CN116261681A - Oriented liquid crystal film, manufacturing method thereof, and image display device - Google Patents

Abstract

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

Description

Oriented liquid crystal film, its manufacturing method, and image display device

technical field

The present invention relates to an alignment liquid crystal film in which liquid crystal molecules are aligned, a method for producing the same, and an image display device including the alignment liquid crystal film.

Background technique

As an optical film having functions such as optical compensation of a liquid crystal display device and prevention of external light reflection of an organic EL element, a liquid crystal film (aligned liquid crystal film) in which a liquid crystal compound is oriented in a predetermined direction is used. Since the birefringence of an oriented liquid crystal film is larger than that of a polymer stretched film, it is advantageous for thinning and lightening. In an image display device, an oriented liquid crystal film is bonded to an organic EL panel or a liquid crystal display panel as a polarizing plate integrally laminated with a polarizer via an adhesive (pressure-sensitive adhesive) or an adhesive (for example, Patent Document 1 ).

The liquid crystal compound can orient the liquid crystal molecules in a predetermined direction due to the shearing force during coating on the substrate, the alignment restricting force of the alignment film, etc., and an aligned liquid crystal film having various optical anisotropies can be obtained. For example, a parallel alignment (horizontal alignment) liquid crystal layer in which nematic liquid crystal molecules having positive refractive index anisotropy are aligned parallel to the substrate plane can be used as a positive A plate having refractive index anisotropy of nx>ny=nz.

When using a thermotropic liquid crystal, a solution containing a liquid crystal compound (liquid crystal composition) is applied on a substrate, and the liquid crystal molecules are aligned by heating so that the compound contained in the composition becomes a liquid crystal state. When the liquid crystal composition contains a photopolymerizable liquid crystal compound (liquid crystal monomer), after aligning the liquid crystal molecules, the liquid crystal monomer is cured by light irradiation to fix the alignment state.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2015-7700

Contents of the invention

The problem to be solved by the invention

Higher durability is required for image display devices such as liquid crystal display devices and organic EL display devices, and optical members constituting the image display devices are required to have little change in optical characteristics even when exposed to a high temperature environment for a long time. The aforementioned Patent Document 1 describes that by controlling the alignment parameters of the liquid crystal compound, it is possible to reduce the change in phase retardation in a high-temperature environment of an alignment liquid crystal film.

Not only the alignment state of the liquid crystal but also the optical properties of the aligned liquid crystal film may change in a high-temperature environment due to the influence of layers arranged adjacent to the liquid crystal layer. For example, when the parallel alignment liquid crystal layer and the polarizer are bonded via an adhesive layer (pressure-sensitive adhesive layer), there is almost no retardation change in a high-temperature environment, while via an ultraviolet-curable adhesive In the sample in which the parallel alignment liquid crystal layer and the polarizer were bonded together, it was found that the retardation tended to increase under a high-temperature environment.

In view of this subject, an object of the present invention is to provide an aligned liquid crystal film having a small change in optical characteristics and excellent heating durability even when exposed to a high-temperature environment for a long time.

means to solve the problem

The alignment liquid crystal film includes an alignment liquid crystal layer in which liquid crystal molecules are aligned in a predetermined direction. The alignment liquid crystal layer, for example, is formed by coating a liquid crystalline composition containing a photopolymerizable liquid crystal monomer on a support substrate, heating the liquid crystal composition on the support substrate, and aligning the liquid crystal monomer in a liquid crystal state, and irradiating light to make the liquid crystal layer Liquid crystal monomers are formed by polymerization or crosslinking. In the alignment liquid crystal layer, liquid crystal molecules can be aligned in parallel (horizontal alignment). The supporting substrate for forming the alignment liquid crystal layer may be a resin film.

The alignment liquid crystal film of this invention is equipped with the resin coating layer which contacts the 1st main surface of an alignment liquid crystal layer, and is equipped with the optical layer bonded via the adhesive layer on the resin coating layer. A polarizer and a transparent film are mentioned as an optical layer bonded to an alignment liquid crystal layer. The optical layers may be other aligned liquid crystal layers.

The alignment liquid crystal film may be one in which another optical layer is bonded to the second main surface of the alignment liquid crystal layer via an adhesive layer. A resin coating may also be provided on the second main surface of the alignment liquid crystal layer. The alignment liquid crystal film may be one in which another optical layer is bonded to the second main surface of the alignment liquid crystal layer via an adhesive layer.

In one embodiment, the alignment liquid crystal film may be a circular polarizing plate including a polarizer as an optical layer. In an alignment liquid crystal film formed by laminating an alignment liquid crystal layer in which liquid crystal molecules are parallel aligned and a polarizer, the angle formed by the alignment direction of the liquid crystal molecules in the alignment liquid crystal layer and the absorption axis direction of the polarizer may be 10 ~80°.

In one embodiment of the circularly polarizing plate, a resin coating is provided on one side (first main surface) of the parallel alignment liquid crystal layer as the first alignment liquid crystal layer, and a second alignment layer is provided on the resin coating via an adhesive layer. The liquid crystal layer vertically aligns the liquid crystal layer. A polarizer or a polarizing plate is attached to the other surface (second main surface) of the parallel alignment liquid crystal layer. The parallel alignment liquid crystal layer and the polarizer or polarizing plate can be bonded via an adhesive layer in contact with the second main surface of the parallel alignment liquid crystal layer.

The resin coating is preferably a non-curable resin layer. The weight average molecular weight of the resin material constituting the resin coating layer is preferably 20,000 or more. Examples of the resin material of the resin coating include non-curable acrylic resins, non-curable epoxy resins, and the like. The glass transition temperature of the resin coating may be 20° C. or higher. The thickness of the resin coating is preferably 0.05 to 3 μm. In the resin coating layer, an uncured liquid crystal compound constituting the alignment liquid crystal layer may be contained.

The resin coating is formed by coating a resin solution containing a resin and an organic solvent on the alignment liquid crystal layer. The organic solvent of the resin solution is preferably soluble in the photopolymerizable liquid crystal monomer, and does not dissolve or hardly dissolves the photocured product of the photopolymerizable liquid crystal monomer. After coating the resin solution on the surface of the alignment liquid crystal layer, before laminating the optical layer, it may heat at 40-150 degreeC.

It is preferable that the thickness of the adhesive bond layer which bonds together the resin coating layer on the alignment liquid crystal layer, and an optical layer is 0.01-5 micrometers. The adhesive may be an active energy ray-curable adhesive.

Invention effect

The alignment liquid crystal film of the present invention is excellent in heat durability, and has little change in retardation even when exposed to a high-temperature environment for a long time. Therefore, it is suitably used as an optical member for image display devices, such as a liquid crystal display device and an organic EL display device.

Description of drawings

FIG. 1 is a cross-sectional view of an aligned liquid crystal film according to one embodiment.

Fig. 2 is a cross-sectional view of a laminate including an alignment liquid crystal layer on a support substrate.

Fig. 3 is an end view of a laminate in which a resin coating layer is formed on an aligned liquid crystal layer.

FIG. 4 is a cross-sectional view of an aligned liquid crystal film according to one embodiment.

Fig. 5 is a cross-sectional view of an alignment liquid crystal film provided with an adhesive layer.

FIG. 6 is a cross-sectional view of an aligned liquid crystal film according to one embodiment.

Fig. 7 is a cross-sectional view of an aligned liquid crystal film according to one embodiment.

FIG. 8 is a cross-sectional view of an aligned liquid crystal film according to one embodiment.

FIG. 9 is a cross-sectional view of an aligned liquid crystal film according to one embodiment.

FIG. 10 is a cross-sectional view showing an example of a stacked configuration of an image display device.

Detailed ways

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

[Alignment liquid crystal layer]

The alignment liquid crystal layer 1 contains liquid crystal molecules aligned in a predetermined direction. For example, by coating a liquid crystal composition containing a liquid crystal compound on the support substrate 8, aligning the liquid crystal compound in a predetermined direction, and then fixing the alignment state, an aligned liquid crystal is formed on the support substrate 8 as shown in FIG. Layer 1.

＜Liquid Crystal Composition＞

Examples of the liquid crystal compound include rod-shaped liquid crystal compounds, discotic liquid crystal compounds, and the like. The liquid crystal compound is preferably a rod-like liquid crystal compound from the point of view of easy parallel alignment due to the alignment restriction force of the support substrate. The rod-shaped liquid crystal compound may be 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 crystallinity, it does not need to exhibit liquid crystallinity after polymerization.

The liquid crystal compound is preferably a thermotropic liquid crystal that develops liquid crystallinity by heating. Thermotropic liquid crystals undergo phase transitions of crystalline phase, liquid crystal phase, and isotropic phase as temperature changes. The liquid crystal compound contained in the liquid crystal composition may be any of nematic liquid crystal, smectic liquid crystal and cholesteric liquid crystal. A chiral agent can be added to the nematic liquid crystal to have cholesteric alignment.

