KR20190090027A - Liquid crystal display device, polarizing plate, and polarizer protective film - Google Patents

Abstract

A liquid crystal display device using a polarizer protective film made of a polyester film and having good visibility is provided.
A liquid crystal display having a liquid crystal cell disposed between a backlight light source and two polarizing plates, wherein the backlight light source is a white light source having a continuous emission spectrum, and the polarizing plate has a structure in which polarizer protective films are laminated on both sides of the polarizer At least one of the polarizer protective films has a retardation of 3,000 to 30,000 nm and has a center plane average roughness (SRa) of the outermost layer surface of 0.008 to 0.02 탆 and a ten-point average roughness (SRz) of 0.3 to 1.5 탆. Wherein the liquid crystal display device is an ester film.

Description

[0001] The present invention relates to a liquid crystal display device, a polarizing plate, and a polarizer protective film,

The present invention relates to a liquid crystal display, a polarizing plate and a polarizer protective film. To a liquid crystal display device, a polarizing plate and a polarizer protective film which are excellent in visibility and suitable for thinning.

A polarizing plate used in a liquid crystal display (LCD) is constituted by sandwiching a polarizer obtained by dyeing iodine to polyvinyl alcohol (PVA) or the like between two polarizer protective films. As the polarizer protective film, triacetyl Cellulose (TAC) films have been used. In recent years, along with the thinning of LCDs, a thin polarizing plate has been required. However, if the thickness of the TAC film used as the protective film is reduced, sufficient mechanical strength can not be obtained, the moisture permeability increases, and the polarizer tends to deteriorate. In addition, TAC films are very expensive, and inexpensive alternative materials are strongly demanded.

In order to make the polarizing plate thinner, it has been proposed to use a polyester film instead of the TAC film so as to maintain high durability even when the polarizer protective film is thin (Patent Documents 1 to 3).

Japanese Patent Application Laid-Open No. 2002-116320 Japanese Patent Application Laid-Open No. 2004-219620 Japanese Patent Application Laid-Open No. 2004-205773

The polyester film has excellent durability as compared with the TAC film but has birefringence unlike the TAC film. Therefore, when the polyester film is used as a polarizer protective film, the image quality is deteriorated due to optical distortion. That is, since the polyester film having birefringence has a predetermined optical anisotropy (retardation), when used as a polarizer protective film, irregular color unevenness occurs when observed in an oblique direction, and image quality is deteriorated. Therefore, Patent Literatures 1 to 3 have adopted countermeasures for reducing retardation by using copolymerized polyester as a polyester. However, even in such a case, the irregular color irregularity could not be completely eliminated.

An object of the present invention is to provide a liquid crystal display device that can respond to the thinness of a liquid crystal display device and does not cause deterioration of visibility due to irregular color unevenness, And to provide a small polarizer protective film.

The inventors of the present invention have made intensive studies on the mechanism of occurrence of irregular color unevenness which occurs when a polyester film is used as a polarizer protective film. As a result, it was found that the iridescence-like color unevenness was caused by the retardation of the polyester film and the emission spectrum of the backlight light source. As a backlight source of the conventional liquid crystal display device, a fluorescent tube such as a cold cathode tube or a hot cathode tube is used. The spectral distribution of a fluorescent lamp such as a cold cathode tube or a hot cathode tube shows a luminescence spectrum having a plurality of peaks, and these discontinuous luminescence spectra are combined to obtain a white light source. When light passes through a film having a high retardation, it exhibits a different transmitted light intensity depending on the wavelength. Therefore, if the backlight light source is a discontinuous luminescence spectrum, only a specific wavelength is strongly transmitted, and it is thought that iridescence-like color unevenness occurs.

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that the above problem can be solved by using a specific backlight light source and a polyester film having a specific retardation in combination. Further, it has been found that it is effective to give a specific surface form in order to secure high transparency while suppressing optical defects of the polyester film.

That is, the present invention is as follows.

(1) A liquid crystal display having a liquid crystal cell disposed between a backlight source and two polarizers, wherein the backlight source is a white light source having a continuous emission spectrum, wherein the polarizer comprises a polarizer protective film Wherein at least one of the polarizer protective films has a retardation of 3,000 to 30,000 nm and the center plane average roughness (SRa) of the outermost layer surface is 0.008 to 0.02 탆 and the ten-point average roughness (SRz) is 0.3 to 1.5 탆 Which is a polyester film.

(2) The polarizing plate of the polarizing plate disposed on the side of the outgoing light with respect to the liquid crystal cell has a retardation of 3,000 to 30,000 nm, a center plane average roughness (SRa) of the outermost layer surface is 0.008 to 0.02 탆, And a ten-point average roughness (SRz) of 0.3 to 1.5 占 퐉.

(3) The liquid crystal display according to the above (1), wherein the ratio (Re / Rth) of the retardation of the polyester film to the thickness direction retardation is 0.2 or more.

(4) A polarizing plate in which a polarizer protective film is laminated on both sides of a polarizer, at least one polarizer protective film on one side has a retardation of 3,000 to 30,000 nm, a center plane average roughness (SRa) of the outermost layer surface is 0.008 to 0.02 탆 , And a ten-point average roughness (SRz) of 0.3 to 1.5 占 퐉 is a white light source having a continuous emission spectrum as a backlight light source.

(5) A continuous polyester film having a retardation of 3,000 to 30,000 nm and a center plane average roughness (SRa) of the outermost layer surface of 0.008 to 0.02 탆 and a ten-point average roughness (SRz) of 0.3 to 1.5 탆 A polarizer protective film for a liquid crystal display device comprising a white light source having an emission spectrum as a backlight source.

(6) The polarizer protective film according to any one of (1) to (6), wherein the ratio (Re / Rth) of the retardation of the polyester film to the retardation in the thickness direction is 0.2 or more.

(7) The polarizer protective film described above wherein the polyester film has an easy adhesion layer.

(8) The polarizer protective film as described in any one of (1) to (3), wherein the polyester film comprises at least three layers, and the outermost layer contains inactive particles having an average particle size of 1.0 to 3.5 탆 and the outermost layer has an average particle size of the inactive particles.

(9) The polarizer protective film according to any one of (1) to (9), wherein the content of the inert particles in the outermost layer of the polyester film is 0.005 to 0.05% by mass and the haze of the polyester film is 3% or less.

(10) The polarizer protective film as described in any one of (1) to (3), wherein the ultraviolet absorber is contained in a layer other than the outermost layer of the polyester film and the light transmittance at 380 nm is 20% or less.

In the liquid crystal display device, the polarizing plate and the polarizer protective film of the present invention, it is possible to obtain a spectrum in which the spectrum of the transmitted light is close to the light source at any viewing angle, and good visibility without irregular color unevenness can be ensured. Further, since the polarizer protective film of the present invention has a specific surface roughness, the polarizer protective film is excellent in handling property and is less prone to scratches due to friction or the like. Therefore, the polarizer protective film of the present invention has high transparency and very few optical defects such as scratches.

