TWI875755B - Curable composition, cured product layer, optical laminate and image display device - Google Patents

Abstract

An objective of the present invention is to provide a curable composition that can impart an optical laminate having good optical durability in high temperature and high humidity environments, which includes a cured product layer composed of a cured product of the curable composition.

The solution of the present invention is a curable composition which includes at least an aqueous resin and a silane compound having a silanol group. The optical laminate includes an optical layer and a first cured product layer composed of a cured product of the curable composition.

Description

Curable composition, cured layer, optical laminate and image display device

The present invention relates to a curable composition. In addition, the present invention relates to a cured material layer formed by a cured product of the curable composition, an optical laminate including the cured material layer, and an image display device including the optical laminate.

In recent years, LCD devices have been developed for portable devices such as smartphones and tablet terminals, or for in-vehicle devices such as car navigation systems. In these applications, they may be exposed to harsher environments than previous indoor TV applications, so improving the durability of the device has become a topic.

The same durability is also required for optical films that constitute liquid crystal display devices. That is, optical films assembled in liquid crystal display devices are sometimes in high temperature or high temperature and high humidity environments or in environments with repeated high and low temperatures. In such environments, the optical properties are also required not to deteriorate.

Optical films include polarizing plates that use adhesives to bond protective films to one or both sides of a polarizer (Patent Document 1, etc.).

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2017-82026

The purpose of the present invention is to provide a curable composition that can be applied to an optical laminate, wherein the optical laminate comprises a hardened layer composed of a hardened material of the curable composition and has good optical durability in a high temperature and high humidity environment.

The purpose of the present invention is to provide an optical laminate and an image display device including the optical laminate, wherein the optical laminate includes a hardened material layer composed of a hardened material of a hardening composition and has good optical durability in a high temperature and high humidity environment.

The present invention provides the following curable composition, curable layer, optical laminate and image display device.

[1] A curable composition comprising at least: a water-based resin and a silane compound having a silanol group.

[2] The curable composition as described in [1], wherein the silane compound further has: one or more functional groups selected from the group consisting of an amino group, a carboxyl group, an epoxy group, an acetylacetyl group, a hydroxyalkyl group, an alkylene group, an oxyalkylene group and an alkenyl group which may have a substituent.

[3] The curable composition as described in [1] or [2], wherein the silane compound further has: a functional group of at least one of an amino group and a carboxyl group which may have a substituent.

[4] The curable composition as described in [2] or [3], wherein the silane compound further comprises a Si-O-Si bond; and the silane compound has the functional group in its structure.

[5] The curable composition as described in any one of [1] to [4], wherein the water-based resin comprises at least one of a hydroxyl-containing resin and a (meth)acrylic resin.

[6] The curable composition as described in [5], wherein the hydroxyl-containing resin comprises at least one of a polyvinyl alcohol-based resin and a polyvinyl acetal-based resin.

[7] A hardened layer formed by hardening the hardening composition described in any one of [1] to [6].

[8] An optical laminate comprising: an optical layer and a first hardened material layer;

The first hardened layer is the hardened layer described in [7].

[9] The optical layered structure as described in [8], further comprising a first thermoplastic resin film;

The optical layer, the first hardened material layer, and the first thermoplastic resin film are sequentially stacked in the optical laminate.

[10] The optical laminate as described in [8] or [9], further comprising: a second hardened material layer and a second thermoplastic resin film;

On the side of the optical layer opposite to the side of the first cured layer, the second cured layer and the second thermoplastic resin film are sequentially laminated.

[11] The optical multilayer body as described in [10], wherein the second hardened layer is the hardened layer as described in [7].

[12] An optical layered structure as described in any one of [8] to [11], wherein the optical layer is a polarizer.

[13] An image display device comprising: an optical multilayer body as described in any one of [8] to [12], and an image display element.

A curable composition that can be applied to an optical laminate can be provided. The optical laminate includes a hardened layer composed of a hardened material of the curable composition and has good optical durability in a high temperature and high humidity environment.

An optical laminate and an image display device including the optical laminate can be provided. The optical laminate includes a hardened material layer composed of a hardened material of a hardening composition and has good optical durability in a high temperature and high humidity environment.

10: Thermoplastic resin film No. 1

15: First hardened layer

20: Second thermoplastic resin film

25: Second hardened layer

30: Optical layer

40: Adhesive layer

FIG1 is a schematic cross-sectional view showing an example of the optical laminate of the present invention.

FIG2 is a schematic cross-sectional view showing another example of the layer structure of the optical multilayer body of the present invention.

FIG3 is a schematic cross-sectional view showing another example of the layer structure of the optical multilayer body of the present invention.

FIG4 is a schematic cross-sectional view showing another example of the layer structure of the optical multilayer body of the present invention.

FIG5 is a schematic cross-sectional view showing another example of the layer structure of the optical multilayer body of the present invention.

FIG6 is a schematic cross-sectional view showing another example of the layer structure of the optical multilayer body of the present invention.

〈Hardening composition〉

The curable composition of the present invention at least comprises: a water-based resin and a silane compound having a silanol group. Hereinafter, the curable composition of the present invention is sometimes referred to as "curable composition (S)", the water-based resin is referred to as "water-based resin (A)", and the silane compound having a silanol group is referred to as "silane compound (B)".

The curable composition (S) can be used as a coating liquid for forming a coating film (coating layer) on a substrate. For example, the coating film can be formed by applying the curable composition (S) on a substrate and curing the coating layer. The substrate is preferably an optical layer. The optical layer is as described below. In this case, the optical laminate includes: An optical layer and a first cured material layer composed of a cured product of the curable composition (S).

The curable composition (S) can also be used as an adhesive composition. In one embodiment, the curable composition (S) is an adhesive composition for bonding the optical layer and the first thermoplastic resin film. In this case, the optical laminate includes in sequence: an optical layer, a first curing material layer (adhesive layer) composed of a cured product of the curable composition (S), and a first thermoplastic resin film. This optical laminate can be produced by coating a curable composition (S) on the bonding surface of at least one of the optical layer and the first thermoplastic resin film, laminating the optical layer and the first thermoplastic resin film via the coating layer to obtain a laminate, and then curing the coating layer.

The curable composition (S) is a water-based composition containing a water-based resin (A). The so-called water-based composition is a solution in which the formulation components are dissolved in a solvent containing water or a dispersion (such as an emulsion) in which the formulation components are dispersed in a solvent containing water.

The viscosity of the curable composition (S) at 25°C is preferably 50mPa‧sec or less, more preferably 1mPa‧sec or more and 30mPa‧sec or less, and even more preferably 2mPa‧sec or more and 20mPa‧sec or less. When the viscosity at 25°C exceeds 50mPa‧sec, it is difficult to apply uniformly and uneven application may occur. In addition, defects such as clogging of the piping may occur.

The viscosity of the curable composition (S) at 25°C can be measured by an E-type viscometer.

[1] Water-based resin (A)

The water-based resin (A) includes at least one of a water-soluble resin that can be dissolved in a water-based solvent and a water-dispersible resin that can be dispersed in a water-based solvent. In this specification, the so-called water-based solvent means water or a solvent with water as the main component, and the so-called water as the main component means that 50% by weight or more of the total weight of the components constituting the solvent is water. The solvent other than water in the aqueous solvent is not particularly limited as long as it is a solvent that is not easy to form layer separation in the presence of water. It is preferably a solvent that is soluble in water, for example: Alcohols such as methanol or ethanol, isopropanol, and n-propanol; ketones such as acetone or butanone; glycols such as ethylene glycol and diethylene glycol; glycol ethers such as N-methylpyrrolidone (NMP), tetrahydrofuran, and butyl solvent, etc.

The water-soluble resin is not particularly limited as long as it is a resin that can be dissolved in an aqueous solvent. In addition, the water-dispersible resin is not particularly limited as long as it is a resin that can be dispersed in an aqueous solvent. Examples of water-soluble resins or water-dispersible resins include: (meth)acrylic acid resins; polyvinyl alcohol resins; polyvinyl acetal resins; ethylene-vinyl alcohol copolymer resins; polyvinyl pyrrolidone resins; polyamide amine resins; epoxy resins; melamine resins; urea resins; polyamide resins; polyester resins; polyurethane resins; cellulose resins such as methyl cellulose, hydroethyl cellulose, and carboxymethyl cellulose; polysaccharides such as sodium alginate and starch, and the like. Among these, (meth) acrylic resins are preferred; hydroxyl-containing resins such as polyvinyl alcohol resins or polyvinyl acetal resins are more preferred, and (meth) acrylic resins, polyvinyl alcohol resins, and polyvinyl acetal resins are more preferred. In this specification, "(meth) acrylic acid" means at least one selected from the group consisting of acrylic acid and methacrylic acid. The same applies to "(meth) acryl" and "(meth) acrylate".

The curable composition (S) may contain one or more of the above-mentioned water-based resins (A).

When the solid concentration of the curable composition (S) is set to 100 mass%, the content of the water-based resin is preferably 30 mass% to 95 mass%, more preferably 35 mass% to 90 mass%, and even more preferably 40 mass% to 85 mass%. The content of the water-based resin is preferably within the above range from the perspective of improving the optical durability of the optical laminate in a high temperature and high humidity environment, the adhesion between the optical layer and the first cured layer in the optical laminate, and the adhesion between the first cured layer and the first thermoplastic resin film.

The so-called solid content concentration refers to the total concentration of components other than the solvent contained in the curable composition (S).

[1-1] (Meth) acrylic resin

(Meth) acrylic resins are polymers or copolymers obtained by using compounds having one or more (meth) acrylic groups in the molecule as the main monomer. (Meth) acrylic resins can be water-soluble or water-dispersible. Relative to 100% by mass of all structural units, (meth) acrylic resins preferably contain more than 50% by mass of structural units from compounds having one or more (meth) acrylic groups in the molecule, more preferably more than 70% by mass, and even more preferably more than 90% by mass of polymers or copolymers.

Compounds having more than one (meth)acryl group in the molecule include: (meth)acrylates and (meth)acrylamide having at least one (meth)acryloxy group in the molecule.

In addition, other monomers that can be copolymerized with compounds having more than one (meth)acryl group in the molecule include compounds having more than one ethylenic unsaturated bond in the molecule, represented by vinyl compounds such as styrene, styrene sulfonic acid, vinyl acetate, vinyl propionate, and N-vinyl-2-pyrrolidone.

