JP2007025089A - Light-transmissive film, its manufacturing method, polarizer, its manufacturing method, polarizing plate, optical film and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-transmissive film which has sufficient durability, hardly causes optical irregularities and can provide a polarizer having a satisfactory polarizing characteristic with respect to the light-transmissive film using a mixture consisting of ethylene-vinyl alcohol copolymer and polyvinyl alcohol polymer. <P>SOLUTION: The light-transmissive film has such a structure that micro-regions are dispersed in a matrix formed by a water-soluble resin mixture consisting of ethylene-vinyl alcohol copolymer and polyvinyl alcohol polymer. The polarizer uses the uniaxially stretched light-transmissive film and contains a dichroic light absorbing body in a matrix formed with the water-soluble resin mixture of ethylene-vinyl alcohol copolymer and polyvinyl alcohol polymer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a translucent film and a method for producing the same. Moreover, this invention relates to the polarizer using the said translucent 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. In recent years, not only the indoor applications but also the range of use such as outdoors, in-cars, ships, and airplanes has been expanded. 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 particular, displays with higher brightness and higher contrast are required for applications such as TV. Polarizers with higher brightness (high transmittance) and higher contrast (high degree of polarization) have been developed. Has been introduced.

  Currently, for example, iodine is adsorbed on a polyvinyl alcohol polymer film, which is a translucent film, and an iodine-based polarizer having a stretched structure is widely used because it has a high transmittance and a high degree of polarization. Yes. Moreover, the polarizer is used as a polarizing plate in which protective films such as triacetyl cellulose are bonded to both surfaces. However, a general polyvinyl alcohol polymer is unstable with respect to heat and humidity, and there is a problem in durability that a polarizing plate is deformed or polarization performance is lowered. In order to solve this problem, as a material for a light-transmitting film of a polarizer, a mixture (Patent Document 1) composed of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer, or a polyvinyl alcohol polymer having a high degree of polymerization is used. It is proposed to use.

However, when the above mixture is used as a material for the translucent film, phase separation tends to occur during film formation. Further, when a polyvinyl alcohol polymer having a high degree of polymerization is used as a material for the translucent film, the viscosity becomes high and film formation becomes difficult. Therefore, when the material is used as the translucent film, in any case, unevenness is likely to occur during film formation, and it is difficult to obtain a film with good in-plane uniformity. As a result, optical unevenness occurred in the polarization performance of the polarizer obtained using the translucent film.
JP 11-1119023 A

  The present invention relates to a light-transmitting film using a mixture of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer, which has good durability, is less likely to cause optical unevenness, and has good polarization characteristics. An object of the present invention is to provide a translucent film capable of providing the above and a method for producing the same.

  Moreover, this invention aims at providing the polarizer using the said translucent film, and its manufacturing method. Furthermore, it aims at providing the polarizing plate and optical film which used the said 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 a translucent film or the like shown below, and have completed the present invention.

  That is, the present invention is a translucent film characterized by having a structure in which microregions are dispersed in a matrix formed by a water-soluble resin mixture comprising an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer, About.

  In the translucent film, the minute region is preferably formed of a birefringent material. In the translucent film, the birefringent material preferably exhibits liquid crystallinity at least at the time of alignment treatment.

  In the translucent film, the blending amount of the ethylene-vinyl alcohol copolymer with respect to 100 parts by weight of the polyvinyl alcohol polymer is preferably 0.1 to 1000 parts by weight.

  In the translucent film, the ethylene content of the ethylene-vinyl alcohol copolymer is preferably 1 to 25 mol%.

  The translucent film preferably has a haze value of 50 to 95%.

Further, the present invention is a method for producing the translucent film,
(1) A step of preparing a mixed solution in which a material that becomes a microregion is dispersed in a water-soluble resin mixture composed of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer that serve as a matrix;
(2) It has the process of forming the mixed solution of said (1) into a film, It is related with the manufacturing method of the translucent film characterized by the above-mentioned.

  In the present invention, the light-transmitting film is uniaxially stretched, and the dichroic absorption is carried out in a matrix formed by a water-soluble resin mixture composed of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer. The present invention relates to a polarizer characterized by containing a body.

The present invention also provides a method for producing the polarizer,
(1) A step of preparing a mixed solution in which a material that becomes a microregion is dispersed in a water-soluble resin mixture composed of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer that serve as a matrix;
(2) forming a film of the mixed solution of (1),
(3) A step of stretching the film obtained in (2),
(4) A method for producing a polarizer, comprising a step of incorporating a dichroic absorber into the water-soluble resin mixture serving as the matrix.

