TW202415987A - Optical laminate body and circularly polarizing plate - Google Patents

Abstract

To provide an optical laminate body and a circularly polarizing plate which can suppress coloring of reflected light even if the optical laminate body and the circularly polarizing plate are exposed to a highly moisture environment. An optical laminate body 10 includes: an orientation liquid crystal layer 11 in which a liquid crystal compound is oriented; an optical layer 12; and an adhesive layer 13 for making the orientation liquid crystal layer 11 and the optical layer 12 adhere to each other. In the optical laminate body 10, the change rate of an in-plane retardation at the wavelength of 550 nm before and after a humidification environment test under the condition that the temperature is maintained at 20 DEG C and the relative moisture is maintained at 98% for 30 days is 0.50% or smaller. In the optical laminate body 10, the saturation c*={(a*)2+(b*)2}1/2 of reflected light when light is emitted from the orientation liquid crystal layer 11 after a humidification environment test under the condition that the temperature is maintained at 20 DEG C and the relative moisture is maintained at 98% for 30 days is preferably not larger than 0.25.

Description

Optical laminates and circular polarizers

The present invention relates to an optical multilayer body and a circular polarizer.

As an optical laminate (optically anisotropic element) having functions such as optical compensation for a liquid crystal display device and anti-external light reflection for an organic EL display device, an optical laminate having an oriented liquid crystal layer in which a liquid crystal compound is oriented in a predetermined direction is used. The optical laminate having an oriented liquid crystal layer has a larger birefringence Δn than a stretched film of a polymer, and is therefore advantageous for thinning or weight reduction of an image display device (more specifically, a liquid crystal display device, an organic EL display device, etc.). In an image display device, the optical laminate is attached to an organic EL panel or a liquid crystal display panel as a laminate plate obtained by laminating with a polarizing element or the like via an adhesive or a bonding agent (for example, refer to Patent Document 1).

Liquid crystal compounds can be aligned in a prescribed direction by the shear force when coated on a support or the alignment limiting force of an alignment film. By aligning the liquid crystal compounds, optical laminates with various optical anisotropies can be obtained. For example, a horizontally aligned liquid crystal layer obtained by aligning nematic liquid crystal molecules with positive refractive index anisotropy parallel to the support surface can be used as a positive A plate with a refractive index anisotropy of nx>ny=nz. Furthermore, in this specification, "nx" represents the refractive index of the slow axis direction within the plane of an optical layer (aligned liquid crystal layer, etc.). Also, in this specification, "ny" represents the refractive index of the direction within the plane of an optical layer (aligned liquid crystal layer, etc.) that is orthogonal to the above-mentioned slow axis direction. In this specification, "nz" represents the refractive index in the thickness direction of an optical layer (aligned liquid crystal layer, etc.).

When thermotropic liquid crystals are used, a solution containing a liquid crystal compound (liquid crystal composition) is applied to a support, and the liquid crystal compound contained in the composition is heated in such a way that the liquid crystal compound exhibits a liquid crystal state, thereby aligning the liquid crystal compound. When the liquid crystal composition contains a photopolymerizable liquid crystal compound (liquid crystal monomer), after aligning the liquid crystal compound, the liquid crystal composition is hardened by irradiating light, thereby fixing the alignment state. [Prior art literature] [Patent literature]

[Patent Document 1] Japanese Patent Publication No. 2015-7700

[The problem the invention is trying to solve]

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

In view of this topic, the purpose of the present invention is to provide an optical layered body and circular polarizer that can suppress the coloring of reflected light even when exposed to a high humidity environment for a long time. [Technical means to solve the problem]

<Forms of the present invention> The present invention includes the following forms.

[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 bonding the aligned liquid crystal layer to the optical layer, wherein the optical laminate has an in-plane retardation variation rate of less than 0.50% at a wavelength of 550 nm before and after being subjected to a humidified environment test at a temperature of 20°C and a relative humidity of 98% for 30 days.

[2] The optical multilayer structure as described in the above [1], wherein after being kept in a humidified environment test at a temperature of 20°C and a relative humidity of 98% for 30 days, the chromaticity c ^* ={(a ^* ) ²⁺ (b ^* ) ² } ^1/2 of the reflected light when the light is incident from the above-mentioned aligned liquid crystal layer side is less than 0.25.

[3] An optical multilayer as described in [1] or [2] above, wherein the in-plane retardation of the aligned liquid crystal layer at a wavelength of 450 nm is set to Re(450), the in-plane retardation of the aligned liquid crystal layer at a wavelength of 550 nm is set to Re(550), and the in-plane retardation of the aligned liquid crystal layer at a wavelength of 650 nm is set to Re(650), and Re(450)/Re(550)≦1.00, Re(650)/Re(550)≧1.00, and 100 nm＜Re(550)＜160 nm are satisfied.

[4] An optical multilayer body as described in any one of the above [1] to [3], wherein the refractive index of the optical layer in the slow axis direction within the plane is set to nx, the refractive index of the optical layer in the direction orthogonal to the slow axis direction within the plane is set to ny, and the refractive index of the optical layer in the thickness direction is set to nz, then nz＞nx≧ny.

[5] A circular polarizing plate having an optical layered structure and a polarizing element as described in any one of [1] to [4] above. [Effect of the invention]

According to the present invention, an optical multilayer and a circular polarizer can be provided which can suppress the coloring of reflected light even when exposed to a high humidity environment for a long time.

The following is a description of the preferred embodiment of the present invention. Furthermore, all the academic documents and patent documents described in this specification are cited as references in this specification.

First, the terms used in this manual are explained. The "main surface" of a layer (more specifically, an aligned liquid crystal layer, an optical layer, a bonding agent layer, an adhesive layer, a polarizing element, a support, etc.) refers to the surface of the layer that is orthogonal to the thickness direction. The thickness of the layer is obtained by observing the cross section of the layer cut along the thickness direction using an electron microscope, randomly selecting 10 measurement locations from the cross-sectional image, and measuring the thickness of the selected 10 measurement locations to obtain the arithmetic average of the 10 measurement values.

"In-plane retardation (unit: nm)" is a value measured in an atmosphere at a temperature of 23°C. In the following, in-plane retardation may be abbreviated as "Re". In addition, in-plane retardation at a wavelength of 450 nm, in-plane retardation at a wavelength of 550 nm, and in-plane retardation at a wavelength of 650 nm may be respectively expressed as "Re(450)", "Re(550)", and "Re(650)".

"Chroma c ^* " is a value calculated using the color indices a ^* and b ^* of the CIE 1976 L ^* a ^* b ^* color space and the formula "Chroma c ^* = {(a ^* ) ² + (b ^* ) ² } ^1/2 ". Chroma c ^* indicates the degree of color. When c ^* is 0, there is no color. The larger the c ^* , the more obvious the color.

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

In the following, "" is sometimes added after the compound name to collectively refer to the compound and its derivatives. Also, when "" is added after the compound name to indicate the name of a polymer, it means that the repeating units of the polymer are derived from the compound or its derivatives. Also, acrylic acid and methacrylic acid are sometimes collectively referred to as "(meth)acrylic acid". Also, acrylate and methacrylate are sometimes collectively referred to as "(meth)acrylate". Also, acryl and methacryl are sometimes collectively referred to as "(meth)acryl".

