Adhesive composition, adhesive sheet, optical laminate and picture display unit

Abstract

To provide a photo-curable adhesive composition suitable for producing an adhesive sheet improving an adhesive force while having a high refractive index.SOLUTION: A photo-curable adhesive composition includes a monomer component M including a monomer a having a double bond-containing ring, inorganic particles, and a polymer B with a weight-average molecular weight of 1500 to 30000.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, an optical laminate, and an image display device. [Background technology]

[0002] In recent years, image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices and inorganic EL display devices), have rapidly become popular. Image display devices generally include an optical laminate containing optical substrates such as a polarizing film and a retardation film. In an optical laminate containing multiple optical substrates, a bonding layer is usually disposed between adjacent optical substrates to bond them together. One example of the bonding layer is a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition.

[0003] Patent Document 1 discloses an example of a pressure-sensitive adhesive sheet. In Patent Document 1, the pressure-sensitive adhesive sheet is produced from a thermosetting pressure-sensitive adhesive composition. In addition to the thermosetting pressure-sensitive adhesive composition, a photocurable pressure-sensitive adhesive composition that can be used to produce a pressure-sensitive adhesive sheet by utilizing light is also known. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-14376 Summary of the Invention [Problem to be solved by the invention]

[0005] The use of a pressure-sensitive adhesive sheet having a high refractive index is advantageous for improving the surface brightness of an image display device. However, according to the studies of the present inventors, there is room for improvement in the adhesive strength of a pressure-sensitive adhesive sheet having a high refractive index.

[0006] An object of the present invention is to provide a photocurable pressure-sensitive adhesive composition that has a high refractive index and is suitable for producing a pressure-sensitive adhesive sheet with improved adhesive strength. [Means for solving the problem]

[0007] [1] The photocurable pressure-sensitive adhesive composition according to an embodiment of the present invention comprises: a monomer component M including a monomer a having a double bond-containing ring; Inorganic particles; and polymer B having a weight-average molecular weight of 1,500 to 30,000. [2] In the pressure-sensitive adhesive composition according to the above item [1], the double bond-containing ring may be an aromatic ring. [3] In the pressure-sensitive adhesive composition according to the above [1] or [2], the monomer a may contain the (meth)acrylic monomer having the double bond-containing ring. [4] In the pressure-sensitive adhesive composition according to any one of the above [1] to [3], the monomer a may contain phenoxybenzyl acrylate. [5] In the pressure-sensitive adhesive composition according to any one of [1] to [4] above, the content of the monomer a may be 45 parts by weight or more relative to 100 parts by weight of the total of the monomer component M and the inorganic particles. [6] In the pressure-sensitive adhesive composition according to any one of the above [1] to [5], the weight-average molecular weight of the polymer B may be 4,000 to 16,000. [7] In the pressure-sensitive adhesive composition according to any one of the above [1] to [6], the polymer B may contain a structural unit derived from a monomer b having a double bond-containing ring. [8] In the pressure-sensitive adhesive composition according to the above item [7], the content of the structural unit derived from the monomer b in the polymer B may be 70 wt % or more. [9] In the pressure-sensitive adhesive composition according to any one of [1] to [8] above, the content of the polymer B may be 1 to 30 parts by weight relative to 100 parts by weight of the total of the monomer component M and the inorganic particles.

[10] In the pressure-sensitive adhesive composition according to any one of the above [1] to [9], the inorganic particles may contain zirconium oxide.

[11] In the pressure-sensitive adhesive composition according to any one of [1] to

[10] above, the content of the inorganic particles may be 45 parts by weight or more relative to 100 parts by weight of the total of the monomer component M and the inorganic particles.

[12] In the pressure-sensitive adhesive composition according to any one of the above items [1] to

[11] , the inorganic particles may be surface-treated with a surface treatment agent.

[13] In the pressure-sensitive adhesive composition according to the above item

[12] , the surface treatment agent may contain a silane coupling agent.

[14] A pressure-sensitive adhesive sheet according to an embodiment of the present invention is formed from the pressure-sensitive adhesive composition according to any one of [1] to

[13] above.

[15] In the pressure-sensitive adhesive sheet according to the above item

[14] , the change Δn in refractive index of the pressure-sensitive adhesive sheet due to the polymer B may be 0.15 or less.

[16] In the pressure-sensitive adhesive sheet according to the above

[14] or

[15] , the polymer B contained in the pressure-sensitive adhesive sheet may have an acidic group content of 0.001 wt % or less.

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

[14] to

[16] above and an optical film.

[18] An image display device according to an embodiment of the present invention includes the optical laminate described in

[17] above. [Effects of the Invention]

[0008] According to an embodiment of the present invention, it is possible to provide a photocurable pressure-sensitive adhesive composition that has a high refractive index and is suitable for producing a pressure-sensitive adhesive sheet with improved adhesive strength. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating an example of a method for forming a pressure-sensitive adhesive sheet from the pressure-sensitive adhesive composition of the present invention. [Figure 3] 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 4] 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 5] 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 6] 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 7] 1 is a schematic cross-sectional view of an image display device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Terminology] In this specification, when the expression "weight" appears, it may be read as "mass," which is the commonly used SI unit for 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 the reference is made to "100 parts by weight of the total of monomer component M and inorganic particles" as a standard for the content of various components in a pressure-sensitive adhesive composition, this refers to the total amount of non-partially polymerized monomer component M contained in the pressure-sensitive adhesive composition, monomer component M consumed in forming partially polymerized product A that may be contained in the pressure-sensitive adhesive composition, and inorganic particles.

[0013] <<1. Pressure-sensitive adhesive composition>> A pressure-sensitive adhesive composition according to an embodiment of the present invention comprises a monomer component M including a monomer a having a double bond-containing ring, inorganic particles, and a polymer B having a weight-average molecular weight of 1,500 to 30,000. A portion of the monomer component M may be a partially polymerized product A. The pressure-sensitive adhesive composition is a photocurable pressure-sensitive adhesive composition that forms a pressure-sensitive adhesive sheet by irradiation with light. Note that being a photocurable pressure-sensitive adhesive composition is particularly preferred in terms of environmental protection and sustainability, as 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.

[0014] ≪1-1. Monomer component M≫ <1-1-a. Monomer a having a double bond-containing ring> As described above, the monomer component M includes a monomer a having a double bond-containing ring. Monomer a is a component suitable for improving the refractive index of the pressure-sensitive adhesive sheet. In this specification, the double bond-containing ring refers to a ring in which at least one of the bonds constituting the ring is a double bond. Examples of double bonds include carbon-carbon double bonds, carbon-heteroatom double bonds, and heteroatom-heteroatom double bonds. Examples of heteroatoms include nitrogen, sulfur, and oxygen.

[0015] The number of double bonds in the double bond-containing ring is not particularly limited and may be, for example, 1 to 10, or 2 to 5. When the double bond-containing ring contains two or more double bonds, these double bonds may be conjugated or non-conjugated. The double bond-containing ring is preferably an aromatic ring.

[0016] The double bond-containing ring may be a carbocyclic ring. Examples of the carbocyclic ring include a benzene ring (which may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure), a naphthalene ring, an indene ring, an azulene ring, an anthracene ring, and a phenanthrene ring. The double bond-containing ring may be a heterocyclic ring. Examples of the heterocyclic ring include a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, and a thiophene ring. Examples of heteroatoms that may be contained in the heterocyclic ring as ring-constituting atoms include at least one selected from the group consisting of nitrogen, sulfur, and oxygen. The heteroatom may be either or both nitrogen and sulfur. The double bond-containing ring may be a fused ring. An example of the monomer a has a structure in which one or more carbocyclic rings and one or more heterocyclic rings are fused, such as a dinaphthothiophene structure.

[0017] The double bond-containing ring may have one or more substituents (excluding ethylenically unsaturated groups, which will be described later) on the ring-constituting atoms, or may have no substituents. Examples of the substituents include alkyl groups, alkoxy groups, aryloxy groups, hydroxyl groups, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, etc.), hydroxyalkyl groups, hydroxyalkyloxy groups, and glycidyloxy groups. However, the substituents are not limited to the above examples. The substituents may contain carbon atoms, and in such cases, the number of carbon atoms contained in the substituent is, for example, 1 to 4, 1 to 3, or even 1 to 2. One example of the double bond-containing ring has no substituents on the ring-constituting atoms. Another example of the double bond-containing ring has one or more substituents selected from the group consisting of alkyl groups, alkoxy groups, and halogen atoms (e.g., bromine atoms) on the ring-constituting atoms.

[0018] In the monomer a, the number of double bond-containing rings contained in one molecule is, for example, 1, and may be 2 or more. The upper limit of the number of double bond-containing rings is not particularly limited and is, for example, 16 or less. The upper limit may be 12 or less, 8 or less, 6 or less, 5 or less, 4 or less, 3 or less, or even 2 or less.

[0019] In the monomer a, the double bond-containing ring is preferably located in a side chain. In other words, the monomer a preferably has at least one double bond-containing ring and at least one ethylenically unsaturated group in one molecule. As the monomer a, a compound having one ethylenically unsaturated group in one molecule (in other words, a monofunctional monomer) is preferably used.

[0020] Examples of the ethylenically unsaturated group are 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. In other words, monomer a preferably contains a (meth)acrylic monomer having a double bond-containing ring, and more preferably contains an acrylic monomer having a double bond-containing ring. Examples of the (meth)acrylic monomer having a double bond-containing ring include aromatic ring-containing (meth)acrylates. Specific examples of aromatic ring-containing (meth)acrylates will be described later.

[0021] The double bond-containing ring and the ethylenically unsaturated group may be bonded directly or via a linking group. Examples of the linking group include one or more 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 A, the double bond-containing ring and the ethylenically unsaturated group are bonded directly. In another example of Monomer A, the double bond-containing 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.

[0022] Specific examples of the monomer a 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.

[0023] Monomer a may contain two or more aromatic rings (preferably carbon rings) in one molecule. A monomer having two or more aromatic rings and at least one ethylenically unsaturated group in one molecule (aromatic ring-containing monomer) is particularly suitable for increasing the refractive index of the pressure-sensitive adhesive sheet.

[0024] 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 later) is preferably used.

