Optical laminate and image display device

Abstract

Provided is an optical laminate which includes a first liquid crystal alignment solidified layer, an adhesive sheet, and a second liquid crystal alignment solidified layer in this order. The adhesive sheet contains a crosslinked body of a base polymer. The base polymer is composed of a plurality of monomers. When the product of the refractive index of each monomer and the ratio of the weight of each monomer to all the monomers that constitute the base polymer is obtained for each one of the monomers that constitute the base polymer, the sum of the products with respect to the base polymer is 1.51 or more, and the weight average molecular weight of the base polymer is 800,000 or more. This optical laminate is suitable for the achievement of both of reflection reduction and high temperature durability, while bonding the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer by the intermediary of the adhesive sheet.

Description

Optical laminate and image display device

[0001] The present invention relates to an optical laminate and an image display device.

[0002] Various image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices, generally include an optical laminate including optical substrates such as a polarizing film and a retardation layer. In an optical laminate including a plurality of optical substrates, a bonding layer is typically disposed between adjacent optical substrates to bond them together. Patent Document 1 discloses a polarizing plate with a retardation layer, which includes a polarizer, a first retardation layer, and a second retardation layer in this order, and which is bonded to the first retardation layer and the second retardation layer via an adhesive layer. Patent Document 1 also discloses that the first retardation layer and / or the second retardation layer may be a layer of solidified alignment of a liquid crystal compound (hereinafter referred to as a liquid crystal alignment solidification layer).

[0003] Japanese Patent Application Laid-Open No. 2019-204111

[0004] It is conceivable to bond the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer via a pressure-sensitive adhesive sheet instead of an adhesive layer, but according to the inventors' investigations, it has been found that when a pressure-sensitive adhesive sheet is used, it is difficult to achieve both reduced reflection and durability at high temperatures in the optical laminate.

[0005] The present invention aims to provide an optical laminate that is suitable for achieving both reduced reflection and durability at high temperatures while bonding a first liquid crystal alignment solidified layer and a second liquid crystal alignment solidified layer via an adhesive sheet.

[0006] As a result of extensive research, the present inventors have completed the present invention by focusing on the combination of the refractive index and weight average molecular weight of the base polymer that forms the pressure-sensitive adhesive sheet, and the thickness of the pressure-sensitive adhesive sheet.

[0007] The present invention provides an optical laminate comprising, in this order, a first liquid crystal alignment solidified layer, an adhesive sheet, and a second liquid crystal alignment solidified layer, wherein the adhesive sheet comprises a crosslinked base polymer, the base polymer is composed of a plurality of monomers, and when the product of the refractive index of each monomer constituting the base polymer and the weight ratio of each monomer to all monomers constituting the base polymer is calculated for each monomer constituting the base polymer, the sum of the products for the base polymer is 1.51 or more, and the weight average molecular weight of the base polymer is 800,000 or more.

[0008] Furthermore, the present invention provides an image display device comprising the optical laminate of the present invention.

[0009] The optical laminate of the present invention is suitable for achieving both reduced reflection and durability at high temperatures, while bonding the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer via an adhesive sheet.

[0010] Fig. 1 is a cross-sectional view schematically showing an example of an optical laminate of the present invention. Fig. 2 is a cross-sectional view schematically showing an example of an optical laminate of the present invention. Fig. 3 is a cross-sectional view schematically showing an example of an optical laminate of the present invention. Fig. 4 is a cross-sectional view schematically showing an example of an optical laminate of the present invention. Fig. 5 is a cross-sectional view schematically showing an example of an image display device of the present invention.

[0011] An optical laminate according to a first aspect of the present invention comprises a first liquid crystal alignment solidified layer, an adhesive sheet, and a second liquid crystal alignment solidified layer in this order, wherein the adhesive sheet comprises a crosslinked base polymer, the base polymer is composed of a plurality of monomers, and when the product of the refractive index of each monomer and the weight ratio of each monomer to all monomers constituting the base polymer is calculated for each monomer constituting the base polymer, the sum of the products for the base polymer is 1.51 or more, and the weight average molecular weight of the base polymer is 800,000 or more.

[0012] In a second aspect of the present invention, for example, in the optical laminate according to the first aspect, the absolute values ​​of the differences between the average refractive index of each of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer and the sum of the products are each 0.08 or less.

[0013] In a third aspect of the present invention, for example, in the optical laminate according to the first or second aspect, the first liquid crystal alignment solidified layer and / or the second liquid crystal alignment solidified layer is a retardation layer.

[0014] In a fourth aspect of the present invention, for example, in the optical laminate according to any one of the first to third aspects, the monomers constituting the base polymer include an aromatic ring-containing monomer.

[0015] In a fifth aspect of the present invention, for example, in the optical layered body according to the fourth aspect, the aromatic ring-containing monomer is a high-boiling point monomer.

[0016] In a sixth aspect of the present invention, for example, in the optical laminate according to the fourth or fifth aspect, the aromatic ring-containing monomer is phenoxybenzyl acrylate.

[0017] In a seventh aspect of the present invention, for example, in an optical laminate according to any one of the fourth to sixth aspects, the weight ratio of the aromatic ring-containing monomer to all monomers constituting the base polymer is 50% or more.

[0018] In an eighth aspect of the present invention, for example, in the optical laminate according to any one of the first to seventh aspects, the crosslinked body has a crosslinked structure formed by a peroxide-based crosslinking agent.

[0019] In a ninth aspect of the present invention, for example, in the optical laminate according to any one of the first to eighth aspects, the crosslinked body has a crosslinked structure formed by an isocyanate-based crosslinking agent.

[0020] In a tenth aspect of the present invention, for example, in the optical laminate according to any one of the first to ninth aspects, the pressure-sensitive adhesive sheet has a thickness of 4 μm or more.

[0021] In an eleventh aspect of the present invention, for example, the optical laminate according to any one of the first to tenth aspects further includes a polarizing film, and the polarizing film faces the main surface of the first liquid crystal alignment solidified layer opposite to the pressure-sensitive adhesive sheet side.

[0022] An image display device according to a twelfth aspect of the present invention includes the optical laminate according to any one of the first to eleventh aspects.

[0023] 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.

[0024] [Optical Laminate] An example of the optical laminate of this embodiment is shown in Fig. 1. The optical laminate 1 (1A) in Fig. 1 includes a first liquid crystal alignment solidified layer 2, an adhesive sheet 3, and a second liquid crystal alignment solidified layer 4, in this order. The first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 are bonded via the adhesive sheet 3. In the optical laminate 1A in Fig. 1, adjacent layers are in contact with each other.

[0025] The pressure-sensitive adhesive sheet 3 includes a crosslinked base polymer. The pressure-sensitive adhesive sheet 3 is typically formed by curing a pressure-sensitive adhesive composition containing the base polymer. The base polymer is typically a polymer of two or more types of monomers, and has structural units formed by polymerization of each monomer. For each monomer constituting the base polymer, the product of the refractive index of that monomer and the weight ratio of that monomer to all monomers constituting the base polymer can be calculated. However, the refractive index of a monomer is specified by the refractive index of a homopolymer of that monomer for light with a wavelength of 550 nm. For example, when the base polymer is composed of monomer A, monomer B, monomer C, and monomer D, the above product for each monomer can be expressed as follows: Monomer A: a1 x a2 (where a1 is the refractive index of monomer A, and a2 is the weight ratio of monomer A to all monomers) Monomer B: b1 x b2 (where b1 is the refractive index of monomer B, and b2 is the weight ratio of monomer B to all monomers) Monomer C: c1 x c2 (where c1 is the refractive index of monomer C, and c2 is the weight ratio of monomer C to all monomers) Monomer D: d1 x d2 (where d1 is the refractive index of monomer D, and d2 is the weight ratio of monomer D to all monomers) When the above products are calculated for each monomer, the sum of the products in the base polymer (hereinafter referred to as the sum of products) is 1.51 or more. The sum of the products in the above-exemplified base polymers can be expressed by the formula: a1 x a2 + b1 x b2 + c1 x c2 + d1 x d2. In addition, the weight average molecular weight (hereinafter referred to as Mw) of the base polymer is 800,000 or more.

