TWI750280B - Liquid crystal display device, polarizer and polarizer protective film - Google Patents

Abstract

In order to provide a polarizer protective film as a structural member of a polarizing plate, when a polyethylene terephthalate-based resin film is used in a liquid crystal display device that supports wide color gamut, or when it is thinned The liquid crystal display device, the polarizing plate, and the polarizer protective film, which can suppress the occurrence of rainbow spots and improve the visibility, are also provided.

It is a polarizer protective film, which is a polarizer protective film comprising a polyethylene terephthalate-based resin film, characterized in that the aforementioned polyethylene terephthalate-based resin film satisfies the following (1) and ( 2). (1) The polyethylene terephthalate-based resin film has a retardation amount of 3,000 or more and 30,000 nm or less; (2) The degree of orientation of the (100) plane of the crystal with respect to the film surface measured by X-ray diffraction is 0.70 or less .

Description

Liquid crystal display device, polarizing plate and polarizer protective film

The present invention relates to a liquid crystal display device, a polarizer, and a polarizer protective film.

The polarizers used in liquid crystal display devices (LCDs) are usually constructed by sandwiching a polarizer dyed with iodine such as polyvinyl alcohol (PVA) between two polarizer protective films. Triacetate cellulose is mainly used as the polarizer protective film. Acetate (TAC) membrane. In recent years, along with thinning of LCDs, thinning of polarizing plates has been demanded. However, if the thickness of the TAC film used as a protective film is reduced for this purpose, sufficient mechanical strength cannot be obtained, and there is a problem that moisture permeability deteriorates. In addition, TAC films are very expensive, and polyester films have been proposed as inexpensive alternatives (Patent Documents 1 to 3), but there is a problem that rainbow-like color spots are observed.

When the birefringent oriented polyester film is arranged on one side of the polarizer, the linearly polarized light emitted from the backlight unit or the polarizer changes the polarization state when passing through the polyester film. The transmitted light exhibits an interference color peculiar to the retardation of the product of birefringence and thickness of the oriented polyester film. Therefore, if a discontinuous luminescence spectrum such as a cold cathode tube or a hot cathode tube is used as the light source, the transmitted light intensity varies depending on the wavelength, resulting in rainbow-like color spots (see: Proceedings of the 15th Micro-Optics Conference, No. 30~31 pages).

As a means to solve the above-mentioned problems, some people have proposed to use a white light source with a continuous and wide emission spectrum, such as a white light-emitting diode, as a backlight light source, and also use an oriented polyester film with a certain retardation amount as a polarizer protective film (Patent Reference 4). White light-emitting diodes have a continuous and broad emission spectrum in the visible light region. Therefore, if attention is paid to the envelope shape of the interference color spectrum generated by the transmitted light passing through the birefringent, it is possible to obtain a spectrum similar to the emission spectrum of the light source by controlling the retardation of the oriented polyester film. Can suppress rainbow spots.

prior art literature Patent Literature

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

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

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

Patent Document 4 WO2011/162198

As the backlight source of liquid crystal display devices, the combination of blue light-emitting diodes and yttrium has been widely used in the past. aluminum. A white light-emitting diode (white LED) of a light-emitting element of a garnet-based yellow phosphor (YAG-based yellow phosphor). The emission spectrum of this white light source has a broad spectrum in the visible light region and is also excellent in luminous efficiency, so it is widely used as a backlight light source. However, a liquid crystal display device using this white LED as a backlight light source can only reproduce about 20% of the color of the spectrum that can be recognized by the human eye.

On the other hand, in recent years, the demand for the expansion of the color gamut has increased, so the support of the emission spectrum of the white light source having a clear peak shape in each wavelength region of R (red), G (green), and B (blue) has been developed. Wide color gamut liquid crystal display device. For example, there are developed and used white light sources using quantum dot technology, phosphors using excitation light with clear emission peaks in the R (red) and G (green) regions, and phosphors using blue LEDs A liquid crystal display device that supports wide color gamut for various types of light sources such as white LED light sources of the 3-wavelength method and white LED light sources of the 3-wavelength method. In the case of a liquid crystal display device using a white light source using quantum dot technology as a backlight light source, it is said that more than 60% of the colors of the spectrum discernible to the human eye can be reproduced.

Recently, it is known that these white light sources have a narrower half-height width at the peak than those of conventional light sources including white light-emitting diodes using YAG-based yellow phosphors. When a diester-based resin film is used as a polarizer protective film for a structural member of a polarizing plate, rainbow unevenness may occur depending on the type of light source.

In addition, the expectation for further thinning of the polarizer protective film has grown, and even in such a case, there is a demand for a polyethylene terephthalate-based polyethylene terephthalate system that can further control rainbow irregularities when viewing a display screen from an oblique direction. Resin film (polarizer protective film).

That is, the subject of the present invention is to provide a case where a polyethylene terephthalate-based resin film is used as a polarizer protective film of a liquid crystal display device supporting wide color gamut, or to provide a thin film of the polarizer protective film In the case of a polarizer protective film, a polarizer including the same, and a liquid crystal display device that can suppress the occurrence of rainbow spots.

As a result of earnest review by the present inventors, they have found that the (100) plane of the crystal measured by X-ray diffraction is relative to the film surface, except that the polyethylene terephthalate-based resin film has a specific range of hysteresis. The lower the degree of alignment, the more effective it is in suppressing rainbow spots.

Representative inventions are as follows.

Item 1.

A polarizer protective film is a polarizer protective film comprising a polyethylene terephthalate-based resin film, characterized in that the polyethylene terephthalate-based resin film satisfies the following (1) and (2) ).

(1) The polyethylene terephthalate-based resin film has a retardation amount of 3000 nm or more and 30000 nm or less; (2) The orientation degree of the (100) plane of the crystal with respect to the film surface measured by X-ray diffraction is 0.70 or less .

Item 2.

The polarizer protective film of item 1, wherein the crystal size of the (-105) plane of the crystal measured in the slow axis direction of the polyethylene terephthalate-based resin film is 36 Å or more.

Item 3.

A polarizer, the polarizer protective film of item 1 or 2 is layered on at least one area of the polarizer.

Item 4.

A liquid crystal display device, which is a liquid crystal display device having a backlight source, two polarizers, and a liquid crystal cell disposed between the two polarizers, wherein at least one of the two polarizers is the polarizer of item 3 .

In the case of the liquid crystal display device, polarizing plate, and polarizer protective film of the present invention, even when a polyethylene terephthalate-based resin film serving as a polarizer protective film is used for liquid crystal display that supports wide color gamut In the case of a device, or when it is thinned, it is possible to suppress the occurrence of rainbow unevenness on the display screen.