Examples of rod-shaped liquid crystal compounds exhibiting thermotropism include azomethines, azo oxides, cyanobiphenyls, cyanophenyl esters, benzoate esters, and cyclohexanecarboxylic acid phenyl esters. , cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanylacetylenes, alkenylcyclohexylbenzonitriles, etc.

As the polymerizable liquid crystal compound, for example, a polymerizable liquid crystal compound that can fix the orientation state of the rod-shaped liquid crystal compound using a polymer binder; a polymerizable functional group that can fix the orientation state of the liquid crystal compound by polymerization liquid crystal compounds, etc. Among them, a photopolymerizable liquid crystal compound having a photopolymerizable functional group is preferable.

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

Examples of the mesogenic group of liquid crystal monomers include biphenyl, phenylbenzoate, phenylcyclohexyl, azophenyl oxide, azomethine, azophenyl, and phenylpyrimidine. Cyclic structures such as diphenylethynyl, diphenylbenzoate, bicyclohexyl, cyclohexylphenyl, terphenyl, etc. These cyclic units may have a substituent such as a cyano group, an alkyl group, an alkoxy group, or a halogen group at the terminal.

As a photopolymerizable functional group, a (meth)acryloyl group, an epoxy group, a vinyl ether group etc. are mentioned. Among them, a (meth)acryloyl group is preferable. The photopolymerizable liquid crystal monomer preferably has two or more photopolymerizable functional groups in one molecule. By using a liquid crystal monomer containing two or more photopolymerizable functional groups, since a crosslinked structure is introduced into the photocured liquid crystal layer, the durability of the aligned liquid crystal film tends to improve.

As the photopolymerizable liquid crystal monomer, any appropriate liquid crystal monomer can be used. Examples include International Publication No. 00/37585, U.S. Patent No. 5,211,877, U.S. Patent No. 4,388,453, International Publication No. 93/22397, European Patent No. 0261712, German Patent No. 19504224, German Patent No. 4408171, British Patent No. 2280445, Japanese Patent Application Publication No. 2017-206460, International Publication No. 2014/126113, International Publication No. 2016/114348, International Publication No. 2014/010325, Japanese Patent Application Publication No. 2015-200877, Japanese Patent Application Publication No. Publication No. 2010-31223, International 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 Publication No. 2008/119427, Compounds described in JP-A-2008-107767, JP-A-2008-273925, International Publication No. 2016/125839, JP-A-2008-273925, etc. The appearance of birefringence and the wavelength dispersion of retardation can also be adjusted by selection of liquid crystal monomers.

In addition to the liquid crystal monomer, the liquid crystal composition may contain a compound that controls the alignment of the liquid crystal monomer in a specific direction. For example, by making the liquid crystalline composition contain a side chain type liquid crystal polymer, the liquid crystal compound (monomer) can be homeotropically aligned. In addition, by adding a chiral agent to the liquid crystal composition, the liquid crystal compound can be cholesterically aligned.

The liquid crystalline composition may contain a photopolymerization initiator. When curing the liquid crystal monomer by ultraviolet irradiation, in order to accelerate photocuring, the liquid crystalline composition preferably contains a photopolymerization initiator (photoradical generator) that generates radicals by light irradiation. Depending on the type of liquid crystal monomer (the type of photopolymerizable functional group), a photocation generator and a photoanion generator can be used. The usage-amount of a photoinitiator is about 0.01-10 weight part with respect to 100 weight part of liquid crystal monomers. In addition to the photopolymerization initiator, a sensitizer and the like can be used.

A liquid crystalline composition can be prepared by mixing a liquid crystalline monomer and, if necessary, various alignment control agents, a polymerization initiator, and the like with a solvent. The solvent is not particularly limited as long as it can dissolve the liquid crystal monomer and does not corrode the substrate (or has low corrosivity). Examples include: chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethylene Alkanes, trichloroethylene, tetrachloroethylene, chlorobenzene, o-dichlorobenzene and other halogenated hydrocarbons; phenols such as phenol and p-chlorophenol; benzene, toluene, xylene, methoxybenzene, 1,2-dimethyl Aromatic hydrocarbons such as oxybenzene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N-methyl-2-pyrrolidone and other ketone solvents; ethyl acetate, acetic acid Butyl ester and other ester solvents; tert-butanol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diglyme, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentane Alcohol-based solvents such as glycols; amide-based solvents such as dimethylformamide and dimethylacetamide; nitrile-based solvents such as acetonitrile and butyronitrile; ether-based solvents such as diethyl ether, dibutyl ether, and tetrahydrofuran; ethyl cellosolve , Butyl cellosolve, etc. A mixed solvent of two or more solvents can be used.

The solid content concentration of the liquid crystalline composition is usually about 5 to 60% by weight. The liquid crystalline composition may contain additives such as surfactants and leveling agents.

＜Support substrate＞

Examples of the support substrate 8 on which the liquid crystalline composition is applied include a glass plate, a metal plate, a metal belt, a resin film substrate, and the like. The support substrate has a first main surface and a second main surface, and the liquid crystalline composition is coated on the first main surface.

By using a film substrate as the support substrate 8, a series of steps from application of the liquid crystalline composition on the substrate to photocuring of the liquid crystal monomer and subsequent heat treatment can be implemented by a roll-to-roll method, so that the alignment can be improved. Productivity of liquid crystal film. The resin material constituting the film substrate is not particularly limited as long as it is insoluble in the solvent of the liquid crystalline composition and has heat resistance during heating for aligning the liquid crystalline composition, and examples thereof include: polyterephthalic acid Polyesters such as ethylene glycol ester and polyethylene naphthalate; Polyolefins such as polyethylene and polypropylene; Cyclic polyolefins such as norbornene-based polymers; Cellulose such as diacetyl cellulose and triacetyl cellulose Polymers; Acrylic polymers; Styrenic polymers; Polycarbonate, polyamide, polyimide, etc.

The support substrate 8 may have alignment capability for aligning liquid crystal molecules in a predetermined direction. For example, by using a stretched film as a supporting substrate, liquid crystal molecules can be aligned in parallel along the stretching direction thereof. The stretching ratio of the stretched film should just be the grade which can exhibit the orientation ability, for example, it is about 1.1 times - 5 times. The stretched film may be a biaxially stretched film. Even if it is a biaxially stretched film, liquid crystal molecules can be aligned along the direction with a large stretching ratio if the stretching ratio of a longitudinal direction and a horizontal direction differs from one another. The stretched film may be a diagonally stretched film. By using a stretched film as the support substrate 8 , it is possible to align the liquid crystal molecules in a direction that is neither parallel to the longitudinal direction nor the transverse direction of the support substrate.

The support substrate 8 may include an alignment film on the first main surface. As for the alignment film, an appropriate one can be appropriately selected according to the type of liquid crystal compound, the material of the substrate, and the like. As an alignment film for aligning liquid crystal molecules in parallel in a predetermined direction, one obtained by rubbing a polyimide-based or polyvinyl alcohol-based alignment film is preferably used. In addition, a photo-alignment film may be used. A rubbing treatment may be performed on a resin film as a support substrate without providing an alignment film.

The support substrate 8 may include an alignment film for vertically aligning liquid crystal molecules. As an alignment agent for forming a vertical alignment film (vertical alignment film), lecithin, stearic acid, cetyltrimethylammonium bromide, stearylamine hydrochloride, alkali Chromium carboxylate complexes, silane coupling agents, organosilanes such as siloxane compounds, perfluorodimethylcyclohexane, tetrafluoroethylene, polytetrafluoroethylene, etc.

<Formation of an aligned liquid crystal layer on a support substrate>

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

The method of coating the liquid crystalline composition on the support substrate 8 is not particularly limited, and spin coating, die coating, roll lick coating, gravure coating, reverse coating, spray coating, wire bar coating, doctor roll coating, etc. can be used. Coating, air knife coating, etc. After applying 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 after the solvent drying (thickness of the oriented liquid crystal film) becomes about 0.1 to 20 μm.

The liquid crystalline compound is oriented by heating the liquid crystalline composition layer formed on the support substrate to change into a liquid crystalline phase. Specifically, after coating the liquid crystalline composition on the support substrate, heating the liquid crystalline composition to the N (nematic phase)-I (isotropic liquid phase) transition temperature or higher, so that the liquid crystalline composition becomes each Homotropic liquid state. Thereafter, the nematic phase is developed by cooling slowly if necessary. At this time, it is desirable to keep the temperature at which the liquid crystal phase temporarily appears, and grow the liquid crystal phase domain to form a single domain. Alternatively, after coating the liquid crystalline composition on the support substrate, the temperature may be maintained for a certain period of time within the temperature range in which the nematic phase appears to align the liquid crystal molecules in a predetermined direction.

