TWI912245B - Optical laminate and image display device - Google Patents

Abstract

An object of the present invention is to provide an optical laminate having excellent optical durability in high temperature and high humidity environments, and an image display device including the same.

The optical laminate contains an optical layer and a cured product layer, and the cured product layer contains a first cured product layer which is a cured product of the polyvinyl acetal resin-containing composition (S). The polyvinyl acetal resin-containing composition (S) contains a polyvinyl acetal resin (A) and a cross-linking agent (B), and the crosslinking agent (B) contains a crosslinking agent (B1) which is at least one of an isocyanate-based crosslinking agent and a carbodiimide-based crosslinking agent.

Description

Optical laminates and image display devices

This invention relates to an optical laminate and an image display device having the optical laminate.

In recent years, LCD displays have been developed for applications in mobile devices, such as smartphones and tablets, and in automotive devices, such as car navigation systems. In these applications, compared to traditional indoor television, improving device durability is a challenge due to the potential exposure to harsher environments.

The same requirement applies to optical films constituting liquid crystal display devices. That is, optical films assembled in liquid crystal display devices are sometimes placed in high-temperature or high-temperature-high-humidity environments, or in environments with repeated high and low temperatures, but even under these conditions, their optical properties must not deteriorate.

Patent document 1 describes a polarizing plate composed of a laminate formed by stacking a polarizer and a protective film with an adhesive component in between, used as an optical film for a display device.

[Previous Technical Documents]

[Patent Documents]

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

The purpose of this invention is to provide an optical laminate with good optical durability under high temperature and high humidity environments, and an image display device having the optical laminate.

This invention provides an optical laminate and an image display device, as shown below.

[1] An optical laminate comprising an optical layer and a hardening layer; wherein,

The aforementioned hardened layer includes a first hardened layer, which is a hardened material containing a composition (S) of polyvinyl alcohol acetal resin;

The aforementioned composition (S) containing polyvinyl acetal resin includes polyvinyl acetal resin (A) and a crosslinking agent (B);

The aforementioned crosslinking agent (B) includes crosslinking agents (B1) that belong to at least one of isocyanate-based crosslinking agents and carbodiimide-based crosslinking agents.

[2] As described in [1], in which the degree of acetalization of the aforementioned polyvinyl alcohol acetal resin (A) does not reach 50 moles.

[3] The optical laminate as described in [1] or [2], wherein, relative to 100 parts by mass of the aforementioned polyvinyl acetal resin (A) and the aforementioned crosslinking agent (B1), the content of the aforementioned crosslinking agent (B1) in the aforementioned composition (S) containing polyvinyl acetal resin is 10 parts by mass or more and 60 parts by mass or less.

[4] The optical laminate described in any of [1] to [3] consists of, in sequence, the aforementioned optical layer, the aforementioned first hardened layer, and the first thermoplastic resin film.

[5] The optical laminate as described in [4], wherein the aforementioned first thermoplastic resin film is a film comprising one or more thermoplastic resins selected from the group consisting of cellulose ester resins, polyester resins, (meth)acrylate resins, and cyclic olefin resins.

[6] An optical laminate as described in [4] or [5], wherein the aforementioned first thermoplastic resin film is a cellulose ester resin film comprising a cellulose ester resin;

The aforementioned cellulose ester resin film directly contacts the aforementioned first hardened layer;

In the aforementioned cellulose ester resin film, on the surface of the first hardened layer, where the hydroxyl groups on that surface have been derivatized using a fluorine-based derivatization reagent, the concentration of fluorine is 2.0 atomic percent or less.

[7] An optical laminate as described in any of [1] to [6], wherein the aforementioned hardened layer comprises a second hardened layer;

On the side of the aforementioned optical layer opposite to the side of the aforementioned first hardened layer, the aforementioned second hardened layer and the second thermoplastic resin film are sequentially deposited.

[8] An optical laminate as described in [7], wherein the aforementioned second thermoplastic resin film is a film comprising one or more thermoplastic resins selected from the group consisting of cellulose ester resins, polyester resins, (meth)acrylate resins, and cyclic olefin resins.

[9] An optical laminate as described in [7] or [8], wherein the aforementioned second hardened layer is a hardened form of the aforementioned composition (S) containing polyvinyl acetal resin.

[10] The optical laminate as described in [9], wherein the aforementioned second thermoplastic resin film is a cellulose ester resin film comprising a cellulose ester resin;

The aforementioned cellulose ester resin film directly contacts the aforementioned second hardened layer;

In the aforementioned cellulose ester resin film, on the surface of the second hardened layer, where the hydroxyl groups on that surface have been derivatized using a fluorine-based derivatization reagent, the concentration of fluorine is 2.0 atomic% or less.

[11] An optical laminate as described in any of [1] to [10], wherein the aforementioned optical layer is a polarizer.

[12] An image display device comprising the optical laminate and image display element described in any one of [1] to [11].

According to the present invention, an optical laminate with good optical durability under high temperature and high humidity environments and an image display device having the optical laminate can be provided.

10: First thermoplastic resin film

15: First hardened layer

20: Second thermoplastic resin film

25: Second hardened layer

30: Optical layer

40: Adhesive layer

Figure 1 is a schematic cross-sectional view showing an example of the optical laminate of the present invention.

Figure 2 is a schematic cross-sectional view showing another example of the layered structure of the optical laminate of the present invention.

Figure 3 is a schematic cross-sectional view showing another example of the layered structure of the optical laminate of the present invention.

Figure 4 is a schematic cross-sectional view showing another example of the layered structure of the optical laminate of the present invention.

Figure 5 is a schematic cross-sectional view showing another example of the layered structure of the optical laminate of the present invention.

Figure 6 is a schematic cross-sectional view showing another example of the layered structure of the optical laminate of the present invention.

Figure 7 is a schematic cross-sectional view showing another example of the layered structure of the optical laminate of the present invention.

<Optical Laminations>

The optical laminate of the present invention includes an optical layer and a hardening layer, the hardening layer including a first hardening layer, which is a hardened composition (S) containing polyvinyl alcohol acetal resin (hereinafter, sometimes referred to as "composition (S)").

Composition (S) is a curable composition and comprises polyvinyl acetal resin (A) and a crosslinking agent (B), wherein the crosslinking agent (B) comprises a crosslinking agent (B1) belonging to at least one of isocyanate-based crosslinking agents and carbodiimide-based crosslinking agents.

The optical laminate of this invention exhibits excellent optical durability in high-temperature and high-humidity environments because its first hardened layer is a hardened form of component (S).

Furthermore, the optical laminate of this invention, even without undergoing the surface modification treatments described later, such as saponification, plasma treatment, corona treatment, and primer treatment, can still become an optical laminate with good interlayer adhesion.

[1] Composition of optical layers

Examples of the layered structure of optical laminates are shown in Figures 1 to 6.

The optical laminate shown in Figure 1 includes an optical layer 30 and a first hardened layer 15 deposited on one side of it. The first hardened layer 15 can function as a cover layer to cover and protect the surface of the optical layer 30, or as an optical functional layer to add optical functions to the optical layer 30.

Optical layer 30 and the first hardened layer 15 are preferably in direct contact.

The optical laminate shown in Figure 2 includes an optical layer 30 and a first thermoplastic resin film 10 laminated and adhered to one side of it, separated by a first hardening layer 15. The first hardening layer 15 functions as an adhesive layer between the optical layer 30 and the first thermoplastic resin film 10.

Preferably, the first hardened layer 15 and the first thermoplastic resin film 10 are in direct contact.

Optical layer 30 and the first hardened layer 15 are preferably in direct contact.

The optical laminate shown in Figure 3 includes an optical layer 30, a first thermoplastic resin film 10 laminated and bonded to one side of the optical layer 30 through a first curing layer 15, and a second thermoplastic resin film 20 laminated and bonded to the other side of the optical layer 30 through a second curing layer 25. That is, the optical laminate of the present invention may sequentially 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. The first hardened layer 15 and the second hardened layer 25 function as adhesive layers between the optical layer 30 and the first thermoplastic resin film 10, and between the optical layer 30 and the second thermoplastic resin film 20, respectively.

The second hardened layer 25 and the second thermoplastic resin film 20 are preferably in direct contact.

Optical layer 30 and the second hardened layer 25 are preferably in direct contact.

The optical laminate shown in Figure 4 includes an optical layer 30, a first hardened layer 15 deposited on one side of the optical layer 30, and a second thermoplastic resin film 20 deposited and bonded to the other side of the optical layer 30 via a second hardened layer 25. The first hardened layer 15 functions as a cover layer to cover and protect the surface of the optical layer 30, or as an optical functional layer to add optical functions to the optical layer 30. The second hardened layer 25 functions as an adhesive layer between the optical layer 30 and the second thermoplastic resin film 20.

Optical layer 30 and the first hardened layer 15 are preferably in direct contact.

The second hardened layer 25 and the second thermoplastic resin film 20 are preferably in direct contact.

Optical layer 30 and the second hardened layer 25 are preferably in direct contact.

The optical laminate shown in Figure 5 includes an optical layer 30, a first thermoplastic resin film 10 laminated and adhered to one side of the optical layer 30 through a first hardening layer 15, and a second hardening layer 25 laminated to the other side of the optical layer 30. The first hardening layer 15 functions as an adhesive layer between the optical layer 30 and the first thermoplastic resin film 10. The second hardening layer 25 functions as a cover 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.