[0026] The liquid crystal alignment solidified layer is an alignment solidified layer of a liquid crystal compound. More specifically, it refers to a layer in which the liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. The liquid crystal alignment solidified layer includes an alignment solidified layer obtained by curing a liquid crystal monomer. Compared to typical optical substrates made of resin films, the liquid crystal alignment solidified layer is suitable for achieving desired optical properties, such as retardation, while reducing the thickness. However, according to the inventors' studies, the liquid crystal alignment solidified layer has a higher electron density than typical optical substrates, and therefore tends to have a high refractive index. In the optical laminate 1, the sum of the products of the adhesive sheet 3 sandwiched between the two liquid crystal alignment solidified layers 2 and 4 is 1.51 or more, which alleviates the mismatch in refractive index between the liquid crystal alignment solidified layers 2 and 4 and the adhesive sheet 3, thereby contributing to reducing reflection in the optical laminate 1. The reduced reflection can contribute to improving the visibility of an image display device incorporating the optical laminate 1. The degree of reflection can be evaluated by measuring the reflectance of light incident on the optical laminate 1 from either one of the liquid crystal alignment solidified layers 2 and 4 .

[0027] Having a base polymer Mw of 800,000 or more contributes to ensuring the durability of the optical laminate 1 at high temperatures, for example, 60°C or higher, 70°C or higher, or even 80°C or higher. It is presumed that ensuring durability at high temperatures is due to the above Mw improving the stress relaxation property of the pressure-sensitive adhesive sheet 3. Improved stress relaxation property is thought to contribute to suppressing interlayer peeling caused by shrinkage of the optical substrate at high temperatures. Optical substrates equipped with polarizers, typically polarizing films, tend to shrink at high temperatures. For this reason, the present invention is particularly advantageous when the optical laminate 1 further includes a polarizing film.

[0028] According to the studies of the present inventors, it has been difficult to achieve a base polymer with a sum of products of 1.51 or more and an Mw of 800,000 or more for the following reasons. In order to achieve a sum of products of 1.51 or more, a monomer with a refractive index of 1.51 or more (hereinafter referred to as a high refractive index monomer) must be used to form the base polymer. However, the refractive index of alkyl (meth)acrylates widely used in PSA sheets is only about 1.4 (for example, n-butyl acrylate has a refractive index of 1.42). As a high refractive index monomer, for example, a monomer having an aromatic ring could be considered. Aromatic rings have a higher electron density than alkyl groups, and this high electron density can contribute to an increase in the refractive index. However, studies based on the above findings have shown that using a large amount of aromatic ring-containing monomer to increase the sum of products makes the base polymer more susceptible to gelation during polymerization, and that adopting formation conditions to suppress gelation, such as a low monomer concentration during polymerization, makes it difficult to achieve an Mw of 800,000 or more. Based on this finding, further investigation was conducted and it was found that gelation can be suppressed and Mw can be improved by limiting the amount of residual impurities contained in the aromatic ring-containing monomer used in polymerization. The present invention is based on this new finding.

[0029] The pressure-sensitive adhesive sheet 3 may have a thickness of 4 μm or more. Having a thickness of 4 μm or more for the pressure-sensitive adhesive sheet 3 can contribute to improving the stress relaxation properties of the pressure-sensitive adhesive sheet 3. The thickness of the pressure-sensitive adhesive sheet 3 may be 4.5 μm or more, or even 5 μm or more. The upper limit of the thickness is, for example, 8 μm or less, 7 μm or less, or even 6 μm or less. The thickness may be 4 μm or more and 8 μm or less, or 4 μm or more and 7 μm or less.

[0030] According to the study by the present inventors, the thickness unevenness of the pressure-sensitive adhesive sheet 3 tends to be smaller than that of the adhesive layer. The smaller thickness unevenness can contribute to the reduction of reflection unevenness by suppressing the unevenness of the interface with an adjacent layer, for example, a liquid crystal alignment cured layer.

[0031] The sum of the products in the base polymer may be 1.515 or more, 1.52 or more, 1.53 or more, 1.54 or more, or even 1.545 or more. The upper limit of the sum of the products is, for example, 1.90 or less, 1.80 or less, 1.70 or less, 1.65 or less, or even 1.60 or less. The sum of the products may be 1.515 or more and 1.60 or less, or 1.52 or more and 1.60 or less.

[0032] The Mw of the base polymer may be 850,000 or more, 900,000 or more, 950,000 or more, or even 1,000,000 or more. The upper limit of Mw is, for example, 2,000,000 or less. The Mw of the base polymer can vary depending on the composition of the base polymer, the polymerization conditions, and the amount of residual impurities in the raw material monomers. Examples of polymerization conditions include the type and amount of polymerization initiator, the type and amount of additives such as chain transfer agents, the type of polymerization solvent, and the monomer concentration in the polymerization system.

[0033] (Liquid Crystal Alignment Solidified Layer) In the liquid crystal alignment solidified layers 2 and 4, rod-shaped liquid crystal compounds are typically aligned in a predetermined direction (homogeneous alignment). Examples of liquid crystal compounds include nematic liquid crystals and discotic liquid crystals. Liquid crystal polymers or liquid crystal monomers can be used as the liquid crystal compounds. The liquid crystal monomers may be polymerizable and / or crosslinkable.

[0034] Specific examples of the liquid crystal monomer are the polymerizable mesogenic compounds described in JP-A-2002-533742, EP 358208, EP 66137, WO 93 / 22397, EP 0261712, DE 19504224, DE 4408171, and GB 2280445. Examples of the polymerizable mesogenic compound include LC242 manufactured by BASF, E7 manufactured by Merck, and LC-Silicon-CC3767 manufactured by Wacker-Chem. The liquid crystal monomer is preferably a nematic monomer.

[0035] The liquid crystal alignment solidified layers 2 and 4 can be formed by applying a coating liquid containing a liquid crystal compound to the surface of a substrate film that has been subjected to an alignment treatment, orienting the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the alignment state. A release film may be used as the substrate. The liquid crystal alignment solidified layers 2 and 4 formed on the release film can be transferred to another layer that may be included in the optical laminate 1, such as the pressure-sensitive adhesive sheet 3. However, the method for forming the liquid crystal alignment solidified layers 2 and 4 is not limited to the above example.

[0036] For further specific examples of liquid crystal compounds and details of the method for forming the liquid crystal alignment solidified layer, refer to JP 2006-163343 A. However, the liquid crystal alignment solidified layers 2 and 4 and the method for forming them are not limited to the contents described in the publication.

[0037] The average refractive index of the first liquid crystal alignment solidified layer 2 and / or the second liquid crystal alignment solidified layer 4 may be 1.50 or more, such as 1.52 or more, 1.53 or more, 1.55 or more, 1.57 or more, or even 1.59 or more. The upper limit of the average refractive index is, for example, 1.70 or less. When incorporated into an image display device, the liquid crystal alignment solidified layer located on the viewing side, such as the first liquid crystal alignment solidified layer 2, and the liquid crystal alignment solidified layer located on the opposite side from the viewing side, such as the second liquid crystal alignment solidified layer 4, may have the same or different average refractive indexes. The average refractive index of the liquid crystal alignment solidified layer is given by the formula: average refractive index = (nx + ny + nz) / 3, where nx is the refractive index in the direction in the plane of the layer where the refractive index is maximum (slow axis), ny is the refractive index in the direction perpendicular to the slow axis in the plane (fast axis), and nz is the refractive index in the thickness direction. In this specification, nx, ny, and nz are values ​​for light with a wavelength of 550 nm.

[0038] The absolute value of the difference between the average refractive index of each of the first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 and the sum of the products may be 0.08 or less, or may be 0.075 or less, 0.07 or less, 0.06 or less, 0.05 or less, or even 0.045 or less.

[0039] The first liquid crystal alignment solidified layer 2 and / or the second liquid crystal alignment solidified layer 4 may be a retardation layer. The retardation layer has, for example, a refractive index characteristic represented by the formula nx>ny. However, the refractive index characteristic of the retardation layer is not limited to the above example. The retardation layer can have various refractive index characteristics known as retardation layers, such as a refractive index characteristic represented by the formula nz>nx=ny.

[0040] The retardation layer may have an Re(550) of 10 nm or more, 30 nm or more, 50 nm or more, 80 nm or more, or even 100 nm or more. Re(550) is the in-plane retardation of the retardation layer for light with a wavelength of 550 nm. The in-plane retardation is given by the formula Re=(nx-ny)×d, where d (nm) is the thickness of the retardation layer.

