JP2006225496A - Water-soluble resin film and method for producing the same, polarizer and method for producing the same, polarizing plate, optical film, and image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-soluble resin film having a structure having a minute domain dispersed in a matrix formed of a water-soluble resin and having good in-plane uniformity, and to provide a method for producing the same. <P>SOLUTION: The water-soluble resin film having a structure having a minute domain dispersed in a matrix formed of a water-soluble resin has a thickness variation in the transverse direction of 15% or less and a haze variation in the transverse direction of 5% or less. The water-soluble resin film is produced by coating a mixed solution having a minute domain formed of a birefringence material dispersed in a water-soluble resin solution on a metal surface having a surface roughness (Ra) of 1.5 μm or less and drying the coating to form the film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a water-soluble resin film and a method for producing the same. The water-soluble resin film can be used, for example, as a raw film for manufacturing a polarizer. Moreover, this invention relates to the polarizer using the said water-soluble resin film, and its manufacturing method. The present invention also relates to a polarizing plate and an optical film using the polarizer. Furthermore, the present invention relates to an image display device such as a liquid crystal display device, an organic EL display device, a CRT, or a PDP using the polarizer, polarizing plate, or optical film.

  Liquid crystal display devices are rapidly marketed in watches, mobile phones, PDAs, notebook computers, personal computer monitors, DVD players, TVs, and the like. A liquid crystal display device visualizes a change in polarization state due to switching of liquid crystal, and a polarizer is used from the display principle. In recent years, liquid crystal monitors, liquid crystal TVs, and the like are rapidly spreading. Accordingly, in these applications, display with high brightness and high contrast is required, and the polarizer is also brighter (high transmittance) and higher. The one with contrast (high polarization degree) has been developed and introduced. Further, due to the increase in size of the screen, a polarizer having good optical characteristics such as in-plane uniformity (dyeing unevenness, variation in polarization characteristics) is required even in a large area.

  As a polarizer, for example, an iodine-based polarizer having a stretched structure by adsorbing iodine to a water-soluble resin such as polyvinyl alcohol is widely used because it has a high transmittance and a high degree of polarization (Patent Document 1). . In such a polarizer, in order to achieve uniform optical properties, a uniform thickness original film (water-soluble resin film such as a polyvinyl alcohol film) is used. The original film is a dichroic material such as iodine. However, the uniformity of the raw film as the material is particularly important. Therefore, in order to obtain a polarizer having a large area and satisfying optical characteristics such as in-plane uniformity (dyeing unevenness, variation in polarization characteristics), for example, improvements have been made to devise control of the thickness of the original film.

  As a method for producing a raw film, for example, a film-forming raw material containing a water-soluble resin such as a solution or a melted polyvinyl alcohol is discharged from a die onto a heated belt or drum and dried to form a film. The method used is industrially used.

  However, since the said raw film is used for manufacture of the polarizer for optical uses, there are various problems. For example, in a film-forming method in which a solution or molten film-forming raw material is discharged onto a belt and dried, the required quality of the belt is that the belt seam is uniform, and the surface is glossy over a width of 2 m or more and a length of tens of m or more. In some cases, it is necessary to manufacture a belt that is technically wide and long. In addition, there may be a problem that the optical uniformity is lost due to transfer of stains on the belt due to resin adhesion at the time of film formation to the film-forming film, or disturbance of the film refractive index of the dirty portion. On the other hand, in a drum film forming machine, a seamless uniform drum can be produced industrially, and a film forming method for a raw film using the drum has also been proposed (Patent Documents 2 and 3). However, even if a polarizer is produced using a raw film formed by these methods, the uniformity of optical characteristics required for recent large-screen liquid crystal TVs is insufficient.

  In addition, since iodine-type polarizers have a relatively low degree of polarization on the short wavelength side, they have problems in hue such as blue loss in black display and yellowness in white display on the short wavelength side. In addition, the iodine-based polarizer tends to generate unevenness during iodine adsorption. For this reason, there is a problem in that visibility is deteriorated because it is detected as unevenness of transmittance particularly in black display.

  In response to the above problem, the present applicant, as a polarizer, further water-soluble resin film obtained by filming a solution in which a liquid crystalline birefringent material is dispersed as a microregion in a water-soluble resin such as polyvinyl alcohol, and further iodine dyeing Proposed (Japanese Patent Application No. 2003-329744). When the polymer composite film (water-soluble resin film) containing the liquid crystalline birefringent material in a dispersed region is stretched, the microregion formed by the liquid crystalline birefringent material is also stretched and exists in the film as an ellipsoid. . Scattering occurs when linearly polarized light in the absorption axis direction of the polarizer is incident. By increasing the optical path length due to scattering, the probability that light in the absorption axis direction is absorbed by iodine increases, and a high degree of polarization, high transmittance, and hue neutral in a short wavelength region can be achieved.

However, since the polarizer using the polymer composite film utilizes the anisotropic scattering effect, the orientation state of the microregion formed from the liquid crystalline birefringent material dispersed in the film is poor. In some cases, not only the anisotropic scattering effect is not exhibited, but also the depolarization occurs due to a fine region with poor alignment, and the effect as a polarizer cannot be fully exhibited.
JP 2001-296427 A Japanese Patent No. 3422759 Japanese Patent No. 3478532

  The present invention provides a water-soluble resin film having a structure in which microregions are dispersed in a matrix formed of a water-soluble resin, having excellent in-plane uniformity, and a method for producing the same. With the goal.

  Moreover, an object of this invention is to provide the polarizer using the said water-soluble resin film, and its manufacturing method.

  Another object of the present invention is to provide a polarizing plate and an optical film using the polarizer. Furthermore, it aims at providing the image display apparatus using the said polarizer, a polarizing plate, and an optical film.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by the following water-soluble resin film and the like, and have completed the present invention.

  That is, the present invention is a water-soluble resin film having a structure in which minute regions are dispersed in a matrix formed of a water-soluble resin, the thickness unevenness in the width direction of the film is 15% or less, and the width direction It is related with a water-soluble resin film that the nonuniformity of haze is 5% or less.

  In the water-soluble resin film of the present invention, the thickness unevenness in the width direction of the film is controlled to be 15% or less, and the in-plane uniformity is good. The optical unevenness can be suppressed. When the thickness unevenness in the width direction of the film exceeds 15%, the in-plane uniformity is insufficient. The thickness unevenness in the width direction of the film is preferably as small as possible, and is preferably 12% or less, more preferably 9% or less, and further preferably 6% or less.

  In the water-soluble resin film of the present invention, haze unevenness in the width direction of the film is controlled to 5% or less. A large haze unevenness indicates a possibility that the micro regions are not uniformly dispersed. If the unevenness in the width direction of the film is larger than 5%, when the film is used as a raw film as a polarizer, the anisotropic scattering effect is uneven due to the poor alignment of the dispersed microregions, and the film is uniform. The polarization characteristics may be impaired, which is not preferable. The haze unevenness in the width direction of the film is preferably 3% or less, more preferably 1% or less.

  In the water-soluble resin film, the water-soluble resin is preferably a polyvinyl alcohol resin.

  In the water-soluble resin film, the micro area is preferably formed of a birefringent material. In the water-soluble resin film, the birefringent material preferably exhibits liquid crystallinity at least at the time of the alignment treatment.

The present invention is a method for producing the water-soluble resin film,
A mixed solution in which a minute region formed of a birefringent material is dispersed in a water-soluble resin solution is applied to a metal surface having a surface roughness (Ra) of 1.5 μm or less and dried to form a film. It is related with the manufacturing method of the water-soluble resin film characterized by performing.

  The orientation of the microregion is considered to be controlled by, for example, the stress applied to the microregion when the water-soluble resin film is stretched. For this reason, if the stress applied to the film is non-uniform, the micro regions dispersed in the film will vary, and the anisotropic scattering effect will not be exhibited, and it will be considered that depolarization will occur due to poor alignment. .

  About the orientation defect of a micro area | region, it examined about the thickness of the water-soluble resin film before extending | stretching. If the thickness of the film is non-uniform in the surface, adsorption unevenness such as iodine occurs in the dyeing process as in the case of a polarizer produced by a conventional polyvinyl alcohol film, and further, poor alignment in a minute region. It was a cause to cause. The water-soluble resin film can reduce dyeing unevenness as compared with the conventional polyvinyl alcohol film, but it has been found that the thickness uniformity of the film is important because it has a minute region.

  Therefore, in the present invention, when the water-soluble resin film is produced, the mixed solution is formed by applying and drying the mixed solution on a metal surface having a surface roughness (Ra) of 1.5 μm or less. By performing the film formation on a metal surface having a surface roughness (Ra) of 1.5 μm or less, thickness unevenness in the width direction of the film is controlled to 15% or less, and thickness uniformity is good, and The unevenness of the haze in the width direction of the film is controlled to 5% or less, and a water-soluble resin film with good dispersibility in a minute region can be obtained.

