TWI873286B - Optical laminate - Google Patents

Abstract

An object of the present invention is to provide a polarizing plate which has a polarizer, a pressure-sensitive adhesive layer, and an optically anisotropic layer in this order, and has a decrease in the degree of polarization (Py) is suppressed even when a wet heat resistance test is performed; an image display device including the polarizing plate, and a method for manufacturing the polarizing plate.

The polarizing plate has a polarizer, a pressure-sensitive adhesive layer, and an optically anisotropic layer in this order, wherein the optically anisotropic layer is a layer containing a cured product of a composition containing a liquid crystal compound having a polymerizable group and a photopolymerization initiator, the photopolymerization initiator comprises a photopolymerization initiator having a base dissociation constant pKb of less than 8, and the pressure-sensitive adhesive layer contains the resin (A).

Description

Optical laminates

The present invention relates to an optical laminate, and more particularly to a polarizing plate including an adhesive layer attached to the optical laminate, an image display device, and a method for manufacturing the optical laminate.

Patent document 1 discloses a polarizing plate, which has a polarizer, an adhesive layer and an optical anisotropic layer in sequence, and the optical anisotropic layer is obtained by curing a composition containing a liquid crystal compound having a polymerizable group and a photopolymerization initiator having an alkali dissociation constant pKb of 8 or more.

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] International Publication No. 2016/194792

In a polarizing plate having a polarizer, an adhesive layer, and an optically anisotropic layer in sequence, the degree of polarization (Py) may decrease during a moisture and heat resistance test.

The present invention provides a polarizing plate having a polarizer, an adhesive layer and an optical anisotropic layer in sequence, and suppressing the decrease of polarization degree (Py) even when performing a moisture and heat resistance test, an image display device including the polarizing plate, and a method for manufacturing the polarizing plate.

The present invention provides a method for manufacturing the polarizing plate, image display device, polarizing plate with adhesive layer and optical laminate shown below.

[1] An optical laminate having a polarizer, an adhesive layer, and an optical anisotropic layer in sequence; wherein,

The aforementioned optically anisotropic layer is a layer comprising a cured product of a composition, and the composition contains a liquid crystal compound having a polymerizable group and a photopolymerization initiator.

The aforementioned photopolymerization initiator includes a photopolymerization initiator having a base dissociation constant pKb of less than 8,

The aforementioned adhesive layer includes a resin (A),

The aforementioned adhesive layer satisfies the following formula (1),

0≦α≦60 (1)

[In the formula, α represents the product of the content (mass %) of the acid component in all monomer components constituting the aforementioned resin (A) and the thickness (μm) of the aforementioned adhesive layer. ]

[2] The optical layered product as described in [1], wherein the content of the acid component in all monomer components constituting the resin (A) is greater than 0 mass % and less than 1.0 mass %.

[3] An optical laminate as described in [1] or [2], wherein the thickness of the adhesive layer is less than 100 μm.

[4] An optical laminate as described in any one of [1] to [3], wherein a protective film is provided on the side of the polarizer opposite to the optical anisotropic layer.

[5] A polarizing plate with an adhesive layer, comprising an optical laminate as described in any one of [1] to [4], and further comprising an adhesive layer on the side of the optical anisotropic layer opposite to the polarizer side.

[6] An image display device comprising a polarizing plate with an adhesive layer as described in [5].

[7] A method for manufacturing an optical laminate, which is to manufacture the optical laminate described in [1], and the manufacturing method comprises the following steps:

Steps for preparing the aforementioned polarizer;

A step of curing the composition containing the aforementioned liquid crystal compound having a polymerizable group and a photopolymerization initiator to form an optically anisotropic layer;

A step of forming an adhesive layer comprising the aforementioned resin (A); and

The step of bonding the aforementioned polarizer and the aforementioned optical anisotropic layer via the aforementioned adhesive layer.

The content of the acid component in all monomer components of the resin (A) contained in the above-mentioned adhesive layer is the mass ratio of the content of the monomer with an acidic group relative to the mass of all monomers used to make the resin (A). The adhesive layer may contain multiple types of resins (A), but at this time, only the content of the monomer with an acidic group relative to the mass of all monomers used to make the multiple types of resins (A) is required.

According to the present invention, a polarizing plate having a polarizer, an adhesive layer and an optical anisotropic layer in sequence and capable of suppressing the decrease of polarization degree (Py) even when a moisture and heat resistance test is performed, an image display device including the polarizing plate and a method for manufacturing the polarizing plate can be provided.

1: Optical laminate

2: Polarizer

3,13: Adhesive layer

4: Optical anisotropic layer

10: Polarizing plate with adhesive layer

11: Protective film

12: Next is the agent layer

FIG1 is a schematic cross-sectional view showing an example of the layer structure of the optical multilayer body of the present invention.

FIG2 is a schematic cross-sectional view showing an example of the layer structure of the polarizing plate with an adhesive layer of the present invention.

The following describes the implementation of the present invention with reference to the drawings, but the present invention is not limited to the following implementation. In order to facilitate the understanding of each component, the scale of the components shown in the drawings is appropriately adjusted, and the scale of the components shown in the drawings may not be consistent with the scale of the actual components.

<Optical layered structure>

The optical laminate of the present disclosure is described with reference to FIG1. As shown in FIG1, the optical laminate 1 can be formed by sequentially laminating a polarizer 2, an adhesive layer 3, and an optical anisotropic layer 4. Although not shown, the optical laminate 1 can have layers other than those shown in FIG1, such as a protective film and an adhesive layer described later.

(Polarizer)

Polarizer 2 may be an absorption-type polarizer, which has the property of absorbing linear polarization with a vibration plane parallel to its absorption axis and allowing linear polarization with a vibration plane orthogonal to the absorption axis (parallel to the transmission axis) to pass through. Polarizer 2 may be suitably a polarizer formed by adsorbing and aligning a dichroic dye on a uniaxially stretched polyvinyl alcohol resin film. Polarizer 2 may be manufactured, for example, by a method including: a step of uniaxially stretching a polyvinyl alcohol resin film; a step of dyeing a polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye; a step of treating the polyvinyl alcohol resin film adsorbed with the dichroic dye with a crosslinking liquid such as a boric acid aqueous solution; and a step of washing with water after treatment with the crosslinking liquid.

Polyvinyl alcohol resins are obtained by saponifying polyvinyl acetate resins. Polyvinyl acetate resins include copolymers of vinyl acetate and other monomers copolymerizable with the vinyl acetate, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having ammonium groups. In this specification, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid. The same applies to "(meth)acryl", "(meth)acrylate", etc.

The saponification degree of polyvinyl alcohol resin is usually 85 mol% to 100 mol%, preferably 98 mol% to 100 mol%. Polyvinyl alcohol resin can be modified, for example, polyvinyl formaldehyde or polyvinyl acetal modified with aldehydes can also be used. The average polymerization degree of polyvinyl alcohol resin is usually 1000 to 10000, preferably 1500 to 5000. The average polymerization degree of polyvinyl alcohol resin can be obtained according to JIS K 6726.

The polyvinyl alcohol resin film can be used as the embryo membrane of the polarizer. There is no particular limitation on the method of manufacturing the polyvinyl alcohol resin film, and a known method can be used. There is no particular limitation on the thickness of the polyvinyl alcohol embryo membrane, but it can be determined by the method of manufacturing a polarizer of a preferred thickness described later.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, during, or after dyeing with a dichroic dye. When the uniaxial stretching is performed after dyeing, the uniaxial stretching can be performed before or during the crosslinking treatment. Furthermore, the uniaxial stretching can also be performed at multiple stages.

During uniaxial stretching, the film can be stretched along the single axis between rollers with different rotation speeds, or a hot roller can be used to stretch the film along the single axis. In addition, uniaxial stretching can be dry stretching in the atmosphere, or wet stretching using a solvent or water to swell the polyvinyl alcohol resin film. The stretching ratio is usually 3 to 8 times.

The method of dyeing the polyvinyl alcohol resin film with a dichroic dye can be, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing a dichroic dye. The dichroic dye is iodine or a dichroic organic dye. In addition, the polyvinyl alcohol resin film is preferably immersed in water before the dyeing treatment.

The cross-linking treatment after dyeing with dichroic pigments is usually carried out by immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid. When iodine is used as the dichroic pigment, the aqueous solution containing boric acid preferably contains potassium iodide.

The thickness of the polarizer 2 is usually less than 30μm, preferably less than 20μm, more preferably less than 15μm, and even more preferably less than 13μm. The thickness of the polarizer 2 is usually more than 2μm, preferably more than 3μm.