[0025] 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. However, the linking group does not have to contain any of the above atoms. Examples of linking groups include an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (e.g., -O-(CH2)), and the like. 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 groups 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-condensed aromatic rings are bonded via a linking group include phenoxybenzyl (meth)acrylate, thiophenoxybenzyl (meth)acrylate, and benzyl benzyl (meth)acrylate.

[0026] Examples of monomers having a structure in which two or more non-fused aromatic rings are directly bonded include biphenyl structure-containing (meth)acrylates, triphenyl structure-containing (meth)acrylates, and vinyl group-containing biphenyls. Specific examples include o-phenylphenol (meth)acrylate, biphenyl (meth)acrylate, and biphenylmethyl (meth)acrylate.

[0027] Examples of monomers having a condensed 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.

[0028] 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.

[0029] 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)acryloyloxymethyl dinaphthothiophene (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)acryloyloxyethyl dinaphthothiophene (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), vinyl dinaphthothiophene (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)allyloxy dinaphthothiophene. 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.

[0030] 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.

[0031] Monomer a may be 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).

[0032] Examples of aromatic ring-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-nonylphenyl acrylate, 2,6-dibromo-4-dodecylphenyl acrylate; carbon-containing 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.

[0033] Monomer a may have a structure in which an oxyethylene chain is interposed between the ethylenically unsaturated group and the double bond-containing ring in the various monomers a 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 a 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.

[0034] Monomer a may include a high refractive index monomer. In this specification, the high refractive index monomer refers to a monomer having a refractive index of 1.51 or more, 1.53 or more, 1.55 or more, 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, 1.60 or more, 1.61 or more, 1.62 or more, 1.63 or more, 1.64 or more, 1.65 or more, 1.66 or more, 1.67 or more, 1.68 or more, or even 1.69 or more. The upper limit of the refractive index of the high refractive index monomer is not particularly limited, and may be, for example, 3.00 or less, 2.50 or less, 2.00 or less, 1.90 or less, 1.80 or less, or even 1.70 or less. The high refractive index monomer may be used alone or in combination of two or more.

[0035] The refractive index of the monomer can be measured using an Abbe refractometer at a wavelength of 589 nm and a temperature of 25°C. The Abbe refractometer may be a DR-M4 model manufactured by ATAGO or an equivalent (e.g., DR-M2 model). If the nominal value of the refractive index at 25°C is provided by the monomer manufacturer, this nominal value can be used as the refractive index.

[0036] Examples of high refractive index monomers are phenoxybenzyl acrylate (refractive index 1.566), 1-naphthylmethyl acrylate (refractive index 1.595), ethoxylated o-phenylphenol acrylate (refractive index 1.578 when the number of repeating oxyethylene units is 1), benzyl acrylate (refractive index 1.519), phenoxyethyl acrylate (refractive index 1.517), and phenoxydiethylene glycol acrylate (refractive index 1.510). ), 6-acryloyloxymethyldinaphthothiophene (refractive index 1.75), 6-methacryloyloxymethyldinaphthothiophene (refractive index 1.726), 5-acryloyloxyethyldinaphthothiophene (refractive index 1.786), 6-acryloyloxyethyldinaphthothiophene (refractive index 1.722), 6-vinyldinaphthothiophene (refractive index 1.802), and 5-vinyldinaphthothiophene (refractive index 1.793). However, the high refractive index monomer is not limited to the above examples. It is preferable that monomer a contains phenoxybenzyl acrylate as a high refractive index monomer.

[0037] The content of monomer a relative to 100 parts by weight of the total of monomer component M and inorganic particles (specifically, a mixture of inorganic particles and a dispersant) is, for example, 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 36 parts by weight or more, 37 parts by weight or more, 38 parts by weight or more, 39 parts by weight or more, 40 parts by weight or more, 41 parts by weight or more, 42 parts by weight or more, 43 parts by weight or more, 44 parts by weight or more, 45 parts by weight or more, 46 parts by weight or more, 47 parts by weight or more, 48 parts by weight or more, 49 parts by weight or more, 50 parts by weight or more, 51 parts by weight or more, 52 parts by weight or more, 53 parts by weight or more, 54 parts by weight or more, 55 parts by weight or more, 56 parts by weight or more, 57 parts by weight or more, 58 parts by weight or more, or even 59 parts by weight or more. The upper limit of the content may be, for example, 90 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, or even 60 parts by weight or less. The content is preferably 40 to 60 parts by weight.

[0038] <1-1-b. Other Monomers> The monomer component M may contain a monomer other than the above-mentioned monomer a. An example of the other monomer is a hydroxyl group-containing monomer. The hydroxyl group-containing monomer has at least one hydroxyl group and at least one ethylenically unsaturated group in one molecule. The monomer component M may contain one or more hydroxyl group-containing monomers.

[0039] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The hydroxyl group-containing monomer may be a (meth)acrylic monomer.

[0040] Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. The hydroxyl group-containing monomer is preferably 4-hydroxybutyl (meth)acrylate. The content of the hydroxyl group-containing monomer in the monomer component M is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, or even 2% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may not contain a hydroxyl group-containing monomer.

[0041] Another example of a monomer that can be contained in the monomer component M is a (meth)acrylic acid alkyl ester having an alkyl group of 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. Examples of the (meth)acrylic acid alkyl ester 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.

[0042] The content of (meth)acrylic acid alkyl ester in the monomer component M is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, or even 4% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may not contain a (meth)acrylic acid alkyl ester.

[0043] Another example of a monomer that can be included in the monomer component M is an aliphatic ring-containing monomer. The aliphatic ring-containing monomer has at least one aliphatic ring and at least one ethylenically unsaturated group in one molecule. The aliphatic ring-containing monomer may be used alone or in combination of two or more types.

[0044] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The aliphatic ring-containing monomer may be a (meth)acrylic monomer.

[0045] Examples of the aliphatic ring-containing monomer include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate.

[0046] The content of the alicyclic monomer in the monomer component M is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, or even 4% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may not contain an alicyclic monomer.

[0047] Another example of a monomer that can be contained in the monomer component M is a carboxyl group-containing monomer. The carboxyl group-containing monomer that can be contained in the monomer component M has at least one carboxyl group and at least one ethylenically unsaturated group in one molecule. The monomer component M may contain one or more types of carboxyl group-containing monomers.

[0048] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The carboxyl group-containing monomer may be a (meth)acrylic monomer.

[0049] Examples of carboxyl group-containing monomers include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. The content of the carboxyl group-containing monomer in the monomer component M is, for example, 10% by weight or less, and may be 7% by weight or less, 5% by weight or less, 3% by weight or less, or even 1% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. It is preferred that the monomer component M does not contain a carboxyl group-containing monomer.

[0050] The content of the other monomer relative to 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant) may be, for example, 30 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1.5 parts by weight or less. The lower limit of the content may be, for example, 0.01 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, or even 1 part by weight or more. The monomer component M may not contain other monomers.

[0051] The content of monomer component M relative to 100 parts by weight of the total of monomer component M and inorganic particles (specifically, a mixture of inorganic particles and a dispersant) is, for example, 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 36 parts by weight or more, 37 parts by weight or more, 38 parts by weight or more, 39 parts by weight or more, 40 parts by weight or more, 41 parts by weight or more, 42 parts by weight or more, 43 parts by weight or more, 44 parts by weight or more, 45 parts by weight or more, 46 parts by weight or more, 47 parts by weight or more, 48 parts by weight or more, 49 parts by weight or more, 50 parts by weight or more, 51 parts by weight or more, 52 parts by weight or more, 53 parts by weight or more, 54 parts by weight or more, 55 parts by weight or more, 56 parts by weight or more, 57 parts by weight or more, 58 parts by weight or more, 59 parts by weight or more, or even 60 parts by weight or more. The upper limit of the content may be, for example, 90 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, or even 60 parts by weight or less. The content is preferably 40 to 60 parts by weight.

[0052] ≪1-2. Partial polymer A≫ The pressure-sensitive adhesive composition may contain a partial polymer A of the above-mentioned monomer component M. The partial polymer A may be either a homopolymer or a copolymer. The partial polymer A appropriately increases the viscosity of the pressure-sensitive adhesive composition, thereby contributing to the stable formation of a coating layer, which will be described later. The pressure-sensitive adhesive composition does not necessarily contain the partial polymer A.

[0053] The weight-average molecular weight of the partial polymer A may be, for example, greater than 30,000, 50,000 or more, 100,000 or more, 500,000 or more, or even 1,000,000 or more. The upper limit of the weight-average molecular weight is not particularly limited, and may be, for example, 3,000,000 or less, or 2,000,000 or less. The weight-average molecular weight is determined by measuring using GPC (gel permeation chromatography) and calculating the value in terms of polystyrene.

[0054] ≪1-3. Inorganic particles≫ As described above, the pressure-sensitive adhesive composition contains inorganic particles. The inorganic particles are a component suitable for improving the refractive index of the pressure-sensitive adhesive sheet. The inorganic particles are preferably in a dispersed state in the pressure-sensitive adhesive composition.

[0055] The inorganic particles can be selected from, for example, metal compound particles and metal particles, one or more types depending on the desired purpose, such as improving the refractive index. The metal compound particles may be metal oxide particles. Examples of materials constituting the metal oxide particles include titanium oxide, zirconium oxide, cerium oxide, aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, and niobium oxide. The metal oxide particles can be used alone or in combination of two or more types. The inorganic particles preferably contain zirconium oxide, and may be zirconium oxide particles composed essentially of zirconium oxide alone. The zirconium oxide particles can contribute to increasing the refractive index of the pressure-sensitive adhesive sheet.

[0056] The material constituting the metal compound particles may be a metal hydroxide such as aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, iron hydroxide, copper hydroxide, barium hydroxide, basic magnesium carbonate, hydrotalcite, or a hydrated metal compound. Examples of the material constituting the metal particles are iron, zinc, tungsten, and platinum.

[0057] The material of the inorganic particles may be a high-entropy alloy in which multiple types of elements are mixed.

[0058] The inorganic particles may be surface-treated. One example of the surface treatment is hydrophobization. In this specification, it is preferable that the inorganic particles do not include carbon black particles.

[0059] The inorganic particles may be surface-treated with a surface treatment agent. The surface treatment agent may contain a silane coupling agent. The surface treatment agent may contain an aromatic compound having an aromatic ring. Examples of the aromatic ring in the surface treatment agent are the same as those described above in the description of monomer a. The aromatic compound having an aromatic ring can contribute to increasing the refractive index of the pressure-sensitive adhesive sheet.

