JP2005202368A - Polarizing plate, optical film, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate that has a high polarization degree on a short wavelength side and, further, to provide a polarizing plate that has a high polarization degree and satisfactory durability. <P>SOLUTION: In the polarizing plate in which protective films are layered on one or both sides of a polarizer, the polarizer is formed of a film that has a structure in which minute areas are dispersed in a matrix formed of a transmissive water soluble resin containing an iodine-based light absorbing body. The protective film has an in-plane phase difference of 20 nm or less and a thickness direction phase difference of 30 nm or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polarizing plate. The present invention also relates to the polarizing plate and the optical film. Further, the present invention relates to an image display device such as a polarizing plate, a liquid crystal display device using an optical film, an organic EL display device, a CRT, or a PDP.

  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 particular, displays with higher brightness and higher contrast are required for applications such as TV, and light polarizers with higher brightness (high transmittance) and higher contrast (high polarization degree) have been developed and introduced. Yes.

  As a polarizer, for example, an iodine-based polarizer having a stretched structure obtained by adsorbing iodine to polyvinyl alcohol is widely used because it has a high transmittance and a high degree of polarization (see, for example, Patent Document 1). However, since iodine-type polarizers have a relatively low degree of polarization on the short wavelength side, the short wavelength side has problems in hue such as bluish in black display and yellowness in white display.

  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. As a method for solving this problem, for example, the amount of iodine adsorbed on an iodine polarizer is increased so that the transmittance during black display is below the human eye's detection limit, or the unevenness itself is reduced. A method of adopting a stretching process that hardly occurs has been proposed. However, the former has a problem that the transmittance at the time of white display is lowered at the same time as the transmittance of black display, and the display itself becomes dark. Further, the latter has a problem that it is necessary to replace the process itself, which deteriorates productivity.

  Conventionally, a polarizer has been used as a polarizing plate having both surfaces sandwiched between protective films such as a triacetyl cellulose film. However, since a triacetyl cellulose film has a retardation value, it is not sufficient from the above-mentioned problem of hue.

  In recent years, liquid crystal display devices are used in various fields. Therefore, it is necessary to assume even when used under harsh conditions, and the polarizing plate has excellent durability with little change in characteristics such as light transmittance, polarization degree, and hue of the image even at high temperature or high humidity. Is requested. However, in fields where high thermal reliability at high humidity or high temperature is required, such as for outdoor use or in-vehicle use, the triacetyl cellulose film has a high moisture permeability and water absorption rate. It has been a problem that the deterioration of the material is large. Therefore, it has been studied to use a transparent film having a low moisture permeability and water absorption rate as a protective layer for a polarizer using polyvinyl alcohol (see, for example, Patent Document 2, Patent Document 3, Patent Document 4 and the like).

However, because the polarizer using polyvinyl alcohol is hydrophilic, the polarizer itself has a high hygroscopicity, and simply using a film with low moisture permeability and low water absorption as described above as a protective film, The transmission of moisture emitted from the polarizer is hindered, and the inside of the polarizing plate itself becomes a high temperature and high humidity state in a high temperature environment, resulting in a large amount of change in light transmittance, degree of polarization, etc. The reliability as a polarizing plate was low.
JP 2001-296427 A JP-A-6-511117 JP-A-7-77608 JP-A-11-142645

  An object of the present invention is to provide a polarizing plate having a protective film laminated on one or both sides of a polarizer, and having a high degree of polarization even on the short wavelength side. It is another object of the present invention to provide a polarizing plate having a high degree of polarization and good durability.

  Another object of the present invention is to provide a polarizing plate having a high transmittance and a high degree of polarization and capable of suppressing unevenness in transmittance during black display, and further a polarizing plate with good durability. To do.

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

That is, the present invention is a polarizing plate in which a protective film is laminated on one side or both sides of a polarizer.
The polarizer consists of a film having a structure in which minute regions are dispersed in a matrix formed of a light-transmitting water-soluble resin containing an iodine-based absorber.
In the protective film, the direction in which the in-plane refractive index in the film plane is the maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the film is the Z axis. When nx, ny, nz, and film thickness d (nm),
In-plane retardation Re = (nx−ny) × d is 20 nm or less,
And a thickness direction retardation Rth = {(nx + ny) / 2−nz) × d) is 30 nm or less.

  The microregion of the polarizer is preferably formed of an oriented birefringent material. The birefringent material preferably exhibits liquid crystallinity at least at the time of alignment treatment.

  In the polarizer of the present invention, an iodine polarizer formed of a translucent water-soluble resin and an iodine light absorber is used as a matrix, and minute regions are dispersed in the matrix. The minute region is preferably formed of an oriented birefringent material, and particularly the minute region is preferably formed of a material exhibiting liquid crystallinity. In this way, in addition to the function of absorption dichroism by the iodine-based absorber, the function of scattering anisotropy is combined, so that the polarization performance is improved by the synergistic effect of the two functions, and the transmittance and degree of polarization are increased. 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 ⁻ , It believed to be caused by the interaction with such) ^- I _5. Iodine absorbers are also called iodine complexes. Polyiodine ions are thought to be generated from iodine and iodide ions.

  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.

  In the polarizing plate of the present invention, a protective film having a small retardation is used, and the optical coloring problem related to the protective film can be almost solved. The in-plane retardation of the protective film is 20 nm or less, more preferably 10 nm or less. The thickness direction retardation is 30 nm or less, more preferably 20 nm or less.

  In the polarizing plate, it is preferable that the birefringence of the minute region of the polarizer 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 polarizing plate, the refractive index difference between the birefringent material forming the minute region of the polarizer and the light-transmitting water-soluble resin 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 polarizing plate, it is preferable that the iodine-based light absorber of the polarizer has the absorption axis of the material oriented in the Δn ¹ direction.

Iodine based light absorbing material in the matrix, by the absorption axis of the material is oriented to be parallel to the △ n ¹ direction, thereby selectively absorbing certain scattering polarizing direction △ n ¹ direction of linearly polarized light Can do. As a result, the linearly polarized light component in the Δn ² direction of the incident light is not scattered and hardly absorbed by the iodine absorber as is the case with conventional iodine-based polarizers that do not have anisotropic scattering performance. On the other hand, the linearly polarized light component in the Δn ¹ 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 Δn ¹ 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 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, 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 manufactured, 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 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 polarizing plate, as the film used as the polarizer, a film produced by stretching can be suitably used.