In the following description, the drawings referred to are schematically shown in the main body for the sake of ease of understanding. In order to facilitate the preparation of the drawings, the size, number, shape, etc. of the components shown in the drawings may be different from the actual situation. In addition, in the drawings described later, the same components as those in the drawings described earlier may be marked with the same symbols, and their descriptions may be omitted.

<First embodiment: optical laminate> The optical laminate of the first embodiment of the present invention comprises an oriented liquid crystal layer in which liquid crystal compounds are aligned, an optical layer, and a bonding agent layer bonding the oriented liquid crystal layer to the optical layer. The optical laminate has a Re (550) variation rate of less than 0.50% before and after a 30-day humidified environment test at a temperature of 20°C and a relative humidity of 98%.

Hereinafter, a humidified environment test at a temperature of 20°C and a relative humidity of 98% for 30 days is sometimes referred to as a "humidified environment test". In addition, the rate of change of Re (550) before and after the humidified environment test is sometimes referred to as a "Re change rate". When Re (550) before the humidified environment test is set as Re1 and Re (550) after the humidified environment test is set as Re2, the Re change rate (unit: %) is calculated by the formula "Re change rate = 100 × |Re2-Re1|/Re1". Furthermore, |Re2-Re1| represents the absolute value of the difference between Re2 and Re1.

The Re change rate of the optical laminate of the first embodiment is less than 0.50%, so the change of the optical characteristics in a high humidity environment is relatively small. Therefore, according to the optical laminate of the first embodiment, the coloring of the reflected light can be suppressed even if it is exposed to a high humidity environment for a long time.

In the first embodiment, in order to further suppress the coloration of the 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 further preferably 0.35% or less. In addition, the lower limit of the Re change rate is not particularly limited, and can be 0.00%, for example. The Re change rate can be adjusted by, for example, changing the composition of the adhesive when the alignment liquid crystal layer is bonded to 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, it is preferred that the chromaticity c ^* of the reflected light when the light is incident from the side of the aligned liquid crystal layer after the humidified environment test is less than 0.25, and more preferably less than 0.23. Furthermore, the lower limit of the chromaticity c ^* of the above-mentioned reflected light is not particularly limited, and for example, it can be 0.00. Hereinafter, the chromaticity c ^* of the reflected light when the light is incident from the side of the aligned liquid crystal layer after the humidified environment test is sometimes abbreviated as "reflected light chromaticity". The reflected light chromaticity can be adjusted by, for example, changing the formulation composition of the adhesive when the aligned liquid crystal layer and the optical layer are bonded.

The structure of the optical multilayer body of the first embodiment is described in detail below with reference to the attached drawings. FIG1 is a cross-sectional view showing an example of the optical multilayer body of the first embodiment. The optical multilayer body 10 shown in FIG1 has an alignment liquid crystal layer 11 in which liquid crystal compounds are aligned, an optical layer 12, and an adhesive layer 13 connecting the alignment liquid crystal layer 11 and the optical layer 12, and the Re change rate is less than 0.50%.

The optical laminate of the first embodiment may have components other than the alignment liquid crystal layer, the optical layer, and the adhesive layer. For example, the optical laminate of the first embodiment may be an optical laminate having an adhesive layer, such as the optical laminate 20 shown in FIG. 2 . The optical laminate 20 shown in FIG. 2 has an adhesive layer 21 on the main surface 11a of the alignment liquid crystal layer 11 on the side opposite to the adhesive layer 13, based on the structure of the optical laminate 10.

The adhesive constituting the adhesive layer 21 is not particularly limited, and can be appropriately selected from acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluorine polymers, rubber polymers, etc. as base polymers. Particularly preferred are adhesives such as acrylic adhesives or rubber adhesives that have excellent transparency, moderate wettability, cohesion and adhesion, and excellent weather resistance or heat resistance. The thickness of the adhesive layer 21 is appropriately set according to the type of adherend, for example, 3 μm or more and 300 μm or less.

The adhesive layer 21 is deposited on the alignment liquid crystal layer 11 by, for example, attaching an adhesive previously formed into a sheet to the surface of the alignment liquid crystal layer 11. Alternatively, the adhesive layer 21 may be formed by applying an adhesive composition on the alignment liquid crystal layer 11 and then drying, crosslinking, photocuring, etc. the solvent. In order to improve the adhesion (anchoring force) between the alignment liquid crystal layer 11 and the adhesive layer 21, the surface of the alignment liquid crystal layer 11 may be subjected to surface treatment such as corona treatment or plasma treatment or an easy-adhesion agent layer may be formed before depositing the adhesive layer 21.

As shown in FIG2 , it is preferred that a peeling pad 22 is temporarily attached to the surface of the adhesive layer 21. In FIG2 , a peeling pad 22 is temporarily attached to the main surface 21a of the adhesive layer 21 on the side opposite to the side of the aligned liquid crystal layer 11. The peeling pad 22 protects the surface of the adhesive layer 21 until, for example, the optical laminate 20 with the adhesive attached is attached to the polarizing plate 101 (see FIG3 ) described later. As a constituent material of the peeling pad 22, a plastic film formed of acrylic resin, polyolefin, cyclic polyolefin, polyester, etc. is preferably used. The thickness of the release pad 22 is, for example, 5 μm or more and 200 μm or less. Preferably, a release treatment is applied to the surface of the release pad 22. Examples of release agents used in the release treatment include polysilicone-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 FIG2, the Re (550) change rate before and after the humidified environment test was measured for the laminate obtained by bonding the adhesive layer 21 exposed after peeling off the peelable pad 22 to a glass plate, for example. The Re change rate of the optical laminate 20 shown in FIG2 was also less than 0.50%.

The optical multilayer structure of the first embodiment is described above with reference to the attached drawings. The optical multilayer of the present invention is not limited to the above-mentioned embodiment. For example, in the optical multilayer of the present invention, in order to be attached to the image display unit (not shown), an adhesive layer (not shown) may be formed on the main surface of the optical layer 12 on the side opposite to the adhesive layer 13, and a peeling pad (not shown) may be temporarily attached to the surface of the adhesive layer.

Next, the elements of the optical multilayer body of the first embodiment are described.

[Alignment liquid crystal layer] As the liquid crystal compound constituting the alignment liquid crystal layer 11, rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds can be cited. From the perspective of homogeneous alignment, the liquid crystal compound is preferably a rod-shaped liquid crystal compound. The rod-shaped liquid crystal compound can be a polymer. For example, the rod-shaped liquid crystal compound can 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. If the liquid crystal compound (monomer) before polymerization shows liquid crystal properties, it may not show liquid crystal properties after polymerization.

The liquid crystal compound is preferably a thermotropic liquid crystal that exhibits liquid crystal properties by heating. Thermotropic liquid crystal undergoes phase transitions between a crystalline phase, a liquid crystal phase, and an isotropic phase as the temperature changes. The liquid crystal compound may be any of nematic liquid crystal, lamellar liquid crystal, and cholesteric liquid crystal. A chiral agent may be added to the nematic liquid crystal to impart cholesteric orientation.

