TW201337407A - Liquid crystal display device, polarizing plate and polarizer protection film - Google Patents

Abstract

The present invention provides a liquid crystal display device which not only uses polarizer protective film comprising polyester film but also has excellent visibility. The liquid crystal display device is a liquid crystal display device that has backlight source and liquid crystal cell disposed between two polarizing plates. The backlight source is a white light source having a continuous emission spectrum. The polarizing plate comprises structure formed by laminating polarizer protective film on both sides of the polarizer. The polarizer protective film is a polyester film that has a retardation of 3000-30000nm, center plane average roughness of the surface of the outermost layer (SRa) of 0.008-0.02 μ m and the ten-point average roughness (SRz) of 0.3-1.5 μ m.

Description

Liquid crystal display device, polarizing plate and polarizer protective film

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

A polarizing plate used for a liquid crystal display device (LCD) is usually composed of two polarizing mirror protective films sandwiching a polarizing lens coated with iodine on polyvinyl alcohol (PVA) or the like, usually using triacetyl cellulose ( The TAC) film acts as a polarizer protective film. In recent years, with the thinning of LCDs, there has been a demand for thinning of polarizing plates. However, if the thickness of the TAC film used as the protective film is made thin, sufficient mechanical strength cannot be obtained, and the moisture permeability becomes high, and the polarizer is easily deteriorated. Also, TAC films are very expensive and are strongly pursuing inexpensive alternative materials.

Therefore, the thickness of the polarizing plate is reduced, and even if the thickness of the polarizer protective film is reduced, it is proposed to use a polyester film instead of the TAC film in order to maintain high durability (Patent Documents 1 to 3).

Prior technical literature Patent literature

Patent Document 1 Japanese Patent Laid-Open Publication No. 2002-116320

Patent Document 2 Japanese Patent Laid-Open Publication No. 2004-219620

Patent Document 3 Japanese Patent Laid-Open Publication No. 2004-205773

The polyester film is superior in durability to the TAC film, but has a birefringence different from that of the TAC film. When it is used as a polarizer protective film, there is a problem that image quality is lowered due to optical distortion. That is, the polyester film having birefringence has a specified optical anisotropy (hysteresis value), and when used as a polarizer protective film, if it is observed obliquely, a rainbow-like stain will occur, and the image quality will be reduce. Therefore, in Patent Documents 1 to 3, measures for reducing the hysteresis value by using a copolyester as a polyester are carried out. However, even in this case, it is impossible to completely eliminate the rainbow-like stain.

The present invention has been made in order to solve the problem, and an object thereof is to provide a liquid crystal display device and a polarizer protective film which can be made thinner in accordance with a liquid crystal display device without causing an off-color spot The deterioration of the visibility is caused; the polarizer protective film has high transparency and few optical defects.

The inventors of the present invention have conducted intensive studies on a mechanism for generating a rainbow-like stain generated when a polyester film is used as a polarizer protective film. As a result, it is known that the rainbow-like color ray is caused by the hysteresis value of the polyester film and the luminescence spectrum of the backlight source. Conventionally, a fluorescent tube such as a cold cathode tube or a hot cathode tube can be used as the backlight source of the liquid crystal display device. The spectral distribution of a fluorescent lamp such as a cold cathode tube or a hot cathode tube exhibits an emission spectrum having a complex peak, and these discontinuous emission spectra are superimposed to obtain a white light source. When light penetrates a film with a high hysteresis value, it shows different transmitted light intensities depending on the wavelength. Therefore, it is considered that if the backlight source is a discontinuous luminescence spectrum, only a certain wavelength will penetrate strongly to produce an iridescent stain.

The inventors of the present invention have found that in order to achieve the above problems, it has been found that the above problems can be solved by combining a specific backlight source and a polyester film having a specific hysteresis value. Further, in order to suppress the optical defects of the polyester film while ensuring high transparency, it has been found that imparting a specific surface morphology is effective.

That is, the representative invention is as follows.

(1) A liquid crystal display device comprising a backlight source and a liquid crystal cell disposed between two polarizing plates, wherein the backlight source is a white light source having a continuous emission spectrum, and the polarizing plate is a polarizer. The protective film is laminated on the polarizing plates on both sides of the polarizer. At least one of the polarizer protective films has a hysteresis value of 3,000 to 30,000 nm, and the center surface average roughness (SRa) of the outermost surface is 0.008 to 0.02 μm. And a polyester film having a ten-point average roughness (SRz) of 0.3 to 1.5 μm.

(2) The liquid crystal display device of the present invention, wherein the polarizer protective film disposed on the light-emitting side of the polarizing plate on the light-emitting side has a hysteresis value of 3,000 to 30,000 nm, and the center-surface average roughness of the outermost surface is opposite to the liquid crystal cell. (SRa) is a polyester film having a ten point average roughness (SRz) of 0.3 to 1.5 μm and a ten point average roughness (SRz) of 0.3 to 1.5 μm.

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

(4) A polarizing plate for a liquid crystal display device, wherein the polarizer protective film is laminated on the polarizing plates on both sides of the polarizing mirror, wherein at least one of the polarizing mirror protective films has a hysteresis value of 3000 to 30000 nm, and the outermost surface The center plane average roughness (SRa) is 0.008 to 0.02 μm, and the ten point is flat. A polyester film having a uniform roughness (SRz) of 0.3 to 1.5 μm and a white light source having a continuous luminescence spectrum as a backlight source.

(5) A polarizer protective film for a liquid crystal display device having a hysteresis value of 3,000 to 30,000 nm, a center-surface average roughness (SRa) of the outermost surface of the surface is 0.008 to 0.02 μm, and a ten-point average roughness (SRz) It is a polyester film of 0.3 to 1.5 μm, and a white light source having a continuous luminescence spectrum is used as a backlight source.

(6) The polarizer protective film according to the above aspect, wherein the ratio (Re/Rth) of the retardation value to the thickness direction hysteresis value of the polyester film is 0.2 or more.

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

(8) The polarizer protective film, wherein the polyester film contains at least three layers, and the outermost layer contains inert particles having an average particle diameter of 1.0 to 3.5 μm, and the outermost layer has a thickness of at least the average particle diameter of the inert particles.

(9) The polarizer protective film, 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 value of the polyester film is 3% or less.

(10) The polarizer protective film according to the above aspect, wherein the layer other than the outermost layer of the polyester film contains an ultraviolet absorber, and the light transmittance at 380 nm is 20% or less.

The liquid crystal display device, the polarizing plate and the polarizer protective film of the present invention can obtain a spectrum close to the light source at any viewing angle, and can ensure good visibility of the rainbow-free color spot. . Further, the polarizer protective film of the present invention has a specific surface Roughness is excellent in handleability, and it is difficult to cause damage due to friction or the like. Therefore, the polarizer protective film of the present invention has high transparency and extremely few optical defects such as damage.

[Formation for carrying out the invention]

Generally, the liquid crystal panel has a rear module, a liquid crystal cell, and a front module in the order of the side of the display image (the visual recognition side or the emission light side) from the backlight source side. The rear module and the front module are generally composed of a transparent substrate, a transparent conductive film formed on the surface of the liquid crystal cell, and a polarizing plate disposed on the opposite side. Here, in the latter module, the polarizing plate is disposed on the backlight source side, and in the front module, it is disposed on the display image side (visual identification side or emission light side).