  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 translucent film of the present invention has fine regions dispersed in a matrix formed of a water-soluble resin mixture composed of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer. The translucent film has good durability because the water-soluble resin mixture is used as a matrix. In addition, the polarizer obtained from the translucent film has a function of scattering anisotropy in addition to the polarization function, and improves the polarization performance by the synergistic effect of the two functions. Therefore, even when phase separation occurs by using the water-soluble resin mixture as a matrix, the synergistic effect suppresses the decrease in polarization performance due to optical unevenness, and the transmittance and polarization degree are improved. A polarizer with good visibility is obtained.

  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 water-soluble resin mixture in the matrix, so that the difference in the refractive index of the scattering axis increases toward the shorter wavelength side. The shorter the wavelength, the greater the amount of scattering. Therefore, the shorter the wavelength, the greater the effect of improving the polarization performance. As a whole, a highly polarized and hue neutral polarizer can be realized.

  In the polarizer, it is preferable that the birefringence of the minute region is 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.

In the polarizer, the refractive index difference between the birefringent material forming a microregion and the water-soluble resin mixture with respect to each optical axis direction is:
The refractive index difference (Δn ¹ ) in the axial direction showing the maximum value is 0.03 or more,
The refractive index difference (Δn ² ) in the ^two axial directions perpendicular to the Δn ¹ direction is preferably 50% or less of the Δn ¹ .

A straight line in the Δn ¹ direction as proposed in US Pat. No. 2,213,902 by controlling the refractive index difference (Δn ¹ ), (Δn ² ) in each optical axis direction within the above range. A scattering anisotropic film having a function of selectively scattering only polarized light can be obtained. That is, since the refractive index difference is large in the Δn ¹ direction, linearly polarized light is scattered, while in the Δn ² direction, the linearly polarized light can be transmitted because the refractive index difference is small. The refractive index difference (Δn ² ) in ^two axial directions orthogonal to the Δn ¹ direction is preferably equal.

In order to increase the scattering anisotropy, the refractive index difference (Δn ¹ ) in the Δn ¹ direction is 0.03 or more, preferably 0.05 or more, particularly preferably 0.10 or more. Further, the refractive index difference (Δn ² ) in two directions orthogonal to the Δn ¹ direction is preferably 50% or less, more preferably 30% or less of the Δn ¹ .

In the polarizer, it is preferable that the absorption axis of the water-soluble resin mixture is oriented in the Δn ¹ direction of the birefringent material forming the minute region.

Wherein the absorption axis of the water-soluble resin mixture be oriented to be parallel to the △ n ¹ direction, the △ n ¹ direction of linearly polarized light which is scattered polarization direction may be selectively absorbed. As a result, in the incident light, the linearly polarized light component in the Δn ² direction is not scattered and almost absorbed by the water-soluble resin mixture as in the case of a conventional iodine-based polarizer having no anisotropic scattering performance. Absent. On the other hand, the linearly polarized light component in the Δn ¹ direction is scattered and absorbed by the water-soluble resin mixture. 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 Δn ¹ direction is absorbed excessively compared to a conventional iodine-based polarizer or the like. 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 direction = linear polarization transmittance in Δn ² direction)) and second main transmittance k ₂ (minimum direction of transmittance = used for linear polarizers) The following will be discussed using Δn ¹ direction linearly polarized light transmission)).

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 polarized light in the Δn ¹ direction is scattered, the average optical path length is α (> 1) times, and depolarization due to scattering is assumed to be negligible. The main 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, under the same conditions (staining amount and production procedure are the same) as a commercially available iodine-based polarizer (parallel transmittance 0.385, polarization degree 0.965: k ₁ = 0.877, k ₂ = 0.016 ³ ). Assuming that the polarizer of the present invention is produced, when α is doubled in the calculation, k _{2 is} reduced to 0.0003, and as a result, the parallel transmittance remains 0.385 and the degree of polarization becomes 0.999. Can be improved. 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 Δn ¹ 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.

In the polarizer, the microregion of the polarizer preferably has a length in the Δn ² direction of 0.05 to 500 μm.

In order to strongly scatter linearly polarized light having a vibration surface in the Δn ¹ direction among wavelengths in the visible light region, the dispersion-distributed microregion has a length in the Δn ² direction of 0.05 to 500 μm, It is preferably controlled so as to be 0.5 to 100 μm. If the length of the minute region in the Δn ² 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 Δn ² 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 aligned in the micro area.

In the polarizer, as the dichroic light absorber to be contained in the water-soluble resin mixture, one having an absorption region in a wavelength band of at least 400 to 700 nm is used. The absorption axis of the dichroic light absorber is preferably oriented in the Δn ¹ direction.

  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 polarizer of the present invention having the transmittance and haze value has high transmittance and good visibility for linearly polarized light in the transmission direction, and strong light diffusibility for linearly polarized light in the absorption direction. have. 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 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 dichroic absorber. When the light intensity of linearly polarized light is 100, it preferably has a light transmittance of 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.

