TWI898032B - Optical laminate and elliptical polarizing plate containing the same - Google Patents

Abstract

The object of the present invention is to provide an optical laminate that is less prone to deformation when bent, has high bendability, and has excellent oblique reflectivity, particularly an optical laminate suitable for flexible displays. The optical multilayer of the present invention comprises a phase difference film, a polarizing element, and a transparent protective film in sequence. The phase difference film comprises: a substrate film having a moisture permeability of 100 g/ ^m2 /24 hours or more; and a liquid crystal curing film formed on the substrate film, having a thickness of 0.5 μm or more and 3 μm or less, and satisfying the following formulas (1) and (2) in a single layer: Re(450)/Re(550)≦1.00 (1) 1.00≦Re(650)/Re(550) (2) [wherein, Re(λ) represents the in-plane phase difference value at wavelength λ]; the polarizing element is composed of a polyvinyl alcohol resin film containing a dichroic pigment; the transparent protective film has a total light transmittance of 90% or more and a 380 nm transmittance of 30% or less, The retardation film, the polarizing element, and the transparent protective film are adjacent to each other via an adhesive layer.

Description

Optical laminate and elliptical polarizing plate containing the same

The present invention relates to an optical laminate, a roll of the optical laminate, an elliptical polarizer including the optical laminate, and an organic EL (electroluminescence) display device.

An elliptical polarizing plate is an optical component composed of a laminated polarizing plate and a phase shift plate. For example, in devices that display images in a planar state, such as organic EL image displays, the elliptical polarizing plate is used to prevent light reflection at the electrodes that constitute the device. A so-called λ/4 plate is typically used as the phase shift plate that constitutes the elliptical polarizing plate. A known example of such a phase shift plate is a phase shift plate that uses a liquid crystal cured film produced by coating a polymerizable liquid crystal compound on a substrate and curing it (Patent Document 1). [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Publication No. 2011-207765

[Identify the problem you want to solve]

In recent years, the industry has demanded flexible displays, and thinner, highly bendable elliptical polarizing plates are in demand. Retardation films obtained by curing polymerizable liquid crystal compounds, as described in Reference 1, achieve thinning and are therefore suitable for flexible displays. By transferring this retardation plate (film) formed from a liquid crystal cured film to a polarizing plate using a pressure-sensitive adhesive, an elliptical polarizing plate (film) can be produced. However, the inventors have discovered that when a pressure-sensitive adhesive is used to transfer a retardation plate formed from a liquid crystal cured film, the resulting elliptical polarizing plate is easily deformed at the bend point when bent. This can result in streaky defects and an increase in the reflectivity of light from oblique directions (oblique reflectivity).

The object of the present invention is to provide an optical multilayer that is resistant to deformation when bent, has high bendability, and exhibits excellent oblique reflectivity, particularly an optical multilayer suitable for flexible displays. [Technical Solution]

The inventors have diligently researched to solve the above-mentioned problems and have completed the present invention. Specifically, the present invention includes the following aspects. [1] An optical multilayer structure comprising a phase difference film, a polarizing element, and a transparent protective film in sequence, wherein the phase difference film comprises: a substrate film having a moisture permeability of 100 g/ ^m2 /24 hours or more; and a liquid crystal curing film formed on the substrate film, having a thickness of 0.5 μm or more and 3 μm or less, and satisfying the following formulas (1) and (2) in a single layer: Re(450)/Re(550)≦1.00 (1) 1.00≦Re(650)/Re(550) (2) [wherein, Re(λ) represents the in-plane phase difference value at wavelength λ]; the polarizing element is composed of a polyvinyl alcohol resin film containing a dichroic pigment; the transparent protective film has a total light transmittance of 90% or more and a 380 nm transmittance of 30% or less, The phase difference film, the polarizing element and the transparent protective film are adjacent to each other via an adhesive layer. [2] The optical multilayer body as described in [1] above, wherein the total light transmittance of the substrate film is greater than 90%, and the absolute value of the phase difference value Rth(550) in the thickness direction for light of 550 nm is less than 5 nm. [3] The optical multilayer body as described in [1] or [2] above, wherein the phase difference film has a photo-alignment film with a thickness of greater than 10 nm and less than 1000 nm between the substrate film and the liquid crystal cured film. [4] The optical multilayer body as described in any one of [1] to [3] above, wherein the liquid crystal cured film is a film formed by curing at least one compound having at least one maximum absorption between a wavelength of 300 and 400 nm. [5] The optical laminate as described in any one of [1] to [4] above, wherein the liquid crystal cured film satisfies the following formula (3): 100 nm ≤ Re (550) ≤ 170 nm (3) [wherein Re (λ) represents the in-plane phase difference value at wavelength λ]. [6] The optical laminate as described in any one of [1] to [5] above, wherein the transparent protective film has a moisture permeability of 100 g/m ² /24 hours or more. [7] The optical laminate as described in any one of [1] to [6] above, wherein the adhesive layer is a layer formed of a dry-curing adhesive. [8] The optical laminate as described in [7] above, wherein the dry-curing adhesive contains polyvinyl alcohol. [9] An optical laminate as described in any one of [1] to [8] above, wherein the phase difference film and the adhesive layer for bonding the phase difference film and the polarizing element are in contact with each other on the liquid crystal cured film side. [10] An optical laminate roll, which is formed by rolling up the optical laminate as described in any one of [1] to [9] above. [11] An elliptical polarizing plate, which comprises the optical laminate as described in any one of [1] to [9] above. [12] An organic EL display device, which comprises the elliptical polarizing plate as described in [11] above. [13] A flexible image display device, which comprises the elliptical polarizing plate as described in [11] above. [14] The flexible image display device of [13] further comprises a window and a touch sensor. [Effects of the invention]

According to the present invention, an optical laminate can be provided that is not easily deformed when bent, has high bendability and excellent oblique reflectivity, and is particularly suitable for flexible displays.

The following describes the embodiments of the present invention in detail. Furthermore, the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without detracting from the spirit of the present invention.

The optical laminate of the present invention comprises a phase difference film, a polarizing element and a transparent protective film in sequence, and the phase difference film, the polarizing element and the transparent protective film are adjacent to each other via an adhesive layer.

(Adhesive Layer) In the optical laminate of the present invention, the retardation film and polarizing element, and the polarizing element and transparent protective film, are laminated via adhesive layers. By bonding the retardation film and polarizing element, and the polarizing element and transparent protective film, respectively, via adhesive layers, it is believed that when the resulting optical laminate is repeatedly bent, deformation in the liquid crystal cured film constituting the retardation film and deformation of the optical laminate as a whole are more easily tracked, making deformation at the bend point less likely. This can suppress the occurrence of streaky defects or increased oblique reflectivity caused by such deformation.

The adhesive layer that bonds the retardation film to the polarizing element, and the polarizing element to the transparent protective film, can be formed using an adhesive. Examples of adhesives that can form this adhesive layer include dry-curing adhesives such as water-based adhesives, and chemically reactive adhesives such as active energy ray-curing adhesives. The adhesive layers that bond the retardation film to the polarizing element, and the polarizing element to the transparent protective film, can be formed using different adhesives, but are preferably formed using the same adhesive.

Examples of dry-curing adhesives include polymers of monomers containing protic functional groups such as hydroxyl, carboxyl, or amine groups and ethylenically unsaturated groups; or compositions containing a urethane resin as a main component and further containing crosslinkers or curing compounds such as polyaldehydes, epoxy compounds, epoxy resins, melamine compounds, zirconium oxide compounds, and zinc compounds. Examples of polymers of monomers containing protic functional groups such as hydroxyl, carboxyl, or amine groups and ethylenically unsaturated groups include ethylene-maleic acid copolymers, itaconic acid copolymers, acrylic acid copolymers, acrylamide copolymers, saponified polyvinyl acetate, and polyvinyl alcohol resins.

Examples of polyvinyl alcohol-based resins include polyvinyl alcohol, partially saponified polyvinyl alcohol, completely saponified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, hydroxymethyl-modified polyvinyl alcohol, and amino-modified polyvinyl alcohol. The content of the polyvinyl alcohol-based resin in a water-based dry-curing adhesive is typically 1 to 10 parts by mass, preferably 1 to 5 parts by mass, per 100 parts by mass of water.

Examples of urethane resins include polyester-based ionic polymer urethane resins. The polyester-based ionic polymer urethane resins mentioned here have a polyester backbone with a small amount of ionic components (hydrophilic components) incorporated into it. These ionic polymer urethane resins do not require an emulsifier, but are emulsified in water to form a latex, making them suitable for use as water-based, dry-curing adhesives. When using polyester-based ionic polymer urethane resins, the addition of a water-soluble epoxy compound as a crosslinking agent is effective.

Examples of epoxy resins include polyamide epoxy resins obtained by reacting epichlorohydrin with a polyamide polyamine obtained by reacting a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a dicarboxylic acid such as adipic acid. Commercially available products of such polyamide epoxy resins include "Sumirez Resin (registered trademark) 650" and "Sumirez Resin (registered trademark) 675" (both manufactured by Sumika Chemtex Co., Ltd.) and "WS-525" (manufactured by PMC Co., Ltd., Japan). When preparing epoxy resin, its addition amount is generally 1 to 100 parts by mass, preferably 1 to 50 parts by mass, relative to 100 parts by mass of polyvinyl alcohol resin.

Among them, the dry-curing adhesive is preferably a water-based dry-curing adhesive containing a polyvinyl alcohol resin.

Dry-curing adhesives may contain a solvent. Examples of the solvent include water, a mixture of water and a hydrophilic organic solvent (e.g., alcohol solvent, ether solvent, ester solvent, etc.), and an organic solvent.

Active energy ray-curing adhesives, which are chemically reactive adhesives, are adhesives that cure upon exposure to active energy rays. Active energy ray-curing adhesives may also contain a solvent. Examples of active energy ray-curing adhesives include cationic polymerizable adhesives containing epoxy compounds and cationic polymerization initiators, free radical polymerizable adhesives containing acrylic curing components and free radical polymerization initiators, adhesives containing both cationic polymerizable curing components such as epoxy compounds and free radical polymerizable curing components such as acrylic compounds, adhesives containing both cationic polymerization initiators and free radical polymerization initiators, and adhesives that do not contain these polymerization initiators and cure upon electron beam irradiation.

Among these, preferred active energy ray-curing adhesives are free radical polymerizable active energy ray-curing adhesives containing an acrylic curing component and a free radical polymerization initiator, and cationic polymerizable active energy ray-curing adhesives containing an epoxy compound and a cationic polymerization initiator. Examples of acrylic curing components include (meth)acrylates such as methyl (meth)acrylate and hydroxyethyl (meth)acrylate, and (meth)acrylic acid. Active energy ray-curing adhesives containing epoxy compounds may further contain compounds other than epoxy compounds. Examples of compounds other than epoxy compounds include cyclohexyloxybutane compounds and acrylic compounds.

Examples of free radical polymerization initiators include the photopolymerization initiators described below as those that can be formulated into the polymerizable liquid crystal composition for forming a liquid crystal cured film. Examples of commercially available cationic polymerization initiators include the "Kayarad" (registered trademark) series (manufactured by Nippon Kayaku Co., Ltd.), the "Cyracure UVI" series (manufactured by The Dow Chemical Company), the "CPI" series (manufactured by SAN-APRO Co., Ltd.), "TAZ," "BBI," and "DTS" (all manufactured by Nippon Green Chemical Co., Ltd.), the "Adeka Optomer" series (manufactured by ADEKA Co., Ltd.), and "RHODORSIL" (registered trademark) (manufactured by Rhodia Co., Ltd.). The content of the free radical polymerization initiator and the cationic polymerization initiator is generally 0.5 to 20 parts by mass, preferably 1 to 15 parts by mass, relative to 100 parts by mass of the active energy ray-curable adhesive.

In an optical laminate formed by sequentially laminating a phase difference film, a polarizing element, and a transparent protective film, it is considered more advantageous to use adhesives such as dry-curing adhesives or chemical reaction adhesives than pressure-sensitive adhesives formed from highly viscous materials from the viewpoints of thinning the laminate and improving its bendability. On the other hand, the optical laminate of the present invention includes a liquid crystal cured film exhibiting the optical properties represented by formulas (1) and (2) in a single layer. The polymerizable liquid crystal compound forming this liquid crystal cured film is described below and generally has a maximum absorption wavelength between 300 and 400 nm. Furthermore, when incorporated into an image display device, the transparent protective film located on the viewing side has a UV-absorbing function to protect the internal structure of the optical laminate from UV damage. Therefore, during the manufacture of such an optical laminate, the irradiated UV light may be absorbed by the liquid crystal curing film and the transparent protective film, making it difficult for sufficient UV light to cure the adhesive to reach the interior of the laminate. Therefore, from the perspectives of achieving thinner and improved bendability, as well as obtaining an optical laminate with better interlayer adhesion, it is advantageous to use a dry-curing adhesive as the adhesive for bonding the retardation film to the polarizing element, and the polarizing element to the transparent protective film, in the optical laminate of the present invention, which may be sandwiched between layers having a UV-absorbing function (a liquid crystal cured film and a transparent protective film).