The (meth)acrylic resin is preferably a (meth)acrylic resin having an oxazolyl group in the molecule (hereinafter sometimes referred to as "oxazolyl-containing (meth)acrylic resin"), and more preferably a (meth)acrylic resin having an oxazolyl group in the side chain.

By using an oxazole-containing (meth) acrylic resin as the water-based resin (A), the optical durability of the optical laminate in a high temperature and high humidity environment, or the adhesion between the optical layer and the first cured layer in the optical laminate, and the adhesion between the first cured layer and the first thermoplastic resin film can be easily improved.

The (meth) acrylic resin containing oxazolyl groups may be water-soluble or water-dispersible, but from the viewpoint of the optical properties of the cured layer formed by the cured product of the curable composition (S), a water-soluble polymer is preferred.

The (meth) acrylic resin containing an oxazole group may include: a constituent unit having an oxazole group in the side chain (a constituent unit derived from an oxazole group-containing monomer) and a constituent unit not having an oxazole group.

A preferred example of an oxazolyl-containing (meth) acrylic resin includes a skeleton structure composed of a (meth) acrylic skeleton as a main component of the constituent unit, and a constituent unit having an oxazolyl group in the side chain (a constituent unit derived from an oxazolyl-containing monomer) is introduced as a copolymer component.

Oxazolyl-containing (meth) acrylic resins are obtained by copolymerizing oxazole-containing monomers or by modifying the side chain functional groups of the polymer to contain oxazole groups.

Examples of oxazolyl include 2-oxazolyl, 3-oxazolyl, 4-oxazolyl, etc. Oxazolyl is preferably 2-oxazolyl, etc.

The above-mentioned monomers containing oxazolyl groups can be listed as follows: 2-isopropenyl-2-oxazoline, vinyl-2-oxazoline, etc.

The weight average molecular weight of the oxazolyl-containing (meth) acrylic resin is preferably 5,000 or more, and more preferably 10,000 or more. The weight average molecular weight within the above range is more advantageous from the perspective of improving the optical durability of the optical laminate in a high temperature and high humidity environment, the adhesion between the optical layer and the first cured layer in the optical laminate, and the adhesion between the first cured layer and the first thermoplastic resin film.

The weight average molecular weight of oxazolyl-containing (meth) acrylic resins is usually less than 1,000,000.

The weight average molecular weight of the oxazolyl-containing (meth) acrylic resin can be measured by gel permeation chromatography (GPC) as a standard polystyrene conversion value.

The oxazole content of the oxazole-containing (meth) acrylic resin (the number of moles of oxazole per 1g solid of the oxazole-containing (meth) acrylic resin) is preferably 0.4mmol/g‧solid or more. When the oxazole content is less than the above range, it may be detrimental to the optical durability of the optical laminate in a high temperature and high humidity environment. From this point of view, the oxazole content of the oxazole-containing polymer is preferably 3mmol/g‧solid or more, and more preferably 5mmol/g‧solid or more and 9mmol/g‧solid or less.

There is no particular upper limit on the amount of oxazole groups, but it is usually below 50 mmol/g‧solid.

Commercially available (meth) acrylic resins containing oxazolyl groups can also be used. Specifically, oxazolyl-containing acrylic polymers such as Epocros WS-300, Epocros WS-500, and Eqocros WS-700 (all trade names) manufactured by Nippon Catalyst Co., Ltd.; oxazolyl-containing acrylic/styrene polymers such as Epocros K-1000 series, Epocros K-2000 series, and Epocros RPS series (all trade names) manufactured by Nippon Catalyst Co., Ltd.

Two or more oxazolyl-containing (meth) acrylic resins may be used in combination.

From the perspective of the optical durability or optical properties of the optical laminate in a high temperature and high humidity environment, the adhesion between the optical layer and the first cured layer in the optical laminate, the adhesion between the first cured layer and the first thermoplastic resin film, and the water resistance of the first cured layer, the oxazolyl-containing (meth) acrylic resin is preferably an oxazolyl-containing acrylic polymer such as Epocros WS-300, Epocros WS-500, Epocros WS-700.

[1-2] Polyvinyl alcohol resin

By using a polyvinyl alcohol-based resin as the water-based resin (A), the optical durability of the optical laminate in a high temperature and high humidity environment, or the adhesion between the optical layer and the first cured layer, and the adhesion between the first cured layer and the first thermoplastic resin film in the optical laminate can be easily improved.

Polyvinyl alcohol resins can be obtained by saponifying polyvinyl acetate resins. Polyvinyl acetate resins include copolymers of vinyl acetate and other monomers copolymerizable therewith, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, and acrylamides having an ammonium group.

The polyvinyl alcohol resin used in the curable composition (S) preferably has an appropriate degree of polymerization. For example, when it is formed into a 4 wt% aqueous solution, the viscosity is preferably in the range of 4 to 50 mPa‧sec, and more preferably in the range of 6 to 30 mPa‧sec.

The saponification degree of the polyvinyl alcohol resin is not particularly limited, and is generally preferably 70 mol% or more, and more preferably 80 mol% or more. When the saponification degree of the polyvinyl alcohol resin is low, the water resistance of the cured layer composed of the cured product of the curable composition (S), the adhesion between the optical layer and the first cured layer in the optical laminate, and the adhesion between the first cured layer and the first thermoplastic resin film tend to be insufficient.

The polyvinyl alcohol resin used in the curable composition (S) is preferably modified. Examples of such modified polyvinyl alcohol resins include polyvinyl alcohol resins modified with acetoacetyl groups, polyvinyl alcohol resins modified with carboxylic acids, polyvinyl alcohol resins modified with carbonyl groups, polyvinyl alcohol resins modified with sulfonic acids, polyvinyl alcohol resins modified with hydrazide groups, polyvinyl alcohol resins modified with thiol groups, polyvinyl alcohol resins modified with alkyl groups, polyvinyl alcohol resins modified with silane groups, polyvinyl alcohol resins modified with polyethylene glycol groups, polyvinyl alcohol resins modified with oxirane groups, polyvinyl alcohol resins modified with groups having urethane bonds, and polyvinyl alcohol resins modified with phosphate groups. When such a modified polyvinyl alcohol-based resin is used, the water resistance of the cured layer composed of the cured product of the curable composition (S), the adhesion between the optical layer and the first cured layer in the optical laminate, and the adhesion between the first cured layer and the first thermoplastic resin film can be improved, so it is preferred.

The polyvinyl alcohol resin modified with acetylacetyl group has an acetylacetyl group (CH ₃ COCH ₂ CO-) in addition to the hydroxyl group constituting the polyvinyl alcohol skeleton, and may have other groups, such as acetyl group. The acetylacetyl group typically exists in a state where the hydrogen atom of the hydroxyl group is substituted. The polyvinyl alcohol resin modified with acetylacetyl group can be produced, for example, by reacting polyvinyl alcohol with diketene. Since the polyvinyl alcohol resin modified with acetylacetyl group has an acetylacetyl group which is a highly reactive functional group, it is preferable for improving the durability of the cured layer composed of the cured product of the curable composition (S).

The content of acetylacetyl groups in the acetylacetyl-modified polyvinyl alcohol resin is not particularly limited as long as it is 0.1 mol % or more. The acetylacetyl content referred to herein is a value expressed in % as the molar fraction of acetylacetyl groups relative to the total amount of hydroxyl groups, acetylacetyl groups and other ester groups (acetyl groups, etc.) in the polyvinyl alcohol resin, and is sometimes referred to as "acetylacetyl degree" hereinafter. When the degree of acetylacetylization in the polyvinyl alcohol resin is lower than 0.1 mol %, the effect of improving the water resistance of the cured material layer composed of the cured material of the curable composition (S) may not be sufficient. The degree of acetylation in the polyvinyl alcohol resin is preferably about 0.1 to 40 mol%, more preferably 1 to 20 mol%, and particularly preferably 2 to 7 mol%. When the degree of acetylation exceeds 40 mol%, the effect of improving water resistance becomes smaller.

Commercially available polyvinyl alcohol resins modified with acetyl groups can also be used. Specific examples include the "Gohsefimer Z" series sold by Nippon Synthetic Chemical Industry Co., Ltd.

In addition to the hydroxyl groups that constitute the polyvinyl alcohol skeleton, polyvinyl alcohol resins modified with carboxylic acid also have carboxyl groups (-COOH). Polyvinyl alcohol resins modified with carboxylic acid can be produced by copolymerizing unsaturated monomers with carboxyl groups with vinyl acetate and then using a saponification method.

Commercially available polyvinyl alcohol resins modified with carboxylic acid may also be used. Specific examples include: "KL-318" and "KM-118" manufactured by Kuraray Co., Ltd., "Gohsenol T-330" and "Gohsenol T-215" manufactured by Mitsubishi Chemical Co., Ltd., and "A-Polymer" series manufactured by Japan Vam & Poval Co., Ltd.

In addition to the hydroxyl group constituting the polyvinyl alcohol skeleton, the carbonyl-modified polyvinyl alcohol resin also has a carbonyl-containing group. The carbonyl-containing group is not particularly limited as long as it is represented by -COR, and examples thereof include amide groups, acyl groups, aldehyde groups, etc. The carbonyl-modified polyvinyl alcohol resin can be produced by copolymerizing an unsaturated monomer having a carbonyl-containing group (such as amide groups, acyl groups, aldehyde groups, etc.) with vinyl acetate and then using a saponification method.

Specific examples of carbonyl-modified polyvinyl alcohol resins include the "D Polymer" series of Japan Vam & Poval Co., Ltd. In addition, examples include the resins described in Japanese Patent Publication No. 8-151412 and the resins described in Japanese Patent Publication No. 9-324095.

Sulfonic acid modified polyvinyl alcohol resins have sulfonic acid groups (-SO ₂ OH) in addition to the hydroxyl groups that constitute the polyvinyl alcohol skeleton. Sulfonic acid modified polyvinyl alcohol resins can be produced by copolymerizing unsaturated monomers having sulfonic acid groups with vinyl acetate and then using a saponification method.

Commercially available polyvinyl alcohol resins modified with sulfonic acid can also be used. Specific examples include: "L-3266" from Mitsubishi Chemical Co., Ltd., "AS-Polymer" series from Japan Vam & Poval Co., Ltd., etc.

