocuring was calculated based on the following formula. The values are shown in Tables 2 and 3. The gel fraction G shown in Tables 2 and 3 for each optical adhesive sheet (having photocurability) of Examples 1 to 4 and Comparative Example 1 is the gel fraction before photocuring of the optical adhesive sheet.

Gel fraction (% by mass) = ( _W2 / _W1 ) x 100

<Shear storage modulus>
Dynamic viscoelasticity was measured for each of the optical adhesive sheets of Examples 1 to 7 and Comparative Examples 1 and 2. Specifically, it is as follows.

First, the required number of samples for measurement was prepared for each optical adhesive sheet. Specifically, first, 20 pieces of the optical adhesive sheet cut out from the optical adhesive sheet were pasted together to prepare a sample sheet having a thickness of about 2 mm. Next, this sheet was punched out to obtain cylindrical pellets (diameter 7.9 mm) as samples for measurement.

Then, the measurement sample was fixed to a parallel plate jig with a diameter of 7.9 mm using a dynamic viscoelasticity measuring device (product name “Advanced Rheometric Expansion System (ARES)”, manufactured by Rheometric Scientific) and then moved. A viscoelasticity measurement was performed. In this measurement, the measurement mode was the shear mode, the measurement temperature range was −50° C. to 150° C., the temperature increase rate was 5° C./min, and the frequency was 1 Hz. From the measurement results, the shear storage modulus E (MPa) at 25°C was read. The values are shown in Tables 2 and 3. Tables 2 and 3 also show the product (G×E) of the above-described gel fraction G and shear storage modulus E of the optical adhesive sheet. The shear storage elastic modulus E shown in Tables 2 and 3 for each of the optical adhesive sheets (having photocurable properties) of Examples 1 to 4 and Comparative Example 1 is the shear storage elastic modulus of the optical adhesive sheet before photocuring.

In addition, the measurement results of the gel fraction G and the shear storage elastic modulus E for each of the optical adhesive sheets of Examples 1 to 7 and Comparative Examples 1 and 2 are shown in the graph of FIG. In the graph of FIG. 4, the horizontal axis represents the shear storage modulus E (MPa) of the optical adhesive sheet at 25° C., and the vertical axis represents the gel fraction G (mass %) of the optical adhesive sheet. In FIG. 4, plots E1 to E7 represent measurement results in Examples 1 to 7, respectively, and plots C1 and C2 represent measurement results in Comparative Examples 1 and 2, respectively. A curve L indicates a line of G=5/E (that is, a line where the product of G and E is 5). All of the optical adhesive sheets of Examples 1 to 7 satisfy the product of G and E (G×E) of 5 or more. The optical pressure-sensitive adhesive sheets of Examples 1 to 7 showed good results in the step conformability test described later, and also showed good results in the storage test described later.

<Step followability test>
The step followability of each of the optical adhesive sheets of Examples 1 to 7 and Comparative Examples 1 and 2 was examined as follows.

First, a first sample sheet (75 mm x 45 mm) was cut out from the optical adhesive sheet with a double-sided release liner. Next, one release liner was peeled off from the optical adhesive sheet of the first sample sheet, and the exposed surface of the optical adhesive sheet thus exposed was adhered to the center of a PET film (thickness: 125 μm, 100 mm×50 mm). In the bonding, a roll laminator was used, the pressure between rolls was set to 0.2 MPa, and the feed rate was set to 100 mm/min (the same applies to bonding described later). Next, the other release liner was peeled off from the optical adhesive sheet on the PET film, and the exposed surface of the optical adhesive sheet exposed by this was applied to a glass plate (500 µm thick, 100 mm long x 50 mm wide) with a printed layer. They were bonded together to obtain a joined body. FIG. 5 shows the positional relationship between the glass plate 41 and the optical adhesive sheet 42 in the joined body. A print layer 43 (thickness 45 μm, black ink) is formed on one surface of the glass plate 41 in the thickness direction H along the entire periphery of the edge of the glass plate 41 . The printed layer 43 is formed within a range of 15 mm inward from each end of the glass plate 41 in the length direction D1, and is formed within a range of 5 mm inward from each end of the glass plate 41 in the width direction D2. there is The optical adhesive sheet 42 is adhered to the center of one side of the glass plate 41 in the thickness direction H, and is in contact with the printed layer 43 over the entire circumference of the edge of the sheet. That is, the printed layer 43 on the glass plate 41 is sandwiched between the glass plate 41 and the optical adhesive sheet 42 within a range of 2.5 mm outward from the inner edge of the same layer.