The thickness of the adhesive layer between the retardation film and the polarizing element, and between the polarizing element and the transparent protective film, is preferably 10 nm or greater, more preferably 30 nm or greater, and even more preferably 50 nm or greater, and preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 2 μm or less. When the adhesive layer thickness falls within this range, deformation at the bend point during repeated bending is less likely to occur, which can easily suppress the resulting streaking defects and increased oblique reflectivity. The thickness of the adhesive layer between the retardation film and the polarizing element, and between the polarizing element and the transparent protective film, can be the same or different. The thickness of the adhesive layer can be measured using, for example, an interferometer, a laser microscope, or a stylus film thickness gauge.

(Phase Difference Film) The phase difference film constituting the optical multilayer of the present invention comprises: a substrate film having a moisture permeability of 100 g/ ^m² /24 hours or greater; and a liquid crystal cured film formed on the substrate film. The moisture permeability of the substrate film is preferably 150 g/ ^m² /24 hours or greater, and more preferably 200 g/ ^m² /24 hours or greater. If the moisture permeability of the substrate film constituting the retardation film is above the aforementioned lower limit, it becomes easier to control the moisture composition in the optical laminate formed by laminating the retardation film and the polarizing element. In particular, when a dry-curing adhesive is used as the adhesive for forming the adhesive layer, the solvent in the adhesive is easily removed, making it easier to prepare an adhesive layer having physical properties similar to the elasticity and bendability of the liquid crystal cured film formed on the substrate film. Therefore, when the optical laminate is bent, the adhesive layer bonding the layers is less likely to affect the deformation of the liquid crystal cured film, and the deformation of the optical laminate as a whole and the deformation of the individual layers can easily track each other. This reduces deformation at the bend point during repeated bending, thereby suppressing the resulting streak-like defects and increased oblique reflectivity. The upper limit of the substrate film's moisture permeability is not particularly limited, but is typically 1000 g/ ^m² /24 hours or less, preferably 500 g/ ^m² /24 hours or less. The moisture permeability of the substrate film can be measured, for example, using JIS Z 0208 (cupping method). Specifically, the measurement can be performed according to the method described in the following examples.

The moisture permeability of the substrate film can be controlled by the type of resin constituting the film, the thickness of the film, the surface treatment, etc.

Examples of resins that form a substrate film having a moisture permeability of 100 g/ ^m² /24 hours or greater include triacetyl cellulose, polyvinyl pyrrolidone polymers, and (meth)acrylamide polymers. Triacetyl cellulose is preferred for its availability. These resins can be formed into a film to form a substrate film using known methods such as solvent casting and melt extrusion. Commercially available products can also be used.

The thickness of the substrate film can be appropriately determined according to the desired structure of the optical laminate. From the perspectives of thinness, processability, bendability, and strength of the optical laminate, it is generally 5 μm to 300 μm, preferably 15 μm to 200 μm, and more preferably 20 μm to 150 μm.

The base film preferably has a total light transmittance of 90% or greater, more preferably 92% or greater. A total light transmittance above the lower limit can produce an optical laminate with high transparency and excellent optical properties. The upper limit of the total light transmittance of the base film is not particularly limited, as long as it is 100% or less. Total light transmittance can be measured, for example, in accordance with JIS K 7361.

The absolute value of the phase difference value Rth(550) in the thickness direction of the substrate film for 550 nm light is preferably less than 5 nm, more preferably less than 3 nm. By controlling the phase difference value in the thickness direction of the substrate film, it is less likely to affect the optical properties expected by the liquid crystal cured film, so that the oblique reflectivity of the obtained optical multilayer body can be suppressed to a lower level. Such an optical multilayer body is excellent in suppressing light leakage and hue change during black display when incorporated into a display device, etc., and thus becomes an optical multilayer body with advantages in terms of optical properties. The smaller the above-mentioned phase difference value Rth(550) of the substrate film, the better, and it can also be 0 nm. The phase difference value Rth(550) of the substrate film can be controlled by formulating additives, and can also be controlled by a casting method, etc.

The surface of the substrate film may be subjected to surface treatment such as corona treatment or plasma treatment in accordance with the components constituting the liquid crystal curing film and alignment film to be formed, and the components of the adhesive that can be in contact with the substrate film, in order to improve the adhesion thereto.

In the present invention, the liquid crystal cured film constituting the phase difference film is a liquid crystal cured film that satisfies the following formulas (1) and (2) in a single layer: Re(450)/Re(550)≦1.00 (1) 1.00≦Re(650)/Re(550) (2) [wherein, Re(λ) represents the in-plane phase difference value at wavelength λ]. The so-called "satisfying in a single layer" means that a single layer of cured film obtained from a polymerizable liquid crystal compound containing a liquid crystal compound exhibits the optical properties expressed by the above formulas (1) and (2) in a single layer.

When the liquid crystal cured film satisfies equations (1) and (2), the liquid crystal cured film exhibits so-called reverse wavelength dispersion, in which the in-plane phase difference value at a short wavelength is smaller than the in-plane phase difference value at a long wavelength. When reverse wavelength dispersion is exhibited, there is a tendency to exhibit uniform phase difference performance over a wider wavelength range of visible light, and the optical properties of the optical laminate are easily improved. By using a liquid crystal cured film having optical properties that satisfy equations (1) and (2) above in a single layer (hereinafter also referred to as "liquid crystal cured film (x)"), a thinner phase difference film with excellent optical properties can be obtained.

In order to improve the reverse wavelength dispersion and thus further enhance the effect of improving the reflected hue of the front direction of the liquid crystal cured film, Re(450)/Re(550) is preferably 0.70 or more, more preferably 0.78 or more, and further preferably 0.95 or less, and further preferably 0.92 or less. Furthermore, Re(650)/Re(550) is preferably 1.0 or more, more preferably 1.01 or more, and further preferably 1.02 or more.

The above-mentioned in-plane retardation value can be adjusted by adjusting the thickness d1 of the liquid crystal cured film. The in-plane retardation value of the liquid crystal cured film is determined by Re = (nx(λ) - ny(λ)) × d (where d represents the thickness of the liquid crystal cured film, nx represents the principal refractive index of the refractive index ellipse formed by the liquid crystal cured film at a wavelength of λ nm in a direction parallel to the plane of the liquid crystal cured film, and ny represents the refractive index of the refractive index ellipse formed by the liquid crystal cured film at a wavelength of λ nm in a direction parallel to the plane of the liquid crystal cured film and orthogonal to the direction of nx). Therefore, to obtain the desired in-plane retardation value, it is sufficient to adjust the three-dimensional refractive index and the film thickness d.

Furthermore, the liquid crystal cured film (x) preferably satisfies the following formula (3): 100 nm ≤ Re (550) ≤ 170 nm (3) [wherein, Re (λ) represents the in-plane phase difference value at wavelength λ]. If the liquid crystal cured film (x) satisfies formula (3), it is easy to improve the front reflection hue during black display when the optical laminate (elliptical polarizing plate) including the liquid crystal cured film (x) is applied to an organic EL display device. The in-plane phase difference value is further preferably in the range of 130 nm ≤ Re A (550) ≤ 150 nm.

In the present invention, the liquid crystal cured film (x) can be formed from a cured product of a polymerizable liquid crystal composition containing at least one polymerizable liquid crystal compound. The polymerizable liquid crystal compound is not particularly limited as long as it can form a liquid crystal cured film having the desired optical properties. Polymerizable liquid crystal compounds previously known in the field of retardation films can be used.

A polymerizable liquid crystal compound is a liquid crystal compound having a polymerizable group. Examples of polymerizable liquid crystal compounds generally include polymerizable liquid crystal compounds in which the polymer (cured product) obtained by polymerizing the polymerizable liquid crystal compound in a state where the polymer is aligned in a specific direction exhibits positive wavelength dispersion, and polymerizable liquid crystal compounds in which the polymer exhibits reverse wavelength dispersion. From the perspective of easily obtaining a liquid crystal cured film that satisfies the optical properties expressed by the above formulas (1) and (2) alone, in the present invention, the liquid crystal cured film (x) constituting the phase difference film is preferably a cured product of a polymerizable liquid crystal composition comprising a polymerizable liquid crystal compound in which the polymer (cured product) obtained by polymerizing the polymer in a state where the polymer is aligned in a specific direction exhibits reverse wavelength dispersion.

The so-called polymerizable group refers to a group that can participate in the polymerization reaction. In the present invention, the polymerizable group possessed by the polymerizable liquid crystal compound that forms the liquid crystal cured film is preferably a photopolymerizable group. The so-called photopolymerizable group refers to a polymerizable group that can participate in the polymerization reaction through reactive species generated by a photopolymerization initiator, such as active free radicals or acids. Examples of the photopolymerizable group include: vinyl, vinyloxy, 1-chlorovinyl, isopropenyl, 4-vinylphenyl, acryloxy, methacryloyloxy, oxirane, and cyclobutyl. Among them, acryloxy, methacryloyloxy, vinyloxy, oxirane, and cyclobutyl are preferred, and acryloxy is more preferred.

The liquid crystal properties exhibited by polymerizable liquid crystal compounds can be either thermotropic or hydrotropic. Thermotropic liquid crystals are preferred because they allow for precise control of film thickness. Furthermore, the phase structure of thermotropic liquid crystals can be nematic, smectic, or discotic. Polymerizable liquid crystal compounds can be used alone or in combination of two or more.

Polymerizable liquid crystal compounds having a so-called T-shaped or H-shaped molecular structure tend to exhibit inverse wavelength dispersion, and polymerizable liquid crystal compounds having a T-shaped molecular structure tend to exhibit stronger inverse wavelength dispersion.

Preferred polymerizable liquid crystal compounds exhibiting reverse wavelength dispersion are those having the following characteristics (A) to (D). (A) Compounds capable of forming a nematic phase or a smectic phase. (B) The polymerizable liquid crystal compound has π electrons in the long axis direction (a). (C) The polymerizable liquid crystal compound has π electrons in a direction intersecting the long axis direction (a) (cross direction (b)). (D) The π electron density in the long axis direction (a) of the polymerizable liquid crystal compound is defined by the following formula (i), where the total number of π electrons present in the long axis direction (a) is N(πa) and the total number of molecular weights present in the long axis direction is N(Aa): D(πa)＝N(πa)/N(Aa)     (i) And the π electron density in the cross direction (b) of the polymerizable liquid crystal compound is defined by the following formula (ii), where the total number of π electrons present in the cross direction (b) is N(πb) and the total number of molecular weights present in the cross direction (b) is N(Ab): D(πb)＝N(πb)/N(Ab)    (ii) In formula (iii) 0≦[D(πa)/D(πb)]＜1    (iii) [i.e., the π electron density in the cross direction (b) is greater than the π electron density in the long axis direction (a)]. As described above, polymerizable liquid crystal compounds with π electrons in the long axis and in the direction opposite to the cross direction generally tend to form a T-shaped structure.

In the above characteristics (A) to (D), the long axis direction (a) and the number of π electrons N are defined as follows. For compounds having a rod-like structure, for example, the long axis direction (a) is the direction of the long axis of the rod. The number of π electrons N(πa) along the long axis direction (a) does not include π electrons lost due to polymerization reactions. The number of π electrons N(πa) along the long axis direction (a) is the total number of π electrons along the long axis and their coaxial π electrons, including, for example, the number of π electrons in regular rings that are in the long axis direction (a). The number of π electrons N(πb) along the cross direction (b) does not include π electrons lost due to polymerization reactions. The polymerizable liquid crystal compound meeting the above requirements has a mesogen structure along the long axis. This mesogen structure exhibits a liquid crystal phase (nematic phase, smectic phase).

By heating a polymerizable liquid crystal compound that satisfies the above (A) to (D) to a temperature above the phase transition temperature, a nematic phase or a smectic phase can be formed. In the nematic phase or the smectic phase formed by the alignment of the polymerizable liquid crystal compound, the polymerizable liquid crystal compound is usually aligned in such a way that the long axis directions become parallel to each other, and the long axis direction becomes the alignment direction of the nematic phase or the smectic phase. If such a polymerizable liquid crystal compound is made into a film and polymerized in the nematic phase or the smectic phase state, a polymer film composed of a polymer polymerized in a state aligned in the long axis direction (a) can be formed. The polymer film absorbs ultraviolet light by π electrons in the long axis direction (a) and π electrons in the cross direction (b). Here, the absorption maximum wavelength of the ultraviolet light absorbed by the π electrons in the cross direction (b) is set to λbmax. λbmax is typically 300 nm to 400 nm. The π electron density satisfies the above formula (iii), and the π electron density in the cross direction (b) is greater than the π electron density in the long-axis direction (a). Consequently, the polymer film absorbs linearly polarized ultraviolet light (wavelength λbmax) having a vibrational plane in the cross direction (b) more than it absorbs linearly polarized ultraviolet light (wavelength λbmax) having a vibrational plane in the long-axis direction (a). The ratio (absorbance of linearly polarized ultraviolet light in the cross direction (b) / absorbance in the long-axis direction (a)) is, for example, greater than 1.0, preferably greater than 1.2, and typically less than 30, for example, less than 10.

