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

Abstract

A liquid crystal alignment film (100) comprises: a first aligned liquid crystal layer (1) in which liquid crystal molecules are aligned; a resin coating (6) in contact with a first main surface of the first aligned liquid crystal layer; and an optical layer (4) bonded to the resin coating (6) via an adhesive layer (3). The resin coating is a non-curable resin layer. The glass transition temperature of the resin coating may be 20°C or higher. The first aligned liquid crystal layer may have liquid crystal molecules aligned in parallel. In one embodiment, the resin coating is formed by coating the first main surface of the first aligned liquid crystal layer with a resin solution comprising a resin and an organic solvent, and the resin coating is bonded to the optical layer via an adhesive to form an aligned liquid crystal film.

Description

Technical Field

[0001] This 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 having the oriented liquid crystal film. Background Technology

[0002] As an optical film that provides optical compensation for liquid crystal display devices and prevents external light reflection from organic EL elements, a liquid crystal film (aligned liquid crystal film) is used, in which a liquid crystal compound is aligned in a specified direction. Since the birefringence of an aligned liquid crystal film is greater than that of a stretched polymer film, it is advantageous for thinning and lightweighting. In image display devices, the aligned liquid crystal film is bonded to an organic EL panel or liquid crystal display panel as a polarizer integrally laminated with an adhesive (pressure-sensitive adhesive) or bonding agent (e.g., Patent Document 1).

[0003] Liquid crystal compounds can be used to orient liquid crystal molecules in a specified direction through shear forces during coating on a substrate and orientation-restricting forces of alignment films, resulting in aligned liquid crystal films with various optical anisotropies. For example, a parallel-aligned (horizontally aligned) liquid crystal layer in which nematic liquid crystal molecules with positive refractive index anisotropy are aligned parallel to the substrate surface can be used as a positive A-plate with refractive index anisotropy of nx > ny = nz.

[0004] In the case of using thermotropic liquid crystals, a solution containing a liquid crystal compound (liquid crystal composition) is coated onto a substrate, and the liquid crystal molecules are oriented by heating so that the compound contained in the composition is in a liquid crystal state. When the liquid crystal composition contains a photopolymerizable liquid crystal compound (liquid crystal monomer), after the liquid crystal molecules are oriented, the liquid crystal monomer is cured by irradiation with light, thereby fixing the orientation state.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2015-7700 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] Image display devices such as liquid crystal displays and organic EL displays require higher durability, demanding that the optical properties of the optical components constituting the image display device remain relatively stable even when exposed to high temperatures for extended periods. Patent Document 1 describes a method for reducing phase retardation changes in aligned liquid crystal films under high-temperature conditions by controlling the alignment parameters of the liquid crystal compound.

[0010] Not only the alignment state of the liquid crystal, but also the optical properties of the aligned liquid crystal film can sometimes change in high-temperature environments due to the influence of layers arranged adjacent to the liquid crystal layer. For example, when the parallel-aligned liquid crystal layer and the polarizer are bonded together via an adhesive layer (pressure-sensitive adhesive layer), almost no delay change occurs in high-temperature environments, while the sample in which the parallel-aligned liquid crystal layer and the polarizer are bonded together via an ultraviolet-curable adhesive shows a tendency for delay to increase in high-temperature environments.

[0011] In view of this problem, the object of the present invention is to provide an alignment liquid crystal film that exhibits minimal changes in optical properties and excellent heat resistance even when exposed to high-temperature environments for extended periods.

[0012] Methods for solving problems

[0013] 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 crystal composition containing photopolymerizable liquid crystal monomers onto a support substrate, heating the liquid crystal composition on the support substrate to orient the liquid crystal monomers in a liquid crystal state, and then polymerizing or crosslinking the liquid crystal monomers by light irradiation. In the oriented liquid crystal layer, the liquid crystal molecules can be horizontally oriented. The support substrate used to form the oriented liquid crystal layer can be a resin film.

[0014] The alignment liquid crystal film of the present invention includes a resin coating in contact with a first main surface of the alignment liquid crystal layer, and an optical layer bonded to the resin coating via an adhesive layer. Examples of optical layers bonded to the alignment liquid crystal layer include a polarizer and a transparent film. The optical layer may also be other alignment liquid crystal layers.

[0015] The alignment liquid crystal film can be a second main surface of the alignment liquid crystal layer to which other optical layers are bonded via an adhesive layer. Alternatively, a resin coating can be provided on the second main surface of the alignment liquid crystal layer.

[0016] In one embodiment, the alignment liquid crystal film can be a circular polarizer that includes a polarizer as an optical layer. In an alignment liquid crystal film formed by stacking an alignment liquid crystal layer in which liquid crystal molecules are aligned in parallel with a polarizer, the angle between the alignment direction of the liquid crystal molecules in the alignment liquid crystal layer and the absorption axis direction of the polarizer can be 10 to 80°.

[0017] In one embodiment of a circular polarizer, a resin coating is provided on one side (first main surface) of a parallel-aligned liquid crystal layer serving as a first alignment liquid crystal layer, and a vertically aligned liquid crystal layer serving as a second alignment liquid crystal layer is provided on the resin coating via an adhesive layer. A polarizer or polarizer is attached to the other side (second main surface) of the parallel-aligned liquid crystal layer. The parallel-aligned liquid crystal layer and the polarizer or polarizer can be attached via an adhesive layer in contact with the second main surface of the parallel-aligned liquid crystal layer.

[0018] The resin coating is preferably a non-curing resin layer. The weight-average molecular weight of the resin material constituting the resin coating is preferably 20,000 or more. Examples of resin materials for the resin coating include non-curing acrylic resins and non-curing epoxy resins. The glass transition temperature of the resin coating can be 20°C or higher. The thickness of the resin coating is preferably 0.05–3 μm. The resin coating may contain uncured liquid crystal compounds constituting the alignment liquid crystal layer.

[0019] A resin coating is formed by coating an alignment liquid crystal layer with a resin solution containing a resin and an organic solvent. The organic solvent in the resin solution is preferably a photocurable that is soluble in photopolymerizable liquid crystal monomers and does not dissolve or has difficulty dissolving photopolymerizable liquid crystal monomers. After coating the surface of the alignment liquid crystal layer with the resin solution, heating can be performed at 40–150°C before attaching the optical layer.

[0020] The thickness of the adhesive layer used to bond the resin coating and optical layer on the aligned liquid crystal layer is preferably 0.01–5 μm. The adhesive can be an active energy ray curable adhesive.

[0021] Invention Effects

[0022] The alignment liquid crystal film of the present invention exhibits excellent heat durability, with minimal change in delay even after prolonged exposure to high-temperature environments. Therefore, it is suitable for use as an optical component in image display devices such as liquid crystal displays and organic EL displays. Attached Figure Description

[0023] Figure 1 This is a cross-sectional view of an oriented liquid crystal film according to one embodiment.

[0024] Figure 2 This is a cross-sectional view of a laminate having an aligned liquid crystal layer on a support substrate.

[0025] Figure 3 This is an end view of a laminate in which a resin coating has been formed on an oriented liquid crystal layer.

[0026] Figure 4 This is a cross-sectional view of an oriented liquid crystal film according to one embodiment.

[0027] Figure 5This is a cross-sectional view of an oriented liquid crystal film with an adhesive layer.

[0028] Figure 6 This is a cross-sectional view of an oriented liquid crystal film according to one embodiment.

[0029] Figure 7 This is a cross-sectional view of an oriented liquid crystal film according to one embodiment.

[0030] Figure 8 This is a cross-sectional view of an oriented liquid crystal film according to one embodiment.

[0031] Figure 9 This is a cross-sectional view of an oriented liquid crystal film according to one embodiment.

[0032] Figure 10 This is a cross-sectional view illustrating an example of a stacked configuration of an image display device. Detailed Implementation

[0033] Figure 1 This is a cross-sectional view showing the structure of an alignment liquid crystal film according to one embodiment. The alignment liquid crystal film 100 includes a resin coating 6 that is in contact with one main surface of the alignment liquid crystal layer 1, and an optical layer 4 is attached to the resin coating 6 via an adhesive layer 3.

[0034] [Orientation liquid crystal layer]

[0035] The oriented liquid crystal layer 1 contains liquid crystal molecules oriented in a predetermined direction. For example, by coating a liquid crystal composition containing a liquid crystal compound onto a support substrate 8, oriented the liquid crystal compound in a predetermined direction, and fixing the orientation state, thereby achieving the desired effect. Figure 2 As shown, an alignment liquid crystal layer 1 is formed on the support substrate 8.

