Adhesive sheet, optical laminate, image display device, partially polymerized product, monomer syrup, photocurable adhesive composition, and method for producing adhesive sheet

Abstract

Provided is an adhesive sheet having improved durability.　This adhesive sheet according to an embodiment is formed from a photocurable adhesive composition containing a monomer syrup. The monomer syrup contains a monomer component M1 and a partially polymerized product of the monomer component M1. The partially polymerized product has a constituent unit derived from an aromatic ring-containing monomer a1.

Description

Pressure-sensitive adhesive sheet, optical laminate, image display device, partially polymerized product, monomer syrup, photocurable pressure-sensitive adhesive composition, and method for producing pressure-sensitive adhesive sheet

[0001] The present invention relates to a pressure-sensitive adhesive sheet, an optical laminate, an image display device, a partially polymerized product, a monomer syrup, a photocurable pressure-sensitive adhesive composition, and a method for producing a pressure-sensitive adhesive sheet.

[0002] In image display devices (such as liquid crystal display devices, organic EL display devices, and quantum dot display devices), an optical laminate including an optical element such as a polarizing film is often disposed on at least one side of a display cell due to the image formation method used. A pressure-sensitive adhesive sheet is usually used to bond the optical elements together or to bond the optical laminate to an image display panel. Patent Document 1 discloses an example of a pressure-sensitive adhesive sheet.

[0003] JP 2012-153788 A

[0004] According to the investigations of the present inventors, there is room for improvement in the durability of pressure-sensitive adhesive sheets.

[0005] An object of the present invention is to provide a pressure-sensitive adhesive sheet with improved durability.

[0006] [1] A pressure-sensitive adhesive sheet according to one embodiment of the present invention is formed from a photocurable pressure-sensitive adhesive composition containing a monomer syrup, the monomer syrup containing a monomer component M1 and a partial polymer of the monomer component M1, the partial polymer having a structural unit derived from a monomer a1 having an aromatic ring. [2] In the pressure-sensitive adhesive sheet described in [1] above, the photocurable pressure-sensitive adhesive composition may further contain a monomer component M2. [3] In the pressure-sensitive adhesive sheet described in [1] or [2] above, the weight-average molecular weight of the partial polymer may be 3,000,000 or more. [4] In the pressure-sensitive adhesive sheet described in any of [1] to [3] above, the gel fraction may be 80% by weight or more. [5] In the pressure-sensitive adhesive sheet described in any of [1] to [4] above, the haze may be 3.0% or less. [6] In the pressure-sensitive adhesive sheet described in any of [1] to [5] above, the content of the monomer a1 in the total monomer components M contained in the photocurable pressure-sensitive adhesive composition may be 2 to 80% by weight. [7] In the pressure-sensitive adhesive sheet described in any of [1] to [6] above, the content of structural units derived from monomer a1 in the partial polymer may be 2 to 80 wt %. [8] In the pressure-sensitive adhesive sheet described in any of [1] to [7] above, the absolute value of the difference between the content of monomer a1 in all monomer components M contained in the photocurable pressure-sensitive adhesive composition and the content of structural units derived from monomer a1 in the partial polymer may be 30 wt % or less. [9] In the pressure-sensitive adhesive sheet described in any of [1] to [8] above, the partial polymer may further contain structural units derived from carboxyl group-containing monomer a2.

[10] In the pressure-sensitive adhesive sheet described in any of [1] to [9] above, the partial polymer may further contain structural units derived from nitrogen atom-containing monomer a3.

[11] In the pressure-sensitive adhesive sheet described in any of [1] to

[10] above, the glass transition temperature calculated from the FOX equation may be 0°C or less.

[12] The pressure-sensitive adhesive sheet according to any one of [1] to

[11] above may have a thickness of 50 μm or less.

[13] An optical laminate according to one embodiment of the present invention comprises the pressure-sensitive adhesive sheet according to any one of [1] to

[12] above and an optical film.

[14] In the optical laminate according to

[13] above, the optical film may be a polarizing film.

[15] An image display device according to one embodiment of the present invention comprises the optical laminate according to

[13] or

[14] above.

[16] A partial polymer for a photocurable pressure-sensitive adhesive composition according to one embodiment of the present invention is a partial polymer of a monomer component M1, wherein the monomer component M1 has a structural unit derived from a monomer a1 having an aromatic ring and has a weight-average molecular weight of 3,000,000 or more.

[17] A monomer syrup according to one embodiment of the present invention comprises the partial polymer for a photocurable pressure-sensitive adhesive composition according to

[16] above.

[18] A photocurable pressure-sensitive adhesive composition according to one embodiment of the present invention comprises the monomer syrup according to

[17] above.

[19] A method for producing a pressure-sensitive adhesive sheet according to one embodiment of the present invention includes: Step I, in which a monomer component M1 containing a monomer a1 having an aromatic ring is partially polymerized to form a monomer syrup containing a partially polymerized product; and Step II, in which a photocurable pressure-sensitive adhesive composition containing the monomer syrup is cured to form a pressure-sensitive adhesive sheet.

[20] In the method for producing a pressure-sensitive adhesive sheet according to

[19] above, in Step I, the monomer component M1 may be partially polymerized so that the polymerization rate is 1 to 30%.

[21] In the method for producing a pressure-sensitive adhesive sheet according to

[19] or

[20] above, in Step I, the partially polymerized product may be formed so that the weight-average molecular weight is 3,000,000 or more.

[22] In the method for producing a pressure-sensitive adhesive sheet according to any one of

[19] to

[21] above, in Step II, the pressure-sensitive adhesive sheet may be formed so that the gel fraction of the pressure-sensitive adhesive sheet is 80% by weight or more.

[23] The method for producing a pressure-sensitive adhesive sheet according to any one of

[19] to

[22] above may further comprise step III of adding a monomer component M2 to the monomer syrup between step I and step II.

[24] In the method for producing a pressure-sensitive adhesive sheet according to

[23] above, the total amount of the monomer a1 in the monomer component M2 may be less than 50% by weight of the total amount of the monomer a1 in the monomer syrup.

[25] A photocurable pressure-sensitive adhesive composition according to one embodiment of the present invention is a photocurable pressure-sensitive adhesive composition comprising a monomer syrup, the monomer syrup comprising a monomer component M1 and a partial polymer of the monomer component M1, and the partial polymer having a constituent unit derived from a monomer a1 having an aromatic ring.

[0007] [P1] Another embodiment of the present invention provides a pressure-sensitive adhesive sheet formed from a photocurable pressure-sensitive adhesive composition comprising: a monomer component M; and a partial polymer of the monomer component M; the partial polymer having a structural unit derived from a monomer a1 having an aromatic ring; and a thickness of 50 μm or less. [P2] In the pressure-sensitive adhesive sheet described in [P1] above, the weight-average molecular weight of the partial polymer may be 3,000,000 or more. [P3] In the pressure-sensitive adhesive sheet described in [P1] or [P2] above, the gel fraction may be 80% by weight or more. [P4] In the pressure-sensitive adhesive sheet described in any of [P1] to [P3] above, the haze may be 3.0% or less. [P5] In the pressure-sensitive adhesive sheet described in any of [P1] to [P4] above, the content of the monomer a1 in the monomer component M may be 2 to 80% by weight. [P6] In the pressure-sensitive adhesive sheet described in any of [P1] to [P5] above, the partial polymer may further have a structural unit derived from a carboxyl group-containing monomer a2. [P7] In the pressure-sensitive adhesive sheet described in any of [P1] to [P6] above, the partial polymer may further have a structural unit derived from nitrogen-atom-containing monomer a3. [P8] In the pressure-sensitive adhesive sheet described in any of [P1] to [P7] above, the glass transition temperature calculated from the FOX formula may be 0°C or lower. [P9] An optical laminate according to another embodiment of the present invention comprises the pressure-sensitive adhesive sheet described in any of [P1] to [P8] above and an optical film. [P10] In the optical laminate described in any of [P1] to [P9] above, the optical film may be a polarizing film. [P11] An image display device according to another embodiment of the present invention comprises the optical laminate described in [P9] or [P10] above. [P12] A partial polymer for a photocurable pressure-sensitive adhesive composition according to another embodiment of the present invention is a partial polymer of monomer component M, wherein the monomer component M has a structural unit derived from monomer a1 having an aromatic ring, and has a weight-average molecular weight of 3,000,000 or more.[P13] A method for producing a pressure-sensitive adhesive sheet according to another embodiment of the present invention includes: Step I, in which a monomer component M containing a monomer a1 having an aromatic ring is partially polymerized to form a partial polymer; and Step II, in which a photocurable pressure-sensitive adhesive composition containing the partial polymer is cured to form a pressure-sensitive adhesive sheet. [P14] In the method for producing a pressure-sensitive adhesive sheet described in [P13] above, in Step I, the monomer component M may be partially polymerized so that the polymerization rate is 1 to 30%. [P15] In the method for producing a pressure-sensitive adhesive sheet described in [P13] or [P14] above, in Step I, the partial polymer may be formed so that the weight-average molecular weight is 3,000,000 or more. [P16] In the method for producing a pressure-sensitive adhesive sheet described in any of [P13] to [P15] above, in Step II, the pressure-sensitive adhesive sheet may be formed so that the gel fraction of the pressure-sensitive adhesive sheet is 80% by weight or more.

[0008] According to an embodiment of the present invention, a pressure-sensitive adhesive sheet with improved durability can be provided.

[0009] FIG. 1 is a schematic cross-sectional view of an example of a pressure-sensitive adhesive sheet according to an embodiment of the present invention. FIG. 2 is a schematic view of an example of a method for manufacturing a pressure-sensitive adhesive sheet according to an embodiment of the present invention. FIG. 3 is a schematic view of another example of a method for manufacturing a pressure-sensitive adhesive sheet according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of an example of an optical laminate according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of an example of an optical laminate according to an embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of an example of an optical laminate according to an embodiment of the present invention. FIG. 7 is a schematic cross-sectional view of an example of an optical laminate according to an embodiment of the present invention. FIG. 8 is a schematic cross-sectional view of an example of an optical laminate according to an embodiment of the present invention.

[0010] [Terminology] In this specification, when the expression "weight" appears, it may be read as "mass," which is commonly used as an SI unit indicating weight, and vice versa.

[0011] In this specification, the expression "(meth)acrylic" means "acrylic and / or methacrylic", the expression "(meth)acrylate" means "acrylate and / or methacrylate", the expression "(meth)allyl" means "allyl and / or methallyl", and the expression "(meth)acrolein" means "acrolein and / or methacrolein".

[0012] In this specification, when "monomer component M1: 100 parts by weight" is used as a reference for the amount of each component in the photocurable pressure-sensitive adhesive composition, it refers to the total amount of the unpolymerized monomer component M1 contained in the photocurable pressure-sensitive adhesive composition and the monomer component M1 used to form the partially polymerized product contained in the photocurable pressure-sensitive adhesive composition. Furthermore, when "content" is used as the amount of each component contained in the monomer component M1, it refers to the total content of the component contained in the unpolymerized monomer component M1 and the component contained in the monomer component M1 used to form the partially polymerized product. Furthermore, when "total amount" is used as the amount of each component contained in the monomer component M1, it refers to the total amount of the component contained in the unpolymerized monomer component M1 and the component contained in the monomer component M1 used to form the partially polymerized product.

[0013] <<1. Pressure-Sensitive Adhesive Sheet>> FIG. 1 shows a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. The pressure-sensitive adhesive sheet 1 of FIG. 1 is formed from a photocurable pressure-sensitive adhesive composition containing a monomer syrup. The monomer syrup contains a monomer component M1 and a partial polymer of the monomer component M1. In one preferred embodiment, the monomer syrup contains a monomer component M1 (monomer component M1 not used in forming the partial polymer) obtained by partially polymerizing the monomer component M1, and a partial polymer of the monomer component M1. The viscosity of the monomer syrup is not particularly limited. The partial polymer of the monomer component M1 has a structural unit derived from a monomer contained in the monomer component M1. The partial polymer of the monomer component M1 has a structural unit derived from a monomer a1 having an aromatic ring. In other words, the monomer component M1 contains a monomer a1 having an aromatic ring.

[0014] In a photocurable pressure-sensitive adhesive composition containing a monomer syrup, the monomer component M1 contained in the monomer syrup and a partial polymer of the monomer component M1 tend to form a sea-island structure due to polymerization-induced phase separation rather than a co-continuous structure when forming the pressure-sensitive adhesive sheet 1. It is presumed that a crosslinked polymer formed by reaction of the monomer component M1 with a polyfunctional monomer such as a crosslinking agent forms an "island phase" in the sea-island structure, and that the partial polymer of the monomer component M1 forms a continuous "sea phase" surrounding the "island phase" in the sea-island structure. It is presumed that the formation of this sea-island structure causes the partial polymer of the monomer component M1 to segregate at the interface between the pressure-sensitive adhesive sheet 1 and the adherend, and therefore it is presumed that the structural unit derived from the monomer a1 in the partial polymer of the monomer component M1 is also unevenly distributed at the interface between the pressure-sensitive adhesive sheet 1 and the adherend. The monomer a1 is a monomer having an aromatic ring, and tends to have a high glass transition temperature when formed into a single polymer. It is presumed that the uneven distribution of the structural unit derived from the monomer a1 at the interface improves the cohesive strength of the pressure-sensitive adhesive sheet 1 at the interface with the adherend. Therefore, the pressure-sensitive adhesive sheet 1 is suitable for improving durability, and preferably also for improving impact resistance and reducing haze. The above-described effects of the present invention are presumed to be based on the above-described mechanism of action, but are not limited thereto. In other words, similar effects may be obtained by other mechanisms of action, and the technical scope of the present invention is not necessarily based on these mechanisms of action. The monomer component M1 and the partial polymer of the photocurable pressure-sensitive adhesive composition will be described later.