In general, the liquid crystal panel has a rear module, a liquid crystal cell, and a front module in order from the backlight source side toward the side (the viewer side or the emission side) on which an image is displayed. The rear module and the front module are generally composed of a transparent substrate, a transparent conductive film formed on the liquid crystal cell side surface thereof, and a polarizing plate disposed on the opposite side thereof. Here, the polarizing plate is disposed on the backlight source side in the rear module and on the side (visible side or emission side) on which the image is displayed in the front module.

The liquid crystal display device of the present invention comprises at least a liquid crystal cell arranged between a backlight light source and two polarizing plates as constituent members. Other configurations other than the above may be used, such as a color filter, a lens film, a diffusion sheet, an anti-reflection film, and the like.

The configuration of the backlight light source may be an edge light method using a light guide plate or a reflective plate as a constituent member or a direct light type method, but it is preferable to use a white light source having a continuous and broad emission spectrum. Here, the continuous and broad emission spectrum means an emission spectrum in which there is no wavelength at which the intensity of light is zero in a wavelength region of at least 450 nm to 650 nm, preferably visible light. A white light source having such a continuous and broad emission spectrum includes, for example, a white light emitting diode (white LED). White LEDs include a device emitting a white light by combining a phosphor type, that is, a blue light using a compound semiconductor, or a light emitting diode emitting ultraviolet light and a phosphor, and an organic light emitting diode (OLED). Among white LEDs, white light emitting diodes comprising a blue light emitting diode using compound semiconductors and a light emitting device using a combination of yttrium, aluminum and garnet yellow phosphors are continuous and have a wide emission spectrum and excellent luminous efficiency. And is suitable as a backlight light source. It is also effective in energy saving by using a light source such as a white LED which consumes less power.

Conventionally, fluorescent tubes such as cold cathode tubes and hot cathode tubes widely used as a backlight source have a discrete luminescence spectrum in which the luminescence spectrum has a peak at a specific wavelength, so that it is difficult to obtain the effect of the present invention as described above.

In the present invention, at least one polarizer protective film constituting a polarizing plate is used as a polarizing plate in which both sides of a polarizer in which iodine is dyed to PVA or the like is sandwiched between two polarizer protective films. Is used.

The mechanism by which the occurrence of rainbow-shaped color unevenness is suppressed by the above-described aspect is considered as follows. When a polyester film having birefringence is disposed on one side of the polarizer, the linearly polarized light emitted from the polarizer is disturbed when passing through the polyester film. The transmitted light exhibits interference color peculiar to retardation, which is a product of the birefringence and the thickness of the polyester film. Therefore, when a discontinuous luminescence spectrum such as a cold cathode tube or a thermal cathode tube is used as a light source, a different transmitted light intensity is exhibited depending on the wavelength, and irregular color unevenness occurs (see, for example, 15th Micro Optics Conference, ).

On the other hand, the white light emitting diode usually has a continuous and broad emission spectrum in a wavelength region of at least 450 nm to 650 nm, preferably in a visible light region. Since the interference color spectrum due to the transmitted light transmitted through the birefringent body becomes an envelope shape, it is possible to obtain a spectrum similar to the emission spectrum of the light source by controlling the retardation of the polyester film. In this manner, it is considered that the irregular color unevenness does not occur and the visibility is remarkably improved by making the envelope shape of the interference color spectrum by the transmitted light transmitted through the light source and the birefringent element a similar shape.

From the above principle, in the present invention, by using a white light emitting diode having a broad emission spectrum as a light source, the envelope shape of the spectrum of the transmitted light is approximated to the light emission spectrum of the light source by a relatively simple constitution and consequently suppresses rainbow stains on the liquid crystal display Is expected to become possible.

(Polyester film)

The polyester film used for the polarizer protective film is preferably an oriented polyester film having a retardation of 3,000 to 30,000 nm. When the retardation is less than 3,000 nm, when used as a polarizer protective film, a strong interference color is exhibited when observed in the oblique direction, so that the envelope shape is different from the light emission spectrum of the light source and good visibility can not be ensured. The lower limit of the preferable retardation is 4,500 nm or more, more preferably 6,000 nm or more, still more preferably 8,000 nm or more, even more preferably 10,000 nm or more.

On the other hand, the upper limit of the retardation is 30,000 nm. Even when a polyester film having a retardation higher than that is used, the effect of further improving the visibility is not substantially obtained, and the thickness of the film is considerably increased, and the handleability as an industrial material is lowered.

Retardation of the polyester film can be obtained by measuring the refractive index and thickness in the biaxial direction, or can be obtained by using a commercially available automatic birefringence measuring device such as KOBRA-21ADH (Oji Measurement Instruments Co., Ltd.). In the present specification, retardation means retardation in a plane.

In the present invention, at least one of the polarizer protective films is a polarizer protective film having the specific retardation. The arrangement of the polarizer protective film having the specific retardation is not particularly limited. The polarizer protective film on the incident light side of the polarizing plate disposed on the incident light side of the liquid crystal display device or the polarizer protective film on the exit light side of the polarizing plate disposed on the emergent light side It is preferable that the protective film is a polarizer protective film made of a polyester film having the specific retardation. Particularly preferred is a mode in which the polarizer protective film on the exit light side of the polarizing plate disposed on the exit light side is a polyester film having the specific retardation. When the polyester film is disposed at a position other than the above position, the polarization characteristics of the liquid crystal cell may be changed.

The polarizing plate of the present invention has a structure in which both sides of a polarizer in which iodine is dyed in polyvinyl alcohol (PVA) or the like are sandwiched between two polarizer protective films, and one of the polarizer protective films is a polarizer protective film . It is preferable to use a birefringence-free film typified by a TAC film, an acrylic film or a norbornene-based film as the other polarizer protective film.

The polarizing plate used in the present invention preferably has various functional layers on its surface for the purpose of prevention of non-exposure, suppression of glare, and prevention of scratches. The functional layer is not particularly limited and may be, for example, a hard coat layer, an antiglare layer AG, an antireflection layer AR, a low reflection layer LR, a low reflection antiglare layer AG / LR, / AR). The functional layer is preferably provided on the surface of the polyester film opposite to the side in contact with the polarizer. Only one of these layers may be provided on the polyester film, or two or more of these layers may be laminated according to need. By forming these layers, it is possible to expect an effect of further reducing rainbow shape color unevenness.

When the various functional layers are provided, it is preferable to previously provide this adhesive layer on the surface of the oriented polyester film. It is preferable to adjust the refractive index of the adhesive layer so as to be close to the rising average of the refractive index of the functional layer and the refractive index of the polyester film from the viewpoint of suppressing the interference by the reflected light. The adjustment of the refractive index of the adhesive layer can be carried out by a known method. For example, it can be easily adjusted by containing titanium, germanium or other metal species in a binder resin such as polyester or polyurethane.

The polyester film can be obtained by condensing a dicarboxylic acid with a diol. Examples of the dicarboxylic acid component that can be used in the production of the polyester film include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 1,4- Naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, diphenylcarboxylic acid, diphenoxyethane dicarboxylic acid, diphenylsulfonic acid, anthracene dicarboxylic acid, 1,3-cyclopentane Dicarboxylic acid, 1,3-cyclohexane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethyl malonic acid, But are not limited to, ethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, Carboxylic acid and the like.