In the polarizing plate, 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 polarizing plate, as the iodine-based absorber of the polarizer, one having an absorption region in a wavelength band of at least 400 to 700 nm is used.

  In the polarizing plate, the protective film comprises (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a thermoplastic resin having a substituted and / or unsubstituted phenyl group and a nitrile group in the side chain. Any one selected from a resin composition containing a resin and a norbornene-based resin can be preferably used. In addition, at least one selected from polyolefin resins, polyester resins, and polyamide resins can be preferably used. Moreover, the cellulose resin film which performed the specific process can be used.

  The protective film using the material can ensure a stable retardation value even when the polarizer undergoes dimensional change under high temperature or high humidity and is subjected to the stress. That is, it is possible to obtain an optical film that hardly causes a phase difference even in an environment of high temperature and high humidity and has little characteristic change. In particular, a protective film containing a mixture of the thermoplastic resins (A) and (B) is preferable.

  In general, the film material can be improved in strength by stretching, and tougher mechanical properties can be obtained. However, in many materials, since a phase difference is generated by the stretching treatment, it cannot be used as a protective film for a polarizer. The protective film containing the mixture of the thermoplastic resins (A) and (B) is preferable in that it can satisfy the in-plane retardation and the thickness direction retardation even when it is stretched. The stretching treatment may be either uniaxial stretching or biaxial stretching. In particular, a biaxially stretched film is preferred.

  The polarizing plate 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 polarizing plate having the transmittance and haze value has high transmittance and good visibility for linearly polarized light in the transmission direction, and has strong light diffusibility for linearly polarized light in the absorption direction. ing. 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. That is, when black is displayed, unevenness due to local transmittance variation is concealed by scattering, and when white is displayed, the image has a clear image without scattering, that is, the visibility is improved, and the liquid crystal display device is When applied, re-light leakage observed from the front and diagonal is reduced.

  The polarizing plate 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 between the front and back surfaces of the polarizing plate, the ideal limit is 100% minus this surface reflection.

  In addition, it is desirable that the polarizing plate 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, More preferably, it is 1% or less. On the other hand, in the polarizing plate, it is desirable that the 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 transmittance and high degree of polarization.

  The present invention also relates to an optical film in which at least one polarizing plate is laminated.

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

  In the polarizing plate of the present invention, a protective film is laminated on one side or both sides of a polarizer.

  First, the polarizer of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of a polarizer of the present invention, in which a film is formed of a translucent water-soluble resin 1 containing an iodine-based absorber 2, and the microregion 3 is dispersed using the film as a matrix. Has a structured.

FIG. 1 shows an example in which the iodine-based absorber 2 is oriented in the axial direction (Δn ¹ direction) in which the difference in refractive index between the minute region 3 and the translucent water-soluble resin 1 is maximum. It is. In the minute region 3, the polarization component in the Δn ¹ direction is scattered. In FIG. 1, 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.

  As translucent water-soluble resin 1, what has translucency in visible region and can disperse and adsorb iodine type light absorber can be used without particular limitation. For example, polyvinyl alcohol or its derivative conventionally used for a polarizer is mentioned. Derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, alkyl esters thereof, acrylamide and the like. can give. Examples of the translucent water-soluble resin 1 include polyvinyl pyrrolidone resins and amylose resins. The translucent water-soluble resin 1 may have an isotropic property that hardly causes orientation birefringence due to molding distortion or the like, or may have anisotropy that easily causes orientation birefringence.

  The material forming the microregion 3 is not particularly limited as to whether it is isotropic or birefringent, but a birefringent material is preferable. 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 3 may exhibit liquid crystallinity or may lose liquid crystallinity.

  The birefringent material (liquid crystalline material) forming the minute region 3 may be 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. It is preferable to use a glass that is at least at room temperature. The liquid crystalline thermoplastic resin is usually oriented by heating, cooled and fixed to form the microregion 3 while maintaining liquid crystallinity. The liquid crystalline monomer can form the microregion 3 in a state where it is fixed by polymerization, cross-linking or the like after blending, but the liquid crystallinity is lost in the microregion 3 formed.

  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 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 3 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 polyvinyl alcohol and derivatives thereof, polyolefin, polyarylate, polymethacrylate, polyacrylamide, polyethylene terephthalate, and acrylic styrene copolymer. Further, as a material for forming the minute region 3, 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 3 is preferably the liquid crystalline material, but the liquid crystalline material can be mixed with a non-liquid crystalline material. Furthermore, a non-liquid crystalline material can be used alone as a material for forming the minute region 3.

The polarizer of the present invention produces a film in which a matrix is formed with a translucent water-soluble resin 1 containing an iodine-based absorber 2 and is formed in the matrix with a minute region 3 (for example, a liquid crystalline material). The oriented birefringent material) is dispersed. Further, in the film, the △ n ¹ direction refractive index difference ^{(△ n 1), △ n} 2 direction of the refractive index difference (△ n ²⁾ is controlled to be in the range.

The manufacturing process of the polarizer of the present invention is not particularly limited.
(1) As a representative example, a case where a liquid crystal water-soluble resin serving as a matrix is made of a material that becomes a minute region (hereinafter, a liquid crystalline material is used as a material that becomes a minute region. A process for producing a mixed solution in which the same is applied to
(2) forming a film of the mixed solution of (1),
(3) A step of orienting (stretching) the film obtained in (2) above,
(4) A step of dispersing (staining) an iodine-based light absorber in a light-transmitting water-soluble resin serving as the matrix,
It is obtained by applying. Note that the order of the steps (1) to (4) can be determined as appropriate.

