Alignment liquid crystal film and method for manufacturing the same, and image display device

Abstract

To provide an aligned liquid crystal film which has superior heat durability and exhibits less variations in optical properties even when exposed to a high-temperature environment for a prolonged period of time.SOLUTION: An aligned liquid crystal film (100) provided herein comprises a first aligned liquid crystal layer (1) having liquid crystal molecules aligned therein, a resin coating layer (6) abutting a first principal surface of the first aligned liquid crystal layer, and an optical layer (4) bonded to the resin coating layer (6) via an adhesive layer (3). The resin coating layer is a non-curable resin layer. The resin coating layer may have a glass transition temperature of 20°C or higher. The first aligned liquid crystal layer may contain homogeneously aligned liquid crystal molecules.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an oriented liquid crystal film in which liquid crystal molecules are oriented, a method for manufacturing the same, and an image display device equipped with the oriented liquid crystal film. [Background technology]

[0002] As an optical film having functions such as optical compensation for liquid crystal display devices and prevention of external light reflection in organic EL elements, liquid crystal films in which liquid crystal compounds are oriented in a predetermined direction (oriented liquid crystal films) are used. Oriented liquid crystal films have a larger birefringence than stretched polymer films, making them advantageous for thinning and weight reduction. In image display devices, the oriented liquid crystal film is laminated to an organic EL panel or liquid crystal display panel as a polarizing plate, integrally laminated with a polarizer via an adhesive or bonding agent (for example, Patent Document 1).

[0003] Liquid crystal compounds can be oriented in a predetermined direction by shear force applied during coating onto a substrate or by the orientation-regulating force of the alignment film, resulting in oriented liquid crystal films with various optical anisotropies. For example, a homogeneous oriented liquid crystal layer in which nematic liquid crystal molecules with positive refractive index anisotropy are oriented parallel to the substrate surface can be used as a positive A plate with refractive index anisotropy nx>ny=nz.

[0004] When using thermorotopic liquid crystals, a solution containing a liquid crystal compound (liquid crystal composition) is applied to a substrate, and the composition is heated to orient the liquid crystal molecules so that the compounds in the composition become liquid crystal. If the liquid crystal composition contains a photopolymerizable liquid crystal compound (liquid crystal monomer), the orientation state is fixed by curing the liquid crystal monomer with light irradiation after the liquid crystal molecules have been oriented. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2015-7700 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Image display devices such as liquid crystal displays and organic EL displays are increasingly required to have higher durability, and the optical components constituting these image display devices are required to exhibit minimal changes in optical properties even when exposed to high-temperature environments for extended periods. Patent Document 1 describes that changes in retardation of an oriented liquid crystal film in high-temperature environments can be reduced by controlling the orientation parameters of the liquid crystal compound.

[0007] The optical properties of an oriented liquid crystal film may change in high-temperature environments due to the influence of layers adjacent to the liquid crystal layer, as well as the orientation of the liquid crystal itself. For example, when a homogeneous oriented liquid crystal layer and a polarizer were bonded together via an adhesive layer, there was almost no change in retardation in high-temperature environments. In contrast, a sample in which a homogeneous oriented liquid crystal layer and a polarizer were bonded together via an ultraviolet-curing adhesive showed a tendency for increased retardation in high-temperature environments.

[0008] In view of these challenges, the present invention aims to provide an oriented liquid crystal film that exhibits minimal changes in optical properties and excellent heat resistance even when exposed to high-temperature environments for extended periods. [Means for solving the problem]

[0009] An oriented liquid crystal film comprises an oriented liquid crystal layer in which liquid crystal molecules are oriented in a predetermined direction. The oriented liquid crystal layer is formed, for example, by coating a liquid crystalline composition containing a photopolymerizable liquid crystal monomer onto a support substrate, heating the liquid crystalline composition on the support substrate to orient the liquid crystal monomer in a liquid crystal state, and polymerizing or crosslinking the liquid crystal monomer by light irradiation. In the oriented liquid crystal layer, the liquid crystal molecules may be homogeneously oriented. The support substrate used to form the oriented liquid crystal layer may be a resin film.

[0010] The oriented liquid crystal film of the present invention comprises a resin coating layer in contact with the first main surface of the oriented liquid crystal layer, and an optical layer bonded to the resin coating layer via an adhesive layer. Examples of the optical layer bonded to the oriented liquid crystal layer include a polarizer and a transparent film. The optical layer may be any other oriented liquid crystal layer.

[0011] The alignment liquid crystal film may have other optical layers bonded to the second main surface of the alignment liquid crystal layer via an adhesive layer. A resin coating layer may also be provided on the second main surface of the alignment liquid crystal layer. The alignment liquid crystal film may have other optical layers bonded to the second main surface of the alignment liquid crystal layer via an adhesive layer.

[0012] In one embodiment, the oriented liquid crystal film may be a circular polarizer containing a polarizer as an optical layer. In an oriented liquid crystal film in which an oriented liquid crystal layer in which liquid crystal molecules are homogeneously oriented and a polarizer are laminated, the angle between the orientation direction of the liquid crystal molecules in the oriented liquid crystal layer and the absorption axis direction of the polarizer may be 10 to 80°.

[0013] In one embodiment of a circular polarizer, a resin coating layer is provided on one side (first main surface) of a homogeneous oriented liquid crystal layer, which is a first oriented liquid crystal layer, and a homeotropic oriented liquid crystal layer, which is a second oriented liquid crystal layer, is provided on the resin coating layer via an adhesive layer. A polarizer or polarizing plate is bonded to the other side (second main surface) of the homogeneous oriented liquid crystal layer. The homogeneous oriented liquid crystal layer and the polarizer or polarizing plate may be bonded via an adhesive layer in contact with the second main surface of the homogeneous oriented liquid crystal layer.

[0014] The resin coating layer is preferably a non-curing resin layer. The weight-average molecular weight of the resin material constituting the resin coating layer is preferably 20,000 or more. Examples of resin materials for the resin coating layer include non-curing acrylic resin and non-curing epoxy resin. The glass transition temperature of the resin coating layer may be 20°C or higher. The thickness of the resin coating layer is preferably 0.05 to 3 μm. The resin coating layer may contain uncured liquid crystal compounds constituting the oriented liquid crystal layer.

[0015] A resin coat layer is formed by applying a resin solution containing a resin and an organic solvent onto the alignment liquid crystal layer. The organic solvent of the resin solution preferably has solubility in the photopolymerizable liquid crystal monomer and is insoluble or hardly soluble in the photocured product of the photopolymerizable liquid crystal monomer. After applying the resin solution onto the surface of the alignment liquid crystal layer, heating may be performed at 40 to 150 °C before laminating the optical layer.

[0016] The thickness of the adhesive layer for laminating the resin coat layer on the alignment liquid crystal layer and the optical layer is preferably 0.01 to 5 μm. The adhesive may be an active energy ray curable adhesive.

Advantages of the Invention

[0017] The alignment liquid crystal film of the present invention is excellent in heat durability, and even when exposed to a high temperature environment for a long time, the change in retardation is small. Therefore, it is preferably used as an optical member for an image display device such as a liquid crystal display device or an organic EL display device.

Brief Description of the Drawings

[0018] [Figure 1] It is a cross-sectional view of an alignment liquid crystal film of an embodiment. [Figure 2] It is a cross-sectional view of a laminate including an alignment liquid crystal layer on a support substrate. [Figure 3] It is an end view of a laminate in which a resin coat layer is formed on an alignment liquid crystal layer. [Figure 4] It is a cross-sectional view of an alignment liquid crystal film of an embodiment. [Figure 5] It is a cross-sectional view of an alignment liquid crystal film including an adhesive layer. [Figure 6] It is a cross-sectional view of an alignment liquid crystal film of an embodiment. [Figure 7] It is a cross-sectional view of an alignment liquid crystal film of an embodiment. [Figure 8] It is a cross-sectional view of an alignment liquid crystal film of an embodiment. [Figure 9] It is a cross-sectional view of an alignment liquid crystal film of an embodiment. [Figure 10]This is a cross-sectional view showing an example of a stacked configuration for an image display device. [Modes for carrying out the invention]

[0019] Figure 1 is a cross-sectional view showing the configuration of an oriented liquid crystal film according to one embodiment. The oriented liquid crystal film 100 includes a resin coating layer 6 in contact with one main surface of the oriented liquid crystal layer 1, and an optical layer 4 bonded to the resin coating layer 6 via an adhesive layer 3.

[0020] [Aligned liquid crystal layer] The oriented liquid crystal layer 1 contains liquid crystal molecules oriented in a predetermined direction. For example, by applying a liquid crystalline composition containing a liquid crystal compound onto a support substrate 8, oriented the liquid crystal compound in a predetermined direction, and then fixing the orientation, the oriented liquid crystal layer 1 is formed on the support substrate 8 as shown in Figure 2.