Examples of the diol component usable in the production of the polyester film include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol Propane diol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis (4-hydroxyphenyl) propane, bis Sulfone, and the like.

The dicarboxylic acid component and the diol component constituting the polyester film may be used alone or in combination of two or more. Specific examples of the polyester resin constituting the polyester film include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and the like, and preferably polyethylene terephthalate and polyethylene naphthalate . These resins have excellent transparency and excellent thermal and mechanical properties, and can easily control retardation by stretching. In particular, polyethylene terephthalate is the most suitable material because it has a large intrinsic birefringence and a relatively large retardation even if the thickness of the film is small.

It is preferable that the polyester film of the present invention contains inactive particles in both outermost layers in a laminated structure of three or more layers by a coextrusion method. As a result, the concavo-convex shape can be imparted to the outermost layer surface, and the workability (activity) by the film processing becomes good. A / B, B / A / C / B, or B / A / B, the layer configuration in the film thickness direction is set to be B / A / C / A / B and the like can be conceived. Each of the layers of the A to C layers may have the same or different constitution of the polyester resin, but in order to suppress the generation of curl due to the bimetallic constitution, the polyester resin of each layer has the same constitution and / or B / A / B (Two-kind three-layer structure).

In the present invention, the polyester resin constituting the central layer (for example, the A layer in the case of the B / A / B configuration) other than the outermost layer may contain particles, but in order to obtain high transparency, The resin is preferably substantially free from particles. By containing the inert particles only in the outermost layer, more excellent transparency can be obtained. When particles are added to the center layer other than the outermost layer, it is preferably not more than 50 ppm, more preferably not more than 10 ppm.

Examples of the inert particles contained in the outermost layer include calcium carbonate, calcium phosphate, amorphous silica, spherical silica, crystalline glass filler, kaolin, talc, titanium dioxide, alumina, silica- alumina composite oxide particles, barium sulfate, calcium fluoride, Zeolite, molybdenum sulfide, and mica, crosslinked polystyrene particles, crosslinked acrylic resin particles, crosslinked methyl methacrylate particles, benzoguanamine-formaldehyde condensation particles, melamine formaldehyde condensate particles, polytetrafluoro And heat-resistant polymer fine particles such as ethylene particles. Among them, silica is most suitable because it has a refractive index relatively close to that of polyester and thus can secure a film having excellent transparency.

The average particle diameter of the inert particles contained in the outermost layer of the film of the present invention is preferably 1.0 to 3.5 占 퐉, more preferably 1.5 to 3.0 占 퐉, still more preferably 2.1 to 2.5 占 퐉. If the average particle diameter of the inert particles is less than 1.0 占 퐉, the cohesive force of the particles is so great that coarse abnormal particles due to agglomeration of the particles are liable to be generated. In this case, aggregated particles are a factor, and optical defects that can be visually recognized on the surface of the film may occur.

On the other hand, when the average particle diameter exceeds 3.5 μm, the content of coarse particles as a single particle increases, which is not preferable. In this case, coarse particles are a factor and optical defects may occur on the surface of the film. It is preferable to use such a specific range of particles in order to reduce the coarse particles that cause optical defects to the limit.

Here, the range of the average particle size of the inert particles is measured by a measuring method described later. For example, in the case of secondary particles in which primary particles are aggregated as described later, the average particle diameter of the secondary particles is referred to. That is, the average particle size of the inert particles herein is an average particle size in the sun which can be present as a mass actually as inert particles in the film.

The content of the inert particles in the outermost layer is preferably 0.005 to 0.05 mass%, more preferably 0.010 to 0.04 mass%, and still more preferably 0.015 to 0.03 mass%. When the content of the inert particles is 0.005 mass% or more, it is preferable to exhibit effective activity (slipperiness) to such an extent as to reduce minute scratches. When the content of the inert particles is 0.05 mass% or less, it is preferable to maintain high transparency.

The upper limit of the thickness of the outermost layer is not particularly limited, but if the thickness is excessively increased, the amount of the inert particles in the film becomes excessively large, and scattering of light generated in the film increases, thereby decreasing the transparency. If the thickness of the outermost layer is much smaller than that of the inert particles, there may be optical flaws that can be visually recognized on the surface of the film due to powder falling off of the particles. Therefore, the thickness of the outermost layer is preferably at least equal to the average particle size of the inert particles, more preferably at least 2 times, and particularly preferably at least 5 times. The surface protrusions are formed by inert particles present in the outermost layer. In order to form gentle surface protrusions, it is preferable that inert particles are not located directly under the surface but particles having a certain size or more are present at an appropriate depth of the film. If the thickness of the outermost layer is at least equal to the average particle size of the inert particles, more preferably at least 2 times, and more preferably at least 5 times, the shape of the surface protrusions due to the inert particles becomes comparatively gentle, Loses. Here, the thickness of the outermost layer refers to the thickness of one side of the outermost layer laminated on both sides of the film.

As described above, by controlling the thickness of the inert particles and the inert particle-containing layer, it is possible to appropriately control the projection shape of the film surface, thereby making it possible to more appropriately reduce optical defects while suppressing the deterioration of transparency to the maximum.

Further, in order to more suitably form the specific surface shape, for example, there are (1) a method of making the surface shape gentle by increasing the intrinsic viscosity of the polyester resin, (2) A gentle method or the like may be combined. In addition, as described later, it is also preferable to use inert particles which are likely to undergo further deformation by stretching the film (3).

As the inert particles which tend to undergo subsequent deformation by stretching the film, it is preferable that the secondary particles have agglomerated primary particles of several nm to several hundreds of nm and have a pore volume of 1.5 ml / g or more. Particularly, from the viewpoints of transparency, handleability and cost, amorphous lumpy silica is suitable. When the pore volume of the inert particles is 1.5 ml / g or more, deformation of the particles by stretching tends to occur, and the projection deformation can be easily controlled. Further, the pore volume of the inert particles can be calculated by the known nitrogen desorption, such as the BJH method. When the inert particles are present in the film, they can be dissolved by, for example, a phenol / tetrachloroethane mixed solution, and the inert particles as a residue can be recovered and sufficiently dried and then can be calculated by known nitrogen desorption, such as the BJH method.

As a method of blending the inert particles with the polyester, a known method may be employed. For example, it may be added at any stage of producing the polyester. Preferably, it is added as a slurry dispersed in ethylene glycol or the like in the step of esterification or after the transesterification reaction and before the start of the polycondensation reaction, The reaction may proceed. A method of blending a polyester raw material with a slurry of a particle dispersed in ethylene glycol or water using a vented kneading extruder, a method of blending the polyester raw material with particles dried by using a kneading extruder, and the like.

Among them, in the present invention, there is a method in which aggregated inorganic particles are homogeneously dispersed in a monomer solution which is a part of a polyester raw material and then filtered and added to the remainder of the polyester raw material before the esterification reaction, during the esterification reaction or after the esterification reaction desirable. According to this method, since the monomer liquid has a low viscosity, it is possible to easily perform homogeneous dispersion of the particles or fixation of the slurry, and at the same time, when added to the remainder of the raw material, the dispersibility of the particles is good and new aggregates are hardly generated.

