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

Abstract

The provided adhesive composition is a photocurable adhesive composition containing a monomer component M, inorganic particles being included, and the rate of change in the refractive index as defined by the absolute value of [1–(n'1 / n1)] × 100 being 1% or less, where n1 is the initial refractive index of an adhesive sheet formed from the adhesive composition and n'1 is the refractive index after a reliability test with a testing time of 240 hours at 85°C. The provided adhesive composition is suitable for forming an adhesive sheet that, despite containing inorganic particles, makes it possible to suppress display defects.

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] To improve the surface brightness of an image display device, it is advantageous to use a pressure-sensitive adhesive sheet having a high refractive index (see Patent Document 1). Patent Document 1 discloses a thermosetting pressure-sensitive adhesive composition containing an acrylic polymer having a specific composition and weight-average molecular weight as a base polymer, inorganic particles, a plasticizer, and a silane coupling agent.

[0004] JP 2017-14376 A

[0005] In addition to heat-curable pressure-sensitive adhesive compositions, photo-curable pressure-sensitive adhesive compositions are also available. According to the studies of the present inventors, when the refractive index of a pressure-sensitive adhesive sheet is increased by inorganic particles, display defects tend to occur particularly in photo-curable pressure-sensitive adhesive compositions.

[0006] An object of the present invention is to provide a photocurable pressure-sensitive adhesive composition suitable for forming a pressure-sensitive adhesive sheet that can suppress display defects even when containing inorganic particles.

[0007] [1] A pressure-sensitive adhesive composition according to an embodiment of the present invention is a photocurable pressure-sensitive adhesive composition containing a monomer component M, and inorganic particles. When the initial refractive index of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition is n1 and the refractive index after a reliability test at 85°C for 240 hours is n'1, the refractive index change rate, defined as the absolute value of [1-(n'1 / n1)] x 100, is 1% or less. [2] In the pressure-sensitive adhesive composition described in [1] above, the content of the inorganic particles may be 10 to 70 parts by weight per 100 parts by weight of the total of the monomer component M and the inorganic particles. [3] In the pressure-sensitive adhesive composition described in [1] or [2] above, the inorganic particles may have an average particle size of 100 nm or less. [4] In the pressure-sensitive adhesive composition described in any of [1] to [3] above, the pressure-sensitive adhesive sheet may have a haze of 2.0% or less. [5] In the pressure-sensitive adhesive composition described in any of [1] to [4] above, the monomer component M may include a monomer a having a first double bond-containing ring. [6] In the pressure-sensitive adhesive composition described in [5] above, the first double-bond-containing ring may be an aromatic ring. [7] In the pressure-sensitive adhesive composition described in [5] or [6] above, the monomer a may include a (meth)acrylic monomer having the first double-bond-containing ring. [8] In the pressure-sensitive adhesive composition described in any of [1] to [7] above, the monomer component M may include phenoxybenzyl acrylate. [9] In the pressure-sensitive adhesive composition described in any of [1] to [8] above, the amount of residual monomer in the pressure-sensitive adhesive sheet may be 10,000 ppm (by weight) or less.

[10] The pressure-sensitive adhesive composition described in any of [1] to [9] above may further include a compound having an alkoxysilane group.

[11] The pressure-sensitive adhesive composition described in any of [1] to

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

[12] In the pressure-sensitive adhesive composition described in the above

[11] , the polymer B may contain a structural unit derived from a monomer b having a second double bond-containing ring.

[13] In the pressure-sensitive adhesive composition described in the above

[12] , the second double bond-containing ring may be an aromatic ring.

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

[13] above may further contain an antioxidant.

[15] A pressure-sensitive adhesive composition according to another embodiment of the present invention, different from [1] above, is a photocurable pressure-sensitive adhesive composition containing a monomer component M, wherein the pressure-sensitive adhesive composition contains inorganic particles. When a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition is measured for refractive index after a reliability test at 85°C for 240 hours using a prism coupler, no peak indicating a decrease in light intensity is observed at an angle higher than the critical angle in a graph showing the relationship between the angle of incidence to the prism and the measured light intensity.

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

[15] above.

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

[16] above and an optical film.

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

[17] above.

[0008] According to an embodiment of the present invention, a photocurable pressure-sensitive adhesive composition suitable for forming a pressure-sensitive adhesive sheet that can suppress display defects even while containing inorganic particles can be provided. A pressure-sensitive adhesive sheet formed from such a pressure-sensitive adhesive composition can also be provided. Furthermore, an optical laminate including such a pressure-sensitive adhesive sheet and an optical film can be provided. Furthermore, an image display device including such an optical laminate 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 of the present invention from a pressure-sensitive adhesive composition of the present invention. FIG. 3 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of an image display device according to one embodiment of the present invention. FIG. 7 is a graph showing an example of the relationship between the angle of incidence on a prism and the amount of measured light, which can be obtained when measuring the refractive index of a pressure-sensitive adhesive sheet using a prism coupler. FIG. 8 is a graph showing another example of the relationship between the angle of incidence on a prism and the amount of measured light, which can be obtained when measuring the refractive index of a pressure-sensitive adhesive sheet using a prism coupler.

[0010] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be implemented in any modified form without departing from the gist of the present invention.

[0011] [Terminology, etc.] 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.

[0012] 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".

[0013] In this specification, when the term "100 parts by weight of the total of the monomer component M and the inorganic particles" is used as a standard for the content of various components in the 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, the monomer component M that is consumed for forming a partially polymerized product that may be contained in the pressure-sensitive adhesive composition, and the inorganic particles.

[0014] <<1. Pressure-sensitive adhesive composition>> A pressure-sensitive adhesive composition according to an embodiment of the present invention (hereinafter referred to as "pressure-sensitive adhesive composition (A)") is a photocurable pressure-sensitive adhesive composition containing a monomer component M and inorganic particles. A portion of the monomer component M may be partially polymerized. The weight-average molecular weight of the partially polymerized product may be greater than 10,000, 20,000 or more, 20,000 or more, 30,000 or more, 30,000 or more, 40,000 or more, 50,000 or more, 75,000 or more, or even 100,000 or more. Being a photocurable pressure-sensitive adhesive composition is particularly preferable in terms of environmental protection and sustainability, since the amount of energy required to form a pressure-sensitive adhesive sheet can be reduced compared to a thermosetting pressure-sensitive adhesive composition, which mainly uses heat to form a pressure-sensitive adhesive sheet.

[0015] Furthermore, when the initial refractive index of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (A) is n1 and the refractive index after a 240-hour reliability test at 85°C is n'1, the refractive index change rate, defined as the absolute value of [1-(n'1 / n1)] x 100 (hereinafter referred to as "refractive index change rate (240)"), is 1% or less. According to the inventors' studies, the display defects may be due to the migration and aggregation of inorganic particles in the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition. Furthermore, when a pressure-sensitive adhesive sheet is formed from a photocurable pressure-sensitive adhesive composition, inorganic particles tend to collect on the sheet surface, which may promote the migration and aggregation. The ease of migration and aggregation of inorganic particles is thought to be assessable by the change in refractive index in the reliability test. Note that "initial" typically refers to the time up to two days after the formation of a pressure-sensitive adhesive sheet from the pressure-sensitive adhesive composition (A) at a temperature of 0 to 30°C. Furthermore, according to the inventors' studies, the refractive index of a pressure-sensitive adhesive sheet stored at a temperature of 0 to 30°C after formation shows little change. Therefore, the refractive index of a pressure-sensitive adhesive sheet stored at a temperature of 0 to 30°C can be considered to be the initial refractive index even after two days have passed since its formation.

[0016] The refractive index n1 of the PSA sheet formed from the PSA composition (A) 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, or even 1.64 or more. The upper limit of the refractive index n1 is, for example, 1.70 or less, and may be 1.69 or less, 1.68 or less, 1.67 or less, 1.66 or less, 1.65 or less, 1.64 or less, 1.63 or less, or even 1.62 or less.

[0017] The refractive index change rate (240) of the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (A) may be 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, 0.2% or less, or even 0.1% or less. The lower limit of the refractive index change rate (240) may be 0.0%.

[0018] When the initial refractive index of a PSA sheet formed from the PSA composition (A) is n1 and the refractive index after a reliability test at 85°C for 500 hours is n"1, the refractive index change rate defined as the absolute value of [1-(n"1 / n1)] x 100 (hereinafter referred to as "refractive index change rate (500)") may be 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, 1.1% 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, 0.2% or less, or even 0.1% or less. The lower limit of the refractive index change rate (500) may be 0.0%, or may be 0.1% or more.

[0019] In this specification, the refractive index of a pressure-sensitive adhesive sheet refers to the refractive index of the surface of the pressure-sensitive adhesive sheet. The refractive index of a pressure-sensitive adhesive sheet can be measured using a prism coupler at a measurement temperature of 25°C and a measurement wavelength of 594 nm. When measuring the refractive index using a prism coupler, the amount of light totally reflected at the interface between the prism and the pressure-sensitive adhesive sheet is measured while changing the angle of incidence of the measurement light relative to the prism. When the angle of incidence reaches an angle corresponding to the refractive index of the pressure-sensitive adhesive sheet (critical angle), a drop in the measured light amount from the baseline (commonly referred to as a "shoulder" by those skilled in the art) is observed. In other words, by identifying the angle of incidence at which the measured light amount drops from the baseline in a graph showing the relationship between the angle of incidence on the prism and the measured light amount, the refractive index can be calculated using that angle of incidence as the critical angle. The angle of incidence at which the measured light amount drops from the baseline can be identified as the angle of incidence corresponding to the intersection of the baseline and the line corresponding to the slope of the drop (see Figure 9). For pressure-sensitive adhesive sheets with a thickness of less than 20 μm, measurement using the light propagation mode is generally suitable. For pressure-sensitive adhesive sheets with a thickness of 20 μm or more, measurement using the critical angle mode is generally suitable. A commercially available measuring device can be used for the prism coupler, such as a Model 2010 / M prism coupler manufactured by Metricon, Inc., or an equivalent product. The refractive index n1, refractive index change rate (240), and refractive index change rate (500) of the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (A) can be specifically evaluated by the procedures described in the Examples (including the procedures for forming a pressure-sensitive adhesive sheet from the pressure-sensitive adhesive composition).

[0020] According to the inventors' studies, depending on the state of migration and aggregation of inorganic particles in the pressure-sensitive adhesive sheet, a temporary decrease in the measured light intensity from the baseline may be observed at an incident angle on the higher refractive index side than the critical angle on the graph. The temporary decrease in the measured light intensity is usually observed as a downward-convex peak on the graph. Further studies suggest that the likelihood of migration and aggregation of inorganic particles in a pressure-sensitive adhesive sheet can also be evaluated based on whether the temporary decrease is observed in the pressure-sensitive adhesive sheet after a reliability test at a temperature of 85°C and a test time of 240 hours. In a pressure-sensitive adhesive sheet in which the migration and aggregation of inorganic particles is suppressed in a reliability test, the temporary decrease may not be observed even after the reliability test (FIG. 9 shows an example in which the temporary decrease was not observed, and FIG. 10 shows an example in which the temporary decrease was observed. Note that in FIGS. 9 and 10, amplitudes are observed at angles on the lower refractive index side than the critical angle, but these are amplitudes that can be observed at angles on the lower refractive index side than the critical angle in the sheet refractive index measurement method using a prism coupler, and are unrelated to the migration and aggregation of inorganic particles). In view of the above aspect, the pressure-sensitive adhesive composition according to an embodiment of the present invention may be a photocurable pressure-sensitive adhesive composition containing a monomer component M and inorganic particles, and when a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition is subjected to a reliability test at 85°C for 240 hours and the refractive index is measured using a prism coupler, the composition may be such that, in a graph showing the relationship between the angle of incidence onto the prism and the measured light intensity, no peak indicating a decrease in light intensity is observed at an angle on the higher refractive index side than the critical angle (hereinafter referred to as "pressure-sensitive adhesive composition (α)"). The "peak indicating a decrease in light intensity" typically refers to a peak showing a decrease in light intensity of 10% or more of the decrease in light intensity at the critical angle. The decrease in light intensity is the amount of decrease from the baseline.