[0015] The pressure-sensitive adhesive sheet 1 has a thickness of 50 μm or less. The upper limit of the thickness may be 40 μm, 35 μm, 30 μm, 25 μm, or even 20 μm. The lower limit of the thickness may be, for example, 3 μm, 5 μm, 10 μm, 12 μm, or even 15 μm. The thickness of the pressure-sensitive adhesive sheet 1 is preferably 3 to 50 μm, more preferably 3 to 40 μm, even more preferably 3 to 35 μm, and particularly preferably 3 to 30 μm. When the thickness of the pressure-sensitive adhesive sheet 1 is within the above range, it can be suitably used as a pressure-sensitive adhesive sheet for a polarizing film.

[0016] <<2. Photocurable Pressure-Sensitive Adhesive Composition>> The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive sheet 1 is a photocurable pressure-sensitive adhesive composition that forms a pressure-sensitive adhesive sheet by irradiation with light. The photocurable pressure-sensitive adhesive composition contains a monomer syrup. Note that a photocurable pressure-sensitive adhesive composition is a particularly preferred embodiment in terms of environmental protection and sustainability, because it can reduce the amount of energy required to form a pressure-sensitive adhesive sheet compared to a thermosetting pressure-sensitive adhesive composition that mainly uses heat to form a pressure-sensitive adhesive sheet.

[0017] In this specification, the monomer component M is defined as the sum of the non-partially polymerized monomer components contained in the photocurable pressure-sensitive adhesive composition and the monomer components used to form the partially polymerized monomers contained in the photocurable pressure-sensitive adhesive composition. The photocurable pressure-sensitive adhesive composition may contain a monomer component M2. This monomer component M2 is a monomer component that can be added to the monomer syrup described below and can be distinguished from the monomer component M1. Therefore, when the photocurable pressure-sensitive adhesive composition does not contain the monomer component M2, the monomer component M is the sum of the monomer components constituting the monomer syrup, i.e., the monomer component M1 and the partially polymerized monomer of the monomer component M1. When the photocurable pressure-sensitive adhesive composition contains the monomer component M2, the monomer component M is the sum of the monomer components constituting the monomer syrup (the sum of the monomer component M1 and the partially polymerized monomer of the monomer component M1) and the monomer component M2.

[0018] <2-1. Monomer Syrup> The monomer syrup contains a monomer component M1 and a partial polymer of the monomer component M1. The monomer component M1 contains a monomer a1 having an aromatic ring, and the partial polymer of the monomer component M1 has a structural unit derived from the monomer a1 having an aromatic ring.

[0019] <2-1-1. Monomer component M1> (2-1-1-1. Monomer a1 having an aromatic ring) As described above, monomer component M1 includes monomer a1 having an aromatic ring. Monomer a1 is a component suitable for improving the durability of PSA sheet 1.

[0020] In the monomer a1, the number of aromatic rings contained in one molecule is, for example, 1, and may be 2 or more. The upper limit of the number of aromatic rings is not particularly limited and is, for example, 16. The upper limit may be 12, 8, 6, 5, 4, 3, or even 2.

[0021] In the monomer a1, the aromatic ring is preferably located on a side chain. In other words, the monomer a1 preferably has at least one aromatic ring and at least one ethylenically unsaturated group per molecule. As the monomer a1, a compound containing one ethylenically unsaturated group per molecule (in other words, a monofunctional monomer) is preferably used.

[0022] Examples of the ethylenically unsaturated group include a (meth)acryloyl group, a vinyl group, and a (meth)allyl group. From the viewpoint of polymerization reactivity, a (meth)acryloyl group is preferred, and from the viewpoint of flexibility and adhesiveness, an acryloyl group is more preferred. Examples of (meth)acrylic monomers having an aromatic ring include aromatic ring-containing (meth)acrylates. Specific examples of aromatic ring-containing (meth)acrylates will be described later.

[0023] The aromatic ring and the ethylenically unsaturated group may be bonded directly or via a linking group. An example of the linking group includes one or more groups selected from the group consisting of alkylene groups, oxyalkylene groups, poly(oxyalkylene) groups, phenyl groups, alkylphenyl groups, alkoxyphenyl groups, groups in which one or more hydrogen atoms in these groups have been substituted with hydroxyl groups (e.g., hydroxyalkylene groups), oxy groups (-O-), and thiooxy groups (-S-). In one example of monomer a1, the aromatic ring and the ethylenically unsaturated group are bonded directly. In another example of monomer a1, the aromatic ring and the ethylenically unsaturated group are bonded via a linking group selected from the group consisting of alkylene groups, oxyalkylene groups, and poly(oxyalkylene) groups. The number of carbon atoms in the alkylene group and oxyalkylene group that can be included in the linking group is, for example, 1 to 4, and may be 1 to 3, or even 1 to 2. The number of repeating oxyalkylene units in the poly(oxyalkylene) group that can be contained in the linking group is, for example, 1 to 8, and may be 1 to 6, 1 to 4, 1 to 3, 2 to 3, or even 1 to 2, 2, or 1.

[0024] Specific examples of the monomer a1 include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds may be used alone or in combination of two or more.

[0025] Monomer a1 may contain two or more aromatic rings in one molecule.

[0026] Examples of the aromatic ring-containing monomer include a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, a monomer having a structure in which two or more non-condensed aromatic rings are directly bonded, a monomer having a condensed ring, a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, and a monomer having a dibenzothiophene structure. Among these, a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group (for example, phenoxybenzyl (meth)acrylate described below) is preferably used.

[0027] The linking group may contain atoms such as P, Ge, Te, Se, N, S, and Si, and these atoms may be bonded to an oxygen atom. Examples of the linking group include an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (e.g., -O-(CH2) n -; n is 1 to 3, preferably 1), a thiooxyalkylene group (e.g., -S-(CH2) n -; n is 1 to 3, preferably 1), a straight chain alkylene group (-(CH2) n -; n is 1 to 6, preferably 1 to 3), and the above-mentioned oxyalkylene group, the above-mentioned thiooxyalkylene group, and the above-mentioned straight-chain alkylene group in which the alkylene group is partially or completely halogenated. The linking group may contain one or more types selected from the group consisting of an oxy group, a thiooxy group, an oxyalkylene group, and a straight-chain alkylene group. Specific examples of monomers having a structure in which two or more non-fused aromatic rings are bonded via a linking group include phenoxybenzyl (meth)acrylate, thiophenoxybenzyl (meth)acrylate, and benzyl benzyl (meth)acrylate.

[0028] Examples of the monomer having a structure in which two or more non-fused aromatic rings are directly bonded include biphenyl structure-containing (meth)acrylate, triphenyl structure-containing (meth)acrylate, and vinyl group-containing biphenyl. Specific examples include o-phenylphenol (meth)acrylate, biphenyl (meth)acrylate, and biphenylmethyl (meth)acrylate.

[0029] Examples of monomers having a fused ring include naphthalene ring-containing (meth)acrylates, anthracene ring-containing (meth)acrylates, vinyl group-containing naphthalenes, and vinyl group-containing anthracenes. Specific examples include 1-naphthylmethyl (meth)acrylate (also known as 1-naphthalenemethyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, and 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate.

[0030] Examples of monomers having a fluorene structure include 9,9-bis(4-hydroxyphenyl)fluorene(meth)acrylate and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene(meth)acrylate. Note that, since monomers having a fluorene structure have a structure in which two benzene rings are directly bonded, they are included in the concept of monomers having a structure in which two or more non-fused aromatic rings are directly bonded.

[0031] Examples of the monomer having a dinaphthothiophene structure are (meth)acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, and (meth)allyl group-containing dinaphthothiophene. Specific examples include (meth)acryloyloxymethyldinaphthothiophene (e.g., a compound having a structure in which a CHCH(R)C(O)OCH group is bonded to the 5th or 6th position of the dinaphthothiophene ring; R is a hydrogen atom or a methyl group), (meth)acryloyloxyethyldinaphthothiophene (e.g., a compound having a structure in which a CHCH(R)C(O)OCH(CH) group or a CHCH(R)C(O)OCHCH group is bonded to the 5th or 6th position of the dinaphthothiophene ring; R is a hydrogen atom or a methyl group), vinyldinaphthothiophene (e.g., a compound having a structure in which a vinyl group is bonded to the 5th or 6th position of the naphthothiophene ring), and (meth)allyloxydinaphthothiophene. Incidentally, a monomer having a dinaphthothiophene structure is included in the concept of a monomer having a fused ring because it has a naphthalene structure and also has a structure in which a thiophene ring and two naphthalene structures are fused together.

[0032] Examples of monomers having a dibenzothiophene structure include (meth)acryloyl group-containing dibenzothiophenes and vinyl group-containing dibenzothiophenes. Note that, since monomers having a dibenzothiophene structure have a structure in which a thiophene ring and two benzene rings are fused, they are included in the concept of monomers having fused rings. Neither the dinaphthothiophene structure nor the dibenzothiophene structure corresponds to a structure in which two or more non-fused aromatic rings are directly bonded.

[0033] Monomer a1 is preferably a monomer having one aromatic ring (preferably a carbon ring) and at least one ethylenically unsaturated group in one molecule (aromatic ring-single-containing monomer).

[0034] Examples of aromatic ring unit-containing monomers include carbon aromatic ring-containing (meth)acrylates such as benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxybutyl (meth)acrylate, cresyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and chlorobenzyl (meth)acrylate; 2-(4,6-dibromo-2-s-butylphenoxy)ethyl (meth)acrylate, 2-(4,6-dibromo-2-isopropylphenoxy)ethyl (meth)acrylate, and 6-(4 bromine-substituted aromatic ring-containing (meth)acrylates such as 2,6-dibromo-4-isopropyl-2-(4,6-dibromo-2-s-butylphenoxy)hexyl (meth)acrylate, 6-(4,6-dibromo-2-isopropylphenoxy)hexyl (meth)acrylate, 2,6-dibromo-4-nonylphenyl acrylate, and 2,6-dibromo-4-dodecylphenyl acrylate; carbon-substituted aromatic ring-containing vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and tert-butylstyrene; and compounds having a vinyl substituent on a heteroaromatic ring such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, and N-vinyloxazole.

[0035] Monomer a1 may have a structure in which an oxyethylene chain is interposed between the ethylenically unsaturated group and the aromatic ring in the various monomers a1 described above. Monomers having such a structure can be understood as ethoxylated products of the original monomers. The number of repeating oxyethylene units (—CHCHO—) in the oxyethylene chain is, for example, 1 to 8, and may be 1 to 6, 1 to 4, 1 to 3, or even 1 to 2, or even 1. Examples of monomer a1 that is an ethoxylated product include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol (meth)acrylate. Monomer a1 may include at least one selected from the group consisting of benzyl (meth)acrylate and phenoxyethyl (meth)acrylate, or may be at least one selected from the group consisting of benzyl (meth)acrylate and phenoxyethyl (meth)acrylate.

[0036] The content of monomer a1 in monomer component M1 may be, for example, 1% by weight or more, 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 10% by weight or more, or even 15% by weight or more. The upper limit of the content may be, for example, 99% by weight, 95% by weight, 90% by weight, 85% by weight, 80% by weight, 75% by weight, 70% by weight, 65% by weight, 60% by weight, 55% by weight, 50% by weight, 45% by weight, 40% by weight, 35% by weight, or even 30% by weight. The content may be, for example, 2 to 99% by weight, 2 to 95% by weight, 2 to 80% by weight, 5 to 80% by weight, 5 to 75% by weight, 5 to 70% by weight, 10 to 70% by weight, 10 to 55% by weight, 10 to 50% by weight, 10 to 45% by weight, 10 to 35% by weight, or even 10 to 30% by weight. When the content of monomer a1 in monomer component M1 is high, residual monomers are likely to remain in the pressure-sensitive adhesive sheet 1. As the aromatic ring-containing monomer a1, benzyl (meth)acrylate and phenoxyethyl (meth)acrylate are preferred from the viewpoints of copolymerizability and adhesive properties, and benzyl (meth)acrylate is more preferred from the viewpoint of less residual monomers remaining in the pressure-sensitive adhesive sheet.

[0037] (2-1-1-2. Carboxyl Group-Containing Monomer a2) The monomer component M1 may further contain a carboxyl group-containing monomer a2 (hereinafter also referred to as "monomer a2"). In this case, the partial polymer further contains a structural unit derived from the carboxyl group-containing monomer a2. The carboxyl group-containing monomer a2 refers to a monomer that contains a carboxyl group in its structure and also contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group.

[0038] Examples of the carboxyl group-containing monomer a2 include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, etc. Among these, acrylic acid is preferred from the viewpoints of copolymerizability, cost, and improving the adhesive properties of the adhesive sheet.

[0039] The content of monomer a2 in monomer component M1 is, for example, 1% by weight or more, 2% by weight or more, or even 3% by weight or more. The upper limit of this content is, for example, 25% by weight, and may be 20% by weight, 15% by weight, 10% by weight, 8% by weight, 7% by weight, 6% by weight, or even 5% by weight. The content is preferably 1 to 20% by weight, more preferably 1 to 10% by weight, and even more preferably 1 to 5% by weight.

[0040] (2-1-1-3. Nitrogen-atom-containing monomer a3) Monomer component M1 may further contain nitrogen-atom-containing monomer a3 (hereinafter also referred to as "monomer a3"). In this case, the partial polymer further has a structural unit derived from nitrogen-atom-containing monomer a3. Monomer a3 is a component suitable for improving the impact resistance of the pressure-sensitive adhesive sheet 1. Nitrogen-atom-containing monomer a3 refers to a monomer having at least one nitrogen atom in the molecule (per molecule).

[0041] Monomer a3 may have a cyclic skeleton. An example of monomer a3 having a cyclic skeleton is a monomer having a cyclic amide structure. An example of monomer a3 having a cyclic amide structure is N-vinyl cyclic amide. Monomer a3 may not have a cyclic skeleton. An example of monomer a3 not having a cyclic skeleton is (meth)acrylamide. Monomer a3 may be used alone or in combination of two or more types.