  Conventionally, when a water-soluble resin film is formed on a metal surface (metal drum, metal belt, etc.) having a rough surface, when the dried film is peeled off from the metal surface, the liquid crystallinity A minute region formed of a birefringent material or the like was transferred to the metal surface and became cloudy, and contaminated the metal surface. Since the metal surface is moving continuously, if the metal surface is contaminated, the solution will be repelled when a new solution is cast. This is due to coating unevenness and transfer of the liquid crystalline birefringent material to a new film surface, which causes non-uniform film thickness, as well as optical properties due to adhesion of the liquid crystalline birefringent material to the film surface. It was the cause of the problem. As in the present invention, by performing the film formation on a metal surface having a surface roughness (Ra) of 1.5 μm or less, contamination of the metal surface can be prevented, and there is a problem of optical defects due to the contamination. It can also be eliminated.

  The metal surface roughness (Ra) is preferably 1 μm or less, more preferably 0.7 μm or less, and further preferably 0.2 μm or less. The smaller the surface roughness (Ra), the higher the uniformity of the coated surface and the better the uniformity of the film thickness after drying. Moreover, it can suppress that the micro area | region formed from a liquid crystalline birefringent material transfers to a metal surface.

  In the method for producing the water-soluble resin film, the metal surface is preferably a metal surface formed by metal plating. Metal plating is preferable in terms of smoothness and durability of the metal surface. As the metal plating, chrome plating is suitable.

  The present invention also relates to a polarizer, wherein the water-soluble resin film is stretched and contains a dichroic material in a matrix formed of the water-soluble resin.

  The polarizer of the present invention uses a water-soluble resin film having good thickness uniformity and good haze uniformity as a raw film, and has good optical properties. In addition, the orientation of a minute region formed by a liquid crystalline birefringent material or the like is good, and the optical characteristics are good. Further, a polarizer satisfying optical characteristics such as in-plane uniformity (dyeing unevenness, variation in polarization characteristics) and the like in a large area can be obtained.

  The present invention also relates to a method for producing a polarizer, wherein the water-soluble resin film is subjected to a stretching process and a dyeing process using a dichroic material.

  The present invention also relates to a polarizing plate in which a transparent protective layer is provided on at least one surface of the polarizer.

  The present invention also relates to an optical film, wherein at least one of the polarizer and the polarizing plate is laminated.

  Furthermore, this invention relates to the image display apparatus characterized by using the said polarizer, the said polarizing plate, or the said optical film.

  The water-soluble resin film and polarizer of the present invention will be described below. The water-soluble resin film has a structure in which a film is formed of a water-soluble resin, and minute regions are dispersed using the film as a matrix. The polarizer has a structure in which a film is formed of the water-soluble resin, and the micro-region is dispersed using the film as a matrix, and the dichroic absorber is dispersed in the water-soluble resin as a matrix. Yes.

  Examples of the water-soluble resin include a polyvinyl alcohol resin or a derivative thereof conventionally used for a polarizer.

  As the polyvinyl alcohol resin, a resin obtained by saponifying a polyvinyl ester polymer obtained by radical polymerization of a vinyl ester monomer and using the vinyl ester unit as a vinyl alcohol unit can be used.

  Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valenate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, and the like. Among these, it is preferable to use vinyl acetate.

  When the above vinyl ester monomer is copolymerized, if necessary, the proportion of the copolymerizable monomer is within a range that does not impair the object of the present invention, preferably 15 mol% or less, more preferably 5 mol% or less. Can also be copolymerized.

  Examples of such copolymerizable monomers include olefins having 3 to 30 carbon atoms such as ethylene, propylene, 1-butene and isobutene; acrylic acid and salts thereof; methyl acrylate, ethyl acrylate, and acrylic acid n. Acrylic esters such as -propyl, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid and Salts thereof: methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate , Octadecyl methacrylate Methacrylic acid esters; acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetone acrylamide, acrylamide propane sulfonic acid and its salts, acrylamidopropyldimethylamine and its salts, N-methylol acrylamide and Acrylamide derivatives such as derivatives thereof; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and salts thereof, methacrylamidepropyldimethylamine and salts thereof or quaternary salts thereof, N-methylolmethacrylamide And methacrylamide derivatives such as derivatives thereof; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl Vinyl ethers such as nyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride Vinyl halides such as allyl acetate and allyl chloride; maleic acid and its salts or esters thereof; itaconic acid and its salts or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate, N- Examples thereof include N-vinylamides such as vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone.

The degree of polymerization and the degree of saponification of the polyvinyl alcohol resin are appropriately selected from the viewpoints of film strength, polarization characteristics, and durability. The degree of polymerization is preferably about 1000 to 10,000, more preferably 1700 to 5000, and further preferably 2000 to 4000. The degree of polymerization (P) of the polyvinyl alcohol resin is measured according to JIS-K6726. In other words, re-saponified polyvinyl alcohol resin, after purification, the intrinsic viscosity measured in water at 30 ℃ [η] (unit: dl / g) from the following equation: P = ([η] × 10 3/8. 29) ^{(1 / 0.62)} .

  The saponification degree of the polyvinyl alcohol resin is preferably 90 mol% or more, and more preferably 95 mol% or more from the viewpoint of the durability of the polarizer. Furthermore, 98 mol% or more, further 99 mol% or more is preferable. On the other hand, 99.99 mol% or less is preferable from the viewpoint of dyeability of the film. The degree of saponification indicates the proportion of units that are actually saponified to vinyl alcohol units among the units that can be converted to vinyl alcohol units by saponification. In addition, the saponification degree of polyvinyl alcohol-type resin can be measured by the method of JIS description.

  It is not particularly limited whether the material forming the microregion is isotropic or birefringent, but it is preferable to use a birefringent material. As the birefringent material, a material exhibiting liquid crystallinity at the time of alignment treatment (hereinafter referred to as a liquid crystalline material) is preferably used. That is, as long as the liquid crystalline material exhibits liquid crystallinity at the time of the alignment treatment, the formed microregion 2 may exhibit liquid crystallinity or may lose liquid crystallinity.

  The birefringent material (liquid crystalline material) forming the minute region may be nematic liquid crystalline, smectic liquid crystalline, cholesteric liquid crystalline, or lyotropic liquid crystalline. The liquid crystalline birefringent material may be a liquid crystalline thermoplastic resin or may be formed by polymerization of a liquid crystalline monomer. In the case of a liquid crystalline thermoplastic resin, those having a high glass transition temperature are preferred from the viewpoint of heat resistance after film formation. It is preferable to use a glass that is at least at room temperature. The liquid crystalline thermoplastic resin is usually aligned by heating, fixed by cooling, and forms a minute region in the film while maintaining liquid crystallinity. After blending, the liquid crystalline monomer can form microregions in the film in a state of being fixed by polymerization, cross-linking, etc., but in some microregions formed, liquid crystallinity is lost.

  As the liquid crystalline thermoplastic resin, polymers of various skeletons of main chain type, side chain type, or a composite type thereof can be used without particular limitation. Examples of the main chain type liquid crystal polymer include condensation polymers having a structure in which mesogenic groups composed of aromatic units and the like are bonded, for example, polymers such as polyester, polyamide, polycarbonate, and polyesterimide. Examples of the aromatic unit that becomes a mesogenic group include phenyl, biphenyl, and naphthalene types, and these aromatic units have substituents such as a cyano group, an alkyl group, an alkoxy group, and a halogen group. May be.

  Side chain type liquid crystal polymers include polyacrylate, polymethacrylate, poly-α-halo-acrylate, poly-α-halo-cyanoacrylate, polyacrylamide, polysiloxane, and polymalonate main chains. Examples of the skeleton include those having a mesogenic group composed of a cyclic unit or the like in the side chain. Examples of the cyclic unit serving as a mesogenic group include biphenyl, phenylbenzoate, phenylcyclohexane, azoxybenzene, azomethine, azobenzene, phenylpyrimidine, diphenylacetylene, diphenylbenzoate, and bicyclohexane. Cyclohexylbenzene, terphenyl and the like. In addition, the terminal of these cyclic units may have substituents, such as a cyano group, an alkyl group, an alkenyl group, an alkoxy group, a halogen group, a haloalkyl group, a haloalkoxy group, a haloalkenyl group, for example. Moreover, what has a halogen group can be used for the phenyl group of a mesogenic group.

  Further, the mesogenic group of any liquid crystal polymer may be bonded via a spacer portion that imparts flexibility. Examples of the spacer portion include a polymethylene chain and a polyoxymethylene chain. The number of repeating structural units forming the spacer portion is appropriately determined depending on the chemical structure of the mesogenic portion, but the repeating unit of the polymethylene chain is 0 to 20, preferably 2 to 12, and the repeating unit of the polyoxymethylene chain is 0 to 0. 10, preferably 1-3.