(Adhesive layer)

The adhesive layer 3 is disposed between the polarizer 2 and the optical anisotropic layer 4. The adhesive layer 3 can bond the polarizer 2 or the linear polarizer described later to the optical anisotropic layer 4. The adhesive layer 3 can be composed of one layer or two or more layers, but is preferably composed of one layer. The adhesive layer 3 is preferably laminated in contact with the polarizer 2 or the linear polarizer. In addition, the adhesive layer 3 is preferably laminated in contact with the optical anisotropic layer 4.

The adhesive layer 3 includes a resin (A). The resin (A) may be, for example, a (meth)acrylic resin, a rubber resin, a urethane resin, an ester resin, a silicone resin, or a polyvinyl ether resin. From the perspective of transparency, weather resistance, and heat resistance, the resin (A) is preferably a (meth)acrylic resin. The resin (A) used to form the adhesive layer 3 is sometimes referred to as a "base polymer" below. The adhesive layer 3 may include only one type of resin (A), or may include two or more types.

The (meth)acrylic resin may be a polymer or copolymer having one or more of (meth)acrylic acid esters such as butyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isoborneol (meth)acrylate as monomer components. The (meth)acrylic resin may be one obtained by copolymerizing polar monomers. Polar monomers include monomers having carboxylic acid groups, carboxyl groups, hydroxyl groups, amide groups, amino groups, epoxy groups, etc., such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate. However, when copolymerizing polar monomers, when the polar monomer is an acidic group such as a carboxylic acid group (when the polar monomer is (meth)acrylic acid, etc.), the copolymerization ratio must be adjusted so that the content of the acid component is within the above range.

(Adhesive composition)

The adhesive layer 3 may be composed of an adhesive composition containing a resin (A). The adhesive composition may be an active energy ray curing type or a heat curing type. From the perspective of transparency, weather resistance and heat resistance, the adhesive layer 3 is preferably composed of an adhesive composition having a (meth) acrylic resin as a base polymer.

The adhesive composition may contain only the above-mentioned base polymer, but usually further contains a crosslinking agent. Examples of crosslinking agents include: when a (meth)acrylic resin has a carboxylic acid group, a metal ion having a valence of more than 2 valence forms a metal salt with the carboxylic acid group; a polyamine compound that forms an amide bond with the carboxylic acid group; when the (meth)acrylic resin has an ester bond (carboxyl group), a polyamine compound that forms an amide bond by an ester-amide exchange reaction; a polyepoxide or polyol that forms an ether bond with a hydroxyl group; or, as described above, when the base polymer has a carboxyl group, a polyisocyanate compound that forms a urethane bond with the hydroxyl group; or a polyisocyanate compound that forms an amide bond with the carboxyl group. Among these, polyisocyanate compounds are preferred. Furthermore, the crosslinking agent usually does not have an acidic group such as a carboxylic acid group.

Examples of the polyisocyanate compounds include aliphatic isocyanate compounds (e.g., hexamethylene diisocyanate), alicyclic isocyanate compounds (e.g., isophorone diisocyanate), hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, aromatic isocyanate compounds (e.g., toluene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, etc.), and the like. In addition, the polyisocyanate compounds may be derivatives of the above-mentioned isocyanate compounds and adducts produced by polyol compounds (e.g., adducts produced by glycerol, trihydroxymethyl propane, etc.), isocyanurate compounds, urea-type compounds, and urethane prepolymer-type isocyanate compounds formed by addition reactions with polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc. The polyisocyanate compounds may be used alone or in combination of two or more. Among these, toluene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, and these polyol compounds or these isocyanurate compounds are preferred from the viewpoint of durability.

The ratio of the crosslinking agent to 100 parts by mass of the base polymer can be, for example, 0.01 parts by mass to 10 parts by mass, preferably 0.1 parts by mass to 3 parts by mass, and even more preferably 0.1 parts by mass to 1 part by mass.

The so-called active energy ray-curing adhesive composition is an adhesive composition that has the property of being cured by being irradiated with active energy rays such as ultraviolet rays or electron rays, and has the property of being adhesive and closely attached to an adherend such as a film even before being irradiated with active energy rays, and can be cured and the adhesive force can be adjusted by being irradiated with active energy rays.

The active energy ray-curing adhesive composition is preferably ultraviolet-curing. In addition to the base polymer and the crosslinking agent, the active energy ray-curing adhesive composition also contains an active energy ray polymerizable compound. It can further contain a photopolymerization initiator or a photosensitizer as needed.

Active energy ray polymerizable compounds include, for example: (meth)acrylic acid compounds containing (meth)acrylic acid groups, such as (meth)acrylic acid ester monomers having at least one (meth)acrylic acid group in the molecule; (meth)acrylic acid ester oligomers having at least two (meth)acrylic acid groups in the molecule obtained by reacting two or more compounds containing functional groups; and (meth)acrylic acid compounds containing (meth)acrylic acid groups.

The adhesive composition system may further contain a silane compound. By containing a silane compound, the adhesion between the adhesive layer and the deposited layer can be improved. In addition, two or more silane compounds can be used.

Examples of silane compounds include vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tris(2-methoxyethoxy)silane, 3-glycidyl propyl trimethoxysilane, 3-glycidyloxypropyl triethoxysilane, 3-glycidyloxypropyl methyl dimethoxysilane, 3-glycidyloxypropyl ethoxy dimethyl silane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, 3-chloropropyl methyl dimethoxysilane, 3-chloropropyl trimethoxysilane, 3-methacryloyloxypropyl trimethoxysilane, and 3-hydrothiopropyl trimethoxysilane.

Furthermore, the silane compound may include an oligomer derived from the above-mentioned silane compound.

The content of the silane compound in the adhesive composition is generally 0.01 to 10 parts by mass relative to 100 parts by mass of the base polymer, preferably 0.03 to 5 parts by mass, more preferably 0.05 to 2 parts by mass, and even more preferably 0.1 to 1 part by mass.

The adhesive composition may include additives such as microparticles, beads (resin beads, glass beads, etc.), glass fibers, resins other than base polymers, thickeners, fillers (metal powder or other inorganic powders, etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, defoamers, anticorrosive agents, photopolymerization initiators, etc., for imparting light scattering properties.

The adhesive layer 3 can be formed by applying the above-mentioned adhesive composition, such as an organic solvent dilution, on the substrate and drying it. When an active energy ray-curing adhesive composition is used, a hardened material with a desired degree of hardening can be formed by irradiating the formed adhesive layer with active energy rays.

Adhesive layer 3 satisfies formula (1).

0≦α≦60 (1)

[In the formula, α represents the product of the content (mass %) of the acid component in all monomer components constituting the aforementioned resin (A) and the thickness (μm) of the adhesive layer. ]

By making the adhesive composition satisfy the above formula, the optically anisotropic layer is a layer containing a cured product of a composition containing a liquid crystal compound having a polymerizable group and a photopolymerization initiator having a base dissociation constant pKb of less than 8. In this case, the polarization degree (Py) of the optical laminate tends to be less likely to decrease in the moisture and heat resistance test.

The acid component is as described above, for example, monomers having acidic groups such as carboxyl groups can be listed. Monomers having carboxyl groups can be listed, for example, (meth) acrylic acid, etc. From the content of the acid component constituting the resin (A) and the thickness of the adhesive layer (the preferred range is described later), it is possible to obtain α that easily satisfies formula (1). When the adhesive layer contains two or more resins (A), the content of the acid component (mass %) is the ratio of the mass of the acid component to the mass of all monomer components (including the acid component) used to make the resin (A).

From the perspective of suppressing the decrease in the polarization degree (Py) of the optical laminate in the moisture and heat resistance test, the upper limit of α in formula (1) is preferably 50 or less, more preferably 45 or less, still more preferably 40 or less, particularly preferably 30 or less, and particularly preferably 25 or less. The lower limit of α in formula (1) can be, for example, 0.01 or more, 0.1 or more, or 1 or more.

The content of the acid component in all monomer components constituting the resin (A) may be, for example, 5% by mass or less, preferably 4% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less, and particularly preferably 1% by mass or less. The content of the acid component in all monomer components constituting the resin (A) is preferably 0% by mass or more and 1.0% by mass or less, for example, 0.01% by mass or more or 0.1% by mass or more. It is particularly preferred that the acid component is not contained in all monomer components constituting the resin (A).