Optical layer 30 and the first hardened layer 15 are preferably in direct contact.

Preferably, the first hardened layer 15 and the first thermoplastic resin film 10 are in direct contact.

Optical layer 30 and the second hardened layer 25 are preferably in direct contact.

The optical laminate shown in Figure 6 includes an optical layer 30, a first hardened layer 15 deposited on one side of the optical layer 30, and a second hardened layer 25 deposited on the other side of the optical layer 30. The first hardened layer 15 and the second hardened layer 25 can function as cover layers to cover and protect the surface of the optical layer 30, or as optical functional layers to add optical functions to the optical layer 30.

Optical layer 30 and the first hardened layer 15 are preferably in direct contact.

Optical layer 30 and the second hardened layer 25 are preferably in direct contact.

Each of the aforementioned optical laminates may include an adhesive layer in place of the second hardened layer 25. That is, the second thermoplastic resin film 20 may be bonded to the optical layer 30 through the adhesive layer. The description of the adhesive layer, as described later, is used for reference.

The optical layer 30 can be various optical films (films with optical properties) that can be assembled into image display devices such as liquid crystal displays. Examples of optical layers 30 include polarizers, retardation films, brightness enhancement films, anti-glare films, anti-reflective films, diffusion films, and light-concentrating films.

The optical laminate may include other layers (or films) besides those described above. Other layers may include, for example: an adhesive layer deposited on the outer surfaces of the first thermoplastic resin film 10, the second thermoplastic resin film 20, the first hardened layer 15, the second hardened layer 25, and/or the optical layer 30; a release membrane (also called a "peel-off membrane") deposited on the outer surface of the adhesive layer; and layers deposited on the first thermoplastic resin film 10, the second thermoplastic resin film 20, the first hardened layer 15, the second hardened layer 25, and/or the optical layer 30. A protective film (also referred to as a "surface protective film") on the outer surface of the hardened layer 15, the second hardened layer 25, and/or the optical layer 30; an optically functional film (or layer) deposited on the outer surface of the first thermoplastic resin film 10, the second thermoplastic resin film 20, the first hardened layer 15, the second hardened layer 25, and/or the optical layer 30 through an adhesive layer or bonding agent layer, etc.

[2] Hardened layer

The optical laminate of this invention may include a first hardened layer 15, or it may further include a second hardened layer 25.

The first hardened layer 15 is a hardened form of composition (S), which is a hardening component. Composition (S) comprises polyvinyl acetal resin (A) and a crosslinking agent (B), wherein the crosslinking agent (B) comprises a crosslinking agent (B1) that is at least one of an isocyanate-based crosslinking agent and a carbodiimide-based crosslinking agent. Composition (S) can be hardened by, for example, heat.

The second hardening layer 25 is not particularly limited to being a hardened form of a hardening component; it can be a hardened form of component (S) or a hardened form of another hardening component different from component (S). From the viewpoint of optical durability of the optical laminate in high-temperature and high-humidity environments, the second hardening layer 25 is preferably a hardened form of component (S).

In the case where the first hardened layer 15 and the second hardened layer 25 are formed of a hardening component (S), these hardening components may be of the same composition or different compositions.

[2-1] Composition (S) containing polyvinyl alcohol acetal resin (Composition (S))

The composition (S) can be used as a coating liquid for forming a coating film (coating layer) on a substrate. A coating film can be formed by, for example, applying the composition (S) to the substrate and allowing the coating layer to harden. The substrate is preferably an optical layer. The optical layer will be described later. In this case, the optical laminate includes an optical layer and a first hardened layer composed of a hardened portion of the composition (S) (Figures 1, 4, and 6).

Composition (S) can also be used as an adhesive composition. In one embodiment, composition (S) is an adhesive composition used to bond the optical layer and the first thermoplastic resin film. In this case, the optical laminate sequentially includes an optical layer, a first cured layer (adhesive layer) composed of a cured portion of composition (S), and a first thermoplastic resin film (Figures 2, 3, and 5). The optical laminate can be manufactured by laminating the optical layer and the first thermoplastic resin film through a coating composition (S) applied to at least one of the bonding surfaces of the optical layer and the first thermoplastic resin film, thereby obtaining the laminate, and then curing the coating.

Composition (S) is preferably an aqueous composition. An aqueous composition refers to a solution formed by dissolving the formulation ingredients in water or an aqueous solvent with water as the main component, or a dispersion (e.g., an emulsion) formed by dispersing the formulation ingredients in water or an aqueous solvent. "Water as the main component" means that at least 50% by mass of the total components constituting the solvent are water.

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

The viscosity of component (S) at 25°C is preferably 50 mPa·sec or less, more preferably 1 mPa·sec to 30 mPa·sec, and even more preferably 2 mPa·sec to 20 mPa·sec. If the viscosity at 25°C exceeds 50 mPa·sec, it becomes difficult to coat evenly, which may result in uneven coating and may also cause problems such as pipe blockage.

The viscosity of component (S) at 25°C can be determined using an E-type viscometer.

[2-1-1] Polyvinyl alcohol acetal resin (A)

Polyvinyl alcohol acetal resin (A) can be obtained by acetalizing polyvinyl alcohol resin using at least one of aldehydes and ketones. Polyvinyl alcohol acetal resin (A) may use only one type or two or more types in combination.

Polyvinyl alcohol acetal resin (A) typically contains acetylated and hydroxyl groups in addition to the acetal group. Besides these functional groups, polyvinyl alcohol acetal resin (A) may also have imine structures (-N=CRR’ (R and R’ independently represent a hydrogen atom or hydrocarbon group)), primary amino groups, secondary amino groups, acetylated groups (-C(=O)NH-), carboxyl groups, sulfonic acid groups, sulfinic acid groups, hyposulfonic acid groups, phosphoric acid groups, phosphonic acid groups, thiol groups, and other functional groups (hereinafter sometimes referred to as "modified functional groups"). Regarding the modified functional groups that polyvinyl alcohol acetal resin (A) may possess, they can be introduced by modifying unmodified polyvinyl alcohol acetal resin, or by using polyvinyl alcohol resin with the above-mentioned modified functional groups and introducing them through acetalization.

The polyvinyl alcohol resin used to obtain polyvinyl alcohol acetal resin (A) is not particularly limited, and examples include ethylene ester-vinyl alcohol copolymers. Ethylene ester-vinyl alcohol copolymers can be manufactured by conventional methods such as saponification of polyvinyl ester with an alkaline catalyst or transesterification reaction with an alcohol; for example, ethylene acetate-vinyl alcohol copolymers obtained by saponification of polyvinyl acetate. The constituent units of ethylene ester-vinyl alcohol copolymers may also have modified functional groups such as imine structures (-N=CRR’ (R and R’ represent the same meaning as above)), primary amino groups, secondary amino groups, amide groups (-C(=O)NH-), carboxyl groups, sulfonic acid groups, sulfinic acid groups, hyposulfonic acid groups, phosphoric acid groups, and phosphonic acid groups.

There are no particular limitations on the degree of saponification of polyvinyl alcohol (PVA) resins, but it is typically 70 mol% or higher, preferably 75 mol% or higher, more preferably 80 mol% or higher, and usually below 99.9 mol%, and can be below 99.8 mol%. The degree of saponification is expressed as a unit ratio (mol%) of the proportion of acetate groups in polyvinyl alcohol-based resins (polyvinyl acetate-based resins) converted to hydroxyl groups through the saponification step, and is expressed by the following formula:

The degree of saponification [moles %] is a value defined as (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100. It can be obtained using the method specified in JIS K6726 (1994).

There are no particular restrictions on the aldehydes used to obtain polyvinyl alcohol acetal resin (A), and examples include aldehydes having 1 to 10 carbon atoms, such as chain aliphatic groups, cyclic aliphatic groups, or aromatic groups. Examples of such aldehydes include aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-pentanaldehyde, n-hexanaldehyde, 2-ethylbutanaldehyde, 2-ethylhexanaldehyde, n-heptanaldehyde, n-octanaldehyde, n-nonanaldehyde, n-decanaldehyde, and pentanaldehyde; and aromatic aldehydes such as benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde. One or more of these aldehydes may be used in combination.

There are no particular restrictions on the ketones used to obtain polyvinyl alcohol acetal resin (A), and examples include acetone, ethyl methyl ketone, diethyl ketone, tributyl ketone, dipropyl ketone, allyl ethyl ketone, acetophenone, p-methyl acetophenone, 4'-aminoacetophenone, p-chloroacetophenone, 4'-methoxyacetophenone, 2'-hydroxyacetophenone, 3'-nitroacetophenone, p-(1-piperidinyl)acetophenone, styrylphenyl ketone, acetone, benzophenone, 4-nitrobenzophenone, 2-methylbenzophenone, p-bromobenzophenone, cyclohexyl(phenyl) methyl ketone, 2-naphthone (2-butyronaphthone), 1-naphthone, 2-hydroxy-1-naphthone, 8'-hydroxy-1'-naphthone, etc.

