TWI795086B - Liquid crystal display device, polarizing plate, and polyethylene terephthalate-based resin film - Google Patents

Abstract

The problem is to provide a method of using a polyethylene terephthalate-based resin film in a liquid crystal display device supporting a wide color gamut even in a polarizer protective film that is a structural member of a polarizing plate, or making it thinner. Even in this case, a liquid crystal display device, a polarizing plate, and a protective film for polarizers can suppress the occurrence of iridescent spots and improve visibility. The solution is a polarizer protective film, which 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-based resin film has a retardation of 3,000 to 30,000 nm; (2) The orientation degree of the (100) plane of the crystal relative to the film surface measured by X-ray diffraction is 0.70 or less .

Description

Liquid crystal display device, polarizing plate, and polyethylene terephthalate-based resin film

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

Polarizers used in liquid crystal displays (LCDs) generally have a structure in which a polarizer dyed with iodine such as polyvinyl alcohol (PVA) is sandwiched between two polarizer protective films. As the polarizer protective film, triacetate fiber is mainly used prime (TAC) film. In recent years, along with the thinning of LCDs, the thinning of polarizing plates has been demanded. However, if the thickness of the TAC film used as a protective film is thinned for this reason, there arises a problem that sufficient mechanical strength cannot be obtained, and 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 iridescent spots are observed.

When a birefringent aligned polyester film is disposed on one side of the polarizer, the linearly polarized light emitted from the backlight unit or the polarizer changes its polarization state when passing through the polyester film. The transmitted light shows an interference color peculiar to the retardation of the birefringence-thickness product of the aligned polyester film. Therefore, if a discontinuous luminescent spectrum such as a cold cathode tube or a hot cathode tube is used as a light source, different transmitted light intensities will be displayed depending on the wavelength, and a rainbow-like color spot will be formed (see: Proceedings of the 15th Micro-Optics Conference, No. 30-31 pages).

As a means to solve the above problems, someone proposed to use a white light source with a continuous and wide luminous spectrum as a backlight light source such as a white light-emitting diode, and also use an aligned polyester film with a certain amount of hysteresis as a polarizer protective film (patent Document 4). White light-emitting diodes have a continuous and broad emission spectrum in the visible light region. Therefore, if we focus on the envelope shape of the interference color spectrum produced by the transmitted light passing through the birefringent body, we can obtain a spectrum similar to the light emission spectrum of the light source by controlling the hysteresis of the aligned polyester film. Can suppress rainbow spots. [Prior Art Literature] [Patent Document]

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 Laid-Open No. 2004-205773 Patent Document 4 WO2011/162198

[Problem to be solved by the invention]

As a backlight source for liquid crystal display devices, white light-emitting diodes including light-emitting elements that combine blue light-emitting diodes and yttrium-aluminum-garnet-based yellow phosphors (YAG-based yellow phosphors) have been widely used in the past. (White LED). The light emission spectrum of this white light source has a wide spectrum in the visible light region, and the light emission efficiency is also excellent, so it is widely used as a backlight light source. However, the liquid crystal display device using this white LED as the backlight source can only reproduce about 20% of the color spectrum that can be recognized by human eyes.

On the other hand, the demand for expanding the color gamut has increased in recent years, so the emission spectrum of the white light source has a clear peak shape in each wavelength region of R (red), G (green), and B (blue). Wide color gamut liquid crystal display device. For example, there are developments using white light sources using quantum dot technology, phosphors that have clear emission peaks in the R (red) and G (green) regions by excitation light, and blue LEDs. Liquid crystal display devices that support wide color gamut for various types of light sources such as white LED light sources of the 3-wavelength system and white LED light sources of the 3-wavelength system. In the case of a liquid crystal display device using a white light source using quantum dot technology as a backlight source, it is said that it can reproduce colors of more than 60% of the spectrum recognizable by the human eye.

It is newly known that compared with light sources including white light-emitting diodes using YAG-based yellow phosphors in the past, these white light sources have a narrow half-maximum width of the peak, and polyethylene terephthalate with hysteresis is used. When a diester resin film is used as a polarizer protective film as a structural member of a polarizing plate, iridescent spots may be generated depending on the type of light source.

In addition, the expectation of further thinning of the polarizer protective film is strong. In such a case, it is also required to provide a polyethylene terephthalate system that can further control the iris when the display screen is viewed from an oblique direction. Resin film (polarizer protective film).