The heating temperature for aligning the liquid crystal compound in a predetermined direction may be appropriately selected according to the type of the liquid crystal composition, and is usually about 40 to 200°C. When the heating temperature is too low, the transition to the liquid crystal phase tends to be insufficient, and when the heating temperature is too high, alignment defects may increase. The heating time may be adjusted so that the liquid crystal domains grow sufficiently, and is usually about 30 seconds to 30 minutes.

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

By irradiating the liquid crystal layer with light, photocuring is performed in a state where the photopolymerizable liquid crystal compound (liquid crystal monomer) has liquid crystal regularity. The light to be irradiated should only polymerize the photopolymerizable liquid crystal compound, and ultraviolet ambient light or visible light with a wavelength of 250 to 450 nm is usually used. When the liquid crystalline composition contains a photopolymerization initiator, what is necessary is just to select the light of the wavelength which a photopolymerization initiator has sensitivity. As the irradiation light source, low pressure mercury lamp, high pressure mercury lamp, ultrahigh pressure mercury lamp, metal halide lamp, xenon lamp, LED (Light Emitting Diode, light emitting diode), black light, chemical lamp, etc. can be used. In order to accelerate the photocuring reaction, it is preferable to perform photoirradiation under an inert gas atmosphere such as nitrogen.

The liquid crystal compound can also be aligned in a predetermined direction by utilizing polarized light in a predetermined direction during photocuring of the liquid crystalline composition. As described above, in the case where the liquid crystal compound is aligned by the alignment restricting force of the support substrate 8, the irradiation light may be non-polarized light (natural light).

The irradiation intensity may be appropriately adjusted according to the composition of the liquid crystalline composition, the added amount of the photopolymerization initiator, and the like. The irradiation energy (cumulative irradiation light amount) is usually about 20 to 10000 mJ/cm ² , preferably 50 to 5000 mJ/cm ² , and more preferably 100 to 800 mJ/cm ² . In order to promote photocuring reaction, photoirradiation may be performed under heating conditions.

The polymer after the liquid crystal monomer is photocured by light irradiation is non-liquid crystal, and the transition of liquid crystal phase, glass phase, and crystal phase does not occur due to temperature changes. Therefore, in the liquid crystal layer that has been photocured in a state where the liquid crystal monomers are aligned in a predetermined direction, changes in molecular orientation due to temperature changes are less likely to occur. In addition, since the birefringence of an oriented liquid crystal film is very large compared with a film including a non-liquid crystal material, the thickness of an optically anisotropic element having a desired retardation can be significantly reduced. The thickness of the alignment liquid crystal film (liquid crystal layer) may be set only according to a target retardation value, etc., and is usually about 0.1 to 20 μm, preferably 0.2 to 10 μm, and more preferably 0.5 to 7 μm.

The optical properties of the aligned liquid crystal layer are not particularly limited. The front retardation and the retardation in the thickness direction of the alignment liquid crystal layer may be appropriately set according to applications and the like. When liquid crystals are aligned in parallel, the front retardation of the aligned liquid crystal layer is, for example, about 20 to 1000 nm. When the alignment liquid crystal layer is a 1/4 wavelength plate, the front retardation is preferably 100 to 180 nm, more preferably 120 to 150 nm. When the alignment liquid crystal layer is a 1/2 wavelength plate, the front retardation is preferably 200 to 340 nm, more preferably 240 to 300 nm.

Retardation values are measured at a wavelength of 550 nm unless otherwise specified. The front-side retardation R(450) at a wavelength of 450 nm of the alignment liquid crystal layer may be smaller than the front-side retardation R(550) at a wavelength of 550 nm. In addition to R(450)<R(550), the front retardation R(650) of the alignment liquid crystal layer at a wavelength of 650 nm is greater than R(550), and R(550)<R(650) can be satisfied. R(450)/R(550) of the alignment liquid crystal layer may be 0.70-0.95, 0.75-0.90 or 0.80-0.87. R(650)/R(550) of the alignment liquid crystal layer may be 1.05-1.30, 1.10-1.25 or 1.13-1.20. As described above, by selection of liquid crystal monomers, it is possible to form an aligned liquid crystal layer whose retardation has a desired wavelength dispersion.

When the liquid crystal is vertically aligned, the front retardation of the aligned liquid crystal layer is approximately 0 (for example, 5 nm or less, preferably 3 nm or less), and the absolute value of the retardation in the thickness direction is about 30 to 500 nm.

[resin coating]

As described above, since the photocured liquid crystal layer does not undergo phase transition even when heated, it is superior in thermal stability compared to an 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 characteristics may change, and there is room for improvement in the heating durability. In particular, an oriented liquid crystal film obtained by laminating another optical layer to a parallel oriented liquid crystal layer via an adhesive tends to have retardation fluctuations when heated for a long time, and has a problem with heating durability.

As shown in FIG. 3 , by providing the resin coating layer 6 on the surface of the alignment liquid crystal layer 1 , it is expected that the thermal stability of the optical characteristics of the alignment liquid crystal layer will be improved. The resin coating layer 6 is formed by coating a resin solution containing a resin and an organic solvent on the surface of the alignment liquid crystal layer 1 .

＜Resin material＞

As the resin material of the resin coating layer 6, a non-curable resin is preferable. The non-curable resin refers to a material capable of forming a resin layer without a curing reaction such as photocuring or thermal curing after applying a resin solution. The non-curable resin does not contain photocurable or thermosetting reactive groups, but a small amount of reactive groups may remain. For example, the reactive functional group equivalent (the mass of the resin containing 1 equivalent of the reactive functional group) is preferably 3,000 or more, more preferably 4,000 or more, and may be 5,000 or 6,000 or more.

The resin material preferably has high transparency and little coloring. Examples of resin materials include epoxy resin, silicone resin, acrylic resin, polyurethane, polyamide, polyether, polyvinyl alcohol, polyester, polycarbonate, polyarylate, polyphenylene sulfide, and polyethersulfone. , polyether ether ketone, polyamide, polyimide, polyolefin, cyclic polyolefin, polystyrene, polyvinyl chloride, polyvinylidene chloride and other polymers. Among them, non-curable acrylic resins and non-curable epoxy resins are preferable because of high adhesiveness with the alignment liquid crystal layer 1 and the adhesive layer 3 .

The so-called "non-curable acrylic resin" is a polymer obtained by polymerizing the (meth)acryloyl group of a compound (acrylic monomer) having one or more (meth)acryloyl groups in one molecule. After coating the resin solution on the surface of the alignment liquid crystal layer 1, the resin coating layer 6 can be formed without performing photocuring or thermosetting. Non-curable acrylic resins are typically polymers of alkyl (meth)acrylates, and examples thereof include polymethyl methacrylate, polyethyl methacrylate, and polybutyl methacrylate.

The non-curable acrylic resin can be a copolymer of various alkyl (meth)acrylates, or a copolymer of alkyl (meth)acrylates and other monomers.

Examples of monomers other than alkyl (meth)acrylates include (meth)acrylic acid, (meth)acrylamide, (meth)acrylonitrile, vinyl-based monomers, styrene-based monomers, and the like. Comonomers may contain boron-containing functional groups such as boronic acid, borate ester, and the like.

The so-called "non-curable epoxy resin" is a polymer obtained by the polymerization reaction of the epoxy group of a compound (epoxy monomer) having more than one epoxy group in one molecule. After coating the surface of the resin solution, the resin coating 6 can be formed without photocuring or thermal curing. Among non-curable epoxy resins, epoxy resins having an aromatic ring are preferable.

Two or more types of resin materials may be mixed. From the viewpoint of suppressing the haze increase of the resin coating layer, it is preferable that two or more resin materials are compatible. The resin material may be a mixture of non-curable acrylic resin and non-curable epoxy resin. When the resin material contains an acrylic resin and an epoxy resin, the content ratio of the acrylic resin and the epoxy resin is preferably 95:5 to 60:40 or 40:60 to 40:60 in terms of weight ratio from the viewpoint of transparency. 1:99. The weight ratio of the two can be 90:10-70:30 or 30:70-10:90.

The glass transition temperature of the resin material of 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. For polymer materials used for interlayer bonding such as adhesives, the glass transition temperature is generally set to be lower than room temperature in order to have tackiness. On the other hand, since the resin coating layer 6 provided on the surface of the alignment liquid crystal layer has a glass transition temperature higher than room temperature, the change in characteristics in the use environment of the image display device is small. The tendency of the optical properties to change. The weight average molecular weight of the resin material is preferably 20,000 or more, more preferably 30,000 or more, from the viewpoint of maintaining the film strength of the resin coating layer 6 without being accompanied by a curing reaction.