[0021] <Liquid crystal composition> Examples of liquid crystal compounds include rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds. Rod-shaped liquid crystal compounds are preferred as liquid crystal compounds because they readily exhibit homogeneous orientation due to the orientation-regulating force of the support substrate. The rod-shaped liquid crystal compound may be either a main-chain type liquid crystal or a side-chain type liquid crystal. The rod-shaped liquid crystal compound may be a liquid crystal polymer or a polymer of a polymerizable liquid crystal compound. As long as the liquid crystal compound (monomer) before polymerization exhibits liquid crystal properties, it may not exhibit liquid crystal properties after polymerization.

[0022] The liquid crystal compound is preferably a thermotropic liquid crystal that exhibits liquid crystal properties upon heating. Thermotropic liquid crystals undergo phase transitions between crystalline, liquid crystal, and isotropic phases in response to temperature changes. The liquid crystal compound included in the liquid crystal composition may be a nematic liquid crystal, a smectic liquid crystal, or a cholesteric liquid crystal. A chiral agent may be added to the nematic liquid crystal to give it cholesteric orientation.

[0023] Examples of rod-shaped liquid crystal compounds that exhibit thermotropic properties include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyanosubstituted phenylpyrimidines, alkoxysubstituted phenylpyrimidines, phenyldioxanes, trans, and alkenylcyclohexylbenzonitriles.

[0024] Examples of polymerizable liquid crystal compounds include polymerizable liquid crystal compounds in which the orientation state of a rod-shaped liquid crystal compound can be fixed using a polymer binder, and polymerizable liquid crystal compounds having polymerizable functional groups that allow the orientation state of the liquid crystal compound to be fixed by polymerization. Among these, photopolymerizable liquid crystal compounds having photopolymerizable functional groups are preferred.

[0025] 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 crystal properties (liquid crystal phase transition temperature) is preferably 40 to 200°C, more preferably 50 to 150°C, and even more preferably 55 to 100°C.

[0026] Examples of mesogenic groups for liquid crystal monomers include cyclic structures such as biphenyl, phenylbenzoate, phenylcyclohexane, azoxybenzene, azomethine, azobenzene, phenylpyrimidine, diphenylacetylene, diphenylbenzoate, bicyclohexane, cyclohexylbenzene, and terphenyl groups. The ends of these cyclic units may have substituents such as cyano, alkyl, alkoxy, and halogen groups.

[0027] Examples of photopolymerizable functional groups include (meth)acryloyl groups, epoxy groups, and vinyl ether groups. Among these, (meth)acryloyl groups are preferred. Photopolymerizable liquid crystal monomers are preferably those having two or more photopolymerizable functional groups in one molecule. Using liquid crystal monomers containing two or more photopolymerizable functional groups introduces a crosslinked structure into the liquid crystal layer after photocuring, which tends to improve the durability of the oriented liquid crystal film.

[0028] Any suitable liquid crystal monomer can be used as the photopolymerizable liquid crystal monomer. For example, see 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 Examples of compounds described in Japanese Patent Publication No. 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 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. By selecting a liquid crystal monomer, it is also possible to adjust the birefringence and the wavelength dispersion of retardation.

[0029] In addition to liquid crystal monomers, the liquid crystal composition may also contain compounds that control the orientation of the liquid crystal monomers in a predetermined direction. For example, by including a side-chain type liquid crystal polymer in the liquid crystal composition, the liquid crystal compound (monomer) can be homeotropically oriented. Alternatively, by adding a chiral agent to the liquid crystal composition, the liquid crystal compound can be cholesterically oriented.

[0030] The liquid crystalline composition may contain a photopolymerization initiator. When curing liquid crystal monomers by ultraviolet irradiation, it is preferable that the liquid crystalline composition contains a photopolymerization initiator (photoradical generator) that generates radicals upon light irradiation to promote photocuring. 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 photopolymerization initiator used is about 0.01 to 10 parts by weight per 100 parts by weight of liquid crystal monomer. In addition to the photopolymerization initiator, sensitizers and the like may also be used.

[0031] A liquid crystalline composition can be prepared by mixing liquid crystal monomers with a solvent, along with various orientation control agents, polymerization initiators, etc., as needed. The solvent is not particularly limited as long as it can dissolve the liquid crystal monomers and does not (or has low corrosiveness) the substrate, and includes halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene; phenols such as phenol and parachlorophenol; aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, and 1,2-dimethoxybenzene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, and N-methyl-2- Examples include ketone solvents such as pyrrolidone; ester solvents such as ethyl acetate and butyl acetate; alcohol 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 solvents such as dimethylformamide and dimethylacetamide; nitrile solvents such as acetonitrile and butyronitrile; ether solvents such as diethyl ether, dibutyl ether, and tetrahydrofuran; and ethyl cellsolve and butyl cellsolve. A mixture of two or more solvents may also be used.

[0032] The solid content concentration of the liquid crystalline composition is typically around 5-60% by weight. The liquid crystalline composition may contain additives such as surfactants and leveling agents.

[0033] <Support substrate> Examples of support substrates 8 to which the liquid crystalline composition is applied include glass plates, metal plates, metal belts, and resin film substrates. The support substrate has a first main surface and a second main surface, and the liquid crystalline composition is applied to the first main surface.

[0034] By using a film substrate as the support substrate 8, a series of processes from coating the liquid crystalline composition onto the substrate to photocuring the liquid crystal monomer and subsequent heat treatment can be carried out roll-to-roll, thereby improving the productivity of the oriented liquid crystal film. The resin material constituting the film substrate is not particularly limited as long as it does not dissolve in the solvent of the liquid crystalline composition and has heat resistance when heated to orient the liquid crystalline composition. Examples include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cyclic polyolefins such as norbornene polymers; cellulosic polymers such as diacetylcellulose and triacetylcellulose; acrylic polymers; styrene polymers; polycarbonate, polyamide, and polyimide.

[0035] The support substrate 8 may have orientation capabilities to orient liquid crystal molecules in a predetermined direction. For example, by using a stretched film as the support substrate, it is possible to homogeneously orient the liquid crystal molecules along its stretching direction. The stretching ratio of the stretched film only needs to be sufficient to exhibit orientation capabilities, for example, about 1.1 to 5 times. The stretched film may also be a biaxially oriented film. Even with a biaxially oriented film, if the stretching ratios in the longitudinal and transverse directions are different, the liquid crystal molecules can be oriented along the direction with the larger stretching ratio. The stretched film may also be an obliquely stretched film. By using a stretched film as the support substrate 8, the liquid crystal molecules can be oriented in a direction that is not parallel to either the longitudinal or widthwise direction of the support substrate.

[0036] The support substrate 8 may have an alignment film on its first main surface. The alignment film should be appropriately selected depending on the type of liquid crystal compound and the material of the substrate. As an alignment film for homogeneously aligning liquid crystal molecules in a predetermined direction, a polyimide-based or polyvinyl alcohol-based alignment film that has been rubbed is preferably used. Alternatively, a photo-alignment film may be used. Alternatively, the resin film serving as the support substrate may be rubbed without providing an alignment film.

[0037] The support substrate 8 may include an alignment film for homeotropically aligning liquid crystal molecules. Examples of alignment agents for forming a homeotropically oriented alignment film (vertical alignment film) include lecithin, stearic acid, hexadecyltrimethylammonium bromide, octadecylamine hydrochloride, monobasic chromium carboxylate complexes, organosilanes such as silane coupling agents and siloxane compounds, perfluorodimethylcyclohexane, tetrafluoroethylene, and polytetrafluoroethylene.

[0038] <Formation of an oriented liquid crystal layer on a support substrate> If the liquid crystal compound is a thermotropic liquid crystal, the liquid crystal composition is applied to the first main surface of the support substrate 8, and the liquid crystal compound is oriented in a liquid crystal state by heating.

[0039] The method for coating the liquid crystalline composition onto the support substrate 8 is not particularly limited, and methods such as spin coating, die coating, kiss roll coating, gravure coating, reverse coating, spray coating, Meyer bar coating, knife roll coating, and air knife coating can be used. After coating the solution, the solvent is removed to form a liquid crystalline composition layer on the support substrate. The coating thickness is preferably adjusted so that the thickness of the liquid crystalline composition layer (thickness of the oriented liquid crystal film) after drying the solvent is about 0.1 to 20 μm.

[0040] By heating the liquid crystalline composition layer formed on the support substrate to convert it into a liquid crystal phase, the liquid crystal compounds are oriented. Specifically, after coating the liquid crystalline composition onto the support substrate, it is heated to a temperature above the N (nematic phase)-I (isotropic liquid phase) transition temperature of the liquid crystalline composition to make it an isotropic liquid state. From there, it is slowly cooled as needed to induce the nematic phase. At this time, it is desirable to maintain the temperature at which the liquid crystal phase is exhibited and grow the liquid crystal phase domains to form monodomains. Alternatively, after coating the liquid crystalline composition onto the support substrate, the temperature may be maintained for a certain period of time within the temperature range at which the nematic phase is exhibited to orient the liquid crystal molecules in a predetermined direction.