[0036] <Liquid Crystalline Composition>

[0037] Examples of liquid crystal compounds include rod-shaped and disc-shaped liquid crystal compounds. Rod-shaped liquid crystal compounds are preferred because they facilitate parallel alignment by utilizing the orientation-restricting force of the supporting substrate. Rod-shaped liquid crystal compounds can be either main-chain or side-chain liquid crystals. They can be liquid crystal polymers or polymers of polymerizable liquid crystal compounds. As long as the liquid crystal compound (monomer) exhibits liquid crystal properties before polymerization, it may not exhibit liquid crystal properties after polymerization.

[0038] The liquid crystal compound is preferably a thermotropic liquid crystal that exhibits liquid crystal properties upon heating. Thermotropic liquid crystals undergo phase transitions from a crystalline phase to a liquid crystal phase and then to an isotropic phase as the temperature changes. The liquid crystal compound included in the liquid crystal composition can be any of a nematic liquid crystal, a smectic liquid crystal, or a cholesterol-type liquid crystal. A chiral agent can be added to a nematic liquid crystal to impart cholesterol-type orientation.

[0039] Examples of thermotropic rod-shaped liquid crystal compounds include: azobenzene compounds, azo oxide compounds, cyanobiphenyl compounds, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexane compounds, cyano-substituted phenylpyrimidine compounds, alkoxy-substituted phenylpyrimidine compounds, phenyl dioxane compounds, diphenylacetylene compounds, and alkenylcyclohexylbenzonitrile compounds.

[0040] Examples of polymerizable liquid crystal compounds include: polymerizable liquid crystal compounds in which the orientation state of rod-shaped liquid crystal compounds can be fixed using polymer binders; and polymerizable liquid crystal compounds having polymerizable functional groups that can fix the orientation state of liquid crystal compounds through polymerization. Among these, photopolymerizable liquid crystal compounds having photopolymerizable functional groups are preferred.

[0041] The photopolymerizable liquid crystal compound (liquid crystal monomer) has a mesocrystalline 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.

[0042] Examples of mesocrystalline groups that can serve as monomers for liquid crystals include: biphenyl, phenylbenzoate, phenylcyclohexyl, azophenyl, azomethyl, azophenyl, phenylpyrimidinyl, diphenylethynyl, diphenylbenzoate, dicyclohexyl, cyclohexylphenyl, and terphenyl. These cyclic units may have substituents such as cyano, alkyl, alkoxy, or halogen groups at their ends.

[0043] Examples of photopolymerizable functional groups include (meth)acryloyl, epoxy, and vinyl ether groups. Among these, (meth)acryloyl is preferred. The photopolymerizable liquid crystal monomer preferably has two or more photopolymerizable functional groups per molecule. By using a liquid crystal monomer containing two or more photopolymerizable functional groups, a cross-linking structure is introduced into the photocured liquid crystal layer, thus tending to improve the durability of the oriented liquid crystal film.

[0044] As a photopolymerizable liquid crystal monomer, any suitable liquid crystal monomer can be used. Examples include International Patent Publication No. 00 / 37585, US Patent No. 5,211,877, US Patent No. 4,388,453, International Patent Publication No. 93 / 22397, European Patent No. 0261,712, German Patent No. 19,504,224, German Patent No. 4,408,171, British Patent No. 2,280,445, Japanese Patent Application Publication No. 2017-206460, International Patent Publication No. 2014 / 126,113, International Patent Publication No. 2016 / 114,348, International Patent Publication No. 2014 / 010325, and Japanese Patent Application Publication No. 2015- Compounds described in Japanese Patent Application Publication No. 200877, Japanese Patent Application Publication No. 2010-31223, International Patent Application Publication No. 2011 / 050896, Japanese Patent Application Publication No. 2011-207765, Japanese Patent Application Publication No. 2010-31223, Japanese Patent Application Publication No. 2010-270108, International Patent Application Publication No. 2008 / 119427, Japanese Patent Application Publication No. 2008-107767, Japanese Patent Application Publication No. 2008-273925, International Patent Application Publication No. 2016 / 125839, and Japanese Patent Application Publication No. 2008-273925, etc. By selecting the liquid crystal monomer, the manifestation of birefringence and the wavelength dispersion of retardation can also be adjusted.

[0045] In addition to liquid crystal monomers, liquid crystal compositions may also contain compounds that control the orientation of the liquid crystal monomers in a specific direction. For example, by including a side-chain type liquid crystal polymer in the liquid crystal composition, the liquid crystal compound (monomer) can be vertically oriented. Furthermore, by adding a chiral agent to the liquid crystal composition, the liquid crystal compound can be oriented in a cholesterol-type manner.

[0046] The liquid crystal composition may contain a photopolymerization initiator. When the liquid crystal monomer is cured by ultraviolet irradiation, the liquid crystal composition preferably contains a photopolymerization initiator (photoradical generator) that generates free radicals upon light irradiation to promote photocuring. Depending on the type of liquid crystal monomer (the type of photopolymerizable functional group), a photocation generator or a photoanion generator may be used. The amount of photopolymerization initiator used is approximately 0.01 to 10 parts by weight relative to 100 parts by weight of the liquid crystal monomer. In addition to the photopolymerization initiator, sensitizers, etc., may be used.

[0047] Liquid crystal compositions can be prepared by mixing liquid crystal monomers and various orientation control agents, polymerization initiators, etc., as needed, with solvents. The solvent is not particularly limited as long as it can dissolve the liquid crystal monomers and does not corrode the substrate (or has low corrosivity). Examples include: chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, o-dichlorobenzene, and other halogenated hydrocarbons; phenols such as phenol and p-chlorophenol; aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, and 1,2-dimethoxybenzene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, and 2-pyridine. Ketone solvents such as pyrrolidone and N-methyl-2-pyrrolidone; ester solvents such as ethyl acetate and butyl acetate; alcohol solvents such as tert-butanol, glycerol, 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; ethyl cellosolve and butyl cellosolve, etc. Mixed solvents containing two or more solvents may be used.

[0048] The solid content concentration of liquid crystal compositions is typically around 5–60% by weight. Liquid crystal compositions may contain additives such as surfactants and leveling agents.

[0049] <Support substrate>

[0050] Examples of support substrates 8 for coating liquid crystal compositions include glass plates, metal plates, metal strips, and resin film substrates. The support substrate has a first main surface and a second main surface, and the liquid crystal composition is coated on the first main surface.

[0051] By using a film substrate as the support substrate 8, a series of processes, including coating the liquid crystal composition onto the substrate onto the substrate, photocuring the liquid crystal monomers, and subsequent heat treatment, can be performed using a roll-to-roll method, thereby improving the productivity of aligned liquid crystal films. The resin material constituting the film substrate is not particularly limited, as long as it is insoluble in the solvent of the liquid crystal composition and has heat resistance for heating to align the liquid crystal composition. Examples 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 diacetylcellulose and triacetylcellulose; acrylic polymers; styrene polymers; polycarbonate, polyamide, and polyimide.

[0052] The support substrate 8 may have an orientation capability for orienting liquid crystal molecules in a predetermined direction. For example, by using a stretched film as the support substrate, liquid crystal molecules can be parallel-oriented along its stretching direction. The stretching ratio of the stretched film only needs to be sufficient to achieve the orientation capability, for example, about 1.1 to 5 times. The stretched film may be a biaxial stretched film. Even with a biaxial stretched film, if different stretching ratios are used in the longitudinal and transverse directions, liquid crystal molecules can be oriented along the direction with the larger stretching ratio. The stretched film may be an obliquely stretched film. By using a stretched film as the support substrate 8, liquid crystal molecules can be oriented in directions that are not parallel to either the longitudinal or transverse directions of the support substrate.

[0053] The support substrate 8 may have an alignment film on its first main surface. The alignment film can be appropriately selected based on the type of liquid crystal compound and the material of the substrate. As an alignment film used to align liquid crystal molecules in a specified direction, it is preferable to use an alignment film obtained by rubbing a polyimide-based or polyvinyl alcohol-based alignment film. Alternatively, a photo-alignment film can be used. Alternatively, the resin film serving as the support substrate can be rubbed without providing an alignment film.

[0054] The support substrate 8 may have an alignment film for vertically aligning liquid crystal molecules. Examples of alignment agents for forming the vertically aligned alignment film include lecithin, stearic acid, hexadecyltrimethylammonium bromide, octadecylamine hydrochloride, basic carboxylic acid chromium complex, silane coupling agents, siloxane compounds, organosilanes, perfluorodimethylcyclohexane, tetrafluoroethylene, and polytetrafluoroethylene.

[0055] <Forming of an alignment liquid crystal layer on a support substrate>

[0056] When the liquid crystal compound is a thermotropic liquid crystal, a liquid crystal composition is coated on the first main surface of the support substrate 8, and the liquid crystal compound is oriented in a liquid crystal state by heating.