[0042] The N-vinyl cyclic amide is preferably one represented by the following formula (A):

[0043] In formula (A), R 1 is a divalent organic group. 1 may contain heteroatoms such as oxygen. 1 is preferably a divalent saturated hydrocarbon group or an unsaturated hydrocarbon group, and more preferably a divalent saturated hydrocarbon group (for example, an alkylene group having 3 to 5 carbon atoms). 1 are directly bonded via a single bond to form a ring structure.

[0044] The N-vinyl cyclic amide represented by formula (A) is preferably N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-2-caprolactam, N-vinyl-3-morpholinone, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, vinylmethyloxazolidinone, or the like, more preferably N-vinyl-2-pyrrolidone or N-vinyl-2-caprolactam, and even more preferably N-vinyl-2-pyrrolidone.

[0045] Examples of (meth)acrylamides include (meth)acrylamide, N-alkyl(meth)acrylamide, and N,N-dialkyl(meth)acrylamide. Examples of N-alkyl(meth)acrylamides include N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-n-butyl(meth)acrylamide, and N-octylacrylamide. N-Alkyl(meth)acrylamides also include (meth)acrylamides having an amino group, such as dimethylaminoethyl(meth)acrylamide, diethylaminoethyl(meth)acrylamide, and dimethylaminopropyl(meth)acrylamide.

[0046] Examples of N,N-dialkyl(meth)acrylamides include N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide.

[0047] (Meth)acrylamides also include, for example, various N-hydroxyalkyl(meth)acrylamides, such as N-methylol(meth)acrylamide, N-(2-hydroxyethyl)(meth)acrylamide, N-(2-hydroxypropyl)(meth)acrylamide, N-(1-hydroxypropyl)(meth)acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, N-(2-hydroxybutyl)(meth)acrylamide, N-(3-hydroxybutyl)(meth)acrylamide, N-(4-hydroxybutyl)(meth)acrylamide, and N-methyl-N-2-hydroxyethyl(meth)acrylamide.

[0048] (Meth)acrylamides also include, for example, various N-alkoxyalkyl(meth)acrylamides, such as N-methoxymethyl(meth)acrylamide and N-butoxymethyl(meth)acrylamide.

[0049] Examples of the monomer a3 other than N-vinyl cyclic amide and (meth)acrylamide include amino group-containing monomers such as aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; (meth)acryloylmorpholine, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, N-vinylpyrazine, N-vinylmorpholine, N-vinylpyrazole, vinylpyridine, vinylpyrimidine, vinyloxazole, vinylisoxazole, vinylthiazole, vinylisothiazole, vinylpyridazine, (meth)acryloylpyrrolidone, (meth)acryloylpyrrolidine, (meth)acryloylpiperidine, and N-methylbiphenyl. heterocycle-containing monomers such as 2-(2-methyl-2-methyl-1,2-diphenyl ...

[0050] The content of monomer a3 in monomer component M1 is, for example, 1% by weight or more, and may be 2% by weight or more, 3% by weight or more, or even 4% by weight or more. The upper limit of this content is, for example, 10% by weight, and may be 9%, 8%, 7%, 6%, or even 5% by weight. The content is preferably 1 to 10% by weight, more preferably 1 to 8% by weight, and even more preferably 2 to 5% by weight.

[0051] (2-1-1-4. Other Monomers) The monomer component M1 may contain other monomers in addition to the above-mentioned monomers a1 to a3. One example of such other monomers is a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms on the side chain. The number of carbon atoms in the alkyl group may be 7 or less, 6 or less, 5 or less, or even 4 or less. The alkyl group may be linear or branched.

[0052] Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, n-decyl(meth)acrylate, isodecyl(meth)acrylate, n-dodecyl(meth)acrylate (lauryl(meth)acrylate), n-tridecyl(meth)acrylate, n-tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexadecyl(meth)acrylate, heptadecyl(meth)acrylate, and octadecyl(meth)acrylate. The (meth)acrylic acid alkyl ester may be n-butyl(meth)acrylate.

[0053] The content of the (meth)acrylic acid alkyl ester in the monomer component M1 may be, for example, 50% by weight or more, 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, or even 90% by weight or more. The upper limit of the content may be, for example, 95% by weight, 90% by weight, 85% by weight, 80% by weight, or even 75% by weight. The content is preferably 55 to 95% by weight, more preferably 60 to 90% by weight, and even more preferably 70 to 80% by weight.

[0054] The monomer component M1 may contain other monomers in addition to the alkyl (meth)acrylate ester, as long as the effects of the present invention are not impaired.

[0055] <2-1-2. Partial Polymer> As described above, the partial polymer is a partial polymer of monomer component M1, and has a structural unit derived from aromatic ring-containing monomer a1. The partial polymer is suitable for improving the durability of the pressure-sensitive adhesive sheet 1. The aromatic ring-containing monomer a1 is a component contained in monomer component M1. The partial polymer can have a structural unit derived from a monomer that constitutes monomer component M1. As described above, when monomer component M1 further contains carboxyl group-containing monomer a2, the partial polymer has a structural unit derived from carboxyl group-containing monomer a2. When monomer component M1 further contains nitrogen atom-containing monomer a3, the partial polymer has a structural unit derived from nitrogen atom-containing monomer a3.

[0056] The content of the structural unit derived from monomer a1 in the partial polymer may be, for example, 1% by weight or more, 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 10% by weight or more, or even 15% by weight or more. The upper limit of the content may be, for example, 80% by weight, 75% by weight, 70% by weight, 65% by weight, 60% by weight, 55% by weight, 50% by weight, 45% by weight, 40% by weight, 35% by weight, or even 30% by weight. The content may be, for example, 2 to 95% by weight, 5 to 80% by weight, 5 to 75% by weight, 5 to 70% by weight, 10 to 70% by weight, 10 to 55% by weight, 10 to 50% by weight, 10 to 45% by weight, 10 to 35% by weight, or even 10 to 30% by weight.

[0057] The content of the structural unit derived from monomer a2 in the partial polymer is, for example, 1% by weight or more, 2% by weight, or even 3% by weight or more. The upper limit of this content is, for example, 25% by weight, and may be 20% by weight, 15% by weight, 10% by weight, 8% by weight, 7% by weight, 6% by weight, or even 5% by weight. The content is preferably 1 to 20% by weight, more preferably 1 to 10% by weight, and even more preferably 1 to 5% by weight.

[0058] The content of the structural unit derived from monomer a3 in the partial polymer is, for example, 1% by weight or more, and may be 2% by weight or more, 3% by weight or more, or even 4% by weight or more. The upper limit of this content is, for example, 10% by weight, and may be 9%, 8%, 7%, 6%, or even 5% by weight. The content is preferably 1 to 10% by weight, more preferably 1 to 8% by weight, and even more preferably 2 to 5% by weight.

[0059] The content of the partially polymerized product in the photocurable pressure-sensitive adhesive composition, particularly the content of the partially polymerized product in the monomer syrup, is, for example, 1 to 30% by weight. The lower limit of the content is, for example, 2% by weight, and may be 3%, 4%, or even 5% by weight. The upper limit of the content is, for example, 25%, 20%, or even 15% by weight. The content is preferably 1 to 25% by weight, more preferably 2 to 20% by weight, and even more preferably 5 to 15% by weight.

[0060] The weight average molecular weight (Mw) of the partial polymer is, for example, 3 million or more, 3.5 million or more, or even 4 million or more. The upper limit of the weight average molecular weight (Mw) is, for example, 10 million, 9 million, 8 million, 7 million, 6 million, or even 5 million. The weight average molecular weight (Mw) is preferably 3 million to 10 million, more preferably 3 million to 8 million, even more preferably 3 million to 6 million, and particularly preferably 3 million to 5 million. The weight average molecular weight (Mw) is measured by GPC (gel permeation chromatography) and determined from the value calculated in polystyrene equivalent.

[0061] The partial polymer may have a glass transition temperature of 0°C or lower as calculated from the FOX formula. The upper limit of the glass transition temperature may be -5°C, -10°C, -15°C, -20°C, -25°C, -30°C, -35°C, -40°C, or -45°C. The lower limit of the glass transition temperature may be, for example, -60°C, -55°C, -50°C, -45°C, or even -40°C. The glass transition temperature is preferably -60°C to -5°C, more preferably -50°C to -5°C, even more preferably -45°C to -5°C, and particularly preferably -45°C to -30°C. The FOX formula is expressed by the following mathematical formula (N1): 1 / Tg=w1 / Tg1+w2 / Tg2+ ... +w m / Tg m (N1)

[0062] In the above formula (N1), Tg is the glass transition temperature (K) of the partial polymer. m are the weight fractions of the monomers in the monomer component M1 of the photocurable pressure-sensitive adhesive composition that form the partial polymer. m and Tg are the glass transition temperatures (K) of the single polymers of the respective monomers. As an example, w1 is the weight fraction of the first monomer in the monomer component M1, and Tg1 is the glass transition temperature (K) of the single polymer of the first monomer. The glass transition temperature (K) of the partial polymer can be calculated from formula (N1).

[0063] <2-1-3. Other Components> (2-1-3-1. Photopolymerization Initiator) Photocurable pressure-sensitive adhesive compositions, particularly monomer syrups contained in photocurable pressure-sensitive adhesive compositions, typically contain a photopolymerization initiator. An example of a photopolymerization initiator is a photoradical generator that generates radicals upon irradiation with light. The photopolymerization initiator may have an absorption coefficient with respect to light having a wavelength of 340 nm of, for example, 0.1 L / (g cm) or more, 0.5 L / (g cm) or more, 1.0 L / (g cm) or more, 3.0 L / (g cm) or more, or even 5.0 L / (g cm) or more. The upper limit of this absorption coefficient is not particularly limited, and may be, for example, 50 L / (g cm). The absorption coefficient of the photopolymerization initiator is a value calculated from the absorbance of a 0.01 mg / mL methanol solution measured with a visible-ultraviolet spectrophotometer using a quartz cell with an optical path length of 1 cm.

[0064] Examples of the photopolymerization initiator include benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzil dimethyl ketal; substituted benzoin ethers such as anisole methyl ether; substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; α-hydroxyalkylphenones such as 1-hydroxycyclohexyl-phenyl ketone, 2-hydroxy-2-methylpropiophenone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, and 2,2'-dihydroxy-2,2'-dimethyl-1,1'-[methylenebis(4,1-phenylene)]bis(propan-1-one); and substituted alpha alkyl phenones such as 2-methyl-2-hydroxypropiophenone. aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; photoactive oximes such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime; benzophenone-based compounds such as benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone; thioxanthone-based compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and 2,4-diethylthioxanthone;2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine, 2-piperonyl-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxy-naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6-triazine, 2,4-trichloromethyl- Examples of suitable photocurable adhesive compositions include triazine-based compounds such as (4'-methoxystyryl)-6-triazine; oxime ester-based compounds such as 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], and O-(acetyl)-N-(1-phenyl-2-oxo-2-(4'-methoxy-naphthyl)ethylidene)hydroxylamine; phosphine-based compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; quinone-based compounds such as 9,10-phenanthrenequinone, camphorquinone, and ethylanthraquinone; borate-based compounds; carbazole-based compounds; imidazole-based compounds; and titanocene-based compounds. The photocurable adhesive composition may contain one or more photopolymerization initiators. Alpha-hydroxyalkylphenones tend to have high absorption of light with a wavelength of 340±10 nm.

[0065] Another example of the photopolymerization initiator is a compound having a chemical structure shown in the following formula (1) (hereinafter referred to as "chemical structure X") in the molecule.

[0066] R in the formula (1) 1 and R 2 are each independently a C1 to C8 alkyl group; —OH, a C1 to C4 alkoxy group, —CN, —COOR 51 , -OOCR 52 , or -NR 53 R 54a C1-C4 alkyl group in which a hydrogen atom is substituted by -; a C3-C6 alkenyl group; or -CH2-C6H4-R 55 It is. 1 and R 2 may be bonded to each other to form a C2 to C9 alkylene group, a C3 to C6 oxyalkylene group, or an azaalkylene group. 51 is a C1 to C8 alkyl group. 52 is a C1 to C4 alkyl group. 53 and R 54 are each independently a hydrogen atom, a C1 to C12 alkyl group; —OH, a C1 to C4 alkoxy group, —CN, or —COOR 59 a C2-C4 alkyl group in which a hydrogen atom is substituted with at least one group selected from the group consisting of: a C3-C5 alkenyl group; or a cyclohexyl group. 53 and R 54 are bonded to each other to form —O— or —N(R 60 )-Optionally, it may be a C3 to C9 alkylene group. 55 is a C1 to C4 alkyl group. 59 is a C1 to C4 alkyl group. 60 represents a hydrogen atom, a C1-C4 alkyl group, an allyl group, a C1-C4 hydroxyalkyl group, -CH2CH2-COOR 61 Or -CH2CH2CN. 61 is a C1 to C4 alkyl group.

[0067] X is -OR 56 , or -NR 57 R 58 It is. 56 is a hydrogen atom, -SiR 62 3. A C1 to C8 alkyl group or a C3 to C6 alkenyl group. 57 and R 58 represents a C1 to C12 alkyl group; —OH, a C1 to C4 alkoxy group, —CN, and —COOR 63a C2-C4 alkyl group in which a hydrogen atom is substituted with at least one group selected from the group consisting of: a C3-C5 alkenyl group; or a cyclohexyl group. 57 and R 58 are bonded to each other to form —O— or —N(R 64 )-Optionally, it may be a C3 to C9 alkylene group. 62 is a C1 to C6 alkyl group. 63 is a C1 to C4 alkyl group. 64 represents a hydrogen atom, a C1-C4 alkyl group, an allyl group, a C1-C4 hydroxyalkyl group, -CH2CH2-COOR 65 Or -CH2CH2CN. 65 is a C1 to C4 alkyl group.