  In the polarizer, it is desirable that the linearly polarized light in the transmission direction is not scattered from the viewpoint of the visibility of the display image. Therefore, the haze value for linearly polarized light in the transmission direction is preferably 5% or less. More preferably, it is 3% or less, More preferably, it is 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 dichroic 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.

The translucent film and polarizer of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of a translucent film of the present invention, and FIG. 2 is a conceptual diagram of a polarizer of the present invention. The translucent film shown in FIG. 1 has a structure in which a film is formed of a water-soluble resin mixture 1 composed of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer, and the micro regions 2 are dispersed using the film as a matrix. Have In FIG. 2, a film is formed from the water-soluble resin mixture 1, the water-soluble resin has a structure in which micro regions 2 are dispersed using the film as a matrix, and the dichroic light absorber 3 is a matrix. Dispersed in the mixture 1. FIG. 2 shows an example in which the dichroic light absorber 3 is oriented in the axial direction (Δn ¹ direction) in which the difference in refractive index between the minute region 2 and the water-soluble resin mixture 1 is maximum.

In the polarizer shown in FIG. 2, the polarization component in the Δn ¹ direction is scattered in the minute region 2. In FIG. 2, the Δn ¹ direction in ^one direction in the film plane is an absorption axis. In the film plane △ n ¹ perpendicular to the direction △ n ² direction is a transmission axis. Incidentally, another △ n ² direction perpendicular to △ n ¹ direction is the thickness direction.

  The water-soluble resin mixture 1 composed of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer will be described.

  The ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl ester copolymer obtained by copolymerization of ethylene and a vinyl ester monomer such as vinyl acetate to make the vinyl ester unit a vinyl alcohol unit.

  When ethylene and vinyl ester are copolymerized, other monomers may be copolymerized to such an extent that the gist of the present invention is not impaired. Examples of such comonomers include olefins other than ethylene, acrylic acid and salts thereof, acrylic esters, methacrylic acid and salts thereof, methacrylic esters, acrylamide, derivatives thereof, methacrylamide, derivatives thereof, vinyl ethers, Nitriles, vinyl halides, allyl compounds, maleic acid and salts or esters thereof, vinylsilyl compounds such as vinyltrimethoxysilane, and isopropenyl acetate.

The ethylene content of the ethylene-vinyl alcohol copolymer greatly affects the durability (water resistance and heat resistance) of the polarizer. In order to sufficiently exhibit the effect of the ethylene-vinyl alcohol copolymer, the ethylene content is preferably 1 mol% or more, more preferably 1.5 mol% or more, and further preferably 4 mol% or more. . The increase in the ethylene content improves the durability of the polarizer, but if the ethylene content increases, the polarization performance may decrease. Therefore, the ethylene content is usually 50 mol% or less and 25 mol. % Or less, preferably 13 mol% or less, and more preferably 10 mol% or less. The ethylene content was calculated from ¹³ C-NMR measurement spectra using values derived from respective integral curves of polyvinyl alcohol peak and polyethylene peak.

The degree of polymerization of the ethylene-vinyl alcohol copolymer is preferably 300 to 30,000. If the degree of polymerization is less than 300, the performance such as optical characteristics and durability may be deteriorated. The degree of polymerization is preferably 1000 or more, more preferably 1500 or more. On the other hand, it is preferably 30000 or less from the viewpoint of processing characteristics such as film formation and stretching. The degree of polymerization of the ethylene-vinyl alcohol copolymer is measured according to JIS-K6726. That is, after re-saponifying and purifying an ethylene-vinyl alcohol copolymer, the following formula: degree of polymerization = ([η] × 10) from the intrinsic viscosity [η] (unit: dl / g) measured in water at 30 ° C. ^{3 /} 8.29) ^{(1 / 0.62)} .

  The saponification degree in the vinyl alcohol unit of the ethylene-vinyl alcohol polymer also affects the performance of the polarizer of the present invention. The degree of saponification represents 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, and the residue is a vinyl ester unit. The degree of saponification is 90 mol% or more, preferably 95 mol% or more, more preferably 98 mol% or more. The saponification degree was measured by the method described in JIS K0070-1992.

  A polyvinyl alcohol polymer is obtained by saponifying a polyvinyl ester polymer obtained by radical polymerization of a vinyl ester monomer such as vinyl acetate. Examples of the polymerization method of the vinyl ester polymer include a solution polymerization method, a bulk polymerization method, a suspension polymerization method, and an emulsion polymerization method.

  The degree of polymerization of the polyvinyl alcohol polymer is preferably 1000 to 8000, more preferably 1700 to 5000, and still more preferably 2600 to 4500, from the viewpoint of durability performance. When the degree of polymerization is less than 1000, the strength of the translucent film is lowered, and the optical characteristics when the polarizer is produced tend to be inferior. On the other hand, when the degree of polymerization exceeds 8000, it is not preferable from the viewpoint of the solubility and film-forming property of the polyvinyl alcohol polymer. The saponification degree of the polyvinyl alcohol polymer is 95 mol% or more, preferably 98 mol% or more, more preferably 99.9 mol% or more. The degree of polymerization and the degree of saponification were measured by the same method as described above.

