Adhesive composition, adhesive sheet, optical laminate, and image display device

Abstract

The present invention provides an adhesive composition suitable for manufacturing an adhesive sheet having a high refractive index and improved durability. The adhesive composition contains a monomer component M, inorganic particles, and a dispersant. In the adhesive composition, the content of a hydroxyl group-containing monomer with respect to 100 parts by weight of the monomer component M is less than 0.1 parts by weight.

Description

Pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet, optical laminate, and image display device

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

[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 including optical substrates such as a polarizing film and a retardation film. In an optical laminate including a plurality of 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.

[0004] JP 2017-14376 A

[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 durability of pressure-sensitive adhesive sheets having a high refractive index.

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

[0007] [1] A pressure-sensitive adhesive composition according to an embodiment of the present invention comprises a monomer component M, inorganic particles, and a dispersant, wherein the content of the hydroxyl group-containing monomer per 100 parts by weight of the monomer component M is less than 0.1 parts by weight. [2] In the pressure-sensitive adhesive composition described in [1] above, the monomer component M may comprise a monomer a1 having a double bond-containing ring. [3] In the pressure-sensitive adhesive composition described in [2] above, the double bond-containing ring may be an aromatic ring. [4] In the pressure-sensitive adhesive composition described in [2] or [3] above, the content of the monomer a1 per 100 parts by weight of the monomer component M may be 80 parts by weight or more. [5] In the pressure-sensitive adhesive composition described in any of [1] to [4] above, the monomer component M may comprise a monomer a2 having a glass transition temperature of 0°C or lower when formed into a homopolymer. [6] In the pressure-sensitive adhesive composition described in [5] above, the monomer a2 may have an oxyalkylene group. [7] In the pressure-sensitive adhesive composition according to [5] or [6] above, the content of the monomer a2 relative to 100 parts by weight of the monomer component M may be 25 parts by weight or less. [8] In the pressure-sensitive adhesive composition according to any of [1] to [7] above, the inorganic particles may contain zirconium oxide. [9] In the pressure-sensitive adhesive composition according to any of [1] to [8] above, the content of the inorganic particles relative to 100 parts by weight of the monomer component M may be 90 parts by weight or more.

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

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

[11] In the pressure-sensitive adhesive composition according to

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

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

[11] above, the dispersant may have a hydrophilic group.

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

[12] above, the dispersant may have an aromatic ring.

[14] The pressure-sensitive adhesive composition according to any one of the above [1] to

[13] may further contain a polymer B having a weight-average molecular weight of 1,500 to 30,000.

[15] In the pressure-sensitive adhesive composition according to

[14] above, the content of the polymer B relative to 100 parts by weight of the monomer component M may be 0.1 to 20 parts by weight.

[16] The pressure-sensitive adhesive composition according to any one of [1] to

[15] above may be photocurable.

[17] 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

[16] above.

[18] The pressure-sensitive adhesive sheet according to

[17] above may have a refractive index of 1.64 or more.

[19] The pressure-sensitive adhesive sheet according to

[17] or

[18] above has a breaking elongation of 320% or more.

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

[17] to

[19] above and an optical film.

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

[20] above.

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

[0009] FIG. 1 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. FIG. 2 is a schematic view for explaining an example of a method for forming a pressure-sensitive adhesive sheet from the pressure-sensitive adhesive composition of the present invention. FIG. 3 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of an image display device according to one embodiment of the present invention.

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

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

[0012] In this specification, when the term "100 parts by weight of monomer component M" is used as a standard for the content of various components in a pressure-sensitive adhesive composition, it means the total amount of the monomer component M that is not partially polymerized and is contained in the pressure-sensitive adhesive composition, and the monomer component M that is consumed in forming the partially polymerized product A that can be contained in the pressure-sensitive adhesive composition.

[0013] <<1. Pressure-sensitive adhesive composition>> A pressure-sensitive adhesive composition according to an embodiment of the present invention includes a monomer component M, inorganic particles, and a dispersant. A portion of the monomer component M may be a partially polymerized product A. In the pressure-sensitive adhesive composition, the content of the hydroxyl group-containing monomer relative to 100 parts by weight of the monomer component M is less than 0.1 parts by weight. Specifically, in the pressure-sensitive adhesive composition, either (1) the monomer component M does not contain a hydroxyl group-containing monomer, or (2) the monomer component M contains a hydroxyl group-containing monomer, and the content of the hydroxyl group-containing monomer relative to 100 parts by weight of the monomer component M is less than 0.1 parts by weight.

[0014] <1-1. Monomer Component M> <1-1-a. Hydroxyl-Containing Monomer> As described above, in the pressure-sensitive adhesive composition, the content of the hydroxyl-containing monomer relative to 100 parts by weight of the monomer component M is less than 0.1 parts by weight. The content is preferably 0.05 parts by weight or less, and may be 0.01 parts by weight or less. It is particularly preferable that the monomer component M does not contain a hydroxyl-containing monomer (the content is 0 parts by weight).

[0015] The hydroxyl group-containing monomer has at least one hydroxyl group and at least one ethylenically unsaturated group in one molecule. Examples of the ethylenically unsaturated group are a (meth)acryloyl group, a vinyl group, and a (meth)allyl group. The hydroxyl group-containing monomer may be a (meth)acrylic monomer.

[0016] Examples of hydroxyl group-containing monomers are 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.

[0017] <1-1-b. Monomer a1 having a double bond-containing ring> Monomer component M preferably contains monomer a1 having a double bond-containing ring. Monomer a1 is a component suitable for improving the refractive index of the PSA sheet. Monomer a1 preferably does not contain a hydroxyl group. Furthermore, when monomer a1 is made into a homopolymer, the glass transition temperature (Tg) preferably exceeds 0°C, and may be 5°C or higher. Examples of methods for measuring Tg include the method described below for monomer a2.

[0018] As used herein, a 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.

[0019] 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.

[0020] 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 (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 one or both of nitrogen and sulfur. The double bond-containing ring may be a fused ring. An example of the monomer a1 has a structure in which one or more carbocyclic rings and one or more heterocyclic rings are fused, such as a dinaphthothiophene structure.

[0021] 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 may be, 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.

[0022] In the monomer a1, 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.

[0023] In the monomer a1, the double bond-containing ring is preferably located in a side chain. In other words, the monomer a1 preferably has at least one double bond-containing ring and at least one ethylenically unsaturated group per molecule. As the monomer a1, a compound containing one ethylenically unsaturated group per molecule (in other words, a monofunctional monomer) is preferably used.

[0024] Examples of ethylenically unsaturated groups are (meth)acryloyl groups, vinyl groups, and (meth)allyl groups. From the viewpoint of polymerization reactivity, (meth)acryloyl groups are preferred, and from the viewpoint of flexibility and adhesiveness, acryloyl groups are more preferred. In other words, monomer a1 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 (meth)acrylic monomers having a double bond-containing ring include aromatic ring-containing (meth)acrylates. Specific examples of aromatic ring-containing (meth)acrylates will be described later.

[0025] The double bond-containing ring and the ethylenically unsaturated group may be bonded directly or via a linking group. An example of the linking group includes one or more groups selected from the group consisting of alkylene groups, oxyalkylene groups, poly(oxyalkylene) groups, phenyl groups, alkylphenyl groups, alkoxyphenyl groups, groups in which one or more hydrogen atoms in these groups have been substituted with hydroxyl groups (e.g., hydroxyalkylene groups), oxy groups (-O-), and thiooxy groups (-S-). In one example of monomer a1, the double bond-containing ring and the ethylenically unsaturated group are bonded directly. In another example of monomer a1, 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.

[0026] Specific examples of the monomer a1 include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds may be used alone or in combination of two or more.

[0027] Monomer a1 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 PSA sheet.

[0028] Examples of the aromatic ring-containing monomer include a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, a monomer having a structure in which two or more non-condensed aromatic rings are directly bonded, a monomer having a condensed ring, a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, and a monomer having a dibenzothiophene structure. Among these, a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group (for example, phenoxybenzyl (meth)acrylate described below) is preferably used.

[0029] 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 the linking group include an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (e.g., -O-(CH2) n -; n is 1 to 3, preferably 1), a thiooxyalkylene group (e.g., -S-(CH2) n -; n is 1 to 3, preferably 1), a straight chain alkylene group (-(CH2) n-; n is 1 to 6, preferably 1 to 3), and the above-mentioned oxyalkylene group, the above-mentioned thiooxyalkylene group, and the above-mentioned straight-chain alkylene group in which the alkylene group is partially or completely halogenated. The linking group may contain one or more types selected from the group consisting of an oxy group, a thiooxy group, an oxyalkylene group, and a straight-chain alkylene group. Specific examples of monomers having a structure in which two or more non-fused aromatic rings are bonded via a linking group include phenoxybenzyl (meth)acrylate, thiophenoxybenzyl (meth)acrylate, and benzyl benzyl (meth)acrylate.

[0030] Examples of the monomer having a structure in which two or more non-fused aromatic rings are directly bonded include biphenyl structure-containing (meth)acrylate, triphenyl structure-containing (meth)acrylate, and vinyl group-containing biphenyl. Specific examples include o-phenylphenol (meth)acrylate, biphenyl (meth)acrylate, and biphenylmethyl (meth)acrylate.

[0031] 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.

[0032] 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.

[0033] 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. 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.

[0034] 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.

[0035] Monomer a1 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).

[0036] Examples of aromatic ring unit-containing monomers include carbon aromatic ring-containing (meth)acrylates such as benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxybutyl (meth)acrylate, cresyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and chlorobenzyl (meth)acrylate; 2-(4,6-dibromo-2-s-butylphenoxy)ethyl (meth)acrylate, 2-(4,6-dibromo-2-isopropylphenoxy)ethyl (meth)acrylate, and 6-(4 bromine-substituted aromatic ring-containing (meth)acrylates such as 2,6-dibromo-4-isopropyl-2-(4,6-dibromo-2-s-butylphenoxy)hexyl (meth)acrylate, 6-(4,6-dibromo-2-isopropylphenoxy)hexyl (meth)acrylate, 2,6-dibromo-4-nonylphenyl acrylate, and 2,6-dibromo-4-dodecylphenyl acrylate; carbon-substituted aromatic ring-containing vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and tert-butylstyrene; and compounds having a vinyl substituent on a heteroaromatic ring such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, and N-vinyloxazole.