  The liquid crystalline thermoplastic resin preferably has a glass transition temperature of 45 ° C. or higher, more preferably 70 ° C. or higher. Further, those having a weight average molecular weight of about 2,000 to 100,000 are preferred.

  Examples of the liquid crystalline monomer include those having a polymerizable functional group such as an acryloyl group or a methacryloyl group at the terminal, and a mesogenic group composed of the cyclic unit or the like and a spacer portion. In addition, as a polymerizable functional group, one having two or more acryloyl groups, methacryloyl groups and the like can be used to introduce a crosslinked structure to improve durability.

  When using a liquid crystalline monomer, a photopolymerization initiator, a thermal polymerization initiator, a photosensitizer, a polymerization inhibitor, and the like for curing and crosslinking can be used together with the liquid crystalline monomer. These initiators and the like can be contained in the liquid crystalline birefringent material before preparing the mixed solution, in addition to the prepared mixed solution, the water-soluble resin solution before preparing the solution, and the obtained mixed solution. Can be added.

  Various photopolymerization initiators can be used without particular limitation. Examples include Irgacure 184, Irgacure 907, Irgacure 369, Irgacure 651, Irgacure 819, etc., manufactured by Ciba Specialty Chemicals. The blending amount of the photopolymerization initiator is preferably 10 parts by weight or less, more preferably about 0.01 to 10 parts by weight, still more preferably 0.05 to 5 parts by weight with respect to 100 parts by weight of the liquid crystalline birefringent material. Part.

  Examples of the photosensitizer include photosensitizers such as benzoin photosensitizers, acetophenone photosensitizers, and benzyl ketal photosensitizers. For example, acetophenone, benzophenone, 4-methoxybenzophenone, benzoin methyl ether, 2,2-dimethoxy-2-phenyldimethoxy-2-phenylacetophenone, benzyl, benzoyl, 2-methylbenzoin, 2-hydroxy-2-methyl-1- Examples include phenyl-1-one, 1- (4-isopropylphenyl-2-hydroxy-2-methylpropan-1-one, triphenylphosphine, 2-chlorothioxanthone, etc. The amount of photosensitizer added is The same as the photopolymerization initiator.

  Various polymerization inhibitors can be used without particular limitation. For example, hydroquinone monomethyl ether, hydroquinone, methoquinone, p-benzoquinone, phenothiazine, mono-t-butylhydroquinone, catechol, pt-butylcatechol, benzoquinone, 2,5-di-t-butylhydroquinone, anthraquinone, 2, Examples thereof include 6-di-t-butylhydroxytoluene and t-butylcatechol. Any device that exhibits the same effect may be used. The addition amount of the polymerization inhibitor is the same as that of the photopolymerization initiator.

  The material for forming the minute region is not limited to the liquid crystalline birefringent material, and a non-liquid crystalline resin can be used as long as the material is different from the polyvinyl alcohol resin. Examples of the resin include polyvinyl alcohol and derivatives thereof, polyolefin, polyarylate, polymethacrylate, polyacrylamide, polyethylene terephthalate, and acrylic styrene copolymer. As a material for forming the minute region, particles having no birefringence can be used. Examples of the fine particles include resins such as polyacrylate and acrylic styrene copolymer. The size of the fine particles is not particularly limited, but those having a particle size of 0.05 to 500 μm, preferably 0.5 to 100 μm are used. The liquid crystal birefringent material is preferably used as the material for forming the minute region, but the liquid crystalline birefringent material can be used by mixing a non-liquid crystalline birefringent material. Furthermore, a non-liquid crystalline birefringent material can be used alone as a material for forming a minute region.

  The production process of the water-soluble resin film of the present invention is not particularly limited. For example, a mixed solution in which microregions formed of a birefringent material are dispersed in a water-soluble resin solution is used for surface roughness (Ra). Is formed on a metal surface of 1.5 μm or less and dried. Hereinafter, a case where a liquid crystalline birefringent material is used as a material to be a minute region will be described as a representative example. Other materials also conform to the liquid crystal birefringent material.

  The water-soluble resin solution is prepared by dissolving a water-soluble resin such as the polyvinyl alcohol-based resin in water or a solvent that can be uniformly mixed with water by a conventional method. As the solvent other than water, a solvent that can be uniformly mixed with water can be used. Examples thereof include alcohol solvents such as methanol, ethanol, propanol, butanol, isobutanol, amyl alcohol, octanol, ethylene glycol and alkyl cellosolve, and polar solvents such as dimethylformamide, dimethyl sulfoxide, formic acid, acetic acid and propionic acid. Alcohol solvents can be used to promote defoaming.

  The addition amount of the liquid crystalline birefringent material is 1 to 50 parts by weight, preferably 2 to 20 parts by weight, and more preferably 3 to 10 parts by weight with respect to 100 parts by weight of the water-soluble resin. If it is less than 1 part by weight, it is not preferable in terms of anisotropic scattering effect. On the other hand, if the amount exceeds 50 parts by weight, the proportion of the liquid crystalline birefringent material that forms microregions in the resulting film increases, and the orientation of the microregions tends to decrease after stretching the film. It is not preferable.

  The method for preparing the mixed solution is not particularly limited, and for example, it is performed by adding a liquid crystalline birefringent material to a water-soluble resin solution and uniformly dispersing the liquid crystalline birefringent material by stirring.

  A general-purpose stirrer can be used as long as the stirrer can disperse the liquid crystalline birefringent material uniformly. Further, a high shear stirrer such as a homomixer or an ultrasonic homogenizer can be used. When stirring, it is desirable to control the conditions so that bubbles do not enter. The time for performing the defoaming operation on the resulting mixed solution can be shortened, and a film free from bubbles can be produced.

  The concentration of the water-soluble resin solution is not particularly limited, but is preferably 7% by weight or more. When the concentration is low, the solution viscosity becomes low, which is not preferable for film formation. The solution concentration is preferably 7 to 30% by weight, more preferably 12 to 20% by weight. It should be noted that a low concentration solution of less than 7% by weight may be used as long as concentration adjustment is separately performed in film formation. In addition, a low concentration solution of less than 7% by weight can be used by controlling the coating method during film formation.

  The liquid crystalline birefringent material at the time of addition may be added in a solid state, a liquid crystal state, or a liquid state having a liquid crystal isotropic transition temperature or higher. The water-soluble resin solution at the time of adding the liquid crystalline birefringent material or the mixed solution after the addition is heated to a temperature higher than the liquid crystal temperature of the liquid crystalline birefringent material. Thereby, the liquid crystalline birefringent material is in a liquid crystal state.

  When the liquid crystalline birefringent material is added, it is dissolved in a solvent that dissolves the liquid crystalline birefringent material or is used without being dissolved. It is preferable not to use a solvent. If a solvent is a trace amount solvent, it can volatilize with the heat | fever of a water-soluble resin solution. On the other hand, if the solvent is dissolved in the finally obtained mixed solution, there is a possibility that bubbles are formed after film formation. Therefore, it is preferable to use a solvent that does not cause bubbles after film formation and is easily volatilized. Examples of the solvent include water, toluene, xylene, hexane, cyclohexane, dichloromethane, trichloromethane, dichloroethane, trichloroethane, tetrachloroethane, trichloroethylene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, tetrahydrofuran, and ethyl acetate. . The solvent of the water-soluble resin solution and the solvent of the liquid crystalline birefringent material may be the same or different.

  The mixed solution can contain various additives. For example, it is preferable to contain a plasticizer. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include polyhydric alcohols such as glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. These can be used alone or in combination of two or more. The amount of the plasticizer used is not particularly limited, but if the amount used is too large, the flexibility of the film after film formation becomes too high, and the handleability is lowered. The amount is preferably 30 parts by weight or less. Preferably it is 0.5-30 weight part, More preferably, it is 2-20 weight part, More preferably, it is 3-15 weight part. By adding a plasticizer, flexibility can be imparted to the film after film formation, and the peelability from the coated surface and the film winding property can be improved. Moreover, when producing a polarizer, swelling property, dyeability, and stretchability can be improved.

  In addition, various additives such as a surfactant, a dispersant, an antifoaming agent, an ultraviolet absorber, a flame retardant, an antioxidant, a release agent, a lubricant, a colorant, and a fluorescent agent are added to the mixed solution of the present invention. It can be contained as long as the purpose is not impaired.

  These additives can be added to a water-soluble resin solution, a liquid crystalline birefringent material, or a mixed solution obtained by mixing them.

  As for the dispersion of the liquid crystalline birefringent material in the water soluble resin solution, there is a method using the phase separation phenomenon between the water soluble resin such as polyvinyl alcohol resin used in the water soluble resin solution and the liquid crystalline birefringent material. For example, there is a method of selecting a material that is hardly compatible with the water-soluble resin as the liquid crystalline birefringent material and dispersing the liquid crystalline birefringent material in a water-soluble resin solution through a dispersant such as a surfactant. Depending on the combination of the liquid crystal birefringent material and the water-soluble resin, the dispersant may not be added.

