Optical laminate and image display unit

Abstract

To provide an optical laminate that suitably both reduces reflection and has high-temperature durability despite a first liquid crystal orientation solidified layer and a second liquid crystal orientation solidified layer being jointed together across an adhesive sheet.SOLUTION: An optical laminate 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 includes a cross-linked body of a base polymer. The base polymer consists of a plurality of monomers, the total of products of refractive indexes of the respective monomers constituting the base polymer and ratios of weights of the respective monomers to all the monomers constituting the base polymer is 1.51 or more, and the weight average molecular weight of the base polymer is 800,000 or more.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Various image display devices typified by liquid crystal display devices and electroluminescence (EL) display devices generally include an optical laminate including optical base materials such as a polarizing film and a retardation layer. In an optical laminate including a plurality of optical base materials, a bonding layer for bonding both is usually disposed between the adjacent optical base materials. Patent Document 1 discloses a polarizing plate with a retardation layer including a polarizer, a first retardation layer, and a second retardation layer in this order, and the first retardation layer and the second retardation layer are bonded via an adhesive layer. Further, Patent Document 1 describes that the first retardation layer and / or the second retardation layer may be an alignment cured layer of a liquid crystal compound (hereinafter, referred to as a liquid crystal alignment cured layer).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is conceivable to bond a first liquid crystal alignment cured layer and a second liquid crystal alignment cured layer via an adhesive sheet instead of an adhesive layer. However, according to the study by the present inventors, it has been found that when using an adhesive sheet, it is difficult to achieve both reduction of reflection and durability at high temperatures in the optical laminate.

[0005] An object of the present invention is to provide an optical laminate suitable for achieving both reduction of reflection and durability at high temperatures while bonding a first liquid crystal alignment cured layer and a second liquid crystal alignment cured layer via an adhesive sheet.

Means for Solving the Problems

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

[0007] The present invention provides an optical laminate including a first liquid crystal alignment cured layer, a pressure-sensitive adhesive sheet, and a second liquid crystal alignment cured layer in this order, wherein the pressure-sensitive adhesive sheet includes a crosslinked product of a base polymer, the base polymer is composed of a plurality of monomers, and for each monomer constituting the base polymer, when the product of the refractive index of each monomer and the ratio of the weight of each monomer in all the monomers constituting the base polymer is obtained, the sum of the products in 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 including the optical laminate of the present invention.

Advantages of the Invention

[0009] The optical laminate of the present invention is suitable for achieving both reduction of reflection and durability at high temperatures while joining the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer via a pressure-sensitive adhesive sheet.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

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

[0012] In the second aspect of the present invention, for example, in the optical laminate according to the first aspect, the absolute value of the difference between the average refractive index of each of the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer and the sum of the products is 0.08 or less.

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

[0014] In the 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 the fifth aspect of the present invention, for example, in the optical laminate according to the fourth aspect, the aromatic ring-containing monomer is a high-boiling monomer.

[0016] In the 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 the seventh aspect of the present invention, for example, in the optical laminate according to any one of the fourth to sixth aspects, the proportion of the weight of the aromatic ring-containing monomer in all the monomers constituting the base polymer is 50% or more.

[0018] In the 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 by a peroxide-based crosslinking agent.

[0019] In the 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 by an isocyanate-based crosslinking agent.

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

[0021] In the 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 on the side opposite to the side of the adhesive sheet in the first liquid crystal alignment curing layer.

[0022] The image display device according to the 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 arbitrarily modified and implemented without departing from the gist of the present invention.

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

[0025] The adhesive sheet 3 includes a crosslinked product of a base polymer. The adhesive sheet 3 is usually formed by curing an adhesive composition containing a base polymer. The base polymer is usually a polymer of two or more 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 the monomer and the ratio of the weight of the monomer in all the monomers constituting the base polymer can be obtained. However, the refractive index of the monomer is specified by the refractive index of the homopolymer of the monomer with respect to light having a wavelength of 550 nm. For example, when the base polymer is composed of monomer A, monomer B, monomer C, and monomer D, the product for each monomer can be expressed as follows. · Monomer A: a1 × a2 (where a1 is the refractive index of monomer A and a2 is the ratio of the weight of monomer A in all the monomers) · Monomer B: b1 × b2 (where b1 is the refractive index of monomer B and b2 is the ratio of the weight of monomer B in all the monomers) · Monomer C: c1 × c2 (where c1 is the refractive index of monomer C and c2 is the ratio of the weight of monomer C in all the monomers) · Monomer D: d1 × d2 (where d1 is the refractive index of monomer D and d2 is the ratio of the weight of monomer D in all the monomers) When the product is obtained for each monomer, the sum of the products in the base polymer (hereinafter referred to as the sum of the products) is 1.51 or more. The sum of the products in the above-exemplified base polymer can be expressed by the formula: a1 × a2 + b1 × b2 + c1 × c2 + d1 × d2. Further, the weight average molecular weight of the base polymer (hereinafter referred to as Mw) is 800,000 or more.