That is, the subject of the present invention is to provide a polarizer protective film even when a polyethylene terephthalate-based resin film is used as a polarizer protective film of a liquid crystal display device supporting a wide color gamut, or to reduce the thickness of the polarizer protective film. In the case of a polarizer protective film capable of suppressing the occurrence of rainbow spots, a polarizing plate and a liquid crystal display device including the same. [Means to solve the problem]

As a result of careful examination, the inventors of the present invention have found that, except that the polyethylene terephthalate resin film has a specific range of retardation, the ratio of the (100) plane of the crystal measured by X-ray diffraction to the film surface The lower the degree of alignment, the more effective it is to suppress iris.

Representative inventions are as follows. Item 1. A kind of polarizer protective film, is the polarizer protective film that comprises polyethylene terephthalate resin film, it is characterized in that aforementioned polyethylene terephthalate resin film satisfies following (1) and (2) ). (1) The polyethylene terephthalate-based resin film has a hysteresis of not less than 3000 nm and not more than 30000 nm; (2) The degree of orientation of the (100) plane of the crystal relative to the film plane measured by X-ray diffraction is 0.70 or less. Item 2. The protective film for polarizers as in item 1, wherein the crystal size of the (-105) plane of the crystals measured in the direction of the slow axis of the aforementioned polyethylene terephthalate resin film is 36 Å or more. Item 3. A polarizing plate, at least one area layer of the polarizer has the polarizer protective film according to item 1 or 2. Item 4. A liquid crystal display device is a liquid crystal display device having a backlight source, 2 polarizers, and a liquid crystal cell arranged between the aforementioned 2 polarizers, Among the aforementioned two polarizers, at least one is the polarizer according to Item 3. [Effect of Invention]

In the case of the liquid crystal display device, polarizing plate, and polarizer protective film of the present invention, even in a liquid crystal display that uses a polyethylene terephthalate-based resin film as a polarizer protective film to support wide color gamut, Even in the case of the device, or in the case of thinning it, it is possible to suppress occurrence of rainbow spots on the display screen.

[Mode for Carrying Out the Invention] 1. Polarizer protective film

The polyethylene terephthalate resin film used for the polarizer protective film of the present invention preferably has a retardation (Re, in-plane retardation) of not less than 3000 nm and not more than 30000 nm. If the amount of retardation is less than 3000 nm, when used as a polarizer protective film, strong interference colors will appear when viewed from an oblique direction, and good visibility cannot be ensured. A preferable lower limit of the retardation amount is 4000 nm, a second best lower limit is 5000 nm, and a more preferable lower limit is 6000 nm.

On the other hand, the upper limit of the amount of retardation is preferably 30000 nm, and more preferably 10000 nm. If the upper limit of 30,000 nm is clearly exceeded, not only the effect of further improvement in visibility cannot be obtained substantially, but also the film thickness becomes considerably thick, and the handling property as an industrial material decreases, which is not preferable.

The in-plane refractive index difference (refractive index in the slow axis direction−refractive index in the fast axis direction) is preferably at least 0.08, more preferably at least 0.09, and still more preferably at least 0.10. The upper limit of the difference in refractive index is preferably 0.15 or less. From the viewpoint of further suppressing iridescent spots, it is preferable that the film is strongly stretched in one direction and the refractive index difference in the film surface is large.

In addition, the retardation in the present invention can be obtained by measuring the refractive index and film thickness in the biaxial direction 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 of the biaxial direction in a film surface can be calculated|required with the Abbe refractometer (made by Atago Corporation, NAR-4T, measurement wavelength 589nm).

The polyethylene terephthalate-based resin film used in the polarizer protective film of the present invention, in addition to having a specific range of retardation, is preferably The degree of orientation of the (100) plane of the crystal relative to the film plane measured by X-ray diffraction is 0.70 or less. The degree of orientation of the (100) plane of the crystal of the polyethylene terephthalate resin film relative 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 to the film plane is an index showing the orientation around the molecular chain direction (c-axis) of the crystal of the polyethylene terephthalate resin film. Lower values indicate more random alignment around the c-axis. The more random the alignment around the c-axis, the more suppressed the rainbow spots observed from the oblique direction.

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

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

It is considered that the molecular chain direction (c-axis direction) of the crystals of the polyethylene terephthalate 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 is When the specific value is large, and the alignment around the molecular chain direction axis (c-axis) of the crystal is lowered, rainbow-like color spots will become more difficult to generate. 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 follows.

