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

Abstract

The present invention provides a photocurable adhesive composition suitable for manufacturing an adhesive sheet having a high refractive index and improved anchoring force with respect to an optical substrate. The photocurable adhesive composition contains a monomer component M and inorganic particles. The monomer component M includes a monomer a1 having a double bond-containing ring, and a monomer a2 having a glass transition temperature of 0°C or less when formed as a single polymer.

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 anchoring strength of a pressure-sensitive adhesive sheet having a high refractive index with an optical substrate.

[0006] An object of the present invention is to provide a photocurable pressure-sensitive adhesive composition suitable for producing a pressure-sensitive adhesive sheet having a high refractive index and improved anchoring strength to an optical substrate.

[0007] [1] A photocurable pressure-sensitive adhesive composition according to an embodiment of the present invention is a photocurable pressure-sensitive adhesive composition comprising a monomer component M and inorganic particles, wherein the monomer component M comprises a monomer a1 having a double-bond-containing ring and a monomer a2 having at least one ether group and having a glass transition temperature of 0°C or lower when made into a homopolymer. [2] In the pressure-sensitive adhesive composition described in [1] above, the double-bond-containing ring may be an aromatic ring. [3] In the pressure-sensitive adhesive composition described in [1] or [2] above, the monomer a1 may comprise a (meth)acrylic monomer having the double-bond-containing ring. [4] In the pressure-sensitive adhesive composition described in any of [1] to [3] above, the monomer a1 may comprise phenoxybenzyl acrylate. [5] In the pressure-sensitive adhesive composition described in any of [1] to [4] above, the content of the monomer a1 per 100 parts by weight of the monomer component M may be 80 to 99.9 parts by weight. [6] In the pressure-sensitive adhesive composition according to any one of [1] to [5] above, the side chain of the ether group may be linear. [7] In the pressure-sensitive adhesive composition according to any one of [1] to [6] above, the monomer a2 may have an oxyalkylene group. [8] In the pressure-sensitive adhesive composition according to any one of [1] to [7] above, the content of the monomer a2 per 100 parts by weight of the monomer component M may be 1 to 20 parts by weight. [9] In the pressure-sensitive adhesive composition according to any one of [1] to [8] above, the inorganic particles may contain zirconium oxide.

[10] In the pressure-sensitive adhesive composition according to any one of [1] to [9] above, the content of the inorganic particles in the pressure-sensitive adhesive composition may be 80 to 120 parts by weight per 100 parts by weight of the monomer component M.

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

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

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

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

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

[12] , the pressure-sensitive adhesive composition may further contain a polymer B having a weight-average molecular weight of 1,500 to 30,000.

[14] In the pressure-sensitive adhesive composition described in

[13] above, the polymer B may contain a structural unit derived from a monomer b1 having a double bond-containing ring.

[15] In the pressure-sensitive adhesive composition described in

[13] or

[14] above, the content of the polymer B in the pressure-sensitive adhesive composition may be 1 to 20 parts by weight per 100 parts by weight of the monomer component M.

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

[15] above.

[17] In the pressure-sensitive adhesive sheet described in

[16] above, the refractive index may be 1.62 to 1.70.

[18] In the pressure-sensitive adhesive sheet described in

[16] or

[17] above, the anchoring strength with ITO-PET may be 10 N / mm or more.

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

[16] to

[18] above and an optical film.

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

[19] above.

[0008] According to an embodiment of the present invention, a photocurable pressure-sensitive adhesive composition suitable for producing a pressure-sensitive adhesive sheet having a high refractive index and improved anchoring strength with an optical substrate can be provided.

[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 a pressure-sensitive adhesive composition according to one embodiment 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] When the pressure-sensitive adhesive composition contains a partially polymerized product, the weight of the partially polymerized product is converted into the weight of each monomer before polymerization in calculating the proportion and content of the monomer.

[0013] 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.

[0014] <<1. Pressure-sensitive adhesive composition>> A pressure-sensitive adhesive composition according to an embodiment of the present invention includes a monomer component M and inorganic particles. A portion of the monomer component M may be a partially polymerized product A. The monomer component M includes a monomer a1 having a double bond-containing ring and a monomer a2 having at least one ether group and having a glass transition temperature of 0°C or lower when formed into a homopolymer. The pressure-sensitive adhesive composition is a photocurable pressure-sensitive adhesive composition that forms a pressure-sensitive adhesive sheet by irradiation with light. Note that being a photocurable pressure-sensitive adhesive composition is particularly preferred in terms of environmental protection and sustainability, as it can reduce the amount of energy required to form a pressure-sensitive adhesive sheet compared to a thermosetting pressure-sensitive adhesive composition that mainly uses heat to form a pressure-sensitive adhesive sheet.

[0015] <1-1. Monomer Component M> <1-1-a1. Monomer a1 Having a Double Bond-Containing Ring> As described above, monomer component M 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, monomer a1 preferably has a glass transition temperature (Tg) of above 0°C when made into a homopolymer, and may be 5°C or higher. Examples of a method for measuring Tg include the method described below for monomer a2.

[0016] 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.

[0017] 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.

[0018] 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 is a heterocyclic ring. Examples of the heterocyclic ring include a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, and a thiophene ring. Examples of heteroatoms that may be contained in the heterocyclic ring as ring-constituting atoms include at least one selected from the group consisting of nitrogen, sulfur, and oxygen. The 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.

[0019] 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. In such cases, the number of carbon atoms contained in the substituent is, for example, 1 to 4, 1 to 3, or even 1 to 2. One example of the double bond-containing ring has no substituents on the ring-constituting atoms. Another example of the double bond-containing ring has one or more substituents selected from the group consisting of alkyl groups, alkoxy groups, and halogen atoms (e.g., bromine atoms) on the ring-constituting atoms.

[0020] 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 may be, for example, 16 or less, 12 or less, 8 or less, 6 or less, 5 or less, 4 or less, 3 or less, or even 2 or less.

[0021] 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. The monomer a1 is preferably a compound containing one ethylenically unsaturated group per molecule (in other words, a monofunctional monomer).