The aldehyde used to obtain polyvinyl alcohol acetal resin (A) is preferably a resin acetalized with formaldehyde, butyraldehyde (which has good acetalization reactivity), 2-ethylhexanal, or n-nonanal. Furthermore, polyvinyl alcohol acetal resin (A) is preferably polyvinyl alcohol acetal resin or polyvinyl alcohol butyraldehyde resin, and more preferably polyvinyl alcohol butyraldehyde resin.

The degree of acetalization of polyvinyl alcohol acetal resin (A) is not particularly limited, but preferably less than 50 mol%, more preferably less than 45 mol%, and even more preferably less than 40 mol%, typically more than 3 mol%. By achieving a degree of acetalization of less than 50 mol%, it is easy to obtain optical laminates that exhibit good optical durability in high-temperature and high-humidity environments, and even without surface modification treatment, it is still easy to obtain optical laminates with good interlayer adhesion. The degree of acetalization of polyvinyl alcohol acetal resin (A) can be determined using NMR (nuclear magnetic resonance spectroscopy).

The hydroxyl content of polyvinyl alcohol acetal resin (A) is preferably 20 mol% or more, more preferably 25 mol% or more, and can be 35 mol% or more, and more preferably 90 mol% or less. The hydroxyl content of polyvinyl alcohol acetal resin (A) is the ratio (in mol%) of the amount of vinyl groups bonded by the hydroxyl groups to the total amount of vinyl groups in the main chain. The amount of vinyl groups bonded by the hydroxyl groups can be calculated, for example, according to JIS K6728 [Test Method for Polyvinyl Butyral].

The amount of acetylation in polyvinyl alcohol acetal resin (A) is preferably 0.0001 mol% or more, more preferably 0.001 mol% or more, and may be 0.01 mol% or more, and preferably 5 mol% or less, more preferably 3 mol% or less, and may be 2 mol% or less. The amount of acetylation in polyvinyl alcohol acetal resin (A) is the ratio (in mol%) of "the amount of vinyl groups obtained by subtracting the total amount of vinyl groups bonded to acetal groups and the amount of vinyl groups bonded to hydroxyl groups from the total amount of vinyl groups in the main chain" to "the total amount of vinyl groups in the main chain". The amount of vinyl groups bonded to acetal groups can be calculated, for example, by a method according to JIS K6728 [Test Method for Polyvinyl Butyral].

Relating to a total content of 100 parts by weight of polyvinyl acetal resin (A) and crosslinking agent (B1), the content of polyvinyl acetal resin (A) in composition (S) is preferably 40 parts by weight or more, more preferably 50 parts by weight or more, even more preferably 60 parts by weight or more, and preferably 90 parts by weight or less, even more preferably 85 parts by weight or less, and even more preferably 80 parts by weight or less. By maintaining the content of polyvinyl acetal resin (A) within the above range, an optical laminate with excellent optical durability under high temperature and high humidity environments can be obtained, and an optical laminate with good interlayer adhesion can be easily obtained even without surface modification treatment.

[2-1-2] Crosslinking agent (B)

Composition (S) includes a crosslinking agent (B). By including crosslinking agent (B) in composition (S), a crosslinking structure can be formed in the polyvinyl acetal resin (A) contained in composition (S), and composition (S) can be cured. When composition (S) is an aqueous composition, crosslinking agent (B) is preferably an aqueous crosslinking agent. In this specification, an aqueous crosslinking agent refers to a crosslinking agent that is partially or wholly soluble in water or an aqueous solvent with water as the main component, or a crosslinking agent that is partially or wholly dispersed in water or an aqueous solvent with water as the main component.

Crosslinking agent (B) includes crosslinking agents (B1) that are at least one of isocyanate-based crosslinking agents and carbodiimide-based crosslinking agents, and may also include crosslinking agents other than crosslinking agent (B1) (hereinafter sometimes referred to as "other crosslinking agents (B2)"). Crosslinking agent (B1) may include at least one of isocyanate-based crosslinking agents and carbodiimide-based crosslinking agents, or may include both. Furthermore, crosslinking agent (B1) may be used singly or in combination with two or more types.

Isocyanate-based crosslinkers (B1) are compounds having at least two isocyanate groups (-NCO) within their molecules. Specific examples of isocyanate compounds include toluene diisocyanate, hexamethylene diisocyanate, isoflavone diisocyanate, phenyl dimethyl diisocyanate, hydrogenated phenyl dimethyl diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, etc. Furthermore, adducts formed by the reaction of these isocyanate compounds with polyols such as glycerol and trihydroxymethylpropane, as well as dimers and trimers of isocyanate compounds, are also included in isocyanate-based crosslinkers.

The carbodiimide crosslinker that can constitute the crosslinker (B1) is a compound having at least one carbodiimide group (-N=C=N-) within its molecule. Examples of carbodiimide crosslinkers include monocarbodiimide compounds having one carbodiimide group within their molecule and polycarbodiimide compounds having two or more carbodiimide groups within their molecule. Preferably, the carbodiimide crosslinker is a polycarbodiimide compound having two or more carbodiimide groups within its molecule, and more preferably, a polycarbodiimide compound having an average of 3 to 20 carbodiimide groups per molecule.

Examples of single-carbodiimide compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, tributylisopropylcarbodiimide, diphenylcarbodiimide, di-tert-butylcarbodiimide, and di-β-naphthylcarbodiimide.

Regarding polycarbodiimide compounds, for example, they can be synthesized via a decarbonylation condensation reaction of diisocyanate compounds in the presence of a carbodiimide catalyst, preferably as polymers. Examples of polycarbodiimide compounds include: aromatic polycarbodiimides such as poly(4,4'-diphenylmethane carbodiimide), poly(p-epiphenylcarbodiimide), poly(m-epiphenylcarbodiimide), poly(diisopropylphenylcarbodiimide), and poly(triisopropylphenylcarbodiimide); alicyclic polycarbodiimides such as poly(dicyclohexylmethane carbodiimide); and aliphatic polycarbodiimides such as poly(diisopropylcarbodiimide).

Relating to a total content of 100 parts by mass of polyvinyl acetal resin (A) and crosslinker (B1), the content of crosslinker (B1) in composition (S) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and preferably 60 parts by mass or less, even more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less. By maintaining the content of crosslinker (B1) within the above range, an optical laminate with excellent optical durability under high temperature and high humidity environments can be obtained, and even without surface modification treatment, an optical laminate with good interlayer adhesion can be easily obtained.

Relative to a total content of 100 parts by weight of crosslinking agent (B), the content of crosslinking agent (B1) in crosslinking agent (B) is preferably 70 parts by weight or more, more preferably 80 parts by weight or more, even more preferably 90 parts by weight or more, particularly preferably 95 parts by weight or more, and can be 100 parts by weight.

Other crosslinking agents (B2) besides crosslinking agent (B1) that can be included in crosslinking agent (B) include, for example, epoxy compounds, aziridine compounds, vinyl phosphate compounds, metal chelate compounds, polyaldehydes, melamine compounds, glyoxal, glyoxal derivatives, and water-soluble epoxy resins. Other crosslinking agents (B2) may be used alone or in combination of two or more.

Epoxy compounds are compounds having at least two epoxy groups within their molecules. Specific examples of epoxy compounds include bisphenol A type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol diglycidyl ether, trihydroxymethylpropane triglycidyl ether, N,N-diglycidylaniline, N,N,N',N'-tetraglycidylm-phenylenediamine, and 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, etc.

Aziridine compounds are compounds with a three-membered ring skeleton consisting of one nitrogen atom and two carbon atoms, also known as ethylenimine, within their molecules. Specific examples of aziridine compounds include diphenylmethane-4,4'-bis(1-aziridinemethylamine), toluene-2,4-bis(1-aziridinemethylamine), triethylmelamine, isophthalamide-bis-1-(2-methylaziridine), tri-1-aziridineylphosphine oxide, hexamethylene-1,6-bis(1-aziridinemethylamine), trihydroxymethylpropane-tri-β-aziridine propionate, tetrahydroxymethylmethane-tri-β-aziridine propionate, etc.

Vinyl ion compounds are compounds having a vinyl ion group, preferably compounds having a plurality of vinyl ion groups. Specific examples of vinyl ion compounds include N,N'-trimethylenebis[2-(vinylsulfonyl)acetamide], N,N'-epethoxybis[2-(vinylsulfonyl)acetamide], etc.

Specific examples of metal chelate compounds include compounds formed by the coordination of acetone and ethyl acetate with polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium.

While there are no particular limitations on the content of other crosslinking agents (B2), the content of other crosslinking agents (B2) is preferably 30 parts by weight or less, more preferably 20 parts by weight or less, even more preferably 10 parts by weight or less, and most preferably 5 parts by weight or less, relative to the total content of crosslinking agents (B) of 100 parts by weight.

[2-1-3] Other ingredients

Composition (S) may contain components other than polyvinyl acetal resin (A) and crosslinking agent (B). Other components may include, for example: solvents; resins other than polyvinyl acetal resin (A) (hereinafter sometimes referred to as "other resins"); modified polyvinyl alcohol polymers; additives such as coupling agents, adhesives, antioxidants, UV absorbers, heat stabilizers, and hydrolysis inhibitors; solvents, etc.