The thickness of the adhesive layer 3 can be, for example, less than 100 μm, preferably more than 1 μm and less than 100 μm, more preferably more than 2 μm and less than 70 μm, still more preferably more than 3 μm and less than 50 μm, and particularly preferably more than 5 μm and less than 25 μm.

(Optical anisotropic layer)

The optically anisotropic layer 4 is composed of a layer of a hardened material (hereinafter also referred to as a hardened material layer) containing a composition (hereinafter also referred to as a hardened material layer forming composition), and the composition contains a liquid crystal compound having a polymerizable group (hereinafter also referred to as a polymerizable liquid crystal compound) and a photopolymerization initiator. The hardened material layer forming composition used in the present invention is preferably in a liquid state. The liquid hardened material layer forming composition has the advantage of being able to be easily formed into a film-shaped or sheet-shaped hardened material layer by vertical coating on a suitable substrate. Here, the so-called "liquid" hardened material layer forming composition is a concept of a hardened material layer forming composition that includes a solution formed by dissolving the liquid crystal compound or photopolymerization initiator contained in the hardened material layer forming composition in an appropriate solvent (described later).

The photopolymerization initiator includes a photopolymerization initiator with a base dissociation constant pKb of less than 8. In this specification, the base dissociation constant (pKb) refers to the pKb at a temperature of 25°C, typically the base dissociation constant (pKb) in an aqueous solution at a water temperature of 25°C, which is one of the indicators used to quantitatively represent the strength of the base and has the same meaning as the alkalinity constant. The base dissociation constant (pKb) can be obtained from the formula pKb=14.0-pKa after the acid dissociation constant (pKa) is obtained by the method described in A.E.Martell, R.M.Smith, "Critical Stability Constants", Vol.1 to 3, Plenum Press (1974, 1975, 9177).

According to the knowledge of the inventors, it was found that when the composition for forming a cured layer contains a photopolymerization initiator with an alkali dissociation constant pKb of less than 8, the polarization degree (Py) tends to be easily reduced in a moisture and heat resistance test. According to the present invention, by making an optical laminate having a polarizer, an adhesive layer, and an optically anisotropic layer in sequence satisfy the above formula (1), even if the optically anisotropic layer is formed by a composition for forming a cured layer containing a photopolymerization initiator with an alkali dissociation constant pKb of less than 8, the reduction of the polarization degree (Py) in a moisture and heat resistance test can be suppressed.

Examples of photopolymerization initiators with a base dissociation constant pKb of less than 8 include compounds having a morpholine skeleton. Representative commercial products include IRGACURE 907 (pKb=5.6), IRGACURE 369 (pKb=5.3), and IRGACURE 379 (pKb=5.4) manufactured by BASF.

The composition for forming the curable layer may contain, in addition to the photopolymerization initiator having an alkali dissociation constant pKb of less than 8, one or more photopolymerization initiators having an alkali dissociation constant pKb of more than 8 (hereinafter, also referred to as other photopolymerization initiators), but the composition for forming the curable layer preferably contains only one or more photopolymerization initiators having an alkali dissociation constant pKb of less than 8.

The optically anisotropic layer 4 may have an alignment layer described later. As described later, when the optically anisotropic layer 4 is formed on a substrate, the substrate is usually removed when the optically anisotropic layer 4 is attached to a polarizer or a linear polarizer. In addition, "hardened material" refers to a state in which the formed layer will not deform or flow and can exist independently even if it is a single layer.

The optically anisotropic layer 4 may be a layer imparting a phase difference of λ/2, a layer imparting a phase difference of λ/4, or a positive C layer, or may be a laminate of at least two of these layers (hereinafter also referred to as a phase difference layer laminate). Examples of the phase difference layer laminate include a laminate of a layer imparting a phase difference of λ/2 and a layer imparting a phase difference of λ/4, a laminate of a layer imparting a phase difference of λ/4 and a positive C layer, etc. The optical multilayer 1 can function as a circular polarizer by stacking an optical anisotropic layer 4 including a layer that imparts a phase difference of λ/4 on the polarizer 2 or the linear polarizer described later.

In this manual, the so-called "layer that imparts a λ/4 phase difference" refers to a phase difference layer that converts linear polarization of a certain wavelength into circular polarization (or converts circular polarization into linear polarization).

In this manual, the so-called "layer that provides a λ/2 phase difference" refers to a phase difference layer that converts the polarization direction of linear polarization of a certain wavelength by 90°.

In this specification, the so-called "positive C layer" refers to a layer that satisfies the relationship nz _>nx=ny when the refractive index in the slow axis direction in the plane is _nx , the refractive index in the fast axis direction in the _plane is _ny , and _the refractive index in the thickness direction is _nz . If the difference between the value of _nx and the value of _ny is within 0.5% of the value of _ny , it can be regarded as _nx = _ny in practice, and preferably within 0.3%.

The thickness of the optical anisotropic layer 4 is preferably 0.5 μm or more. Furthermore, the thickness of the optical anisotropic layer 4 is preferably 10 μm or less, and more preferably 5 μm or less. Furthermore, the upper limit and lower limit values mentioned above can be arbitrarily combined. If the optical anisotropic layer 4 is greater than the lower limit value mentioned above, sufficient durability can be obtained. If the thickness of the optical anisotropic layer 4 is less than the upper limit value mentioned above, it can contribute to the thinning of the optical laminate 1. The thickness of the optical anisotropic layer 4 can be adjusted to obtain a layer that gives a phase difference of λ/4, a layer that gives a phase difference of λ/2, or a positive C layer, and a desired in-plane phase difference value and a phase difference value in the thickness direction. Furthermore, as described above, when the optically anisotropic layer 4 is a laminate of two or more layers, the thickness of the optically anisotropic layer 4 is the sum of the individual thicknesses of the two or more layers.

The following describes the polymerizable liquid crystal compound and photopolymerization initiator contained in the composition for forming the optically anisotropic layer 4, as well as the additives optionally contained in the composition. In addition, as mentioned above, the composition for forming the curable layer used in the present invention is preferably liquid (as mentioned above, it includes the concept of "solution"), so as described below, the composition for forming the curable layer is preferably one that contains a solvent. Such a solvent is preferably removed by, for example, drying after the curable layer forming composition is vertically coated on an appropriate substrate, so below, the other than the solvent that can be removed from the curable layer forming composition by drying is sometimes referred to as the "solid matter" of the curable layer forming composition.

(Polymerizable liquid crystal compound)

A polymerizable liquid crystal compound is a compound having a polymerizable group and can be in a liquid crystal state. The polymerizable liquid crystal compound is polymerized by the mutual reaction of the polymerizable groups of the polymerizable liquid crystal compound, and the polymerizable liquid crystal compound is hardened.

There is no particular limitation on the types of polymerizable liquid crystal compounds, but they can be classified into rod-shaped (rod-shaped liquid crystal compounds) and disc-shaped (disc-shaped liquid crystal compounds, disc-shaped liquid crystal compounds) based on their shapes. Furthermore, there are low-molecular-weight and high-molecular-weight types. In addition, the so-called polymer generally refers to a polymer with a degree of polymerization of 100 or more (Polymer Physics/Phase Transfer Kinetics, written by Masao Doi, page 2, Iwanami Shoten, 1992).

In this embodiment, any polymerizable liquid crystal compound can be used. Furthermore, two or more rod-shaped liquid crystal compounds, two or more disc-shaped liquid crystal compounds, or a mixture of rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds can also be used.

In addition, the rod-shaped liquid crystal compound may be suitably described in claim 1 of Japanese Unexamined Patent Publication No. 11-513019. The disc-shaped liquid crystal compound may be suitably described in paragraphs [0020] to [0067] of Japanese Unexamined Patent Publication No. 2007-108732 or paragraphs [0013] to [0108] of Japanese Unexamined Patent Publication No. 2010-244038.

When two or more polymerizable liquid crystal compounds are used in combination, at least one of these polymerizable liquid crystal compounds has two or more polymerizable groups in the molecule. That is, the layer hardened by the aforementioned polymerizable liquid crystal compound is preferably a layer formed by fixing the liquid crystal compound having a polymerizable group by polymerization. At this time, it is no longer necessary to show liquid crystal properties after forming the layer.

The polymerizable group possessed by the polymerizable liquid crystal compound is preferably a functional group capable of addition polymerization reaction, such as a polymerizable ethylenic unsaturated group or a cyclic polymerizable group. More specifically, the polymerizable group can be, for example, (meth)acryl, vinyl, styrene, allyl, etc. Among them, (meth)acryl is preferred. In addition, the so-called (meth)acryl is a concept that includes both methacryl and acryl.

