KR20230140478A - Optical laminate and circular polarizing plate - Google Patents

Abstract

An optical laminate and a circularly polarizing plate that can suppress coloring of reflected light even when exposed to a high humidity environment for a long time are provided.
The optical laminate 10 includes an aligned liquid crystal layer 11 in which a liquid crystal compound is aligned, an optical layer 12, and an adhesive layer 13 that bonds the aligned liquid crystal layer 11 and the optical layer 12. The optical laminate 10 has a change rate of in-plane retardation at a wavelength of 550 nm of 0.50% or less before and after a humidified environment test maintained at a temperature of 20°C and a relative humidity of 98% for 30 days. The optical laminate 10 has a saturation of reflected light c*={(a *) ² +(b*) ² } ^1/2 is preferably 0.25 or less.

Description

Optical laminate and circular polarizer {OPTICAL LAMINATE AND CIRCULAR POLARIZING PLATE}

The present invention relates to optical laminates and circularly polarizing plates.

As an optical laminate (optical anisotropic element) that has functions such as optical compensation of a liquid crystal display device and prevention of external light reflection of an organic EL display device, an optical laminate having an aligned liquid crystal layer in which a liquid crystal compound is oriented in a predetermined direction is used. An optical laminate including an aligned liquid crystal layer has a larger birefringence Δn than a stretched polymer film, and is therefore advantageous for reducing the thickness and weight of an image display device (more specifically, a liquid crystal display device, an organic EL display device, etc.). In an image display device, an optical laminate is a laminate that is integrally laminated with a polarizer or the like through a pressure sensitive adhesive or adhesive, and is bonded to an organic EL panel or a liquid crystal display panel (for example, see Patent Document 1).

The liquid crystal compound can be aligned in a predetermined direction by shearing force when applying it on a support or the orientation regulating force of the alignment film, etc. By orienting the liquid crystal compound, an optical laminate having various optical anisotropies is obtained. For example, a homogeneously oriented liquid crystal layer in which nematic liquid crystal molecules with positive refractive index anisotropy are oriented parallel to the support surface can be used as a positive A plate with refractive index anisotropy of nx>ny=nz. In addition, in this specification, “nx” represents the refractive index in the slow axis direction within the plane of the optical layer (alignment liquid crystal layer, etc.). In addition, in this specification, “ny” represents the refractive index in the direction orthogonal to the slow axis direction within the plane of the optical layer (alignment liquid crystal layer, etc.). In addition, in this specification, “nz” represents the refractive index in the thickness direction of the optical layer (alignment liquid crystal layer, etc.).

When using a thermotropic liquid crystal, a solution containing a liquid crystal compound (liquid crystal composition) is applied on a support, and the liquid crystal compound contained in the composition is heated so that it is in a liquid crystal state to orient the liquid crystal compound. When the liquid crystal composition contains a liquid crystal compound (liquid crystal monomer) having photopolymerizability, the alignment state is fixed by aligning the liquid crystal compound and then curing the liquid crystal composition by light irradiation.

Japanese Patent Publication No. 2015-7700

Image display devices are required to have higher durability, and optical members constituting the image display devices are required to be able to suppress coloring of reflected light even when exposed to a high humidity environment for a long time.

In view of these problems, the purpose of the present invention is to provide an optical laminate and a circularly polarizing plate that can suppress coloring of reflected light even when exposed to a high humidity environment for a long time.

<Aspects of the present invention>

The present invention includes the following aspects.

[1] An optical laminate comprising an aligned liquid crystal layer in which a liquid crystal compound is aligned, an optical layer, and an adhesive layer that bonds the aligned liquid crystal layer and the optical layer,

An optical laminate in which the rate of change in in-plane retardation at a wavelength of 550 nm before and after a humidified environment test maintained at a temperature of 20°C and a relative humidity of 98% for 30 days is 0.50% or less.

[2] After a humidified environment test maintained at a temperature of 20°C and a relative humidity of 98% for 30 days, the saturation of the reflected light when light is incident from the above-mentioned aligned liquid crystal layer side c*={(a*) ² +(b*) ² } ^1/2 is 0.25 or less, the optical laminate according to [1] above.

[3] Let the in-plane retardation of the alignment liquid crystal layer at a wavelength of 450 nm be Re (450), the in-plane retardation of the alignment liquid crystal layer at a wavelength of 550 nm be Re (550), and When the in-plane retardation of the alignment liquid crystal layer at a wavelength of 650 nm is set to Re(650), Re(450)/Re(550)≤1.00, Re(650)/Re(550)≥1.00, and 100 nm< The optical laminate according to [1] or [2] above, which satisfies Re(550)<160 nm.

[4] Let the refractive index in the slow axis direction within the plane of the optical layer be nx, let the refractive index in the direction perpendicular to the slow axis direction within the plane of the optical layer be ny, and let the refractive index in the direction perpendicular to the slow axis direction within the plane of the optical layer be ny, and the thickness direction of the optical layer The optical laminate according to any one of [1] to [3] above, which satisfies nz>nx≧ny when the refractive index is nz.

[5] A circularly polarizing plate comprising the optical laminate according to any one of [1] to [4] above and a polarizer.

According to the present invention, it is possible to provide an optical laminate and a circularly polarizing plate that can suppress coloring of reflected light even when exposed to a high humidity environment for a long time.

1 is a cross-sectional view showing an example of an optical laminate according to the present invention.
Figure 2 is a cross-sectional view showing another example of an optical laminate according to the present invention.
Figure 3 is a cross-sectional view showing an example of a circularly polarizing plate according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described. In addition, all academic literature and patent literature described in this specification are incorporated by reference in this specification.

First, the terms used in this specification will be explained. The “main surface” of a layered product (more specifically, an orientation liquid crystal layer, an optical layer, an adhesive layer, an adhesive layer, a polarizer, a support, etc.) refers to a surface orthogonal to the thickness direction of the layered product. The thickness of the layered material is 10 measured values obtained by observing a cross section of the layered material cut in the thickness direction with an electron microscope, randomly selecting 10 measurement points from the cross-sectional image, and measuring the thickness of the 10 selected measurement points. It is the arithmetic mean value of .

“In-plane retardation (unit: nm)” is a value measured in an atmosphere at a temperature of 23°C. Hereinafter, in-plane retardation may simply be described as “Re”. In addition, the in-plane retardation at a wavelength of 450 nm, the in-plane retardation at a wavelength of 550 nm, and the in-plane retardation at a wavelength of 650 nm are “Re(450)” and “Re(550)”, respectively. ” and “Re(650)” may be written.

“Saturation c*” is the formula “Saturation c*={(a*) ² +(b*) ² } ^1/ ” using the chromatic indices a* and b* of the CIE 1976 L*a*b* color space. This value is calculated as ² 」. Saturation c* indicates the degree of coloration. When c* is 0, the color is achromatic, and the larger c*, the greater the coloration.

“Refractive index” refers to the refractive index for light with a wavelength of 550 nm in an atmosphere at a temperature of 23°C.

Hereinafter, “system” may be added to the end of the compound name to comprehensively refer to the compound and its derivatives. In addition, when a polymer name is indicated by adding "system" to the end of the compound name, it means that the repeating unit of the polymer is derived from the compound or its derivative. In addition, acrylic and methacrylic are sometimes collectively referred to as “(meth)acrylic.” In addition, acrylates and methacrylates are sometimes collectively referred to as “(meth)acrylates.” In addition, acryloyl and methacryloyl may be collectively referred to as “(meth)acryloyl.”