[0041] The Re(550) of the retardation layer may be 100 nm to 180 nm, 110 to 170 nm, 120 to 160 nm, or even 135 nm to 155 nm, in which case the retardation layer can function as a so-called λ / 4 plate. The Re(550) of the retardation layer may be 180 nm to 320 nm, 200 to 290 nm, or even 230 to 280 nm, in which case the retardation layer can function as a so-called λ / 2 plate. The first liquid crystal alignment solidified layer 2 and / or the second liquid crystal alignment solidified layer 4 may be a layer that can function as a λ / 4 plate or a λ / 2 plate. The first liquid crystal alignment solidified layer 2 may be a layer that can function as a λ / 4 plate (or a λ / 2 plate), and the second liquid crystal alignment solidified layer 4 may be a layer that can function as a λ / 2 plate (or a λ / 4 plate). The optical laminate 1 in which the first liquid crystal alignment solidified layer 2 and / or the second liquid crystal alignment solidified layer 4 are layers that can function as a λ / 4 plate or a λ / 2 plate and further includes a polarizing film may be an elliptically polarizing film or a circularly polarizing film.

[0042] The first liquid crystal alignment solidified layer 2 and / or the second liquid crystal alignment solidified layer 4 may be an anti-reflection retardation layer, a viewing angle compensation retardation layer, or an obliquely aligned retardation layer for viewing angle compensation.

[0043] The thickness of the liquid crystal alignment solidified layers 2, 4 is, for example, 5 μm or less, and may be 4 μm or less, or even 3 μm or less. The lower limit of the thickness is, for example, 0.5 μm or more, and may be 1 μm or more. The thickness may be 0.5 μm or more and 5 μm or less, or 1 μm or more and 4 μm or less.

[0044] The first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 may have the same structure or different structures.

[0045] The optical laminate 1A including the first liquid crystal alignment solidified layer 2, the pressure-sensitive adhesive sheet 3, and the second liquid crystal alignment solidified layer 4 can function as a retardation layer as a whole.

[0046] (Adhesive Sheet 3) The adhesive sheet 3 is typically formed by curing an adhesive composition (A) containing a base polymer. The monomer constituting the base polymer may contain (meth)acrylate, or the main monomer constituting the base polymer may be (meth)acrylate. In this specification, (meth)acrylate refers to acrylate and / or methacrylate. Furthermore, the main monomer refers to the monomer that accounts for the largest weight proportion of all the monomers constituting the base polymer. The proportion of the main monomer is, for example, 50% or more, and may be 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, or even 92% or more. The upper limit of the proportion is, for example, 100% or less, or may be 99% or less.

[0047] The monomers constituting the base polymer may include an aromatic ring-containing monomer. The main monomer constituting the base polymer may be an aromatic ring-containing monomer. In other words, the weight ratio of the aromatic ring-containing monomer to all monomers constituting the base polymer may be 50% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, or even 92% or more. The ratio may be 60 to 99%, or even 70 to 95%. The aromatic ring-containing monomer may contribute to increasing the total product. The aromatic ring-containing monomer is a compound that contains an aromatic ring in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of aromatic rings are a benzene ring, a naphthalene ring, and a biphenyl ring. The aromatic ring-containing monomer may be an aromatic ring-containing (meth)acrylate. The aromatic ring-containing monomer may be used alone or in combination of two or more types.

[0048] Examples of aromatic ring-containing (meth)acrylates include benzyl (meth)acrylate, phenyl (meth)acrylate, o-phenylphenol (meth)acrylate, phenoxy (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxybenzyl (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, ethylene oxide-modified cresol (meth)acrylate, and phenol ethylene oxide-modified (meth)acrylate. those having a benzene ring such as hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate; and those having a biphenyl ring such as biphenyl (meth)acrylate. From the viewpoint of increasing the total product in the base polymer, benzyl (meth)acrylate and phenoxybenzyl (meth)acrylate are preferred, and phenoxybenzyl acrylate (POB-A) is more preferred.

[0049] The boiling points of aromatic ring-containing monomers typically tend to be higher than those of monomers that do not contain aromatic rings. This tendency, although dependent on the molecular structure, may be stronger as the number of aromatic rings increases. Commercially available monomers and other monomers typically used in forming the PSA sheet 3 are purified to remove impurities such as by-products. However, according to the inventors' studies, for monomers with high boiling points, the increased temperature required for distillation, a common purification method, tends to promote polymerization of impurities during purification. To avoid this, mild purification conditions are required, which tends to result in a large amount of residual impurities. Impurities, particularly polyfunctional ones, can cause gelation during polymerization of the base polymer. To achieve a base polymer Mw of 800,000 or more, for example, for high-boiling point monomers, it is preferable to use monomers that have even lower amounts of residual impurities than the monomers typically used in forming the PSA sheet 3. To achieve this, further purification may be performed. If purification by distillation is difficult, other purification methods, such as adsorption, may be used.

[0050] In accordance with the above viewpoint, the aromatic ring-containing monomer may be a high-boiling point monomer. In this specification, a high-boiling point monomer can be specified as a monomer that satisfies at least one condition selected from the group consisting of the following A to C. The high-boiling point monomer may also be a monomer that satisfies condition C. Phenoxybenzyl acrylate satisfies conditions A to C. A: A boiling point of 240°C or higher under a pressure of 760 mmHg B: A boiling point of 90°C or higher under a pressure of 0.2 mmHg C: A boiling point of 65°C or higher under a pressure of 0.1 mmHg

[0051] An example of an impurity that may be contained in the aromatic ring-containing (meth)acrylate is a polyfunctional acrylate such as a diacrylate. An example of the diacrylate is a compound represented by the following formula (1).

[0052] From another perspective of the above viewpoint, the monomer constituting the base polymer may include a monomer containing two or more aromatic rings. The monomer may be a (meth)acrylate having two or more aromatic rings in its side chain. The upper limit of the number of aromatic rings is, for example, 5 or less, or may be 4 or less, or even 3 or less. The number of aromatic rings may be 2.

[0053] From another aspect of the above viewpoint, the monomers constituting the base polymer may contain a high-boiling point monomer. The high-boiling point monomer may be a (meth)acrylate.

[0054] Other monomers that can constitute the base polymer are described below. One example of such other monomers is alkyl(meth)acrylate. The number of carbon atoms in the alkyl group in the alkyl(meth)acrylate is not particularly limited and may be, for example, 1 to 30. The alkyl group may be linear, branched, or cyclic. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, hexyl, cyclohexyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, decyl, isodecyl, dodecyl, isomyristyl, lauryl, tridecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl. Alkyl(meth)acrylates can be used alone or in combination of two or more. When two or more types are combined, the average carbon number of the alkyl group is preferably 3 to 9. The alkyl(meth)acrylate is preferably butyl acrylate.

[0055] The weight ratio of alkyl (meth)acrylate to all monomers constituting the base polymer may be 50% or less, 40% or less, 35% or less, 30% or less, 25% or less, 22% or less, 20% or less, 17% or less, 15% or less, or even 13% or less. The lower limit of this ratio is, for example, 1% or more, 3% or more, or even 5% or more. The monomers constituting the base polymer may not contain alkyl (meth)acrylate.

[0056] Another example of the other monomer is at least one monomer selected from the group consisting of an amide group-containing monomer, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer. In other words, the monomer constituting the base polymer may include at least one monomer selected from the group consisting of an amide group-containing monomer, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer. These monomers can be used alone or in combination of two or more.

[0057] The hydroxyl group-containing monomer is a compound that contains a hydroxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. The hydroxyl group-containing monomer may be a hydroxyl group-containing (meth)acrylate. Examples of hydroxyl group-containing (meth)acrylates include hydroxyl group-containing alkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; and hydroxyl group-containing cycloalkyl (meth)acrylates such as (4-hydroxymethylcyclohexyl)-methyl acrylate. Among these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred.

[0058] The weight ratio of the hydroxyl group-containing monomer to all monomers constituting the base polymer may be 0.5% or more, 1% or more, 1.5% or more, or even 2% or more. The upper limit of the ratio may be, for example, 9% or less, 7% or less, 5% or less, 4.5% or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, or even 2% or less. The monomers constituting the base polymer may not contain a hydroxyl group-containing monomer. A ratio of 1% or more increases the gel fraction of the PSA sheet 3 immediately after formation (which can be evaluated using the initial gel fraction described below), which can contribute to, for example, suppressing the occurrence of dents on the PSA sheet 3. A typical example of dents related to the initial gel fraction is a foreign-matter mark (indentation) caused by a foreign matter that has become embedded in the PSA composition before it has completely cured. A ratio of 3.5% or less can contribute to improving the pot life of the PSA composition (A). The ratio may be 0.5 to 9%, 1 to 5%, or even 1 to 3.5%.