The liquid crystal properties of polymerizable liquid crystal compounds can be thermotropic liquid crystals or lyotropic liquid crystals. If thermotropic liquid crystals are classified by order, they can be nematic liquid crystals or smectic liquid crystals.

(Other photopolymerization initiators)

The composition for forming the curable layer used in the present invention contains a photopolymerization initiator having a base dissociation constant pKb of less than 8, but may also contain photopolymerization initiators other than such photopolymerization initiators (other photopolymerization initiators). Such other photopolymerization initiators include, for example, acetophenones, benzoins, benzophenones, phosphine oxides, ketals, anthraquinones, thioanthrone compounds, azo compounds, peroxides, 2,3-dialkyldione compounds, disulfide compounds, fluoroamine compounds, aromatic thionium compounds, lophine dimers, onium salts, borates, active esters, active halides, inorganic complexes, coumarins, and the like. Representative commercial products of other photopolymerization initiators include IRGACURE 127 (pKb=13), IRGACURE 184 (pKb=17), and IRGACURE 819 (pKb=24) manufactured by BASF.

(Composition for forming hardened layer)

The content of the polymerizable liquid crystal compound in the composition for forming the curing layer is based on the solid content of the composition for forming the curing layer, for example, it can be 50% by mass or more and 99% by mass or less, preferably 60% by mass or more and 95% by mass or less.

The content of the photopolymerization initiator in the composition for forming the curing layer is based on the solid content of the composition for forming the curing layer, for example, it can be more than 0.01 mass% and less than 20 mass%, preferably more than 0.5 mass% and less than 5 mass%.

From the perspective of uniformity of the coating film and strength of the film, the composition for forming the hardened layer may contain a polymerizable monomer. The polymerizable monomer may be a free radical polymerizable or cationic polymerizable compound. Among them, a multifunctional free radical polymerizable monomer is preferred.

Furthermore, the polymerizable monomer is preferably copolymerizable with the above-mentioned polymerizable liquid crystal compound. The amount of the polymerizable monomer used is preferably 1 to 50 parts by mass, and more preferably 2 to 30 parts by mass, relative to 100 parts by mass of the polymerizable liquid crystal compound.

In addition, from the perspective of uniformity of the coating film and strength of the film, the composition system for forming the hardened layer may include a surfactant. The surfactant may be any of the conventionally known compounds. Among them, fluorine compounds are particularly preferred.

As mentioned above, the composition for forming the hardened layer applicable to the present invention is preferably in liquid form, and such a composition for forming the hardened layer contains a solvent. The solvent at this time is preferably a polymerizable liquid crystal compound or a photopolymerization initiator with high solubility, so it is preferably an organic solvent. Examples of organic solvents include amides (e.g., N,N-dimethylformamide), sulfones (e.g., dimethyl sulfone), heterocyclic compounds (e.g., pyridine), alkyls (e.g., benzene, hexane), alkyl halides (e.g., chloroform, dichloromethane), esters (e.g., methyl acetate, ethyl acetate, butyl acetate), ketones (e.g., acetone, methyl ethyl ketone), and ethers (e.g., tetrahydrofuran, 1,2-dimethoxyethane). Among them, alkyl halides and ketones are preferred. In addition, two or more types of organic solvents may be used together.

In addition, the composition for forming the hardened layer may include various alignment agents such as vertical alignment agents on the interface side of the polarizer and vertical alignment agents on the interface side of the air, and horizontal alignment promoters such as horizontal alignment agents on the interface side of the polarizer and horizontal alignment agents on the interface side of the air. Furthermore, in addition to the above-mentioned components, the composition for forming the hardened layer may also include other components such as adhesion improvers, plasticizers, polymers (thickening agents, etc.).

(hardened layer)

In the optical laminate of the present invention, as described above, the optical anisotropy contained in the optical laminate includes a cured layer. The cured layer can be formed by applying a composition for forming a cured layer on, for example, an alignment layer and irradiating it with active energy rays. More specifically, an alignment layer is provided on a suitable substrate, and a composition for forming a cured layer is applied on the alignment layer, and the polymerizable liquid crystal compound contained in the composition for forming a cured layer applied on the alignment layer is polymerized by irradiating it with active energy rays to convert it into a cured layer.

The above-mentioned active energy rays include ultraviolet rays, visible light, electron rays, and X-rays, preferably ultraviolet rays. The light sources of the above-mentioned active energy rays include, for example, 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 sources emitting light in the wavelength range of 380 to 440 nm, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halogen lamps, etc.

When ultraviolet B wave (wavelength range of 280nm to 310nm) is usually used, the irradiation intensity of ultraviolet light is 100mW/ ^cm2 to 3000mW/ ^cm2 . The ultraviolet irradiation intensity is preferably an intensity in a wavelength region effective for activating cationic polymerization initiators or free radical polymerization initiators. The irradiation time of ultraviolet light is usually 0.1 seconds to 10 minutes, preferably 0.1 seconds to 5 minutes, more preferably 0.1 seconds to 3 minutes, and even more preferably 0.1 seconds to 1 minute.

The ultraviolet light may be irradiated once or multiple times. Although it varies depending on the polymerization initiator used, the accumulated light amount at a wavelength of 365nm is preferably set to be 700mJ/ ^cm2 or more, more preferably 1100mJ/ ^cm2 or more, and even more preferably 1,300mJ/ ^cm2 or more. Setting the accumulated light amount to the above level increases the polymerization rate of the polymerizable liquid crystal compound constituting the liquid crystal layer 103, which is beneficial to improving heat resistance. The accumulated light amount at a wavelength of 365nm is preferably set to be 2,000mJ/ ^cm2 or less, and more preferably set to be 1,800mJ/ ^cm2 or less. Setting the accumulated light amount to the above level may cause coloring of the liquid crystal layer 103.

When the optically anisotropic layer 4 is a phase difference layer stack composed of two or more hardened layers, each hardened layer may be stacked using an adhesive, or a hardened layer forming composition containing a polymerizable liquid crystal compound may be applied on the surface of the formed hardened layer and hardened. The hardened layer forming composition at this time may be the same as or different from the hardened layer forming composition of the already formed hardened layer.

(Base material)

The hardened material layer can be formed, for example, on an alignment layer already provided on a substrate. The substrate can be a substrate having a function of supporting the alignment layer and formed into an elongated shape. The substrate can function as a releasable support and support an optically anisotropic layer (phase difference layer) or an alignment layer for transfer. Furthermore, it is preferred that the surface has a peelable adhesion. The substrate is light-transmissive and preferably is a film made of an optically transparent thermoplastic resin, such as: a polyolefin resin such as a chain polyolefin resin (polypropylene resin, etc.), a cyclic polyolefin resin (norbornene resin, etc.); a cellulose resin such as triacetyl cellulose and diacetyl cellulose; a polyester resin such as polyethylene terephthalate and polybutylene terephthalate; a polycarbonate resin; a methacrylic acid resin; Methyl ester resins, (meth) acrylic resins; polystyrene resins; polyvinyl chloride resins; acrylonitrile/butadiene/styrene resins; acrylonitrile/styrene resins; polyvinyl acetate resins; polyvinylidene chloride resins; polyamide resins; polyacetal resins; modified polyphenylene ether resins; polysulfide resins; polyethersulfone resins; polyarylate resins; polyamide imide resins; polyimide resins; maleimide resins, etc.

In addition, the substrate can be subjected to various anti-adhesion treatments. Examples of anti-adhesion treatments include easy-to-join treatments, treatments such as mixing fillers, and knurling treatments. By subjecting the substrate to such anti-adhesion treatments, it is possible to effectively prevent the substrates from sticking to each other when the substrate is rolled up, i.e., from sticking, and it tends to be easy to improve productivity.

(Orientation layer)

The hardened material layer is preferably formed on the substrate via the alignment layer. That is, the substrate and the alignment layer are sequentially stacked, and the hardened material layer is stacked on the alignment layer.

Furthermore, the alignment layer is not limited to a vertical alignment layer, and may be an alignment layer that aligns the molecular axes of the polymerizable liquid crystal compound horizontally, or may be an alignment layer that aligns the molecular axes of the polymerizable liquid crystal compound obliquely. The alignment layer preferably has solvent resistance that does not dissolve due to the coating of the composition containing the polymerizable liquid crystal compound described later, and has heat resistance in the heat treatment used to remove the solvent or align the liquid crystal compound. The alignment layer may include an alignment layer containing an alignment polymer, a photoalignment film, and a groove alignment layer that forms a concave-convex pattern or a plurality of grooves on the surface and aligns them. The thickness of the alignment layer is usually in the range of 10 nm to 10000 nm.