[0022] Examples of the ethylenically unsaturated group are a (meth)acryloyl group, a vinyl group, and a (meth)allyl group. From the viewpoint of polymerization reactivity, a (meth)acryloyl group is preferred, and from the viewpoint of flexibility and adhesiveness, an acryloyl group is more preferred. In other words, monomer 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. An example of a (meth)acrylic monomer having a double bond-containing ring is an aromatic ring-containing (meth)acrylate. Specific examples of aromatic ring-containing (meth)acrylates will be described later.

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

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

[0025] Monomer a1 may contain two or more aromatic rings (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.

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

[0027] The linking group may contain atoms such as P, Ge, Te, Se, N, S, and Si, and these atoms may be bonded to an oxygen atom. 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 at least one selected from the group consisting of an oxy group, a thiooxy group, an oxyalkylene group, and a straight-chain alkylene group. Specific examples of monomers having a structure in which two or more non-fused aromatic rings are bonded via a linking group include phenoxybenzyl (meth)acrylate, thiophenoxybenzyl (meth)acrylate, and benzyl benzyl (meth)acrylate.

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

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

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

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

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

[0033] Monomer a1 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).

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

[0035] Monomer a1 may have a structure in which an oxyethylene chain is interposed between the ethylenically unsaturated group and the 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.

[0036] 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.

[0037] 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.

[0038] 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 comprises phenoxybenzyl acrylate.

[0039] The content of monomer a1 in 100 parts by weight of monomer component M may be, for example, 70 parts by weight or more, 75 parts by weight, 80 parts by weight, 85 parts by weight or more, 86 parts by weight or more, 87 parts by weight or more, 88 parts by weight or more, 89 parts by weight or more, or even 90 parts by weight or more. The upper limit of the content may be, for example, 99.9 parts by weight or less, 99.8 parts by weight or less, 99.7 parts by weight or less, 99.6 parts by weight or less, 99.5 parts by weight or less, 99 parts by weight or less, 98 parts by weight or less, 97 parts by weight or less, 96 parts by weight or less, or even 95 parts by weight or less. The content is preferably 80 to 99.9 parts by weight.

[0040] <1-1-a2. Monomer a2 having at least one ether group and having a glass transition temperature of 0°C or lower when made into a homopolymer> As described above, monomer component M contains monomer a2 having at least one ether group and 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 anchoring strength F and adhesive strength P of the PSA sheet. Monomer a2 can also be a component suitable for improving the optical properties. It is preferable that monomer a2 does not contain a hydroxyl group.

[0041] 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.

[0042] The Tg can be measured by the following method. First, a homopolymer of monomer a2 is prepared. Next, an aluminum sample pan containing the homopolymer of monomer a2 (measurement sample) and an empty aluminum sample pan (reference material) are prepared. These sample pans are each set in a differential scanning calorimeter, and differential scanning calorimetry (DSC measurement) is performed based on the temperature difference between the temperature of the sample pan containing the measurement sample and the temperature of the empty sample pan. Specifically, three cycles of DSC measurement are performed, each cycle consisting of a temperature increase process at a temperature increase rate of 10°C / min and a temperature decrease process at a temperature decrease rate of 10°C / min. In the DSC measurement, the temperature increase start temperature is set to a value at least 70°C lower than the baseline shift resulting from the Tg of the homopolymer. The temperature decrease start temperature is set to a value at least 70°C higher than the baseline shift resulting from the Tg of the homopolymer.

[0043] 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.

[0044] 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 monomer a1. Monomer a2 may be a (meth)acrylic monomer.

[0045] In the monomer a2, the side chain of the ether group may be linear or branched. The monomer a2 preferably has an oxyalkylene group. The number of oxyalkylene groups in the monomer a2 is, for example, 1 to 30, or may be 1 to 12, or even 1 to 5.

[0046] 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):

[0047] 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 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.

[0048] 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.

[0049] Examples of monomer a2 are 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, ethoxydiethylene glycol (meth)acrylate, and methoxydipropylene glycol (meth)acrylate. Monomer a2 is preferably 2-(2-ethoxyethoxy)ethyl acrylate (CBA; Tg = -55°C), 2-methoxyethyl acrylate (MEA; Tg = -34°C), methoxypolyethylene glycol acrylate (for example, trade names "MPE400A" (Tg = -64°C) and "MPE550A" (Tg = -62°C) manufactured by Osaka Organic Chemical Industry Co., Ltd., and trade names "AM-130G" and "AM-230G" manufactured by Shin-Nakamura Chemical Co., Ltd.), ethoxydiethylene glycol acrylate (for example, trade name "EC-A" manufactured by Kyoeisha Chemical Co., Ltd.), methoxydipropylene glycol acrylate (for example, trade name "LightAcrylate DPM-A" manufactured by Kyoeisha Chemical Co., Ltd.), phenoxydiethylene glycol acrylate (for example, trade name "LightAcrylate P2H-A" (Tg = -16°C) manufactured by Kyoeisha Chemical Co., Ltd.), or the like.

[0050] Monomer a2 may be 2-(2-ethoxyethoxy)ethyl acrylate, which may be a component particularly suitable for improving optical properties.

[0051] The content of monomer a2 in 100 parts by weight of monomer component M is, for example, 0.1 parts by weight or more, and may be 0.2 parts by weight or more, 0.3 parts by weight or more, 0.4 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, or even 5 parts by weight or more. The upper limit of the content is, for example, 30 parts by weight or less, and may be 25 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 14 parts by weight or less, 13 parts by weight or less, 12 parts by weight or less, 11 parts by weight or less, or even 10 parts by weight or less. The content is preferably 1 to 20 parts by weight.

[0052] <1-1-b. Other Monomers> Monomer component M may contain other monomers in addition to the above-described monomers a1 and a2. One example of such other monomers is a hydroxyl group-containing monomer. The hydroxyl group-containing monomer has at least one hydroxyl group and at least one ethylenically unsaturated group in one molecule. Monomer component M may contain one or more types of hydroxyl group-containing monomers.

[0053] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer a1. The hydroxyl group-containing monomer may be a (meth)acrylic monomer.