For ease of understanding, the drawings referred to in the following description schematically depict each component as the main component, and the size, number, shape, etc. of each component shown are actual based on the circumstances of drawing production. There are cases where it is different. In addition, for reasons of explanation, in the drawings described later, the same components as those in the drawings explained previously may be given the same reference numerals and their descriptions may be omitted.

<First embodiment: optical laminate>

The optical laminate according to the first embodiment of the present invention has an aligned liquid crystal layer in which a liquid crystal compound is aligned, an optical layer, and an adhesive layer for bonding the aligned liquid crystal layer and the optical layer, and is provided at a temperature of 20°C and a relative humidity of 98%. The change rate of Re(550) before and after the humidified environment test maintained for 30 days is 0.50% or less.

Hereinafter, the humidified environment test maintained at a temperature of 20°C and a relative humidity of 98% for 30 days may be simply described as a “humidified environment test.” Additionally, the change rate of Re(550) before and after the humidification environment test may be simply described as “Re change rate.” Re change rate (unit: %) is given by the equation “Re change rate = 100 」 is calculated according to. Additionally, |Re2-Re1| represents the absolute value of the difference between Re2 and Re1.

In the optical laminate according to the first embodiment, the Re change rate is 0.50% or less, so the change in optical properties is relatively small under a high humidity environment. For this reason, according to the optical laminate according to the first embodiment, coloring of reflected light can be suppressed even when exposed to a high humidity environment for a long time.

In the first embodiment, in order to further suppress coloring of reflected light when exposed to a high humidity environment for a long time, the Re change rate is preferably 0.45% or less, more preferably 0.40% or less, and even more preferably 0.35% or less. . In addition, the lower limit of the Re change rate is not particularly limited, and may be, for example, 0.00%. The Re change rate can be adjusted, for example, by changing the composition of the adhesive used to bond the alignment liquid crystal layer and the optical layer.

In the first embodiment, in order to further suppress the coloring of the reflected light when exposed to a high humidity environment for a long time, an optical laminate in which the saturation c* of the reflected light when light is incident from the alignment liquid crystal layer side after the humidifying environment test is 0.25 or less is used. A sieve is preferable, and an optical laminate having a thickness of 0.23 or less is more preferable. Additionally, the lower limit of the saturation c* of the reflected light is not particularly limited and may be, for example, 0.00. Hereinafter, the saturation c* of the reflected light when light is incident from the alignment liquid crystal layer side after the humidified environment test may be simply described as “reflected light saturation.” The reflected light saturation can be adjusted, for example, by changing the composition of the adhesive used to bond the alignment liquid crystal layer and the optical layer.

Hereinafter, the structure of the optical laminated body according to the first embodiment will be described in detail with reference to the drawings. 1 is a cross-sectional view showing an example of an optical laminate according to the first embodiment. The optical laminate 10 shown in FIG. 1 includes an aligned liquid crystal layer 11 in which a liquid crystal compound is aligned, an optical layer 12, and an adhesive layer 13 that bonds the aligned liquid crystal layer 11 and the optical layer 12. ), and the Re change rate is 0.50% or less.

The optical laminate according to the first embodiment may include components other than the alignment liquid crystal layer, the optical layer, and the adhesive layer. For example, the optical laminated body according to the first embodiment may be an optical laminated body provided with an adhesive layer like the optical laminated body 20 shown in FIG. 2. The optical laminate 20 shown in FIG. 2 has, in addition to the structure of the optical laminate 10, an adhesive layer 21 on the main surface 11a on the side opposite to the adhesive layer 13 side of the alignment liquid crystal layer 11. ) is provided.

The adhesive constituting the adhesive layer 21 is not particularly limited, and may be appropriately selected and used as a base polymer such as acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine polymer, rubber polymer, etc. You can. In particular, adhesives such as acrylic adhesives and rubber adhesives that have excellent transparency, exhibit appropriate wettability, cohesiveness and adhesiveness, and have excellent weather resistance and heat resistance are preferred. The thickness of the adhesive layer 21 is appropriately set depending on the type of the adherend, etc., and is, for example, 3 μm or more and 300 μm or less.

Lamination of the adhesive layer 21 onto the alignment liquid crystal layer 11 is performed, for example, by bonding an adhesive previously formed into a sheet to the surface of the alignment liquid crystal layer 11 . In addition, after applying the pressure-sensitive adhesive composition on the alignment liquid crystal layer 11, the pressure-sensitive adhesive layer 21 may be formed by drying the solvent, crosslinking, photocuring, etc. In order to increase the adhesion (anchoring force) between the alignment liquid crystal layer 11 and the adhesive layer 21, surface treatment such as corona treatment or plasma treatment or an adhesion facilitator layer is formed on the surface of the alignment liquid crystal layer 11. , the adhesive layer 21 may be laminated.

As shown in FIG. 2, it is preferable that a release liner 22 is temporarily attached to the surface of the adhesive layer 21. In Fig. 2, a release liner 22 is temporarily attached to the main surface 21a of the adhesive layer 21 on the side opposite to the alignment liquid crystal layer 11 side. The release liner 22 protects the surface of the adhesive layer 21 until, for example, the optical laminate 20 with the adhesive is bonded to the polarizing plate 101 (see FIG. 3) described later. do. As a constituent material of the release liner 22, a plastic film formed of acrylic, polyolefin, cyclic polyolefin, polyester, etc. is suitably used. The thickness of the release liner 22 is, for example, 5 μm or more and 200 μm or less. It is preferable that release treatment is performed on the surface of the release liner 22. Release agents used in the mold release treatment include silicone-based materials, fluorine-based materials, long-chain alkyl-based materials, and fatty acid amide-based materials.

When measuring the Re change rate of the optical laminate 20 shown in FIG. 2, after peeling off the release liner 22, a laminate obtained by bonding, for example, a glass plate to the exposed adhesive layer 21 is applied. For this, the change rate of Re(550) before and after the humidification environment test is measured. Also for the optical laminated body 20 shown in FIG. 2, the Re change rate is 0.50% or less.

Although the structure of the optical laminated body according to the first embodiment has been described above with reference to the drawings, the optical laminated body of the present invention is not limited to the above-described embodiment. For example, in the optical laminate of the present invention, in order to bond to an image display cell (not shown), an adhesive layer (not shown) is placed on the main surface of the optical layer 12 on the opposite side to the adhesive layer 13 side. This may be laminated, or a release liner (not shown) may be temporarily attached to the surface of the adhesive layer.

Next, elements of the optical laminated body according to the first embodiment will be described.

[Alignment liquid crystal layer]

Examples of the liquid crystal compound constituting the alignment liquid crystal layer 11 include rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds. From the viewpoint of homogeneous orientation, a rod-shaped liquid crystal compound is preferable as the liquid crystal compound. The rod-shaped liquid crystal compound may be a polymer. For example, the rod-shaped liquid crystal compound may be a liquid crystal polymer (more specifically, a main chain liquid crystal polymer, a side chain liquid crystal polymer, etc.), or a polymer of a polymerizable liquid crystal compound. As long as the liquid crystal compound (monomer) before polymerization exhibits liquid crystallinity, it may not exhibit liquid crystallinity after polymerization.

The liquid crystal compound is preferably a thermotropic liquid crystal that develops liquid crystallinity by heating. Thermotropic liquid crystals produce a phase transition between a crystalline phase, a liquid crystal phase, and an isotropic phase as temperature changes. The liquid crystal compound may be any of nematic liquid crystal, smectic liquid crystal, and cholesteric liquid crystal. A chiral agent may be added to the nematic liquid crystal to provide cholesteric orientation.