[0026] The liquid crystal alignment cured layer is an alignment cured layer of a liquid crystal compound. More specifically, it means 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 cured layer includes an alignment cured layer obtained by curing a liquid crystal monomer. The liquid crystal alignment cured layer is suitable for obtaining desired optical properties, such as retardation, while reducing the thickness as compared with a normal optical substrate composed of a resin film. However, according to the studies of the present inventors, the liquid crystal alignment cured layer has a higher electron density and a tendency to have a high refractive index derived therefrom as compared with a normal optical substrate. The sum of the products in the adhesive sheet 3 sandwiched between the two liquid crystal alignment cured layers 2 and 4 in the optical laminate 1 being 1.51 or more relaxes the refractive index mismatch between the liquid crystal alignment cured layers 2 and 4 and the adhesive sheet 3, contributing to the reduction of reflection of the optical laminate 1. The reduction of reflection can contribute to the improvement of 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 the side of either one of the liquid crystal alignment cured layers 2 and 4.

[0027] The Mw of the base polymer being 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, and further 80°C or higher. Ensuring durability at high temperatures is presumably because the stress relaxation property of the adhesive sheet 3 is improved by the above Mw. The improvement of the stress relaxation property is considered to contribute to the suppression of delamination caused by the shrinkage of the optical substrate at high temperatures. Note that an optical substrate provided with a polarizer, typically a polarizing film, tends to shrink at high temperatures. Therefore, 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 in the past for the sum of products of the base polymer to be 1.51 or more and for the Mw to be 800,000 or more for the following reasons. In order for the sum of products to be 1.51 or more, it is necessary to use a monomer having a refractive index of 1.51 or more (hereinafter referred to as a high refractive index monomer) in the formation of the base polymer. However, the refractive index of alkyl (meth)acrylate widely used in the pressure-sensitive adhesive sheet is only about 1.4 (for example, the refractive index of n-butyl acrylate is 1.42). As the high refractive index monomer, for example, it is conceivable to focus on a monomer having an aromatic ring. The aromatic ring has a higher electron density than the alkyl group, and the high electron density can contribute to an increase in the refractive index. However, according to the studies based on the above focus, when a large amount of the aromatic ring-containing monomer is used to increase the sum of products, gelation is likely to occur during the polymerization of the base polymer. When formation conditions for suppressing gelation, such as a low monomer concentration during polymerization, are adopted, it has been found that it is difficult to achieve an Mw of 800,000 or more. Based on this point, further studies were advanced, and it was found that gelation can be suppressed and Mw can be improved by restricting the residual amount of impurities contained in the aromatic ring-containing monomer used in the 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. The fact that the pressure-sensitive adhesive sheet 3 has a thickness of 4 μm or more can contribute to an improvement in the stress relaxation property of the pressure-sensitive adhesive sheet 3. The thickness of the pressure-sensitive adhesive sheet 3 may be 4.5 μm or more, and further may be 5 μm or more. The upper limit of the thickness may be, for example, 8 μm or less, 7 μm or less, and further may be 6 μm or less. The thickness may be 4 μm or more and 8 μm or less, or may be 4 μm or more and 7 μm or less.

[0030] In addition, according to the studies of the present inventors, the thickness unevenness of the pressure-sensitive adhesive sheet 3 tends to be smaller than that of the adhesive layer. The smallness of the thickness unevenness can contribute to a reduction in 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, and even 1.545 or more. The upper limit of the sum of the products may be, for example, 1.90 or less, 1.80 or less, 1.70 or less, 1.65 or less, and even 1.60 or less. The sum of the products may be from 1.515 to 1.60, or from 1.52 to 1.60.

[0032] The Mw of the base polymer may be 850,000 or more, 900,000 or more, 950,000 or more, and 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 residual amount of impurities in the raw material monomers. Examples of the polymerization conditions are the type and amount of the polymerization initiator, the type and amount of additives such as chain transfer agents, the type of the polymerization solvent, and the monomer concentration in the polymerization system.

[0033] (Liquid crystal alignment curing layer) In the liquid crystal alignment curing layers 2 and 4, typically, rod-shaped liquid crystal compounds are aligned in a state where they are arranged in a predetermined direction (homogeneous alignment). Examples of the liquid crystal compounds are nematic liquid crystals and discotic liquid crystals. As the liquid crystal compounds, liquid crystal polymers or liquid crystal monomers can be used. The liquid crystal monomers may have polymerizability and / or crosslinkability.

[0034] Specific examples of the liquid crystal monomers are polymerizable mesogenic compounds described in each of the publications of JP-T-2002-533742, EP358208, EP66137, WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445. Examples of the polymerizable mesogenic compounds are, for example, LC242 manufactured by BASF, E7 manufactured by Merck, and LC-Sillicon-CC3767 manufactured by Wacker-Chem. The liquid crystal monomers are preferably nematic monomers.

[0035] The liquid crystal alignment cured 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 on the surface, aligning the liquid crystal compound in the direction corresponding to the alignment treatment, and fixing the alignment state. A release film may be used as the substrate. The liquid crystal alignment cured layer 2 and 4 formed on the release film can be transferred to other layers that may be included in the optical laminate 1 such as the adhesive sheet 3, for example. However, the method for forming the liquid crystal alignment cured layers 2 and 4 is not limited to the above example.

[0036] For further specific examples of the liquid crystal compound and details of the method for forming the liquid crystal alignment cured layer, reference can be made to Japanese Patent Application Laid-Open No. 2006-163343. However, the liquid crystal alignment cured layers 2 and 4 and the method for forming them are not limited to the content described in the publication.