[0054] Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. The hydroxyl group-containing monomer is preferably 4-hydroxybutyl (meth)acrylate. The content of the hydroxyl group-containing monomer 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, 12 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, 7 parts by weight or less, 6 parts by weight or less, or even 5 parts by weight or less. The lower limit of the content 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 monomer component M preferably does not contain a hydroxyl group-containing monomer.

[0055] Another example of a monomer that can be contained in the monomer component M is a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms on the side chain. The number of carbon atoms in the alkyl group may be 7 or less, 6 or less, 5 or less, or even 4 or less. The alkyl group may be linear or branched. Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, n-decyl(meth)acrylate, isodecyl(meth)acrylate, n-dodecyl(meth)acrylate (lauryl(meth)acrylate), n-tridecyl(meth)acrylate, n-tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexadecyl(meth)acrylate, heptadecyl(meth)acrylate, and octadecyl(meth)acrylate. The (meth)acrylic acid alkyl ester may be n-butyl(meth)acrylate.

[0056] The content of the (meth)acrylic acid alkyl ester in 100 parts by weight of the monomer component M is, for example, 25 parts by weight or less, and may be 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 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.

[0057] 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.

[0058] 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.

[0059] Examples of carboxyl group-containing monomers include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. The content of the carboxyl group-containing monomer in 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. It is preferable that the monomer component M does not contain a carboxyl group-containing monomer.

[0060] The total content of other monomers in the monomer component M may be, for example, less than 30 parts by weight, and may be 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, or even 5 parts by weight or less. The lower limit of the content may be, for example, 0.01 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, or even 1 part by weight or more.

[0061] <1-2. Partial Polymer A> As described above, 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.

[0062] 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.

[0063] <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.

[0064] 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. An example of a material constituting the metal oxide particles is at least one selected from the group consisting of 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.

[0065] 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.

[0066] The material of the inorganic particles may be a high-entropy alloy in which multiple types of elements are mixed.

[0067] 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.

[0068] 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.

[0069] The amount of the surface treatment agent added relative to 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 amount added 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.

[0070] The inorganic particles may contain a high refractive index material. The refractive index of the high refractive index material may be, for example, 1.60 or more, 1.70 or more, 1.80 or more, or even 2.00 or more. The upper limit of the refractive index of the high refractive index material is not particularly limited, and may be, for example, 3.00 or less, 2.80 or less, 2.50 or less, or even 2.20 or less. The refractive index of the material contained in the inorganic particles can be determined as the refractive index measured for a single layer film of the material using a commercially available spectroscopic ellipsometer under conditions of an ambient temperature of 23°C and irradiation light of 549 nm. For example, the spectroscopic ellipsometer may be an "EC-400" manufactured by JA Woollam Co., Ltd. or an equivalent product.

[0071] 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.

[0072] The content of the inorganic particles in the PSA composition may be, for example, 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, 90 parts by weight or more, 100 parts by weight or more, or even more than 100 parts by weight, relative to 100 parts by weight of the monomer component M. The upper limit of the content may be, for example, 150 parts by weight or less, 140 parts by weight or less, 130 parts by weight or less, 120 parts by weight or less, 110 parts by weight or less, 100 parts by weight or less, less than 100 parts by weight, or 90 parts by weight or less. The content is preferably 80 to 120 parts by weight.

[0073] <1-4. 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 anchoring strength F and adhesive strength P of the PSA sheet, and can function as a tackifier. In this specification, polymer B may be referred to as an oligomer.

[0074] 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 anchoring strength F and adhesive strength P of the PSA sheet tend 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.

[0075] Polymer B may contain a structural unit derived from monomer b1 having a double bond-containing ring. Polymer B containing a structural unit derived from monomer b1 is suitable for improving the refractive index of the pressure-sensitive adhesive sheet. Examples of monomer b1 include those mentioned above for monomer a1. Monomer b1 may be the same as or different from monomer a1.

[0076] In monomer b1, the double bond-containing ring is preferably an aromatic ring. Monomer b1 may contain two or more aromatic rings (preferably carbon rings) in one molecule. Monomer b1 preferably contains a monomer having two or more aromatic rings and at least one ethylenically unsaturated group in one molecule (a monomer containing multiple aromatic rings). Monomer b1 particularly preferably contains phenoxybenzyl acrylate.

[0077] The content of the structural unit derived from monomer b1 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.

[0078] Polymer B may contain a structural unit derived from a monomer other than the above-mentioned monomer b1. Examples of the other monomer include those described above for monomer component M (hydroxyl group-containing monomers, (meth)acrylic acid alkyl esters having an alkyl group of 1 to 20 carbon atoms in the side chain, and carboxyl group-containing monomers).

[0079] 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 is, for example, 0.01% by weight or more, 0.1% by weight or more, or even 0.5% by weight or more.

[0080] The polymer B can be produced by a known polymerization method such as solution polymerization, radiation polymerization using electron beams or UV rays, or various radical polymerizations such as bulk polymerization and emulsion polymerization. The obtained polymer B may be any of a random copolymer, a block copolymer, a graft copolymer, etc.

[0081] The content of polymer B in the PSA composition is 1 part by weight or more, and may be 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, 5 parts by weight or more, 6 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, or even 10 parts by weight or more, relative to 100 parts by weight of monomer component M. The upper limit of the content is, for example, 25 parts by weight or less, and may be 20 parts by weight or less, 15 parts by weight or less, 14 parts by weight or less, 13 parts by weight or less, 12 parts by weight or less, 11 parts by weight or less, or even 10 parts by weight or less. The content is preferably 1 to 20 parts by weight.

[0082] <1-5. Other Components> <1-5-a. Dispersant> The PSA composition may further contain a dispersant for inorganic particles. The dispersant is a component for sufficiently dispersing the inorganic particles in the PSA composition. The dispersant is preferably in contact with the surfaces of the inorganic particles, and more preferably coats the surfaces of the inorganic particles.

[0083] 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 to the inorganic particles, and the monomer component M and its partial polymer A, respectively. The dispersant may or may not have a polymerizable functional group such as an ethylenically unsaturated group.

[0084] The hydrophilic portion of the dispersant preferably has a hydrophilic group, such as an ether group or an ester group.