[0068] The chemical structure X can be bonded to a hydrogen atom or a structure substituted with a hydrogen atom in formula (1) via the carbon atom indicated by *.

[0069] The alkyl group, alkoxy group, alkenyl group, alkylene group, oxyalkylene group, azaalkylene group, and hydroxyalkyl group described in the explanation of formula (1) may be unbranched or branched. Furthermore, in this specification, including the explanation of formula (1), the expression "Cn1 to Cn2" (n1 and n2 are natural numbers) means that the number of carbon atoms is in the range of n1 to n2.

[0070] In formula (1), R 1 and R 2 may be the same.

[0071] R 1 , R 2 and X may take any combination of the above preferred examples.

[0072] The chemical structure X may be a structure shown in the following formula (2): In the chemical structure X of formula (2), when a substitution structure of a hydrogen atom is bonded to the carbon atom indicated by *, the substitution structure and -COCR in formula (2) may be bonded to each other. 1 XR 2 The group is in a para-position relationship with respect to the benzene ring of the chemical structure X.

[0073] The photopolymerization initiator may be a compound having two or more chemical structures X in one molecule.

[0074] The photopolymerization initiator may be a compound represented by the following formula (3). The compound of formula (3) has two chemical structures X in one molecule. The two chemical structures X are located at both ends of the photopolymerization initiator molecule. More specifically, the two chemical structures X are bonded to each other via -A- at the carbon atom of the phenylene group represented by * above.

[0075] R in formula (3) 1 ' and R 2 ' are mutually exclusive and R 1 and R 2 Independently of 1 and R 2 R 1 ' and / or R 2 ' is R 1 and / or R 2 may be the same as R 1 , R 2 , R 1 ' and R 2 ' may all be the same.

[0076] X' in formula (3) is a possible group for X, independently of X in formula (1). X' and X may be the same.

[0077] A is -O-, -CYR 3 - or -C(CH3)R 4 is.

[0078] Y is a hydrogen atom, —Cl, —Br, or —O—R 71 , -NR 72 R 73 , or -S-R 74 It is. 3 represents a hydrogen atom, a C1-C8 alkyl group, a C3-C6 alkenyl group, a benzyl group, -CH2-C6H4-R 75 or a phenyl group. 4is a C1-C6 alkyl or alkylene group, and this alkylene group is bonded to a carbon atom of the phenylene group of the compound of formula (3).

[0079] R 71 is a hydrogen atom, -Si(R 76 ) 3, C1 to C12 alkyl group, C2 to C18 acyl group, —CO—NH—R 77 , a C2 to C20 hydroxyalkyl group, a C2 to C20 methoxyalkyl group, 3-R 78 -2-hydroxypropyl group, 3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]disiloxanyl]propyl group, 2,3-dihydroxypropyl group, or a C2 to C21 hydroxyalkyl group or a C3 to C25 alkyl group in which the carbon chain is interrupted by 1 to 9 oxygen atoms. 72 and R 73 are each independently a C1 to C12 alkyl group; —OH, a C1 to C4 alkoxy group, —CN, and —COOR 79 a C2-C4 alkyl group in which a hydrogen atom is substituted with at least one group selected from the group consisting of: a C3-C5 alkenyl group; a cyclohexyl group; or a C7-C9 phenylalkyl group. 72 and R 73 are bonded to each other to form —O— or —N(R 80 )-Optionally, it may be a C3 to C9 alkylene group. 74 represents a C1 to C18 alkyl group, a hydroxyethyl group, a 2,3-dihydroxypropyl group, a cyclohexyl group, a benzyl group, a phenyl group, a C1 to C12 alkylphenyl group, -CH2-COOR 81 -CH2CH2-COOR 82 , or —CH(CH3)—COOR 83 It is. 75 is a C1 to C4 alkyl group. 76 is a C1 to C6 alkyl group. 77 is a C1 to C12 alkyl group. 78 is a C1 to C18 alkoxy group. 79 is a C1 to C4 alkyl group.80 represents a hydrogen atom, a C1-C4 alkyl group, an allyl group, a benzyl group, a C1-C4 hydroxyalkyl group, -CH2CH2-COOR 84 , or —CH2CH2CN. 81 , R 82 and R 83 are each independently a C1 to C18 alkyl group. 84 is a C1 to C4 alkyl group.

[0080] In the alkyl group, alkenyl group, acyl group, hydroxyalkyl group, methoxyalkyl group, alkoxy group, and phenylalkyl group described in the explanation of formula (3), the alkyl group portion and the alkylene group may be either unbranched or branched.

[0081] R in formula (3) 1 , R 2 , R 1 ' and R 2 Preferred examples of R ′ are those described above in the explanation of formula (1). 1 and R 2 The preferred examples of X′ in formula (3) are the same as the preferred examples of X described above in the explanation of formula (1). A is —CYR 3 -. Y may be a hydrogen atom. R 3 may be a hydrogen atom. 3 - and Y and R 3 and may both be hydrogen atoms. In other words, A may be —CH—.

[0082] R in formula (3) 1 , R 2 , R 1 ', R 2 ', X, X', and A may take any combination of the preferred examples above.

[0083] The photopolymerization initiator may be a compound represented by the following formula (4): The compound of formula (4) is a type of compound of formula (3).

[0084] Specific examples of photopolymerization initiators are shown in the following formulas (5) to (9). The photopolymerization initiator may be a compound represented by at least one formula selected from the group consisting of formulas (5) to (9), a compound represented by at least one formula selected from the group consisting of formulas (5) to (8), a compound represented by at least one formula selected from the group consisting of formulas (5) to (7), or a compound represented by formula (5). The compound of formula (8) is derived from a vinyl compound having chemical structure X in its side chain. More specifically, it is an oligomer of the vinyl compound.

[0085]

[0086]

[0087]

[0088]

[0089]

[0090] The photopolymerization initiators represented by formulas (5) to (9) are commercially available as Omnirad 127D, Esacure KIP160, Esacure one, Esacure KIP150, and Omnirad 1173 (all manufactured by IGM Resins). The photopolymerization initiator may be at least one selected from these groups.

[0091] Specific examples of the photopolymerization initiator include 1-hydroxycyclohexyl-phenyl ketone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)2-methylpropan-1-one. Of these, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)2-methylpropan-1-one is preferred. Each of the above photopolymerization initiators is commercially available as Omnirad 184, Omnirad 819, and Omnirad 127, respectively (all manufactured by IGM Resin).

[0092] The amount of the photopolymerization initiator in the photocurable pressure-sensitive adhesive composition, particularly the amount of the photopolymerization initiator in the monomer syrup, may be, for example, 20 parts by weight or less, 10 parts by weight or less, 5.0 parts by weight or less, 3.0 parts by weight or less, 1.0 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.25 parts by weight or less, or even 0.2 parts by weight or less, relative to 100 parts by weight of the monomer component M1. The lower limit of the amount may be, for example, 0.01 parts by weight, 0.05 parts by weight, 0.10 parts by weight, 0.15 parts by weight or more, or even 0.20 parts by weight, relative to 100 parts by weight of the monomer component M1. The amount is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 5.0 parts by weight, even more preferably 0.1 to 1.0 parts by weight, and particularly preferably 0.1 to 0.5 parts by weight.

[0093] <2-2. Additional Monomer Component M2> The photocurable pressure-sensitive adhesive composition may contain, in addition to the monomer syrup, an additional monomer component M2 (which may be added between Step I and Step II (specifically, Step III) described below). Examples of the monomer contained in the monomer component M2 are the same as the examples of the monomer contained in the monomer component M1 described above. The monomer component M2 can be distinguished from the monomer component M1 that constitutes the monomer syrup.

[0094] The content of monomer a1 in monomer component M2 is, for example, 1 wt% or more, and may be 2 wt% or more, 3 wt% or more, 5 wt% or more, 10 wt% or more, or even 20 wt% or more. The upper limit of the content is, for example, 100 wt%, and may be 90 wt%, 80 wt%, 70 wt%, 60 wt%, or even 50 wt%. The content of monomer a1 in monomer component M2 may be higher than the content of monomer a1 in monomer component M1. Monomer component M2 may contain only monomer a1. If the content of monomer a1 in monomer component M2 is high, residual monomer is likely to remain in the pressure-sensitive adhesive sheet 1.

[0095] <2-3. Total Monomer Components M> When the photocurable pressure-sensitive adhesive composition contains an additional monomer component M2, the total monomer components M contained in the photocurable pressure-sensitive adhesive composition is a mixed monomer component of the monomer component M1 in the monomer syrup and the additional monomer component M2. The content of the monomer component M1 in the total monomer components M is, for example, 50% by weight or more, and may be 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, 95% by weight or more, or even 99% by weight or more. It is preferable that the photocurable pressure-sensitive adhesive composition contains only the monomer component M1 in the monomer syrup and does not contain the additional monomer component M2.

[0096] The content of monomer a1 in all monomer components M contained in the photocurable pressure-sensitive adhesive composition is as described above in the description of the content of monomer a1 in monomer component M1. That is, the content of monomer a1 in all monomer components M is, for example, 1 wt% or more, and may be 2 wt% or more, 3 wt% or more, 4 wt% or more, 5 wt% or more, 10 wt% or more, or even 15 wt% or more. The upper limit of the content is, for example, 99 wt%, and may be 95 wt%, 90 wt%, 85 wt%, 80 wt%, 75 wt%, 70 wt%, 65 wt%, 60 wt%, 55 wt%, 50 wt%, 45 wt%, 40 wt%, 35 wt%, or even 30 wt%. The content is, for example, 2 to 99% by weight, and may be 2 to 95% by weight, 2 to 80% by weight, 5 to 80% by weight, 5 to 75% by weight, 5 to 70% by weight, 10 to 70% by weight, 10 to 55% by weight, 10 to 50% by weight, 10 to 45% by weight, 10 to 35% by weight, or even 10 to 30% by weight. If the content of monomer a1 in monomer component M is high, residual monomer is likely to remain in the pressure-sensitive adhesive sheet 1.

[0097] The absolute value of the difference between the content of monomer a1 in all monomer components M contained in the photocurable pressure-sensitive adhesive composition and the content of structural units derived from monomer a1 in the partial polymer is, for example, 30% by weight or less, and may be 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, 5% by weight or less, 3% by weight or less, or even 1% by weight or less. The difference in content may be substantially zero. "Substantially no difference in content" means that the absolute value of the difference from the content may be, for example, 0.1% by weight or less, preferably 0.05% by weight or less, and more preferably 0.01% by weight or less.

[0098] The content of all monomer components M contained in the photocurable pressure-sensitive adhesive composition may be, for example, 95% by weight or more, 96% by weight or more, 97% by weight or more, 98% by weight or more, 99% by weight or more, or even 99.5% by weight or more. The content is preferably 98% by weight or more but less than 100% by weight, more preferably 99% by weight or more but less than 100% by weight, and even more preferably 99.5% by weight or more but less than 100% by weight.

[0099] <2-4. Crosslinking Agent> The photocurable pressure-sensitive adhesive composition may contain a crosslinking agent. An example of the crosslinking agent is a polyfunctional monomer having two or more polymerizable functional groups in one molecule. The polyfunctional monomer may be a (meth)acrylic monomer. Examples of the polyfunctional monomer are a monomer having two or more C=C bonds in one molecule, and a monomer having one or more C=C bonds and one or more polymerizable functional groups such as epoxy groups, aziridine groups, oxazoline groups, hydrazine groups, methylol groups, etc. in one molecule. The polyfunctional monomer is preferably a monomer having two or more C=C bonds in one molecule.

[0100] Examples of polyfunctional monomers include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol diacrylate (N Polyfunctional acrylates (such as ester compounds of polyhydric alcohols and (meth)acrylic acid) such as 1,12-dodecanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, and hexyl di(meth)acrylate. The polyfunctional monomer is preferably a polyfunctional acrylate, and more preferably 1,9-nonanediol diacrylate, trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, or dipentaerythritol hexa(meth)acrylate.

[0101] <2-5. Solvent> The content of the solvent in the photocurable pressure-sensitive adhesive composition is, for example, 5 wt % or less, and may be 4 wt % or less, 3 wt % or less, 2 wt % or less, 1 wt % or less, or even 0.5 wt % or less. The pressure-sensitive adhesive composition may be substantially free of solvent. "Substantially free of solvent" means that solvents derived from additives and the like are allowed at a content of, for example, 0.1 wt % or less, preferably 0.05 wt % or less, and more preferably 0.01 wt % or less.

[0102] <2-6. Other Additives> The photocurable pressure-sensitive adhesive composition may contain additives other than those described above. Examples of the additives include a silane coupling agent, an antioxidant, an ultraviolet absorber, a chain transfer agent, a viscosity modifier, a tackifier, a plasticizer, a softener, an antioxidant, a filler, a colorant, a surfactant, and an antistatic agent.

[0103] <2-7. Physical Properties of Photocurable Pressure-Sensitive Adhesive Composition> The viscosity of the photocurable pressure-sensitive adhesive composition is, for example, 5 to 100 poise at 25° C. A photocurable pressure-sensitive adhesive composition having a viscosity in the above range is particularly suitable for forming a coating layer, which will be described later.

[0104] <<3. Physical Properties of the Pressure-Sensitive Adhesive Sheet>> The polymerization rate of all monomer components M in the pressure-sensitive adhesive sheet 1 is, for example, 90% or more. The polymerization rate may be 95% or more, 98% or more, or even 99% or more. The polymerization rate can be adjusted to a desired range by adjusting the type and amount of the photopolymerization initiator described below, and the irradiation intensity and irradiation time of actinic rays such as ultraviolet light. The polymerization rate of all monomer components M in the pressure-sensitive adhesive sheet 1 is calculated from the weights before and after heating at 130°C for 3 hours using the following formula (N2): Polymerization rate (%) = (weight after drying) / (weight before drying) × 100 (N2)

[0105] The gel fraction of the pressure-sensitive adhesive sheet 1 is, for example, 80% by weight or more. The gel fraction of the pressure-sensitive adhesive sheet 1 may be 81% by weight or more, 82% by weight or more, 83% by weight or more, 84% by weight or more, or even 85% by weight or more. By adjusting the gel fraction of the pressure-sensitive adhesive sheet 1 to fall within the above range, high durability can be achieved.