[0021] Possible embodiments of the pressure-sensitive adhesive composition (A) and the pressure-sensitive adhesive composition (α) are described below. Unless otherwise specified, the description of the pressure-sensitive adhesive composition (A) also applies to the pressure-sensitive adhesive composition (α). Furthermore, the description of the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (A), the optical laminate including the pressure-sensitive adhesive sheet, and the image display device including the optical laminate also applies to the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (α), the optical laminate including the pressure-sensitive adhesive sheet, and the image display device including the optical laminate, respectively.

[0022] <1-1. Monomer Component M> <1-1-a. Monomer a having a double bond-containing ring> Monomer component M may contain a monomer a having a double bond-containing ring (first double bond-containing ring). Monomer component M may contain one or more types of monomer a. In this specification, 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 a carbon-carbon double bond, a carbon-heteroatom double bond, and a heteroatom-heteroatom double bond. Examples of heteroatoms include nitrogen, sulfur, and oxygen.

[0023] 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.

[0024] The double bond-containing ring may be a carbocyclic ring. Examples of the carbocyclic ring include a benzene ring (which may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure), a naphthalene ring, an indene ring, an azulene ring, an anthracene ring, and a phenanthrene ring. The double bond-containing ring may be a heterocyclic ring (heterocyclic ring). Examples of the heterocyclic ring include a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, and a thiophene ring. Examples of heteroatoms that may be contained in the heterocyclic ring as ring-constituting atoms include at least one selected from the group consisting of nitrogen, sulfur, and oxygen. The heteroatom may be one or both of nitrogen and sulfur. The double bond-containing ring may be a fused ring. An example of the monomer a has a structure in which one or more carbocyclic rings and one or more heterocyclic rings are fused, such as a dinaphthothiophene structure.

[0025] The double bond-containing ring may have one or more substituents (excluding ethylenically unsaturated groups, which will be described later) on the ring-constituting atoms, or may have no substituents. Examples of the substituents include alkyl groups, alkoxy groups, aryloxy groups, hydroxyl groups, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, etc.), hydroxyalkyl groups, hydroxyalkyloxy groups, and glycidyloxy groups. However, the substituents are not limited to the above examples. The substituents may contain carbon atoms, and in such cases, the number of carbon atoms contained in the substituent may be, for example, 1 to 4, 1 to 3, or even 1 to 2. One example of the double bond-containing ring has no substituents on the ring-constituting atoms. Another example of the double bond-containing ring has one or more substituents selected from the group consisting of alkyl groups, alkoxy groups, and halogen atoms (e.g., bromine atoms) on the ring-constituting atoms.

[0026] In the monomer a, the number of double bond-containing rings contained in one molecule is, for example, 1, and may be 2 or more. The upper limit of the number of double bond-containing rings is not particularly limited and is, for example, 16 or less. The upper limit may be 12 or less, 8 or less, 6 or less, 5 or less, 4 or less, 3 or less, or even 2 or less.

[0027] In the monomer a, the double bond-containing ring is preferably located on a side chain. In other words, the monomer a preferably has at least one double bond-containing ring and at least one ethylenically unsaturated group in one molecule. The monomer a may be a monomer (aromatic ring-containing monomer) having at least one aromatic ring and at least one ethylenically unsaturated group in one molecule. As the monomer a, a compound having one ethylenically unsaturated group in one molecule (in other words, a monofunctional monomer) is preferably used.

[0028] Examples of ethylenically unsaturated groups are (meth)acryloyl, vinyl, and (meth)allyl groups. From the viewpoint of polymerization reactivity, (meth)acryloyl groups are preferred, and from the viewpoint of flexibility and adhesiveness, acryloyl groups are more preferred. In other words, monomer a preferably contains a (meth)acrylic monomer having a double bond-containing ring, and more preferably contains an acrylic monomer having a double bond-containing ring. Examples of (meth)acrylic monomers having a double bond-containing ring include aromatic ring-containing (meth)acrylates. Specific examples of aromatic ring-containing (meth)acrylates will be described later.

[0029] The double bond-containing ring and the ethylenically unsaturated group may be bonded directly or via a linking group. An example of the linking group includes one or more groups selected from the group consisting of alkylene groups, oxyalkylene groups, poly(oxyalkylene) groups, phenyl groups, alkylphenyl groups, alkoxyphenyl groups, groups in which one or more hydrogen atoms in these groups have been substituted with hydroxyl groups (e.g., hydroxyalkylene groups), oxy groups (—O—), and thiooxy groups (—S—). In one example of Monomer A, the double bond-containing ring and the ethylenically unsaturated group are bonded directly. In another example of Monomer A, the double bond-containing ring and the ethylenically unsaturated group are bonded via a linking group selected from the group consisting of alkylene groups, oxyalkylene groups, and poly(oxyalkylene) groups. The number of carbon atoms in the alkylene group and oxyalkylene group that can be included in the linking group is, for example, 1 to 4, and may be 1 to 3, or even 1 to 2. The number of repeating oxyalkylene units in the poly(oxyalkylene) group that can be contained in the linking group is, for example, 1 to 8, and may be 1 to 6, 1 to 4, 1 to 3, 2 to 3, or even 1 to 2, 2, or 1.

[0030] Specific examples of the monomer a include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds may be used alone or in combination of two or more.

[0031] Monomer a may contain two or more aromatic rings (preferably carbon rings) in one molecule. A monomer having two or more aromatic rings and at least one ethylenically unsaturated group in one molecule (aromatic ring-containing monomer) is particularly suitable for increasing the refractive index of the PSA sheet.

[0032] Examples of the aromatic ring-containing monomer include a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, a monomer having a structure in which two or more non-condensed aromatic rings are directly bonded, a monomer having a condensed ring, a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, and a monomer having a dibenzothiophene structure. Among these, a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group (for example, phenoxybenzyl (meth)acrylate described below) is preferably used.

[0033] The linking group may contain atoms such as P, Ge, Te, Se, N, S, and Si, and these atoms may be bonded to an oxygen atom. However, the linking group does not have to contain any of the above atoms. Examples of the linking group include an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (e.g., -O-(CH2) n -; n is 1 to 3, preferably 1), a thiooxyalkylene group (e.g., -S-(CH2) n -; n is 1 to 3, preferably 1), a straight chain alkylene group (-(CH2) n -; n is 1 to 6, preferably 1 to 3), and the above-mentioned oxyalkylene group, the above-mentioned thiooxyalkylene group, and the above-mentioned straight-chain alkylene group in which the alkylene group is partially or completely halogenated. The linking group may contain one or more types selected from the group consisting of an oxy group, a thiooxy group, an oxyalkylene group, and a straight-chain alkylene group. Specific examples of monomers having a structure in which two or more non-fused aromatic rings are bonded via a linking group include phenoxybenzyl (meth)acrylate, thiophenoxybenzyl (meth)acrylate, and benzyl benzyl (meth)acrylate.

[0034] Examples of monomers having a structure in which two or more non-fused aromatic rings are directly bonded include biphenyl structure-containing (meth)acrylates, triphenyl structure-containing (meth)acrylates, and vinyl group-containing biphenyls. Specific examples include o-phenylphenol (meth)acrylate, biphenylmethyl (meth)acrylate, and biphenylmethyl (meth)acrylate.

[0035] Examples of monomers having a fused ring include naphthalene ring-containing (meth)acrylates, anthracene ring-containing (meth)acrylates, vinyl group-containing naphthalenes, and vinyl group-containing anthracenes. Specific examples include 1-naphthylmethyl (meth)acrylate (also known as 1-naphthalenemethyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, and 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate.

[0036] 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.

[0037] Examples of the monomer having a dinaphthothiophene structure are (meth)acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, and (meth)allyl group-containing dinaphthothiophene. Specific examples include (meth)acryloyloxymethyl dinaphthothiophene (e.g., a compound having a structure in which a CHCH(R)C(O)OCH group is bonded to the 5th or 6th position of the dinaphthothiophene ring; R is a hydrogen atom or a methyl group), (meth)acryloyloxyethyl dinaphthothiophene (e.g., a compound having a structure in which a CHCH(R)C(O)OCH(CH) group or a CHCH(R)C(O)OCHCH group is bonded to the 5th or 6th position of the dinaphthothiophene ring; R is a hydrogen atom or a methyl group), vinyl dinaphthothiophene (e.g., a compound having a structure in which a vinyl group is bonded to the 5th or 6th position of the naphthothiophene ring), and (meth)allyloxy dinaphthothiophene. A monomer having a dinaphthothiophene structure is included in the concept of a monomer having a fused ring because it has a naphthalene structure and also has a structure in which a thiophene ring and two naphthalene structures are fused together.

[0038] 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.

[0039] Monomer a may be a monomer having one aromatic ring (preferably a carbon ring) and at least one ethylenically unsaturated group in one molecule (aromatic ring-single-containing monomer).

[0040] 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.

[0041] Monomer a may have a structure in which an oxyethylene chain is interposed between the ethylenically unsaturated group and the double bond-containing ring in the various monomers a described above. Monomers having this structure can be understood as ethoxylated products of the original monomers. The number of repeating oxyethylene units (—CHCHO—) in the oxyethylene chain is, for example, 1 to 8, and may be 1 to 6, 1 to 4, 1 to 3, or even 1 to 2, or even 1. Examples of monomer a that is an ethoxylated product include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol (meth)acrylate.

[0042] The proportion of the aromatic ring-containing monomer in the monomer a is not particularly limited, and may be 5% by weight or more, 25% by weight or more, or even 40% by weight or more. From the viewpoint of further increasing the refractive index of the pressure-sensitive adhesive sheet, the proportion may be 50% by weight or more, more than 50% by weight, 60% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, 95% by weight or more, or even 98% by weight or more. Substantially 100% by weight of the monomer a may be a aromatic ring-containing monomer. In other words, only one or two or more aromatic ring-containing monomers may be used as the monomer a. The upper limit of the proportion is not particularly limited, and may be less than 100% by weight, 98% by weight or less, 97% by weight or less, 96% by weight or less, or even 95% by weight or less.

[0043] The proportion of the multiple aromatic ring-containing monomer in the monomer component M is not particularly limited, and may be 3 wt% or more, 10 wt% or more, or even 25 wt% or more. From the viewpoint of increasing the refractive index of the pressure-sensitive adhesive sheet, the proportion may be more than 35 wt%, more than 50 wt%, more than 60 wt%, 70 wt% or more, 75 wt% or more, 80 wt% or more, 85 wt% or more, 90 wt% or more, more than 90 wt%, or even 95 wt% or more. The upper limit of the proportion is not particularly limited, and may be less than 100 wt%, 98 wt% or less, 97 wt% or less, 96 wt% or less, or even 95 wt% or less.