The crystal size of the (-105) plane of the crystal measured in the direction of the slow axis is the θ/2θ diffraction intensity curve that can be measured in the direction of the slow axis using an X-ray diffraction device (manufactured by Rigaku Co., Ltd., RINT2500) From the figure, the diffraction position of the (-105) plane of the crystal and the measured full width at half maximum (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 Cu-Kα line with a wavelength of 1.5418Å. The so-called crystal size of the (-105) plane of the crystal measured in the direction of the slow axis in the present invention refers to the apparent crystal size. (ACS=0.9λ/(βcosθ)). Here, λ is the wavelength of X-rays (1.5418Å), and β is calculated as (B ² -b ² ) ^1/2 from the measured full width at half maximum (B) and the constant (b) for correction half-width of the . 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 radian units.

The in-plane orientation of the (-105) plane of the crystal is preferably at least 0.6, more preferably at least 0.7, still more preferably at least 0.8. The in-plane orientation of the (-105) plane of the crystal can be measured using an X-ray diffractometer (manufactured by Rigaku Co., Ltd., RINT2500). The measurement system fixes θ/2θ and rotates the sample by 360° using the sample holder for azimuth measurement to obtain the circumferential direction distribution of the diffraction intensity of the (-105) plane of the crystal. From the half width of the obtained distribution, a parameter defined by (180-half width)/180 was set as the degree of in-plane alignment. The unit of the so-called full width at half maximum here is degree.

In order to align the molecular chain axes of the crystals to a uniaxial direction, it is preferable to stretch the film in one direction. Generally, in order to increase the degree of alignment in the stretching direction, there are methods of increasing the stretching ratio or lowering the stretching temperature. In addition, when a film 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 the internal stress will change when the dimension in the direction perpendicular to the stretching direction is free or fixed, such as free-end uniaxial stretching and fixed-end uniaxial stretching. very different. This is caused by freeing the Poisson shrinkage generated during stretching in the direction perpendicular to the stretching direction or by suppressing the difference. In the case of transverse stretching with a normal tenter, the ends are clamped with clips, and therefore Boisson shrinkage in the film flow direction (MD) is restricted during transverse stretching. As a result, there is of course a transverse stretching direction (TD), and stress is also generated in the flow direction. Regarding the thickness direction, since it 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 rings 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. Essentially, stress does not act 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 resin film of the protective film of this invention can be manufactured according to the manufacturing method of a general polyester film. For example, polyethylene terephthalate-based resin is melted, extruded and formed into a sheet-like non-oriented polyethylene terephthalate-based resin, at a temperature equal to or higher than the glass transition temperature, by rolling After the speed difference is stretched in the longitudinal direction, it is stretched in the transverse direction using a tenter and then heat-treated.

When the film-forming conditions of a polyethylene terephthalate-type resin film are demonstrated concretely, it is preferable that it is 100-130 degreeC, and it is especially preferable that it is 110-125 degreeC for longitudinal stretching temperature and transverse stretching temperature.

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

On the other hand, when producing a film having a slow axis in the film longitudinal direction (MD direction), the lateral stretch ratio is preferably 1.0 to 3.0 times, more preferably 1.5 to 3.0 times, and still more preferably 2.0 to 3.0 times. times. The longitudinal stretch ratio is preferably from 4.0 to 6.5 times, more preferably from 5.0 to 6.0 times. Also, when producing a film having a slow axis in the film longitudinal direction, 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 amount of hysteresis within the above range, it is preferable to control the ratio of the longitudinal stretch ratio to the transverse stretch ratio, stretching temperature, and film thickness. When the difference in the draw ratios in length and width is too small, it becomes difficult to increase the amount of hysteresis, which is unfavorable.

In order to increase the crystal size of the (-105) plane of the crystal and reduce the orientation degree of the (100) plane of the crystal relative to the film surface, it is necessary to increase the stretching ratio in one direction and set the stretching temperature high. It is preferable to properly 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 from 6 m/sec to 15 m/sec, more preferably from 8 m/sec to 12 m/sec. Since the film is stretched in one direction at a high ratio while applying sufficient heat to the film, the stress and strain in the stretching direction can be maintained, and the stress around the alignment axis can be equalized at the same time, and the crystallized (-105 ) The crystal size of the plane increases, and the degree of alignment of the (100) plane of the crystal relative to the film plane is reduced.

In the subsequent heat treatment, the treatment temperature is preferably 150-250°C, particularly preferably 180-220°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 enlarging the crystal size of the (-105) plane of the crystal, the higher the treatment temperature of the heat treatment, the better, so it is preferable to adjust both in consideration of the balance.