Alkyl-modified polyvinyl alcohol resins have alkyl groups in addition to the hydroxyl groups that constitute the polyvinyl alcohol skeleton. Alkyl-modified polyvinyl alcohol resins can be produced by copolymerizing unsaturated monomers with alkyl groups with vinyl acetate and then using a saponification method.

Alkyl-modified polyvinyl alcohol resins can also be used as commercial products, such as the "Z-Polymer" series of Japan Vam & Poval Co., Ltd.

Silicon-modified polyvinyl alcohol resins have silicon groups in addition to the hydroxyl groups that constitute the polyvinyl alcohol skeleton. Silicon-modified polyvinyl alcohol resins can be produced by copolymerizing unsaturated monomers with silicon groups with vinyl acetate and then using a saponification method.

Examples of silicon-modified polyvinyl alcohol resins include those described in Japanese International Publication No. 2014/112625. In addition, commercially available products may be used, such as "R-1130", "R-2105", and "R-2130" manufactured by Kuraray Co., Ltd.

Polyvinyl alcohol resin modified with polyethylene glycol has polyethylene glycol groups in addition to the hydroxyl groups that constitute the polyvinyl alcohol skeleton. Polyvinyl alcohol resin modified with polyethylene glycol can be produced by copolymerizing unsaturated monomers having polyethylene glycol groups with vinyl acetate and then using a saponification method.

Commercially available polyvinyl alcohol resins modified with polyethylene glycol can also be used, such as the "E Polymer" series of Japan Vam & Poval Co., Ltd.

In addition to the hydroxyl groups that constitute the polyvinyl alcohol skeleton, the polyvinyl alcohol resin modified with ethylene oxide also has ethylene oxide groups (i.e., epoxy groups). The polyvinyl alcohol resin modified with ethylene oxide groups can be produced by copolymerizing unsaturated monomers having ethylene oxide groups with vinyl acetate and then using a saponification method.

The polyvinyl alcohol resin modified with hydrazide group has hydrazide group (-CONR'NR") in addition to the hydroxyl group constituting the polyvinyl alcohol skeleton. Here, R' and R" each independently represent a hydrogen atom or a alkyl group. The polyvinyl alcohol resin modified with hydrazide group can be prepared by copolymerizing an unsaturated monomer having hydrazide group with vinyl acetate and then using saponification method.

The polyvinyl alcohol resin modified with a phosphate group has a phosphate group (-O-PO-(OR) ₂ ) in addition to the hydroxyl group constituting the polyvinyl alcohol skeleton. Here, each R independently represents a hydrogen atom or a hydroxyl group. The polyvinyl alcohol resin modified with a phosphate group can be produced by copolymerizing an unsaturated monomer having a phosphate group with vinyl acetate and then using a saponification method.

The so-called polyvinyl alcohol resin modified with a group having a urethane bond has a group having a urethane bond (a group represented by -CONHR) in addition to the hydroxyl group constituting the polyvinyl alcohol skeleton.

The polyvinyl alcohol resin may contain two or more of the above-mentioned modified polyvinyl alcohol resins, and may also contain both unmodified polyvinyl alcohol resins (specifically, completely or partially saponified polyvinyl acetate) and the above-mentioned modified polyvinyl alcohol resins.

Commercially available polyvinyl alcohol-based resins may also be used. Specifically, for example, polyvinyl alcohol with a high saponification degree, "PVA-117H" sold by Kuraray Co., Ltd. or "Gohsenol NH-20" sold by Nippon Gosei Kagaku Kogyo Co., Ltd.; polyvinyl alcohol modified with acetyl groups, "Gohsefimer Z" series sold by Nippon Gosei Kagaku Kogyo Co., Ltd.; polyvinyl alcohol modified with anions, "KL-318" and "KM-118" sold by Kuraray Co., Ltd. or "Gohsenol T-330" sold by Nippon Gosei Kagaku Kogyo Co., Ltd.; polyvinyl alcohol modified with cations, "CM-318" sold by Kuraray Co., Ltd. or "Gohsefimer K-210" sold by Nippon Gosei Kagaku Kogyo Co., Ltd., etc.

[1-3] Polyvinyl acetal resin

By using a polyvinyl acetal resin as the water-based resin (A), the optical durability of the optical laminate in a high temperature and high humidity environment, or the adhesion between the optical layer and the first cured layer in the optical laminate, and the adhesion between the first cured layer and the first thermoplastic resin film can be easily improved.

Polyvinyl acetal resins can be obtained by acetalizing polyvinyl alcohol resins with at least one of aldehydes and ketones. Polyvinyl acetal resins can be used alone or in combination of two or more.

The saponification degree of the polyvinyl alcohol resin used to obtain the polyvinyl acetal resin is not particularly limited, but is usually 70 mol% or more, preferably 75 mol% or more, and more preferably 80 mol% or more. In addition, it is usually 99.9 mol% or less, and can be 99.8 mol% or less.

The aldehyde used to obtain the polyvinyl acetal resin is not particularly limited, and examples thereof include aldehydes having a chain aliphatic group, a cyclic aliphatic group, or an aromatic group having 1 to 10 carbon atoms. Examples of such aldehydes include: aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, n-hexanal, 2-ethylbutyraldehyde, 2-ethylhexanal, n-heptylaldehyde, n-octanal, n-nonanal, n-decanal, and valeraldehyde; aromatic aldehydes such as benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde. Such aldehydes may be used alone or in combination of two or more. Among these aldehydes, butyraldehyde, 2-ethylhexanal, and n-nonanal, which have excellent acetalization reactivity, are preferred, and butyraldehyde is more preferred.

The ketones used to obtain the polyvinyl acetal resin are not particularly limited, and the following can be cited: acetone, butanone, diethyl ketone, tertiary butanone, diacetone, allyl acetophenone, acetophenone, p-methylacetophenone, 4'-aminoacetophenone, p-chloroacetophenone, 4'-methoxyacetophenone, 2'-hydroxyacetophenone, 3'-nitroacetophenone, P-(1-piperidyl)acetophenone, benzylideneacetophenone, phenylacetophenone, diphenyl ketone, 4-nitrodiphenyl ketone, 2-methyldiphenyl ketone, p-bromodiphenyl ketone, cyclohexyl (phenyl) ketone, 2-naphthyl butyl ketone, 1-naphthyl acetophenone, 2-hydroxy-1-naphthyl acetophenone, 8'-hydroxy-1'-naphthyl benzophenone, etc.

The amount of aldehyde and ketone added can be appropriately set according to the acetalization degree of the desired polyvinyl acetal resin. For example, relative to 100 mol% of the polyvinyl alcohol resin, the total amount of aldehyde and ketone is 60 to 95 mol%, preferably 70 to 90 mol%.

The hydroxyl content of polyvinyl acetal resin is preferably 30 mol% or more, more preferably 40 mol% or more, and can be 50 mol% or more. In addition, it is preferably 90 mol% or less, and more preferably 85 mol% or less. The hydroxyl content of polyvinyl acetal resin is the ratio (mol%) of the amount of vinyl groups bonded with hydroxyl groups to the total amount of vinyl groups in the main chain. The amount of vinyl groups bonded with hydroxyl groups can be calculated, for example, by the method according to JIS K6728 "Testing methods for polyvinyl acetal".

The acetyl group content of polyvinyl acetal resin is not particularly limited, and is preferably 0.0001 mol% or more, more preferably 0.001 mol% or more, and can be 0.01 mol% or more. In addition, it is preferably 5 mol% or less, more preferably 3 mol% or less, and can be 2 mol% or less. The acetyl group content of polyvinyl acetal resin is the ratio (mol%) of the total vinyl content of the main chain to the total vinyl content of the main chain minus the total vinyl content of the vinyl content of the acetal group and the vinyl content of the hydroxyl group. The vinyl content of the acetal group can be calculated, for example, by the method according to JIS K6728 "Testing Methods for Polyvinyl Acetal".

[2] Silane compound having a silanol group (B)

The silane compound (B) is a compound having a silanol group (-SiOH). The curable composition (S) may contain one or more silane compounds (B). By adding the silane compound (B) to the curable composition (S), the optical durability of the optical laminate in a high temperature and high humidity environment can be improved.

The silane compound (B) is not particularly limited as long as it has a silanol group. In addition, even if the silane compounds having a silanol group form a dimer, trimer, or three-dimensional network structure through a condensation reaction, as long as the formed body contains a silanol group, it is included in the silane compound (B) in this specification.

In addition to the silanol group, the silane compound (B) preferably has one or more functional groups selected from the group consisting of an amino group that may have a substituent, a carboxyl group, an epoxy group, an acetylacetyl group, a hydroxyalkyl group, an alkylene group, an oxyalkylene group, and an alkenyl group. Among them, the silane compound (B) preferably has at least one functional group of an amino group that may have a substituent and a carboxyl group, and more preferably has a carboxyl group.

The amino group which may have a substituent may include an unsubstituted amino group ( _-NH2 ), an alkylamino group in which 1 or 2 hydrogen atoms are substituted by an alkyl group, a (hydroxyalkyl)amino _{group in which 1 or 2 hydrogen atoms are substituted by a hydroxyalkyl group (e.g., -N(CH2HC(OH)CH2OH2)2 ) , an} aminoalkylamino group ( _-NHC2H4NH2 ) _, and _the like.

Specific examples of the functional groups include _-NH2 , _-NHC2H4NH2 , _-COOH , -SH, -CH(OH _{) CH2OH} , -N( _CH2HC (OH ₎ CH2OH2 _{) 2} , _and -CHCH2.

When the silane compound (B) has two or more of the above functional groups, the functional groups may be the same or different from each other.

By making the silane compound (B) have the above-mentioned functional group, the optical durability of the optical laminate in a high temperature and high humidity environment, or the adhesion between the optical layer and the first cured layer in the optical laminate, and the adhesion between the first cured layer and the first thermoplastic resin film can be easily improved.

In addition to the silanol group and the above functional group, the silane compound (B) preferably contains a Si-O-Si bond. The silanol group and the above functional group can be present anywhere in the structure of the silane compound (B) containing the Si-O-Si bond, but it is preferred that the above functional group is present at the end of the silane compound (B) containing the Si-O-Si bond.