[0060] The amount of the surface treatment agent added per 100 parts by weight of the inorganic particles is, for example, 16 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, or even 2 parts by weight or less. The lower limit of the addition amount is, for example, 0.01 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, or even 1 part by weight or more. The inorganic particles do not need to be surface-treated with a surface treatment agent.

[0061] The inorganic particles may contain a high refractive index material. The refractive index of the high refractive index material is, for example, 1.60 or more, and may be 1.70 or more, 1.80 or more, or even 2.00 or more. The upper limit of the refractive index of the high refractive index material is not particularly limited and may be, for example, 3.00 or less, 2.80 or less, 2.50 or less, or even 2.20 or less. The refractive index of the material contained in the inorganic particles can be determined as the refractive index measured for a monolayer film of the material using a commercially available spectroscopic ellipsometer at 23°C and 549 nm. The spectroscopic ellipsometer may be, for example, an "EC-400" (manufactured by J.A. Woolam) or an equivalent.

[0062] The inorganic particles may be nanoparticles having an average particle size of less than 1 μm. The average particle size of the inorganic particles may be 100 nm or less. The average particle size may be 70 nm or less, 50 nm or less, 30 nm or less, 20 nm or less, 15 nm or less, 10 nm or less, 7 nm or less, 5 nm or less, or even 4 nm or less. The lower limit of the average particle size may be, for example, 1 nm or more, 1.5 nm or more, 2 nm or more, or even 2.5 nm or more. The average particle size can be specified as the median diameter (D50) in the particle size distribution measured by dynamic light scattering.

[0063] The content of the inorganic particles relative to 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant) is, for example, 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 36 parts by weight or more, 37 parts by weight or more, 38 parts by weight or more, 39 parts by weight or more, 40 parts by weight or more, 41 parts by weight or more, 42 parts by weight or more, 43 parts by weight or more, 44 parts by weight or more, 45 parts by weight or more, 46 parts by weight or more, 47 parts by weight or more, 48 parts by weight or more, 49 parts by weight or more, 50 parts by weight or more, 51 parts by weight or more, 52 parts by weight or more, 53 parts by weight or more, 54 parts by weight or more, 55 parts by weight or more, 56 parts by weight or more, 57 parts by weight or more, 58 parts by weight or more, 59 parts by weight or more, or even 60 parts by weight or more. The upper limit of the content is, for example, 90 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, or even 60 parts by weight or less. The content is preferably 40 to 60 parts by weight.

[0064] ≪1-4. Polymer B≫ As described above, the pressure-sensitive adhesive composition contains polymer B having a weight-average molecular weight of 1,500 to 30,000. Polymer B is a component suitable for improving the adhesive strength of the pressure-sensitive adhesive sheet and can function as a tackifier. In this specification, polymer B may be referred to as an oligomer.

[0065] The weight-average molecular weight of polymer B may be 25,000 or less, or may be 20,000 or less, 18,000 or less, 16,000 or less, 15,000 or less, 13,000 or less, 10,000 or less, 8,000 or less, or even 6,000 or less. The smaller the weight-average molecular weight of polymer B, the more the adhesive strength of the pressure-sensitive adhesive sheet tends to improve. The lower limit of the weight-average molecular weight is 1,500 or more, or may be 2,000 or more, 2,500 or more, 3,000 or more, 3,500 or more, or even 4,000 or more. The weight-average molecular weight may be 2,000 to 16,000, and preferably 4,000 to 16,000. The weight-average molecular weight of polymer B can be determined by the method described above for partial polymer A.

[0066] Polymer B preferably contains a structural unit derived from monomer b having a double bond-containing ring. Polymer B containing a structural unit derived from monomer b is suitable for improving the refractive index of the pressure-sensitive adhesive sheet. Examples of monomer b include those mentioned above for monomer a. Monomer b may be the same as or different from monomer a.

[0067] In the monomer b, the double bond-containing ring is preferably an aromatic ring. The monomer b may contain two or more aromatic rings (preferably carbon rings) in one molecule, and preferably contains a monomer having two or more aromatic rings and at least one ethylenically unsaturated group in one molecule (aromatic ring-multiple-containing monomer). The monomer b particularly preferably contains phenoxybenzyl acrylate.

[0068] The content of the structural units derived from monomer b in polymer B is, for example, 10% by weight or more, and may be 30% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, 97% by weight or more, 98% by weight or more, 99% by weight or more, or even 100% by weight. In some cases, the content may be 10% by weight or less, 5% by weight or less, or even 1% by weight or less. Polymer B may not contain any structural units derived from monomer b.

[0069] Polymer B may contain structural units derived from other monomers than the above-mentioned monomer b. Examples of other monomers include those mentioned above for monomer component M (hydroxyl group-containing monomers, (meth)acrylic acid alkyl esters having an alkyl group of 1 to 20 carbon atoms in the side chain, aliphatic ring-containing monomers, and carboxyl group-containing monomers).

[0070] The content of structural units derived from hydroxyl group-containing monomers in polymer B is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, or even 0.5% by weight or more. Polymer B may not contain structural units derived from hydroxyl group-containing monomers.

[0071] The content of structural units derived from a (meth)acrylic acid alkyl ester in polymer B is, for example, 50% by weight or less, and may be 40% 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, 7% by weight or less, 5% by weight or less, or even 4% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, and may be 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. In some cases, the lower limit of the content may be 50% by weight or more. Polymer B may not contain structural units derived from a (meth)acrylic acid alkyl ester.

[0072] The content of the structural units derived from the alicyclic-containing monomer in the polymer B is, for example, 50% by weight or less, and may be 40% 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, 7% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, or even 2% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. In some cases, the lower limit of the content may be 50% by weight or more, 80% by weight or more, or even 90% by weight or more. The polymer B may not contain any structural units derived from the alicyclic-containing monomer.

[0073] The content of structural units derived from carboxyl group-containing monomers in polymer B is, for example, 10% by weight or less, and may be 7% by weight or less, 5% by weight or less, 3% by weight or less, or even 1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. It is preferable that polymer B does not contain structural units derived from carboxyl group-containing monomers.

[0074] Another example of the other monomer is a nitrogen atom-containing monomer. The nitrogen atom-containing monomer refers to a monomer having at least one nitrogen atom in the molecule (per molecule).

[0075] Examples of the nitrogen atom-containing monomer include N-vinyl cyclic amide, (meth)acrylamide, etc. The nitrogen atom-containing monomer may be used alone or in combination of two or more kinds.

[0076] Examples of N-vinyl cyclic amides include 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, and vinylmethyloxazolidinone. Examples of (meth)acrylamides include (meth)acrylamide, N-alkyl(meth)acrylamide, and N,N-dialkyl(meth)acrylamide. Examples of (meth)acrylamides include various N-hydroxyalkyl(meth)acrylamides and N-alkoxyalkyl(meth)acrylamides.

[0077] Examples of nitrogen atom-containing monomers other than N-vinyl cyclic amides and (meth)acrylamides 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, N-methylvinyl heterocycle-containing monomers such as N-isopropylpyrrolidone; maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide-based monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-laurylitaconimide, and N-cyclohexylitaconimide; imide group-containing monomers such as succinimide-based monomers of N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; and isocyanate group-containing monomers such as 2-(meth)acryloyloxyethylisocyanate.

[0078] The content of the constitutional units derived from the nitrogen atom-containing monomer in polymer B is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, or even 0.5% by weight or more. Polymer B may not contain constitutional units derived from the nitrogen atom-containing monomer.

[0079] Another example of the other monomer is an ether group-containing monomer. The ether group-containing monomer has at least one ether group and at least one ethylenically unsaturated group in one molecule. The ether group-containing monomer may be used alone or in combination of two or more kinds.

[0080] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The ether group-containing monomer may be a (meth)acrylic monomer.

[0081] Examples of the ether group-containing monomer are 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and methoxydipropylene glycol (meth)acrylate. The ether group-containing monomer is preferably 2-(2-ethoxyethoxy)ethyl acrylate (CBA).

[0082] The content of the structural units derived from the ether group-containing monomer in polymer B is, for example, 40% by weight or less, and may be 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, 0.1% by weight or more, or even 0.5% by weight or more. Polymer B may not contain any structural units derived from the ether group-containing monomer.

[0083] Polymer B can be produced by known polymerization methods such as solution polymerization, radiation polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations such as polymerization under supercritical conditions. Radiation that can be used for radiation polymerization includes electron beams, UV rays, and microwaves. The resulting polymer B may be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

[0084] The content of polymer B relative to 100 parts by weight of the total of monomer component M and inorganic particles (specifically, a mixture of inorganic particles and a dispersant) is, for example, 0.1 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, 5 parts by weight or more, 6 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, or even 20 parts by weight or more. The upper limit of the content is, for example, 50 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, or even 30 parts by weight or less. The content is preferably 1 to 30 parts by weight, and more preferably 2 to 30 parts by weight.

[0085] ≪1-5. Other ingredients≫ <1-5-a. Dispersants> The PSA composition may further contain a dispersant for inorganic particles. The dispersant is a component for sufficiently dispersing the inorganic particles in the PSA composition. The dispersant is preferably in contact with the surfaces of the inorganic particles, and more preferably coats the surfaces of the inorganic particles.

[0086] An example of a dispersant is a compound having a hydrophilic portion and a hydrophobic portion in one molecule. The hydrophilic portion and the hydrophobic portion of the dispersant are presumed to exhibit relatively high affinity for the inorganic particles and the monomer component M, respectively. The dispersant may or may not have a polymerizable functional group such as an ethylenically unsaturated group.

[0087] The hydrophilic portion of the dispersant preferably has a hydrophilic group, such as an ether group or an ester group.

[0088] The hydrophilic portion of the dispersant preferably has a functional group F that exhibits adsorptivity or reactivity with inorganic particles. Examples of the functional group F include at least one selected from the group consisting of alkaline groups and acidic groups. Specific examples of the functional group F include a hydroxy group, a carboxy group, a nitrogen atom-containing group, a sulfur atom-containing group, a phosphorus atom-containing group, and a silicon atom-containing group. The number of functional groups F contained in one molecule of the dispersant may be 1, or 2 or more (for example, about 2 to 5). The types of the two or more functional groups F present in one molecule may be the same or different from each other.