Examples of the thermotropic rod-shaped liquid crystal compound include azomethine compounds, azoxy compounds, cyanobiphenyl compounds, cyanophenyl ester compounds, benzoate compounds, cyclohexanecarboxylic acid phenyl ester compounds, cyanophenylcyclohexane compounds, cyano-substituted phenylpyrimidine compounds, alkoxy-substituted phenylpyrimidine compounds, phenyldioxane compounds, tolan compounds, and alkenylcyclohexylbenzonitrile compounds.

Examples of polymerizable liquid crystal compounds include polymerizable liquid crystal compounds capable of fixing the alignment state of rod-shaped liquid crystal compounds using a polymer binder, polymerizable liquid crystal compounds having polymerizable functional groups capable of fixing the alignment state of liquid crystal compounds by polymerization, etc. Among them, photopolymerizable liquid crystal compounds having photopolymerizable functional groups are preferred.

The photopolymerizable liquid crystal compound (liquid crystal monomer) has a mesogen 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 further preferably 55°C or higher and 100°C or lower.

Examples of the mesogen group of the liquid crystal monomer include cyclic structures such as biphenyl, phenylbenzoate, phenylcyclohexyl, azoxyphenyl, azophenyl, phenylpyrimidinyl, diphenylethynyl, diphenylbenzoate, bicyclohexyl, cyclohexylphenyl, and terphenyl. The ends of these cyclic units may be substituted with cyano, alkyl, alkoxy, halogen, and the like.

As the photopolymerizable functional group, there can be exemplified a (meth)acryl group, an epoxy group, a vinyl ether group, etc. Among them, a (meth)acryl group is preferred. 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 cross-linked structure is introduced into the liquid crystal layer after light curing, and therefore, there is a tendency to improve the durability of the optical laminate.

As the liquid crystal monomer, any appropriate liquid crystal monomer may be used. For example, the liquid crystal monomers disclosed in International Publication No. 00/37585, U.S. Patent No. 5211877, U.S. Patent No. 4388453, International Publication No. 93/22397, European Patent No. 0261712, German Patent No. 19504224, German Patent No. 4408171, British 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 may be used. , 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 No. 2008/119427, Japanese Patent Publication No. 2008-107767, Japanese Patent Publication No. 2008-273925, International Publication No. 2016/125839, Japanese Patent Publication No. 2008-273925, etc. are used as liquid crystal monomers. By selecting liquid crystal monomers, the expression of birefringence or the wavelength dispersion of Re can also be adjusted.

Furthermore, as a liquid crystal compound constituting the aligned liquid crystal layer 11, a liquid crystal compound showing reverse wavelength dispersion can be used. As a liquid crystal compound showing reverse wavelength dispersion, for example, a polymerizable compound showing reverse wavelength dispersion described in Japanese Patent Publication No. 2020-147749 can be cited. If a liquid crystal compound showing reverse wavelength dispersion is used, it is easy to optimize the optical properties in the entire visible light region. If a liquid crystal compound showing reverse wavelength dispersion is used as a liquid crystal compound constituting the aligned liquid crystal layer 11, for example, an aligned liquid crystal layer 11 that satisfies all of the following formula (I), the following formula (II), and the following formula (III) can be obtained. Re(450)/Re(550)≦1.00     (I) Re(650)/Re(550)≧1.00     (II) 100 nm＜Re(550)＜160 nm     (III)

In the following, an alignment liquid crystal layer satisfying all of formula (I), formula (II) and formula (III) is sometimes referred to as a "reverse wavelength dispersion alignment liquid crystal layer". Generally, a reverse wavelength dispersion alignment liquid crystal layer is easy to optimize optical properties and is not prone to light leakage, but there is a tendency for the color of the reflected light to become obvious 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, the color of the reflected light when exposed to a high humidity environment for a long time can be suppressed.

When forming the aligned liquid crystal layer 11, for example, a solution containing the above-mentioned liquid crystal compound (liquid crystal composition) is applied to a support, and the liquid crystal compound contained in the composition is heated in a manner such that the liquid crystal compound presents a liquid crystal state, thereby aligning the liquid crystal compound. The liquid crystal composition may contain a compound (alignment control agent) that controls the alignment of the liquid crystal compound in a predetermined direction on the basis of the liquid crystal compound. For example, by adding a chiral agent to the liquid crystal composition, the liquid crystal compound can be made to align in a cholesterol-like manner.

The liquid crystal composition may include a photopolymerization initiator. When the liquid crystal monomer is cured by ultraviolet irradiation, in order to promote photocuring, the liquid crystal composition preferably includes a photoradical polymerization initiator (photoradical generator) that generates free radicals by light irradiation. A photocation generator or a photoanion generator may be used according to the type of liquid crystal monomer (type of photopolymerizable functional group). The amount of the photopolymerization initiator used is, for example, not less than 0.01 parts by weight and not more than 10 parts by weight relative to 100 parts by weight of the liquid crystal monomer. In addition to the photopolymerization initiator, a sensitizer or the like may also be used.

By mixing a liquid crystal monomer, various alignment control agents as needed, a polymerization initiator, etc. with a solvent, a liquid crystal composition can be prepared. As the solvent, there is no particular limitation as long as it can dissolve the liquid crystal monomer and does not corrode the support (or has low corrosiveness), and examples thereof include halogenated hydrocarbon compounds such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, o-dichlorobenzene, etc.; phenol compounds such as phenol and p-chlorophenol; aromatic hydrocarbon compounds such as benzene, toluene, xylene, methoxybenzene, 1,2-dimethoxybenzene, etc.; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrole Ketone solvents such as pyridone and N-methyl-2-pyrrolidone; ester solvents such as ethyl acetate and butyl acetate; alcohol solvents such as tert-butyl alcohol, glycerol, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol; amide solvents such as dimethylformamide and dimethylacetamide; nitrile solvents such as acetonitrile and butyronitrile; ether solvents such as diethyl ether, dibutyl ether, tetrahydrofuran; solvent solvents such as ethyl solvent and butyl solvent, etc. A mixed solvent of two or more solvents may also be used.

The solid content concentration of the liquid crystal composition is, for example, 5 wt % or more and 60 wt % or less. The liquid crystal composition may contain additives such as a surfactant or a leveling agent.

The support (support to be coated with the liquid crystal composition) when forming the oriented liquid crystal layer 11 is not particularly limited, and examples thereof include a glass plate, a metal plate, a metal tape, a resin film substrate, etc. If a resin film substrate is used as a support, the optical laminate can be manufactured by a roll-to-roll method, thereby improving the productivity of the optical laminate. The thickness of the support is not particularly limited, for example, it is greater than 1 μm and less than 500 μm. The support has a first main surface and a second main surface, and the liquid crystal composition is coated on the first main surface.

The resin material constituting the resin film substrate is not particularly limited as long as it is insoluble in the solvent of the liquid crystal composition and has heat resistance when heated for aligning the liquid crystal composition. Examples thereof include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cyclic polyolefins such as norbornene polymers; cellulose polymers such as diacetyl cellulose and triacetyl cellulose; acrylic polymers; styrene polymers; polycarbonate; polyamide; polyimide, etc.