[0085] The hydrophilic portion of the dispersant may include a functional group F that exhibits adsorptivity or reactivity to 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 one, or two or more (for example, about 2 to 5). The types of two or more functional groups F present in one molecule may be the same or different from each other.

[0086] 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.

[0087] The dispersant may be an aliphatic compound, for example, represented by the following formula (2):

[0088] 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.

[0089] The dispersant may be an aromatic compound, for example, represented by the following formula (3):

[0090] 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 2is 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.

[0091] In formula (3), R 1 may be a styrenated phenyl group represented by the following formula (4):

[0092] In formula (4), k is an average value and is 1 to 5. For example, k is 2 to 4, and may be 3.

[0093] 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.

[0094] In formula (3), X may be an O atom.

[0095] 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).

[0096] 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.

[0097] 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.

[0098] The aromatic compound in the dispersant may be a compound having an aromatic ring as described above in the description of monomer a1.

[0099] 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 the dispersant is preferably an anionic surfactant.

[0100] 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.

[0101] <1-5-b. Photopolymerization initiator> The pressure-sensitive adhesive composition usually contains a photopolymerization initiator. The photopolymerization initiator may be a photoradical generator that generates radicals when exposed to visible light and / or ultraviolet light having a wavelength shorter than 450 nm.

[0102] 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.

[0103] Specific examples of the photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one (trade name "Omnirad 651" manufactured by IGM Resins), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819" manufactured by IGM Resins), and 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184" manufactured by IGM Resins).

[0104] The content of the photopolymerization initiator in the pressure-sensitive adhesive composition is, for example, 0.01 to 5 parts by weight, or may be 0.01 to 2 parts by weight, 0.02 to 1 part by weight, or even 0.05 to 0.5 parts by weight, relative to 100 parts by weight of the monomer component M.

[0105] <1-5-c. Crosslinking Agent> The pressure-sensitive adhesive composition may contain a crosslinking agent. An example of the crosslinking agent is a polyfunctional monomer having two or more polymerizable functional groups in one molecule. The polyfunctional monomer may be a (meth)acrylic monomer. Examples of the polyfunctional monomer are a monomer having two or more C=C bonds in one molecule, and a monomer having one or more C=C bonds and one or more polymerizable functional groups such as epoxy groups, aziridine groups, oxazoline groups, hydrazine groups, methylol groups, etc. in one molecule. The polyfunctional monomer is preferably a monomer having two or more C=C bonds in one molecule.

[0106] 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.

[0107] The content of the crosslinking agent in the pressure-sensitive adhesive composition is, for example, 0.1 to 0.5 parts by weight, or may be 0.01 to 0.4 parts by weight, 0.01 to 0.3 parts by weight, or even 0.01 to 0.2 parts by weight, relative to 100 parts by weight of the monomer component M.

[0108] <1-5-d. Silane Coupling Agent> The pressure-sensitive adhesive composition may contain a silane coupling agent. 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.

[0109] The content of the silane coupling agent in the pressure-sensitive adhesive composition is, for example, 0.1 to 2 parts by weight, or may be 0.2 to 1.8 parts by weight, 0.3 to 1.5 parts by weight, 0.4 to 1.2 parts by weight, or even 0.5 to 1.0 parts by weight, relative to 100 parts by weight of the monomer component M.

[0110] 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.

[0111] Examples of the phenolic antioxidant include monophenolic antioxidants, bisphenolic antioxidants, and polymeric phenolic antioxidants. Examples of the monophenolic antioxidant include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, and stearin-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. Examples of the bisphenol antioxidant are 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), and 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane. Examples of 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.

[0112] 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).

[0113] 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).

[0114] 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).

[0115] The content of the antioxidant in the pressure-sensitive adhesive composition is, for example, 0.1 to 2 parts by weight, or may be 0.2 to 1.8 parts by weight, 0.5 to 1.5 parts by weight, or even 0.8 to 1.2 parts by weight, relative to 100 parts by weight of the monomer component M.

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

[0117] <1-5-g. Other Additives> The PSA composition may contain additives other than those described above. Examples of the additives include an ultraviolet absorber, a chain transfer agent, a viscosity modifier, a tackifier, a plasticizer, a softener, an antioxidant, a filler, a colorant, a surfactant, and an antistatic agent.

[0118] <1-6. Physical Properties> The viscosity of the pressure-sensitive adhesive composition is preferably 5 to 100 poise at 25° C. A pressure-sensitive adhesive composition having a viscosity in the above range is particularly suitable for forming a coating layer, which will be described later.

[0119] <<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.

[0120] 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.

[0121] 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, or even 85% or more.

[0122] The refractive index of the pressure-sensitive adhesive sheet 1 is, for example, 1.55 or more, and may be 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, 1.60 or more, 1.61 or more, 1.62 or more, 1.63 or more, 1.64 or more, or even 1.65 or more. The upper limit of the refractive index is, for example, 1.70 or less, and may be 1.69 or less, 1.68 or less, 1.67 or less, or even 1.66 or less. A preferred example of the refractive index of the pressure-sensitive adhesive sheet 1 is 1.62 to 1.70. Optical substrates that can be provided in the optical laminate include optical substrates with high refractive indexes. 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.

[0123] 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 optical 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 for the prism coupler. For example, a Model 2010 / M prism coupler manufactured by Metricon, Inc., or an equivalent can be used as the measuring device.

[0124] The adhesive sheet 1 has an adhesive strength P with alkali-free glass of, for example, 1.5 N / 25 mm or more, 1.6 N / 25 mm or more, 1.7 N / 25 mm or more, 1.8 N / 25 mm or more, 1.9 N / 25 mm or more, 2.0 N / 25 mm or more, 3.0 N / 25 mm or more, 4.0 N / 25 mm or more, 5.0 N / 25 mm or more, 6.0 N / 25 mm or more, 7.0 N / 25 mm or more, 8.0 N / 25 mm or more, 9.0 N / 25 mm or more, or even 10.0 N / 25 mm or more. The upper limit of the adhesive strength P may be, for example, 50.0 N / 25 mm or less, 30.0 N / 25 mm or less, 20.0 N / 25 mm or less, even 10.0 N / 25 mm or less, or even 5.0 N / 25 mm or less. A preferred example of the adhesive strength P is 1.5 to 10.0 N / 25 mm, and another preferred example of the adhesive strength P is 2.0 to 5.0 N / 25 mm.