[0037] Monomer a1 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 a1 described above. Monomers having such a structure can be understood as ethoxylated products of the original monomers. The number of repeating oxyethylene units (—CHCHO—) in the oxyethylene chain is, for example, 1 to 8, and may be 1 to 6, 1 to 4, 1 to 3, or even 1 to 2, or even 1. Examples of monomer a1 that is an ethoxylated product include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0038] Monomer a1 may contain 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.

[0039] 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, etc., this nominal value can be used as the refractive index.

[0040] 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), 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. Monomer a1 preferably contains phenoxybenzyl acrylate as a high refractive index monomer.

[0041] The content of monomer a1 relative to 100 parts by weight of monomer component M is, for example, 10 parts by weight or more, and may be 30 parts by weight or more, 50 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, 85 parts by weight or more, or even 90 parts by weight or more. Monomer component M may be composed essentially of monomer a1 alone. The upper limit of the content may be 99 parts by weight or less, or 95 parts by weight or less, depending on the case.

[0042] <1-1-c. Monomer a2 having a glass transition temperature of 0°C or lower when made into a homopolymer> Monomer component M may contain monomer a2 having a glass transition temperature (Tg) of 0°C or lower when made into a homopolymer. Monomer a2 is a component suitable for improving the adhesive strength of the PSA sheet. Monomer a2 preferably does not contain a hydroxyl group.

[0043] In the monomer a2, the Tg is preferably −10° C. or lower, and may be −20° C. or lower, −30° C. or lower, −40° C. or lower, or even −50° C. The lower limit of the Tg is, for example, −100° C. or higher.

[0044] The Tg can be measured by the following method. First, a homopolymer of monomer a2 is prepared. The homopolymer is placed in a differential scanning calorimeter, and differential scanning calorimetry (DSC) is performed. Specifically, three cycles of DSC measurement are performed, each cycle consisting of a temperature increase step at a temperature increase rate of 10°C / min and a temperature decrease step at a temperature decrease rate of 10°C / min. In the DSC measurement, the temperature increase start temperature is set to a value 70°C or more lower than the baseline shift resulting from the Tg of the homopolymer. The temperature decrease start temperature is set to a value 70°C or more higher than the baseline shift resulting from the Tg of the homopolymer.

[0045] In the DSC measurement, a calorimetry curve is created during the temperature rise process of each cycle. From the calorimetry curve, a temperature T corresponding to the midpoint of the line segment connecting the inflection point on the low-temperature side of the baseline shift and the inflection point on the high-temperature side of the baseline shift is identified. The average value of the temperature T (°C) in the second cycle and the temperature T (°C) in the third cycle can be considered as the Tg of the homopolymer of monomer a2.

[0046] Monomer a2 has at least one ethylenically unsaturated group in one molecule. Examples of the ethylenically unsaturated group are the same as those described above in the description of the hydroxyl group-containing monomer. Monomer a2 may be a (meth)acrylic monomer.

[0047] Monomer a2 preferably has at least one ether group. In particular, monomer a2 preferably has an oxyalkylene group. The number of oxyalkylene groups in monomer a2 is, for example, 1 to 30, and may be 1 to 12, or even 1 to 5.

[0048] Examples of the oxyalkylene group include an oxymethylene group, an oxyethylene group, and an oxypropylene group. Monomer a2 preferably has an oxyethylene group. Monomer a2 having an oxyethylene group is represented, for example, by the following formula (1):

[0049] R in formula (1) 1 is a hydrogen atom or a methyl group. 2 is a hydrocarbon group. In a preferred example, the hydrocarbon group is an alkyl group. The alkyl group may be linear or branched. Examples of the alkyl group are a methyl group and an ethyl group. In another preferred example, the hydrocarbon group contains a carbon ring. Examples of the carbon ring are the same as those mentioned above in the description of the double bond-containing ring. An example of a hydrocarbon group containing a carbon ring is a phenyl group.

[0050] In formula (1), n ​​is an integer of 1 to 30, preferably an integer of 1 to 12, and may be an integer of 1 to 5.

[0051] Examples of monomer a2 include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and methoxydipropylene glycol (meth)acrylate. Monomer a2 is preferably 2-methoxyethyl acrylate (MEA), 2-(2-ethoxyethoxy)ethyl acrylate (CBA), or the like.

[0052] The content of monomer a2 relative to 100 parts by weight of monomer component M may be, for example, 50 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, or even 10 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. Monomer component M may not contain monomer a2.

[0053] <1-1-d. Other Monomers> The monomer component M may contain other monomers in addition to the hydroxyl group-containing monomer, monomer a1, and monomer a2. An example of the other monomer 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, 2-ethylhexyl (meth)acrylate, and the like. 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.

[0054] The content of the (meth)acrylic acid alkyl ester per 100 parts by weight of the monomer component M may be, for example, 25 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, 7 parts by weight or less, 5 parts by weight or less, or even 4 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 a (meth)acrylic acid alkyl ester.

[0055] 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.

[0056] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer a1. The carboxyl group-containing monomer may be a (meth)acrylic monomer.

[0057] 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 per 100 parts by weight of the monomer component M may be, for example, 10 parts by weight or less, 7 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less, or even 1 part 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 a carboxyl group-containing monomer.

[0058] <1-2. Partial Polymer A> The PSA 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 can contribute to the stable formation of a coating layer, which will be described later, by appropriately increasing the viscosity of the PSA composition. Note that the PSA composition does not necessarily need to contain the partial polymer A.

[0059] 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 measured by GPC (gel permeation chromatography) and calculated in polystyrene equivalent.

[0060] <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.

[0061] 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.

[0062] 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.

[0063] The material of the inorganic particles may be a high-entropy alloy in which multiple types of elements are mixed.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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 on a monolayer film of the material using a commercially available spectroscopic ellipsometer under conditions of 23°C and 549 nm. The spectroscopic ellipsometer may be, for example, an "EC-400" (manufactured by J.A. Woollam) or an equivalent.

[0068] 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.

[0069] The content of the inorganic particles relative to 100 parts by weight of the monomer component M is, for example, 10 parts by weight or more, and may be 30 parts by weight or more, 50 parts by weight or more, 80 parts by weight or more, 85 parts by weight or more, 90 parts by weight or more, 95 parts by weight or more, or even 100 parts by weight or more. The upper limit of the content may be, for example, 200 parts by weight or less, 180 parts by weight or less, 150 parts by weight or less, or even 130 parts by weight or less. The content is preferably 80 to 130 parts by weight.

[0070] <1-4. Dispersant> As described above, the PSA composition contains a dispersant. The dispersant is a component for sufficiently dispersing 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.

[0071] 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.

[0072] The hydrophilic portion of the dispersant preferably has a hydrophilic group, such as an ether group or an ester group.

[0073] 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 may be 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.

[0074] 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 include, 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 located on a side chain of a chain structure whose one end is linked to the hydrophobic portion; or a structure in which a functional group F is not located on the other end of a chain structure whose one end is linked to the hydrophobic portion (for example, the other end of the chain structure is open). The dispersant may have two or more of the above structures.

[0075] The dispersant may be an aliphatic compound, for example, represented by the following formula (2):

[0076] In formula (2), 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.

[0077] The dispersant may be an aromatic compound having an aromatic ring, for example, represented by the following formula (3):

[0078] In formula (3), 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.

[0079] In formula (3), R 1 may be a styrenated phenyl group represented by the following formula (4):

[0080] In formula (4), k is an average value and is 1 to 5. For example, k is 2 to 4, and may be 3.

[0081] In formula (3), 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.

[0082] In formula (3), X may be an O atom.

[0083] In formula (3), Y is, for example, an alkylene group having 1 to 15 carbon atoms, or a functional group represented by the following formula (5).

[0084] Z in formula (5) 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.

[0085] In formula (3), 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.

[0086] The aromatic ring in the dispersant may be the same as the examples given above in the description of monomer a1.

[0087] 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.

[0088] The content of the dispersant relative to 100 parts by weight of inorganic particles may be, 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 may be, for example, 30 parts by weight or less, 20 parts by weight or less, or even 10 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.

[0089] The content of the dispersant relative to 100 parts by weight of the monomer component M may be, for example, 0.1 parts by weight or more, 1 part by weight or more, or even 3 parts by weight or more. The upper limit of the content may be, for example, 20 parts by weight or less, 10 parts by weight or less, or even 8 parts by weight or less.

[0090] <1-5. Other Components> <1-5-a. Polymer B> The PSA composition may further contain 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 PSA sheet and can function as a tackifier. In this specification, polymer B may be referred to as an oligomer.

[0091] 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 may be 2,000 or more, or may be 2,500 or more, 3,000 or more, 3,500 or more, or even 4,000 or more. The weight average molecular weight is preferably 2,000 to 16,000. The weight average molecular weight of polymer B can be determined by the method described above for partial polymer A.

[0092] 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 a1. Monomer b may be the same as or different from monomer a1.

[0093] 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.

[0094] The content of the structural unit 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 unit derived from monomer b.

[0095] 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 (for example, hydroxyl group-containing monomers).

[0096] The content of the structural unit derived from the hydroxyl group-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 any structural unit derived from the hydroxyl group-containing monomer.

[0097] Polymer B can be produced by known polymerization methods such as various radical polymerizations, including solution polymerization, radiation polymerization, bulk polymerization, emulsion polymerization, and polymerization under supercritical conditions. Examples of radiation that can be used for radiation polymerization include 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.

[0098] The content of polymer B relative to 100 parts by weight of monomer component M is, for example, 0.1 parts by weight or more, and may be 0.5 parts by weight or more, 1 part by weight or more, 2 parts by weight or more, 5 parts by weight or more, 8 parts by weight or more, or even 10 parts by weight or more. The upper limit of the content may be, for example, 50 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, or even 20 parts by weight or less. The content is preferably 0.1 to 20 parts by weight.