  The blending ratio of the ethylene-vinyl alcohol copolymer and the polyvinyl alcohol polymer is preferably 0.1 to 1000 parts by weight, more preferably 0, with respect to 100 parts by weight of the polyvinyl alcohol polymer. 0.5 to 200 parts by weight, more preferably 1 to 100 parts by weight, and most preferably 2 to 20 parts by weight. When the blending ratio of the ethylene-vinyl alcohol copolymer is smaller than 0.1 parts by weight, it is not preferable from the viewpoint of improving the durability, and when it is more than 1000 parts by weight, it is not preferable from the viewpoint of polarization performance.

  The water-soluble resin mixture comprising the ethylene-vinyl alcohol copolymer and the polyvinyl alcohol polymer can also contain additives such as a plasticizer. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but is preferably 20% by weight or less based on the water-soluble resin mixture.

  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 2 may be any of nematic liquid crystalline, smectic liquid crystalline, cholesteric liquid crystalline, or lyotropic liquid crystalline. The birefringent material may be a liquid crystalline thermoplastic resin, or may be formed by polymerization of a liquid crystalline monomer. When the liquid crystalline material is a liquid crystalline thermoplastic resin, those having a high glass transition temperature are preferable from the viewpoint of the heat resistance of the finally obtained structure, and those having a glass state at least at room temperature are preferably used. . The liquid crystalline thermoplastic resin is usually oriented by heating, cooled and fixed to form the microregion 2 while maintaining liquid crystallinity. The liquid crystalline monomer can form the microregion 2 in a state where it is fixed by polymerization, cross-linking or the like after blending, but the microregion 2 formed may lose liquid crystallinity.

  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 or 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 50 ° C. or higher, more preferably 80 ° 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.

  The material for forming the minute region 2 is not limited to the liquid crystalline material, and a non-liquid crystalline resin can be used as long as the material is different from the matrix material. Examples of the resin include polyolefin, polyarylate, polysulfone, polyimide, polycarbonate, polyacrylamide, polyethylene terephthalate, and acrylic styrene copolymer. Further, as a material for forming the minute region 2, 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 material for forming the minute region 2 is preferably the liquid crystalline material, but the liquid crystalline material can be mixed with a non-liquid crystalline material. In addition, the liquid crystalline material and the non-liquid crystalline material may each form a small region in the same matrix. Furthermore, as the material for forming the minute region 2, a non-liquid crystal material can be used alone.

  The translucent film of the present invention is a film in which a matrix is formed with a water-soluble resin mixture 1 composed of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer, and a micro region 2 (for example, liquid crystal) is formed in the matrix. Orientated birefringent material formed of a conductive material is dispersed.

  The haze of the translucent film is preferably 50 to 95%, and can be adjusted by the amount of dispersion of the microregions, the film forming method, and the like. When the formed film is processed and used as an optical film such as a polarizer, the haze of the translucent film is further 70 to 93%, more preferably 80 to 80, considering optical characteristics such as light dispersion performance. More preferably, it is 88%.

Although the manufacturing process of the translucent film of the present invention is not particularly limited, for example,
(1) The case where a liquid crystal material is used as a material for the microregion (hereinafter, a liquid crystal material is used as the material for the microregion in the water-soluble resin mixture resin used as the matrix will be described as a representative example. A step of preparing a mixed solution in which is dispersed,
(2) forming a film of the mixed solution of (1),
It is obtained by applying.

  In the step (1), first, a mixed solution is prepared in which a liquid crystalline material that becomes a microregion is dispersed in a water-soluble resin mixture that forms a matrix.

  The method for preparing the mixed solution is not particularly limited, and examples thereof include a method using a phase separation phenomenon between the matrix component (water-soluble resin mixture) and the liquid crystalline material. For example, a material that is not compatible with the matrix component is selected as the liquid crystalline material, and the liquid crystalline material is dispersed in a solution of the matrix component via a dispersant such as a surfactant. A dispersant may not be added depending on the combination of the materials. Of course, the preparation method is not limited to these, and an appropriate method can be adopted.

  The amount of the liquid crystalline material to be dispersed in the matrix is not particularly limited, but 0.01 to 100 parts by weight, preferably 0.1 to 10 parts by weight of the liquid crystalline material with respect to 100 parts by weight of the water-soluble resin mixture. It is.

  The liquid crystalline material is used in a solvent or without being dissolved. 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. . In the case of preparation by a solution, the solvent of the matrix component and the solvent of the liquid crystal material may be the same or different.