Examples of rod-shaped liquid crystal compounds exhibiting thermotropic properties include azomethine-based compounds, subzocyl compounds, cyanobiphenyl-based compounds, cyanophenyl ester-based compounds, benzoic acid ester-based compounds, cyclohexanecarboxylic acid phenyl ester-based compounds, and cyanoacid compounds. Examples include phenylcyclohexane-based compounds, cyano-substituted phenylpyrimidine-based compounds, alkoxy-substituted phenylpyrimidine-based compounds, phenyldioxane-based compounds, tolan-based compounds, and alkenylcyclohexylbenzonitrile-based compounds.

Examples of the polymerizable liquid crystal compound include, for example, a polymerizable liquid crystal compound capable of fixing the orientation state of the rod-shaped liquid crystal compound using a polymer binder, and a polymerizable liquid crystal compound having a polymerizable functional group that can fix the orientation state of the liquid crystal compound by polymerization. liquid crystal compounds, etc. can be mentioned. Among these, a photopolymerizable liquid crystal compound having a photopolymerizable functional group is preferable.

A photopolymerizable liquid crystal compound (liquid crystal monomer) has a mesogenic group and at least one photopolymerizable functional group in one molecule. The temperature at which the liquid crystal monomer exhibits liquid crystallinity (liquid crystal phase transition temperature) is preferably 40°C or higher and 200°C or lower, more preferably 50°C or higher and 150°C or lower, and even more preferably 55°C or higher and 100°C or lower.

Examples of the mesogenic group of the liquid crystal monomer include biphenyl group, phenylbenzoate group, phenylcyclohexane group, azoxybenzene group, azobenzene group, phenylpyrimidine group, diphenylacetylene group, diphenylbenzoate group, bicyclohexane group, and cyclohexane group. Cyclic structures such as hexylbenzene group and terphenyl group can be mentioned. The terminals of these cyclic units may be substituted with cyano groups, alkyl groups, alkoxy groups, halogen groups, etc.

Examples of the photopolymerizable functional group include (meth)acryloyl group, epoxy group, and vinyl ether group. Among them, (meth)acryloyl group is preferable. The liquid crystal monomer preferably has two or more photopolymerizable functional groups in one molecule. By using a liquid crystal monomer containing two or more photopolymerizable functional groups, a crosslinked structure is introduced into the liquid crystal layer after photocuring, so the durability of the optical laminate tends to improve.

As the liquid crystal monomer, any suitable liquid crystal monomer can be employed. For example, International Publication No. 00/37585, US Patent No. 5211877, US Patent No. 4388453, International Publication No. 93/22397, European Patent No. 0261712, German Patent No. 19504224, German Patent No. 4408171, British-Japanese Patent No. 2280445, Japanese Patent Publication No. 2017-206460, International Publication No. 2014/126113, International Publication No. 2016/114348, International Publication No. 2014/010325, Japanese Patent Publication No. 2015-200877 , Japanese Patent Publication No. 2010-31223, International Publication No. 2011/050896, Japanese Patent Publication No. 2011-207765, Japanese Patent Publication No. 2010-31223, Japanese Patent Publication No. 2010-270108, International Publication Compounds described in Publication No. 2008/119427, Japanese Patent Application Publication No. 2008-107767, Japanese Patent Application Publication No. 2008-273925, International Publication No. 2016/125839, Japanese Patent Application Publication No. 2008-273925, etc. are used in liquid crystals. It can be used as a monomer. Depending on the selection of the liquid crystal monomer, the occurrence of birefringence and the wavelength dispersion of Re can be adjusted.

Additionally, as the liquid crystal compound constituting the alignment liquid crystal layer 11, a liquid crystal compound exhibiting reverse wavelength dispersion may be used. Examples of the liquid crystal compound exhibiting reverse wavelength dispersion include polymerizable compounds exhibiting reverse wavelength dispersion described in Japanese Patent Application Laid-Open No. 2020-147749. Using a liquid crystal compound exhibiting inverse wavelength dispersion makes it easier to optimize optical properties across the entire visible spectrum. When a liquid crystal compound exhibiting reverse wavelength dispersion is used as the liquid crystal compound constituting the alignment liquid crystal layer 11, for example, it satisfies all of the following formula (I), the following formula (II), and the following formula (III). An aligned liquid crystal layer 11 is obtained.

Re(450)/Re(550)≤1.00 … (I)

Re(650)/Re(550)≥1.00... (II)

100㎚<Re(550)<160㎚... (III)

Hereinafter, an alignment liquid crystal layer that satisfies all of Formula (I), Formula (II), and Formula (III) may be described as a “reverse wavelength dispersion alignment liquid crystal layer.” In general, the reverse wavelength dispersion orientation liquid crystal layer makes it easy to optimize optical properties and makes light leakage less likely to occur, but the coloring of reflected light tends to increase when exposed to a high humidity environment for a long time. In the first embodiment, even if a reverse wavelength dispersion alignment liquid crystal layer is used as the alignment liquid crystal layer 11, coloring of reflected light when exposed to a high humidity environment for a long time can be suppressed.

In the case of forming the alignment liquid crystal layer 11, for example, a solution (liquid crystal composition) containing the above-described liquid crystal compound is applied on a support, and the liquid crystal compound contained in the composition is heated so that it is in a liquid crystal state to form a liquid crystal. Orient the compound. In addition to the liquid crystal compound, the liquid crystal composition may contain a compound (orientation control agent) that controls the orientation of the liquid crystal compound in a predetermined direction. For example, by adding a chiral agent to the liquid crystal composition, the liquid crystal compound can be cholesterically aligned.

The liquid crystal composition may contain a photopolymerization initiator. When curing a liquid crystal monomer by ultraviolet irradiation, in order to promote photocuring, the liquid crystal composition preferably contains a photo radical polymerization initiator (photo radical generator) that generates radicals by light irradiation. Depending on the type of liquid crystal monomer (type of photopolymerizable functional group), a photocation generator or a photoanion generator may be used. The amount of the photopolymerization initiator used is, for example, 0.01 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the liquid crystal monomer. In addition to the photopolymerization initiator, a sensitizer or the like may be used.

A liquid crystal composition can be prepared by mixing the liquid crystal monomer and, if necessary, various orientation control agents, polymerization initiators, etc. with a solvent. The solvent is not particularly limited as long as it can dissolve the liquid crystal monomer and does not erode the support (or has low erosiveness), and includes chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, Halogenated hydrocarbon-based compounds such as chlorobenzene and orthodichlorobenzene; Phenol-based compounds such as phenol and parachlorophenol; Aromatic hydrocarbon compounds such as benzene, toluene, xylene, methoxybenzene, and 1,2-dimethoxybenzene; Ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, and N-methyl-2-pyrrolidone; Ester solvents such as ethyl acetate and butyl acetate; alcohol-based solvents such as t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, and 2-methyl-2,4-pentanediol; Amide-based solvents such as dimethylformamide and dimethylacetamide; Nitrile-based solvents such as acetonitrile and butyronitrile; Ether-based solvents such as diethyl ether, dibutyl ether, and tetrahydrofuran; and cellosolve-based solvents such as ethyl cellosolve and butyl cellosolve. A mixed solvent of two or more types of solvents may be used.