  The type of the surfactant is not particularly limited, but an anionic or nonionic surfactant is preferable. As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate, a sulfate type such as octyl sulfate, and a sulfonic acid type anionic surfactant such as dodecylbenzene sulfonate are suitable.

  Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether, alkylphenyl ether types such as polyoxyethylene octylphenyl ether, alkyl ester types such as polyoxyethylene laurate, and polyoxyethylene laurylamino. Alkylamine type such as ether, alkylamide type such as polyoxyethylene lauric acid amide, polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether, alkanolamide type such as oleic acid diethanolamide, polyoxyalkylene allyl phenyl ether, etc. Nonionic surfactants such as allyl phenyl ether type are preferred. These surfactants can be used alone or in combination of two or more.

  The addition amount of the surfactant is 1 part by weight or less with respect to 100 parts by weight of the water-soluble resin, more preferably 0.01 to 1 part by weight, more preferably 0.02 to 0.5 part by weight. 0.05 to 0.3 parts by weight is most preferable. When the amount is less than 0.01 part by weight, the effect of improving stretchability and dyeing property is hardly exhibited, and when the amount is more than 1 part by weight, it may elute on the film surface and cause blocking, and the handleability may be lowered.

  Although the volatile content concentration of the mixed solution is not particularly limited, it is preferably prepared so that the volatile concentration is 55 to 90% by weight, more preferably 60 to 90% by weight. When the volatile concentration decreases, it becomes difficult to dissolve polyvinyl alcohol, and the viscosity of the solution increases, so that the uniform dispersibility of the liquid crystalline birefringent material is added, and film formation becomes difficult. On the other hand, when the concentration of volatile components increases, the viscosity of the solution becomes too low, and it may be difficult to form a film with good thickness uniformity.

  The water-soluble resin film is produced by coating the mixed solution on a metal surface having a surface roughness (Ra) of 1.5 μm or less, and drying to form a film. Thereby, a film in which minute regions are dispersed in the matrix is produced.

  Although there is no restriction | limiting in particular in the metal material which apply | coats a mixed solution, Usually, stainless steel is used suitably. The metal surface can be formed by metal plating. The object to be metal-plated may be metal or other than metal. Metal plating is preferable for preventing scratches on the surface. As the type of metal plating, for example, chromium plating, chromium oxide plating, nickel plating, zinc plating, and the like are suitable. These can be used alone or in combination of two or more kinds of multilayers, but chrome plating is particularly preferable from the viewpoint of ease of obtaining surface smoothness and durability.

  The metal surface is industrially a metal drum or a metal belt, but may have a planar shape. In consideration of productivity, a metal drum is preferable.

  Examples of the method for forming a mixed solution include a casting film formation method, a wet film formation method (discharge into a poor solvent), a dry and wet film formation method, and a gel film formation method (cooling the solution once). After gelling, a method of extracting and removing the solvent to form a film), and further a combination of these methods can be mentioned. Among these, the casting film forming method is preferable because a highly transparent film can be obtained. The solvent in the solution is removed by heat drying. The thickness of the water-soluble resin film thus obtained is not particularly limited, but is usually about 15 to 3000 μm, and further 30 to 1500 μm.

  The haze of the water-soluble resin film in which the minute regions are dispersed is usually 0.5 to 100%, and can be adjusted by the amount of dispersion of the minute regions, the film forming method, or the like. When processing the formed film and using it as an optical film such as a polarizer, it is preferable to use a water-soluble resin film having a haze of 1% or more, considering optical characteristics such as light dispersion performance. More preferably, 5% or more is used, and more preferably 10% or more.

When using a water-soluble resin film as a polarizer,
(I) a step of orienting (stretching) the film obtained above,
(II) A step of dispersing (dying) a dichroic material such as an iodine-based absorber in the polyvinyl alcohol-based resin serving as the matrix;
Apply. In addition, the order of process (I) thru | or (II) can be determined suitably.

  Step (I) of orienting the film can be performed by stretching the film. Stretching includes uniaxial stretching, biaxial stretching, oblique stretching, etc., but uniaxial stretching is usually performed. The stretching method may be either dry stretching in air or wet stretching in an aqueous bath. In the case of adopting wet drawing, additives (boron compounds such as boric acid, alkali metal iodides and the like) can be appropriately contained in the aqueous bath. Although the draw ratio is not particularly limited, it is usually preferably about 2 to 10 times.

  By such stretching, the liquid crystalline birefringent material forming the micro-region is oriented in the stretching direction and develops birefringence. In step (II), the dichroic material can be oriented in the direction of the stretching axis. As the dichroic material, an absorbing dichroic dye can be used in place of the iodine-based absorber.

  It is desirable that the minute region is deformed according to stretching. When the microregion is a non-liquid crystalline birefringent material, the stretching temperature is close to the glass transition temperature of the resin, and when the microregion is a liquid crystalline birefringent material, the liquid crystalline birefringent material is nematic or smectic, etc. It is desirable to select the temperature at which the liquid crystal state or isotropic phase state is reached. If the orientation is insufficient at the time of stretching, a step such as a heat orientation treatment may be separately added.

  In addition to the above stretching, an external field such as an electric field or a magnetic field may be used for the orientation of the liquid crystalline birefringent material. In addition, photoreactive substances such as azobenzene are mixed with liquid crystalline birefringent materials, or photoreactive groups such as cinnamoyl groups are introduced into liquid crystalline birefringent materials, and this is aligned by alignment treatment such as light irradiation. You may let them. Furthermore, the stretching treatment and the orientation treatment described above can be used in combination. In the case where the liquid crystalline birefringent material is a liquid crystalline thermoplastic resin, the orientation is fixed and stabilized by being oriented at the time of stretching and then cooled to room temperature. The liquid crystalline monomer does not necessarily need to be cured because the desired optical properties are exhibited as long as it is oriented. However, liquid crystalline monomers having a low isotropic transition temperature are in an isotropic state when a little temperature is applied. In this case, the anisotropic scattering is eliminated and the polarization performance is not bad. In such a case, it is preferable to cure. In addition, many liquid crystalline monomers crystallize when left at room temperature. In this case, anisotropic scattering is eliminated, and conversely the polarization performance is not bad. Therefore, it is preferable to cure even in such a case. From this point of view, it is preferable to cure the liquid crystalline monomer in order for the alignment state to exist stably under any conditions. Curing of the liquid crystalline monomer is, for example, mixed with a photopolymerization initiator and dispersed in a solution of a matrix component, and after alignment, at any timing (before dyeing with a dichroic material such as an iodine-based absorber, After dyeing, the film is cured by irradiating with ultraviolet rays or the like to stabilize the orientation. Desirably, before dyeing with a dichroic material.

  In the step (II) of dispersing an iodine-based absorber in the polyvinyl alcohol-based resin serving as the matrix, generally, the above-described process is performed in an aqueous bath in which iodine is dissolved together with an auxiliary such as an iodide of an alkali metal such as potassium iodide. The method of immersing a film is mentioned. An iodine light absorber is formed by the interaction between iodine dispersed in the matrix and the matrix resin. The timing of immersion may be before or after the stretching step (I). The iodine-based light absorber is generally formed remarkably through a stretching process. The concentration of the aqueous bath containing iodine and the ratio of the auxiliary agent such as alkali metal iodide are not particularly limited, and a general iodine staining method can be adopted, and the concentration and the like can be arbitrarily changed.

  Further, the proportion of iodine in the obtained polarizer is not particularly limited, but the proportion of the polyvinyl alcohol resin and iodine is about 0.05 to 50 parts by weight of iodine with respect to 100 parts by weight of the polyvinyl alcohol resin, It is preferable to control so that it may become 0.1-10 weight part.

  In producing the polarizer, in addition to the steps (I) to (II), a step (III) for various purposes can be performed. The step (III) includes, for example, a step of swelling the film by immersing the film in a water bath mainly for the purpose of improving the iodine dyeing efficiency of the film. Moreover, the process etc. which are immersed in the water bath which melt | dissolved arbitrary additives are mention | raise | lifted. A step of immersing the film in an aqueous solution containing additives such as boric acid and borax is mainly used for the purpose of crosslinking the water-soluble resin (matrix). Further, there is a step of immersing the film in an aqueous solution containing an additive such as an alkali metal iodide for the purpose of adjusting the amount balance of the dispersed iodine light absorber and adjusting the hue.

  The step (I) of orienting (stretching) the film, the step (II) of dispersing and dyeing an iodine-based absorber on the matrix resin, and the step (III) are performed at least once each of the steps (I) and (II). If present, the number of steps, order, and conditions (bath temperature, immersion time, etc.) can be arbitrarily selected, and each step may be performed separately or a plurality of steps may be performed simultaneously. For example, you may perform simultaneously the bridge | crosslinking process of process (III), and extending process (I).