[0037] The average refractive index of the first liquid crystal alignment cured layer 2 and / or the second liquid crystal alignment cured layer 4 may be 1.50 or more, and may be 1.52 or more, 1.53 or more, 1.55 or more, 1.57 or more, and further may be 1.59 or more. The upper limit of the average refractive index is, for example, 1.70 or less. The liquid crystal alignment cured layer located on the viewing side when incorporated into the image display device, for example, the first liquid crystal alignment cured layer 2, and the liquid crystal alignment cured layer located on the side opposite to the viewing side, for example, the second liquid crystal alignment cured layer 4, may have the same average refractive index or different average refractive indices. The average refractive index of the liquid crystal alignment cured layer is given by the formula: average refractive index = (nx + ny + nz) / 3, where nx is the refractive index in the direction (slow axis) where the refractive index is maximum in the plane of the layer, ny is the refractive index in the direction (fast axis) orthogonal to the slow axis in the plane, 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 cured layer 2 and the second liquid crystal alignment cured layer 4 and the sum of the products may each be 0.08 or less, and may be 0.075 or less, 0.07 or less, 0.06 or less, 0.05 or less, and further may be 0.045 or less.

[0039] The first liquid crystal alignment cured layer 2 and / or the second liquid crystal alignment cured 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, for example, a refractive index characteristic represented by the formula nz > nx = ny.

[0040] The retardation layer may have a Re(550) of 10 nm or more, 30 nm or more, 50 nm or more, 80 nm or more, and further 100 nm or more. Re(550) is the in-plane retardation of the retardation layer with respect to light having 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, and further 135 nm to 155 nm. In this 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, and further 230 to 280 nm. In this case, the retardation layer can function as a so-called λ / 2 plate. The first liquid crystal alignment cured layer 2 and / or the second liquid crystal alignment cured layer 4 may be a layer that can function as a λ / 4 plate or a λ / 2 plate. The first liquid crystal alignment cured 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 cured layer 4 may be a layer that can function as a λ / 2 plate (or a λ / 4 plate). When the first liquid crystal alignment cured layer 2 and / or the second liquid crystal alignment cured layer 4 is a layer that can function as a λ / 4 plate or a λ / 2 plate and the optical laminate 1 further includes a polarizing film, the optical laminate 1 may be an elliptical polarizing film or a circular polarizing film.

[0042] The first liquid crystal alignment cured layer 2 and / or the second liquid crystal alignment cured layer 4 may be an antireflection retardation layer, a viewing angle compensation retardation layer, or an inclined alignment retardation layer for viewing angle compensation.

[0043] The thickness of the liquid crystal alignment cured layers 2 and 4 may be, 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 may be, 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 may be 1 μm or more and 4 μm or less.

[0044] The configurations of the first liquid crystal alignment cured layer 2 and the second liquid crystal alignment cured layer 4 may be the same or different from each other.

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

[0046] (Adhesive sheet 3) The adhesive sheet 3 is usually formed by curing an adhesive composition (A) containing a base polymer. The monomer constituting the base polymer may contain (meth)acrylate, and the main monomer constituting the base polymer may be (meth)acrylate. In this specification, (meth)acrylate means acrylate and / or methacrylate. Also, the main monomer means the monomer having the largest weight ratio in all the monomers constituting the base polymer. The ratio of the main monomer may be, 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 ratio may be, for example, 100% or less, and may be 99% or less.

[0047] The monomers constituting the base polymer may include aromatic ring-containing monomers. 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 in all the monomers constituting the base polymer may be 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 ratio may be 60 to 99%, or may be 70 to 95%. The aromatic ring-containing monomer can contribute to increasing the sum of the products. The aromatic ring-containing monomer is a compound that contains an aromatic ring in its structure and contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of the aromatic ring 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 can be used alone or in combination of two or more.

[0048] Examples of the aromatic ring-containing (meth)acrylate include those having a benzene ring such as 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, phenol ethylene oxide-modified (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, methoxybenzyl (meth)acrylate, chlorobenzyl (meth)acrylate, cresyl (meth)acrylate, polystyryl (meth)acrylate; those having a naphthalene ring such as hydroxyethylated β-naphthol acrylate, 2-naphthylethyl (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 sum of products 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 generally tend to be higher than those of monomers without an aromatic ring. This tendency can be stronger depending on the molecular structure and increases with the number of aromatic rings contained. Among commercially available monomers and monomers commonly used for forming the adhesive sheet 3, impurities such as by-products are removed by purification. However, according to the study by the present inventors, for monomers with high boiling points, due to the increase in the temperature required for distillation, which is a common purification method, the polymerization of impurities during purification easily progresses. To avoid this, purification under mild conditions is inevitable, resulting in a tendency for the residual amount of impurities to increase. Impurities, especially polyfunctional ones, can be a factor in gelation during the polymerization of the base polymer. In order to make the Mw of the base polymer 800,000 or more, for example, for high boiling point monomers, it is preferable to use monomers with an even lower residual amount of impurities compared to the monomers commonly used for forming the adhesive sheet 3. Therefore, further purification may be carried out. When purification by distillation is difficult, other purification methods, such as adsorption methods, may be used.

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

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

Chemical formula

[0052] Viewed from another aspect of the above perspective, the monomers constituting the base polymer may include monomers 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 may be, for example, 5 or less, 4 or less, or even 3 or less. The number of aromatic rings may be 2.

[0053] Viewed from yet another aspect of the above perspective, the monomers constituting the base polymer may include high-boiling monomers. The high-boiling monomer may be a (meth)acrylate.