[0125] The adhesive strength P 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 P. 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.

[0126] 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 rate of 60 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 P.

[0127] 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, 1 μm or more, 2 μm or more, 5 μm or more, or even 10 μm or more. The thickness of the pressure-sensitive adhesive sheet 1 is preferably 1 to 100 μm, and may be 2 to 80 μm, or even 5 to 50 μm.

[0128] The haze of the pressure-sensitive adhesive sheet 1 is, for example, 5.0% or less, and may be 3.0% or less, 2.0% or less, 1.7% or less, 1.5% or less, 1.2% or less, 1.0% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, or even 0.2% or less. The lower limit of the haze is not particularly limited and may be 0.1% or more. A low-haze pressure-sensitive adhesive sheet 1 is particularly suitable for use in optical laminates.

[0129] In this specification, haze refers to the ratio of diffuse transmitted light to total transmitted light when visible light is irradiated onto the pressure-sensitive adhesive sheet 1, which is the object to be measured. Haze can be calculated using the following formula: In the formula, Th is haze (%), Td is scattered light transmittance, and Tt is total light transmittance. Th (%) = Td / Tt x 100

[0130] <2-2. Manufacturing method> The PSA sheet 1 can be formed from the PSA composition by, for example, irradiating light 14 onto a first laminate 10 comprising, in this order, a base sheet 11, a coating layer 12 containing the PSA composition, and a release liner 13 (see FIG. 2 ). The coating layer 12 is irradiated with light 14 and cured to form the PSA sheet 1. Irradiation with light 14 is typically carried out from the side of the base sheet 11. In this case, the light 14 passes through the base sheet 11 and reaches the coating layer 12, curing the coating layer 12. However, irradiation with light 14 may also be carried out from the side of the release liner 13, or from both the side of the release liner 13 and the side of the base sheet 11.

[0131] 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.

[0132] The light 14 is, for example, visible light or ultraviolet light having a wavelength shorter than 450 nm. The light 14 may include light having a wavelength in the same region as the absorption wavelength of the photopolymerization initiator contained in the pressure-sensitive adhesive composition. Light having a wavelength of 300 nm or less may be irradiated by filtering out short-wavelength light using a filter or the like. Filtering out short-wavelength light is suitable for suppressing deterioration of the base sheet 11 and / or release liner 13 caused by the light 14. The light source 18 of the light 14 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.

[0133] 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:

[0134] 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.

[0135] 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 2 Below, 20000mJ / cm 2 Below, 18000 mJ / cm 2 It may be the following:

[0136] 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.

[0137] 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.

[0138] 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.

[0139] The release liner 13 may be in the form of a sheet or a continuous piece.

[0140] 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.

[0141] The thickness of the base sheet 11 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

[0142] 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.

[0143] 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.

[0144] The base sheet 11 may be in the form of a sheet or a continuous sheet.

[0145] 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.

[0146] 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.

[0147] The thickness of the coating layer 12 can be adjusted depending on the desired thickness of the pressure-sensitive adhesive sheet 1, and may be, for example, 500 μm or less, 250 μm or less, 150 μm or less, 100 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness of the coating layer 12 is, for example, 1 μm or more, and may be 2 μm or more, 5 μm or more, or even 10 μm or more.

[0148] 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.

[0149] <<3. Optical Laminate>> An example of an optical laminate according to an embodiment of the present invention is shown in Fig. 3. The optical laminate 20A in Fig. 3 includes an adhesive sheet 1 and an optical film 2. The adhesive sheet 1 and the optical film 2 are laminated together. The optical laminate 20A can be used as an optical film with an adhesive sheet.

[0150] 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.

[0151] 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 .

[0152] 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.

[0153] 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.

[0154] The thickness of the polarizer is not particularly limited and may be, for example, 80 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the polarizer thickness is not particularly limited and may be, for example, 1 μm or more, 5 μm or more, 10 μm or more, or even 15 μm or more. A thin polarizer (for example, a thickness of 20 μm or less) is suppressed in dimensional change and can contribute to improving the durability of the optical laminate, particularly durability at high temperatures.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] The polarizing film may be a circular polarizing film.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] The thickness of the optical film 2 is, for example, 1 to 200 μm.

[0165] 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.

[0166] The anchoring force F between the pressure-sensitive adhesive sheet 1 and the optical film 2 is, for example, more than 5.0 N / 25 mm, and may be 6.0 N / 25 mm or more, 7.0 N / 25 mm or more, 8.0 N / 25 mm or more, 9.0 N / 25 mm or more, 10.0 N / 25 mm or more, 11.0 N / 25 mm or more, 12.0 N / 25 mm or more, 13.0 N / 25 mm or more, 14.0 N / 25 mm or more, 15.0 N / 25 mm or more, 20.0 N / 25 mm or more, or even 25.0 N / 25 mm or more. The anchoring force F is preferably 10.0 N / 25 mm or more. The upper limit of the anchoring force F is, for example, 50 N / 25 mm or less, 40 N / 25 mm or less, or 30 N / 25 mm or less. A preferred example of the anchoring force F is 10.0 to 50.0 N / 25 mm.

[0167] The anchoring force F between the pressure-sensitive adhesive sheet 1 and the optical film 2 can be measured by the following method. First, the optical laminate 20A comprising the pressure-sensitive adhesive sheet 1 and the optical film 2 is cut into a strip of 25 mm wide x 150 mm long to prepare a test piece. Next, the entire surface of the optical film 2 provided in the test piece is placed on a stainless steel test plate via double-sided tape, and a 2 kg roller is moved back and forth once to press them together. Next, the pressure-sensitive adhesive sheet 1 provided in the test piece is placed on an evaluation sheet, and a 2 kg roller is moved back and forth once to press them together. The evaluation sheet is not particularly limited as long as it has a size of 30 mm wide x 150 mm long and does not peel off from the pressure-sensitive adhesive sheet 1 during the test. As the evaluation sheet, for example, a polyethylene terephthalate (ITO-PET) film vapor-deposited with indium tin oxide (for example, "125 Tetolite OES" manufactured by Oike Kogyo Co., Ltd.) can be used. Next, using a commercially available tensile tester, while gripping the evaluation sheet, the pressure-sensitive adhesive sheet 1 is peeled from the optical film 2 at a peel angle of 180° and a pulling rate of 300 mm / min, and the average value of the peel force is specified as the anchoring force F between the pressure-sensitive adhesive sheet 1 and the optical film 2. The above test is performed in an atmosphere of 23°C.