[0057] There are no particular limitations on the method for coating the liquid crystal composition on the support substrate 8; methods such as spin coating, die coating, roller coating, gravure coating, reverse coating, spraying, wire rod coating, doctor blade coating, and air knife coating can be used. After coating the solution, the solvent is removed, thereby forming a liquid crystal composition layer on the support substrate. The coating thickness is preferably adjusted so that the thickness of the liquid crystal composition layer (the thickness of the alignment liquid crystal film) after the solvent dries is approximately 0.1 to 20 μm.

[0058] The liquid crystal compound is oriented by heating a liquid crystal composition layer formed on a support substrate to form a liquid crystal phase. Specifically, after coating the liquid crystal composition onto the support substrate, it is heated to above the N (nematic)-I (isotropic liquid phase) transition temperature of the liquid crystal composition to make it an isotropic liquid state. Thereafter, it is slowly cooled as needed to allow the nematic phase to emerge. At this time, it is desirable to maintain a temperature that temporarily reveals the liquid crystal phase, allowing the liquid crystal phase domain regions to grow into single-domain regions. Alternatively, after coating the liquid crystal composition onto the support substrate, the temperature can be maintained for a certain period within the nematic phase emergence temperature range to orient the liquid crystal molecules in a predetermined direction.

[0059] The heating temperature for aligning the liquid crystal compound in a specified direction can be appropriately selected based on the type of liquid crystal composition, typically ranging from 40 to 200°C. If the heating temperature is too low, the transition to the liquid crystal phase tends to be incomplete; if the heating temperature is too high, orientation defects may increase. The heating time can be adjusted to ensure sufficient growth of the liquid crystal phase domains, typically ranging from 30 seconds to 30 minutes.

[0060] Preferably, the liquid crystal compound is oriented by heating, followed by cooling to a temperature below the glass transition temperature. There are no particular limitations on the cooling method; for example, it can be removed from the heated atmosphere to room temperature. Forced cooling such as air cooling or water cooling can be used.

[0061] Photocuring occurs when the liquid crystal layer is irradiated with light, allowing the photopolymerizable liquid crystal compound (liquid crystal monomer) to exhibit liquid crystal regularity. The irradiation light only needs to polymerize the photopolymerizable liquid crystal compound; ultraviolet or visible light with wavelengths of 250–450 nm is typically used. If the liquid crystal composition contains a photopolymerization initiator, light of a wavelength to which the photopolymerization initiator is sensitive can be selected. As the irradiation light source, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, LEDs (Light Emitting Diodes), black lights, chemical lamps, etc., can be used. To promote the photocuring reaction, irradiation is preferably carried out in an atmosphere of inert gas such as nitrogen.

[0062] During the photocuring of the liquid crystal composition, the liquid crystal compound can be oriented in a predetermined direction by using polarized light of a predetermined direction. As described above, when the liquid crystal compound is oriented by the orientation limiting force of the support substrate 8, the irradiation light can be unpolarized light (natural light).

[0063] The irradiation intensity can be adjusted appropriately based on the composition of the liquid crystal composition and the amount of photopolymerization initiator added. The irradiation energy (cumulative irradiation light dose) is typically 20–10000 mJ / cm². 2Around 50 to 5000 mJ / cm² 2 More preferably 100–800 mJ / cm 2 To promote the photocuring reaction, light irradiation can be applied under heating conditions.

[0064] The polymer cured by photocuring liquid crystal monomers by light irradiation is non-liquid crystal and does not undergo phase transitions from liquid crystal to glass to crystalline phases caused by temperature changes. Therefore, liquid crystal layers cured by photocuring with liquid crystal monomers aligned in a specified direction are less prone to changes in molecular orientation due to temperature variations. Furthermore, since the birefringence of the aligned liquid crystal film is much higher than that of films containing non-liquid crystal materials, the thickness of optical anisotropic elements with the desired retardation can be significantly reduced. The thickness of the aligned liquid crystal film (liquid crystal layer) can be set only according to the target retardation value, and is typically around 0.1 to 20 μm, preferably 0.2 to 10 μm, and more preferably 0.5 to 7 μm.

[0065] The optical properties of the aligned liquid crystal layer are not particularly limited. The front retardation and thickness retardation of the aligned liquid crystal layer can be appropriately set according to the application, etc. When the liquid crystal is parallel aligned, the front retardation of the aligned liquid crystal layer is, for example, about 20 to 1000 nm. When the aligned liquid crystal layer is a quarter-wavelength sheet, the front retardation is preferably 100 to 180 nm, more preferably 120 to 150 nm. When the aligned liquid crystal layer is a half-wavelength sheet, the front retardation is preferably 200 to 340 nm, more preferably 240 to 300 nm.

[0066] Unless otherwise specified, the retardation value is a measurement at a wavelength of 550 nm. The front retardation R(450) of the aligned liquid crystal layer at a wavelength of 450 nm can be less than the front retardation R(550) at a wavelength of 550 nm. In addition to R(450) < R(550), the front retardation R(650) of the aligned liquid crystal layer at a wavelength of 650 nm is greater than R(550), and R(550) < R(650) can be satisfied. The R(450) / R(550) of the aligned liquid crystal layer can be 0.70 to 0.95, 0.75 to 0.90, or 0.80 to 0.87. The R(650) / R(550) of the aligned liquid crystal layer can be 1.05 to 1.30, 1.10 to 1.25, or 1.13 to 1.20. As described above, by selecting the liquid crystal monomers, it is possible to form an aligned liquid crystal layer with a desired wavelength dispersion in retardation.

[0067] When the liquid crystal is vertically aligned, the front-side delay of the aligned liquid crystal layer is approximately 0 (e.g., less than 5 nm, preferably less than 3 nm), and the absolute value of the thickness direction delay is approximately 30 to 500 nm.

[0068] [Resin Coating]

[0069] As mentioned above, since the photocured liquid crystal layer does not undergo a phase transition even when heated, it exhibits superior thermal stability compared to the uncured aligned liquid crystal layer. However, if the photocured liquid crystal layer is exposed to a high-temperature environment for an extended period, its optical properties may change, leaving room for improvement in heat durability. In particular, aligned liquid crystal films obtained by bonding other optical layers to parallel aligned liquid crystal layers with adhesives tend to exhibit delayed changes under prolonged heating, raising concerns about heat durability.

[0070] like Figure 3 As shown, by providing a resin coating 6 on the surface of the alignment liquid crystal layer 1, the thermal stability of the optical properties of the alignment liquid crystal layer can be expected to be improved. The resin coating 6 is formed by coating the surface of the alignment liquid crystal layer 1 with a resin solution containing resin and organic solvent.

[0071] <Resin Materials>

[0072] As the resin material for the resin coating 6, a non-curing resin is preferred. A non-curing resin refers to a material that can form a resin layer without undergoing a curing reaction such as photocuring or thermal curing after the resin solution is applied. The non-curing resin does not contain photocurable or thermally curable reactive groups, but may retain a small amount of reactive groups. For example, the reactive functional group equivalent (the mass of resin containing 1 equivalent of reactive functional groups) is preferably 3000 or more, more preferably 4000 or more, and may also be 5000 or more, or 6000 or more.

[0073] The preferred resin material has high transparency and minimal coloring. Examples of suitable resin materials include 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 due to their high adhesion to the alignment liquid crystal layer 1 and the adhesive layer 3.

[0074] The so-called "non-curing acrylic resin" is a polymer obtained by polymerizing the (meth)acryloyl groups of compounds (acrylic monomers) that have one or more (meth)acryloyl groups in one molecule. After coating the surface of the oriented liquid crystal layer 1 with a resin solution, a resin coating 6 can be formed without photocuring or heat curing. Non-curing acrylic resins are typically polymers of (meth)acrylate alkyl esters, such as polymethyl methacrylate, polyethyl methacrylate, and polybutyl methacrylate.

[0075] Non-curing acrylic resins can be copolymers of various alkyl (meth)acrylates, or copolymers of alkyl (meth)acrylates with other monomers.

[0076] Other monomers besides alkyl methacrylates include (meth)acrylic acid, (meth)acrylamide, (meth)acrylonitrile, vinyl monomers, and styrene monomers. Comonomers may contain boron-containing functional groups such as boric acid and borate esters.

[0077] The term "non-curing epoxy resin" refers to a polymer obtained by polymerizing the epoxy groups of a compound (epoxy monomer) having one or more epoxy groups in one molecule. After coating the surface of the alignment liquid crystal layer 1 with a resin solution, a resin coating 6 can be formed without photocuring or thermal curing. Among non-curing epoxy resins, epoxy resins having aromatic rings are preferred.

[0078] Two or more resin materials can be mixed. From the viewpoint of suppressing the increase of haze in the resin coating, it is preferable that the two or more resin materials are compatible. The resin material can be a mixture of non-curing acrylic resin and 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 can be 90:10 to 70:30 or 30:70 to 10:90.