Form for carrying out the invention 1. Polarizer protective film

The polyethylene terephthalate-based resin film used for the polarizer protective film of the present invention preferably has a retardation amount (Re, in-plane retardation amount) of 3000 nm or more and 30000 nm or less. When the retardation amount is less than 3000 nm, when it is used as a polarizer protective film, a strong interference color is exhibited when viewed from an oblique direction, and good visibility cannot be ensured. The lower limit value of the preferable hysteresis amount is 4000 nm, the next best lower limit value is 5000 nm, and the more preferable lower limit value is 6000 nm.

On the other hand, the upper limit of the hysteresis amount is preferably 30000 nm, and a more preferable upper limit is 10000 nm. When the upper limit of 30000 nm is clearly exceeded, not only the effect of improving the visibility further is not substantially obtained, but also the film thickness becomes considerably thick, and the handleability as an industrial material decreases, which is not good.

The refractive index difference in the film plane (refractive index in the slow axis direction - refractive index in the fast axis direction) is preferably 0.08 or more, more preferably 0.09 or more, and still more preferably 0.10 or more. The upper limit of the difference in refractive index is preferably 0.15 or less. From the viewpoint of further suppressing rainbow unevenness, it is preferable that the refractive index difference in the film plane is large by strong stretching in one direction.

In addition, the hysteresis of the present invention can be obtained by measuring the refractive index and film thickness in the two-axis directions in the film plane, and a commercially available automatic birefringence measurement such as KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.) can also be used. device to find out. The refractive index system in the two-axis direction in the film plane can be determined with an Abbe refractometer (manufactured by Atago, NAR-4T, measurement wavelength: 589 nm).

The polyethylene terephthalate-based resin film used in the polarizer protective film of the present invention has a hysteresis amount in a specific range, and is preferably from the viewpoint of suppressing rainbow unevenness observed from an oblique direction The degree of orientation of the (100) plane of the crystal with respect to the film surface measured by X-ray diffraction was 0.70 or less. The degree of orientation of the (100) plane of the crystal of the polyethylene terephthalate resin film with respect to the film surface is preferably 0.70 or less, more preferably 0.65 or less, more preferably 0.60 or less, more preferably 0.59 or less, More preferably, it is 0.58 or less. The lower limit is preferably 0.40. The degree of orientation of the (100) plane of the crystal with respect to the film surface is an index indicating the orientation around the molecular chain direction (c axis) of the crystal of the polyethylene terephthalate-based resin film. The lower this value, the more random the alignment around the c-axis. The more random the alignment around the c-axis is, the more the rainbow unevenness observed from the oblique direction can be suppressed.

The degree of orientation of the (100) plane of the crystal with respect to the film surface was measured using an X-ray diffraction apparatus (Rigaku Co., Ltd., RINT2100PC) using the diffraction intensity obtained by pole measurement with the slow axis. The direction is the half-width of the axis, and is defined as a parameter of (180-half-width)/180. The unit of width at half maximum is degrees. The slow axis direction of the film can be determined using a molecular alignment meter (manufactured by Oji Scientific Instruments Co., Ltd., MOA-6004 type molecular alignment meter). Details of the measurement of the degree of alignment will be described later in Examples.

The polyethylene terephthalate-based resin film preferably has a crystal size of 36 Å (angstroms) or more on the (-105) plane of the crystal measured in the slow axis direction by X-ray diffraction. The crystal size of the (-105 plane) of the aforementioned crystal is preferably 36 Å or more, more preferably 38 Å or more, and further preferably 39 Å or more. The upper limit is preferably 60 Å, but around 45 Å is sufficient.

It is considered that the molecular chain direction (c-axis direction) of the crystals of the polyethylene terephthalate-based resin film is aligned in the slow axis direction of the film, and the crystal size ratio of the molecular chain direction (c-axis direction) of the crystals When the specific value is large, the alignment around the molecular chain direction axis (c-axis) of the crystal decreases, and it becomes more difficult to generate rainbow-like color spots. The crystal size in the direction of the molecular chain axis of the crystal can be measured as the apparent crystal size of the (-105) plane of the crystal as described below.

The crystal size of the (-105) plane of the crystal measured in the slow axis direction can be obtained from the θ/2θ diffraction intensity curve measured in the slow axis direction using an X-ray diffraction apparatus (Rigaku Co., Ltd., RINT2500). Figure, the diffraction position of the (-105) plane of the crystal and the measured half-height width (B) were read and calculated as the apparent crystal size (ACS) using the following equation (Scherrer's equation). The X-ray used in the measurement is a Cu-Kα line with a wavelength of 1.5418 Å. The crystal size of the (-105) plane of the crystal measured in the slow axis direction in the present invention means the apparent crystal size. (ACS=0.9λ/(βcosθ)). Here, λ is the wavelength of X-ray (1.5418Å), and β is calculated ^{as (B 2} -b ² ) ^1/2 from the measured half-height width (B) and the constant (b) for correction. half-height width. In addition, the constant (b) for correction is the full width at half maximum when the silicon powder NIST640b is measured under the same conditions. β, B, and b are all values in radians.

The in-plane orientation degree of the (-105) plane of the crystal is preferably 0.6 or more, more preferably 0.7 or more, and still more preferably 0.8 or more. The in-plane orientation system of the (-105) plane of the crystal can be measured using an X-ray diffraction apparatus (manufactured by Rigaku Co., Ltd., RINT2500). The measurement system fixed θ/2θ and rotated the sample by 360° using the sample holder for azimuth angle measurement, thereby obtaining the circumferential distribution of the diffraction intensity of the crystal (−105) plane. From the half width of the obtained distribution, a parameter defined by (180-half width)/180 was used as the in-plane alignment degree. The unit of the so-called half-width here is degrees.

In order to align the molecular chain axis direction of the crystals in a uniaxial direction, it is preferable to stretch the film in a uniaxial direction. Generally, in order to increase the degree of orientation in the stretching direction, there are methods of increasing the stretching ratio or lowering the stretching temperature. In addition, when the film-like article is uniaxially stretched, the stress generated inside may be different in the stretching direction, the direction perpendicular to the stretching direction in the film plane, and the thickness direction. In general, it is known that when the dimension in the direction perpendicular to the stretching direction is freed or fixed, as called free-end uniaxial stretching and fixed-end uniaxial stretching, the internal stress is known to increase. very different. This is caused by making the Poisson shrinkage generated during stretching free in the direction perpendicular to the stretching direction, or by suppressing the difference. In the case of transverse stretching in a normal tenter frame, since the ends are clamped by clips, the Boisson shrinkage in the film flow direction (MD) is restricted during transverse stretching. As a result, the transverse tensile direction (TD) is naturally present, and stress is also generated in the flow direction. Since the thickness direction is not limited, it is considered that no stress is generated. That is, it is considered that the stress distribution around the molecular chain axis aligned in the stretching direction is different in the flow direction and the thickness direction, whereby the alignment of the crystallized benzene ring faces progresses. Therefore, in order to reduce the alignment around the molecular chain direction axis (c-axis) of the crystal, it is preferable to equalize the stress around the alignment axis while maintaining the stress and strain in the stretching direction. In essence, the stress does not work in the thickness direction, so it is preferable to reduce the stress in the direction perpendicular to the stretching direction (flow direction).