Particularly, in the case of using the amorphous bulk silica, the particles may aggregate due to the addition and mixing of the slurry, resulting in coagulated coarse particles. When the ethylene glycol solution containing the amorphous bulk silica is added in order to reduce cohesive coarse particles which are factors of optical defects because aggregation of silica is likely to occur at high temperatures, an esterification reaction or an ester exchange reaction is carried out to obtain an oligomer It is preferable to blend with the polyester raw material while maintaining the temperature in the range of preferably 10 to 50 캜, more preferably 10 to 30 캜. By adding the slurry at this timing, it is possible to add the slurry while maintaining the slurry temperature at a low temperature, and generation of new agglomerates can be suppressed.

In general, the particle diameter of the inert particles shows a distribution having a certain width. The inert particles used in the present invention preferably have an inert particle having a particle diameter of 10 m or more, preferably 1% or less of the total. When the amount of the inert particles having a particle diameter of 10 탆 or more exceeds 1%, the number of coarse particles that cause optical defects may increase. Examples of the method of setting the distribution of the inert particles within the above range include (1) a method of microfiltration of ethylene glycol or polyester in which inert particles are dispersed, (2) a method in which ethylene glycol or polyester in which inert particles are dispersed is placed in a batch or intermittent manner (3) a method of selecting inert particles having a predetermined particle size distribution, or the like can be used.

The three-dimensional center plane average roughness (SRa) of the film of the present invention is preferably 0.008 to 0.02 탆, more preferably 0.009 to 0.015 탆. The ten-point average roughness (SRz) is preferably 0.3 to 1.5 占 퐉, more preferably 0.5 to 1.0 占 퐉. When the three-dimensional center face average roughness (SRa) or the ten-point mean roughness (SRz) is within the above range, it is preferable that transparency can be maintained while effectively preventing minute scratches.

The haze of the film of the present invention is preferably 3% or less. More preferably not more than 2.5%, and still more preferably not more than 2%. If the haze exceeds 3%, the screen brightness of the liquid crystal display device may be lowered, which is not preferable.

In order to suppress deterioration of an optically functional dye such as iodine dye, the film of the present invention preferably has a light transmittance of 380 nm or less at 20% or less. The light transmittance at 380 nm is more preferably 15% or less, further preferably 10% or less, particularly preferably 5% or less. When the light transmittance is 20% or less, deterioration due to ultraviolet rays of the optically functional dye can be suppressed. The transmittance in the present invention is measured by a method perpendicular to the plane of the film and can be measured using a spectrophotometer (for example, Hitachi U-3500 type).

To make the transmittance of the film of the present invention 380 nm at a wavelength of 380 nm or less to 20% or less, it is preferable to add an ultraviolet absorber to the film, to apply the coating liquid containing the ultraviolet absorber to the film surface, And adjusting the thickness appropriately. The ultraviolet absorber used in the present invention is a known substance. Examples of the ultraviolet absorber include an organic ultraviolet absorber and an inorganic ultraviolet absorber. From the viewpoint of transparency, an organic ultraviolet absorber is preferable.

Examples of the organic ultraviolet absorber include benzotriazole-based, benzophenone-based, cyclic iminoester-based, and the like, and combinations thereof, but are not particularly limited as long as they are in the range of absorbance as defined by the present invention. From the viewpoint of durability, benzotriazole-based cyclic imino ester-based ones are particularly preferable. When two or more kinds of ultraviolet absorbers are used in combination, ultraviolet rays of respective wavelengths can be simultaneously absorbed, so that the ultraviolet absorption effect can be further improved. When an ultraviolet absorber is blended with a polyester film, it is preferable that the polyester film is composed of three or more layers and an ultraviolet absorber is blended in a layer (that is, an intermediate layer) other than the outermost layer.

Examples of the benzophenone-based ultraviolet absorber, benzotriazole-based ultraviolet absorber and acrylonitrile-based ultraviolet absorber include 2- [2'-hydroxy-5 '- (methacryloyloxymethyl) phenyl] -2H- Sol, 2- [2'-hydroxy-5'- (methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'- ) Phenyl] -2H-benzotriazole, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 2,4-di (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, Methyl-6- (tert-butyl) phenol, 2,2'-methylenebis (4- (1,1,3,3 -Tetramethylbutyl) -6- (2H-benzotriazole-2-yl) phenol, etc. The cyclic imino ester-based ultraviolet absorber includes, for example, 2,2 '- (1,4- ) Bis (4H-3,1-benzoxazinone-4-one), 2- Methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazin-4-one and 2-phenyl-3,1-benzoxazin- But are not limited to these.

It is also preferable to add various additives in addition to the ultraviolet absorber within the range not hindering the effect of the present invention. Examples of the additive include inorganic particles, heat resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light stabilizers, flame retardants, heat stabilizers, antioxidants, antigelling agents and surfactants. In order to exhibit high transparency, it is also preferable that the polyester film contains substantially no particles. The phrase " substantially not containing particles " means that, for example, in the case of inorganic particles, when the inorganic element is quantified by fluorescent X-ray analysis, the amount is 50 ppm or less, preferably 10 ppm or less, Means the content below the limit.

Further, the polyester film of the present invention may be subjected to a corona treatment, a coating treatment, a flame treatment, or the like in order to improve the adhesion to the polarizer.

In the present invention, it is preferable that at least one side of the film of the present invention has this adhesive layer containing at least one kind of polyester resin, polyurethane resin or polyacrylic resin as a main component in order to improve the adhesiveness to the polarizer. Here, the " main component " refers to a component that accounts for 50 mass% or more of the solid components constituting the adhesive layer. The coating liquid used for forming the adhesive layer is preferably an aqueous coating liquid containing at least one of a water-soluble or water-dispersible copolymer polyester resin, an acrylic resin and a polyurethane resin. Examples of such coating liquids include water-soluble organic solvents such as those disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, Japanese Patent No. 4150982, Or a water-dispersible copolymer polyester resin solution, an acrylic resin solution, and a polyurethane resin solution.

This adhesive layer can be obtained by applying the coating liquid on one side or both sides of an unstretched or longitudinally uniaxially stretched film, drying at 100 to 150 ° C, and further stretching in the transverse direction. The final application amount of the adhesive layer is preferably controlled to 0.05 to 0.20 g / m < 2 >. If the coating amount is less than 0.05 g / m < 2 >, the adhesion to the obtained polarizer may become insufficient. On the other hand, if the coating amount exceeds 0.20 g / m < 2 >, the blocking resistance may be lowered. When the adhesive layer is provided on both sides of the polyester film, the application amount of the adhesive layer on both sides may be the same or different and can be independently set within the above range.

Particles are preferably added to the adhesive layer in order to impart lubricity. The average particle size of the fine particles is preferably 2 m or less. If the average particle diameter of the particles exceeds 2 탆, the particles tend to fall off from the adhesive layer. The particles contained in the adhesive layer are the same as the above-mentioned fine particles.