[0089] The hydrophilic portion of the dispersant may have a chain structure, or may have a composite structure of a chain structure and a cyclic structure. The dispersant may have, for example, a structure in which a functional group F and a hydrophobic portion are linked via a chain structure; a structure in which a functional group F is attached to a side chain of a chain structure whose one end is linked to the hydrophobic portion; or a structure in which a chain structure whose other end is linked to the hydrophobic portion does not have a functional group F (for example, the other end of the chain structure is open). The dispersant may have two or more of the above structures.

[0090] The dispersant may be an aliphatic compound, for example, represented by the following formula (1): [ka]

[0091] In formula (1), R is an alkyl group, preferably an alkyl group having 1 to 3 carbon atoms, and more preferably an ethyl group. m is 1 to 10, preferably 2 to 8, and more preferably 3 to 7. n is 5 to 20, and preferably 8 to 12.

[0092] The dispersant may be an aromatic compound having an aromatic ring, for example, represented by the following formula (2): [ka]

[0093] In equation (2), R 1 represents a hydrocarbon group containing at least one aromatic ring, AO represents an oxyalkylene group having 1 to 4 carbon atoms, n is a number ranging from 1 to 30 representing the average number of moles of alkylene oxide added, and X represents an O atom, a S atom, or -NR 2 -(R 2 is a linking group composed of either an H atom or a group composed of either a C atom, an H atom, or an O atom), and Y is a linking group composed of either a C, H, or O atom.

[0094] In equation (2), R 1 may be a styrenated phenyl group represented by the following formula (3): [ka]

[0095] In formula (3), k is an average value of 1 to 5. For example, k is 2 to 4, and may be 3.

[0096] In formula (2), AO is, for example, an oxyalkylene group having 2 to 4 carbon atoms, and may be an oxyalkylene group having 2 to 3 carbon atoms, or even an oxyethylene group.

[0097] In formula (2), X may be an O atom.

[0098] In formula (2), Y is, for example, an alkylene group having 1 to 15 carbon atoms, or a functional group represented by the following formula (4). [ka]

[0099] Z in the formula (4) is any one selected from an alkylene group having 1 to 15 carbon atoms, a vinylene group, a phenylene group, and a carboxyl group-containing phenylene group.

[0100] In formula (2), Y may be an alkylene group having 1 to 10 carbon atoms, an alkylene group having 1 to 5 carbon atoms, an alkylene group having 1 to 3 carbon atoms, or even a methylene group.

[0101] The aromatic ring in the dispersant may be the same as the examples given above in the description of monomer a.

[0102] The dispersant may be selected from known surfactants. Examples of surfactants include anionic surfactants (carboxylic acid type, phosphate ester type, sulfate ester type, sulfonic acid type, etc.), nonionic surfactants, cationic surfactants, and amphoteric surfactants. The surfactant that can be used as the dispersant is preferably an anionic surfactant.

[0103] The content of the dispersant relative to 100 parts by weight of inorganic particles is, for example, 0.1 parts by weight or more, 0.5 parts by weight or more, or even 1.0 part by weight or more. The upper limit of the content is, for example, 30 parts by weight or less, or may be 20 parts by weight or less. A preferred example of the content is 1 to 10 parts by weight. Another preferred example of the content is 10 to 20 parts by weight, 10 to 18 parts by weight, or even 10 to 15 parts by weight.

[0104] <1-5-b. Photopolymerization initiator> The pressure-sensitive adhesive composition usually contains a photopolymerization initiator. The photopolymerization initiator may be a photoradical generator that generates radicals when exposed to visible light and / or ultraviolet light with a wavelength shorter than 450 nm.

[0105] Examples of photopolymerization initiators 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; substituted alpha-ketols 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; and benzophenone 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 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, and 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine triazine-based compounds such as 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, and 2,4-trichloromethyl-(4'-methoxystyryl)-6-triazine;Oxime ester compounds such as 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], O-(acetyl)-N-(1-phenyl-2-oxo-2-(4'-methoxy-naphthyl)ethylidene)hydroxylamine; phosphine compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; quinone compounds such as 9,10-phenanthrenequinone, camphorquinone, and ethylanthraquinone; borate compounds; carbazole compounds; imidazole compounds; and titanocene compounds. The pressure-sensitive adhesive composition may contain one or more photopolymerization initiators.

[0106] Specific examples of the photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651, manufactured by IGM Resins), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins), and 1-hydroxycyclohexyl phenyl ketone (Omnirad 184, manufactured by IGM Resins).

[0107] The content of the photopolymerization initiator relative to a total of 100 parts by weight of the monomer component M and the inorganic particles (more specifically, a mixture of the inorganic particles and the dispersant) is, for example, 0.02 to 10 parts by weight, and may be 0.05 to 5 parts by weight, 0.1 to 3 parts by weight, or even 0.2 to 2 parts by weight.

[0108] <1-5-c. Crosslinking agents> The 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.

[0109] 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 dimethyl acrylate (DDA), 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, more preferably trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, or dipentaerythritol hexa(meth)acrylate.

[0110] The content of the crosslinking agent relative to a total of 100 parts by weight of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant) is, for example, 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less. The lower limit of the content is, for example, 0.01 parts by weight or more, 0.03 parts by weight or more, or even 0.05 parts by weight or more.

[0111] <1-5-d. Silane coupling agents> The pressure-sensitive adhesive composition may contain a silane coupling agent. Specific examples of the silane coupling agent include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane.

[0112] The content of the silane coupling agent relative to a total of 100 parts by weight of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant) is, for example, 5 parts by weight or less, and may be 3 parts by weight or less, 1 part by weight or less, 0.8 parts by weight or less, 0.5 parts by weight or less, 0.4 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, or even 0.1 parts by weight or less. The lower limit of the content is, for example, 0.01 parts by weight or more, and may even be 0.05 parts by weight or more. The pressure-sensitive adhesive composition does not necessarily contain a silane coupling agent.

[0113] <1-5-e. Antioxidants> The pressure-sensitive adhesive composition may contain an antioxidant. Examples of the antioxidant include phenol-based antioxidants, hindered phenol-based antioxidants, amine-based antioxidants, and phosphite-based antioxidants.

[0114] Examples of the phenolic antioxidant include monophenolic antioxidants, bisphenolic antioxidants, and polymeric phenolic antioxidants. Examples of the monophenolic antioxidant include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, and stearin-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. Examples of the bisphenol antioxidant are 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), and 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane. Examples of polymeric phenolic antioxidants include 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, and tocopherol.

[0115] The hindered phenol-based antioxidant may have a structure in which a tertiary butyl group is bonded to at least one carbon atom adjacent to a carbon atom on an aromatic ring to which a phenolic OH group is bonded. Examples of hindered phenolic antioxidants include dibutylhydroxytoluene (BHT); and Irganox1010, Irganox1010FF, Irganox1035, Irganox1035FF, Irganox1076, Irganox1076FD, Irganox1076DWJ, Irganox1098, Irganox1135, Irganox1330, Irganox1726, Irganox1425WL, Irganox1520L, Irganox245, Irganox245FF, Irganox259, Irganox3114, Irganox565, and Irganox295 (all of which are trade names manufactured by BASF).

[0116] The amine antioxidant is preferably a hindered amine antioxidant. The hindered amine antioxidant may have at least one hindered piperazine group in one molecule. Examples of the hindered amine antioxidant include ADK STAB LA-63, ADK STAB LA-63P, ADK STAB LA-52, and ADK STAB LA-57 (all of which are trade names, manufactured by ADEKA Corporation).

[0117] Examples of the phosphite antioxidants are triphenyl phosphite, diphenyl isodecyl phosphite, and phenyl diisodecyl phosphite; and Adeka STAB 2112, Adeka STAB 2112RG, Adeka STAB 1178, and Adeka STAB 3010 (all of which are trade names, manufactured by ADEKA Corporation).

[0118] The content of the antioxidant relative to a total of 100 parts by weight of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant) is, for example, 5 parts by weight or less, and may be 3 parts by weight or less, 1 part by weight or less, 0.8 parts by weight or less, or even 0.5 parts by weight or less. The lower limit of the content is, for example, 0.01 parts by weight or more, and may even be 0.05 parts by weight or more. The pressure-sensitive adhesive composition does not necessarily contain an antioxidant.

[0119] <1-5-f. UV absorbers> The pressure-sensitive adhesive composition may contain an ultraviolet absorber (UVA). Examples of UVA include triazine-based UVA, benzotriazole-based UVA, benzophenone-based UVA, oxybenzophenone-based UVA, salicylic acid ester-based UVA, and cyanoacrylate-based UVA. Each UVA is a compound having a triazine skeleton, a benzotriazole skeleton, a benzophenone skeleton, an oxybenzophenone skeleton, a salicylic acid ester structure, and a cyanoacrylate structure, respectively. The UVA is preferably a triazine-based or benzotriazole-based UVA, and more preferably a benzotriazole-based UVA.

[0120] Examples of triazine-based UVAs include 2,4-bis-[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (Tinosorb S, manufactured by BASF), 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (TINUVIN460, manufactured by BASF), reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl with [(C10-C16 (mainly C12-C13) alkyloxy)methyl]oxirane (TINUVIN400, manufactured by BASF), and 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-[3-(dodecyloxy)methyl]oxirane. (2-hydroxypropoxy)phenol, reaction products of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine with (2-ethylhexyl)-glycidic acid ester (TINUVIN 405, BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]phenol (TINUVIN 1577, BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol (ADK STAB LA46 (manufactured by ADEKA), and 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (TINUVIN479 (manufactured by BASF)).

[0121] Examples of benzotriazole-based UVAs include 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN 928, manufactured by BASF), 2-(2H-1,2,3-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (TINUVIN 571, manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (TINUVIN PS, manufactured by BASF), ester compound of benzenepropanoic acid and 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy(C7-9 branched and linear alkyl) (TINUVIN 384-2, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN 900, manufactured by BASF), reaction product of methyl-3-(3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate / polyethylene glycol 300 (TINUVIN 1130, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (TINUVIN P, manufactured by BASF), 2(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN234, manufactured by BASF), 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (TINUVIN326, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (TINUVIN328, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN234, manufactured by BASF), 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (TINUVIN326, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (TINUVIN328, manufactured by BASF), -yl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN329, manufactured by BASF), reaction products of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate with polyethylene glycol 300 (TINUVIN213, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (TINUVIN571, manufactured by BASF), 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimido-methyl)-5-methylphenyl]benzotriazole (Sumisorb 250, manufactured by Sumitomo Chemical Co., Ltd.).