[0106] The gel fraction of the PSA sheet 1 can be evaluated, for example, by the following method. First, a portion of the PSA sheet 1 is scraped off to obtain a small piece. Next, the obtained small piece is wrapped in a stretched porous polytetrafluoroethylene film and tied with kite string. This results in a test piece. Next, the total weight (weight Wa) of the small piece of PSA sheet 1, the stretched porous film, and the kite string is measured. The total weight of the stretched porous film and kite string used is defined as weight Wb. Next, the test piece is immersed in a container filled with ethyl acetate and left to stand at 23°C for one week. After standing, the test piece is removed from the container and dried for two hours in a dryer set at 130°C, and then the weight Wc of the test piece is measured. The gel fraction of the PSA sheet 1 can be calculated from weight Wa, weight Wb, and weight Wc based on the following mathematical formula (N3): Gel fraction (wt %) = (Wc - Wb) / (Wa - Wb) x 100 (N3)

[0107] The haze of the pressure-sensitive adhesive sheet 1 is, for example, 3.0% or less. The haze of the pressure-sensitive adhesive sheet 1 may be 2.5% or less, 2.0% or less, 1.5% or less, 1.0% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, or even 0.3% or less. The haze of the pressure-sensitive adhesive sheet 1 can be measured in accordance with JIS K7136:1981.

[0108] The pressure-sensitive adhesive sheet 1 may have a glass transition temperature Tg calculated from the FOX formula of 0°C or lower. The upper limit of the glass transition temperature Tg may be -5°C, -10°C, -15°C, -20°C, -25°C, -30°C, -35°C, -40°C, or even -45°C. The lower limit of the glass transition temperature may be, for example, -60°C, -55°C, -50°C, -45°C, or even -40°C. The glass transition temperature Tg is preferably -60°C to -5°C, more preferably -50°C to -5°C, even more preferably -45°C to -5°C, and particularly preferably -45°C to -30°C. The glass transition temperature of the pressure-sensitive adhesive sheet 1 calculated from the FOX formula can be calculated in accordance with the method for calculating the glass transition temperature of a partially polymerized product using the above-mentioned formula (N1).

[0109] 2A , a method for producing the above-mentioned pressure-sensitive adhesive sheet 1 will be described. The method for producing the pressure-sensitive adhesive sheet 1 includes: Step I of partially polymerizing a monomer component M1 containing a monomer a1 having an aromatic ring to form a monomer syrup containing a partial polymer; and Step II of curing a photocurable pressure-sensitive adhesive composition containing the monomer syrup to form a pressure-sensitive adhesive sheet.

[0110] <4-1. Step I> When performing step I, first, a mixture Cm containing a monomer component M1 and a photopolymerization initiator is prepared. The types and amounts of the monomer component M1 and the photopolymerization initiator are as described above. Thereafter, the mixture Cm is irradiated with light L1 to partially polymerize the monomer component M1. This results in a monomer syrup Cs containing a partial polymer A and the monomer component M1 that did not form the partial polymer A.

[0111] The light L1 is, for example, visible light or ultraviolet light having a wavelength shorter than 450 nm. The light L1 may include light having a wavelength in the same region as the absorption wavelength of the photopolymerization initiator contained in the mixture Cm. The light source of the light L1 is, for example, a light irradiation device equipped with an ultraviolet irradiation lamp. Examples of ultraviolet irradiation lamps include ultraviolet LEDs, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, microwave-excited mercury lamps, black light lamps, chemical lamps, germicidal lamps, low-pressure discharge mercury lamps, and excimer lasers. Two or more ultraviolet irradiation lamps may be combined.

[0112] The illuminance of the light L1 irradiated onto the mixture Cm is, for example, 0.1 to 10 mW / cm 2 The lower limit of the illuminance is 0.2 mW / cm 2 , 0.3 mW / cm 2 , 0.4 mW / cm 2 , 0.5 mW / cm 2 , 0.6 mW / cm 2 , 0.7 mW / cm 2 , 0.8 mW / cm 2 , 0.9 mW / cm 2 , and even 1.0 mW / cm 2 The upper limit of the illuminance may be, for example, 9 mW / cm 2 and 8 mW / cm 2 , 7 mW / cm 2 , 6 mW / cm 2 , 5 mW / cm 2 , 4 mW / cm 2 , 3 mW / cm 2 , and even 2 mW / cm 2 may be.

[0113] The light L1 may be irradiated onto the mixture Cm in multiple stages. The illuminance and / or the integrated light amount of the light L1 in each stage may be the same or different from each other. Furthermore, the light source in each stage may be the same or different from each other.

[0114] In step I, for example, the monomer component M1 is partially polymerized so that the polymerization rate is 1 to 30%. The lower limit of the polymerization rate is, for example, 2%, and may be 3%, 4%, or even 5% or more. The upper limit of the polymerization rate is, for example, 25%, 20%, or even 15%. The polymerization rate is preferably 1 to 25%, more preferably 2 to 20%, and even more preferably 5 to 15%. The polymerization rate can be adjusted to a desired range by adjusting the type and amount of photopolymerization initiator, the irradiation intensity and irradiation time of actinic rays such as UV light, and the like.

[0115] In step I, for example, the partial polymer A is formed so that the weight average molecular weight (Mw) is 3,000,000 or more. The lower limit of the weight average molecular weight (Mw) may be 3.5 million, or even 4,000,000. The upper limit of the weight average molecular weight (Mw) may be, for example, 10,000,000, 9,000,000, 8,000,000, 7,000,000, 6,000,000, or even 5,000,000. The weight average molecular weight (Mw) is preferably 3,000,000 to 10,000,000, more preferably 3,000,000 to 8,000,000, even more preferably 3,000,000 to 6,000,000, and particularly preferably 3,000,000 to 4,000,000.

[0116] After the monomer syrup Cs is obtained in step I, an additive such as a crosslinking agent may be mixed with the monomer syrup Cs. Furthermore, as in step III (see FIG. 2B ) described below, an additional monomer component M2 may be mixed with the monomer syrup Cs within a range that does not impair the effects of the present invention. The monomer contained in the additional monomer component M2 may be any monomer, and the additional monomer component M2 may include, for example, a monomer other than monomer a1. When an additive or monomer component M2 is additionally mixed, the additive or monomer component M2 may contribute to the production of a photocurable pressure-sensitive adhesive composition C. It is preferable not to add the monomer component M2. In such a case, when a pressure-sensitive adhesive sheet 1 is formed from the photocurable pressure-sensitive adhesive composition C, the resulting pressure-sensitive adhesive sheet 1 is more likely to be homogenized, thereby reducing the occurrence of differences in physical properties within the pressure-sensitive adhesive sheet 1. This makes the pressure-sensitive adhesive sheet 1 more likely to have excellent durability and impact resistance, and also reduces haze.

[0117] <4-2. Step II> In Step II, for example, a laminate S1 including, in this order, a base sheet R1, a coating layer 10 containing a photocurable pressure-sensitive adhesive composition C, and a release liner R2 is irradiated with light L2. The coating layer 10 is irradiated with light L2 and cured to form a pressure-sensitive adhesive sheet 1. Monomer a1 having an aromatic ring tends to have a high glass transition temperature when formed into a single polymer. In a pressure-sensitive adhesive sheet 1 formed from a photocurable pressure-sensitive adhesive composition C containing such a monomer component M1 and a partial polymer of monomer component M1, it is presumed that the structural units derived from monomer a1 in the partial polymer of monomer component M1 are unevenly distributed at the interface of the pressure-sensitive adhesive sheet 1 due to segregation of the partial polymer of monomer component M1 caused by polymerization-induced phase separation in the photocurable pressure-sensitive adhesive composition C. It is presumed that the uneven distribution of the structural units derived from monomer a1 at the interface improves the cohesive force at the interface of the pressure-sensitive adhesive sheet 1. As a result, the resulting pressure-sensitive adhesive sheet 1 is likely to have excellent durability and impact resistance, and also tends to have reduced haze.

[0118] Irradiation with light L2 is typically performed from the side of the base sheet R1. At this time, light L2 passes through the base sheet R1 and reaches the coating layer 10, curing the coating layer 10. However, irradiation with light L2 may also be performed from the side of the release liner R2, or from both the side of the release liner R2 and the side of the base sheet R1.

[0119] In step II, for example, the pressure-sensitive adhesive sheet 1 is formed so that the gel fraction of the pressure-sensitive adhesive sheet 1 is 80% by weight or more. The gel fraction may be 81% by weight or more, 82% by weight or more, 83% by weight or more, 84% by weight or more, or even 85% by weight or more. By adjusting the gel fraction of the pressure-sensitive adhesive sheet 1 within the above range, high durability can be achieved.

[0120] The formed pressure-sensitive adhesive sheet 1 is sandwiched between the base sheet R1 and the release liner R2 and constitutes part of the laminate S1 until the release liner R2 is peeled off. By peeling the release liner R2 from the laminate S1, a laminate S2 containing the base sheet R1 and the pressure-sensitive adhesive sheet 1 is obtained. In the laminate S2, the surface of the pressure-sensitive adhesive sheet 1 is exposed to the outside. An optical film can be laminated onto the exposed surface of the pressure-sensitive adhesive sheet 1 directly or via another layer.

[0121] Light L2 is, for example, visible light or ultraviolet light in the same wavelength range as light L1. Light L2 may include light with a wavelength in the same range as the absorption wavelength of the photopolymerization initiator contained in photocurable pressure-sensitive adhesive composition C. Light with a wavelength of 300 nm or less may be irradiated, with short wavelength light being filtered out using a filter or the like. Filtering out short wavelength light is suitable for suppressing deterioration of base sheet R1 and / or release liner R2 caused by light L2. The light source of light L2 may be selected from the light sources exemplified as the light source of light L1.

[0122] The illuminance of the light L2 irradiated onto the laminate S1 (specifically, the coating layer 10) is, for example, 2.0 to 30 mW / cm 2 The lower limit of the illuminance is 2.5 mW / cm 2 , 3.0 mW / cm 2 , 3.5 mW / cm 2 , 4.0 mW / cm 2 , 5.0 mW / cm 2 , 6.0 mW / cm 2 , 7.0 mW / cm 2 , 8.0 mW / cm 2 , 9.0 mW / cm 2 , and even 10 mW / cm 2 The upper limit of the illuminance may be, for example, 25 mW / cm 2 and 20 mW / cm 2 may be.

[0123] The time for irradiating the laminate S1 (specifically, the coating layer 10) with the light L2 is, for example, 10 to 1,000 seconds. The lower limit of the irradiation time may be 60 seconds, 100 seconds, 150 seconds, or even 200 seconds. The upper limit of the irradiation time is, for example, 800 seconds, and may be 600 seconds, 500 seconds, 400 seconds, 300 seconds, or even 250 seconds. The irradiation with the light L2 may be continuous or intermittent.

[0124] The integrated light amount of the light L2 on the laminate S1 (specifically, the coating layer 10) is, for example, 25 mJ / cm 2 or more, and 100 mJ / cm 2 Above, 500mJ / cm 2 Above, 1000mJ / cm 2 Above, 2000mJ / cm 2 Above, 2500mJ / cm 2 Above, 3000mJ / cm 2 Above, 5000mJ / cm 2 Above, 7500mJ / cm 2 or more, and even 10,000 mJ / cm 2 The upper limit of the integrated light amount is not particularly limited, and may be, for example, 30,000 mJ / cm 2 and 25,000 mJ / cm 2 , 20000mJ / cm 2 , and even 18000 mJ / cm 2 may be.

[0125] The light L2 may be irradiated onto the laminate S1 in multiple stages. The illuminance and / or the integrated light amount of the light L2 in each stage may be the same or different from each other. Furthermore, the light sources in each stage may be the same or different from each other.

[0126] An example of the substrate of the release liner R2 (hereinafter referred to as the "liner substrate") is a resin film. Examples of resins that can be contained in the liner substrate include polyesters such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resins, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, and polyphenylene sulfide. The resin is preferably a polyester such as polyethylene terephthalate.

[0127] The release liner R2 may include a layer other than the liner substrate. The release liner R2 may include a release layer. The release liner R2 includes, for example, a liner substrate and a release layer formed on one surface of the liner substrate. This release liner R2 can be used with the release layer facing the coating layer 10. The release layer is typically a cured layer of a release agent composition containing a release agent. Various release agents can be used as the release agent, such as silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, fatty acid amide-based release agents, and silica powder.

[0128] The release liner R2 may be in the form of a sheet or a continuous piece.

[0129] An example of the base sheet R1 is a resin film. Examples of the resin contained in the base sheet R1 are the same as the examples of the resin that can be contained in the liner base material.

[0130] The thickness of the base sheet R1 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

[0131] The base sheet R1 may have a release layer on the surface facing the coating layer 10. Examples of the release layer that may be provided on the base sheet R1 are the same as the examples of the release layer that may be provided on the release liner R2. Both the release liner R2 and the base sheet R1 may have a release layer.

[0132] For the base sheet R1, a sheet having a greater peel strength from the pressure sensitive adhesive sheet 1 than the release liner R2 can usually be selected.

[0133] The base sheet R1 may be in the form of a sheet or a continuous sheet.

[0134] The laminate S1 can be formed, for example, by forming a coating layer 10 on a base sheet R1 (or a release liner R2) and then placing a release liner R2 (or a base sheet R1) on the formed coating layer 10. Alternatively, the laminate S1 may be formed by applying the photocurable composition in a poured manner into the space between the base sheet R1 and the release liner R2, which are held at a predetermined distance so that their main surfaces face each other.

[0135] The coating layer 10 can be formed by various coating methods such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating.