As a method of applying the coating liquid, a known method can be used. Examples of the method include a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brush method, a spray coating method, an air knife coating method, a wire bar coating method and a pipe doctor method. .

The average particle diameter of the particles can be measured by the following method. The particles were photographed with a scanning electron microscope (SEM) to measure the maximum diameter (the distance between the two most distant points) of 300 to 500 particles at a magnification of 2 to 5 mm in size of one smallest particle, The average value is taken as the average particle diameter.

The most common method for producing a polyester film is a method in which a polyester resin is melted and extruded in a sheet form to stretch the molded non-oriented polyester in the longitudinal direction at a temperature equal to or higher than the glass transition temperature using the speed difference of the roll , And a method of stretching in the transverse direction by a tenter and performing heat treatment.

The polyester film of the present invention may be a uniaxially stretched film or a biaxially stretched film. However, when a biaxially stretched film is used as a polarizer protective film, iridescence-like color unevenness is not observed even when viewed from directly above the film surface, Attention is necessary because there is a case that the shape color unevenness is observed.

This phenomenon is attributable to the fact that the biaxially stretched film is made of a fracture ellipsoid having a different refractive index in the running direction, the width direction and the thickness direction, and has a retardation of zero according to the transmission direction of light in the film (the refractive index ellipsoid ) Direction. Therefore, when the liquid crystal display screen is observed in a specific direction of the oblique direction, a point where retardation becomes zero may be generated, and a rainbow-shaped color unevenness occurs concentrically around the point. When the angle from the position directly above the film surface (normal direction) to the position where the iridescence color unevenness is visible is denoted by?, The angle? Increases as the birefringence in the film surface increases, and irregular color unevenness becomes less visible. In the case of the biaxially stretched film, the angle? Tends to become smaller, so that the uniaxially stretched film is preferable because iridescence-like color unevenness becomes less visible.

However, in a complete uniaxial (uniaxial) film, the mechanical strength in the direction orthogonal to the alignment direction is significantly lowered, which is undesirable. It is preferable that the present invention has biaxiality (biaxial symmetry) within a range that does not cause substantially irregular color unevenness or a range of viewing angles required for a liquid crystal display screen within a range that does not cause irregular color unevenness.

As an index for judging the difficulty of visibility of this iridescent color unevenness, there is a method of evaluating a difference between retardation (in-plane retardation) and retardation in the thickness direction (Rth). This retardation in the thickness direction means an average of retardation obtained by multiplying two birefringences ΔNxz and ΔNyz in the film thickness direction cross section, respectively, by the film thickness d. The smaller the difference between the in-plane retardation and the thickness direction retardation is, the more the action of the birefringence depending on the viewing angle increases the isotropy, so that the change in retardation with the viewing angle decreases. Therefore, it is considered that iridescence-like color unevenness due to the observation angle is less likely to occur.

The ratio (Re / Rth) of retardation to thickness direction retardation of the polyester film of the present invention is preferably 0.2 or more, more preferably 0.5 or more, further preferably 0.6 or more. The larger the ratio of retardation to retardation in the thickness direction (Re / Rth) is, the more the action of birefringence increases the isotropy, and the irregular color unevenness depending on the observation angle is less likely to occur. In the case of a complete uniaxial (uniaxial) film, the ratio of the retardation to the thickness direction retardation (Re / Rth) is 2. However, as described above, the mechanical strength in the direction orthogonal to the alignment direction is remarkably lowered as the film approaches the complete uniaxial (uniaxial) film.

On the other hand, the ratio (Re / Rth) of retardation to thickness direction retardation of the polyester film of the present invention is preferably 1.2 or less, more preferably 1 or less. In order to completely suppress the occurrence of rainbow-shaped color unevenness depending on the observation angle, the ratio of the retardation to the retardation in the thickness direction (Re / Rth) does not need to be 2, and 1.2 or less is sufficient. Even if the above ratio is 1.0 or less, it is sufficiently possible to satisfy the viewing angle characteristics (about 180 degrees in the right and left direction, about 120 degrees in the vertical direction) required for the liquid crystal display device.

The film forming conditions of the present invention will be concretely described. The longitudinal stretching temperature and transverse stretching temperature are preferably 80 to 130 占 폚, and particularly preferably 90 to 120 占 폚. The longitudinal stretching magnification is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times. The transverse draw ratio is preferably 2.5 to 6.0 times, particularly preferably 3.0 to 5.5 times. In order to control the retardation within the above-mentioned range, it is preferable to control the ratio of the longitudinal drawing magnification and the lateral drawing magnification. If the difference between the longitudinal and transverse stretching ratios is too small, it is difficult to make a difference in retardation. Also, setting the stretching temperature to a lower value is a preferable countermeasure for increasing the retardation. In the subsequent heat treatment, the treatment temperature is preferably 100 to 250 占 폚, particularly preferably 180 to 245 占 폚.

In order to suppress the fluctuation of the retardation, it is preferable that the thickness variation of the film is small. Since the stretching temperature and stretching magnification have a great influence on the thickness variation of the film, it is necessary to optimize the film formation conditions from the viewpoint of the thickness deviation. In particular, when the longitudinal stretching magnification is lowered in order to differentiate the retardation, the value of the longitudinal thickness deviation may be increased. Since the value of the longitudinal thickness deviation is extremely high in a certain range of the draw ratio, it is preferable to set the film formation condition at a point outside this range.

The thickness variation of the film of the present invention is preferably 5.0% or less, more preferably 4.5% or less, even more preferably 4.0% or less, and particularly preferably 3.0% or less. The thickness variation of the film can be measured by any means. For example, a tape-shaped sample (length 3 m) continuous in the flow direction of the film is sampled, and an electric micrometer (manufactured by Seiko Instruments Inc.) (Dmax), the minimum value (dmin), and the average value (d) are obtained by measuring the thickness of 100 points at a pitch of 1 cm using a measuring device .

As described above, controlling the retardation of the film to a specific range can be performed by appropriately setting the stretching magnification, the stretching temperature, and the thickness of the film. For example, the higher the stretching magnification difference in longitudinal stretching and transverse stretching, the lower the stretching temperature, and the thicker the film, the easier it is to obtain a higher retardation. Conversely, the lower the stretching magnification difference between longitudinal stretching and transverse stretching, the higher the stretching temperature, and the thinner the film, the easier to obtain a lower retardation. Further, the higher the stretching temperature and the lower the total stretching ratio, the easier to obtain a film having a lower ratio of retardation to thickness direction retardation (Re / Rth). Conversely, the lower the stretching temperature and the higher the total stretching ratio, the easier to obtain a film having a higher ratio of retardation to thickness direction retardation (Re / Rth). The final film forming conditions need to be set in consideration of the properties required for processing in addition to the retardation control.