(formation of resin layer)

The organic solvent of the resin solution is not particularly limited as long as it can dissolve the above-mentioned resin material. The organic solvent is preferably one that does not dissolve the alignment liquid crystal layer. For example, when the alignment liquid crystal layer contains a photocured product of a photopolymerizable liquid crystal monomer, it is preferably an organic solvent that does not dissolve or hardly dissolves the cured product. On the other hand, the organic solvent may show solubility to the liquid crystal compound (monomer) before photocuring. The organic solvent may be one kind of solvent or a mixed solvent of two or more kinds.

The solid content concentration of the resin solution may be adjusted within a range of about 1 to 50% by weight so as to have a viscosity suitable for coating. 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 be 15% by weight or less or 10% by weight or less.

The method of coating the resin solution on the surface of the alignment liquid crystal layer 1 is not particularly limited, and various coating methods can be appropriately employed. After applying the resin solution, heating may be performed in order to remove the organic solvent. The heating temperature is preferably 40°C or higher, more preferably 50°C or higher. When the heating temperature is too high, the heating stability of the aligned liquid crystal film may decrease due to thermal damage to the substrate, reorientation of the liquid crystal compound, and the like. 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.

The thickness of the resin coating layer 6 is not particularly limited, but is preferably 3 μm or less, more preferably 2 μm or less, and may be 1 μm or less from the viewpoint of thinning, adhesiveness, and transparency maintenance. On the other hand, the thickness of the resin coating 6 is preferably 0.05 μm or more, more preferably 0.1 μm or more, from the viewpoint of enclosing uncured monomers and the like from the elution from the alignment liquid crystal layer 1 in the resin coating 6 and suppressing bleeding. .

The reason why the heating durability of the alignment liquid crystal layer is improved by providing a resin coating layer is not clear, but it is considered that uncured monomers remaining in the photocured liquid crystal layer and the part where the formation of the three-dimensional network structure is insufficient contain Dissociated additives and the like are eluted from the organic solvent of the resin solution and taken into the resin coating. Therefore, removal of substances that cause retardation changes due to heating from the aligned liquid crystal layer is considered to be one cause. Even when the uncured matter in the alignment liquid crystal layer is eluted into the organic solvent, since the eluted components are taken into the resin coating, it is possible to prevent contamination and loss of transparency caused by the precipitates on the surface of the alignment liquid crystal layer, etc. reduce. It is considered that liquid crystal reorientation during heating for removal of an organic solvent, stabilization of an orientation state, and the like also contribute to improvement of heating stability.

The laminated body shown in FIG. 1 is obtained by laminating|stacking the resin coating layer 6 provided on the alignment liquid crystal layer 1, and the optical layer 4 via the adhesive bond layer 3.

[optical layer]

The optical layer 4 is not particularly limited, and an optically isotropic or optically anisotropic film generally used as an optical film can be used without particular limitation. Specific examples of the optical layer 4 include transparent films such as retardation films and polarizer protective films, functional films such as polarizers, viewing angle widening films, viewing angle limiting (peep prevention) films, and brightness improving films. The optical layer 4 may be a single layer or a laminated body. The optical layer 4 can be an aligned liquid crystal layer. For example, the optical layer 4 may be a polarizer with a transparent protective film attached to one or both sides of the polarizer. When a polarizing plate is provided with a transparent protective film on one surface, a polarizer may be bonded to an alignment liquid crystal layer, or a transparent protective film may be bonded to an alignment liquid crystal layer.

For example, in a liquid crystal display device, there are cases where an image display unit (liquid crystal unit) and a polarizer A retardation film as an optical compensation film is disposed between them. In an organic EL display device, there are cases where a 1/4 wavelength plate is disposed between the cell and the polarizing plate in order to prevent external light from being reflected by the metal electrode layer to look like a mirror.

[adhesive layer]

As described above, by providing the resin coating layer 6 on the surface of the alignment liquid crystal layer 1, and bonding the optical layer 4 thereon via the adhesive layer 3, the heating durability of the alignment liquid crystal layer 1 in the alignment liquid crystal film 100 can be improved. .

The material of the adhesive constituting the adhesive layer 3 is not particularly limited as long as it is optically transparent, and examples thereof include epoxy resin, silicone resin, acrylic resin, polyurethane, polyamide, polyether, poly vinyl alcohol etc. For the resin coating layer 6 described above, a non-curable resin is used, and for the adhesive, a curable composition is used. The thickness of the adhesive layer 3 is appropriately set according to the type of the adherend, the material of the adhesive, and the like. When using a curable adhesive that exhibits adhesiveness through a crosslinking reaction after coating, the thickness of the adhesive layer 3 is preferably 0.01 to 5 μm, more preferably 0.03 to 3 μm.

As the adhesive, various forms such as water-based adhesives, solvent-based adhesives, hot-melt adhesives, and active energy ray-curable adhesives can be used. Among the above, a water-based adhesive or an active energy ray-curable adhesive is preferable because the thickness of the adhesive layer can be reduced.

Examples of water-based adhesives include those containing water-soluble or water-dispersible polymers such as vinyl polymer-based, gelatin-based, vinyl-based latex-based, polyurethane-based, isocyanate-based, polyester-based, and epoxy-based. The adhesive layer formed of such a water-based adhesive is formed by applying an aqueous solution on a film and drying it. When preparing an aqueous solution, catalysts such as crosslinking agents, other additives, and acids may be blended as necessary.

Examples of the crosslinking agent compounded in the water-based adhesive include: boric acid, borax; carboxylic acid compounds; alkyldiamines; isocyanates; epoxies; monoaldehydes; dialdehydes; amino-formaldehyde Resins; divalent or trivalent metal salts and their oxides, etc.

The active energy ray-curable adhesive is an adhesive capable of radical polymerization, cationic polymerization, or anionic polymerization by irradiation with active energy rays such as electron beams and ultraviolet rays. Among them, from the point that curing can be performed with low energy, a photoradical polymerizable adhesive that initiates radical polymerization by ultraviolet irradiation is preferable.

As a monomer of a radically polymerizable adhesive agent, the compound which has a (meth)acryloyl group, and the compound which has a vinyl group are mentioned. Among them, compounds having a (meth)acryloyl group are preferable. Examples of compounds having a (meth)acryloyl group include: C _1-20 chain alkyl (meth)acrylate, alicyclic alkyl (meth)acrylate, polycyclic (meth)acrylate Alkyl (meth)acrylates such as alkyl esters; (meth)acrylates containing hydroxyl groups; (meth)acrylates containing epoxy groups such as glycidyl (meth)acrylates, etc. Radical polymerizable adhesives may contain hydroxyethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxy Nitrogen-containing monomers such as methyl (meth)acrylamide, (meth)acrylamide, (meth)acryloylmorpholine, etc. Free radically polymerizable adhesives may include tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylolpropane formal acrylate, dioxin Multifunctional monomers such as alkanediol diacrylate and EO (Ethylene oxide; ethylene oxide) modified diglycerol tetraacrylate are used as crosslinking components.

It is preferable that photocurable adhesives, such as a photoradical polymerizable adhesive, contain a photoinitiator. What is necessary is just to select a photoinitiator suitably according to a reaction species. For example, in a radically polymerizable adhesive, it is preferable to mix a photoradical generator that generates radicals by light irradiation as a photopolymerization initiator. Specific examples of photoradical generators will be described below. Content of a photoradical generator is about 0.1-10 weight part normally with respect to 100 weight part of monomers, Preferably it is 0.5-3 weight part. In addition, when using a radically polymerizable adhesive agent as an electron beam hardening type, a photoinitiator is not especially necessary. A photosensitizer represented by a carbonyl compound or the like may be added to the radically polymerizable adhesive if necessary. Photosensitizers are used to improve the curing speed and sensitivity obtained by electron beams. The usage-amount of a photosensitizer is about 0.001-10 weight part normally with respect to 100 weight part of monomers, Preferably it is 0.01-3 weight part.

The adhesive may contain appropriate additives as necessary. Examples of additives include coupling agents such as silane coupling agents and titanium coupling agents, adhesion promoters such as ethylene oxide, ultraviolet absorbers, anti-aging agents, dyes, processing aids, ion scavengers , Antioxidant, tackifier, filler, plasticizer, leveling agent, foam inhibitor, antistatic agent, heat-resistant stabilizer, hydrolysis-resistant stabilizer, etc.

By applying an adhesive to either or both of the surface of the resin coating layer 6 provided on the alignment liquid crystal layer 1 and the surface of the optical layer 4, and curing it, resin layers are stacked via the adhesive layer 3. The coating 6 aligns the liquid crystal layer 1 and the optical layer 4 . The curing of the adhesive may be appropriately selected according to the type of adhesive. For example, water-based adhesives can be cured by heating. The active energy ray-curable adhesive can be cured by irradiation with active energy rays such as ultraviolet rays.