In the liquid crystal display device of the present invention, at least a backlight source and a liquid crystal cell disposed between the two polarizing plates are used as constituent members. Further, other configurations than these may include, for example, a color filter, a lens film, a diffusion sheet, an antireflection film, and the like.

The configuration of the backlight source may be an edge light method in which a light guide plate, a reflector, or the like is used as a constituent member, and may be a direct-down type. However, it is preferable to use a white light source having a wide and wide emission spectrum. The term "continuous broad-spectrum luminescence spectrum" as used herein means a luminescence spectrum having a wavelength of at least 450 nm to 650 nm, preferably in the region of visible light, without a wavelength at which the light intensity is zero. As a white light source having such a wide and wide luminescence spectrum, for example, a white light-emitting diode (white LED) can be cited. The white LED includes a phosphor mode, that is, a light-emitting diode that combines blue light or ultraviolet light using a compound semiconductor A device that emits white with a phosphor, an organic light-emitting diode (OLED), or the like. In the white LED, a blue light-emitting diode and a germanium combined using a compound semiconductor are included. aluminum. A white light-emitting diode comprising a garnet-based yellow phosphor and comprising a light-emitting element is suitable as a backlight source of the present invention because it has not only a wide and wide emission spectrum but also excellent light-emitting efficiency. It is also effective for energy saving by using a white LED or the like that consumes less power as a light source.

Since the luminescence spectrum of a fluorescent tube such as a cold cathode tube or a hot cathode tube which has been widely used as a backlight source has only a discontinuous luminescence spectrum having a peak at a specific wavelength, it is difficult to obtain the effects of the present invention as described above.

The polarizing plate has a configuration in which two polarizing mirror protective films are sandwiched between two sides of a PVA or the like which are dyed with iodine, but the present invention is characterized in that a polyester film having a specific range of hysteresis value is used as a constituent polarizing film. At least one of the polarizer protective film of the plate.

The mechanism for suppressing the occurrence of rainbow-like stains by the above-described aspects is conceived as follows. When a polyester film having birefringence is disposed on one side of the polarizer, linear polarized light emitted from the polarizer may be scattered when passing through the polyester film. The transmitted light shows a characteristic interference color in terms of the hysteresis value of the product of the birefringence and the thickness of the polyester film. Therefore, if a discontinuous luminescence spectrum such as a cold cathode tube or a hot cathode tube is used as a light source, different penetration light intensities are displayed depending on the wavelength, and a rainbow-like color spot is generated (reference: 15th micro-optical conference (Microoptics) Conference), drafts, 30-31).

On the other hand, in the white light-emitting diode, it is usually at least in the wavelength region of 450 nm to 650 nm, preferably in the visible light region, and has a wide and wide emission spectrum. Therefore, since the interference color spectrum caused by the penetrating light passing through the birefringent becomes an envelope curve shape, a spectrum similar to the light emission spectrum of the light source can be obtained by controlling the hysteresis value of the polyester film. As described above, it is considered that since the envelope curve shape of the interference color spectrum caused by the luminescence spectrum of the light source and the penetrating light penetrating the birefringent body is similar, the rainbow-like color patch does not occur and the vision is remarkably improved. Identification.

Based on the above principle, it is considered that in the present invention, by using a white light-emitting diode having a wide light-emitting spectrum for a light source, the shape of the envelope curve of the transmitted light can be approximated to the light source with only a relatively simple configuration. The luminescence spectrum, as a result, suppresses rainbow spots on the liquid crystal display.

(Polyester film)

The polyester film used for the polarizer protective film is preferably an oriented polyester film having a hysteresis value of 3,000 to 30,000 nm. When the hysteresis value is less than 3000 nm, when it is used as a polarizer protective film, since it exhibits a strong interference color when viewed obliquely, the shape of the envelope curve is different from that of the light source, and good visibility cannot be ensured. The lower limit of the preferable hysteresis value is 4,500 nm or more, more preferably 6000 nm or more, still more preferably 8000 nm or more, still more preferably 10,000 nm or more.

On the other hand, the upper limit of the hysteresis value is 30000 nm. Even if a polyester film having a hysteresis value exceeding the hysteresis value is used, not only the improvement effect of further visibility is substantially not obtained, but also the thickness of the film becomes relatively thick, and the workability as an industrial material is lowered, which is not preferable.

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

The present invention is characterized in that at least one of the polarizer protective films is a polarizer protective film having the above specific hysteresis value. The arrangement of the polarizer protective film having the specific hysteresis value is not particularly limited, and the polarizer protective film disposed on the incident light side of the polarizing plate on the incident light side of the liquid crystal display device or the polarizing plate disposed on the light emitting side is disposed. The polarizer protective film on the light-emitting side is preferably a polarizer protective film containing a polyester film having the specific hysteresis value. A particularly preferable aspect is that the polarizer protective film disposed on the light-emitting side of the polarizing plate on the light-emitting side adopts a polyester film having the specific hysteresis value. When the polyester film is disposed at a position other than the above, the polarization characteristics of the liquid crystal cell may be changed.

The polarizing plate of the present invention is characterized in that it has a configuration in which two polarizing mirror protective films are sandwiched on both sides of a polarizing lens which is dyed with iodine on polyvinyl alcohol (PVA) or the like, and any one of the polarizer protective films has the above-mentioned A polarizer protective film with a specific hysteresis value. It is preferable to use a film having no birefringence such as a TAC film or an acrylic film or a norbornene film for another polarizer protective film. The polarizing plate used in the present invention can provide various functional layers for the purpose of preventing reflection, suppressing glare, and suppressing scratches. The functional layer is not particularly limited, and examples thereof include a hard coat layer, an antiglare layer (AG), an antireflection layer (AR), a low reflection layer (LR), and a low reflection antiglare layer (AG/LR). ), anti-reflective anti-glare layer (AG / AR). The functional layer is preferably a table disposed on the opposite side of the side of the polyester film that is in contact with the polarizing mirror. surface. Only one type of these layers may be provided on the polyester film, and two or more layers may be combined as needed. By forming these layers, it is also expected to have an effect of reducing the rainbow-like color spots.

When various functional layers are provided, it is preferred to provide an easy-adhesion layer on the surface of the alignment polyester film. At this time, from the viewpoint of suppressing interference due to reflected light, it is preferable to adjust the refractive index of the easy-adhesion layer to the vicinity of the multiplication and average of the refractive index of the functional layer and the refractive index of the polyester film. The refractive index of the easy-adhesion layer can be adjusted by a conventional method, for example, by adjusting the adhesive resin such as polyester or polyurethane to contain titanium or niobium and other metal species.

A polyester film can be obtained by condensing a dibasic acid with a glycol. The dibasic acid component used for the production of the polyester film may, for example, be terephthalic acid, isophthalic acid, phthalic acid, 2,5-naphthalene dicarboxylic acid or 2,6-naphthalene. Carboxylic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, diphenylcarboxylic acid, diphenoxyethane dicarboxylic acid, diphenylphosphonium carboxylic acid, stilbene dicarboxylic acid, 1 , 3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, Dimethylmalonic acid, succinic acid, 3,3-diethyl succinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, three Methyl adipate, pimelic acid, sebacic acid, dimer acid, sebacic acid, suberic acid, dodecanedioic acid, and the like.