In addition, the alignment layer has the function of supporting the liquid crystal layer and can function as a releasable support. It can be a layer that can support the liquid crystal layer for transfer and has a peelable adhesion on its surface.

The resin used in the alignment layer is a resin obtained by polymerizing a polymerizable compound. The polymerizable compound is a compound having a polymerizable group, and is usually a non-liquid crystal polymerizable non-liquid crystal compound that does not become a liquid crystal state. The polymerizable groups of the polymerizable compound react with each other to polymerize the polymerizable compound to form a resin. Such a resin is not particularly limited as long as it is used as an alignment layer for aligning the polymerizable liquid crystal compound in the formation stage of the liquid crystal layer, is not included in the liquid crystal layer, and is used as a material for a known alignment layer. A cured product obtained by curing a previously known monofunctional or polyfunctional (meth)acrylate monomer under a polymerization initiator can be used. Specifically, (meth)acrylate monomers include, for example, 2-ethylhexyl acrylate, cyclohexyl acrylate, diethylene glycol mono-2-ethylhexyl ether acrylate, diethylene glycol monophenyl ether acrylate, tetraethylene glycol monophenyl ether acrylate, trihydroxymethylpropane triacrylate, lauryl acrylate, lauryl methacrylate, isoborneol acrylate, isoborneol methacrylate, 2-phenoxyethyl acrylate, tetrahydrofuranyl methyl acrylate, 2-hydroxypropyl acrylate, benzyl acrylate, tetrahydrofuranyl methyl methacrylate, 2-hydroxyethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, methacrylic acid, and urethane acrylate. The resin may be one of these or a mixture of two or more.

After the hardened layer is formed, the alignment layer can be peeled off and removed together with the substrate before or after the step of laminating with the polarizer 2 or the linear polarizer.

In addition, in order to improve the releasability from the substrate and to impart film strength to the cured layer, the cured layer may contain an alignment layer. When the cured layer includes the alignment layer, the resin used in the alignment layer is preferably a cured product formed by curing a monofunctional or bifunctional (meth)acrylate monomer, an imide monomer, or a vinyl ether monomer.

Monofunctional (meth)acrylate monomers include alkyl (meth)acrylates with 4 to 16 carbon atoms, β-carboxyl alkyl (meth)acrylates with 2 to 14 carbon atoms, alkylated phenyl (meth)acrylates with 2 to 14 carbon atoms, methoxy polyethylene glycol (meth)acrylates, phenoxy polyethylene glycol (meth)acrylates, and isoborneol (meth)acrylate, etc.

The bifunctional (meth)acrylate monomers include: 1,3-butanediol di(meth)acrylate; 1,3-butanediol (meth)acrylate; 1,6-hexanediol di(meth)acrylate; ethylene glycol di(meth)acrylate; diethylene glycol di(meth)acrylate; neopentyl glycol di(meth)acrylate; triethylene glycol di(meth)acrylate; tetraethylene glycol di(meth)acrylate; polyethylene glycol diacrylate; bis(acryloyloxyethyl) ether of bisphenol A; ethoxylated bisphenol A di(meth)acrylate; propoxylated neopentyl glycol di(meth)acrylate; ethoxylated neopentyl glycol di(meth)acrylate and 3-methylpentanediol di(meth)acrylate, etc.

In addition, examples of imide resins formed by curing imide monomers include polyamide and polyimide. In addition, the imide resin may be one type or a mixture of two or more types.

In addition, the resin forming the alignment layer may contain monomers other than monofunctional or bifunctional (meth)acrylate monomers, imide monomers and vinyl ether monomers, but the content ratio of monofunctional or bifunctional (meth)acrylate monomers, imide monomers and vinyl ether monomers in the total monomers may be 50% by mass or more, preferably 55% by mass or more, and more preferably 60% by mass or more.

When the optical anisotropic layer 4 includes an alignment layer, the thickness of the alignment layer is usually in the range of 10nm to 10000nm. When the alignment of the optical anisotropic layer 4 is in-plane alignment relative to the film surface, the thickness of the alignment layer is preferably 10nm to 1000nm. When the alignment of the optical anisotropic layer 4 is vertical alignment relative to the film surface, the thickness is preferably 100nm to 10000nm. If the thickness of the optical anisotropic layer 4 is within the above range, the substrate can be given improved releasability and appropriate film strength.

(Protective film)

The optical laminate may have more than one protective film. The protective film may have the function of protecting an optically anisotropic layer or a polarizer. The protective film may be disposed on one side or both sides of at least one of the polarizer and the optically anisotropic layer, preferably disposed on at least one of the side of the polarizer opposite to the side of the optically anisotropic layer and the side of the optically anisotropic layer opposite to the side of the polarizer, and more preferably disposed on the side of the polarizer opposite to the side of the optically anisotropic layer. The protective film may be bonded to other layers such as the optically anisotropic layer or the polarizer via an adhesive layer described later. The laminate composed of polarizer and protective film is also called linear polarizer.

The optical laminate is substantially rectangular, and when the protective film is a stretched film, it is preferred that the stretching direction of the protective film is substantially parallel to the short side direction of the optical laminate (circular polarizer). If the stretching direction and the short side direction are in such a relationship, regardless of the direction of the slow axis of the phase difference film, the hue change of the circular polarizer tends to be smaller in a high temperature environment. It is generally believed that when the stretching direction of the protective film is parallel to the short side, the shrinkage force of the protective film in the stretching direction generated by the relaxation of the stretching of the polarizer and the protective film in a high temperature environment is smaller than when it is parallel to the long side, and the hue change is smaller.

The so-called extension direction of the protective film is substantially parallel to the short side direction of the circular polarizer. Strictly speaking, it not only includes the situation where the two are parallel, but also includes the situation where the angle between the two is 0±10°. The angle between the extension direction of the protective film and the short side direction of the circular polarizer is preferably 0±5°.

The protective film may be a film made of a light-transmitting (preferably optically transparent) thermoplastic resin, such as: a polyolefin resin such as a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a norbornene resin); a cellulose resin such as triacetyl cellulose or diacetyl cellulose; a polyester resin such as polyethylene terephthalate or polybutylene terephthalate; a polycarbonate resin; Such as methyl methacrylate resins, (meth) acrylic resins; polystyrene resins; polyvinyl chloride resins; acrylonitrile/butadiene/styrene resins; acrylonitrile/styrene resins; polyvinyl acetate resins; polyvinylidene chloride resins; polyamide resins; polyacetal resins; modified polyphenylene ether resins; polysulfide resins; polyethersulfide resins; polyarylate resins; polyamide imide resins; polyimide resins, etc.

Chain polyolefin resins include homopolymers of chain olefins such as polyethylene resin (polyethylene resin that is a homopolymer of ethylene, or a copolymer with ethylene as the main component) and polypropylene resin (polypropylene resin that is a homopolymer of propylene, or a copolymer with propylene as the main component), as well as copolymers composed of two or more chain olefins.

Cyclic polyolefin resins are a general term for resins polymerized with cyclic olefins as polymerizable units, and examples thereof include resins described in Japanese Patent Application Laid-Open No. 1-240517, Japanese Patent Application Laid-Open No. 3-14882, Japanese Patent Application Laid-Open No. 3-122137, etc. Specific examples of cyclic polyolefin resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (typically random copolymers), graft polymers of these modified with unsaturated carboxylic acids or their derivatives, and hydrogenated products thereof. Among them, it is preferred to use a norbornene resin using a norbornene monomer such as norbornene or a polycyclic norbornene monomer as the cyclic olefin.

Polyester resins are resins with ester bonds, except for the cellulose ester resins described below, and are generally composed of polycondensates of polycarboxylic acids or their derivatives and polyols. Polycarboxylic acids or their derivatives may be divalent dicarboxylic acids or their derivatives, such as terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalene dicarboxylate. Polyols may be divalent diols, such as ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexanedimethanol. A representative example of polyester resins is polyethylene terephthalate, which is a condensate of terephthalic acid and ethylene glycol.

(Meth)acrylic resins are resins having a compound having a (meth)acryloyl group as a main constituent monomer. Specific examples of (meth)acrylic resins include: poly(meth)acrylates such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymers; methyl methacrylate-(meth)acrylic acid copolymers; methyl methacrylate-(meth)acrylic acid copolymers; methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymers; methyl (meth)acrylate-styrene copolymers (MS resins, etc.); copolymers of methyl methacrylate and compounds having alicyclic hydrocarbon groups (e.g., methyl methacrylate-cyclohexyl methacrylate copolymers, methyl methacrylate-norbornene (meth)acrylate copolymers, etc.). Preferably, a polymer having a poly(meth)acrylic acid C _1-6 alkyl ester such as poly(methyl)acrylate as a main component is used, and more preferably, a methyl methacrylate-based resin having methyl methacrylate as a main component (50 mass % to 100 mass %, preferably 70 mass % to 100 mass %) is used.