The polyethylene terephthalate-type resin film of the protective film of this invention can be manufactured according to the manufacturing method of a general polyester film. For example, the polyethylene terephthalate-based resin is melted, extruded and molded into a sheet-like non-aligned polyethylene terephthalate-based resin at a temperature equal to or higher than the glass transition temperature, using a roll. A method of stretching in the transverse direction with a tenter after stretching in the longitudinal direction with a speed difference of 1, and performing heat treatment.

When the film forming conditions of the polyethylene terephthalate-based resin film are specifically described, the longitudinal stretching temperature and the transverse stretching temperature are preferably 100 to 130°C, particularly preferably 110 to 125°C.

When producing a film having a slow axis in the film width direction (TD direction), the longitudinal stretching ratio is preferably 0.7 to 1.0 times. In addition, the lateral stretching ratio is preferably 4.0 to 6.0 times, more preferably 4.0 to 5.5 times, and most preferably 4.5 to 5.5 times.

On the other hand, in the case of producing a film having a slow axis in the film longitudinal direction (MD direction), the transverse stretching ratio is preferably 1.0 to 3.0 times, more preferably 1.5 to 3.0 times, and further preferably 2.0 to 3.0 times. times. The longitudinal stretching ratio is preferably 4.0 to 6.5 times, more preferably 5.0 to 6.0 times. When producing a film having a slow axis in the longitudinal direction of the film, from the viewpoint of reducing the degree of orientation of the (100) plane of the crystal with respect to the film surface, it is preferable to perform longitudinal stretching after transverse stretching.

In order to control the retardation amount within the above-mentioned range, it is preferable to control the ratio of the longitudinal stretching ratio to the transverse stretching ratio, the stretching temperature, and the film thickness. When the difference between the vertical and horizontal draw ratios is too small, it becomes difficult to increase the amount of hysteresis, which is not preferable.

In order to increase the crystal size of the (-105) plane of the crystal, reduce the degree of orientation of the (100) plane of the crystal relative to the film plane, increase the stretching ratio in one direction, and set the stretching temperature to be high. It is preferable to appropriately adjust the wind speed of the hot air so that sufficient heat is applied to the film. The wind speed of the hot air is preferably 6m/sec to 15m/sec, more preferably 8m/sec to 12m/sec. Since the film is stretched in one direction at a high magnification while applying sufficient heat to the film, the stress and strain in the stretching direction can be maintained, the stress around the alignment axis can be equalized, and the crystalline (-105 The crystal size of the ) plane increases, and the degree of orientation of the (100) plane of the crystal relative to the film plane decreases.

In the subsequent heat treatment, the treatment temperature is preferably 150 to 250°C, and particularly preferably 180 to 220°C. From the viewpoint of reducing the degree of orientation of the (100) plane of the crystal with respect to the film plane, the lower the treatment temperature of the heat treatment, the better. On the other hand, from the viewpoint of increasing the crystal size of the (-105) plane of the crystal, the higher the treatment temperature of the heat treatment, the better. Therefore, it is preferable to adjust the two in consideration of the balance.

The polyethylene terephthalate-based resin constituting the polyethylene terephthalate-based resin film is preferably such that 85 mol % or more of the monomer units are ethylene terephthalate. The ethylene terephthalate unit system is preferably 90 mol % or more, more preferably 95 mol % or more. Moreover, a well-known acid component and a glycol component can be contained as a copolymerization component. As a polyethylene terephthalate-type resin, the polyethylene terephthalate of a homopolymer is especially preferable. The ratio of the monomer unit can be ^{confirmed by 1} H-NMR measurement.

These resin-based resins are excellent in transparency, and are also excellent in thermal properties and mechanical properties, and the amount of retardation can be easily controlled by stretching. Polyethylene terephthalate-based materials have high intrinsic birefringence and can relatively easily obtain a large retardation amount even if the film thickness is thin, and are the most suitable materials.

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

In order to set the light transmittance of the protective film of the present invention at a wavelength of 380 nm to 20% or less, it is preferable to appropriately adjust the type, concentration, and film thickness of the ultraviolet absorber. The ultraviolet absorber used by this invention is a well-known thing. Examples of the ultraviolet absorber include organic ultraviolet absorbers and inorganic ultraviolet absorbers, but from the viewpoint of transparency, organic ultraviolet absorbers are preferred. The organic ultraviolet absorber includes benzotriazole-based, benzophenone-based, cyclic imidoester-based, etc., and combinations thereof, but within the range of absorbance specified in the present invention, There is no particular limitation. However, from the viewpoint of durability, benzotriazole-based and cyclic imidoester-based are particularly preferred. When two or more types of ultraviolet absorbers are used in combination, since ultraviolet rays of different wavelengths can be absorbed at the same time, the ultraviolet absorption effect can be further improved.

-4-酮)、2-甲基-3,1-苯并

-4-酮、2-丁基-3,1-苯并

-4-酮、2-苯基-3,1-苯并

-4-酮等。然而，不特別限於此等。 Examples of benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, and acrylonitrile-based ultraviolet absorbers include 2-[2'-hydroxy-5'-(methacryloyloxy) Methyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxyethyl)phenyl]-2H-benzotriazole, 2-[2 '-Hydroxy-5'-(methacryloyloxypropyl)phenyl]-2H-benzotriazole, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-Tetrahydroxybenzophenone, 2,4-di-tert-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-(tertiary butyl)phenol, 2,2'-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole) -2-yl)phenol, etc. Cyclic imidoester-based ultraviolet absorbers include, for example, 2,2'-(1,4-phenylene)bis(4H-3,1-benzophene)

-4-keto), 2-methyl-3,1-benzo

-4-keto, 2-butyl-3,1-benzo

-4-keto, 2-phenyl-3,1-benzo

-4-keto, etc. However, it is not particularly limited to these.

In addition to the ultraviolet absorber, various additives other than the catalyst are preferably contained within a range that does not impair the effects of the present invention. Examples of additives include inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, lightfast agents, flame retardants, thermal stabilizers, antioxidants, and antigelling agents. , surfactants, etc. Moreover, in order to exhibit high transparency, it is also preferable that particle|grains are not substantially contained in a polyethylene terephthalate-type resin film. The term "substantially not containing particles" means, for example, in the case of inorganic particles, 50 ppm or less, preferably 10 ppm or less, particularly preferably less than the detection limit, when the inorganic element is quantified by fluorescent X-ray analysis. content.