As for the polyethylene terephthalate-based resin constituting the polyethylene terephthalate-based resin film, it is preferable that 85 mol% or more of monomer units are polyethylene terephthalate. The ethylene terephthalate unit is preferably at least 90 mol%, more preferably at least 95 mol%. Moreover, a well-known acid component and a diol component may be contained as a copolymerization component. As the polyethylene terephthalate-based resin, a homopolymer polyethylene terephthalate is particularly preferable. The ratio of monomer units can be confirmed by ¹ H-NMR measurement.

These resins are excellent in transparency as well as thermal and mechanical properties, and can easily control the amount of hysteresis by stretching. Polyethylene terephthalate has a large birefringence inherently, and is the most suitable material because it can relatively easily obtain a large retardation even if the film thickness is thin.

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

In order to set the light transmittance at a wavelength of 380 nm of the protective film of the present invention to 20% or less, it is preferable to appropriately adjust the type, concentration, and film thickness of the ultraviolet absorber. The ultraviolet absorber used in this invention is a well-known thing. Examples of the ultraviolet absorber include organic ultraviolet absorbers and inorganic ultraviolet absorbers, but organic ultraviolet absorbers are preferred from the viewpoint of transparency. As for organic ultraviolet absorbers, benzotriazole-based, benzophenone-based, cyclic imidoester-based, etc., and combinations thereof are mentioned, but if the absorbance is within the range specified in the present invention, is not particularly limited. However, from the viewpoint of durability, benzotriazole-based and cyclic iminoester-based are particularly preferable. When two or more ultraviolet absorbers are used in combination, since ultraviolet rays of different wavelengths can be absorbed simultaneously, the ultraviolet absorbing 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'-hydroxyl-5'-(methacryloxy Methyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxyl-5'-(methacryloxyethyl)phenyl]-2H-benzotriazole, 2-[2 '-Hydroxy-5'-(methacryloxypropyl)phenyl]-2H-benzotriazole, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2,4-di-tertiary butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 2-(2'-Hydroxy-3'-tertiarybutyl-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. As the cyclic imido ester UV absorber, for example, 2,2'-(1,4-phenylene)bis(4H-3,1-benzo

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

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

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

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

In addition to the ultraviolet absorber, it is also a preferable aspect to contain various additives other than the catalyst within the range that does not hinder the effect 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, light stabilizers, flame retardants, heat stabilizers, antioxidants, and antigelling agents. , Surfactants, etc. Moreover, in order to exhibit high transparency, it is also preferable that a polyethylene terephthalate-type resin film does not contain particle|grains substantially. The so-called "substantially does not contain particles" means, for example, in the case of inorganic particles, it means that in the case of quantitative inorganic elements by fluorescent X-ray analysis, it is 50 ppm or less, preferably 10 ppm or less, particularly preferably below the detection limit. content.

For the method of blending the ultraviolet absorber to the polyethylene terephthalate resin film in the present invention, a combination of known methods can be used, for example, the dried ultraviolet absorber and The polymer raw materials are blended to prepare a master batch, and blending is carried out by blending predetermined master batches and polymer raw materials at the time of film formation.

At this time, in order to uniformly disperse the ultraviolet absorber and blend it economically, the concentration of the ultraviolet absorber in the masterbatch is preferably set to a concentration of 5 to 30% by mass. As far as the conditions for making the masterbatch are concerned, it is preferable to use a kneading extruder, and the extrusion temperature is above the melting point of the polyethylene terephthalate resin raw material and below 290°C for 1 to 15 minutes. extrude. Above 290°C, the UV absorber will lose a lot, and the viscosity of the masterbatch will decrease greatly. When the extrusion time is 1 minute or less, uniform mixing of the ultraviolet absorber becomes difficult. At this time, a stabilizer, a color adjustment agent, and an antistatic agent may be added as needed.

In the present invention, it is preferable that the film has a multilayer structure of at least three layers, and that an ultraviolet absorber is added to the middle layer of the film. A film having a three-layer structure including an ultraviolet absorber in an intermediate layer can be specifically produced as follows. The polyethylene terephthalate-based resin pellets are used alone as the outer layer, and the masterbatch containing the ultraviolet absorber and the polyethylene terephthalate-based resin pellets are mixed in a predetermined ratio and dried as the middle layer. For the layer, it is supplied to a known extruder for fusion lamination, extruded into a sheet form from a slit-shaped die (die), cooled and solidified on a casting roll, and an unstretched film is produced. That is, using two or more extruders, three-layer manifolds or confluence blocks (for example, confluence blocks with square-shaped confluence parts), the film layers constituting the two outer layers and the film layers constituting the middle layer are stacked, A three-layer sheet was extruded and cooled with a casting roll to produce an unstretched film. In addition, in the present invention, in order to remove foreign substances contained in the polyethylene terephthalate-based resin that may cause optical defects, it is preferable to perform high-precision filtration at the time of melt extrusion. The filter particle size (initial filter efficiency 95%) of the filter material used for high-precision filtration of molten resin 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 tends to be insufficient.