From the perspective of improving the optical durability of the optical laminate in a high temperature and high humidity environment, the content of the silane compound (B) is usually 0.5 parts by mass or more, preferably 1 part by mass or more, and more preferably 3 parts by mass or more, relative to 100 parts by mass of the water-based resin (A). In addition, it is usually 200 parts by mass or less, preferably 180 parts by mass or less, and more preferably 150 parts by mass or less.

By setting the content of the silane compound (B) in the curable composition (S) to the above range, the optical durability of the optical laminate in a high temperature and high humidity environment can be improved, and good adhesion can be obtained between the optical layer and the first curing layer in the optical laminate, and between the first curing layer and the first thermoplastic resin film.

However, when the content of the silane compound (B) is too low, it is difficult to obtain the optical durability of the optical laminate in a high temperature and high humidity environment. In addition, when the content of the silane compound (B) is too high, the optical durability of the optical laminate in a high temperature and high humidity environment tends to be easily reduced.

[3] Other ingredients

The curable composition (S) may contain other components besides the water-based resin (A) and the silane compound (B).

Other ingredients include: glyoxal, glyoxal derivatives and other polyaldehydes, melamine compounds, aziridine compounds, water-soluble epoxy resins, zirconium compounds, zinc compounds, titanium compounds, aluminum compounds and other metal compounds and other hardening components or crosslinking agents; modified polyvinyl alcohol polymers other than carboxyl-modified polyvinyl alcohol polymers; coupling agents, thickeners, antioxidants, ultraviolet absorbers, heat stabilizers, anti-hydrolysis agents and other additives; aqueous solvents; the compound (C) described below, etc.

The curable composition (S) may contain one or more other components.

[3-1] Aqueous solvents

The curable composition (S) preferably contains an aqueous solvent for dissolving or dispersing the aqueous resin (A). The aqueous solvent may be the one exemplified above. The aqueous solvent preferably contains water at least 80% by mass of the total mass of the aqueous solvent, more preferably at least 90% by mass, and even more preferably at least 95% by mass. It may also contain only water.

The solid content concentration of the curable composition (S) is usually 0.5 mass% to 20 mass%, preferably 1 mass% to 15 mass%.

[3-2] Compound (C)

When the water-based resin (A) contains an oxazolyl-containing (meth) acrylic resin and the silane compound (B) has the above-mentioned functional group, it is preferred to contain: a compound that promotes the reaction between the oxazolyl group of the oxazolyl-containing (meth) acrylic resin and the above-mentioned functional group of the silane compound (B) (hereinafter sometimes referred to as "compound (C)"). Here, the so-called promotion also includes the situation of initiating the reaction.

The curable composition (S) may contain one compound (C) or two or more compounds (C).

The compound (C) may also be formulated into the curable composition (S) as a solution (e.g., aqueous solution) containing the compound (C).

Preferred examples of compound (C) include acid compounds. The acid compound may be a compound that functions as a catalyst to promote the reaction between the oxazole group of the oxazole group-containing (meth) acrylic resin and the above-mentioned functional group of the silane compound (B).

The above acid compounds can be listed as follows: inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, phosphorous acid, and boric acid; organic acids such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, methanesulfonic acid, benzenesulfonic acid, phenylphosphoric acid, sulfanilic acid, phenylphosphonic acid, acetic acid, and propionic acid.

From the perspective of improving the optical durability of the optical laminate in a high temperature and high humidity environment, the adhesion between the optical layer and the first hardened layer in the optical laminate, and the adhesion between the first hardened layer and the first thermoplastic resin film, the acid compound is preferably a relatively strong acid, and examples of such acid compounds include sulfuric acid, hydrochloric acid (hydrochloric acid), nitric acid, p-toluenesulfonic acid, etc.

When the above-mentioned strong acid is used as the acid compound, it tends to improve the adhesion between the optical layer and the first cured layer in the optical laminate or the adhesion between the first cured layer and the first thermoplastic resin film.

The content of the acid compound is preferably 5 to 80 parts by mass, more preferably 10 to 70 parts by mass, and even more preferably 15 to 60 parts by mass, relative to 100 parts by mass of the oxazolyl-containing (meth) acrylic resin.

When the content of the acid compound is too low, it is difficult to obtain at least one of the adhesion between the optical layer and the first cured layer in the optical laminate and the adhesion between the first cured layer and the first thermoplastic resin film. In addition, when the content of the acid compound is too high, at least one of the adhesion between the optical layer and the first cured layer in the optical laminate and the adhesion between the first cured layer and the first thermoplastic resin film tends to be easily reduced.

〈Optical multilayers〉

The optical laminate of the present invention comprises: an optical layer and a first hardened material layer (a hardened material layer composed of a hardened material of a hardening composition (S)) laminated on at least one surface thereof.

According to the present invention, since the hardened material layer included in the optical laminate is composed of a hardened material of the curable composition (S), the optical durability of the optical laminate can be improved in a high temperature and high humidity environment.

[1] Composition of optical laminates

Examples of the layer structure of an optical multilayer are shown in Figures 1 to 5.

The optical layered structure shown in FIG1 includes an optical layer 30 and a first hardened layer 15 stacked on one surface thereof. The first hardened layer 15 can function as a protective layer that covers and protects the surface of the optical layer 30, or as an optical functional layer that adds optical functions to the optical layer 30.

The optical layer 30 and the first hardened material layer 15 are preferably in direct contact.

The optical laminate shown in FIG2 includes: an optical layer 30, and a first thermoplastic resin film 10 laminated on one side thereof via a first curing layer 15. The first curing layer 15 can function as an adhesive layer connecting the optical layer 30 and the first thermoplastic resin film 10.

The first hardened material layer 15 is preferably in direct contact with the first thermoplastic resin film 10.

The optical layer 30 and the first hardened material layer 15 are preferably in direct contact.

The optical laminate shown in FIG3 includes: an optical layer 30, a first thermoplastic resin film 10 laminated on one side thereof via a first curing layer 15, and a second thermoplastic resin film 20 laminated on the other side of the optical layer 30 via a second curing layer 25. That is, the optical laminate of the present invention may include: a second thermoplastic resin film 20, a second curing layer 25, an optical layer 30, a first curing layer 15, and a first thermoplastic resin film 10 in sequence. The first cured layer 15 and the second cured layer 25 can function as an adhesive layer connecting the optical layer 30 and the first thermoplastic resin film 10, and an adhesive layer connecting the optical layer 30 and the second thermoplastic resin film 20, respectively.

The second hardened material layer 25 is preferably in direct contact with the second thermoplastic resin film 20.

The optical layer 30 and the second hardened material layer 25 are preferably in direct contact.

The optical laminate shown in FIG. 4 includes: an optical layer 30, a first cured layer 15 laminated on one side thereof, and a second thermoplastic resin film 20 laminated on the other side of the optical layer 30 via a second cured layer 25. The first cured layer 15 can function as a protective layer that covers and protects the surface of the optical layer 30, or as an optical functional layer that adds optical functions to the optical layer 30. The second cured layer 25 can function as an adhesive layer that connects the optical layer 30 and the second thermoplastic resin film 20.

The optical layer 30 and the first hardened material layer 15 are preferably in direct contact.

The second hardened material layer 25 is preferably in direct contact with the second thermoplastic resin film 20.

The optical layer 30 and the second hardened material layer 25 are preferably in direct contact.

The optical layered structure shown in FIG5 includes: an optical layer 30, a first hardened layer 15 stacked on one side thereof, and a second hardened layer 25 stacked on the other side of the optical layer 30. The first hardened layer 15 and the second hardened layer 25 can function as a protective layer that covers and protects the surface of the optical layer 30, or as an optical functional layer that adds an optical function to the optical layer 30.

The optical layer 30 and the first hardened material layer 15 are preferably in direct contact.

The optical layer 30 and the second hardened material layer 25 are preferably in direct contact.

The optical layer 30 can be various optical films (films with optical properties) that can be assembled in image display devices such as liquid crystal display devices. Examples of the optical layer 30 include: polarizers, phase difference films, brightness enhancement films, anti-glare films, anti-reflection films, diffusion films, and light-focusing films.

The optical laminate may include other layers (or films) other than those mentioned above. Examples of other layers include: an adhesive layer laminated on the outer surface of the first thermoplastic resin film 10, the second thermoplastic resin film 20, the first hardened material layer 15, the second hardened material layer 25 and/or the optical layer 30; a separation film (also referred to as a "peeling film") laminated on the outer surface of the adhesive layer; a first thermoplastic resin film 10, the second thermoplastic resin film 20, the first hardened material layer 15, the second hardened material layer 25 and/or the optical layer 30; a separation film (also referred to as a "peeling film") laminated on the outer surface of the adhesive layer; a second thermoplastic resin film 10, the second thermoplastic resin film 20, the first hardened material layer 15, the second hardened material layer 25 and/or the optical layer 30; a separation film (also referred to as a "peeling film") laminated on the outer surface of the adhesive layer; a second thermoplastic resin film 10, the second thermoplastic resin film 20, the first hardened material layer 15, the second hardened material layer 25 and/or the optical layer 30; a second thermoplastic resin film 10 ... A protective film on the outer surface of the first cured layer 15, the second cured layer 25 and/or the optical layer 30 (also referred to as a "surface protective film"); an optical functional film (or layer) laminated on the outer surface of the first thermoplastic resin film 10, the second thermoplastic resin film 20, the first cured layer 15, the second cured layer 25 and/or the optical layer 30 via a bonding agent layer or an adhesive layer, etc.

[2] Polarizer

A polarizer is a layer or film that has the function of selectively allowing linear polarized light in a certain direction to pass through natural light.

For example, polarizers include: films that adsorb and align dichroic pigments on polyvinyl alcohol resin films. Examples of dichroic pigments include iodine, dichroic organic dyes, etc.

In addition, the polarizer may be a coated polarizing film in which a dichroic dye in a lyotropic liquid crystal state is coated on a substrate film and then aligned and fixed.

Since the above polarizer selectively allows linear polarization in a certain direction to pass through natural light and absorbs linear polarization in another direction, it is called an absorption polarizer.