The solid content concentration of the liquid crystal composition is, for example, 5% by weight or more and 60% by weight or less. The liquid crystal composition may contain additives such as surfactants and leveling agents.

The support (support on which the liquid crystal composition is applied) for forming the alignment liquid crystal layer 11 is not particularly limited and includes glass plates, metal plates, metal belts, and resin film substrates. When a resin film base material is used as a support, an optical laminated body can be manufactured by a roll-to-roll method, and thus productivity of the optical laminated body can be improved. The thickness of the support is not particularly limited, but is, for example, 1 μm or more and 500 μm or less. The support has a first main surface and a second main surface, and the liquid crystal composition is applied on the first main surface.

The resin material constituting the resin film base is not particularly limited as long as it is not soluble in the solvent of the liquid crystal composition and has heat resistance when heated to orient the liquid crystal composition. Polyethylene terephthalate, polyethylene naphthalate, etc. ester; Polyolefins such as polyethylene and polypropylene; Cyclic polyolefins such as norbornene-based polymers; Cellulose-based polymers such as diacetylcellulose and triacetylcellulose; Acrylic polymer; Styrene-based polymer; polycarbonate; polyamide; Polyimide etc. are mentioned.

The support may have an orientation ability to orient the liquid crystal compound in a predetermined direction. For example, by using a stretched film as a support, it is possible to homogeneously orient the liquid crystal compound along the stretching direction. The stretching ratio of the stretched film may be sufficient to exhibit orientation ability, for example, 1.1 times or more and 5 times or less. The stretched film may be a biaxially stretched film. Even if it is a biaxially stretched film, if a film with different stretching ratios in the longitudinal and transverse directions is used, the liquid crystal compound can be oriented along the direction in which the stretching ratio is greater. The stretched film may be an obliquely stretched film. By using an obliquely stretched film as a support, the liquid crystal compound can be oriented in directions that are not parallel to both the longitudinal and width directions of the support.

The support may be provided with an alignment film on the first main surface. The alignment film may be selected as appropriate depending on the type of liquid crystal compound, the material of the support, etc. As an alignment film for homogeneously aligning the liquid crystal compound in a predetermined direction, a polyimide-based or polyvinyl alcohol-based alignment film subjected to a rubbing treatment is suitably used. Additionally, a photo-alignment film may be used. A rubbing treatment may be performed on the resin film substrate serving as a support without providing an alignment film.

When the liquid crystal compound is a thermotropic liquid crystal, the liquid crystal composition is applied onto the first main surface of the support, and the liquid crystal compound is oriented in a liquid crystal state by heating.

The method for applying the liquid crystal composition on the support is not particularly limited, and spin coat, die coat, kiss roll coat, gravure coat, reverse coat, spray coat, Meyer bar coat, knife roll coat, air knife coat, etc. are employed. can do. After applying the liquid crystalline composition, the solvent is removed, thereby forming a liquid crystalline composition layer on the support. The thickness of the application layer formed by applying the liquid crystal composition is preferably adjusted so that the thickness of the liquid crystal composition layer after solvent removal is 0.1 μm or more and 20 μm or less.

By heating the liquid crystal composition layer formed on the support to form a liquid crystal phase, the liquid crystal compound is aligned and the aligned liquid crystal layer 11 is formed. Specifically, after applying the liquid crystal composition on a support, the liquid crystal composition is heated above the N (nematic phase)-I (isotropic liquid phase) transition temperature of the liquid crystal composition to change the liquid crystal composition into an isotropic liquid state. There, if necessary, it is slowly cooled to develop a nematic phase. At this time, it is desirable to first maintain the temperature at which a liquid crystalline phase appears and grow the liquid crystalline domain to form a mono domain. Alternatively, after applying the liquid crystal composition on the support, the temperature may be maintained for a certain period of time within the temperature range at which the nematic phase develops to orient the liquid crystal compound in a predetermined direction.

The heating temperature when orienting the liquid crystal compound in a predetermined direction may be appropriately selected depending on the type of the liquid crystal composition, and is, for example, 40°C or more and 200°C or less. If the heating temperature is excessively low, transition to the liquid crystal phase tends to be insufficient, and if the heating temperature is excessively high, alignment defects may increase. The heating time can be adjusted to ensure sufficient growth of the liquid crystalline domain, for example, from 30 seconds to 30 minutes.

After aligning the liquid crystal compound by heating, it is preferable to cool it to a temperature below the glass transition temperature. The cooling method is not particularly limited, and for example, it may be taken out from a heating atmosphere at room temperature. Forced cooling such as air cooling or water cooling may be performed.

By irradiating light to the aligned photopolymerizable liquid crystal compound, photocuring is performed in a state where the photopolymerizable liquid crystal compound (liquid crystal monomer) has liquid crystal regularity. The irradiated light can be used as long as it can polymerize the photopolymerizable liquid crystal compound, and usually, ultraviolet light or visible light with a wavelength of 250 nm or more and 450 nm or less is used. When the liquid crystal composition contains a photopolymerization initiator, light of a wavelength to which the photopolymerization initiator is sensitive may be selected. As irradiation light sources, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high pressure mercury lamps, metal halide lamps, xenon lamps, LEDs, black lights, chemical lamps, etc. are used. In order to promote the photocuring reaction, light irradiation is preferably performed under an inert gas atmosphere such as nitrogen gas.

When photo-curing the liquid crystal composition, the liquid crystal compound can also be oriented in a predetermined direction by using polarized light in a predetermined direction. When the liquid crystal compound is aligned by the orientation regulating force of the support, the irradiated light may be non-polarized light (natural light).

The irradiation intensity of the irradiated light may be adjusted appropriately depending on the composition of the liquid crystal composition, the amount of photopolymerization initiator added, etc. The irradiation energy (integrated light quantity) is, for example, 20 mJ/cm2 or more and 10000 mJ/cm2 or less, and is preferably 50 mJ/cm2 or more and 5000 mJ/cm2 or less. In order to promote the photocuring reaction, light irradiation may be performed under heating conditions.

The polymer product after photocuring the liquid crystal monomer by light irradiation is non-liquid crystalline and does not undergo phase transition due to temperature changes. Additionally, since the optical laminate having the alignment liquid crystal layer 11 has a significantly larger birefringence Δn compared to a film made of a non-liquid crystal material, the thickness of the optically anisotropic element having the desired retardation can be significantly reduced. The thickness of the alignment liquid crystal layer 11 may be set according to the desired retardation value, etc., and for example, it is preferably 0.1 μm or more and 20 μm or less, preferably 0.2 μm or more and 10 μm or less, and 0.5 μm or more and 7 μm or less. It is more preferable.

The optical properties of the alignment liquid crystal layer 11 are not particularly limited. The in-plane retardation and the thickness direction retardation of the alignment liquid crystal layer 11 may be set appropriately according to the purpose, etc. In the alignment liquid crystal layer 11, when the liquid crystal compound is homogeneously aligned, the in-plane retardation of the alignment liquid crystal layer 11 is, for example, 20 nm or more and 1000 nm or less. When the alignment liquid crystal layer 11 is a quarter wave plate, the in-plane retardation is preferably 100 nm or more and 180 nm or less, and more preferably 120 nm or more and 150 nm or less. When the alignment liquid crystal layer 11 is a half wave plate, the in-plane retardation is preferably 200 nm or more and 340 nm or less, and more preferably 240 nm or more and 300 nm or less.