  In the step (1), first, a mixed solution is prepared in which a liquid crystalline material that forms a minute region is dispersed in a light-transmitting water-soluble resin that forms a matrix. A 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 (translucent water-soluble resin) and a liquid crystal material. For example, as a liquid crystalline material, a material that is not compatible with the matrix component is selected, and a solution of the material that forms the liquid crystalline material is dispersed in an aqueous solution of the matrix component through a dispersant such as a surfactant. . In the preparation of the mixed solution, a dispersant may not be added depending on a combination of a light-transmitting material forming a matrix and a liquid crystal material forming a micro region. 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 100 parts by weight of the liquid crystalline material with respect to 100 parts by weight of the light-transmitting water-soluble resin. 10 parts by weight. 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. . 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 matrix component solution, a liquid crystal material solution, or a mixed solution, a dispersant, a surfactant, an ultraviolet absorber, a flame retardant, an antioxidant, a plasticizer, a release agent, a lubricant, a colorant, etc. These various additives 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, the mixed solution is heated and dried, and the solvent is removed to produce a film in which micro regions are dispersed in the matrix. As a film forming method, various methods such as a casting method, an extrusion molding method, an injection molding method, a roll molding method, and a casting method can be employed. 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 dispersant, the thermal process (cooling rate) of the mixed solvent, and the drying rate, the size and dispersibility of the microregion can be controlled. For example, by using a stirrer such as a homomixer while heating a mixed solution of a highly viscous translucent water-soluble resin that forms a matrix and a liquid crystalline material that forms a microscopic region to a temperature above the liquid crystal temperature range. By dispersing, the minute region can be dispersed smaller.

  The step (3) 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 iodine-based absorber can be oriented in the stretching axis direction. In addition, the liquid crystalline material that becomes a birefringent material in the minute region is oriented in the stretching direction in the minute region by the above stretching, and exhibits 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 at the stretching temperature. 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. 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, anisotropic scattering is eliminated and the polarization performance is adversely affected. In such a case, curing is preferable. In addition, many liquid crystalline monomers crystallize when left at room temperature. In this case, anisotropic scattering is lost and, on the other hand, polarization performance deteriorates. In such a case, it is preferable to cure. 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 or after staining with an iodine-based absorber), ultraviolet rays, etc. Is cured by irradiation to stabilize the orientation. Desirably, it is before dyeing | staining with an iodine type light absorber.

  In the step (4) of dispersing the iodine-based absorber in the light-transmitting water-soluble resin serving as the matrix, generally, an aqueous system in which iodine is dissolved together with an assistant such as an alkali metal iodide such as potassium iodide. There is a method of immersing the film in a bath. As described above, an iodine-based 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 (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.

  Further, the ratio of iodine in the obtained polarizer is not particularly limited, but the ratio of iodine of translucent water-soluble resin to iodine is 0.05 to 50 with respect to 100 parts by weight of translucent water-soluble resin. It is preferable to control the amount to be about parts by weight, more preferably 0.1 to 10 parts by weight.

  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 orienting (stretching) the film, the step (4) of dispersing and dyeing an iodine-based absorber on the matrix resin, and the step (5) are performed at least once each of the steps (3) and (4). 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 the bridge | crosslinking process and extending process (3) of a process (5) simultaneously.

  In addition, the iodine-based light absorber used for dyeing, boric acid used for crosslinking, etc. are mixed in the step (1) instead of the method of permeating into the film by immersing the film in an aqueous solution as described above. It is also possible to adopt a method of adding any kind and amount before or after preparation and before film formation in 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 iodine-based absorber is used. The step (4) of disperse dyeing is preferably performed after the 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 3 mm, preferably 5 μm to 1 mm, and more preferably 10 to 500 μm.

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. Further, the iodine light absorber has a direction in which the stretching direction exhibits the maximum absorption, and is a polarizer in which the effect of absorption + scattering is expressed to the maximum.

  In the protective film, the direction in which the in-plane refractive index in the film plane is the maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the film is the Z axis. When nx, ny, nz, and film thickness d (nm), in-plane retardation Re = (nx−ny) × d is 20 nm or less, and thickness direction retardation Rth = {(nx + ny) / 2-nz) × d) is 30 nm or less.

  As the material of the protective film, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain and (B) a thermoplastic resin having a substituted and / or unsubstituted phenyl group and a nitrile group in the side chain And a norbornene-based resin. Further, polyolefin resins, polyester resins, polyamide resins, polyacrylic resins and the like that satisfy the conditions of the present invention can be mentioned. Moreover, the cellulose resin film which performed the specific process can be used.

  As described above, the protective film containing the thermoplastic resins (A) and (B) is less likely to cause retardation even when subjected to stress due to dimensional change of the polarizer, and is in-plane even when stretched. The phase difference Re and the thickness direction phase difference Rth can be controlled to be small. Such a protective film containing the thermoplastic resins (A) and (B) is described in, for example, WO01 / 37007. The protective film can also contain other resins even when the thermoplastic resins (A) and (B) are the main components.

  The thermoplastic resin (A) has a substituted and / or unsubstituted imide group in the side chain, and the main chain is an arbitrary thermoplastic resin. The main chain may be, for example, a main chain composed only of carbon, or atoms other than carbon may be inserted between carbons. Moreover, you may consist of atoms other than carbon. The main chain is preferably a hydrocarbon or a substituted product thereof. The main chain is obtained, for example, by addition polymerization. Specifically, for example, polyolefin or polyvinyl. The main chain is obtained by condensation polymerization. For example, it can be obtained by an ester bond or an amide bond. The main chain is preferably a polyvinyl skeleton obtained by polymerizing a substituted vinyl monomer.

  Any conventionally known method can be adopted as a method for introducing a substituted and / or unsubstituted imide group into the thermoplastic resin (A). For example, a method of polymerizing a monomer having the imide group, a method of polymerizing various monomers to form a main chain, and then introducing the imide group, a method of grafting the compound having the imide group to a side chain, etc. It is done. As the substituent of the imide group, a conventionally known substituent that can replace the hydrogen of the imide group can be used. For example, an alkyl group etc. are mention | raise | lifted.

  The thermoplastic resin (A) is a binary copolymer having at least one repeating unit derived from at least one olefin and at least one repeating unit having a substituted and / or unsubstituted maleimide structure. Is preferred. The olefin / maleimide copolymer can be synthesized from an olefin and a maleimide compound by a known method. The synthesis method is described, for example, in JP-A-5-59193, JP-A-5-195801, JP-A-6-1336058 and JP-A-9-328523.

  Examples of the olefin include isobutene, 2-methyl-1-butene, 2-methyl-1-pentene, 2-methyl-1-hexene, 2-methyl-1-heptene, 2-methyl-1-heptene, Examples thereof include 1-isooctene, 2-methyl-1-octene, 2-ethyl-1-pentene, 2-ethyl-2-butene, 2-methyl-2-pentene, 2-methyl-2-hexene and the like. Of these, isobutene is preferred. These olefins may be used alone or in combination of two or more.