[0044] Monomer a may contain a high refractive index monomer. In this specification, the high refractive index monomer means 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.

[0045] 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.

[0046] 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), phenoxydiethylene glycol acrylate (refractive index 1.510), 6-acryloyloxymethyldinaphthothiophene (refractive index 1.75), 6-methacryloyloxymethyldinaphthothiophene (refractive index 1.726), 5-acryloyloxyethyldinaphthothiophene (refractive index 1.786), 6-acryloyloxyethyldinaphthothiophene (refractive index 1.722), 6-vinyldinaphthothiophene (refractive index 1.802), and 5-vinyldinaphthothiophene (refractive index 1.793). However, the high refractive index monomer is not limited to the above examples.

[0047] The proportion of the high refractive index monomer in monomer a is not particularly limited and may be, for example, 5 wt% or more, 25 wt% or more, 35 wt% or more, or even 40 wt% or more. From the viewpoint of further increasing the refractive index of the pressure-sensitive adhesive sheet, the proportion may be 50 wt% or more, 70 wt% or more, 85 wt% or more, 90 wt% or more, or even 95 wt% or more. Only the high refractive index monomer may be contained in the monomer component M as monomer a. The upper limit of the proportion may be less than 100 wt%, 98 wt% or less, 97 wt% or less, 96 wt% or less, or even 95 wt% or less.

[0048] The proportion of the high refractive index monomer in the monomer component M is not particularly limited, and may be 3 wt% or more, 10 wt% or more, 25 wt% or more, or even more than 35 wt%. From the viewpoint of increasing the refractive index of the pressure-sensitive adhesive sheet, the proportion may be more than 50 wt%, more than 60 wt%, 70 wt% or more, 75 wt% or more, 80 wt% or more, 85 wt% or more, 90 wt% or more, more than 90 wt%, 95 wt% or more, or even 100 wt%. The upper limit of the proportion is not particularly limited, and may be less than 100 wt%, 98 wt% or less, 97 wt% or less, 96 wt% or less, or even 95 wt% or less.

[0049] Monomer a may contain a low Tg monomer having a Tg of 10°C or less when made into a homopolymer (hereinafter, the Tg will be referred to as "Tg of the monomer"). The Tg of the low Tg monomer is, for example, 5°C or less, and may be 0°C or less, -10°C or less, -20°C or less, -25°C or less, or even -30°C or less. The lower limit of the Tg of the low Tg monomer is not particularly limited, and may be, for example, -70°C or more, -55°C or more, or even -45°C or more. The low Tg monomers can be used alone or in combination of two or more.

[0050] Examples of low Tg monomers are phenoxybenzyl acrylate (Tg: -35°C), benzyl acrylate (Tg: 6°C), phenoxyethyl acrylate (Tg: 2°C), and phenoxydiethylene glycol acrylate (Tg: -35°C).

[0051] The proportion of the low Tg monomer in the monomer a is not particularly limited and may be, for example, 5% by weight or more, 25% by weight or more, 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 75% by weight or more, 85% by weight or more, 90% by weight or more, or even 95% by weight or more. Only the low Tg monomer as the monomer a may be contained in the monomer component M. The upper limit of the proportion may be less than 100% by weight, 98% by weight or less, 97% by weight or less, 96% by weight or less, or even 95% by weight or less.

[0052] The proportion of the low Tg monomer in the monomer component M is not particularly limited, and may be 3 wt% or more, 10 wt% or more, 25 wt% or more, or even more than 35 wt%. From the viewpoint of increasing the refractive index of the pressure-sensitive adhesive sheet, the proportion may be more than 50 wt%, more than 60 wt%, 70 wt% or more, 75 wt% or more, 80 wt% or more, 85 wt% or more, 90 wt% or more, more than 90 wt%, 95 wt% or more, or even 100 wt%. The upper limit of the proportion is not particularly limited, and may be less than 100 wt%, 98 wt% or less, 97 wt% or less, 96 wt% or less, or even 95 wt% or less.

[0053] As the monomer a, a low Tg monomer and a high Tg monomer may be combined and contained in the monomer component M. The Tg of the high Tg monomer is greater than 10°C, and may be greater than 15°C, or even greater than 20°C.

[0054] Monomer a may contain phenoxybenzyl acrylate, which is particularly suitable for achieving both a high refractive index and adhesiveness of the PSA sheet due to its refractive index and Tg.

[0055] Monomer a may be selected from compounds that do not have a structure in which two or more non-fused aromatic rings are directly bonded (e.g., a biphenyl structure). The proportion of compounds in monomer a that have a structure in which two or more non-fused aromatic rings are directly bonded may be 5% by weight or less, less than 3% by weight, or even 0% by weight.

[0056] The content of monomer a in monomer component M may be, for example, 30% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, more than 70% by weight, 75% by weight or more, 80% by weight or more, 85% by weight or more, 87% by weight or more, 90% by weight or more, 92% by weight or more, 93% by weight or more, 94% by weight or more, or even 95% by weight or more. The upper limit of the content may be, for example, 100% by weight, or 98% by weight or less, 97% by weight or less, 96% by weight or less, 95% by weight or less, 93% by weight or less, 90% by weight or less, less than 90% by weight, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 25% by weight or less, 10% by weight or less, or even 5% by weight or less.

[0057] <1-1-b. Hydroxyl-containing monomer> Monomer component M may contain a hydroxyl-containing monomer. The hydroxyl-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-containing monomers.

[0058] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The hydroxyl group-containing monomer may be a (meth)acrylic monomer or an acrylic monomer.

[0059] Examples of the hydroxyl group-containing monomer 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 2-hydroxyethyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate. The content of the hydroxyl group-containing monomer in the monomer component M may be, for example, 25% by weight or less, 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, or even 2% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, and may be 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. Monomer component M may not contain a hydroxyl group-containing monomer. In calculating the content in monomer component M, a monomer containing a double bond-containing ring and a hydroxyl group is treated as monomer a.

[0060] <1-1-c. Other Monomers> The monomer component M may contain other monomers in addition to the above-mentioned monomers. One example of such other monomers is a (meth)acrylic acid alkyl ester having an alkyl group of 1 to 20 carbon atoms on the side chain. The number of carbon atoms in the alkyl group may be 7 or less, 6 or less, 5 or less, or even 4 or less. The alkyl group may be linear or branched. Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, n-decyl(meth)acrylate, isodecyl(meth)acrylate, n-dodecyl(meth)acrylate (lauryl(meth)acrylate), n-tridecyl(meth)acrylate, n-tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexadecyl(meth)acrylate, heptadecyl(meth)acrylate, and octadecyl(meth)acrylate. The (meth)acrylic acid alkyl ester may be n-butyl(meth)acrylate.

[0061] The content of the (meth)acrylic acid alkyl ester in the monomer component M is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, or even 4% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may not contain a (meth)acrylic acid alkyl ester.

[0062] Another example of a monomer that can be included in the monomer component M is an aliphatic ring-containing monomer. The aliphatic ring-containing monomer has at least one aliphatic ring and at least one ethylenically unsaturated group in one molecule. The aliphatic ring-containing monomer may be used alone or in combination of two or more types.

[0063] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The aliphatic ring-containing monomer may be a (meth)acrylic monomer.

[0064] Examples of the aliphatic ring-containing monomer include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate.

[0065] The content of the alicyclic monomer in the monomer component M is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, or even 4% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may not contain an alicyclic monomer.

[0066] 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.

[0067] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The carboxyl group-containing monomer may be a (meth)acrylic monomer or an acrylic monomer.

[0068] Examples of carboxyl group-containing monomers include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. The content of the carboxyl group-containing monomer in the monomer component M may be, for example, 10% by weight or less, 7% by weight or less, 5% by weight or less, 3% by weight or less, or even 1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may not contain a carboxyl group-containing monomer. In calculating the content in the monomer component M, a monomer containing a double bond-containing ring and a carboxyl group is treated as monomer a.

[0069] The monomer component M may contain monomers other than those mentioned above.

[0070] The content of the (meth)acrylic monomer in the monomer component M may be 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or even 95% by weight or more. In other words, the monomer component M may be a (meth)acrylic monomer component M. The monomer component M may contain only a (meth)acrylic monomer as a monomer.

[0071] <1-2. Inorganic Particles> The pressure-sensitive adhesive composition (A) contains inorganic particles. The inorganic particles are preferably in a dispersed state in the pressure-sensitive adhesive composition (A).

[0072] The inorganic particles can be selected from, for example, metal compound particles and metal particles, one or more types depending on the desired purpose, such as improving the refractive index. The metal compound particles may be metal oxide particles. Examples of materials constituting the metal compound particles include titanium oxide, zirconium oxide, cerium oxide, aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, and niobium oxide. The metal oxide particles can be used alone or in combination of two or more types. The inorganic particles preferably contain zirconium oxide, and may be zirconium oxide particles composed essentially of zirconium oxide alone. The zirconium oxide particles can contribute to increasing the refractive index of the pressure-sensitive adhesive sheet.

[0073] 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.

[0074] The material of the inorganic particles may be a high-entropy alloy in which multiple types of elements are mixed.

[0075] 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.

[0076] The inorganic particles may contain a high refractive index material. The refractive index of the high refractive index material is, for example, 1.60 or more, and may be 1.70 or more, 1.80 or more, or even 2.00 or more. The upper limit of the refractive index of the high refractive index material is not particularly limited, and may be, for example, 3.00 or less, 2.80 or less, 2.50 or less, or even 2.20 or less. The refractive index of the material contained in the inorganic particles can be determined as the refractive index measured on a monolayer film of the material using a commercially available spectroscopic ellipsometer under conditions of 23°C and 549 nm. The spectroscopic ellipsometer may be, for example, an "EC-400" (manufactured by J.A. Woollam) or an equivalent.

[0077] 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.

[0078] The content of the inorganic particles relative to 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant) is, for example, 10 to 70 parts by weight, and may also be 20 to 65 parts by weight, 30 to 60 parts by weight, 35 to 55 parts by weight, or even 40 to 50 parts by weight.

[0079] <1-2-a. Dispersant> The PSA composition (A) 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.

[0080] 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 inorganic particles, and the monomer component M and its polymer, respectively. The dispersant may or may not have a polymerizable functional group such as an ethylenically unsaturated group.

[0081] The hydrophilic portion of the dispersant preferably has a hydrophilic group, such as an ether group or an ester group.

[0082] The hydrophilic portion of the dispersant preferably has a functional group F that exhibits adsorptivity or reactivity with inorganic particles. Examples of the functional group F include at least one selected from the group consisting of alkaline groups and acidic groups. Specific examples of the functional group F include a hydroxy group, a carboxy group, a nitrogen atom-containing group, a sulfur atom-containing group, a phosphorus atom-containing group, and a silicon atom-containing group. The number of functional groups F contained in one molecule of the dispersant may be 1, or may be 2 or more (for example, about 2 to 5). The types of the two or more functional groups F present in one molecule may be the same or different from each other.

[0083] 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.

[0084] The dispersant may be an aliphatic compound, for example, represented by the following formula (1):

[0085] In formula (1), R is an alkyl group, preferably an alkyl group having 1 to 3 carbon atoms, and more preferably an ethyl group. m is 1 to 10, preferably 2 to 8, and more preferably 3 to 7. n is 5 to 20, and preferably 8 to 12.