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

[0055] The weight ratio of the alkyl (meth)acrylate in all the 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 the ratio may be, 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 contain 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 contains 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 the hydroxyl group-containing (meth)acrylate 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, 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 proportion of the hydroxyl group-containing monomer in all the monomers constituting the base polymer may be 0.5% or more, and may be 1% or more, 1.5% or more, or even 2% or more. The upper limit of the proportion 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. The fact that the proportion is 1% or more can increase the gel fraction of the pressure-sensitive adhesive sheet 3 immediately after formation (which can be evaluated by the initial gel fraction described later), and can contribute to, for example, suppressing the occurrence of indentations on the pressure-sensitive adhesive sheet 3. A typical example of the indentation related to the initial gel fraction is a foreign matter mark (indentation) caused by a foreign object bitten in before the pressure-sensitive adhesive composition is completely cured. The fact that the proportion is 3.5% or less can contribute to improving the pot life of the pressure-sensitive adhesive composition (A). The proportion 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 also contains 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-based 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 also contains 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 are (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid.

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

[0062] Examples of other monomers are monomers copolymerizable with each of the monomers described above (copolymerizable monomers). 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 allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, and sulfopropyl (meth)acrylate; phosphate group-containing monomers such as 2-hydroxyethylacryloyl 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; 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, fluoro (meth)acrylate, and silicone (meth)acrylate; silane-based 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 proportion of the weight of the copolymer monomer in all the monomers constituting the base polymer is, for example, 5% or less, and may be 3% or less, or even 1% or less. The monomers constituting the base polymer may not contain a copolymer monomer.

[0064] (Adhesive Composition (A)) The 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 or ultraviolet rays (UV), 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, etc. However, the method for forming the base polymer is not limited to the above examples.

[0065] For the polymerization solvent in solution polymerization, known polymerization solvents such as ethyl acetate and toluene can be used, for example. Solution polymerization can be carried out, for example, by using a polymerization initiator and under an inert gas stream 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 radical polymerization are not particularly limited and can be appropriately selected.

[0067] Examples of polymerization initiators 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'-dimethylenebisobutylamidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate (e.g., VA-057 manufactured by Wako Pure Chemical Industries, Ltd.); persulfates such as potassium persulfate and ammonium persulfate; peroxide initiators such as di(2-ethylhexyl) peroxydicarbonate, di(4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, 1,1-di(t-hexylperoxy) cyclohexane, t-butyl hydroperoxide, and hydrogen peroxide; redox initiators that are combinations of peroxides and reducing agents such as combinations of persulfates and sodium bisulfite, and combinations of peroxides and sodium ascorbate. However, the polymerization initiator is not limited to the above examples.

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

[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 agent 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 part by weight or less with respect to 100 parts by weight of the monomer component.

[0070] In radiation polymerization, polymerization is advanced by irradiating radiation such as an electron beam or ultraviolet rays (UV) to the monomer to form a base polymer. When radiation polymerization is carried out with an electron beam, the use of a photoinitiator is not particularly necessary. When radiation polymerization is carried out with UV, a photoinitiator may be used because of advantages such as shortening the polymerization time. The photoinitiator can be used alone or in combination of two or more.

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

[0072] The pressure-sensitive adhesive composition (A) is typically a composition that can form the pressure-sensitive adhesive sheet 3 by drying. In this case, the pressure-sensitive adhesive sheet 3 formed from the pressure-sensitive adhesive composition (A) usually becomes a solvent type (also referred to as a thermosetting type).

[0073] The pressure-sensitive adhesive composition (A) may contain a crosslinking agent. Examples of the crosslinking agent that the pressure-sensitive adhesive composition (A) may contain are 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 by a peroxide-based crosslinking agent, may have a crosslinked structure by 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 are aromatic isocyanate compounds, alicyclic isocyanate compounds, and aliphatic isocyanate compounds.

[0075] Examples of the aromatic isocyanate compound are phenylenediisocyanate, 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 multimer (dimer, trimer, pentamer, etc.) of the above isocyanate compound, an adduct obtained by adding to a polyhydric alcohol such as trimethylolpropane, a urea-modified product, a biuret-modified product, an allophanate-modified product, an isocyanurate-modified product, a carbodiimide-modified product, a urethane prepolymer obtained by adding 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 derivative, more preferably tolylene diisocyanate and its derivative, in other words, a tolylene diisocyanate-based (TDI-based) crosslinking agent. From the viewpoint of reactivity, the TDI-based crosslinking agent is more suitable than xylylene diisocyanate and its derivative, in other words, a xylylene diisocyanate-based (XDI-based) crosslinking agent. The isocyanate-based crosslinking agent may contain, as a TDI-based crosslinking agent, an adduct of a polyhydric alcohol and tolylene diisocyanate. Specific examples of the adduct are trimethylolpropane / tolylene diisocyanate trimer adduct.

[0080] Commercially available products can be used as the isocyanate-based crosslinking agent. Examples of commercially available products include Millionate MT, Millionate MTL, Millionate MR-200, Millionate MR-400, Coronate L, Coronate HL, Coronate HX (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, Takenate 600 (manufactured by Mitsui Chemicals, Inc.). Among these, Takenate D-101E and Takenate D-110N are preferred.

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

[0082] The compounding amount of the isocyanate-based crosslinking agent in the pressure-sensitive adhesive composition (A) is, for example, 0.01 to 20 parts by weight with respect to 100 parts by weight of the base polymer. The lower limit of the compounding amount may be 0.02 parts by weight or more, 0.03 parts by weight or more, 0.04 parts by weight or more, and further may be 0.05 parts by weight or more. The upper limit of the compounding 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, and further may be 0.08 parts by weight or less. The compounding amount may be 0.03 to 1 part by weight, or may be 0.05 to 0.5 part by weight.