Solvents may include, for example, water, organic solvents, or mixtures thereof. The solvent is preferably water or an aqueous solvent with water as its main component, and an aqueous solvent is preferably a mixture of water and a water-soluble organic solvent. As mentioned above, "with water as its main component" means that at least 50% by mass of the total components constituting the solvent are water. For aqueous solvents, there are no particular restrictions if the solvent (other than water) does not readily separate into layers when coexisting with water. Preferably, it is a water-soluble solvent, such as: alcohols like methanol, ethanol, isopropanol, and n-propanol; ketones like acetone and methyl ethyl ketone; glycols like ethylene glycol and diethylene glycol; and glycol ethers like N-methylpyrrolidone (NMP), tetrahydrofuran, and butyl cellosolve.

Resins other than polyvinyl alcohol acetal resin (A) include, for example: (meth)acrylic resins; polyvinyl alcohol resins; ethylene-vinyl alcohol copolymer resins; polyvinylpyrrolidone resins; polyamide resins; epoxy resins; melamine resins; urea resins; polyamide resins; polyester resins; polyurethane resins; cellulose resins such as methylcellulose, hydroxyethylcellulose, and carboxymethylcellulose; and polysaccharides such as sodium alginate and starch. Among these, aqueous resins that can be dissolved or dispersed in water or aqueous solvents are preferred. In this specification, "(meth)acrylic acid" refers to at least one species selected from the group consisting of acrylic acid and methacrylic acid. The designations for "(meth)acrylyl" and "(meth)acrylate," etc., are similar.

[2-2] Other hardening components

There are no particular limitations on other curing components that may constitute the second curing layer 25. Examples include, for instance, conventional aqueous compositions (including aqueous adhesives) formed by dissolving or dispersing curing resin components in water, and conventional active energy line curing compositions (including active energy line curing adhesives) containing active energy line curing compounds.

Regarding the resin components contained in aqueous solutions, examples include polyvinyl alcohol resins and amine resins.

To improve adhesion and bonding properties, aqueous compositions containing polyvinyl alcohol resins may further contain curing components such as polyaldehydes, melamine compounds, zirconium oxide compounds, zinc compounds, glyoxal, glyoxal derivatives, and water-soluble epoxy resins, as well as crosslinking agents.

Aqueous compositions containing amine resins include, for example, aqueous compositions containing polyester-based ionic polymer amine resins and compounds having glycidyl groups. Polyester-based ionic polymer amine resins refer to amine resins with a polyester backbone, wherein a small amount of ionic components (hydrophilic components) have been incorporated.

The active energy line curable composition is a composition that is cured by irradiation with active energy lines such as ultraviolet light, visible light, electron beams, and X-rays. In the case of using an active energy line curable composition, the second cured layer 25 is the cured layer of that composition.

The active energy-curing component can be a component containing an epoxy compound that is cured by cationic polymerization as a curing element, preferably an ultraviolet-curing component containing such an epoxy compound as a curing element. An epoxy compound refers to a compound having an average of one or more epoxy groups within its molecule, preferably two or more. Only one epoxy compound may be used, or two or more may be used in combination.

Examples of epoxide compounds include: alicyclic polyols obtained by hydrogenation of the aromatic ring of an aromatic polyol; hydrogenated epoxide compounds (glycidyl ethers of polyols with alicyclic rings) obtained by reaction with epichlorohydrin; aliphatic epoxide compounds such as polyglycidyl ethers of aliphatic polyols or their epoxide adducts; and epoxide compounds having one or more epoxy groups bonded to an alicyclic ring, i.e., alicyclic epoxide compounds.

The active energy line curing component may contain a radical-polymerizable (meth)acrylic acid compound to replace the aforementioned epoxy compound as the curing agent, or may contain both a radical-polymerizable (meth)acrylic acid compound and the aforementioned epoxy compound as curing agents. Examples of (meth)acrylic acid compounds include: (meth)acrylate monomers having one or more (meth)acrylic acid groups within their molecules; (meth)acrylate oligomers having at least two (meth)acrylic acid groups within their molecules obtained by reacting two or more compounds containing functional groups; and other compounds containing (meth)acrylic acid groups.

In active energy line curing components that include epoxy compounds that are cured by cationic polymerization as curing components, it is preferable to include a photocatalytic polymerization initiator. Examples of photocatalytic polymerization initiators include: aromatic diazonium salts; aromatic monazine salts, aromatic strontium salts, and other onium salts; iron-aromatic complexes, etc.

In the case where the active energy line hardening component contains free radical polymerizable components such as (meth)acrylic acid compounds, it is preferable to contain a photoradical polymerization initiator. Examples of photoradical polymerization initiators include acetophenone-based initiators, benzophenone-based initiators, benzoin ether-based initiators, thioanthraquinone-based initiators, oxanthraquinones, fumonisins, camphorquinone, benzaldehyde, and anthraquinones.

[3] Polarizing film

A polarizer is a layer or film that allows linearly polarized light from a specific direction to selectively pass through from natural light.

Polarizing films can be, for example, films made by adsorbing/orienting dichroic pigments onto polyvinyl alcohol-based resin films. Examples of dichroic pigments include iodine and dichroic organic dyes.

Furthermore, the polarizer can be a coated polarizing film formed by applying a dichroic dye in a lyotropic liquid crystal state to a substrate film and then aligning/immobilizing it.

The polarizers described above are called absorption polarizers because they selectively allow linearly polarized light from one direction to pass through while absorbing linearly polarized light from another direction.

Polarizing films are not limited to absorptive polarizing films; they can also be reflective polarizing films that selectively transmit linearly polarized light from one direction and reflect linearly polarized light from another direction, or scattering polarizing films that scatter linearly polarized light from another direction. From the viewpoint of better discernibility, absorptive polarizing films are preferred. More preferably, they are polyvinyl alcohol (PVA) based polarizing films composed of a PVA-based resin film; even more preferably, they are PVA-based polarizing films formed by adsorbing/aligning dichroic pigments such as iodine or dichroic dyes onto the PVA-based resin film; and most preferably, they are PVA-based polarizing films formed by adsorbing/aligning iodine onto the PVA-based resin film.

Polyvinyl alcohol (PVA) resins can be saponified forms of polyvinyl acetate (PVC) resins. Regarding PVC resins, besides homopolymers of PVC, examples include copolymers of PVC and other monomers that can copolymerize with PVC. Other monomers that can copolymerize with PVC include unsaturated carboxylic acids, alkenes, vinyl ethers, unsaturated sulfonic acids, and ammonium-containing (meth)acrylamides.

The degree of saponification of polyvinyl alcohol (PVA) resins is typically between 85 and 100 mol%, preferably above 98 mol. PVA resins can be modified, for example, using aldehyde-modified PVA formaldehyde or PVA acetal. The average degree of polymerization of PVA resins is typically between 1000 and 10000, preferably between 1500 and 5000.

The average degree of polymerization of polyvinyl alcohol resins can be determined according to JIS K6726:1994.

Films made from such polyvinyl alcohol (PVA) resins can be used as raw materials for polarizing films composed of PVA resin films. There are no particular limitations on the method for fabricating the PVA resin film; conventional methods can be used. The thickness of the PVA raw material film is, for example, 150 μm or less, preferably 100 μm or less (e.g., 50 μm or less), and at least 5 μm.

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

The thickness of the polarizer can be 40 μm or less, preferably 30 μm or less (e.g., 20 μm or less, more preferably 15 μm or less, and further preferably 10 μm or less, or 8 μm or less). According to the methods disclosed in Japanese Patent Application Publication Nos. 2000-338329 and 2012-159778, it is easier to manufacture thin-film polarizers and to achieve a polarizer thickness of, for example, 20 μm or less, more preferably 15 μm or less, and further preferably 10 μm or less, or 8 μm or less. The thickness of the polarizer is typically 2 μm or more. A smaller polarizer thickness facilitates the miniaturization of the optical laminate (polarizing plate) and the image display device containing it.

[4] Phase difference film

Examples of retardation films include: extended films formed by uniaxial or biaxial stretching of a transparent thermoplastic resin; films in which liquid crystal compounds such as disk-type liquid crystals or nematic liquid crystals are aligned and fixed; and films on which the aforementioned liquid crystal layer is formed on a substrate film. Furthermore, in this specification, zero-retardation films are also included in the category of retardation films.

The substrate film is typically composed of thermoplastic resins, such as cellulose ester resins like triacetin.

Translucent thermoplastic resins include, for example, the resins constituting the first thermoplastic resin film 10, as described later.

A zero-delay film refers to a film with an in-plane phase difference (Re) and a thickness-direction phase difference (Rth) both ranging from -15 to 15 nm. This phase difference film is suitable for use in IPS-mode liquid crystal displays. Preferably, both the in-plane phase difference (Re) and the thickness-direction phase difference (Rth) are -10 to 10 nm, more preferably -5 to 5 nm. The in-plane phase difference (Re) and thickness-direction phase difference (Rth) values described here are at a wavelength of 590 nm.

The in-plane phase difference Re and the thickness-direction phase difference Rth are respectively expressed by the following formulas:

Re=(n _x -n _y )×d

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

Zero-delay films can be made from resins such as cellulose-based resins, chain-based polyolefin resins, and cyclic polyolefin resins, as well as polyethylene terephthalate resins or (meth)acrylate resins. In particular, cellulose-based resins, polyolefin resins, or (meth)acrylate resins are preferred because they are easy to control and readily available.