[Optical layer]

The optical layer 12 is not particularly limited. As the optical layer 12, for example, a commonly used optically isotropic or optically anisotropic optical film can be used without limitation. Specific examples of the optical layer 12 include transparent films (more specifically, retardation films, polarizer protective films, etc.), functional films (more specifically, polarizers, viewing angle expansion films, viewing angle limiting (anti-peeping) films, luminance improvement film, etc.), etc. can be mentioned. The optical layer 12 may be a single layer or a laminate. The optical layer 12 may be an alignment liquid crystal layer (another alignment liquid crystal layer). Additionally, the optical layer 12 may be a polarizing plate in which a transparent protective film is bonded to one main surface or both main surfaces of the polarizer. When the polarizing plate is provided with a transparent protective film on one main surface, the polarizer and the alignment liquid crystal layer 11 may be bonded together, or the transparent protective film and the alignment liquid crystal layer 11 may be bonded together. The thickness of the optical layer 12 is appropriately adjusted depending on the required optical performance, but is, for example, 0.1 μm or more and 1000 μm or less, and is preferably 0.1 μm or more and 100 μm or less.

Additionally, a positive C plate may be used as the optical layer 12. The positive C plate is an optical layer that exhibits refractive index characteristics of nz>nx≥ny. The optical laminate having a positive C plate as the optical layer 12 can be applied to a circularly polarizing plate capable of shielding reflected light even from external light from an oblique direction, as will be described later.

[Adhesive layer]

The adhesive constituting the adhesive layer 13 is not particularly limited as long as it is optically transparent, and includes epoxy resin adhesives, silicone resin adhesives, acrylic resin adhesives, polyurethane adhesives, polyamide adhesives, and polyether adhesives. , an active energy ray-curable adhesive is preferred. The thickness of the adhesive layer 13 is, for example, 0.9 μm or more and 1.4 μm or less.

An active energy ray-curable adhesive is an adhesive that can undergo radical polymerization, cationic polymerization, or anionic polymerization by irradiation of active energy rays such as electron beams or ultraviolet rays. Among them, since they can be cured with low energy, radical photopolymerizable adhesives, photocationic polymerizable adhesives, or hybrid adhesives that use both photocationic polymerization and photoradical polymerization in which polymerization is initiated by ultraviolet irradiation are preferred.

When bonding the alignment liquid crystal layer 11 and the optical layer 12 with an adhesive, the adhesive is applied to one or both of the surface of the alignment liquid crystal layer 11 and the surface of the optical layer 12, and the adhesive is cured. do. As a result, the alignment liquid crystal layer 11 and the optical layer 12 are adhered via the adhesive layer 13 formed by curing the adhesive.

Monomers of radical photopolymerizable adhesives include compounds having a (meth)acryloyl group and compounds having a vinyl group. Among them, compounds having a (meth)acryloyl group are suitable. Examples of the compound having a (meth)acryloyl group include alkyl (meth)acrylates such as C _1-20 chain alkyl (meth)acrylate, alicyclic alkyl (meth)acrylate, and polycyclic alkyl (meth)acrylate; (meth)acrylate containing a hydroxyl group; Epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate; Acetoacetyl group-containing (meth)acrylates such as 2-acetoacetoxyethyl (meth)acrylate, etc. can be mentioned. Radical photopolymerizable adhesives include hydroxyethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, (meth)acrylamide, ) It may contain nitrogen-containing monomers such as acrylamide and (meth)acryloylmorpholine. The radical photopolymerizable adhesive contains, as a crosslinking component, tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, dioxane glycol diacrylate, and polyoxyethylene glycol diacrylate. It may contain polyfunctional monomers such as latex.

Examples of the curable component of the cationic photopolymerizable adhesive include compounds having an epoxy group or an oxetanyl group. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various generally known curable epoxy compounds are used. Preferred epoxy compounds include compounds having at least two epoxy groups and at least one aromatic ring in the molecule (aromatic epoxy compounds), and adjacent compounds having at least two epoxy groups in the molecule, at least one of which constitutes an alicyclic ring. and compounds formed between two carbon atoms (alicyclic epoxy compounds). A cationically polymerizable adhesive can also be made into a hybrid adhesive by containing a radically polymerizable compound such as a compound having a (meth)acryloyl group.

In order to obtain an adhesive with a low cure shrinkage rate, it is desirable to adjust the formulation of the adhesive so that the number of bonds formed when the adhesive cures is reduced. In order to reduce the number of bonds formed, it is preferable to use a monomer with a high molecular weight per reactive functional group (for example, (meth)acryloyl group, etc.). Monomers with a high molecular weight per reactive functional group include alkyl (meth)acrylates having an alkyl group having a carbon atom number of 10 or more, 12 or more, 14 or more, 16 or more, or 18 or more (e.g., isostearyl acrylate, etc.), and polyoxyethylene glycol diacrylate, where the number of oxyethylene groups per molecule is 5 or more, 7 or more, or 9 or more.

Additionally, even when the adhesive before curing contains an oligomer with a weight average molecular weight of 1000 or more, an adhesive with a low cure shrinkage rate can be obtained. Examples of oligomers with a weight average molecular weight of 1000 or more (hereinafter sometimes referred to as “specific oligomers”) include oligomers (acrylic oligomers) formed from monomers having a (meth)acryloyl group. The acrylic oligomer may have a cationically polymerizable functional group (for example, an epoxy group, etc.).

In order to manufacture an optical laminate excellent in heat durability while ensuring adhesion reliability, the weight average molecular weight of the specific oligomer is preferably 1000 or more and 10000 or less, more preferably 1000 or more and 5000 or less, and even more preferably 1000 or more and 3000 or less. It is preferable, and it is more preferable that it is 1500 or more and 3000 or less.

In order to manufacture an optical laminate with excellent heat durability while ensuring adhesion reliability, the content ratio of the specific oligomer is preferably 5% by weight or more and 20% by weight or less, and 8% by weight or more 15 with respect to the total amount of the adhesive before curing. It is more preferable that it is % by weight or less.

The weight average molecular weight of a specific oligomer can be measured by gel permeation chromatography (GPC). In addition, in this specification, the weight average molecular weight of an oligomer or polymer, if not specified at all, is a standard polystyrene conversion value measured under the following conditions.

(Molecular weight measurement conditions)

GPC measuring device: Tosoh Corporation “HLC-8120GPC”

Sample concentration: 2.0g/L (tetrahydrofuran solution)

Sample injection volume: 20μL

Column: Tosoh Corporation 「TSKgel, SuperAWM-H+superAW4000+superAW2500」

Column size: 6.0mmI.D.×150mm each

Eluent: tetrahydrofuran

Flow rate: 0.4mL/min

Detector: Differential refractometer (RI)

Column temperature (measurement temperature): 40℃

It is preferable that light-curing adhesives such as ultraviolet curing adhesives contain a photopolymerization initiator. The photopolymerization initiator may be appropriately selected depending on the reactive species. For example, it is preferable to mix a radical photopolymerization initiator that generates radicals by irradiation of light as a photopolymerization initiator in a radical photopolymerizable adhesive. It is preferable to mix, as a photopolymerization initiator, a photocationic polymerization initiator (photoacid generator) that generates cationic species or Lewis acid by light irradiation in the photocationic polymerizable adhesive. It is preferable to mix a photocationic polymerization initiator and a photoradical polymerization initiator in the hybrid adhesive.

The content of the photopolymerization initiator is, for example, 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the monomer. If necessary, a photosensitizer may be added to the photocurable adhesive. The amount of the photosensitizer used is, for example, 0.001 parts by weight or more and 10 parts by weight or less, and preferably 0.01 parts by weight or more and 3 parts by weight or less, based on 100 parts by weight of monomer.