  As maleimide compounds, maleimide, N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, Ni-propylmaleimide, Nn-butylmaleimide, Ni-butylmaleimide, Nt-butyl Maleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-laurylmaleimide, N-stearylmaleimide, N-cyclopropylmaleimide, N-cyclo Examples thereof include butyl maleimide, N-cyclopentyl maleimide, N-cyclohexyl maleimide, N-cycloheptyl maleimide, N-cyclooctyl maleimide and the like. Of these, N-methylmaleimide is preferred. These maleimide compounds may be used alone or in combination of two or more.

  In the olefin / maleimide copolymer, the content of the repeating unit of the olefin is not particularly limited, but is about 20 to 70 mol%, preferably 40 to 60 mol%, more preferably about the total repeating unit of the thermoplastic resin (A). It is 45 to 55 mol%. The content of repeating units having a maleimide structure is about 30 to 80 mol%, preferably 40 to 60 mol%, and more preferably 45 to 55 mol%.

  A thermoplastic resin (A) contains the repeating unit of the said olefin and the repeating unit of a maleimide structure, and can be formed only with these units. In addition to the above, repeating units of other vinyl monomers may be contained in a proportion of 50 mol% or less. Other vinyl monomers include acrylic acid monomers such as methyl acrylate and butyl acrylate, methacrylic acid monomers such as methyl methacrylate and cyclohexyl methacrylate, and vinyl ester monomers such as vinyl acetate. And vinyl ether monomers such as methyl vinyl ether, acid anhydrides such as maleic anhydride, and styrene monomers such as styrene, α-methylstyrene and p-methoxystyrene.

The weight average molecular weight of the thermoplastic resin (A) is not particularly limited, but is about 1 × 10 ^{3 to} 5 × 10 ⁶ . The weight average molecular weight is preferably 1 × 10 ⁴ or more, and more preferably 5 × 10 ⁵ or less. The glass transition temperature of the thermoplastic resin (A) is 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 130 ° C. or higher.

  Moreover, as a thermoplastic resin (A), a glutarimide type thermoplastic resin can be used. Glutarimide resins are described in JP-A-2-153904. The glutarimide-based resin has a glutarimide structural unit and a methyl acrylate or methyl methacrylate structural unit. The other vinyl monomers can also be introduced into the glutarimide resin.

  The thermoplastic resin (B) is a thermoplastic resin having a substituted and / or unsubstituted phenyl group and a nitrile group in the side chain. The main chain of a thermoplastic resin (B) can illustrate the thing similar to a thermoplastic resin (A).

  Examples of the method of introducing the phenyl group into the thermoplastic resin (B) include a method of polymerizing the monomer having the phenyl group, a method of introducing a phenyl group after polymerizing various monomers to form a main chain, Examples thereof include a method of grafting a compound having a phenyl group onto a side chain. As the substituent of the phenyl group, a conventionally known substituent that can replace hydrogen of the phenyl group can be used. For example, an alkyl group etc. are mention | raise | lifted. The method for introducing a nitrile group into the thermoplastic resin (B) can be the same as the method for introducing a phenyl group.

  The thermoplastic resin (B) is a binary or ternary multi-copolymer comprising a repeating unit derived from an unsaturated nitrile compound (nitrile unit) and a repeating unit derived from a styrene compound (styrene unit). It is preferably a coalescence. For example, an acrylonitrile / styrene copolymer can be preferably used.

  The unsaturated nitrile compound includes any compound having a cyano group and a reactive double bond. Examples thereof include α-substituted unsaturated nitriles such as acrylonitrile and methacrylonitrile, and nitrile compounds having an α, β-disubstituted olefinically unsaturated bond such as fumaronitrile.

  Examples of the styrenic compound include any compound having a phenyl group and a reactive double bond. Examples thereof include unsubstituted or substituted styrene compounds such as styrene, vinyl toluene, methoxystyrene, and chlorostyrene, and α-substituted styrene compounds such as α-methylstyrene.

  The content of the nitrile unit in the thermoplastic resin (B) is not particularly limited, but is about 10 to 70% by weight, preferably 20 to 60% by weight, more preferably 20 to 50% by weight based on the total repeating units. is there. 20 to 40 weight% and 20 to 30 weight% are especially preferable. The styrenic unit is about 30 to 80% by weight, preferably 40 to 80% by weight, and more preferably 50 to 80% by weight. 60 to 80 weight% and 70 to 80 weight% are especially preferable.

  A thermoplastic resin (B) contains the said nitrile unit and a styrene-type unit, and can be formed only with these units. In addition to the above, repeating units of other vinyl monomers may be contained in a proportion of 50 mol% or less. Examples of the other vinyl monomers include those exemplified for the thermoplastic resin (A), olefin repeating units, maleimide, substituted maleimide repeating units, and the like. Examples of the thermoplastic resin (B) include AS resin, ABS resin, ASA resin, and the like.

The weight average molecular weight of the thermoplastic resin (B) is not particularly limited, but is about 1 × 10 ^{3 to} 5 × 10 ⁶ . It is preferably 1 × 10 ⁴ or more and 5 × 10 ⁵ or less.

  The ratio of the thermoplastic resin (A) and the thermoplastic resin (B) is adjusted according to the retardation required for the protective film. In general, the content of the thermoplastic resin (A) is preferably 50 to 95% by weight, more preferably 60 to 95% by weight, based on the total amount of the resin in the film. More preferably, it is 65 to 90% by weight. The content of the thermoplastic resin (B) is preferably 5 to 50% by weight of the total amount of the resin in the film, more preferably 5 to 40% by weight, and still more preferably 10 to 35% by weight. %. The thermoplastic resin (A) and the thermoplastic resin (B) are mixed by hot-melt kneading them.

  Examples of norbornene-based resins include, for example, ring-opening (co) polymers of norbornene-based monomers, which are subjected to modifications such as maleic acid addition and cyclopentadiene addition, and then hydrogenated, and norbornene-based monomers are subjected to addition polymerization. Addition resin, norbornene monomer and addition polymerized olefin monomer such as ethylene and α-olefin, norbornene monomer and cyclic olefin monomer such as cyclopentene, cyclooctene and 5,6-dihydrodicyclopentadiene Examples thereof include polymerized resins. Specific examples of the thermoplastic saturated norbornene resin include ZEONEX and ZEONOR manufactured by Nippon Zeon Co., Ltd., and ARTON manufactured by JSR Corporation.