Regarding films that exhibit optical anisotropy through the coating/alignment of liquid crystal compounds, examples include:

First morphology: A retardation film in which rod-shaped liquid crystal compounds are horizontally aligned relative to the supporting substrate;

Second form: A retardation film in which rod-shaped liquid crystal compounds are aligned vertically relative to the supporting substrate;

Third state: A phase reversal film in which rod-shaped liquid crystal compounds change their alignment direction in a helical manner within the plane;

Fourth form: a phase reversal film with a tilted alignment of a disk-shaped liquid crystal compound;

Fifth type: A biaxial retardation film in which a disc-shaped liquid crystal compound is vertically aligned relative to the supporting substrate.

For example, the first, second, and fifth forms are suitable for use as optical layers in organic light-emitting diode (OLED) displays. Alternatively, these forms can be laminated together.

In the case where the retardation film is a layer composed of polymeric liquid crystal compounds in an aligned state (hereinafter sometimes referred to as an "optical anisotropy layer"), the retardation film preferably exhibits anti-wavelength dispersibility. Anti-wavelength dispersibility refers to the optical characteristic that the phase difference value within the alignment plane of the liquid crystal at shorter wavelengths becomes smaller than the phase difference value within the alignment plane at longer wavelengths. Preferably, the retardation film satisfies the following equations (1) and (2). Furthermore, Re(λ) represents the in-plane phase difference value for light with a wavelength of λ nm.

Re(450)/Re(550)≦1 (1)

1≦Re(630)/Re(550) (2)

When the phase retardation film is of the first form and has anti-wavelength dispersion, it is preferable because it reduces the color rendering of the display device when displaying black. In equation (1), it is more preferably 0.82≦Re(450)/Re(550)≦0.93. Even more preferably, it is 120≦Re(550)≦150.

Polymerizable liquid crystal compounds in which the retardation film is a film having an optically anisotropic layer can be exemplified by: compounds with polymerizable groups described in "3.8.6 Networks (Fully Crosslinked Type)" and "6.5.1 Liquid Crystal Materials b. Polymerizable Nematic Liquid Crystal Materials" of the Liquid Crystal Manual (edited by the Liquid Crystal Manual Editorial Committee, Maruzen Co., Ltd., published on October 30, 2013); and Japanese Patent Application Publication No. 1. Polymerizable liquid crystal compounds as described in Japanese Publication No. 2010-31223, Japanese Patent Application Publication No. 2010-270108, Japanese Patent Application Publication No. 2011-6360, Japanese Patent Application Publication No. 2011-207765, Japanese Patent Application Publication No. 2016-81035, International Publication No. 2017/043438, and Japanese Patent Publication No. 2011-207765.

Methods for manufacturing retardation films from polymers of polymeric liquid crystal compounds in an aligned state include, for example, the method disclosed in Japanese Patent Application Publication No. 2010-31223.

In the second configuration, the in-plane phase difference Re(550) is adjusted to a range of 0 to 10 nm, preferably 0 to 5 nm, and the thickness-direction phase difference Rth is adjusted to a range of -10 to -300 nm, preferably -20 to -200 nm.

The thickness-direction phase difference Rth, which implies refractive index anisotropy in the thickness direction, can be calculated from the phase difference R50 measured by tilting the fast axis in the plane by 50 degrees and the in-plane phase difference Re. That is, the thickness-direction phase difference Rth can be obtained from the in-plane phase difference Re, the phase difference R50 measured by tilting the fast axis by 50 degrees, the thickness _d of the phase difference film, and the average refractive index _n0 of the phase _difference film according to the following equations (4) to (6), and _these are substituted into equation (3) to calculate the thickness.

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,

Phase retardation films can be multilayer films with two or more layers. Examples include those with a protective film layered on one or both sides, or those formed by laminating two or more phase retardation films with an adhesive or bonding agent between them.

[5] Thermoplastic resin film

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 (hereinafter, the two are sometimes referred to together as "thermoplastic resin film") can each be a thermoplastic resin with light transmittance (preferably optical transparency), such as chain polyolefin resins (polypropylene resins, etc.), cyclic polyolefin resins (norcamphene resins, etc.), etc. Films composed of hydrocarbon resins; cellulose ester resins such as triacetyl cellulose and diacetyl cellulose; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate resins; (meth)acrylic resins; polystyrene resins; or mixtures or copolymers thereof.

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

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 can each be either an unstretched film or a film stretched uniaxially or biaxially. Biaxial stretching can be simultaneous biaxial stretching in two stretching directions, or it can be sequential biaxial stretching, where the film is stretched in the first direction followed by stretching in a different second direction.

The first thermoplastic resin film 10 and/or the second thermoplastic resin film 20 can be protective films that protect the optical layer 30, or they can be protective films with optical functions such as phase retardation films.

Regarding the phase retardation film, refer to the description in [4] above.

From the viewpoint of improving adhesion, surface modification treatments such as saponification, plasma treatment, corona treatment, and primer treatment can be performed on the surfaces of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 where the composition (S) is to be coated, or on the surfaces that adhere to the composition (S). Alternatively, surface modification treatment may not be performed. This is because by using the composition (S), even without performing surface modification treatments on the first thermoplastic resin film 10 and the second thermoplastic resin film 20, the adhesion between the first thermoplastic resin film 10 and the first hardened layer 15 formed by the composition (S), and the adhesion between the second thermoplastic resin film 20 and the second hardened layer 25 formed by the composition (S), can still be ensured. Therefore, according to this invention, the surface modification treatment described above can be omitted when obtaining the optical laminate, thus simplifying the process. For the bonding surface of the optical layer 30, for the same reasons as above, surface modification treatment may or may not be performed.

When the first thermoplastic resin film 10 or the second thermoplastic resin film 20 is a cellulose ester-based resin film, from the viewpoint of improving adhesion, saponification treatment can be performed on the surface to which the composition (S) is to be coated, or on the surface to which it is to be bonded. When the first hardened layer 15 and the second hardened layer 25 are formed using the composition (S), the adhesion between the first thermoplastic resin film 10 and the first hardened layer 15, and the adhesion between the second thermoplastic resin film 20 and the second hardened layer 25, can be ensured even without saponification treatment. Saponification treatment can be, for example, by immersion in an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide.

In optical laminates where the first thermoplastic resin film 10 or the second thermoplastic resin film 20 is a cellulose ester-based resin film and these laminates are in direct contact with the first hardened layer 15 and the second hardened layer 25, respectively, the fluorine concentration in the cellulose ester-based resin film, where the hydroxyl groups on the surface of the first hardened layer 15 or the second hardened layer 25 have been derivatized using a fluorine-based derivatization reagent, can be 2.0 atomic percent or less. The fluorine concentration can be 1.8 atomic percent or less, 1.6 atomic percent or less, or 1.5 atomic percent or less. The aforementioned fluorine-based derivatization reagent can be trifluoroacetic anhydride, and the aforementioned fluorine concentration can be determined according to the method described in the embodiments.

The fluorine concentrations mentioned above generally indicate the amount of hydroxyl groups on the surface of cellulose ester resin films. Generally, surface modification treatment of cellulose ester resin films increases the amount of hydroxyl groups on their surface. Cellulose ester resin films with fluorine concentrations within the above range are generally referred to as untreated or poorly modified cellulose ester resin films.

Therefore, by forming the first hardened layer 15 and the second hardened layer 25 using composition (S) within the optical laminate, good adhesion between the cellulose ester resin film and the first hardened layer 15 and the second hardened layer 25 can be ensured even when the first hardened layer 15 and the second hardened layer 25 are formed in direct contact with a cellulose ester resin film that has not undergone surface modification or has only undergone a low degree of surface modification.

When using other curing components instead of component (S) to form the second curing layer 25, from the viewpoint of improving adhesion, it is preferable to perform the aforementioned surface modification treatment on the surface of the second thermoplastic resin film 20 where the curing component is to be coated. However, from the viewpoint of simplifying the process, surface modification treatment may not be performed. Surface modification treatment can be performed on the bonding surfaces of the thermoplastic resin film and the bonding surfaces of the optical layer 30.

When the second thermoplastic resin film 20 is a cellulose ester resin film, the above-mentioned saponification treatment can be performed from the viewpoint of improving adhesion.

Regarding chain polyolefin resins that form thermoplastic resin films, in addition to homopolymers of chain olefins such as polyethylene and polypropylene resins, copolymers of two or more chain olefins can also be cited as examples.

Cyclic polyolefin resins, which form thermoplastic resin films, are a general term for resins that use cyclic alkenes as polymeric units, with norcamphene, tetracyclododecene (also known as dimethyl benzo[a](x](x)-) or their derivatives as examples. Examples of cyclic polyolefin resins include ring-opening (co)polymers of cyclic alkenes and their hydroxides, addition polymers of cyclic alkenes, copolymers of cyclic alkenes with cyclic alkenes and chain alkenes such as ethylene and propylene, or aromatic compounds containing vinyl groups, as well as modified (co)polymers obtained by modifying these with unsaturated carboxylic acids or their derivatives.