When polymerizable liquid crystal compounds having the above characteristics are polymerized in a state aligned in one direction, the birefringence of the polymer often exhibits reverse wavelength dispersion. Specifically, for example, the compound represented by the following formula (X) (hereinafter also referred to as "polymerizable liquid crystal compound (X)") can be cited. [Chemistry 1]

In formula (X), Ar represents a divalent group having an aromatic group which may have a substituent. The aromatic group mentioned here includes, for example, the groups exemplified below in (Ar-1) to (Ar-23). In addition, Ar may have two or more aromatic groups. The aromatic group may also contain at least one of a nitrogen atom, an oxygen atom, and a sulfur atom. When there are two or more aromatic groups contained in Ar, the two or more aromatic groups may be bonded to each other via a single bond, a divalent bond such as -CO-O-, or -O-. ^G1 and ^G2 each independently represent a divalent aromatic group or a divalent alicyclic alkyl group. Here, a hydrogen atom contained in the divalent aromatic group or divalent alicyclic alkyl group may be substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group, or a nitro group. The carbon atoms constituting the divalent aromatic group or divalent alicyclic alkyl group may be substituted with an oxygen atom, a sulfur atom, or a nitrogen atom. ^L1 , ^L2 , ^B1 , and ^B2 each independently represent a single bond or a divalent linking group. k and l each independently represent an integer from 0 to 3, and satisfy the relationship 1 ≤ k + l. Here, when 2 ≤ k + l, ^B1 and ^B2 , ^G1 , and ^G2 may be the same or different. ^E1 and ^E2 each independently represent an alkanediyl group having 1 to 17 carbon atoms, more preferably an alkanediyl group having 4 to 12 carbon atoms. Furthermore, a hydrogen atom contained in the alkanediyl group may be substituted with a halogen atom, _{and -CH2-} contained in the alkanediyl group may be substituted with -O-, -S-, or -C(=O)-. ^P1 and ^P2 each independently represent a polymerizable group or a hydrogen atom, and at least one of them is a polymerizable group.

^G1 and ^G2 are each independently preferably a 1,4-phenylenediyl group which may be substituted with at least one substituent selected from the group consisting of a halogen atom and an alkyl group having 1 to 4 carbon atoms, or a 1,4-cyclohexanediyl group which may be substituted with at least one substituent selected from the group consisting of a halogen atom and an alkyl group having 1 to 4 carbon atoms. More preferably, it is a methyl-substituted 1,4-phenylenediyl group, an unsubstituted 1,4-phenylenediyl group, or an unsubstituted 1,4-trans-cyclohexanediyl group. Even more preferably, it is an unsubstituted 1,4-phenylenediyl group or an unsubstituted 1,4-trans-cyclohexanediyl group. Furthermore, it is preferred that at least one of the multiple G ¹ and G ² groups is a divalent alicyclic alkyl group, and it is even more preferred that at least one of the G ¹ and G ² groups bonded to L ¹ or L ² is a divalent alicyclic alkyl group.

^L1 and ^L2 are each preferably independently a single bond, an alkylene group having 1 to 4 carbon atoms, -O- ^{, -S-} , -Ra1ORa2-, -Ra3COORa4-, -Ra5OCORa6- ^, -Ra7OC= ^OORa8- , ^-N =N-, ^{-CRc = CRd-} , or -C≡C-. Here ^{, Ra1} - ^Ra8 are each independently a single bond or an alkylene group having 1 to 4 carbon atoms, and ^{Rc and Rd} are each a C1-4 alkyl group or a hydrogen atom. ^L1 and ^L2 are each more preferably independently a single bond, ^-ORa2-1- _{, -CH2-} , _-CH2CH2- , ^-COORa4-1- , or ^-OCORa6-1- . Here, ^Ra2-1 , ^Ra4-1 , and ^Ra6-1 each independently represent a single bond, _-CH2- , _{or -CH2CH2-} . ^L1 and ^L2 each independently represent preferably a single bond, -O-, _{-CH2CH2- ,} -COO- _{, -COOCH2CH2-} , or -OCO-.

^B1 and ^B2 are each preferably independently a single bond, an alkylene group having 1 to 4 carbon atoms, -O-, -S-, -R ^a9 OR ^a10 -, -R ^a11 COOR ^a12 -, -R ^a13 OCOR ^a14 -, or -R ^a15 OC=OOR ^a16 -. Here, R ^a9 to R ^a16 each independently represent a single bond or an alkylene group having 1 to 4 carbon atoms. ^B1 and ^B2 are each more preferably independently a single bond, -OR ^a10-1 -, -CH ₂ -, -CH ₂ CH ₂ -, -COOR ^a12-1 -, or -OCOR ^a14-1 -. Here, R ^a10-1 , R ^a12-1 , and R ^a14-1 each independently represent a single bond, -CH ₂ -, or -CH ₂ CH ₂ -. ^B1 and ^B2 are each independently and preferably a single bond, -O- _{, -CH2CH2-} , _-COO- , _-COOCH2CH2- , _-OCO- or _-OCOCH2CH2- .

From the perspective of inverse wavelength dispersion, k and l are preferably within the range of 2 ≤ k + l ≤ 6, more preferably k + l = 4, and even more preferably k = 2 and l = 2. k = 2 and l = 2 are preferred, as they form a symmetrical structure.

Examples of the polymerizable group represented by ^P1 or ^P2 include epoxy, vinyl, vinyloxy, 1-chlorovinyl, isopropenyl, 4-vinylphenyl, acryloxy, methacryloxy, oxirane, and cyclobutyl. Preferred are acryloxy, methacryloxy, vinyl, and vinyloxy, and more preferred are acryloxy and methacryloxy.

Ar preferably has at least one member selected from an aromatic hydrocarbon ring which may have a substituent, an aromatic heterocyclic ring which may have a substituent, and an electron-withdrawing group. Examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, and an anthracene ring, with a benzene ring and a naphthalene ring being preferred. Examples of the aromatic heterocyclic ring include a furan ring, a benzofuran ring, a pyrrole ring, an indole ring, a thiophene ring, a benzothiophene ring, a pyridine ring, a pyrrolidine ring, a pyrimidine ring, a triazole ring, a trilazole ring, a pyrroline ring, an imidazole ring, a pyrazole ring, a thiazole ring, a benzothiazole ring, a thiazole ring, a benzothiazole ring, a benzothiazole ring, a benzophenone ring, and a phenanthroline ring. Among these, a thiazole ring, a benzothiazole ring, or a benzofuran ring is preferred, and a benzothiazole ring is more preferred. Furthermore, when Ar contains a nitrogen atom, it is preferred that the nitrogen atom has π electrons.

In formula (X), the total number _Nπ of π electrons possessed by the groups represented by Ar is usually 6 or more, preferably 8 or more, more preferably 10 or more, further preferably 14 or more, and particularly preferably 16 or more. Furthermore, it is preferably 32 or less, more preferably 26 or less, and further preferably 24 or less.

Examples of the aromatic group contained in Ar include the following groups.

[Chemistry 2]

In formulas (Ar-1) to (Ar-23), the symbol * represents a linking moiety, and Z ⁰ , Z ¹ , and Z ² each independently represent a hydrogen atom, a halogen atom, a C 1-12 alkyl group, a cyano group, a nitro group, a C 1-12 alkylsulfinyl group, a C 1-12 alkylsulfonyl group, a C 1-12 fluoroalkyl group, a C 1-12 alkoxy group, a C 1-12 alkylthio group, a C 1-12 N-alkylamino group, a C 2-12 N,N-dialkylamino group, a C 1-12 N-alkylaminesulfonyl group, or a C 2-12 N,N-dialkylaminesulfonyl group. Furthermore, Z ⁰ , Z ¹ , and Z ² may also include a polymerizable group.

Q ¹ and Q ² each independently represent -CR ^{2 '} R ^{3 '} -, -S-, -NH-, -NR ^{2 '} -, -CO-, or -O-, and R ^{2 '} and R ^{3 '} each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

J ¹ and J ² each independently represent a carbon atom or a nitrogen atom.

Y ¹ , Y ² and Y ³ each independently represent an aromatic alkyl group or an aromatic heterocyclic group which may be substituted.

^W1 and ^W2 each independently represent a hydrogen atom, a cyano group, a methyl group or a halogen atom, and m represents an integer from 0 to 6.

Examples of the aromatic alkyl group in Y ¹ , Y ² , and Y ³ include aromatic alkyl groups having 6 to 20 carbon atoms, such as phenyl, naphthyl, anthracenyl, phenanthrenyl, and biphenyl. Phenyl and naphthyl are preferred, and phenyl is more preferred. Examples of the aromatic heterocyclic group include aromatic heterocyclic groups having 4 to 20 carbon atoms, such as furyl, pyrrolyl, thienyl, pyridyl, thiazolyl, and benzothiazolyl, which have at least one heteroatom such as a nitrogen atom, an oxygen atom, or a sulfur atom. Furyl, thienyl, pyridyl, thiazolyl, and benzothiazolyl are preferred.

Y ¹ , Y ² , and Y ³ may each independently represent an optionally substituted polycyclic aromatic alkyl group or a polycyclic aromatic heterocyclic group. A polycyclic aromatic alkyl group refers to a condensed polycyclic aromatic alkyl group or a group derived from an aromatic ring group. A polycyclic aromatic heterocyclic group refers to a condensed polycyclic aromatic heterocyclic group or a group derived from an aromatic ring group.

Preferably, Z ⁰ , Z ¹ , and Z ² independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, a cyano group, a nitro group, or an alkoxy group having 1 to 12 carbon atoms. More preferably, Z ⁰ represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or a cyano group. Still more preferably, Z ¹ and Z ² represent a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, or a cyano group. Furthermore, Z ⁰ , Z ¹ , and Z ² may also contain a polymerizable group.

Q ¹ and Q ² are preferably -NH-, -S-, -NR ^{2 '} -, or -O-, and R ^{2 '} is preferably a hydrogen atom. Among them, -S-, -O-, and -NH- are particularly preferred.

Among formulae (Ar-1) to (Ar-23), formulae (Ar-6) and (Ar-7) are preferred from the viewpoint of molecular stability.

In formulas (Ar-16) to (Ar-23), ^Y1 may form an aromatic heterocyclic group together with the nitrogen atom to which it is bonded and ^Z0 . Examples of the aromatic heterocyclic group include those described above as aromatic heterocyclic rings that Ar may have, such as a pyrrole ring, an imidazole ring, a pyrroline ring, a pyridine ring, a pyrrolidine ring, a pyrimidine ring, an indole ring, a quinoline ring, an isoquinoline ring, a purine ring, and a pyrrolidinyl ring. The aromatic heterocyclic group may also have a substituent. Furthermore, ^Y1 may form a polycyclic aromatic alkyl group or a polycyclic aromatic heterocyclic group that may be substituted as described above together with the nitrogen atom to which it is bonded and ^Z0 . For example, a benzofuran ring, a benzothiazole ring, a benzoxazole ring, etc. can be cited.

In the present invention, the liquid crystal cured film (x) constituting the retardation film preferably has at least one maximum absorption wavelength between 300 and 400 nm, and the polymerizable liquid crystal compound forming the liquid crystal cured film (x) preferably has a maximum absorption wavelength between 300 and 400 nm. When a photopolymerization initiator is included in the polymerizable liquid crystal composition, there is a risk of polymerization and gelation of the polymerizable liquid crystal compound during long-term storage. However, if the polymerizable liquid crystal compound has a maximum absorption wavelength of 300 to 400 nm, even when exposed to ultraviolet light during storage, the generation of reactive species from the photopolymerization initiator and the subsequent polymerization and gelation of the polymerizable liquid crystal compound due to these reactive species can be effectively suppressed. This improves the long-term stability of the polymerizable liquid crystal composition and enhances the alignment and thickness uniformity of the resulting cured liquid crystal film. Furthermore, the maximum absorption wavelength of the polymerizable liquid crystal compound can be measured using a UV-visible spectrophotometer in a solvent capable of dissolving the polymerizable liquid crystal compound, such as chloroform or tetrahydrofuran.

Specific examples of polymerizable liquid crystal compounds capable of forming a liquid crystal cured film (x) include those described in Japanese Patent Application Laid-Open No. 2011-207765 and Japanese Patent Application Laid-Open No. 2010-031223. Furthermore, as long as a liquid crystal cured film (x) satisfying the above formulas (1) and (2) can be formed as a monolayer, a polymerizable liquid crystal compound whose homopolymer exhibits positive wavelength dispersibility may be used in an appropriate amount.