[0122] The content of UVA relative to a total of 100 parts by weight of the monomer component M and inorganic particles (specifically, a mixture of inorganic particles and a dispersant) is, for example, 10 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less, or even 2 parts by weight or less. The lower limit of the content is, for example, 0.1 parts by weight or more, 0.5 parts by weight or more, or even 1 part by weight or more. The pressure-sensitive adhesive composition does not necessarily contain UVA.

[0123] <1-5-g. Solvent> The content of the solvent in the PSA 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 PSA 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.

[0124] <1-5-h. Other additives> The PSA composition may contain additives other than those described above. Examples of the additives include chain transfer agents, viscosity modifiers, tackifiers, plasticizers, softeners, antioxidants, fillers, colorants, surfactants, and antistatic agents.

[0125] 1-6. Physical Properties The viscosity of the pressure-sensitive adhesive composition is preferably 5 to 150 poise at 25° C. A pressure-sensitive adhesive composition having a viscosity in the above range is particularly suitable for forming a coating layer, which will be described later.

[0126] ≪1-7. Manufacturing Method≫ The pressure-sensitive adhesive composition can be prepared, for example, by the following method. First, a dispersion liquid in which inorganic particles are dispersed in a solvent is prepared. This dispersion liquid is mixed with a dispersant and at least some of the monomers contained in the monomer component M. The solvent is removed from the resulting mixture to prepare a dispersion containing inorganic particles, a dispersant, and a monomer. The method for removing the solvent from the mixture is not particularly limited, and methods such as removal under reduced pressure can be used. Next, the remaining monomers, polymer B, and additives such as a photopolymerization initiator are added to the dispersion and mixed. This allows the pressure-sensitive adhesive composition to be prepared.

[0127] ≪≪2. Adhesive sheet≫≫ <2-1. Adhesive sheet> An example of a pressure-sensitive adhesive sheet according to an embodiment of the present invention is shown in Fig. 1. The pressure-sensitive adhesive sheet 1 in Fig. 1 is a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition.

[0128] The polymerization rate of the monomer component M in the pressure-sensitive adhesive sheet 1 is preferably 90% or more, and may be 95% or more, 98% or more, or even 99% or more.

[0129] The gel fraction of the pressure-sensitive adhesive sheet 1 is, for example, 50% or more, and may be 75% or more, 80% or more, 85% or more, or even 90% or more.

[0130] The refractive index of the pressure-sensitive adhesive sheet 1 is, for example, 1.55 or more, and may be 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, 1.60 or more, 1.61 or more, 1.62 or more, 1.63 or more, 1.64 or more, or even 1.65 or more. The upper limit of the refractive index is, for example, 1.70 or less, and may be 1.69 or less, 1.68 or less, 1.67 or less, or even 1.66 or less. In some cases, the upper limit of the refractive index may be 1.65 or less, 1.64 or less, or even 1.63 or less. A preferred example of the refractive index of the pressure-sensitive adhesive sheet 1 is 1.63 to 1.66. Another preferred example of the refractive index of the pressure-sensitive adhesive sheet 1 is 1.60 to 1.63. Some optical substrates that can be included in the optical laminate have a high refractive index. Using a pressure-sensitive adhesive sheet 1 with a high refractive index to bond the optical substrate is advantageous in reducing reflected light at the interface between the optical substrate and the pressure-sensitive adhesive sheet.

[0131] In this specification, the refractive index of the adhesive sheet 1 refers to the refractive index of the surface of the adhesive sheet 1. The refractive index of the adhesive sheet 1 can be measured using a prism coupler under conditions of a measurement temperature of 25°C and a measurement wavelength of 594 nm. For adhesive sheets 1 with a thickness of less than 20 μm, measurement in the optical propagation mode is generally suitable. For adhesive sheets 1 with a thickness of 20 μm or more, measurement in the critical angle mode is generally suitable. A commercially available measuring device can be used as the prism coupler, for example, a Model 2010 / M prism coupler manufactured by Metricon or an equivalent can be used.

[0132] As described above, the pressure-sensitive adhesive sheet 1 is formed from a pressure-sensitive adhesive composition and contains polymer B derived from the pressure-sensitive adhesive composition. In this embodiment, the change in refractive index Δn of the pressure-sensitive adhesive sheet 1 due to polymer B is, for example, 0.15 or less, and may be 0.10 or less, 0.05 or less, 0.03 or less, or even 0.01 or less. The lower limit of the change in refractive index Δn is not particularly limited, and is, for example, 0.001 or more. In this specification, the change in refractive index Δn refers to the difference (|n0-n1|) between the refractive index n0 of a pressure-sensitive adhesive sheet (comparison sheet) that has the same composition and thickness as the pressure-sensitive adhesive sheet 1 except that it does not contain polymer B, and the refractive index n1 of the pressure-sensitive adhesive sheet 1. Note that the production conditions (coating conditions and curing conditions) and storage conditions of the comparison sheet are preferably the same as those of the pressure-sensitive adhesive sheet 1.

[0133] The haze of the pressure-sensitive adhesive sheet 1 is, for example, 5.0% or less, and may be 3.0% or less, 2.0% or less, 1.7% or less, 1.5% or less, 1.2% 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, 0.3% or less, or even 0.2% or less. The lower limit of the haze is not particularly limited and may be 0.1% or more. A pressure-sensitive adhesive sheet 1 with low haze is particularly suitable for use in optical laminates.

[0134] In this specification, haze refers to the ratio of diffuse transmitted light to total transmitted light when visible light is irradiated onto the pressure-sensitive adhesive sheet 1, which is the object to be measured. Haze can be calculated using the following formula: In the following formula, Th is haze (%), Td is scattered light transmittance, and Tt is total light transmittance. Th(%)=Td / Tt×100

[0135] The color of the adhesive sheet 1 is CIE1976 L defined in the Japanese Industrial Standard (JIS) Z8781-4:2013. * ,a * ,b * Color space chromaticity b * The absolute value of chromaticity b may be 2.0 or less. *The absolute value of chromaticity b may be 1.7 or less, 1.5 or less, 1.2 or less, 1.0 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, or even 0.5 or less. * The lower limit of the absolute value of chromaticity b of the pressure-sensitive adhesive sheet 1 is, for example, 0 or more, and may be 0.1 or more. * can be evaluated using a commercially available colorimeter capable of measurements in accordance with JIS Z8781-4:2013.

[0136] The content of acidic groups (particularly COOH groups) in polymer B contained in pressure-sensitive adhesive sheet 1 is, for example, 0.1 wt % or less, 0.01 wt % or less, or even 0.001 wt % or less. Polymer B preferably contains substantially no acidic groups. The acidic group content can be measured, for example, by the following method. First, a sol component (non-crosslinked component) contained in pressure-sensitive adhesive sheet 1 is extracted using a solvent (e.g., toluene). A component (polymer B) having a weight-average molecular weight of 1,500 to 30,000 is separated using preparative gel permeation chromatography (GPC). This component is dried in an oven at 130°C for 2 hours to remove the solvent. The acidic group content can be determined by evaluating the dried component using infrared spectroscopy.

[0137] The adhesive sheet 1 preferably has an adhesive strength to alkali-free glass of 1.0 N / 25 mm or more, and may be 1.5 N / 25 mm or more, 2.0 N / 25 mm or more, 3.0 N / 25 mm or more, 4.0 N / 25 mm or more, 5.0 N / 25 mm or more, 6.0 N / 25 mm or more, 7.0 N / 25 mm or more, 8.0 N / 25 mm or more, 9.0 N / 25 mm or more, or even 10.0 N / 25 mm or more. The upper limit of the adhesive strength is, for example, 50.0 N / 25 mm or less, 30.0 N / 25 mm or less, or even 20.0 N / 25 mm or less. In some cases, the upper limit of the adhesive strength may be 10.0 N / 25 mm or less, 5.0 N / 25 mm or less, or even 4.0 N / 25 mm or less. A preferred example of the adhesive strength is 1.0 to 4.0 N / 25 mm. Another preferred example of the adhesive strength is 4.0 to 20.0 N / 25 mm.

[0138] The adhesive strength can be measured by the following method. First, a laminate including a pressure-sensitive adhesive sheet 1 and a substrate is prepared under a measurement environment of 23°C and 50% RH. The substrate is not particularly limited as long as it supports the pressure-sensitive adhesive sheet 1 and does not affect the measurement results of the adhesive strength. As an example, the substrate may be a polyethylene terephthalate film. Next, the laminate is cut into a strip of 100 mm length x 25 mm width to prepare a test piece. Next, the test piece is placed on alkali-free glass via the pressure-sensitive adhesive sheet 1, and they are pressed together by moving a 2 kg roller back and forth once. The alkali-free glass is glass that is substantially free of alkali components (alkali metal oxides). Specifically, the weight ratio of the alkali components in the glass is, for example, 1000 ppm or less, and even 500 ppm or less. The alkali-free glass is, for example, in the form of a plate, having a thickness of 0.5 mm or more.

[0139] After leaving the test piece in the above environment for 30 minutes, it was placed in a pressure degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. It was then left for 24 hours in an atmosphere of 23°C and 50% RH. Next, using a universal tension and compression tester, the test piece was peeled from the alkali-free glass at a peel rate of 300 mm / min and a peel angle of 180°. The force (peel strength) required to peel the test piece from the alkali-free glass was determined as the adhesive strength.

[0140] The thickness of the pressure-sensitive adhesive sheet 1 is, for example, 500 μm or less, and may be 250 μm or less, 150 μm or less, 100 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness of the pressure-sensitive adhesive sheet 1 is, for example, 2 μm or more, and may be 5 μm or more. In some cases, the lower limit of the thickness of the pressure-sensitive adhesive sheet 1 may be 20 μm or more, or may be 30 μm or more. A preferred example of the thickness of the pressure-sensitive adhesive sheet 1 is 2 to 30 μm. Another preferred example of the thickness of the pressure-sensitive adhesive sheet 1 is 30 to 100 μm.