[0168] 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.

[0169] 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.

[0170] Another example of an optical laminate according to an embodiment of the present invention is shown in Figure 5. The optical laminate in Figure 5 includes a polarizing film 2A and a retardation film 2B as the optical sheet 2 (see Figures 3 and 4). The optical laminate 20C in Figure 5 has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, and a polarizing film 2A are layered in this order. After peeling off the release liner 3, the optical laminate 20C can be used by being attached to, for example, an image-forming layer.

[0171] 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.

[0172] Another example of an optical laminate according to an embodiment of the present invention is shown in Figure 6. The optical laminate in Figure 6 includes a polarizing film 2A and a retardation film 2B as the optical sheet 2 (see Figures 3 and 4). The optical laminate 20D in Figure 6 has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, a polarizing film 2A, and a protective film 5 are layered in this order. After peeling off the release liner 3, the optical laminate 20D can be used by being attached to, for example, an image-forming layer.

[0173] 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.

[0174] The protective film 5 may be bonded to the optical film 2 (polarizing film 2A) with any adhesive. Bonding with an adhesive sheet 1 is also possible.

[0175] The optical laminate may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and the optical film 2 .

[0176] 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.

[0177] 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.

[0178] 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.

[0179] ≪≪4. Image Display Device≫≫ An example of an image display device according to an embodiment of the present invention is shown in FIG. 7. The image display device 21 of FIG. 7 has a layered structure in which a substrate 7, an image forming layer (e.g., an organic EL layer or a liquid crystal layer) 6, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, a polarizing film 2A, and a protective film 5 are layered in this order. The image display device 21 of FIG. 7 includes the optical laminate 20D of FIG. 6 (excluding the release liner 3). The image display device 21 may include the optical laminates 20A, 20B, and 20C of FIGS. 3 to 5 instead of the optical laminate 20D. The substrate 7 and the image forming layer 6 may have the same configurations as the substrate and the image forming layer, respectively, of known image display devices.

[0180] The image display device 21 in Fig. 7 may be an organic EL display or a liquid crystal display. However, the image display device 21 is not limited to this example. The image display device 21 may 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.

[0181] The image display device 21 may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and an optical laminate (for example, one of the optical laminates 20A to 20D).

[0182] 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.

[0183] <Preparation of Dispersion D1> [Synthesis of Dispersant d] 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 d (R 1 = styrenephenyl group (in the above formula (4), k = 3, AO = oxyethylene group, n = 8, X = O, Y = methylene group).

[0184] [Preparation of Dispersion D1] 1.5 parts by weight of the above-mentioned Dispersant d and 28.5 parts by weight of phenoxybenzyl acrylate (trade name "Light Acrylate POB-A" manufactured by Kyoeisha Chemical Co., Ltd.; hereinafter referred to as "POB-A") were added to 100 parts by weight of a methanol dispersion of zirconium oxide particles (in this example, "zirconia (ZrO) particles") (manufactured by Sakai Chemical Industry Co., Ltd., grade "SZR-M," average particle size (D50) measured by dynamic light scattering: 3 nm, ZrO particle concentration: 30 wt %) and mixed. Next, the solvent was removed under reduced pressure using a rotary evaporator to obtain Dispersion D1, a dispersion of ZrO particles. The contents of each component in Dispersion D1 are shown in Table 1.

[0185] <Preparation of Dispersion D2> 50 parts by mass of a methanol dispersion of zirconium oxide particles (in this example, "zirconia (ZrO) 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.

[0186]

[0187] The abbreviations in Table 1 are as follows: POB-A: Phenoxybenzyl acrylate (trade name "Light Acrylate POB-A" manufactured by Kyoeisha Chemical Co., Ltd.) P2HA: Phenoxydiethylene glycol acrylate (trade name "Light Acrylate P2H-A" manufactured by Kyoeisha Chemical Co., Ltd.)

[0188] <Synthesis of Polymer B> 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 1 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 B. The solution was then heated at 90°C for 12 hours, and then subjected to reduced pressure treatment at 120°C for 3 hours to remove the ethyl acetate. This yielded Polymer B, in which the amount of ethyl acetate detected by gas chromatography was less than 0.1 parts by weight.

[0189] The weight-average molecular weight (Mw) of Polymer B was 4,000. The weight-average molecular weight (Mw) of Polymer B was measured by GPC (gel permeation chromatography). Analytical device: Alliance manufactured by Waters Column: TSKgel SuperHZM-H x 2 manufactured by Tosoh Column temperature: 40°C Eluent: THF Flow rate: 0.2 mL / min Injection volume: 30 μL Detector: Refractive index (RI) Standard sample: Polystyrene (PS) manufactured by Agilent

[0190] Example 1 The above dispersion D1 was mixed with phenoxybenzyl acrylate (POB-A) as a monomer a1 having a double bond-containing ring, 2-(2-ethoxyethoxy)ethyl acrylate (CBA) as a monomer a2 having at least one ether group and having a glass transition temperature of 0°C or less when made into a homopolymer, the above polymer B, 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent, 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184" manufactured by IGM Resins) and 1,2-diphenylethan-1-one (trade name "Omnirad 651" manufactured by IGM Resins) as photopolymerization initiators, and pentaerythritol as an antioxidant, so that the contents of each component were as shown in Table 2. Tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (trade name "Irganox 1010" manufactured by BASF) and 3-glycidoxypropyltrimethoxysilane (trade name "KBM-403" manufactured by Shin-Etsu Silicones Co., Ltd.) as a silane coupling agent were mixed together. This gave a pressure-sensitive adhesive composition of Example 1.