  Examples of the polyolefin-based resin include homopolymers or copolymers of α-olefins having 1 to 6 carbon atoms such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly-4-methylpentene-1. Examples of the polyester resin include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polyethylene terephthalate-isophthalate copolymer. In addition, various polyamide-based resins are exemplified.

  Moreover, the cellulose resin film which performed the specific process can be used. Examples of the material for the cellulose resin film include fatty acid-substituted cellulose polymers such as diacetyl cellulose and triacetyl cellulose. The treatment means for the cellulose resin film can be performed by the following means. For example, a base material such as polyethylene terephthalate, polypropylene, and stainless steel coated with a solvent such as cyclopentanone and methyl ethyl ketone is bonded to a general cellulose resin film and dried by heating (about 80 to 150 ° C. for about 3 to 10 minutes) ) And then peeling the substrate film; a solution obtained by dissolving norbornene resin, acrylic resin, etc. in a solvent such as cyclopentanone, methyl ethyl ketone, etc., is applied to a general cellulose resin film and dried by heating (80 (About 150 degreeC, about 3-10 minutes), and the method etc. which peel a coating film are mention | raise | lifted. As the cellulose resin film, a fatty acid substituted cellulose polymer having a controlled degree of fatty acid substitution can be used. Generally used triacetyl cellulose has an acetic acid substitution degree of about 2.8. The acetic acid substitution degree is 1.8 to 2.7, and the propionic acid substitution degree is 0.1. By using the one controlled to ˜1, the thickness direction retardation (Rth) can be controlled to be small. Furthermore, the thickness direction retardation (Rth) can be controlled to be small by adding a plasticizer such as dibutyl phthalate, p-toluenesulfonanilide, and acetyltriethyl citrate to the fatty acid-substituted cellulose polymer. The addition amount of the plasticizer is preferably about 40 parts by weight or less, more preferably 1 to 20 parts by weight, and further preferably 1 to 15 parts by weight with respect to 100 parts by weight of the fatty acid-substituted cellulose polymer.

  The thickness of the protective film is arbitrary, but generally 1 to 500 μm, 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 protective film on both sides of a polarizer, the protective film which consists of a polymer etc. which is different in the front and back can be used.

The moisture permeability of the protective film is not particularly limited, moisture permeability is preferably not more than 500g / m ² / 24h. Further is preferably not more than 120g / m ² / 24h. Protective film of less moisture permeability of 500g / m ² / 24h well durability at high temperatures and high humidity, is excellent moisture resistance related hues. As a material used for the protective film, a norbornene-based resin is preferable because of low moisture permeability.

  Moreover, various resin layers can be provided in a protective film, and it can affix on a polarizer with an adhesive agent through a resin layer.

  The resin layer is not particularly limited as long as it is in good contact with the protective film. For example, various resins such as ester, ether, carbonate, urethane, and silicone can be used. The resin layer may be either water-based or solvent-based. Of these, water-based urethane resins and silicone resins are preferable. Furthermore, it is possible to add a coupling agent such as a silane coupling agent or a titanium coupling agent to the resin that forms the resin layer, and a catalyst such as a titanium-based or tin-based catalyst for efficiently reacting the coupling agent. it can. Thereby, the adhesive force between the polarizer and the protective film can be further strengthened. Moreover, you may add another additive to the said resin layer. Specifically, terpene resins, phenol resins, terpene-phenol resins, rosin resins, xylene resins and other tackifiers, UV absorbers, antioxidants, heat stabilizers and other stabilizers may be used.

  The resin layer is formed by coating and drying a solution diluted to an appropriate concentration in consideration of the thickness after drying, the smoothness of coating, and the like by a known technique. The thickness of the resin layer after drying is preferably 0.01 to 10 μm, more preferably 0.1 to 2 μm. Even when a plurality of resin layers are provided, the total thickness of the resin layers is preferably in the above range.

  In addition, the surface which adhere | attaches with the polarizer of a protective film can provide an easily bonding process besides providing a resin layer. Examples of the easy adhesion treatment include dry treatment such as plasma treatment and corona treatment, chemical treatment such as alkali treatment, and coating treatment for forming an easy adhesive layer.

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

  Hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film having excellent hardness and slipping properties with an appropriate ultraviolet curable resin such as acrylic or silicone is applied to the protective film. It can be formed by a method of adding to the surface. 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 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, diffusion layer, antiglare layer, and the like can be provided on the 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 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 protective film and the polarizer together using the adhesive. Application | coating of an adhesive agent may be performed to any of a protective film and a polarizer, and may be performed 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 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 vapor-deposited film made of a reflective metal such as aluminum on one surface of a protective film matted as necessary. In addition, the protective film may contain fine particles to form 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. Moreover, the 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 with a fine concavo-convex structure reflecting the surface fine concavo-convex structure of the protective film is transparently protected by an appropriate method such as a vapor deposition method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of attaching directly to the surface of the layer.

  The reflective plate can be used as a reflective sheet in which a reflective layer is provided on an appropriate film according to the transparent film, instead of the method of directly imparting to the protective film of the polarizing plate. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a protective film, a polarizing plate or the like is used to prevent a decrease in reflectance due to oxidation, and thus the long-term sustainability of the initial reflectance. More preferable is the point of avoiding the additional 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. That is, when light is incident through the polarizer from the back side of the liquid crystal cell without using a brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost polarized. It is absorbed by the polarizer and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display or the like is reduced accordingly, resulting in a dark image. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be reflected once by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflective layer provided on the rear side thereof. Repeatedly re-enter the brightness enhancement film, and the brightness enhancement film transmits only polarized light whose polarization direction is such that the polarization direction of light reflected and inverted between the two can pass through the polarizer. Therefore, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

  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 directly incident on a polarizer. However, 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. It can be obtained by a method of superposing a retardation layer, for example, a retardation layer functioning as a half-wave plate. Therefore, 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, protective film, optical film, etc. 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 cyanoacrylate compounds. A compound or a compound having ultraviolet absorbing ability by a method such as a method of treating with a UV absorber such as a nickel complex salt compound may be used.