[0041] The heating temperature for orienting liquid crystal compounds in a predetermined direction can be appropriately selected depending on the type of liquid crystal composition, and is usually around 40 to 200°C. If the heating temperature is too low, the transition to the liquid crystal phase tends to be insufficient, and if the heating temperature is too high, the orientation defects may increase. The heating time should be adjusted to allow sufficient growth of the liquid crystal phase domains, and is typically around 30 seconds to 30 minutes.

[0042] It is preferable to orient the liquid crystal compound by heating and then cool it to a temperature below the glass transition temperature. The cooling method is not particularly limited; for example, it may be removed from the heating atmosphere to room temperature. Forced cooling such as air cooling or water cooling may also be performed.

[0043] By irradiating the liquid crystal layer with light, the photopolymerizable liquid crystal compound (liquid crystal monomer) is photocured while exhibiting liquid crystal regularity. The irradiation light can be any light capable of polymerizing the photopolymerizable liquid crystal compound, and typically ultraviolet or visible light with a wavelength of 250 to 450 nm is used. If the liquid crystal composition contains a photopolymerization initiator, light of a wavelength to which the photopolymerization initiator is sensitive should be selected. Suitable irradiation sources include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, LEDs, black lights, chemical lamps, etc. To promote the photocuring reaction, it is preferable to perform the light irradiation under an inert gas atmosphere such as nitrogen gas.

[0044] During the photocuring of the liquid crystalline composition, the liquid crystal compound can be oriented in a predetermined direction by utilizing polarization in a predetermined direction. As described above, when the liquid crystal compound is oriented by the orientation restricting force of the support substrate 8, the irradiation light may be unpolarized (natural light).

[0045] The irradiation intensity should be adjusted as appropriate depending on the composition of the liquid crystalline composition and the amount of photopolymerization initiator added. The irradiation energy (cumulative irradiation dose) is typically 20 to 10,000 mJ / cm². 2 It is approximately 50-5000 mJ / cm². 2 Preferably, 100-800 mJ / cm² 2This is more preferable. To accelerate the photocuring reaction, light irradiation may be carried out under heating conditions.

[0046] The polymer obtained by photocuring liquid crystal monomers with light irradiation is non-liquidental, and no transition between liquid crystal, glass, and crystalline phases occurs due to temperature changes. Therefore, a liquid crystal layer photocured with liquid crystal monomers oriented in a predetermined direction is less susceptible to changes in molecular orientation due to temperature changes. Furthermore, since oriented liquid crystal films have significantly greater birefringence than films made of non-liquid crystal materials, the thickness of optically anisotropic elements with the desired retardation can be significantly reduced. The thickness of the oriented liquid crystal film (liquid crystal layer) can be set according to the desired retardation value, etc., and is usually around 0.1 to 20 μm, preferably 0.2 to 10 μm, and more preferably 0.5 to 7 μm.

[0047] The optical properties of the oriented liquid crystal layer are not particularly limited. The front-facing retardation and thickness-direction retardation of the oriented liquid crystal layer can be set appropriately depending on the application. When the liquid crystal is homogeneously oriented, the front-facing retardation of the oriented liquid crystal layer is, for example, about 20 to 1000 nm. When the oriented liquid crystal layer is a quarter-wave plate, the front-facing retardation is preferably 100 to 180 nm, and more preferably 120 to 150 nm. When the oriented liquid crystal layer is a half-wave plate, the front-facing retardation is preferably 200 to 340 nm, and more preferably 240 to 300 nm.

[0048] The retardation value is the measured value at a wavelength of 550 nm unless otherwise specified. The aligned liquid crystal layer may have a front retardation R(450) at a wavelength of 450 nm that is smaller than the front retardation R(550) at a wavelength of 550 nm. In addition to R(450) < R(550), the aligned liquid crystal layer may satisfy R(550) < R(650), where the front retardation R(650) at a wavelength of 650 nm is larger than R(550). The R(450) / R(550) of the aligned liquid crystal layer may be 0.70 - 0.95, 0.75 - 0.90, or 0.80 - 0.87. The R(650) / R(550) of the aligned liquid crystal layer may be 1.05 - 1.30, 1.10 - 1.25, or 1.13 - 1.20. As described above, by selecting the liquid crystal monomer, an aligned liquid crystal layer having a desired wavelength dispersion of retardation can be formed.

[0049] When the liquid crystal is in a homeotropic alignment, the front retardation of the aligned liquid crystal layer is approximately 0 (e.g., 5 nm or less, preferably 3 nm or less), and the absolute value of the retardation in the thickness direction is on the order of 30 - 500 nm.

[0050] [Resin coating layer] As described above, since the liquid crystal layer after photocuring does not undergo a phase transition even when heated, it has excellent thermal stability compared to the uncured aligned liquid crystal layer. However, when the photocured liquid crystal layer is exposed to a high-temperature environment for a long time, the optical properties may change, and there is room for improvement in heat resistance. In particular, an aligned liquid crystal film in which another optical layer is bonded to a homogeneous alignment liquid crystal layer via an adhesive tends to have a variation in retardation due to long-term heating, and there are problems with heat resistance.

[0051] As shown in FIG. 3, by providing a resin coating layer 6 on the surface of the aligned liquid crystal layer 1, an improvement in the heat stability of the optical properties of the aligned liquid crystal layer can be expected. The resin coating layer 6 is formed by applying a resin solution containing a resin and an organic solvent to the surface of the aligned liquid crystal layer 1.

[0052] [Resin material] A non-curing resin is preferred as the resin material for the resin coating layer 6. A non-curing resin is a material that can form a resin layer without curing reactions such as photocuring or thermocuring after coating with a resin solution. A non-curing resin does not contain photocurable or thermocurable reactive groups, but a small amount of reactive groups may remain. For example, the reactive functional group equivalent (mass of resin containing 1 equivalent of reactive functional groups) is preferably 3000 or more, more preferably 4000 or more, and may be 5000 or more or 6000 or more.

[0053] The resin material is preferably highly transparent and has little coloration. Examples of resin materials include polymers such as epoxy resin, silicone resin, acrylic resin, polyurethane, polyamide, polyether, polyvinyl alcohol, polyester, polycarbonate, polyarylate, polyphenylene sulfide, polyethersulfone, polyetheretherketone, polyamide, polyimide, polyolefin, cyclic polyolefin, polystyrene, polyvinyl chloride, and polyvinylidene chloride. Among these, non-curing acrylic resin and non-curing epoxy resin are preferred because they have high adhesion to the oriented liquid crystal layer 1 and the adhesive layer 3.

[0054] A "non-curing acrylic resin" is a polymer obtained by a polymerization reaction of the (meth)acryloyl groups of a compound (acrylic monomer) having one or more (meth)acryloyl groups in one molecule. It is possible to form a resin coating layer 6 on the surface of the oriented liquid crystal layer 1 without photocuring or thermal curing after coating it with a resin solution. Non-curing acrylic resins are typically polymers of alkyl (meth)acrylates, such as polymethyl methacrylate, polyethyl methacrylate, and polybutyl methacrylate.

[0055] The non-curing acrylic resin may be a copolymer of multiple alkyl (meth)acrylate esters, or a copolymer of alkyl (meth)acrylate esters and other monomers. Examples of monomers other than alkyl (meth)acrylate esters include (meth)acrylic acid, (meth)acrylamide, (meth)acrylonitrile, vinyl monomers, styrene monomers, etc. The copolymer monomer may contain boron-containing functional groups such as boronic acid or boronic acid esters.

[0056] A "non-curing epoxy resin" is a polymer obtained by a polymerization reaction of epoxy groups in a compound (epoxy monomer) having one or more epoxy groups in one molecule, and allows for the formation of a resin coating layer 6 on the surface of the oriented liquid crystal layer 1 without photocuring or thermal curing. Among non-curing epoxy resins, epoxy resins having aromatic rings are preferred.

[0057] The resin material may be a mixture of two or more types. From the viewpoint of suppressing haze rise in the resin coating layer, it is preferable that the two or more resin materials are compatible. The resin material may be a mixture of a non-curing acrylic resin and a non-curing epoxy resin. When the resin material contains both acrylic resin and epoxy resin, from the viewpoint of transparency, the weight ratio of acrylic resin to epoxy resin is preferably 95:5 to 60:40, or 40:60 to 1:99. The weight ratio of the two may be 90:10 to 70:30, or 30:70 to 10:90.

[0058] The glass transition temperature of the resin material in the resin coating layer 6 is preferably 20°C or higher, more preferably 30°C or higher, and may be 40°C or higher or 50°C or higher. Polymer materials used for interlayer bonding, such as adhesives, generally have a glass transition temperature lower than room temperature in order to provide viscosity. On the other hand, the resin coating layer 6 provided on the surface of the oriented liquid crystal layer has a glass transition temperature higher than room temperature, which reduces the change in properties in the operating environment of the image display device, and consequently tends to suppress changes in the optical properties of the oriented liquid crystal layer. From the viewpoint of maintaining the film strength of the resin coating layer 6 without curing reactions, the weight-average molecular weight of the resin material is preferably 20,000 or higher, and more preferably 30,000 or higher.