As for the method of blending the ultraviolet absorber with the polyethylene terephthalate-based resin film in the present invention, a combination of known methods can be used. The polymer raw materials are blended to make a master batch, and the blending is performed by mixing the predetermined master batch with the polymer raw materials, etc. at the time of film forming.

In this case, in order to uniformly disperse the ultraviolet absorber and blend it economically, the concentration of the ultraviolet absorber in the master batch is preferably a concentration of 5 to 30% by mass. In terms of the conditions for producing the master batch, it is preferable to use a kneading extruder, and the extrusion temperature is higher than the melting point of the polyethylene terephthalate-based resin raw material and 290°C or lower, and it takes 1 to 15 minutes. extrude. At 290°C or higher, the weight loss of the ultraviolet absorber is increased, and the viscosity of the master batch is decreased. When the extrusion 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 necessary.

In the present invention, it is preferable that the film has a multilayer structure of at least three or more layers, and an ultraviolet absorber is added to the intermediate layer of the film. Specifically, the film of the three-layer structure including the ultraviolet absorber in the intermediate layer can be produced as follows. The pellets of polyethylene terephthalate-based resin are used alone as the outer layer, and the masterbatch containing the ultraviolet absorber and the pellets of polyethylene terephthalate-based resin are mixed in a predetermined ratio and dried as an intermediate layer. For layering, it was supplied to a known extruder for fusion lamination, extruded from a slit-shaped die into a sheet shape, cooled and solidified on a casting roll, and an unstretched film was produced. That is, using 2 or more extruders, a 3-layer manifold or a junction block (for example, a junction block with a square junction), the film layers constituting the two outer layers and the film layers constituting the intermediate layer are stacked, and the film layers are formed from the extrusion nozzle. A three-layer sheet was extruded and cooled with a casting roll to produce an unstretched film. Moreover, in this invention, in order to remove the foreign material contained in the polyethylene terephthalate-type resin which becomes the raw material which becomes the cause of an optical defect, it is preferable to perform high precision filtration at the time of melt extrusion. The filter particle size (initial filtration efficiency 95%) of the filter medium used for high-precision filtration of molten resin is preferably 15 μm or less. When the filter particle size of a filter medium exceeds 15 micrometers, the removal of the foreign material of 20 micrometers or more tends to become inadequate.

In addition, in order to improve the adhesiveness with a polarizer, a corona treatment, a coating treatment, a flame treatment, etc. may be applied to the polyethylene terephthalate-based resin film of the present invention.

In the present invention, in order to improve the adhesiveness with the polarizer, it is preferable that at least one side (preferably the side in contact with the polarizer) of the film of the present invention has a polyester resin, a polyurethane An easy-bonding layer in which at least one of an ester resin or a polyacrylic resin is a main component. Here, the "main component" refers to a component of 50 mass % or more of the solid components constituting the easily bonded layer. The coating liquid used for the formation of the easily adhesive layer of the present invention is preferably an aqueous coating liquid containing at least one of water-soluble or water-dispersible copolyester resins, acrylic resins and polyurethane resins . Examples of such coating liquids include aqueous solutions disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, and Japanese Patent No. 4150982. Copolymerized polyester resin solution, acrylic resin solution, polyurethane resin solution, etc.

The easily bonding layer can be obtained by applying the coating liquid to one side or both sides of an unstretched film or a longitudinally uniaxially stretched film, drying at 100 to 150° C., and further stretching in the transverse direction. The coating amount of the final easy-bonding layer is preferably controlled to be 0.05 to 0.20 g/m ² . When the coating amount is less than 0.05 g/m ² , the adhesiveness with the obtained polarizer may become insufficient. On the other hand, when the coating amount exceeds 0.20 g/m ² , the sticking resistance may decrease. When the easily bonding layers are provided on both sides of the polyethylene terephthalate-based resin film, the coating amounts of the easily bonding layers on both sides may be the same or different, and can be independently set within the above range.

In the easily bonding layer, it is preferable to add particles for the purpose of imparting slipperiness. 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 tend to fall off the coating layer. Examples of particles to be contained in the easily bonding layer include titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, oxide Inorganic particles such as zirconium, tungsten oxide, lithium fluoride, and calcium fluoride, or organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles, etc. These may be added to the easily bonding layer alone or in combination of two or more.

In addition, a well-known method can be used for the method of apply|coating a coating liquid. For example, a reverse roll coating method, a gravure coating method, a coincidence coating method, a roll brush method, a spray coating method, an air knife coating method, a wire bar coating method, a pipe doctor method, etc. are mentioned, and these methods can be used. Do it alone or in combination.

In addition, the measurement of the average particle diameter of the said particle|grains was performed according to the following method. The particles are photographed with a scanning electron microscope (SEM), and the maximum diameter (the distance between the two farthest points) of 300 to 500 particles is measured at a magnification of 2 to 5 mm with the size of one smallest particle. The average value was taken as the average particle size.

Although the thickness of the polyethylene terephthalate-type resin film of this invention is arbitrary, it is preferable that it is the range of 30-300 micrometers. In principle, a hysteresis amount of 3000 nm or more can be obtained even for a film with a thickness of less than 30 μm. However, in this case, the anisotropy of the mechanical properties of the film becomes obvious, and cracking, breakage, etc. tend to occur, and the practicality as an industrial material is remarkably reduced. A preferable lower limit of thickness is 40 μm, and a particularly preferable lower limit of thickness is 45 μm. On the other hand, if the upper limit of the thickness of the polarizer protective film exceeds 300 μm, the thickness of the polarizing plate becomes too thick, which is not preferable. From the viewpoint of practicality as a polarizer protective film, the upper limit of the thickness is preferably 200 μm, more preferably 120 μm, more preferably 100 μm or less, still more preferably 80 μm or less, still more preferably 65 μm or less, and still more preferably 60 μm or less, more preferably 55 μm or less.