Among these, nobornene resins, which preferably use nobornene monomers such as norbornene monomers or polycyclic nobornene monomers as cyclic olefins, are preferred.

The cellulose ester resin that forms the thermoplastic resin film is a resin in which at least a portion of the hydroxyl groups in cellulose has been esterified with acetate, or it can be a mixed ester in which some cellulose groups have been esterified with acetate and others with other esterifications. The cellulose ester resin is preferably an acetylated cellulose resin.

Acetyl cellulose resins include, for example, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate.

Polyester resins that form thermoplastic resin films are resins other than the aforementioned cellulose ester resins containing ester bonds, and are generally condensates of polycarboxylic acids or their derivatives and polyols.

Examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate (PET), polyethylene naphthalate (PET), polybutylene naphthalate (PET), polypropylene terephthalate (PPD), polypropylene naphthalate (PPD), polycyclohexanedimethyl terephthalate (PCT), and polycyclohexanedimethyl naphthalate (PCD).

From the perspectives of mechanical properties, solvent resistance, scratch resistance, and cost, polyethylene terephthalate (PET) is preferred. PET refers to a resin in which at least 80 moles of repeating units are composed of polyethylene terephthalate, and may contain constituent units from other copolymerizing components (dicarboxylic acids such as isophthalic acid; diols such as propylene glycol, etc.).

Polycarbonate resins that form thermoplastic resin films are polyesters derived from carbonic acid and glycols or bisphenols. Among these, aromatic polycarbonates with diphenylane molecular chains are preferred from the perspectives of heat resistance, weather resistance, and acid resistance.

Polycarbonates can be exemplified by 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 1,1-bis(4-hydroxyphenyl)ethane.

(Meth)acrylate resins that form thermoplastic resin films are polymers containing constituent units derived from (meth)acrylate monomers, such as methacrylates and acrylates.

Examples of methacrylates include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tributyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxyethyl methacrylate.

Acrylic esters include, for example, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tributyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate.

(Meth)acrylate resins can be polymers composed solely of monomers derived from (meth)acrylate, or they may contain other monomers.

In a preferred embodiment, the (meth)acrylate resin includes methyl methacrylate as a copolymerizing component, or includes methyl methacrylate and methyl acrylate as copolymerizing components.

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

The preferred glass transition temperature for (meth)acrylate resins is between 80°C and 160°C. The glass transition temperature can be controlled by adjusting the polymerization ratio of methacrylate and acrylate monomers, the carbon chain length of their respective ester groups, the types of functional groups they possess, and the polymerization ratio of polyfunctional monomers relative to the total monomer.

Introducing cyclic structures into the polymer backbone is also an effective method for increasing the glass transition temperature of (meth)acrylic resins. Preferred cyclic structures include heterocyclic structures such as cyclic anhydrides, cyclic amides, and lactones. Specifically, examples include cyclic anhydride structures such as glutaric anhydride and succinic anhydride; cyclic amide structures such as glutaric anhydride and succinic anhydride; and lactone ring structures such as butyrolactone and valerolactone.

A higher content of ring structures in the main chain tends to increase the glass transition temperature of (meth)acrylic resins.

Cyclic anhydride and cyclic propylene oxide structures can be introduced by the following methods: copolymerization of monomers with cyclic structures such as maleic anhydride and maleimide; post-polymerization dehydration/demethanolification condensation; and reaction of amine compounds to introduce cyclic propylene oxide structures.

Resins (polymers) with a lactone ring structure can be obtained by the following method: after preparing a polymer with hydroxyl and ester groups in its polymer chain, the hydroxyl and ester groups in the resulting polymer are subjected to cyclization condensation in the presence of a catalyst such as an organophosphorus compound, by heating, to form a lactone ring structure.

(Meth)acrylate resins and the thermoplastic resin films formed therefrom may contain additives as needed. Additives may include, for example, lubricants, anti-caking agents, heat stabilizers, antioxidants, antistatic agents, lightfastness agents, impact modifiers, and surfactants.

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

From the perspective of membrane fabrication properties and impact resistance, (meth)acrylate resins may contain acrylic rubber particles, which are impact modifiers. Acrylic rubber particles refer to particles that use an elastic polymer, primarily composed of acrylate, as a necessary component. Examples include monolayer structures consisting entirely of this elastic polymer, and multilayer structures where the elastic polymer is one layer.

Examples of the aforementioned elastic polymers include crosslinked elastic copolymers, which are formed by copolymerizing alkyl acrylate with other vinyl monomers and crosslinking monomers that can copolymerize alkyl acrylate.

Regarding alkyl acrylates that become the main component of elastic polymers, examples include methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, where the alkyl group has 1 to 8 carbon atoms. Alkyl acrylates with alkyl groups having 4 or more carbon atoms are preferred.

Regarding other vinyl monomers that can copolymerize with alkyl acrylates, examples include compounds with a single polymerizable carbon-carbon double bond within the molecule. More specifically, examples include: methyl methacrylate and other methacrylates; aromatic vinyl compounds such as styrene; vinyl cyanide compounds such as acrylonitrile, etc.

Regarding the aforementioned crosslinking monomers, examples include crosslinking compounds having at least two polymerizable carbon-carbon double bonds within the molecule. More specifically, examples include: (meth)acrylates of polyols such as ethylene glycol di(meth)acrylate and butanediol di(meth)acrylate; alkenyl esters of (meth)acrylic acid such as allyl (meth)acrylate; and divinylbenzene, etc.

A laminate of a film made of (meth)acrylate resin without rubber particles and a film made of (meth)acrylate resin containing rubber particles can be used as a thermoplastic resin film to be laminated to the optical layer 30. Furthermore, a thermoplastic resin film that displays phase retardation by forming a (meth)acrylate resin layer on one or both sides of a phase retardation display layer composed of a resin different from (meth)acrylate resin can also be used as a thermoplastic resin film to be laminated to the optical layer 30.

Thermoplastic resin films may contain ultraviolet absorbers, infrared absorbers, organic dyes, pigments, inorganic pigments, antioxidants, antistatic agents, surfactants, lubricants, dispersants, and thermal stabilizers. When optical laminates are applied to image display devices, by placing a thermoplastic resin film containing ultraviolet absorbers on the viewing side of the image display element (e.g., liquid crystal unit, organic EL display element), the degradation of the image display element caused by ultraviolet radiation can be suppressed.

Examples of ultraviolet absorbers include salicylate compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel salt compounds.

The first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be composed of the same thermoplastic resin or of different thermoplastic resins. The first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be the same or different in thickness, presence and type of additives, and phase difference characteristics.

Thermoplastic resin films may have surface treatment layers (coatings) on their outer surface (the surface opposite to the optical layer 30), such as a hard coating layer, anti-glare layer, anti-reflective layer, light diffusion layer, antistatic layer, antifouling layer, and conductive layer.

The thicknesses of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 are typically 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 thicknesses 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. Smaller thicknesses of the first thermoplastic resin film 10 and the second thermoplastic resin film 20 facilitate the thinning of the optical laminate (polarizing plate) and the image display device containing it.

[6] Fabrication of optical laminates

The optical laminate structure shown in FIG2 can be obtained by depositing the first thermoplastic resin film 10 onto one side of the optical layer 30, separated by the first hardening layer 15. The optical laminate structure shown in FIG3 can be obtained by further depositing the second thermoplastic resin film 20 onto the other side of the optical layer 30, separated by the second hardening layer 25.

In manufacturing an optical laminate having both a first thermoplastic resin film 10 and a second thermoplastic resin film 20, these films can be deposited sequentially on one side in stages, or both sides can be deposited simultaneously.

Regarding the method of attaching the optical layer 30 to the first thermoplastic resin film 10, examples include: applying the composition (S) to either or both of the bonding surfaces of the optical layer 30 and the first thermoplastic resin film 10, and then bonding it to the other bonding surface using, for example, a bonding roller, by pressing from above and below.

The coating of composition (S) can be achieved using various methods, such as a scraper, wire rod, die-casting machine, corner-cutting wheel coating machine, gravure coating machine, etc. Furthermore, the composition (S) can be continuously supplied between the adhesive surfaces of the optical layer 30 and the first thermoplastic resin film 10, with the latter being the inner side.

After the optical layer 30 is bonded to the first thermoplastic resin film 10, it is preferable to perform heat treatment on the laminate comprising the optical layer 30, the first hardened layer 15, and the first thermoplastic resin film 10. The heat treatment temperature is, for example, 40°C to 100°C, preferably 50°C to 90°C. By heat treatment, the solvent contained in the hardened component layer can be removed. Furthermore, by this heat treatment, the hardening/crosslinking reaction of the hardened component can be carried out.

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

When using an active energy line curable component as the curable component constituting the second curable layer, after the curable component layer is dried as needed, it is irradiated with active energy lines to harden the curable component layer.

The light source used to irradiate the active energy lines can be any source capable of producing ultraviolet, electron, or X-rays. It is particularly suitable for use with light-emitting distributions below 400nm, such as low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, insect-trapping fluorescent lamps, black lights, microwave-excited mercury lamps, and metal halide lamps.