[0136] The thickness of the coating layer 10 is, for example, 50 μm or less, and may be 40 μm or less, 35 μm or less, or even 30 μm or less. The lower limit of the thickness is, for example, 1 μm, and may be 2 μm, 3 μm, 5 μm, or even 10 μm. The thickness of the coating layer 10 is preferably 1 to 50 μm, more preferably 1 to 40 μm, even more preferably 2 to 35 μm, and particularly preferably 3 to 30 μm. When the thickness of the coating layer 10 is within the above range, the pressure-sensitive adhesive sheet 1 formed from the coating layer 10 can be suitably used as a pressure-sensitive adhesive sheet for a polarizing film.

[0137] The laminate S1 may include a long base sheet R1, a long coating layer 10, and a long release liner R2, or in other words, may be long. The long laminate S1 can be obtained, for example, by forming the coating layer 10 between the base sheet R1 and the release liner R2 while conveying them from a roll.

[0138] <4-3. Step III> Step III is an optional step that is performed between Steps I and II. As shown in FIG. 2B , in Step III, a monomer component M2 is added to a monomer syrup Cs. In Step III, an additive such as a crosslinking agent may be mixed with the monomer syrup Cs. This allows a photocurable pressure-sensitive adhesive composition Ca to be obtained. Even when Step III is performed, the same method as when Step III is not performed is used. For example, in Step II, after Step III, a laminate S10 including, in this order, a base sheet R1, a coating layer 10a including the photocurable pressure-sensitive adhesive composition Ca, and a release liner R2 is irradiated with light L2. The coating layer 10a is irradiated with light L2 and cured to form a pressure-sensitive adhesive sheet 1a. The release liner R2 is then peeled off from the laminate S10 to obtain a laminate S20 including the base sheet R1 and the pressure-sensitive adhesive sheet 1a.

[0139] In step III, for example, the monomer component M2 is added to the monomer syrup Cs so that the total amount of the monomers a1 in the monomer component M2 is less than 50% by weight of the total amount of the monomers a1 in the monomer syrup Cs. The total amount of the monomers a1 in the monomer component M2 may be 45% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, or even 5% by weight or less of the total amount of the monomers a1 in the monomer syrup Cs.

[0140] In step III, for example, the monomer component M2 is added to the monomer syrup Cs so that the total amount of the monomer component M2 is less than 50% by weight of the total amount of the monomer component M1 in the monomer syrup Cs. The total amount of the monomer component M2 may be 45% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, or even 5% by weight or less of the total amount of the monomer component M1 in the monomer syrup Cs.

[0141] 5. Optical Laminate An example of an optical laminate according to an embodiment of the present invention is shown in FIG. 3. The optical laminate 20A of FIG. 3 includes the above-described pressure-sensitive adhesive sheet 1 and an optical film 2. The pressure-sensitive adhesive sheet 1 and the optical film 2 are laminated together. The optical laminate 20A can be used as an optical film with a pressure-sensitive adhesive sheet. Examples of the optical film 2 include a polarizing film, a retardation film, a laminate film containing a polarizing film and / or a retardation film, a surface anti-reflection film, an impact-resistant film, a decorative printed film, a brightness-enhancing film, a glass film, an anti-fouling film, a hard-coated film, a UV-absorbing film, and a hue-adjusting film. However, the optical film 2 is not limited to the above examples. The optical film 2 may also include a glass film.

[0142] Among optical films, polarizing films tend to undergo large dimensional changes due to heat. Dimensional changes in polarizing films can cause peeling from adhesive films. For this reason, the present invention is particularly advantageous when the optical laminate includes a polarizing film.

[0143] The polarizing film includes a polarizer. The polarizing film typically includes a polarizer and a protective film (transparent protective film). The protective film is disposed, for example, in contact with a main surface (the surface having the largest area) of the polarizer. The polarizer may be disposed between two protective films. The protective film may be disposed on at least one surface of the polarizer.

[0144] The polarizer is not particularly limited, and examples thereof include a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partially saponified film, which has been uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye; a polyene-based oriented film such as a dehydrated polyvinyl alcohol or a dehydrochlorinated polyvinyl chloride; etc. A polarizer typically comprises a polyvinyl alcohol film (polyvinyl alcohol films include an ethylene-vinyl acetate copolymer partially saponified film) and a dichroic substance such as iodine.

[0145] The thickness of the polarizer is not particularly limited and may be, for example, 80 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 18 μm or less, 15 μm or less, or even 12 μm or less. The lower limit of the polarizer thickness is not particularly limited and may be, for example, 1 μm, 5 μm, or even 10 μm. The lower limit of the polarizer thickness may be 15 μm in some cases. A thin polarizer (for example, a thickness of 20 μm or less) has reduced dimensional change and can contribute to improving the durability of the optical laminate, particularly durability at high temperatures.

[0146] The polarizer preferably exhibits absorptive dichroism at any wavelength in the range of 380 to 780 nm. The single transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 42.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

[0147] The polarizer can be produced by any appropriate method. Specifically, the polarizer may be produced from a single-layer resin film or a laminate of two or more layers.

[0148] A method for producing a polarizer from the above-mentioned single-layer resin film typically includes subjecting the resin film to a dyeing treatment with a dichroic substance such as iodine or a dichroic dye and a stretching treatment. Examples of the resin film that can be used include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and partially saponified ethylene-vinyl acetate copolymer-based films. This method may further include an insolubilization treatment, a swelling treatment, a crosslinking treatment, and the like. Such production methods are well known and commonly used in the art, and therefore a detailed description thereof will be omitted.

[0149] A polarizer obtained using the laminate can be produced, for example, using a laminate of a resin substrate and a resin film or resin layer (typically, a PVA-based resin layer). Specifically, a polarizer can be produced by applying a PVA-based resin solution to a resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; and stretching and dyeing the laminate to convert the PVA-based resin layer into a polarizer. In this embodiment, a PVA-based resin layer containing a halide and a PVA-based resin is preferably formed on one side of the resin substrate. The stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, the stretching may optionally further include in-air stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution. In addition, in this embodiment, the laminate is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being transported in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes subjecting a laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching treatment, it is possible to increase the crystallinity of the PVA, even when the PVA is coated on a thermoplastic resin, thereby achieving high optical properties. Furthermore, by simultaneously increasing the orientation of the PVA in advance, problems such as a decrease in orientation or dissolution of the PVA when immersed in water in the subsequent dyeing or stretching steps can be prevented, thereby achieving high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the PVA molecular orientation disorder and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide, thereby achieving high optical properties. Furthermore, by shrinking the laminate in the width direction by a drying shrinkage treatment, high optical properties can be achieved. A polarized film can be obtained by laminating a protective film on the peeled surface of the obtained resin substrate / polarizer laminate after peeling the resin substrate, or on the surface opposite to the peeled surface. Details of such a method for manufacturing a polarizer are described in, for example, JP 2012-73580 A and Japanese Patent No. 6470455. The entire disclosures of these publications are incorporated herein by reference.

[0150] The material for the protective film may be, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture-blocking properties, isotropy, etc. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene-based resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material for the protective film may be a thermosetting resin or an ultraviolet-curable resin such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone-based resin. When the polarizing film has two protective films, the materials of the two protective films may be the same or different. For example, a protective film made of a thermoplastic resin may be bonded to one main surface of the polarizer via an adhesive, and a protective film made of a thermosetting resin or an ultraviolet-curable resin may be bonded to the other main surface of the polarizer. The protective film may contain one or more optional additives, such as ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

[0151] The thickness of the protective film can be determined as appropriate, but is generally about 10 to 200 μm in view of strength, workability such as handling, thinness, and the like.

[0152] The polarizer and the protective film are usually adhered to each other via an aqueous adhesive or the like. Examples of aqueous adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex, aqueous polyurethane, and aqueous polyester. Examples of adhesives other than the above-mentioned adhesives include ultraviolet-curable adhesives and electron beam-curable adhesives. Electron beam-curable polarizing film adhesives exhibit suitable adhesiveness to various protective films. The adhesive may contain a metal compound filler.

[0153] In the polarizing film, a retardation film or the like can be formed on the polarizer instead of the protective film. Another protective film or a retardation film or the like can be further provided on the protective film.

[0154] The protective film may have a hard coat layer on the surface opposite to the surface bonded to the polarizer, and may also be subjected to treatments for purposes such as anti-reflection, anti-sticking, diffusion, and anti-glare.

[0155] The polarizing film may be a circular polarizing film.

[0156] The thickness of the polarizing film is, for example, 500 μm or less, and may be 300 μm or less, 200 μm or less, 100 μm or less, or even 60 μm or less. The lower limit of the thickness is, for example, 10 μm, 25 μm, or even 40 μm.

[0157] The retardation film is a film having birefringence in the in-plane direction and / or the thickness direction, and is, for example, a stretched resin film or a film in which a liquid crystal material is oriented and fixed.

[0158] The retardation film may be a λ / 4 plate, a λ / 2 plate, an anti-reflection retardation film (see, for example, paragraphs 0221, 0222, and 0228 of JP 2012-133303 A), a viewing angle compensation retardation film (see, for example, paragraphs 0225 and 0226 of JP 2012-133303 A), or an inclined orientation retardation film for viewing angle compensation (see, for example, paragraph 0227 of JP 2012-133303 A). The retardation film is not limited to the above examples as long as it has birefringence in the in-plane direction and / or the thickness direction. There are also no limitations on the retardation value, arrangement angle, three-dimensional birefringence, whether the retardation film is single-layer or multi-layer, etc. of the retardation film. Known films can be used as the retardation film.

[0159] The thickness of the optical film 2 is, for example, 1 to 200 μm.

[0160] The optical film 2 may be a single layer or a laminated film composed of two or more layers. When the optical film 2 is a laminated film, the pressure-sensitive adhesive sheet 1 may be used to bond the layers together.

[0161] Another example of an optical laminate according to an embodiment of the present invention is shown in Figure 4. Optical laminate 20B in Figure 4 has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 1, and an optical film 2 are layered in this order. By peeling off release liner 3, optical laminate 20B can be used as an optical film with a pressure-sensitive adhesive sheet.

[0162] The release liner 3 is typically a resin film. Examples of resins that make up the release liner 3 include polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene and polypropylene, polycarbonate, acrylic, polystyrene, polyamide, and polyimide. The surface of the release liner 3 that comes into contact with the pressure-sensitive adhesive sheet 1 may be subjected to a release treatment. The release treatment is, for example, a treatment with a silicone compound. However, the release liner 3 is not limited to the above examples. The release liner 3 is peeled off when the optical laminate 20B is used, for example, when it is attached to the image forming layer.

[0163] Another example of an optical laminate according to an embodiment of the present invention is shown in Figure 5. The optical laminate 20C in Figure 5 includes a polarizing film 2A and a retardation film 2B as the optical film 2 (see Figures 3 and 4). The optical laminate 20C in Figure 5 has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, and a polarizing film 2A are layered in this order. After peeling off the release liner 3, the optical laminate 20C can be used by being attached to, for example, an image-forming layer.

[0164] A known adhesive sheet can be used as the adhesive sheet 4. The adhesive sheet 1 may also be used as the adhesive sheet 4.

[0165] Another example of an optical laminate according to an embodiment of the present invention is shown in Figure 6. The optical laminate 20D in Figure 6 includes a polarizing film 2A and a retardation film 2B as the optical film 2 (see Figures 3 and 4). The optical laminate 20D in Figure 6 has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, a polarizing film 2A, and a protective film 5 are layered in this order. After peeling off the release liner 3, the optical laminate 20D can be used by being attached to, for example, an image-forming layer.

[0166] The protective film 5 has the function of protecting the optical film 2 (polarizing film 2A), which is the outermost layer, during distribution and storage of the optical laminate 20D and when the optical laminate 20D is incorporated into an image display device. The protective film 5 may also function as a window to the external space when incorporated into an image display device. The protective film 5 is typically a resin film. Examples of resins constituting the protective film 5 include polyesters such as PET, polyolefins such as polyethylene and polypropylene, acrylics, cycloolefins, polyimides, and polyamides, with polyesters being preferred. However, the protective film 5 is not limited to the above examples. The protective film 5 may be a glass film or a laminate film including a glass film. The protective film 5 may be subjected to surface treatments such as anti-glare, anti-reflection, and anti-static.

[0167] The protective film 5 may be bonded to the optical film 2 (polarizing film 2A) with any adhesive. Bonding with an adhesive sheet 1 is also possible.

[0168] Another example of an optical laminate according to an embodiment of the present invention is shown in Fig. 7. The optical laminate 20E in Fig. 7 has a layered structure in which a polarizing film 2A, a first adhesive layer 30, a first retardation film 2B, a second adhesive layer 35, a second retardation film 2C, a pressure-sensitive adhesive sheet 1, and a release liner 3 are layered in this order. After the release liner 3 is peeled off, the optical laminate 20E can be used by being attached to, for example, an image forming layer.

[0169] In the optical laminate 20E, the polarizing film 2A has a laminated structure in which a first protective film 26A, a polarizer 25, and a second protective film 26B are laminated in this order.

[0170] The first protective film 26A can be formed of, for example, any appropriate resin film that can be used as a protective layer for the polarizer 25. Specific examples of resins that serve as the main component of the resin film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based resins, polyvinyl alcohol-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyethersulfone-based resins, polysulfone-based resins, polystyrene-based resins, cycloolefin-based resins such as polynorbornene, polyolefin-based resins, (meth)acrylic resins, and acetate-based resins.

[0171] The optical laminate 20E is typically disposed on the viewing side of an image display device (e.g., an organic EL display device), and the first protective film 26A is disposed on the viewing side. Therefore, the first protective film 26A may be subjected to surface treatment such as hard coat (HC) treatment, anti-reflection treatment, anti-sticking treatment, anti-glare treatment, etc., as needed.