[0141] ≪2-2. Manufacturing Method≫ The pressure-sensitive adhesive sheet 1 can be formed from the pressure-sensitive adhesive composition by, for example, irradiating light 14 onto a first laminate 10 comprising, in this order, a base sheet 11, a coating layer 12 containing the pressure-sensitive adhesive composition, and a release liner 13 (see FIG. 2). The coating layer 12 is cured by irradiation with light 14 to form the pressure-sensitive adhesive sheet 1. Irradiation with light 14 is typically carried out from the side of the base sheet 11. In this case, the light 14 passes through the base sheet 11 and reaches the coating layer 12, curing the coating layer 12. However, irradiation with light 14 may also be carried out from the side of the release liner 13, or from both the side of the release liner 13 and the side of the base sheet 11.

[0142] The formed pressure-sensitive adhesive sheet 1 is sandwiched between the base sheet 11 and the release liner 13 until the release liner 13 is peeled off, and constitutes a part of the second laminate 17. By peeling the release liner 13 from the second laminate 17, a third laminate 15 including the base sheet 11 and the pressure-sensitive adhesive sheet 1 is obtained. In the third laminate 15, 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.

[0143] The light 14 is, for example, visible light or ultraviolet light having a wavelength shorter than 450 nm. The light may include light having a wavelength in the same region as the absorption wavelength of the photopolymerization initiator contained in the pressure-sensitive adhesive composition. Light having a wavelength of 300 nm or less may be irradiated by filtering out short-wavelength light using a filter or the like. Filtering out short-wavelength light is suitable for suppressing deterioration of the base sheet 11 and / or release liner 13 due to the light 14. The light source 18 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.

[0144] The illuminance of the light 14 irradiated onto the first laminate 10 (specifically, the coating layer 12) is, for example, 2.0 to 30 mW / cm2 The illuminance is 2.5mW / cm 2 More than 3.0mW / cm 2 More than 3.5mW / cm 2 More than 4.0mW / cm 2 More than 5.0mW / cm 2 More than 6.0mW / cm 2 More than 7.0mW / cm 2 More than 8.0mW / cm 2 More than 9.0mW / cm 2 or more, and even 10mW / cm 2 The upper limit of the illuminance may be, for example, 25 mW / cm 2 less than 20 mW / cm 2 It may be the following:

[0145] The time for irradiating the first laminate 10 (specifically, the coating layer 12) with light 14 is, for example, 10 to 1000 seconds, and may be 60 seconds or more, 100 seconds or more, 150 seconds or more, or even 200 seconds or more. The upper limit of the time is, for example, 800 seconds or less, and may be 600 seconds or less, 500 seconds or less, 400 seconds or less, 300 seconds or less, or even 250 seconds or less. Irradiation with light 14 may be continuous or intermittent.

[0146] The integrated light amount of the light 14 on the first laminate 10 (specifically, the coating layer 12) is, for example, 25 mJ / cm 2 2 or more, 100 mJ / cm 2 More than 500mJ / cm 2 More than 1000mJ / cm 2 More than 2000mJ / cm 2 More than 2500mJ / cm 2 More than 3000mJ / cm 2 More than 5000mJ / cm 2 More than 7500mJ / cm 2 or more, even 10,000 mJ / cm 2 The upper limit of the cumulative light amount is not particularly limited, and may be, for example, 30,000 mJ / cm 2 or more. 2 Less than 25,000 mJ / cm 2 Below, 20000mJ / cm 2Below that, even 18000mJ / cm 2 It may be the following:

[0147] The light 14 may be irradiated onto the first laminate 10 in multiple stages. The illuminance and / or integrated light amount of the light 14 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.

[0148] An example of the substrate of the release liner 13 (hereinafter referred to as "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.

[0149] The release liner 13 may include a layer other than the liner substrate. The release liner 13 may include a release layer. The release liner 13 includes, for example, a liner substrate and a release layer formed on one surface of the liner substrate. This release liner 13 can be used so that the release layer faces the coating layer 12. 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.

[0150] The release liner 13 may be in the form of a sheet or a continuous piece.

[0151] An example of the base sheet 11 is a resin film. Examples of the resin contained in the base sheet 11 are the same as the examples of the resin that can be contained in the liner base material.

[0152] The thickness of the base sheet 11 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

[0153] The base sheet 11 may have a release layer on the surface on the side of the coating layer 12. Examples of the release layer that may be provided on the base sheet 11 are the same as the examples of the release layer that may be provided on the release liner 13. Both the release liner 13 and the base sheet 11 may have a release layer.

[0154] For the base sheet 11, a sheet having a greater peel strength from the adhesive sheet 1 than the release liner 13 can usually be selected.

[0155] The base sheet 11 may be in the form of a sheet or a continuous sheet.

[0156] The first laminate 10 can be formed, for example, by forming a coating layer 12 on a base sheet 11 (or a release liner 13) and then placing the release liner 13 (or base sheet 11) on the formed coating layer 12. Alternatively, the first laminate 10 may be formed by applying the photocurable composition in a poured manner into the space between the base sheet 11 and the release liner 13, which are held at a predetermined distance so that their main surfaces face each other.

[0157] The coating layer 12 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.

[0158] The thickness of coating layer 12 can be adjusted depending on the desired thickness of pressure-sensitive adhesive sheet 1, and may be, for example, 500 μm or less, 250 μm or less, 150 μm or less, 100 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness of coating layer 12 is, for example, 2 μm or more, and may be 5 μm or more.

[0159] The first laminate 10 may include a long base sheet 11, a long coating layer 12, and a long release liner 13, in other words, it may be long. The long first laminate 10 can be obtained, for example, by forming the coating layer 12 between the base sheet 11 and the release liner 13 while conveying them after they have been unwound from a roll.

[0160] ≪≪3. 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 in Fig. 3 includes an adhesive sheet 1 and an optical film 2. The adhesive sheet 1 and the optical film 2 are laminated together. The optical laminate 20A can be used as an optical film with an adhesive sheet.

[0161] Examples of the optical film 2 include a polarizing film, a retardation film, and a laminated film including a polarizing film and / or a retardation film. However, the optical film 2 is not limited to the above examples. The optical film 2 may also include a glass film.

[0162] The optical film 2 may be a polarizing film, and the pressure-sensitive adhesive sheet 1 may be in contact with the optical film 2 .

[0163] 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 the 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.

[0164] The polarizer is not particularly limited, and examples include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye; and oriented polyene films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Polarizers typically consist of a polyvinyl alcohol film (including partially saponified ethylene-vinyl acetate copolymer films) and a dichroic substance such as iodine.

[0165] 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, or even 20 μm or less. The lower limit of the polarizer thickness is not particularly limited and may be, for example, 1 μm or more, 5 μm or more, 10 μm or more, or even 15 μm or more. A thin polarizer (for example, a thickness of 20 μm or less) is suppressed in dimensional change and can contribute to improving the durability of the optical laminate, particularly durability at high temperatures.

[0166] The material for the protective film may be, for example, a thermoplastic resin that is excellent in transparency, mechanical strength, thermal stability, moisture barrier 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 a 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.

[0167] The thickness of the protective film can be determined as appropriate, but is generally about 10 to 200 μm in terms of strength, workability such as handling, thinness, and the like.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] The polarizing film may be a circular polarizing film.

[0172] 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 may be, for example, 10 μm or more, 25 μm or more, or even 40 μm or more.

[0173] A 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.

[0174] 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 obliquely oriented viewing angle compensation retardation film (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. The retardation value, arrangement angle, three-dimensional birefringence, whether the retardation film is single-layer or multi-layer, and the like are also not limited. Known films can be used as the retardation film.

[0175] The optical film 2 has a thickness of, for example, 1 to 200 μm.

[0176] 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.

[0177] 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.

[0178] The release liner 3 is typically a resin film. Examples of resins that can be used to form 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 may be, for example, a treatment using 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.

[0179] Another example of an optical laminate according to an embodiment of the present invention is shown in Fig. 5. Optical laminate 20C in Fig. 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 release liner 3, optical laminate 20C can be used by being attached to, for example, an image-forming layer.

[0180] A known adhesive sheet can be used for the adhesive sheet 4. The adhesive sheet 1 may also be used for the adhesive sheet 4.

[0181] Another example of an optical laminate according to an embodiment of the present invention is shown in Fig. 6. Optical laminate 20D in Fig. 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 release liner 3, optical laminate 20D can be used by being attached to, for example, an image-forming layer.

[0182] 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 also be a glass film or a laminated film including a glass film. The protective film 5 may be subjected to surface treatments such as anti-glare, anti-reflection, and anti-static.

[0183] The protective film 5 may be bonded to the optical film 2 with any adhesive. Bonding with an adhesive sheet 1 is also possible.

[0184] The optical laminate may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and the optical film 2.

[0185] 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.

[0186] 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.

[0187] The optical laminate according to the embodiment of the present invention is typically used in image display devices, such as liquid crystal displays, organic EL displays, and inorganic EL displays.

[0188] ≪≪4. Image display device≫≫ An example of an image display device according to an embodiment of the present invention is shown in Fig. 7. The image display device 21 in Fig. 7 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, an adhesive sheet 4, a retardation film 2B, an adhesive sheet 1, a polarizing film 2A, and a protective film 5 are layered in this order. The image display device 21 has the optical laminate 20D of Fig. 6 (excluding the release liner 3). The image display device 21 may have the optical laminates 20A, 20B, and 20C of Figs. 3 to 5 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.

[0189] The image display device 21 in Fig. 7 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.

[0190] The image display device 21 may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and / or the optical laminate 20. [Example]

[0191] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples in any way.

[0192] <Preparation of Dispersion D1> [Synthesis of dispersant d1] To 1.0 mol of propionic acid, 8.0 mol of ε-caprolactone, 0.2 mol of p-toluenesulfonic acid monohydrate, and 2.2 mol of pure water were added, and the mixture was stirred at 80°C for 8 hours. Next, stirring was continued for another 2 hours while dehydrating under reduced pressure (30 kPa). Next, the propionic acid remaining in the reaction system was distilled off, and the mixture was subjected to a purification step (washed with water three times) and a drying step to obtain dispersant d1 (a compound represented by the above formula (1) in which R is an ethyl group, m is 5, and n is 10).