[0086] The dispersant may be an aromatic compound having an aromatic ring. Examples of the aromatic ring are the same as those mentioned above in the description of monomer a.

[0087] The dispersant may be selected from known surfactants. Examples of surfactants include anionic surfactants (carboxylic acid type, phosphate ester type, sulfate ester type, sulfonic acid type, etc.), nonionic surfactants, cationic surfactants, and amphoteric surfactants. The surfactant that can be used as the dispersant is preferably an anionic surfactant.

[0088] The content of the dispersant relative to 100 parts by weight of the inorganic particles is, for example, 0.1 parts by weight or more, or may be 0.5 parts by weight or more, or even 1.0 part by weight or more. The upper limit of the content is, for example, 30 parts by weight or less, or may be 20 parts by weight or less.

[0089] <1-3. Other Components> Other components that may be contained in the pressure-sensitive adhesive composition (A) will now be described.

[0090] <1-3-a. Photopolymerization initiator> The pressure-sensitive adhesive composition (A) 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.

[0091] 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 (A) may contain one or more photopolymerization initiators.

[0092] Specific examples of the photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651, manufactured by IGM Resins) and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins). However, the photopolymerization initiator that can be contained in the pressure-sensitive adhesive composition (A) is not limited to the above examples.

[0093] The photopolymerization initiator has a concentration of 1 x 10 -4 When the solution was prepared as a 370 nm wavelength solution of 3 × 10 -2 It may be more than that.

[0094] The residual amount of the photopolymerization initiator in the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (A) may be 200 ppm (by weight; the same applies hereinafter) or less. -4 When the solution was prepared as a 370 nm wavelength solution of 3 × 10 -2The remaining amount of the photopolymerization initiator, which is equal to or greater than the predetermined absorbance at a wavelength of 370 nm, may be 200 ppm or less. According to the studies of the present inventors, if a large amount of photopolymerization initiator remaining has an absorbance at a wavelength of 370 nm or greater, fine bubbles may occur when the pressure-sensitive adhesive sheet is used. The bubble generation may be influenced by the absorption of visible light close to the ultraviolet range by the photopolymerization initiator. Reducing the remaining amount of the photopolymerization initiator in the formed pressure-sensitive adhesive sheet can contribute to the suppression of the above-mentioned bubble generation.

[0095] The content of the photopolymerization initiator in the pressure-sensitive adhesive composition (A) is, for example, 0.02 to 10 parts by weight, or may be 0.05 to 5 parts by weight, 0.1 to 3 parts by weight, or even 0.2 to 2 parts by weight, per 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant).

[0096] <1-3-b. Crosslinking Agent> The pressure-sensitive adhesive composition (A) 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.

[0097] 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.

[0098] The amount of crosslinking agent to be added varies depending on the molecular weight, the number of functional groups, etc., but may be, for example, 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less per 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, the mixture of the inorganic particles and the dispersant). The lower limit of the amount to be added may be, for example, 0.01 parts by weight or more, or even 0.05 parts by weight or more.

[0099] <1-3-c. Compound having an alkoxysilane group> The pressure-sensitive adhesive composition (A) may contain a compound having an alkoxysilane group. One example of the compound having an alkoxysilane group is a silane coupling agent.

[0100] The compound having an alkoxysilane group may further contain an epoxy group.

[0101] The amount of the compound having an alkoxysilane group is, for example, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less per 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant). The lower limit of the amount is, for example, 0.1 parts by weight or more, or even 0.2 parts by weight or more. The pressure-sensitive adhesive composition (A) does not need to contain a compound having an alkoxysilane group.

[0102] <1-3-d. Polymer B> The pressure-sensitive adhesive composition (A) may further contain a polymer B having a weight-average molecular weight of 1500 to 30000. Depending on its composition, the polymer B may function as a tackifier.

[0103] The weight average molecular weight of polymer B may be 25,000 or less, 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 lower limit of the weight average molecular weight is 1,500 or more, 2,000 or more, 2,500 or more, 3,000 or more, 3,500 or more, or even 4,000 or more. The weight average molecular weight may be 2,000 to 16,000, and preferably 4,000 to 16,000. The weight average molecular weight is determined by measurement using GPC (gel permeation chromatography) and a value calculated in terms of polystyrene.

[0104] Polymer B preferably contains a structural unit derived from monomer b having a double bond-containing ring (second double bond-containing ring). Polymer B containing a structural unit derived from monomer b can contribute to improving the refractive index of the pressure-sensitive adhesive sheet. Examples of monomer b include those mentioned above for monomer a. Monomer b may be the same as or different from monomer a.

[0105] In the monomer b, the double bond-containing ring is preferably an aromatic ring. The monomer b may contain two or more aromatic rings (preferably carbon rings) in one molecule, and preferably contains a monomer having two or more aromatic rings and at least one ethylenically unsaturated group in one molecule (aromatic ring-multiple-containing monomer). The monomer b particularly preferably contains phenoxybenzyl acrylate.

[0106] The content of the structural unit derived from monomer b in polymer B is, for example, 10% by weight or more, and may be 30% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, 97% by weight or more, 98% by weight or more, 99% by weight or more, or even 100% by weight. In some cases, the content may be 10% by weight or less, 5% by weight or less, or even 1% by weight or less. Polymer B may not contain any structural unit derived from monomer b.

[0107] Polymer B may contain a structural unit derived from a monomer other than the above-mentioned monomer b. Examples of the other monomer include those mentioned above for monomer component M (hydroxyl group-containing monomers, (meth)acrylic acid alkyl esters having an alkyl group of 1 to 20 carbon atoms on the side chain, aliphatic ring-containing monomers, and carboxyl group-containing monomers).

[0108] The content of the structural unit derived from the hydroxyl group-containing monomer in polymer B is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, or even 0.5% by weight or more. Polymer B may not contain any structural unit derived from the hydroxyl group-containing monomer.

[0109] The content of structural units derived from a (meth)acrylic acid alkyl ester in polymer B may be, for example, 50% by weight or less, 40% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, or even 4% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. In some cases, the lower limit of the content may be 50% by weight or more. Polymer B may not contain structural units derived from a (meth)acrylic acid alkyl ester.

[0110] The content of the structural units derived from the alicyclic-containing monomer in the polymer B is, for example, 50% by weight or less, and may be 40% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, or even 2% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. In some cases, the lower limit of the content may be 50% by weight or more, 80% by weight or more, or even 90% by weight or more. The polymer B may not contain any structural units derived from the alicyclic-containing monomer.

[0111] The content of the structural unit derived from the carboxyl group-containing monomer in the polymer B is, for example, 10% by weight or less, and may be 7% by weight or less, 5% by weight or less, 3% by weight or less, or even 1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. It is preferable that the polymer B does not contain any structural unit derived from the carboxyl group-containing monomer.

[0112] Another example of the other monomer is a nitrogen atom-containing monomer. The nitrogen atom-containing monomer refers to a monomer having at least one nitrogen atom in the molecule (in one molecule).

[0113] Examples of the nitrogen atom-containing monomer include N-vinyl cyclic amide, (meth)acrylamide, etc. The nitrogen atom-containing monomer may be used alone or in combination of two or more kinds.

[0114] Examples of N-vinyl cyclic amides include N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-2-caprolactam, N-vinyl-3-morpholinone, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, and vinylmethyloxazolidinone. Examples of (meth)acrylamides include (meth)acrylamide, N-alkyl(meth)acrylamide, and N,N-dialkyl(meth)acrylamide. Examples of (meth)acrylamides also include various N-hydroxyalkyl(meth)acrylamides and N-alkoxyalkyl(meth)acrylamides.

[0115] Examples of nitrogen atom-containing monomers other than N-vinyl cyclic amides and (meth)acrylamides include amino group-containing monomers such as aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; (meth)acryloylmorpholine, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, N-vinylpyrazine, N-vinylmorpholine, N-vinylpyrazole, vinylpyridine, vinylpyrimidine, vinyloxazole, vinylisoxazole, vinylthiazole, vinylisothiazole, vinylpyridazine, (meth)acryloylpyrrolidone, (meth)acryloylpyrrolidine, (meth)acryloylpiperidine, N-methylvinyl heterocycle-containing monomers such as propylpyrrolidone; maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide-based monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-laurylitaconimide, and N-cyclohexylitaconimide; imide group-containing monomers such as succinimide-based monomers of N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; and isocyanate group-containing monomers such as 2-(meth)acryloyloxyethylisocyanate.

[0116] The content of the constitutional unit derived from the nitrogen atom-containing monomer in polymer B is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, or even 0.5% by weight or more. Polymer B may not contain any constitutional unit derived from the nitrogen atom-containing monomer.

[0117] Another example of the other monomer is an ether group-containing monomer. The ether group-containing monomer has at least one ether group and at least one ethylenically unsaturated group in one molecule. The ether group-containing monomer may be used alone or in combination of two or more kinds.

[0118] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The ether group-containing monomer may be a (meth)acrylic monomer.

[0119] Examples of the ether group-containing monomer are 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and methoxydipropylene glycol (meth)acrylate. The ether group-containing monomer is preferably 2-(2-ethoxyethoxy)ethyl acrylate (CBA).

[0120] The content of the structural unit derived from the ether group-containing monomer in polymer B is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, or even 0.5% by weight or more. Polymer B may not contain any structural unit derived from the ether group-containing monomer.

[0121] Polymer B can be produced by known polymerization methods such as various radical polymerizations, including solution polymerization, radiation polymerization, bulk polymerization, emulsion polymerization, and polymerization under supercritical conditions. Examples of radiation that can be used for radiation polymerization include electron beams, UV rays, and microwaves. The resulting polymer B may be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

[0122] When the PSA composition (A) contains polymer B, the content of polymer B relative to 100 parts by weight of the total of monomer component M and inorganic particles (specifically, a mixture of inorganic particles and a dispersant) may be, for example, 0.1 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, 5 parts by weight or more, 6 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, or even 20 parts by weight or more. The upper limit of the content may be, for example, 50 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, or even 15 parts by weight or less. The content may be, for example, 1 to 40 parts by weight, 2 to 35 parts by weight, 3 to 30 parts by weight, 5 to 25 parts by weight, 7 to 20 parts by weight, or even 8 to 15 parts by weight.

[0123] <1-3-e. Antioxidant> The PSA composition (A) may contain an antioxidant. Examples of the antioxidant include phenol-based antioxidants, hindered phenol-based antioxidants, amine-based antioxidants, and phosphite-based antioxidants.

[0124] 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.

[0125] 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).

[0126] 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).

[0127] 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).

[0128] The amount of antioxidant blended is, for example, 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, 0.4 parts by weight or more, or even 0.5 parts by weight or more per 100 parts by weight of the total of monomer component M and inorganic particles (specifically, a mixture of inorganic particles and a dispersant). The upper limit of the blended amount is not particularly limited, and may be, for example, 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less, 2.0 parts by weight or less, 1.0 parts by weight or less, or even 0.8 parts by weight or less. The pressure-sensitive adhesive composition (A) does not need to contain an antioxidant.