The glycol component used for the production of the polyester film may, for example, be ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4. -cyclohexanedimethanol, decanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyl Phenyl)propane, bis(4-hydroxyphenyl)anthracene, and the like.

One type or two or more types of the dibasic acid component and the diol component which are constituting the polyester film can be used. Specific examples of the polyester resin constituting the polyester film include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. And the like, preferably ethylene terephthalate or polyethylene naphthalate. These resins are excellent in transparency and excellent in heat and mechanical properties, and the hysteresis value can be easily controlled by extension processing. In particular, polyethylene terephthalate is the most suitable material because of its large intrinsic birefringence, and even if the thickness of the film is thin, it is relatively easy to obtain a high hysteresis value.

The polyester film of the present invention is a laminate of three or more layers formed by a co-extrusion method, and preferably contains inert particles in both outermost layers. Thereby, the uneven shape can be imparted to the outermost surface, and the workability (lubricity) by the film processing becomes good. In the laminated structure of the present invention, for example, if the outermost layer is defined as the B layer and the other layers are defined as the A layer and the C layer, the layer constitution in the film thickness direction is conceivable as B/A/B, B/A/C/. B, or B / A / C / A / B and so on. Each of the layers A to C may be the same as or different from the composition of the polyester resin. However, in order to suppress the occurrence of warpage due to the bimetallic structure, it is preferred to make the polyester resin of each layer the same. And/or B/A/B (two types of three-layer structure).

In the present invention, the polyester resin constituting the center layer other than the outermost layer (for example, the layer A in B/A/B) may contain particles, and in order to obtain high transparency, the polyester resin constituting the center layer is preferably It does not substantially contain particles. More suitable high transparency can be obtained by including inert particles only in the outermost layer. When particles are added to the center layer other than the outermost layer, it is preferably 50 ppm or less, preferably 10 ppm or less.

Examples of the inert particles contained in the outermost layer include calcium carbonate, calcium phosphate, amorphous cerium oxide, spherical cerium oxide, crystalline glass fiber, kaolin, talc, titanium oxide, aluminum oxide, and dioxide.矽-alumina composite oxide particles, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, mica and other inorganic particles, or crosslinked polystyrene particles, crosslinked acrylic resin particles, crosslinked methacrylic acid Methyl ester particles, benzoguanamine. Formaldehyde condensate particles, melamine. Heat-resistant polymer microparticles such as formaldehyde condensate particles and polytetrafluoroethylene particles. Among them, since the refractive index of cerium oxide and polyester is relatively close, it is most suitable at the point of ensuring a film having more excellent transparency.

The average particle diameter of the inert particles contained in the outermost layer of the film of the present invention is preferably from 1.0 to 3.5 μm, more preferably from 1.5 to 3.0 μm, still more preferably from 2.1 to 2.5 μm. When the average particle diameter of the inert particles is less than 1.0 μm, the cohesive force of the particles is extremely large, and coarse abnormal particles due to aggregation of the particles are likely to be easily generated. At this time, the aggregated particles are the main cause, and optical defects that are visually recognized by the surface may be generated on the surface of the film.

In addition, when the average particle diameter exceeds 3.5 μm, the content of coarse particles as a monomer monomer is not preferable. At this time, coarse particles are the main cause, and optical defects sometimes occur on the surface of the film. In order to reduce the coarse particles causing optical defects to the limit, it is preferred to use a specific range of particles as described above.

The average particle size range of the inert particles herein is measured by a measurement method described later. Further, for example, as will be described later, in the case where the primary particles are agglomerated into secondary particles, the average particle diameter of the secondary particles is meant. In summary, the average particle diameter of the inert particles herein is an average particle diameter in a state in which the film can actually exist as agglomerates of inert particles.

The content of the inert particles in the outermost layer is preferably from 0.005 to 0.05% by mass, more preferably from 0.010 to 0.04% by mass, still more preferably from 0.015 to 0.03% by mass. When the content of the inert particles is 0.005% by mass or more, it is preferable because it can exhibit an effective lubricity which reduces the degree of minute damage. When the content of the inert particles is 0.05% by mass or less, it is preferable because high transparency is maintained.

The upper limit of the thickness of the outermost layer is not particularly limited. If the thickness is too thick, the amount of inert particles present inside the film may become excessive, and the scattering of light generated inside the film may increase and the transparency may decrease. Not good. Compared with the inert particles, if the thickness of the outermost layer becomes very thin, optical defects which are visually identifiable on the surface of the film sometimes occur due to the falling of the particles. Therefore, the thickness of the outermost layer is preferably equal to or more than the average particle diameter of the inert particles, more preferably 2 times or more, and particularly preferably 5 times or more. Surface protrusions are formed by inert particles that are most present in the outer layer. In order to form a smooth surface protrusion, the inert particles are not present directly under the surface, and it is preferred that particles having a certain size or more exist at an appropriate depth of the film. If the thickness of the outermost layer is equal to or more than the average particle diameter of the inert particles, more preferably 2 times or more, still more preferably 5 times or more, since the shape of the surface protrusion due to the inert particles is smooth, it is difficult Produce falling powder. Further, the thickness of the outermost layer herein is the thickness of one side of the outermost layer laminated on both sides of the film.

By controlling the thickness of the layer containing the inert particles and the inert particles as described above, the shape of the protrusion on the surface of the film can be appropriately controlled, and not only the reduction in transparency but also a more appropriate reduction in optical defects can be suppressed.

Further, in order to more appropriately form the specific surface shape described above, it is also possible to use a combination of, for example, (1) a method of smoothing the surface shape by increasing the intrinsic viscosity of the polyester resin, and (2) performing heat at a high temperature. A method of smoothing the surface shape by a fixed treatment or the like. Further, as will be described later, (3) it is also suitable to use inert particles which tend to undergo conformational deformation under the extension of the film.

In the case of the inert particles which are easily deformed by the extension of the film, secondary particles in which primary particles of several nm to several hundreds nm are aggregated are preferable, and the pore volume thereof is 1.5 ml/g or more. In particular, amorphous block-shaped cerium oxide is suitable from the viewpoints of transparency, workability, and price. When the pore volume of the inert particles is 1.5 ml/g or more, deformation of the particles due to stretching is likely to occur, and the shape of the protrusions can be easily controlled. Further, the pore volume of the inert particles can be calculated by a conventional nitrogen desorption such as the BJH method. When the inert particles are present in the film, for example, the particles may be dissolved by a phenol/tetrachloroethane mixed solution or the like, and the inert particles of the residue may be recovered and sufficiently dried, and then calculated by a conventional nitrogen desorption such as the BJH method.

As a method of formulating the above inert particles in the polyester, a conventional method can be employed. For example, it may be added at any stage of the production of the polyester, but it is preferably at a stage before the end of the esterification reaction or after the end of the transesterification reaction, and it is dispersed in ethylene glycol or the like to form a syrup. Addition may also be carried out by a polycondensation reaction. Can also use the mix of the use of the outlet a method of blending a particle paste dispersed in ethylene glycol or water or the like with a polyester raw material, or a method of blending dried particles and a polyester raw material using a kneading extruder, etc. Come on.