[0059] The amide group-containing monomer is a compound that contains an amide group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. The amide group-containing monomer may be an amide group-containing (meth)acrylate. Examples of the amide group-containing (meth)acrylate include acrylamide-based monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylol-N-propane(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(meth)acrylamide, and mercaptoethyl(meth)acrylamide; N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine; and N-vinyl group-containing lactam monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam.

[0060] The carboxyl group-containing monomer is a compound that contains a carboxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. The carboxyl group-containing monomer may be a carboxyl group-containing (meth)acrylate. Examples of the carboxyl group-containing (meth)acrylate include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid.

[0061] The total weight ratio of the amide-containing monomer and the carboxyl-containing monomer to all the monomers constituting the base polymer is, for example, 10% or less, 7% or less, 5% or less, or even 3% or less. The lower limit of the ratio is, for example, 0.5% or more, or even 1% or more. The monomers constituting the base polymer may not contain the amide-containing monomer or the carboxyl-containing monomer.

[0062] Examples of the other monomers are monomers that can be copolymerized with the above-mentioned monomers (copolymerizable monomers). The copolymerizable monomers usually have a polymerizable functional group containing an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group. Examples of copolymerizable monomers include acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; sulfonic acid group-containing monomers such as allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, and sulfopropyl (meth)acrylate; phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate; alkylaminoalkyl (meth)acrylates such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; and succinimide-based monomers such as N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, and N-(meth)acryloyl-8-oxyoctamethylene succinimide. 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-cyclohexylitaconimide, and N-laurylitaconimide; vinyl-based monomers such as vinyl acetate and vinyl propionate; cyanoacrylate-based monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate; glycol-based (meth)acrylates such as carbitol (meth)acrylate, ethyl carbitol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate;(Meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, and silicone (meth)acrylate; and silane monomers containing silicon atoms such as 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, and 10-acryloyloxydecyltriethoxysilane;

[0063] The weight ratio of the copolymerizable monomer to all the monomers constituting the base polymer is, for example, 5% or less, or may be 3% or less, or even 1% or less. The monomers constituting the base polymer do not necessarily contain the copolymerizable monomer.

[0064] (Pressure-sensitive adhesive composition (A)) The pressure-sensitive adhesive composition (A) contains a base polymer. The base polymer can be formed by various known polymerization methods such as solution polymerization, radiation polymerization using electron beams, ultraviolet rays (UV), or the like, bulk polymerization, and emulsion polymerization. The polymerization is typically radical polymerization. The base polymer may be any of a random copolymer, a block copolymer, a graft copolymer, and the like. However, the method for forming the base polymer is not limited to the above examples.

[0065] As the polymerization solvent for solution polymerization, known polymerization solvents such as ethyl acetate and toluene can be used. Solution polymerization can be carried out, for example, using a polymerization initiator and under a stream of an inert gas such as nitrogen. The polymerization conditions are, for example, 50 to 70°C and 5 to 30 hours.

[0066] The polymerization initiator, chain transfer agent, emulsifier, etc. used in the radical polymerization are not particularly limited and can be selected appropriately.

[0067] Examples of the polymerization initiator include azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (for example, VA-057 manufactured by Wako Pure Chemical Industries, Ltd.); persulfates such as potassium persulfate and ammonium persulfate; di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-s Examples of the polymerization initiator include peroxide initiators such as ec-butyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butyl hydroperoxide, and hydrogen peroxide; and redox initiators that combine a peroxide and a reducing agent, such as a combination of a persulfate and sodium hydrogen sulfite, or a combination of a peroxide and sodium ascorbate. However, the polymerization initiator is not limited to the above examples.

[0068] The polymerization initiators can be used alone or in combination of two or more. The total amount of the polymerization initiators used is, for example, 0.005 to 1 part by weight, or may be 0.02 to 0.5 parts by weight, per 100 parts by weight of the monomer components.

[0069] Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. The chain transfer agents can be used alone or in combination of two or more. The total amount of the chain transfer agent used is, for example, 0.1 parts by weight or less per 100 parts by weight of the monomer components.

[0070] In radiation polymerization, a monomer is irradiated with radiation such as an electron beam or ultraviolet (UV) light to cause polymerization to proceed and form a base polymer. When radiation polymerization is carried out using an electron beam, the use of a photopolymerization initiator is not particularly necessary. When radiation polymerization is carried out using UV light, a photopolymerization initiator may be used because of advantages such as the ability to shorten the polymerization time. The photopolymerization initiators can be used alone or in combination of two or more.

[0071] Examples of the photopolymerization initiator include various photopolymerization initiators such as benzoin ether-based, acetophenone-based, α-ketol-based, photoactive oxime-based, benzoin-based, benzil-based, benzophenone-based, ketal-based, and thioxanthone-based photopolymerization initiators. However, the photopolymerization initiator is not limited to the above examples. The amount of the photopolymerization initiator used is, for example, 0.05 to 1.5 parts by weight, or may be 0.1 to 1 part by weight, per 100 parts by weight of the monomer component.

[0072] The pressure-sensitive adhesive composition (A) is typically a composition that can be dried to form a pressure-sensitive adhesive sheet 3. In this case, the pressure-sensitive adhesive sheet 3 formed from the pressure-sensitive adhesive composition (A) is usually a solvent-based pressure-sensitive adhesive (also called a thermosetting pressure-sensitive adhesive).

[0073] The pressure-sensitive adhesive composition (A) may contain a crosslinking agent. Examples of crosslinking agents that the pressure-sensitive adhesive composition (A) may contain include isocyanate-based crosslinking agents, peroxide-based crosslinking agents, epoxy-based crosslinking agents, imine-based crosslinking agents, and polyfunctional metal chelates. The pressure-sensitive adhesive composition (A) preferably contains an isocyanate-based crosslinking agent and / or a peroxide-based crosslinking agent, and more preferably contains an isocyanate-based crosslinking agent. In other words, the crosslinked product of the base polymer that the pressure-sensitive adhesive sheet 3 may contain may have a crosslinked structure due to a peroxide-based crosslinking agent, may have a crosslinked structure due to an isocyanate-based crosslinking agent, or may have both crosslinked structures.

[0074] As the isocyanate-based crosslinking agent, a compound having at least two isocyanate groups (isocyanate compound) can be used. The number of isocyanate groups contained in the isocyanate compound is preferably 3 or more. The upper limit of the number of isocyanate groups is not particularly limited, and is, for example, 5. Examples of the isocyanate compound include aromatic isocyanate compounds, alicyclic isocyanate compounds, and aliphatic isocyanate compounds.

[0075] Examples of aromatic isocyanate compounds are phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and xylylene diisocyanate.

[0076] Examples of the alicyclic isocyanate compound are 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

[0077] Examples of aliphatic isocyanate compounds are trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0078] The isocyanate-based crosslinking agent may be a polymer (dimer, trimer, pentamer, etc.) of the above-mentioned isocyanate compound, an adduct obtained by adding the compound to a polyhydric alcohol such as trimethylolpropane, a urea-modified compound, a biuret-modified compound, an allophanate-modified compound, an isocyanurate-modified compound, a carbodiimide-modified compound, or a urethane prepolymer obtained by adding the compound to a polyether polyol, a polyester polyol, an acrylic polyol, a polybutadiene polyol, a polyisoprene polyol, or the like.

[0079] The isocyanate-based crosslinking agent is preferably an aromatic isocyanate compound and its derivatives, more preferably tolylene diisocyanate and its derivatives, in other words, a tolylene diisocyanate-based (TDI-based) crosslinking agent. From the viewpoint of reactivity, a TDI-based crosslinking agent is more suitable than xylylene diisocyanate and its derivatives, in other words, a xylylene diisocyanate-based (XDI-based) crosslinking agent. The isocyanate-based crosslinking agent may contain an adduct of a polyhydric alcohol and tolylene diisocyanate as the TDI-based crosslinking agent. A specific example of the adduct is a trimethylolpropane / tolylene diisocyanate trimer adduct.