  In the step (2), in order to reduce foaming in the drying step after film formation, a solvent for dissolving the liquid crystalline material forming the microregion is not used in the preparation of the mixed solution in the step (1). Is preferred. For example, when a solvent is not used, a liquid crystal material is directly added to an aqueous solution of a translucent material that forms a matrix, and the liquid crystal material is heated and dispersed above the liquid crystal temperature range in order to disperse the liquid crystal material in a smaller and uniform manner. The method etc. are mention | raise | lifted.

  In addition, in a solution of a matrix component, a solution of a liquid crystal material, or a mixed solution thereof, a dispersant, a surfactant, an ultraviolet absorber, a flame retardant, an antioxidant, a plasticizer, a release agent, a lubricant, a coloring Various additives such as an agent can be contained within a range not impairing the object of the present invention.

In the step (2) of forming the mixed solution into a film, when the mixed solution is used, it is dried by heating, and the solvent is removed to produce a film in which micro regions are dispersed in the matrix. As a film forming method, a casting film forming method, a wet film forming method (discharging into a poor solvent), a dry and wet film forming method, a gel film forming method (after cooling and gelating the mixed aqueous solution, A method of extracting and removing to obtain a light-transmitting film), a method using a combination thereof, a melt extrusion film forming method in which the water-soluble mixture (which may contain an organic solvent, etc.) in a water-containing state is melted, and the like Can be adopted. In forming the film, the size of the minute region in the film is finally controlled to be 0.05 to 500 μm in the Δn ² direction. By adjusting the viscosity of the mixed solution, the selection and combination of the solvent of the mixed solution, the dispersing agent, the heating process (cooling rate) of the mixed solvent, and the drying rate, the size and dispersibility of the microregion can be controlled. The thickness of the obtained translucent film is about 50-100 micrometers.

In the polarizer of the present invention, the translucent film is uniaxially stretched, and the matrix is formed of a water-soluble resin mixture 1 made of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer. A chromatic light absorber 3 is contained. Further, in the film, the △ n ¹ direction refractive index difference ^{(△ n 1), △ n} 2 direction of the refractive index difference (△ n ²⁾ is preferably is controlled to be in the range.

  Examples of the dichroic light absorber 3 include iodine light absorbers, absorbing dichroic dyes, and pigments. Examples of the absorbing dichroic dye include, for example, JP-A-5-296281, JP-A-5-295282, JP-A-5-311086, JP-A-6-122830, JP-A-6-128498, The dichroic dyes disclosed in JP-A-7-3172, JP-A-8-67824, JP-A-8-73762, JP-A-8-127727 and the like can be used without limitation. JP-A-5-53014, JP-A-5-53015, JP-A-6-122831, JP-A-6-265723, JP-A-6-337312, JP-A-7-159615, JP-A-7-318728, JP-A-7-325215, JP-A-7-325220, JP-A-8-225750, JP-A-8-291259, JP-A-8-302219, JP-A-8-302219 JP-A-9-73015, JP-A-9-132726, JP-A-9-302249, JP-A-9-302250, JP-A-10-259111, JP-A-2000-319633, JP-A-2000- No. 327936, JP-A No. 2001-2631, JP-A No. 2001-4833, JP-A No. 2001-108828 JP, JP-A-2001-240762, JP-A-2002-105348, JP-A-2002-155218, JP-A-2002-179937, JP-A-2002-220544, JP-A-2002-275382, JP 2002-357719 A, JP 2003-64276 A, JP 2-13903 A, JP 2-89008 A, JP 3-89203 A, JP 2003-313451 A, JP JP-A-9-230142, JP-A-11-218610, JP-A-11-218611, JP-A-2001-27708, JP-A 2001 -33627, JP-A-2001-56412, JP-A-2002-296 17, JP-A No. 1-313568, JP-A No. 3-12606, JP 2003-215338, JP-dichroic dye represented by like WO00 / 37 973 pamphlet can be preferably used. Of course, in the present invention, the absorbing dichroic dye is not limited to these, and any one that can dye the water-soluble resin mixture 1 or can be dispersed to express dichroism is preferably used. it can.

The production process of the polarizer of the present invention is not particularly limited.
(1) A step of preparing a mixed solution in which a material that becomes a microregion is dispersed in a water-soluble resin mixture composed of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer that serve as a matrix;
(2) forming a film of the mixed solution of (1),
(3) A step of stretching the film obtained in (2),
(4) It is obtained by subjecting the water-soluble resin mixture to be the matrix to a step of containing a dichroic light absorber. Note that the order of the steps (1) to (4) can be determined as appropriate. A process similar to the manufacturing method of a translucent film is employable for a process (1) and a process (2).

  In the step (3) of stretching the film, the film is stretched. 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 stretching, an additive 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 dichroic light absorber 3 can be oriented in the stretching axis direction. In addition, the liquid crystalline material forming the minute region 2 is oriented in the stretching direction in the minute region by the stretching and develops birefringence.