In order to suppress fluctuations in the amount of hysteresis, it is preferable that the thickness unevenness of the film is small. Since the stretching temperature and the stretching ratio greatly affect the thickness unevenness of the film, it is also preferable to optimize the film forming conditions from the viewpoint of the thickness unevenness. In particular, when the longitudinal stretch ratio is lowered in order to increase the amount of retardation, the thickness unevenness in the longitudinal direction may be deteriorated. Since there is a region where the thickness unevenness in the longitudinal direction becomes very poor within a certain range of the draw ratio, it is preferable to set the film forming conditions to exclude this 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 polyethylene terephthalate-based resin film preferably has a ratio (Re/Rth) of retardation (Re) to thickness-direction retardation (Rth) of 0.2 or more, more preferably 0.5 or more, still more preferably is 0.6 or more. From the viewpoint of suppressing rainbow unevenness when viewed from an oblique direction, the larger the ratio (Re/Rth), the better. The upper limit of the ratio (Re/Rth) is preferably 2.0 or less, more preferably 1.8 or less. On the other hand, it is preferable that the upper limit of the said ratio (Re/Rth) is less than 1.0 from a viewpoint of thickness unevenness and planarity. In addition, the retardation in the thickness direction is obtained by multiplying the two birefringences ΔNxz (=|nx-nz|) and ΔNyz (=|ny-nz|) by the film thickness d, respectively, when viewed from a cross section in the film thickness direction The parameter that represents the average of the hysteresis. The thickness direction hysteresis amount (Rth) can be obtained by calculating the average value of (ΔNxz×d) and (ΔNyz×d) by obtaining nx, ny, nz, and the film thickness d (nm). In addition, nx, ny, and nz were calculated|required by an Abbe refractometer (made by Atago, NAR-4T, measurement wavelength 589nm).

2. Polarizer

The polarizing plate of the present invention preferably has a structure in which a polarizer protective film is attached to at least one side of a polarizer dyed with iodine such as polyvinyl alcohol (PVA), and any polarizer protective film of the present invention described above polarizer protective film. As the polarizer protective film on the other side, it is preferable to use a film without birefringence such as a TAC film, an acrylic film, or a norbornene-based film. Alternatively, there may be no polarizer protective film on the other side. For the polarizing plate used in the present invention, it is also preferable to apply various hard coats on the surface for the purpose of preventing reflection, suppressing glare, and suppressing scratches.

3. Liquid crystal display device

Generally speaking, a liquid crystal panel is composed of a rear module, a liquid crystal cell, and a front module in the order from the side (viewable side) opposite to the backlight source where the image is displayed laterally. The rear module and the front module are generally composed of a transparent substrate, a transparent conductive film formed on the side surface of the liquid crystal cell, and a polarizer arranged on the opposite side. Here, the polarizing plate is arranged on the side opposite to the backlight light source in the rear module, and is arranged on the side (viewable side) where the image is displayed in the front module.

The liquid crystal display device of the present invention includes at least a backlight light source and a liquid crystal cell arranged between two polarizers as structural members. In addition, other structures other than these, for example, a color filter, a fluorine film, a diffusion sheet, an antireflection film, etc., may be suitably provided. Preferably, among the aforementioned two polarizing plates, at least one polarizing plate is the aforementioned polarizing plate of the present invention.

The structure of the backlight may be an edge light type in which a light guide plate or a reflection plate is used as a structural member, or a direct type type.

The backlight source of the liquid crystal display device is not particularly limited. For example, the backlight source may be a white LED combined with a phosphor (ie, an element that emits white light by combining a light emitting diode that emits blue light or ultraviolet light using a compound semiconductor and a phosphor). As far as phosphors are concerned, there is yttrium. aluminum. Garnet is a yellow phosphor or scorpion. aluminum. Garnet-based yellow phosphors, etc.

In one embodiment, the backlight light source is preferably a white light source having a peak top of an emission spectrum in each wavelength region of 400 nm or more and less than 495 nm, 495 nm or more and less than 600 nm, and 600 nm or more and 780 nm or less. Examples include white light sources using quantum dot technology, phosphor systems using phosphors that have emission peaks in R (red) and G (green) regions by excitation light, and blue LEDs, respectively. the white LED light source, a white LED light source three-wavelength mode, the combination of a red laser light source is a white LED, for example, other experiments using the formula K ₂ SiF _6: Mn ⁴⁺ phosphor of fluoride (also referred to as "KSF ”), etc., and white LED light sources with blue LEDs, etc. These are attracting attention as backlight light sources for liquid crystal display devices supporting a wide color gamut.

The arrangement in the liquid crystal display device of the polarizer protective film of the present invention having the specific hysteresis is not particularly limited, but it is preferable to arrange a polarizer and a liquid crystal cell arranged on the incident light side (light source side). , and in the case of a liquid crystal display device with a polarizing plate arranged on the light-emitting side (visible side), a polarizer protective film arranged on the incident light side of the polarizing plate on the incident light side, and/or arranged on the light-emitting side The polarizer protective film on the outgoing light side of the polarizing plate is a polarizer protective film including a polyethylene terephthalate-based resin film having the specific retardation amount. In a particularly preferred embodiment, the polarizer protective film disposed on the light-emitting side of the polarizing plate on the light-emitting side is a polyethylene terephthalate-based resin film having the specific retardation amount. When the polyethylene terephthalate-type resin film is arrange|positioned in the position other than the above, the polarization characteristic of a liquid crystal cell may be changed. It is not preferable to use the polymer film of the present invention where polarizing properties are required, so it is preferable to use it as a protective film for a polarizing plate in such a specific position.

[Example]

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples, and can be implemented with appropriate modifications within the scope of the gist of the present invention. Included in the technical scope of the present invention. In addition, evaluation methods of physical properties in the following examples are as follows.

(1) Hysteresis (Re)

The retardation refers to a parameter defined as the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy=|nx-ny|) and the film thickness d (nm) of the orthogonal biaxial on the film, is a measure of optical isotropy or anisotropy. Biaxial refractive index anisotropy (ΔNxy) was obtained by the following method. The slow axis direction of the film was determined using a molecular orientation meter (MOA-6004 type molecular orientation meter, manufactured by Oji Scientific Instruments Co., Ltd.), and a rectangle of 4 cm × 2 cm was cut out so that the slow axis direction was parallel to the long side of the sample for measurement. as a sample for measurement. For this sample, the refractive index of the orthogonal biaxial (refractive index in the slow axis direction: ny, the refractive index in the slow axis direction: ny) The refractive index in the direction: nx) and the refractive index in the thickness direction (nz), and the absolute value of the biaxial refractive index difference (|nx-ny|) was regarded as the refractive index anisotropy (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 retardation amount (Re) was obtained from the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy) and the film thickness d (nm).

(2) Thickness direction hysteresis (Rth)

The retardation in the thickness direction refers to the expression obtained by multiplying the two birefringences ΔNxz (=|nx-nz|) and ΔNyz (=|ny-nz|) by the film thickness d when viewed from a cross section in the film thickness direction. The parameter for averaging the hysteresis. The thickness direction hysteresis (Rth) was obtained by calculating the average value of (ΔNxz×d) and (ΔNyz×d) by the same method as the measurement of hysteresis. ).