  In addition, iodine-based absorbers used for dyeing, boric acid used for crosslinking, and the like are prepared or mixed in preparation of the mixed solution instead of the method of penetrating into the film by immersing the film in an aqueous solution as described above. Thereafter, a method of adding any kind and amount before film formation may be employed. Moreover, you may use both methods together. However, in the step (I), when it is necessary to increase the temperature at the time of stretching or the like (for example, 80 ° C. or higher) and the iodine-based absorber deteriorates at the temperature, the iodine-based absorber is used. The step (II) of disperse dyeing is preferably performed after the step (I).

  The film subjected to the above treatment is desirably dried under appropriate conditions. Drying is performed according to a conventional method.

  The thickness of the obtained polarizer (film) is not particularly limited, but is usually 1 μm to 3 mm, preferably 5 μm to 1 mm, and more preferably 10 to 500 μm.

  The polarizer is made of a film having a structure in which minute regions formed of a liquid crystalline birefringent material are dispersed in a matrix formed of a polyvinyl alcohol-based resin containing an iodine-based absorber. Such a polarizer has a function of scattering anisotropy in addition to the function of absorption dichroism by an iodine-based absorber, thereby improving the polarization performance by the synergistic effect of the two functions. A polarizer with good visibility and compatibility is obtained.

The iodine-based light absorber means a seed composed of iodine that absorbs visible light. Generally, a light-transmitting water-soluble resin (particularly polyvinyl alcohol-based resin) and polyiodine ions (I ₃ ⁻ , I _6- ^{and the} like). Iodine absorbers are also called iodine complexes. Polyiodine ions are thought to be generated from iodine and iodide ions. As the iodine-based absorber, one having an absorption region in a wavelength band of at least 400 to 700 nm is used.

  The scattering performance of anisotropic scattering is caused by the difference in refractive index between the matrix and the minute region. If the material forming the microregion is, for example, a liquid crystal material, the wavelength dispersion of Δn is higher than that of the light-transmitting water-soluble resin of the matrix. It becomes larger and the amount of scattering increases as the wavelength becomes shorter. Therefore, the effect of improving the polarization performance increases as the wavelength becomes shorter, and a polarizer having a high polarization and a neutral hue can be realized by compensating for the relatively low polarization performance of the iodine-based polarizer on the short wavelength side.

  The birefringence of the minute region is preferably 0.02 or more. As the material used for the minute region, a material having the birefringence is preferably used from the viewpoint of obtaining a larger anisotropic scattering function.

The refractive index difference for each optical axis direction between the birefringent material forming the minute region and the translucent water-soluble resin is as follows:
The refractive index difference (Δn1) in the axial direction showing the maximum value is 0.03 or more,
The refractive index difference (Δn2) in the two axial directions perpendicular to the Δn1 direction is preferably 50% or less of the Δn1.

  By controlling the refractive index difference (Δn1) and (Δn2) with respect to each optical axis direction within the above range, only linearly polarized light in the Δn1 direction as proposed in US Pat. No. 2,213,902 can be obtained. A scattering anisotropic film having a selectively scattered function can be obtained. That is, since the refractive index difference is large in the Δn1 direction, linearly polarized light is scattered, while in the Δn2 direction, the linearly polarized light can be transmitted because the refractive index difference is small. The refractive index difference (Δn2) in the two axial directions orthogonal to the Δn1 direction is preferably equal.

  In order to increase the scattering anisotropy, the refractive index difference (Δn1) in the Δn1 direction is 0.03 or more, preferably 0.05 or more, particularly preferably 0.10 or more. Further, the refractive index difference (Δn2) in two directions orthogonal to the Δn1 direction is preferably 50% or less, more preferably 30% or less of the Δn1.

  The iodine-based absorber preferably has the absorption axis of the material oriented in the Δn1 direction.

  By aligning the iodine-based absorber in the matrix so that the absorption axis of the material is parallel to the Δn1 direction, linearly polarized light in the Δn1 direction, which is the scattering polarization direction, can be selectively absorbed. . As a result, the linearly polarized light component in the Δn2 direction of the incident light is not scattered and hardly absorbed by the iodine absorber as in the case of a conventional iodine-based polarizer that does not have anisotropic scattering performance. On the other hand, the linearly polarized light component in the Δn1 direction is scattered and absorbed by the iodine-based absorber. Usually, absorption is determined by the absorption coefficient and thickness. When light is scattered in this way, the optical path length is dramatically increased as compared to the case where there is no scattering. As a result, the polarization component in the Δn1 direction is absorbed excessively compared to the conventional iodine-based polarizer. That is, a higher degree of polarization can be obtained with the same transmittance.

Hereinafter, an ideal model will be described in detail. Generally, two main transmittances (first main transmittance k ₁ (maximum transmittance azimuth = Δn2 direction linearly polarized transmittance)) and second main transmittance k ₂ (minimum transmittance direction = Δ) used for linear polarizers. The following discussion will be made using the linearly polarized light transmittance in the n1 direction)).

In a commercially available iodine polarizer, if the iodine absorber is oriented in one direction, the parallel transmittance and the polarization degree are
Parallel transmittance = 0.5 × ((k ₁ ) ² + (k ₂ ) ² ),
Degree of polarization = (k ₁ −k ₂ ) / (k ₁ + k ₂ )

On the other hand, in the polarizer of the present invention, it is assumed that the polarization in the Δn1 direction is scattered, the average optical path length is α (> 1) times, and it is assumed that depolarization due to scattering can be ignored. The transmittances are represented by k ₁ and k ₂ ′ = 10 ^X (where x is αlogk ₂ ), respectively.

In other words, the parallel transmittance and polarization degree in this case are
Parallel transmittance = 0.5 × ((k ₁ ) ² + (k ₂ ′) ² ),
Degree of polarization = (k ₁ −k ₂ ) / (k ₁ + k ₂ )

For example, a commercially available iodine-based polarizer (parallel transmittance 0.385, polarization degree 0.965: k ₁ = 0.877, k ₂ = 0.016) and the same conditions (staining amount and production procedure are the same) Assuming that the polarizer of the invention was created, when α was doubled in the calculation, k ₂ decreased to 0.0003, and as a result, the parallel transmittance remained 0.385 and the degree of polarization improved to 0.999. To do. The above is computational, and of course the function is somewhat degraded due to the effects of depolarization due to scattering, surface reflection and backscattering. As can be seen from the above formula, the higher the α, the better. The higher the dichroic ratio of the iodine-based absorber, the higher the function can be expected. In order to increase α, the scattering anisotropy function should be made as high as possible, and the polarized light in the Δn1 direction should be selectively strongly scattered. Further, it is better that the backscattering is small, and the ratio of the backscattering intensity to the incident light intensity is preferably 30% or less, and more preferably 20% or less.

  The minute region preferably has a length in the Δn2 direction of 0.05 to 500 μm.

  In order to strongly scatter linearly polarized light having a vibration surface in the Δn1 direction among wavelengths in the visible light region, the dispersion-distributed microregion has a length in the Δn2 direction of 0.05 to 500 μm, preferably It is preferably controlled to be 0.5 to 100 μm. If the length of the minute region in the Δn2 direction is too short compared to the wavelength, sufficient scattering will not occur. On the other hand, if the length of the micro area in the Δn2 direction is too long, there is a possibility that the film strength is lowered, or that the liquid crystalline material forming the micro area is not sufficiently oriented in the micro area.

  The polarizer preferably has a transmittance of 80% or more for linearly polarized light in the transmission direction, a haze value of 5% or less, and a haze value of 30% or more for linearly polarized light in the absorption direction.

  The iodine polarizer of the present invention having the above transmittance and haze value has high transmittance and good visibility for linearly polarized light in the transmission direction, and strong light for linearly polarized light in the absorption direction. Has diffusivity. Therefore, it is possible to reduce the unevenness of the transmittance during black display with a high transmittance and a high degree of polarization without sacrificing other optical characteristics by a simple method.

  The polarizer of the present invention preferably has a transmittance as high as possible for linearly polarized light in the transmission direction, that is, linearly polarized light in a direction orthogonal to the maximum absorption direction of the iodine-based absorber. When the light intensity of the linearly polarized light is 100, the light transmittance is preferably 80% or more. The light transmittance is more preferably 85% or more, and more preferably 88% or more. Here, the light transmittance corresponds to a Y value calculated based on the CIE1931 XYZ color system from the spectral transmittance of 380 nm to 780 nm measured using a spectrophotometer with an integrating sphere. Since about 8% to 10% is reflected by the air interface on the front and back surfaces of the polarizer, the ideal limit is 100% minus this surface reflection.