[Lamination structure of alignment liquid crystal film]

The alignment liquid crystal film 103 formed by providing the resin coating layer 6 on the surface of the alignment liquid crystal layer 1 on the support substrate 8 and bonding the optical layer 4 to the resin coating layer 6 via the adhesive layer 3 can be used as an optical member as it is. In this case, the support substrate 8 constitutes a part of the alignment liquid crystal film 103 . Like the aligned liquid crystal film 100 shown in FIG. 1 , the supporting substrate can be peeled from the aligned liquid crystal layer 1 . On the surface of the alignment liquid crystal layer 1 exposed by peeling off the support substrate, an appropriate pressure-sensitive adhesive layer 2 can be laminated as shown in FIG. 5 .

In the form shown in FIG. 5 , the adhesive layer 2 is laminated 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, but the alignment liquid crystal film may be formed on the alignment liquid crystal layer. An adhesive layer is laminated on the air surface side during formation, and an optical layer is bonded to the substrate surface side of the alignment liquid crystal layer via a resin coating layer and an adhesive layer.

The adhesive constituting the adhesive layer 2 is not particularly limited, and acrylic polymers, silicone-based polymers, polyesters, polyurethanes, polyamides, polyethers, fluorine-based polymers, and rubber-based adhesives can be appropriately selected and used. A polymer etc. are used as a base polymer. Particularly preferred are adhesives such as acrylic adhesives and rubber adhesives that are excellent in transparency, exhibit moderate wettability, cohesiveness, and adhesiveness, and are excellent in weather resistance, heat resistance, and the like. The thickness of the pressure-sensitive adhesive layer is appropriately set depending on the type of adherend, and is generally about 5 to 500 μm.

The lamination of the pressure-sensitive adhesive layer 2 on the alignment liquid crystal layer 1 is performed, for example, by bonding a sheet-shaped pressure-sensitive adhesive in advance to the surface of the alignment liquid crystal layer 1 . After coating the adhesive composition on the alignment liquid crystal layer 1 , solvent drying, crosslinking, photocuring, etc. may be performed to form the adhesive layer 2 . In order to improve the bonding force (grip force) between the alignment liquid crystal layer 1 and the adhesive layer 2, surface treatments such as corona treatment and plasma treatment can be carried out on the surface of the alignment liquid crystal layer 1 to form an easily bonding layer, and then laminated Adhesive layer 2.

The separator 9 is preferably temporarily bonded to the surface of the adhesive layer 2 . The spacer 9 protects the surface of the adhesive layer 2 until the adhesive-attached optical film is bonded to the image display unit 50 . As a constituent material of the separator, plastic films such as acrylic resin, polyolefin, cyclic polyolefin, and polyester are preferably used. The thickness of the separator is usually about 5 to 200 μm. It is preferable to perform a release treatment on the surface of the separator. Examples of the release agent include silicone-based materials, fluorine-based materials, long-chain alkyl-based materials, fatty amide-based materials, and the like.

Another optical layer may be laminated on the exposed surface of the alignment liquid crystal layer 1 after the support substrate 8 is peeled off via an appropriate adhesive layer or pressure-sensitive adhesive layer. For example, as shown in FIG. 6 , another optical layer 5 can be laminated on the alignment liquid crystal layer 1 via a suitable adhesive layer 7 . An adhesive layer (not shown) may be further laminated on the optical layer 5, and a spacer may be temporarily bonded to the surface of the adhesive layer.

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

In FIG. 7 , the resin coatings 6 and 16 are provided on both sides of the alignment liquid crystal layer 1 , but the resin coating may be provided on only one side of the alignment liquid crystal layer 1 . The surface of the alignment liquid crystal layer 1 (the air surface when the alignment liquid crystal layer is formed) of the laminated body 101 in which the alignment liquid crystal layer 1 is laminated in close contact with the support substrate 8 may be formed without forming a resin coating layer via an adhesive layer, The adhesive layer is bonded to other layers, and after the support substrate 8 is peeled off from the alignment liquid crystal layer 1, the resin coating layer 16 is formed only on the exposed surface of the alignment liquid crystal layer 1 (substrate surface when the alignment liquid crystal layer is formed).

＜Circular Polarizer＞

An oriented liquid crystal film can be used as an optical film for displays for the purpose of improving visibility and the like. For example, in a liquid crystal display device, there are cases where a polarizer is placed between the image display unit (liquid crystal unit) and the polarizer in order to appropriately change the polarization state of light emitted from the liquid crystal unit to the viewing side to improve viewing angle characteristics, etc. A retardation film as an optical compensation film is arranged between them.

In one embodiment, the alignment liquid crystal film is a circular polarizing plate in which a polarizing plate serving as the optical layer 4 is bonded to the surface on which the resin coating layer 6 is formed on the alignment liquid crystal layer 1 via the adhesive layer 3 . A circularly polarizing plate may include two or more alignment liquid crystal layers.

The polarizing plate may be formed of only one polarizer, and a transparent protective film may be bonded to one or both surfaces of the polarizer as described above. Examples of the polarizer include: iodine adsorption to a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, and an ethylene-vinyl acetate copolymer partially saponified film; dichroism Those obtained by uniaxially stretching dichroic substances such as dyes; polyene-based oriented films such as dehydration-treated products of polyvinyl alcohol and dehydrochloric acid-treated products of polyvinyl chloride, etc.

Among them, polyvinyl alcohol-based films such as polyvinyl alcohol and partially formalized polyvinyl alcohol are preferably oriented in a predetermined direction by absorbing dichroic substances such as iodine and dichroic dyes, in view of having a high degree of polarization. Alcohol (PVA) based polarizer. For example, a PVA-based polarizer is obtained by iodine dyeing and stretching of a polyvinyl alcohol-based film. A PVA-based resin layer can be formed on a resin substrate, and iodine dyeing and stretching can be performed in the state of a laminate.

In the circular polarizing plate in which the polarizing plate and the alignment liquid crystal layer are laminated, it is preferable that the liquid crystal molecules of at least one alignment liquid crystal layer are aligned in parallel. In the circularly polarizing plate, the alignment direction of the liquid crystal molecules in the alignment liquid crystal layer in which the liquid crystal molecules are parallel aligned is neither parallel nor perpendicular to the absorption axis direction of the polarizer.

For example, in the case where the circular polarizing plate has only one alignment liquid crystal layer, the alignment liquid crystal layer 1 is a 1/4 wavelength plate, and the direction of the absorption axis of the polarizer and the alignment direction of the liquid crystal molecules (generally the direction of the slow axis) The formed angle is set to 45°. The angle formed by the direction of the absorption axis of the polarizer and the alignment direction of the liquid crystal molecules may be 35-55°, 40-50°, or 43-47°.

In the configuration in which the polarizing plate 4 and the alignment liquid crystal layer 1 as a 1/4 wavelength plate are laminated so that the angle formed by the optical axes thereof becomes 45°, the liquid crystal molecules may be vertically aligned with respect to the substrate surface ( homeotropicalalignment) as the optical layer 5. By sequentially stacking the alignment liquid crystal layer 1 serving as a 1/4 wavelength plate and the vertical alignment liquid crystal layer 5 functioning as a positive C plate on a polarizing plate, it is possible to form a circular polarization that shields reflected light even from external light from an oblique direction. piece. A vertical alignment liquid crystal layer (positive C plate) and a parallel alignment liquid crystal layer (1/4 wavelength plate as a positive A plate) can be sequentially laminated on the polarizer.

As shown in FIGS. 6 and 7 , in a circular polarizing plate in which a plurality of alignment liquid crystal layers 1 and 5 are stacked on the polarizing plate 4 as an optical layer, the alignment liquid crystal layers 1 and 5 can be parallel alignment liquid crystal layers. In this case, it is preferable that the alignment liquid crystal layer 1 disposed on the side closer to the polarizing plate 4 is a 1/2 wavelength plate, and the alignment liquid crystal layer 5 disposed on the side farther from the polarizing plate is a 1/4 wavelength plate. In this laminated structure, it is preferable to arrange it so that the angle formed by the direction of the slow axis of the 1/2 wavelength plate and the direction of the absorption axis of the polarizer is 75°±5°, and that of the 1/4 wavelength plate The angle formed by the slow axis direction and the absorption axis direction of the polarizer was 15°±5°. A circular polarizing plate having such a laminated structure functions as a circular polarizing plate in a wide wavelength range of visible light, and therefore can reduce coloring of reflected light.