Cellulose ester resins are esters of cellulose and fatty acids. Specific examples of cellulose ester resins include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. In addition, copolymers of these resins or resins in which a portion of the hydroxyl groups is modified with other substituents may be cited. Among these, cellulose triacetate (triacetylcellulose) is particularly preferred.

Polycarbonate resins are engineering plastics composed of polymers bonded to monomer units via carbonate groups.

The thickness of the protective film is usually between 1μm and 100μm, but from the perspective of strength and operability, it is preferably between 5μm and 60μm, more preferably between 10μm and 55μm, and even more preferably between 15μm and 40μm.

When the optical laminate has two or more protective films, the protective films may be made of the same type of thermoplastic resin or different types of thermoplastic resin. Also, the thicknesses may be the same or different. Furthermore, they may have the same phase difference characteristics or different phase difference characteristics.

As mentioned above, at least one of the protective films may be a surface treatment layer (coating layer) having a hard coating layer, an anti-glare layer, a light diffusion layer, an anti-reflection layer, a low refractive index layer, an anti-static layer, or an anti-fouling layer on its outer surface (the surface opposite to the polarizer). In addition, the thickness of the protective film includes the thickness of the surface treatment layer.

(followed by the agent layer)

The adhesive layer can be arranged, for example, between the polarizer 2 and the protective film, between the hardened layers of the phase difference layer stack, and has the function of bonding the layers. The adhesive layer can be a single layer or multiple layers.

The adhesive forming the adhesive layer may be a water-based adhesive, an active energy ray-hardening adhesive, or a heat-hardening adhesive, preferably a water-based adhesive or an active energy ray-hardening adhesive. The adhesive layer may be any of the above adhesive layers.

Examples of water-based adhesives include adhesives composed of polyvinyl alcohol resin aqueous solutions, water-based two-component urethane emulsion adhesives, etc. Among them, water-based adhesives composed of polyvinyl alcohol resin aqueous solutions are preferably used. In addition to vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, polyvinyl alcohol copolymers obtained by saponifying copolymers of vinyl acetate and other monomers copolymerizable with the vinyl acetate, or modified polyvinyl alcohol polymers in which the hydroxyl groups of these monomers are partially modified can be used as polyvinyl alcohol resins. Water-based adhesives can include crosslinking agents such as aldehyde compounds (glyoxal, etc.), epoxy compounds, melamine compounds, hydroxymethyl compounds, isocyanate compounds, amine compounds, and polyvalent metal salts.

When using a water-based adhesive, it is preferred to perform a drying step to remove the water contained in the water-based adhesive after the layers are bonded to each other. After the drying step, a aging step may be performed at a temperature of, for example, 20°C to 45°C.

The so-called active energy ray-curable adhesive refers to an adhesive containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron rays, and X-rays, and is preferably an ultraviolet ray-curable adhesive.

The curable compound may be a cationically polymerizable curable compound or a free radically polymerizable curable compound. Examples of cationically polymerizable curable compounds include epoxy compounds (compounds having one or more epoxy groups in the molecule), cyclohexane compounds (compounds having one or more cyclohexane rings in the molecule), or combinations thereof. Examples of free radically polymerizable curable compounds include (meth)acrylic compounds (compounds having one or more (meth)acryloyloxy groups in the molecule), or other vinyl compounds having a free radically polymerizable double bond, or combinations thereof. A cationically polymerizable curable compound and a free radically polymerizable curable compound may also be used together. The active energy ray-curable adhesive generally further comprises at least one of a cationic polymerization initiator and a free radical polymerization initiator for initiating the curing reaction of the above-mentioned curable compound.

In order to improve the adhesion, the bonding surface of at least one of the adhesive layer and the layer bonded to the adhesive layer may be subjected to a surface activation treatment. The surface activation treatment may include dry treatment such as corona treatment, plasma treatment, discharge treatment (fluorescence discharge treatment, etc.), flame treatment, ozone treatment, UV ozone treatment, ionization active ray treatment (ultraviolet ray treatment, electron beam treatment, etc.); wet treatment such as ultrasonic treatment using solvents such as water or acetone, saponification treatment, and anchor coating treatment. These surface activation treatments may be performed alone or in combination of two or more.

When there are two or more adhesive layers, the adhesives used in the adhesive layers may be of the same type or different types.

<Polarizing plate with adhesive layer>

The optical laminate can also be a polarizing plate with an adhesive layer, wherein an adhesive layer is further provided on the side of the optical anisotropic layer opposite to the polarizer side. The polarizing plate with an adhesive layer 10 shown in FIG. 2 has a protective film 11, an adhesive layer 12, a polarizer 2, an adhesive layer 3, an optical anisotropic layer 4, and an adhesive layer 13 in this order. At this time, in the optical laminate 10, the polarizer 2 can also be a polarizing plate with a protective film (straight line) on one side having the protective film 10 via the adhesive layer 12. Adhesive layer 13 may be of the same type as the adhesive composition forming adhesive layer 3, or may be of a different type. Adhesive layer 13 is applicable to the description of the adhesive composition forming adhesive layer 3.

In a polarizing plate with an adhesive layer, the decrease in polarization degree (Py) in a moisture and heat resistance test has a significant impact on the inclination of the adhesive layer disposed between the polarizer and the optical anisotropic layer. In a polarizing plate with an adhesive layer, it is preferred that the adhesive layer disposed between the polarizer and the optical anisotropic layer satisfies the above formula (1).

<Image display device>

The optical multilayer can be used in an image display device. The image display device is not particularly limited, and for example, an organic electroluminescent (organic EL) display device, an inorganic electroluminescent (inorganic EL) display device, a liquid crystal display device, a touch panel display device, an electroluminescent display device, etc. When the optical multilayer is applied to the image display device, the polarizer 2 side can be attached to the image display element in such a way that the side becomes the identification side.

<Method for manufacturing optical multilayer body>

The optical laminate system includes: a step of preparing a polarizer (polarizer preparation step); a step of hardening a composition containing a liquid crystal compound having a polymerizable group and a photopolymerization initiator to form an optically anisotropic layer (optically anisotropic layer formation step); a step of forming an adhesive layer containing a resin (A) (adhesive layer formation step), and a step of laminating the polarizer and the optically anisotropic layer via the adhesive layer (laminating step).

In the polarizer preparation step, the polarizer can be manufactured in the manner described in the above description of the polarizer.

In the step of forming an optically anisotropic layer, the optically anisotropic layer can be manufactured by coating a curing layer-forming composition containing a polymerizable liquid crystal compound on a substrate or on an alignment film when the substrate is present, so that the polymerizable liquid crystal compound is polymerized. The curing layer-forming composition further includes a solvent, a polymerization initiator, and, depending on the circumstances, may further include other components mentioned above or a photosensitizer, a polymerization inhibitor, a leveling agent, etc. The substrate and the alignment film may be assembled on the optically anisotropic layer, or may be peeled off from the optically anisotropic layer and not become a constituent element of the optically laminated body.

The coating, drying and polymerization of the composition for forming the hardened layer and the polymerizable liquid crystal compound can be carried out by conventionally known coating methods, drying methods and polymerization methods.

For example, the coating method of the composition for forming the hardened layer can adopt wire rod coating, extrusion coating, direct gravure coating, reverse gravure coating, and die-stitch coating, etc.

The polymerization method of the polymerizable liquid crystal compound can be selected according to the type of the polymerizable group of the polymerizable liquid crystal compound. If the polymerizable group is a photopolymerizable group, polymerization can be performed by photopolymerization. If the polymerizable group is a thermal polymerizable group, polymerization can be performed by thermal polymerization. The polymerization method of the polymerizable liquid crystal compound is preferably photopolymerization. Since the photopolymerization method does not necessarily require heating the transparent substrate to a high temperature, a transparent substrate with low heat resistance can be used. The photopolymerization method is performed by irradiating a film composed of a polarizer forming composition or a phase difference layer forming composition containing a polymerizable liquid crystal compound with visible light or ultraviolet light. In terms of ease of operation, ultraviolet light is preferred.