The content of the polymerizable liquid crystal compound in the polymerizable liquid crystal composition used to form the liquid crystal cured film (x) is, for example, 70 to 99.5 parts by mass, preferably 80 to 99 parts by mass, more preferably 85 to 98 parts by mass, and even more preferably 90 to 95 parts by mass, relative to 100 parts by mass of the solid content of the polymerizable liquid crystal composition. If the content of the polymerizable liquid crystal compound is within the above range, it is more advantageous from the perspective of the alignment of the obtained liquid crystal cured film (x). Furthermore, in this specification, the so-called solid content of the polymerizable liquid crystal composition refers to all components of the polymerizable liquid crystal composition excluding volatile components such as organic solvents.

The polymerizable liquid crystal composition used to form the liquid crystal cured film (x) may further contain additives such as a solvent, a polymerization initiator, a leveling agent, an antioxidant, a photosensitizer, and a reactive additive in addition to the polymerizable liquid crystal compound. These components may be used alone or in combination of two or more.

The polymerizable liquid crystal composition is typically applied to a substrate film or the like while dissolved in a solvent, so it is preferred that the composition contain a solvent. The solvent is preferably one that dissolves the polymerizable liquid crystal compound but is inert to the polymerization reaction of the polymerizable liquid crystal compound. Furthermore, it is preferred that the solvent does not dissolve the substrate film to be used. Examples of the solvent include alcohol solvents such as water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, propylene glycol methyl ether acetate, and ethyl lactate; acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, and methyl isobutyl ketone. Ketone solvents such as butyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; aliphatic hydrocarbon solvents such as ethylcyclohexane; aromatic hydrocarbon solvents such as toluene, xylene, and anisole; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide solvents such as dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone (NMP), and 1,3-dimethyl-2-imidazolidinone. These solvents may be used alone or in combination. Among them, from the perspective of film coating, it is preferred to use at least one selected from alcohol solvents, ester solvents, ketone solvents, chlorine-containing solvents, amide solvents, and aromatic hydrocarbon solvents. From the perspective of solubility of polymerizable liquid crystal compounds, it is more preferred to use at least one selected from ester solvents, ketone solvents, amide solvents, and aromatic hydrocarbon solvents.

The solvent content in the polymerizable liquid crystal composition is preferably 50-98 parts by weight, more preferably 70-95 parts by weight, per 100 parts by weight of the polymerizable liquid crystal composition. Therefore, the solid content is preferably 2-50 parts by weight per 100 parts by weight of the polymerizable liquid crystal composition. If the solid content is 50 parts by weight or less, the viscosity of the polymerizable liquid crystal composition decreases, resulting in a generally uniform film thickness with less tendency to unevenness. The solid content can be appropriately determined taking into account the thickness of the desired polymerizable liquid crystal cured film.

A polymerization initiator is a compound that generates reactive species upon exposure to heat or light, initiating the polymerization reaction of polymerizable liquid crystal compounds. Examples of reactive species include free radicals, cations, and anions. Photopolymerization initiators, which generate free radicals upon exposure to light, are preferred because they facilitate reaction control.

Examples of the photopolymerization initiator include benzoin compounds, benzophenone compounds, benzoyl ketal compounds, oxime compounds, α-hydroxyketone compounds, α-aminoketone compounds, tris(iodine) compounds, iodonium salts, and codonium salts. Commercially available products may also be used. Specifically, Irgacure (Irgacure, registered trademark) 907, Irgacure 184, Irgacure 651, Irgacure 819, Irgacure 250, Irgacure 369, Irgacure 379, Irgacure 127, Irgacure 2959, Irgacure 754, Irgacure 379EG (all manufactured by BASF JAPAN Co., Ltd.), Seikuol BZ, Seikuol Z, Seikuol BEE (all manufactured by Seiko Chemical Co., Ltd.), Kayacure BP100 (manufactured by Nippon Kayaku Co., Ltd.), Kayacure UVI-6992 (manufactured by Dow Chemical Co., Ltd.), Adeka Optomer SP-152, Adeka Optomer SP-170, Adeka Optomer N-1717, Adeka Optomer N-1919, Adeka Arkls NCI-831, Adeka Arkls NCI-930 (all manufactured by ADEKA Co., Ltd.), TAZ-A, TAZ-PP (all manufactured by Nihon SiberHegner Co., Ltd.), and TAZ-104 (manufactured by Sanwa Chemical Co., Ltd.). The polymerizable liquid crystal composition contains at least one photopolymerization initiator, and multiple types may be used in combination. The appropriate photopolymerization initiator should be selected based on its relationship with the polymerizable liquid crystal compound contained in the polymerizable liquid crystal composition.

Photopolymerization initiators can fully utilize the energy emitted by the light source and have excellent productivity. Therefore, the maximum absorption wavelength is preferably 300 nm to 400 nm, more preferably 300 nm to 380 nm. Among them, α-acetophenone-based polymerization initiators and oxime-based photopolymerization initiators are preferred.

Examples of the α-acetophenone compound include 2-methyl-2-morpholinyl-1-(4-methylphenyl)propane-1-one, 2-dimethylamino-1-(4-morpholinylphenyl)-2-benzylbutane-1-one, and 2-dimethylamino-1-(4-morpholinylphenyl)-2-(4-methylphenylmethyl)butane-1-one. More preferred examples include 2-methyl-2-morpholinyl-1-(4-methylphenyl)propane-1-one and 2-dimethylamino-1-(4-morpholinylphenyl)-2-benzylbutane-1-one. Examples of commercially available α-acetophenone compounds include Irgacure 369, 379EG, and 907 (all manufactured by BASF Japan Co., Ltd.) and Seikuol BEE (manufactured by Seiko Chemical Industries, Ltd.).

Oxime ester-based photopolymerization initiators generate free radicals such as phenyl radicals or methyl radicals upon exposure to light. Polymerization of polymerizable liquid crystal compounds proceeds appropriately due to these free radicals. Oxime ester-based photopolymerization initiators that generate methyl radicals have a higher polymerization reaction initiation efficiency and are therefore preferred in this regard. Furthermore, from the perspective of more efficient polymerization, it is preferred to use a photopolymerization initiator that can effectively utilize ultraviolet light with a wavelength of 350 nm or longer. As photopolymerization initiators that can effectively utilize ultraviolet light with a wavelength of 350 nm or longer, tris(II) compounds or carbazole compounds containing an oxime ester structure are preferred. From the perspective of sensitivity, carbazole compounds containing an oxime ester structure are more preferred. Examples of carbazole compounds containing an oxime ester structure include 1,2-octanedione, 1-[4-(phenylthio)-2-(O-benzoyl oxime)], acetone, and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyl oxime). Commercially available oxime ester photopolymerization initiators include Irgacure OXE-01, Irgacure OXE-02, and Irgacure OXE-03 (all manufactured by BASF Japan Co., Ltd.), Adeka Optomer N-1919, and Adeka Arkls NCI-831 (all manufactured by ADEKA Co., Ltd.).

The amount of the photopolymerization initiator is generally 0.1 to 30 parts by weight, preferably 1 to 20 parts by weight, and more preferably 1 to 15 parts by weight, relative to 100 parts by weight of the polymerizable liquid crystal compound. Within this range, the reaction of the polymerizable groups proceeds sufficiently and the alignment of the polymerizable liquid crystal compound is less likely to be disrupted.

Leveling agents are additives that adjust the fluidity of polymerizable liquid crystal compositions, resulting in a smoother coating. Examples include silicone-based, polyacrylate-based, and perfluoroalkyl-based leveling agents. Commercially available products can also be used as leveling agents. Specifically, examples include: DC3PA, SH7PA, DC11PA, SH28PA, SH29PA, SH30PA, ST80PA, ST86PA, SH8400, SH8700, FZ2123 (all manufactured by Toray Dow Corning Co., Ltd.), KP321, KP323, KP324, KP326, KP340, KP341, X22-161A, KF6001 (all manufactured by Shin-Etsu Chemical Co., Ltd.), TSF400, TSF401, TSF410, TSF4300, TSF4440, TSF4445, TSF-4446, TSF4452, TSF4460 (all manufactured by Momentive Performance Materials Co., Ltd. Japan Contract Company), Fluorinert (registered trademark) FC-72, Fluorinert FC-40, Fluorinert FC-43, Fluorinert FC-3283 (all manufactured by Sumitomo 3M Co., Ltd.), Megafac (registered trademark) R-08, Megafac R-30, Megafac R-90, Megafac F-410, Megafac F-411, Megafac F-443, Megafac F-445, Megafac F-470, Megafac F-477, Megafac F-479, Megafac F-482, Megafac F-483, Megafac F-556 (all manufactured by DIC Co., Ltd.), Eftop (trade name) EF301, Eftop EF303, Eftop EF351, Eftop EF352 (all manufactured by Mitsubishi Materials Corporation), Surflon (registered trademark) S-381, Surflon S-382, Surflon S-383, Surflon S-393, Surflon SC-101, Surflon SC-105, KH-40, SA-100 (all manufactured by AGC Seimi Chemical Co., Ltd.), E1830, E5844 (manufactured by Daikin Fine Chemicals Laboratories), BM-1000, BM-1100, BYK-352, BYK-353, and BYK-361N (all manufactured by BM Chemie). Leveling agents can be used alone or in combination.

The leveling agent content is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, per 100 parts by weight of the polymerizable liquid crystal compound. Leveling agent content within this range is preferred because it facilitates alignment of the polymerizable liquid crystal compound and tends to produce a smoother cured liquid crystal film.

The polymerization reaction of the polymerizable liquid crystal compound can be controlled by adding an antioxidant. The antioxidant can be a primary antioxidant selected from phenolic, amine, quinone, and nitroso antioxidants, or a secondary antioxidant selected from phosphorus and sulfur antioxidants. To ensure polymerization of the polymerizable liquid crystal compound without disrupting its alignment, the antioxidant content is typically 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, and even more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the polymerizable liquid crystal compound. Antioxidants can be used alone or in combination of two or more.

By using a photosensitizer, the photopolymerization initiator can be made highly sensitive. Examples of photosensitizers include thiophene, 9-oxothiophene, Ketones such as anthracene; anthracenes with substituents such as anthracene and alkyl ethers; phenanthrene; and rubrene. Photosensitizers can be used alone or in combination. The content of the photosensitizer is typically 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, and even more preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the polymerizable liquid crystal compound.

The use of reactive additives can improve the adhesion between the substrate film and the liquid crystal curing film, as well as the adhesion between the retardation film and the adhesive layer. Reactive additives preferably contain carbon-carbon unsaturated bonds and active hydrogen-reactive groups within their molecules. The term "active hydrogen-reactive group" as used herein refers to groups reactive toward groups with active hydrogens, such as carboxyl (-COOH), hydroxyl (-OH), and amino ( _-NH2 ). Representative examples include glycidyl, oxazoline, carbodiimide, aziridine, imide, isocyanate, thioisocyanate, and maleic anhydride groups. The number of carbon-carbon unsaturated bonds or active hydrogen reactive groups possessed by the reactive additive is usually 1 to 20, preferably 1 to 10.

The reactive additive preferably contains at least two active hydrogen-reactive groups. In this case, the multiple active hydrogen-reactive groups may be the same or different.

The carbon-carbon unsaturated bonds of the reactive additive may be carbon-carbon double bonds, carbon-carbon triple bonds, or combinations thereof, preferably carbon-carbon double bonds. Preferred reactive additives include vinyl and/or (meth)acrylic acid groups as carbon-carbon unsaturated bonds. Furthermore, reactive additives having an active hydrogen-reactive group selected from at least one of the group consisting of epoxy, glycidyl, and isocyanate groups are preferred, with reactive additives having both acryl and isocyanate groups being more preferred.

Specific examples of reactive additives include compounds having a (meth)acrylate group and an epoxy group, such as methacryloyloxyglycidyl ether or acryloxyglycidyl ether; compounds having a (meth)acrylate group and an oxycyclobutane group, such as oxycyclobutane acrylate or oxycyclobutane methacrylate; compounds having a (meth)acrylate group and a lactone group, such as lactone acrylate or lactone methacrylate; compounds having a vinyl group and an oxazoline group, such as vinyloxazoline or isopropenyloxazoline; and oligomers of compounds having a (meth)acrylate group and an isocyanate group, such as isocyanatomethyl acrylate, isocyanatomethyl methacrylate, 2-isocyanatoethyl acrylate, or 2-isocyanatoethyl methacrylate. Examples include compounds having a vinyl group or a vinylidene group and an acid anhydride, such as methacrylic anhydride, acrylic anhydride, maleic anhydride, or vinyl maleic anhydride. Among these, preferred are methacryloyloxyglycidyl ether, acryloyloxyglycidyl ether, isocyanatomethyl acrylate, isocyanatomethyl methacrylate, vinyl oxazoline, 2-isocyanatoethyl acrylate, 2-isocyanatoethyl methacrylate, or oligomers thereof, and particularly preferred are isocyanatomethyl acrylate, 2-isocyanatoethyl acrylate, or oligomers thereof.