[0079] The glass transition temperature of the resin material in the resin coating 6 is preferably 20°C or higher, more preferably 30°C or higher, and may also be 40°C or higher or 50°C or higher. Regarding polymer materials used for interlayer bonding, such as adhesives, the glass transition temperature is typically set below room temperature to ensure adhesion. On the other hand, the resin coating 6, which is disposed on the surface of the alignment liquid crystal layer, has a glass transition temperature higher than room temperature, resulting in minimal changes in properties under the operating environment of the image display device, and consequently, a tendency to suppress changes in the optical properties of the alignment liquid crystal layer. From the viewpoint of maintaining the film strength of the resin coating 6 without a curing reaction, the weight-average molecular weight of the resin material is preferably 20,000 or higher, more preferably 30,000 or higher.

[0080] (Formation of the resin layer)

[0081] The organic solvent used in the resin solution is not particularly limited as long as it can dissolve the aforementioned resin material. The organic solvent is preferably one that does not dissolve the alignment liquid crystal layer. For example, in the case of a photocurable material in which the alignment liquid crystal layer comprises photopolymerizable liquid crystal monomers, an organic solvent that is insoluble or difficult to dissolve the cured material is preferred. On the other hand, the organic solvent may be one that shows solubility in the liquid crystal compound (monomer) before photocuring. The organic solvent may be a single solvent or a mixture of two or more solvents.

[0082] The concentration of the solids in the resin solution can be adjusted within the range of about 1 to 50% by weight to achieve a viscosity suitable for coating. From the viewpoint of uniformly forming a thin resin coating, the concentration of the solids in 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.

[0083] The method for coating the resin solution onto the surface of the alignment liquid crystal layer 1 is not particularly limited, and various coating methods can be appropriately employed. After coating the resin solution, heating can be performed to remove the organic solvent. The heating temperature is preferably 40°C or higher, more preferably 50°C or higher. If the heating temperature is too high, the heating stability of the alignment liquid crystal film may decrease due to thermal damage to the substrate, realignment of the liquid crystal compound, etc. Therefore, the heating temperature is preferably 150°C or lower, more preferably 130°C or lower, and may be 110°C or lower or 100°C or lower.

[0084] The thickness of the resin coating 6 is not particularly limited, but from the viewpoints of thinness, adhesion, and transparency maintenance, it is preferably 3 μm or less, more preferably 2 μm or less, and can be 1 μm or less. On the other hand, from the viewpoint of encapsulating uncured monomers and the like from the dissolution of the alignment liquid crystal layer 1 into the resin coating 6 and suppressing exudation, the thickness of the resin coating 6 is preferably 0.05 μm or more, more preferably 0.1 μm or more.

[0085] The rationale for improving the heat resistance of aligned liquid crystal layers by applying a resin coating is still uncertain. However, it is believed that uncured monomers remaining in the photocured liquid crystal layer and free additives contained in areas where the three-dimensional network structure is not fully formed are dissolved by the organic solvent in the resin solution and absorbed into the resin coating. Therefore, removing substances from the aligned liquid crystal layer that cause delayed changes due to heating is considered one reason. Even if uncured substances in the aligned liquid crystal layer dissolve into the organic solvent, the absorption of the dissolved components into the resin coating prevents contamination and reduced transparency caused by precipitates on the surface of the aligned liquid crystal layer. It is also believed that liquid crystal reorientation and stabilization of the alignment state during heating to remove organic solvents also contribute to improving heat stability.

[0086] By laminating the resin coating 6 and the optical layer 4 disposed on the alignment liquid crystal layer 1 via the adhesive layer 3, a solution is obtained. Figure 1 The layered structure shown.

[0087] [Optical layer]

[0088] There are no particular limitations on optical layer 4; optically isotropic or optically anisotropic films commonly used as optical films can be used without special restrictions. Specific examples of optical layer 4 include transparent films such as phase retardation films and polarizer protective films, polarizers themselves, viewing angle widening films, viewing angle limiting (anti-spy) films, and brightness enhancement films. Optical layer 4 can be a single layer or a laminate. Optical layer 4 can be an aligned liquid crystal layer. For example, optical layer 4 can be a polarizer with a transparent protective film bonded to one or both sides of the polarizer. When the polarizer has a transparent protective film on one side, the polarizer can be bonded to the aligned liquid crystal layer, or the transparent protective film can be bonded to the aligned liquid crystal layer.

[0089] For example, in liquid crystal display devices, a phase retardation film, serving as an optical compensation film, is placed between the image display unit (liquid crystal unit) and the polarizer to appropriately change the polarization state of the light emitted from the liquid crystal unit to the viewing side, thereby improving viewing angle characteristics. In organic EL display devices, a quarter-wavelength plate is placed between the unit and the polarizer to suppress the reflection of external light on the metal electrode layer, thus creating a mirror-like appearance.

[0090] [Adhesive layer]

[0091] As described above, by providing a resin coating 6 on the surface of the alignment liquid crystal layer 1 and then bonding an 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.

[0092] The adhesive constituting the adhesive layer 3 only needs to be optically transparent, and its material is not particularly limited. Examples include epoxy resin, silicone resin, acrylic resin, polyurethane, polyamide, polyether, and polyvinyl alcohol. For the resin coating 6, a non-curing resin is used, while for the adhesive, a curing composition is used. The thickness of the adhesive layer 3 is appropriately set according to the type of substrate and the material of the adhesive. When using a curing adhesive that exhibits adhesion through a cross-linking reaction after coating, the thickness of the adhesive layer 3 is preferably 0.01–5 μm, more preferably 0.03–3 μm.

[0093] As an adhesive, various forms can be used, including water-based adhesives, solvent-based adhesives, hot-melt adhesives, and active energy radiation-cured adhesives. Among these, water-based adhesives or active energy radiation-cured adhesives are preferred from the perspective of reducing the thickness of the adhesive layer.

[0094] Examples of aqueous adhesives include those comprising water-soluble or water-dispersible polymers such as vinyl polymers, gelatin polymers, vinyl latex polymers, polyurethane polymers, isocyanate polymers, polyester polymers, and epoxy polymers. The adhesive layer formed by such an aqueous adhesive is created by coating an aqueous solution onto a film and allowing it to dry. When preparing the aqueous solution, crosslinking agents, other additives, and catalysts such as acids may be added as needed.

[0095] Crosslinking agents that can be mixed in water-based adhesives include: boric acid, borax; carboxylic acid compounds; alkyl diamines; isocyanates; epoxy resins; monoaldehydes; dialdehydes; amino-formaldehyde resins; salts of divalent or trivalent metals and their oxides, etc.

[0096] Active energy radiation-cured adhesives are adhesives that can undergo free radical polymerization, cationic polymerization, or anionic polymerization when irradiated by active energy rays such as electron beams or ultraviolet rays. Among them, photoradiatively free radical polymerizable adhesives that are initiated by ultraviolet irradiation are preferred, considering that curing can be performed with low energy.

[0097] Monomers for free 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: (meth)acrylic acid C... 1-20 Alkyl esters, cyclic alkyl esters, and polycyclic alkyl esters of methacrylate are examples of alkyl methacrylates; hydroxyl-containing methacrylates; glycidyl methacrylates and epoxy-containing methacrylates are also examples. Free radical polymerizable adhesives may contain nitrogen-containing monomers such as hydroxyethyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, (meth)acrylamide, and (meth)acryloylmorpholine. Free radical polymerizable adhesives may also contain multifunctional monomers such as tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecanediethanol diacrylate, cyclic trimethylolpropane formal acrylate, dioxanediol diacrylate, and EO (ethylene oxide) modified diglycerol tetraacrylate as crosslinking components.

[0098] Photopolymerizable adhesives, such as photoradical polymerizable adhesives, preferably contain a photopolymerization initiator. The photopolymerization initiator can be appropriately selected based on the reactants. For example, in free radical polymerizable adhesives, a photoradical generator that generates free radicals through light irradiation is preferably incorporated as the photopolymerization initiator. Specific examples of photoradical generators will be described below. The content of the photoradical generator is typically about 0.1 to 10 parts by weight relative to 100 parts by weight of the monomer, preferably 0.5 to 3 parts by weight. Furthermore, when the free radical polymerizable adhesive is used in an electron beam curing form, a photopolymerization initiator is not particularly necessary. In free radical polymerizable adhesives, photosensitizers, such as carbonyl compounds, may also be added as needed. Photosensitizers are used to improve the curing speed and sensitivity obtained using an electron beam. The amount of photosensitizer used is typically about 0.001 to 10 parts by weight relative to 100 parts by weight of the monomer, preferably 0.01 to 3 parts by weight.