The thickness of the polyester film of the present invention is arbitrary, but is preferably in the range of 15 to 200 mu m. Even in the case of a film having a thickness of less than 15 占 퐉, in principle, it is possible to obtain retardation of 3,000 nm or more. In this case, however, the anisotropy of the mechanical properties of the film becomes remarkable, which tends to cause tearing, cracking, and the like, so that practical utility as an industrial material is remarkably deteriorated. A particularly preferable lower limit of the thickness is 25 占 퐉. On the other hand, in view of practicality as a polarizer protective film, the upper limit of the thickness is 200 mu m. If it exceeds 200 μm, the thickness of the polarizing plate becomes excessively thick, which is not preferable. A particularly preferable upper limit of the thickness is 100 탆 which is equivalent to that of a general TAC film. In order to control the retardation within the range of the above-mentioned thickness in the above-mentioned thickness range, polyethylene terephthalate is suitable as the polyester used as the film base.

As a method for blending the ultraviolet absorber in the polyester film of the present invention, a known method may be used in combination. For example, the ultraviolet absorber previously dried by using a kneading extruder is blended with the polymer raw material, And a method of mixing the predetermined master batch with the polymer raw material at the time of film formation can be used. The added weight of the ultraviolet absorber added to the film is preferably 0.3 to 1.5%, more preferably 0.4 to 1.0%.

At this time, the concentration of the ultraviolet absorber in the master batch is preferably 5 to 30% by mass in order to uniformly disperse the ultraviolet absorber and formulate it economically. As a condition for producing the master batch, it is preferable to use a kneading extruder and extrude at a temperature of not lower than the melting point of the polyester raw material and not more than 290 캜 for 1 to 15 minutes. Above 290 占 폚, the weight loss of the ultraviolet absorber is large, and the viscosity drop of the master batch is large. When the residence time is 1 minute or less, uniform mixing of the ultraviolet absorber becomes difficult. At this time, a stabilizer, a color tone adjusting agent and an antistatic agent may be added as necessary.

In the present invention, it is preferable that the film has a multilayer structure of at least three layers, inert particles are added to the surface layer, and an ultraviolet absorber is added to the intermediate layer of the film. The three-layer structure film containing the inert particles on the surface layer and the ultraviolet absorber on the intermediate layer can be specifically manufactured as follows. The master batch containing the inert particles and the polyester pellets as the outer layer are mixed at a predetermined ratio, and the master batch containing the ultraviolet absorbent for the intermediate layer and the pellets of the polyester are mixed at a predetermined ratio and dried. And extruded into a sheet form from a slit-shaped die and cooled and solidified on a casting roll to form an unstretched film. That is, a film layer constituting the both outer layers and a film layer constituting the intermediate layer are laminated by using two or more extruders, a three-layer manifold or a confluence block (for example, a confluence block having a rectangular confluent portion) The sheet of the layer is extruded and cooled with a casting roll to form an unstretched film. Further, in the present invention, it is preferable to perform high-degree filtration at the time of melt extrusion in order to remove foreign matters contained in the polyester of the raw material which causes optical defects. The filtration particle size (initial filtration efficiency 95%) of the filter medium used for high-precision filtration of the molten resin is preferably 15 μm or less. If the filter particle size of the filter material exceeds 15 μm, the removal of foreign matter of 20 μm or more tends to be insufficient.

Example

The present invention will be described in more detail with reference to the following examples, but it should be understood that the present invention is not limited to the following examples, but can be carried out by appropriately changing the scope of the present invention, Are included in the technical scope of In the following examples, evaluation methods of physical properties are as follows.

(1) retardation (Re)

Is a parameter defined by a product (DELTA Nxy x d) of the anisotropy (DELTA Nxy = | Nx-Ny |) of the refractive index of the orthogonal biaxial film on the film and the film thickness d (nm), and is a measure for optical anisotropy and anisotropy. The anisotropy (? Nxy) of the refractive index of the biaxial axis is obtained by the following method. Using two polarizing plates, the orientation axis direction of the film was determined, and a rectangle of 4 cm x 2 cm was cut out so as to be orthogonal to the orientation axis direction. The refractive index (Nx, Ny) and the refractive index (Nz) in the thickness direction orthogonal to the sample were determined by Abbe's refractometer (NAR-4T manufactured by Atago Corporation) and the absolute value of the refractive index difference -Ny |) was defined as anisotropy of refractive index (? Nxy). The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D, manufactured by Pahrung Paste), and the unit was converted to nm. The retardation (Re) was determined from the product (Nxy x d) of the anisotropy (DELTA Nxy) of the refractive index and the thickness d (nm) of the film.

(2) Thickness direction retardation (Rth)

Is a parameter representing the average of the retardations obtained by multiplying the birefringence ΔNxz (= | Nx-Nz |) and ΔNyz (= | Ny-Nz | Nx, Ny and Nz and film thickness d (nm) were obtained in the same manner as in the measurement of the retardation, and the average value of (DELTA Nxz x d) and (DELTA Nyz x d) Respectively.

(3) Light transmittance at a wavelength of 380 nm

Using a spectrophotometer (model: U-3500, manufactured by Hitachi, Ltd.), the light transmittance at a wavelength of 380 nm was determined by measuring the light transmittance of each film in the wavelength region of 300 to 500 nm with the air layer as a standard.

(4) Rainbow spot observation

The polyester film of the present invention was applied to one side of a polarizer made of PVA and iodine so that the absorption axis of the polarizing film and the main axis of alignment of the film were perpendicular to each other and a TAC film (manufactured by Fuji Film Co., Thickness: 80 mu m) was pasted to produce a polarizing plate. The obtained polarizing plate was a liquid crystal display device (a liquid crystal cell comprising a liquid crystal cell and two TAC films on the side of incident light, which is a white LED comprising a light emitting element in combination of a blue light emitting diode and a yttrium aluminum garnet yellow fluorescent substance as a light source (Nichia Corporation, NSPW500CS) (Having a polarizing plate made of a polarizer protective film) so that the polyester film is on the viewer side. The polarizing plate of the liquid crystal display was visually observed from the front and the oblique direction of the polarizing plate to determine whether rainbow stains occurred or not.

In Comparative Example 3, instead of a white LED, a backlight source using a cold cathode tube as a light source was used.

◎: Rainbow stains do not occur in any direction.

○: When observing in oblique direction, some very thin rainbow stains can be observed.

X: Irregular irregularity can be clearly observed when observed in the oblique direction.

(5) Mechanical strength

The obtained film was cut to a width of 10 mm and an initial length of 50 mm and a tensile speed of 200 mm / min were measured in accordance with JIS-K-7127 (2000) using "Tensilon universal testing machine RTA-T-4M" And a tensile test was conducted. The tensile elastic modulus was obtained by dividing the difference in stress between two points on a straight line by the difference in strain between two identical points using the first straight portion of the stress-strain curve obtained by the tensile test. This measurement was carried out under a standard environment adjusted to a temperature of 23 占 占 폚 and a relative humidity of 50 占 15% RH, and the measurement was made in the longitudinal and transverse directions. The tensile modulus of elasticity in the longitudinal direction or the transverse direction was evaluated as "Good" when the smaller value was 5% or more and "Good" when the value was less than 5%.