As shown in FIG. 8, the circular polarizing plate formed by laminating a plurality of alignment liquid crystal layers 1 and 5 on the polarizing plate 4 may also have the following structure: a resin coating layer 6 is disposed between the alignment liquid crystal layer 1 and the alignment liquid crystal layer 5. , there is no resin coating between the alignment liquid crystal layer 1 and the polarizer 4 . For example, as shown in FIG. 3, after the resin coating 6 is provided on the surface of the alignment liquid crystal layer 1, the alignment liquid crystal layer 5 is attached via the adhesive layer 7 on the resin coating 6, thereby as shown in FIG. 9, the obtained A laminate (orientation liquid crystal film) 113 having an orientation liquid crystal layer is bonded to the resin coating layer 6 forming surface of the orientation liquid crystal layer 1 via an adhesive layer 7 . By peeling the support substrate 8 from this laminate, and bonding the polarizing plate 4 via the adhesive layer 12 on the alignment liquid crystal layer 1 exposed by the peeling of the support substrate, the orientation of the alignment liquid crystal layer 1 is obtained as shown in FIG. A resin coating layer 6 is provided on one side, an alignment liquid crystal layer 5 is laminated thereon via an adhesive layer 7 , and a polarizer 4 is bonded to the other side of the alignment liquid crystal layer 1 via an adhesive layer 12 .

In one embodiment of the laminate 107, the alignment liquid crystal layer 1 arranged on the side close to the polarizer 4 is a parallel alignment liquid crystal layer as a 1/4 wavelength plate, and the alignment liquid crystal layer 1 arranged on the side away from the polarizer 4 Layer 5 is a vertically aligned liquid crystal layer as a positive C plate. In this embodiment, the alignment liquid crystal layer 5 is bonded to the resin coating layer formation surface 6 of the alignment liquid crystal layer 1 through the adhesive layer 7 .

The adhesive layer 7 is formed by curing the adhesive that is a curable material, and since the non-curable resin coating layer 6 is formed on the alignment liquid crystal layer 1, the front retardation of the alignment liquid crystal layer 1 caused by heating is suppressed. The change. The bonding surface of the alignment liquid crystal layer 1 and the polarizing plate 4 is not provided with a resin coating, but the alignment liquid crystal layer 1 and the polarizing plate 4 are bonded via the adhesive layer 12 (non-curable material), so it is difficult to produce a gap in the alignment liquid crystal. Decrease in heat durability seen when an adhesive layer is formed directly on the layer.

In this way, the laminated body 107 shown in FIG. 8 has the following configuration: a non-curable resin coating layer 6 is provided on the parallel alignment liquid crystal layer 1, and the positive C plate ( The alignment liquid crystal layer 5 of the optical layer), so even in the case of long-term exposure to a high temperature environment, the change in front retardation is small, and it is suitable for use as a circular polarizing plate for liquid crystal display devices, organic EL display devices, and the like. In addition, in the laminated body 107, the alignment liquid crystal layer 5 which is a positive C plate is in contact with the adhesive layer 7, but the front retardation of the positive C plate is substantially zero, so even if the laminated body 107 is exposed to a high temperature environment for a long time , and produces little positive latency change.

[Image display device]

10 is a cross-sectional view showing an example of a stacked structure of an image display device, in which an alignment liquid crystal film including an alignment liquid crystal layer 1 is bonded to the surface of an image display unit 50 via an adhesive layer 2 . The alignment liquid crystal film may include two or more alignment liquid crystal layers. Examples of the image display unit 50 include a liquid crystal unit, an organic EL unit, and the like.

As described above, the alignment liquid crystal film improves the heating durability of the alignment liquid crystal layer by providing a resin coating on the surface of the alignment liquid crystal layer. An image display device having an aligned liquid crystal layer formed with a resin coating on its surface has little change in retardation even when exposed to a heated environment for a long period of time, and therefore has little change in visibility and is excellent in heating durability.

[Example]

Hereinafter, the present invention will be described in more detail by citing production examples of an alignment liquid crystal film, but the present invention is not limited to the following examples.

[Production of Parallel Alignment Liquid Crystal Film]

＜Comparative example 1＞

A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase ("Paliocolor LC242" manufactured by BASF) was dissolved in cyclopentanone to prepare a solution having 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 crystalline composition solution. The addition amount of a leveling agent and a polymerization initiator is set to 0.01 weight part and 3 weight part with respect to 100 weight part of photopolymerizable liquid crystal compounds, respectively.

A biaxially stretched norbornene-based film ("Zeonor Film" manufactured by Zeon Japan, thickness: 33 μm, front retardation: 135 nm) was used as a film base material. The above-mentioned liquid crystal composition was coated on the surface of the film substrate with a bar coater so that the thickness after drying was 1 μm, and the liquid crystal was aligned by heating at 100° C. for 3 minutes. After cooling to room temperature, ultraviolet rays with a cumulative light intensity of 400 mJ/cm ² were irradiated in a nitrogen atmosphere to perform photocuring to obtain a laminate in which a parallel-aligned liquid crystal layer was formed on a film substrate.

<Examples 1 to 6>

In a mixed solvent of cyclopentanone and ethyl acetate, the resins shown in Table 1 were dissolved so that the solid content concentration became 3% by weight, to prepare resin solutions. The surface of the alignment liquid crystal layer of the laminate of Comparative Example 1 was coated with a resin solution using a wire bar (#10), and then heated at 85° C. to remove the solvent, thereby forming a resin coating layer on the surface of the alignment liquid crystal layer. In addition, in Table 1, the acrylic resin of Examples 1-3 is resin obtained from Kusumoto Chemicals, and the epoxy resin of Examples 4-6 and Comparative Example 3 is resin obtained from Mitsubishi Chemical.

＜Comparative example 2＞

After applying cyclopentanone to the surface of the aligned liquid crystal layer of the laminate of Comparative Example 1 using a wire bar (#10), it was heated at 85° C. for 1 minute to remove the solvent.

＜Comparative example 3＞

In a mixed solvent of cyclopentanone and ethyl acetate, dissolve a bisphenol A-type epoxy resin with an epoxy equivalent of about 190 ("jER828" manufactured by Mitsubishi Chemical Co., Ltd.) and a photocationic polymerization initiator ("CPI100P" manufactured by SAN-APRO) To make the epoxy resin concentration 3% by weight, a photocurable resin composition (solution) was prepared. On the surface of the alignment liquid crystal layer of the laminate of Comparative Example 1, after coating the composition with a wire bar (#10), Heat at 85°C to remove the solvent, and then irradiate with ultraviolet light to photocure the epoxy resin.

[Production of Polarizing Plate (Circular Polarizing Plate) Equipped with Aligned Liquid Crystal Layer]

A laminate ( single protective polarizer).

62 parts by weight of hydroxyethylacrylamide ("HEAA" manufactured by Koeito), 25 parts by weight of acryloylmorpholine ("ACMO" manufactured by Koeito), PEG400# diacrylate ("Light" manufactured by Kyoeisha Chemical Co., Ltd.) Acrylate 9EG-A") 7 parts by weight, photopolymerization initiator ("Omnirad 907" manufactured by IGM Resins) 3 parts by weight, and 2,4-diethylthioxanthone ("Kayacure DETX-S manufactured by Nippon Kayaku ”) 3 parts by weight were mixed to prepare a UV curable adhesive composition. On the surface of the above-mentioned single protective polarizer, apply the adhesive with a thickness of about 1 μm, and stick the layered body of Examples 1 to 6 and Comparative Examples 1 to 3 on the side of the oriented liquid crystal layer on the coated layer of the adhesive. After the surface, the adhesive is cured by irradiating ultraviolet rays with a cumulative light intensity of 1000mJ/cm ² . At the time of bonding, the angle formed by the absorption axis direction of the polarizer and the orientation direction (slow axis direction of the film base material) of the liquid crystal molecules in the orientation liquid crystal layer was 45°.

Peel the film substrate from the oriented liquid crystal film, stick an acrylic adhesive sheet with a thickness of 15 μm on the surface of the oriented liquid crystal film, and stick the oriented liquid crystal layer on the polarizer of the single protective polarizer via a UV-curable adhesive layer, A polarizing plate provided with an acrylic adhesive sheet thereon was obtained.

In Examples 1 to 6 and Comparative Example 3, a resin layer having a thickness of about 300 nm was formed between the adhesive layer and the alignment liquid crystal layer.

[evaluate]

＜Appearance＞

The surface of the film after the formation of the resin coating layer (Comparative Example 2 is after the surface treatment with cyclopentanone) was visually observed, and the case where no precipitate was confirmed was marked as OK, and the case where the precipitate was confirmed was marked as NG .

＜Delay change＞

The adhesive layer of the said polarizing plate was bonded to a glass plate, and the sample for evaluation was produced. After measuring the front retardation at a wavelength of 590 nm with a phase difference meter ("KOBRA 21-ADH" manufactured by Oji Scientific Instruments), the sample for evaluation was put into an air circulation type constant temperature oven at 85° C. for 120 hours. After the sample was taken out of the oven, the frontal retardation was measured again, and the rate of change in retardation before and after the heating test was calculated.