Moreover, corona treatment, coating treatment, flame treatment, etc. may be given to the polyethylene terephthalate-type resin film of this invention in order to improve the adhesiveness with a polarizer.

In the present invention, in order to improve the adhesion with the polarizer, it is preferable to have polyester resin, polyurethane, etc. An easy-adhesive layer mainly composed of at least one of ester resin and polyacrylic resin. Here, the "main component" refers to a component of 50% by mass or more among the solid components constituting the easily-adhesive layer. The coating liquid used for forming the easy-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 . Such coating liquids include, for example, water-soluble coatings disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, and Japanese Patent No. 4150982. Sexual or water-dispersible copolyester resin solution, acrylic resin solution, polyurethane resin solution, etc.

The easy-adhesive layer can be obtained by applying the aforementioned coating solution to one or both surfaces of an unstretched film or a longitudinally uniaxially stretched film, drying at 100 to 150° C., and stretching in the transverse direction. The coating amount of the final easy-adhesive layer is preferably managed so as to be 0.05 to 0.20 g/m ² . If the coating amount is less than 0.05 g/m ² , the adhesiveness with the obtained polarizer may become insufficient. On the other hand, if the coating amount exceeds 0.20 g/m ² , the sticking resistance may decrease. When providing an easily-adhesive layer on both surfaces of a polyethylene terephthalate-type resin film, the application|coating quantity of the easily-adhesive layer of both surfaces may be the same or different, and it can set each independently within the said range.

In the easy-adhesive layer, it is preferable to add particles in order to provide slipperiness. As for the average particle diameter of the fine particles, it is preferable to use particles of 2 μm or less. When the average particle diameter of the particles exceeds 2 μm, the particles tend to fall off from the coating layer. For the particles contained in the easy-adhesive layer, for example, 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, acrylic, melamine, benzoguanamine, and silicone. These may be added to the easy-adhesive layer individually, and may be added in combination of 2 or more types.

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

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

The thickness of the polyethylene terephthalate-based resin film of the present invention is optional, but is preferably in the range of 30 to 300 μm. Even a film with a thickness of less than 30 μm can theoretically obtain a retardation value of 3000 nm or more. However, in this case, the anisotropy of the mechanical properties of the film becomes prominent, and cracks, breakage, etc. tend to occur easily, and the practicality as an industrial material is remarkably reduced. A preferable lower limit of the thickness is 40 μm, and an especially preferable lower limit of the thickness is 45 μm. On the other hand, when 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, preferably 120 μm, more preferably 100 μm or less, further preferably 80 μm or less, still more preferably 65 μm or less, still more preferably 65 μm or less. 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 have a large influence on 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, if the vertical stretch ratio is lowered in order to increase the hysteresis, the longitudinal thickness unevenness may be deteriorated. Since there is a region where longitudinal thickness unevenness becomes extremely poor within a certain range of draw ratio, it is preferable to set film forming conditions at a point excluding this range.

The thickness unevenness of the film of the present invention is preferably 5.0% or less, more preferably 4.5% or less, further preferably 4.0% or less, particularly preferably 3.0% or less.

The polyethylene terephthalate-based resin film is preferably a ratio (Re/Rth) of the retardation (Re) to the thickness direction retardation (Rth) of 0.2 or more, more preferably 0.5 or more, still more preferably 0.6 or more. From the viewpoint of suppressing rainbow spots when viewed from an oblique direction, the larger the ratio (Re/Rth), the better. The upper limit of the ratio (Re/Rth) is preferably at most 2.0, more preferably at most 1.8. On the other hand, from the viewpoint of uneven thickness and planarity, the upper limit of the ratio (Re/Rth) is preferably less than 1.0. In addition, the retardation in the thickness direction refers to the expression obtained by multiplying the two birefringence ΔNxz (=∣nx-nz∣) and ΔNyz(=∣ny-nz∣) by the film thickness d when viewed from the film thickness direction section The average parameter of the hysteresis. The thickness direction retardation (Rth) can be calculated by calculating nx, ny, nz and film thickness d (nm), and calculating the average value of (ΔNxz×d) and (ΔNyz×d). In addition, nx, ny, and nz were determined with an Abbe refractometer (manufactured by Atago, NAR-4T, measurement wavelength: 589 nm).