[0099] Adhesives may contain appropriate additives as needed. Examples of additives include: silane coupling agents, titanium coupling agents, and other coupling agents; ethylene oxide and other adhesion promoters; UV absorbers; anti-aging agents; dyes; processing aids; ion scavengers; antioxidants; tackifiers; fillers; plasticizers; leveling agents; foaming inhibitors; antistatic agents; heat stabilizers; and hydrolysis stabilizers.

[0100] An adhesive is applied to either or both of the surfaces of the resin coating 6 and the optical layer 4 on the aligned liquid crystal layer 1, and then cured, thereby stacking the aligned liquid crystal layer 1 and the optical layer 4 via an adhesive layer 3. The curing of the adhesive can be appropriately selected based on the type of adhesive. For example, water-based adhesives can be cured by heating. Active energy ray-cured adhesives can be cured by irradiation with active energy rays such as ultraviolet light.

[0101] [Layering structure of alignment liquid crystal films]

[0102] An aligned liquid crystal film 103, formed by depositing a resin coating 6 on the surface of an aligned liquid crystal layer 1 on a support substrate 8 and bonding an optical layer 4 to the resin coating 6 via an adhesive layer 3, can be directly used as an optical component. In this case, the support substrate 8 constitutes a part of the aligned liquid crystal film 103. Figure 1 As shown in the alignment liquid crystal film 100, the support substrate can be peeled off from the alignment liquid crystal layer 1. On the surface of the alignment liquid crystal layer 1 exposed by peeling off the support substrate, as... Figure 5 Lay the appropriate adhesive layer 2 as shown.

[0103] exist Figure 5In the manner shown, the adhesive layer 2 is stacked on the exposed surface of the alignment liquid crystal layer 1 (the substrate surface when the alignment liquid crystal layer is formed) after the support substrate 8 is peeled off. However, the alignment liquid crystal film can also be stacked on the air surface side when the alignment liquid crystal layer is formed, and the optical layer is bonded on the substrate surface side of the alignment liquid crystal layer via a resin coating and an adhesive layer.

[0104] There are no particular limitations on the adhesive constituting adhesive layer 2; it is permissible to select base polymers such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluoropolymers, and rubber polymers. Acrylic adhesives and rubber adhesives are particularly preferred, exhibiting excellent transparency, moderate wetting, coagulation, and adhesion, as well as excellent weather resistance and heat resistance. The thickness of the adhesive layer is appropriately set according to the type of substrate being adhered, generally ranging from 5 to 500 μm.

[0105] The adhesive layer 2 on the alignment liquid crystal layer 1 is laminated, for example, by attaching a pre-formed sheet-like adhesive to the surface of the alignment liquid crystal layer 1. After applying the adhesive composition to the alignment liquid crystal layer 1, solvent drying, crosslinking, photocuring, etc., can be performed to form the adhesive layer 2. To improve the adhesion (holding force) between the alignment liquid crystal layer 1 and the adhesive layer 2, surface treatments such as corona treatment and plasma treatment can be performed on the surface of the alignment liquid crystal layer 1 to form an easy-to-adhere layer before laminating the adhesive layer 2.

[0106] Preferably, the partition 9 is temporarily bonded to the surface of the adhesive layer 2. The partition 9 protects the surface of the adhesive layer 2 until the optical film with adhesive is adhered to the image display unit 50. As the constituent material of the partition, acrylic resin, polyolefin, cyclic polyolefin, polyester, and other plastic films are preferably used. The thickness of the partition is typically about 5 to 200 μm. It is preferable to perform a release treatment on the surface of the partition. Examples of release agents include silicone-based materials, fluorine-based materials, long-chain alkyl-based materials, and fatty amide-based materials.

[0107] Other optical layers can be laminated onto the exposed surface of the aligned liquid crystal layer 1 after the support substrate 8 has been peeled off, via a suitable adhesive layer or bonding agent layer. For example, such as Figure 6 As shown, other optical layers 5 can be stacked on the oriented liquid crystal layer 1 via a suitable adhesive layer 7. An adhesive layer (not shown) can then be stacked on the optical layer 5, and a spacer can be temporarily adhered to the surface of the adhesive layer.

[0108] Alternatively, the support substrate 8 can be peeled off from the alignment liquid crystal layer 1, and a resin solution can 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 16. For example... Figure 7 As shown, the optical layer 5 can be bonded to the resin coating 16 exposed on the surface of the alignment liquid crystal layer 1 by peeling off the support substrate via the adhesive layer 7.

[0109] exist Figure 7 In this process, resin coatings 6 and 16 are provided on both sides of the alignment liquid crystal layer 1, but the resin coating may also be provided on only one side of the alignment liquid crystal layer 1. In the laminate 101 formed by tightly stacking the alignment liquid crystal layer 1 on the support substrate 8, the surface of the alignment liquid crystal layer 1 (the air surface during the formation of the alignment liquid crystal layer) may not have a resin coating formed, but other layers may be bonded together via an adhesive layer and a bonding agent layer. After the support substrate 8 is peeled off from the alignment liquid crystal layer 1, the resin coating 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).

[0110] <Circular Polarizer>

[0111] Alignment liquid crystal films can be used as optical films for displays for purposes such as improving visibility. For example, in liquid crystal display devices, there are cases where, in order to appropriately change the polarization state of light emitted from the liquid crystal cell to the viewing side to improve viewing angle characteristics, a phase retardation film as an optical compensation film is disposed between the image display unit (liquid crystal cell) and the polarizer.

[0112] In one embodiment, the alignment liquid crystal film is a circular polarizer formed by bonding a polarizer as an optical layer 4 to the resin coating 6 forming surface on the alignment liquid crystal layer 1 via an adhesive layer 3. The circular polarizer may have two or more alignment liquid crystal layers.

[0113] Polarizing films can be formed from a single polarizer layer, and as mentioned above, a transparent protective film can be attached to one or both sides of the polarizer. Examples of polarizers include: those obtained by uniaxially stretching hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films after adsorbing dichroic substances such as iodine and dichroic dyes; and polyene-based oriented films such as dehydrated polyvinyl alcohol products and dehydrochlorinated polyvinyl chloride products.

[0114] Among these, a preferred polarizer, based on high polarization, is a polyvinyl alcohol (PVA)-based polarizer that orients itself in a specified direction by adsorbing iodine and dichroic dyes onto a polyvinyl alcohol film, such as a partially formalized polyvinyl alcohol film. For example, a PVA-based polarizer can be obtained by iodizing and stretching a polyvinyl alcohol film. A PVA-based resin layer can be formed on a resin substrate, and iodine staining and stretching can be performed in a laminated state.

[0115] In a circular polarizer consisting of a polarizer and an aligned liquid crystal layer, preferably at least one aligned liquid crystal layer has its liquid crystal molecules aligned in parallel. In the circular polarizer, the orientation direction of the liquid crystal molecules in the aligned liquid crystal layer, where the liquid crystal molecules are aligned in parallel, is arranged in a manner that is neither parallel nor orthogonal to the absorption axis direction of the polarizer.

[0116] For example, when the circular polarizer has only one oriented liquid crystal layer, the oriented liquid crystal layer 1 is a 1 / 4 wavelength plate, and the angle between the absorption axis of the polarizer and the orientation direction of the liquid crystal molecules (generally the hysteresis axis) is set to 45°. The angle between the absorption axis of the polarizer and the orientation direction of the liquid crystal molecules can be 35-55°, 40-50°, or 43-47°.

[0117] In a configuration where the polarizer 4 and the oriented liquid crystal layer 1, which serves as a quarter-wavelength plate, are stacked at a 45° angle between their optical axes, an oriented liquid crystal layer 5, in which the liquid crystal molecules are vertically aligned with respect to the substrate surface, can be included as an optical layer. By sequentially stacking the oriented liquid crystal layer 1, which serves as a quarter-wavelength plate, and the vertically oriented liquid crystal layer 5, which functions as a positive C-plate, on the polarizer, a circular polarizer that can block reflected light even from external light coming from an inclined direction can be formed. A vertically oriented liquid crystal layer (positive C-plate) and a parallel-oriented liquid crystal layer (a quarter-wavelength plate serving as a positive A-plate) can be sequentially stacked on the polarizer.

[0118] like Figure 6 , 7 As shown, in a circular polarizer consisting of a polarizer 4 as an optical layer and multiple aligned liquid crystal layers 1 and 5 stacked together, both aligned liquid crystal layers 1 and 5 can be parallel aligned liquid crystal layers. In this case, it is preferable that the aligned liquid crystal layer 1 disposed near the polarizer 4 is a half-wavelength layer, and the aligned liquid crystal layer 5 disposed away from the polarizer is a quarter-wavelength layer. In this stacked configuration, it is preferable that the angle between the hysteresis axis direction of the half-wavelength layer and the absorption axis direction of the polarizer is 75°±5°, and the angle between the hysteresis axis direction of the quarter-wavelength layer and the absorption axis direction of the polarizer is 15°±5°. This stacked configuration of the circular polarizer functions as a circular polarizer over a wide wavelength range of visible light, thus reducing the coloration of reflected light.