Next, the joined body was autoclaved for 30 minutes under conditions of 50°C and 0.5 MPa. After that, the vicinity of the inner edge of the printed layer in the joined body was observed. Specifically, using a digital microscope, the inside of the inner edge of the printed layer (the area where the optical adhesive sheet should be brought into close contact with the glass plate) was observed from the PET film side of the joined body at an observation magnification of 20. Then, the conformability of the optical adhesive sheet to steps was evaluated as "excellent" when no air bubbles were observed in the observation range, and as "bad" when air bubbles were observed. The results are shown in Tables 2 and 3.

<Storage test>
The shape retention properties of the optical adhesive sheets of Examples 1 to 7 and Comparative Examples 1 and 2 were examined as follows.

First, 30 second sample sheets (150 mm x 100 mm) were cut out from the optical adhesive sheet with a double-sided release liner. The 30 second sample sheets were then stacked to form a sheet stack. The stack of sheets was then stored for 3 months while resting on the substantially horizontal tray surface of the tray in the storage room. During the storage period, the temperature in the storage room was 18° C.-30° C., and the relative humidity was 45%-65%. Next, the second sample sheet, the second from the bottom in the sheet bundle, was placed between the projection screen and the light source (the projection screen was placed in a posture that spreads vertically and horizontally, and the light source It is placed at a position about 40 cm away in the direction perpendicular to the screen surface of the screen). Specifically, the second sample sheet was placed at a position about 10 cm away from the light source with the sheet surface parallel to the screen surface (the second sample sheet was about 30 cm away from the screen). ). The light source was then turned on to illuminate the second sample sheet toward the projection screen. Next, the projected image (transmitted image) formed on the projection screen by the light emitted from the light source and transmitted through the second sample sheet was observed (first observation). The shape retention of the optical adhesive sheet was evaluated as "excellent" when a uniform transmitted image without uneven brightness was observed. In the first observation, for optical pressure-sensitive adhesive sheets in which light and dark unevenness due to surface unevenness of the optical pressure-sensitive adhesive sheet was observed in the transmitted image, after peeling off one release liner from the optical pressure-sensitive adhesive sheet, the exposed surface of the optical pressure-sensitive adhesive sheet was attached to non-alkali glass (manufactured by Matsunami Glass Co., Ltd.), and the other release liner was peeled off from the optical adhesive sheet on the glass. Next, the optical adhesive sheet on the glass is placed between the light source and the screen under the same conditions as the first observation described above, and the projected image formed on the projection screen by the light transmitted through the optical adhesive sheet. (Transmission image) was observed (second observation). Regarding the shape retainability of the optical adhesive sheet, when unevenness in brightness was observed in the first observation, but a uniform transmitted image without unevenness in brightness was observed in the second observation, it was evaluated as "good". Further, regarding the shape retention property of the optical adhesive sheet, when uneven brightness was observed in the transmitted image even in the second observation, it was evaluated as "poor". The results are shown in Tables 2 and 3.

The optical pressure-sensitive adhesive sheet of the present invention is used, for example, in the manufacturing process of display panels to bond elements included in the laminated structure of the same panels.

10 adhesive sheet (optical adhesive sheet)
11, 12 Adhesive surface

H Thickness direction

21, 22 Release liner 31 Cover glass 32 Printed layer 33 Member

Claims

An optical pressure-sensitive adhesive sheet containing a base polymer,
Having a gel fraction G (%) of 90% or less,
has a shear storage modulus E (MPa) at 25°C,
The optical pressure-sensitive adhesive sheet, wherein the product of the gel fraction G and the shear storage modulus E is 5 or more.
The optical adhesive sheet according to claim 1, wherein the gel fraction G is 40% or more.
The optical pressure-sensitive adhesive sheet according to claim 1, wherein the shear storage elastic modulus E is 0.1 MPa or more.
The optical pressure-sensitive adhesive sheet according to claim 1, wherein the shear storage elastic modulus E is 0.3 MPa or less.
The optical pressure-sensitive adhesive sheet according to claim 1, wherein the base polymer has a weight average molecular weight of 300,000 or more.
The optical adhesive sheet according to claim 1, which is a photocurable adhesive sheet.
a first release liner releasably in contact with one side in the thickness direction of the optical adhesive sheet;
The optical pressure-sensitive adhesive sheet according to any one of claims 1 to 6, further comprising a second release liner releasably contacting the other side in the thickness direction of said optical pressure-sensitive adhesive sheet.