[0083] The compounding amount of a crosslinking agent other than the isocyanate-based crosslinking agent, for example, a peroxide-based crosslinking agent, in the pressure-sensitive adhesive composition (A) is, for example, 2 parts by weight or less with respect to 100 parts by weight of the base polymer, and may be 1 part by weight or less, and further may be 0.5 parts by weight or less. The lower limit of the compounding amount is, for example, 0.1 parts by weight or more, and may be 0.2 parts by weight or more, and further may be 0.3 parts by weight or more. The compounding amount may be 0.1 to 1 part by weight, or may be 0.3 to 0.5 part by weight. The pressure-sensitive adhesive composition (A) may not contain a crosslinking agent other than the isocyanate-based crosslinking agent.

[0084] The pressure-sensitive adhesive composition (A) may further contain known additives. Examples of the additives include silane coupling agents, solvents, colorants, pigments, powders, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, and foils. Within a controllable range, a redox system with a reducing agent added may be used. However, the additives are not limited to the above examples. The total blending amount of the additives may be, for example, 10 parts by weight or less, 5 parts by weight or less, further 1 part by weight or less, based on 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-isocyanatopropyltriethoxysilane.

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

[0087] The pressure-sensitive adhesive composition (A) may not substantially contain a photo-curing agent such as a photoinitiator.

[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. Heating 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, for example, to other layers that may be included in the optical laminate 1 such as the first liquid crystal alignment curing layer 2 and the second liquid crystal alignment curing layer 4. The substrate may 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] For 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 according to the composition of the pressure-sensitive adhesive composition (A), and is, for example, 30 seconds to 300 seconds, and may be 40 seconds to 240 seconds, or even 60 seconds to 180 seconds.

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

[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 that a coating film is formed, and the coating film is dried at 120 °C for 300 seconds to form a pressure-sensitive adhesive sheet for evaluation. Next, with respect to the formed pressure-sensitive adhesive sheet, a part is scraped off within 2 hours after formation to obtain small pieces. Next, the obtained small pieces are wrapped with a stretched porous film of polytetrafluoroethylene and tied with a kite string. Thereby, a test piece is obtained. Next, the total weight (weight A) of the small piece of the pressure-sensitive adhesive sheet, the stretched porous film, and the kite string is measured. Note that the total 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 left standing at 23 °C for 1 week. After standing, the test piece is taken out from the container, dried in a dryer set at 130 °C for 2 hours, and then the weight C of the test piece is measured. Based on the following formula, the initial gel fraction can be calculated from weight A, weight B, and weight C. Formula: Initial gel fraction (%) = (C - B) / (A - B) × 100

[0093] The optical laminate 1 of the present embodiment may optionally include layers other than the liquid crystal alignment curing layers 2 and 4 and the pressure-sensitive 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] Typically, the polarizing film 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-protection polarizing film, a so-called single-protection polarizing film, or may be composed of only a polarizer.

[0095] A polarizer typically consists 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 ethylene - vinyl acetate copolymer - based partially saponified products.

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

[0097] The polarizer preferably contains an 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, per 100 parts by weight of the PVA - based resin. The halide can be blended into the coating liquid for forming the PVA - based resin layer, which is a precursor of the polarizer, in the manufacturing method described below and finally introduced into the polarizer. By introducing the halide into the polarizer, the orientation of PVA molecules in the polarizer can be enhanced, so that a polarizer having excellent optical properties (typically, the co - existence of a high degree of polarization and a high single - transmittance) can be realized.

[0098] The polarizer preferably exhibits absorption dichroism at any wavelength in the range of 380 nm to 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 still more preferably 3 μm to 7 μm. By combining such a thin polarizer with the liquid crystal alignment curing layer, significant thinning of the optical laminate becomes possible.

[0100] The polarizer can be produced by any suitable 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-based films, partially formalized PVA-based films, and ethylene-vinyl acetate copolymer-based partially saponified films, which are subjected to dyeing treatment with dichroic substances such as iodine and dichroic dyes and stretching treatment, and polyene-based alignment films such as dehydrated products of PVA and dehydrochlorinated products of polyvinyl chloride. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching it is used because of its excellent optical properties.

[0102] The above-mentioned dyeing with iodine is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, during the dyeing, or after the stretching. If necessary, the PVA-based film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA-based film in water and washing it before dyeing, not only can the dirt and anti-blocking agent on the surface of the PVA-based film be washed, but also the PVA-based film can be swollen to prevent uneven dyeing.