[0129] <1-3-f. UVA> The pressure-sensitive adhesive composition (A) may contain an ultraviolet absorber (UVA). Examples of UVAs include triazine-based UVAs, benzotriazole-based UVAs, benzophenone-based UVAs, oxybenzophenone-based UVAs, salicylic acid ester-based UVAs, and cyanoacrylate-based UVAs. Each UVA is a compound having a triazine skeleton, a benzotriazole skeleton, a benzophenone skeleton, an oxybenzophenone skeleton, a salicylic acid ester structure, and a cyanoacrylate structure, respectively. The UVA is preferably a triazine-based or benzotriazole-based UVA, and more preferably a benzotriazole-based UVA.

[0130] Examples of triazine-based UVAs include 2,4-bis-[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (Tinosorb S, manufactured by BASF), 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (TINUVIN), 460, manufactured by BASF), reaction products of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl with [(C10-C16 (mainly C12-C13) alkyloxy)methyl]oxirane (TINUVIN 400, manufactured by BASF), 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol, 2-(2,4-dihydroxyphenyl)-1,3,5-triazin-2-yl Reaction products of 2-(4,6-diphenyl-1,3,5-triazine and (2-ethylhexyl)-glycidic acid ester (TINUVIN 405, manufactured by BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol (TINUVIN 1577, manufactured by BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol (ADK STAB LA46, manufactured by ADEKA), and 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (TINUVIN 479, manufactured by BASF).

[0131] Examples of benzotriazole-based UVAs include 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN 928, manufactured by BASF), 2-(2H-1,2,3-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (TINUVIN 571, manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (TINUVIN PS, manufactured by BASF), ester compound of benzenepropanoic acid and 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy(C7-9 branched and linear alkyl) (TINUVIN 384-2, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN 900, manufactured by BASF), reaction product of methyl-3-(3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate / polyethylene glycol 300 (TINUVIN 1130, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (TINUVIN P, manufactured by BASF), 2(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN 234, manufactured by BASF), 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (TINUVIN 326, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (TINUVIN 328, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (TINUVIN 329, manufactured by BASF), -yl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN 329, manufactured by BASF), reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate with polyethylene glycol 300 (TINUVIN 213, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (TINUVIN 571, manufactured by BASF), 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimido-methyl)-5-methylphenyl]benzotriazole (Sumisorb 250, manufactured by Sumitomo Chemical Co., Ltd.).

[0132] The UVA may be in a liquid state at 25° C. Being in a liquid state at 25° C. can contribute to suppressing precipitation of the UVA in a PSA sheet formed from the PSA composition (A).

[0133] The UVA may be a benzotriazole-based UVA that is liquid at 25°C.

[0134] The pressure-sensitive adhesive composition (A) may contain one or more UVAs.

[0135] The amount of UVA in the pressure-sensitive adhesive composition (A) is, for example, 0.1 parts by weight or more, 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, 0.6 parts by weight or more, 0.7 parts by weight or more, 0.8 parts by weight or more, 0.9 parts by weight or more, 1.0 parts by weight or more, 1.1 parts by weight or more, 1.2 parts by weight or more, 1.3 parts by weight or more, or even 1.4 parts by weight or more per 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant). The upper limit of the amount is not particularly limited and may be, for example, 10.0 parts by weight or less, 8.0 parts by weight or less, 6.0 parts by weight or less, 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less, or even 2.0 parts by weight or less. The pressure-sensitive adhesive composition (A) does not necessarily contain UVA.

[0136] The PSA composition (A) may contain additives other than those described above. Examples of the additives include 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.

[0137] The content of the solvent in the PSA composition (A) 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 (A) 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, more preferably 0.01 wt% or less.

[0138] The viscosity of the pressure-sensitive adhesive composition (A) is preferably 5 to 100 poise at 25° C. The pressure-sensitive adhesive composition (A) having a viscosity in the above range is particularly suitable for forming a coating layer, which will be described later.

[0139] <1-4. Properties> <1-4-a. Haze> The haze of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (A) may be 2.0% or less. The haze may be 1.7% or less, 1.5% or less, 1.2% or less, 1.0% or less, 0.9% or less, 0.8% or less, or even 0.7% or less. The lower limit of the haze is not particularly limited, and may be 0.1% or more. Pressure-sensitive adhesive compositions capable of forming pressure-sensitive adhesive sheets with low haze are particularly suitable for forming pressure-sensitive adhesive sheets included in optical laminates.

[0140] In this specification, the haze of a pressure-sensitive adhesive sheet refers to the ratio of diffuse transmitted light to total transmitted light when a 50 μm thick pressure-sensitive adhesive sheet, which is the measurement object, is irradiated with visible light. Haze can be determined by the following formula. In the following formula, Th is haze (%), Td is scattered light transmittance, and Tt is total light transmittance. It may be evaluated using a commercially available haze meter. The above-mentioned haze, which is a property of the pressure-sensitive adhesive composition, can be specifically evaluated by the procedure described in the Examples (including the procedure for forming a pressure-sensitive adhesive sheet from the pressure-sensitive adhesive composition). Formula: Th (%) = (Td / Tt) × 100

[0141] In the pressure-sensitive adhesive composition (A), the content of the inorganic particles may be 10 to 70 parts by weight relative to 100 parts by weight of the total of the monomer component M and the inorganic particles (more specifically, a mixture of the inorganic particles and the dispersant), and the haze of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (A) may be 2.0% or less or within the above-mentioned range.

[0142] <1-4-b. Chromaticity> The chromaticity of the PSA sheet formed from the PSA composition (A) is determined based on the CIE1976 L standard specified in Japanese Industrial Standards (JIS) Z8781-4:2013. * , a * , b * Color space chromaticity b * The chromaticity b may be expressed as an absolute value of 2.0 or less. *A low absolute value of chromaticity b means that coloring such as yellowing is suppressed. * The absolute value of chromaticity b may be 1.7 or less, 1.5 or less, 1.2 or less, 1.0 or less, 0.9 or less, 0.8 or less, or even 0.7 or less. * The lower limit of the absolute value of is 0, and it may be 0.1 or more.

[0143] Chromaticity of adhesive sheet b * The color b as a characteristic of the pressure-sensitive adhesive composition can be evaluated using a commercially available colorimeter capable of measurement in accordance with JIS Z8781-4:2013. * Specifically, it can be evaluated by the procedures described in the Examples (including the procedure for forming a pressure-sensitive adhesive sheet from the pressure-sensitive adhesive composition).

[0144] <1-4-c. Residual Monomer Amount> The residual monomer amount in a PSA sheet formed from the PSA composition (A) may be 10,000 ppm or less (by weight; the same applies hereinafter), 9,000 ppm or less, 8,000 ppm or less, 7,000 ppm or less, 6,000 ppm or less, 5,000 ppm or less, 4,000 ppm or less, 3,500 ppm or less, or even 3,000 ppm or less. The lower limit of the residual monomer amount is, for example, 500 ppm or more. The residual monomer amount as a property of the PSA composition can be specifically evaluated by the procedures described in the Examples (including the procedures for forming a PSA sheet from the PSA composition).

[0145] A pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (A) can have any combination of two or more properties selected from the group consisting of the above-mentioned haze, chromaticity, and residual monomer amount.

[0146] <<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 pressure-sensitive adhesive composition (A).

[0147] The refractive index of the pressure-sensitive adhesive sheet 1 may be 1.55 or more. The refractive index of the pressure-sensitive adhesive sheet 1 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, or even 1.64 or more. The upper limit of the refractive index is, for example, 1.70 or less, 1.69 or less, 1.68 or less, 1.67 or less, 1.66 or less, 1.65 or less, 1.64 or less, 1.63 or less, or even 1.62 or less. Some optical substrates that can be provided in the optical laminate have a high refractive index. Using a pressure-sensitive adhesive sheet 1 with a high refractive index to bond the optical substrate is advantageous in reducing reflected light at the interface between the optical substrate and the pressure-sensitive adhesive sheet.

[0148] The refractive index of the pressure-sensitive adhesive sheet 1 before the reliability test at 85°C for 240 hours was I , the refractive index after the reliability test is n' I When [1-(n' I / n I ) × 100 (hereinafter referred to as "refractive index change rate (240')") may be 1% or less. The refractive index change rate (240') may be 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, 0.2% or less, or even 0.1% or less. The lower limit of the refractive index change rate (240') may be 0.0%.

[0149] The refractive index of the pressure-sensitive adhesive sheet 1 before the reliability test at 85°C for 500 hours was I The refractive index after the reliability test is n" I When [1-(n" I / n I ) × 100 (hereinafter referred to as "refractive index change rate (500')") may be 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, 1.1% 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, 0.2% or less, or even 0.1% or less. The lower limit of the refractive index change rate (500') may be 0.0%, or may be 0.1% or more.

[0150] The haze of the PSA sheet 1 can be 2.0% or less. The haze may be 1.7% or less, 1.5% or less, 1.2% or less, 1.0% or less, 0.9% or less, 0.8% or less, or even 0.7% or less. The lower limit of the haze is not particularly limited, and may be 0.1% or more.

[0151] The color of the adhesive sheet is CIE1976 L defined in JIS Z8781-4:2013. * , a * , b * Color space chromaticity b * The chromaticity b may be expressed as an absolute value of 2.0 or less. * The absolute value of chromaticity b may be 1.7 or less, 1.5 or less, 1.2 or less, 1.0 or less, 0.9 or less, 0.8 or less, or even 0.7 or less. * The lower limit of the absolute value of is 0, and it may be 0.1 or more.

[0152] The residual monomer amount of the PSA sheet 1 may be 10,000 ppm or less, 9,000 ppm or less, 8,000 ppm or less, 7,000 ppm or less, 6,000 ppm or less, 5,000 ppm or less, 4,000 ppm or less, 3,500 ppm or less, or even 3,000 ppm or less. The lower limit of the residual monomer amount is, for example, 500 ppm or more.

[0153] The pressure-sensitive adhesive sheet 1 can have any combination of two or more properties selected from the group consisting of the above-mentioned haze, chromaticity, and residual monomer amount.

[0154] The adhesive sheet 1 has a density of 1 x 10 -4 When the solution was prepared as a 370 nm wavelength solution of 3 × 10 -2 The above photopolymerization initiators may be contained.

[0155] The residual amount of the photopolymerization initiator in the pressure-sensitive adhesive sheet 1 may be 200 ppm or less. -4 When the solution was prepared as a 370 nm wavelength solution of 3 × 10 -2 The remaining amount of the photopolymerization initiator may be 200 ppm or less.

[0156] 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.

[0157] The thickness of the pressure-sensitive adhesive sheet 1 is, for example, 2 to 500 μm, and may be 2 to 300 μm, 2 to 200 μm, or even 2 to 150 μm. The upper limit of the thickness may be 100 μm or less, 70 μm or less, 60 μm or less, 55 μm or less, 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, or even 30 μm or less. The lower limit of the thickness may be 5 μm or more, 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, or even 50 μm or more.

[0158] The pressure-sensitive adhesive sheet 1 can be used in, for example, an optical laminate or an image display device, but the uses of the pressure-sensitive adhesive sheet 1 are not limited to the above examples.

[0159] <2-2. Manufacturing method> The PSA sheet 1 can be formed from the PSA composition (A) 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 (A), 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.

[0160] 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.