  It is desirable that the minute region is deformed according to stretching. When the microregion is a non-liquid crystalline material, the stretching temperature is close to the glass transition temperature of the resin, and when the microregion is a liquid crystalline material, the liquid crystalline material is in a liquid crystal state such as a nematic phase or a smectic phase or isotropic phase It is desirable to select the temperature at which the condition 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 stretching described above, an external field such as an electric field or a magnetic field may be used for the orientation of the liquid crystalline material. Alternatively, a liquid-reactive material such as azobenzene mixed with a photoreactive substance or a liquid-reactive material into which a photoreactive group such as a cinnamoyl group is introduced may be aligned by an alignment treatment such as light irradiation. . Furthermore, the stretching treatment and the orientation treatment described above can be used in combination. In the case where the liquid crystalline 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. 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, is cured by irradiation with ultraviolet rays or the like at any timing to stabilize the alignment. . 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, dispersed in a solution of a matrix component, and after alignment, ultraviolet rays at any timing (before dyeing with a dichroic light absorber or after dyeing). Etc. are cured by irradiation, and the orientation is stabilized. Desirably, it is before dyeing | staining with a dichroic light absorber.

  In general, the step (4) of adding a dichroic light absorber to the light-transmitting water-soluble resin serving as the matrix, specifically, the film in a bath in which the dichroic light absorber is dissolved in a solvent. And a method of coating the film with a solution containing a dichroic light absorber. In the case of an iodine-based absorber, a method of immersing the film in an aqueous bath in which iodine is dissolved together with an auxiliary agent such as an iodide of an alkali metal such as potassium iodide. The timing of immersion may be before or after the stretching step (3). 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.

  The ratio of the dichroic light absorber in the obtained polarizer is not particularly limited, but the ratio of the water-soluble resin mixture comprising the ethylene-vinyl alcohol copolymer and the polyvinyl alcohol polymer to the light absorbing dichroic light absorber It is preferable to control the dichroic light absorber to be 100 parts by weight or less, further about 0.05 to 100 parts by weight, and further 0.1 to 50 parts by weight with respect to 100 parts by weight of the neutral resin.

  In producing the polarizer, in addition to the steps (1) to (4), a step (5) for various purposes can be performed. Examples of the step (5) include 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 (3) of stretching the film, the step (4) of dyeing and dyeing the matrix resin with a dichroic light absorber, and the step (5) include steps (3) and (4) at least once. For example, the number of steps, order, and conditions (such as bath temperature and immersion time) 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 the bridge | crosslinking process and extending process (3) of a process (5) simultaneously.

  In addition, the dichroic light absorber used for dyeing and boric acid used for crosslinking are mixed in the step (1) instead of the method of infiltrating into the film by immersing the film in an aqueous solution as described above. It is also possible to employ a method of adding any kind and amount before or after preparing the solution and before forming the film in the step (2). Moreover, you may use both methods together. However, in the step (3), when it is necessary to increase the temperature at the time of stretching or the like (for example, 80 ° C. or more), and the iodine-based absorber is deteriorated at the temperature, the step (4) Desirably after step (3).

  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 5 mm, preferably 5 μm to 3 mm, and more preferably 10 μm to 1 mm.

The polarizer thus obtained usually has no particular relationship between the refractive index of the birefringent material forming the microregion and the refractive index of the matrix resin in the stretching direction, and the stretching direction is in the Δn ¹ direction. ing. Two vertical directions perpendicular to the stretching axis are Δn ² directions. The dichroic light absorber has a direction in which the stretching direction exhibits maximum absorption, and is a polarizer in which the effect of absorption + scattering is expressed to the maximum.

  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 a polarizing plate provided with a transparent protective layer on at least one surface thereof as required. 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 a thermoplastic resin having unsubstituted phenyl and 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 and ny are the main refractive index in the plane of the film, nz is the refractive index in the film thickness direction, and d is the film thickness). A protective film having a 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.

  Furthermore, a water-soluble resin mixture composed of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer, which is a matrix resin of the polarizer obtained in the present invention, a micro-region forming material, the heat resistance and dimensions of a dichroic light absorber. If mechanical properties such as stability and reliability are sufficient, the polarizer can be used as a polarizing plate as it is without providing a transparent protective layer.

  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 fine 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.

  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.

  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 (reflection type) 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.

  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.

  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, nonwoven fabric, net, foamed sheet or metal foil, or a laminate thereof, 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, the transparent protective film, the optical film, and the like that form the polarizing plate described above, and each layer such as an adhesive layer include, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, and a cyanoacrylate. 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 reflecting plate 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 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.

  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.