(3) Orientation of the (100) plane of the crystal with respect to the film plane

The degree of orientation of the (100) plane of the crystal with respect to the film surface was determined by using an X-ray diffraction apparatus (manufactured by Rigaku Co., Ltd., RINT2100PC) from the diffraction intensity obtained by the pole measurement with the slow axis direction as the axis. Half-height width, parameter defined by (180-half-height width)/180. The X-ray used in the measurement is a Cu-Kα line with a wavelength of 1.5418 Å. The pole measurement was carried out according to the Schulz reflection method by installing a RINT2000 goniometer (Goniometer) which can be mounted on a RINT2100PC and a multipurpose test stage for poles. The sample was cut out into a circular shape with a diameter of 5 cm, and was mounted on the sample stage so that the slow axis direction was aligned with the directions of β=90 degrees and 270 degrees. In addition, the slow-axis direction of a sample was calculated|required using the molecular orientation meter (Oji Scientific Instruments Co., Ltd. make, MOA-6004 type molecular orientation meter). The details of the measurement conditions are that the tube voltage is set to 40 kV, the tube current is set to 40 mA, the 2θ fixed angle is set to 25.830 degrees, the divergence vertical limit is set to 1.2 mm, the divergence slit is set to 1 degree, and the scattering slit is set to 1 degree. It was set to 7 mm, and the light-receiving slit was set to 7 mm. In the transmission measurement, α start angle = 0 degrees, α end angle = 35 degrees, and α step angle = 5 degrees. In reflection measurement, α start angle=25 degrees, α end angle=90 degrees, and α step angle=5 degrees. The scanning method is in concentric circles with β start angle = 0 degrees, β end angle = 360 degrees, and β step angle = 5 degrees.

Below, the calculation method of the orientation degree of the (100) plane of a crystal with respect to a film surface is shown. The reflection and diffraction intensity graphs of β=0 degrees and β=180 degrees obtained in the measurement are defined as I(α) (25≦α≦90). The horizontal axis is α' (α'=α when β=0 degrees, α'=180-α when β=180 degrees), and the vertical axis is the diffraction intensity of each α', thereby connecting β= Diffraction intensity graphs at 0 degrees and 180 degrees are obtained to obtain diffraction intensity graph I(α') (25≦α'≦155). At this time, the average value of β=0 degrees and β=180 degrees was used for the diffraction intensity of α'=90 degrees. The straight line connecting the diffraction intensities at α' = 25 degrees and 155 degrees is subtracted as the bottom line, and the half-height width is used from the obtained diffraction intensity graph, and the crystal is calculated by (180-half-height width)/180 The degree of orientation of the (100) plane relative to the film plane. The unit of width at half maximum is degrees.

(4) Crystal size of the (-105) plane of the crystal

The crystal size of the (-105) plane of the crystal in the slow axis direction of the film is obtained from the θ/2θ diffraction intensity graph measured in the slow axis direction using an X-ray diffraction apparatus (manufactured by Rigaku Co., Ltd., RINT2500). , read the measured half-height width (B) of the diffraction peak at the diffraction position (2θ=42.7 degrees) of the (-105) plane of the crystal, and use the following formula (Scherer equation) to calculate the apparent crystal size (ACS) form to calculate. The X-ray used in the measurement is a Cu-Kα line with a wavelength of 1.5418 Å. In addition, the bottom line is defined as a line connecting two points with a straight line between the point where the diffraction intensity is the smallest between 30 degrees and 42.7 degrees in 2θ, and the point where the diffraction intensity is the smallest between 42.7 degrees and 50 degrees. (ACS=0.9λ/(βcosθ)). Here, λ is the wavelength of X-ray (1.5418Å), β is the measured half-height width (B) read by the system and the constant (b) for correction, which is calculated by (B ² -b ² ) ^1/2 Calculated half-height width. In addition, the constant (b) for correction is the full width at half maximum when the silicon powder NIST640b is measured under the same conditions. Here, β, B, and b are all values in units of radians. In addition, the slow-axis direction of a sample was calculated|required using the molecular orientation meter (Oji Scientific Instruments Co., Ltd. make, MOA-6004 type molecular orientation meter).

(5) Rainbow spot observation

A polyethylene terephthalate film prepared by the method described later was attached to one side of the polarizer containing PVA and iodine so that the absorption axis of the polarizer and the alignment principal axis of the film were perpendicular, and the opposite side was A commercially available TAC film was attached to prepare a polarizing plate including a polyethylene terephthalate film/polarizer/TAC film. The polarizing plate originally existing on the light-emitting side of a commercially available liquid crystal display device (BRAVIA KDL-40W920A manufactured by SONY) was replaced with the obtained polarizing plate. Moreover, the polarizing plate was replaced so that a polyethylene terephthalate film might become the visible side so that the absorption axis of the polarizing plate would coincide with the absorption axis direction of the polarizing plate originally attached to the liquid crystal display device. The aforementioned liquid crystal display device includes a light source for emitting excitation light and a backlight light source including quantum dots. The emission spectrum of the backlight light source of this liquid crystal display device was measured using a multi-channel spectroscope PMA-12 manufactured by Hamamatsu Photonics. As a result, emission spectra with peaks near 450 nm, 528 nm, and 630 nm were observed, and the half width of each peak was 16 nm. ~34nm. In addition, the exposure time at the time of measuring a spectrum was made into 20 msec.

The liquid crystal display device produced in this way was made to display a white image, and was visually observed from the front of the display and from an oblique direction, and the occurrence of rainbow spots was determined according to the following criteria. The observation angle is defined as the angle between a line drawn from the center of the screen of the display in the normal direction (vertical) and a straight line connecting the center of the display and the position of the eyes during observation.

⊚: Rainbow spots are not observed in the range of the observation angle of 0 to 65 degrees.

○: Some rainbow spots are observed in the range of the observation angle of 0 to 65 degrees.

×: Rainbow spots are observed in the range of the observation angle of 0 to 65 degrees.

(Production Example 1 - Polyester A)

, when the temperature of the esterification reactor reached 200°C, 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were fed, and 0.017 parts by mass of antimony trioxide and acetic acid were fed as catalysts while stirring. 0.064 parts by mass of magnesium tetrahydrate and 0.16 parts by mass of triethylamine. Then, after pressurizing and raising the temperature, and performing a pressurized esterification reaction under the conditions of a gauge pressure of 0.34 MPa and 240° C., the esterification reactor was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. The temperature was further raised to 260° C. over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. Then, after 15 minutes, dispersion treatment was performed with a high-pressure disperser, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction vessel, and a polycondensation reaction was performed at 280° C. under reduced pressure.