[0172] The thickness of the first protective film 26A is preferably 5 to 80 μm, more preferably 10 to 40 μm, and even more preferably 15 to 35 μm. If the first protective film 26A has been subjected to the above-mentioned surface treatment, the thickness of the first protective film 26A includes the thickness of the surface treatment layer.

[0173] The second protective film 26B can be formed of, for example, any appropriate resin film that can be used as a protective layer for the polarizer 25. When the second protective film 26B is formed of a resin film, the same explanation as for the first protective film 26A can be applied. Furthermore, for example, the second protective film 26B can be a solidified or cured layer of a coating film of an organic solvent solution containing a resin. When the second protective film 26B is a solidified or cured layer of a coating film of an organic solvent solution containing a resin, adhesion to the polarizer 25 can be improved.

[0174] In one embodiment, the resin (base polymer) forming the solidified or cured layer may have a glass transition temperature (Tg) of 85°C or higher and a weight average molecular weight (Mw) of 25,000 or higher. By having the Tg and Mw of the resin within these ranges, excellent durability can be achieved in high-temperature, high-humidity environments despite a very thin thickness. The Tg of the resin is preferably 90°C or higher, more preferably 100°C or higher, even more preferably 110°C or higher, and particularly preferably 120°C or higher. The Tg may be, for example, 200°C or lower. The Mw of the resin is preferably 30,000 or higher, more preferably 35,000 or higher, and even more preferably 40,000 or higher. The Mw may be, for example, 150,000 or lower.

[0175] As the resin, any suitable resin can be used as long as it can form a solidified or cured product (e.g., a thermoset product) of the coating film of the organic solvent solution. Thermoplastic resins or thermosetting resins having the above-mentioned Tg and Mw are preferred, and thermoplastic resins are more preferred. Only one type of resin may be used, or two or more types may be used in combination.

[0176] Examples of thermoplastic resins include acrylic resins and epoxy resins. Acrylic resins and epoxy resins may be used in combination.

[0177] The second protective film 26B can be formed by applying an organic solvent solution of the resin to form a coating film, and then solidifying or thermally curing the coating film. Any suitable organic solvent capable of dissolving or uniformly dispersing an acrylic resin or epoxy resin can be used as the organic solvent. Specific examples of organic solvents include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone. The resin concentration in the solution is preferably 3 to 20 parts by weight per 100 parts by weight of the solvent. Such a resin concentration allows for the formation of a uniform coating film.

[0178] The solution may be applied to any suitable substrate or to the polarizer 25. When the solution is applied to the substrate, the solidified or cured product (resin layer) of the coating film formed on the substrate is transferred to the polarizer 25. When the solution is applied to the polarizer 25, the second protective film 26B is formed directly on the polarizer 25 by drying (solidifying) or curing the coating film. Preferably, the solution is applied to the polarizer 25, and the second protective film 26B is formed directly on the polarizer 25. This configuration eliminates the need for an adhesive or pressure-sensitive adhesive layer required for transfer, thereby enabling the polarizing film 2A to be made even thinner. Any suitable method can be used to apply the solution. Specific examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (such as comma coating).

[0179] The second protective film 26B can be formed by solidifying or thermally curing the applied film of the solution. The heating temperature for solidification or thermal curing is preferably 100°C or lower, and more preferably 50°C to 70°C. If the heating temperature is within this range, adverse effects on the polarizer 25 can be prevented. The heating time can vary depending on the heating temperature. The heating time can be, for example, 1 to 10 minutes.

[0180] The second protective film 26B (essentially, the organic solvent solution of the resin) may contain any suitable additive depending on the purpose. Specific examples of additives include ultraviolet absorbers; leveling agents; hindered phenol-based, phosphorus-based, sulfur-based, and other antioxidants; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fiber and carbon fiber; near-infrared absorbers; flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic or inorganic fillers; resin modifiers; organic or inorganic fillers; plasticizers; lubricants; and flame retardants. The type, number, combination, and amount of additives can be appropriately determined depending on the purpose.

[0181] When the second protective film 26B is a solidified or hardened layer of a coating film of an organic solvent solution containing a resin, the thickness of the second protective film 26B is preferably 0.05 to 10 μm, more preferably 0.08 to 5 μm, even more preferably 0.1 to 1 μm, and particularly preferably 0.2 to 0.7 μm.

[0182] The first retardation film 2B may have any appropriate optical and / or mechanical properties depending on the purpose. The first retardation film 2B typically has a slow axis. In one embodiment, the angle θ between the slow axis of the first retardation film 2B and the absorption axis of the polarizer 25 is, for example, 40° to 50°, preferably 42° to 48°, and more preferably about 45°. If the angle θ is within this range, by using a λ / 4 plate as the first retardation film 2B, an optical laminate 20E having excellent circular polarization properties (and, as a result, excellent antireflection properties) can be obtained.

[0183] The first retardation film 2B preferably has a refractive index characteristic that satisfies the relationship nx>ny≧nz. In one embodiment, the first retardation film 2B can function as a λ / 4 plate. In this case, the in-plane retardation Re(550) of the first retardation film 2B is, for example, 100 to 190 nm, preferably 110 to 170 nm, and more preferably 130 to 160 nm. Note that "ny = nz" here encompasses not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, there may be cases where ny < nz, as long as the effects of the present invention are not impaired.

[0184] The first retardation film 2B is typically made of a stretched resin film. The thickness of the first retardation film 2B is, for example, 70 μm or less, preferably 60 μm or less, more preferably 10 to 50 μm, and even more preferably 20 to 45 μm. If the thickness of the first retardation film 2B is within this range, good bendability can be ensured, making it suitable for flexible applications.

[0185] The second retardation film 2C can be typically a so-called positive C plate whose refractive index characteristics satisfy the relationship nz > nx = ny. By using a positive C plate as the second retardation film 2C, reflection in oblique directions can be effectively prevented, and the anti-reflection function can be extended to a wide viewing angle.

[0186] The thickness direction retardation Rth(550) of the second retardation film 2C is preferably −50 nm to −300 nm, more preferably −70 nm to −250 nm, even more preferably −90 nm to −200 nm, and particularly preferably −100 nm to −180 nm. Here, "nx = ny" encompasses not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the second retardation film 2C can be less than 10 nm.

[0187] The second retardation film 2C having the refractive index characteristic of nz > nx = ny can be formed from any appropriate material. The second retardation film 2C is preferably made of a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the second retardation film 2C include the liquid crystal compound and the method for forming the retardation layer described in paragraphs

[0020] to

[0028] of JP 2002-333642 A. In this case, the thickness of the second retardation film 2C is preferably 0.5 to 10 μm, more preferably 0.5 to 8 μm, and even more preferably 0.5 to 5 μm.

[0188] Any appropriate adhesive may be used as the adhesive constituting the first adhesive layer 30 and the second adhesive layer 35. Examples of the adhesive include those described above for the optical laminate 20A.

[0189] The optical laminate may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and the optical film 2 .

[0190] The pressure-sensitive adhesive sheet 1 can be disposed between any layers included in the optical laminate. In other words, the pressure-sensitive adhesive sheet 1 may be a so-called interlayer pressure-sensitive adhesive layer.

[0191] The optical laminate according to the embodiment of the present invention can be distributed and stored, for example, as a rolled body obtained by rolling up a strip-shaped optical laminate, or as a sheet-shaped optical laminate.

[0192] The optical laminate according to the embodiment of the present invention is typically used in an image display device, such as a liquid crystal display, an EL display such as an organic EL display, or an inorganic EL display.

[0193] 6. Image Display Device An example of an image display device according to an embodiment of the present invention is shown in FIG. 8. The image display device 21 of FIG. 8 has a layered structure in which a substrate 7, an image forming layer (e.g., an organic EL layer or a liquid crystal layer) 6, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, a polarizing film 2A, and a protective film 5 are layered in this order. The image display device 21 of FIG. 8 includes the optical laminate 20D of FIG. 6 (excluding the release liner 3). The image display device 21 may include the optical laminate 20A, 20B, 20C, and 20E of FIGS. 3 to 5 and 7 instead of the optical laminate 20D. The substrate 7 and the image forming layer 6 may have the same configurations as the substrate and the image forming layer, respectively, of known image display devices.

[0194] The image display device 21 in Fig. 8 may be an organic EL display or a liquid crystal display. However, the image display device 21 is not limited to this example. The image display device 21 may also be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), or the like. The image display device 21 may be used for home appliances, in-vehicle applications, public information displays (PID), and the like.

[0195] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples shown below.

[0196] <Preparation of Monomer Syrup> [Preparation of Monomer Syrup A1] 90.2 parts by weight of n-butyl acrylate (BA), 4.8 parts by weight of acrylic acid (AA), 5.0 parts by weight of phenoxyethyl acrylate (PEA), and 0.2 parts by weight of Omnirad 127D (manufactured by IGM Resin) as a photopolymerization initiator were placed in a four-neck flask. Next, a light source was placed at a height of 5 cm from the liquid surface in the flask, and the syrup was heated to an illuminance of 1.2 mW / cm under a nitrogen atmosphere. 2 The UV irradiation was continued until the viscosity of the liquid in the flask reached 20 Pa s (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C).

[0197] [Preparation of Monomer Syrups A2 to A11] Monomer syrups A2 to A11 were prepared in the same manner as for the monomer syrup A1, except that the composition of the monomer component M1 was changed as shown in Table 1.

[0198] <Evaluation of Monomer Syrups> [Measurement of Weight-Average Molecular Weight (Mw) of Partially Polymerized Products] The weight-average molecular weights (Mw) of the partially polymerized products formed in the monomer syrups A1 to A11 were measured. The weight-average molecular weights (Mw) of the partially polymerized products were measured by GPC (gel permeation chromatography). The measurement conditions were as follows. The measurement results of the weight-average molecular weights (Mw) of the partially polymerized products are shown in Table 1. - Analytical device: Alliance manufactured by Waters - Column: TSKgel SuperHZM-H x 2 manufactured by Tosoh - Column temperature: 40°C - Eluent: THF - Flow rate: 0.2 mL / min - Injection volume: 30 μL - Detector: Refractive index (RI) - Standard sample: Polystyrene (PS) manufactured by Agilent

[0199] [Glass transition temperature (Tg) of partial polymer] The glass transition temperatures (Tg) of the partial polymers formed in the monomer syrups A1 to A11 were calculated from the FOX formula. The calculated glass transition temperatures (Tg) of the partial polymers are shown in Table 1.

[0200] [Measurement of polymerization rate of monomer syrup] The polymerization rates of the monomer syrups A1 to A11 were measured by the method described above. The polymerization rates of the monomer syrups A1 to A11 were all about 10%.

[0201]

[0202] The abbreviations in Table 1 are as follows: BA: n-butyl acrylate AA: acrylic acid PEA: phenoxyethyl acrylate BzA: benzyl acrylate NVP: N-vinyl-2-pyrrolidone Omnirad127D: 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one (Omnirad127D, manufactured by IGM Resin).

[0203] <Preparation of Photocurable Pressure-Sensitive Adhesive Composition> [Preparation of Photocurable Pressure-Sensitive Adhesive Composition C1] For the above-mentioned Monomer Syrup A1, 100 parts by weight of the Monomer Component M1 of the Monomer Syrup A1 was mixed with 0.1 parts by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent to obtain Photocurable Pressure-Sensitive Adhesive Composition C1.

[0204] [Preparation of Photocurable Pressure-Sensitive Adhesive Compositions C2 to C9] Photocurable Pressure-Sensitive Adhesive Compositions C2 to C9 were obtained in the same manner as for Photocurable Pressure-Sensitive Adhesive Composition C1, except that the monomer syrup used was changed as shown in Table 2.

[0205] [Preparation of Photocurable Pressure-Sensitive Adhesive Composition C10] For the above-mentioned Monomer Syrup A10, 35.0 parts by weight of benzyl acrylate as Monomer Component M2 was further added to 100 parts by weight of Monomer Component M1 of Monomer Syrup A10, 0.07 parts by weight of Omnirad 127D (manufactured by IGM Resin) as a photopolymerization initiator, and 0.13 parts by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent were mixed in. Photocurable Pressure-Sensitive Adhesive Composition C10 was thus obtained.

[0206] [Preparation of Photocurable Pressure-Sensitive Adhesive Composition C11] For the above-mentioned Monomer Syrup A11, 2.3 parts by weight of acrylic acid and 5.6 parts by weight of benzyl acrylate were further added as Monomer Component M2 to 100 parts by weight of Monomer Component M1 of Monomer Syrup A11, 0.02 parts by weight of Omnirad 127D (manufactured by IGM Resin) as a photopolymerization initiator, and 0.11 parts by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent were mixed in. Photocurable Pressure-Sensitive Adhesive Composition C11 was thereby obtained.

[0207] [Preparation of Photocurable Pressure-Sensitive Adhesive Composition C12] For the above-mentioned Monomer Syrup A11, 5.0 parts by weight of acrylic acid and 58.1 parts by weight of benzyl acrylate were further added as Monomer Component M2 to 100 parts by weight of Monomer Component M1 of Monomer Syrup A11, 0.13 parts by weight of Omnirad 127D (manufactured by IGM Resin) as a photopolymerization initiator, and 0.16 parts by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent were mixed in. Photocurable Pressure-Sensitive Adhesive Composition C12 was thereby obtained.

[0208] For photocurable pressure-sensitive adhesive compositions C1 to C12, the components additionally mixed with the monomer syrups A1 to A11 are shown in Table 2, and the final compositions of the monomer component M contained in the photocurable pressure-sensitive adhesive compositions C1 to C12 are shown in Table 3. The final compositions of the monomer component M in the photocurable pressure-sensitive adhesive compositions C1 to C9 are the same as the composition of the monomer component M1 in the monomer syrups A1 to A9.