The polarizer is not limited to an absorption type polarizer, and may also be a reflection type polarizer that selectively transmits linear polarization in a certain direction from natural light and reflects linear polarization in another direction, or a scattering type polarizer that scatters linear polarization in another direction. However, from the perspective of excellent viewing, an absorption type polarizer is preferred. Among them, a polyvinyl alcohol polarizing film composed of a polyvinyl alcohol resin film is more preferred, and a polyvinyl alcohol polarizing film in which a dichroic pigment such as iodine or a dichroic dye is adsorbed and aligned on the polyvinyl alcohol resin film is more preferred, and a polyvinyl alcohol polarizing film in which iodine is adsorbed and aligned on the polyvinyl alcohol resin film is particularly preferred.

Polyvinyl alcohol resins can be saponified polyvinyl acetate resins. Polyvinyl acetate resins include copolymers of vinyl acetate and other monomers copolymerizable therewith, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. Other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group.

The saponification degree of polyvinyl alcohol resin is usually 85 mol% to 100 mol%, preferably 98 mol% or more. Polyvinyl alcohol resin can be modified, for example, polyvinyl formaldehyde or polyvinyl acetal modified with aldehydes can also be used. The average polymerization degree of polyvinyl alcohol resin is usually 1000 to 10000, preferably 1500 to 5000.

The average degree of polymerization of polyvinyl alcohol resin can be obtained according to JIS K 6726:1994.

The polyvinyl alcohol resin film can be used as the embryo membrane of the polarizing film composed of the polyvinyl alcohol resin film. The method of forming the polyvinyl alcohol resin film is not particularly limited, and a generally known method can be adopted. The film thickness of the polyvinyl alcohol embryo membrane is, for example, less than 150 μm, preferably less than 100 μm (for example, less than 50 μm) and more than 5 μm.

Polarizing films made of polyvinyl alcohol resin films can be manufactured by generally known methods. Specifically, they can be manufactured by a method comprising the following steps: a step of uniaxially stretching the polyvinyl alcohol resin film; a step of dyeing the polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye; a step of treating (crosslinking) the polyvinyl alcohol resin film adsorbed with the dichroic dye with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution.

The thickness of the polarizer can be set to be less than 40 μm, preferably less than 30 μm (for example, less than 20 μm, more preferably less than 15 μm, even less than 10 μm or less than 8 μm). According to the method described in Japanese Patent Publication No. 2000-338329 or Japanese Patent Publication No. 2012-159778, a thin film polarizer can be manufactured more easily, and the thickness of the polarizer can be more easily made, for example, less than 20 μm, more preferably less than 15 μm, even less than 10 μm or less than 8 μm. The thickness of the polarizer is usually more than 2 μm. Reducing the thickness of the polarizer is beneficial to the thinning of the optical laminate (polarizer) and the image display device containing it. Generally speaking, the thinner the polarizer, the lower its optical durability tends to be. However, by using the curable composition of the present invention, even a thin-film polarizer can have good durability.

[3] Phase difference film

The phase difference film can be listed as follows: a stretched film obtained by uniaxially stretching or biaxially stretching a light-transmitting thermoplastic resin; a film having a liquid crystal compound such as a discotic liquid crystal or a nematic liquid crystal aligned and fixed; a film having the above-mentioned liquid crystal layer formed on a substrate film, etc. In addition, in this specification, a zero phase difference film is also included in the phase difference film.

The substrate film is usually a film made of a thermoplastic resin, and an example of the thermoplastic resin is a cellulose ester resin such as cellulose triacetate.

Examples of light-transmitting thermoplastic resins include the resin constituting the first thermoplastic resin film 10 described below.

The so-called zero phase difference film is a film with an in-plane phase difference value _Re and a thickness direction phase difference value _Rth of -15 to +15nm. This phase difference film can be preferably used in an IPS mode liquid crystal display device. The in-plane phase difference value _Re and the thickness direction phase difference value _Rth are preferably both -10 to +10nm, and more preferably both -5 to +5nm. Here, the so-called in-plane phase difference value _Re and the thickness direction phase difference value _Rth are the values at a wavelength of 590nm.

The in-plane phase difference value _Re and the thickness direction phase difference value _Rth are defined by the following formulas:

_Re =( _nx - _ny )×d

_Rth =[( _nx + _ny )/2- _nz ]×d, where _nx is the refractive index in the slow axis direction (x-axis direction) within the film plane, _ny is the refractive index in the fast axis direction (y-axis direction orthogonal to the x-axis in the plane), _nz is the refractive index in the film thickness direction (z-axis direction perpendicular to the film plane), and d is the thickness of the film.

For example, the zero phase difference film can be made of a resin film composed of a cellulose resin, a polyolefin resin such as a chain polyolefin resin and a ring polyolefin resin, a polyethylene terephthalate resin or a (meth) acrylic resin. In particular, from the perspective of easy control of the phase difference value and easy acquisition, it is preferable to use a cellulose resin, a polyolefin resin or a (meth) acrylic resin.

Films that exhibit optical anisotropy by coating and aligning liquid crystal compounds include the following phase difference films:

The first type: a phase difference film that aligns the rod-shaped liquid crystal compound to the supporting substrate in the horizontal direction.

The second type: a phase difference film that aligns the rod-shaped liquid crystal compound in a vertical direction to the supporting substrate.

The third type: a phase difference film that changes the orientation direction of the rod-shaped liquid crystal compound in a spiral shape within the plane.

The fourth type: a phase difference film that makes the disc-shaped liquid crystal compound oriented in an inclined manner,

Fifth type: a biaxial phase difference film that aligns the discotic liquid crystal compound in a vertical direction to the supporting substrate.

For example, the first type, the second type, and the fifth type can be preferably used as optical films used in organic electroluminescent displays. Alternatively, they can also be used by stacking them.

In the case where the phase difference film is a layer composed of polymers of polymerizable liquid crystal compounds in an aligned state (hereinafter sometimes referred to as an "optically anisotropic layer"), the phase difference film preferably has reverse wavelength dispersion. The so-called reverse wavelength dispersion is an optical property that the in-plane phase difference value of the liquid crystal alignment at a short wavelength is smaller than the in-plane phase difference value of the liquid crystal alignment at a long wavelength. The preferred phase difference film is one that satisfies the following formulas (1) and (2). Re(λ) represents the in-plane phase difference value relative to light of wavelength λ.

Re(450)/Re(550)≦1 (1)

1≦Re(630)/Re(550) (2)

When the phase difference film is of the first type and has reverse wavelength dispersion, the coloring of the black display in the display device can be reduced, so it is better. In formula (1), it is more preferable that 0.82≦Re(450)/Re(550)≦0.93. Furthermore, it is more preferable that 120≦Re(550)≦150.

When the phase difference film is a film having an optically anisotropic layer, the polymerizable liquid crystal compound can be listed as follows: compounds having a polymerizable group among the compounds described in "3.8.6 Network (Completely Crosslinked Type)" and "6.5.1 Liquid Crystal Material b. Polymerizable Nematic Liquid Crystal Material" in Liquid Crystal Handbook (Compiled by Liquid Crystal Handbook Editorial Committee, published by Maruzen Co., Ltd. on October 30, 2001), and polymerizable liquid crystal compounds described in Japanese Patent Publication No. 2010-31223, Japanese Patent Publication No. 2010-270108, Japanese Patent Publication No. 2011-6360, Japanese Patent Publication No. 2011-207765, Japanese Patent Publication No. 2016-81035, and Japanese International Publication No. 2017/043438.

The method of manufacturing a phase difference film from a polymer of a polymerizable liquid crystal compound in an aligned state can be exemplified by the method described in Japanese Patent Publication No. 2010-31223.

In the case of the second type, the in-plane phase difference value Re(550) can be adjusted in the range of 0 to 10 nm, preferably in the range of 0 to 5 nm, and the phase difference value R _th in the thickness direction can be adjusted in the range of -10 to -300 nm, preferably in the range of -20 to -200 nm.

The thickness direction retardation value _Rth , which means the refractive index anisotropy in the thickness direction, can be calculated from the retardation value R50 measured with the in-plane fast axis as the tilt axis at an inclination of 50 degrees and the in-plane retardation value _R0 . That is, the thickness direction retardation value Rth can be calculated by the following equations (4) to (6), by obtaining nx _{, ny} and _nz from the in-plane retardation value _R0 , the retardation value R50 measured with the fast axis as the tilt axis at an inclination of 50 degrees, the thickness d of the retardation film and the average refractive index _n0 of the retardation film, and substituting these into equation (3).

Rth=[(n _x +n _y )/2-n _z ]×d (3)

Re = (n _x - _{n y} ) × d (4)

(n _x +n _y +n _z )/3=n ₀ (6)

Here,

The phase difference film may be a multi-layer film having two or more layers. For example, a protective film is laminated on one or both sides of the phase difference film, or two or more phase difference films are laminated via an adhesive or bonding agent.

[4] First hardened layer

The first hardened material layer 15 is a hardened material layer composed of a hardened material of a hardening composition (S). The hardening composition (S) is as described above. The hardening composition (S) can be hardened, for example, by heat.

[5] Thermoplastic resin film

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 can be films made of light-transmitting (preferably optically transparent) thermoplastic resins, such as polyolefin resins such as chain polyolefin resins (polypropylene resins, etc.), cyclic polyolefin resins (norbornene resins, etc.); cellulose ester resins such as cellulose triacetate and cellulose diacetate; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate resins; (meth) acrylic resins; polystyrene resins or mixtures and copolymers thereof.

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be either an unstretched film or a uniaxially or biaxially stretched film. Biaxial stretching may be synchronous biaxial stretching in which the film is stretched in two stretching directions simultaneously, or sequential biaxial stretching in which the film is stretched in a first direction and then in a second direction different from the first direction.

The first thermoplastic resin film 10 and/or the second thermoplastic resin film 20 may be a protective film that performs the function of protecting the optical layer 30, or a protective film that also has an optical function such as a phase difference film.

The phase difference film can refer to the above description [4].

Chain polyolefin resins include homopolymers of chain olefins such as polyethylene resin and polypropylene resin, as well as copolymers composed of two or more chain olefins.

Cyclic polyolefin resins are a general term for resins containing cyclic olefins as polymerized units, with norbornene or tetracyclododecene (also known as dimethyl octahydronaphthalene) or their derivatives as representative examples. Examples of cyclic polyolefin resins include: ring-opening (co)polymers of cyclic olefins and their hydrogenates, addition polymers of cyclic olefins, copolymers of cyclic olefins with chain olefins such as ethylene and propylene or aromatic compounds having a vinyl group, and modified (co)polymers of these modified with unsaturated carboxylic acids or their derivatives.