[0119] like Figure 8 As shown, a circular polarizer formed by stacking multiple alignment liquid crystal layers 1 and 5 on polarizer 4 can also be configured as follows: a resin coating 6 is disposed between alignment liquid crystal layer 1 and alignment liquid crystal layer 5, and no resin coating is present between alignment liquid crystal layer 1 and polarizer 4. For example, as... Figure 3 As shown, after a resin coating 6 is formed on the surface of the alignment liquid crystal layer 1, the alignment liquid crystal layer 5 is bonded to the resin coating 6 via an adhesive layer 7, thereby achieving the desired effect. Figure 9As shown, a laminate (aligned liquid crystal film) 113 is obtained by bonding the aligned liquid crystal layer 1 to the resin coating 6 forming surface of the aligned liquid crystal layer 1 via an adhesive layer 7. By peeling the support substrate 8 from the laminate, a polarizer 4 is bonded to the aligned liquid crystal layer 1 exposed by the peeling of the support substrate via an adhesive layer 12, thereby achieving the desired effect. Figure 8 The resulting laminate 107 has a resin coating 6 on one side of the alignment liquid crystal layer 1, an alignment liquid crystal layer 5 stacked thereon via an adhesive layer 7, and a polarizer 4 attached to the other side of the alignment liquid crystal layer 1 via an adhesive layer 12.

[0120] In one embodiment of the laminate 107, the alignment liquid crystal layer 1 disposed on the side near the polarizer 4 is a parallel alignment liquid crystal layer serving as a quarter-wavelength plate, and the alignment liquid crystal layer 5 disposed on the side away from the polarizer 4 is a vertical alignment liquid crystal layer serving as a positive C-plate. In this embodiment, the alignment liquid crystal layer 5 is bonded to the resin coating forming surface 6 of the alignment liquid crystal layer 1 via an adhesive layer 7.

[0121] The adhesive layer 7 is formed by curing the adhesive, which is a curable material. Since a non-curable resin coating 6 is formed on the alignment liquid crystal layer 1, changes in the frontal delay of the alignment liquid crystal layer 1 caused by heating are suppressed. Although no resin coating is provided on the bonding surface between the alignment liquid crystal layer 1 and the polarizer 4, the alignment liquid crystal layer 1 and the polarizer 4 are bonded together via the adhesive layer 12 (a non-curable material). Therefore, it is difficult to produce the reduction in heat durability seen when the adhesive layer is formed directly on the alignment liquid crystal layer.

[0122] In this way, Figure 8 The laminate 107 shown has the following configuration: a non-curable resin coating 6 is provided on the parallel alignment liquid crystal layer 1, and an alignment liquid crystal layer 5 serving 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 frontal retardation is small, making it suitable for use as a circular polarizer in liquid crystal display devices, organic EL display devices, etc. Furthermore, in the laminate 107, the alignment liquid crystal layer 5 serving as the positive C-plate is in contact with the adhesive layer 7, but the frontal retardation of the positive C-plate is approximately 0. Therefore, even when the laminate 107 is exposed to a high-temperature environment for a long time, almost no change in frontal retardation occurs.

[0123] [Image display device]

[0124] Figure 10 This is a cross-sectional view showing an example of the stacked configuration of an image display device. An alignment liquid crystal film having an alignment liquid crystal layer 1 is bonded to the surface of the image display unit 50 via an adhesive layer 2. The alignment liquid crystal film may have two or more alignment liquid crystal layers. Examples of image display units 50 include liquid crystal units and organic EL units.

[0125] As described above, the alignment liquid crystal film improves the heat durability of the alignment liquid crystal layer by providing a resin coating on its surface. Image display devices equipped with an alignment liquid crystal layer having a resin coating formed on its surface exhibit minimal changes in the delay of the alignment liquid crystal layer even after prolonged exposure to a heated environment, resulting in minimal changes in visibility and excellent heat durability.

[0126] [Example]

[0127] The following examples of the fabrication of alignment liquid crystal films will be used to further illustrate the present invention in detail, but the present invention is not limited to the examples described below.

[0128] Fabrication of parallel-aligned liquid crystal films

[0129] <Comparative Example 1>

[0130] A photopolymerizable liquid crystal compound (Paliocolor LC242 manufactured by BASF) displaying a nematic liquid crystal phase was dissolved in cyclopentanone to prepare a solution with a solid content concentration of 30% by weight. A surfactant (BYK-360 manufactured by BYK-Chemie) and a photopolymerization initiator (Omnirad 907 manufactured by IGM Resins) were added to this solution to prepare a liquid crystal composition solution. The amount of leveling agent and polymerization initiator added was set to 0.01 parts by weight and 3 parts by weight, respectively, relative to 100 parts by weight of the photopolymerizable liquid crystal compound.

[0131] A biaxially stretched norbornene film (Zeonor Film manufactured by Zeon, Japan, thickness: 33 μm, front retardation: 135 nm) was used as the film substrate. The aforementioned liquid crystal composition was coated onto the surface of the film substrate using a bar coater to a dry thickness of 1 μm. The liquid crystals were then oriented by heating at 100°C for 3 minutes. After cooling to room temperature, the cumulative light intensity was 400 mJ / cm² under a nitrogen atmosphere. 2 UV light is used for photocuring to obtain a laminate with parallel-aligned liquid crystal layers formed on the film substrate.

[0132] <Examples 1-6>

[0133] A resin solution was prepared by dissolving the resins shown in Table 1 in a mixed solvent of cyclopentanone and ethyl acetate to a solids concentration of 3% by weight. The resin solution was then applied to the surface of the alignment liquid crystal layer of the laminate in Comparative Example 1 using a wire rod (#10), and the solvent was removed by heating at 85°C, thus forming a resin coating on the surface of the alignment liquid crystal layer. It should be noted that in Table 1, the acrylic resins of Examples 1-3 were obtained from Kusunoki Chemical, and the epoxy resins of Examples 4-6 and Comparative Example 3 were obtained from Mitsubishi Chemical.

[0134] <Comparative Example 2>

[0135] After coating the surface of the alignment liquid crystal layer of the laminate of Comparative Example 1 with cyclopentanone using a wire rod (#10), the solvent was removed by heating at 85°C for 1 minute.

[0136] <Comparative Example 3>

[0137] In a mixed solvent of cyclopentanone and ethyl acetate, a bisphenol A type epoxy resin (Mitsubishi Chemical's "jER828") with an epoxy equivalent of approximately 190 and a photocationic polymerization initiator (SAN-APRO's "CPI100P") were dissolved to achieve an epoxy resin concentration of 3% by weight, thus preparing a photocurable resin composition (solution). The composition was coated onto the surface of the alignment liquid crystal layer of the laminate of Comparative Example 1 using a wire rod (#10), heated at 85°C to remove the solvent, and then irradiated with ultraviolet light to photocur the epoxy resin.

[0138] Fabrication of a polarizer (circular polarizer) with an aligned liquid crystal layer

[0139] A laminate (single protective polarizer) is prepared by attaching a 5μm thick PVA polarizer to one side of an unstretched norbornene film (Zeonor Film manufactured by Japan) with a 20μm thick film using a UV-curable adhesive.

[0140] 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 acryloylmorpholine (ACMO, manufactured by Kojin), 7 parts by weight of PEG400# diacrylate (Light Acrylate 9EG-A, manufactured by Kyoeisha Chemical), 3 parts by weight of photopolymerization initiator (Omnirad 907, manufactured by IGM Resins), and 3 parts by weight of 2,4-diethylthioxanthone (Kayacure DETX-S, manufactured by Nippon Kayaku). An adhesive composition of approximately 1 μm thickness was coated onto the surface of the aforementioned single-protected polarizer. After attaching the alignment liquid crystal layer side of the laminates of Examples 1-6 and Comparative Examples 1-3 to the adhesive coating layer, a cumulative light intensity of 1000 mJ / cm² was irradiated. 2 The ultraviolet light cures the adhesive. During bonding, the angle between the absorption axis of the polarizer and the orientation direction of the liquid crystal molecules in the alignment liquid crystal layer (the hysteresis axis of the film substrate) is 45°.

[0141] The film substrate is peeled off from the alignment liquid crystal film, and an acrylic adhesive sheet with a thickness of 15 μm is bonded to the surface of the alignment liquid crystal film. The alignment liquid crystal layer is then bonded to the polarizer of the single protective polarizer via a UV-curable adhesive layer to obtain a polarizer with an acrylic adhesive sheet on it.