[0099] <1-5-b. Silane Coupling Agent> 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.

[0100] The content of the silane coupling agent relative to 100 parts by weight of the monomer component M may be, for example, 5 parts by weight or less, 3 parts by weight or less, 1 part by weight or less, or even 0.8 parts by weight or less. The lower limit of the content may be, for example, 0.01 parts by weight or more, or even 0.05 parts by weight or more. The pressure-sensitive adhesive composition may not contain a silane coupling agent.

[0101] <1-5-c. Antioxidant> The PSA composition may contain an antioxidant. Examples of the antioxidant include phenol-based antioxidants, hindered phenol-based antioxidants, amine-based antioxidants, and phosphite-based antioxidants.

[0102] Examples of the phenolic antioxidants include monophenolic antioxidants, bisphenolic antioxidants, and polymeric phenolic antioxidants. Examples of the monophenolic antioxidants 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 the polymeric phenolic antioxidant are 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.

[0103] The hindered phenolic antioxidant may have a structure in which a tertiary butyl group is bonded to at least one carbon atom adjacent to the carbon atom on the aromatic ring to which the phenolic OH group is bonded. Examples of the hindered phenolic antioxidant include dibutylhydroxytoluene (BHT); Irganox 1010, Irganox 1010FF, Irganox 1035, Irganox 1035FF, Irganox 1076, Irganox 1076FD, Irganox 1076DWJ, Irganox 1098, Irganox 109 ... Irganox 1135, Irganox 1330, Irganox 1726, Irganox 1425WL, Irganox 1520L, Irganox 245, Irganox 245FF, Irganox 259, Irganox 3114, Irganox 565 and Irganox 295 (all of which are trade names manufactured by BASF).

[0104] 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 hindered amine antioxidants include Adeka STAB LA-63, Adeka STAB LA-63P, Adeka STAB LA-52, and Adeka STAB LA-57 (all of which are trade names, manufactured by ADEKA Corporation).

[0105] 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).

[0106] The content of the antioxidant relative to 100 parts by weight of the monomer component M may be, for example, 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 may be, for example, 0.01 parts by weight or more, 0.05 parts by weight or more, or even 0.1 parts by weight or more. The pressure-sensitive adhesive composition may not contain an antioxidant.

[0107] <1-5-d. Other Additives> The PSA composition may contain additives other than those described above. Examples of the additives include ultraviolet absorbers (UVAs), chain transfer agents, viscosity modifiers, tackifiers, plasticizers, softeners, antioxidants, fillers, colorants, surfactants, and antistatic agents.

[0108] <1-6. Curing Type> <1-6-a. Photocuring Type> The pressure-sensitive adhesive composition is typically a photocuring type pressure-sensitive adhesive composition that forms a pressure-sensitive adhesive sheet by irradiation with light. Note that being a photocuring type is particularly preferred from the perspective of environmental protection and sustainability, since the amount of energy required to form a pressure-sensitive adhesive sheet can be reduced compared to a thermosetting type that forms a pressure-sensitive adhesive sheet mainly by utilizing heat.

[0109] The photocurable pressure-sensitive adhesive composition may contain, in addition to the above-mentioned additives, a photopolymerization initiator, a crosslinking agent, etc. The photopolymerization initiator may be a photoradical generator that generates radicals when exposed to visible light and / or ultraviolet light having a wavelength shorter than 450 nm.

[0110] Examples of the photopolymerization initiator include benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzil dimethyl ketal; substituted benzoin ethers such as anisole methyl ether; substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; α-hydroxyalkylphenones such as 1-hydroxycyclohexyl-phenyl ketone; substituted alpha-ketol 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 , 2-piperonyl-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxy-naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6-triazine, 2,4-trichloromethyl-(4'-methoxystyryl)-6-triazine and other triazine-based compounds;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.

[0111] 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).

[0112] The content of the photopolymerization initiator relative to 100 parts by weight of the monomer component M 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.

[0113] 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.

[0114] Examples of polyfunctional monomers include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol diacrylate (N Polyfunctional acrylates (such as ester compounds of polyhydric alcohols and (meth)acrylic acid) such as 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, and hexyl di(meth)acrylate. The polyfunctional monomer is preferably a polyfunctional acrylate, and more preferably trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, or dipentaerythritol hexa(meth)acrylate.

[0115] The content of the crosslinking agent relative to 100 parts by weight of the monomer component M may be, 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 may be, 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.

[0116] The solvent content in the photocurable pressure-sensitive adhesive composition is, for example, 5 wt% or less, and may be 4 wt% or less, 3 wt% or less, 2 wt% or less, 1 wt% or less, or even 0.5 wt% or less. The pressure-sensitive adhesive composition may be substantially free of solvent. "Substantially free of solvent" means that solvents derived from additives and the like are allowed at a content of, for example, 0.1 wt% or less, preferably 0.05 wt% or less, and more preferably 0.01 wt% or less.

[0117] The viscosity of the photocurable pressure-sensitive adhesive composition is preferably 5 to 150 poise at 25° C. A pressure-sensitive adhesive composition having a viscosity within the above range is particularly suitable for forming a coating layer, which will be described later.

[0118] The photocurable 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 vacuum removal can be used. Next, the remaining monomers and additives such as a photopolymerization initiator are added to the dispersion and mixed. This allows the photocurable pressure-sensitive adhesive composition to be prepared.

[0119] <1-6-b. Thermosetting type> The pressure-sensitive adhesive composition may be a thermosetting type pressure-sensitive adhesive composition that forms a pressure-sensitive adhesive sheet by utilizing heat. The thermosetting type pressure-sensitive adhesive composition may contain a base polymer instead of the above-mentioned monomer component M. The base polymer is typically a polymer of the monomer component M.

[0120] The thermosetting adhesive composition may contain a crosslinking agent, a solvent, etc. in addition to the above-mentioned additives. Examples of the crosslinking agent include an isocyanate-based crosslinking agent, a peroxide-based crosslinking agent, an epoxy-based crosslinking agent, an imine-based crosslinking agent, and a polyfunctional metal chelate. The thermosetting adhesive composition preferably contains an isocyanate-based crosslinking agent and / or a peroxide-based crosslinking agent, and more preferably contains an isocyanate-based crosslinking agent.

[0121] The amount of the crosslinking agent in the thermosetting adhesive composition is, for example, 0.01 to 20 parts by weight per 100 parts by weight of the base polymer.

[0122] <<2. Pressure-sensitive adhesive sheet>> <<2-1. Pressure-sensitive adhesive sheet>> An example of a pressure-sensitive adhesive sheet according to an embodiment of the present invention is shown in Fig. 1. Pressure-sensitive adhesive sheet 1 in Fig. 1 is a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition.

[0123] 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.

[0124] 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.

[0125] 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, 1.69 or less, 1.68 or less, 1.67 or less, or even 1.66 or less. The refractive index of the pressure-sensitive adhesive sheet 1 is preferably 1.63 to 1.66. Some optical substrates that can be provided 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.

[0126] In this specification, the refractive index of the pressure-sensitive adhesive sheet 1 refers to the refractive index of the surface of the pressure-sensitive adhesive sheet 1. The refractive index of the pressure-sensitive 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 pressure-sensitive adhesive sheets 1 with a thickness of less than 20 μm, measurement in the light propagation mode is generally suitable. For pressure-sensitive 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, and for example, a Model 2010 / M prism coupler manufactured by Metricon or an equivalent can be used.

[0127] The adhesive sheet 1 preferably has an adhesive strength to alkali-free glass of 0.5 N / 25 mm or more, and may be 0.8 N / 25 mm or more, 1.0 N / 25 mm or more, 1.3 N / 25 mm or more, 1.5 N / 25 mm or more, 1.8 N / 25 mm or more, 2.0 N / 25 mm or more, 2.3 N / 25 mm or more, or even 2.5 N / 25 mm or more. The upper limit of the adhesive strength may be, for example, 30.0 N / 25 mm or less, 10.0 N / 25 mm or less, or even 5.0 N / 25 mm or less.

[0128] 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. 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 an optical film described below, and the laminate may be an optical laminate. Next, the laminate is cut into a strip measuring 150 mm in length and 25 mm in width to prepare a test piece. Next, the test piece is attached to alkali-free glass via the pressure-sensitive adhesive sheet 1. 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, and has a thickness of 0.5 mm or more.

[0129] The test piece is attached to the alkali-free glass using, for example, a laminator, taking care not to trap air bubbles between the alkali-free glass and the adhesive sheet 1. After attaching the test piece, the test piece is placed in an autoclave at 50°C and 5 atmospheres (absolute pressure) for 15 minutes to homogenize the bond between the alkali-free glass and the adhesive sheet 1, and to adhere the adhesive sheet 1 to the alkali-free glass. Next, the test piece is peeled from the alkali-free glass at a peel speed of 300 mm / min and a peel angle of 90° (measurement length: 80 mm). At this time, the force required to peel the test piece from the alkali-free glass is measured once every 0.5 s. The average of the obtained measurements is determined as the adhesive strength.

[0130] The Young's modulus of the pressure-sensitive adhesive sheet 1 is, for example, 0.1 to 5.0 MPa, and may be 0.5 to 3.5 MPa. The Young's modulus can be measured by the following method. First, the pressure-sensitive adhesive sheet 1 is cut into a strip measuring 100 mm in length and 30 mm in width to prepare a test piece. This test piece is set in a tensile tester, and a tensile test is performed under conditions of an initial chuck distance of 10 mm and a tensile speed of 300 mm / min. From the results of the tensile test, the ratio Δσ / Δε of the change in stress Δσ to the change in strain Δε in the elastic deformation region is determined and regarded as the Young's modulus.

[0131] The breaking strength of the pressure-sensitive adhesive sheet 1 is, for example, 3.0 MPa or less, and may be 2.5 MPa or less, 2.0 MPa or less, 1.5 MPa or less, 1.3 MPa or less, or even 1.0 MPa or less. The lower limit of the breaking strength is, for example, 0.1 MPa or more, and may be 0.5 MPa or more.