[0059] (Formation of resin layer) The organic solvent in the resin solution is not particularly limited as long as it is capable of dissolving the above-mentioned resin material. Preferably, the organic solvent does not dissolve the oriented liquid crystal layer. For example, if the oriented liquid crystal layer contains a photocured product of a photopolymerizable liquid crystal monomer, an organic solvent that is insoluble or sparingly soluble in the cured product is preferred. On the other hand, the organic solvent may also be soluble in the liquid crystalline compound (monomer) before photocuring. The organic solvent may be a single solvent or a mixture of two or more solvents.

[0060] The solid content concentration of the resin solution can be adjusted to a viscosity suitable for coating, within a range of approximately 1 to 50% by weight. From the viewpoint of uniformly forming a thin resin coating layer, the solid content concentration of the resin solution is preferably 30% by weight or less, more preferably 20% by weight or less, and may also be 15% by weight or less or 10% by weight or less.

[0061] The method for applying the resin solution to the surface of the oriented liquid crystal layer 1 is not particularly limited, and various coating methods can be used as appropriate. After applying the resin solution, heating may be performed to remove the organic solvent. The heating temperature is preferably 40°C or higher, and more preferably 50°C or higher. If the heating temperature is excessively high, the heating stability of the oriented liquid crystal film may decrease due to thermal damage to the substrate or re-orientation of the liquid crystal compound. Therefore, the heating temperature is preferably 150°C or lower, more preferably 130°C or lower, and may also be 110°C or lower or 100°C or lower.

[0062] The thickness of the resin coating layer 6 is not particularly limited, but from the viewpoint of thinning, adhesion, and maintaining transparency, it is preferably 3 μm or less, more preferably 2 μm or less, and may be 1 μm or less. On the other hand, from the viewpoint of encapsulating eluted substances from the oriented liquid crystal layer 1, such as uncured monomers, in the resin coating layer 6 and suppressing bleed-out, the thickness of the resin coating layer 6 is preferably 0.05 μm or more, and more preferably 0.1 μm or more.

[0063] The reason why the application of a resin coating layer improves the heat resistance of the oriented liquid crystal layer is not entirely clear. However, one possible reason is that uncured monomers remaining in the liquid crystal layer after photocuring, as well as free additives contained in areas where the 3D network structure is not sufficiently formed, are eluted by the organic solvent in the resin solution and incorporated into the resin coating layer. This removes substances that cause retardation changes due to heating from the oriented liquid crystal layer. Even if uncured materials in the oriented liquid crystal layer are eluted by the organic solvent, the eluted components are incorporated into the resin coating layer, preventing contamination and loss of transparency caused by precipitates on the surface of the oriented liquid crystal layer. The re-orientation of the liquid crystal during heating to remove the organic solvent and the stabilization of its orientation state are also thought to contribute to improved heat stability.

[0064] By laminating a resin coating layer 6 and an optical layer 4, which are provided on an oriented liquid crystal layer 1, via an adhesive layer 3, the laminate shown in Figure 1 is obtained.

[0065] [Optical layer] The optical layer 4 is not particularly limited, and optically isotropic or optically anisotropic films commonly used as optical films can be used without any particular restrictions. Specific examples of the optical layer 4 include transparent films such as phase difference films and polarizer protective films, polarizers, and functional films such as viewing angle expanding films, viewing angle limiting (privacy screen) films, and brightness enhancing films. The optical layer 4 may be a single layer or a laminate. The optical layer 4 may also be an aligning liquid crystal layer. For example, the optical layer 4 may be a polarizer plate in which a transparent protective film is laminated to one or both sides of the polarizer. If the polarizer plate has a transparent protective film on one side, the polarizer may be laminated to the aligning liquid crystal layer, or the transparent protective film may be laminated to the aligning liquid crystal layer.

[0066] For example, in liquid crystal display devices, a phase difference plate, which acts as an optical compensation film, may be placed between the image display cell (liquid crystal cell) and the polarizer to appropriately convert the polarization state of the light emitted from the liquid crystal cell towards the viewer, thereby improving the viewing angle characteristics. In organic EL display devices, a quarter-wave plate may be placed between the cell and the polarizer to suppress the reflection of ambient light by the metal electrode layer, which can cause it to appear like a mirror.

[0067] [Adhesive layer] As described above, by providing a resin coating layer 6 on the surface of the alignment liquid crystal layer 1 and bonding the optical layer 4 thereon via an adhesive layer 3, the heat resistance of the alignment liquid crystal layer 1 in the alignment liquid crystal film 100 can be improved.

[0068] The adhesive constituting the adhesive layer 3 is not particularly limited in material as long as it is optically transparent, and examples include epoxy resin, silicone resin, acrylic resin, polyurethane, polyamide, polyether, and polyvinyl alcohol. While a non-curing resin is used for the aforementioned resin coating layer 6, a curing composition is used for the adhesive. The thickness of the adhesive layer 3 is appropriately set depending on the type of adherend and the material of the adhesive. When using a curing adhesive that exhibits adhesion through a crosslinking reaction after application, the thickness of the adhesive layer 3 is preferably 0.01 to 5 μm, and more preferably 0.03 to 3 μm.

[0069] Various types of adhesives can be used, including water-based adhesives, solvent-based adhesives, hot-melt adhesives, and active-energy ray-curing adhesives. Among these, water-based adhesives or active-energy ray-curing adhesives are preferred because they allow for a smaller adhesive layer thickness.

[0070] Examples of water-based adhesives include those containing water-soluble or water-dispersible polymers such as vinyl polymers, gelatin, vinyl latex, polyurethanes, isocyanates, polyesters, and epoxys. An adhesive layer made of such a water-based adhesive is formed by applying an aqueous solution to a film and drying it. When preparing the aqueous solution, crosslinking agents, other additives, or catalysts such as acids may be added as needed.

[0071] Examples of crosslinking agents used in water-based adhesives include boric acid and borax; carboxylic acid compounds; alkyldiamines; isocyanates; epoxy compounds; monoaldehydes; dialdehydes; amino-formaldehyde resins; salts of divalent or trivalent metals and their oxides.

[0072] Active energy ray curing adhesives are adhesives that can undergo radical polymerization, cationic polymerization, or anionic polymerization by irradiation with active energy rays such as electron beams or ultraviolet rays. Among these, photoradical polymerizable adhesives, in which radical polymerization is initiated by ultraviolet irradiation, are preferred because they can be cured at low energy.

[0073] Examples of monomers for radical polymerizable adhesives include compounds having a (meth)acryloyl group and compounds having a vinyl group. Among these, compounds having a (meth)acryloyl group are preferred. Examples of compounds having a (meth)acryloyl group include C 1-20Examples include alkyl(meth)acrylates such as linear alkyl(meth)acrylates, alicyclic alkyl(meth)acrylates, and polycyclic alkyl(meth)acrylates; hydroxyl group-containing (meth)acrylates; and epoxy group-containing (meth)acrylates such as glycidyl(meth)acrylate. Radical polymerizable adhesives may also contain nitrogen-containing monomers such as hydroxyethyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, (meth)acrylamide, and (meth)acryloylmorpholine. Radical polymerizable adhesives may also contain polyfunctional monomers as crosslinking components, such as tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecanedimethanol diacrylate, cyclic trimethylolpropaneformal acrylate, dioxane glycol diacrylate, and EO-modified diglycerin tetraacrylate.

[0074] Photocurable adhesives, such as photoradical polymerizable adhesives, preferably contain a photopolymerization initiator. The photopolymerization initiator can be appropriately selected depending on the reaction species. For example, in radical polymerizable adhesives, it is preferable to incorporate a photoradical generator that generates radicals upon light irradiation as the photopolymerization initiator. Specific examples of photoradical generators will be described later. The amount of photoradical generator is usually about 0.1 to 10 parts by weight, preferably 0.5 to 3 parts by weight, per 100 parts by weight of monomer. Note that a photopolymerization initiator is not particularly necessary when using a radical polymerizable adhesive as an electron beam curing type. Photosensitizers, such as carbonyl compounds, can also be added to radical polymerizable adhesives as needed. Photosensitizers are used to increase the curing speed and sensitivity by electron beam. The amount of photosensitizer used is usually about 0.001 to 10 parts by weight, preferably 0.01 to 3 parts by weight, per 100 parts by weight of monomer.

[0075] 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, UV absorbers, degradation inhibitors, dyes, processing aids, ion trapping agents, antioxidants, tackifiers, fillers, plasticizers, leveling agents, foam inhibitors, antistatic agents, heat stabilizers, hydrolysis stabilizers, and the like.

[0076] By applying an adhesive to either or both the surface of the resin coating layer 6 and the surface of the optical layer 4, which are provided on the oriented liquid crystal layer 1, and curing it, the oriented liquid crystal layer 1 with the resin coating layer 6 and the optical layer 4 are laminated via the adhesive layer 3. The curing method of the adhesive can be appropriately selected depending on the type of adhesive. For example, water-based adhesives can be cured by heating. Active energy ray curing adhesives can be cured by irradiation with active energy rays such as ultraviolet light.