As the reactive additive, a commercial product can be used directly or after purification as needed. Examples of commercial products include Laromer (registered trademark) LR-9000 (manufactured by BASF).

When the polymerizable liquid crystal composition contains a reactive additive, the content of the reactive additive is generally 0.01 to 10 parts by mass, preferably 0.1 to 7 parts by mass, relative to 100 parts by mass of the polymerizable liquid crystal compound.

The polymerizable liquid crystal composition used to form the liquid crystal cured film (x) can be obtained by separately stirring a polymerizable liquid crystal compound with a solvent or a polymerization initiator and other components at a specific temperature.

The liquid crystal cured film (x) can be produced, for example, by a method comprising the following steps: Forming a coating of a polymerizable liquid crystal composition containing at least one polymerizable liquid crystal compound on a substrate film or an alignment film described below, drying the coating, and aligning the polymerizable liquid crystal compounds in the polymerizable liquid crystal composition; and Maintaining the alignment state, polymerizing the polymerizable liquid crystal compound to form the liquid crystal cured film.

The coating film of the polymerizable liquid crystal composition can be formed by coating the polymerizable liquid crystal composition on a substrate film or an alignment film formed on the substrate film as described below.

Examples of methods for coating the polymerizable liquid crystal composition on a substrate film include known methods such as spin coating, extrusion coating, gravure coating, die coating, rod coating, and applicator coating, and printing methods such as flexographic coating.

Next, the solvent is removed by drying, etc., to form a dried coating. Examples of drying methods include natural drying, ventilation drying, heat drying, and reduced-pressure drying. By heating the coating obtained from the polymerizable liquid crystal composition, the solvent can be dried out of the coating, and the polymerizable liquid crystal compound can be aligned in a desired direction, such as a horizontal direction relative to the coating plane. The heating temperature of the coating can be appropriately determined based on the polymerizable liquid crystal compound used and the material of the substrate film forming the coating. In order to cause the polymerizable liquid crystal compound to transition to a liquid crystal phase, a temperature above the liquid crystal phase transition temperature is generally required. To remove the solvent contained in the polymerizable liquid crystal composition while simultaneously achieving the desired alignment of the polymerizable liquid crystal compound, the composition can be heated to a temperature above the liquid crystal phase transition temperature (smectic phase transition temperature or nematic phase transition temperature) of the polymerizable liquid crystal compound. The heating temperature is preferably at least 3°C higher than the liquid crystal phase transition temperature of the polymerizable liquid crystal compound, more preferably at least 5°C higher. While the upper limit of the heating temperature is not particularly limited, to avoid damage to the coating or substrate film, it is preferably below 180°C, more preferably below 150°C. The liquid crystal phase transition temperature can be measured, for example, using a polarizing microscope equipped with a temperature stage, a differential scanning calorimeter (DSC), or a thermogravimetric differential thermal analyzer (TG-DTA). When two or more polymerizable liquid crystal compounds are used, the phase transition temperature described above refers to the temperature measured using a mixture of polymerizable liquid crystal compounds, obtained by mixing all the polymerizable liquid crystal compounds constituting the polymerizable liquid crystal composition in the same ratio as in the composition of the polymerizable liquid crystal composition, in the same manner as when using a single polymerizable liquid crystal compound. Furthermore, it is generally known that the liquid crystal phase transition temperature of a polymerizable liquid crystal compound in a polymerizable liquid crystal composition may sometimes be lower than the liquid crystal phase transition temperature of the polymerizable liquid crystal compound as a single entity.

The heating time can be appropriately determined according to the heating temperature, the type of polymerizable liquid crystal compound used, the type of solvent, its boiling point and its amount, etc., and is generally 0.5 to 10 minutes, preferably 0.5 to 5 minutes.

The removal of the solvent from the coating can be performed simultaneously with or separately from the heating of the polymerizable liquid crystal compound to a temperature above the liquid crystal phase transition temperature. From the perspective of improving productivity, it is preferably performed simultaneously. Before heating the polymerizable liquid crystal compound to a temperature above the liquid crystal phase transition temperature, a pre-drying step can be provided to appropriately remove the solvent from the coating under conditions where the polymerizable liquid crystal compound contained in the coating obtained from the polymerizable liquid crystal composition will not polymerize. Examples of drying methods in the pre-drying step include natural drying, ventilation drying, heating drying, and reduced pressure drying. The drying temperature (heating temperature) in the drying step can be appropriately determined based on the type of polymerizable liquid crystal compound used, the type of solvent, its boiling point, and its amount.

Then, in the resulting dried coating, the alignment of the polymerizable liquid crystal compound is maintained and the polymerizable liquid crystal compound is polymerized directly by light irradiation, thereby forming a liquid crystal cured film that is a polymer of the polymerizable liquid crystal compound in the desired alignment. Photopolymerization is generally used as the polymerization method. In photopolymerization, the light irradiated onto the dried coating is appropriately selected based on the type of photopolymerization initiator contained in the dried coating, the type of polymerizable liquid crystal compound (particularly the type of polymerizable group possessed by the polymerizable liquid crystal compound), and its amount. Specific examples include light selected from one or more of the group consisting of visible light, ultraviolet light, infrared light, X-rays, α-rays, β-rays, and γ-rays, or active energy rays such as active electron beams. Among them, ultraviolet light is preferred in terms of ease of controlling the progress of the polymerization reaction or its use as a photopolymerization device for a wide range of users in this field. It is preferred to preselect the types of polymerizable liquid crystal compounds and photopolymerization initiators contained in the polymerizable liquid crystal composition so that they can be photopolymerized by ultraviolet light. Furthermore, during polymerization, the dried coating can be cooled by a suitable cooling mechanism while light irradiation is performed, thereby controlling the polymerization temperature. By adopting such a cooling mechanism, as long as the polymerization of the polymerizable liquid crystal compound is carried out at a relatively low temperature, a liquid crystal cured film can be properly formed even if the substrate used has relatively low heat resistance. Furthermore, the polymerization reaction can be promoted by raising the polymerization temperature within a range where the heat from light irradiation does not cause adverse effects (such as deformation of the substrate film due to heat). During photopolymerization, a patterned cured film can be obtained by masking and developing.

Examples of light sources for the active energy rays include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, halogen lamps, carbon arc lamps, tungsten lamps, gallium lamps, excimer lasers, LED (light-emitting diode) light sources emitting light in the wavelength range of 380 to 440 nm, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps.

The UV irradiation intensity is typically 10 to 3,000 mW/ ^cm² . The UV irradiation intensity is preferably within the wavelength range effective for activating photopolymerization initiators. The irradiation duration is typically 0.1 second to 10 minutes, preferably 0.1 second to 5 minutes, more preferably 0.1 second to 3 minutes, and even more preferably 0.1 second to 1 minute. If irradiated once or multiple times at this UV irradiation intensity, the cumulative amount of light is 10 to 3,000 mJ/ ^cm² , preferably 50 to 2,000 mJ/ ^cm² , and more preferably 100 to 1,000 mJ/ ^cm² .

The thickness of the liquid crystal cured film (x) is 0.5 μm or greater and 3 μm or less, more preferably 1.0 μm or greater, even more preferably 1.5 μm or greater, and even more preferably 2.5 μm or less. When the film thickness of the liquid crystal cured film (x) is within this range, it is easier to exhibit specific optical properties and also easier to suppress deformation at the bending point during repeated bending. The thickness of the liquid crystal cured film (x) can be measured using an interferometer film thickness gauge, a laser microscope, or a stylus film thickness gauge.

The liquid crystal curing film (x) can also be formed on the alignment film. The alignment film has an alignment limiting force that allows the polymerizable liquid crystal compound to align along the desired direction. By forming a liquid crystal curing film using a horizontal alignment film having an alignment limiting force that allows the polymerizable liquid crystal compound to align along the horizontal direction or a vertical alignment film having an alignment limiting force that allows the polymerizable liquid crystal compound to align along the vertical direction, the polymerizable liquid crystal compound can be aligned along the desired direction with relatively high precision, and a liquid crystal curing film that exhibits excellent optical properties when incorporated into a display device can be obtained. The alignment limiting force can be arbitrarily adjusted by the type of alignment film, surface state, or friction conditions. When the alignment film is formed of a photo-alignable polymer, it can be arbitrarily adjusted by polarized light irradiation conditions.

Alignment films are preferably solvent-resistant, preventing dissolution during coating of the polymerizable liquid crystal composition, and heat-resistant enough for solvent removal or heat treatment to align the polymerizable liquid crystal compound. Examples of alignment films include those containing aligning polymers, photo-alignment films, trench-alignment films with a concave-convex pattern or multiple grooves on the surface, and stretched films extending along the alignment direction. Photo-alignment films are preferred for their accuracy and quality in terms of alignment angle.

Examples of aligning polymers include polyamides or gelatins having amide bonds within their molecules, polyimides having imide bonds within their molecules and their hydrolyzates, polyvinyl alcohol, alkyl-modified polyvinyl alcohol, polyacrylamide, polyazole, polyethyleneimine, polystyrene, polyvinylpyrrolidone, polyacrylic acid, and polyacrylates. Among these, polyvinyl alcohol is preferred. Aligning polymers may be used alone or in combination of two or more.

Alignment films containing an alignment polymer are typically obtained by applying a composition comprising the alignment polymer dissolved in a solvent (hereinafter referred to as the "alignment polymer composition") to the surface of a substrate film or the like where the alignment film is to be formed, followed by removing the solvent; or by applying the alignment polymer composition to the substrate, removing the solvent, and then rubbing the substrate (rubbing method). Examples of solvents include those listed above as solvents for polymerizable liquid crystal compositions.

The concentration of the alignment polymer in the alignment polymer composition can be within a range where the alignment polymer material can be completely dissolved in the solvent, and is preferably 0.1 to 20%, more preferably 0.1 to 10%, calculated as solid content relative to the solution.

As the alignment polymer composition, a commercially available alignment film material may be used directly. Examples of commercially available alignment film materials include Sunever (registered trademark, manufactured by Nissan Chemical Industries, Ltd.) and Optomer (registered trademark, manufactured by JSR Corporation).

Examples of a method for applying the aligning polymer composition on the surface of a substrate film or the like on which the alignment film is to be formed include the same methods as those exemplified as the method for applying the polymerizable liquid crystal composition on the substrate film.

Examples of methods for removing the solvent contained in the alignment polymer composition include natural drying, ventilation drying, heat drying, and reduced pressure drying.

To impart alignment-controlling forces to the alignment film, a rubbing treatment (rubbing method) can be performed as needed. One example of a method for imparting alignment-controlling forces by rubbing is to bring an alignment polymer film formed on the substrate surface by coating and annealing an alignment polymer composition. This film is then brought into contact with a rotating rubbing roll wrapped with a rubbing cloth. By masking during the rubbing treatment, multiple regions (patterns) with different alignment directions can be formed on the alignment film.

Photo-alignment films are typically produced by applying a composition containing a polymer and/or monomer with photoreactive groups and a solvent (hereinafter referred to as the "photo-alignment film-forming composition") to the surface of a substrate film on which the alignment film is to be formed. After removing the solvent, the composition is then irradiated with polarized light (preferably polarized UV light). Photo-alignment films are advantageous in that the direction of the alignment-controlling force can be arbitrarily controlled by selecting the polarization direction of the irradiated light.

Photoreactive groups are groups that induce liquid crystal alignment upon exposure to light. Specifically, they include groups that participate in photoreactions such as molecular alignment induction, isomerization, dimerization, photocrosslinking, or photodecomposition reactions, which are the origin of the liquid crystal alignment. Groups that participate in dimerization or photocrosslinking reactions are preferred due to their superior alignment properties. The photoreactive group is preferably a group having an unsaturated bond, especially a double bond, and particularly preferably a group having at least one selected from the group consisting of a carbon-carbon double bond (C=C bond), a carbon-nitrogen double bond (C=N bond), a nitrogen-nitrogen double bond (N=N bond), and a carbon-oxygen double bond (C=O bond).

Examples of photoreactive groups having a C=C bond include vinyl, polyenyl, stilbene, styrylpyridyl, styrylpyridinium, chalcone, and cinnamyl groups. Examples of photoreactive groups having a C=N bond include groups having structures such as aromatic Schiff bases and aromatic hydrazones. Examples of photoreactive groups having an N=N bond include azophenyl, azonaphthyl, aromatic heterocyclic azo groups, bisazo groups, formyl groups, and groups having an oxyazobenzene structure. Examples of photoreactive groups having a C=O bond include benzophenone, coumarin, anthraquinone, and cis-butylenediimide groups. These groups may have a substituent such as an alkyl group, an alkoxy group, an aryl group, an allyloxy group, a cyano group, an alkoxycarbonyl group, a hydroxyl group, a sulfonic acid group, or a halogenated alkyl group.