[0080] Commercially available isocyanate crosslinking agents can be used. Examples of commercially available products include Millionate MT, Millionate MTL, Millionate MR-200, Millionate MR-400, Coronate L, Coronate HL, and Coronate HX (all manufactured by Tosoh Corporation), Takenate D-101E, Takenate D-110N, Takenate D-120N, Takenate D-140N, Takenate D-160N, Takenate D-165N, Takenate D-170HN, Takenate D-178N, Takenate 500, and Takenate 600 (all manufactured by Mitsui Chemicals, Inc.). Of these, Takenate D-101E and Takenate D110N are preferred.

[0081] The isocyanate-based crosslinking agents may be used alone or in combination of two or more kinds.

[0082] The amount of the isocyanate crosslinking agent in the PSA composition (A) is, for example, 0.01 to 20 parts by weight relative to 100 parts by weight of the base polymer. The lower limit of the amount may be 0.02 parts by weight or more, 0.03 parts by weight or more, 0.04 parts by weight or more, or even 0.05 parts by weight or more. The upper limit of the amount may be 15 parts by weight or less, 13 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.1 parts by weight or less, or even 0.08 parts by weight or less. The amount may be 0.03 to 1 part by weight, or 0.05 to 0.5 parts by weight.

[0083] The amount of the non-isocyanate crosslinking agent, for example, a peroxide crosslinking agent, blended in the pressure-sensitive adhesive composition (A) may be, for example, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less, relative to 100 parts by weight of the base polymer. The lower limit of the blending amount may be, for example, 0.1 parts by weight or more, 0.2 parts by weight or more, or even 0.3 parts by weight or more. The blending amount may be 0.1 to 1 part by weight, or 0.3 to 0.5 parts by weight. The pressure-sensitive adhesive composition (A) may not contain a non-isocyanate crosslinking agent.

[0084] The pressure-sensitive adhesive composition (A) may further contain known additives. Examples of additives include silane coupling agents, solvents, colorants, pigments, powders, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, antiaging agents, light stabilizers, UV absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, and foil-like materials. Redox systems containing reducing agents may also be used within controllable limits. However, the additives are not limited to the above examples. The total amount of additives may be, for example, 10 parts by weight or less, 5 parts by weight or less, or even 1 part by weight or less, per 100 parts by weight of the base polymer.

[0085] The pressure-sensitive adhesive composition (A) may contain a silane coupling agent as an additive. Examples of the silane coupling agent include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane.

[0086] When the pressure-sensitive adhesive composition (A) contains a silane coupling agent, the amount thereof may be, for example, 5 parts by weight or less, 3 parts by weight or less, 1 part by weight or less, 0.5 parts by weight or less, 0.4 parts by weight or less, 0.2 parts by weight or less, or even 0.1 parts by weight or less, relative to 100 parts by weight of the base polymer. The lower limit of the amount is not particularly limited, and is, for example, 0.02 parts by weight or more. The pressure-sensitive adhesive composition (A) does not need to contain a silane coupling agent.

[0087] The pressure-sensitive adhesive composition (A) may be substantially free of a photocuring agent such as a photopolymerization initiator.

[0088] The pressure-sensitive adhesive sheet 3 can be formed, for example, by drying a coating film of the pressure-sensitive adhesive composition (A) provided on a substrate. Heat can be used for drying. A release film may be used as the substrate. The pressure-sensitive adhesive sheet 3 formed on the release film can be transferred to other layers that may be included in the optical laminate 1, such as the first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4. The substrate may also be other layers that may be included in the optical laminate 1. However, the method for forming the pressure-sensitive adhesive sheet 3 from the pressure-sensitive adhesive composition (A) is not limited to the above example.

[0089] As the release film, a known film that can be used when forming a solvent-based pressure-sensitive adhesive sheet can be used.

[0090] The drying temperature of the coating film is, for example, 130° C. or lower, and may be 125° C. or lower, 120° C. or lower, 110° C. or lower, or even 100° C. or lower. The drying temperature is, for example, 60° C. or higher, and may be 80° C. or higher. The drying time of the coating film can be appropriately adjusted depending on the composition of the pressure-sensitive adhesive composition (A), and may be, for example, 30 to 300 seconds, 40 to 240 seconds, or even 60 to 180 seconds.

[0091] The initial gel fraction of the pressure-sensitive adhesive composition (A) may be 10% or more, 15% or more, 18% or more, 20% or more, 25% or more, 29% or more, 30% or more, 35% or more, 40% or more, or even 43% or more. The upper limit of the initial gel fraction is, for example, 80% or less, and may be 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, or even 50% or less.

[0092] The initial gel fraction of the pressure-sensitive adhesive composition (A) can be evaluated, for example, by the following method. First, the pressure-sensitive adhesive composition (A) is applied to a substrate so as to form a coating film, and the coating film is dried at 120°C for 300 seconds to form a pressure-sensitive adhesive sheet for evaluation. Next, a portion of the formed pressure-sensitive adhesive sheet is scraped off within 2 hours of formation to obtain a small piece. Next, the obtained small piece is wrapped in a stretched porous polytetrafluoroethylene film and tied with kite string. This results in a test piece. Next, the total weight (weight A) of the pressure-sensitive adhesive sheet piece, the stretched porous film, and the kite string is measured. The total weight of the stretched porous film and the kite string used is defined as weight B. Next, the test piece is immersed in a container filled with ethyl acetate and allowed to stand at 23°C for 1 week. After standing, the test piece is removed from the container and dried in a dryer set to 130°C for 2 hours, and then the weight C of the test piece is measured. The initial gel fraction can be calculated from weight A, weight B, and weight C according to the following formula. Formula: Initial gel fraction (%) = (C - B) / (A - B) x 100

[0093] The optical laminate 1 of this embodiment may optionally include layers other than the liquid crystal alignment solidified layers 2, 4 and the adhesive sheet 3. An example of such a layer is an optical substrate. Examples of the optical substrate are a polarizing film and a surface protection film. The optical substrate may be a glass film. The optical laminate 1 may further include one or more optical substrates. The optical substrate is not limited to the above examples.

[0094] A polarizing film typically includes a polarizer and protective layers disposed on both sides of the polarizer. Depending on the purpose, at least one of the protective layers may be omitted. Therefore, the polarizing film may be a so-called double-protected polarizing film, a so-called single-protected polarizing film, or may be composed of a polarizer alone.

[0095] A polarizer is typically made of a film made of a polyvinyl alcohol (PVA)-based resin containing a dichroic substance (e.g., iodine). Examples of PVA-based resins include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and partially saponified ethylene-vinyl acetate copolymer.

[0096] The PVA-based resin preferably contains an acetoacetyl-modified PVA-based resin, and the amount of the acetoacetyl-modified PVA-based resin is preferably 5 to 20% by weight, and more preferably 8 to 12% by weight, based on 100% by weight of the total PVA-based resin.

[0097] The polarizer preferably contains iodide or sodium chloride (sometimes collectively referred to as a halide). Examples of iodides include potassium iodide, sodium iodide, and lithium iodide. The content of the halide in the polarizer is preferably 5 to 20 parts by weight, more preferably 10 to 15 parts by weight, relative to 100 parts by weight of the PVA-based resin. In the manufacturing method described below, the halide is blended into a coating liquid that forms a PVA-based resin layer, which is a precursor of the polarizer, and can be finally introduced into the polarizer. Introducing a halide into the polarizer can improve the orientation of PVA molecules in the polarizer, thereby realizing a polarizer with excellent optical properties (typically, both a high degree of polarization and a high single-unit transmittance).

[0098] The polarizer preferably exhibits absorptive dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is preferably 41.0% to 46.0%, more preferably 42.0% to 45.0%. 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.

[0099] The thickness of the polarizer is, for example, 12 μm or less, preferably 10 μm or less, more preferably 1 μm to 8 μm, and even more preferably 3 μm to 7 μm. By combining such a thin polarizer with a liquid crystal alignment solidified layer, it is possible to significantly reduce the thickness of the optical laminate.

[0100] The polarizer can be produced by any appropriate method. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

[0101] Specific examples of polarizers composed of a single-layer resin film include hydrophilic polymer films such as PVA films, partially formalized PVA films, and partially saponified ethylene-vinyl acetate copolymer films that have been dyed with iodine or a dichroic substance such as a dichroic dye and stretched, and polyene-based oriented films such as dehydrated PVA films and dehydrochlorinated polyvinyl chloride films. Preferably, a polarizer obtained by dyeing a PVA film with iodine and uniaxially stretching it is used because of its excellent optical properties.