[0077] [Laminated structure of aligned liquid crystal film] An aligning liquid crystal film 103, in which a resin coating layer 6 is provided on the surface of an aligning liquid crystal layer 1 on a support substrate 8, and an optical layer 4 is bonded to the resin coating layer 6 via an adhesive layer 3, may be used as an optical component as is. In this case, the support substrate 8 constitutes a part of the aligning liquid crystal film 103. The support substrate may be peeled off from the aligning liquid crystal layer 1, as shown in the aligning liquid crystal film 100 in Figure 1. An appropriate adhesive layer 2 may be laminated on the surface of the aligning liquid crystal layer 1 exposed by peeling off the support substrate, as shown in Figure 5.

[0078] In the embodiment shown in Figure 5, the adhesive layer 2 is laminated on the exposed surface of the alignment liquid crystal layer 1 after peeling off the support substrate 8 (the substrate surface when the alignment liquid crystal layer is formed). However, the alignment liquid crystal film may also be constructed by laminating the adhesive layer on the air surface side when the alignment liquid crystal layer is formed, and bonding the optical layer to the substrate surface side of the alignment liquid crystal layer via a resin coating layer and an adhesive layer.

[0079] The adhesive constituting the adhesive layer 2 is not particularly limited, and can be appropriately selected and used from acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluoropolymers, rubber polymers, etc., which are used as base polymers. In particular, adhesives such as acrylic adhesives and rubber adhesives that have excellent transparency, exhibit appropriate wettability, cohesiveness and adhesion, and have excellent weather resistance and heat resistance are preferred. The thickness of the adhesive layer is appropriately set according to the type of substrate, etc., and is generally about 5 to 500 μm.

[0080] The adhesive layer 2 is laminated onto the aligning liquid crystal layer 1 by, for example, bonding a pre-formed sheet of adhesive to the surface of the aligning liquid crystal layer 1. Alternatively, the adhesive composition may be applied to the aligning liquid crystal layer 1, followed by solvent drying, crosslinking, photocuring, etc., to form the adhesive layer 2. To enhance the adhesion (anchoring force) between the aligning liquid crystal layer 1 and the adhesive layer 2, the adhesive layer 2 may be laminated after surface treatment such as corona treatment or plasma treatment, or after forming an easy-adhesion layer on the surface of the aligning liquid crystal layer 1.

[0081] It is preferable that a separator 9 is temporarily attached to the surface of the adhesive layer 2. The separator 9 protects the surface of the adhesive layer 2 until the adhesive optical film is bonded to the image display cell 50. Suitable materials for the separator include plastic films such as acrylic, polyolefin, cyclic polyolefin, and polyester. The thickness of the separator is usually about 5 to 200 μm. It is preferable that the surface of the separator is treated with a release agent. Examples of release agents include silicone-based materials, fluorine-based materials, long-chain alkyl-based materials, and fatty acid amide-based materials.

[0082] After peeling off the support substrate 8, other optical layers may be laminated onto the exposed surface of the alignment liquid crystal layer 1 via an appropriate adhesive layer or tack layer. For example, as shown in Figure 6, another optical layer 5 may be laminated on the alignment liquid crystal layer 1 via an appropriate adhesive layer 7. An adhesive layer (not shown) may be further laminated on the optical layer 5, and a separator may be temporarily attached to the surface of the adhesive layer.

[0083] The support substrate 8 may be peeled off from the alignment liquid crystal layer 1, and a resin solution may be applied to the surface of the alignment liquid crystal layer 1 exposed by the peeling off of the support substrate to form a resin coating layer 16. As shown in Figure 7, the optical layer 5 may be bonded to the resin coating layer 16 provided on the surface of the alignment liquid crystal layer 1 exposed by the peeling off of the support substrate via an adhesive layer 7.

[0084] In Figure 7, resin coating layers 6 and 16 are provided on both sides of the alignment liquid crystal layer 1, but the resin coating layer may be provided on only one side of the alignment liquid crystal layer 1. Alternatively, in a laminate 101 in which the alignment liquid crystal layer 1 is tightly laminated on a support substrate 8, the resin coating layer may not be formed on the surface of the alignment liquid crystal layer 1 (the air surface during the formation of the alignment liquid crystal layer), and other layers may be bonded to it via an adhesive layer or bonding agent. After peeling the support substrate 8 from the alignment liquid crystal layer 1, the resin coating layer 16 may be formed only on the exposed surface of the alignment liquid crystal layer 1 (the substrate surface during the formation of the alignment liquid crystal layer).

[0085] <Circular polarizer> Aligned liquid crystal films can be used as optical films for displays to improve visibility and other purposes. For example, in liquid crystal display devices, a phase difference plate, which acts as an optical compensation film, may be placed between the image display cell (liquid crystal cell) and the polarizer to appropriately change the polarization state of the light emitted from the liquid crystal cell to the viewing side, thereby improving viewing angle characteristics.

[0086] In one embodiment, the aligning liquid crystal film is a circular polarizing plate in which a polarizing plate as an optical layer 4 is bonded to the resin coating layer 6 forming surface on the aligning liquid crystal layer 1 via an adhesive layer 3. The circular polarizing plate may have two or more aligning liquid crystal layers.

[0087] A polarizing plate may consist of only one polarizer layer, or, as mentioned above, a transparent protective film may be laminated to one or both sides of the polarizer. Examples of polarizers include hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing dichroic substances such as iodine or dichroic dyes, as well as polyene-based oriented films such as dehydrated polyvinyl alcohol or dehydrochlorinated polyvinyl chloride.

[0088] Among these, polyvinyl alcohol (PVA) polarizers are preferred because they have a high degree of polarization. These polarizers are made by adsorbing dichroic substances such as iodine or dichroic dyes onto a polyvinyl alcohol-based film, such as polyvinyl alcohol or partially formalized polyvinyl alcohol, and oriented them in a predetermined direction. For example, a PVA polarizer can be obtained by iodine dyeing and stretching a polyvinyl alcohol-based film. Alternatively, a PVA-based resin layer may be formed on a resin substrate, and iodine dyeing and stretching may be performed on the laminated structure.

[0089] In a circular polarizing plate in which a polarizing plate and an oriented liquid crystal layer are laminated, it is preferable that at least one oriented liquid crystal layer has liquid crystal molecules that are homogeneously oriented. In the circular polarizing plate, the orientation direction of the liquid crystal molecules in the oriented liquid crystal layer, in which the liquid crystal molecules are homogeneously oriented, is arranged such that it is neither parallel nor orthogonal to the absorption axis direction of the polarizer.

[0090] For example, if a circular polarizer has only one oriented liquid crystal layer, the oriented liquid crystal layer 1 is a quarter-wave plate, and the angle between the polarizer's absorption axis and the orientation direction of the liquid crystal molecules (generally the slow-phase axis) is set to 45°. The angle between the polarizer's absorption axis and the orientation direction of the liquid crystal molecules may be 35-55°, 40-50°, or 43-47°.

[0091] In a configuration in which a polarizing plate 4 and an oriented liquid crystal layer 1 as a quarter-wave plate are stacked such that the angle between their optical axes is 45°, an oriented liquid crystal layer in which liquid crystal molecules are perpendicularly oriented (homeotropically oriented) to the substrate surface may be further provided as an optical layer 5. By sequentially stacking the oriented liquid crystal layer 1 as a quarter-wave plate and the homeotropically oriented liquid crystal layer 5, which functions as a positive C plate, on the polarizing plate, a circular polarizing plate capable of shielding reflected light even from oblique external light can be formed. Alternatively, a homeotropically oriented liquid crystal layer (positive C plate) and a homogeneous oriented liquid crystal layer (a quarter-wave plate which is a positive A plate) may be sequentially stacked on the polarizing plate.

[0092] As shown in Figures 6 and 7, in a circular polarizer in which multiple aligning liquid crystal layers 1 and 5 are laminated on a polarizing plate 4 as an optical layer, both aligning liquid crystal layers 1 and 5 may be homogeneous aligning liquid crystal layers. In this case, it is preferable that the aligning liquid crystal layer 1 located closer to the polarizing plate 4 is a half-wave plate, and the aligning liquid crystal layer 5 located further away from the polarizing plate is a quarter-wave plate. In this laminated configuration, it is preferable that the angle between the slow axis direction of the half-wave plate and the absorption axis direction of the polarizer is 75°±5°, and the angle between the slow axis direction of the quarter-wave plate and the absorption axis direction of the polarizer is 15°±5°. A circular polarizer with such a laminated configuration functions as a circular polarizer over a wide wavelength range of visible light, thus reducing the coloration of reflected light.