[0142] In Examples 1-6 and Comparative Example 3, a resin layer with a thickness of about 300 nm was formed between the adhesive layer and the alignment liquid crystal layer.

[0143] [evaluate]

[0144] <Appearance>

[0145] After visually inspecting the film surface after the resin coating was formed (Comparative Example 2 was after surface treatment with cyclopentanone), cases where no precipitates were found were marked as OK, and cases where precipitates were found were marked as NG.

[0146] <Delayed Changes>

[0147] The adhesive layer of the polarizer was bonded to a glass plate to prepare the evaluation sample. The frontal retardation at 590 nm was measured using a phase difference meter (KOBRA 21-ADH manufactured by Oji Ketsuki). The evaluation sample was then placed in an air-circulating constant-temperature oven at 85°C for 120 hours. After removing the sample from the oven, the frontal retardation was measured again, and the rate of change of retardation before and after the heating test was calculated.

[0148] <Hue Changes>

[0149] An evaluation sample was prepared by bonding the adhesive layer of the polarizer to Corning Gorilla Glass. An aluminum vapor-deposited polyester film (Toray Advanced Films "DMS-X42") was placed under the alkali-free glass of the evaluation sample. Light was irradiated from the polarizer side using a spectrophotometer (Konica Minolta "CM-2600d"), and the hue of the reflected light (a in the Lab color space) was measured using the SCI method. * and b * The value of the test sample was then placed in an air-circulating constant-temperature oven at 85°C for 120 hours. After removing the sample from the oven, the hue of the reflected light was measured again on the aluminum vapor-deposited polyester film, and the change in hue of the reflected light before and after the heating test was calculated as √{(Δa)}. ＊ ) 2 +(Δb ＊ ) 2}

[0150] The evaluation results of the types of resins used to form resin coatings and the orientation liquid crystal films in Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 1.

[0151] [Table 1]

[0152]

[0153] In Comparative Example 1, where no surface treatment of the alignment liquid crystal layer was performed, 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 the accompanying hue change of the reflected light was also suppressed. However, in Comparative Example 2, precipitates were found on the surface of the alignment liquid crystal layer, resulting in poor appearance.

[0154] In Examples 1-6, where a resin coating was formed on an alignment 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 better. The resin coating surface of Example 1 was dissolved in tetrahydrofuran to extract the resin components, and analysis by MALDI-TOF mass spectrometry confirmed the presence of unreacted liquid crystal monomers. These results suggest that by coating with a resin solution, uncured substances and the like in the alignment liquid crystal layer can be extracted and incorporated into the resin coating, which helps improve the heat resistance of the alignment liquid crystal layer.

[0155] In Comparative Example 3, where a photocationically curable resin composition was applied to an alignment liquid crystal layer and then UV-cured, the front Re value decreased after a heat durability test, indicating insufficient heat durability. These results demonstrate that by forming a non-curable resin coating on the alignment liquid crystal layer, the heat durability of the alignment liquid crystal layer can be improved, resulting in a circular polarizer with minimal retardation, light reflection, and color variation.

[0156] [Example of fabrication of a circular polarizer with multiple aligned liquid crystal layers]

[0157] <Fabrication of Parallel Alignment Liquid Crystal Layers>

[0158] 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 and stirred to dissolve it. After cooling to room temperature, a solution with a solid content of 20% by weight was prepared.

[0159] [Chemical Formula Number 1]

[0160]

[0161] A liquid crystal composition solution was prepared by adding 0.2 parts by weight of surfactant (DIC "MEGAFAC F-554"), 3 parts by weight of photopolymerization initiator (IGM Resins "Omnirad 907"), and 0.1 parts by weight of p-methoxyphenol to the solution.

[0162] As the membrane substrate, a membrane with a milled alignment film on a triacetyl cellulose membrane was used. The aforementioned liquid crystal composition was spin-coated onto the alignment film of the membrane substrate, and the liquid crystal was aligned by heating at 100°C for 2 minutes. After cooling to room temperature, the cumulative light intensity was irradiated under a nitrogen atmosphere to a value of 900 mJ / cm². 2 UV curing was performed to obtain a laminate A with a parallel-aligned liquid crystal layer (4 μm thick) formed on the film substrate. The aligned liquid crystal layer was transferred onto a glass plate, and the front retardation was measured. The results showed that the front retardation R(550) at a wavelength of 550 nm was 130 nm, and the ratio of the front retardation R(550) at a wavelength of 550 nm to that at a wavelength of 450 nm, R(450) / R(550), was 0.85.

[0163] <Fabrication of Vertically Aligned Liquid Crystal Layer>

[0164] A liquid crystal composition was prepared by dissolving 20 parts by weight of a side-chain liquid crystal polymer with a weight average molecular weight of 5000 (n = 0.35, for convenience, it is represented by a block polymer body), 80 parts by weight of a polymerizable liquid crystal compound (BASF's "Paliocolor LC242") displaying a nematic liquid crystal phase, and 5 parts by weight of a photopolymerization initiator (IGM Resins' "Omnirad 907") in 400 parts by weight of cyclopentanone.

[0165] [Chemical Formula Number 2]

[0166]

[0167] As the film substrate, a biaxially stretched norbornene film (ZEONOA film manufactured by Zeon Corporation, Japan, thickness: 52 μm, front retardation: 50 nm) was used. The aforementioned liquid crystal composition was coated onto the surface of the film substrate using a bar coater to a dry thickness of 1 μm. The coating was heated at 80°C for 2 minutes, cooled to room temperature for liquid crystal alignment, and then irradiated under a nitrogen atmosphere at 700 mJ / cm². 2 Ultraviolet light is used to photocur the liquid crystal monomers, resulting in a laminate B in which a vertically oriented liquid crystal layer is formed on the film substrate.

[0168] <Making Adhesive Sheets>

[0169] 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, 0.1 parts by weight of 2-hydroxyethyl acrylate, and 0.1 parts by weight of 2,2'-azobisisobutyronitrile (2,2'-azobisisobutyronitrile) as polymerization initiators were added together with ethyl acetate, and the reaction was carried out at 55°C for 8 hours under a nitrogen atmosphere. Then, 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. In this solution, relative to 100 parts by weight of the polymer, 0.15 parts by weight of benzoyl peroxide (NYPER BMT, manufactured by Nippon Yushi) as a crosslinking agent and 0.6 parts by weight of trimethylolpropane / toluene diisocyanate adduct (Coronate L, manufactured by Tosoh) were added to obtain an adhesive composition. The adhesive composition was applied to the release surface of a release film (a silicone-treated polyethylene terephthalate film), and dried and crosslinked at 150°C to produce an adhesive sheet with a thickness of 5 μm.

[0170] <Example 7>

[0171] An acrylic polymer with a weight average molecular weight of 80,000, obtained by copolymerizing methyl methacrylate and 3-methacryloylaminophenylboronic acid in a weight ratio of 97:3, was dissolved in ethyl acetate to achieve a solids concentration of 3% by weight, thus preparing a resin solution. The resin solution was then applied to the surface of the parallel-aligned liquid crystal layer of laminate A using a wire rod (#10), followed by heating at 85°C to remove the solvent, forming a resin coating approximately 300 nm thick on the surface of the parallel-aligned liquid crystal layer. This resulted in laminate D, which sequentially has a parallel-aligned liquid crystal layer and a resin coating on a film substrate.

[0172] The aforementioned UV-curable adhesive is applied to the resin coating of laminate D with a thickness of approximately 1 μm. After the vertically aligned liquid crystal layer side of laminate B is attached to the adhesive coating layer, it is irradiated with a cumulative light intensity of 1000 mJ / cm². 2 The ultraviolet light causes the adhesive to cure.

[0173] Next, the film substrate is peeled off from the surface of the parallel-aligned liquid crystal layer, and the polarizer side of the single protective polarizer is bonded to the exposed parallel-aligned liquid crystal layer via the aforementioned adhesive layer. During bonding, the angle between the absorption axis direction of the polarizer and the alignment direction of the liquid crystal molecules in the parallel-aligned liquid crystal layer (the friction direction of the alignment film of the film substrate) is 45°. Then, the film substrate is peeled off from the surface of the vertically aligned liquid crystal layer, and the parallel-aligned liquid crystal layer is bonded to the polarizer side of the single protective polarizer via an adhesive layer, resulting in a laminate (circular polarizer) on which the vertically aligned liquid crystal layer is bonded via a resin coating and an adhesive layer.

[0174] <Comparative Example 4>

[0175] Similar to Example 7, a resin coating with a thickness of approximately 300 nm was formed on the surface of the parallel-aligned liquid crystal layer to obtain a laminate D. The polarizer side of the single protective polarizer was then bonded to the resin coating of laminate D via the aforementioned adhesive layer. During bonding, the angle between the absorption axis direction of the polarizer and the alignment direction of the liquid crystal molecules in the parallel-aligned liquid crystal layer (the friction direction of the alignment film of the film substrate) was set to 45°.