[0161] The light 14 is, for example, visible light or ultraviolet light having a wavelength shorter than 450 nm. The light may include light having a wavelength in the same region as the absorption wavelength of the photopolymerization initiator contained in the pressure-sensitive adhesive composition (A). Light having a wavelength of 300 nm or less may be irradiated by filtering or the like. Filtering out short-wavelength light is suitable for suppressing deterioration of the base sheet 11 and / or release liner 13 due to the light 14. The light source 18 is, for example, a light irradiation device equipped with an ultraviolet irradiation lamp. Examples of ultraviolet irradiation lamps include ultraviolet LEDs, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, microwave-excited mercury lamps, black light lamps, chemical lamps, germicidal lamps, low-pressure discharge mercury lamps, and excimer lasers. Two or more ultraviolet irradiation lamps may be combined.

[0162] 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:

[0163] 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.

[0164] 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 2 Below, 20000mJ / cm 2 Below, 18000 mJ / cm 2 It may be the following:

[0165] 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.

[0166] 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.

[0167] 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.

[0168] The release liner 13 may be in the form of a sheet or a continuous piece.

[0169] 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.

[0170] The thickness of the base sheet 11 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

[0171] 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.

[0172] 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.

[0173] The base sheet 11 may be in the form of a sheet or a continuous sheet.

[0174] 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.

[0175] 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.

[0176] The thickness of the coating layer 12 can be adjusted depending on the desired thickness of the PSA sheet 1, and may be, for example, 2 to 500 μm, 2 to 300 μm, 2 to 200 μm, or even 2 to 150 μm. The upper limit of the thickness may be 100 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness may be 5 μm or more, 10 μm or more, or even 15 μm or more.

[0177] 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.

[0178] A pressure-sensitive adhesive sheet according to another embodiment of the present invention may be a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition (α).

[0179] <<3. Optical Laminate>> An example of an optical laminate according to an embodiment of the present invention is shown in Fig. 3. The optical laminate 20A in Fig. 3 includes a pressure-sensitive adhesive sheet 1 and an optical film 2. The pressure-sensitive adhesive sheet 1 and the optical film 2 are laminated to each other. The optical laminate 20A can be used as an optical film with a pressure-sensitive adhesive sheet.

[0180] 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.

[0181] 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 .

[0182] 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.

[0183] 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.

[0184] The thickness of the polarizer is not particularly limited and may be, for example, 80 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 18 μm or less, 15 μm or less, or even 12 μm or less. The lower limit of the polarizer thickness is not particularly limited and may be, for example, 1 μm or more, 5 μm or more, or even 10 μm or more. In some cases, the lower limit of the polarizer thickness may be 15 μm or more. A thin polarizer (for example, a thickness of 20 μm or less) has reduced dimensional change and can contribute to improving the durability of the optical laminate, particularly durability at high temperatures.

[0185] The polarizer preferably exhibits absorptive dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 42.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

[0186] The polarizer can be produced by any appropriate method. Specifically, the polarizer may be produced from a single-layer resin film or a laminate of two or more layers.

[0187] A method for producing a polarizer from the above-mentioned single-layer resin film typically includes subjecting the resin film to a dyeing treatment with a dichroic substance such as iodine or a dichroic dye and a stretching treatment. Examples of the resin film that can be used include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and partially saponified ethylene-vinyl acetate copolymer-based films. This method may further include an insolubilization treatment, a swelling treatment, a crosslinking treatment, and the like. Such production methods are well known and commonly used in the art, and therefore a detailed description thereof will be omitted.

[0188] A polarizer obtained using the laminate can be produced, for example, using a laminate of a resin substrate and a resin film or resin layer (typically, a PVA-based resin layer). Specifically, a polarizer can be produced by applying a PVA-based resin solution to a resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; and stretching and dyeing the laminate to convert the PVA-based resin layer into a polarizer. In this embodiment, a PVA-based resin layer containing a halide and a PVA-based resin is preferably formed on one side of the resin substrate. The stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, the stretching may optionally further include in-air stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution. In addition, in this embodiment, the laminate is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being transported in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes subjecting a laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching treatment, it is possible to increase the crystallinity of the PVA, even when the PVA is coated on a thermoplastic resin, thereby achieving high optical properties. Furthermore, by simultaneously increasing the orientation of the PVA in advance, problems such as a decrease in orientation or dissolution of the PVA when immersed in water in the subsequent dyeing or stretching steps can be prevented, thereby achieving high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the PVA molecular orientation disorder and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide, thereby achieving high optical properties. Furthermore, by shrinking the laminate in the width direction by a drying shrinkage treatment, high optical properties can be achieved. A polarized film can be obtained by laminating a protective film on the peeled surface of the obtained resin substrate / polarizer laminate after peeling the resin substrate, or on the surface opposite to the peeled surface. Details of such a method for manufacturing a polarizer are described in, for example, JP 2012-73580 A and Japanese Patent No. 6470455. The entire disclosures of these publications are incorporated herein by reference.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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.

[0193] 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.

[0194] The polarizing film may be a circular polarizing film.

[0195] 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.

[0196] 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.

[0197] 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.

[0198] The thickness of the optical film 2 is, for example, 1 to 200 μm.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] Another example of an optical laminate according to an embodiment of the present invention is shown in Fig. 5. Optical laminate 20C in Fig. 5 has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, and a polarizing film 2A are layered in this order. After peeling off release liner 3, optical laminate 20C can be used by being attached to, for example, an image-forming layer.

[0203] 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.

[0204] Another example of an optical laminate according to an embodiment of the present invention is shown in Fig. 6. Optical laminate 20D in Fig. 6 has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, a polarizing film 2A, and a protective film 5 are layered in this order. After peeling off the release liner 3, optical laminate 20D can be used by being attached to, for example, an image-forming layer.

[0205] 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.

[0206] The protective film 5 may be bonded to the optical film 2 by any adhesive. Bonding by an adhesive sheet 1 is also possible.

[0207] Another example of an optical laminate according to an embodiment of the present invention is shown in Fig. 7. The optical laminate 20E in Fig. 7 has a layered structure in which a polarizing film 2A, a first adhesive layer 30, a first retardation film 2B, a second adhesive layer 35, a second retardation film 2C, a pressure-sensitive adhesive sheet 1, and a release liner 3 are layered in this order. After the release liner 3 is peeled off, the optical laminate 20E can be used by being attached to, for example, an image forming layer.

[0208] In the optical laminate 20E, the polarizing film 2A has a laminated structure in which a first protective film 26A, a polarizer 25, and a second protective film 26B are laminated in this order.

[0209] The first protective film 26A can be formed of, for example, any appropriate resin film that can be used as a protective layer for the polarizer 25. Specific examples of resins that serve as the main component of the resin film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based resins, polyvinyl alcohol-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyethersulfone-based resins, polysulfone-based resins, polystyrene-based resins, cycloolefin-based resins such as polynorbornene, polyolefin-based resins, (meth)acrylic resins, and acetate-based resins.

[0210] The optical laminate 20E is typically disposed on the viewing side of an image display device (e.g., an organic EL display device), and the first protective film 26A is disposed on the viewing side. Therefore, the first protective film 26A may be subjected to surface treatment such as hard coat (HC) treatment, anti-reflection treatment, anti-sticking treatment, anti-glare treatment, etc., as needed.

[0211] The thickness of the first protective film 26A is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and even more preferably 15 μm to 35 μm. If the above-mentioned surface treatment is applied, the thickness of the first protective film 26A includes the thickness of the surface treatment layer.

[0212] The second protective film 26B can be formed of, for example, any appropriate resin film that can be used as a protective layer for the polarizer 25. When the second protective film 26B is formed of a resin film, the same explanation as for the first protective film 26A can be applied. Furthermore, for example, the second protective film 26B can be a solidified or cured layer of a coating film of an organic solvent solution containing a resin. When the second protective film 26B is a solidified or cured layer of a coating film of an organic solvent solution containing a resin, adhesion to the polarizer 25 can be improved.

[0213] In one embodiment, the resin (base polymer) forming the solidified or cured layer may have a glass transition temperature (Tg) of 85°C or higher and a weight average molecular weight (Mw) of 25,000 or higher. By having the Tg and Mw of the resin within these ranges, excellent durability can be achieved in high-temperature, high-humidity environments despite a very thin thickness. The Tg of the resin is preferably 90°C or higher, more preferably 100°C or higher, even more preferably 110°C or higher, and particularly preferably 120°C or higher. The Tg may be, for example, 200°C or lower. The Mw of the resin is preferably 30,000 or higher, more preferably 35,000 or higher, and even more preferably 40,000 or higher. The Mw may be, for example, 150,000 or lower.

[0214] As the resin, any suitable resin can be used as long as it can form a solidified or cured product (e.g., a thermoset product) of the coating film of the organic solvent solution. Thermoplastic resins or thermosetting resins having the above-mentioned Tg and Mw are preferred, and thermoplastic resins are more preferred. Only one type of resin may be used, or two or more types may be used in combination.

[0215] Examples of thermoplastic resins include acrylic resins and epoxy resins. Acrylic resins and epoxy resins may be used in combination.

[0216] Acrylic resins typically contain, as their main component, repeating units derived from (meth)acrylic acid ester monomers having a linear or branched structure. Acrylic resins may contain repeating units derived from any appropriate copolymerizable monomer depending on the purpose. Examples of copolymerizable monomers (comonomers) include carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocyclic ring-containing vinyl monomers. By appropriately setting the type, number, combination, and copolymerization ratio of the monomer units, an acrylic resin having the above-mentioned predetermined Mw can be obtained. Specific examples of acrylic resins include boron-containing acrylic resins and lactone ring-containing acrylic resins described in

[0034] to

[0056] of JP 2021-117484 A.

[0217] As the epoxy resin, an epoxy resin having an aromatic ring is preferably used. By using an epoxy resin having an aromatic ring as the epoxy resin, the adhesion between the second protective film 26B and the polarizer 25 can be improved. Furthermore, the anchoring strength of the first adhesive layer 30 adjacent to the second protective film 26B can be improved. Examples of epoxy resins having an aromatic ring include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and bisphenol S-type epoxy resins; novolac-type epoxy resins such as phenol novolac epoxy resins, cresol novolac epoxy resins, and hydroxybenzaldehyde phenol novolac epoxy resins; multifunctional epoxy resins such as glycidyl ether of tetrahydroxyphenylmethane, glycidyl ether of tetrahydroxybenzophenone, and epoxidized polyvinylphenol; naphthol-type epoxy resins, naphthalene-type epoxy resins, and biphenyl-type epoxy resins. Bisphenol A-type epoxy resins, biphenyl-type epoxy resins, and bisphenol F-type epoxy resins are preferably used. Only one type of epoxy resin may be used, or two or more types may be used in combination.

[0218] The second protective film 26B can be formed by applying an organic solvent solution of the resin to form a coating film, and then solidifying or thermally curing the coating film. Any suitable organic solvent capable of dissolving or uniformly dispersing an acrylic resin or epoxy resin can be used as the organic solvent. Specific examples of organic solvents include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone. The resin concentration of the solution is preferably 3 to 20 parts by weight per 100 parts by weight of the solvent. Such a resin concentration allows for the formation of a uniform coating film.

[0219] The solution may be applied to any suitable substrate or to the polarizer 25. When the solution is applied to the substrate, the solidified or cured product (resin layer) of the coating film formed on the substrate is transferred to the polarizer 25. When the solution is applied to the polarizer 25, the second protective film 26B is formed directly on the polarizer 25 by drying (solidifying) or curing the coating film. Preferably, the solution is applied to the polarizer 25, and the second protective film 26B is formed directly on the polarizer 25. This configuration eliminates the need for an adhesive or pressure-sensitive adhesive layer required for transfer, thereby enabling the polarizing film 2A to be made even thinner. Any suitable method can be used to apply the solution. Specific examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (such as comma coating).