Among them, it is preferable to use: a norbornene resin using a norbornene monomer such as norbornene or a polycyclic norbornene monomer as the cyclic olefin.

Cellulose ester resins are resins in which at least a portion of the hydroxyl groups in cellulose are esterified with acetic acid, and may be mixed esters in which a portion is esterified with acetic acid and a portion is esterified with other acids. Cellulose ester resins are preferably cellulose acetate resins.

Cellulose acetate resins include cellulose triacetate, cellulose diacetate, cellulose acetate propionate, cellulose acetate butyrate, etc.

Polyester resins are resins other than the above-mentioned cellulose resins that have ester bonds, and are generally composed of polycondensates of polycarboxylic acids or their derivatives and polyols.

Polyester resins include: polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, polycyclohexane dimethyl naphthalate, etc.

Among them, polyethylene terephthalate is preferably used from the perspectives of mechanical properties, solvent resistance, scratch resistance, cost, etc. The so-called polyethylene terephthalate means a resin in which more than 80 mol% of the repeating units are composed of ethylene terephthalate, and may contain constituent units from other copolymer components (dicarboxylic acid components such as isophthalic acid; glycol components such as propylene glycol, etc.).

Polycarbonate resins are polyesters formed from carbonic acid and diols or bisphenols. From the perspective of heat resistance, weather resistance, and acid resistance, aromatic polycarbonates with diphenylalkane in the molecular chain are preferably used.

Examples of polycarbonates include polycarbonates derived from bisphenols such as 2,2-bis(4-hydroxyphenyl)propane (also known as bisphenol A), 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)isobutane, and 1,11-bis(4-hydroxyphenyl)ethane.

(Meth) acrylic resins are polymers containing constituent units derived from (meth) acrylic monomers, and examples of (meth) acrylic monomers include methacrylate and acrylate.

Methacrylates include: methyl methacrylate, ethyl methacrylate, n-butyl, iso-butyl or tert-butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, etc.

Acrylates include: ethyl acrylate, n-butyl, iso-butyl or tertiary butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, etc.

(Meth) acrylic resins may be polymers composed only of constituent units derived from (meth) acrylic acid monomers, or may contain other constituent units.

In a preferred embodiment, the (meth)acrylic resin contains methyl methacrylate, or contains methyl methacrylate and methyl acrylate as copolymer components.

In a preferred embodiment, the (meth) acrylic resin may be a polymer having methacrylate as the main monomer (containing 50% by mass or more), preferably a copolymer of methyl methacrylate and other copolymer components.

The glass transition temperature of (meth) acrylic resin is preferably above 80°C and below 160°C. The glass transition temperature can be controlled by adjusting the polymerization ratio of methacrylate monomers and acrylate monomers, the carbon chain length of each ester group and the type of functional groups they have, and the polymerization ratio of multifunctional monomers relative to the total monomers.

Introducing a ring structure into the main chain of a polymer is also effective as a means for increasing the glass transition temperature of a (meth) acrylic resin. The ring structure is preferably a mixed ring structure such as a cyclic anhydride structure, a cyclic imide structure, and a lactone structure. Specifically, the following can be cited: cyclic anhydride structures such as glutaric anhydride structure and succinic anhydride structure; cyclic imide structures such as glutaramide structure and succinamide structure; lactone ring structures such as butyrolactone and valerolactone.

The greater the content of ring structure in the main chain, the tendency will be to increase the glass transition temperature of (meth) acrylic resin.

The cyclic anhydride structure and cyclic imide structure can be introduced by the following methods, namely, by copolymerizing monomers having a cyclic structure such as maleic anhydride and maleic imide; by introducing the cyclic anhydride structure by dehydration/demethylation condensation reaction after polymerization; by reacting an amino compound to introduce the cyclic imide structure, etc.

The resin (polymer) having a lactone ring structure can be obtained by preparing a polymer having a hydroxyl group and an ester group in the polymer chain, and then heating and optionally in the presence of a catalyst such as an organic phosphorus compound to cyclocondense the hydroxyl group and the ester group in the obtained polymer to form a lactone ring structure.

(Meth) acrylic resins and thermoplastic resin films formed therefrom may contain additives as needed. Examples of additives include lubricants, anti-caking agents, thermal stabilizers, antioxidants, antistatic agents, light-resistant agents, impact resistance improvers, surfactants, etc.

These additives can also be used when other thermoplastic resins other than (meth)acrylic resins are used as the thermoplastic resin constituting the thermoplastic resin film.

From the perspective of film-forming properties or impact resistance of the film, (meth) acrylic resins may contain acrylic rubber particles, which are impact modifiers. The so-called acrylic rubber particles are particles that use an elastic polymer mainly composed of acrylic ester as an essential component, and can be exemplified by: a single-layer structure consisting essentially of this elastic polymer, or a multi-layer structure that uses this elastic polymer as one layer.

Examples of the above-mentioned elastic polymer include: crosslinked elastic copolymers having alkyl acrylate as the main component and copolymerizing other vinyl monomers and crosslinking monomers that can be copolymerized with alkyl acrylate.

Examples of alkyl acrylates that are the main components of the elastic polymer include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc., where the carbon number of the alkyl group is about 1 to 8. Alkyl acrylates having an alkyl group with a carbon number of 4 or more are preferably used.

Other vinyl monomers that can be copolymerized with the above-mentioned alkyl acrylates include compounds having one polymerizable carbon-carbon double bond in the molecule. More specifically, they include: methyl methacrylate and other methacrylates; aromatic vinyl compounds such as styrene; vinyl cyanide compounds such as acrylonitrile, etc.

The above cross-linking monomers include cross-linking compounds having at least two polymerizable carbon-carbon double bonds in the molecule. More specifically, they include: (meth)acrylates of polyols such as ethylene glycol di(meth)acrylate and butylene glycol di(meth)acrylate; (meth)acrylate esters such as allyl (meth)acrylate; divinylbenzene, etc.

A thermoplastic resin film bonded to the optical layer 30 may be formed by laminating a film composed of a (meth) acrylic resin containing no rubber particles and a film composed of a (meth) acrylic resin containing rubber particles. In addition, a (meth) acrylic resin layer may be formed on one or both sides of a phase difference display layer composed of a resin different from the (meth) acrylic resin to display a phase difference, and the film may be formed as a thermoplastic resin film bonded to the optical layer 30.

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 are preferably films respectively containing one or more thermoplastic resins selected from the group consisting of cellulose ester resins, polyester resins, (meth) acrylic resins and cyclic polyolefin resins, and are more preferably cellulose ester resin films, polyester resin films, (meth) acrylic resin films or cyclic polyolefin resin films.

The first thermoplastic resin film 10 and/or the second thermoplastic resin film 20 may contain: ultraviolet absorbers, infrared absorbers, organic dyes, pigments, inorganic pigments, antioxidants, antistatic agents, surfactants, lubricants, dispersants, thermal stabilizers, etc. When the optical laminate is applied to an image display device, the thermoplastic resin film containing the ultraviolet absorber is arranged on the viewing side of the image display element (such as a liquid crystal unit or an organic EL display element, etc.), so that the degradation of the image display device caused by ultraviolet rays can be suppressed.

Ultraviolet absorbers include: salicylate compounds, diphenyl ketone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex salt compounds, etc.

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be films composed of the same thermoplastic resin film or films composed of different thermoplastic resin films. The first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be the same or different in thickness, presence or absence of additives or their types, phase difference characteristics, etc.

The first thermoplastic resin film 10 and/or the second thermoplastic resin film 20 may have a surface treatment layer (coating layer) such as a hard coating layer, an anti-glare layer, an anti-reflection layer, a light diffusion layer, an anti-static layer, an anti-fouling layer, and a conductive layer on its outer surface (the surface opposite to the optical layer 30).

The thickness of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is usually 5 μm to 200 μm, preferably 10 μm to 120 μm, more preferably 10 μm to 85 μm, and even more preferably 15 μm to 65 μm. The thickness of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 can be 50 μm or less, or 40 μm or less. Reducing the thickness of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is beneficial to the thinning of the optical laminate (polarizing plate) and the image display device containing the same.

The surfaces of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 coated with the curable composition may be subjected to surface modification treatments such as saponification treatment, plasma treatment, corona treatment, and primer treatment from the viewpoint of improving adhesion, but may not be subjected to surface modification treatment from the viewpoint of simplifying the steps. The surface modification treatment may be performed on the bonding surface of the optical layer 30 instead of or in conjunction with the bonding surface of the thermoplastic resin film.

When the first thermoplastic resin film 10 or the second thermoplastic resin film 20 is a cellulose ester resin film, it is preferable to perform a saponification treatment from the viewpoint of improving adhesion. The saponification treatment may include a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

[6] Second hardened layer

The curable composition forming the second curable layer 25 may be the above-mentioned curable composition (S) or another curable composition different therefrom. From the perspective of the optical durability of the optical laminate in a high temperature and high humidity environment, the second curable layer 25 is preferably a curable layer of the curable composition (S).

When the first hardened material layer 15 and the second hardened material layer 25 are formed of hardening compositions (S), these hardening compositions may be of the same composition or different compositions.

Other curable compositions include: generally known water-based compositions (containing water-based adhesives) in which a curable resin component is dissolved or dispersed in water, and generally known active-energy-ray-curable compositions (containing active-energy-ray-curable adhesives) containing active-energy-ray-curable compounds, etc.

The resin components contained in the water-based composition include polyvinyl alcohol resins or urethane resins.

In order to improve adhesion or bonding, the water-based composition containing polyvinyl alcohol resin may further contain: polyaldehyde, melamine compound, zirconium dioxide compound, zinc compound, glyoxal, glyoxal derivatives, water-soluble epoxy resin and other hardening components or crosslinking agents.

The water-based composition containing urethane resin can be listed as follows: the water-based composition containing polyester-based ionic polymer urethane resin and a compound having a glycidyloxy group. The so-called polyester-based ionic polymer urethane resin is a urethane resin having a polyester skeleton and into which a small amount of ionic components (hydrophilic components) are introduced.

The active energy ray-curable composition is a composition that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. When the active energy ray-curable composition is used, the second cured layer 25 is a cured layer of the composition.