The adhesive may contain appropriate additives as needed. Examples of additives include coupling agents such as silane coupling agents and titanium coupling agents, adhesion promoters such as ethylene oxide, ultraviolet absorbers, anti-deterioration agents, dyes, processing aids, ion trapping agents, antioxidants, tackifiers, fillers, plasticizers, Leveling agents, foaming inhibitors, antistatic agents, heat-resistant stabilizers, hydrolysis-resistant stabilizers, etc. can be mentioned.

[Usage]

The optical laminated body according to the first embodiment can be used, for example, as an optical film for displays for the purpose of improving visibility. Additionally, it can also be applied to the circular polarizing plate described below.

<Second embodiment: circular polarizer>

Next, a circularly polarizing plate according to a second embodiment of the present invention will be described with appropriate reference to the drawings. The circularly polarizing plate according to the second embodiment of the present invention has the optical laminate according to the first embodiment and a polarizer. Since the circularly polarizing plate according to the second embodiment has the optical laminate according to the first embodiment, coloring of reflected light can be suppressed even when exposed to a high humidity environment for a long time. In the following description, the description of content that overlaps with the first embodiment may be omitted.

Fig. 3 is a cross-sectional view showing an example of a circularly polarizing plate according to the second embodiment. The circularly polarizing plate 100 shown in FIG. 3 has an optical laminate 10 and a polarizing plate 101 laminated on the optical laminate 10 with an adhesive layer 21 interposed therebetween. In FIG. 3 , the alignment liquid crystal layer 11 of the optical laminate 10 and the polarizing plate 101 are bonded via the adhesive layer 21.

The polarizing plate 101 may be composed of only one layer of polarizer (not shown), or a transparent protective film may be bonded to one main surface or both main surfaces of the polarizer. As a polarizer, a dichroic substance such as iodine or a dichroic dye is adsorbed on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or an ethylene/vinyl acetate copolymer-based partially saponified film, and the film is uniaxially stretched. and polyene-based oriented films such as dehydrated products of polyvinyl alcohol and dehydrochlorinated products of polyvinyl chloride.

Among them, because it has a high degree of polarization, polyvinyl alcohol is oriented in a predetermined direction by adsorbing a dichroic substance such as iodine or a dichroic dye to a polyvinyl alcohol-based film such as polyvinyl alcohol or partially formalized polyvinyl alcohol. (PVA)-based polarizer is preferred. For example, a PVA-based polarizer is obtained by subjecting a polyvinyl alcohol-based film to iodine dyeing and stretching. A PVA-based resin layer may be formed on a resin substrate, and iodine dyeing and stretching may be performed in the laminate state.

The thickness of the polarizer is not particularly limited, but is preferably 1 μm or more and 60 μm or less, more preferably 2 μm or more and 30 μm or less, and still more preferably 5 μm or more and 15 μm or less.

In the circularly polarizing plate 100, for example, the aligned liquid crystal layer 11 is an aligned liquid crystal layer in which a liquid crystal compound is homogeneously aligned. In the circularly polarizing plate 100, the orientation direction of the liquid crystal compound in the alignment liquid crystal layer 11 is arranged so that the absorption axis direction of the polarizer is neither parallel nor perpendicular.

In the circularly polarizing plate 100, for example, the alignment liquid crystal layer 11 is a quarter wave plate, and the absorption axis direction of the polarizing plate 101 and the orientation direction of the liquid crystal compound of the alignment liquid crystal layer 11 (generally The angle formed by the slow axis direction is set to 45°. The angle formed by the absorption axis direction of the polarizing plate 101 and the orientation direction of the liquid crystal compound may be 35° or more and 55° or less, 40° or more and 50° or less, or 43° or more and 47° or less.

In the circularly polarizing plate 100 in which a polarizing plate 101 and a quarter wave plate as the alignment liquid crystal layer 11 are laminated so that the angle between their optical axes is 45°, as the optical layer 12, a liquid crystal compound This homeotropically oriented liquid crystal layer (homeotropically oriented liquid crystal layer) may be provided. The polarizing plate 101, the quarter wave plate (alignment liquid crystal layer 11), and the homeotropic alignment liquid crystal layer (optical layer 12) functioning as a positive C plate are sequentially stacked to allow external light from the oblique direction to be transmitted. A circularly polarizing plate capable of shielding reflected light can also be formed.

Additionally, in the circularly polarizing plate 100, both the alignment liquid crystal layer 11 and the optical layer 12 may be homogeneous alignment liquid crystal layers. In this case, the alignment liquid crystal layer 11 disposed on the side close to the polarizer 101 is a 1/2 wave plate, and the optical layer 12 disposed on the side farthest from the polarizer 101 is a 1/4 wave plate. desirable. In this layer configuration, the angle between the slow axis direction of the 1/2 wave plate and the absorption axis direction of the polarizer 101 is 75°±5°, and the slow axis direction of the 1/4 wave plate and the absorption axis direction of the polarizer 101 are 75°±5°. It is desirable to arrange it so that the angle formed by the direction is 15°±5°. Since the circularly polarizing plate 100 with this layer structure functions as a circularly polarizing plate over a wide wavelength range of visible light, it can reduce coloring of reflected light over a wide wavelength range of visible light.

[Example]

Below, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

<Preparation of adhesives A-1 to A-4>

Hereinafter, the preparation method of the adhesive used in Examples 1 to 3 and Comparative Example 1 will be described.

[Preparation of adhesive A-1]

7.7 parts by weight of polyoxyethylene glycol diacrylate (“Light Acrylate (registered trademark) 9EG-A” manufactured by Kyoesha Chemical Co., Ltd., number of oxyethylene groups per molecule: 9), and unsaturated fatty acid hydroxyalkyl ester modification 61.5 parts by weight of ε-caprolactone (“Flaxel (registered trademark) FA1DDM” manufactured by Daicel), 30.8 parts by weight of acryloylmorpholine (“ACMO (registered trademark)” manufactured by KJ Chemicals, and an acrylic oligomer (DoA) 15.3 parts by weight of “ARUFON (registered trademark) UP-1190” manufactured by Kose Corporation, weight average molecular weight: 1700), 3.5 parts by weight of photo radical polymerization initiator (“KAYACURE (registered trademark) DETX-S” manufactured by Nippon Kayaku Corporation), and light Adhesive A-1 was prepared by mixing 3.5 parts by weight of a radical polymerization initiator (“Omnirad (registered trademark) 907” manufactured by IGM Resins).

[Preparation of adhesive A-2]

40.0 parts by weight of m-phenoxybenzyl acrylate (“Light Acrylate (registered trademark) POB-A” manufactured by Kyoesha Chemical Co., Ltd.), and unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone (“Flaxel” manufactured by Daicel Co., Ltd. (registered trademark) "FA1DDM") 10.0 parts by weight, acryloylmorpholine ("ACMO (registered trademark)" manufactured by KJ Chemicals) 40.0 parts by weight, and an acrylic oligomer ("ARUFON (registered trademark)" UP-1190 manufactured by Toa Kosei Co., Ltd. ”, weight average molecular weight: 1700) 10.0 parts by weight, a radical photopolymerization initiator (“KAYACURE (registered trademark) DETX-S” manufactured by Nippon Kayaku Co., Ltd.), 3.0 parts by weight, and a radical photopolymerization initiator (“Omnirad (registered trademark)” manufactured by IGM Resins Co., Ltd. Adhesive A-2 was prepared by mixing 3.0 parts by weight of (trademark) 907").