  Further, it is desirable that the polarizer does not scatter linearly polarized light in the transmission direction from the viewpoint of clarity of display image visibility. Therefore, the haze value for linearly polarized light in the transmission direction is preferably 5% or less. More preferably, it is 3% or less, and further preferably 1% or less. On the other hand, it is desirable that the polarizer linearly polarized light in the absorption direction, that is, the linearly polarized light in the maximum absorption direction of the iodine-based absorber is strongly scattered from the viewpoint of concealing unevenness due to local transmittance variation by scattering. Therefore, the haze value for linearly polarized light in the absorption direction is preferably 30% or more. More preferably, it is 40% or more, and further preferably 50% or more. The haze value is a value measured based on JIS K 7136 (Plastic—How to determine haze of transparent material).

  The optical characteristics are caused by the composite of the function of scattering anisotropy in addition to the function of absorption dichroism of the polarizer. The same is true for the scattering differences described in U.S. Pat. No. 2,213,902 and JP-A-9-274108 and JP-A-9-297204, which have the function of selectively scattering only linearly polarized light. It can also be achieved by superimposing the isotropic film and the dichroic absorption polarizer in an axial arrangement in which the scattering maximum axis and the absorption maximum axis are parallel to each other. However, it is necessary to separately form a scattering anisotropic film, and the alignment accuracy at the time of superimposing becomes a problem. The effect of increasing the optical path length cannot be expected, and it is difficult to achieve high transmission and high degree of polarization.

  Since the polarizer obtained by the present invention has the same function as an existing absorption polarizing plate, it can be used without any change to various application fields using the absorption polarizing plate.

  The obtained polarizer can be made into a polarizing plate provided with a transparent protective layer on at least one surface thereof according to a conventional method. The transparent protective layer can be provided as a polymer-coated layer or a film laminate layer. As the transparent polymer or film material for forming the transparent protective layer, an appropriate transparent material can be used, but a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property and the like is preferably used. Examples of the material for forming the transparent protective layer include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as cellulose diacetate and cellulose triacetate, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile, Examples thereof include styrene polymers such as styrene copolymers (AS resins), polycarbonate polymers, and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of the polymer that forms the transparent protective layer.

  Moreover, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substitution in the side chain And / or a resin composition containing an unsubstituted phenyl and a thermoplastic resin having a nitrile group. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used.

  The transparent protective layer that can be particularly preferably used in terms of polarization characteristics and durability is a triacetyl cellulose film whose surface is saponified with alkali or the like. The thickness of the transparent protective layer is arbitrary, but is generally 500 μm or less, more preferably 1 to 300 μm, and particularly preferably 5 to 300 μm for the purpose of reducing the thickness of the polarizing plate. In addition, when providing a transparent protective layer on both sides of a polarizer, the transparent protective film which consists of a polymer etc. which are different in the front and back can be used.

  Moreover, it is preferable that a transparent protective film has as little color as possible. Therefore, Rth = (nx−nz) · d (where nx is the refractive index in the slow axis direction in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness). A protective film having a direction retardation value of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the protective film can be almost eliminated. The thickness direction retardation value (Rth) is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.

  The surface of the transparent protective film to which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment for diffusion or antiglare.

  The hard coat treatment is applied for the purpose of preventing scratches on the surface of the polarizing plate. For example, a transparent protective film with a cured film excellent in hardness, sliding properties, etc. by an appropriate ultraviolet curable resin such as acrylic or silicone is used. It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  The anti-glare treatment is applied for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a blending method of transparent particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, antisticking layer, diffusing layer, antiglare layer and the like can be provided on the transparent protective film itself, or can be provided separately from the transparent protective layer as an optical layer.

  An adhesive is used for the adhesion treatment between the polarizer and the transparent protective film. Examples of the adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, and water-based polyesters. The said adhesive agent is normally used as an adhesive agent which consists of aqueous solution, and contains 0.5 to 60 weight% of solid content normally.

  The polarizing plate of the present invention is produced by bonding the transparent protective film and the polarizer using the adhesive. The adhesive may be applied to either the transparent protective film or the polarizer, or to both. After the bonding, a drying process is performed to form an adhesive layer composed of a coating dry layer. Bonding of a polarizer and a transparent protective film can be performed with a roll laminator or the like. The thickness of the adhesive layer is not particularly limited, but is usually about 0.1 to 5 μm.

  The polarizing plate of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), and a viewing angle compensation film. One or more optical layers that may be used can be used. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a polarizing plate or a semi-transmissive reflecting plate is further laminated on the polarizing plate of the present invention, an elliptical polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on the polarizing plate. A wide viewing angle polarizing plate obtained by further laminating a viewing angle compensation film on a plate or a polarizing plate, or a polarizing plate obtained by further laminating a brightness enhancement film on the polarizing plate is preferable.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like as necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one side of a transparent protective film matted as necessary. Moreover, the transparent protective film contains fine particles so as to have a surface fine concavo-convex structure and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance and to suppress unevenness in brightness and darkness. The transparent protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it, and light and dark unevenness can be further suppressed. The reflective layer of the fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film is formed by transparent the metal by an appropriate method such as a vapor deposition method such as a vacuum vapor deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of directly attaching to the surface of the protective layer.

  Instead of the method of directly applying the reflecting plate to the transparent protective film of the polarizing plate, the reflecting plate can be used as a reflecting sheet provided with a reflecting layer on an appropriate film according to the transparent film. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a transparent protective film, a polarizing plate or the like is used to prevent the reflectance from being lowered due to oxidation, and thus to maintain the initial reflectance for a long time. In addition, it is more preferable to avoid a separate attachment of the protective layer.

  The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate is useful for forming a liquid crystal display device of a type that can save energy of using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source even in a relatively dark atmosphere. It is.

  An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

  The elliptically polarizing plate is effectively used for black and white display without the above color by compensating (preventing) the coloration (blue or yellow) generated by the birefringence of the liquid crystal layer of the super twist nematic (STN) type liquid crystal display device. It is done. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has an antireflection function. Specific examples of the retardation plate include a birefringent film obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, and polyamide. And an alignment film of a liquid crystal polymer, and a liquid crystal polymer alignment layer supported by a film. The retardation plate may have an appropriate retardation according to the purpose of use, such as those for the purpose of compensating for various wavelength plates or birefringence of the liquid crystal layer, viewing angle, and the like. What laminated | stacked the phase difference plate and controlled optical characteristics, such as phase difference, etc. may be used.

  The elliptical polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can also be formed by sequentially laminating them sequentially in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflective) polarizing plate and a retardation plate. An optical film such as a polarizing plate has an advantage that it can improve the production efficiency of a liquid crystal display device and the like because of excellent quality stability and lamination workability.

  The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. As such a viewing angle compensation phase difference plate, for example, a retardation film, an alignment film such as a liquid crystal polymer, or an alignment layer such as a liquid crystal polymer supported on a transparent substrate is used. A normal retardation plate uses a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film stretches biaxially in the plane direction. Birefringent polymer film, biaxially stretched film such as polymer with birefringence with a controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and stretched in the thickness direction, etc. Used. Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, and a film obtained by obliquely aligning a liquid crystal polymer. Can be mentioned. The raw material polymer for the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloration due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good visual recognition. An appropriate one for the purpose can be used.

  Also, from the viewpoint of achieving a wide viewing angle with good visibility, an optically compensated phase difference in which a liquid crystal polymer alignment layer, in particular an optically anisotropic layer composed of a discotic liquid crystal polymer gradient alignment layer, is supported by a triacetylcellulose film. A plate can be preferably used.

  A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually provided on the back side of a liquid crystal cell. The brightness enhancement film reflects a linearly polarized light with a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the back side, and transmits other light. In addition, a polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter to obtain transmitted light in a predetermined polarization state, and reflects light without transmitting the light other than the predetermined polarization state. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer or the like provided behind the brightness enhancement film and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. Luminance can be improved by increasing the amount of light transmitted through the enhancement film and increasing the amount of light that can be used for liquid crystal display image display or the like by supplying polarized light that is difficult to be absorbed by the polarizer.

  A diffusion plate may be provided between the brightness enhancement film and the reflective layer. The polarized light reflected by the brightness enhancement film is directed to the reflective layer or the like, but the installed diffuser plate uniformly diffuses the light passing therethrough and simultaneously cancels the polarized state and becomes a non-polarized state. That is, the diffuser plate returns the polarized light to the original natural light state. The light in the non-polarized state, that is, the natural light state is directed toward the reflection layer and the like, reflected through the reflection layer and the like, and again passes through the diffusion plate and reenters the brightness enhancement film. Thus, while maintaining the brightness of the display screen by providing a diffuser plate that returns polarized light to the original natural light state between the brightness enhancement film and the reflective layer, etc., the brightness unevenness of the display screen is reduced at the same time, A uniform and bright screen can be provided. By providing such a diffuser plate, it is considered that the first incident light has a moderate increase in the number of repetitions of reflection, and in combination with the diffusion function of the diffuser plate, a uniform bright display screen can be provided.

  The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies. Such as an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate things, such as a thing, can be used.

  Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is incident on the polarizing plate with the polarization axis aligned as it is, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in a brightness enhancement film of a type that emits circularly polarized light such as a cholesteric liquid crystal layer, it can be incident on a polarizer as it is, but from the viewpoint of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable to make it enter into a polarizing plate. Note that circularly polarized light can be converted to linearly polarized light by using a quarter wave plate as the retardation plate.

  A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region exhibits, for example, a retardation layer that functions as a quarter-wave plate for light-color light having a wavelength of 550 nm and other retardation characteristics. A phase difference layer, for example, a phase difference layer that functions as a half-wave plate, can be used to superimpose. Accordingly, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

  In addition, the cholesteric liquid crystal layer can also be obtained by reflecting circularly polarized light in a wide wavelength range such as a visible light region by combining two or more layers having different reflection wavelengths and having an overlapping structure. Based on this, transmitted circularly polarized light in a wide wavelength range can be obtained.

  Further, the polarizing plate may be formed by laminating a polarizing plate and two or more optical layers as in the above-described polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-mentioned reflective polarizing plate or transflective polarizing plate and a retardation plate are combined may be used.

  An optical film in which the optical layer is laminated on a polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. There is an advantage that the manufacturing process of a liquid crystal display device or the like can be improved because of excellent stability and assembly work. For the lamination, an appropriate adhesive means such as an adhesive layer can be used. When adhering the polarizing plate and other optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  An adhesive layer for adhering to other members such as a liquid crystal cell may be provided on the polarizing plate described above or an optical film in which at least one polarizing plate is laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. Can be used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  In addition to the above, in terms of prevention of foaming and peeling phenomena due to moisture absorption, deterioration of optical properties and liquid crystal cell warpage due to differences in thermal expansion, etc., as well as formability of liquid crystal display devices with high quality and excellent durability An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The adhesive layer is, for example, natural or synthetic resins, in particular, tackifier resins, fillers or pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, antioxidants, etc. It may contain an additive to be added to the adhesive layer. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  Attachment of the adhesive layer to one or both sides of the polarizing plate or the optical film can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method in which it is directly attached on a polarizing plate or an optical film by an appropriate development method such as a casting method or a coating method, or an adhesive layer is formed on a separator according to the above, and this is applied to a polarizing plate or an optical film. The method of moving up is mentioned.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as a superimposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as the adhesion layers of a different composition, a kind, thickness, etc. in the front and back of a polarizing plate or an optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 5 to 200 μm, particularly preferably 10 to 100 μm.

  On the exposed surface of the adhesive layer, a separator is temporarily attached and covered for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet, metal foil, laminate thereof, and the like, silicone type or Appropriate ones according to the prior art, such as those coated with an appropriate release agent such as a long mirror alkyl type, fluorine type or molybdenum sulfide, can be used.

  In the present invention, the polarizer, transparent protective film, optical film, and the like that form the polarizing plate described above, and each layer such as an adhesive layer include, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, and cyanoacrylates. It may be a compound having an ultraviolet absorbing ability by a method such as a method of treating with an ultraviolet absorber such as a compound based on nickel or a nickel complex salt compound.

  The polarizing plate or the optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate or an optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the polarizing plate or optical film by invention, and it can apply according to the former. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the polarizing plate or optical film by this invention can be installed in the one side or both sides of a liquid crystal cell. When providing a polarizing plate or an optical film on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  Next, an organic electroluminescence device (organic EL display device) will be described. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light emitting layer, and electron injection layer is known. It has been.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation plate can be provided between the transparent electrode and the polarizing plate.

  Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation plate with a quarter-wave plate and adjusting the angle formed by the polarization direction of the polarizing plate and the retardation plate to π / 4. .

  Hereinafter, the present invention will be described in more detail with reference to examples. In the following, “parts” means parts by weight.

  Surface roughness (Ra): Measured according to JIS B0601-1994 using Surfcom 470A manufactured by Tokyo Seimitsu Co., Ltd. as a stylus type surface roughness measuring machine. The measurement is performed by scanning the uneven surface with a length of 3 mm in a fixed direction through a measuring needle having a diameter of 1 mm with a tip portion made of diamond having a conical shape with an apex angle of 55 degrees. The centerline average surface roughness (Ra) was determined by measuring the change in the movement of.

  Film thickness characteristics: The thickness (μm) of the film was measured in the width direction of the film by Film Thickness Tester KG601B manufactured by Anritsu Corporation. In the measurement, the thickness in the width direction of the film was measured at 1 cm intervals. The average thickness is an average value of these. The difference in film thickness was calculated as the difference between the maximum thickness and the minimum thickness. Thickness unevenness (%) was expressed as% by multiplying 100 by the value obtained by dividing the thickness difference between the maximum thickness and the minimum thickness of the film by the average thickness.

  Haze characteristics of film: The haze in the width direction of the film was measured according to JIS K7136 using a haze meter HM-150 manufactured by Murakami Color Research Laboratory. In the measurement, the haze in the width direction of the film was measured at 1 cm intervals. Average haze is the average of these. For haze unevenness (%), the difference between the highest haze value and the lowest haze value was calculated, and the difference divided by the average haze was multiplied by 100 to give%.

Example 1
(Preparation of mixed solution)
A polyvinyl alcohol aqueous solution having a solid content of 15% by weight dissolving polyvinyl alcohol having a polymerization degree of 2400 and a saponification degree of 99.9%, and a liquid crystalline monomer having an acryloyl group at each end of the mesogenic group (nematic liquid crystal temperature) A range of 55 to 75 ° C.) and glycerin were mixed with polyvinyl alcohol: liquid crystalline monomer: glycerin = 100: 5: 15 (weight ratio) to prepare a solution. The solution was stirred with a homomixer manufactured by Tokushu Kika Kogyo Co., Ltd. for 6000 rpm × 20 minutes to prepare a mixed solution in which liquid crystalline monomers were dispersed. At this time, the temperature of the solution was kept constant at 80 ° C. Bubbles mixed in the solution were degassed by being allowed to stand at room temperature (23 ° C.).

(Production of water-soluble resin film)
After the temperature of the solution was 90 ° C., this was cast on a metal drum surface having a surface roughness (Ra) of 0.1 μm, which was subjected to chromium plating on the surface of the stainless steel plate to form a film. The film formed on the surface of the metal drum was dried with hot air at 110 ° C. to obtain a water-soluble resin film having an average thickness of 75 μm that was cloudy. The difference in thickness was 0.89 μm, and the thickness unevenness was 0.1%. The average haze was 80, and the haze unevenness was 0.4%.

Example 2
(Preparation of mixed solution)
A polyvinyl alcohol aqueous solution having a solid content of 14% by weight in which polyvinyl alcohol having a polymerization degree of 3500 and a saponification degree of 99.9% is dissolved, and a liquid crystalline monomer having an acryloyl group at both ends of the mesogenic group (nematic liquid crystal temperature) A range of 55 to 75 ° C.) and glycerin were mixed with polyvinyl alcohol: liquid crystalline monomer: glycerin = 100: 7: 105 (weight ratio) to prepare a solution. The solution was stirred with a homomixer manufactured by Tokushu Kika Kogyo Co., Ltd. for 6000 rpm × 20 minutes to prepare a mixed solution in which liquid crystalline monomers were dispersed. At this time, the temperature of the solution was kept constant at 80 ° C. Bubbles mixed in the solution were degassed by being allowed to stand at room temperature (23 ° C.).

(Production of water-soluble resin film)
After the temperature of the solution was 90 ° C., this was cast on a metal drum surface having a surface roughness (Ra) of 0.1 μm, which was subjected to chromium plating on the surface of the stainless steel plate to form a film. The film formed on the surface of the metal drum was dried with hot air at 120 ° C. to obtain a white turbid water-soluble resin film having an average thickness of 80 μm. The difference in thickness was 1.15 μm, and the thickness unevenness was 1.3%. The average haze was 85, and the haze unevenness was 0.9%.

Example 3
(Production of water-soluble resin film)
After the mixed solution prepared in Example 1 was heated to 90 ° C., it was cast on a metal drum surface having a surface roughness (Ra) of 0.5 μm, which was subjected to chromium plating on the stainless steel plate surface. Membrane was performed. The film formed on the surface of the metal drum was dried with hot air at 110 ° C. to obtain a white turbid water-soluble resin film having an average thickness of 75 μm. The difference in thickness was 1.37 μm, and the thickness unevenness was 1.8%. The average haze was 81 and the haze unevenness was 1.5%.

Example 4
(Production of water-soluble resin film)
After the mixed solution prepared in Example 1 was heated to 90 ° C., it was cast on a metal drum surface having a surface roughness (Ra) of 1.0 μm, which was subjected to chromium plating on the stainless steel plate surface. Membrane was performed. The film formed on the surface of the metal drum was dried with hot air at 110 ° C. to obtain a white turbid water-soluble resin film having an average thickness of 75 μm. The difference in thickness was 2.51 μm, and the thickness unevenness was 3.3%. The average haze was 81 and the haze unevenness was 2.7%.