After the polycondensation reaction is completed, it is filtered with a filter made of naslon with a 95% cut-off diameter of 5 μm, extruded from a nozzle into strands, and filtered in advance using a filter (pore size: 1 μm or less). ) was cooled with cooling water, solidified, and cut into pellets. The intrinsic viscosity of the obtained polyethylene terephthalate resin (A) was 0.62 dl/g, and the inactive particles and internally precipitated particles were not substantially contained. (Hereinafter abbreviated as PET(A).)

(Production Example 2 - Polyester B)

-4-酮)10質量份、實質上不含有粒子的PET(A)(固有黏度為0.62dl/g)90質量份混合，並使用混練擠出機，得到了含有紫外線吸收劑的聚對苯二甲酸乙二酯樹脂(B)。(以下簡記為PET(B)。) The dried UV absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzoyl)

-4-keto) 10 parts by mass, and 90 parts by mass of PET (A) (intrinsic viscosity: 0.62 dl/g) substantially free of particles were mixed, and kneaded using a kneading extruder to obtain a UV absorber-containing polyparaphenylene Ethylene Diformate Resin (B). (hereinafter abbreviated as PET(B).)

(Manufacturing Example 3 - Adjustment of Adhesion-Modifying Coating Liquid)

Transesterification reaction and polycondensation reaction were carried out by common methods to prepare a water-dispersible sulfonic acid metal salt group-containing copolyester resin, the composition of which was as a dibasic acid component (with respect to the entire dibasic acid component) 46 mol % of phthalic acid, 46 mol % of isophthalic acid, and 8 mol % of sodium isophthalic acid-5-sulfonate, as diol components (with respect to the whole diol component) Ethylene glycol was 50 mol % and neopentyl glycol was 50 mol %. Then, after mixing 51.4 parts by mass of water, 38 parts by mass of isopropanol, 5 parts by mass of n-butyl cellosolve, and 0.06 parts by mass of nonionic surfactant, the mixture was heated and stirred, and when the temperature reached 77°C, the above water dispersibility was added. After 5 parts by mass of the copolyester resin containing a sulfonic acid metal salt group, stirring was continued until there was no agglomeration of the resin, the aqueous resin dispersion was cooled to normal temperature, and uniform water dispersibility with a solid content concentration of 5.0 mass % was obtained. Copolyester resin liquid. Further, after dispersing 3 parts by mass of aggregated silica particles (manufactured by Fuji Silysia Co., Ltd., Sylysia 310) in 50 parts by mass of water, 0.54 parts by mass of an aqueous dispersion of Sylysia 310 was added to 99.46 parts by mass of the above-mentioned water-dispersible copolyester resin solution. 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 (A) resin pellets containing no particles and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber as raw materials for the intermediate layer of the base film were dried under reduced pressure (1 Torr) at 135°C. ) After 6 hours, it was supplied to extruder 2 (for intermediate layer II), and the PET (A) was dried by a conventional method and supplied to extruder 1 (for outer layer I and outer layer III), respectively, and Melt at 285°C. The two kinds of polymers were filtered with a stainless steel sintered filter material (nominal filtration accuracy 10μm particle 95% interception), and layered in two kinds of three-layer confluence blocks, extruded into sheets from the extrusion port, and cast by electrostatic application. It was cooled and solidified on a casting drum having a surface temperature of 30° C. by the method of winding, and an unstretched film was produced. 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, on both sides of the unstretched PET film by the reverse roll method, the above-mentioned adhesive-improving coating liquid was ^{applied so that the coating amount after drying would be 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 guided to a tenter stretching machine, and while the end of the film was clamped with a clip, it was guided to a hot air zone with a temperature of 110° C. and a wind speed of 12 m/sec at the hot air outlet, It stretched to 4.0 times in the width direction (TD) and 0.7 times in the film flow direction (MD). Next, while maintaining the width stretched in the width direction, heat treatment was performed in a hot air zone with a temperature of 200° C. and a wind speed of a hot air outlet of 10 m/sec, and a relaxation treatment was further performed by 3% in the width direction to obtain A uniaxially oriented PET film with a film thickness of about 50 μm was prepared.

(Example 2)

The unstretched film produced in the same manner as in Example 1 was guided to a tenter stretching machine, and the end of the film was clamped with clips, and the film was guided to a temperature of 125° C. and the wind speed of the hot air outlet was 10 m/sec. The hot air area of the clock is stretched to 4.5 times in the width direction. Next, while maintaining the width stretched in the width direction, heat treatment was performed in a hot air zone with a temperature of 200° C. and a wind speed of a hot air outlet of 10 m/sec, and a relaxation treatment was further performed by 3% in the width direction to obtain A uniaxially oriented PET film with a film thickness of about 80 μm was prepared.

(Example 3)

The unstretched film produced in the same manner as in Example 1 was guided to a tenter stretching machine, and the end portion of the film was clamped with clips, and the film was guided to a temperature of 120° C. and a hot air outlet with a wind speed of 12 m/sec. The hot air area of the clock is stretched to 4.5 times in the width direction. Next, while maintaining the width stretched in the width direction, heat treatment was performed in a hot air zone with a temperature of 200° C. and a wind speed of a hot air outlet of 10 m/sec, and a relaxation treatment was further performed by 3% in the width direction to obtain A uniaxially oriented PET film with a film thickness of about 100 μm was prepared.

(Example 4)

The unstretched film produced in the same manner as in Example 1 was guided to a tenter stretching machine, and the end of the film was clamped with clips, and the film was guided to a temperature of 130° C. and the wind speed of the hot air outlet was 9 m/sec. The hot air area of the clock is stretched to 5.5 times in the width direction. Next, while maintaining the width stretched in the width direction, heat treatment was performed in a hot air zone with a temperature of 200° C. and a wind speed of a hot air outlet of 10 m/sec, and a relaxation treatment was further performed by 3% in the width direction to obtain A uniaxially oriented PET film with a film thickness of about 60 μm was prepared.

(Example 5)

The unstretched film produced in the same manner as in Example 1 was guided to a tenter stretching machine, and the end of the film was clamped with clips, and the film was guided to a temperature of 125° C. and the wind speed of the hot air outlet was 10 m/sec. The hot-air zone of the clock was stretched to 5.0 times in the width direction and 0.9 times in the flow direction. Next, while maintaining the width stretched in the width direction, heat treatment was performed in a hot air zone with a temperature of 200° C. and a wind speed of a hot air outlet of 10 m/sec, and a relaxation treatment was further performed by 3% in the width direction to obtain A uniaxially oriented PET film with a film thickness of about 60 μm was prepared.

(Example 6)

The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and the end of the film was clamped with clips, and the film was guided to a temperature of 120° C. and the wind speed of the hot air outlet was 10 m/sec. The hot-air zone of the clock is stretched to 5.0 times in the width direction. Next, while maintaining the width stretched in the width direction, heat treatment was performed in a hot air zone with a temperature of 200° C. and a wind speed of a hot air outlet of 10 m/sec, and a relaxation treatment was further performed by 3% in the width direction to obtain A uniaxially oriented PET film with a film thickness of about 40 μm was prepared.