[0191] (Examples 2 to 15 and Comparative Examples 1 to 5) The PSA compositions of Examples 2 to 15 and Comparative Examples 1 to 5 were obtained by the same method as the method for preparing the PSA composition of Example 1, except that the content of each component was changed as shown in Table 2 or Table 3. In Examples 12 to 15, Dispersion D2 was added instead of Dispersion D1. In the PSA compositions of Examples 5, 10 to 15 and Comparative Example 1, Polymer B was not added. In the PSA compositions of Examples 2 to 4, 8 to 9, 11, 13 to 15 and Comparative Examples 4 and 5, a monomer other than POB-A was added instead of CBA, while in the PSA compositions of Comparative Examples 1 to 3, no monomer other than POB-A was added.

[0192]

[0193]

[0194] The abbreviations in Tables 2 and 3 are as follows: POB-A: phenoxybenzyl acrylate (monomer a1) (trade name "Light Acrylate POB-A" manufactured by Kyoeisha Chemical Co., Ltd.) CBA: 2-(2-ethoxyethoxy)ethyl acrylate (monomer a2) MEA: 2-methoxyethyl acrylate (monomer a2) MPE400A: methoxypolyethylene glycol acrylate (molecular weight: approximately 470 g / mol) (monomer a2) (trade name "MPE400A" manufactured by Osaka Organic Chemical Industry Ltd.) MPE550A: methoxypolyethylene glycol acrylate (molecular weight: 620 g / mol) (monomer a2) (trade name "MPE550A" manufactured by Osaka Organic Chemical Industry Ltd.) P2HA: phenoxydiethylene glycol acrylate (monomer a2) (trade name "Light Acrylate P2H-A" manufactured by Kyoeisha Chemical Co., Ltd.) 4HBA: 4-hydroxybutyl acrylate (hydroxyl group-containing monomer) BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate NDDA: 1,9-nonanediol diacrylate (trade name "Viscoat #260" manufactured by Osaka Organic Chemical Industry Co., Ltd.) Omni.184: 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184" manufactured by IGM Resins) Omni.651: 1,2-diphenylethan-1-one (trade name "Omnirad 651" manufactured by IGM Resins) Irganox 1010: pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (trade name "Irganox 1010" manufactured by BASF) KBM403: 3-glycidoxypropyltrimethoxysilane (trade name "KBM-403" manufactured by Shin-Etsu Silicones Co., Ltd.)

[0195] <Evaluation> [Measurement of Tg when made into a homopolymer] For each monomer contained in the pressure-sensitive adhesive compositions of Examples and Comparative Examples, Tg when made 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 (manufactured by Topcon Technohouse Corporation under the trade name "UD-T36T2").

[0196] 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" manufactured by TA Instruments. The Tg of each monomer when made into a homopolymer is shown in Table 4. The abbreviations in Table 4 are the same as those in Tables 2 and 3.

[0197]

[0198] (Adhesive Sheet 1 for Evaluation) Using the adhesive composition of Example 1, an adhesive sheet 1 for evaluation was produced by the following method, and various evaluation tests were carried out.

[0199] [Preparation of Release Liner A] A silicone-based release agent composition was obtained by mixing 30 parts by weight of an addition reaction curable silicone (LTC761 containing a hexenyl group-containing polyorganosiloxane, a 30 wt% toluene solution, manufactured by Dow Corning Toray 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. The concentration of silicone solids in the release agent composition was 1.0 wt%. Next, the release agent composition was applied with a wire bar to one side of a liner substrate (Lumirror XD500P, a polyester film, 75 μm thick), and heated at 130° C. for 1 minute to prepare a release liner A having a release layer (thickness 60 nm) on one side.

[0200] [Preparation of Pressure-Sensitive Adhesive Sheet 1 and Laminate S1] A pressure-sensitive adhesive composition was applied to the release surface of release liner B (a release-treated PET film, manufactured by Mitsubishi Chemical, MRF38) using an applicator to form a coating layer of a predetermined thickness. Next, release liner A was placed on the formed coating layer to obtain laminate S1. Release liner A was placed so that the release layer was in contact with the coating layer. Next, an illuminance of 9 mW / cm was applied from the side of release liner B in laminate S1. 2 and irradiation time was 400 seconds (integrated light dose 3600 mJ / cm 2 ). An LED was used as the light source, and the peak wavelength of the irradiated light was 340 nm. This photo-cured the coating layer, and a PSA sheet (thickness 20 μm) sandwiched between release liner A and release liner B 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 release liner B.

[0201] Next, the release liner B was peeled off from the laminate S1, and a discharge amount of 61 W / m was applied to the exposed surface (first surface) of the pressure-sensitive adhesive sheet 1. 2 The pressure-sensitive adhesive sheet 1 of Example 1 was thus obtained.

[0202] [Evaluation of Refractive Index] The refractive index of the first surface of the pressure-sensitive adhesive sheet 1 was measured in critical angle mode using a prism coupler (Model "2010M" manufactured by Metricon) at a measurement temperature of 25°C and a measurement wavelength of 594 nm.

[0203] [Haze Evaluation] The substrate sheet and release liner were peeled off from the pressure-sensitive adhesive sheet 1, and alkali-free glass plates (thickness 0.7 to 0.8 mm, total light transmittance 92%, haze 0.06%) were attached to each exposed surface, to obtain a test piece in which the pressure-sensitive adhesive sheet was sandwiched between the two alkali-free glass plates. This test piece was left in an environment of 23°C and 50% RH for 30 minutes, and then placed in a pressure degassing apparatus (autoclave) and autoclaved for 30 minutes under conditions of a temperature of 50°C and a pressure of 0.5 MPa. Next, it was left in an atmosphere of 23°C and 50% RH for 24 hours. Next, the haze of the test piece was measured using a spectroscopic haze meter (HSP-150vis, manufactured by Murakami Color Research Laboratory) in a measurement environment of 23°C.

[0204] [Preparation of Optical Laminate L1] (Preparation of Polarizing 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 corona treatment. 100 parts by weight of a PVA-based resin prepared by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIRMER") in a 9:1 ratio was added to 13 parts by weight of potassium iodide, and the resulting mixture 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 laminate S2.