[0193] [Preparation of Dispersion D1] 5 parts by weight of the above-mentioned dispersant d1 and 45 parts by weight of phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Industry Co., Ltd., trade name "Light Acrylate POB-A"; hereinafter referred to as "POB-A") were added to and mixed with 167 parts by weight of a methanol dispersion of zirconium oxide particles (manufactured by Sakai Chemical Industry Co., Ltd., grade name "SZR-GM," average particle diameter (D50) based on dynamic light scattering: approximately 10 nm, zirconium oxide particle concentration: 30% by weight). Next, the solvent was removed under reduced pressure using a rotary evaporator to obtain Dispersion D1, a dispersion of zirconium oxide particles. Dispersion D1 contained zirconium oxide particles / Dispersant d1 / POB-A in a weight ratio of 50 / 5 / 45.

[0194] <Preparation of Dispersion D2> [Synthesis of dispersant d2] 415 g (1 mol) of tristyrenated phenol and 1 g (0.018 mol) of potassium hydroxide were charged into an autoclave and mixed uniformly. The resulting reaction system was then heated to 130°C, and 352 g (8 mol) of ethylene oxide (EO) was added dropwise. After the dropwise addition was completed, the mixture was aged for 1 hour at 130°C while maintaining the pressure at 0.1 MPa, yielding a tristyrenated phenol-EO 8 mol adduct. Next, 767 g (1 mol) of the resulting tristyrenated phenol-EO 8 mol adduct and 152 g (1.3 mol) of sodium monochloroacetate were added to the reactor and stirred until homogeneous. Next, the reaction system was heated to 60°C, 52 g of sodium hydroxide was added, and the mixture was then heated to 80°C and aged for 3 hours. After aging, the mixture was cooled to 50°C, and 117 g (1.2 mol) of 98 wt% sulfuric acid was added dropwise at the same temperature, yielding a white suspension. The resulting suspension was washed with distilled water, and the solvent was removed by distillation under reduced pressure to obtain dispersant d2 (R 1 = styrenephenyl group (in the above formula (3), k=3, AO=oxyethylene group, n=8, X=O, Y=methylene group).

[0195] To 100 parts by weight of a methanol dispersion of zirconium oxide particles (manufactured by Sakai Chemical Industry Co., Ltd., grade name "SZR-M", average particle size (D50) based on dynamic light scattering: 3 nm, zirconium oxide particle concentration: 30 wt %), 1.5 parts by weight of the above-mentioned dispersant d2 and 28.5 parts by weight of POB-A were added and mixed. Next, the solvent was removed under reduced pressure using a rotary evaporator to obtain Dispersion D2, a dispersion of zirconium oxide particles. Dispersion D2 contained zirconium oxide particles / Dispersant d2 / POB-A in a weight ratio of 50 / 2.5 / 47.5.

[0196] <Preparation of Dispersion D3> 50 parts by weight of a methanol dispersion of zirconium oxide ("SZR-GM" manufactured by Sakai Chemical Industry Co., Ltd., average particle size (D50): approximately 10 nm based on dynamic light scattering) was mixed with 7 parts by weight of the above-mentioned Dispersant d2, 4 parts by weight of a silane coupling agent ("KBM-103" manufactured by Shin-Etsu Chemical Co., Ltd.), 36 parts by weight of POB-A, and 3 parts by weight of phenoxydiethylene glycol acrylate ("Light Acrylate P2H-A" manufactured by Kyoeisha Chemical Co., Ltd.; hereinafter referred to as "P2HA"). The solvent was then removed under reduced pressure using a rotary evaporator to obtain Dispersion D3, a dispersion of zirconium oxide. Dispersion D3 contained zirconium oxide particles / Dispersant d2 / Silane coupling agent / POB-A / P2HA in a weight ratio of 50 / 7 / 4 / 36 / 3.

[0197] <Synthesis of Polymer B1> A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 99 parts by weight of POB-A, 1 part by weight of 4-hydroxybutyl acrylate (4HBA), 0.30 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator, 3 parts by weight of 1-thioglycerol as a chain transfer agent, and 300 parts by weight of ethyl acetate. The mixture was maintained at 70°C and stirred gently while introducing nitrogen gas. After sufficient nitrogen substitution for at least 1 hour, the liquid temperature in the flask was maintained at 72-74°C and the polymerization reaction was carried out for 6 hours to prepare a solution of polymer B1. The solution was then heated at 90°C for 12 hours, followed by 3 hours of reduced pressure treatment at 120°C to remove the ethyl acetate. This yielded polymer B1, in which the amount of ethyl acetate detected by gas chromatography was less than 0.1 parts by weight.

[0198] <Synthesis of Polymers B2 to B15> Polymers B2 to B15 were synthesized in the same manner as for polymer B1, except that the types and contents of the monomer, polymerization initiator, and chain transfer agent were changed as shown in Table 1.

[0199] [Weight average molecular weight of polymer B] The weight-average molecular weight (Mw) of the obtained polymer B was measured by GPC (gel permeation chromatography). The measurement equipment and conditions were as follows. The measurement equipment and conditions were different for the nitrogen-containing composition and the nitrogen-free composition. (Nitrogen-containing composition) Analytical equipment: Agilent 1200 Column: Tosoh TSKgel SuperAWM-H + superAW4000 + superAW2500 Column temperature: 40℃ Eluent: DMF (salt added) ·Flow rate: 0.4mL / min ·Injection volume: 40μL Detector: Refractive index (RI) Standard sample: Agilent, polystyrene (PS) (Nitrogen-free composition) Analytical equipment: Waters, Alliance Column: Tosoh TSKgel SuperHZM-H x 2 Column temperature: 40℃ ·Eluent:THF ·Flow rate: 0.2mL / min ·Injection volume: 30μL Detector: Refractive index (RI) Standard sample: Agilent, polystyrene (PS)

[0200] [Table 1]

[0201] The abbreviations in Table 1 are as follows: POB-A: Phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical, product name "Light Acrylate POB-A") 4HBA: 4-hydroxybutyl acrylate ACMO: acryloylmorpholine BA: n-butyl acrylate CHMA: Cyclohexyl methacrylate IBXMA: Isobornyl methacrylate CBA: 2-(2-ethoxyethoxy)ethyl acrylate NVP: N-vinylpyrrolidone AIBN: Azo polymerization initiator, 2,2'-azobisisobutyronitrile (Kishida Chemical Co., Ltd.)

[0202] Example 1 100 parts by weight of Dispersion D1 was mixed with 10 parts by weight of the polymer B1, 0.05 parts by weight of 1,2-diphenylethan-1-one (manufactured by IGM Resins, trade name "Omnirad651") as a photopolymerization initiator, and 0.05 parts by weight of 1-hydroxycyclohexylphenylketone (manufactured by IGM Resins, trade name "Omnirad184"), 0.5 parts by weight of Irganox1010 (manufactured by BASF) as an antioxidant, 0.3 parts by weight of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicones, trade name "KBM-403") as a silane coupling agent, and 0.05 parts by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent. This gave the adhesive composition of Example 1.

[0203] (Examples 2 to 17 and Comparative Examples 1 to 3) The PSA compositions of Examples 2 to 15 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that the type of dispersion, the type of polymer B, and the content of polymer B were changed as shown in Table 2. In Examples 11 to 15 and Comparative Example 2, Dispersion D2 was used instead of Dispersion D1, and in Examples 16 and 17 and Comparative Example 3, Dispersion D3 was used instead of Dispersion D1. In Comparative Examples 1 to 3, polymer B was not added to the dispersions.

[0204] <Evaluation> First, pressure-sensitive adhesive sheets for evaluation were produced using the pressure-sensitive adhesive compositions of Examples 1 to 17 and Comparative Examples 1 to 3 by the following method.

[0205] [Preparation of release liner] A silicone-based release agent composition was prepared 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 Co., Ltd.), 0.9 parts by weight of a release control agent (BY24-850 containing an unreactive silicone resin, manufactured by Dow Corning Toray Co., Ltd.), 2 parts by weight of a curing catalyst (SRX212 containing a platinum catalyst, manufactured by Dow Corning Toray Co., Ltd.), and a toluene / hexane mixed solvent (volume ratio 1:1) as a diluent. The silicone solids concentration in the release agent composition was 1.0 wt%. Next, the release agent composition was applied to one side of a liner substrate (Lumirror XD500P polyester film, 75 μm thick) using a wire bar and heated at 130°C for 1 minute to prepare a release liner with a release layer (60 nm thick) on one side.

[0206] [Preparation of adhesive sheet] The adhesive composition was applied to one side of a substrate sheet (PET separator, Mitsubishi Plastics, MRF38) using an applicator to form a coating layer. Next, the release liner described above was placed on top of the formed coating layer to obtain a first laminate. The release liner was placed so that the release layer was in contact with the coating layer.

[0207] Next, an illuminance of 9 mW / cm was applied from the side of the base sheet of the first laminate. 2 and cumulative light intensity of 714 mJ / cm 2 The coating was irradiated with ultraviolet light under the following conditions. An LED was used as the light source, and the peak wavelength of the irradiated light was 340 nm. This photocured the coating layer, yielding a pressure-sensitive adhesive sheet (20 μm thick) sandwiched between the base sheet and release liner. The illuminance of the light was measured using an illuminance meter (UD-T3040T2, manufactured by Topcon Technohouse Co., Ltd.) near the surface of the base sheet where the ultraviolet light was incident.

[0208] Thereafter, following the above operation, an illuminance of 18 mW / cm was applied from the side of the base sheet of the first laminate. 2 and cumulative light intensity 667mJ / cm 2The adhesive sheet was irradiated with ultraviolet light under the following conditions. A metal halide lamp was used as the light source. This removed any uncured monomer and unreacted initiator remaining on the adhesive sheet. The illuminance of the light was measured using an illuminance meter (U0-T36T2, manufactured by Topcon Technohouse Co., Ltd.) near the ultraviolet light incident surface of the base sheet.

[0209] [Adhesion strength evaluation] Under a measurement environment of 23°C and 50% RH, the release liner was peeled from the pressure-sensitive adhesive sheet, and a polyethylene terephthalate film (50 μm thick) was attached and backed. The resulting laminate was cut into a 100 mm long x 25 mm wide strip to prepare a test piece. The substrate sheet was peeled from the test piece, and placed on alkali-free glass (manufactured by Corning Incorporated, product name "EG-XG", thickness 0.7 mm), and the two were pressed together by moving a 2 kg roller back and forth once.