(Example 7)

The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and the end of the film was clamped with clips, and the film was guided to a temperature of 110° C. and the wind speed of the hot air outlet was 12 m/sec. The hot air area of the clock is stretched to 4.5 times in the width direction. Next, while maintaining the width stretched in the width direction, heat treatment was performed in a hot air zone with a temperature of 200° C. and a wind speed of a hot air outlet of 10 m/sec, and a relaxation treatment was further performed by 3% in the width direction to obtain A uniaxially oriented PET film with a film thickness of about 125 μm was prepared.

(Example 8)

The unstretched film produced in the same manner as in Example 1 was guided to a tenter stretching machine, and the end of the film was clamped with clips, and the film was guided to a temperature of 115° C. and the wind speed of the hot air outlet was 10 m/sec. The hot air area of the clock is stretched to 4.5 times in the width direction. Next, while maintaining the width stretched in the width direction, heat treatment was performed in a hot air zone with a temperature of 200° C. and a wind speed of a hot air outlet of 10 m/sec, and a relaxation treatment was further performed by 3% in the width direction to obtain A uniaxially oriented PET film with a film thickness of about 60 μm was prepared.

(Example 9)

The unstretched film produced in the same manner as in Example 1 was guided to a tenter stretching machine, and the end portion of the film was clamped with clips, and the film was guided to a temperature of 120° C. and a hot air outlet with a wind speed of 12 m/sec. The hot air area of the clock is stretched to 5.0 times in the width direction. Next, heat treatment was performed in a hot air zone with a temperature of 130° C. and a wind speed of a hot air outlet of 10 m/sec while maintaining the width stretched in the width direction, and further relaxation treatment was performed by 3% in the width direction to obtain A uniaxially oriented PET film with a film thickness of about 50 μm was prepared.

(Comparative Example 1)

The unstretched film produced in the same manner as in Example 1 was guided to a tenter stretching machine, and the end of the film was clamped with clips, and the film was guided to a temperature of 125° C. and the wind speed of the hot air outlet was 5 m/sec. The hot air area of the clock is stretched to 4.0 times in the width direction. Next, heat treatment was performed in a hot air zone with a temperature of 225° C. and a wind speed of a hot air outlet of 5 m/sec while maintaining the width stretched in the width direction, and further relaxation treatment was performed by 3% in the width direction to obtain A uniaxially oriented PET film with a film thickness of about 50 μm was prepared.

(Comparative Example 2)

The unstretched film produced in the same manner as in Example 1 was guided to a tenter stretching machine, and the end of the film was clamped with clips, and the film was guided to a temperature of 95° C. and the wind speed of the hot air outlet was 10 m/sec. The hot air area of the clock is stretched to 4.0 times in the width direction. Next, heat treatment was performed in a hot air zone with a temperature of 150° C. and a wind speed of a hot air outlet of 10 m/sec while maintaining the width stretched in the width direction, and further relaxation treatment was performed by 3% in the width direction to obtain A uniaxially oriented PET film with a film thickness of about 60 μm was prepared.

(Comparative Example 3)

The unstretched film produced in the same manner as in Example 1 was heated to 105° C. using a heated roll group and an infrared heater, and then stretched 1.5 times in the traveling direction with a roll group having a peripheral speed difference. , was guided to a hot air zone with a temperature of 100° C. and a hot air outlet with a wind speed of 10 m/sec, and stretched to 4.0 times in the width direction. Next, heat treatment was performed in a hot air zone with a temperature of 200° C. and a wind speed of a hot air outlet of 10 m/sec while maintaining the width stretched in the width direction, and further relaxation treatment was performed by 3% in the width direction to obtain A biaxially oriented PET film with a film thickness of about 50 μm was prepared.

(Comparative Example 4)

The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and the end of the film was clamped with clips, and the film was guided to a temperature of 90° C. and the wind speed of the hot air outlet was 10 m/sec. The hot air area of the clock is stretched to 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, heat treatment was performed in a hot air zone with a temperature of 200° C. and a wind speed of a hot air outlet of 10 m/sec, and a relaxation treatment was further performed by 3% in the width direction to obtain A uniaxially oriented PET film with a film thickness of about 50 μm was prepared.

(Comparative Example 5)

The unstretched film produced in the same manner as in Example 1 was heated to 105° C. using a heated roll group and an infrared heater, and then stretched 3.5 times in the traveling direction with a roll group having a peripheral speed difference. , led to a tenter stretching machine, and while sandwiching the end of the film with clips, led to a hot air zone with a temperature of 130°C and a wind speed of 10 m/sec at the hot air outlet, and stretched so that the film was stretched in the width direction. becomes 4.0 times. Next, heat treatment was performed in a hot air zone with a temperature of 220° C. and a wind speed of a hot air outlet of 10 m/sec while maintaining the width stretched in the width direction, and further relaxation treatment was performed by 3% in the width direction to obtain A biaxially oriented PET film with a film thickness of about 100 μm was prepared.

For the PET films of Examples 1 to 9 and Comparative Examples 1 to 5, the results of physical properties, X-ray structure analysis, and rainbow spot observation are shown in Table 1 below. In addition, the PET film systems obtained in Examples 2 to 4 and 6 to 9 had Re/Rth of less than 1 and were excellent in film flatness.

Industrial Availability

In the case of the liquid crystal display device, polarizing plate, and polarizer protective film of the present invention, even when a polyethylene terephthalate-based resin film serving as a polarizer protective film is used for liquid crystal display that supports wide color gamut In the case of a device, or when it is thinned, the occurrence of rainbow irregularities observed on the display screen can be suppressed.

Claims (4)

A polarizer protective film is a polarizer protective film comprising a polyethylene terephthalate resin film, characterized in that the polyethylene terephthalate resin film satisfies the following (1) and ( 2), (1) The polyethylene terephthalate resin film has a retardation of more than 3000 nm and less than 30000 nm; (2) The degree of orientation of the (100) plane of the crystal relative to the film surface measured by X-ray diffraction is 0.70 or less. The polarizer protective film according to claim 1, wherein the crystal size of the (-105) plane of the crystal measured in the slow axis direction of the polyethylene terephthalate-based resin film is 36 Å or more. A polarizer is provided with the polarizer protective film of claim 1 or 2 on at least one area of the polarizer. A liquid crystal display device, which is a liquid crystal display device having a backlight source, two polarizers, and a liquid crystal cell arranged between the two polarizers, at least one of the two polarizers is polarized light as claimed in claim 3 plate.