2. Polarizer The polarizer of the present invention preferably has a structure in which a polarizer protective film is attached to at least one side of a polarizer stained with polyvinyl alcohol (PVA) or the like, 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 represented by a TAC film, an acrylic film, or a norbornene-based film. Alternatively, the other side can have no polarizer protection film present. In the polarizing plate used in the present invention, for the purposes of anti-reflection, anti-glare, anti-scratch, etc., it is also a preferred aspect to coat various hard coats on the surface.

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 order from the side opposite to the backlight source for displaying images (visible side). 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 facing the backlight light source in the rear module, and is arranged on the side where images are displayed (viewable side) in the front module.

The liquid crystal display device of the present invention has at least a backlight light source and a liquid crystal cell disposed between two polarizers as structural components. In addition, other structures other than these, for example, color filters, enamel films, diffusion sheets, antireflection films, and the like 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 reflector is used as a structural member, or may be a direct type type.

The backlight light source of the liquid crystal display device is not particularly limited. For example, the backlight light source may be a white LED of a combined phosphor system (that is, an element that emits white by combining a light-emitting diode that emits blue light or ultraviolet light using a compound semiconductor and a phosphor). As phosphors, there are yttrium‧aluminum‧garnet-based yellow phosphors, cerium‧aluminum‧garnet-based yellow phosphors, and the like.

In one embodiment, the backlight light source is preferably a white light source having peaks of emission spectra in each wavelength region of 400nm to 495nm, 495nm to 600nm, and 600nm to 780nm. Examples include a white light source utilizing quantum dot technology, a phosphor system that uses a phosphor that has light emission peaks in the R (red) and G (green) regions by excitation light, and a blue LED. White LED light source, 3-wavelength white LED light source ^, white LED light source combined with red laser, and other _{fluoride phosphors} (also known as "KSF ”), etc. and blue LEDs for white LED light sources, etc. These have attracted attention as a backlight source for liquid crystal display devices supporting a wide color gamut.

The arrangement of the polarizer protective film of the present invention having the specific retardation in the liquid crystal display device is not particularly limited, but it is preferable to arrange the polarizer and the liquid crystal cell arranged on the incident light side (light source side). , and in the case of a liquid crystal display device with a polarizer arranged on the light-emitting side (visible side), the polarizer protective film on the light-incident side of the polarizer arranged on the light-incident side, and/or arranged on the light-emitting side The polarizer protective film on the light-emitting side of the polarizing plate is a polarizer protective film containing a polyethylene terephthalate-based resin film having the specified retardation. A particularly preferable aspect is an aspect in which 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. When the polyethylene terephthalate-based resin film is arranged in a position other than the above, the polarization characteristics of the 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 of a polarizing plate at such a specific position. [Example]

Hereinafter, examples are given to illustrate the present invention more specifically, but the present invention is not limited by the following examples, and can also be implemented with appropriate changes within the scope of the gist of the present invention, and these are also included in the technical scope of the present invention. In addition, the evaluation methods of the physical properties in the following examples are as follows.

(1) Hysteresis (Re) The amount of retardation refers to the parameter defined as the product (ΔNxy×d) of the anisotropy of the refractive index (ΔNxy=|nx-ny|) and the film thickness d (nm) of the orthogonal biaxial axes on the film, which means A measure of isotropy or anisotropy in optics. The biaxial refractive index anisotropy (ΔNxy) was obtained by the following method. The direction of the slow axis of the film was determined using a molecular alignment meter (Molecular Orientation Meter MOA-6004, manufactured by Oji Scientific Instruments Co., Ltd.), and a rectangle of 4 cm x 2 cm was cut out so that the direction of the slow axis became parallel to the long side of the sample for measurement. as a sample for measurement. For this sample, using an Abbe refractometer (manufactured by Atago Corporation, NAR-4T, measurement wavelength 589nm) to obtain the refractive index of the orthogonal biaxial (refractive index in the slow axis direction: ny, the refractive index perpendicular to the slow axis direction) For the refractive index in the direction: nx) and the refractive index in the thickness direction (nz), the absolute value (|nx-ny|) of the aforementioned biaxial refractive index difference is regarded 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 retardation (Re) was obtained from the product (ΔNxy×d) of the anisotropy of the refractive index (ΔNxy) and the film thickness d (nm).

(2) Thickness hysteresis (Rth) The retardation in the thickness direction refers to the retardation obtained by multiplying the two birefringence ΔNxz (=|nx-nz|) and ΔNyz (=|ny-nz|) by the film thickness d when viewed from the film thickness direction section The average parameter of . Obtain nx, ny, nz and film thickness d (nm) by the same method as the measurement of retardation, and calculate the average value of (ΔNxz×d) and (ΔNyz×d) to obtain thickness direction retardation (Rth).