[0093] A circular polarizing plate, in which multiple alignment liquid crystal layers 1 and 5 are laminated on a polarizing plate 4, may have a resin coating layer 6 placed between the alignment liquid crystal layer 1 and the alignment liquid crystal layer 5, as shown in Figure 8, and may not have a resin coating layer between the alignment liquid crystal layer 1 and the polarizing plate 4. For example, as shown in Figure 3, after providing a resin coating layer 6 on the surface of the alignment liquid crystal layer 1, the alignment liquid crystal layer 5 is bonded onto the resin coating layer 6 via an adhesive layer 7, resulting in a laminate (aligning liquid crystal film) 113, as shown in Figure 9, in which the alignment liquid crystal layer is bonded to the resin coating layer 6-forming surface of the alignment liquid crystal layer 1 via an adhesive layer 7. By peeling the support substrate 8 from this laminate and bonding the polarizing plate 4 to the alignment liquid crystal layer 1 exposed by the peeling of the support substrate via an adhesive layer 12, a laminate 107 is obtained, as shown in Figure 8, in which a resin coating layer 6 is provided on one side of the alignment liquid crystal layer 1, the alignment liquid crystal layer 5 is laminated on it via an adhesive layer 7, and the polarizing plate 4 is bonded to the other side of the alignment liquid crystal layer 1 via an adhesive layer 12.

[0094] In one embodiment of this laminate 107, the orientation liquid crystal layer 1 located closer to the polarizing plate 4 is a homogeneous orientation liquid crystal layer acting as a quarter-wave plate, and the orientation liquid crystal layer 5 located further away from the polarizing plate 4 is a homeotropic orientation liquid crystal layer acting as a positive C plate. In this embodiment, the orientation liquid crystal layer 5 is bonded to the resin coating layer forming surface 6 of the orientation liquid crystal layer 1 via an adhesive layer 7.

[0095] The adhesive layer 7 is formed by the curing of the adhesive, which is a curable material. However, since a non-curing resin coating layer 6 is formed on the alignment liquid crystal layer 1, changes in the frontal retardation of the alignment liquid crystal layer 1 due to heating are suppressed. Although there is no resin coating layer on the bonding surface of the alignment liquid crystal layer 1 with the polarizing plate 4, the alignment liquid crystal layer 1 and the polarizing plate 4 are bonded together via an adhesive layer 12 (non-curing material). Therefore, a decrease in heat durability, which can occur when an adhesive layer is directly formed on the alignment liquid crystal layer, is unlikely to occur.

[0096] As described above, the laminate 107 shown in Figure 8 has a structure in which a non-curing resin coating layer 6 is provided on a homogeneous oriented liquid crystal layer 1, and an oriented liquid crystal layer 5 as a positive C plate (optical layer) is bonded thereon via an adhesive layer 7. Therefore, even when exposed to a high-temperature environment for a long time, the change in front letteration is small, making it suitable for use as a circular polarizer in liquid crystal displays and organic EL displays. In the laminate 107, the oriented liquid crystal layer 5, which is the positive C plate, is in contact with the adhesive layer 7, but since the positive C plate has a front letteration of approximately 0, even when the laminate 107 is exposed to a high-temperature environment for a long time, there is almost no change in front letteration.

[0097] [Image display device] Figure 10 is a cross-sectional view showing an example of a stacked configuration of an image display device, in which an alignment liquid crystal film comprising an alignment liquid crystal layer 1 is bonded to the surface of an image display cell 50 via an adhesive layer 2. The alignment liquid crystal film may have two or more alignment liquid crystal layers. Examples of image display cells 50 include liquid crystal cells and organic EL cells.

[0098] As described above, the heat resistance of the alignment liquid crystal film is improved by providing a resin coating layer on the surface of the alignment liquid crystal layer. Image display devices equipped with an alignment liquid crystal layer with a resin coating layer formed on its surface exhibit minimal changes in the retardation of the alignment liquid crystal layer even when exposed to a heated environment for a long time, resulting in minimal changes in visibility and excellent heat resistance. [Examples]

[0099] The present invention will be described in more detail below with reference to examples of the production of oriented liquid crystal films, but the present invention is not limited to the following examples.

[0100] [Fabrication of homogeneous oriented liquid crystal films] <Comparative Example 1> A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF's "Paliocolor LC242") was dissolved in cyclopentanone to prepare a solution with a solid content of 30% by weight. A surfactant (Bic Chemie's "BYK-360") and a photopolymerization initiator (IGM Resins' "Omnirad907") were added to this solution to prepare a liquid crystalline composition solution. The amounts of the leveling agent and polymerization initiator added were 0.01 parts by weight and 3 parts by weight, respectively, per 100 parts by weight of the photopolymerizable liquid crystal compound.

[0101] A biaxially oriented norbornene-based film (Zeonor Film, manufactured by Nippon Zeon Co., Ltd., thickness: 33 μm, frontal retardation: 135 nm) was used as the film substrate. The above liquid crystalline composition was applied to the surface of the film substrate using a bar coater to a dry thickness of 1 μm, and the liquid crystals were oriented by heating at 100°C for 3 minutes. After cooling to room temperature, the film was subjected to a nitrogen atmosphere with an integrated light intensity of 400 mJ / cm². 2 By irradiating with ultraviolet light, photocuring was performed to obtain a laminate in which a homogeneous oriented liquid crystal layer was formed on a film substrate.

[0102] <Examples 1-6> A resin solution was prepared by dissolving the resins shown in Table 1 in a mixed solvent of cyclopentanone and ethyl acetate to a solid content concentration of 3% by weight. The resin solution was applied to the surface of the oriented liquid crystal layer of the laminate of Comparative Example 1 using a wire bar (#10), and then heated at 85°C to remove the solvent, forming a resin coating layer on the surface of the oriented liquid crystal layer. In Table 1, the acrylic resins for Examples 1-3 were obtained from Kusumoto Chemical, and the epoxy resins for Examples 4-6 and Comparative Example 3 were obtained from Mitsubishi Chemical.

[0103] <Comparative Example 2> Cyclopentanone was applied to the surface of the oriented liquid crystal layer of the laminate in Comparative Example 1 using a wire bar (#10), and then the solvent was removed by heating at 85°C for 1 minute.

[0104] <Comparative Example 3> A photocurable resin composition (solution) was prepared by dissolving a bisphenol A type epoxy resin (Mitsubishi Chemical's "jER828") with an epoxy equivalent of approximately 190 and a photocationic polymerization initiator (Sunapro's "CPI100P") in a mixed solvent of cyclopentanone and ethyl acetate to an epoxy resin concentration of 3% by weight. The composition was applied to the surface of the oriented liquid crystal layer of the laminate of Comparative Example 1 using a wire bar (#10), then heated at 85°C to remove the solvent, and subsequently irradiated with ultraviolet light to photocur the epoxy resin.

[0105] [Fabrication of polarizing plates (circular polarizing plates) equipped with an oriented liquid crystal layer] A laminate (single protective polarizer) was prepared by attaching a 5 μm thick PVA polarizer to one side of a 20 μm thick unoriented norbornene-based film (Zeonor Film, manufactured by Nippon Zeon Co., Ltd.) via a UV-curing adhesive.

[0106] A UV-curable adhesive composition was prepared by mixing 62 parts by weight of hydroxyethyl acrylamide (HEAA, manufactured by Kojin), 25 parts by weight of acryloyl morpholine (ACMO, manufactured by Kojin), 7 parts by weight of PEG400# diacrylate (Light Acrylate 9EG-A, manufactured by Kyoeisha Chemical), 3 parts by weight of a photopolymerization initiator (Omnirad907, manufactured by IGM Resins), and 3 parts by weight of 2,4-diethylthioxanthone (Kayacure DETX-S, manufactured by Nippon Kayaku). This adhesive was applied to the surface of the above-mentioned protective polarizing plate to a thickness of approximately 1 μm, and the oriented liquid crystal layer side of the laminates of Examples 1-6 and Comparative Examples 1-3 was bonded onto the adhesive coating layer, followed by exposure to an integrated light intensity of 1000 mJ / cm². 2 The adhesive was cured by irradiation with ultraviolet light. During bonding, the angle between the absorption axis direction of the polarizer and the orientation direction of the liquid crystal molecules in the oriented liquid crystal layer (the slow phase axis direction of the film substrate) was set to 45°.

[0107] The film substrate was peeled off from the aligned liquid crystal film, and an acrylic adhesive sheet with a thickness of 15 μm was laminated on the surface of the aligned liquid crystal film. The aligned liquid crystal layer was laminated on the polarizer of the single-side protective polarizer via a UV-curable adhesive layer, and a polarizer provided with an acrylic adhesive sheet was obtained thereon. In Examples 1 to 6 and Comparative Example 3, a resin layer with a thickness of about 300 nm was formed between the adhesive layer and the aligned liquid crystal layer.

[0108] [Evaluation] <Appearance> The film surface after forming the resin coating layer (Comparative Example 2 after surface treatment with cyclopentanone) was visually observed, and those with no precipitate confirmed were rated as OK, and those with precipitate confirmed were rated as NG.

[0109] <Retardation change> The adhesive layer of the above polarizer was laminated on a glass plate to prepare an evaluation sample. After measuring the front retardation at a wavelength of 590 nm using a retardation meter (KOBRA 21-ADH manufactured by Oji Scientific Instruments), the evaluation sample was placed in an air-circulating constant-temperature oven at 85 °C for 120 hours. After taking out the sample from the oven, the front retardation was measured again, and the change rate of retardation before and after the heating test was calculated.