[0132] The breaking elongation of the pressure-sensitive adhesive sheet 1 is, for example, 320% or more, and may be 350% or more, 400% or more, 450% or more, 500% or more, 550% or more, 600% or more, 650% or more, or even 700% or more. The upper limit of the breaking elongation may be, for example, 1500% or less, 1000% or less, or even 900% or less. The breaking elongation is preferably 320% to 900%.

[0133] The breaking strength and breaking elongation of the pressure-sensitive adhesive sheet 1 can be measured by the following method. First, the pressure-sensitive adhesive sheet 1 is cut into a strip measuring 100 mm long x 30 mm wide to prepare a test piece. This test piece is set in a tensile tester, and a tensile test is performed under conditions of an initial chuck distance of 10 mm and a tensile speed of 300 mm / min until the test piece breaks. This allows the strength (breaking strength) and elongation (breaking elongation) at the time the test piece breaks to be measured.

[0134] 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.

[0135] <2-2. Manufacturing Method> The pressure-sensitive adhesive sheet 1 can be formed from the pressure-sensitive adhesive composition by a known method. When the pressure-sensitive adhesive composition is a photocurable type, the pressure-sensitive adhesive sheet 1 can be formed, for example, by irradiating light 14 onto a first laminate 10 including, 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 transmits through the base sheet 11 to reach 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.

[0136] 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 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.

[0137] 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 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.

[0138] 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 / cm 2 The illuminance is 2.5 mW / cm 2 Above, 3.0mW / cm 2 Above, 3.5mW / cm 2 Above, 4.0mW / cm 2 Above, 5.0mW / cm 2 Above, 6.0mW / cm 2 Above, 7.0mW / cm 2 Above, 8.0mW / cm 2 Above, 9.0mW / cm 2 or more, and even 10 mW / 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:

[0139] The time for irradiating the first laminate 10 (specifically, the coating layer 12) with the light 14 is, for example, 10 to 1,000 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. The irradiation with the light 14 may be continuous or intermittent.

[0140] 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 or more, and 100 mJ / cm 2 Above, 500mJ / cm 2 Above, 1000mJ / cm 2 Above, 2000mJ / cm 2 Above, 2500mJ / cm 2 Above, 3000mJ / cm 2 Above, 5000mJ / cm 2 Above, 7500mJ / cm 2 or more, and even 10,000 mJ / cm 2 The upper limit of the integrated light amount is not particularly limited, and may be, for example, 30,000 mJ / cm 2 or less, and 25,000 mJ / cm 2Below, 20000mJ / cm 2 Below, 18000 mJ / cm 2 It may be the following:

[0141] The light 14 may be irradiated onto the first laminate 10 in multiple stages. The illuminance and / or the integrated amount of light of the light 14 in each stage may be the same or different from each other. Furthermore, the light sources in each stage may be the same or different from each other.

[0142] An example of the substrate of the release liner 13 (hereinafter referred to as the "liner substrate") is a resin film. Examples of resins that can be contained in the liner substrate include polyesters such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resins, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, and polyphenylene sulfide. The resin is preferably a polyester such as polyethylene terephthalate.

[0143] 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.

[0144] The release liner 13 may be in the form of a sheet or a continuous piece.

[0145] An example of the substrate sheet 11 is a resin film. Examples of the resin contained in the substrate sheet 11 are the same as the examples of the resin that can be contained in the liner substrate.

[0146] The thickness of the base sheet 11 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

[0147] The base sheet 11 may have a release layer on the surface facing 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.

[0148] For the base sheet 11 , a sheet having a greater peel strength from the pressure-sensitive adhesive sheet 1 than the release liner 13 can usually be selected.

[0149] The base sheet 11 may be in the form of a sheet or a continuous sheet.

[0150] 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.

[0151] The coating layer 12 can be formed by various coating methods such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating.

[0152] The thickness of the coating layer 12 can be adjusted depending on the desired thickness of the PSA 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 the coating layer 12 is, for example, 2 μm or more, and may be 5 μm or more.

[0153] The first laminate 10 may include a long base sheet 11, a long coating layer 12, and a long release liner 13, or in other words, 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.

[0154] <<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 a pressure-sensitive adhesive sheet 1 and an optical film 2. The pressure-sensitive adhesive sheet 1 and the optical film 2 are laminated to each other. The optical laminate 20A can be used as an optical film with a pressure-sensitive adhesive sheet.

[0155] Examples of the optical film 2 include a polarizing film, a retardation film, and a laminate 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.

[0156] 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 .

[0157] The polarizing film includes a polarizer. The polarizing film typically includes a polarizer and a protective film (transparent protective film). The protective film is disposed, for example, in contact with a main surface (the surface having the largest area) of the polarizer. The polarizer may be disposed between two protective films. The protective film may be disposed on at least one surface of the polarizer.

[0158] The polarizer is not particularly limited, and examples thereof include a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partially saponified film, which has been uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye; a polyene-based oriented film such as a dehydrated polyvinyl alcohol or a dehydrochlorinated polyvinyl chloride; etc. A polarizer typically comprises a polyvinyl alcohol film (polyvinyl alcohol films include an ethylene-vinyl acetate copolymer partially saponified film) and a dichroic substance such as iodine.

[0159] The thickness of the polarizer is not particularly limited and may be, for example, 80 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 18 μm or less, 15 μm or less, or even 12 μm or less. The lower limit of the polarizer thickness is not particularly limited and may be, for example, 1 μm or more, 5 μm or more, or even 10 μm or more. In some cases, the lower limit of the polarizer thickness may be 15 μm or more. A thin polarizer (for example, a thickness of 20 μm or less) has reduced dimensional change and can contribute to improving the durability of the optical laminate, particularly durability at high temperatures.

[0160] The polarizer preferably exhibits absorptive dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 42.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

[0161] The polarizer can be produced by any appropriate method. Specifically, the polarizer may be produced from a single-layer resin film or a laminate of two or more layers.

[0162] A method for producing a polarizer from the above-mentioned single-layer resin film typically includes subjecting the resin film to a dyeing treatment with a dichroic substance such as iodine or a dichroic dye and a stretching treatment. Examples of the resin film that can be used include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and partially saponified ethylene-vinyl acetate copolymer-based films. This method may further include an insolubilization treatment, a swelling treatment, a crosslinking treatment, and the like. Such production methods are well known and commonly used in the art, and therefore a detailed description thereof will be omitted.

[0163] A polarizer obtained using the laminate can be produced, for example, using a laminate of a resin substrate and a resin film or resin layer (typically, a PVA-based resin layer). Specifically, a polarizer can be produced by applying a PVA-based resin solution to a resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; and stretching and dyeing the laminate to convert the PVA-based resin layer into a polarizer. In this embodiment, a PVA-based resin layer containing a halide and a PVA-based resin is preferably formed on one side of the resin substrate. The stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, the stretching may optionally further include in-air stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution. In addition, in this embodiment, the laminate is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being transported in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes subjecting a laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching treatment, it is possible to increase the crystallinity of the PVA, even when the PVA is coated on a thermoplastic resin, thereby achieving high optical properties. Furthermore, by simultaneously increasing the orientation of the PVA in advance, problems such as a decrease in orientation or dissolution of the PVA when immersed in water in the subsequent dyeing or stretching steps can be prevented, thereby achieving high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the PVA molecular orientation disorder and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide, thereby achieving high optical properties. Furthermore, by shrinking the laminate in the width direction by a drying shrinkage treatment, high optical properties can be achieved. A polarized film can be obtained by laminating a protective film on the peeled surface of the obtained resin substrate / polarizer laminate after peeling the resin substrate, or on the surface opposite to the peeled surface. Details of such a method for manufacturing a polarizer are described in, for example, JP 2012-73580 A and Japanese Patent No. 6470455. The entire disclosures of these publications are incorporated herein by reference.

[0164] The material for the protective film may be, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture-blocking properties, isotropy, etc. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene-based resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material for the protective film may be a thermosetting resin or an ultraviolet-curable resin such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone-based resin. When the polarizing film has two protective films, the materials of the two protective films may be the same or different. For example, a protective film made of a thermoplastic resin may be bonded to one main surface of the polarizer via an adhesive, and a protective film made of a thermosetting resin or an ultraviolet-curable resin may be bonded to the other main surface of the polarizer. The protective film may contain one or more optional additives, such as ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

[0165] The thickness of the protective film can be determined as appropriate, but is generally about 10 to 200 μm in view of strength, workability such as handling, thinness, and the like.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] The polarizing film may be a circular polarizing film.

[0170] 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.

[0171] The retardation film is a film having birefringence in the in-plane direction and / or the thickness direction, and is, for example, a stretched resin film or a film in which a liquid crystal material is oriented and fixed.

[0172] The retardation film may be a λ / 4 plate, a λ / 2 plate, an anti-reflection retardation film (see, for example, paragraphs 0221, 0222, and 0228 of JP 2012-133303 A), a viewing angle compensation retardation film (see, for example, paragraphs 0225 and 0226 of JP 2012-133303 A), or an inclined orientation retardation film for viewing angle compensation (see, for example, paragraph 0227 of JP 2012-133303 A). The retardation film is not limited to the above examples as long as it has birefringence in the in-plane direction and / or the thickness direction. There are also no limitations on the retardation value, arrangement angle, three-dimensional birefringence, whether the retardation film is single-layer or multi-layer, etc. of the retardation film. Known films can be used as the retardation film.

[0173] The thickness of the optical film 2 is, for example, 1 to 200 μm.

[0174] 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.

[0175] 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.

[0176] The release liner 3 is typically a resin film. Examples of resins that make up the release liner 3 include polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene and polypropylene, polycarbonate, acrylic, polystyrene, polyamide, and polyimide. The surface of the release liner 3 that comes into contact with the pressure-sensitive adhesive sheet 1 may be subjected to a release treatment. The release treatment is, for example, a treatment with a silicone compound. However, the release liner 3 is not limited to the above examples. The release liner 3 is peeled off when the optical laminate 20B is used, for example, when it is attached to the image forming layer.

[0177] 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.

[0178] A known adhesive sheet can be used as the adhesive sheet 4. The adhesive sheet 1 may also be used as the adhesive sheet 4.