(6) The thickness of the outermost layer (inert particle-containing layer)

The prepared film was cut perpendicular to the film flow direction and embedded with a photo-curing resin. The embedded specimen was stained with ruthenium oxide vapor for 30 minutes using a microtome as a thin section with a thickness of about 70 to 100 nm. The cross-section was observed using a transmission electron microscope (TEM2010, manufactured by Japan Electronics Co., Ltd.) and the thickness of the outermost layer (inactive particle-containing layer) was determined from the position of the inert particles. The observation magnification was appropriately set in the range of 1,500 to 10,000 times.

(7) Hayes

The haze of the film was measured using a turbidimeter (NHD2000, manufactured by Nippon Seiro Co., Ltd.) in accordance with JIS-K7105.

(8) Three-dimensional surface roughness (SRa, SRz) of the outermost layer surface

A polarizer protective film prepared without the application layer in each of the examples and comparative examples was prepared and the outermost layer surface of the film was stuck to the surface of the needle using a three-dimensional stain sensor (SE-3AK, manufactured by Kosaka Laboratory Co., Ltd.) A cut-off value of 0.25 mm in the longitudinal direction of the film under the conditions of a radius of 2 占 퐉 and a load of 30 占 퐉 was measured at a needle sending speed of 0.1 mm / sec over a measurement length of 1 mm and divided into 500 points at a 2 占 퐉 pitch, And the height was input to the three-dimensional roughness analyzer (SPA-11). The same operation was repeated 150 times at intervals of 2 탆 with respect to the film width direction, that is, 0.3 mm in the width direction of the film, and data was inputted to the analyzing apparatus. Next, the center surface average roughness (SRa) and the ten-point mean roughness (SRz) were obtained using an analyzer.

(9) average particle size of inert particles, number of particles of 10 탆 or more

Inert particles were observed with a scanning electron microscope (S-51O type, manufactured by Hitachi, Ltd.), and magnification was appropriately changed according to the particle size. Subsequently, the outer periphery of each particle was traced for at least 200 randomly selected particles, and the circle equivalent diameter of the particles was measured from these trace images by an image analyzer, and the average thereof was taken as an average particle size. The ratio of particles having a particle diameter of 10 mu m or more was calculated from the particle diameter of 200 or more particles thus obtained.

(10) Scratch evaluation

With respect to the obtained polyester film, the film was taken out from a film roll having a width of 1 m and a length of 100 m, and was stretched in a vertical direction. At this time, 100 m of the surface layer of the film roll was removed and the subsequent 100 m was used as a sample. Then, a black cloth with no gloss was arranged on the entire back surface of the film, and defects (locally shining points) were observed and marked from the front side. Then, the size of the long diameter was measured using a magnifying glass (SCALE LUPE x 10 manufactured by PEAK Co., Ltd.) with a magnification of 10 times at the marked portion. The determination was made based on the following criteria.

○ Number of optical defects more than 1 ㎜ in size / ㎡

△ Number of optical defects larger than 1 mm in size 1 to 3 / ㎡

× Number of optical defects greater than 1 ㎜ and more than 3 / ㎡

(Production Example 1-Polyester A)

86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were added while the temperature of the esterification reaction tube was elevated to 200 ° C, and 0.017 parts by mass of antimony trioxide, 0.064 parts by mass of magnesium acetate tetrahydrate, 0.164 parts by mass of triethylamine Mass part was added. Subsequently, the mixture was subjected to pressure esterification under the conditions of a gauge pressure of 0.34 MPa and a temperature of 240 DEG C, and then the esterification reaction tube was returned to normal pressure and 0.014 part of phosphoric acid was added. The temperature was further raised to 260 DEG C over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. Then, 15 minutes later, dispersion treatment was carried out with a high-pressure dispersing machine. Further, an aqueous solution of sodium tripolyphosphate was contained in an amount of 0.1% by mass as sodium atoms in the silica particles, and the granules were cut by 35% An ethylene glycol slurry of silica particles having an average particle size of 2.3 占 퐉 and a pore volume of 1.60 ml / g obtained by filtration with a metal filter having a diameter of 5 占 퐉 was added in an amount of 0.2 parts by mass as a particle content. After 15 minutes, the resulting esterification reaction product was transferred to a polycondensation reaction tube and subjected to a condensation reaction under reduced pressure at 280 ° C.

After completion of the polycondensation reaction, filtration was performed with a Naslon-made filter having a 95% cut diameter of 5 탆, extruded from a nozzle into a strand shape, and cooled using cooling water previously subjected to filtration treatment (pore diameter: And solidified and cut into pellets. The intrinsic viscosity of the obtained polyethylene terephthalate resin (A) is 0.62 dl / g (hereinafter abbreviated as PET (A)).

(Production Example 2-Polyester B)

On the other hand, a polyethylene terephthalate resin (B) having an intrinsic viscosity of 0.62 dl / g and containing no silica particles was obtained in the production of the PET (A) (hereinafter abbreviated as PET (B)).

(Production Example 3 - Polyester C)

A polyethylene terephthalate resin (C) having an intrinsic viscosity of 0.62 dl / g was obtained in the same manner as in the production of the PET (A) except that silica particles having an average particle size of 2.8 탆 were used (hereinafter abbreviated as PET (C)). ).

(Production Example 4-Polyester D)

A polyethylene terephthalate resin (D) having an intrinsic viscosity of 0.62 dl / g (hereinafter, abbreviated as PET (D)) was obtained in the same manner as in the preparation of the PET (A) except that silica particles having an average particle diameter of 3.7 탆 were used. ).

(Production Example 5-Polyester E)

A polyethylene terephthalate resin (E) having an intrinsic viscosity of 0.62 dl / g (hereinafter abbreviated as PET (E)) was obtained in the same manner as in the production of the PET (A) except that calcium carbonate particles having an average particle diameter of 0.5 탆 were used .).

(Production Example 6-Polyester F)

10 parts by mass of a dried ultraviolet absorber (2,2 '- (1,4-phenylene) bis (4H-3,1-benzoxazinone-4-one), PET (B) Of 0.62 dl / g) were mixed, and a polyethylene terephthalate resin (F) containing an ultraviolet absorber was obtained by using a kneading extruder (hereinafter abbreviated as PET (F)).

(Preparation Example 7-Preparation of Coating Solution for Adhesive Layer Formation)

Ester exchange reaction and polycondensation reaction were carried out in a usual manner to obtain 46 mol% of terephthalic acid (relative to the entire dicarboxylic acid component), 46 mol% of isophthalic acid and 8 mol% of sodium 5-sulfonate isophthalate (% By mol) of a glycol component (relative to the entire glycol component), and 50 mol% of ethylene glycol and 50 mol% of neopentyl glycol. Subsequently, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve and 0.06 parts by mass of a nonionic surfactant were mixed and heated with stirring. When the temperature reached 77 占 폚, And 5 parts by mass of a copolymer polyester resin was added. After stirring until the resin mass was no longer present, the resin aqueous dispersion was cooled to room temperature to obtain a homogeneous water dispersible copolymer polyester resin liquid having a solid content concentration of 5.0% by mass. Further, 3 parts by mass of agglomerated silica particles (Silysia 310, manufactured by Fuji Silysia Co., Ltd.) were dispersed in 50 parts by mass of water. To 99.46 parts by mass of the above water-dispersible copolymerized polyester resin solution was added an aqueous dispersion of Silysia 310 , And 20 parts by mass of water was added with stirring to obtain an adhesive modified coating liquid.