[0110] <Hue change> The adhesive layer of the above polarizer was laminated on a Corning non-alkali glass to prepare an evaluation sample. An aluminum-deposited polyester film (DMS-X42 manufactured by Toray Advanced Film) was placed under the non-alkali glass of the evaluation sample, and using a spectrophotometer (CM-2600d manufactured by Konica Minolta), light was irradiated from the polarizer side, and the hue of the reflected light (the values of a * and b * in the Lab color space) was measured. Then, the evaluation sample was placed in an air-circulating constant-temperature oven at 85 °C for 120 hours. After taking out the sample from the oven, the hue of the reflected light was measured again on the aluminum-deposited polyester film, and the change amount of the hue of the reflected light before and after the heating test √{(Δa * ) 2 +(Δb * )2 The result was calculated.

[0111] Table 1 shows the types of resins used to form the resin coating layer in Examples 1-6 and Comparative Examples 1-3, as well as the evaluation results of the oriented liquid crystal films.

[0112] [Table 1]

[0113] In Comparative Example 1, where no surface treatment was performed on the oriented liquid crystal layer, the Re change before and after the heating test was 3%, and the hue change of the reflected light was 2.2. In contrast, in Comparative Example 2, where treatment with cyclopentanone was performed, the Re change was suppressed, and consequently, the hue change of the reflected light was also suppressed. However, in Comparative Example 2, precipitates were observed on the surface of the oriented liquid crystal layer, resulting in an appearance defect.

[0114] In Examples 1-6, where a resin coating layer was formed on an oriented liquid crystal layer using a non-curing resin, the Re change and hue change of reflected light were suppressed compared to Comparative Example 1, and the appearance was also good. When the resin coating layer surface of Example 1 was dissolved in tetrahydrofuran to extract the resin component and analyzed by MALDI-TOF mass spectrometry, unreacted liquid crystal monomers were confirmed. From these results, it is considered that applying the resin solution extracts uncured material from the oriented liquid crystal layer, and this is incorporated into the resin coating layer, which contributes to improving the heat durability of the oriented liquid crystal layer.

[0115] In Comparative Example 3, where a photocationically curable resin composition was used and the resin layer was UV-cured after coating on an oriented liquid crystal layer, the frontal Re was reduced after the heat durability test, indicating insufficient heat durability. These results show that forming a non-curable resin coating layer on an oriented liquid crystal layer improves the heat durability of the oriented liquid crystal layer, resulting in a circular polarizer with minimal retardation and less coloration or change in reflected light.

[0116] [Example of fabrication of a circular polarizing plate with multiple oriented liquid crystal layers] <Fabrication of homogeneous oriented liquid crystal layers> 55 parts by weight of the compound represented by formula (I), 25 parts by weight of the compound represented by formula (II), and 20 parts by weight of the compound represented by formula (III) were added to 400 parts by weight of cyclopentanone. The mixture was heated to 60°C, stirred, and dissolved, then cooled to room temperature to prepare a solution with a solid content of 20% by weight.

[0117] [ka]

[0118] To this solution, 0.2 parts by weight of a surfactant (DIC's "Megafac F-554"), 3 parts by weight of a photopolymerization initiator (IGM Resins' "Omnirad907"), and 0.1 parts by weight of p-methoxyphenol were added to prepare a liquid crystalline composition solution.

[0119] As the film substrate, a film comprising an alignment film rubbed onto a triacetylcellulose film was used. The above liquid crystalline composition was applied to the alignment film of the film substrate by spin coating, and the liquid crystals were aligned by heating at 100°C for 2 minutes. After cooling to room temperature, the film was subjected to a nitrogen atmosphere with an integrated light intensity of 900 mJ / cm². 2 A laminate A was obtained by photocuring with ultraviolet light to form a homogeneous oriented liquid crystal layer (thickness 4 μm) on a film substrate. When the oriented liquid crystal layer was transferred onto a glass plate and the frontal retardation was measured, the frontal retardation R(550) at a wavelength of 550 nm was 130 nm, and the ratio R(450) / R(550) of the frontal retardation R(550) at a wavelength of 550 nm to the frontal retardation R(450) at a wavelength of 450 nm was 0.85.

[0120] <Fabrication of homeotropically oriented liquid crystal layers> A liquid crystalline composition was prepared by dissolving 20 parts by weight of a side-chain liquid crystal polymer with a weight-average molecular weight of 5000, as shown in the following chemical formula (n=0.35, shown as a block polymer for convenience), 80 parts by weight of a polymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF's "Paliocolor LC242"), and 5 parts by weight of a photopolymerization initiator (IGM Resins' "Omnirad907") in 400 parts by weight of cyclopentanone.

[0121] [ka]

[0122] A biaxially oriented norbornene-based film (Zeonor Film, manufactured by Nippon Zeon Co., Ltd., thickness: 52 μm, frontal retardation: 50 nm) was used as the film substrate. The above liquid crystalline composition was applied to the surface of the film substrate by bar coating to a dry thickness of 1 μm, heated at 80°C for 2 minutes to orient the liquid crystals, cooled to room temperature, and then subjected to a nitrogen atmosphere at 700 mJ / cm². 2 By irradiating with ultraviolet light, the liquid crystal monomer was photocured to obtain a laminate B in which a homeotropically oriented liquid crystal layer was formed on a film substrate.

[0123] <Making adhesive sheets> In a reaction vessel, 92 parts by weight of butyl acrylate, 5 parts by weight of N-acryloylmorpholine, 2.9 parts by weight of acrylic acid, and 0.1 parts by weight of 2-hydroxyethyl acrylate as monomers, and 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator were added together with ethyl acetate, and the mixture was reacted at 55°C for 8 hours under a nitrogen gas stream. Subsequently, ethyl acetate was added to the reaction solution to obtain a solution of an acrylic polymer with a weight-average molecular weight of 1.78 million. To this solution, 0.15 parts by weight of dibenzoyl peroxide (Nippon Oil & Fats Co., Ltd. "Nippon Oil & Fats Co., Ltd. "Nippon Oil & Fats Co., Ltd.") and 0.6 parts by weight of trimethylolpropane / tolylene diisocyanate adduct (Tosoh Co., Ltd. "Coronate L") were added as crosslinking agents per 100 parts by weight of the polymer to obtain an adhesive composition. This adhesive composition was applied to the release surface of a release film (polyethylene terephthalate film treated with silicone release agent), and dried and crosslinked at 150°C to produce an adhesive sheet with a thickness of 5 μm.

[0124] <Example 7> A resin solution was prepared by dissolving an acrylic polymer with a weight-average molecular weight of 80,000, obtained by copolymerizing methyl methacrylate and 3-methacrylamide phenylboronic acid in a weight ratio of 97:3, in ethyl acetate to a solid content concentration of 3% by weight. The resin solution was applied to the surface of the homogeneous oriented liquid crystal layer of laminate A using a wire bar (#10), and then heated at 85°C to remove the solvent, forming a resin coating layer with a thickness of approximately 300 nm on the surface of the homogeneous oriented liquid crystal layer. Laminate D was obtained, which sequentially comprises a homogeneous oriented liquid crystal layer and a resin coating layer on a film substrate.

[0125] The above UV-curing adhesive is applied to the resin coating layer of laminate D to a thickness of approximately 1 μm, and the side of laminate B with the homeotropically oriented liquid crystal layer is bonded onto the adhesive coating layer, after which an integrated light intensity of 1000 mJ / cm² is applied. 2 The adhesive was cured by irradiating it with ultraviolet light.

[0126] Subsequently, the film substrate was peeled off from the surface of the homogeneous-oriented liquid crystal layer, and the polarizer-side surface of the single protective polarizer was bonded to the exposed homogeneous-oriented liquid crystal layer via the adhesive layer. During bonding, the angle between the absorption axis direction of the polarizer and the orientation direction of the liquid crystal molecules in the homogeneous-oriented liquid crystal layer (rubbing direction of the orientation film of the film substrate) was set to 45°. Then, the film substrate was peeled off from the surface of the homeotropic-oriented liquid crystal layer, and a laminate (circular polarizer) was obtained in which the homogeneous-oriented liquid crystal layer was bonded to the polarizer-side surface of the single protective polarizer via the adhesive layer, and the homeotropic-oriented liquid crystal layer was bonded on top of that via a resin coating layer and an adhesive layer.

[0127] <Comparative Example 4> In the same manner as in Example 7, a resin coating layer with a thickness of approximately 300 nm was formed on the surface of the homogeneous oriented liquid crystal layer to obtain laminate D. The polarizer side of a protective polarizer plate was bonded to the resin coating layer of laminate D via the adhesive layer described above. At the time of bonding, the angle between the absorption axis direction of the polarizer and the orientation direction of the liquid crystal molecules in the homogeneous oriented liquid crystal layer (rubbing direction of the orientation film of the film substrate) was set to 45°.