The support may have an alignment capability for orienting the liquid crystal compound in a predetermined direction. For example, by using a stretch film as a support, the liquid crystal compound can be horizontally aligned along its stretching direction. The stretching ratio of the stretch film only needs to be such that the alignment capability can be exerted, for example, greater than 1.1 times and less than 5 times. The stretch film may also be a biaxial stretch film. Even if it is a biaxial stretch film, as long as different longitudinal and transverse stretch ratios are used, the liquid crystal compound can be aligned in a direction with a larger stretch ratio. The stretch film may also be a tilted stretch film. By using a tilted stretch film as a support, the liquid crystal compound can be aligned in a direction that is not parallel to the length direction and the width direction of the support.

The support may be provided with an alignment film on the first main surface. The alignment film may be appropriately selected according to the type of liquid crystal compound or the material of the support. As the alignment film for aligning the liquid crystal compound horizontally in a predetermined direction, a film obtained by rubbing a polyimide-based or polyvinyl alcohol-based alignment film may be used. Alternatively, a photo-alignment film may be used. Alternatively, the resin film substrate serving as the support may be rubbed without providing an alignment film.

When the liquid crystal compound is a thermotropic liquid crystal, a liquid crystal composition is coated on the first main surface of the support, and the liquid crystal compound is aligned in a liquid crystal state by heating.

The method of coating the liquid crystal composition on the support is not particularly limited, and spin coating, die coating, contact roller coating, gravure coating, reverse coating, spray coating, mier bar coating, knife roller coating, air knife coating, etc. can be used. The solvent is removed after coating the liquid crystal composition, thereby forming a liquid crystal composition layer on the support. The thickness of the coating layer formed by coating the liquid crystal composition is preferably adjusted in such a way that the thickness of the liquid crystal composition layer after removing the solvent becomes 0.1 μm or more and 20 μm or less.

The liquid crystal phase is formed by heating the liquid crystal composition layer formed on the support, so that the liquid crystal compound is aligned to form an aligned liquid crystal layer 11. Specifically, after the liquid crystal composition is applied to the support, it is heated to above the N (nematic phase)-I (isotropic liquid phase) phase transition temperature of the liquid crystal composition to make the liquid crystal composition into an isotropic liquid state. From then on, it is slowly cooled as needed to show a nematic phase. At this time, it is ideal to temporarily maintain the temperature at which the liquid crystal phase is presented, so that the liquid crystal phase domain grows and forms a single domain. Alternatively, after the liquid crystal composition is applied to the support, the temperature can be maintained for a certain period of time within the temperature range at which the nematic phase is presented to align the liquid crystal compound in a specified direction.

The heating temperature for aligning the liquid crystal compound in a predetermined direction can be appropriately selected according to the type of liquid crystal composition, for example, 40°C or higher and 200°C or lower. If the heating temperature is too low, there is a tendency for insufficient transition to the liquid crystal phase, and if the heating temperature is too high, there is a tendency for increased alignment defects. The heating time can be adjusted in such a way that the liquid crystal phase domain grows sufficiently, for example, 30 seconds or higher and 30 minutes or lower.

It is preferred that the liquid crystal compound is aligned by heating and then cooled to a temperature below the glass transition temperature. The cooling method is not particularly limited, for example, it can be taken out of the heated atmosphere and cooled to room temperature. Strong cooling such as air cooling or water cooling can be performed.

By irradiating the aligned photopolymerizable liquid crystal compound with light, the photopolymerizable liquid crystal compound (liquid crystal monomer) is photocured in a state where it has liquid crystal regularity. The irradiated light only needs to be able to polymerize the photopolymerizable liquid crystal compound, and generally ultraviolet light or visible light with a wavelength of more than 250 nm and less than 450 nm is used. When the liquid crystal composition contains a photopolymerization initiator, it is sufficient to select light with a wavelength to which the photopolymerization initiator is sensitive. As the irradiation light source, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a xenon lamp, an LED, a black light lamp, a chemical lamp, etc. can be used. In order to promote the photocuring reaction, the light irradiation is preferably carried out in an atmosphere of an inert gas such as nitrogen.

When the liquid crystal composition is photocured, the liquid crystal compound can be aligned along a predetermined direction by using polarized light in a predetermined direction. When the liquid crystal compound is aligned by the alignment restraining force of the support, the irradiated light can also be non-polarized light (natural light).

The intensity of the irradiation light can be appropriately adjusted according to the composition of the liquid crystal composition or the amount of photopolymerization initiator added. The irradiation energy (accumulated light amount) is, for example, 20 mJ/ ^cm2 or more and 10000 mJ/ ^cm2 or less, preferably 50 mJ/ ^cm2 or more and 5000 mJ/ ^cm2 or less. In order to promote the photocuring reaction, the light irradiation can be carried out under heating conditions.

The polymer formed by photocuring the liquid crystal monomer by light irradiation is non-liquid crystal and does not undergo phase transition due to temperature changes. In addition, the optical laminate having the oriented liquid crystal layer 11 has a significantly larger birefringence Δn than a film containing non-liquid crystal material, so the thickness of the optical anisotropic element with the desired delay can be significantly reduced. The thickness of the oriented liquid crystal layer 11 can be set according to the target delay value, for example, 0.1 μm or more and 20 μm or less, preferably 0.2 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 7 μm or less.

The optical properties of the aligned liquid crystal layer 11 are not particularly limited. The in-plane retardation and thickness direction retardation of the aligned liquid crystal layer 11 can be appropriately set according to the purpose, etc. In the aligned liquid crystal layer 11, when the liquid crystal compound is horizontally aligned, the in-plane retardation of the aligned liquid crystal layer 11 is, for example, greater than 20 nm and less than 1000 nm. When the aligned liquid crystal layer 11 is a 1/4 wavelength plate, the in-plane retardation is preferably greater than 100 nm and less than 180 nm, and more preferably greater than 120 nm and less than 150 nm. When the aligned liquid crystal layer 11 is a 1/2 wavelength plate, the in-plane retardation is preferably greater than 200 nm and less than 340 nm, and more preferably greater than 240 nm and less than 300 nm.

[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, phase difference films, polarizing element protective films, etc.), functional films (more specifically, polarizing elements, viewing angle expansion films, viewing angle limiting (anti-obstruction) films, brightness enhancement films, etc.). The optical layer 12 can be a single layer or a laminate. The optical layer 12 can be an oriented liquid crystal layer (other oriented liquid crystal layers). In addition, the optical layer 12 can be a polarizing plate having a transparent protective film bonded to one or both main surfaces of a polarizing element. When a polarizing plate is provided with a transparent protective film on one main surface, the polarizing element can be bonded to the oriented liquid crystal layer 11, or the transparent protective film can be bonded to the oriented liquid crystal layer 11. The thickness of the optical layer 12 is appropriately adjusted according to the required optical performance, for example, more than 0.1 μm and less than 1000 μm, preferably more than 0.1 μm and less than 100 μm.

Furthermore, a positive C plate can be used as the optical layer 12. The positive C plate is an optical layer showing a refractive index characteristic of nz>nx≧ny. As described below, an optical laminate having a positive C plate as the optical layer 12 can be applied to a circular polarizer that can shield reflected light even from external light from an oblique direction.

[Adhesive layer] The adhesive constituting the adhesive layer 13 is not particularly limited as long as it is optically transparent, and examples thereof include epoxy resin adhesives, silicone resin adhesives, acrylic resin adhesives, polyurethane adhesives, polyamide adhesives, polyether adhesives, etc., preferably active energy ray-curing adhesives. The thickness of the adhesive layer 13 is, for example, not less than 0.9 μm and not more than 1.4 μm.