(Example 1)

90 parts by mass of PET (B) resin pellets containing no particles and 10 parts by mass of PET (F) resin pellets containing ultraviolet absorber were dried at 135 ° C for 6 hours under reduced pressure (1 Torr) as raw materials for the base film intermediate layer raw material, PET (A) and PET (B) were mixed and adjusted so as to have a content of silica particles of 0.020% by mass and dried by an ordinary method to prepare an extruder 1 (outer layer (I layer) And outer layer (III layer)], respectively, and dissolved at 285 ° C. These two kinds of polymers were each filtered with a filter material of a stainless steel sintered body (nominal filtration accuracy of 10 탆 particles of 95% cut), laminated with a two-kind three-layer confluence block, extruded from the indentation into a sheet shape, Was wound around a casting drum having a surface temperature of 30 占 폚 to cool and solidify to form an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thicknesses of the I layer, the II layer and the III layer was 10:80:10.

Subsequently, the adhesive layer-forming coating liquid was applied on both sides of the unstretched PET film by a reverse roll method so that the coating amount after drying was 0.08 g / m 2, and then dried at 80 ° C for 20 seconds.

The unstretched film on which the coating layer was formed was led to a tenter stretching machine and led to a hot air zone at a temperature of 125 캜 while grasping the end of the film with a clip and stretched 4.0 times in the width direction.

Then, while maintaining the stretched width in the width direction, the film was treated at a temperature of 225 占 폚 for 30 seconds and further subjected to a relaxation treatment of 3% in the width direction to obtain a uniaxially oriented PET film having a film thickness of about 50 占 퐉.

(Example 2)

A uniaxially oriented PET film having a thickness of about 100 탆 was obtained by changing the thickness of the unstretched film by using the same method as in Example 1 except that the silica concentration of the outer layer (I, III layer) was changed to 400 ppm.

(Example 3)

The unstretched film prepared in the same manner as in Example 1 was heated to 105 DEG C using a heated roll group and an infrared heater and then stretched 1.5 times in the running direction with a roll having a peripheral speed, To 4.0 times in the transverse direction to obtain a biaxially oriented PET film having a film thickness of about 50 mu m.

(Example 4)

A biaxially oriented PET film having a film thickness of about 50 탆 was obtained by stretching 2.0 times in the running direction and 4.0 times in the width direction in the same manner as in Example 3 except that the polyester C was used in place of the polyester A.

(Example 5)

The laminate was stretched 3.3 times in the running direction and 4.0 times in the width direction in the same manner as in Example 3 except that the polyester C was used in place of the polyester A and the silica concentration of the outer layer (I, III layer) was changed to 50 ppm, A biaxially oriented PET film having a thickness of about 75 탆 was obtained.

(Example 6)

A uniaxially-oriented PET film having a film thickness of 50 占 퐉 was obtained in the same manner as in Example 1, without using the PET resin (B) containing an ultraviolet absorber in the intermediate layer (II layer).

(Example 7)

A biaxially oriented PET film having a film thickness of about 250 탆 was obtained by stretching 3.5 times in the running direction and 3.7 times in the width direction in the same manner as in Example 3 except that the silica concentration of the outer layer (I, III layer) was changed to 100 ppm. The resulting film had a Re of 4,500 nm or more, but the Re / Rth ratio was less than 0.2, and thus very thin rainbow stains in the oblique direction were confirmed.

(Example 8)

A uniaxially oriented PET film having a thickness of about 275 占 퐉 was obtained by changing the thickness of the unstretched film by using the same method as in Example 1. [

(Example 9)

The same tests as in Example 1 were carried out except that a rainbow stain observation was performed using a liquid crystal display device in which an organic light emitting diode (OLED) was a light source.

(Comparative Example 1)

The biaxially oriented PET film having a film thickness of about 38 占 퐉 was obtained by stretching it 3.6 times in the running direction and 4.0 times in the width direction in the same manner as in Example 3.

(Comparative Example 2)

A uniaxially oriented PET film having a thickness of about 10 占 퐉 was obtained by changing the thickness of the unstretched film by using the same method as in Example 1 except that no polyester was used and no silica was added to the outer layer (I, III layer) .

(Comparative Example 3)

The same procedure as in Example 1 was carried out except that the light source of the liquid crystal display device was used as a cold-cathode tube to observe iridescent stains.

(Comparative Example 4)

A uniaxially oriented PET film having a film thickness of about 100 탆 was obtained by stretching 4.0 times in the running direction and 1.0 time in the width direction in the same manner as in Example 3 except that the polyester D was used in place of the polyester A.

(Comparative Example 5)

A uniaxially oriented PET film having a film thickness of about 75 탆 was obtained by stretching it 1.0 times in the running direction and 3.5 times in the width direction in the same manner as in Example 1 except that the polyester E was used in place of the polyester A.

By using the liquid crystal display device, the polarizing plate and the polarizer protective film of the present invention, it is possible to contribute to the thinning of the LCD and the low cost without decreasing the visibility due to irregular color unevenness, and the industrial applicability is very high.

Claims (8)

(1) having a polyester film having an in-plane retardation of 3,000 to 30,000 nm and a center plane average roughness (SRa) of the outermost layer surface of 0.008 to 0.02 탆 and a ten-point average roughness (SRz) of 0.3 to 1.5 탆 A polarizer protective film,
The polarizing plate being laminated on the polarizer such that the alignment main axis of the polyester film and the absorption axis of the polarizer are perpendicular to each other. The method according to claim 1,
Wherein a ratio (Re / Rth) of in-plane retardation to thickness direction retardation of the polyester film is 0.2 or more and 1.2 or less. 3. The method according to claim 1 or 2,
Wherein the in-plane retardation of the polyester film is 8,000 nm or more. 3. The method according to claim 1 or 2,
A polarizing plate on which polarizer protective films are laminated on both sides of a polarizer,
At least one polarizer protective film on one side,
(1) having a polyester film having an in-plane retardation of 3,000 to 30,000 nm and a center plane average roughness (SRa) of the outermost layer surface of 0.008 to 0.02 탆 and a ten-point average roughness (SRz) of 0.3 to 1.5 탆 A polarizer protective film made of
Polarizer. 3. The method according to claim 1 or 2,
A polarizing plate for a liquid crystal display device which uses a white light source having a continuous emission spectrum as a backlight source. A liquid crystal display device having the polarizing plate according to claim 1 or 2. A liquid crystal display device having a liquid crystal cell arranged between a backlight light source and two polarizing plates,
Wherein the backlight source is a white light source having a continuous emission spectrum,
Wherein at least one of the two polarizing plates is the polarizing plate according to claim 1 or 2. A liquid crystal display device having a liquid crystal cell arranged between a backlight light source and two polarizing plates,
Wherein the backlight source is a white light source having a continuous emission spectrum,
Wherein the polarizing plate disposed on the side of the emergent light with respect to the liquid crystal cell is the polarizing plate according to claim 1 or 2.