Among these, photoreactive groups that participate in photodimerization reactions are preferred. Cinnamyl and chalcone groups are particularly preferred, as they facilitate the production of photo-alignment films with relatively low polarized light exposure requirements and excellent thermal and temporal stability. In particular, when the liquid crystal cured film is formed from a polymerizable liquid crystal compound having (meth)acryloyloxy groups as polymerizable groups, using a polymer having cinnamic acid structures at the end of the polymer side chains as the polymer containing photoreactive groups for forming the alignment film can improve adhesion to the liquid crystal cured film.

The solvent contained in the photo-alignment film-forming composition may be the same solvents as those exemplified above as solvents that can be used in the polymerizable liquid crystal composition, and may be appropriately selected based on the solubility of the polymer or monomer having a photoreactive group.

The content of the polymer or monomer having a photoreactive group in the photo-alignment film-forming composition can be appropriately adjusted based on the type of polymer or monomer and the desired thickness of the photo-alignment film. It is preferably at least 0.2% by mass, and more preferably within the range of 0.3-10% by mass, relative to the mass of the photo-alignment film-forming composition. The photo-alignment film-forming composition may also contain polymer materials such as polyvinyl alcohol and polyimide, or photosensitizers, within a range that does not significantly impair the properties of the photo-alignment film.

The method for applying the photo-alignment film-forming composition to the surface where the alignment film is to be formed can be the same as the method for applying the aligning polymer composition. The method for removing the solvent from the applied photo-alignment film-forming composition can be exemplified by natural drying, air drying, heat drying, and reduced pressure drying.

Polarized light irradiation can be performed by directly irradiating the substrate film with polarized UV light after removing the solvent from the photo-alignment film-forming composition applied to the substrate film. Alternatively, polarized light can be irradiated from the substrate film side and transmitted through the substrate film. The polarized light is preferably substantially parallel. The wavelength of the polarized light irradiated can be within the wavelength range where the photoreactive groups of the polymer or monomer containing the photoreactive groups can absorb light energy. Specifically, ultraviolet light (UV) with a wavelength of 250 to 400 nm is particularly preferred. Examples of light sources used for polarized light irradiation include xenon lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, and ultraviolet lasers such as KrF and ArF. High-pressure mercury lamps, ultra-high-pressure mercury lamps, and metal halide lamps are particularly preferred. High-pressure mercury lamps, ultra-high-pressure mercury lamps, and metal halide lamps are particularly preferred due to their high intensity of ultraviolet light at a wavelength of 313 nm. Polarized UV irradiation can be achieved by passing light from these light sources through an appropriate polarizing element. As the polarizing element, a polarizing filter, a polarizing prism such as a Glenn-Thompson prism or a Glenn-Taylor prism, or a wire-grid type polarizing element can be used.

Furthermore, if shielding is performed during rubbing or polarized light irradiation, multiple regions (patterns) with different liquid crystal alignment directions can also be formed.

Groove alignment films have a concave-convex pattern or multiple grooves on their surface. When a polymerizable liquid crystal compound is applied to a film with multiple linear grooves arranged at equal intervals, the liquid crystal molecules align along the grooves.

Examples of methods for obtaining a groove alignment film include: exposing the surface of a photosensitive polyimide film through an exposure mask having slits in the shape of the pattern, followed by development and rinsing to form a concave-convex pattern; forming a pre-cured UV-curable resin layer on a plate-shaped master having grooves on its surface, transferring the formed resin layer to a substrate, etc., and then curing the layer; and forming a concave-convex pattern by pressing a roll-shaped master having a plurality of grooves against a pre-cured UV-curable resin film formed on the surface of the alignment film, followed by curing the layer.

The thickness of the alignment film (an alignment film comprising an alignment polymer or a photo-alignment film) is generally in the range of greater than 10 nm and less than 10,000 nm, preferably greater than 10 nm and less than 2,500 nm, more preferably greater than 10 nm and less than 1,000 nm, further preferably greater than 10 nm and less than 500 nm, and particularly preferably greater than 50 nm and less than 250 nm.

(Polarizing Element) The polarizing element constituting the optical multilayer of the present invention is a film having the function of extracting linearly polarized light from incident natural light. It is a polyvinyl alcohol-based resin film containing a dichroic dye. The polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film can be a saponified polyvinyl acetate-based resin. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith (e.g., ethylene-vinyl acetate copolymers). Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, alkenes, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The saponification degree of polyvinyl alcohol resins is typically around 85-100 mol%, preferably 98 mol% or higher. Polyvinyl alcohol resins can also be modified, for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can be used. The degree of polymerization of polyvinyl alcohol resins is typically around 1,000-10,000, preferably 1,500-5,000.

Films made from this polyvinyl alcohol-based resin are used as the base film for polarizing films. The method for forming the polyvinyl alcohol-based resin film is not particularly limited, and a known method can be used. The film thickness of the polyvinyl alcohol-based base film can be set to approximately 10 to 150 μm, for example.

Polarizing elements are typically manufactured through the following steps: uniaxially stretching a polyvinyl alcohol resin film; dyeing the polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye; treating the polyvinyl alcohol resin film with the adsorbed dichroic dye with an aqueous boric acid solution; and finally, washing the film with water after the boric acid treatment. Furthermore, the polyvinyl alcohol resin film is dyed with the dichroic dye to incorporate the dichroic dye into the film. When a polarizing element is manufactured using this manufacturing method, the polarizing element becomes a stretched polyvinyl alcohol resin film that incorporates the dichroic dye.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing with a dichroic dye. When uniaxial stretching is performed after dyeing, it can be performed before or during the boric acid treatment. It can also be performed in multiple stages. Uniaxial stretching can be performed between reels with different circumferential speeds or using a heated reel. Furthermore, uniaxial stretching can be performed dry in the open air or wet while the polyvinyl alcohol-based resin film is swollen using a solvent. From the perspective of suppressing deformation of the polarizer, the stretch ratio is preferably 8 times or less, more preferably 7.5 times or less, and even more preferably 7 times or less. Furthermore, from the perspective of ensuring the function of the polarizer, the stretch ratio is generally 4.5 times or more. By setting the stretch ratio within this range, the polarizer's deformation over time can be suppressed.

One method for dyeing a polyvinyl alcohol resin film with a dichroic dye is to immerse the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Examples of dichroic dyes include iodine or a dichroic dye. Examples of dichroic dyes include dichroic direct dyes containing bisazo compounds such as C.I. DIRECT RED 39, and dichroic direct dyes containing trisazo and tetrakisazo compounds. Furthermore, the polyvinyl alcohol resin film is preferably immersed in water before dyeing.

When using iodine as a dichroic dye, dyeing typically involves immersing the polyvinyl alcohol resin film in an aqueous solution containing iodine and potassium iodide. The iodine content of this aqueous solution is typically 0.01 to 1 part by mass per 100 parts by mass of water. Furthermore, the potassium iodide content is typically 0.5 to 20 parts by mass per 100 parts by mass of water. The temperature of the aqueous solution used for dyeing is typically around 20 to 40°C. Furthermore, the immersion time (dyeing time) in this aqueous solution is typically around 20 to 1,800 seconds. Alternatively, to swell the polyvinyl alcohol resin film and facilitate dyeing, the film can be immersed in water before immersing it in the aqueous solution containing iodine and potassium iodide. The immersion temperature is usually 20-80°C, preferably 30-60°C, and the immersion time (dyeing time) is usually 20-1800 seconds.

On the other hand, when using a dichroic organic dye as the dichroic pigment, a dyeing method is typically employed in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing a water-soluble dichroic dye. The content of the dichroic organic dye in the aqueous solution is typically about 1× ^10-4 to 10 parts by mass per 100 parts by mass of water, preferably 1× ^10-3 to 1 part by mass, and further preferably 1× ^10-3 to 1× ^10-2 parts by mass. The aqueous solution may also contain an inorganic salt such as sodium sulfate as a dyeing auxiliary. The temperature of the dichroic dye aqueous solution used for dyeing is typically about 20 to 80°C. Furthermore, the immersion time in the aqueous solution (dyeing time) is typically about 10 to 1,800 seconds.

Boric acid treatment after dyeing with a dichroic dye is typically performed by immersing the dyed polyvinyl alcohol-based resin film in an aqueous boric acid solution. The boric acid content in the aqueous boric acid solution is typically 2 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. When iodine is used as the dichroic dye, the aqueous boric acid solution preferably contains potassium iodide, in which case the potassium iodide content is typically 0.1 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. The immersion time in the aqueous boric acid solution is typically 60 to 1,200 seconds, preferably 150 to 600 seconds, and even more preferably 200 to 400 seconds. The temperature for the boric acid treatment is usually above 50°C, preferably 50-85°C, and further preferably 60-80°C.

The polyvinyl alcohol-based resin film treated with boric acid is typically washed with water. This washing process can be performed, for example, by immersing the boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of the water used in the washing process is typically between 5 and 40°C. The immersion time is typically between 1 and 120 seconds.

After washing, a drying process is performed to obtain a polarizing element. Drying can be performed using, for example, a hot air dryer or a far-infrared heater. The drying temperature is generally around 30-100°C, preferably 50-80°C. The drying time is generally around 60-600 seconds, preferably 120-600 seconds. The drying process reduces the moisture content of the polarizing element to a level suitable for practical use. The moisture content is generally around 5-20% by mass, preferably 8-15% by mass. If the moisture content is within the above range, a polarizing element with moderate flexibility and excellent thermal stability is obtained.

The polyvinyl alcohol-based resin film was uniaxially stretched, dyed with a dichroic dye, treated with boric acid, washed with water, and dried in the above manner to obtain a film.

The thickness of the polarizing element is preferably 5 to 40 μm, more preferably 5 to 20 μm.

(Transparent Protective Film) The optical laminate of the present invention includes a transparent protective film bonded to the surface of the polarizing element opposite the retardation film via an adhesive layer. Polarizing elements are thin and easily damaged. To protect against external damage and contamination, protective films are often applied to both sides of the polarizing element. However, the optical laminate of the present invention does not have a protective film applied to the surface of the polarizing element facing the retardation film. This results in a thinner optical laminate with lower oblique reflectivity.

In the present invention, the transparent protective film has a total light transmittance of 90% or greater, more preferably 92% or greater. A total light transmittance above the lower limit can produce an optical laminate with high transparency and excellent optical properties. The upper limit of the total light transmittance of the substrate film is not particularly limited and can be 100% or less. Total light transmittance can be measured, for example, in accordance with JIS K 7361.

Furthermore, the 380 nm transmittance of the transparent protective film is 30% or less, preferably 25% or less, and more preferably 20% or less. If the 380 nm transmittance of the transparent protective film is below the above upper limit, when the optical multilayer including the transparent protective film is incorporated into an image display device, the internal layers (polarizing element and liquid crystal curing film, etc.) constituting the optical multilayer can be protected from damage by ultraviolet rays exposed on the viewing side. The lower limit of the 380 nm transmittance of the transparent protective film is not particularly limited and may be 0%. In order to set the 380 nm transmittance of the transparent protective film to below 30%, the transparent protective film may also contain an ultraviolet absorber, etc. The 380 nm transmittance can be measured, for example, by a spectrophotometer.

The transparent protective film, which is bonded to the polarizing element via an adhesive layer, can be made of any known resin film that meets the aforementioned requirements for total light transmittance and 380 nm transmittance. Examples of resins that can constitute the transparent protective film include polyolefins such as polyethylene, polypropylene, and northene polymers; cyclic olefin resins; polyvinyl alcohol; polyethylene terephthalate; polymethacrylate; polyacrylates; cellulose esters such as triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate; polyethylene naphthalate; polycarbonate; polysulfone; polyethersulfone; polyetherketone; polyphenylene sulfide and polyphenylene ether. This resin can be formed into a film by known methods such as solvent casting and melt extrusion. The surface of the transparent protective film can also be subjected to surface treatment such as silicone treatment, mold release treatment, corona treatment, plasma treatment, etc.

In one embodiment of the present invention, the transparent protective film preferably has a moisture permeability of 100 g/ ^m² /24 hours or more, more preferably 150 g/ ^m² /24 hours or more, and even more preferably 200 g/ ^m² /24 hours or more. If the moisture permeability of the transparent protective film is above the aforementioned lower limit, when the retardation film and the polarizing element are laminated using a dry-curing adhesive to form an optical laminate, the solvent in the dry-curing adhesive can be efficiently removed from the transparent protective film, in addition to the substrate film constituting the retardation film. This allows deformation of the liquid crystal cured film formed on the substrate film during bending to easily track deformation of the optical laminate, and prevents deformation at the bending point even with repeated bending. Furthermore, compared to a case where only the substrate film has a high moisture permeability, the time required to remove the solvent from the adhesive can be shortened, potentially improving productivity. The upper limit of the moisture permeability of the transparent protective film is not particularly limited, but is generally 1000 g/ ^m² /24 hours or less, preferably 500 g/ ^m² /24 hours or less. The moisture permeability of the transparent protective film can be measured using the same method as the moisture permeability of the substrate film.