The optical laminate shown in Figure 1, which does not have a first thermoplastic resin film on the first hardened layer 15, can be manufactured by coating the surface of the optical layer 30 with the composition (S) and then subjecting the resulting laminate to heat treatment at 80°C for 300 seconds using, for example, a hot air dryer. Furthermore, the optical laminate shown in Figure 1 can also be manufactured by peeling off the separator after manufacturing the laminate composed of the separator film/composition (S)/optical layer 30, and then subjecting it to heat treatment.

The thickness of the first hardened layer 15 and the second hardened layer 25 formed from 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 layer formed from the conventional aqueous composition described above may also have a similar thickness.

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

The first hardened layer 15 and the second hardened layer 25 may have the same thickness or different thicknesses.

[7] Other constituent elements of optical layers

[7-1] Optical functional membranes

The optical laminate may have other optically functional films besides the optical layer 30 (e.g., a polarizer) to impart desired optical functions; a preferred example is a retardation film.

As described above, the first thermoplastic resin film 10 and/or the second thermoplastic resin film 20 can also serve as a retardation film, but a retardation film can also be deposited separately on top of these films. In the latter case, the retardation film can be deposited on the outer surfaces 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 through an adhesive layer or a bonding agent layer. Regarding the retardation film, refer to the description in [4] above.

Examples of other optical functional films (optical components) that can be included in optical laminates such as polarizing plates include light-concentrating plates, brightness enhancement films, reflective layers (reflective films), semi-transparent reflective layers (semi-transparent reflective films), and light-diffusing layers (light-diffusing films).

Concentrating plates are used for purposes such as controlling the light path, and therefore can be prism arrays, lens arrays, or thin sheets with attachment points, etc.

Brightness enhancement films are used to improve the brightness of liquid crystal displays that utilize optical layers such as polarizers. Specifically, examples include: reflective polarizers with anisotropic reflectivity, created by designing multiple layers of films with different refractive indices; and circular polarizers that use alignment films or alignment liquid crystal layers of cholesterol-based liquid crystal polymers supported on a substrate film.

The reflective layer, semi-transparent reflective layer, and light-diffusing layer are optical components used to configure the polarizer as reflective, semi-transparent, and diffuser, respectively. Reflective polarizers are used in liquid crystal displays (LCDs) that reflect incident light from the viewing side, eliminating the need for a backlight and facilitating thinner designs. Semi-transparent polarizers are used in LCDs that reflect light in bright areas but utilize backlighting in dark areas. Diffusion polarizers are used to impart light diffusion and suppress undesirable display features such as moiré patterns in LCDs. The reflective layer, semi-transparent reflective layer, and light-diffusing layer can be formed using conventional methods.

[7-2] Adhesive layer

Optical multilayers may include adhesive layers. Adhesive layers may be, for example, adhesive layers used to bond optical multilayers to image display elements such as liquid crystal cells, organic EL display elements, or other optical components. The adhesive layer can be deposited on the outer surface of the optical layer 30 in the optical laminates shown in Figures 1 and 2, the outer surface of the first thermoplastic resin film 10 or the second thermoplastic resin film 20 in the optical laminates shown in Figure 3, the outer surface of the first hardened layer 15 or the second thermoplastic resin film 20 in the optical laminates shown in Figure 4, the outer surface of the first thermoplastic resin film 10 or the second hardened layer 25 in the optical laminates shown in Figure 5, and the outer surface of the first hardened layer 15 or the second hardened layer 25 in the optical laminates shown in Figure 6.

An example of the outer surface adhesive layer 40 of the second thermoplastic resin film 20 in the optical laminate structure shown in Figure 3 is illustrated in Figure 7.

Regarding the adhesive used in the adhesive layer, adhesives with (meth)acrylic resins, polysiloxane resins, polyester resins, polyurethane resins, and polyether resins as the base polymer can be used. Among these, (meth)acrylic adhesives are preferred from the viewpoints of transparency, adhesion, reliability, weather resistance, heat resistance, and reworkability.

A (meth)acrylate resin containing alkyl groups with 20 or fewer carbon atoms, such as methyl, ethyl, n-butyl, isobutyl, or tributyl, as well as (meth)acrylate monomers containing functional groups, such as hydroxyethyl methacrylate and methyl methacrylate, and having a weight average molecular weight of 100,000 or more, is useful as a matrix polymer in (meth)acrylate adhesives, wherein the glass transition temperature is preferably below 25°C (more preferably below 0°C).

The formation of an adhesive layer on an optical laminate can be achieved, for example, by dissolving or dispersing an adhesive component in an organic solvent such as toluene or ethyl acetate to prepare an adhesive solution, and then directly applying the solution to the object surface of the optical laminate; or by first forming a sheet-like adhesive layer on a release liner and then transferring it to the object surface of the optical laminate.

The thickness of the adhesive layer can be determined based on factors such as adhesion strength, and is suitable in the range of 1μm to 50μm, with 2μm to 40μm being preferred.

The optical laminate may include the aforementioned separator membrane. The separator membrane may be a membrane composed of polyethylene resins such as polyethylene, polypropylene resins such as polypropylene, polyester resins such as polyethylene terephthalate, etc. Preferably, it is an extended polyethylene terephthalate membrane.

The adhesive layer may, as needed, include fillers such as glass fibers, glass beads, resin beads, metal powder, and other inorganic powders, as well as pigments, colorants, antioxidants, UV absorbers, and antistatic agents.

[7-3] Protective film

The optical laminate may include a protective film to protect its surfaces (typically the surfaces 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). For example, after the optical laminate is bonded to an image display element or other optical component, the protective film is peeled off together with its adhesive layers.

The protective film may, for example, consist of a substrate film and an adhesive layer deposited thereon. Regarding the adhesive layer, refer to the above description.

The resin constituting the substrate film can be, for example, a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, a polyester-based resin such as polyethylene terephthalate (PET) and polyethylene naphthalate (PAN), or a thermoplastic resin such as polycarbonate. Polyester-based resins such as polyethylene terephthalate (PET) are preferred.

<Image display device>

The optical laminate of this invention can be applied to image display devices such as liquid crystal displays and organic electroluminescent (EL) displays. In this case, the image display device includes the optical laminate and an image display element. Examples of image display elements include liquid crystal cells and organic EL display elements. These image display elements can be those conventionally known.

In the application of optical multilayers belonging to polarizing plates in liquid crystal display devices, the optical multilayers can be disposed on the backlight side (rear side) of the liquid crystal cell, on the viewing side, or both. In the application of optical multilayers belonging to polarizing plates in organic EL display devices, the optical multilayers are disposed on the viewing side of the organic EL display element.

[Implementation Example]

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

[Determination of Fluorine Concentration]

The membrane to be tested was cut into 1 cm square samples and placed in a small vial so that they would lean against each other. Then, approximately 150 mg of trifluoroacetic anhydride, used as a fluorine derivative reagent, was added to a weighing bottle with a folded cap. The vial containing the sample was then placed inside the weighing bottle containing the trifluoroacetic anhydride, without capping. The weighing bottle was sealed with a folded cap and heated at 40°C for 1 hour to derivative the hydroxyl groups on the surface of the unmodified triacetin (TAC) membrane (hereinafter sometimes referred to as "unmodified TAC membrane"). The sample from the vial was then removed from the weighing bottle and dried under reduced pressure at 40°C for 1 hour to obtain the test sample. The concentration of derivatived fluorine in the obtained test samples was determined using an X-ray photoelectron spectrophotometer (XPS) system (K-Alpha, Thermo Fisher Scientific, X-ray irradiation: Al Ka (12kV/6mA), 400μm).

[Example: Manufacturing a Polarizing Film]

A 60 μm thick polyvinyl alcohol (PVA) film (average degree of polymerization: approximately 2,400, degree of saponification: ≥99.9 moles) was immersed in pure water at 30°C, followed by immersion in an aqueous solution at 30°C containing iodine/potassium iodide/water at a mass ratio of 0.02/2/100. Then, it was immersed in an aqueous solution at 56.5°C containing potassium iodide/boric acid/water at a mass ratio of 12/5/100. After washing with pure water at 8°C, it was dried at 65°C to obtain a 23 μm thick polarizer with iodine adsorbed and aligned to the PVA film. Stretching was mainly carried out during the iodine staining and boric acid treatment steps, with a total stretching ratio of 5.5 times.

[Implementation Examples 1 to 7, Comparative Examples 1 to 7]

(1) Preparation of the ingredients The preparation ...

The components listed in Table 1, in the amounts shown in Table 1, were mixed with pure water as an aqueous solvent to prepare a composition (adhesive aqueous solution). The units for the amounts of each component in Table 1 are parts by mass, and the amounts of each component are the equivalent amounts of solid content. In Examples 1 to 7 and Comparative Examples 1 to 7, the resin concentration in the obtained composition was set to 5% by mass.