Active energy ray curing adhesives are adhesives that can undergo free radical polymerization, cationic polymerization, or anionic polymerization by irradiation with active energy rays such as electron beams or ultraviolet rays. Among them, from the aspect of being able to cure with low energy, photo-radical polymerizable adhesives, photo-cationic polymerizable adhesives, or mixed adhesives that use both photo-cationic polymerization and photo-radical polymerization are preferred.

When the alignment liquid crystal layer 11 and the optical layer 12 are bonded together by an adhesive, the adhesive is applied to one or both of the surfaces of the alignment liquid crystal layer 11 and the optical layer 12, and the adhesive is cured. Thus, the alignment liquid crystal layer 11 and the optical layer 12 are bonded together by an adhesive layer 13 formed by curing the adhesive.

As the monomer of the photo-radical polymerizable adhesive, there can be exemplified compounds having a (meth)acryloyl group or compounds having a vinyl group. Among them, compounds having a (meth)acryloyl group are suitable. As the compound having a (meth)acryloyl group, there can be exemplified (meth)acrylic acid alkyl esters such as (meth)acrylic acid C _1-20 chain alkyl esters, (meth)acrylic acid cyclic alkyl esters, and (meth)acrylic acid polycyclic alkyl esters; (meth)acrylic acid esters containing a hydroxyl group; (meth)acrylic acid esters containing an epoxy group such as (meth)acrylic acid glycidyl ester; (meth)acrylic acid esters containing an acetylacetyl group such as (meth)acrylic acid 2-acetylacetoxyethyl ester, and the like. The photo-radical polymerizable adhesive may include nitrogen-containing monomers such as hydroxyethyl (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, (meth) acrylamide, (meth) acrylamide, (meth) acrylamide, and (meth) acryl morpholine. The photo-radical polymerizable adhesive may include multifunctional monomers such as tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, dialkylene glycol diacrylate, and polyoxyethylene glycol diacrylate as crosslinking components.

As the curable component of the photopolymerizable adhesive, compounds having an epoxy group or an oxycyclobutyl group can be cited. 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 can be used. As preferred epoxy compounds, compounds having at least two epoxy groups and at least one aromatic ring in the molecule (aromatic epoxy compounds), compounds having at least two epoxy groups in the molecule and at least one of which is formed between two adjacent carbon atoms constituting an alicyclic ring (alicyclic epoxy compounds), etc. can be cited. By making the cationic polymerizable adhesive contain a radical polymerizable compound such as a compound having a (meth)acryloyl group, a mixed adhesive can also be prepared.

In order to obtain an adhesive with a small curing shrinkage rate, it is preferred to adjust the formulation of the adhesive so that the number of bonds decreases when the adhesive is cured. In order to reduce the number of bonds, it is preferred to use a monomer with a high molecular weight per reactive functional group (e.g., (meth)acrylic acid group, etc.). Examples of monomers with a high molecular weight per reactive functional group include (meth)acrylic acid alkyl esters having an alkyl group with 10 or more, 12 or more, 14 or more, 16 or more, or 18 or more carbon atoms (e.g., isostearyl acrylate, etc.), and polyoxyethylene glycol diacrylates having 5 or more, 7 or more, or 9 or more oxyethylene groups per molecule.

In addition, when the adhesive before curing contains an oligomer having a weight average molecular weight of 1000 or more, an adhesive having a small curing shrinkage rate can also be obtained. As an oligomer having a weight average molecular weight of 1000 or more (hereinafter sometimes referred to as a "specific oligomer"), for example, an oligomer formed from a monomer having a (meth)acryl group (acrylic oligomer) can be cited. The acrylic oligomer may have a cationic polymerizable functional group (e.g., an epoxy group, etc.).

In order to manufacture an optical laminate having excellent thermal durability while ensuring continuous reliability, the weight average molecular weight of the specific oligomer is preferably 1000 to 10000, more preferably 1000 to 5000, further preferably 1000 to 3000, and even more preferably 1500 to 3000.

In order to manufacture an optical laminate with guaranteed bonding reliability and better thermal durability, the content ratio of the specific oligomer is preferably 5 wt % or more and 20 wt % or less, and more preferably 8 wt % or more and 15 wt % or less relative to the total amount of the adhesive before curing.

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, unless otherwise specified, is a standard polystyrene conversion value measured under the following conditions.

(Molecular weight measurement conditions) GPC measurement device: "HLC-8120GPC" manufactured by Tosoh Corporation Sample concentration: 2.0 g/L (tetrahydrofuran solution) Sample injection volume: 20 μL Column: "TSKgel, SuperAWM-H + superAW4000 + superAW2500" manufactured by Tosoh Corporation Column size: 6.0 mm I.D. × 150 mm each Eluent: Tetrahydrofuran Flow rate: 0.4 mL/min Detector: Differential refractometer (RI) Column temperature (measurement temperature): 40°C

It is preferred that a light-curing adhesive such as an ultraviolet-curing adhesive contains a photopolymerization initiator. The photopolymerization initiator can be appropriately selected according to the type of reaction. For example, it is preferred to mix a photoradical polymerization initiator that generates free radicals by light irradiation into a photoradical polymerizable adhesive as a photopolymerization initiator. It is preferred to mix a photocationic polymerization initiator (photoacid generator) that generates cationic species or Lewis acid by light irradiation into a photocationic polymerizable adhesive as a photopolymerization initiator. It is preferred to mix a photocationic polymerization initiator and a photoradical polymerization initiator into a mixed adhesive.

The content of the photopolymerization initiator is, for example, 0.1 parts by weight or more and 10 parts by weight or less relative to 100 parts by weight of the monomer. A photosensitive agent may also be added to the photocurable adhesive as needed. The amount of the photosensitive agent used is, for example, 0.001 parts by weight or more and 10 parts by weight or less relative to 100 parts by weight of the monomer, preferably 0.01 parts by weight or more and 3 parts by weight or less.

The bonding agent may contain appropriate additives as required. Examples of the additives include coupling agents such as silane coupling agents and titanium coupling agents, bonding promoters such as ethylene oxide, ultraviolet absorbers, anti-degradation agents, dyes, processing aids, ion scavengers, antioxidants, thickeners, fillers, plasticizers, leveling agents, foaming inhibitors, antistatic agents, heat stabilizers, hydrolysis stabilizers, etc.

[Application] The optical multilayer body of the first embodiment can be used as an optical film for a display for the purpose of improving visibility, etc. It can also be applied to the circular polarizing plate described below.

<Second embodiment: circular polarizing plate> Next, the circular polarizing plate of the second embodiment of the present invention is described with reference to the attached drawings. The circular polarizing plate of the second embodiment of the present invention has the optical laminate and polarizing element of the first embodiment. Since the circular polarizing plate of the second embodiment has the optical laminate of the first embodiment, it can suppress the coloring of the reflected light even when exposed to a high humidity environment for a long time. In the following description, the description of the content repeated with the first embodiment is sometimes omitted.