Example 1
(Creation of translucent film)
An ethylene-vinyl alcohol copolymer having a polymerization degree of 500, a saponification degree of 97.5 to 99 mol%, and an ethylene 6 mol% modification, and a polyvinyl alcohol polymer having a polymerization degree of 2400 and a saponification degree of 98.5 mol%, An aqueous solution having a solid content of 13% by weight in which the water-soluble resin mixture formulated at 1:99 was dissolved was prepared. The aqueous solution, a liquid crystalline monomer having an acryloyl group at each end of the mesogenic group (nematic liquid crystal temperature range: 40 to 70 ° C.) and glycerin, water-soluble resin mixture: liquid crystalline monomer: glycerin = 100: 5: 15 (weight ratio) The mixture was heated to a temperature higher than the liquid crystal temperature and stirred with a homomixer to obtain a mixed solution. The air bubbles mixed in the solution were allowed to defoam by standing at room temperature (23 ° C.), then coated by a casting method, and then dried to obtain a white turbid 70 μm thick translucent film. This film was heat-treated at 130 ° C. for 10 minutes.

  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%. Table 1 shows the haze of the obtained translucent film.

(Creating a polarizer)
This translucent film was swollen and stretched 3 times in a 30 ° C. warm water bath, and then dissolved in 30 ° C. aqueous solution (concentration: 0.32 wt.%) With iodine: potassium iodide = 1: 7 (weight ratio). %). Subsequently, after crosslinking in a 3% by weight aqueous solution of boric acid at 30 ° C., the film was stretched so that the total draw ratio was 6 times while being crosslinked in a 4% by weight aqueous solution of boric acid at 60 ° C. This was adjusted in hue in a 5% by weight aqueous solution of potassium iodide at 30 ° C. and further dried at 50 ° C. for 4 minutes to obtain the polarizer of the present invention.

(Confirmation of anisotropic scattering and measurement of refractive index)
When the obtained polarizer was observed with a polarizing microscope, it was confirmed that minute regions of innumerable liquid crystalline monomers were formed in the water-soluble resin mixture. This liquid crystal polymer was oriented in the stretching direction, and the average size of the microregions in the Δn ² direction was 5 to 10 μm.

The refractive indexes of the matrix and the liquid crystal monomer (microregion) were measured separately. The measurement was performed at 20 ° C. First, when the refractive index of the water-soluble resin mixture alone stretched under the same stretching conditions was measured with an Abbe refractometer (measurement light 589 nm), the refractive index in the stretching direction (Δn ¹ direction) = 1.54, Δn ² direction The refractive index was 1.52. Moreover, 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 Δn ¹ direction) = 1.64, no (corresponding to the refractive index in the Δn ² direction) = 1.52. Therefore, Δn ¹ = 1.64−1.54 = 0.10 and Δn ² = 1.52−1.52 = 0 were calculated. From the above, it was confirmed that desired anisotropic scattering was expressed.

(Creation of polarizing plate)
A polarizing plate was obtained by laminating a triacetyl cellulose film having a thickness of 80 μm on both sides of the obtained polarizer using a polyurethane resin.

Example 2
In Example 1, when preparing the aqueous solution for translucent films, it is the same as Example 1 except having changed the compounding ratio of the ethylene-vinyl alcohol copolymer and the polyvinyl alcohol polymer to 1:18. Thus, a translucent film, a polarizer and a polarizing plate were prepared.

Example 3
In Example 1, when preparing an aqueous solution for a translucent film, a water-soluble resin mixture was prepared as a water-soluble resin mixture of ethylene-vinyl alcohol having a polymerization degree of 1700, a saponification degree of 97.5 to 99 mol%, and an ethylene of 9 mol%. In the same manner as in Example 1, except that a water-soluble resin mixture in which a polymer and a polyvinyl alcohol polymer having a polymerization degree of 2400 and a saponification degree of 98.5 mol% were mixed at a ratio of 1:99 was used. Film, polarizer and polarizing plate were prepared.

Example 4
In Example 1, when preparing an aqueous solution for a light-transmitting film, an ethylene-vinyl alcohol copolymer having a polymerization degree of 500, a saponification degree of 97.5 to 99 mol%, and ethylene of 2 mol% modified ethylene- A translucent film, a polarizer, and a polarizing plate were prepared in the same manner as in Example 1 except that a vinyl alcohol copolymer was used.

Example 5
In Example 1, when preparing an aqueous solution for a translucent film, an ethylene-vinyl alcohol copolymer having a polymerization degree of 500, a saponification degree of 97.5 to 99 mol%, and an ethylene of 12 mol% modified ethylene- A translucent film, a polarizer, and a polarizing plate were prepared in the same manner as in Example 1 except that a vinyl alcohol copolymer was used.

Example 6
In Example 1, when preparing an aqueous solution for a translucent film, an ethylene-vinyl alcohol copolymer having a polymerization degree of 500, a saponification degree of 97.5 to 99 mol%, and ethylene of 27 mol% modified ethylene- A translucent film, a polarizer, and a polarizing plate were prepared in the same manner as in Example 1 except that a vinyl alcohol copolymer was used.