[0179] 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 the release liner 3, optical laminate 20D can be used by being attached to, for example, an image-forming layer.

[0180] The protective film 5 has the function of protecting the optical film 2 (polarizing film 2A), which is the outermost layer, during distribution and storage of the optical laminate 20D and when the optical laminate 20D is incorporated into an image display device. The protective film 5 may also function as a window to the external space when incorporated into an image display device. The protective film 5 is typically a resin film. Examples of resins constituting the protective film 5 include polyesters such as PET, polyolefins such as polyethylene and polypropylene, acrylics, cycloolefins, polyimides, and polyamides, with polyesters being preferred. However, the protective film 5 is not limited to the above examples. The protective film 5 may be a glass film or a laminate film including a glass film. The protective film 5 may be subjected to surface treatments such as anti-glare, anti-reflection, and anti-static.

[0181] The protective film 5 may be bonded to the optical film 2 by any adhesive. Bonding by an adhesive sheet 1 is also possible.

[0182] Another example of an optical laminate according to an embodiment of the present invention is shown in Fig. 7. The optical laminate 20E in Fig. 7 has a layered structure in which a polarizing film 2A, a first adhesive layer 30, a first retardation film 2B, a second adhesive layer 35, a second retardation film 2C, a pressure-sensitive adhesive sheet 1, and a release liner 3 are layered in this order. After the release liner 3 is peeled off, the optical laminate 20E can be used by being attached to, for example, an image forming layer.

[0183] In the optical laminate 20E, the polarizing film 2A has a laminated structure in which a first protective film 26A, a polarizer 25, and a second protective film 26B are laminated in this order.

[0184] The first protective film 26A can be formed of, for example, any appropriate resin film that can be used as a protective layer for the polarizer 25. Specific examples of resins that serve as the main component of the resin film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based resins, polyvinyl alcohol-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyethersulfone-based resins, polysulfone-based resins, polystyrene-based resins, cycloolefin-based resins such as polynorbornene, polyolefin-based resins, (meth)acrylic resins, and acetate-based resins.

[0185] The optical laminate 20E is typically disposed on the viewing side of an image display device (e.g., an organic EL display device), and the first protective film 26A is disposed on the viewing side. Therefore, the first protective film 26A may be subjected to surface treatment such as hard coat (HC) treatment, anti-reflection treatment, anti-sticking treatment, anti-glare treatment, etc., as needed.

[0186] The thickness of the first protective film 26A is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and even more preferably 15 μm to 35 μm. If the above-mentioned surface treatment is applied, the thickness of the first protective film 26A includes the thickness of the surface treatment layer.

[0187] The second protective film 26B can be formed of, for example, any appropriate resin film that can be used as a protective layer for the polarizer 25. When the second protective film 26B is formed of a resin film, the same explanation as for the first protective film 26A can be applied. Furthermore, for example, the second protective film 26B can be a solidified or cured layer of a coating film of an organic solvent solution containing a resin. When the second protective film 26B is a solidified or cured layer of a coating film of an organic solvent solution containing a resin, adhesion to the polarizer 25 can be improved.

[0188] In one embodiment, the resin (base polymer) forming the solidified or cured layer may have a glass transition temperature (Tg) of 85°C or higher and a weight average molecular weight (Mw) of 25,000 or higher. By having the Tg and Mw of the resin within these ranges, excellent durability can be achieved in high-temperature, high-humidity environments despite a very thin thickness. The Tg of the resin is preferably 90°C or higher, more preferably 100°C or higher, even more preferably 110°C or higher, and particularly preferably 120°C or higher. The Tg may be, for example, 200°C or lower. The Mw of the resin is preferably 30,000 or higher, more preferably 35,000 or higher, and even more preferably 40,000 or higher. The Mw may be, for example, 150,000 or lower.

[0189] As the resin, any suitable resin can be used as long as it can form a solidified or cured product (e.g., a thermoset product) of the coating film of the organic solvent solution. Thermoplastic resins or thermosetting resins having the above-mentioned Tg and Mw are preferred, and thermoplastic resins are more preferred. Only one type of resin may be used, or two or more types may be used in combination.

[0190] Examples of thermoplastic resins include acrylic resins and epoxy resins. Acrylic resins and epoxy resins may be used in combination.

[0191] Acrylic resins typically contain, as their main component, repeating units derived from (meth)acrylic acid ester monomers having a linear or branched structure. Acrylic resins may contain repeating units derived from any appropriate copolymerizable monomer depending on the purpose. Examples of copolymerizable monomers (comonomers) include carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocyclic ring-containing vinyl monomers. By appropriately setting the type, number, combination, and copolymerization ratio of the monomer units, an acrylic resin having the above-mentioned predetermined Mw can be obtained. Specific examples of acrylic resins include boron-containing acrylic resins and lactone ring-containing acrylic resins described in

[0034] to

[0056] of JP 2021-117484 A.

[0192] As the epoxy resin, an epoxy resin having an aromatic ring is preferably used. By using an epoxy resin having an aromatic ring as the epoxy resin, the adhesion between the second protective film 26B and the polarizer 25 can be improved. Furthermore, the anchoring strength of the first adhesive layer 30 adjacent to the second protective film 26B can be improved. Examples of epoxy resins having an aromatic ring include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and bisphenol S-type epoxy resins; novolac-type epoxy resins such as phenol novolac epoxy resins, cresol novolac epoxy resins, and hydroxybenzaldehyde phenol novolac epoxy resins; multifunctional epoxy resins such as glycidyl ether of tetrahydroxyphenylmethane, glycidyl ether of tetrahydroxybenzophenone, and epoxidized polyvinylphenol; naphthol-type epoxy resins, naphthalene-type epoxy resins, and biphenyl-type epoxy resins. Bisphenol A-type epoxy resins, biphenyl-type epoxy resins, and bisphenol F-type epoxy resins are preferably used. Only one type of epoxy resin may be used, or two or more types may be used in combination.

[0193] The second protective film 26B can be formed by applying an organic solvent solution of the resin to form a coating film, and then solidifying or thermally curing the coating film. Any suitable organic solvent capable of dissolving or uniformly dispersing an acrylic resin or epoxy resin can be used as the organic solvent. Specific examples of organic solvents include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone. The resin concentration of the solution is preferably 3 to 20 parts by weight per 100 parts by weight of the solvent. Such a resin concentration allows for the formation of a uniform coating film.

[0194] The solution may be applied to any suitable substrate or to the polarizer 25. When the solution is applied to the substrate, the solidified or cured product (resin layer) of the coating film formed on the substrate is transferred to the polarizer 25. When the solution is applied to the polarizer 25, the second protective film 26B is formed directly on the polarizer 25 by drying (solidifying) or curing the coating film. Preferably, the solution is applied to the polarizer 25, and the second protective film 26B is formed directly on the polarizer 25. This configuration eliminates the need for an adhesive or pressure-sensitive adhesive layer required for transfer, thereby enabling the polarizing film 2A to be made even thinner. Any suitable method can be used to apply the solution. Specific examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (such as comma coating).

[0195] The second protective film 26B can be formed by solidifying or thermally curing the applied film of the solution. The heating temperature for solidification or thermal curing is preferably 100°C or lower, and more preferably 50°C to 70°C. If the heating temperature is within this range, adverse effects on the polarizer 25 can be prevented. The heating time can vary depending on the heating temperature. The heating time can be, for example, 1 minute to 10 minutes.

[0196] The second protective film 26B (essentially, the organic solvent solution of the resin) may contain any suitable additive depending on the purpose. Specific examples of additives include ultraviolet absorbers; leveling agents; hindered phenol-based, phosphorus-based, sulfur-based, and other antioxidants; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fiber and carbon fiber; near-infrared absorbers; flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic or inorganic fillers; resin modifiers; organic or inorganic fillers; plasticizers; lubricants; and flame retardants. The type, number, combination, and amount of additives can be appropriately determined depending on the purpose.

[0197] When the second protective film 26B is a solidified or hardened layer of a coating film of an organic solvent solution containing a resin, the thickness of the second protective film 26B is preferably 0.05 μm to 10 μm, more preferably 0.08 μm to 5 μm, even more preferably 0.1 μm to 1 μm, and particularly preferably 0.2 μm to 0.7 μm.

[0198] The first retardation film 2B may have any appropriate optical and / or mechanical properties depending on the purpose. The first retardation film 2B typically has a slow axis. In one embodiment, the angle θ between the slow axis of the first retardation film 2B and the absorption axis of the polarizer 25 is, for example, 40° to 50°, preferably 42° to 48°, and more preferably about 45°. If the angle θ is within this range, by using a λ / 4 plate as the first retardation film 2B, an optical laminate 20E having excellent circular polarization properties (and, as a result, excellent antireflection properties) can be obtained.

[0199] The first retardation film 2B preferably has a refractive index characteristic that satisfies the relationship nx>ny≧nz. In one embodiment, the first retardation film 2B can function as a λ / 4 plate. In this case, the in-plane retardation Re(550) of the first retardation film 2B is, for example, 100 nm to 190 nm, preferably 110 nm to 170 nm, and more preferably 130 nm to 160 nm. Note that "ny = nz" here encompasses not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, there may be cases where ny < nz, as long as the effects of the present invention are not impaired.

[0200] The Nz coefficient of the first retardation film 2B is preferably 0.9 to 3, more preferably 0.9 to 2.5, even more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. By satisfying such a relationship, when the obtained optical laminate 20E is used in an image display device, an extremely excellent reflected hue can be achieved.

[0201] The first retardation film 2B may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases with the wavelength of the measurement light, a positive wavelength dispersion characteristic in which the retardation value decreases with the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which the retardation value hardly changes with the wavelength of the measurement light. In one embodiment, the first retardation film 2B exhibits a reverse dispersion wavelength characteristic. In this case, the Re(450) / Re(550) of the first retardation film 2B is, for example, 0.8 or more and less than 1, preferably 0.8 or more and 0.95 or less. With such a configuration, extremely excellent antireflection properties can be achieved.