[0210] After leaving the test piece in the above environment for 30 minutes, it was placed in a pressure degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. It was then left for 24 hours in an atmosphere of 23°C and 50% RH. Next, using a universal tension and compression tester (Shimadzu Corporation, Autograph SHIMAZU AGX-V 50N), the test piece was peeled from the alkali-free glass at a peel rate of 300 mm / min and a peel angle of 180°. The force (peel strength) required to peel the test piece from the alkali-free glass was determined as the adhesive strength.

[0211] [Refractive index evaluation] The refractive index of the surface of the above pressure-sensitive adhesive sheet was measured in critical angle mode using a prism coupler (manufactured by Metricon, model "2010M") at a measurement temperature of 25°C and a measurement wavelength of 594 nm by peeling off the release liner.

[0212] [Hayes's Review] The base sheet and release liner were removed from the pressure-sensitive adhesive sheet, and alkali-free glass plates (0.7-0.8 mm thick, 92% total light transmittance, 0.06% haze) were attached to each exposed surface to obtain a test piece in which the pressure-sensitive adhesive sheet was sandwiched between the two alkali-free glass plates. This test piece was left in an environment of 23°C and 50% RH for 30 minutes, then placed in a pressure-degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. The test piece was then left in an atmosphere of 23°C and 50% RH for 24 hours. The haze of the test piece was then measured using a spectroscopic haze meter (HSP-150vis, manufactured by Murakami Color Research Laboratory) at 23°C.

[0213] [chromaticity b * Evaluation The adhesive sheet was peeled off from the base sheet and release liner, and a non-alkali glass plate (thickness 0.7-0.8 mm, total light transmittance 92%, chromaticity b * 0.20) was bonded together to obtain a test piece in which the adhesive sheet was sandwiched between two alkali-free glass plates. This test piece was left in an environment of 23°C and 50% RH for 30 minutes, then placed in a pressure degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. Next, it was left in an atmosphere of 23°C and 50% RH for 24 hours. Next, in a measurement environment of 23°C, the transmittance of the above test piece for light with wavelengths from 300 nm to 800 nm was measured using a UV-Visible-Near-Infrared Spectrophotometer (Hitachi High-Tech, UH4150). Chromaticity b was calculated from the obtained spectral data using a color calculation program (Hitachi High-Tech, UV Solutions). * The absolute value of the chromaticity b * The values ​​were based on reference data (blank data) measured without placing a sample in the measurement chamber of the ultraviolet-visible-near-infrared spectrophotometer.

[0214] [Table 2]

[0215] The abbreviations in Table 2 are as follows: POB-A: Phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical, product name "Light Acrylate POB-A") P2HA: Phenoxydiethylene glycol acrylate (Kyoeisha Chemical's "Light Acrylate P2H-A")

[0216] Example 18 Phenoxybenzyl acrylate (POB-A) and 4-hydroxybutyl acrylate (4HBA) were mixed with the above dispersion D1 to obtain a mixture containing zirconium oxide particles, dispersant d1, POB-A, and 4HBA in the amounts shown in Table 3. 100 parts by weight of this mixture was mixed with 10 parts by weight of the polymer B10, 0.6 parts by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins, trade name "Omnirad819") as a photopolymerization initiator, 2.5 parts by weight of TINUVIN384-2 (manufactured by BASF) as a UVA, 0.5 parts by weight of Irganox1010 (manufactured by BASF) as an antioxidant, 0.5 parts by weight of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicones, trade name "KBM-403") as a silane coupling agent, and 0.03 parts by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent. This gave the adhesive composition of Example 18.

[0217] (Examples 19 to 25 and Comparative Example 4) PSA compositions of Examples 19 to 25 and Comparative Example 4 were obtained in the same manner as in Example 18, except that the composition of the mixture, the type of additive, and the content of the additive were changed as shown in Table 3. In Example 25, Dispersion D2 was used instead of Dispersion D1. In Comparative Example 4, Polymer B was not added to the mixture.

[0218] <Evaluation> Pressure-sensitive adhesive sheets for evaluation were prepared by the following method using the pressure-sensitive adhesive compositions of Examples 18 to 25 and Comparative Example 4. Furthermore, the adhesive strength, refractive index, haze and chromaticity b were measured using the prepared pressure-sensitive adhesive sheets by the same method as in Example 1. *The following evaluation was conducted.

[0219] The adhesive composition was applied to one side of a substrate sheet (PET separator, Mitsubishi Plastics, MRF38) using an applicator to form a coating layer. Next, the release liner described above was placed on top of the formed coating layer to obtain a first laminate. The release liner was placed so that the release layer was in contact with the coating layer.

[0220] Next, an illuminance of 9 mW / cm was applied from the side of the base sheet of the first laminate. 2 and cumulative light intensity of 1467mJ / cm 2 At the same time, ultraviolet light was irradiated from a black light source at an illuminance of 9 mW / cm from the release liner side of the first laminate. 2 and cumulative light intensity of 714 mJ / cm 2 The coating was irradiated with light (peak wavelength 340 nm) from an LED under the conditions shown above. This photocured the coating layer, yielding a pressure-sensitive adhesive sheet (50 μm thick) sandwiched between the base sheet and release liner. The illuminance of the ultraviolet light from the black light source was measured using an illuminance meter (U0-T36T2, manufactured by Topcon Technohouse) near the surface of the base sheet where the ultraviolet light was incident. The illuminance of the light from the LED was measured using an illuminance meter (UD-T3040T2, manufactured by Topcon Technohouse) near the surface of the release liner where the ultraviolet light was incident.

[0221] Thereafter, following the above operation, an illuminance of 18 mW / cm was applied from the side of the base sheet of the first laminate. 2 and cumulative light intensity 667mJ / cm 2 The adhesive sheet was irradiated with ultraviolet light under the following conditions. A metal halide lamp was used as the light source. This removed any uncured monomer and unreacted initiator remaining on the adhesive sheet. The illuminance of the light was measured using an illuminance meter (U0-T36T2, manufactured by Topcon Technohouse Co., Ltd.) near the ultraviolet light incident surface of the base sheet.

[0222] [Table 3]

[0223] [Table 4]

[0224] The abbreviations in Table 3 are as follows: POB-A: Phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical, product name "Light Acrylate POB-A") 4HBA: 4-hydroxybutyl acrylate P2HA: Phenoxydiethylene glycol acrylate (Kyoeisha Chemical's "Light Acrylate P2H-A") Omni.819: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins, trade name "Omnirad 819") Tinuvin 384-2: Benzotriazole-based UVA (manufactured by BASF, trade name "Tinuvin 384-2") Tinuvin 405: Triazine UVA (manufactured by BASF, product name "Tinuvin 405") Tinuvin 571: Benzotriazole-based UVA (manufactured by BASF, trade name "Tinuvin 571") KBM403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicones Co., Ltd., product name "KBM-403")

[0225] As can be seen from Tables 2 to 4, the pressure-sensitive adhesive sheets formed from the pressure-sensitive adhesive compositions of the Examples containing a monomer having a double bond-containing ring, inorganic particles, and polymer B had higher adhesive strengths than the pressure-sensitive adhesive sheets of the Comparative Examples, provided that the thicknesses were the same. Furthermore, all of the pressure-sensitive adhesive sheets formed from the pressure-sensitive adhesive compositions of the Examples had high refractive indices. [Industrial Applicability]

[0226] The pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition of the present invention can be used in image display devices such as EL displays and liquid crystal displays. [Explanation of symbols]

[0227] 1 adhesive sheet 2 Optical Film 20A, 20B, 20C, 20D Optical laminate 21 Image display device

Claims

1. a monomer component M containing a monomer a having a double bond-containing ring; Inorganic particles; and a polymer B having a weight average molecular weight of 1,500 to 30,000. A photocurable pressure-sensitive adhesive composition.

2. The pressure-sensitive adhesive composition according to claim 1 , wherein the double bond-containing ring is an aromatic ring.

3. The pressure-sensitive adhesive composition according to claim 1 , wherein the monomer a comprises a (meth)acrylic monomer having the double bond-containing ring.

4. The pressure-sensitive adhesive composition according to claim 1 , wherein the monomer a comprises phenoxybenzyl acrylate.

5. The pressure-sensitive adhesive composition according to claim 1 , wherein the content of the monomer a is 45 parts by weight or more relative to 100 parts by weight of the total of the monomer component M and the inorganic particles.

6. The pressure-sensitive adhesive composition according to claim 1, wherein the weight average molecular weight of the polymer B is 4,000 to 16,000.

7. The pressure-sensitive adhesive composition according to claim 1 , wherein the polymer B comprises a structural unit derived from a monomer b having a double bond-containing ring.

8. The pressure-sensitive adhesive composition according to claim 7 , wherein the content of the structural unit derived from the monomer b in the polymer B is 70% by weight or more.

9. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the content of said polymer B is 1 to 30 parts by weight based on 100 parts by weight of the total of said monomer component M and said inorganic particles.

10. The pressure-sensitive adhesive composition according to claim 1 , wherein the inorganic particles comprise zirconium oxide.

11. The pressure-sensitive adhesive composition according to claim 1 , wherein the content of the inorganic particles is 45 parts by weight or more relative to a total of 100 parts by weight of the monomer component M and the inorganic particles.

12. The pressure-sensitive adhesive composition according to claim 1 , wherein the inorganic particles are surface-treated with a surface treatment agent.

13. The pressure-sensitive adhesive composition according to claim 12 , wherein the surface treatment agent comprises a silane coupling agent.

14. A pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 13.

15. The pressure-sensitive adhesive sheet according to claim 14 , wherein a change Δn in the refractive index of the pressure-sensitive adhesive sheet due to the polymer B is 0.15 or less.

16. The pressure-sensitive adhesive sheet according to claim 14 , wherein the polymer B contained in the pressure-sensitive adhesive sheet has an acidic group content of 0.001% by weight or less.

17. An optical laminate comprising the pressure-sensitive adhesive sheet according to claim 14 and an optical film.

18. An image display device comprising the optical laminate according to claim 17.

Images