＜Hue change＞

The adhesive layer of the said polarizing plate was bonded to the non-alkali glass manufactured by Corning, and the sample for evaluation was produced. An aluminum vapor-deposited polyester film ("DMS-X42" manufactured by Toray Advanced Film Co., Ltd.) was placed under the alkali-free glass of the evaluation sample, and a spectrophotometer ("CM-2600d" manufactured by Konica Minolta) was used. , irradiate light from the polarizer side, and measure the hue of the reflected light (the values of a ^* and b ^* in the Lab color space) by the SCI method. Then, the sample for evaluation was put into the 85 degreeC air circulation type constant temperature oven for 120 hours. After the sample was taken out of the oven, the hue of the reflected light was measured again on the aluminum vapor-deposited polyester film, and the amount of change in the hue of the reflected light before and after the heating test √{(Δa ^* ) ² +(Δb ^* ) ² } was calculated.

Table 1 shows the types of resins used for forming the resin coating layer and the evaluation results of the alignment liquid crystal film in Examples 1 to 6 and Comparative Examples 1 to 3 above.

[Table 1]

In Comparative Example 1 in which no surface treatment for aligning the liquid crystal layer was performed, the amount of change in Re before and after the heating test was 3%, and the change in hue of reflected light was 2.2, whereas in Comparative Example 1 treated with cyclopentanone In 2, the change in Re is suppressed, and the hue change of reflected light accompanying this is also suppressed. However, in Comparative Example 2, precipitates were confirmed on the surface of the alignment liquid crystal layer, resulting in poor appearance.

In Examples 1 to 6 in which a resin coating was formed on the alignment liquid crystal layer using a non-curable resin, the change in Re and the change in hue of reflected light were suppressed compared with Comparative Example 1, and the appearance was also good. The surface of the resin coating layer of Example 1 was dissolved in tetrahydrofuran to extract the resin components, and analyzed by MALDI-TOF mass spectrometry. As a result, unreacted liquid crystal monomers were confirmed. From these results, it is considered that by applying the resin solution, uncured substances in the alignment liquid crystal layer are extracted and taken into the resin coating layer, which contributes to the improvement of the heating durability of the alignment liquid crystal layer.

In Comparative Example 3, in which UV curing of the resin layer was performed after coating the alignment liquid crystal layer using a photocationically curable resin composition, the front Re was lowered after the heat durability test, and the heat durability was insufficient. From these results, it was found that by forming a non-curable resin coating layer on the alignment liquid crystal layer, the heating durability of the alignment liquid crystal layer was improved, and a circular polarizing plate with little change in retardation and little coloring and color change of reflected light was obtained.

[Example of Circular Polarizing Plate with Multiple Alignment Liquid Crystal Layers]

＜Fabrication of parallel alignment liquid crystal layer＞

55 parts by weight of a compound represented by formula (I), 25 parts by weight of a compound represented by formula (II) and 20 parts by weight of a compound represented by formula (III) were added to 400 parts by weight of cyclopentanone, After heating, stirring and dissolving at 60°C, it was cooled to room temperature to prepare a solution having a solid content concentration of 20% by weight.

[Chemical formula number 1]

To this solution were added 0.2 parts by weight of a surfactant ("MEGAFAC F-554" manufactured by DIC), 3 parts by weight of a photopolymerization initiator ("Omnirad 907" manufactured by IGM Resins) and 0.1 parts by weight of p-methoxyphenol , to prepare liquid crystal composition solution.

As the film base material, a film having a rubbing-treated alignment film on a triacetyl cellulose film was used. On the alignment film of the film substrate, the above-mentioned liquid crystal composition was applied by spin coating, and the liquid crystal was aligned by heating at 100° C. for 2 minutes. After cooling to room temperature, under a nitrogen atmosphere, irradiated with ultraviolet rays with a cumulative light intensity of 900 mJ/cm ² for photocuring to obtain a laminate A in which a parallel-aligned liquid crystal layer (thickness 4 μm) was formed on the film substrate. Transfer the oriented liquid crystal layer to a glass plate and measure the front retardation. As a result, the front retardation R(550) at a wavelength of 550nm is 130nm, and the ratio R of the front retardation R(550) at a wavelength of 550nm to the front retardation R(450) at a wavelength of 450nm (450)/R(550) is 0.85.

＜Fabrication of Vertically Aligned Liquid Crystal Layer＞

The following chemical formula (n=0.35, for convenience, represented by block polymer bodies) is a side chain type liquid crystal polymer with a weight average molecular weight of 5000: 20 parts by weight, a polymerizable liquid crystal compound showing a nematic liquid crystal phase ( "Paliocolor LC242" manufactured by BASF): 80 parts by weight and a photopolymerization initiator ("Omnirad 907" manufactured by IGM Resins): 5 parts by weight were dissolved in 400 parts by weight of cyclopentanone to prepare a liquid crystalline composition.

[Chemical formula number 2]

As the film substrate, a biaxially stretched norbornene-based film ("ZEONOA film" manufactured by Zeon Japan, thickness: 52 μm, front retardation: 50 nm) was used. On the surface of the film substrate, apply the above-mentioned liquid crystalline composition with a bar coater so that the thickness after drying becomes 1 μm, heat at 80° C. for 2 minutes, cool to room temperature for aligning liquid crystals, and irradiate in a nitrogen atmosphere. Ultraviolet rays of 700 mJ/cm ² photocured the liquid crystal monomers to obtain a laminate B in which a vertically aligned liquid crystal layer was formed on a film substrate.

<Preparation of adhesive sheet>

In a reaction vessel, 92 parts by weight of butyl acrylate as a monomer, 5 parts by weight of N-acryloylmorpholine, 2.9 parts by weight of acrylic acid, 0.1 part by weight of 2-hydroxyethyl acrylate and 2,2 0.1 part by weight of '-azobisisobutyronitrile was added together with ethyl acetate, and it was made to react at 55 degreeC for 8 hours under nitrogen flow. Then, ethyl acetate was added to the reaction liquid to obtain a solution of an acrylic polymer having a weight average molecular weight of 1,780,000. In this solution, 0.15 parts by weight of dibenzoyl peroxide ("NYPER BMT" manufactured by NOF) as a crosslinking agent, and trimethylolpropane/toluene diisocyanate plus 0.6 parts by weight of the finished product ("Coronate L" manufactured by Tosoh) was used to obtain an adhesive composition. This adhesive composition was applied to the release-treated surface of a release film (polyethylene terephthalate film treated with silicone release), and dried and cross-linked at 150°C to produce Adhesive sheet with a thickness of 5 μm.

<Example 7>

An acrylic polymer having a weight average molecular weight of 80,000 obtained by copolymerizing methyl methacrylate and 3-methacrylamidophenylboronic acid in a weight ratio of 97:3 was dissolved in ethyl acetate so that the solid content concentration became 3% by weight to prepare a resin solution. On the surface of the parallel alignment liquid crystal layer of laminate A, after coating the resin solution with a wire bar (#10), the solvent was removed by heating at 85° C., and a resin coating with a thickness of about 300 nm was formed on the surface of the parallel alignment liquid crystal layer to obtain A laminate D having a parallel alignment liquid crystal layer and a resin coating in this order on a film substrate was obtained.

On the resin coating layer of the laminate D, apply the above-mentioned UV curable adhesive to a thickness of about 1 μm, and attach the surface of the vertical alignment liquid crystal layer of the laminate B to the coated layer of the adhesive. , and irradiate ultraviolet rays with a cumulative light intensity of 1000mJ/cm ² to cure the adhesive.

Then, the film substrate was peeled and removed from the surface of the parallel alignment liquid crystal layer, and the polarizer-side surface of a single protective polarizing plate was bonded to the exposed parallel alignment liquid crystal layer via the above-mentioned adhesive layer. When laminating, the angle formed by the absorption axis direction of the polarizer and the alignment direction of the liquid crystal molecules in the parallel alignment liquid crystal layer (the rubbing direction of the alignment film of the film substrate) was 45°. Then, the film substrate was peeled off from the surface of the vertical alignment liquid crystal layer, and the parallel alignment liquid crystal layer was bonded to the surface of the polarizer side of the single protective polarizing plate via an adhesive layer to obtain a film on which a resin coating layer and a liquid crystal layer were formed. A laminate (circularly polarizing plate) in which a vertically aligned liquid crystal layer is bonded to the adhesive layer.

＜Comparative example 4＞

In the same manner as in Example 7, a resin coating layer with a thickness of about 300 nm was formed on the surface of the parallel alignment liquid crystal layer to obtain a laminate D. On the resin coating layer of the laminated body D, the polarizer-side surface of the single protective polarizing plate was bonded via the above-mentioned pressure-sensitive adhesive layer. When bonding, the angle formed by the absorption axis direction of the polarizer and the alignment direction of the liquid crystal molecules in the parallel alignment liquid crystal layer (the rubbing direction of the alignment film of the film substrate) was set to 45°.