  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. .

  That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light becomes generally elliptically polarized light by the phase difference plate, but becomes circularly polarized light particularly when the phase difference plate is a quarter wavelength plate and the angle formed by the polarization direction of the polarizing plate and the phase difference plate is π / 4. .

  This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

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

  The refractive indexes nx, ny, and nz of the protective film were measured with an automatic birefringence measuring device (manufactured by Oji Scientific Instruments, automatic birefringence meter KOBRA21ADH), and the in-plane retardation Re and the thickness direction retardation Rth were calculated.

Example 1
(Polarizer)
A 13% by weight polyvinyl alcohol aqueous solution in which a polyvinyl alcohol resin having a polymerization degree of 2400 and a saponification degree of 98.5% is dissolved, and a liquid crystalline monomer having one acryloyl group at both ends of the mesogenic group (nematic liquid crystal) The temperature range is 40-70 ° C.) and glycerin are mixed such that polyvinyl alcohol: liquid crystalline monomer: glycerin = 100: 5: 15 (weight ratio), and heated to a temperature higher than the liquid crystal temperature range. To obtain a mixed solution. The bubbles present in the mixed solution were degassed by leaving them at room temperature (23 ° C.), and then coated by a casting method, followed by drying to obtain a white turbid mixed film having a thickness of 70 μm. This mixed film was heat-treated at 130 ° C. for 10 minutes.

  The mixed film is immersed in a 30 ° C. water bath to swell, and then immersed in an aqueous solution (dye bath: concentration 0.32% by weight) of iodine: potassium iodide = 1: 7 (weight ratio) at 30 ° C. The film was stretched about 3 times, then stretched so that the total stretch ratio was about 6 times while immersed in a 3% by weight boric acid aqueous solution (crosslinking bath) at 50 ° C., and then further 4% by weight boric acid at 60 ° C. It was immersed in an aqueous solution (crosslinking bath). Furthermore, the hue was adjusted by dipping in a 5% by weight aqueous solution of potassium iodide at 30 ° C. Then, it dried at 50 degreeC for 4 minute (s), and obtained the polarizer of this invention.

(Confirmation of anisotropic scattering and measurement of refractive index)
Further, when the obtained 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 (Δn ² 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 was measured with an Abbe refractometer (measurement light 589 nm), the refractive index in the stretching direction (Δn ¹ direction) = 1.54, in the Δn ² direction. Refractive index = 1.52. The refractive index of the liquid crystal monomer (n _e: extraordinary refractive index and n _o: ordinary index) was measured. n _o is oriented Coating liquid crystal monomer onto a high refractive index glass with a vertical alignment treatment was measured with an Abbe refractometer (measurement light 589 nm). 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, a cell gap by a light interference method to measure (d), to calculate the Δn from the phase difference / cell gap, the sum of the Δn and n _o was ne. n (corresponding to △ n ¹ the refractive index in the direction) _e = 1.64, (corresponding to △ n ² the refractive index in the direction) n _o = 1.52, was. Therefore, Δn ¹ = 1.64−1.54 = 0.10 and Δn ² = 1.52−1.52 = 0.00 were calculated. From the above, it was confirmed that desired anisotropic scattering was expressed.

(Protective film)
75 parts by weight of an alternating copolymer composed of isobutene and N-methylmaleimide (N-methylmaleimide content: 50 mol%) and 25 parts by weight of acrylonitrile-styrene copolymer having an acrylonitrile content of 28% by weight are chlorinated. This was dissolved in methylene to obtain a solution having a solid concentration of 15% by weight. This solution was spread on a glass plate, cast on a polyethylene terephthalate film, allowed to stand at room temperature for 60 minutes, and then peeled off from the film. After drying at 100 ° C. for 10 minutes, it was dried at 140 ° C. for 10 minutes and further at 160 ° C. for 30 minutes to obtain a protective film having a thickness of 100 μm. The in-plane retardation Re of the protective film was 4 nm, and the thickness direction retardation Rth was 4 nm.

(Polarizer)
The said protective film was laminated | stacked on both surfaces of the said polarizer using the polyurethane-type adhesive agent, and the polarizing plate was produced.

Example 2
In Example 1, a norbornene-based film having a thickness of 80 μm (manufactured by JSR, Arton: in-plane retardation Re is 4 nm, thickness direction retardation Rth is 20 nm) was used as the protective film in the same manner as in Example 1. Thus, a polarizing plate was obtained.

Example 3
In Example 1, a 40 μm-thick norbornene film (manufactured by Nippon Zeon Co., Ltd., ZEONOR: in-plane retardation Re is 0.3 nm, thickness direction retardation Rth is 7.8 nm) is used as the protective film. A polarizing plate was obtained in the same manner as in Example 1.

Example 4
(Protective film)
100 parts by weight of a cyclic olefin resin (Ticona, TOPAS 6013) and 5 parts by weight of an ultraviolet absorber (Asahi Denka Co., LA31) are mixed, dried for 5 hours, and then supplied to an extruder set at 270 ° C. for melting. After kneading, the film was extruded from a T die and taken up with a cooling roll to obtain a protective film having a thickness of 40 μm. The protective film obtained above was subjected to corona treatment. Further, a mixture obtained by mixing and stirring 67 parts by weight of isopropyl alcohol with respect to 100 parts by weight of silanol (manufactured by Nihon Unicar, APZ6601) was applied to the corona-treated surface, and then dried at 120 ° C. for 2 minutes to form a resin layer. . The thickness of the resin layer was 30 nm.

  In Example 1, a polarizing plate was prepared in the same manner as in Example 1 except that the protective film on which the resin layer was formed (in-plane retardation Re was 0.8 nm and thickness direction retardation Rth was 1.3 nm) was used. Obtained. The protective film on which the resin layer was formed was such that the resin layer was on the polarizer side.

Example 5
(Protective film)
5 ml of cyclopentanone was applied on a polyethylene terephthalate film (thickness 75 μm, length 10 cm × width 20 cm) by a bar coating method. A triacetyl cellulose film (Fuji Photo Film, UZ-TAC; thickness 40 μm, length 10 cm × width 20 cm) was laminated on the surface coated with cyclopentanone. The laminate was dried at 100 ° C. for 5 minutes, and then the polyethylene terephthalate film was peeled from the laminate to obtain a protective film made of a cellulose resin film alone.