[0202] The absolute value of the photoelastic coefficient of the first retardation film 2B is preferably 2×10 -11 m 2 / N or less, more preferably 2.0 × 10 -13 m 2 / N ~ 1.5 x 10 -11 m 2 / N, more preferably 1.0 × 10 -12 m 2 / N ~ 1.2 × 10 -11 m 2 When the absolute value of the photoelastic coefficient is in this range, the retardation is less likely to change when shrinkage stress occurs during heating. As a result, thermal unevenness in the resulting image display device can be effectively prevented.

[0203] The first retardation film 2B is typically made of a stretched resin film. The thickness of the first retardation film 2B is, for example, 70 μm or less, preferably 60 μm or less, more preferably 10 μm to 50 μm, and even more preferably 20 μm to 45 μm. If the thickness of the first retardation film 2B is within this range, good bendability can be ensured, making it suitable for flexible applications.

[0204] The first retardation film 2B can be composed of any appropriate resin film that can satisfy the above characteristics. Typical examples of such resins include polycarbonate-based resins, polyester carbonate-based resins, polyester-based resins, polyvinyl acetal-based resins, polyarylate-based resins, cyclic olefin-based resins, cellulose-based resins, polyvinyl alcohol-based resins, polyamide-based resins, polyimide-based resins, polyether-based resins, polystyrene-based resins, and acrylic-based resins. These resins may be used alone or in combination (e.g., blended or copolymerized). When the first retardation film 2B is composed of a resin film that exhibits reverse dispersion wavelength characteristics, polycarbonate-based resins or polyester carbonate-based resins (hereinafter sometimes simply referred to as polycarbonate-based resins) can be suitably used.

[0205] As the polycarbonate-based resin, any suitable polycarbonate-based resin can be used as long as the effects of the present invention can be obtained. For example, the polycarbonate-based resin contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanols, di-, tri-, or polyethylene glycols, and alkylene glycols or spiroglycols. Preferably, the polycarbonate-based resin contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, structural units derived from an alicyclic dimethanol and / or structural units derived from di-, tri-, or polyethylene glycol; more preferably, it contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from di-, tri-, or polyethylene glycol. The polycarbonate-based resin may contain structural units derived from other dihydroxy compounds as needed. Details of polycarbonate-based resins that can be suitably used for the first retardation film 2B and methods for forming the first retardation film 2B are described in, for example, JP 2014-10291 A, JP 2014-26266 A, JP 2015-212816 A, JP 2015-212817 A, and JP 2015-212818 A, the descriptions of which are incorporated herein by reference.

[0206] In one embodiment, an organic solvent is brought into contact with the surface of the first retardation film 2B facing the second adhesive layer 35, and then the second adhesive layer 35 is provided on the contact surface. This allows a compatible region in which the composition continuously changes toward the second adhesive layer 35 side of the first retardation film 2B. The formation of a compatible region in which the components of the first retardation film 2B and the components of the second adhesive layer 35 are compatible can improve the adhesion between the first retardation film 2B and the second retardation film 2C. On the other hand, from the viewpoint of strictly suppressing moisture penetration into the first retardation film 2B, it is preferable not to provide a compatible region. Therefore, it is preferable to form the compatible region as needed, taking into account the adhesion strength between the first retardation film 2B and the second retardation film 2C, the application or use environment of the optical laminate 20E, etc. Details of the method for forming the compatible region are described in JP 2019-56820 A, the disclosure of which is incorporated herein by reference.

[0207] The second retardation film 2C can be typically a so-called positive C plate whose refractive index characteristics satisfy the relationship nz > nx = ny. By using a positive C plate as the second retardation film 2C, reflection in oblique directions can be effectively prevented, and the anti-reflection function can be extended to a wide viewing angle.

[0208] The thickness direction retardation Rth(550) of the second retardation film 2C is preferably −50 nm to −300 nm, more preferably −70 nm to −250 nm, even more preferably −90 nm to −200 nm, and particularly preferably −100 nm to −180 nm. Here, "nx = ny" encompasses not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the second retardation film 2C can be less than 10 nm.

[0209] The second retardation film 2C having the refractive index characteristic of nz > nx = ny can be formed from any appropriate material. The second retardation film 2C is preferably made of a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the second retardation film 2C include the liquid crystal compound and the method for forming the retardation layer described in paragraphs

[0020] to

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

[0210] Any appropriate adhesive may be used as the adhesive constituting the first adhesive layer 30 and the second adhesive layer 35. Examples of the adhesive include those described above for the optical laminate 20A.

[0211] The optical laminate may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and the optical film 2 .

[0212] 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.

[0213] 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.

[0214] The optical laminate according to the embodiment of the present invention is typically used in an image display device, such as a liquid crystal display, an EL display such as an organic EL display, or an inorganic EL display.

[0215] <<4. Image Display Device>> An example of an image display device according to an embodiment of the present invention is shown in Figure 8. The image display device 21 of Figure 8 has a layered structure in which a substrate 7, an image forming layer (e.g., an organic EL layer or a liquid crystal layer) 6, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, a polarizing film 2A, and a protective film 5 are layered in this order. The image display device 21 has the optical laminate 20D of Figure 6 (excluding the release liner 3). The image display device 21 may have the optical laminates 20A, 20B, 20C, and 20E of Figures 3 to 5 and 7 instead of the optical laminate 20D. The substrate 7 and the image forming layer 6 may have the same configurations as the substrate and the image forming layer, respectively, of known image display devices.

[0216] The image display device 21 in Fig. 8 may be an organic EL display or a liquid crystal display. However, the image display device 21 is not limited to this example. The image display device 21 may also be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), or the like. The image display device 21 may be used for home appliances, in-vehicle applications, public information displays (PID), and the like.

[0217] 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 .

[0218] 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.

[0219] <Preparation of Dispersion D1> [Synthesis of Dispersant d1] 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 reaction system obtained was heated to 130 ° C., and 352 g (8 mol) of ethylene oxide (EO) was added dropwise. After the dropwise addition was completed, the pressure was maintained at 0.1 MPa at 130 ° C. and the mixture was aged for 1 hour to obtain an EO 8 mol adduct of tristyrenated phenol. Next, 767 g (1 mol) of the obtained EO 8 mol adduct of tristyrenated phenol and 152 g (1.3 mol) of sodium monochloroacetate were placed in a reactor and stirred to become uniform. Next, the reaction system was heated to 60 ° C. and 52 g of sodium hydroxide was added, followed by heating to 80 ° C. and aging 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 to obtain a white suspension. The resulting suspension was washed with distilled water, and the solvent was removed by distillation under reduced pressure to obtain dispersant d1 (R 1 = styrenephenyl group (in the above formula (4), k = 3, AO = oxyethylene group, n = 8, X = O, Y = methylene group).

[0220] [Preparation of Dispersion D1] 1.5 parts by weight of the above-mentioned Dispersant d1 and 28.5 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 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) determined by dynamic light scattering: 3 nm, zirconium oxide particle concentration: 30 wt %). 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 / 2.5 / 47.5.

[0221] [Preparation of Dispersion D2] 50 parts by mass of a methanol dispersion of zirconium oxide particles ("SZR-GM" manufactured by Sakai Chemical Industry Co., Ltd., average particle size (D50): approximately 10 nm as determined by dynamic light scattering) were mixed with 7 parts by mass of the above-mentioned Dispersant d, 4 parts by mass of a silane coupling agent ("KBM-103" manufactured by Shin-Etsu Chemical Co., Ltd.), 36 parts by mass of POB-A, and 3 parts by mass 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 D2, a dispersion of zirconium oxide. The contents of each component in Dispersion D2 are shown in Table 1. Dispersion D2 contained zirconium oxide particles / dispersant d1 / silane coupling agent / POB-A / P2HA in a weight ratio of 50 / 7 / 4 / 36 / 3.

[0222] <Preparation of Dispersion D3> [Synthesis of Dispersant d2] 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 d2 (a compound represented by the above formula (2) in which R is an ethyl group, m is 5, and n is 10).

[0223] [Preparation of Dispersion D3] 5 parts by weight of the above-mentioned Dispersant d2 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 size (D50) determined by dynamic light scattering: approximately 10 nm, zirconium oxide particle concentration: 30 wt %). Next, the solvent was removed under reduced pressure using a rotary evaporator to obtain Dispersion D3, a dispersion of zirconium oxide particles. Dispersion D3 contained zirconium oxide particles / Dispersant d2 / POB-A in a weight ratio of 50 / 5 / 45.

[0224] <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. Nitrogen gas was introduced while maintaining the temperature at 70°C and stirring gently, and the mixture was thoroughly purged with nitrogen for at least one hour. The liquid temperature in the flask was then maintained at 72-74°C, and a polymerization reaction was carried out for 6 hours to prepare a solution of Polymer B1. Next, the solution was heated at 90°C for 12 hours, and then subjected to reduced pressure treatment at 120°C for 3 hours to remove 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.

[0225] The weight-average molecular weight (Mw) of Polymer B1 was 4,000. The weight-average molecular weight (Mw) of Polymer B1 was measured by GPC (gel permeation chromatography). ・Analyzer: Alliance manufactured by Waters ・Column: TSKgel SuperHZM-H x 2 manufactured by Tosoh ・Column temperature: 40°C ・Eluent: THF ・Flow rate: 0.2 mL / min ・Injection volume: 30 μL ・Detector: Refractive index (RI) ・Standard sample: Polystyrene (PS) manufactured by Agilent

[0226] Example 1 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent, 1,2-diphenylethan-1-one (manufactured by IGM Resins, trade name "Omnirad 651") and 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins, trade name "Omnirad 184") as photopolymerization initiators, Irganox 1010 (manufactured by BASF) as an antioxidant, and 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicones, trade name "KBM-403") as a silane coupling agent were mixed with the above-mentioned dispersion D1 so that the contents of each component were as shown in Table 1. This gave a pressure-sensitive adhesive composition of Example 1.