[0128] Subsequently, the film substrate is peeled off from the surface of the homogeneous-aligned liquid crystal layer, and the above-mentioned UV-curing adhesive is applied to the exposed homogeneous-aligned liquid crystal layer to a thickness of approximately 1 μm. The homeotropic-aligned liquid crystal layer side of laminate B is then bonded onto the adhesive layer, and an integrated light intensity of 1000 mJ / cm² is applied. 2 The adhesive was cured by irradiation with ultraviolet light. Then, the film substrate was peeled off from the surface of the homeotropic-oriented liquid crystal layer, and a laminate of the resin coating layer and the homogeneous-oriented liquid crystal layer was bonded to the polarizer side of the protective polarizer plate via an adhesive layer, and a laminate (circular polarizer) was obtained in which the homeotropic-oriented liquid crystal layer was bonded to the homogeneous-oriented liquid crystal layer via an adhesive layer.

[0129] <Example 8> Instead of an acrylic polymer solution, a methyl ethyl ketone solution with a solid content of 3% by weight, containing an acrylic polymer and epoxy resin (Mitsubishi Chemical's "jER YX7200B35") in a weight ratio of 85:15, was used. Otherwise, the procedure was the same as in Example 7, and a resin coating layer with a thickness of approximately 300 nm was formed on the surface of the homogeneous oriented liquid crystal layer. Subsequently, in the same manner as in Example 7, the homogeneous oriented liquid crystal layer was bonded to the polarizer side of a single protective polarizing plate via an adhesive layer, and a homeotropic oriented liquid crystal layer was bonded on top of it via a resin coating layer and an adhesive layer to obtain a laminate (circular polarizing plate).

[0130] <Example 9> A circular polarizing plate was fabricated in the same manner as in Example 8, except that the thickness of the resin coating layer was changed to approximately 600 nm.

[0131] <Comparative Example 5> In the same manner as in Example 8, a resin coating layer with a thickness of approximately 300 nm was formed on the surface of the homogeneous oriented liquid crystal layer using a mixed resin solution of acrylic polymer and epoxy resin. Thereafter, in the same manner as in Comparative Example 4, the laminate of the resin coating layer and the homogeneous oriented liquid crystal layer was bonded to the polarizer side of a single protective polarizing plate via an adhesive layer, and a laminate (circular polarizing plate) was obtained in which the homeotropic oriented liquid crystal layer was bonded to the homogeneous oriented liquid crystal layer via an adhesive layer.

[0132] [evaluation] For the circular polarizers of Examples 7-9 and Comparative Examples 4 and 5, a 15 μm thick acrylic adhesive sheet was bonded to the homeotropically aligned liquid crystal layer side, and this adhesive sheet was then bonded to a glass plate to prepare evaluation samples. After measuring the frontal retardation (initial value) at a wavelength of 590 nm using a phase difference meter (KOBRA 21-ADH, manufactured by Oji Instruments Co., Ltd.), the evaluation samples were placed in an 85°C air-circulating constant-temperature oven, and the frontal retardation was measured after 120 hours, 240 hours, and 500 hours, and the rate of change from the initial value was calculated.

[0133] Table 2 shows the lamination configuration of the circular polarizers in Examples 7-9 and Comparative Examples 4 and 5, the polymer type and thickness of the resin coating layer, and the rate of change in frontal retardation after heat durability tests (120 hours, 240 hours, and 500 hours).

[0134] [Table 2]

[0135] In Comparative Examples 4 and 5, where an adhesive layer was provided in contact with a homogeneous alignment layer and a homeotropic alignment liquid crystal layer was bonded to it, a decrease of more than 1% in frontal retardation was observed after a 120-hour heating test. In contrast, in Examples 7 to 9, where a resin coating layer was provided on the homogeneous alignment liquid crystal layer and a homeotropic alignment liquid crystal layer was bonded thereon via an adhesive layer, the change in frontal retardation during the heating durability test was suppressed.

[0136] These results show that by providing a resin coating layer so that the homogeneous oriented liquid crystal layer and the curable adhesive layer do not come into contact, the heat durability of the oriented liquid crystal layer is improved and the retardation change is suppressed. A comparison of Example 8 and Example 9 shows that a larger resin coating layer tends to result in higher heat durability (suppression of retardation change). [Explanation of Symbols]

[0137] 1. Aligned liquid crystal layer 6. Resin coating layer 8. Support substrate 4 Optical layer (polarizing plate) 5. Optical layer (alignment liquid crystal layer) 3,7 Adhesive layer 2,12 Adhesive layer 9 Separator 50 Image Display Cells

Claims

1. The device comprises a first-aligned liquid crystal layer in which liquid crystal molecules are oriented, a resin coating layer in contact with the first main surface of the first-aligned liquid crystal layer, and an optical layer bonded to the resin coating layer via an adhesive layer. The first orientation liquid crystal layer is a homogeneous orientation liquid crystal layer in which liquid crystal molecules are homogeneously oriented. The resin coating layer is a resin coating layer that does not contain photocurable or thermosetting reactive groups, or contains an acrylic resin or epoxy resin having a functional group equivalent of 3,000 or more photocurable or thermosetting reactive groups and a weight-average molecular weight of 20,000 or more. Alignment liquid crystal film.

2. The oriented liquid crystal film according to claim 1, wherein the glass transition temperature of the resin coating layer is 20°C or higher.

3. The orientation liquid crystal film according to claim 1 or 2, wherein the thickness of the adhesive layer is 0.01 to 5 μm.

4. The oriented liquid crystal film according to any one of claims 1 to 3, wherein the adhesive constituting the adhesive layer is an active energy ray curing type adhesive.

5. The orientation liquid crystal film according to any one of claims 1 to 4, wherein the optical layer is a polarizer, a transparent film, or another orientation liquid crystal layer.

6. The orientation liquid crystal film according to any one of claims 1 to 5, wherein the thickness of the resin coating layer is 0.05 to 3 μm.

7. The orientation liquid crystal film according to any one of claims 1 to 6, wherein the resin coating layer contains uncured liquid crystal compound constituting the first orientation liquid crystal layer.

8. The orientation liquid crystal film according to any one of claims 1 to 7, wherein an adhesive layer is provided on the second main surface side of the first orientation liquid crystal layer.

9. The optical layer includes a polarizer, The orientation liquid crystal film according to any one of claims 1 to 8, wherein the angle between the orientation direction of the liquid crystal molecules in the first orientation liquid crystal layer and the absorption axis direction of the polarizer is 10 to 80°.

10. The optical layer is a second-aligned liquid crystal layer in which liquid crystal molecules are homeotropically oriented. The orientation liquid crystal film according to any one of claims 1 to 9, wherein a polarizing plate is bonded to the second main surface side of the first orientation liquid crystal layer.

11. The orientation liquid crystal film according to claim 10, wherein the first orientation liquid crystal layer and the polarizing plate are bonded together via an adhesive layer.

12. The orientation liquid crystal film according to claim 11, wherein the adhesive layer is in contact with the second main surface of the first orientation liquid crystal layer.

13. An image display device in which an oriented liquid crystal film according to any one of claims 1 to 12 is arranged on an image display cell.

14. A method for manufacturing an oriented liquid crystal film according to any one of claims 10 to 12, A resin solution containing an acrylic resin or epoxy resin that does not contain photocurable or thermosetting reactive groups, or in which the functional group equivalent of photocurable or thermosetting reactive groups is 3000 or more and the weight-average molecular weight is 20,000 or more, and an organic solvent is applied to the first main surface of the first orientation liquid crystal layer to form the resin coating layer. The resin coating layer and the second orientation liquid crystal layer are bonded together via an adhesive. A method for manufacturing an oriented liquid crystal film.

15. A method for manufacturing an oriented liquid crystal film according to claim 14, wherein after applying the resin solution, heating is performed at 40 to 150°C before bonding the second oriented liquid crystal layer.

16. A liquid crystalline composition containing a photopolymerizable liquid crystal monomer is coated onto a support substrate. The liquid crystalline composition on the support substrate is heated to cause the liquid crystal monomers to be homogeneously oriented in a liquid crystal state. By polymerizing or crosslinking the liquid crystal monomer by light irradiation, A method for manufacturing an oriented liquid crystal film according to claim 14 or 15, for forming the first oriented liquid crystal layer.

17. The method for manufacturing an oriented liquid crystal film according to claim 16, wherein the support substrate is a resin film.

18. A method for manufacturing an oriented liquid crystal film according to claim 16 or 17, wherein the first oriented liquid crystal layer is provided on the support substrate, and the resin solution is applied to the surface of the first oriented liquid crystal layer that is not in contact with the support substrate.

19. The support substrate is peeled off from the first orientation liquid crystal layer. A method for manufacturing an oriented liquid crystal film according to claim 16 or 17, comprising applying the resin solution to the surface of the first oriented liquid crystal layer exposed by peeling off the support substrate.

20. A method for producing an oriented liquid crystal film according to any one of claims 16 to 19, wherein the organic solvent of the resin solution is soluble in the photopolymerizable liquid crystal monomer, and the photocured product of the photopolymerizable liquid crystal monomer is insoluble or poorly soluble.

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