(3) The degree of orientation of the (100) plane of the crystal relative to the film plane The orientation degree of the (100) plane of the crystal with respect to the film plane is obtained from the diffraction intensity obtained by pole measurement using an X-ray diffraction device (manufactured by Rigaku Co., Ltd., RINT2100PC) with the slow axis as the axis. Half-height width, a parameter defined by (180-half-height width)/180. The X-ray used in the measurement is Cu-Kα line with a wavelength of 1.5418Å. The pole measurement is carried out by installing the RINT2000 goniometer (Goniometer) which can be mounted on the RINT2100PC and the multi-purpose sample table for the pole, according to the Schulz reflection method. The sample is cut out into a circle with a diameter of 5 cm, and installed on the sample table in such a way that the direction of the slow axis is consistent with the directions of β=90 degrees and 270 degrees. In addition, the direction of the slow axis of the sample was determined using a molecular alignment meter (manufactured by Oji Scientific Instruments Co., Ltd., MOA-6004 molecular alignment 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 longitudinal limit is set to 1.2 mm, the divergence slit is set to 1 degree, and the scattering slit is set to Set it to 7mm, and set the light-receiving slit to 7mm. In 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 the concentric circles: β start angle = 0 degrees, β end angle = 360 degrees, β step angle = 5 degrees. The calculation method of the degree of orientation of the (100) plane of the crystal with respect to the film plane is shown below. The reflection-diffraction intensity curves of β=0° and β=180° obtained in the measurement are defined as I(α) (25≦α≦90). Set the horizontal axis as α' (α'=α when β=0 degree, α'=180-α when β=180 degree), and set the vertical axis as the diffraction intensity of each α', thereby connecting β= Diffraction intensity curves at 0 degrees and 180 degrees, and the diffraction intensity curve I(α') (25≦α'≦155) is obtained. At this time, the average value of β=0 degree and β=180 degree is used for the diffraction intensity of α'=90 degree. The straight line connecting the diffraction intensity at α'=25 degrees and 155 degrees is taken as the bottom line, and the crystallization is calculated by (180-full width at half maximum)/180 from the obtained diffraction intensity graph. The degree of alignment 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 direction of the slow axis of the film was obtained from an X-ray diffraction device (manufactured by Rigaku Co., Ltd., RINT2500) in the slow axis direction. Measure the θ/2θ diffraction intensity curve in the axial direction, read the measured half-maximum 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 (Scherrer's equation) was calculated as the apparent crystal size (ACS). The X-ray used in the measurement is Cu-Kα line with a wavelength of 1.5418Å. In addition, the bottom line is a line connecting two points of the minimum diffraction intensity point between 30° and 42.7° and the minimum diffraction intensity point between 42.7° and 50°. (ACS=0.9λ/(βcosθ)). Here, λ is the wavelength of the X-ray (1.5418Å), and β is the actual measured full width at half maximum (B) read and the constant (b) for correction, calculated by (B ² -b ² ) ^1/2 Computed 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 radian units. In addition, the direction of the slow axis of the sample was determined using a molecular alignment meter (manufactured by Oji Scientific Instruments Co., Ltd., MOA-6004 molecular alignment meter).

(5) Observation of rainbow spots In such a way that the absorption axis of the polarizer and the alignment axis of the film are perpendicular, a polyethylene terephthalate film prepared by the method described later is attached to one side of the polarizer containing PVA and iodine, and on the opposite side A commercially available TAC film was attached to prepare a polarizing plate including a polyethylene terephthalate film/polarizer/TAC film. The obtained polarizing plate was substituted for the polarizing plate originally present on the light-emitting side of a commercially available liquid crystal display device (BRAVIA KDL-40W920A manufactured by SONY Corporation). In addition, a polyethylene terephthalate film was used instead of the polarizer so that the absorption axis of the polarizer coincided with the direction of the absorption axis of the polarizer attached to the liquid crystal display device so that it would be on the visible side. The aforementioned liquid crystal display device has a backlight light source including a light source that emits excitation light and quantum dots. The emission spectrum of the backlight light source of this liquid crystal display device was measured using a multi-channel spectrometer PMA-12 manufactured by Hamamatsu Photonics. As a result, emission spectra with peaks around 450nm, 528nm, and 630nm were observed, and the full width at half maximum of each peak was 16nm. ~34nm. Moreover, the exposure time at the time of measuring a spectrum was set to 20 msec. The liquid crystal display device produced in this way was made to display a white image, and it observed visually from the front of a display and oblique direction, and the occurrence of rainbow spots was judged according to the following criteria. In addition, 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 (perpendicular) and a line connecting the center of the display and the position of the eyes during observation. ⊚: No rainbow spots were observed within the range of the observation angle of 0 to 65 degrees. ◯: Slight rainbow spots are observed within the range of the observation angle of 0 to 65 degrees. ×: Rainbow spots were observed within the range of the observation angle of 0 to 65 degrees.