[0227] (Examples 2 to 10 and Comparative Examples 1 to 5) PSA compositions of Examples 2 to 10 and Comparative Examples 1 to 5 were obtained by the same method as Example 1, except that the content of each component was changed as shown in Table 1. In Examples 6 to 8 and Comparative Examples 1 and 2, Dispersion D3 was used instead of Dispersion D1, and in Examples 9 and 10 and Comparative Example 5, Dispersion D2 was used instead of Dispersion D1. In Comparative Example 3, no dispersion was used. In Examples 3 to 5 and 10, and Comparative Examples 1 to 2 and 4 to 5, a monomer other than POB-A was further added to Dispersion D1, D2, or D3.

[0228] <Evaluation of Monomers> [Glass Transition Temperature (Tg) when Formed into a Homopolymer] For each monomer contained in the pressure-sensitive adhesive compositions of Examples and Comparative Examples, the Tg when formed into a homopolymer was measured by the following method. First, 0.04 parts by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins, trade name "Omnirad 819") as a photopolymerization initiator was added to 100 parts by weight of the monomer, and the mixture was stirred. The obtained coating liquid was applied between two release liners to prepare a coating layer (thickness 1 mm). The coating layer was then irradiated with ultraviolet light (illuminance 2.5 mW / cm) from a black light source. 2 ) for 16 minutes. As a result, the coating layer was photocured to obtain a homopolymer. The illuminance of the light was measured using an illuminance meter (UD-T36T2, manufactured by Topcon Technohouse Corporation).

[0229] Next, the obtained homopolymer was subjected to the above-mentioned DSC measurement to identify the Tg of the homopolymer. The differential scanning calorimeter used was a "Q2000" product manufactured by TA Instruments.

[0230] <Evaluation of Pressure-Sensitive Adhesive Compositions> Pressure-sensitive adhesive sheets for evaluation were prepared by the following methods for the pressure-sensitive adhesive compositions of the Examples and Comparative Examples, and various evaluation tests were carried out.

[0231] [Preparation of Release Liner] 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 dilution solvent were mixed to obtain a silicone-based release agent composition. The concentration of silicone solids in the release agent composition was 1.0 wt%. Next, the release agent composition was applied with a wire bar to one side of a liner substrate (Lumirror XD500P, a polyester film, 75 μm thick), and heated at 130° C. for 1 minute to prepare a release liner having a release layer (thickness 60 nm) on one side.

[0232] [Preparation of Pressure-Sensitive Adhesive Sheet] The pressure-sensitive adhesive composition was applied to one side of a substrate sheet (PET separator, manufactured by Mitsubishi Plastics, MRF38) using an applicator to form a coating layer (thickness: 20 μm). Next, a release liner was placed on 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. Next, an illuminance of 9 mW / cm was applied from the substrate sheet side of the first laminate. 2 and irradiation time was 400 seconds (integrated light dose 3600 mJ / cm 2 ). An LED was used as the light source, and the peak wavelength of the irradiated light was 340 nm. This photocured the coating layer, and a PSA sheet (thickness 20 μm) sandwiched between the base sheet and release liner was obtained. The illuminance of the light was measured using an illuminance meter (UD-T3040T2, manufactured by Topcon Technohouse Co., Ltd.) at a position near the ultraviolet light incident surface of the base sheet.

[0233] [Evaluation of Refractive Index] The release liner of the pressure-sensitive adhesive sheet was peeled off to expose the surface, and the refractive index 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.

[0234] [Evaluation of Adhesion Strength] (Preparation of Polarized Film) A long, amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) with a Tg of approximately 75°C was used as the thermoplastic resin substrate, and one side of the resin substrate was subjected to a corona treatment. A PVA-based resin (a 9:1 mixture of polyvinyl alcohol (degree of polymerization: 4200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIRM") was prepared by mixing 100 parts by weight of the resin with 13 parts by weight of potassium iodide, and the resulting solution was dissolved in water to prepare an aqueous PVA solution (coating solution). The PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a 13 μm-thick PVA-based resin layer, producing a laminate.

[0235] The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (machine direction) in an oven at 130°C (auxiliary in-air stretching treatment). Next, the laminate was immersed for 30 seconds in an insolubilizing bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40°C (insolubilizing treatment). Next, the laminate was immersed for 60 seconds in a dyeing bath (an iodine aqueous solution obtained by blending iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by weight of water) at a liquid temperature of 30°C while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would be a desired value (dyeing treatment).

[0236] Next, the laminate was immersed for 30 seconds in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40° C. (crosslinking treatment). Thereafter, while being immersed in a boric acid aqueous solution (boric acid concentration 4% by weight, potassium iodide concentration 5% by weight) at a liquid temperature of 70° C., the laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls operating at different peripheral speeds so that the total stretch ratio was 5.5 times (underwater stretching treatment).

[0237] Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20°C (cleaning treatment), and then brought into contact with a SUS heated roll whose surface temperature was maintained at about 75°C while being dried in an oven maintained at about 90°C (drying shrinkage treatment).

[0238] In this way, a polarizer with a thickness of approximately 5 μm was formed on the resin substrate. An HC-TAC film (first protective film) was bonded to the surface of the obtained polarizer (the surface opposite to the resin substrate) via a UV-curable adhesive. Specifically, the curable adhesive was applied to a thickness of 1.0 μm, and the films were bonded using a rolling mill. The adhesive was then cured by irradiating it with UV light from the protective film side. The HC-TAC film was a film in which a hard coat (HC) layer (7 μm thick) was formed on a triacetyl cellulose (TAC) film (25 μm thick), and the TAC film was bonded to the polarizer side.

[0239] 97.0 parts by weight of methyl methacrylate (MMA, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "Methyl Methacrylate Monomer"), 3.0 parts by weight of a copolymerizable monomer represented by the following formula (6), and 0.2 parts by weight of a polymerization initiator (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "2,2'-azobis(isobutyronitrile)") were dissolved in 200 parts by weight of toluene. Next, a polymerization reaction was carried out for 5.5 hours while heating to 70°C under a nitrogen atmosphere, yielding a boron-containing acrylic resin solution (solids concentration: 33%). The resulting boron-containing acrylic polymer had a Tg of 110°C and an Mw of 80,000. 20 parts by weight of the resulting boron-containing acrylic resin was dissolved in 80 parts by weight of methyl ethyl ketone to obtain a resin solution (20%).

[0240] The resin substrate was peeled from the polarizer, and a resin solution was applied to the peeled surface using a wire bar. The resulting coating was then dried at 60° C. for 5 minutes to form a second protective film (thickness: 400 nm) composed of a solidified coating of the organic solvent solution of the resin. This resulted in a polarized film having a configuration of [TAC film with HC layer (first protective film) / polarizer / solidified layer of boron-containing acrylic resin (second protective film)].

[0241] (Preparation of First Retardation Film) In a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and reflux condensers controlled at 100°C, 29.60 parts by weight (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane, 29.21 parts by weight (0.200 mol) of isosorbide (ISB), 42.28 parts by weight (0.139 mol) of spiroglycol (SPG), 63.77 parts by weight (0.298 mol) of diphenyl carbonate (DPC), and 1.19 × 10 mol of calcium acetate monohydrate as a catalyst were added. -2 Parts by weight (6.78 x 10 -5 mol) was charged. After purging the reactor with nitrogen under reduced pressure, heating was performed with a heat medium, and stirring was initiated when the internal temperature reached 100°C. 40 minutes after the start of the temperature increase, the internal temperature reached 220°C, and while controlling to maintain this temperature, pressure reduction was initiated. 90 minutes after reaching 220°C, the pressure was reduced to 13.3 kPa. Phenol vapor by-produced during the polymerization reaction was introduced into a reflux condenser at 100°C, and a small amount of monomer components contained in the phenol vapor were returned to the reactor, while uncondensed phenol vapor was introduced into a condenser at 45°C and recovered. Nitrogen was introduced into the first reactor, and the pressure was temporarily restored to atmospheric pressure. The oligomerized reaction liquid in the first reactor was then transferred to the second reactor. Next, heating and pressure reduction in the second reactor were initiated, and the internal temperature reached 240°C and the pressure reached 0.2 kPa in 50 minutes. Polymerization was then allowed to proceed until the predetermined stirring power was achieved. When the predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, and 100 parts by weight of the produced polyester carbonate resin was melt-kneaded with 0.7 parts by mass of PMMA, and the mixture was extruded into water, and the strands were cut to obtain pellets.

[0242] The obtained polyester carbonate resin (pellets) was vacuum dried at 80 ° C. for 5 hours, and then a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250 ° C.), a T-die (width 200 mm, set temperature: 250 ° C.), a chill roll (set temperature: 120-130 ° C.) and a film-forming device equipped with a winder were used to produce a long resin film having a thickness of 105 μm. The obtained long resin film was stretched 2.8 times in the width direction at 138 ° C. while adjusting to obtain a predetermined retardation, to obtain a first retardation film having a thickness of 38 μm. The Re (550) of the obtained first retardation film was 144 nm, and Re (450) / Re (550) was 0.86.

[0243] (Preparation of second retardation film) 20 parts by weight of a side-chain liquid crystal polymer represented by the following chemical formula (7) (the numbers 65 and 35 in the formula indicate the mol% of the monomer unit, and are conveniently represented as a block polymer: weight average molecular weight 5000), 80 parts by weight of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name Paliocolor LC242) and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals: trade name Irgacure 907) were dissolved in 200 parts by weight of cyclopentanone to prepare a liquid crystal coating solution. Then, the coating solution was applied to a PET substrate that had been subjected to vertical alignment treatment using a bar coater, and the liquid crystal was aligned by heating and drying at 80 ° C. for 4 minutes. This liquid crystal layer was irradiated with ultraviolet light, and the liquid crystal layer was cured, thereby forming a liquid crystal alignment solidified layer (second retardation film, thickness 3 μm) exhibiting a refractive index characteristic of nz > nx = ny on the substrate.

[0244] (Preparation of adhesive G1) 5 parts by weight of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-303"), 35 parts by weight of 4-hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.), 24 parts by weight of neopentyl glycol diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate NP-A"), 10 parts by weight of isocyanuric acid EO-modified triacrylate (manufactured by Toagosei Co., Ltd., trade name "Aronix M-315"), 5 parts by weight of pentaerythritol triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "A-TMM-3LM-N"), 15 parts by weight of polyurethane-based acrylic oligomer (manufactured by Mitsubishi Chemical Corporation, trade name "UV3000B"), 3 parts by weight of photopolymerization initiator (manufactured by IGM Resins, trade name "Omnirad" 184"), 2 parts by weight of a photopolymerization initiator (manufactured by San-Apro Co., Ltd., trade name "CPI-100P"), and 1 part by weight of boric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed and stirred for 3 hours to obtain active energy ray-curable adhesive G1.