  A polarizing plate was obtained in the same manner as in Example 1 except that the protective film (in-plane retardation Re was 0.5 nm and thickness direction retardation Rth was 5.1 nm) was used.

Comparative Example 1
In Example 1, a polarizing plate was prepared in the same manner as in Example 1 except that a 80 μm thick triacetylcellulose film (in-plane retardation Re was 2 nm and thickness direction retardation Rth was 40 nm) was used as the protective film. Obtained.

Comparative Example 2
In Example 1, a polarizing film was formed in the same manner as in Example 1 except that a biaxially stretched polycarbonate film (in-plane retardation Re was 10 nm, thickness direction retardation Rth was 120 nm) having a thickness of 80 μm was used as the protective film. I got a plate.

Comparative Example 3
In Example 1, a polarizer was produced in the same manner as in Example 1 except that the liquid crystalline monomer was not used. Moreover, the polarizing plate was produced like the comparative example 1 using the said polarizer.

Comparative Example 4
In Example 1, a polarizer was produced in the same manner as in Example 1 except that the liquid crystalline monomer was not used. Further, using the polarizer, a polarizing plate was produced in the same manner as in Example 1.

(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 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.

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.

Further, with respect to the polarizers obtained in Example 1 and Comparative Example 3, the maximum transmittance (k ₁ ) obtained by measuring the polarization absorption spectrum with a spectrophotometer equipped with a Glan-Thompson prism (manufactured by Hitachi, Ltd., U4100). ): Parallel transmittance and transmittance of linearly polarized light in the orthogonal direction (k ₂ ): The orthogonal transmittance is shown in FIG.

Regarding the parallel transmittance (k ₁ ), the polarizers of Example 1 and Comparative Example 3 are substantially equal in the entire visible range, whereas the polarizer of Example 1 has an orthogonal transmittance (k ₂₎ due to the absorption + scattering axis. ) Is significantly smaller than the polarizer of Comparative Example 3 on the short wavelength side. That is, on the short wavelength side, it shows that the polarization performance of the polarizer of Example 1 exceeded the polarizer of Comparative Example 3. In Example 1 and Comparative Example 3, all the conditions such as stretching and dyeing are the same, so the degree of orientation of the iodine-based absorber is also considered to be equal. Therefore, the orthogonal transmittance (k ₂ ) of the polarizer of Example 1 indicates that the polarization performance is improved by the effect of adding the anisotropic scattering effect to the absorption by iodine as described above.

  For the haze value, the haze value for linearly polarized light in the maximum transmittance direction and the haze value for linearly polarized light in the absorption direction (the orthogonal direction thereof) were measured. The haze value is measured according to JIS K 7136 (Plastic—How to determine haze of transparent material) using a haze meter (HM-150 manufactured by Murakami Color Research Laboratory) and a commercially available polarizing plate (NPF manufactured by Nitto Denko Corporation). -SEG1224DU: single transmittance of 43%, polarization degree of 99.96%) placed on the incident surface side of the measurement light of the sample and measured with the commercially available polarizing plate and the sample (polarizing plate) extending in the orthogonal direction The haze value of However, with a commercially available light source of a Heizometer, the amount of light when orthogonal is less than the sensitivity limit of the detector, so the light of a separately provided high-intensity halogen lamp is incident using an optical fiber, and within the detection sensitivity After that, the shutter was manually opened and closed, and the haze value was calculated.

For the evaluation of unevenness, a sample (polarizing plate) is placed on the upper surface of a backlight used in a liquid crystal display in a dark room, and the polarizing axis is orthogonal with a commercially available polarizing plate (NPF-SEG1224DU manufactured by Nitto Denko Corporation) as an analyzer. The levels were visually confirmed according to the following criteria. The unevenness was evaluated for unevenness in stretching of the polarizer and interference due to retardation.
X: Level at which unevenness can be confirmed visually.
○: Level at which unevenness cannot be confirmed visually.

上記表１に示す通り、実施例と比較例の偏光板では、略単体透過率、偏光度等の偏光特性は良好である。しかし、実施例１、２と比較例１、２の偏光板では、ヨウ素系吸光体を含有する透光性の水溶性樹脂により形成されるマトリクス中に、微小領域が分散された構造の偏光子を用いているため、通常の偏光子を用いている比較例３の偏光板よりも、直交時の透過率のヘイズ値が高くバラツキによるムラが、散乱によって隠蔽され確認できなくなっていることが分かる。また、実施例１、２では、本願発明の構成により、従来の偏光子の延伸ムラが偏光散乱により感知されなくなっていることが比較例３、４との対比から明らかである。また位相差値の小さい保護フィルムを用いているため、比較例１、２、３に比べても干渉ムラが小さく抑えられていることが分かる。

As shown in Table 1 above, the polarizing plates of Examples and Comparative Examples have good polarization characteristics such as substantially single transmittance and degree of polarization. However, in the polarizing plates of Examples 1 and 2 and Comparative Examples 1 and 2, a polarizer having a structure in which minute regions are dispersed in a matrix formed of a translucent water-soluble resin containing an iodine-based absorber. Therefore, it can be seen that the haze value of the transmittance at the time of orthogonality is higher than that of the polarizing plate of Comparative Example 3 using a normal polarizer, and unevenness due to dispersion is hidden by scattering and cannot be confirmed. . Further, in Examples 1 and 2, it is clear from the comparison with Comparative Examples 3 and 4 that due to the configuration of the present invention, the stretching unevenness of the conventional polarizer is not detected by the polarization scattering. Moreover, since the protective film with a small phase difference value is used, it can be seen that the interference unevenness is suppressed to be smaller than those of Comparative Examples 1, 2, and 3.

  As a polarizer similar to the structure of the polarizer of the present invention, JP-A No. 2002-207118 discloses a resin matrix in which a mixed phase of a liquid crystalline birefringent material and an absorbing dichroic material is dispersed. Has been. The effect is the same as that of the present invention. However, as compared with the case where the absorbing dichroic material is present in the dispersed phase as in JP-A-2002-207118, the one where the absorbing dichroic material is present in the matrix layer as in the present invention, Although the scattered polarized light passes through the absorption layer, the optical path length becomes long, so that more scattered light can be absorbed. Therefore, the effect of improving the polarization performance is much higher in the present invention. Also, the manufacturing process is simple.