In particular, in the present invention, it is preferred that the aggregated inorganic particles are homogeneously dispersed in a monomer liquid of a part of the polyester raw material, and added to the esterification reaction, the esterification reaction, or the esterification reaction through a filter. The method in the remainder of the polyester raw material. According to this method, since the monomer liquid has a low viscosity, not only the homogeneous dispersion of the particles or the high-precision filtration of the paste can be easily performed, but also the dispersibility of the particles is good and is not easily generated when added to the residual portion of the raw material. New condensate.

In particular, when the above-mentioned amorphous bulk cerium oxide is used, particles are aggregated and aggregated coarse particles are generated by the addition and mixing of the syrup. Since the aggregation of cerium oxide is likely to occur at a high temperature, in order to reduce aggregated coarse particles causing optical defects, when an ethylene glycol solution containing the amorphous bulk cerium oxide is added, an esterification reaction or a transesterification reaction is carried out. In the step before the formation of the oligomer, it is preferred to blend the polyester raw material while maintaining the preferred range of 10 to 50 ° C, more preferably 10 to 30 ° C. By adding the paste at this time, it can be added while the temperature of the paste is kept low, and the formation of new aggregates 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 preferably 10 μm or more, and 1% or less of the total. When the inert particles having a particle diameter of 10 μm or more exceed 1%, the number of coarse particles causing optical defects sometimes increases. In the method of making the distribution of the inert particles into the above range, (1) the inert particles may be dispersed. a method of precision filtration of ethylene glycol or polyester, (2) a method of treating ethylene glycol or polyester which disperses inert particles by a batch or batch type centrifugal separator, and (3) selecting a predetermined particle size distribution The method of inert particles and the like.

The three-dimensional center plane average roughness (SRa) of the film of the present invention is preferably from 0.008 to 0.02 μm, more preferably from 0.009 to 0.015 μm. Further, the ten point average roughness (SRz) is preferably from 0.3 to 1.5 μm, more preferably from 0.5 to 1.0 μm. If the three-dimensional center-surface average roughness (SRa) or the ten-point average roughness (SRz) is within the above range, it is preferable not only to effectively suppress minute damage but also to maintain transparency.

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

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

When the transmittance of the film of the present invention at a wavelength of 380 nm is 20% or less, the ultraviolet absorber can be added to the film, and the coating liquid containing the ultraviolet absorber can be applied to the surface of the film to appropriately adjust the type and concentration of the ultraviolet absorber. And the thickness of the film and the like are achieved. The ultraviolet absorber used in the present invention is a conventional one. In the case of UV absorbers, An organic ultraviolet absorber and an inorganic ultraviolet absorber are preferable, and an organic ultraviolet absorber is preferable from the viewpoint of transparency.

Examples of the organic ultraviolet absorber include a benzotriazole-based, a diphenylketone-based, a cyclic imido ester-based, and the like, and a combination thereof is not particularly limited as long as it is within the range of the absorbance specified in the present invention. . From the viewpoint of durability, a benzotriazole-based or cyclic imido ester-based system is particularly preferred. When two or more types of ultraviolet absorbers are used in combination, since ultraviolet rays of respective wavelengths can be simultaneously absorbed, the ultraviolet absorption effect can be further improved. When the ultraviolet absorber is blended in the polyester film, it is preferred to form the polyester film to have three or more layers, and to incorporate a UV absorber in a layer other than the outermost layer (i.e., the intermediate layer).

Examples of the diphenylketone-based ultraviolet absorber, the benzotriazole-based ultraviolet absorber, and the acrylonitrile-based ultraviolet absorber include, for example, 2-[2'-hydroxy-5'-(methacryloxyl group A). Phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloxyethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloxypropyl)phenyl]-2H-benzotriazole,2,2'-dihydroxy-4,4'-dimethoxydiphenyl ketone, 2 , 2',4,4'-tetrahydroxydiphenyl ketone, 2,4-di-t-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 2-(2'- Hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(5-chloro(2H)-benzotriazol-2-yl)-4-methyl -6-(t-butyl)phenol, 2,2'-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole- 2-yl)phenol, etc. Examples of the cyclic imido ester-based ultraviolet absorber include 2,2'-(1,4-phenylene)bis(4H-3,1-benzo). Keto-4-one), 2-methyl-3,1-benzo 4-ketone, 2-butyl-3,1-benzo 4-ketone, 2-phenyl-3,1-benzo 4-ketone and the like. However, it is not particularly limited to this.

Further, in addition to the ultraviolet absorber, it is preferable to contain various additives within a range that does not impair the effects 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, and antigels. Chemical agent, surfactant, and the like. Further, in order to exhibit high transparency, it is preferred that the polyester film contains substantially no particles. The term "substantially free of particles" means, for example, inorganic particles. When the inorganic element is quantified by fluorescent X-ray analysis, the weight is 50 ppm or less, preferably 10 ppm or less, and particularly preferably the detection limit. The following content.

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

In the present invention, in order to improve the adhesion to the polarizer, it is preferred that at least one of the polyester resin, the polyurethane resin or the polyacrylic resin is mainly composed of at least one side of the film of the present invention. Easy to adhere to the layer. Here, the "main component" means a component of 50% by mass or more of the solid component constituting the easy-adhesion layer. The coating liquid used for the formation of the easy-adhesion layer is preferably an aqueous coating liquid containing at least one of a water-soluble or water-dispersible copolymerized polyester resin, an acrylic resin, and a polyurethane resin. Examples of the coating liquids include those disclosed in, for example, Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, Japanese Patent No. 4150982, and the like. A water-soluble or water-dispersible copolyester resin solution, an acrylic resin solution, a polyurethane resin solution, or the like.

The easy-adhesion layer is obtained by coating the coating liquid on one or both sides of the unstretched or longitudinal uniaxially stretched film, drying at 100 to 150 ° C, and extending in the lateral direction. The coating amount of the final easy-adhesion layer is preferably managed at 0.05 to 0.20 g/m ² . When the coating amount is less than 0.05 g/m ² , the adhesion to the obtained polarizer may be insufficient. On the other hand, when the coating amount exceeds 0.20 g/m ² , the anti-blocking property may be lowered. When the easy-adhesion layer is provided on both sides of the polyester film, the coating amounts of the easy-adhesion layers on both sides may be the same or different, and may be independently set within the above range.

In order to impart slipperiness to the easy-adhesion layer, it is preferred to add particles. The average particle diameter of the fine particles is preferably 2 μm or less. When the average particle diameter of the particles exceeds 2 μm, the particles are likely to fall off from the easy-adhesion layer. The particles contained in the easy-adhesion layer are exemplified by the same as the above-mentioned fine particles.

Further, as a method of applying the coating liquid, a conventional method can be used. For example, a reverse roll coating method, a gravure roll coating method, a roll coating method, a roll brush method, a spray coating method, an air knife coating method, a wire rod coating method, a tube scraping method, etc. may be mentioned, and these methods may be used alone or in combination. get on.

Further, the measurement of the average particle diameter of the above particles was carried out by the following method. A photograph of the particles was taken by a scanning electron microscope (SEM), and the maximum diameter of 300 to 500 particles (distance between the farthest points) was measured with a minimum particle size of 2 to 5 mm. The value is taken as the average particle diameter.