Then, the film base material is peeled off from the surface of the parallel alignment liquid crystal layer, and the above-mentioned UV curable adhesive is applied to a thickness of about 1 μm on the exposed parallel alignment liquid crystal layer, and the coating layer of the adhesive is pasted. After the surface of the laminated body B on the side of the vertical alignment liquid crystal layer was laminated, ultraviolet rays with a cumulative light intensity of 1000 mJ/cm ² were irradiated to cure the adhesive. Then, the film substrate was peeled and removed from the surface of the vertical alignment liquid crystal layer, and a laminate of the resin coating layer and the parallel alignment liquid crystal layer was bonded to the surface of the polarizer side of the single protective polarizer through an adhesive layer to obtain the A laminate (circularly polarizing plate) having a vertical alignment liquid crystal layer is bonded to the parallel alignment liquid crystal layer via an adhesive layer.

<Example 8>

Instead of the solution of the acrylic polymer, a methyl ethyl ketone solution containing an acrylic polymer and an epoxy resin ("jER YX7200B35" manufactured by Mitsubishi Chemical) at a weight ratio of 85:15 and having a solid content concentration of 3% by weight was used. Other than that, in the same manner as in Example 7, a resin coating with a thickness of about 300 nm was formed on the surface of the parallel alignment liquid crystal layer. Thereafter, in the same manner as in Example 7, on the surface of the polarizer side of the single protective polarizing plate, a parallel alignment liquid crystal layer was bonded via an adhesive layer to obtain a liquid crystal layer bonded thereon via a resin coating layer and an adhesive layer. A laminate (circularly polarizing plate) composed of a vertically aligned liquid crystal layer.

<Example 9>

A circular polarizing plate was produced in the same manner as in Example 8 except that the thickness of the resin coating was changed to about 600 nm.

＜Comparative example 5＞

In the same manner as in Example 8, a resin coating with a thickness of about 300 nm was formed on the surface of the parallel alignment liquid crystal layer using a mixed resin solution of an acrylic polymer and an epoxy resin. Thereafter, in the same manner as in Comparative Example 4, on the face of the polarizer side of the single protective polarizing plate, a laminate of the resin coating layer and the parallel alignment liquid crystal layer was bonded via an adhesive layer to obtain a laminate on the parallel alignment liquid crystal layer. A laminate (circularly polarizing plate) in which a homeotropic alignment liquid crystal layer is bonded via an adhesive layer.

[evaluate]

On the surface of the circularly polarizing plates of Examples 7 to 9 and Comparative Examples 4 and 5 on the side of the vertical alignment liquid crystal layer, an acrylic adhesive sheet with a thickness of 15 μm was attached, and the adhesive sheet was attached to a glass plate to produce Samples for evaluation. After measuring the frontal retardation (initial value) at a wavelength of 590 nm with a phase difference meter (manufactured by Oji Scientific Instruments "KOBRA 21-ADH"), the sample for evaluation was placed in an air-circulating constant temperature oven at 85°C, and after 120 hours, Frontal delay was measured after 240 hours and after 500 hours, and the rate of change from the initial value was calculated.

The lamination structure of the circular polarizing plates of the above-mentioned Examples 7 to 9 and Comparative Examples 4 and 5, the polymer type and thickness of the resin coating, and the front side of the heat durability test (after 120 hours, after 240 hours and after 500 hours) The rate of change of delay is shown in Table 2.

[Table 2]

For Comparative Examples 4 and 5 in which an adhesive layer was provided in contact with the parallel alignment layer and a vertical alignment liquid crystal layer was bonded, a reduction in frontal retardation of 1% or more was observed through a 120-hour heating test, while in the parallel alignment layer In Examples 7 to 9 in which a resin coating layer was provided on the alignment liquid crystal layer and a vertical alignment liquid crystal layer was bonded thereon via an adhesive layer, the change in frontal retardation caused by the heating durability test was suppressed.

From these results, it can be seen that by providing the resin coating so that the parallel alignment liquid crystal layer does not come into contact with the curable adhesive layer, the heat durability of the alignment liquid crystal layer is improved and the change in retardation is suppressed. As can be seen from the comparison between Example 8 and Example 9, when the thickness of the resin coating layer is large, the heating durability tends to be improved (retardation change is suppressed).

[Description of Reference Signs]

1 Alignment liquid crystal layer

6 resin coating

8 Support base plate

4 Optical layer (polarizer)

5 Optical layer (orientation liquid crystal layer)

3, 7 Adhesive layer

2, 12 Adhesive layer

9 partitions

50 image display units.

Claims (23)

1. An alignment liquid crystal film, which possesses: a first alignment liquid crystal layer in which liquid crystal molecules have been aligned; a resin coating contacting the first main surface of the first alignment liquid crystal layer; and on the resin coating The optical layer bonded via an adhesive layer, wherein the resin coating layer is a non-curable resin layer. 2 . The aligned liquid crystal film according to claim 1 , wherein the glass transition temperature of the resin coating is 20° C. or higher. 3. The oriented liquid crystal film according to claim 1 or 2, wherein the thickness of the adhesive layer is 0.01 to 5 μm. 4 . The alignment liquid crystal film according to claim 1 , wherein the adhesive constituting the adhesive layer is an active energy ray-curable adhesive. 5. The oriented liquid crystal film according to any one of claims 1-4, wherein the optical layer is a polarizer, a transparent film or other oriented liquid crystal layers. 6. The oriented liquid crystal film according to any one of claims 1 to 5, wherein the resin coating has a thickness of 0.05 to 3 μm. 7. The alignment liquid crystal film according to any one of claims 1 to 6, wherein the weight average molecular weight of the resin material constituting the resin coating layer is 20,000 or more. 8. The alignment liquid crystal film according to any one of claims 1 to 7, wherein the resin coating layer comprises a non-curable acrylic resin or a non-curable epoxy resin. 9 . The alignment liquid crystal film according to claim 1 , wherein an uncured liquid crystal compound constituting the first alignment liquid crystal layer is contained in the resin coating layer. 10 . The alignment liquid crystal film according to claim 1 , wherein an adhesive layer is provided on the second main surface side of the first alignment liquid crystal layer. 11 . 11. The alignment liquid crystal film according to any one of claims 1 to 10, wherein in the first alignment liquid crystal layer, liquid crystal molecules are aligned in parallel. 12. The alignment liquid crystal film according to claim 11, wherein the optical layer comprises a polarizer, and the alignment direction of the liquid crystal molecules in the first alignment liquid crystal layer is formed by the absorption axis direction of the polarizer. The angle is 10-80°. 13. The alignment liquid crystal film according to claim 11 or 12, wherein the optical layer is a second alignment liquid crystal layer in which liquid crystal molecules have been vertically aligned, and is attached to the second main surface side of the first alignment liquid crystal layer With polarizer. 14 . The oriented liquid crystal film according to claim 13 , wherein the first oriented liquid crystal layer is attached to the polarizer through an adhesive layer. 15. The aligned liquid crystal film according to claim 14, wherein the adhesive layer is in contact with the second main surface of the first aligned liquid crystal layer. 16. An image display device, which is formed by disposing the oriented liquid crystal film according to any one of claims 1 to 15 on an image display unit. 17. A method for manufacturing an aligned liquid crystal film, which is the method for manufacturing an aligned liquid crystal film according to any one of claims 1 to 15, wherein the coating on the first main surface of the first aligned liquid crystal layer includes A resin solution of a resin and an organic solvent is used to form the resin coating; the resin coating is bonded to the optical layer via an adhesive. 18 . The method for producing an aligned liquid crystal film according to claim 17 , wherein heating is performed at 40 to 150° C. after applying the resin solution and before bonding the optical layer. 19. The manufacturing method of an alignment liquid crystal film according to claim 17 or 18, wherein, by coating a liquid crystalline composition containing a photopolymerizable liquid crystal monomer on a support substrate, the liquid crystal on the support substrate The composition is heated to align the liquid crystal monomers in a liquid crystal state, and the liquid crystal monomers are polymerized or cross-linked by light irradiation, thereby forming the first aligned liquid crystal layer. 20. The method for manufacturing an aligned liquid crystal film according to claim 19, wherein the support substrate is a resin film. 21. The manufacturing method of an alignment liquid crystal film according to claim 19 or 20, wherein, in the state where the first alignment liquid crystal layer is provided on the support substrate, the alignment between the first alignment liquid crystal layer and the alignment liquid crystal layer The resin solution is applied to the non-contact surface of the support substrate. 22. The manufacturing method of an alignment liquid crystal film according to claim 19 or 20, wherein the support substrate is peeled from the first alignment liquid crystal layer, and the first alignment liquid crystal layer exposed by the peeling of the support substrate is The surface is coated with the resin solution. 23. The method for producing an aligned liquid crystal film according to any one of claims 17 to 22, wherein the organic solvent of the resin solution has solubility to the photopolymerizable liquid crystal monomer and is insoluble or difficult to dissolve The photocured product of the photopolymerizable liquid crystal monomer.

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