[0220] The second protective film 26B can be formed by solidifying or thermally curing the applied film of the solution. The heating temperature for solidification or thermal curing is preferably 100°C or lower, and more preferably 50°C to 70°C. If the heating temperature is within this range, adverse effects on the polarizer 25 can be prevented. The heating time can vary depending on the heating temperature. The heating time can be, for example, 1 minute to 10 minutes.

[0221] The second protective film 26B (essentially, the organic solvent solution of the resin) may contain any suitable additive depending on the purpose. Specific examples of additives include ultraviolet absorbers; leveling agents; hindered phenol-based, phosphorus-based, sulfur-based, and other antioxidants; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fiber and carbon fiber; near-infrared absorbers; flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic or inorganic fillers; resin modifiers; organic or inorganic fillers; plasticizers; lubricants; and flame retardants. The type, number, combination, and amount of additives can be appropriately determined depending on the purpose.

[0222] When the second protective film 26B is a solidified or hardened layer of a coating film of an organic solvent solution containing a resin, the thickness of the second protective film 26B is preferably 0.05 μm to 10 μm, more preferably 0.08 μm to 5 μm, even more preferably 0.1 μm to 1 μm, and particularly preferably 0.2 μm to 0.7 μm.

[0223] The first retardation film 2B may have any appropriate optical and / or mechanical properties depending on the purpose. The first retardation film 2B typically has a slow axis. In one embodiment, the angle θ between the slow axis of the first retardation film 2B and the absorption axis of the polarizer 25 is, for example, 40° to 50°, preferably 42° to 48°, and more preferably about 45°. If the angle θ is within this range, by using a λ / 4 plate as the first retardation film 2B, an optical laminate 20E having excellent circular polarization properties (and, as a result, excellent antireflection properties) can be obtained.

[0224] The first retardation film 2B preferably has a refractive index characteristic that satisfies the relationship nx>ny≧nz. In one embodiment, the first retardation film 2B can function as a λ / 4 plate. In this case, the in-plane retardation Re(550) of the first retardation film 2B is, for example, 100 nm to 190 nm, preferably 110 nm to 170 nm, and more preferably 130 nm to 160 nm. Note that "ny = nz" here encompasses not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, there may be cases where ny < nz, as long as the effects of the present invention are not impaired.

[0225] The Nz coefficient of the first retardation film 2B is preferably 0.9 to 3, more preferably 0.9 to 2.5, even more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. By satisfying such a relationship, when the obtained optical laminate 20E is used in an image display device, an extremely excellent reflected hue can be achieved.

[0226] The first retardation film 2B may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases with the wavelength of the measurement light, a positive wavelength dispersion characteristic in which the retardation value decreases with the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which the retardation value hardly changes with the wavelength of the measurement light. In one embodiment, the first retardation film 2B exhibits a reverse dispersion wavelength characteristic. In this case, the Re(450) / Re(550) of the first retardation film 2B is, for example, 0.8 or more and less than 1, preferably 0.8 or more and 0.95 or less. With such a configuration, extremely excellent antireflection properties can be achieved.

[0227] The absolute value of the photoelastic coefficient of the first retardation film 2B is preferably 2.0×10 -11 m 2 / N or less, more preferably 2.0 × 10 -13 m 2 / N ~ 1.5 x 10 -11 m 2 / N, more preferably 1.0 × 10 -12 m 2 / N ~ 1.2 × 10 -11 m 2 When the absolute value of the photoelastic coefficient is in this range, the retardation is less likely to change when shrinkage stress occurs during heating. As a result, thermal unevenness in the resulting image display device can be effectively prevented.

[0228] The first retardation film 2B is typically made of a stretched resin film. The thickness of the first retardation film 2B is, for example, 70 μm or less, preferably 60 μm or less, more preferably 10 μm to 50 μm, and even more preferably 20 μm to 45 μm. If the thickness of the first retardation film 2B is within this range, good bendability can be ensured, making it suitable for flexible applications.

[0229] The first retardation film 2B can be composed of any appropriate resin film that can satisfy the above characteristics. Typical examples of such resins include polycarbonate-based resins, polyester carbonate-based resins, polyester-based resins, polyvinyl acetal-based resins, polyarylate-based resins, cyclic olefin-based resins, cellulose-based resins, polyvinyl alcohol-based resins, polyamide-based resins, polyimide-based resins, polyether-based resins, polystyrene-based resins, and acrylic-based resins. These resins may be used alone or in combination (e.g., blended or copolymerized). When the first retardation film 2B is composed of a resin film that exhibits reverse dispersion wavelength characteristics, polycarbonate-based resins or polyester carbonate-based resins (hereinafter sometimes simply referred to as polycarbonate-based resins) can be suitably used.

[0230] As the polycarbonate-based resin, any suitable polycarbonate-based resin can be used as long as the effects of the present invention can be obtained. For example, the polycarbonate-based resin contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanols, di-, tri-, or polyethylene glycols, and alkylene glycols or spiroglycols. Preferably, the polycarbonate-based resin contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, structural units derived from an alicyclic dimethanol and / or structural units derived from di-, tri-, or polyethylene glycol; more preferably, it contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from di-, tri-, or polyethylene glycol. The polycarbonate-based resin may contain structural units derived from other dihydroxy compounds as needed. Details of polycarbonate-based resins that can be suitably used for the first retardation film 2B and methods for forming the first retardation film 2B are described in, for example, JP 2014-10291 A, JP 2014-26266 A, JP 2015-212816 A, JP 2015-212817 A, and JP 2015-212818 A, the descriptions of which are incorporated herein by reference.

[0231] In one embodiment, an organic solvent is brought into contact with the surface of the first retardation film 2B facing the second adhesive layer 35, and then the second adhesive layer 35 is provided on the contact surface. This allows a compatible region in which the composition continuously changes toward the second adhesive layer 35 side of the first retardation film 2B. The formation of a compatible region in which the components of the first retardation film 2B and the components of the second adhesive layer 35 are compatible can improve the adhesion between the first retardation film 2B and the second retardation film 2C. On the other hand, from the viewpoint of strictly suppressing moisture penetration into the first retardation film 2B, it is preferable not to provide a compatible region. Therefore, it is preferable to form the compatible region as needed, taking into account the adhesion strength between the first retardation film 2B and the second retardation film 2C, the application or use environment of the optical laminate 20E, etc. Details of the method for forming the compatible region are described in JP 2019-56820 A, the disclosure of which is incorporated herein by reference.

[0232] The second retardation film 2C can be typically a so-called positive C plate whose refractive index characteristics satisfy the relationship nz > nx = ny. By using a positive C plate as the second retardation film 2C, reflection in oblique directions can be effectively prevented, and the anti-reflection function can be extended to a wide viewing angle.

[0233] The thickness direction retardation Rth(550) of the second retardation film 2C is preferably −50 nm to −300 nm, more preferably −70 nm to −250 nm, even more preferably −90 nm to −200 nm, and particularly preferably −100 nm to −180 nm. Here, "nx = ny" encompasses not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the second retardation film 2C can be less than 10 nm.

[0234] The second retardation film 2C having the refractive index characteristic of nz > nx = ny can be formed from any appropriate material. The second retardation film 2C is preferably made of a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the second retardation film 2C include the liquid crystal compound and the method for forming the retardation layer described in paragraphs

[0020] to

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

[0235] Any appropriate adhesive may be used as the adhesive constituting the first adhesive layer 30 and the second adhesive layer 35. Examples of the adhesive include those described above for the optical laminate 20A.

[0236] The optical laminate may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and the optical film 2 .

[0237] 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.

[0238] 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.

[0239] 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.

[0240] An optical laminate according to another embodiment of the present invention different from the above may include a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (α) and an optical film.

[0241] <<4. Image Display Device>> An example of an image display device according to an embodiment of the present invention is shown in Figure 8. The image display device 21 of Figure 8 has a layered structure in which a substrate 7, an image forming layer (e.g., an organic EL layer or a liquid crystal layer) 6, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, a polarizing film 2A, and a protective film 5 are layered in this order. The image display device 21 has the optical laminate 20D of Figure 6 (excluding the release liner 3). The image display device 21 may have the optical laminates 20A, 20B, 20C, and 20E of Figures 3 to 5 and 7 instead of the optical laminate 20D. The substrate 7 and the image forming layer 6 may have the same configurations as the substrate and the image forming layer, respectively, of known image display devices.

[0242] The image display device 21 in Fig. 8 may be an organic EL display or a liquid crystal display. However, the image display device 21 is not limited to this example. The image display device 21 may also be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), or the like. The image display device 21 may be used for home appliances, in-vehicle applications, public information displays (PID), and the like.

[0243] The image display device 21 may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and / or the optical laminate 20 .

[0244] An image display device according to another embodiment of the present invention may include an optical laminate including a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (α) and an optical film.

[0245] 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.

[0246] [Synthesis of Dispersant] 415 g (1 mol) of tristyrenated phenol and 1 g (0.018 mol) of potassium hydroxide were charged into an autoclave and mixed uniformly. The resulting reaction system was 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 resulting EO 8 mol adduct of tristyrenated phenol and 152 g (1.3 mol) of sodium monochloroacetate were placed in a reactor and stirred until 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 solution. The resulting suspension was washed with distilled water, and the solvent was removed by distillation under reduced pressure to obtain a dispersant.

[0247] [Preparation of Zirconium Oxide Dispersion] 1.5 parts by weight of the dispersant prepared above and 28.5 parts by weight of phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Industry Co., Ltd., trade name "Light Acrylate POB-A"; hereinafter referred to as "POB-A") were added to 100 parts by weight of a methanol dispersion of zirconium oxide particles (manufactured by Sakai Chemical Industry Co., Ltd., grade name "SZR-M", average particle size (D50) based on dynamic light scattering: 3 nm, zirconium oxide particle concentration: 30 wt %) and mixed. Next, the solvent was removed under reduced pressure using a rotary evaporator to obtain a zirconium oxide dispersion. The obtained zirconium oxide dispersion contained zirconia particles / dispersant / POB-A in a weight ratio of 50 / 2.5 / 47.5.

[0248] [Preparation of Polymer B] (Polymer B1) A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 99 parts by weight of POB-A, 1 part by weight of 4-hydroxybutyl acrylate (4HBA), 0.30 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator, 3 parts by weight of 1-thioglycerol as a chain transfer agent, and 300 parts by weight of ethyl acetate. The mixture was maintained at 70°C and stirred gently while introducing nitrogen gas to thoroughly replace the atmosphere with nitrogen for at least one hour. The liquid temperature in the flask was then maintained at 72-74°C, and a polymerization reaction was carried out for 6 hours to prepare a solution of Polymer B. Next, the solution was heated at 90°C for 12 hours, and then subjected to reduced pressure treatment at 120°C for 3 hours to remove the ethyl acetate. This yielded Polymer B1 (weight average molecular weight 4000), in which the amount of ethyl acetate detected by gas chromatography was less than 0.1 parts by weight.

[0249] (Polymers B2 and B3) Polymers B2 (weight average molecular weight: 3,300) and B3 (weight average molecular weight: 6,000) were prepared in the same manner as in the preparation of Polymer B1, except that the weight average molecular weight was changed by adjusting the amounts of the polymerization initiator and the chain transfer agent.