In the method for producing a polyester film, the most common production method is to melt the polyester resin, and to form an unaligned polyester which is formed into a sheet shape, and to use a speed difference of the rolls at a temperature higher than the glass transition temperature. After extending in the longitudinal direction, the film is extended in the lateral direction by a stretcher and subjected to a heat treatment.

The polyester film of the present invention may be a uniaxially stretched film, and may be a biaxially stretched film. However, when a biaxially stretched film is used as the polarizer protective film, even if it is observed from directly above the film face, no rainbow is observed. The color spots, but since the rainbow-like stains are observed when viewed from an oblique direction, care must be taken.

This phenomenon is due to the fact that the biaxially stretched film contains refractive index ellipsoids having different refractive indices in the traveling direction, the width direction, and the thickness direction, and has a hysteresis value of zero (refraction) as the direction of light penetration inside the film is different. The direction of the ellipsoid looks like a true circle. Therefore, if the liquid crystal display screen is viewed from a specific direction in the oblique direction, there is a case where the hysteresis value becomes zero, and the rainbow-like color spots are concentrically formed around the point. Further, if the angle from the directly above (normal direction) of the film surface to the position of the rainbow-colored stain is set to θ, the larger the birefringence in the film plane, the larger the angle θ becomes. The rainbow-like stains will become more difficult to see. In the case of the biaxially stretched film, since the angle θ tends to be small, it is preferable that the uniaxially stretched film becomes difficult to see a rainbow-like color patch.

However, in the case of a completely uniaxial (uniaxial symmetry) film, the mechanical strength in the direction orthogonal to the alignment direction is remarkably lowered, which is not preferable. The present invention preferably has biaxiality (biaxial symmetry) in a range in which a rainbow-like color patch does not substantially occur or in a range in which a rainbow-like color patch does not occur in a viewing angle range required for a liquid crystal display screen. .

As for the W which is judged by the difficulty of judging the rainbow-like stain, there is a method of evaluating the difference between the hysteresis value (in-plane hysteresis value) and the thickness direction hysteresis value (Rth). The phase difference in the thickness direction means that the film is viewed from the thickness direction of the film. The average of the phase differences obtained by multiplying the two birefringences ΔNxz and ΔNyz by the film thickness d. Since the difference between the in-plane hysteresis value and the thickness direction hysteresis value is smaller, the effect of the birefringence due to the observation angle increases the isotropic property, so the change in the hysteresis value due to the observation angle becomes small. Therefore, it is considered that the rainbow-like color spots due to the observation angle are difficult to produce.

The ratio (Re/Rth) of the hysteresis value to the thickness direction hysteresis value of the polyester film of the present invention is preferably 0.2 or more, more preferably 0.5 or more, still more preferably 0.6 or more. The greater the contrast between the hysteresis value and the thickness direction hysteresis value (Re/Rth), the more the birefringence will increase the isotropic direction, and the generation of rainbow-like color spots caused by the different observation angles will become more difficult. Further, in the case of a completely uniaxial (uniaxial symmetry) film, the ratio of the hysteresis value to the thickness direction hysteresis value (Re/Rth) is 2. However, as described above, with an approximately completely uniaxial (uniaxial symmetry) film, the mechanical strength in a direction orthogonal to the alignment direction is remarkably lowered.

On the other hand, the ratio (Re/Rth) of the hysteresis value to the thickness direction hysteresis value 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 generation of rainbow-like color spots caused by the difference in observation angle, the ratio of the retardation value to the thickness direction phase difference (Re/Rth) need not be 2, and it is sufficient to be 1.2 or less. Moreover, even if the ratio is 1.0 or less, the viewing angle characteristics (about 180 degrees left and right and 120 degrees above and below) required for the liquid crystal display device can be sufficiently satisfied.

When the film forming conditions of the present invention are specifically described, the longitudinal stretching temperature and the lateral stretching temperature are preferably 80 to 130 ° C, particularly preferably 90 to 120 ° C. The longitudinal stretching ratio is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times. Further, the lateral stretching ratio is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. in order to The hysteresis value is controlled within the above range, and it is more preferable to control the ratio of the longitudinal stretching ratio to the lateral stretching ratio. If the difference between the vertical and horizontal stretching ratios is too small, it becomes difficult to produce a hysteresis value difference. Further, in terms of increasing the hysteresis value, setting a low extension temperature is also a preferable correspondence. In the subsequent heat treatment, the treatment temperature is preferably from 100 to 250 ° C, particularly preferably from 180 to 245 ° C.

In order to suppress the variation of the hysteresis value, it is preferable that the thickness unevenness of the film is small. Since the stretching temperature and the stretching ratio have a large influence on the thickness unevenness of the film, it is necessary to optimize the film forming conditions from the viewpoint of thickness unevenness. In particular, if the longitudinal stretching ratio is lowered in order to generate a hysteresis value difference, the value of the vertical thickness unevenness may become high. Since there is a region in which the value of the longitudinal thickness unevenness becomes extremely high in a certain range of the stretching ratio, it is preferable to set the film forming conditions outside the range.

The thickness unevenness of the film of the present invention is preferably 5.0% or less, more preferably 4.5% or less, still more preferably 4.0% or less, and particularly preferably 3.0% or less. The thickness unevenness of the film can be measured by any means, for example, taking a continuous strip sample (length 3 m) in the flow direction of the film, using SEIKO. Measuring machine such as an EM (Millitron 1240) electronic measuring instrument, measuring the thickness of 100 points at intervals of 1 cm, and obtaining the maximum thickness (dmax), the minimum value (dmin), and the average value (d). The thickness can be calculated as the thickness unevenness (%).

Uneven thickness (%) = ((dmax-dmin) / d) × 100

As described above, in order to control the hysteresis value of the film to a specific range, it can be carried out by appropriately setting the stretching ratio or the stretching temperature and the thickness of the film. For example, the higher the difference between the stretching ratio of the longitudinal extension and the lateral extension, the lower the extension temperature, and the thicker the thickness of the film, the easier it is to obtain a high Hysteresis value. On the contrary, the lower the difference between the stretching ratio of the longitudinal extension and the lateral extension, the higher the extension temperature, and the thinner the thickness of the film, the easier it is to obtain a low hysteresis value. Further, the higher the elongation temperature and the lower the total stretching ratio, the easier it is to obtain a film having a low ratio of hysteresis value to retardation value (Re/Rth). On the contrary, the lower the extension temperature is, the higher the total stretching ratio is, the easier it is to obtain a film having a higher ratio of hysteresis value to the retardation value in the thickness direction (Re/Rth). Further, in addition to the control of the hysteresis value, the final film forming conditions must be set in consideration of physical properties required for processing.

The polyester film of the present invention has an arbitrary thickness, but preferably has a range of 15 to 200 μm. Even in the case of a film having a thickness of less than 15 μm, a hysteresis value of 3000 nm or more can be obtained in principle. However, in this case, the directionality of the mechanical properties of the film is remarkable, and cracks, breakage, and the like are likely to occur, and the practicality as an industrial material is remarkably lowered. A particularly preferred lower limit of thickness is 25 μm. On the other hand, the upper limit of the thickness is 200 μm from the viewpoint of practicality as a polarizer protective film. If it exceeds 200 μm, the thickness of the polarizing plate may become too thick. The upper limit of the particularly preferable thickness is 100 μm which is equivalent to that of a general TAC film. In the above thickness range, in order to control the hysteresis value within the scope of the present invention, polyethylene terephthalate which is used as a film substrate is also suitable.