The active energy radiation curable composition may be a composition containing an epoxy compound that cures by cationic polymerization as a curable component, preferably a UV curable composition containing the epoxy compound as a curable component. The so-called epoxy compound means a compound having an average of more than one, preferably more than two epoxy groups in the molecule. Only one epoxy compound may be used or two or more epoxy compounds may be used in combination.

Epoxy compounds include: hydrogenated epoxide compounds (glycidyl ethers of polyols having alicyclic rings) obtained by reacting alicyclic polyols obtained by hydrogenating aromatic rings of aromatic polyols with epichlorohydrin; aliphatic epoxide compounds such as polyglycidyl ethers of aliphatic polyols or oxirane adducts; alicyclic epoxide compounds having one or more epoxy groups bonded to alicyclic rings in the molecule, etc.

The active energy radiation curable composition may contain a free radical polymerizable (meth) acrylic compound to replace the above-mentioned epoxy compound or together with the epoxy compound as a curable component. The (meth) acrylic compound can be listed as: (meth) acrylic ester monomers having one or more (meth) acrylic ester groups in the molecule; (meth) acrylic ester oligomers having at least two (meth) acrylic ester groups in the molecule obtained by reacting two or more functional group-containing compounds, etc.

In the case of containing an epoxy compound that cures by cationic polymerization as a curing component, the active energy radiation curing composition preferably contains a photo-cationic polymerization initiator. Examples of photo-cationic polymerization initiators include: onium salts such as aromatic diazonium salts, aromatic iodonium salts, or aromatic stibnium salts; and iron-allene complexes, etc.

In the case of containing free radical polymerizable components such as (meth) acrylic acid compounds, the active energy radiation curable composition preferably contains a photo radical polymerization initiator. Examples of photo radical polymerization initiators include: acetophenone initiators, diphenyl ketone initiators, benzoin ether initiators, thioxanthone initiators, xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone, etc.

The optical laminate may contain an adhesive layer instead of the second hardened material layer 25. That is, the second thermoplastic resin film 20 may be bonded to the optical layer 30 via the adhesive layer. Regarding the adhesive layer, the description of the adhesive layer described later may be cited.

[7] Fabrication of optical laminates

The first thermoplastic resin film 10 is laminated on one side of the optical layer 30 via the first curing layer 15, thereby obtaining the optical laminate structure shown in FIG. 2, and the second thermoplastic resin film 20 is laminated on the other side of the optical layer 30 via the second curing layer 25, thereby obtaining the optical laminate structure shown in FIG. 3.

When manufacturing an optical laminate having both the first thermoplastic resin film 10 and the second thermoplastic resin film 20, the films can be laminated one side at a time, or the films on both sides can be laminated at the same time.

The method of bonding the optical layer 30 and the first thermoplastic resin film 10 can be listed as follows: applying the curable composition (S) to one or both of the bonding surfaces of the optical layer 30 and the first thermoplastic resin film 10, laminating the bonding area of the other side thereon, and bonding them by pressing from the top and bottom using, for example, a bonding roller.

The curable composition (S) can be applied by various coating methods such as scraper coating, winding bar coating, die coating machine, comma wheel coating machine, gravure coating machine, etc. In addition, the curable composition (S) can be poured between the optical layer 30 and the first thermoplastic resin film 10 while continuously supplying them with the bonding surface of the two facing the inner side.

After the optical layer 30 and the first thermoplastic resin film 10 are bonded, it is preferred to heat the laminate including the optical layer 30, the first curing layer 15 and the first thermoplastic resin film 10. The temperature of the heat treatment is, for example, 40°C to 100°C, preferably 50°C to 90°C. The heat treatment can remove the solvent contained in the curable composition layer. In addition, the heat treatment can perform a curing/crosslinking reaction of the curable composition.

The above bonding method can also be applied to the bonding between the optical layer 30 and the second thermoplastic resin film 20.

When an active energy ray-curable composition is used as the curable composition constituting the second curable layer, the curable composition layer may be cured by irradiating the active energy ray after drying the curable composition layer as needed.

The light source used for irradiating the active energy ray can be any light source that can generate ultraviolet rays, electron beams, X-rays, etc. It is preferable to use a light source that has a luminescence distribution below a wavelength of 400nm, such as a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, etc.

As shown in FIG. 1 , an optical laminate having no first thermoplastic resin film on the first curing material layer 15 can be manufactured by applying a curable composition (S) on the surface of the optical layer 30 and subjecting the obtained laminate to a heat treatment at 80°C for 30 seconds, for example, using a hot air dryer. In addition, after manufacturing a laminate consisting of a separation film/curable composition (S)/optical layer 30, even if a heat treatment is applied after the separation film is peeled off, the optical laminate shown in FIG. 1 can be manufactured.

The thickness of the first hardened material layer 15 or the second hardened material layer 25 formed by the hardening composition (S) is, for example, 1 nm to 20 μm, preferably 5 nm to 10 μm, more preferably 10 nm to 5 μm, and even more preferably 20 nm to 1 μm. The hardened material layer formed by the above-mentioned generally known aqueous composition may also have a thickness of the same degree.

The thickness of the hardened layer formed by the active energy radiation-hardening composition is, for example, 10 nm to 20 μm, preferably 100 nm to 10 μm, and more preferably 500 nm to 5 μm.

The thickness of the first hardened layer 15 and the second hardened layer 25 may be the same or different.

[8]Other components of optical laminates

[8-1]Optical functional films

The optical laminate may also have other optical functional films besides the optical layer 30 (such as a polarizer) for imparting the desired optical function, a preferred example of which is a phase difference film.

As described above, the first thermoplastic resin film 10 and/or the second thermoplastic resin film 20 can also serve as a phase difference film, but a phase difference film different from these films can also be laminated. In the latter case, the phase difference film can be laminated on the outer surface of the first thermoplastic resin film 10, the second thermoplastic resin film 20, the first hardened material layer 15 and/or the second hardened material layer 25 via an adhesive layer or a bonding agent layer. Regarding the phase difference film, the above-mentioned description [4] can be cited.

Examples of other optical functional films (optical components) that can be included in optical laminates such as polarizing plates include focusing plates, brightness enhancement films, reflective layers (reflective films), semi-transmissive reflective layers (semi-transmissive reflective films), light diffusion layers (light diffusion films), etc.

The focusing plate is used for the purpose of controlling the light diameter, etc. It can be a prism array plate or a lens array plate, a thin plate with dots, etc.

Brightness enhancement films are used to enhance the brightness of image display devices that use optical laminates such as polarizers. Specifically, they include: reflective polarizing separators designed to produce anisotropy in reflectivity by laminating multiple sheets of thin films with different refractive indices, circular polarizing separators that support the alignment film of cholesterol liquid crystal polymer or its alignment liquid crystal layer on a substrate film, etc.

The reflective layer, semi-transmissive reflective layer, and light diffusion layer are used to set the polarizer as a reflective, semi-transmissive, and diffusion optical component, respectively. The reflective polarizer is used in a liquid crystal display device that reflects the incident light from the viewing side and displays it. Since light sources such as backlight can be omitted, it is easy to make the liquid crystal display device thinner. The semi-transmissive polarizer is used in a liquid crystal display device that is reflective in bright places and displays with light from the backlight in dark places. In addition, the diffusion polarizer is used in a liquid crystal display device that imparts light diffusion properties to suppress display defects such as moire. The reflective layer, semi-transmissive reflective layer, and light diffusion layer can be formed by generally known methods.

[8-2] Adhesive layer

The optical laminate may include an adhesive layer. The adhesive layer may include an adhesive layer used to attach the optical laminate to an image display element such as a liquid crystal unit or an organic EL display element or other optical components. In the optical laminate structure shown in FIG. 1 or FIG. 2, the adhesive layer can be deposited on the outer surface of the optical layer 30, in the optical laminate structure shown in FIG. 3, it can be deposited on the outer surface of the first thermoplastic resin film 10 or the second thermoplastic resin film 20, in the optical laminate structure shown in FIG. 4, it can be deposited on the outer surface of the first hardened material layer 15 or the second thermoplastic resin film 20, and in the optical laminate structure shown in FIG. 5, it can be deposited on the outer surface of the first hardened material layer 15 or the second hardened material layer 25.

An example of an adhesive layer 40 being layered on the outer surface of the second thermoplastic resin film 20 of the optical laminate structure shown in FIG3 is shown in FIG6.

The adhesive used in the adhesive layer can be: (meth) acrylic resin, silicone resin, polyester resin, polyurethane resin, polyether resin, etc. as the base polymer. Among them, from the perspective of transparency, adhesion, reliability, weather resistance, heat resistance, heavy processability, etc., (meth) acrylic adhesive is preferred.

In the (meth)acrylic adhesive, the following (meth)acrylic resin is used as a base polymer, that is, it is formulated in a manner such that the glass transition temperature is preferably below 25°C, and more preferably below 0°C: (meth)acrylic acid alkyl ester having an alkyl group with a carbon number of 20 or less such as methyl, ethyl, or n-, iso- or tert-butyl, and a (meth)acrylic acid monomer containing a functional group such as (meth)acrylic acid or hydroxyethyl (meth)acrylate, and the weight average molecular weight of the (meth)acrylic resin is above 100,000.

The adhesive layer can be formed on the optical laminate by, for example: dissolving or dispersing the adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare an adhesive liquid, and applying the adhesive liquid directly to the target surface of the optical laminate to form the adhesive layer; or forming the adhesive layer in a sheet form on a release film after a mold release treatment, and then transferring the adhesive layer to the target surface of the optical laminate.

The thickness of the adhesive layer is determined according to its adhesion, etc., and is preferably in the range of 1μm to 50μm, and preferably in the range of 2μm to 40μm.

The optical laminate may include the above-mentioned separation film. The separation film may be a film composed of polyethylene resins such as polyethylene, polypropylene resins such as polypropylene, polyester resins such as polyethylene terephthalate, etc. Among them, the stretched film of polyethylene terephthalate is preferred.

The adhesive layer may contain glass fibers, glass beads, resin beads, fillers composed of metal powder or other inorganic powders, pigments, colorants, antioxidants, ultraviolet absorbers, antistatic agents, etc. as needed.