In the adhesive layer forming step, first, the monomer component can be polymerized to prepare the resin (A), and then the resin (A) and other components can be mixed to prepare the adhesive composition. The content of the acid component in the monomer component can be, for example, 0 mass % or more and 1.0 mass % or less.

Then, an adhesive layer can be prepared as an adhesive sheet. The adhesive sheet can be prepared, for example, by dissolving or dispersing an adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare an adhesive liquid, forming a layer composed of the adhesive into a sheet on a release film subjected to a release treatment, and then laminating another release film on the adhesive layer.

The adhesive liquid can be applied to the release film by using general coating techniques such as die-cut coaters, notch wheel coaters, reverse roller coaters, gravure coaters, rod coaters, wire rod coaters, scraper coaters, air knife coaters, etc.

The release film is preferably composed of a plastic film and a release layer. Examples of the plastic film include polyester films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film, or polyolefin films such as polypropylene film. In addition, the release layer can be formed, for example, from a release layer forming composition. The main component (resin) constituting the release layer forming composition is not particularly limited, but examples thereof include silicone resins, alkyd resins, acrylic resins, and long-chain alkyl resins.

The thickness of the adhesive layer can be adjusted by the coating conditions of the adhesive liquid. In order to thin the thickness of the adhesive layer, it is effective to reduce the coating thickness.

In the laminating step, the layers can be laminated by laminating the adhesive sheet with the release film peeled off on one side to the middle layer, and then peeling off the release film on the other side and laminating it to the other layer. For one or both of the laminating surfaces, it is preferred to perform a surface activation treatment such as a corona treatment.

(Implementation example)

The following examples and comparative examples are listed to more specifically illustrate the present invention, but the present invention is not limited to these examples. The "%" and "parts" in the examples and comparative examples are mass % and mass parts unless otherwise specified. In addition, the determination of each physical property in the following examples is carried out by the following method.

(Manufacturing Example 1: Manufacturing of a polarizing plate with a protective film on one side)

A polyvinyl alcohol film with an average degree of polymerization of about 2400, a saponification degree of more than 99.9 mol% and a thickness of 30 μm was immersed in pure water at 30°C, and then immersed in an aqueous solution at a mass ratio of iodine: potassium iodide: water of 0.02:2:100 at 30°C for iodine dyeing (hereinafter, also referred to as the iodine dyeing step). The polyvinyl alcohol film that had undergone the iodine dyeing step was immersed in an aqueous solution at a mass ratio of potassium iodide: boric acid: water of 12:5:100 at 56.5°C for boric acid treatment (hereinafter, also referred to as the boric acid treatment step). The polyvinyl alcohol film that had undergone the boric acid treatment step was washed with pure water at 8°C and dried at 65°C to obtain a polarizer with iodine adsorbed and aligned on the polyvinyl alcohol (thickness 12 μm after stretching). At this time, extension was performed in the iodine staining step and the boric acid treatment step. The total extension ratio in such extension was 5.3 times.

A water-based adhesive consisting of a polyvinyl alcohol resin aqueous solution is applied to one side of the obtained polarizer, and a protective film (ZEON COP film ZONOR ZF14) is attached to one side of the polarizer to obtain a polarizing plate with a protective film on one side.

(Manufacturing Example 2: Preparation of Adhesive Layer (1))

In a reaction container equipped with a stirrer, a thermometer, a reflux cooler, a dripping device and a nitrogen inlet tube, 100 parts by mass of monomer components (97.0% by mass of n-butyl acrylate, 3.0% by mass of 2-hydroxyethyl acrylate), 200 parts by mass of ethyl acetate, and 0.08 parts by mass of 2,2'-azobisisobutyronitrile were loaded, and the air in the above reaction container was replaced with nitrogen gas. While stirring in a nitrogen gas environment, the reaction solution was heated to 60°C, reacted for 6 hours, and then cooled to room temperature. By such production, a (meth)acrylate polymer A with a weight average molecular weight of 1.8 million was obtained.

The coating solution of the adhesive composition is obtained by mixing 100 parts by mass (solid conversion value; the same below) of the (meth)acrylate polymer A obtained in the above step, 1.0 parts by mass of trihydroxymethylpropane-modified xylene diisocyanate (Mitsui Chemicals Co., Ltd., trade name "TAKENATE (registered trademark) D-110N") as an isocyanate crosslinking agent, and 0.30 parts by mass of 3-glycidyloxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., trade name "KBM403") as a silane coupling agent, stirring well, and diluting with ethyl acetate.

The coating solution was applied to the release treatment surface (peeling layer surface) of the release film (Lintech Co., Ltd.: SP-PLR382190) by a thin coater to a thickness of 20 μm after drying, and then dried at 100°C for 1 minute. A release film (Lintech Co., Ltd.: SP-PLR381031) was attached to the adhesive layer on the opposite side to the release film, thereby obtaining an adhesive layer with release films attached on both sides (Adhesive layer (1)).

(Manufacturing Example 3: Preparation of Adhesive Layer (2))

In a reaction container equipped with a stirrer, a thermometer, a reflux cooler, a dripping device and a nitrogen inlet tube, 100 parts by mass of monomer components (98.5% by mass of n-butyl acrylate, 1.0% by mass of acrylic acid, 0.5% by mass of 2-hydroxyethyl acrylate), 200 parts by mass of ethyl acetate, and 0.08 parts by mass of 2,2'-azobisisobutyronitrile were loaded, and the air in the above reaction container was replaced with nitrogen gas. While stirring in a nitrogen gas environment, the reaction solution was heated to 60°C, reacted for 6 hours, and then cooled to room temperature. By such production, a (meth)acrylate polymer B with a weight average molecular weight of 1.8 million was obtained.

The coating solution of the adhesive composition is obtained by mixing 100 parts by mass (solid conversion value; the same below) of the (meth)acrylate polymer B obtained in the above step, 0.30 parts by mass of trihydroxymethylpropane-modified toluene diisocyanate (manufactured by TOSOH Co., Ltd., trade name "CORONATE (registered trademark) L") as an isocyanate crosslinking agent, and 0.30 parts by mass of 3-glycidyloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM403") as a silane coupling agent, stirring well, and diluting with ethyl acetate.

The coating solution was applied to the release treatment surface (peeling layer surface) of the release film (Lintech Co., Ltd.: SP-PLR382190) by a thin coater to a thickness of 25 μm after drying, and then dried at 100°C for 1 minute. Another release film (Lintech Co., Ltd.: SP-PLR381031) was attached to the adhesive layer on the opposite side to the release film, thereby obtaining an adhesive layer with release films attached on both sides (Adhesive layer (2)).

(Manufacturing Examples 4 to 7: Preparation of Adhesive Layers (3) to (6))

In a reaction container equipped with a stirrer, a thermometer, a reflux cooler, a dripping device and a nitrogen inlet tube, 100 parts by mass of monomer components (95.0 parts by mass of n-butyl acrylate, 4.0 parts by mass of acrylic acid, 1.0 parts by mass of 2-hydroxyethyl acrylate), 200 parts by mass of ethyl acetate, and 0.08 parts by mass of 2,2'-azobisisobutyronitrile were loaded, and the air in the reaction container was replaced with nitrogen gas. While stirring in a nitrogen gas environment, the reaction solution was heated to 60°C, reacted for 6 hours, and then cooled to room temperature. By such production, a (meth)acrylate polymer C with a weight average molecular weight of 1.8 million was obtained.

The (meth)acrylate polymer C obtained in the above step was prepared by mixing 100 parts by weight (solid conversion value; the same applies hereinafter), 1.5 parts by weight of trihydroxymethylpropane-modified toluene diisocyanate (manufactured by TOSOH Co., Ltd., trade name "CORONATE (registered trademark) L") as an isocyanate crosslinking agent, 0.30 parts by weight of 3-glycidyloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM403") as a silane coupling agent, and 100 parts by weight of ... 7.5 parts by weight of ethoxylated isocyanuric acid triacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.: product name "A-9300") as a photopolymerization initiator and 0.5 parts by weight of 2-methyl-1-(4-methylthiophenyl)-2-morpholinylpropane-1-one (manufactured by BASF: IRGACURE (registered trademark) 907) as a photopolymerization initiator were mixed, stirred thoroughly, and diluted with ethyl acetate to obtain a coating solution of the adhesive composition.