Example 5
(Production of water-soluble resin film)
After the mixed solution prepared in Example 1 was heated to 90 ° C., it was cast on a metal drum surface having a surface roughness (Ra) of 1.0 μm, which was subjected to chromium plating on the stainless steel plate surface. Membrane was performed. The film formed on the surface of the metal drum was dried with hot air at 110 ° C. to obtain a white turbid water-soluble resin film having an average thickness of 73 μm. The difference in thickness was 2.04 μm, and the thickness unevenness was 2.8%. The average haze was 82, and the haze unevenness was 2.5%.

Comparative Example 1
(Production of water-soluble resin film)
After the mixed solution prepared in Example 1 was heated to 90 ° C., it was cast on a metal drum surface having a surface roughness (Ra) of 2.0 μm, which was subjected to chromium plating on the surface of the stainless steel plate. Membrane was performed. The film formed on the surface of the metal drum was dried with hot air at 110 ° C. to obtain a white turbid water-soluble resin film having an average thickness of 75 μm. The difference in thickness was 4.98 μm, and the thickness unevenness was 6.6%. The average haze was 81, and the haze unevenness was 6.0%.

Comparative Example 2
(Production of water-soluble resin film)
After the mixed solution prepared in Example 5 was brought to 90 ° C., it was applied in the same manner as in Example 5 except that it was coated on a 100 μm-thick polyethylene tetalate film (Ra = 0.1 μm) by the casting method. Thus, a cloudy water-soluble resin film having an average thickness of 70 μm was obtained. However, thermal wrinkles with a height of 2 mm were generated during drying after film formation. The difference in thickness was 11.69 μm, and the thickness unevenness was 16.7%. The average haze was 82, and the haze unevenness was 10.7%.

  The following steps were applied to the water-soluble resin films obtained in the examples and comparative examples to prepare polarizers and polarizing plates.

(Production of polarizer)
The film was expanded in a warm water bath at 30 ° C., and then immersed in an aqueous solution (concentration 0.32% by weight) dissolved in iodine: potassium iodide = 1: 7 (weight ratio) at 30 ° C. The uniaxial stretching process was performed 3 times. Next, the film was stretched so that the total draw ratio was 6 times while being crosslinked in a 3% by weight boric acid aqueous solution bath at 50 ° C, and then further crosslinked in a 4% by weight boric acid aqueous solution bath at 50 ° C. Next, the hue was adjusted by dipping in a 30 ° C. aqueous potassium iodide solution for 15 seconds. Furthermore, it washed with water and dried and obtained the polarizer.

  The obtained polarizer has scattering anisotropy. When polarized light having a vibration plane parallel to the stretching direction is incident, the light is scattered, and when polarized light having a vibration plane perpendicular thereto is incident. No light was scattered. Further, when the polarizer was observed with a polarizing microscope, it was confirmed that minute regions of liquid crystal monomers dispersed innumerably in the polyvinyl alcohol matrix were formed. This liquid crystalline monomer was oriented in the stretching direction, and the average size in the stretching direction (Δn2 direction) of the microregion was 5 to 10 μm.

  The refractive indexes of the matrix and the minute region were measured separately. The measurement was performed at 20 ° C. First, when the refractive index of a polyvinyl alcohol film alone stretched under the same stretching conditions (stretching at 110 ° C. at 3 times) was measured with an Abbe refractometer (measurement light 589 nm), the refractive index in the stretching direction (Δn1 direction) = 1. 54, Δn2 direction refractive index = 1.52. Further, the refractive index (ne: extraordinary light refractive index and no: ordinary light refractive index) of the liquid crystalline monomer was measured. No was measured by an Abbe refractometer (measurement light 589 nm) after aligning and coating a liquid crystalline monomer on a high refractive index glass subjected to vertical alignment treatment. On the other hand, a liquid crystalline monomer is injected into a horizontally aligned liquid crystal cell, and the phase difference (Δn × d) is measured with an automatic birefringence measuring apparatus (manufactured by Oji Scientific Instruments, automatic birefringence meter KOBRA21ADH). Separately, the cell gap (d) was measured by optical interferometry, Δn was calculated from the phase difference / cell gap, and the sum of Δn and no was defined as ne. ne (corresponding to the refractive index in the Δn1 direction) = 1.64, no (corresponding to the refractive index in the Δn2 direction) = 1.52. Accordingly, Δn1 = 1.64−1.54 = 0.10 and Δn2 = 1.52−1.52 = 0.00 were calculated.

(Preparation of polarizing plate)
A triacetyl cellulose film having a thickness of 80 μm was adhered to both surfaces of the obtained polarizer with a water-soluble adhesive to obtain a polarizing plate.

(Evaluation)
The following evaluation was performed about the polarizing plate obtained by the Example and the comparative example. Moreover, the following evaluation was performed about the metal surface after producing a water-soluble resin film. The results are shown in Table 1.

<Optical unevenness>
The produced polarizing plate was produced with respect to the absorption axis of the two polarizing plates arranged in the crossed Nicol state between the two polarizing plates (manufactured by Nitto Denko, NPF-SEG1224DU) arranged in the crossed Nicol state. The polarizing plate was arranged so that the absorption axis was 45 °, and optical unevenness (dyeing unevenness) was observed and evaluated according to the following criteria.
(Double-circle): The optical nonuniformity was not confirmed.
◯: Although optical unevenness was slightly confirmed, it is at a level that does not cause a problem even when mounted on a display device.
(Triangle | delta): When an optical nonuniformity is confirmed slightly and it mounts | wears with a display apparatus, it is a level in which a characteristic is inferior as a display apparatus.
X: Optical unevenness was confirmed.

<Bright spot>
The produced polarizing plate is arranged so that the absorption axis thereof is parallel to the absorption axis of either the analyzer or the polarizer of a polarizing microscope (ECRIPEES E600 POL) manufactured by Nikon Corporation. Visual observation was performed. The observation magnification is 400 times, and the observation area is 640 μm × 480 μm. When the orientation of the micro area is good, depolarization does not occur and it is observed as black, but when the orientation of the micro area is poor, depolarization occurs and it is observed as a bright spot.
A: Bright spots were not observed at all in the micro area within the observation area.
A: Ten or less bright spots were observed in the micro area within the observation area.
Δ: Slightly bright spots were observed in the micro area.
X: Many things with a bright spot were observed in the minute area in the minute area.

<Dirt on metal surface>
After producing the water-soluble resin film, the state of the metal surface after peeling the film was evaluated according to the following criteria.
A: Contamination due to remaining liquid crystalline birefringent material was not confirmed.
○: Remaining liquid crystalline birefringent material that does not affect the film characteristics was confirmed. There is no contamination.
Δ: Remaining liquid crystalline birefringent material having slightly inferior film characteristics was confirmed. There is no contamination.
X: Contamination with white turbidity due to the remaining liquid crystalline birefringent material was confirmed over the entire metal surface.

表中＊は、ポリエチレンテタレートフィルムのＲａである。

In the table, * indicates Ra of the polyethylene tetalate film.

Claims (12)

  A water-soluble resin film having a structure in which minute regions are dispersed in a matrix formed of a water-soluble resin, wherein the thickness unevenness in the width direction of the film is 15% or less, and the haze unevenness in the film width direction. The water-soluble resin film has a content of 5% or less.   The water-soluble resin film according to claim 1, wherein the water-soluble resin is a polyvinyl alcohol resin.   The water-soluble resin film according to claim 1 or 2, wherein the minute region is formed of a birefringent material.   4. The water-soluble resin film according to claim 3, wherein the birefringent material exhibits liquid crystallinity at least at the time of the alignment treatment. A method for producing the water-soluble resin film according to claim 1,
A mixed solution in which a minute region formed of a birefringent material is dispersed in a water-soluble resin solution is applied to a metal surface having a surface roughness (Ra) of 1.5 μm or less and dried to form a film. A method for producing a water-soluble resin film, which is performed.   6. The method for producing a water-soluble resin film according to claim 5, wherein the metal surface is a metal surface formed by metal plating.   The method for producing a water-soluble resin film according to claim 6, wherein the metal plating is chromium plating.   A polarizer, wherein the water-soluble resin film according to claim 1 is stretched and contains a dichroic material in a matrix formed of the water-soluble resin.   The manufacturing method of the polarizer characterized by performing the extending | stretching process and the dyeing | staining process by a dichroic material to the water-soluble resin film in any one of Claims 1-4.   The polarizing plate which provided the transparent protective layer in the at least single side | surface of the polarizer of Claim 8.   An optical film, wherein at least one of the polarizer according to claim 8 or the polarizing plate according to claim 10 is laminated. An image display device comprising the polarizer according to claim 8, the polarizing plate according to claim 10, or the optical film according to claim 11.