[0102] The dyeing with iodine is carried out, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be carried out after the dyeing treatment or while dyeing. Alternatively, the PVA-based film may be stretched and then dyed. If necessary, the PVA-based film may be subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, or the like. For example, by immersing the PVA-based film in water and washing it before dyeing, it is possible to wash away dirt and antiblocking agents from the surface of the PVA-based film and also to swell the PVA-based film, thereby preventing uneven dyeing and the like.

[0103] Specific examples of laminate polarizers include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying the solution to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer, and then stretching and dyeing the laminate to convert the PVA-based resin layer into a polarizer. Preferably, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate.

[0104] The stretching typically involves immersing the laminate polarizer in a boric acid aqueous solution and stretching it. Furthermore, the stretching may further include, if necessary, in-air stretching of the laminate at a high temperature (e.g., 95°C or higher) before stretching in the boric acid aqueous solution. Preferably, the laminate is 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 method involves subjecting the laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment, in this order. The introduction of auxiliary stretching makes it 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 can be prevented when the PVA is immersed in water in the subsequent dyeing or stretching steps, thereby achieving high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disordering of the polyvinyl alcohol molecules and the decrease in the orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of a polarizer obtained through treatment processes in which the laminate is immersed in a liquid, such as a dyeing treatment and an underwater stretching treatment. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction through a drying shrinkage treatment. The obtained resin substrate / polarizer laminate may be used as is (i.e., the resin substrate may serve as a protective layer for the polarizer). Alternatively, any suitable protective layer may be laminated on the peeled surface of the resin substrate / polarizer laminate after peeling the resin substrate from the resin substrate / polarizer laminate, or on the surface opposite to the peeled surface. Details of such a polarizer manufacturing method are described, for example, in JP-A-2012-73580 and JP-A-6470455. The entire disclosures of these publications are incorporated herein by reference.

[0105] The protective layers that can be disposed on both sides of the polarizer are typically composed of any appropriate resin film. Typical materials for such resin films include cellulose-based resins such as triacetyl cellulose (TAC), cycloolefin-based resins such as polynorbornene, (meth)acrylic resins, polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin-based resins such as polyethylene, and polycarbonate-based resins. Representative examples of (meth)acrylic resins include (meth)acrylic resins having a lactone ring structure. Examples of (meth)acrylic resins having a lactone ring structure are described in, for example, JP 2000-230016 A, JP 2001-151814 A, JP 2002-120326 A, JP 2002-254544 A, and JP 2005-146084 A. These publications are incorporated herein by reference. From the viewpoint of ease of processing into modified shapes, etc., cellulose-based resins are preferred, and TAC is more preferred. From the viewpoint of obtaining a polarizing plate with low moisture permeability and excellent durability, cycloolefin-based resins and (meth)acrylic resins are preferred.

[0106] The protective layer may be subjected to a surface treatment as needed. Examples of surface treatments include hard coating, anti-reflection, anti-sticking, and anti-glare treatments. The protective layer may be subjected to a treatment to improve visibility when viewed through polarized sunglasses (typically, by imparting an (elliptically) circular polarization function or an ultra-high phase difference) as needed. By performing such treatments, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses.

[0107] The protective layer may be optically isotropic, for example, the in-plane retardation Re(550) may be 0 nm to 10 nm, and the thickness direction retardation Rth(550) may be −10 nm to +10 nm.

[0108] The thickness of each protective layer is preferably 10 μm to 80 μm, more preferably 12 μm to 40 μm, and even more preferably 15 μm to 35 μm. When the protective layer is surface-treated, the thickness of the protective layer includes the thickness of the surface-treated layer.

[0109] An example of an optical laminate 1 including a polarizer film is shown in Figure 2. The optical laminate 1 (1B) in Figure 2 includes a polarizing film 5, a first liquid crystal alignment solidified layer 2, an adhesive sheet 3, and a second liquid crystal alignment solidified layer 4, in this order. The polarizing film 5 faces the main surface of the first liquid crystal alignment solidified layer 2 opposite the adhesive sheet 3. The first liquid crystal alignment solidified layer 2 is located between the adhesive sheet 3 and the polarizing film 5. Adjacent layers included in the optical laminate 1B in Figure 2 are in contact with each other. However, another layer may be further disposed between each layer.

[0110] The optical laminate 1 may include an additional adhesive sheet other than the adhesive sheet 3. An example of the optical laminate 1 including an additional adhesive sheet is shown in FIG. 3. The optical laminate 1 (1C) in FIG. 3 includes, in this order, a polarizing film 5, a first liquid crystal alignment solidified layer 2, an adhesive sheet 3, a second liquid crystal alignment solidified layer 4, and an additional adhesive sheet 6. The adhesive sheet 6 constitutes one exposed surface of the optical laminate 1C. When the optical laminate 1C is bonded to another member, the adhesive sheet 6 can constitute the bonding surface with the other member.

[0111] The adhesive sheet 6 may be a known adhesive sheet contained in an optical laminate that can be used in an image display device. The adhesive sheet 6 is, for example, a (meth)acrylic adhesive sheet. The adhesive sheet 6 can be formed by a known method. The configuration of the adhesive sheet 6 may be the same as the configuration of the adhesive sheet 3.

[0112] The optical laminate 1 may include a release liner. An example of an optical laminate 1 including a release liner is shown in Figure 4. The optical laminate 1 (1D) in Figure 4 is the same as the optical laminate 1C in Figure 3 except that it includes a release liner 7 on the side of the pressure-sensitive adhesive sheet 6 opposite to the side of the second liquid crystal alignment solidified layer 4. The release liner 7 in Figure 4 is in contact with the pressure-sensitive adhesive sheet 6. The optical laminate 1D can be used by peeling off the release liner 7.

[0113] The release liner 7 is, for example, a film, paper, woven fabric, nonwoven fabric, porous material, net, foam, foil, or laminate thereof made of resin, paper, fiber, metal, or a composite material thereof. Examples of resins include polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polyethylene terephthalate, polybutylene terephthalate, polyurethane, ethylene-vinyl acetate copolymer, and polyester. However, the release liner 7 is not limited to the above examples. Furthermore, the materials and resins that can be used to make the release liner 7 are not limited to the above examples.

[0114] The thickness of the release liner 7 is, for example, 5 to 200 μm, and may be 5 to 100 μm. The surface of the release liner 7 may be subjected to various surface treatments such as release treatment, antifouling treatment, and antistatic treatment as needed. For the release treatment, various release agents such as silicone-based, fluorine-based, long-chain alkyl-based, and fatty acid amide-based release agents, or particles such as silica powder can be used.

[0115] The release film used in forming the pressure-sensitive adhesive sheet 6 may also be used as the release liner 7 .

[0116] The optical laminate 1 of this embodiment can be distributed and stored, for example, as a rolled body obtained by rolling up a strip-shaped optical laminate 1 or as a sheet-shaped optical laminate 1 .

[0117] The optical laminate 1 of this embodiment is typically used in an image display device. The image display device is, for example, an EL display such as a liquid crystal display, an organic EL display, or an inorganic EL display. The use of the optical laminate 1 of this embodiment is not limited to the above examples. Furthermore, the image display device in which the optical laminate 1 of this embodiment can be used is not limited to the above examples.

[0118] The optical laminate 1 of this embodiment can be formed by laminating each of the layers included therein. Layers that have been subjected to a surface modification treatment may be laminated. The surface modification treatment is, for example, at least one selected from the group consisting of corona treatment, plasma treatment, excimer UV light treatment, and flame treatment, and may be corona treatment and / or plasma treatment, or may be corona treatment. Each surface modification treatment can be performed using a corresponding known treatment device.

[0119] [Image display device] An example of an image display device of this embodiment is shown in Fig. 5. The image display device 11 of Fig. 5 has a layered structure in which a polarizing film 5, a first liquid crystal alignment solidified layer 2, an adhesive sheet 3, a second liquid crystal alignment solidified layer 4, an adhesive sheet 6, an image forming layer (e.g., an organic EL layer or a liquid crystal layer) 8, and a substrate 9 are layered in this order. The image display device 11 has the optical laminate 1C of Fig. 3. The substrate 9 and the image forming layer 8 may have the same configurations as the substrate and the image forming layer, respectively, provided in known image display devices.

[0120] The image display device 11 in Fig. 5 may be an organic EL display or a liquid crystal display. However, the image display device 11 is not limited to this example. The image display device 11 may also be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), or the like. The image display device 11 can be used for home appliances, in-vehicle applications, public information displays (PID), and the like.