[8-3] Protective film

The optical laminate may include a protective film for protecting its surface (typically the surface of the first thermoplastic resin film 10, the second thermoplastic resin film 20, the first hardened layer 15 and/or the second hardened layer 25). The protective film is completely peeled off and removed together with the adhesive layer after the optical laminate is attached to an image display device or other optical components.

The protective film may be composed of, for example, a substrate film and an adhesive layer laminated thereon. The adhesive layer may be the one described above.

The resin constituting the substrate film may be, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, a polycarbonate resin, or other thermoplastic resin. Polyester resins such as polyethylene terephthalate are preferred.

〈Image display device〉

The optical multilayer of the present invention can be used in image display devices such as liquid crystal display devices or organic electroluminescent (EL) display devices. In this case, the image display device includes an optical multilayer and an image display element. The image display element can include a liquid crystal unit, an organic EL display element, etc. Such image display elements can use those generally known in the past.

When an optical laminate belonging to a polarizing plate is applied to a liquid crystal display device, the optical laminate can be arranged on the backlight side (back side) of the liquid crystal unit, or on the viewing side, or on both sides. When an optical laminate belonging to a polarizing plate is applied to an organic EL display device, the optical laminate is usually arranged on the viewing side of the organic EL display element.

[Implementation example]

The following are examples to more specifically illustrate the present invention, but the present invention is not limited to these examples. The "%" and "parts" in the examples and comparative examples are mass % and mass parts unless otherwise specified.

[Manufacturing example: Production of polarizer]

A 60μm thick polyvinyl alcohol film (average degree of polymerization: about 2,400, saponification degree: 99.9 mol% or more) was immersed in 30°C pure water, and then immersed in a 30°C aqueous solution with a mass ratio of iodine/potassium iodide/water of 0.02/2/100. Then, it was immersed in a 56.5°C aqueous solution with a mass ratio of potassium iodide/boric acid/water of 12/5/100. After washing with 8°C pure water, it was dried at 65°C to obtain a 23μm thick polarizer with iodine adsorption alignment on the polyvinyl alcohol film. Stretching was mainly carried out in the steps of iodine dyeing and boric acid treatment, and the total stretching ratio was 5.5 times.

[Examples 1 to 4, Comparative Examples 1 and 2]

(1) Preparation of hardening composition

The curable composition (adhesive aqueous solution) is prepared by mixing the components shown in Table 1 with pure water as an aqueous solvent in the amounts shown in Table 1. The units of the amounts of each component shown in Table 1 are parts by mass, and the amounts of each component are converted to solid content. In Examples 1 to 4 and Comparative Examples 1 and 2, the concentration of the aqueous resin (A) in the obtained curable composition is 5.0% by mass.

[2] Production of polarizing plates

After saponification treatment was applied to one side of a triacetyl cellulose (TAC) film [trade name "KC4UAW" manufactured by Konica Minolta Opto Co., Ltd., thickness 40 μm], the curable composition prepared in the above (1) was applied to the saponification-treated side using a bar coater. In addition, a zero retardation film composed of a cyclic polyolefin resin [trade name "ZEONOR" manufactured by Zeon Japan Co., Ltd., thickness 23 μm] was subjected to corona treatment on one side, and the curable composition prepared in the above (1) was applied to the corona-treated side using a bar coater. The TAC film that has been saponified is laminated on one side of the polarizer, and the zero phase difference film that has been corona treated is laminated on the other side so that the curable component layer becomes the polarizer side, thereby obtaining a laminate having a layer structure of zero phase difference film/curable component layer/polarizer/curable component layer/TAC film. The laminate is heated at 80°C for 30 seconds in a hot air dryer to produce a polarizing plate having a layer structure of zero phase difference film/curable layer/polarizer/curable layer/TAC film. The thickness of the cured layer in the produced polarizing plate is 20 to 60nm per layer.

(3) Evaluation of optical durability

The obtained polarizing plate was cut into a size of 30 mm × 30 mm, and then attached to a glass substrate via a (meth) acrylic adhesive on the zero phase difference film side to obtain a measurement sample. The layer structure of the measurement sample is glass substrate/(meth) acrylic adhesive layer/zero phase difference film/cured layer/polarizer/cured layer/TAC film. The glass substrate used was an alkali-free glass substrate [trade name "Eagle XG" manufactured by Corning].

Using an integrating sphere spectrophotometer [product name "V7100" manufactured by JASCO Corporation], the MD transmittance and TD transmittance of the obtained measurement sample in the wavelength range of 380 to 780nm were measured, and the polarization degree at each wavelength was calculated. The calculated polarization degree was corrected for visual sensitivity using the 2-degree field (C light source) of JIS Z 8701:1999 "Color display method - XYZ colorimetric system and X10Y10Z10 colorimetric system" to obtain the visual sensitivity corrected polarization degree Py before the durability test. The measurement sample uses the TAC film side of the polarizing plate as the detection side, and the integrating sphere spectrophotometer is set in a way that the light is incident from the glass substrate side.

Polarization degree (%) is defined by the following formula.

Polarization degree (λ)=100×(Tp(λ)-Tc(λ))/(Tp(λ)+Tc(λ))

Tp(λ) is the transmittance (%) of the test sample measured in parallel Nicol relationship with incident linear polarized light of wavelength λ(nm).

Tc(λ) is the transmittance (%) of the test sample measured in the orthogonal Nicol relationship with the incident linear polarization of wavelength λ(nm).

The test sample was then subjected to the following durability test: After being placed in a high temperature and high humidity environment of 85°C and 85%RH for 500 hours, it was placed in an environment of 23°C and 50%RH for 24 hours. After the durability test, the visual sensitivity correction polarization degree Py was obtained using the same method as before the durability test.

The absolute value (|△Py|) of the difference between the corrected polarization degree Py of the visual sensitivity after the durability test and the corrected polarization degree Py of the visual sensitivity before the durability test is calculated. The calculated value of |△Py| is shown in Table 1.

The smaller the value of |△Py|, the better the optical durability in a high temperature and high humidity environment. In any embodiment and comparative example, the difference between the visual sensitivity corrected polarization degree Py after the durability test and the visual sensitivity corrected polarization degree Py before the durability test shows a negative value.

(4) Evaluation of adhesion

On the zero phase difference film side, the obtained polarizing plate was bonded to a glass substrate via a (meth) acrylic adhesive to form an adhesive layer polarizing plate. A test piece with a width of 25 mm and a length of about 200 mm was cut from the obtained adhesive layer polarizing plate, and its adhesive layer surface was bonded to sodium glass. Then, the blade of the cutter was inserted between the polarizing plate and the TAC film, and 30 mm was peeled off from the end in the length direction, and then the peeled part was gripped with the gripping part of a universal tensile testing machine ["AG-1" manufactured by Shimadzu Corporation]. In an environment of 23℃ and relative humidity of 55%, according to JIS K 6854-2:1999 "Adhesives - Peel-off Bond Strength Test Method - Part 2: 180-degree Peel", the test piece in this state was subjected to a 180-degree peel test at a gripping speed of 300mm/minute, and the adhesion of the 30mm gripping part covering a length of 170mm was obtained. The results are shown in Table 1.

[Table 1]

The details of each component shown in Table 1 are described below.

A-1 of water-based resin (A): "Epocros WS-300" manufactured by Nippon Catalyst Co., Ltd. [aqueous solution of an oxazolyl-containing acrylic polymer having 2-oxazolyl groups as side chains, solid content: 10% by mass, oxazoline value (theoretical value): 130 g solid/eq., oxazolyl amount (theoretical value): 7.7 mmol/g, solid, number average molecular weight: 4×10 ⁴ , weight average molecular weight: 12×10 ⁴ ]

A-2 of water-based resin (A): "Gohsefimer Z-200" manufactured by Nippon Synthetic Chemical Industry Co., Ltd. [Polyvinyl alcohol modified with acetyl groups, average degree of polymerization: 1100, saponification degree: 98.5 mol% or more]

Silane compound (B): Product name "X-12-1135" manufactured by Shin-Etsu Chemical Co., Ltd. [Silane compound having carboxyl group and silanol group]

Compound (C): sulfuric acid

15: First hardened layer

30: Optical layer

Claims (14)

A curable composition, which at least comprises: a water-based resin and a silane compound having a silanol group; the water-based resin comprises a (meth) acrylic resin; when the solid concentration of the curable composition is set to 100% by mass, the content of the water-based resin is 30% by mass or more; the silane compound further comprises: a Si-O-Si bond, and one or more functional groups selected from the group consisting of (hydroxyalkyl)amino, carboxyl, acetyl acetyl and oxyalkylene. The curable composition as described in claim 1, wherein the water-based resin further comprises a hydroxyl-containing resin. A curable composition, which at least comprises: a water-based resin and a silane compound having a silanol group; the water-based resin comprises a hydroxyl-containing resin; when the solid concentration of the curable composition is set to 100% by mass, the content of the water-based resin is 35% by mass or more; the silane compound further comprises: a Si-O-Si bond, and one or more functional groups selected from the group consisting of (hydroxyalkyl)amino, carboxyl, acetylacetyl and oxyalkylene. The curable composition as described in claim 3, wherein the water-based resin further comprises a (meth) acrylic resin. The curable composition as described in any one of claims 2 to 4, wherein the hydroxyl-containing resin comprises at least one of a polyvinyl alcohol resin and a polyvinyl acetal resin. A curable composition as described in any one of claims 1 to 4, wherein the functional group is a carboxyl group. A curable composition as described in any one of claims 1 to 4, wherein the structure of the silane compound has the functional group. A hardened layer formed by hardening the hardening composition as described in any one of claims 1 to 7. An optical laminate, comprising: an optical layer and a first hardened layer; the first hardened layer is the hardened layer as described in claim 8. The optical laminate as described in claim 9 further comprises a first thermoplastic resin film; the optical layer, the first hardened material layer and the first thermoplastic resin film are sequentially laminated in the optical laminate. The optical laminate as described in claim 9 or 10 further comprises: a second hardened material layer and a second thermoplastic resin film; the second hardened material layer and the second thermoplastic resin film are sequentially laminated on the side of the optical layer opposite to the side of the first hardened material layer. The optical laminate as described in claim 11, wherein the second hardened layer is the hardened layer as described in claim 8. An optical layered body as described in claim 9 or 10, wherein the optical layer is a polarizer. An image display device, comprising: an optical multilayer as described in any one of claims 9 to 13 and an image display element.

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