FIG3 is a cross-sectional view showing an example of a circular polarizing plate of the second embodiment. The circular polarizing plate 100 shown in FIG3 has an optical laminate 10 and a polarizing plate 101 laminated on the optical laminate 10 via an adhesive layer 21. In FIG3, the oriented 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 polarizing element (not shown), or a transparent protective film may be laminated to one or both main surfaces of the polarizing element. Examples of the polarizing element include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified films of ethylene-vinyl acetate copolymers that adsorb dichroic substances such as iodine or dichroic dyes and then uniaxially stretch them; polyene alignment films such as dehydrated polyvinyl alcohol films and dehydrochlorinated polyvinyl chloride films, etc.

Among them, from the aspect of having a high degree of polarization, a polyvinyl alcohol (PVA) polarizing element in which a polyvinyl alcohol film such as polyvinyl alcohol or partially formalized polyvinyl alcohol adsorbs a dichroic substance such as iodine or a dichroic dye and aligns along a predetermined direction is preferred. For example, a PVA polarizing element is obtained by dyeing and stretching a polyvinyl alcohol film with iodine. Alternatively, a PVA resin layer may be formed on a resin substrate, and iodine dyeing and stretching may be performed in a laminated state.

The thickness of the polarizing element is not particularly limited, but is preferably 1 μm to 60 μm, more preferably 2 μm to 30 μm, and even more preferably 5 μm to 15 μm.

In the circular polarizing plate 100, for example, the aligned liquid crystal layer 11 is an aligned liquid crystal layer obtained by horizontally aligning the liquid crystal compound. In the circular polarizing plate 100, the aligned liquid crystal layer 11 is arranged in such a way that the alignment direction of the liquid crystal compound is neither parallel nor orthogonal to the absorption axis direction of the polarizing element.

In the circular polarizer 100, for example, the aligned liquid crystal layer 11 is a 1/4 wavelength plate, and the angle formed by the absorption axis direction of the polarizer 101 and the alignment direction (generally, the slow axis direction) of the liquid crystal compound of the aligned liquid crystal layer 11 is set to 45°. The angle formed by the absorption axis direction of the polarizer 101 and the alignment direction of the liquid crystal compound can be greater than 35° and less than 55°, or greater than 40° and less than 50°, or greater than 43° and less than 47°.

In the circular polarizing plate 100 obtained by laminating the polarizing plate 101 and the quarter-wave plate as the alignment liquid crystal layer 11 in such a manner that the angle between the optical axes of the polarizing plate 101 and the quarter-wave plate as the alignment liquid crystal layer 11 is 45°, an alignment liquid crystal layer (vertically aligned liquid crystal layer) in which the liquid crystal compound is vertically aligned can be provided as the optical layer 12. By sequentially laminating the polarizing plate 101, the quarter-wave plate (aligned liquid crystal layer 11), and the vertically aligned liquid crystal layer (optical layer 12) functioning as a positive C plate, a circular polarizing plate capable of shielding reflected light even from external light coming from an oblique direction can be formed.

In addition, in the circular polarizing plate 100, both the oriented liquid crystal layer 11 and the optical layer 12 may be horizontally oriented liquid crystal layers. In this case, it is preferred that the oriented liquid crystal layer 11 disposed on the side close to the polarizing plate 101 is a 1/2 wavelength plate, and the optical layer 12 disposed on the side away from the polarizing plate 101 is a 1/4 wavelength plate. In the layer configuration, it is preferred that the angle formed by the slow axis direction of the 1/2 wavelength plate and the absorption axis direction of the polarizing plate 101 is 75°±5°, and the angle formed by the slow axis direction of the 1/4 wavelength plate and the absorption axis direction of the polarizing plate 101 is 15°±5°. The circular polarizer 100 composed of such layers functions as a circular polarizer over a wide wavelength range of visible light, and thus can reduce the color band of reflected light over a wide wavelength range of visible light. [Example]

The present invention is described in more detail below with reference to the following embodiments, but the present invention is not limited to the following embodiments.

<Preparation of Adhesives A-1 to A-4> The following is a description of the preparation method of the adhesives used in Examples 1 to 3 and Comparative Example 1.

[Preparation of adhesive A-1] Polyoxyethylene glycol diacrylate ("Light Acrylate (registered trademark) 9EG-A", number of oxyethylene groups per molecule: 9) 7.7 parts by weight, unsaturated fatty acid hydroxy alkyl ester modified ε-caprolactone ("PLACCEL (registered trademark) FA1DDM" manufactured by Daicellu Co., Ltd.) 61.5 parts by weight, acrylamide morpholine ("ACMO (registered trademark)" manufactured by KJ Chemical Co., Ltd.) 30.8 parts by weight, acrylic acid oligomer ("ARUFON (registered trademark) UP-1190" manufactured by Toagosei Co., Ltd., weight average molecular weight: 1700) 15.3 parts by weight, photoradical polymerization initiator ("KAYACURE (registered trademark) DETX-S" manufactured by Nippon Kayaku Co., Ltd.) 3.5 parts by weight and photoradical polymerization initiator (IGM Adhesive A-1 was prepared by mixing 3.5 parts by weight of "Omnirad (registered trademark) 907" manufactured by Resins Co., Ltd.

[Preparation of Adhesive A-2] By adding m-phenoxybenzyl acrylate ("Light Acrylate (registered trademark) POB-A) 40.0 parts by weight, unsaturated fatty acid hydroxy alkyl ester modified ε-caprolactone ("PLACCEL (registered trademark) FA1DDM" manufactured by Daicellu Co., Ltd.) 10.0 parts by weight, acrylamide morpholine ("ACMO (registered trademark)" manufactured by KJ Chemical Co., Ltd.) 40.0 parts by weight, acrylic acid oligomer ("ARUFON (registered trademark) UP-1190" manufactured by Toagosei Co., Ltd., weight average molecular weight: 1700) 10.0 parts by weight, photoradical polymerization initiator ("KAYACURE (registered trademark) DETX-S" manufactured by Nippon Kayaku Co., Ltd.) 3.0 parts by weight and photoradical polymerization initiator (IGM Adhesive A-2 was prepared by mixing 3.0 parts by weight of "Omnirad (registered trademark) 907" manufactured by Resins Co., Ltd.

[Preparation of Adhesive A-3] 11.9 parts by weight of hydroxyethyl acrylamide ("HEAA (registered trademark)" manufactured by KJ Chemical Co., Ltd.), 59.5 parts by weight of acrylate monomer ("ARONIX (registered trademark) M-220" manufactured by Toagosei Co., Ltd.), 11.9 parts by weight of acrylamide morpholine ("ACMO (registered trademark)" manufactured by KJ Chemical Co., Ltd.), 11.9 parts by weight of acrylic oligomer ("ARUFON (registered trademark) UP-1190" manufactured by Toagosei Co., Ltd., weight average molecular weight: 1700), 4.8 parts by weight of 2-acetyl acetoxyethyl methacrylate ("AAEM" sold by MCC TRADING Co., Ltd.), and photoradical polymerization initiator (IGM Adhesive A-3 was prepared by mixing 2.9 parts by weight of "Omnirad (registered trademark) 907" manufactured by Resins Co., Ltd. and 1.4 parts by weight of a photo-radical polymerization initiator ("KAYACURE (registered trademark) DETX-S" manufactured by Nippon Kayaku Co., Ltd.).