[0121] The image display device of the present invention may have any configuration as long as it includes the optical layered body of the present invention.

[0122] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples shown below.

[0123] In this example, a laminate including a first liquid crystal alignment solidified layer, a pressure-sensitive adhesive sheet, and a second liquid crystal alignment cured layer was prepared, and its properties, such as reflectance and durability at high temperatures, were evaluated. In addition, the pot life and initial gel fraction of the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive sheet were evaluated.

[0124] [Preparation of First Liquid Crystal Alignment Solidified Layer] A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF, Paliocolor LC242) was dissolved in cyclopentanone to prepare a solution with a solids concentration of 30 wt %. A surfactant (BYK-360, BYK-Chemie) and a photopolymerization initiator (IGM Resins, Omnirad 907) were added to this solution to prepare a liquid crystal composition solution. The amounts of the surfactant and polymerization initiator added were 0.01 parts by weight and 3 parts by weight, respectively, per 100 parts by weight of the photopolymerizable liquid crystal compound. A biaxially stretched norbornene-based film (Zeon Corporation, Zeonor Film, thickness 33 μm, Re(550) = 135 nm) was prepared as a substrate film. The liquid crystal composition solution was applied to a substrate film using a bar coater so that Re(550) was 240 nm, and the liquid crystal was aligned by heating at 100°C for 3 minutes. After cooling to room temperature, the liquid crystal was aligned by irradiating the substrate with an integrated light intensity of 400 mJ / cm under a nitrogen atmosphere. 2 The first liquid crystal alignment solidified layer was homogeneously aligned, had a thickness of 1.7 μm, and had an average refractive index of 1.590.

[0125] [Preparation of second liquid crystal alignment solidified layer] A laminate of substrate film / second liquid crystal alignment solidified layer (homogeneous alignment, thickness 0.92 μm, Re(550)=130 nm) was obtained in the same manner as in the preparation of the first liquid crystal alignment solidified layer, except for changing the coating thickness. The average refractive index of the second liquid crystal alignment solidified layer was 1.590.

[0126] [Preparation of Polarizer] A long, amorphous, isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) with a Tg of approximately 75°C was used as the thermoplastic resin substrate. One side of the resin substrate was subjected to a corona treatment. A PVA-based resin (100 parts by weight of a 9:1 mixture of polyvinyl alcohol (degree of polymerization: 4200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIRM") was dissolved in water to prepare an aqueous PVA solution (coating solution). The PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a 13 μm-thick PVA-based resin layer, producing a laminate. The resulting laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130°C (in-air auxiliary stretching treatment). Next, the laminate was immersed for 30 seconds in an insolubilizing bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) having a liquid temperature of 40°C (insolubilization treatment), then immersed for 60 seconds in a dyeing bath (an iodine aqueous solution obtained by blending iodine and potassium iodide with 100 parts by weight of water in a weight ratio of 1:7) having a liquid temperature of 30°C while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would be a desired value (dyeing treatment), then immersed for 30 seconds in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) having a liquid temperature of 40°C (crosslinking treatment). The laminate was then immersed in a boric acid aqueous solution (boric acid concentration 4 wt %, potassium iodide concentration 5 wt %) at a liquid temperature of 70°C and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls operating at different peripheral speeds to a total stretch ratio of 5.5 times (underwater stretching treatment). The laminate was then immersed in a cleaning bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20°C (washing treatment). The laminate was then dried in an oven maintained at approximately 90°C and brought into contact with a SUS heated roll maintained at a surface temperature of approximately 75°C (drying shrinkage treatment). In this way, a polarizer approximately 5 μm thick was formed on the resin substrate, yielding a laminate having a resin substrate / polarizer configuration. The polarizer's single transmittance Ts was 43.3%.

[0127] [Preparation of Polarizing Film] An HC-COP film was bonded to the surface of the polarizer prepared above (the surface opposite to the resin substrate) via a UV-curable adhesive. The HC-COP film was a cycloolefin resin (COP) film (thickness 25 μm) with an HC layer (thickness 4 μm) formed thereon, and the COP film was bonded to the polarizer side. The COP film had an Re(550) of 135 nm. Next, the resin substrate was peeled off, and a triacetyl cellulose (TAC) film (thickness 25 μm) was bonded to the peeled surface via a UV-curable adhesive. In this way, a polarizing film having a configuration of HC layer / COP film (protective layer) / polarizer / TAC film (protective layer) was obtained.

[0128] [Preparation of adhesive for laminating polarizing film and first liquid crystal alignment solidified layer] 10 parts by weight of hydroxyethyl acrylamide (trade name "HEAA", manufactured by KJ Chemicals), 4 parts by weight of 2-acetoacetoxyethyl methacrylate (trade name "AAEM", manufactured by Mitsubishi Chemicals), 60 parts by weight of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals), 11 parts by weight of tripropylene glycol diacrylate (trade name "Aronix M-220", 1 part by weight of 4-vinylphenylboronic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), manufactured by Toagosei Co., Ltd.), 10 parts by weight of acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd.), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM Resins An adhesive was prepared by stirring 1 part by weight of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.) 2 parts by weight of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.) and 1 part by weight of diethyl thioxanthone (trade name "KAYACUREDETX-S", manufactured by Nippon Kayaku Co., Ltd.) at 50°C for 1 hour.

[0129] [Preparation of Pressure-Sensitive Adhesive Sheet] (Preparation of (Meth)Acrylic Polymer P1) 95 parts by weight of phenoxybenzyl acrylate (POB-A) and 5 parts by weight of 4-hydroxybutyl acrylate (4HBA) were charged into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. Furthermore, 0.1 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was charged together with ethyl acetate relative to 100 parts by weight of the monomer mixture. Nitrogen gas was introduced to replace the atmosphere with nitrogen while gently stirring, and the liquid temperature in the flask was maintained at around 55°C, allowing the polymerization reaction to proceed for 7 hours. The monomer concentration during polymerization was 40% by weight. Ethyl acetate was then added to the resulting reaction solution to adjust the solids concentration to 30%, yielding a solution of (meth)acrylic polymer P1. A commercially available monomer (manufactured by Kyoeisha Chemical, purity 94%) was further purified by adsorption for POB-A.

[0130] (Preparation of (meth)acrylic polymers P2 to P23) Solutions of (meth)acrylic polymers P2 to P23 were obtained in the same manner as for (meth)acrylic polymer P1, except that the type and amount of monomer and the monomer concentration during polymerization were changed as shown in Table 1 below. Table 1 also shows the Mw and sum of the products of the formed (meth)acrylic polymers. Mw was evaluated by gel permeation chromatography (GPC) under the following conditions. Analytical device: Acquity APC manufactured by Waters Column: G7000HXL+GMHXL+GMHXL manufactured by Tosoh Column temperature: 40°C Eluent: tetrahydrofuran (acid added) Flow rate: 0.8 mL / min Injection volume: 100 μL Detector: differential refractometer (RI) Standard sample: polystyrene (PS) manufactured by Agilent

[0131]

[0132] The abbreviations and refractive indices of the monomers shown in Table 1 are as follows. The refractive index of a monomer is the refractive index of a homopolymer of that monomer for light with a wavelength of 550 nm. POB-A: phenoxybenzyl acrylate (refractive index 1.566) BzA: benzyl acrylate (refractive index 1.519) 4HBA: 4-hydroxybutyl acrylate (refractive index 1.452) BA: n-butyl acrylate (refractive index: 1.420) CBA: carbitol acrylate (refractive index: 1.420) MEA: methoxyethyl acrylate (refractive index: 1.420) AA: acrylic acid (refractive index: 1.421) ACMO: acryloylmorpholine (refractive index: 1.510)

[0133] The sum of the products for the prepared (meth)acrylic polymers was calculated using the above-mentioned formula. As an example, the formula for calculating the sum of the products for (meth)acrylic polymer P1 is: Sum of Products = 1.566 × 0.95 + 1.452 × 0.05.

[0134] (Preparation of Pressure-Sensitive Adhesive Compositions) The (meth)acrylic polymer prepared above as a base polymer and a crosslinking agent were mixed together to obtain solvent-based pressure-sensitive adhesive compositions A1 to A29 so as to have the compositions shown in Table 2 below.