Example 7
In Example 1, when preparing an aqueous solution for a translucent film, an ethylene-vinyl alcohol copolymer having a polymerization degree of 500, a saponification degree of 97.5 to 99 mol%, and an ethylene 47 mol% modified ethylene- A translucent film, a polarizer, and a polarizing plate were prepared in the same manner as in Example 1 except that a vinyl alcohol copolymer was used.

Comparative Example 1
In Example 1, a translucent film, a polarizer, and a polarizing plate were prepared in the same manner as in Example 1 except that the liquid crystal monomer was not added when preparing the mixed solution for the translucent film. created.

Comparative Example 2
In Example 3, a translucent film, a polarizer, and a polarizing plate were prepared in the same manner as in Example 3 except that the liquid crystal monomer was not added when preparing the mixed solution for the translucent film. created.

(Optical property evaluation)
The optical properties of the polarizing plates obtained in Examples and Comparative Examples were measured with a spectrophotometer with an integrating sphere (U-4100 manufactured by Hitachi, Ltd.). The transmittance for each linearly polarized light (550 nm) was measured with 100% of the completely polarized light obtained through the Glan-Thompson prism polarizer. Note that the transmittance is indicated by a Y value corrected for visual sensitivity calculated based on the CIE 1931 color system. k ₁ represents the transmittance of linearly polarized light in the maximum transmittance direction, and k ₂ represents the transmittance of linearly polarized light in the orthogonal direction. The results are shown in Table 1. In Table 1, ± of the single transmittance indicates variation in the in-plane measurement value.

The degree of polarization P was calculated by P = {(k ₁ −k ₂ ) / (k ₁ + k ₂ )} × 100. The single transmittance T was calculated by T = (k ₁ + k ₂ ) / 2.

  Durability was evaluated by heating the polarizing plate with a constant temperature and humidity chamber of 60 ° C. and 90% RH for 24 hours, and measuring the transmittance and polarization degree of the polarizing plate before and after the test by the above method. .

For the evaluation of unevenness, a sample (polarizer) is placed on the upper surface of a backlight used in a liquid crystal display in a dark room, and a polarizing plate is used with a commercially available polarizing plate (NPF-SEG1224DU manufactured by Nitto Denko Corporation) as an analyzer. The layers were laminated so as to be orthogonal to each other, and the level was visually confirmed according to the following criteria. The results are shown in Table 1.
X: Level at which unevenness can be confirmed visually.
○: Level at which unevenness cannot be confirmed visually.

  As shown in Table 1 above, in the examples, the unevenness is improved by the scattering effect by the minute region, and both the transmittance and the degree of polarization are excellent. Moreover, it turns out that the polarizing plate of an Example has few changes before and after a durability test, and is excellent in durability.

It is a conceptual diagram which shows an example of the translucent film of this invention. It is a conceptual diagram which shows an example of the polarizer of this invention.

Explanation of symbols

1 Water-soluble resin mixture 2 Micro area 3 Dichroic absorber

Claims (12)

  A translucent film having a structure in which minute regions are dispersed in a matrix formed of a water-soluble resin mixture comprising an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer.   The translucent film according to claim 1, wherein the minute region is formed of a birefringent material.   The translucent film according to claim 2, wherein the birefringent material exhibits liquid crystallinity at least at the time of the alignment treatment.   The translucent film according to any one of claims 1 to 3, wherein the blending amount of the ethylene-vinyl alcohol copolymer with respect to 100 parts by weight of the polyvinyl alcohol polymer is 0.1 to 1000 parts by weight.   The translucent film according to any one of claims 1 to 4, wherein the ethylene content of the ethylene-vinyl alcohol copolymer is 1 to 25 mol%.   Haze value is 50 to 95%, The translucent film in any one of Claims 1-5 characterized by the above-mentioned. A method for producing the translucent film according to claim 1,
(1) A step of preparing a mixed solution in which a material that becomes a microregion is dispersed in a water-soluble resin mixture composed of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer that serve as a matrix;
(2) A process for producing a translucent film, comprising the step of forming a film of the mixed solution of (1).   The translucent film according to any one of claims 1 to 6, wherein the translucent film is uniaxially stretched and is formed of a water-soluble resin mixture comprising an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer. A polarizer comprising a dichroic light absorber. A method for producing the polarizer according to claim 8, comprising:
(1) A step of preparing a mixed solution in which a material that becomes a microregion is dispersed in a water-soluble resin mixture composed of an ethylene-vinyl alcohol copolymer and a polyvinyl alcohol polymer that serve as a matrix;
(2) forming a film of the mixed solution of (1),
(3) A step of stretching the film obtained in (2),
(4) A method for producing a polarizer, comprising a step of incorporating a dichroic light absorber into the water-soluble resin mixture serving as the matrix.   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.

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