[0103] Specific examples of the polarizer of the laminate 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 formed by coating on the resin substrate. The polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying it 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; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. Preferably, a PVA-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 includes immersing the polarizer of the laminate in an aqueous boric acid solution and stretching it. Further, the stretching may further include, if necessary, air stretching the laminate at a high temperature (e.g., 95 °C or higher) before stretching in the aqueous boric acid solution. Preferably, the laminate is subjected to a drying shrinkage treatment in which it is heated while being conveyed in the longitudinal direction to shrink by 2% or more in the width direction. Typically, it includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, a stretching treatment in water, and a drying shrinkage treatment in this order. By introducing the assisted stretching, even when PVA is applied on the thermoplastic resin, it becomes possible to enhance the crystallinity of PVA and achieve high optical properties. Also, by enhancing the orientation of PVA in advance at the same time, problems such as a decrease in the orientation of PVA or dissolution when immersed in water in the subsequent dyeing process or stretching process can be prevented, and high optical properties can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, the disturbance of the orientation and the decrease in the orientation of polyvinyl alcohol molecules can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. Thereby, the optical properties of the polarizer obtained through treatment steps such as a dyeing treatment and a stretching treatment in water, which are performed by immersing the laminate in a liquid, can be improved. Further, by shrinking the laminate in the width direction by the drying shrinkage treatment, the optical properties can be improved. The obtained laminate of the resin substrate / polarizer may be used as it is (i.e., the resin substrate may be used as a protective layer for the polarizer), or an arbitrary appropriate protective layer according to the purpose may be laminated on the peeling surface obtained by peeling the resin substrate from the laminate of the resin substrate / polarizer, or on the surface opposite to the peeling surface and used. Details of such a method for manufacturing a polarizer are described, for example, in JP-A-2012-73580 and Patent No. 6470455. The entire descriptions 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 suitable resin film. Representative examples of materials constituting 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. (Meth)acrylic resins having a lactone ring structure are described, for example, in JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, and JP-A-2005-146084. These publications are incorporated herein by reference. From the viewpoint of ease of profiling and the like, 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 surface-treated as necessary. Examples of surface treatment include hard coat treatment, antireflection treatment, anti-sticking treatment, and antiglare treatment. The protective layer may be treated as necessary to improve visibility when viewed through polarized sunglasses (typically, by imparting an (elliptical) polarization function or a very high retardation). By performing such treatment, excellent visibility can be achieved even when viewing a display screen through a polarizing lens 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 retardation Rth(550) in the thickness direction may be -10 nm to +10 nm.

[0108] The thickness of the 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, respectively. When the protective layer is surface-treated, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer.

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

[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 a polarizing film 5, a first liquid crystal alignment cured layer 2, an adhesive sheet 3, a second liquid crystal alignment cured layer 4, and an additional adhesive sheet 6 in this order. 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 included in an optical laminate that can be used in an image display device. The adhesive sheet 6 is, for example, a (meth)acrylic-based 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 the optical laminate 1 including a release liner is shown in FIG. 4. The optical laminate 1(1D) in FIG. 4 is the same as the optical laminate 1C in FIG. 3, except that a release liner 7 is provided on the side opposite to the side of the second liquid crystal alignment cured layer 4 in the adhesive sheet 6. The release liner 7 in FIG. 4 is in contact with the 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, non-woven fabric, porous material, net, foam, foil, or a laminate thereof made of resin, paper, fiber, metal, or a composite material thereof. Examples of the resin are 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. Also, the materials constituting the release liner 7 and the resins that can constitute it 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. Various surface treatments such as a release treatment, an antifouling treatment, and an antistatic treatment may be applied to the surface of the release liner 7 as required. For the release treatment, various release agents such as silicone-based, fluorine-based, long-chain alkyl-based, fatty acid amide-based, or particles such as silica powder can be used.

[0115] The release film used in the formation of the adhesive sheet 6 may be used as the release liner 7.

[0116] The optical laminate 1 of the present embodiment can be distributed and stored, for example, as a wound body obtained by winding a strip-shaped optical laminate 1 or as a sheet-shaped optical laminate 1.

[0117] The optical laminate 1 of the present 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, and an inorganic EL display. The use of the optical laminate 1 of the present embodiment is not limited to the above examples. Further, the image display device that can use the optical laminate 1 of the present embodiment is not limited to the above examples.

[0118] The optical laminate 1 of the present embodiment can be formed by laminating each layer included therein. Layers 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 frame treatment, and may be corona treatment and / or plasma treatment, or may be corona treatment. Each surface modification treatment can be carried out by a corresponding known treatment apparatus.

[0119] [Image display device] An example of the image display device of the present embodiment is shown in FIG. 5. The image display device 11 in FIG. 5 has a laminated 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 (for example, an organic EL layer or a liquid crystal layer) 8, and a substrate 9 are laminated in this order. The image display device 11 has the optical laminate 1C in FIG. 3. The substrate 9 and the image forming layer 8 may have the same configurations as the substrate and the image forming layer provided in a known image display device, respectively.

[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 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 appliance applications, in-vehicle applications, public information display (PID) applications, and the like.

[0121] The image display device of the present invention can have an arbitrary configuration as long as it includes the optical laminate of the present invention.

Example

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

[0123] In this example, a laminate including a first liquid crystal alignment cured layer, an adhesive sheet, and a second liquid crystal alignment cured layer was produced, and its properties such as reflectance and durability at high temperature were evaluated. In addition, the pot life and initial gel fraction of the adhesive composition used for forming the adhesive sheet were evaluated.

[0124] [Production of the first liquid crystal alignment cured layer] As the liquid crystal compound, a photopolymerizable liquid crystal compound (Paliocolor LC242, manufactured by BASF) showing a nematic liquid crystal phase was dissolved in cyclopentanone to prepare a solution with a solid content concentration of 30% by weight. To this solution, a surfactant (BYK-360, manufactured by BYK-Chemie) and a photopolymerization initiator (Omnirad 907, manufactured by IGM Resins) were added to prepare a liquid crystal composition solution. The addition amounts of the surfactant and the polymerization initiator were 0.01 part by weight and 3 parts by weight, respectively, based on 100 parts by weight of the photopolymerizable liquid crystal compound. As the base film, a biaxially stretched norbornene-based film (Zeonoa film, manufactured by Nippon Zeon, thickness 33 μm, Re(550) = 135 nm) was prepared. The above liquid crystal composition solution was applied onto the base film by a bar coater so that Re(550) became 240 nm, and heated at 100 °C for 3 minutes to align the liquid crystal. After cooling to room temperature, ultraviolet rays with an integrated light amount of 400 mJ / cm 2 were irradiated in a nitrogen atmosphere to perform photocuring, and a laminate having a structure of a base film / first liquid crystal alignment cured layer was obtained. The first liquid crystal alignment cured layer was homogeneously aligned, its thickness was 1.7 μm, and its average refractive index was 1.590.