[0135] (Preparation of Pressure-Sensitive Adhesive Sheets) A pressure-sensitive adhesive composition was applied to the surface of a release liner PET film (Mitsubishi Chemical Corporation, MRF38-NS2) so that the thickness of the pressure-sensitive adhesive sheet after drying would be a predetermined thickness. A fountain coater was used to apply the pressure-sensitive adhesive composition. The coating film formed by application was subjected to a drying treatment at 90°C for 1 minute in an air-circulating constant-temperature oven, thereby preparing pressure-sensitive adhesive sheets S1 to S31.

[0136] [Preparation of Optical Laminate] (Example 1) The first liquid crystal alignment solidified layer side of a laminate having a substrate film / first liquid crystal alignment solidified layer configuration was bonded to the TAC film side of the polarizing film prepared above via the adhesive (thickness: 1 μm), and then the substrate film was peeled off to obtain a laminate having a polarizing film / adhesive / first liquid crystal alignment solidified layer configuration. Next, the exposed surface of the first liquid crystal alignment solidified layer was plasma treated, and then this exposed surface was bonded to the exposed surface of a pressure-sensitive adhesive sheet S1 formed on a release liner to obtain a laminate having a polarizing film / adhesive / first liquid crystal alignment solidified layer / pressure-sensitive adhesive sheet S1 / release liner configuration. Next, the release liner was peeled off from the pressure-sensitive adhesive sheet S1, and the second liquid crystal alignment solidified layer side of a laminate having a substrate film / second liquid crystal alignment solidified layer configuration was bonded to the exposed surface of the pressure-sensitive adhesive sheet S1 exposed by the peeling. Prior to bonding, the exposed surface of the second liquid crystal alignment solidified layer in the laminate was corona-treated. Next, the substrate film was peeled off to obtain an optical laminate having a structure of polarizing film / adhesive / first liquid crystal alignment solidified layer / adhesive sheet S1 / second liquid crystal alignment solidified layer. The angle between the transmission axis of the polarizer of the polarizing film and the slow axis of the first liquid crystal alignment solidified layer was 15°, and the angle between the transmission axis of the polarizer of the polarizing film and the slow axis of the second liquid crystal alignment solidified layer was 75°. The refractive index of the first liquid crystal alignment solidified layer in the transmission axis direction of the polarizer was 1.66, and the refractive index of the second liquid crystal alignment solidified layer in the transmission axis direction of the polarizer was 1.56.

[0137] (Examples 2 to 22, Comparative Examples 1 to 9) Optical laminates of Examples 2 to 22 and Comparative Examples 1 to 9 were produced in the same manner as in Example 1, except that adhesive sheets S2 to S31 shown in Table 2 below were used instead of adhesive sheet S1.

[0138] The pressure-sensitive adhesive sheet contained in each of the prepared optical laminates and its thickness, as well as the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive sheet and its composition are shown in Table 2 below.

[0139]

[0140] The abbreviations in Table 2 are as follows: D101E: Trimethylolpropane / tolylene diisocyanate trimer adduct (Takenate D-101E, manufactured by Mitsui Chemicals, Inc.); isocyanate-based crosslinking agent D110N: Trimethylolpropane / xylylene diisocyanate trimer adduct (Takenate D-110N, manufactured by Mitsui Chemicals, Inc.); isocyanate-based crosslinking agent BPO: Benzoyl peroxide; peroxide-based crosslinking agent

[0141] [Evaluation] (Reflectance) The reflectance of each optical laminate of the Examples and Comparative Examples was evaluated by the following method. First, each optical laminate was bonded to a reflector (NEODIS, V3) using an acrylic adhesive (thickness 25 μm). The bonding was performed so that the second liquid crystal alignment solidified layer of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer faced the reflector. Next, a glass plate (Corning, Eagle XG) was bonded to the first liquid crystal alignment solidified layer side of each optical laminate using an acrylic adhesive sheet (thickness 150 μm) to prepare a test sample. The spectral reflectance of the prepared samples was measured under the following measurement conditions using a spectrophotometer (Konica Minolta, CM-26d), and the reflectance was evaluated according to the following criteria. <Measurement conditions> Type of light receiving optical system: SCI (specular reflection included method) Measurement wavelength range: 360 to 740 nm Light source: D65 Measurement diameter (diameter of opening on sample surface): φ8 mm <Criteria> A: Reflectance less than 4.9% B: Reflectance 4.9% or more but less than 4.95% D: Reflectance 4.95% or more but less than 5.0% DD: Reflectance 5.0% or more

[0142] (High-Temperature Durability) The durability at high temperatures of each of the optical laminates of the Examples and Comparative Examples was evaluated by the following method. First, the optical laminate was fixed to the surface of a glass plate (manufactured by Corning, Eagle XG) using an acrylic adhesive sheet (thickness: 25 μm), with the side of the second liquid crystal alignment solidified layer serving as the bonding surface. The fixing was performed in an atmosphere of 23°C and 50% RH. Next, the optical laminate was treated in an autoclave at 50°C and 5 atmospheres (absolute pressure) for 15 minutes, and then left to cool to 23°C to stabilize the bonding of the optical laminate to the glass plate. Next, the entire assembly was left in a heated atmosphere at 80°C for 24 hours. After leaving the assembly, the assembly was returned to an atmosphere of 23°C and 50% RH, and visually confirmed whether the optical laminate had peeled from the glass plate. The durability at high temperatures was evaluated according to the following criteria: A: No peeling was observed. B: Slight peeling was observed at the edge, but within a range that was not problematic in practical use. D: Peeling was observed to a degree that was problematic in practical use.

[0143] (Pot life) The pressure-sensitive adhesive composition after preparation was left to stand for 6 hours in an environment of 30°C, and the viscosity immediately after preparation and after standing were measured, and the pot life was evaluated according to the following criteria: A: Viscosity hardly increased; B: Viscosity increased by less than 20 P; C: Viscosity increased by 20 P or more.

[0144] (Initial Gel Fraction) The initial gel fraction of the pressure-sensitive adhesive composition was determined by the above-mentioned method and evaluated according to the following criteria. The ratings C, B, and A indicate that the composition is more suitable for suppressing dents. A: Initial gel fraction of 29% or more B: Initial gel fraction of 10% or more but less than 29% C: Initial gel fraction of less than 10%

[0145] The evaluation results are shown in Table 3 below.

[0146]

[0147] The optical laminates of the examples were able to achieve both reduced reflection and durability at high temperatures.

[0148] The optical laminate of the present invention can be used in image display devices such as EL displays and liquid crystal displays.

Claims

1. An optical laminate comprising, in that order, a first liquid crystal alignment solidified layer, an adhesive sheet, and a second liquid crystal alignment solidified layer, said adhesive sheet comprising a crosslinked base polymer, said base polymer being composed of a plurality of monomers, wherein, when the product of the refractive index of each monomer constituting said base polymer and the weight ratio of each monomer to all monomers constituting said base polymer is calculated for each monomer constituting said base polymer, the sum of said products for said base polymer is 1.51 or more, and said base polymer has a weight average molecular weight of 800,000 or more.

2. The optical laminate according to claim 1, wherein the absolute value of the difference between the average refractive index of each of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer and the sum of the products is 0.08 or less.

3. The optical laminate according to claim 1, wherein the first liquid crystal alignment solidified layer and / or the second liquid crystal alignment solidified layer is a retardation layer.

4. The optical laminate according to claim 1, wherein the monomers constituting the base polymer include an aromatic ring-containing monomer.

5. The optical laminate according to claim 4, wherein the aromatic ring-containing monomer is a high-boiling point monomer.

6. The optical laminate according to claim 4, wherein the aromatic ring-containing monomer is phenoxybenzyl acrylate.

7. The optical laminate according to claim 4, wherein the weight ratio of the aromatic ring-containing monomer to all monomers constituting the base polymer is 50% or more.

8. The optical laminate according to claim 1, wherein the crosslinked body has a crosslinked structure formed by a peroxide-based crosslinking agent.

9. The optical laminate according to claim 1, wherein the crosslinked body has a crosslinked structure formed by an isocyanate-based crosslinking agent.

10. The optical laminate according to claim 1, wherein the pressure-sensitive adhesive sheet has a thickness of 4 μm or more.

11. The optical laminate according to claim 1, further comprising a polarizing film, said polarizing film facing the main surface of the first liquid crystal alignment solidified layer opposite to the adhesive sheet side.

12. An image display device comprising the optical laminate according to any one of claims 1 to 11.

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