Further, as for the method of blending the ultraviolet absorber in the polyester film of the present invention, a conventional method may be used in combination, for example, by blending a dried ultraviolet absorber by using a kneading extruder in advance. A masterbatch is prepared from a polymer raw material, and a predetermined method of mixing the master batch with a polymer raw material at the time of film formation is blended. The addition weight of the ultraviolet absorber added to the film is preferably from 0.3 to 1.5%, more preferably from 0.4 to 1.0%.

In order to uniformly disperse the ultraviolet absorber and economically blend, it is preferable to set the concentration of the ultraviolet absorber of the master batch to a concentration of 5 to 30% by mass. The conditions for producing the master batch are preferably from 1 to 15 minutes at a temperature at which the extrusion temperature is 290 ° C or more above the melting point of the polyester material, using a kneading extruder. At 290 ° C or higher, the amount of reduction of the ultraviolet absorber becomes large, and the viscosity of the master batch decreases. 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 adjuster, and an antistatic agent may be added as needed.

Further, in the present invention, it is preferred that the film has a multilayer structure of at least three or more layers, and inert particles are added to the surface layer, and an ultraviolet absorber is added to the intermediate layer of the film. A film having a three-layer structure containing inert particles in the surface layer and an ultraviolet absorber in the intermediate layer can be specifically produced as follows. Mixing the masterbatch containing the inert particles and the pellet of the polyester for the outer layer in a specified ratio, and mixing the masterbatch containing the ultraviolet absorber and the pellet of the polyester for the intermediate layer in a specified ratio, drying, and then supplying The well-known melt laminate was extruded into a sheet shape from a slit-shaped die, and cooled and solidified on a casting roll to produce an unstretched film. That is, two or more extruders, three-layer collecting tubes, or confluent sections (for example, confluent sections having rectangular confluences) are used, and a thin film layer constituting the two outer layers and a thin film layer constituting the intermediate layer are laminated, and the metal nozzle is used. Three sheets of the sheet were extruded and cooled on a casting roll to produce an unstretched film. Further, in the present invention, in order to remove foreign matter contained in the polyester of the raw material which causes optical defects, it is preferred to perform high-precision filtration at the time of melt extrusion. Filter particle size of filter media for high-precision filtration of molten resin (initial filtration efficiency 95%) It is preferably 15 μm or less. When the filter particle size of the filter medium exceeds 15 μm, the removal of foreign matter of 20 μm or more is likely to be insufficient.

[Examples]

The present invention is not limited by the following examples, but the present invention is not limited by the following examples, and may be appropriately modified and implemented within the scope of the present invention. The technical scope of the present invention. Further, the evaluation methods of the physical properties in the following examples are as follows.

(1) Hysteresis value (Re)

A parameter defined by the product of the anisotropic refractive index (ΔNxy=|Nx-Ny|) and the film thickness d (nm) (ΔNxy×d) of the orthogonal biaxial refractive index on the film The scale of isotropic and anisotropic. The anisotropy (ΔNxy) of the biaxial refractive index is obtained by the following method. Using two polarizing plates, the direction of the alignment axis of the film was determined, and the direction of the alignment axis was orthogonal, and a rectangle of 4 cm × 2 cm was cut out and used as a sample for measurement. For this sample, an orthogonal biaxial refractive index (Nx, Ny) and a refractive index (Nz) in the thickness direction were obtained by an Abbe refractometer (NAR-4T, manufactured by ATAGO Co., Ltd.), and the above two axes were obtained. The absolute value of the refractive index difference (|Nx-Ny|) is taken as the anisotropy of the refractive index (ΔNxy). The thickness d (nm) of the film was measured using an electric micrometer (manufactured by FEINPRUF, Millitron 1245D), and the unit was converted into nm. The hysteresis value (Re) is obtained by the product of the anisotropy of the refractive index (ΔNxy) and the thickness d (nm) of the film (ΔNxy×d).

(2) Thickness direction hysteresis value (Rth)

The average parameter of the hysteresis value obtained by multiplying the two birefringences ΔNxz (=|Nx-Nz|) and ΔNyz(=|Ny-Nz|) by the film thickness d from the cross section of the film thickness direction is shown. . Nx, Ny, Nz and film thickness d (nm) were obtained by the same method as the measurement of hysteresis value, and the average value of (ΔNxz × d) and (ΔNyz × d) was calculated to obtain the thickness direction hysteresis value. (Rth).

(3) Light transmittance at a wavelength of 380 nm

Using a spectrophotometer (manufactured by Hitachi, Ltd., model U-3500), the light transmittance at a wavelength of 300 to 500 nm was measured with the atmosphere as a standard, and the light transmittance at a wavelength of 380 nm was obtained.

(4) Rainbow spot observation

The polyester film of the present invention is adhered to one side of a polarizer including PVA and iodine so that the absorption axis of the polarizing film is perpendicular to the alignment main axis of the film, and the TAC film is adhered to the opposite surface (Fuji FILM Co., Ltd.) , a thickness of 80 μm), and a polarizing plate was produced. The resulting polarizing plate is arranged in combination with a blue light emitting diode and a crucible. aluminum. A white LED formed by a light-emitting element of a garnet-based yellow phosphor is used as a light source (Nippon Chemical, NSPW500CS) liquid crystal display device (the liquid crystal cell has a polarizing plate having two TAC films as a polarizing mirror protective film on the incident light side) The light exit side is such that the polyester film becomes the visual recognition side. From the front side and the oblique direction of the polarizing plate of the liquid crystal display device, the presence or absence of rainbow spots was determined as follows.

Further, in Comparative Example 3, a backlight source having a cold cathode tube as a light source was used instead of the white LED.

◎: No rainbow spots are produced in any direction.

○: When viewed obliquely, a partially pale rainbow spot was observed.

×: When observed obliquely, the rainbow spot can be clearly observed.

(5) Mechanical strength

The obtained film was cut into a width of 10 mm, and JIS-K-7127 (2000) was used, and the "TENSILON universal testing machine RTA-T-4M" manufactured by ORIENTEC Co., Ltd. was used, and the initial length was 50 mm and the stretching speed was 200 mm/min. Stretching test. Using the first straight line portion of the stress-strain curve obtained by the tensile test, the tensile elastic modulus was obtained by dividing the difference between the stresses at two points on the straight line by the difference between the deformations at the same two points. The measurement was carried out in a standard environment adjusted to a temperature of 23 ± 2 ° C and a relative humidity of 50 ± 15% RH, and was measured in the longitudinal direction and the transverse direction. Regarding the tensile elastic modulus in the longitudinal direction or the transverse direction, the value of any smaller one is 5% or more, and the value is ○, and less than 5% is set to ×.

(6) Thickness of the outermost layer (inert particle-containing layer)

The produced film was cut perpendicularly to the flow direction of the film and embedded with a photohardenable resin. The embedded sample was made into a very thin slice having a thickness of about 70 to 100 nm by a microtome, and dyed in osmium tetroxide vapor for 30 minutes. A cross-sectional observation of the dyed ultrathin section was carried out using a transmission electron microscope (manufactured by JEOL Ltd., TEM2010), and the thickness of the outermost layer (including the inert particle layer) was determined from the position of the inert particles. Further, the observation magnification is appropriately set in the range of 1500 times to 10000 times.