The coating solution was applied to the release treatment surface (peeling layer surface) of a release film (manufactured by Lintech Co., Ltd.: SP-PLR382190) by a thin coater in a manner such that the thickness after drying was 5 μm, 10 μm, 15 μm or 25 μm, respectively. The film was dried at 100° C. for 1 minute, and another release film (manufactured by Lintech Co., Ltd.: SP-PLR381031) was attached to the surface of the adhesive layer opposite to the release film. The adhesive layer was irradiated with ultraviolet light (irradiation intensity 500mW/cm ² , accumulated light quantity 500mJ/cm ² ) across the release sheet using an ultraviolet irradiation device with a conveyor belt (manufactured by FUSION UV System Co., Ltd., using a D Bulb lamp) to obtain an adhesive layer with release films on both sides. Furthermore, an adhesive layer with a separation film attached to both sides and having an adhesive layer thickness of 5 μm is referred to as adhesive layer (3), an adhesive layer with a separation film attached to both sides and having an adhesive layer thickness of 10 μm is referred to as adhesive layer (4), an adhesive layer with a separation film attached to both sides and having an adhesive layer thickness of 15 μm is referred to as adhesive layer (5), and an adhesive layer with a separation film attached to both sides and having an adhesive layer thickness of 25 μm is referred to as adhesive layer (6).

(Manufacturing Example 8: Preparation of the composition for forming the hardened layer)

Mix the following ingredients, stir the resulting mixture at 80°C for 1 hour, and then cool it to room temperature to obtain a composition for forming a hardened layer.

‧Polymerizable liquid crystal compound LC242 (manufactured by BASF) (19.2 mass%):

‧Photopolymerization initiator (0.5 mass%): IRGACURE (registered trademark) 907 (manufactured by BASF JAPAN)

‧Reaction additive (1.1 mass%): Laromer (registered trademark) LR-9000 (manufactured by BASF JAPAN)

‧Solvent (79.1 mass%): Propylene glycol 1-monomethyl ether 2-acetaldehyde

(Manufacturing Example 9: Preparation of the composition for forming the alignment layer)

15 parts by mass of diethylene glycol di(meth)acrylate (A-600 manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), 15 parts by mass of 1,6-hexanediol di(meth)acrylate (A-DCP manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), and 3.0 parts by mass of IRGACURE 907 (manufactured by BASF) as a photopolymerization initiator were dissolved in 70 parts by mass of methyl ethyl ketone as a solvent to prepare a composition for forming an alignment layer.

(Manufacturing Example 10: Manufacturing of an optically anisotropic layer with a substrate layer)

A polyethylene terephthalate (PET) film with a thickness of 38 μm was prepared as the substrate layer. The surface of the substrate layer was subjected to a corona treatment. The corona treatment was performed 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 composition for forming the alignment layer was applied to the surface subjected to the corona treatment using a rod coater. The coating was dried at 90°C for 1 minute to obtain an alignment layer on the substrate layer (substrate layer with an alignment layer attached). The thickness of the obtained alignment layer was measured with a laser microscope and the result was 2.8 μm.

The composition for forming a hardened layer is applied on the alignment layer of the substrate layer attached to the alignment layer using a rod coater. The obtained coating is dried at 90°C for 1 minute. The coating is irradiated with ultraviolet light using a high-pressure mercury lamp (UNICURE VB-15201BY-A, manufactured by USHIO Electric Co., Ltd.). The ultraviolet light irradiation is performed in a nitrogen environment. The wavelength of the ultraviolet light is 365nm, and the accumulated light amount at the wavelength of 365nm is 500mJ/ ^cm2 . In this way, an optically anisotropic layer attached to the substrate layer is obtained.

(Implementation Example 1)

The surface of the polarizing plate with a single-sided protective film obtained in Production Example 1, which is opposite to the protective film surface, was subjected to a corona treatment (800 W, 10 m/min, rod width 700 mm, 1 pass). A release film on one side of the adhesive layer (1) obtained in Production Example 2 was peeled off, and the corona-treated surface of the polarizing plate with a single-sided protective film was bonded to the adhesive layer of the adhesive layer (1) to obtain a polarizing plate with an adhesive layer (I) with a single-sided release film. Then, after the surface of the cured material layer side of the optically anisotropic layer with a substrate layer obtained in Manufacturing Example 10 is similarly subjected to a corona treatment, the release film on the other side of the polarizing plate (I) with a release film attached to one side and an adhesive layer is peeled off and similarly bonded to the corona-treated surface of the optically anisotropic layer with a substrate layer to obtain a laminate (I). After peeling off the substrate on the cured material layer side of the laminate (I), the laminate (II) was obtained by applying a corona treatment in the same manner, peeling off the release film on one side from the adhesive layer (1), and laminating the corona treated surface to the adhesive layer of the adhesive layer (1). The release film on the other side of the laminate (II) was peeled off and laminated to an alkali-free glass plate ("Eagle-XG" manufactured by CORNING) as an evaluation sample. In an autoclave, the evaluation samples were pressurized for 20 minutes at 50°C and 5MPa, and then placed at 23°C and 60% relative humidity for 1 day. Afterwards, the degree of polarization (Py) was measured using an ultraviolet-visible-near-infrared spectrophotometer (V7100, manufactured by JASCO Corporation). Afterwards, after being placed at 80°C and 90% humidity for 24 hours, Py was measured in the same manner, and the change in Py (△Py) was calculated. The results are shown in Table 1.

(Examples 2 to 5, Comparative Example 1)

Except that the adhesive layer (1) of Example 1 is replaced by adhesive layers (2) to (6), the polarization degree (Py) is measured and the change in Py (△Py) is calculated in the same manner. The results are shown in Table 1.

(Reference example)

The surface of the polarizing plate with a single-sided protective film prepared above, which is opposite to the protective film surface, is subjected to a corona treatment (800 W, 10 m/min, rod width 700 mm, 1 pass). The separator film on one side is peeled off from the adhesive layer (3) prepared above, and the corona-treated surface of the polarizing plate and the adhesive layer are bonded to obtain a polarizing plate with a single-sided separator film (II). Then, after peeling off the separator film on the other side of the polarizing plate with a single-sided separator film (II), the plate is bonded to an alkali-free glass plate ("Eagle-XG" manufactured by CORNING) as an evaluation sample. Afterwards, the evaluation was carried out in the same manner as in Example 1. The results are shown in Table 1.

As shown in Table 1, it can be seen that in Examples 1 to 5, △Py is small and the change of polarization degree (Py) is suppressed. In contrast, in Comparative Example 1, △Py is large and the polarization degree (Py) deteriorates.

Claims (6)

An optical laminate comprises a polarizer, an adhesive layer, and an optical anisotropic layer in sequence; wherein the polarizer is a polarizer formed by adsorbing an oriented dichroic pigment on a polyvinyl alcohol resin film, the optical anisotropic layer comprises a layer of a cured product containing a composition, and an alignment layer, wherein the composition comprises a liquid crystal compound having a polymerizable group and a photopolymerization initiator, and the alignment layer comprises a layer of a polymerizable compound cured by the photopolymerization initiator. The photopolymerization initiator comprises a photopolymerization initiator having an alkali dissociation constant pKb of less than 8, the adhesive layer comprises a resin (A), the resin (A) is at least one resin selected from (meth) acrylic acid, rubber, urethane, ester, polysilicone, and polyvinyl ether, the thickness of the adhesive layer is less than 25 μm, and the adhesive layer satisfies the following formula (1), 0≦α≦25 (1) wherein α represents the product of the content (mass %) of the acid component in all monomer components constituting the resin (A) and the thickness (μm) of the adhesive layer. The optical layered body as described in claim 1, wherein the content of the acid component in all monomer components constituting the aforementioned resin (A) is greater than 0 mass % and less than 1.0 mass %. The optical laminate as described in claim 1 or 2, wherein a protective film is provided on the side of the polarizer opposite to the optical anisotropic layer. A polarizing plate with an adhesive layer has an optical laminate as described in any one of claims 1 to 3, and an adhesive layer is further provided on the side of the optical anisotropic layer opposite to the polarizer side. An image display device includes a polarizing plate with an adhesive layer as described in claim 4. A method for manufacturing an optical laminate is to manufacture the optical laminate described in claim 1, the method comprising the following steps: a step of preparing the aforementioned polarizer; a step of curing a composition containing a liquid crystal compound having the aforementioned polymerizable group and a photopolymerization initiator to form an optically anisotropic layer; a step of forming an adhesive layer containing the aforementioned resin (A); and a step of laminating the aforementioned polarizer and the aforementioned optically anisotropic layer via the aforementioned adhesive layer; the aforementioned resin (A) is at least one resin selected from the group consisting of (meth) acrylic, rubber, urethane, ester, polysilicone, and polyvinyl ether.

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