When a transparent protective film having a moisture permeability of 100 g/m ² /24 hours or more is used, the transparent protective film may be the same as or different from the base film.

The thickness of the transparent protective film can be appropriately determined according to the desired optical laminate structure. From the perspectives of thinness, processability, bendability, and strength of the optical laminate, it is generally 5 μm to 300 μm, preferably 20 μm to 200 μm, and more preferably 20 μm to 150 μm.

The following describes an example of the layer structure of the optical laminate of the present invention based on Figures 1 and 2 , but the optical laminate of the present invention is not limited to these embodiments. The optical laminate 100 shown in Figure 1 includes a retardation film 1, a polarizer 3 laminated on one surface of the retardation film via an adhesive layer 2, and a transparent protective film 5 laminated on the surface of the polarizer 3 opposite the retardation film 1 via an adhesive layer 4. In the optical laminate 100 shown in Figure 1 , the retardation film 1 includes a liquid crystal cured film 13 formed on a base film 11 via an alignment film 12.

While the optical multilayer of the present invention may include, in addition to a retardation film, a polarizing element, a transparent protective film, and an adhesive layer bonding these layers together, other layers having various functions that can be incorporated into an image display device, etc., no other layers are incorporated into the layer structure of the adjacent retardation film/adhesive layer/polarizing element/adhesive layer/transparent protective film. Examples of other layers include an adhesive layer for integrating the optical multilayer into an image display device, a second retardation film comprising a liquid crystal cured film having liquid crystal compounds aligned perpendicularly to the film surface and having optical properties different from those of the liquid crystal cured film (x), and the like.

In the present invention, the retardation film can be laminated with a polarizer via an adhesive layer on either side of the substrate film or the liquid crystal cured film that constitutes the retardation film. For example, in the optical laminate 100 shown in Figure 1 , the substrate film 11 that constitutes the retardation film 1 is laminated with a polarizer 3 via an adhesive layer 2 . On the other hand, in the optical laminate 100 shown in Figure 2 , the liquid crystal cured film 13 that constitutes the retardation film 1 is laminated with a polarizer 3 via an adhesive layer 2 .

When the optical multilayer structure of the present invention is incorporated into an image display device, the heat resistance of the optical multilayer structure is easily improved when the liquid crystal cured film (x) constituting the retardation film is not in contact with the adhesive layer used to bond the optical multilayer structure to components such as image display units constituting the image display device. Therefore, in one embodiment of the present invention, it is preferred that the retardation film and the adhesive layer bonding the retardation film to the polarizing element are in contact on the side of the liquid crystal cured film constituting the retardation film.

The optical laminate of the present invention can be manufactured by laminating a retardation film, a polarizing element, and a transparent protective film separately via an adhesive. When using a dry-curing adhesive as the adhesive, the dry-curing adhesive can be applied or injected onto the laminating surfaces of the retardation film, polarizing element, and/or transparent protective film to form a laminate of retardation film/adhesive layer/polarizing element/adhesive layer/transparent protective film. The adhesive is then dried to remove the solvent from the laminate and cured to bond the layers.

The drying process and/or solvent removal can be performed, for example, by blowing hot air. The temperature depends on the type of solvent and is generally in the range of 30-200°C, preferably 35-150°C, more preferably 40-100°C, and even more preferably 50-100°C. The drying time is generally about 10 seconds to 30 minutes.

When using an active energy ray-curable adhesive, the adhesive layer is obtained by curing the active energy ray by irradiation. The active energy ray light source is not particularly limited, but preferably has a wavelength of 400 nm or less, and ultraviolet light is more preferred. Specific examples of light sources include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps.

The intensity of light irradiation for active energy ray-curable adhesives is appropriately determined based on the composition of the active energy ray-curable adhesive and is not particularly limited. The intensity is typically 10 to 3,000 mW/ ^cm² within the wavelength range effective for activation of polymerization initiators. The duration of light irradiation for active energy ray-curable adhesives can be appropriately selected based on the active energy ray-curable adhesive to be cured and is not particularly limited. It is typically 0.1 seconds to 10 minutes, preferably 1 second to 5 minutes, more preferably 5 seconds to 3 minutes, and even more preferably 10 seconds to 1 minute. When irradiating with such ultraviolet irradiation intensity once or multiple times, the cumulative light dose is usually 10 to 3,000 mJ/cm ² , preferably 50 to 2,000 mJ/cm ² , and more preferably 100 to 1,000 mJ/cm ² .

The optical laminate of the present invention can be continuously manufactured using a roll-to-roll process. For example, it can be manufactured continuously by preparing a retardation film comprising a base film and a liquid crystal cured film (x) wound into a roll, unwinding the retardation film while conveying it, sequentially laminating a separately manufactured polarizing element and a transparent protective film onto the retardation film using an adhesive for bonding the layers, and then curing the adhesive by drying or photocuring. Thus, in one embodiment of the present invention, the optical laminate of the present invention can be in the form of a roll of optical laminates.

The optical laminate of the present invention comprising a phase difference film and a polarizing element may also be an elliptical polarizing plate. Therefore, the present invention includes an elliptical polarizing plate comprising the optical laminate of the present invention.

In one embodiment of the present invention, the optical laminate and the elliptical polarizer of the present invention are preferably laminated so that the angle between the retardation axis (optical axis) of the liquid crystal cured film and the absorption axis of the polarizing element is 45±5°.

The elliptical polarizing plate of the present invention can be used in various display devices. A display device is a device having a display element and including a light-emitting element or light-emitting device as a light source. Examples of display devices include liquid crystal display devices, organic electroluminescent (EL) display devices, inorganic electroluminescent (EL) display devices, touch panel display devices, electroluminescent display devices (e.g., field emission display devices (FED), surface field emission display devices (SED)), electronic paper (display devices using electronic ink or electrophoretic elements, plasma display devices, projection display devices (e.g., grating valve imaging system (GLV) display devices, display devices with digital micromirror devices (DMD)), and piezoelectric ceramic displays. Liquid crystal display devices also include transmissive liquid crystal display devices. , transflective liquid crystal display devices, reflective liquid crystal display devices, direct-view liquid crystal display devices, and projection liquid crystal display devices. These display devices can be display devices that display two-dimensional images or stereoscopic display devices that display three-dimensional images. In particular, the elliptical polarizer of the present invention is preferably used in organic electroluminescent (EL) display devices and inorganic electroluminescent (EL) display devices, and the multilayer of the present invention is preferably used in liquid crystal display devices and touch panel display devices. These display devices exhibit excellent image display characteristics by incorporating the multilayer of the present invention, which is less likely to generate interference fringes.

In one embodiment of the present invention, the display device is preferably a flexible image display device. The present invention also includes a flexible image display device including the elliptical polarizing plate of the present invention.

A flexible image display device including the elliptical polarizing plate of the present invention preferably further includes a window and a touch sensor. The flexible image display device, for example, includes a flexible image display device laminate and an organic EL display panel. The flexible image display device laminate is positioned on the viewing side relative to the organic EL display panel and is configured to be flexible. In addition to the elliptical polarizing plate of the present invention, the flexible image display device laminate may also include a window, a touch sensor (touch panel), and the like. The order of lamination is arbitrary, but preferably, the window, elliptical polarizer, and touch sensor are laminated in sequence from the viewing side, or the window, touch sensor, and elliptical polarizer are laminated in sequence.

The presence of an elliptical polarizer on the viewing side of the touch sensor is preferred because the touch sensor pattern is less visible, improving the visibility of the displayed image. Each component can be laminated using adhesives, pressure-sensitive adhesives, or the like. Furthermore, the laminate for a flexible image display device can include a light-shielding pattern formed on at least one surface of any of the aforementioned layers: the window, the elliptical polarizer, or the touch sensor.

The window is located on the viewing side of a flexible image display device, protecting other components from external impact and environmental fluctuations such as temperature and humidity. Previously, glass was used as this protective layer. However, the window in a flexible image display device is not rigid and hard like glass; instead, it has the property of flexibility. The window comprises a flexible transparent substrate and may also include a hard coating on at least one side.

The window, touch sensor, and other components that constitute the multilayer structure of the flexible image display device are not particularly limited and may be any of the previously known ones. [Example]

Hereinafter, the present invention will be described in more detail with reference to the following examples. Furthermore, "%" and "parts" in the examples refer to mass % and mass parts, respectively, unless otherwise specified.

[Example 1] (1) Preparation of a composition for forming a photo-alignment film Two parts of a polymer (1) having a number average molecular weight of 28,000 represented by the following chemical formula were mixed with 98 parts of o-xylene, and the resulting mixture was stirred at 80°C for 1 hour to obtain a composition for forming a photo-alignment film.

Polymer (1) [Chemical 3] [Wherein, Me represents a methyl group].

(2) Preparation of a polymerizable liquid crystal composition for forming a liquid crystal cured film The polymerizable liquid crystal compound A-1 (86.0 parts), polymerizable liquid crystal compound A-2 (14.0 parts), polyacrylate compound (leveler/BYK-361N; manufactured by BYK-Chemie) (0.12 parts), 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butane-1-one (photopolymerization initiator/Irgacure 369; manufactured by Ciba Specialty Chemicals Co., Ltd.) (3.0 parts), and LALOMER LR9000 (manufactured by BASF JAPAN) (2.0 parts) of the following structure were mixed. Furthermore, anisole was added so that the solid content concentration became 9%. A polymerizable liquid crystal composition (A1) containing the polymerizable liquid crystal compound A-1 and the polymerizable liquid crystal compound A-2 was obtained. Furthermore, the polymerizable liquid crystal compound A-1 was synthesized using the method described in Japanese Patent Publication No. 2010-31223. The maximum absorption wavelength λmax(LC) of the polymerizable liquid crystal compound A-1 measured in chloroform was 350 nm.

Polymerizable liquid crystal compound A-1: [Chemical 4]

Polymerizable liquid crystal compound A-2: [Chemical 5]

(3) Preparation of Phase Difference Film A triacetyl cellulose film (KC4CZ-TAC, 40 μm thick, manufactured by Konica Minolta) was treated once using a corona treatment device (AGF-B10; manufactured by Kasuga Electric Co., Ltd.) at an output of 0.3 kW and a treatment speed of 3 m/min. The above-mentioned photo-alignment film-forming composition was applied to the corona-treated surface using a rod coater and dried at 80°C for 1 minute. Polarized UV exposure was performed using a polarized UV irradiation device (SPOT CURE SP-7 with a polarizing element unit; manufactured by Ushio Electric Co., Ltd.) at a cumulative light dose of 100 mJ/ ^cm2 to form a photo-alignment film. The thickness of the obtained photo-alignment film was measured using an elliptical polarimeter M-220 (manufactured by JASCO Corporation) and was found to be 100 nm.

The moisture permeability and total light transmittance of the triacetyl cellulose film (KC4CZ-TAC), used as the base film for the retardation film, were measured using the following methods. (Determination of Moisture Permeability) The moisture permeability of the protective film was measured at a temperature of 40°C and a relative humidity of 90% using the cupping method specified in JIS Z 0208 (g/( ^m² /24 hr)). The moisture permeability of the TAC film was 370 g/ ^m² /24 hours.

(Total Light Transmittance Measurement) Total light transmittance was measured in accordance with JIS K7361 using a haze meter HM150 manufactured by Murakami Color Technology Laboratory Co., Ltd. The total light transmittance of the TAC film described above was 93%.

In addition, the phase difference values [Re(550) and Rth(550)] of the above-mentioned TAC film as the substrate were measured at a wavelength of 550 nm, and the results were approximately 0.

Next, a polymerizable liquid crystal composition (A1) containing the previously prepared polymerizable liquid crystal compound was coated onto the photo-alignment film using a bar coater and dried at 120°C for 1 minute. Subsequently, a high-pressure mercury lamp (Unicure VB-15201BY-A; manufactured by Ushio Electric Co., Ltd.) was used to irradiate the surface coated with the polymerizable liquid crystal composition (A1) with ultraviolet light (500 mJ/ ^cm² at a wavelength of 313 nm in a nitrogen atmosphere). This formed a retardation film consisting of a triacetyl cellulose film (base film), a photo-alignment film, and a liquid crystal cured film. The thickness of the obtained liquid crystal cured film was measured using a laser microscope (LEXT; manufactured by Olympus Corporation) and the result was 2.3 μm.

The retardation value of the obtained retardation film at a wavelength of 550 nm was measured, and the result was Re(550) = 140 nm. In addition, the retardation values of the obtained retardation film at wavelengths of 450 nm and 650 nm were measured, and the results were Re(450)/Re(550) = 0.85 and Re(650)/Re(550) = 1.05.