[Preparation of Adhesive A-4] 10.0 parts by weight of acrylate monomer ("ARONIX (registered trademark) M-220" manufactured by Toagosei Co., Ltd.), 40.0 parts by weight of n-butyl acrylate (manufactured by Mitsubishi Chemical Co., Ltd.), 40.0 parts by weight of 4-hydroxybutyl acrylate (manufactured by Mitsubishi Chemical Co., Ltd.), 5.0 parts by weight of hydroxyethyl acrylamide ("HEAA (registered trademark)" manufactured by KJ Chemical Co., Ltd.), 5.0 parts by weight of acrylamide morpholine ("ACMO (registered trademark)" manufactured by KJ Chemical Co., Ltd.), 0.5 parts by weight of photoradical polymerization initiator ("KAYACURE (registered trademark) DETX-S" manufactured by Nippon Kayaku Co., Ltd.), and 0.5 parts by weight of photoradical polymerization initiator (IGM Adhesive A-4 was prepared by mixing 1.5 parts by weight of "Omnirad (registered trademark) 907" manufactured by Resins Co., Ltd.

<Preparation of optical film F-1> According to the description of Example 1 of Japanese Patent Publication No. 2020-147749, an optical anisotropic film (reverse wavelength dispersion alignment liquid crystal layer, thickness: 2.3 μm) was formed on a triacetyl cellulose film ("Z-TAC" manufactured by Fuji Film Co., Ltd.) as a support to obtain optical film F-1.

<Preparation of optical film F-2> First, prepare a side-chain liquid crystal polymer with a weight average molecular weight of 5000 represented by the following chemical formula (1) (the numbers 65 and 35 in the formula represent the mass ratio of repeating units, and for convenience, block polymers are used to represent it). Also, prepare a polyethylene terephthalate film (PET film) treated with vertical alignment as a support.

[Chemistry 1]

20 parts by weight of the side-chain liquid crystal polymer represented by the chemical formula (1), 80 parts by weight of a photopolymerizable liquid crystal compound showing a nematic liquid crystal phase ("Paliocolor (registered trademark) LC242" manufactured by BASF), and 5 parts by weight of a photoradical polymerization initiator ("Omnirad (registered trademark) 907" manufactured by IGM Resins) were dissolved in 200 parts by weight of cyclopentanone to prepare a coating liquid. Then, the coating liquid was applied to the surface of the above-mentioned PET film using a bar coater, and heated at a temperature of 80°C for 4 minutes to align the liquid crystal compound. Then, after the liquid crystal composition on the PET film was cooled to room temperature (25°C), the liquid crystal composition was irradiated with ultraviolet rays in a nitrogen atmosphere to perform photocuring. Through the above steps, a vertically aligned liquid crystal layer (thickness: 3.0 μm) showing a refractive index characteristic of nz>nx=ny was formed on the PET film to obtain an optical film F-2.

<Production of polarizing plate P-1> Using a roll stretching machine, a long roll of a 30 μm thick polyvinyl alcohol (PVA) resin film ("PE3000" manufactured by Kuraray) was stretched uniaxially in the longitudinal direction to a length of 5.9 times, and then subjected to swelling treatment, dyeing treatment, crosslinking treatment, and washing treatment in sequence, and then dried at a temperature of 70°C for 5 minutes to produce a polarizing element with a thickness of 12 μm (moisture permeability: 350 g/ ^m2・24 h). Specifically, in the above swelling treatment, it was stretched to 2.2 times while being treated with pure water at a temperature of 20°C. In the dyeing treatment, the iodine concentration was adjusted to 45.0% by using an aqueous solution at a temperature of 30°C (an aqueous solution in which the weight ratio of iodine to potassium iodide was 1:7) while the filaments were stretched to 1.4 times. In the crosslinking treatment, a two-stage crosslinking treatment was adopted. In the first stage of the crosslinking treatment, the filaments were stretched to 1.2 times by using an aqueous solution (temperature: 40°C) in which boric acid and potassium iodide were dissolved. In the second stage of the crosslinking treatment, the filaments were stretched to 1.6 times by using an aqueous solution (temperature: 65°C) in which boric acid and potassium iodide were dissolved. In the aqueous solution of the first stage of the crosslinking treatment, the boric acid content was 5.0% by weight, and the potassium iodide content was 3.0% by weight. The aqueous solution in the second stage of 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-mentioned cleaning treatment, a potassium iodide aqueous solution (potassium iodide content: 2.6% by weight) at a temperature of 20°C was used for treatment.

Next, a HC-COP film (moisture permeability: 1.6 g/m ²・24 h, thickness: 29 μm) is bonded to one main surface of the obtained polarizing element via a polyvinyl alcohol-based adhesive as a first protective layer. The HC-COP film is a film having a 3 μm thick hard coat (HC) layer formed on a 26 μm thick cycloolefin resin (COP) film. Furthermore, when bonding the polarizing element to the HC-COP film, the COP film is bonded to the polarizing element side. Next, a triacetyl cellulose (TAC) film (moisture permeability: 810 g/m 2・24 h, thickness: 20 μm) having a Re (550) of 0 nm is bonded to the other main surface of the polarizing element via a polyvinyl alcohol ^- based adhesive as a second protective layer. In this way, a polarizing plate P-1 having a structure of HC-COP film (first protective layer)/polarizing element/TAC film (second protective layer) was obtained.

<Fabrication of optical laminate> The following describes the method for fabricating the optical laminate of Examples 1 to 3 and Comparative Example 1. Furthermore, the optical laminate described below is used as a sample for measuring the Re change rate.

[Preparation of the optical laminate of Example 1] On the reverse wavelength dispersion alignment liquid crystal layer of the optical film F-1, the adhesive A-1 is coated in such a manner that the thickness of the layer containing the adhesive A-1 after curing (adhesive layer) becomes 1.0 μm. Then, the surface of the vertically aligned liquid crystal layer side of the optical film F-2 is bonded to the coating layer containing the adhesive A- ¹ to obtain a laminate. Then, the obtained laminate is irradiated with ultraviolet rays using a high-pressure mercury lamp under the condition of a cumulative light amount of 800 mJ/cm2 to photocure the adhesive A-1. In addition, the ultraviolet irradiation is performed from the optical film F-2 side.

Next, the support of the optical film F-1 was peeled off from the laminate (to be specific, a laminate formed by laminating two optical films through a bonding agent layer) after UV irradiation, and an acrylic adhesive sheet with a thickness of 13 μm was attached to the surface of the exposed reverse wavelength dispersion alignment liquid crystal layer. Next, a glass plate (material: alkali-free glass) was attached to the surface of the attached adhesive sheet, and then the support of the optical film F-2 was peeled off to obtain the optical laminate of Example 1.

[Preparation of optical laminates of Example 2, Example 3 and Comparative Example 1] Except for changing the type of adhesive as shown in Table 1 described below, the optical laminates of Example 2, Example 3 and Comparative Example 1 were prepared by the same method as Example 1.

<Production of circular polarizing plate> Below, the production method of the circular polarizing plate of Examples 1 to 3 and Comparative Example 1 is described. Furthermore, the circular polarizing plate described below is used as a sample for measuring the reflected light chromaticity.