[0176] Then, the film substrate is peeled off from the surface of the parallel-aligned liquid crystal layer. On the exposed parallel-aligned liquid crystal layer, the aforementioned UV-curable adhesive is applied to a thickness of approximately 1 μm. After attaching the vertically aligned liquid crystal layer side of the laminate B to the adhesive coating layer, it is irradiated with a cumulative light intensity of 1000 mJ / cm². 2 The adhesive is cured by ultraviolet light. Then, the film substrate is peeled off from the surface of the vertically aligned liquid crystal layer, and a laminate of the resin coating and the parallel aligned liquid crystal layer is bonded to the polarizer side of the single protective polarizer via an adhesive layer, resulting in a laminate (circular polarizer) formed by bonding the vertically aligned liquid crystal layer to the parallel aligned liquid crystal layer via an adhesive layer.

[0177] <Example 8>

[0178] Instead of the acrylic polymer solution, a methyl ethyl ketone solution containing an acrylic polymer and an epoxy resin (Mitsubishi Chemical "jER YX7200B35") at a weight ratio of 85:15 with a solid content concentration of 3% by weight was used. In addition, following the same procedure as in Example 7, a resin coating with a thickness of approximately 300 nm was formed on the surface of the parallel-aligned liquid crystal layer. Then, following the same procedure as in Example 7, the parallel-aligned liquid crystal layer was bonded to the polarizer side of the single protective polarizer via an adhesive layer, resulting in a laminate (circular polarizer) on which a vertically aligned liquid crystal layer was bonded via a resin coating and an adhesive layer.

[0179] <Example 9>

[0180] Except that the thickness of the resin coating was changed to about 600 nm, a circular polarizer was fabricated in the same manner as in Example 8.

[0181] <Comparative Example 5>

[0182] Similar to Example 8, a resin coating with a thickness of approximately 300 nm was formed on the surface of the parallel-aligned liquid crystal layer using a mixed resin solution of acrylic polymer and epoxy resin. Then, similar to Comparative Example 4, a laminate of the resin coating and the parallel-aligned liquid crystal layer was bonded together via an adhesive layer on the polarizer side of the single protective polarizer, resulting in a laminate (circular polarizer) formed by bonding a vertically aligned liquid crystal layer to the parallel-aligned liquid crystal layer via an adhesive layer.

[0183] [evaluate]

[0184] An acrylic adhesive sheet with a thickness of 15 μm was bonded to the vertically aligned liquid crystal layer side of the circular polarizers in Examples 7-9 and Comparative Examples 4 and 5. The adhesive sheet was then bonded to a glass plate to prepare an evaluation sample. After measuring the frontal retardation (initial value) at a wavelength of 590 nm using a phase difference meter (KOBRA 21-ADH manufactured by Oji Mechatronics), the evaluation sample was placed in an air-circulating constant temperature oven at 85°C. The frontal retardation was measured after 120 hours, 240 hours, and 500 hours, and the rate of change from the initial value was calculated.

[0185] Table 2 shows the stacking structure of the circular polarizers in Examples 7-9 and Comparative Examples 4 and 5, the polymer type and thickness of the resin coating, and the rate of change of frontal delay in the heat durability test (after 120 hours, after 240 hours and after 500 hours).

[0186] [Table 2]

[0187]

[0188] In Comparative Examples 4 and 5, where an adhesive layer is provided in contact with the parallel alignment layer and a vertically aligned liquid crystal layer is bonded thereon, a reduction of more than 1% in frontal delay was observed after a 120-hour heating test. In Examples 7 to 9, where a resin coating is provided on the parallel alignment liquid crystal layer and a vertically aligned liquid crystal layer is bonded thereon via an adhesive layer, changes in frontal delay caused by the heating durability test were suppressed.

[0189] These results show that by setting the resin coating in a manner where the parallel-aligned liquid crystal layer and the cured adhesive layer do not contact each other, the heat durability of the aligned liquid crystal layer is improved, and the delay change is suppressed. A comparison of Examples 8 and 9 shows that a larger resin coating thickness tends to improve heat durability (suppress the delay change).

[0190] [Explanation of the labels in the attached diagram]

[0191] 1. Alignment liquid crystal layer

[0192] 6. Resin coating

[0193] 8 Support base plate

[0194] 4. Optical layer (polarizer)

[0195] 5. Optical layer (alignment liquid crystal layer)

[0196] 3, 7 Adhesive layers

[0197] 2,12 Adhesive layer

[0198] 9 partitions

[0199] 50 Image display units.

Claims

1. An oriented liquid crystal film comprising: a first oriented liquid crystal layer in which liquid crystal molecules are oriented; a resin coating in contact with a first main surface of the first oriented liquid crystal layer; and an optical layer bonded to the resin coating via an adhesive layer, wherein, The first oriented liquid crystal layer is a parallel-oriented liquid crystal layer in which the liquid crystal molecules are aligned in parallel. The resin coating is a resin coating containing acrylic resin or epoxy resin with a weight average molecular weight of 20,000 or more. The acrylic resin or epoxy resin satisfies either (1) or (2) below: (1) It does not contain photocurable or thermocurable reactive groups; (2) The functional group equivalent of the photocurable or thermocurable reactive groups is 3000 or more.

2. The alignment liquid crystal film according to claim 1, wherein, The glass transition temperature of the resin coating is above 20°C.

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

4. The alignment liquid crystal film according to claim 1 or 2, wherein, The adhesive that constitutes the adhesive layer is an active energy radiation-cured adhesive.

5. The alignment liquid crystal film according to claim 1 or 2, wherein, The optical layer is a polarizer, a transparent film, or other oriented liquid crystal layer.

6. The alignment liquid crystal film according to claim 1 or 2, wherein, The thickness of the resin coating is 0.05 to 3 μm.

7. The alignment liquid crystal film according to claim 1 or 2, wherein, The resin coating contains uncured liquid crystal compounds that constitute the first oriented liquid crystal layer.

8. The alignment liquid crystal film according to claim 1 or 2, wherein, An adhesive layer is provided on the second main surface side of the first oriented liquid crystal layer.

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

10. The alignment liquid crystal film according to claim 1 or 9, wherein, The optical layer is a second oriented liquid crystal layer in which the liquid crystal molecules are vertically oriented, and a polarizer is attached to the second main surface side of the first oriented liquid crystal layer.

11. The alignment liquid crystal film according to claim 10, wherein, The first oriented liquid crystal layer is bonded to the polarizer via an adhesive layer.

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

13. An image display device comprising an image display unit having an oriented liquid crystal film as described in any one of claims 1 to 12 disposed thereon.

14. A method for manufacturing an aligned liquid crystal film, which is the method for manufacturing the aligned liquid crystal film according to any one of claims 1 to 12, wherein, The resin coating is formed by coating the first main surface of the first oriented liquid crystal layer with a resin solution containing an acrylic resin or epoxy resin with a weight average molecular weight of 20,000 or more and an organic solvent; the resin coating is then bonded to the optical layer via an adhesive. The acrylic resin or epoxy resin satisfies either (1) or (2) below: (1) It does not contain photocurable or thermocurable reactive groups; (2) The functional group equivalent of the photocurable or thermocurable reactive groups is 3000 or more.

15. The method for manufacturing an alignment liquid crystal film according to claim 14, wherein, After the resin solution is applied and before the optical layer is bonded, the mixture is heated at 40–150°C.

16. The method for manufacturing an alignment liquid crystal film according to claim 14 or 15, wherein, The first oriented liquid crystal layer is formed by coating a liquid crystal composition containing photopolymerizable liquid crystal monomers onto a support substrate, heating the liquid crystal composition on the support substrate to orient the liquid crystal monomers in a liquid crystal state, and then using light irradiation to polymerize or crosslink the liquid crystal monomers.

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

18. The method for manufacturing an alignment liquid crystal film according to claim 16, wherein, With the first alignment liquid crystal layer disposed on the support substrate, the resin solution is coated on the surface of the first alignment liquid crystal layer that is not in contact with the support substrate.

19. The method for manufacturing an alignment liquid crystal film according to claim 16, wherein, The support substrate is peeled off from the first alignment liquid crystal layer, and the resin solution is applied to the surface of the first alignment liquid crystal layer exposed by the peeling off of the support substrate.

20. The method for manufacturing an alignment liquid crystal film according to claim 16, wherein, The organic solvent in the resin solution is soluble in the photopolymerizable liquid crystal monomer, but does not dissolve or has difficulty dissolving the photocured form of the photopolymerizable liquid crystal monomer.

Images