[0209]

[0210] The abbreviations in Table 2 are as follows: AA: acrylic acid BzA: benzyl acrylate Omnirad127D: 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one (Omnirad127D, manufactured by IGM Resin) NDDA: 1,9-nonanediol diacrylate

[0211]

[0212] The abbreviations in Table 3 are the same as those in Table 1. In Table 3, the "difference in content of monomer a1" refers to the absolute value of the difference between the content of monomer a1 in all monomer components M contained in the photocurable pressure-sensitive adhesive composition (the content of monomer a1 in the final composition of monomer components M) and the content of structural units derived from monomer a1 in the partial polymer.

[0213] Example 1 A pressure-sensitive adhesive sheet of Example 1 was produced by the following method.

[0214] [Preparation of Release Liner A] A silicone-based release agent composition was obtained by mixing 30 parts by weight of an addition reaction curable silicone (LTC761 containing a hexenyl group-containing polyorganosiloxane, a 30 wt% toluene solution, manufactured by Dow Corning Toray), 0.9 parts by weight of a release control agent (BY24-850 containing an unreactive silicone resin, manufactured by Dow Corning Toray), 2 parts by weight of a curing catalyst (SRX212 containing a platinum catalyst, manufactured by Dow Corning Toray), and a toluene / hexane mixed solvent (volume ratio 1:1) as a dilution solvent. The concentration of silicone solids in the release agent composition was 1.0 wt%. Next, the release agent composition was applied with a wire bar to one side of a liner substrate (Lumirror XD500P, a polyester film, 75 μm thick), and heated at 130° C. for 1 minute to prepare a release liner A having a release layer (thickness 60 nm) on one side.

[0215] [Preparation of Pressure-Sensitive Adhesive Sheet] The pressure-sensitive adhesive composition was applied to the release surface of release liner B (a release-treated PET film, manufactured by Mitsubishi Chemical Corporation, MRF38) using an applicator to form a coating layer of a predetermined thickness. Next, release liner A was placed on the formed coating layer to obtain a laminate. Release liner A was placed so that the release layer was in contact with the coating layer. Next, an illuminance of 9 mW / cm was applied from the side of release liner B in the laminate. 2 and irradiation time was 400 seconds (integrated light dose 3600 mJ / cm 2). An LED was used as the light source, and the peak wavelength of the irradiated light was 340 nm. This photo-cured the coating layer, and a PSA sheet (thickness 20 μm) sandwiched between release liner B and release liner A was obtained. The illuminance of the light was measured using an illuminance meter (UD-T3040T2, manufactured by Topcon Technohouse Co., Ltd.) at a position near the ultraviolet light incident surface on release liner B.

[0216] (Examples 2 to 10 and Comparative Examples 1 and 2) The pressure-sensitive adhesive sheets of Examples 2 to 10 and Comparative Examples 1 and 2 were obtained by the same method as in Example 1, except that photocurable pressure-sensitive adhesive compositions C2 to C10 were used in Examples 2 to 10, and photocurable pressure-sensitive adhesive compositions C11 to C12 were used in Comparative Examples 1 and 2.

[0217] <Evaluation of Pressure-Sensitive Adhesive Sheets> [Calculation of Glass Transition Temperature (Tg)] The glass transition temperatures (Tg) of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples were calculated using the FOX formula. The calculation results of the glass transition temperatures (Tg) are shown in Table 4.

[0218] [Measurement of Gel Fraction] The gel fractions of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples were measured by the method described above. The measurement results of the gel fractions are shown in Table 4.

[0219] [Haze Measurement] The haze of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples was measured. The haze of the pressure-sensitive adhesive sheet was measured in an atmosphere of 25°C in accordance with JIS K7136:1981 using a haze meter HZ-V3 manufactured by Suga Test Instruments. The measurement was carried out with one layer of the pressure-sensitive adhesive sheet to be evaluated (total thickness 20 µm) attached to a slide glass S012140 (thickness 1.3 mm) manufactured by Matsunami Glass Industrial Co., Ltd.

[0220] [Durability Test (95°C Peel)] The following durability test (hereinafter also referred to as "95°C peel test") was carried out on each of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples.

[0221] <Sample Preparation for Durability Test (95°C Peel Test)> (Preparation of Optical Film 2F) A polyvinyl alcohol film was stretched 3 times between rolls with different speed ratios while dyeing for 1 minute in a 0.3 wt% iodine solution at 30°C. Next, the film was stretched to a total stretch ratio of 6 times while immersing for 0.5 minutes in an aqueous solution containing 4 wt% boric acid and 10 wt% potassium iodide at 60°C. The film was then immersed for 10 seconds in an aqueous solution containing 1.5 wt% potassium iodide at 30°C for cleaning, followed by drying at 50°C for 4 minutes to obtain a polarizer (reference numeral 22F in FIG. 9 ) with a thickness of 18 μm. A 30 μm-thick transparent protective film (reference numeral 21F in FIG. 9 ) made of a modified acrylic polymer having a lactone ring structure was attached to one side of the polarizer using a polyvinyl alcohol adhesive. Furthermore, a 47 μm-thick transparent protective film (reference numeral 23F in FIG. 9 ) made of a triacetyl cellulose film (manufactured by Konica Minolta, product name "KC4UY") with a hard coat layer (HC) formed thereon was bonded to the other surface of the polarizer using a polyvinyl alcohol-based adhesive. This was then heated and dried for 5 minutes in an oven set at 70° C., thereby producing an optical film 2F composed of a transparent protective film 21F, a polarizer 22F, and a transparent protective film 23F, as shown in FIG. 9 . Furthermore, a discharge amount of 63 W / m was applied to the surface of the optical film 2F on the side of the transparent protective film 21F made of a modified acrylic polymer. 2 Corona treatment was carried out for 1 min.

[0222] (Preparation of optical laminate 20F) The optical film 2F described above was placed on the exposed surface of each pressure-sensitive adhesive sheet 1 prepared in the Examples and Comparative Examples, to prepare the optical laminate 20F shown in Fig. 9. The optical film 2F was placed so that the surface on the side of the transparent protective film 21F made of a modified acrylic polymer was in contact with the pressure-sensitive adhesive sheet 1.

[0223] <Evaluation of Durability (95°C Peeling)> The durability of the prepared optical laminate 20F was evaluated by the following 95°C peeling test. First, the optical laminate 20F was cut into a strip measuring 300 mm long x 220 mm wide to prepare a test specimen. Next, the test specimen was attached to the surface of 0.7 mm thick alkali-free glass (manufactured by Corning Incorporated, product name "EG-XG") using adhesive sheet 1. The test specimen was attached to the alkali-free glass using a laminator. After attaching the test specimen, the specimen was placed in an autoclave at 50°C and 0.5 MPa for 15 minutes to homogenize the bond between the alkali-free glass and the adhesive sheet 1, and the adhesive sheet 1 was adhered to the alkali-free glass. Next, the test specimen was subjected to a heat treatment at 95°C under atmospheric pressure for 500 hours. The vicinity of the edge of the test specimen was observed with an optical microscope, and the peeling from the edge of the test specimen was measured. Table 4 shows the peeling length of the test specimens in the 95°C peeling test for each adhesive sheet.

[0224] [Evaluation of Drop Impact Resistance] First, a bonded structure for evaluation was prepared. Specifically, a rectangular sample sheet (75 mm long x 45 mm wide) was cut out from the pressure-sensitive adhesive sheet with a release liner. Next, release liner A was peeled off from the pressure-sensitive adhesive sheet in the sample sheet, and the exposed surface of the pressure-sensitive adhesive sheet was bonded to the center of a rectangular first glass plate (100 mm long x 75 mm wide, 500 μm thick) along its four sides. A roll laminator was used for the bonding, with an inter-roll pressure of 0.2 MPa and a feed rate of 100 mm / min. Next, release liner B was peeled off from the pressure-sensitive adhesive sheet on the first glass plate, and the exposed surface of the pressure-sensitive adhesive sheet was bonded to the center of a second glass plate (100 mm long x 50 mm wide, 500 μm thick) along its four sides by vacuum pressure bonding (surface pressure of 0.3 MPa, pressure of 100 Pa) to obtain a bonded structure. The bonded body was then heat treated (autoclave) at 50° C., 0.5 MPa, and for 30 minutes.

[0225] A drop impact resistance test was conducted using the bonded structure prepared as described above as follows. First, the bonded structure was placed on a predetermined support stand. Specifically, the bonded structure was placed on the support stand so that the first glass plate in the bonded structure was positioned on top and both widthwise ends of the first glass plate were supported from below by the support stand (the lower second glass plate was not in contact with the support stand). Next, the bonded structure on the support stand was fixed to the support stand with adhesive tape. Next, a metal ball was dropped toward the bonded structure on the support stand, colliding with the first glass plate of the bonded structure. The mass of the metal ball was 30 g, and the drop height of the metal ball was 300 mm. The drop position of the metal ball on the bonded structure was at least 10 mm away from the printed layer in both the length and width directions. Three tests (tests on different samples) were conducted for each adhesive sheet (n = 3). The drop impact resistance of the PSA sheet was evaluated as "excellent" if peeling between the first and second glass plates did not occur in any of the tests, "good" if peeling occurred in only one test, "fair" if peeling occurred in only two tests, and "poor" if peeling occurred in both tests. The results of the drop impact resistance test are shown in Table 4.

[0226]

[0227] As can be seen from Tables 1 to 4, all of the PSA sheets of the Examples, which were formed from a photocurable pressure-sensitive adhesive composition containing monomer component M1 and a monomer syrup containing a partial polymer of monomer component M1, and in which the partial polymer had a structural unit derived from monomer a1 having an aromatic ring, were superior in durability as evaluated by a 95°C peel test to the PSA sheets of the Comparative Examples. Furthermore, all of the PSA sheets of the Examples were superior in drop impact resistance to the PSA sheets of the Comparative Examples.

[0228] The pressure-sensitive adhesive sheet of the present invention can be used in image display devices such as EL displays, liquid crystal displays, etc. The pressure-sensitive adhesive sheet of the present invention can be particularly suitably used as a pressure-sensitive adhesive sheet for polarizing films.

Claims

1. A pressure-sensitive adhesive sheet formed from a photocurable pressure-sensitive adhesive composition containing a monomer syrup, the monomer syrup containing a monomer component M1 and a partial polymer of the monomer component M1, the partial polymer having a constituent unit derived from a monomer a1 having an aromatic ring.

2. The pressure-sensitive adhesive sheet according to claim 1, wherein the photocurable pressure-sensitive adhesive composition further comprises a monomer component M2.

3. The pressure-sensitive adhesive sheet according to claim 1, wherein the weight-average molecular weight of the partially polymerized product is 3,000,000 or more.

4. The pressure-sensitive adhesive sheet according to claim 1, having a gel fraction of 80% by weight or more.

5. The pressure-sensitive adhesive sheet according to claim 1, having a haze of 3.0% or less.

6. The pressure-sensitive adhesive sheet according to claim 1, wherein the content of said monomer a1 in the total monomer components M contained in said photocurable pressure-sensitive adhesive composition is 2 to 80% by weight.

7. The pressure-sensitive adhesive sheet according to claim 1, wherein the content of the structural unit derived from said monomer a1 in said partial polymer is 2 to 80% by weight.

8. The adhesive sheet described in claim 1, wherein the absolute value of the difference between the content of said monomer a1 in all monomer components M contained in said photocurable adhesive composition and the content of structural units derived from said monomer a1 in said partial polymer is 30% by weight or less.

9. The pressure-sensitive adhesive sheet according to claim 1, wherein the partially polymerized product further comprises a structural unit derived from a carboxyl group-containing monomer a2.

10. The pressure-sensitive adhesive sheet according to claim 1, wherein the partially polymerized product further comprises a structural unit derived from a nitrogen atom-containing monomer a3.

11. The pressure-sensitive adhesive sheet according to claim 1, which has a glass transition temperature calculated from the FOX formula of 0°C or lower.

12. The pressure-sensitive adhesive sheet according to claim 1, having a thickness of 50 μm or less.

13. An optical laminate comprising: the pressure-sensitive adhesive sheet according to any one of claims 1 to 12; and an optical film.

14. The optical laminate according to claim 13, wherein the optical film is a polarizing film.

15. An image display device comprising the optical laminate according to claim 13.

16. A partial polymer for a photocurable pressure-sensitive adhesive composition, comprising a monomer component M1 having a structural unit derived from a monomer a1 having an aromatic ring, and having a weight-average molecular weight of 3,000,000 or more.

17. A monomer syrup comprising the partially polymerized product of claim 16.

18. A photocurable adhesive composition comprising the monomer syrup of claim 17.

19. A method for producing an adhesive sheet, comprising: Step I: partially polymerizing a monomer component M1 containing a monomer a1 having an aromatic ring to form a monomer syrup containing a partially polymerized product; and Step II: curing a photocurable adhesive composition containing the monomer syrup to form an adhesive sheet.

20. The method for producing a pressure-sensitive adhesive sheet according to claim 19, wherein in step I, the monomer component M1 is partially polymerized so that the polymerization rate is 1 to 30%.

21. The method for producing a pressure-sensitive adhesive sheet according to claim 19, wherein in step I, the partial polymer is formed so that the weight-average molecular weight is 3,000,000 or more.

22. The method for producing a pressure-sensitive adhesive sheet according to claim 19, wherein in step II, the pressure-sensitive adhesive sheet is formed so that the gel fraction of the pressure-sensitive adhesive sheet is 80% by weight or more.

23. The method for producing a pressure-sensitive adhesive sheet according to claim 19, further comprising a step III between steps I and II of adding a monomer component M2 to the monomer syrup.

24. The method for producing a pressure-sensitive adhesive sheet according to claim 23, wherein the total amount of the monomers a1 in the monomer component M2 is less than 50% by weight of the total amount of the monomers a1 in the monomer syrup.

25. A photocurable pressure-sensitive adhesive composition comprising a monomer syrup, the monomer syrup comprising a monomer component M1 and a partial polymer of the monomer component M1, the partial polymer having a constituent unit derived from a monomer a1 having an aromatic ring.

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