[0125] [Production of the second liquid crystal alignment cured layer] A laminate of a substrate film / second liquid crystal alignment cured layer (homogeneous alignment, thickness 0.92 μm, Re(550) = 130 nm) was obtained in the same manner as the production of the first liquid crystal alignment cured layer, except that the coating thickness was changed. The average refractive index of the second liquid crystal alignment cured layer was 1.590.

[0126] [Production of polarizer] As a thermoplastic resin substrate, an amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 μm) in a long strip shape with a Tg of about 75°C was used, and one side of the resin substrate was subjected to corona treatment. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer") at a ratio of 9:1, and the mixture was dissolved in water to prepare a PVA aqueous 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 PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (length direction) in an oven at 130°C (air-assisted stretching treatment). Next, the laminate was immersed in an insolubilization bath with a liquid temperature of 40°C (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment). Next, the laminate was immersed in a dyeing bath with a liquid temperature of 30°C (an aqueous iodine solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7) for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would reach a desired value (dyeing treatment). Next, the laminate was immersed in a cross-linking bath with a liquid temperature of 40°C (an aqueous boric acid 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) for 30 seconds (cross-linking treatment). Thereafter, while the laminate was immersed in an aqueous boric acid solution with a liquid temperature of 70°C (boric acid concentration 4 wt%, potassium iodide concentration 5 wt%), uniaxial stretching was performed in the longitudinal direction (length direction) between rolls with different peripheral speeds so that the total stretching ratio would be 5.5 times (in-water stretching treatment). Thereafter, the laminate was immersed in a washing bath with a liquid temperature of 20°C (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (washing treatment). Thereafter, while drying in an oven maintained at about 90°C, the laminate was brought into contact with a SUS heating roll whose surface temperature was maintained at about 75°C (dry shrinkage treatment). In this way, a polarizer with a thickness of about 5 μm was formed on the resin substrate, and a laminate having a resin substrate / polarizer structure was obtained. The single transmittance Ts of the polarizer was 43.3%.

[0127] [Production of Polarizing Film] An HC-COP film was laminated on the surface of the above-prepared polarizer (the side opposite to the resin substrate) via an ultraviolet-curing adhesive. The HC-COP film is a film in which an HC layer (thickness 4 μm) is formed on a cycloolefin-based resin (COP) film (thickness 25 μm), and it was laminated such that the COP film was on the polarizer side. The Re(550) of the COP film was 135 nm. Next, the resin substrate was peeled off, and a triacetyl cellulose (TAC) film (thickness 25 μm) was laminated on the peeled surface via an ultraviolet-curing adhesive. In this way, a polarizing film having a structure 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 Curing 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", manufactured by Toagosei Co., Ltd.), 1 part of 4-vinylphenylboronic acid (manufactured by Fujifilm Wako Pure Chemical Corporation), 10 parts by weight of an acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd.), 1 part by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad819", manufactured by IGM Resins B.V.), 2 parts by weight of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad184", manufactured by IGM Resins B.V.), and 1 part by weight of diethylthiioxanthone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for 1 hour to prepare an adhesive.

[0129] [Preparation of Adhesive Sheet] [Preparation of (Meth)Acrylic Polymer P1] Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, 95 parts by weight of phenoxybenzyl acrylate (POB-A) and 5 parts by weight of 4-hydroxybutyl acrylate (4HBA) were charged. Further, 0.1 part by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was charged together with ethyl acetate with respect to 100 parts by weight of the monomer mixture, and nitrogen gas was introduced while gently stirring for nitrogen substitution. After that, the polymerization reaction was carried out for 7 hours while maintaining the liquid temperature in the flask at around 55°C. The monomer concentration during polymerization was set to 40% by weight. Then, ethyl acetate was added to the obtained reaction solution to adjust the solid content concentration to 30% to obtain a solution of the (meth)acrylic polymer P1. As POB-A, a commercially available monomer (manufactured by Kyoeisha Chemical Co., Ltd., purity 94%) further purified by an adsorption method was used.

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

[0131]

Table 1

[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 the homopolymer of that monomer with respect to 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 in the prepared (meth)acrylic polymer was calculated by the above calculation formula. As an example, the calculation formula for calculating the sum of the products in the (meth)acrylic polymer P1 is sum of products = 1.566 × 0.95 + 1.452 × 0.05.

[0134] (Preparation of Adhesive Composition) The above-prepared (meth)acrylic polymer as a base polymer and a crosslinking agent were mixed so as to have the composition shown in Table 2 below, and solvent-based adhesive compositions A1 to A29 were obtained.

[0135] (Preparation of Adhesive Sheet) An adhesive composition was applied to the surface of a PET film (MRF38-NS2 manufactured by Mitsubishi Chemical Corporation) which is a release liner so that the thickness of the dried adhesive sheet became a predetermined thickness. A fountain coater was used for applying the adhesive composition. The adhesive sheets S1 to S31 were prepared by performing a drying treatment on the coating film formed by the application at 90°C for 1 minute in an air circulation type constant temperature oven.