(4) Preparation of polarizing element (iodine PVA type polarizing element) A 30 μm thick polyvinyl alcohol film (PVA: average degree of polymerization of approximately 2400, saponification degree of 99.9 mol% or more) was uniaxially stretched to approximately 5 times by dry stretching. The film was then immersed in pure water at 40°C for 40 seconds while maintaining the stretched state. The film was then dyed by immersing it in a dyeing aqueous solution at a mass ratio of iodine/potassium iodide/water of 0.044/5.7/100 at 28°C for 30 seconds. The film was then immersed in a boric acid aqueous solution at a mass ratio of potassium iodide/boric acid/water of 11.0/6.2/100 at 70°C for 120 seconds. After rinsing with pure water at 8°C for 15 seconds, the film was dried at 60°C for 50 seconds and then at 75°C for 20 seconds while maintaining a tension of 300 N. This yielded a 12 μm-thick polarizing element with iodine adsorption aligned on a polyvinyl alcohol film.

(5) Preparation of optical laminates The above-prepared phase difference film and polarizing element, as well as a triacetyl cellulose film (TAC: "KC4UY" manufactured by Konica Minolta Opto Co., Ltd.) as a transparent protective film are laminated in sequence. A water-based dry-curing adhesive is injected so that the triacetyl cellulose side of the phase difference film is in contact with the polarizing element, and the triacetyl cellulose of the transparent protective film is in contact with the side of the polarizing element opposite to the phase difference film. The absorption axis of the polarizing element and the phase axis of the liquid crystal cured film in the phase difference film are bonded together using a nip roller so that the absorption axis of the polarizing element and the phase axis of the liquid crystal cured film in the phase difference film are at 45 degrees. The resulting laminate was dried at 60°C for 2 minutes while maintaining a tension of 430 N/m. This yielded an optical laminate I (elliptical polarizing plate) consisting of a liquid crystal cured film/photo-alignment film/base film/adhesive layer/polarizing element/adhesive layer/transparent protective film. The aqueous dry-curing adhesive was prepared by adding 3 parts of carboxyl-modified polyvinyl alcohol (Kuraray Poval KL318; manufactured by Kuraray Co., Ltd.) and 1.5 parts of a water-soluble polyamide epoxy resin (Sumirez Resin 650; manufactured by Sumika Chemtex Co., Ltd., a 30% solids aqueous solution) to 100 parts of water.

The moisture transmittance and total light transmittance of the transparent protective film were measured in the same manner as the above-mentioned substrate film. The results showed that the moisture transmittance was 350 g/m ² /24 hours and the total light transmittance was 93%.

The 380 nm transmittance of the transparent protective film was measured using a double-beam method using a spectrophotometer (Shimadzu UV-3150) equipped with a clip equipped with a polarizing element. The clip had a mesh on the reference side that cut off 50% of the light. The 380 nm transmittance of the transparent protective film was 8%.

(6) Evaluation of optical multilayers (i) Evaluation of bending properties Bending properties were evaluated using the method of general test methods for coatings described in JIS-K-5600-5-1 - bending resistance (cylindrical mandrel method) and were carried out as follows. The optical multilayer was cut into 25 mm × 200 mm squares and the bending properties were tested using a cylindrical mandrel method bending resistance tester type II (manufactured by TP Technology Co., Ltd.) at a temperature of 25°C and a relative humidity of 55% RH. The liquid crystal cured layer of the retardation film was wound on a mandrel with a diameter of 6 mm (bending radius R = 3 mm) at the outside. After the test, the optical laminates were visually inspected in a darkroom using light to observe the presence of cracks. Those with visible cracks were rated "×" and those without visible cracks were rated "○". The results are shown in Table 1.

(ii) Evaluation of Oblique Reflectivity The oblique reflectivity of the optical laminate was measured as follows. The side of the optical laminate originating from the retardation film (in the case of optical laminate I, the liquid crystal cured film) was bonded to a reflective plate (a mirrored aluminum plate) using an acrylic adhesive to prepare a measurement sample. The oblique reflectivity (reflection Y value) was measured using a spectrophotometer (CM3700A manufactured by Konica Minolta Co., Ltd.) with light from a D65 illuminant incident at an angle of 8°. An oblique reflectivity of 1% or more and less than 6% was evaluated as ○, a 6% or more and less than 8% as △, and a 8% or more as ×. The results are shown in Table 1.

(iii) Heat Resistance Test Evaluation A test sample was prepared by bonding the side of the optical laminate (with the retardation film) to a glass plate using an acrylic adhesive. The resulting test sample was placed in an 85°C oven for 500 hours. The in-plane retardation value was then measured. The change in in-plane retardation at 550 nm before and after the heat resistance test was measured using a KOBRA-WR instrument manufactured by Oji Measuring Instruments Co., Ltd. A score of ○ was assigned if the change was 1 nm or more and less than 3 nm; a score of △ was assigned if the change was 3 nm or more and less than 5 nm; and a score of × was assigned if the change was 5 nm or more. The results are shown in Table 1.

[Example 2] An optical laminate consisting of a substrate film/photo-alignment film/liquid crystal cured film/adhesive layer/polarizing element/adhesive layer/transparent protective film was produced and evaluated in the same manner as in Example 1, except that the liquid crystal cured film side was attached to the polarizing element when the retardation film was attached to the polarizing element. The results are shown in Table 1.

[Example 3] An optical laminate consisting of a substrate film/photo-alignment film/liquid crystal cured film/adhesive layer/polarizer/adhesive layer/transparent protective film was prepared and evaluated in the same manner as in Example 1, except that a polymethyl methacrylate resin film (manufactured by Sumitomo Chemical Co., Ltd., moisture permeability: 50 g/ ^m² /24 hours, total light transmittance: 93%, 380 nm transmittance: 6%) was used as the transparent protective film. The results are shown in Table 1.

[Example 4] An optical laminate consisting of a substrate film/photo-alignment film/liquid crystal cured film/adhesive layer/polarizer/adhesive layer/transparent protective film was prepared and evaluated in the same manner as in Example 1, except that a cycloolefin polymer film ( ^COP ; ZF-14; manufactured by ZEON Co., Ltd., Japan, moisture transmittance: 13 g/m²/24 hours, total light transmittance: 92%, 380 nm transmittance: 8%) containing an ultraviolet absorber was used as the transparent protective film. The results are shown in Table 1.

[Comparative Example 1] The TAC film used as the transparent protective film in Example 1 was used as the substrate film. During the optical laminate fabrication process, the transparent protective film was bonded to the polarizer using the same aqueous dry-curable adhesive as used in Example 1. The unbonded transparent protective film side of the polarizer was then bonded to the liquid crystal cured film side of the retardation film using a 5 μm thick acrylic adhesive after curing. The triacetyl cellulose film used as the substrate film was then peeled off. An optical laminate consisting of a photo-alignment film/liquid crystal cured film/adhesive layer/polarizer/adhesive layer/transparent protective film was fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2] Except that the triacetyl cellulose substrate film was not removed, an optical laminate consisting of a substrate film/photo-alignment film/liquid crystal cured film/adhesive layer/polarizer/adhesive layer/transparent protective film was produced and evaluated in the same manner as in Comparative Example 1. The results are shown in Table 1.

[Reference Example 1] An optical laminate consisting of a substrate film/photo-alignment film/liquid crystal cured film/adhesive layer/polarizer/adhesive layer/transparent protective film was prepared and evaluated in the same manner as in Example 4, except that a cycloolefin polymer film (COP; ^ZF -14; manufactured by ZEON Co., Ltd., Japan, moisture transmittance: 13 g/m²/24 hours, total light transmittance: 92%, 380 nm transmittance: 90%) was used as the substrate film. The results are shown in Table 1.

[Table 1] Example 1 Example 2 Example 3 Implementation 4 Comparative example 1 Comparative example 2 Reference Example 1 Optical laminate composition Transparent protective film Kind TAC TAC PMMA COP TAC TAC COP thickness 40 μm 40 μm 40 μm 40 μm 40 μm 40 μm 40 μm Moisture permeability g/m ² /24 hr 370 370 50 13 370 370 13 Adhesive layer for bonding phase difference film and polarizing element Kind Water system Water system Water system Water system Pressure-sensitive adhesive Pressure-sensitive adhesive Water system thickness 0.1 μm 0.1 μm 0.1 μm 0.1 μm 5 μm 5 μm 0.1 μm Phase difference film base film Kind Zero-TAC Zero-TAC Zero-TAC Zero-TAC - TAC COP thickness 40 μm 40 μm 40 μm 40 μm - 40 μm 40 μm Rth 0 nm 0 nm 0 nm 0 nm - 15 nm 0 nm Moisture permeability g/m ² /24 hr 370 370 370 370 - 370 15 Evaluation results Flexibility test 3R 100,000 times ○ ○ ○ ○ × ○ × oblique reflectivity φ=50° ○ ○ ○ ○ × △ × Heat resistance test △ ○ ○ ○ × × × Comprehensive judgment A A A A C B C

It was confirmed that the optical laminates having the layer structure of the present invention (Examples 1 to 4) had excellent bendability and low oblique reflectivity.

1: Retardation film 2: Adhesive layer 3: Polarizing element 4: Adhesive layer 5: Transparent protective film 11: Base film 12: Alignment film 13: Liquid crystal curing film 100: Optical laminate

Figure 1 is a schematic cross-sectional view showing an example of the layered structure of the optical multilayer body of the present invention. Figure 2 is a schematic cross-sectional view showing an example of the layered structure of the optical multilayer body of the present invention.

Claims (12)

An optical laminate comprises, in order, a phase difference film, a polarizing element, and a transparent protective film, wherein the phase difference film comprises: a substrate film having a moisture permeability of 100 g/m ² /24 hours or more; and a liquid crystal cured film formed on the substrate film, having a thickness of 0.5 μm or more and 3 μm or less, and satisfying the following formulas (1) and (2) in a single layer: Re(450)/Re(550)≦1.00 (1) 1.00≦Re(650)/Re(550) (2) [wherein, Re(λ) represents the in-plane phase difference value at wavelength λ]; the polarizing element is composed of a polyvinyl alcohol-based resin film containing a dichroic pigment, the liquid crystal cured film is formed of a cured product of a polymerizable liquid crystal composition containing a polymerizable liquid crystal compound represented by the following formula (X), the transparent protective film has a total light transmittance of 90% or more and a 380 nm transmittance of 30% or less, and the phase difference film, the polarizing element, and the transparent protective film are adjacent to each other via an adhesive layer formed of a dry-curing adhesive containing polyvinyl alcohol; [In formula (X), Ar represents a divalent group having an aromatic group which may have a substituent, and the aromatic group may contain at least one of a nitrogen atom, an oxygen atom, and a sulfur atom. ^G1 and ^G2 each independently represent a divalent aromatic group or a divalent alicyclic alkyl group. Here, the hydrogen atom contained in the divalent aromatic group or the divalent alicyclic alkyl group may be substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group, or a nitro group. The carbon atoms constituting the divalent aromatic group or the divalent alicyclic alkyl group may be substituted with an oxygen atom, a sulfur atom, or a nitrogen atom. ^L1 , ^L2 , ^B1 , and B ² each independently represents a single bond or a divalent linking group, k and l each independently represent an integer from 0 to 3, and satisfy the relationship 1≦k+1. Here, when 2≦k+1, ^B1 and ^B2 , ^G1 and ^G2 may be the same as or different from each other, ^E1 and ^E2 each independently represent an alkanediyl group having 1 to 17 carbon atoms, and the hydrogen atom contained in the alkanediyl group may be substituted by a halogen atom, and the _-CH2- contained in the alkanediyl group may be substituted by -O-, -S-, or -C(=O)-. ^P1 and ^P2 each independently represent a polymerizing group or a hydrogen atom, and at least one of them is a polymerizing group. The optical laminate of claim 1, wherein the total light transmittance of the substrate film is greater than 90%, and the absolute value of the thickness-direction phase difference Rth(550) for light of 550 nm is less than 5 nm. The optical multilayer body of claim 1 or 2, wherein the phase difference film comprises a photo-alignment film having a thickness of not less than 10 nm and not more than 1000 nm between the substrate film and the liquid crystal cured film. The optical multilayer body of claim 1 or 2, wherein the liquid crystal cured film is formed by curing at least one compound having at least one maximum absorption in the wavelength range of 300 to 400 nm. The optical multilayer body of claim 1 or 2, wherein the liquid crystal cured film satisfies the following formula (3): 100 nm ≤ Re (550) ≤ 170 nm (3) [wherein Re (λ) represents the in-plane phase difference at wavelength λ]. The optical laminate of claim 1 or 2, wherein the transparent protective film has a moisture permeability of 100 g/m ² /24 hours or more. In the optical multilayer body of claim 1 or 2, the retardation film and the adhesive layer for bonding the retardation film and the polarizing element are in contact with the liquid crystal cured film side. An optical multilayer roll is obtained by rolling up the optical multilayer according to any one of claims 1 to 7. An elliptical polarizer comprises the optical laminate according to any one of claims 1 to 7. An organic EL display device includes the elliptical polarizer of claim 9. A flexible image display device comprises the elliptical polarizing plate of claim 9. The flexible image display device of claim 11 further comprises a window and a touch sensor.