[0245] (Preparation of Adhesive G2) A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with 91 parts by weight of n-butyl acrylate (BA), 2.7 parts by weight of acrylic acid (AA), 0.3 parts by weight of 4-hydroxybutyl acrylate (4HBA), 6 parts by weight of acryloylmorpholine (ACMO), and 0.2 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator. Nitrogen gas was introduced with gentle stirring to replace the atmosphere in the flask with nitrogen, and the liquid temperature in the flask was maintained at around 55°C, allowing the polymerization reaction to proceed for 7 hours. Next, ethyl acetate was added to the resulting reaction liquid to adjust the solids concentration to 12% by weight, thereby obtaining a (meth)acrylic polymer solution.

[0246] Adhesive G2 was obtained by mixing 0.15 parts by weight of trimethylolpropane / tolylene diisocyanate trimer adduct (Coronate L, manufactured by Tosoh Corporation), 0.25 parts by weight of benzoyl peroxide (Niper BMT, manufactured by NOF Corporation) and 0.075 parts by weight of 3-glycidoxypropyltrimethoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) into a solution of the (meth)acrylic polymer so that the contents per 100 parts by weight of the solid content of the (meth)acrylic polymer were the same.

[0247] Adhesive G2 was applied to the release surface of a 38 μm thick PET film (Mitsubishi Chemical Polyester Film Corporation, MRF38), a release liner with a silicone-treated release surface, and then dried in an air-circulating constant-temperature oven set to a predetermined temperature to form an adhesive layer (thickness 5 μm).

[0248] (Preparation of Optical Laminate L1) An adhesive layer (5 μm thick) formed from adhesive G2 was transferred from a release liner to the surface of the second protective film of the polarizing film, and a first retardation film was attached to the polarizing film via the adhesive layer to obtain a laminate. At this time, the slow axis of the first retardation film was arranged at an angle of 45° with respect to the absorption axis of the polarizer.

[0249] An active energy ray curable adhesive G1 was applied to one side of the second retardation film using an MCD coater (manufactured by Fuji Machine Co., Ltd.) so that the thickness after curing would be 1 μm, and the laminate was then bonded to the surface of the first retardation film using a roller. Thereafter, the adhesive G1 was cured by irradiating ultraviolet rays from the second retardation film side using an active energy ray irradiation device, and then hot air dried at 70 ° C. for 3 minutes.

[0250] The pressure-sensitive adhesive sheet was transferred from the release liner to the surface of the second retardation film of the laminate obtained as described above, to obtain an optical laminate L1 having a structure of [polarizing film / first adhesive layer (adhesive layer formed from adhesive G2) / first retardation film / second adhesive layer (cured layer of adhesive G1) / second retardation film / pressure-sensitive adhesive sheet].

[0251] (Evaluation of Adhesion Strength) Using the above optical laminate L1, the adhesion strength between the pressure-sensitive adhesive sheet and alkali-free glass was evaluated by the above-mentioned method. The alkali-free glass used was Corning Inc.'s product name "EG-XG" with a thickness of 0.7 mm. The optical laminate was peeled off from the alkali-free glass using a tensile tester (Shimadzu Corporation, Autograph SHIMAZU AG-1 10KN).

[0252] [Reliability Test (85°C)] The above optical laminate L1 was cut into a strip measuring 225 mm long x 155 mm wide to prepare a test specimen. Next, the test specimen was attached to the surface of 0.7 mm thick alkali-free glass (manufactured by Corning Incorporated, product name "EG-XG") using an adhesive sheet. The test specimen was attached to the alkali-free glass using a laminator. After attaching the test specimen, it was placed in an autoclave at 50°C and 0.5 MPa for 15 minutes to homogenize the bond between the alkali-free glass and the adhesive sheet, and the adhesive sheet was adhered to the alkali-free glass. Next, the test specimen was subjected to a heat treatment at 85°C under atmospheric pressure. 500 hours after the start of the heat treatment, the vicinity of the edge of the test specimen was observed with an optical microscope, and the reliability of the adhesive sheet was evaluated according to the following criteria. Evaluation criteria A: No peeling or bubbling that would affect image display was observed. B: There was slight peeling in one location on the edge, but not to the extent that it would affect image display. C: There were multiple slight peelings on the edge, but not to the extent that it would affect image display. D: There was peeling and / or bubbling that would affect image display. E: There was peeling and / or bubbling that would significantly affect image display.

[0253] [Reliability Test (HS)] The optical laminate L1 was cut into a strip measuring 225 mm long x 155 mm wide to prepare a test specimen. Next, the test specimen was attached to the surface of 0.7 mm thick alkali-free glass (manufactured by Corning Incorporated, trade name "EG-XG") using an adhesive sheet. The test specimen was attached to the alkali-free glass using a laminator. After attaching the test specimen, the specimen was placed in an autoclave at 50°C and 0.5 MPa for 15 minutes to homogenize the bond between the alkali-free glass and the adhesive sheet, and the adhesive sheet was adhered to the alkali-free glass. Next, the test specimen was subjected to a heat shock (HS) test, which consisted of one cycle of (1) holding at -40°C for 30 minutes, (2) heating to 85°C in 2 to 5 minutes, (3) holding at 85°C for 30 minutes, and (4) cooling to -40°C in 2 to 5 minutes. In the HS test, the vicinity of the edge of the test piece was observed with an optical microscope at each of the points when the number of cycles reached 100, 200, and 300, and the reliability of the pressure-sensitive adhesive sheet was evaluated according to the following criteria: Evaluation criteria A: No peeling or foaming that would affect image display was observed B: Slight peeling in one location at the edge, but not to a level that would affect image display C: Slight peeling in multiple locations at the edge, but not to a level that would affect image display D: Peeling and / or foaming that would affect image display E: Peeling and / or foaming that would significantly affect image display

[0254] [Young's Modulus, Breaking Strength, and Breaking Elongation] The Young's modulus, breaking strength, and breaking elongation of the pressure-sensitive adhesive sheet were evaluated by the methods described above. The tensile tester used was an Autograph SHIMAZU AG-1 10KN manufactured by Shimadzu Corporation.

[0255]

[0256]

[0257] The abbreviations in Table 1 are as follows: POB-A: phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical, trade name "Light Acrylate POB-A", Tg when made into a homopolymer: 9°C) P2HA: phenoxydiethylene glycol acrylate (manufactured by Kyoeisha Chemical, "Light Acrylate P2H-A") 4HBA: 4-hydroxybutyl acrylate (Tg when made into a homopolymer: -31°C) CBA: 2-(2-ethoxyethoxy)ethyl acrylate (Tg when made into a homopolymer: -55°C) MEA: 2-methoxyethyl acrylate (Tg when made into a homopolymer: -34°C) NDDA: 1,9-nonanediol diacrylate Omni. 651: 1,2-diphenylethan-1-one (manufactured by IGM Resins, trade name "Omnirad 651") Omni. 184: 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins, trade name "Omnirad 184") Irganox 1010: tetrakis[3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionic acid]pentaerythritol (manufactured by BASF) KBM403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicones, trade name "KBM-403")

[0258] As can be seen from Tables 1 and 2, the pressure-sensitive adhesive sheets formed from the pressure-sensitive adhesive compositions of the Examples, which contained inorganic particles and a dispersant and in which the content of the hydroxyl group-containing monomer per 100 parts by weight of the monomer components was less than 0.1 parts by weight, showed better results in reliability tests (especially HS tests) and higher durability than the Comparative Examples. Furthermore, all of the pressure-sensitive adhesive sheets formed from the pressure-sensitive adhesive compositions of the Examples had high refractive indices.

[0259] 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.

Claims

1. A pressure-sensitive adhesive composition comprising: a monomer component M; inorganic particles; and a dispersant, wherein the content of a hydroxyl group-containing monomer per 100 parts by weight of the monomer component M is less than 0.1 parts by weight.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the monomer component M includes a monomer a1 having a double bond-containing ring.

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

4. The pressure-sensitive adhesive composition according to claim 2, wherein the content of said monomer a1 relative to 100 parts by weight of said monomer component M is 80 parts by weight or more.

5. The pressure-sensitive adhesive composition according to claim 1, wherein the monomer component M includes a monomer a2 having a glass transition temperature of 0°C or lower when made into a homopolymer.

6. The pressure-sensitive adhesive composition according to claim 5, wherein the monomer a2 has an oxyalkylene group.

7. The pressure-sensitive adhesive composition according to claim 5, wherein the content of said monomer a2 is 25 parts by weight or less per 100 parts by weight of said monomer component M.

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

9. The pressure-sensitive adhesive composition according to claim 1, wherein the content of the inorganic particles is 90 parts by weight or more per 100 parts by weight of the monomer component M.

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

11. The pressure-sensitive adhesive composition according to claim 10, wherein the surface treatment agent includes a silane coupling agent.

12. The pressure-sensitive adhesive composition according to claim 1, wherein the dispersant has a hydrophilic group.

13. The pressure-sensitive adhesive composition according to claim 1, wherein the dispersant has an aromatic ring.

14. The pressure-sensitive adhesive composition according to claim 1, further comprising a polymer B having a weight-average molecular weight of 1,500 to 30,000.

15. The pressure-sensitive adhesive composition according to claim 14, wherein the content of said polymer B is 0.1 to 20 parts by weight per 100 parts by weight of said monomer component M.

16. The pressure-sensitive adhesive composition according to claim 1, which is a photocurable type.

17. A pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 16.

18. The pressure-sensitive adhesive sheet according to claim 17, having a refractive index of 1.64 or more.

19. The pressure-sensitive adhesive sheet according to claim 17, having a breaking elongation of 320% or more.

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

21. An image display device comprising the optical laminate according to claim 20.

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