[0205] The obtained laminate S2 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 S2 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 S2 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).

[0206] Next, the laminate S2 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 the laminate S2 was 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., it was uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds so that the total stretch ratio was 5.5 times (underwater stretching treatment).

[0207] Thereafter, the laminate S2 was immersed in a cleaning bath (an aqueous solution obtained by blending 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).

[0208] 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.

[0209] 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%).

[0210] 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)].

[0211] (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 -5mol) 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.

[0212] 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.

[0213] (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.

[0214] (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.

[0215] (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.

[0216] 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.

[0217] 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).

[0218] (Preparation of Optical Laminate L1) An adhesive layer (5 μm thick) formed from adhesive G2 was transferred onto the surface of the second protective film of the polarizing film from a release liner, and a first retardation film was attached to the polarizing film via the adhesive layer to obtain a laminate S3. 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.

[0219] 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 applied layer was then attached to the surface of the first retardation film of the laminate S3 using a roller. Thereafter, the adhesive G1 was cured by irradiating it with ultraviolet light from the second retardation film side using an active energy ray irradiation device, and then the adhesive was dried with hot air at 70° C. for 3 minutes.

[0220] The pressure-sensitive adhesive sheet 1 was transferred from the laminate S1 to the surface of the second retardation film of the laminate S3 obtained as described above, to obtain an optical laminate L1 having a configuration 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].

[0221] [Evaluation of anchoring force F] For the optical laminate L1, the anchoring force F between the pressure-sensitive adhesive sheet 1 and the polarizing film was measured by the method described above. The double-sided tape used was "No. 531" manufactured by Nitto Denko Corporation. A SUS304 plate (width 40 mm x length 120 mm) was used as the stainless steel test plate. An ITO-PET film (manufactured by Oike Kogyo Co., Ltd., product name "125 Tetolite OES") was used as the evaluation sheet. The pressure-sensitive adhesive sheet 1 was peeled off from the optical film 2 using a tensile tester (manufactured by Shimadzu Corporation, product name "Autograph SHIMAZU AG-1 10KN").

[0222] [Evaluation of Adhesion Strength P] Using the above optical laminate L1, the adhesive strength between the pressure-sensitive adhesive sheet 1A 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 from the alkali-free glass using a tensile tester (Shimadzu Corporation, Autograph SHIMAZU AG-1 10KN). Using the tensile tester, a test piece was peeled from the alkali-free glass at a peel rate of 60 mm / min and a peel angle of 90° in an environment of 25°C, and the peel strength was measured.

[0223] (Adhesive Sheets 2 to 15, C1 to C5 for Evaluation) Except for changing the adhesive composition used as shown in Table 5, Adhesive Sheets 2 to 15, C1 to C5 were produced by the same method as Adhesive Sheet 1. Using the obtained Adhesive Sheets 2 to 15, C1 to C5, the refractive index, anchoring strength F, and adhesive strength P of Adhesive Sheets 2 to 15, C1 to C5 were evaluated by the same method as Adhesive Sheet 1.

[0224] The evaluation results for PSA sheets 1 to 15 and C1 to C5 are shown in Table 5.

[0225]

[0226] As can be seen from Table 5, all of the pressure-sensitive adhesive sheets formed from the pressure-sensitive adhesive compositions of the Examples, which contained inorganic particles and, as the monomer component M, monomer a1 having a double-bond-containing ring and monomer a2 having at least one ether group and having a glass transition temperature of 0°C or lower when made into a homopolymer, had a higher anchoring strength F than the pressure-sensitive adhesive compositions of the Comparative Examples. Furthermore, all of the pressure-sensitive adhesive sheets formed from the pressure-sensitive adhesive compositions of the Examples had a high refractive index. Furthermore, the pressure-sensitive adhesive sheets formed from the pressure-sensitive adhesive compositions of the Examples had an adhesive strength P equivalent to or higher than that of the pressure-sensitive adhesive compositions of the Comparative Examples.

[0227] 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 photocurable pressure-sensitive adhesive composition comprising: a monomer component M; and inorganic particles, wherein the monomer component M comprises: a monomer a1 having a double bond-containing ring; and a monomer a2 having at least one ether group and having a glass transition temperature of 0°C or lower when made into a homopolymer.

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

3. The pressure-sensitive adhesive composition according to claim 1, wherein the monomer a1 includes a (meth)acrylic monomer having the double bond-containing ring.

4. The pressure-sensitive adhesive composition according to claim 1, wherein the monomer a1 includes phenoxybenzyl acrylate.

5. The pressure-sensitive adhesive composition according to claim 1, wherein the content of said monomer a1 in 100 parts by weight of said monomer component M is 80 to 99.9 parts by weight.

6. The pressure-sensitive adhesive composition according to claim 1, wherein the side chain of the ether group is linear.

7. The pressure-sensitive adhesive composition according to claim 1, wherein the monomer a2 has an oxyalkylene group.

8. The pressure-sensitive adhesive composition according to claim 1, wherein the content of said monomer a2 in 100 parts by weight of said monomer component M is 1 to 20 parts by weight.

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

10. The pressure-sensitive adhesive composition according to claim 1, wherein the content of the inorganic particles in the pressure-sensitive adhesive composition is 80 to 120 parts by weight per 100 parts by weight of the monomer component M.

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

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

13. 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.

14. The pressure-sensitive adhesive composition according to claim 13, wherein the polymer B contains a structural unit derived from a monomer b1 having a double bond-containing ring.

15. The pressure-sensitive adhesive composition according to claim 13, wherein the content of said polymer B in said pressure-sensitive adhesive composition is 1 to 20 parts by weight per 100 parts by weight of said monomer component M.

16. A pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 15.

17. The pressure-sensitive adhesive sheet according to claim 16, having a refractive index of 1.62 to 1.

70.

18. The pressure-sensitive adhesive sheet according to claim 16, which has an anchoring force with ITO-PET of 10 N / mm or more.

19. An optical laminate comprising the pressure-sensitive adhesive sheet according to claim 16 and an optical film.

20. An image display device comprising the optical laminate according to claim 19.

Images