(7) Fog value

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

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

In each of the examples and the comparative examples, a polarizer protective film which was not provided with a coating layer was prepared, and a stylus type three-dimensional roughness meter (SE-3AK, manufactured by Kosaka Research Co., Ltd.) was used, and the radius of the needle was 2 μm. Under the condition of weight of 30mg, the cut-off value is 0.25mm along the length of the film, the length of the measurement is 1mm, and the outermost surface of the film is measured at a needle feeding speed of 0.1mm/sec. The film is divided into 500 points at a pitch of 2μm. The height is read into the three-dimensional roughness analyzer (SPA-11). With respect to the width direction of the film, the same operation was continuously performed 150 times at intervals of 2 μm, that is, across the width direction of the film by 0.3 mm, and the data was read into the analysis device. Next, an analysis device was used to obtain the center plane average roughness (SRa) and the ten point average roughness (SRz).

(9) Average particle diameter of inert particles, number of particles of 10 μm or more

The inert particles were observed with a scanning electron microscope (manufactured by Hitachi, Ltd., model S-510), and the magnification was appropriately changed depending on the size of the particles, and magnified by a photographer. Next, the outer circumference of each particle is mapped to at least 200 randomly selected particles, and the circular equivalent diameter of the particles is measured by a trajectory map using a video analysis device, and the average of these particles is taken as an average particle diameter. Further, the ratio of the particles of 10 μm or more was calculated from the particle diameters of the 200 or more particles thus obtained.

(10) Damage assessment

With respect to the obtained polyester film, the film was drooped in the vertical direction by a film roll having a width of 1 m and a length of 100 m. At this time, the surface layer 100 m of the film roll was removed, and the continuous 100 m was taken as a sample. Next, a matte black cloth was placed on the entire back surface of the film, and from the front, the defective portion (a locally brightened spot) was recognized and marked. Next, a magnifying glass (SCALE LUPE × 10 manufactured by PEAK Co., Ltd.) having a scale of 10 times magnification was used, and the length of the marked portion was measured. The determination was made on the basis of the following criteria.

○ The number of optical defects of 1 mm or more in size is 0/m ²

△ The number of optical defects of 1mm or more in size is 1~3/m ²

× The number of optical defects of 1 mm or more in size is 3/m ² or more

(Manufacturing Example 1 - Polyester A)

The temperature of the esterification reactor was raised, and 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged at a time point of reaching 200 ° C, and 0.017 parts by mass of antimony trioxide and 0.064 parts by mass were charged while stirring. Magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were used as a catalyst. Subsequently, the temperature was raised under pressure, and the pressure esterification reaction was carried out under the conditions of a gauge pressure of 0.34 MPa and 240 ° C. Thereafter, the esterification reaction tank was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Further, the temperature was raised to 260 ° C over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. Then, after 15 minutes, the dispersion treatment was carried out by a high-pressure disperser, and further, an ethylene glycol paste was added at a particle content of 0.2 part by mass, and the ethylene glycol paste was used to make an aqueous solution of sodium tripolyphosphate relative to cerium oxide particles. 0.1% by mass of sodium atom, and 35% of the coarse fraction was cut by centrifugation, and the average particle diameter of 2.3 μm and the pore volume of 1.60 ml/g were filtered by a metal filter of 5 μm mesh. An ethylene glycol paste of cerium oxide particles. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction tank, and a polycondensation reaction was carried out at 280 ° C under reduced pressure.

After completion of the polycondensation reaction, the filter was treated with a 95%-blocking filter of NASLON filter having a diameter of 5 μm, extruded into a strand shape from a nozzle, and cooled by using a cooling water previously subjected to filtration treatment (pore diameter: 1 μm or less). Cured and cut into pellets. The intrinsic viscosity of the obtained polyethylene terephthalate resin (A) was 0.62 dl/g (hereinafter referred to as PET (A)).

(Manufacturing Example 2 - Polyester B)

On the other hand, in the production of the above PET (A), a polyethylene terephthalate resin (B) having an intrinsic viscosity of 0.62 dl/g completely free of cerium oxide particles was obtained. (hereinafter referred to as PET(B))

(Manufacturing Example 3 - Polyester C)

In the production of the above PET (A), a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl/g (C) was obtained by the same method except that cerium oxide particles having an average particle diameter of 2.8 μm were used. . (hereinafter referred to as PET(C))

(Manufacturing Example 4 - Polyester D)

In the production of the above PET (A), a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl/g (D) was obtained by the same method except that cerium oxide particles having an average particle diameter of 3.7 μm were used. . (hereinafter referred to as PET(D))

(Manufacturing Example 5 - Polyester E)

In the production of the above PET (A), a polyethylene terephthalate resin (E) having an intrinsic viscosity of 0.62 dl/g was obtained by the same method except that calcium carbonate particles having an average particle diameter of 0.5 μm were used. (hereinafter referred to as PET(E))

(Manufacturing Example 6 - Polyester F)

Mix 10 parts by mass of dried UV absorber (2,2'-(1,4-phenylene) bis(4H-3,1-benzo) Keto-4-ketone), 90 parts by mass of PET-free (B) (inherent viscosity: 0.62 dl/g), using a kneading extruder to obtain polyethylene terephthalate containing a UV absorber Resin (F) (hereinafter abbreviated as PET (F)).

(Production Example 7 - Modulation of Coating Liquid for Formation of Easy Adhesive Layer)

The transesterification reaction and the polycondensation reaction were carried out by a usual method to prepare 46 mol% of terephthalic acid, 46 mol% of isophthalic acid, and 8 mol of dibasic acid component (for the entire dibasic acid component). % 5-sulfonic acid isophthalic acid sodium, water-dispersible sulfonic acid metal salt having a composition of 50 mol% ethylene glycol and 50 mol% neopentyl glycol as a diol component (for the entire diol component) Base copolyester resin. Next, 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 then heated and stirred. When 77 ° C was reached, 5 was added. The above-mentioned copolymerized polyester resin containing a water-dispersible sulfonic acid metal salt group is further stirred until the resin agglomerates disappear, and the aqueous resin dispersion liquid is cooled to normal temperature to obtain uniform water dispersibility of a solid content concentration of 5.0% by mass. Copolymerized polyester resin solution. Further, after dispersing 3 parts by mass of the aggregated ceria particles (Sylysia 310 manufactured by FUJI SILYSIA Co., Ltd.) in 50 parts by mass of water, 0.54 parts by mass of the above water-dispersible copolymerized polyester resin liquid is added to 0.54 part by weight. Parts by mass of Sylysia An aqueous dispersion of 310 was added with 20 parts by mass of water while stirring to prepare an adhesive modified coating liquid.