[0250] [Weight-average molecular weight of polymer B] The weight-average molecular weight (Mw) of the obtained polymer B was measured by gel permeation chromatography (GPC). The measurement equipment and conditions were as follows: Analytical equipment: 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

[0251] [Preparation of Pressure-Sensitive Adhesive Composition A1] Phenoxybenzyl acrylate (POB-A) and 4-hydroxybutyl acrylate (4HBA) were mixed with the zirconium oxide dispersion prepared above. The amount of zirconium oxide dispersion was such that the weight of the zirconium oxide particles was 81.8 parts by weight per 100 parts by weight of the total weight of POB-A (the total of POB-A contained in the zirconium oxide dispersion and POB-A mixed with the zirconia dispersion) and 4HBA, in other words, the weight of monomer component M. The weight ratio of POB-A, 4HBA, and zirconium oxide particles was 50 / 5 / 45, and the weight ratio of monomer component M and zirconium oxide particles was 55 / 45. The proportion of POB-A in monomer component M was 90.9% by weight, and the proportion of 4HBA was 9.1% by weight. Next, 100 parts by weight of the above mixture were mixed with 0.4 parts by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins) as a photopolymerization initiator, 0.025 parts by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent, 0.5 parts by weight of 3-glycidoxypropyltrimethoxysilane (KBM-403, manufactured by Shin-Etsu Silicones) as a compound having an alkoxysilane group, 0.5 parts by weight of Irganox 1010 (manufactured by BASF) as an antioxidant, and 10 parts by weight of the polymer B1 prepared above. Next, the mixture in the flask was irradiated with ultraviolet light under a nitrogen atmosphere to obtain a photocurable pressure-sensitive adhesive composition A1 in which the monomer component M was partially photopolymerized. The ultraviolet irradiation was continued until the viscosity of the liquid in the flask (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30° C.) reached about 20 Pa·s.

[0252] [Preparation of Pressure-Sensitive Adhesive Compositions A2 to A16] Photocurable pressure-sensitive adhesive compositions A2 to A16 were prepared by the same method as for pressure-sensitive adhesive composition A1, except that the type of monomer, the mixed amount of zirconium oxide particles and monomer, the mixed amount of photopolymerization initiator, the type and mixed amount of compound having an alkoxysilane group, the type and mixed amount of polymer B, and the type and mixed amount of UVA were changed as shown in Table 1. The UVA was mixed into the mixture of zirconium oxide dispersion and monomer component M at the same time as the photopolymerization initiator, crosslinking agent, etc.

[0253]

[0254] The abbreviations in Table 1 are as follows: (Monomers) POB-A: phenoxybenzyl acrylate PEA: phenoxyethyl acrylate 4HBA: 4-hydroxybutyl acrylate (Photopolymerization initiators) Omnirad 819: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins; concentration 1×10 -4 When the solution was prepared as a 370 nm wavelength solution of 100 mg / mL in acetonitrile, the absorbance of the light was 3 x 10 -2 or more) (Compounds having an alkoxysilane group) KBM-403: 3-glycidoxypropyltrimethoxysilane (silane coupling agent manufactured by Shin-Etsu Silicones Co., Ltd.) KBM-4803: 8-glycidoxyoctyltrimethoxysilane (silane coupling agent manufactured by Shin-Etsu Silicones Co., Ltd.) KBM-903: 3-aminopropyltrimethoxysilane (silane coupling agent manufactured by Shin-Etsu Silicones Co., Ltd.) (Polymer B) B1 (Mw 4000): Has a composition of 99 parts by weight of POB-A / 1 part by weight of 4HBA B2 (Mw 3300): Has a composition of 99 parts by weight of POB-A / 1 part by weight of 4HBA B3 (Mw 6000): Has a composition of 99 parts by weight of POB-A / 1 part by weight of 4HBA (Antioxidant) Irganox 1010: tetrakis[3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionic acid]pentaerythritol (manufactured by BASF) (UVA) Tinuvin 571: 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (manufactured by BASF)

[0255] Example 1 Preparation of Release Liner 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 silicone solids concentration in the release agent composition was 1.0 wt %. Next, the release agent composition was applied with a wire bar to one side of a liner substrate (Lumirror XD500P, a polyester film, 75 μm thick), and heated at 130° C. for 1 minute to prepare a release liner having a release layer (thickness 60 nm) on one side.

[0256] [Preparation of Pressure-Sensitive Adhesive Sheet] The pressure-sensitive adhesive composition A1 was applied to the release liner prepared above as a base sheet using an applicator to form a coating layer. The coating layer was formed on the release layer. Next, a release liner was placed on the formed coating layer to obtain a first laminate. The release liner was placed so that the release layer was in contact with the coating layer. Next, a light source with an illuminance of 2.5 mW / cm was applied from the side of the base sheet of the first laminate. 2 and an integrated light intensity of 2400 mJ / cm 2 The coated layer was then irradiated with ultraviolet light from a black light source for 10 seconds. This photocured the coating layer, yielding a PSA sheet (thickness: 50 μm) of Example 1 sandwiched between the base sheet and release liner. The illuminance of the light was measured using an illuminance meter (UD-T36T2, manufactured by Topcon Technohouse Corporation) near the surface of the base sheet where the ultraviolet light was incident.

[0257] (Examples 2 to 14 and Comparative Examples 1 and 2) Pressure-sensitive adhesive sheets of Examples 2 to 14 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive compositions used were changed as shown in Table 2.

[0258]

[0259] [Evaluation] (Refractive index of pressure-sensitive adhesive sheet) For each pressure-sensitive adhesive sheet of the Examples and Comparative Examples, the release liner was peeled off to expose the surface, and the refractive index was measured in critical angle mode using a prism coupler (manufactured by Metricon, model "2010M") at a measurement temperature of 25°C and a measurement wavelength of 594 nm. The measured refractive index was defined as the initial refractive index n1 of the pressure-sensitive adhesive sheet.

[0260] (Rate of change in refractive index of pressure-sensitive adhesive sheet due to reliability test) A reliability test was carried out for each of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples using a thermostatic oven at 85°C for a test time of 240 hours or 500 hours. Next, the pressure-sensitive adhesive sheet after the test was allowed to cool naturally to room temperature, and then the release liner was peeled off to measure the refractive index of the exposed surface in critical angle mode using a prism coupler (manufactured by Metricon, model "2010M") at a measurement temperature of 25°C and a measurement wavelength of 594 nm. The measured refractive indices were designated as the refractive index n'1 (test time 240 hours) and refractive index n"1 (test time 500 hours) of the pressure-sensitive adhesive sheet after the reliability test, and the rate of change in refractive index of the pressure-sensitive adhesive sheet due to each reliability test with different test times was determined.

[0261] (Presence or absence of multiple inflection points) In a graph obtained when evaluating the initial refractive index n1 and the refractive index n'1 after the reliability test (test time 240 hours), it was evaluated whether or not a peak indicating a temporary decrease in light intensity was observed at an angle on the higher refractive index side than the critical angle. Note that a peak indicating a decrease in light intensity of 10% or more of the decrease in light intensity at the critical angle was determined to be a peak indicating the above-mentioned decrease in light intensity.

[0262] (Haze) For each PSA sheet of the Examples and Comparative Examples, the substrate sheet and release liner were peeled off to expose each surface, and an alkali-free glass plate (thickness 0.7 to 0.8 mm, total light transmittance 92%, haze 0.06%) was attached to the exposed surface to prepare a test specimen. Next, the haze of the test specimen was measured using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory) in a measurement environment of 23°C.

[0263] (chromaticity b *For each PSA sheet of the Examples and Comparative Examples, the substrate sheet and release liner were peeled off, and an alkali-free glass plate (thickness 0.7 to 0.8 mm, total light transmittance 92%, chromaticity b * 0.20) were bonded together to prepare a test piece. 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, in a measurement environment of 23°C, the light transmittance of the test piece for light with wavelengths of 300 nm to 800 nm was measured using an ultraviolet-visible-near-infrared spectrophotometer (UH4150, manufactured by Hitachi High-Technologies). Next, chromaticity b was calculated from the obtained spectral data using a color calculation program (UV Solutions, manufactured by Hitachi High-Technologies). * asked for.

[0264] (Amount of Residual Monomer in Pressure-Sensitive Adhesive Sheet) The amount of residual monomer in each of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples was calculated from the change in weight of the pressure-sensitive adhesive sheet before and after 2 hours of heat drying at 130° C. Specifically, the weight of the pressure-sensitive adhesive sheet immediately after peeling off the base sheet and release liner was defined as W0 (weight before drying), and the weight of the pressure-sensitive adhesive sheet after the heating and subsequent cooling at 23° C. for approximately 20 minutes was defined as W1 (weight after drying), using the formula: amount of residual monomer (ppm)=(W0-W1) / W0×10 6 was calculated by

[0265] The evaluation results are shown in Table 3 below.

[0266]

[0267] As shown in Table 3, the pressure-sensitive adhesive sheets of the Examples were able to suppress changes in refractive index compared to the Comparative Examples. Furthermore, as shown in Table 3, with the pressure-sensitive adhesive sheets of the Examples, no peak indicating a decrease in light intensity was observed at an angle on the higher refractive index side than the critical angle, even after a reliability test at a temperature of 85°C for a test time of 240 hours.

[0268] 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 containing a monomer component M, wherein the pressure-sensitive adhesive composition contains inorganic particles, and the rate of change in refractive index, defined as the absolute value of [1-(n'1 / n1)] x 100, is 1% or less, where n1 is the initial refractive index of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition and n'1 is the refractive index after a reliability test at 85°C for 240 hours.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the content of said inorganic particles is 10 to 70 parts by weight per 100 parts by weight of the total of said monomer component M and said inorganic particles.

3. The pressure-sensitive adhesive composition according to claim 1, wherein the inorganic particles have an average particle size of 100 nm or less.

4. The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive sheet has a haze of 2.0% or less.

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

6. The pressure-sensitive adhesive composition according to claim 5, wherein the first double bond-containing ring is an aromatic ring.

7. The pressure-sensitive adhesive composition according to claim 5, wherein the monomer a includes a (meth)acrylic monomer having the first double bond-containing ring.

8. The pressure-sensitive adhesive composition according to claim 1, wherein the monomer component M comprises phenoxybenzyl acrylate.

9. The pressure-sensitive adhesive composition according to claim 1, wherein the amount of residual monomer in the pressure-sensitive adhesive sheet is 10,000 ppm (by weight) or less.

10. The pressure-sensitive adhesive composition according to claim 1, further comprising a compound having an alkoxysilane group.

11. 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.

12. The pressure-sensitive adhesive composition according to claim 11, wherein the polymer B contains a structural unit derived from a monomer b having a second double bond-containing ring.

13. The pressure-sensitive adhesive composition according to claim 12, wherein the second double bond-containing ring is an aromatic ring.

14. The pressure-sensitive adhesive composition according to claim 1, further comprising an antioxidant.

15. A photocurable pressure-sensitive adhesive composition containing a monomer component M, wherein the pressure-sensitive adhesive composition contains inorganic particles, and when the refractive index of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition is measured using a prism coupler after a reliability test at 85°C for 240 hours, no peak indicating a decrease in light intensity is observed at an angle higher than the critical angle in a graph showing the relationship between the angle of incidence onto the prism and the measured light intensity.

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

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

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

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