[0136] [Preparation of Optical Laminate] (Example 1) On the TAC film side of the above-prepared polarizing film, the first liquid crystal alignment cured layer side of a laminate having a substrate film / first liquid crystal alignment cured layer structure was bonded through the above-prepared adhesive (thickness: 1 μm). After that, the substrate film was peeled off to obtain a laminate having a structure of polarizing film / adhesive / first liquid crystal alignment cured layer. Next, after the exposed surface of the first liquid crystal alignment cured layer was subjected to plasma treatment, the exposed surface was bonded to the exposed surface of the pressure-sensitive adhesive sheet S1 formed on the release liner to obtain a laminate having a structure of polarizing film / adhesive / first liquid crystal alignment cured layer / pressure-sensitive adhesive sheet S1 / release liner. Next, the release liner was peeled off from the pressure-sensitive adhesive sheet S1, and the second liquid crystal alignment cured layer side in the laminate having a substrate film / second liquid crystal alignment cured layer structure was bonded to the exposed surface of the pressure-sensitive adhesive sheet S1 exposed by the peeling. Before the bonding, the exposed surface of the second liquid crystal alignment cured layer in the laminate was subjected to corona treatment. Next, the substrate film was peeled off to obtain an optical laminate having a structure of polarizing film / adhesive / first liquid crystal alignment cured layer / pressure-sensitive adhesive sheet S1 / second liquid crystal alignment cured layer. Note that the angle formed between the transmission axis of the polarizer of the polarizing film and the slow axis of the first liquid crystal alignment cured layer was 15°, and the angle formed between the transmission axis of the polarizer of the polarizing film and the slow axis of the second liquid crystal alignment cured layer was 75°. Also, the refractive index of the first liquid crystal alignment cured layer in the direction of the transmission axis of the polarizer was 1.66, and the refractive index of the second liquid crystal alignment cured layer in the direction of the transmission axis 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 the pressure-sensitive adhesive sheets S2 to S31 shown in Table 2 below were used instead of the pressure-sensitive adhesive sheet S1.

[0138] The pressure-sensitive adhesive sheets contained in each of the produced optical laminates, their thicknesses, the pressure-sensitive adhesive compositions used for forming the pressure-sensitive adhesive sheets, and their compositions are shown in Table 2 below.

[0139]

Table 2

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

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

[0142] (High-temperature durability) For each of the optical laminates of the examples and comparative examples, the durability at high temperatures was evaluated by the following method. First, with the side of the second liquid crystal alignment solidification layer in the optical laminate as the bonding surface, an acrylic adhesive sheet (thickness: 25 μm) was used to fix it to the surface of a glass plate (manufactured by Corning, Eagle XG). The fixing was carried out in an atmosphere of 23°C and 50% RH. Next, after treating it in an autoclave at 50°C and 5 atm (absolute pressure) for 15 minutes, it was left to cool to 23°C to stabilize the bonding of the optical laminate to the glass plate. Next, the whole was left in a heating atmosphere of 80°C for 24 hours. After leaving it, it was returned to an atmosphere of 23°C and 50% RH, and it was visually confirmed whether there was any peeling of the optical laminate from the glass plate, and the durability at high temperatures was evaluated according to the following criteria. A: No peeling is observed. B: Slight peeling is observed at the ends, but it is within a range that is not a problem in practical use. D: Peeling that is a problem to some extent in practical use is observed.

[0143] (Pot life) The prepared adhesive composition was left in an environment of 30°C for 6 hours, and the viscosity immediately after preparation and the viscosity after leaving it were measured, and the pot life was evaluated according to the following criteria. A: The viscosity hardly increases. B: The increase in viscosity is less than 20 P. C: The increase in viscosity is 20 P or more.

[0144] (Initial gel fraction) The initial gel fraction of the adhesive composition was determined by the above-described method and evaluated according to the following criteria. In the order of determination C, B, and A, it is more suitable for suppressing indentation. A: The initial gel fraction is 29% or more. B: The initial gel fraction is 10% or more and less than 29%. C: The initial gel fraction is less than 10%.

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

[0146]

Table 3

[0147] In the optical laminate of the example, it was possible to achieve both reduction of reflection and durability at high temperatures.

Industrial Applicability

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

Explanation of Symbols

[0149] 1, 1A, 1B, 1C, 1D Optical laminate 2 First liquid crystal alignment cured layer 3 Adhesive sheet 4 Second liquid crystal alignment cured layer 5 Polarizing film 11 Image display device

Claims

1. An optical laminate including a first liquid crystal alignment cured layer, an adhesive sheet, and a second liquid crystal alignment cured layer in this order, wherein the adhesive sheet includes a crosslinked body of a base polymer, the base polymer is composed of a plurality of monomers, and for each monomer constituting the base polymer, when the product of the refractive index of each monomer and the weight ratio of each monomer in all the monomers constituting the base polymer is obtained, the sum of the products in the base polymer is 1.51 or more, and the weight average molecular weight of the base polymer is 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 cured layer and the second liquid crystal alignment cured 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 cured layer and / or the second liquid crystal alignment cured 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 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 in all the 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 by a peroxide-based crosslinking agent.

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

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

11. Further including a polarizing film, wherein the polarizing film faces the main surface on the side opposite to the side of the adhesive sheet in the first liquid crystal alignment cured layer.

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

Images