(Example 1)

90 parts by mass of the particle-free PET (B) resin ingot and 10 parts by mass of the PET (F) resin ingot containing the ultraviolet absorber were used as a raw material for the base film intermediate layer, and dried under reduced pressure at 135 ° C ( After 6 hours, it is supplied to the extruder 2 (for the intermediate layer II layer), and the PET (A) and the PET (B) are mixed and prepared so that the content of the cerium oxide particles is 0.020% by mass, and is carried out by a usual method. They were dried and supplied to the extruder 1 (for the outer layer I and the outer layer III), and melted at 285 °C. Each of the two types of polymers was filtered with a filter material of a stainless steel sintered body (nominal filtration accuracy of 10 μm particles 95%), and laminated by two types of three-layer joining sections, and extruded into a sheet shape from a metal nozzle, and then used. An electrostatic casting method was applied, and the film was wound on a casting drum having a back surface temperature of 30 ° C to be cooled and solidified to produce an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thickness of the I layer, the II layer, and the III layer was 10:80:10.

Then, the coating liquid for forming an easy-adhesion layer was applied to both surfaces of the unstretched PET film by a reverse roll method so that the coating amount after drying became 0.08 g/m ² , and then dried at 80 ° C for 20 seconds.

The unstretched film formed with the coating layer was guided to a stretcher, and while holding the end of the film with a jig, it was guided to a hot air zone at a temperature of 125 ° C and extended 4.0 times in the width direction. Next, the stretched width was maintained in the width direction, treated at a temperature of 225 ° C for 30 seconds, and then 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 μm.

(Example 2)

A uniaxially oriented PET film having a thickness of about 100 μm was produced by changing the thickness of the unstretched film in the same manner as in Example 1 except that the concentration of the ruthenium dioxide of the outer layer (layers I and III) was changed to 400 ppm.

(Example 3)

The unstretched film produced by the same method as in Example 1 was heated to 105 ° C using a heated roll group and an infrared heater, and then extended by 1.5 times in the traveling direction by a roll group having a peripheral speed difference. A biaxially oriented PET film having a film thickness of about 50 μm was obtained by stretching 4.0 times in the width direction in the same manner as in Example 1.

(Example 4)

A biaxially oriented PET film having a film thickness of about 50 μm was produced in the same manner as in Example 3 except that polyester C was used instead of polyester A in a direction of 2.0 times in the traveling direction and 4.0 times in the width direction.

(Example 5)

In the same manner as in Example 3, except that the polyester C was used in place of the polyester A, the cerium oxide concentration of the outer layer (layers I and III) was changed to 3.0 times in the traveling direction and 4.0 times in the width direction. A biaxially oriented PET film having a film thickness of about 75 μm was obtained.

(Example 6)

In the same manner as in Example 1, the PET resin (B) containing the ultraviolet absorber was not used in the intermediate layer (layer II), and a uniaxially oriented PET film having a film thickness of about 50 μm was obtained.

(Example 7)

A double-axis having a film thickness of about 250 μm was obtained in the same manner as in Example 3 except that the cerium oxide concentration of the outer layer (layers I and III) was changed to 100 ppm in the same manner as in Example 3. Oriented PET film. Although the Re of the obtained film was 4,500 nm or more, since the Re/Rth ratio was less than 0.2, the extremely pale rainbow spot in the oblique direction was recognized.

(Example 8)

Using the same method as in Example 1, a uniaxially oriented PET film having a thickness of about 275 μm was obtained by changing the thickness of the unstretched film.

(Example 9)

The same test as in Example 1 was carried out except that the rainbow spot observation was carried out using a liquid crystal display device using an organic light-emitting diode (OLED) as a light source.

(Comparative Example 1)

In the same manner as in Example 3, a biaxially oriented PET film having a film thickness of about 38 μm was obtained by extending 3.6 times in the traveling direction and 4.0 times in the width direction.

(Comparative Example 2)

A uniaxial alignment having a thickness of about 10 μm was produced by changing the thickness of the unstretched film in the same manner as in Example 1 except that no polyester A was used and no cerium oxide was added to the outer layer (layers I and III). PET film.

(Comparative Example 3)

The same as in the first embodiment except that the light source of the liquid crystal display device was used as a cold cathode tube to perform rainbow spot observation.

(Comparative Example 4)

A uniaxially oriented PET film having a film thickness of about 100 μm was obtained in the same manner as in Example 3 except that polyester D was used instead of polyester A in the same manner as in Example 3, and the film was extended by 4.0 times in the width direction.

(Comparative Example 5)

A uniaxially-oriented PET film having a film thickness of about 75 μm was obtained in the same manner as in Example 1 except that polyester E was used instead of polyester A in the traveling direction by 1.0 times and in the width direction by 3.5 times.

[Industry use possibility]

By using the liquid crystal display device, the polarizing plate, and the polarizer protective film of the present invention, the visibility is not lowered by the rainbow-colored color spots, and the LCD can be made thinner and lower in cost. The possibility of utilization is extremely high.

Claims (10)

A liquid crystal display device having a liquid crystal display device with a backlight source and a liquid crystal cell disposed between two polarizing plates, the backlight source being a white light source having a continuous luminescence spectrum, the polarizing plate being a polarizer protective film A polarizing plate laminated on both sides of the polarizer, at least one of the polarizer protective films has a hysteresis value of 3,000 to 30,000 nm, and a center plane average roughness (SRa) of the outermost surface is 0.008 to 0.02 μm and a ten point average A polyester film having a roughness (SRz) of 0.3 to 1.5 μm. The liquid crystal display device of the first aspect of the invention, wherein the polarizer protective film disposed on the light-emitting side of the polarizing plate on the light-emitting side has a hysteresis value of 3,000 to 30,000 nm and a center surface of the outermost surface. A polyester film having an average roughness (SRa) of 0.008 to 0.02 μm and a ten-point average roughness (SRz) of 0.3 to 1.5 μm. The liquid crystal display device according to claim 1 or 2, wherein a ratio (Re/Rth) of the hysteresis value to the thickness direction hysteresis value of the polyester film is 0.2 or more and 1.2 or less. A polarizing plate for a liquid crystal display device, wherein the polarizer protective film is laminated on a polarizing plate on both sides of the polarizing mirror, wherein at least one of the polarizing mirror protective films has a hysteresis value of 3000 to 30000 nm and a center surface of the outermost surface A polyester film having an average roughness (SRa) of 0.008 to 0.02 μm and a ten-point average roughness (SRz) of 0.3 to 1.5 μm, and a white light source having a continuous luminescence spectrum as a backlight source. A polarizer protective film for a liquid crystal display device comprising a hysteresis value of 3,000 to 30,000 nm and a center plane average of the outermost surface A polyester film having a roughness (SRa) of 0.008 to 0.02 μm and a ten point average roughness (SRz) of 0.3 to 1.5 μm, and a white light source having a continuous luminescence spectrum as a backlight source. The polarizer protective film of claim 5, wherein the ratio of the hysteresis value to the thickness direction retardation value (Re/Rth) of the polyester film is 0.2 or more. A polarizer protective film according to claim 5 or 6, wherein the polyester film has an easy adhesion layer. The polarizer protective film according to any one of claims 5 to 7, wherein the polyester film comprises at least three layers, and the outermost layer contains inert particles having an average particle diameter of 1.0 to 3.5 μm, and the outermost layer is inert. The average particle size of the particles is above. The polarizer protective film according to any one of claims 5 to 8, wherein the outermost layer of the polyester film has an inert particle content of 0.005 to 0.05% by mass, and the polyester film has a haze value of 3% or less. . The polarizer protective film according to any one of claims 5 to 9, wherein the layer other than the outermost layer of the polyester film contains an ultraviolet absorber, and the light transmittance at 380 nm is 20% or less.