[Preparation of circular polarizing plate of Example 1] Adhesive A-1 is applied on the reverse wavelength dispersion alignment liquid crystal layer of optical film F-1 in such a manner that the thickness of the layer containing adhesive A-1 after curing (adhesive layer) becomes 1.0 μm. Then, the surface on the vertical alignment liquid crystal layer side of optical film F-2 is attached to the coating layer containing adhesive A-1 to obtain a laminate. Then, the obtained laminate is irradiated with ultraviolet rays using a high-pressure mercury lamp at a cumulative light amount of 800 mJ/ ^cm2 to photocure adhesive A-1. In addition, ultraviolet irradiation is performed from the optical film F-2 side.

Next, after peeling off the support of the optical film F-1 from the laminate after ultraviolet irradiation (to be specific, a laminate formed by laminating two optical films through a bonding agent layer), a 5 μm thick acrylic adhesive sheet is bonded to the surface of the exposed reverse wavelength dispersion alignment liquid crystal layer. Next, a polarizing plate P-1 is bonded to the surface of the bonded adhesive sheet. At this time, the bonding is performed in such a way that the TAC film of the polarizing plate P-1 becomes the reverse wavelength dispersion alignment liquid crystal layer side. Furthermore, when bonding, the angle between the absorption axis direction of the polarizing element and the alignment direction of the liquid crystal molecules in the reverse wavelength dispersion alignment liquid crystal layer is set to 45°. Next, after the optical film F-2 support was peeled off from the obtained laminate with polarizing plate, an acrylic adhesive sheet with a thickness of 23 μm was attached to the surface of the exposed vertically aligned liquid crystal layer. Then, a glass plate (material: alkaline glass) was attached to the surface of the attached adhesive sheet to obtain the circular polarizing plate of Example 1.

[Preparation of circular polarizing plates of Example 2, Example 3 and Comparative Example 1] Except for changing the type of adhesive as shown in Table 1 below, circular polarizing plates of Example 2, Example 3 and Comparative Example 1 were prepared by the same method as Example 1.

<Measurement method> [Re change rate] Each optical stack was placed in an environment with a temperature of 20°C and a relative humidity of 98% for 30 days to perform a humidified environment test. Before and after the humidified environment test, the Re(550) of each optical stack was measured in an atmosphere with a temperature of 23°C using an Axoscan manufactured by Axometrics, and the Re change rate was calculated from the measured values. In the measurement of Re(550), the surface on the side of the reverse wavelength dispersion alignment liquid crystal layer was set as the light incident surface.

[Reflected chromaticity] Each circular polarizing plate was placed in an environment with a temperature of 20°C and a relative humidity of 98% for 30 days to conduct a humidified environment test. Then, each circular polarizing plate after the humidified environment test was placed on a reflector (specifically, an aluminum plate with a visible light reflectivity of 86%). At this time, the glass plate of each circular polarizing plate was placed on the reflector side. In addition, the incident light from the polarizing plate P-1 side of each circular polarizing plate was measured using a spectrophotometer ("CM-26d" manufactured by KONICA MINOLTA) to measure the reflected spectrum (0° viewing field, standard light source: D65). Based on the obtained reflection spectrum, the color indices a ^* and b ^* of the CIE 1976 L ^* a ^* b ^* color space were obtained according to JIS Z8781-4, and the chromaticity c ^* = {(a ^* ) ² + (b ^* ) ² } ^1/2 was calculated. The obtained chromaticity c ^* was set as the reflection chromaticity in Table 1 described below. When the reflection chromaticity was 0.25 or less, it was evaluated as "the coloration of the reflected light can be suppressed when exposed to a high humidity environment for a long time." When the reflection chromaticity exceeded 0.25, it was evaluated as "the coloration of the reflected light cannot be suppressed when exposed to a high humidity environment for a long time."

<Results> For Examples 1 to 3 and Comparative Example 1, the types of adhesives used, Re change rates, and reflective brilliance are shown in Table 1.

[Table 1] Types of adhesives Re change rate [%] Reflected brilliance Embodiment 1 A-1 0.35 0.23 Embodiment 2 A-2 0.12 0.09 Embodiment 3 A-3 0.27 0.18 Comparison Example 1 A-4 0.58 0.38

As shown in Table 1, in Examples 1 to 3, the Re change rate is 0.50% or less. In addition, in Examples 1 to 3, the reflected light chromaticity is 0.25 or less. Therefore, the circularly polarizing plates (optical laminates) of Examples 1 to 3 can suppress the coloring of reflected light when exposed to a high humidity environment for a long time.

As shown in Table 1, in Comparative Example 1, the Re change rate exceeds 0.50%. In addition, in Comparative Example 1, the reflected light chromaticity exceeds 0.25. Therefore, when the circular polarizing plate (optical laminate) of Comparative Example 1 is exposed to a high humidity environment for a long time, it is impossible to suppress the coloring of the reflected light.

The above results indicate that the present invention can provide an optical multilayer and a circular polarizer that can suppress the coloration of reflected light even when exposed to a high humidity environment for a long time.

10: Optical laminate 11: Alignment liquid crystal layer 11a: Main surface 12: Optical layer 13: Adhesive layer 20: Optical laminate 21: Adhesive layer 21a: Main surface 22: Peel pad 100: Circular polarizer 101: Polarizer

FIG1 is a cross-sectional view showing an example of an optical laminate of the present invention. FIG2 is a cross-sectional view showing another example of an optical laminate of the present invention. FIG3 is a cross-sectional view showing an example of a circular polarizer of the present invention.

10: Optical laminates

11: Alignment of liquid crystal layer

12: Optical layer

13: Next is the agent layer

Claims (5)

An optical laminate having an oriented liquid crystal layer in which a liquid crystal compound is oriented, an optical layer, and a bonding agent layer bonding the oriented liquid crystal layer to the optical layer. The optical laminate has a change rate of in-plane retardation at a wavelength of 550 nm of less than 0.50% before and after being tested in a humidified environment at a temperature of 20°C and a relative humidity of 98% for 30 days. The optical multilayer body of claim 1, wherein after being kept in a humidified environment test at a temperature of 20°C and a relative humidity of 98% for 30 days, the chromaticity c ^* ={(a ^* ) ²⁺ (b ^* ) ² } ^1/2 of the reflected light when the light is incident from the above-mentioned aligned liquid crystal layer side is less than 0.25. An optical laminate as claimed in claim 1 or 2, wherein the in-plane retardation of the above-mentioned aligned liquid crystal layer at a wavelength of 450 nm is set to Re(450), the in-plane retardation of the above-mentioned aligned liquid crystal layer at a wavelength of 550 nm is set to Re(550), and the in-plane retardation of the above-mentioned aligned liquid crystal layer at a wavelength of 650 nm is set to Re(650), and Re(450)/Re(550)≦1.00, Re(650)/Re(550)≧1.00 and 100 nm＜Re(550)＜160 nm are satisfied. For example, in the optical laminate of claim 1 or 2, when the refractive index of the optical layer in the slow axis direction within the plane is set to nx, the refractive index of the optical layer in the direction perpendicular to the slow axis direction within the plane is set to ny, and the refractive index of the optical layer in the thickness direction is set to nz, nz＞nx≧ny is satisfied. A circular polarizer having an optical layered body and a polarizing element as described in claim 1 or 2.