[Preparation of adhesive A-3]

11.9 parts by weight of hydroxyethyl acrylamide (“HEAA (registered trademark)” manufactured by KJ Chemicals), 59.5 parts by weight of acrylate-based monomer (“Aronics (registered trademark) M-220” manufactured by Toago Se, Inc.), and acrylic 11.9 parts by weight of Ilmorpholine (“ACMO (registered trademark)” manufactured by KJ Chemicals), 11.9 parts by weight of an acrylic oligomer (“ARUFON (registered trademark) UP-1190” manufactured by Toagosei Corporation, weight average molecular weight: 1700), 2 - 4.8 parts by weight of acetoacetoxyethyl methacrylate (“AAEM” sold by MCC Trading), 2.9 parts by weight of radical photopolymerization initiator (“Omnirad (registered trademark) 907” manufactured by IGM Resins), and radical photopolymerization initiator (Nippon) Adhesive A-3 was prepared by mixing 1.4 parts by weight of "KAYACURE (registered trademark) DETX-S" manufactured by Kayaku Corporation.

[Preparation of adhesive A-4]

10.0 parts by weight of an acrylate-based monomer (“Aronics (registered trademark) M-220” manufactured by Toagosei Corporation), 40.0 parts by weight of n-butyl acrylate (manufactured by Mitsubishi Chemical Corporation), and 4-hydroxybutylacrylate (manufactured by Mitsubishi Chemical Corporation) ) 40.0 parts by weight, 5.0 parts by weight of hydroxyethyl acrylamide (“HEAA (registered trademark)” manufactured by KJ Chemicals), and 5.0 parts by weight of acryloylmorpholine (“ACMO (registered trademark)” manufactured by KJ Chemicals) By mixing 0.5 parts by weight of a radical photopolymerization initiator (“KAYACURE (registered trademark) DETX-S” manufactured by Nippon Kayaku Co., Ltd.) with 1.5 parts by weight of a radical photopolymerization initiator (“Omnirad (registered trademark) 907” manufactured by IGM Resins Co., Ltd.) Adhesive A-4 was prepared.

<Production of optical film F-1>

According to the description of Example 1 of Japanese Patent Application Laid-Open No. 2020-147749, an optically anisotropic film (reverse wavelength dispersion orientation liquid crystal layer, thickness: 2.3) was formed on a triacetylcellulose film (“Z-TAC” manufactured by Fuji Film Co., Ltd.) as a support. ㎛) was formed, and optical film F-1 was obtained.

<Production of optical film F-2>

First, a side-chain liquid crystal polymer with a weight average molecular weight of 5000 represented by the following formula (1) (the numbers 65 and 35 in the formula represent the material amount ratio of the repeating unit, and are represented as a block polymer for convenience) was prepared. Additionally, as a support, a vertically aligned polyethylene terephthalate film (PET film) was prepared.

20 parts by weight of a side chain liquid crystal polymer represented by the above formula (1), 80 parts by weight of a photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (“Paliocolor (registered trademark) LC242” manufactured by BASF), and a radical photopolymerization initiator ( 5 parts by weight of “Omnirad (registered trademark) 907” manufactured by IGM Resins was dissolved in 200 parts by weight of cyclopentanone to prepare a coating solution. Next, the coating liquid was applied to the surface of the PET film using a bar coater and heated at a temperature of 80°C for 4 minutes to orient the liquid crystal compound. Next, the liquid crystalline composition on the PET film was cooled to room temperature (25°C), and then photocuring was performed by irradiating ultraviolet rays to the liquid crystalline composition under a nitrogen atmosphere. Through the above procedure, a homeotropically aligned liquid crystal layer (thickness: 3.0 μm) exhibiting refractive index characteristics of nz>nx=ny was formed on the PET film, and optical film F-2 was obtained.

<Production of polarizer P-1>

A long roll of a polyvinyl alcohol (PVA)-based resin film (“PE3000” manufactured by Kuraray Co., Ltd.) with a thickness of 30 μm was uniaxially stretched in the longitudinal direction using a roll stretching machine so that the length in the longitudinal direction was 5.9 times the swelling treatment. After performing the dyeing treatment, crosslinking treatment, and washing treatment in this order, it was dried at a temperature of 70°C for 5 minutes to produce a polarizer with a thickness of 12 μm (water vapor transmission rate: 350 g/m2·24h). Specifically, in the swelling treatment, it was stretched 2.2 times while being treated with pure water at a temperature of 20°C. In the dyeing treatment, it was stretched 1.4 times while being treated with an aqueous solution at a temperature of 30°C (an aqueous solution with a weight ratio of iodine and potassium iodide of 1:7) with the iodine concentration adjusted so that the resulting polarizer had a single transmittance of 45.0%. In the above crosslinking treatment, a two-stage crosslinking treatment was adopted, and in the first stage of crosslinking treatment, the material was stretched 1.2 times while being treated with an aqueous solution (temperature: 40°C) in which boric acid and potassium iodide were dissolved. In the second stage of crosslinking treatment, it was stretched 1.6 times while being treated with an aqueous solution of boric acid and potassium iodide (temperature: 65°C). The aqueous solution for the first stage crosslinking treatment had a boric acid content of 5.0% by weight and a potassium iodide content of 3.0% by weight. The aqueous solution for the second stage crosslinking treatment had a boric acid content of 4.3% by weight and a potassium iodide content of 5.0% by weight. In the above washing treatment, treatment was performed with an aqueous potassium iodide solution (potassium iodide content: 2.6% by weight) at a temperature of 20°C.

Next, an HC-COP film (water vapor transmission rate: 1.6 g/m2·24h, thickness: 29 μm) was bonded to one main surface of the obtained polarizer as a first protective layer via a polyvinyl alcohol-based adhesive. Additionally, the HC-COP film is a film in which a 3-μm-thick hard coat (HC) layer is formed on a 26-μm-thick cycloolefin-based resin (COP) film. In addition, when bonding the polarizer and the HC-COP film, the COP film was bonded so that it was on the polarizer side. Next, a second triacetylcellulose (TAC) film (water vapor permeability: 810 g/m2·24h, thickness: 20 μm) with Re (550) of 0 nm was applied to the other main surface of the polarizer through a polyvinyl alcohol-based adhesive. It was bonded as a protective layer. In this way, polarizing plate P-1 having the structure of HC-COP film (first protective layer)/polarizer/TAC film (second protective layer) was obtained.

<Production of optical laminate>

Hereinafter, the manufacturing method of the optical laminated body of Examples 1 to 3 and Comparative Example 1 will be described. In addition, the optical laminate described below was used as a sample for measuring the Re change rate.

[Production of the optical laminate of Example 1]

On the reverse wavelength dispersion orientation liquid crystal layer of the optical film F-1, adhesive A-1 was applied so that the thickness of the layer (adhesive layer) made of adhesive A-1 after curing was 1.0 μm. Next, the surface on the homeotropically aligned liquid crystal layer side of the optical film F-2 was bonded onto the application layer made of adhesive A-1 to obtain a laminate. Next, the obtained laminate was irradiated with ultraviolet rays using a high-pressure mercury lamp under conditions of an integrated light amount of 800 mJ/cm2, and the adhesive A-1 was photocured. In addition, ultraviolet irradiation was performed from the optical film F-2 side.