(2) Fabrication of polarizing plates (optical laminates)

After saponification treatment was performed on one side of the triacetyl cellulose (TAC) membrane [trade name "KC4UAW" manufactured by Konica Minolta Opto Co., Ltd., thickness: 40 μm], the composition prepared in (1) above was applied to the saponified surface using a stick applicator. At the same time, corona treatment was performed on one side of the zero phase difference film made of cyclic polyolefin resin [trade name "ZEONOR" manufactured by ZEON Co., Ltd., thickness: 23 μm], and the composition prepared in (1) above was applied to the corona treated surface using a stick applicator. A saponified TAC film is deposited on one side of a polarizer, with the constituent layers forming the polarizer side, and a corona-treated zero-phase-difference film is deposited on the other side, resulting in a laminate consisting of a zero-phase-difference film, a constituent layer, a polarizer, a constituent layer, and a saponified TAC film. This laminate is then heated in a hot air dryer at 80°C for 300 seconds to produce a polarizing plate consisting of a zero-phase-difference film, a hardened layer, a polarizer, a hardened layer, and a saponified TAC film. The thickness of each hardened layer in the produced polarizing plate is 20 to 60 nm.

The fluorine concentration on the corona-treated surface of the zero-phase-difference film (cyclic polyolefin resin film) used above, measured in the aforementioned order, was 1.8 atomic percent. Furthermore, the fluorine concentration on the saponified surface of the saponified TAC film, measured in the aforementioned order, was 6.1 atomic percent.

(3) Evaluation of optical durability

The obtained polarizing plate was cut into 30mm × 30mm pieces and then bonded to a glass substrate with a (meth)acrylic adhesive on the zero-phase film side to obtain the test sample. The test sample consists of a glass substrate/(meth)acrylic adhesive layer/zero-phase film/cured layer/polarizer/cured layer/saponified TAC film. An alkali-free glass substrate (Corning Material's trade name "Eagle XG") was used as the glass substrate.

For the obtained test samples, the MD transmittance and TD transmittance in the wavelength range of 380 to 780 nm were measured using a spectrophotometer with an integrating sphere (manufactured by Nippon Spectrophotometer Co., Ltd., product name "V7100"). The polarization at each wavelength was calculated. The calculated polarization was then corrected for visual sensitivity using a 2-degree field of view (C light source) according to JIS Z8701:1999 "Color Representation - XYZ Color System and X10Y10Z10 Color System" to obtain the visual sensitivity-corrected polarization Py before the durability test. Furthermore, the test samples were placed on the spectrophotometer with an integrating sphere, with the saponified TAC film side of the polarizing plate as the sensor side and light incident from the glass substrate side.

Polarization (%) is given by the following formula:

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

Definition.

Tp(λ) is the transmittance (%) of the test sample measured in relation to linearly polarized light of incident wavelength λ (nm) in parallel polarization.

Tc(λ) is the transmittance (%) of the test sample measured in relation to linearly polarized light with incident wavelength λ (nm) that is cross-polarized.

Then, the test sample was subjected to a durability test, placed in a high-temperature, high-humidity environment of 85°C and 85%RH for 50 hours, followed by a durability test at 23°C and 50%RH for 24 hours. After the durability test, the polarization Py for visual sensitivity correction was calculated using the same method as before the durability test.

Calculate the absolute value (|ΔPy|) of the difference between the visual perception correction polarization Py after the durability test and the visual perception correction polarization Py before the durability test. The calculated values of |ΔPy| are shown in Table 1.

A smaller value for |△Py| indicates better optical durability under high temperature and humidity conditions. In both embodiments and comparative examples, the difference between the visual sensitivity-corrected polarization Py after the durability test and the visual sensitivity-corrected polarization Py before the durability test is negative.

(4) Evaluation of Adhesion

On one side of a triacetyl cellulose (TAC) film (hereinafter sometimes referred to as "unmodified TAC film") that has not undergone surface modification treatment, the composition prepared in (1) above is applied using a rod coater. An unmodified TAC film is then deposited on the applied composition to obtain an uncured laminate consisting of an unmodified TAC film/composition layer/unmodified TAC film layer. This uncured laminate is then heated in a hot air dryer at 80°C for 300 seconds to produce a cured laminate consisting of an unmodified TAC film/cured layer/unmodified TAC film layer. The thickness of the cured layer in the resulting cured laminate is 20 to 60 nm. The fluorine concentration on the surface of the unmodified TAC film intended for coating was determined to be 1.4 atomic percent in the order described above.

The resulting hardened laminate was cut into test pieces with a width of 25 mm and a length of 150 mm. One side of the unmodified TAC film was adhered to glass using an acrylic adhesive (25 μm thick). In this state, a tensile testing machine was used to clamp the test piece at its length end (the 25 mm wide side) and perform a 180-degree peel test according to JIS K 6854-2:1999 "Adhesives - Test method for peel bond strength - Part 2: 180-degree peel", with a clamping and moving speed of 300 mm/min. The average peel force, excluding the initial 25mm of clamping distance, was obtained from the force-clamping distance curve. This average peel force was then converted to a value per 25mm width (i.e., the average peel force multiplied by 1/4) and used as the adhesion force of the hardened layer of the above composition to the unmodified TAC film. The results are shown in Table 1. In Table 1, "material breakage" for the adhesion items indicates that the unmodified TAC film was not peeled off, but the test piece broke.

[Table 1]

The detailed relationships of each component are shown in Table 1 below.

(resin)

The resin used is from A-1 to A-5 as described below.

A-1: Polyvinyl alcohol acetal resin (S-LEC KW-10, manufactured by Sekisui Chemicals, degree of acetalization 8±3 moles)

A-2: Polyvinyl alcohol acetal resin (S-LEC KW-3, manufactured by Sekisui Chemicals, degree of acetalization 30±3 moles)

A-3: Acetyl-modified polyvinyl alcohol (Gohsefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)

A-4: Low-saponification polyvinyl alcohol (GH-23, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)

A-5: Low-saponification polyvinyl alcohol (KH-17, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)

(Cross-connecting agent)

The cross-linking agents used are B-1 to B-3 as described below.

B-1: Isocyanate crosslinking agent (water-dispersible hexamethylene diisocyanate (HDI) polyisocyanate, Durnate WB40-100, manufactured by Asahi Kasei)

B-2: Polycarbodiimide crosslinking agent (Carbodilite V-02-L2, manufactured by Nisshin Shoku Chemical)

B-3: A crosslinking agent for vinyl ester compounds (N,N'-trimethylenebis[2-(vinylsulfonyl)acetamide], VS-C, manufactured by Fujifilm FILM)

15: First hardened layer

30: Optical layer

Claims (12)

An optical laminate comprises an optical layer and a hardening layer; wherein the hardening layer comprises a first hardening layer, which is a hardened composite containing a polyvinyl alcohol acetal resin (S); the polyvinyl alcohol acetal resin (S) comprises polyvinyl alcohol acetal resin (A) and a crosslinking agent (B); the degree of acetalization of the polyvinyl alcohol acetal resin (A) is less than 50 moles; the crosslinking agent (B) comprises a crosslinking agent (B1) belonging to at least one of isocyanate-based crosslinking agents and carbodiimide-based crosslinking agents. The optical laminate as described in claim 1, wherein the degree of acetalization of the aforementioned polyvinyl alcohol acetal resin (A) is 3 moles or more. As described in claim 1 or 2, in the optical laminate, the content of the aforementioned crosslinking agent (B1) in the composition (S) containing polyvinyl acetal resin is 10 parts by mass or more and 60 parts by mass or less, relative to a total content of 100 parts by mass of the aforementioned polyvinyl acetal resin (A) and the aforementioned crosslinking agent (B1). The optical laminate as described in claim 1 or 2 comprises, in sequence, the aforementioned optical layer, the aforementioned first hardened layer, and the first thermoplastic resin film. The optical laminate as described in claim 4, wherein the aforementioned first thermoplastic resin film is a film comprising one or more thermoplastic resins selected from the group consisting of cellulose ester resins, polyester resins, (meth)acrylate resins, and cyclic olefin resins. As described in claim 4, the optical laminate wherein the first thermoplastic resin film is a cellulose ester-based resin film comprising a cellulose ester-based resin; the cellulose ester-based resin film directly contacts the first hardened layer; and on the surface of the cellulose ester-based resin film on the side of the first hardened layer, where the hydroxyl groups on that surface have been derivatized using a fluorine-based derivatization reagent, the concentration of fluorine is 2.0 atomic% or less. The optical laminate as described in claim 1 or 2, wherein the aforementioned hardened layer includes a second hardened layer; and on the side of the aforementioned optical layer opposite to the side of the aforementioned first hardened layer, the aforementioned second hardened layer and a second thermoplastic resin film are sequentially laminated. The optical laminate as described in claim 7, wherein the aforementioned second thermoplastic resin film is a film comprising one or more thermoplastic resins selected from the group consisting of cellulose ester resins, polyester resins, (meth)acrylate resins, and cyclic olefin resins. The optical laminate as described in claim 7, wherein the aforementioned second cured layer is a cured composite containing the aforementioned polyvinyl alcohol acetal resin composition (S). As described in claim 9, in the optical laminate, the second thermoplastic resin film is a cellulose ester resin film containing a cellulose ester resin; the cellulose ester resin film directly contacts the second hardened layer; and in the surface of the cellulose ester resin film on the side of the second hardened layer, where the hydroxyl groups on that surface have been derivatized using a fluorine-based derivatization reagent, the concentration of fluorine is 2.0 atomic% or less. The optical laminate as described in claim 1 or 2, wherein the aforementioned optical layer is a polarizer. An image display device comprising the optical laminate and image display element described in any one of claims 1 to 11.