  In addition, JP 2000-506990 A discloses an optical body in which a dichroic dye is added to either a continuous phase or a dispersed phase, but the present invention uses iodine instead of a dichroic dye. There is a big feature in that. The use of iodine instead of a dichroic dye has the following advantages. (1) The absorption dichroism expressed by iodine is higher than that of the dichroic dye. Therefore, the polarization property of the obtained polarizer is higher when iodine is used. (2) Iodine does not show absorption dichroism before being added to the continuous phase (matrix phase), and after being dispersed in the matrix, it is stretched to form an iodine-based absorber that exhibits dichroism. Is done. This point is different from a dichroic dye having dichroism before being added to the continuous phase. That is, when iodine is dispersed into the matrix, it remains iodine. In this case, the diffusibility to the matrix is generally much better than that of the dichroic dye. As a result, iodine-based absorbers are dispersed throughout the film rather than the dichroic dye. Therefore, the effect of increasing the optical path length due to scattering anisotropy can be utilized to the maximum, and the polarization function is increased.

  In addition, it is stated in the background of the invention described in Japanese Translation of PCT International Publication No. 2000-506990 that optical properties of a stretched film in which liquid crystal droplets are arranged in a polymer matrix are described by Aphonin. However, Aphonin et al. Mentioned an optical film composed of a matrix phase and a dispersed phase (liquid crystal component) without using a dichroic dye, and the liquid crystal component is not a polymer of a liquid crystal polymer or a liquid crystal monomer. The birefringence of the liquid crystal component in the film is typically temperature dependent and sensitive. On the other hand, the present invention provides a polarizer comprising a film having a structure in which minute regions are dispersed in a matrix formed of a translucent water-soluble resin containing an iodine-based absorber. The liquid crystalline material of the invention is a liquid crystal polymer that is aligned in the liquid crystal temperature range, then cooled to room temperature and fixed in alignment. In other words, the birefringence of a minute region formed of a liquid crystal material does not change with temperature.

(Durability evaluation)
The following evaluation was performed about the polarizing plate. The results are shown in Table 2.

<Water permeability of protective film>
In accordance with JISZ0208, 40 ° C./90% R.D. It was measured under the test condition of H (RH: relative humidity).

<Moisture resistance test>
A polarizing plate cut to a size of 25 mm × 50 mm was attached to a slide glass with an acrylic pressure-sensitive adhesive, and after measuring optical properties (initial optical properties), 60 ° C./95% R.D. The following optical properties (optical properties after the test) after being put in the dryer of H and put in the dryer under the above conditions for 1000 hours were measured, and the following changes were determined. The results are shown in Table 2.

  Change in transmittance: Visibility was corrected in accordance with JISZ-8701, and the light transmittance (hereinafter simply referred to as transmittance) was obtained. Transmittance change amount = transmittance after test−initial transmittance.

Polarization degree change amount: The degree of polarization was determined by the following equation. However, H0: parallel transmittance, H90: orthogonal transmittance. Polarization degree = √ ((H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ )) × 100 (%).
Polarization degree change amount = post-test polarization degree-initial polarization degree Hue change amount: Hue a and hue b were subjected to visibility correction according to JISZ-8701 to obtain hue a and hue b. Hue a change amount = hue after test-initial hue a, hue b change amount = hue after test b-initial hue b.

表２に示す通り、実施例では、比較例に比べて耐湿性試験後の光学特性変化量が小さく、耐久性が良好であることが分かる。

As shown in Table 2, it can be seen that in the examples, the amount of change in optical characteristics after the moisture resistance test is small compared to the comparative example, and the durability is good.

It is a conceptual diagram which shows an example of the polarizer of this invention. 6 is a graph showing polarization absorption spectra of polarizers of Example 1 and Comparative Example 3.

Explanation of symbols

1 Translucent water-soluble resin 2 Iodine absorber 3 Micro area

Claims (13)

In a polarizing plate in which a protective film is laminated on one side or both sides of a polarizer,
The polarizer consists of a film having a structure in which minute regions are dispersed in a matrix formed of a light-transmitting water-soluble resin containing an iodine-based absorber.
In the protective film, the direction in which the in-plane refractive index in the film plane is the maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the film is the Z axis. When nx, ny, nz, and film thickness d (nm),
In-plane retardation Re = (nx−ny) × d is 20 nm or less,
A thickness direction retardation Rth = {(nx + ny) / 2−nz) × d) is 30 nm or less.   2. The polarizing plate according to claim 1, wherein the minute region of the polarizer is formed of an oriented birefringent material.   The polarizing plate according to claim 2, wherein the birefringent material exhibits liquid crystallinity at least at the time of the alignment treatment.   The polarizing plate according to claim 2 or 3, wherein the birefringence of the minute region of the polarizer is 0.02 or more. The refractive index difference for each optical axis direction between the birefringent material that forms the microscopic region of the polarizer and the translucent water-soluble resin 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 two axial directions orthogonal to the Δn ¹ direction is 50% or less of the Δn ^1. 5. Polarizer. The polarizing plate according to claim ¹ , wherein an absorption axis of the iodine-based light absorber in the polarizer is oriented in the Δn ¹ direction.   The polarizing plate according to claim 1, wherein the film used as the polarizer is manufactured by stretching. The polarizing plate according to claim 1, wherein the minute region of the polarizer has a length in the Δn ² direction of 0.05 to 500 μm.   The polarizing plate according to claim 1, wherein the iodine-based absorber in the polarizer has an absorption region in a wavelength band of at least 400 to 700 nm.   The protective film contains (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain and (B) a thermoplastic resin having a substituted and / or unsubstituted phenyl group and a nitrile group in the side chain. The polarizing plate according to claim 1, comprising at least one selected from the group consisting of a resin composition and a norbornene-based resin.   The transmittance for linearly polarized light in the transmission direction is 80% or more, the haze value is 5% or less, and the haze value for linearly polarized light in the absorption direction is 30% or more. The polarizing plate as described in.   An optical film, wherein at least one polarizing plate according to claim 1 is laminated.   An image display device comprising the polarizing plate according to claim 1 or the optical film according to claim 12.

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