Next, after peeling the support of the optical film F-1 from the ultraviolet irradiated laminate (specifically, a laminate in which two optical films are stacked with an adhesive layer interposed between them), the exposed reverse wavelength dispersion orientation liquid crystal layer is An acrylic adhesive sheet with a thickness of 13 μm was attached to the surface. Next, a glass plate (material: alkali-free glass) was bonded to the surface of the bonded adhesive sheet, and then the support of the optical film F-2 was peeled off to obtain the optical laminate of Example 1.

[Production of optical laminates of Example 2, Example 3, and Comparative Example 1]

The optical laminates of Example 2, Example 3, and Comparative Example 1 were produced in the same manner as Example 1, except that the type of adhesive was changed as shown in Table 1 described later.

<Production of circular polarizer>

Hereinafter, the manufacturing method of the circular polarizing plate of Examples 1 to 3 and Comparative Example 1 will be described. In addition, the circularly polarizing plate described below was used as a sample for measuring reflected light saturation.

[Production of circular polarizer plate of Example 1]

On the reverse wavelength dispersion orientation liquid crystal layer of the optical film F-1, adhesive A-1 was applied so that the thickness of the layer (adhesive layer) made of adhesive A-1 after curing was 1.0 μm. Next, the surface on the homeotropically aligned liquid crystal layer side of the optical film F-2 was bonded onto the application layer made of adhesive A-1 to obtain a laminate. Next, the obtained laminate was irradiated with ultraviolet rays using a high-pressure mercury lamp under conditions of an integrated light amount of 800 mJ/cm2, and the adhesive A-1 was photocured. In addition, ultraviolet irradiation was performed from the optical film F-2 side.

Next, after peeling the support of the optical film F-1 from the ultraviolet irradiated laminate (specifically, a laminate in which two optical films are stacked with an adhesive layer interposed between them), the exposed reverse wavelength dispersion orientation liquid crystal layer is An acrylic adhesive sheet with a thickness of 5 μm was attached to the surface. Next, polarizing plate P-1 was bonded to the surface of the bonded adhesive sheet. At this time, the TAC film of polarizer P-1 was bonded so that it was on the reverse wavelength dispersion orientation liquid crystal layer side. Additionally, at the time of bonding, the angle formed between the absorption axis direction of the polarizer and the orientation direction of the liquid crystal molecules in the reverse wavelength dispersion orientation liquid crystal layer was set to 45°. Next, after peeling the support of the optical film F-2 from the obtained laminate with a polarizing plate, an acrylic pressure-sensitive adhesive sheet with a thickness of 23 μm was bonded to the exposed surface of the homeotropically aligned liquid crystal layer. Next, a glass plate (material: alkali glass) was bonded to the surface of the bonded adhesive sheet, and the circularly polarizing plate of Example 1 was obtained.

[Production of circular polarizing plates of Example 2, Example 3 and Comparative Example 1]

The circular polarizing plates of Examples 2, 3, and Comparative Example 1 were produced in the same manner as Example 1, except that the type of adhesive was changed as shown in Table 1 below.

<Measurement method>

[Re change rate]

Each optical laminate was placed in an environment with a temperature of 20°C and a relative humidity of 98% for 30 days, and a humidification environment test was performed. Then, before and after the humidification environment test, Re (550) of each optical laminate was measured in an atmosphere of 23°C using Axoscan manufactured by Axometrics, and the Re change rate was calculated from the obtained measured values. In addition, in the measurement of Re (550), the surface on the reverse wavelength dispersion orientation liquid crystal layer side was used as the light incident surface.

[Reflected Light Saturation]

Each circularly polarizing plate was placed in an environment with a temperature of 20°C and a relative humidity of 98% for 30 days, and a humidification environment test was performed. Next, each circularly polarizing plate after the humidification environment test was placed on a reflector (specifically, an aluminum plate with a reflectance of visible light of 86%). At this time, the glass plate of each circularly polarizing plate was stacked so that it was on the reflector side. Then, light was incident from the polarizer P-1 side of each circular polarizer, and the reflection spectrum (0° field of view, standard light source: D65) was measured using a spectrophotometer (“CM-26d” manufactured by Konica Minolta). From the obtained reflection spectrum, according to JIS Z8781-4, the chromatic indices a* and b* of the CIE 1976 L*a*b* color space are obtained, and the saturation c*={(a*) ² +(b*) ² } ^1/2 was calculated. The obtained saturation c* was set to the reflected light saturation in Table 1 described later. When the reflected light saturation was 0.25 or less, it was evaluated that “coloring of reflected light can be suppressed when exposed to a high humidity environment for a long time.” When the reflected light saturation exceeded 0.25, it was evaluated that "coloring of the reflected light cannot be suppressed when exposed to a high humidity environment for a long time."

<Result>

For Examples 1 to 3 and Comparative Example 1, the type of adhesive used, Re change rate, and reflected light saturation are shown in Table 1.

As shown in Table 1, in Examples 1 to 3, the Re change rate was 0.50% or less. Additionally, in Examples 1 to 3, the reflected light saturation was 0.25 or less. Therefore, coloring of reflected light was suppressed when the circularly polarizing plates (optical laminates) of Examples 1 to 3 were exposed to a high humidity environment for a long time.

As shown in Table 1, in Comparative Example 1, the Re change rate exceeded 0.50%. Additionally, in Comparative Example 1, the reflected light saturation exceeded 0.25. Therefore, when the circularly polarizing plate (optical laminate) of Comparative Example 1 was exposed to a high humidity environment for a long time, coloring of reflected light was not suppressed.

The above results show that according to the present invention, it is possible to provide an optical laminate and a circularly polarizing plate that can suppress coloring of reflected light even when exposed to a high humidity environment for a long time.

10, 20: Optical laminate
11: Orientation liquid crystal layer
12: optical layer
13: Adhesive layer
100: circular polarizer

Claims (5)

An optical laminate comprising an aligned liquid crystal layer in which a liquid crystal compound is aligned, an optical layer, and an adhesive layer for bonding the aligned liquid crystal layer and the optical layer,
An optical laminate in which the rate of change in in-plane retardation at a wavelength of 550 nm before and after a humidified environment test maintained at a temperature of 20°C and a relative humidity of 98% for 30 days is 0.50% or less. According to paragraph 1,
After a humidified environment test maintained at a temperature of 20°C and a relative humidity of 98% for 30 days, the saturation of the reflected light when light is incident from the above-mentioned aligned liquid crystal layer side is c*={(a*) ² +(b*) ² } ^{1 /2} is 0.25 or less, an optical laminate. According to claim 1 or 2,
The in-plane retardation of the alignment liquid crystal layer at a wavelength of 450 nm is set to Re (450), the in-plane retardation of the alignment liquid crystal layer at a wavelength of 550 nm is set to Re (550), and the alignment liquid crystal layer When the in-plane retardation at a wavelength of 650 nm is set to Re(650), Re(450)/Re(550)≤1.00, Re(650)/Re(550)≥1.00, and 100 nm<Re(550) ), optical laminates meeting <160 nm. According to claim 1 or 2,
Let the refractive index in the slow axis direction within the plane of the optical layer be nx, the refractive index in the direction perpendicular to the slow axis direction within the plane of the optical layer be ny, and let the refractive index in the direction perpendicular to the slow axis direction within the plane of the optical layer be ny, and An optical laminate that satisfies nz>nx≥ny when the refractive index is nz. A circularly polarizing plate comprising the optical laminated body according to claim 1 or 2 and a polarizer.