(Manufacturing 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 magnesium acetate were fed as catalysts while stirring. 0.064 parts by mass of tetrahydrate and 0.16 parts by mass of triethylamine. Then, after carrying out pressurization and temperature rise, and carrying out pressurized esterification reaction on gauge pressure 0.34MPa, 240 degreeC conditions, the esterification reactor was returned to normal pressure, and phosphoric acid 0.014 mass part was added. Furthermore, it heated up to 260 degreeC over 15 minutes, and added 0.012 mass parts of trimethyl phosphates. Then, 15 minutes later, dispersion treatment was carried out with a high-pressure disperser, and 15 minutes later, the obtained esterification reaction product was transferred to a polycondensation reactor, and polycondensation reaction was carried out at 280° C. under reduced pressure.

After the polycondensation reaction is completed, filter with a filter made of Naslon with a 95% cut-off diameter of 5 μm, extrude it into a strand from a nozzle, and use a pre-filtered filter (pore size: 1 μm or less) ) cooling water to cool, solidify, and cut into pellets. The obtained polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl/g, and substantially did not contain inert particles and internal precipitated particles. (Hereafter abbreviated as PET(A).)

-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)。)(Production Example 2-Polyester B) The dried UV absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzo

-4-ketone) 10 parts by mass and 90 parts by mass of PET (A) (intrinsic viscosity: 0.62dl/g) substantially free of particles were mixed, and a polyparaphenylene compound containing an ultraviolet absorber was obtained using a kneading extruder. Ethylene dicarboxylate resin (B). (Hereafter abbreviated as PET(B).)

(Manufacturing Example 3-Adjustment of Adhesive Modification Coating Liquid) A water-dispersible copolyester resin containing a sulfonic acid metal salt group was prepared by carrying out transesterification and polycondensation reactions by conventional methods. 46 mol% of phthalic acid, 46 mol% of isophthalic acid, and 8 mol% of sodium isophthalic acid-5-sulfonate, as glycol components (relative to the entire glycol component) Ethylene glycol is 50 mol % and neopentyl glycol is 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 a nonionic surfactant, heat and stir, and when it reaches 77°C, add the above-mentioned water-dispersible Contain 5 mass parts of copolyester resins of sulfonic acid metal salt base, and continue to stir until after there is no agglomeration of resin, the resin water dispersion liquid is cooled to normal temperature, and obtained the uniform water dispersibility of solid content concentration 5.0 mass % Copolyester resin liquid. After further 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 liquid. 20 parts by mass of water was added while stirring to obtain an adhesive modification 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 ultraviolet absorbers as raw materials for the base film intermediate layer were dried under reduced pressure at 135° C. (1 Torr ) 6 hours later, it was supplied to the extruder 2 (for the middle layer II layer), and in addition, PET (A) was dried by a common method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), respectively, and Melts at 285°C. These two kinds of polymers are respectively filtered with stainless steel sintered filter media (95% interception of particles with a nominal filtration accuracy of 10μm), and laminated in two kinds of three-layer confluence blocks, extruded into sheets from the extrusion port, and casted by electrostatic application The unstretched film was produced by winding it on a casting drum with a surface temperature of 30°C and cooling and solidifying it. At this time, the discharge rate of each extruder was adjusted so that the thickness ratio of the I layer, II layer, and III layer was 10:80:10.

Then, the above-mentioned adhesion-improving coating liquid was applied on both sides of the unstretched PET film by the 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 on which this coating layer was formed was guided to a tenter stretching machine, and while clamping the ends of the film with clips, 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. Stretching was performed so as to be 4.0 times in the width direction (TD) and 0.7 times in the film flow direction (MD). Next, heat treatment is carried out in a hot air zone with a temperature of 200°C and a wind speed of 10 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is carried out in the width direction to obtain A uniaxially aligned PET film with a film thickness of about 50 μm was produced.

(Example 2) The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and while clamping the ends of the film with clips, it was guided to a temperature of 125° C. and a wind speed of a hot air outlet of 10 m/sec. The hot air zone of the bell is stretched so that it becomes 4.5 times in the width direction. Next, heat treatment is carried out in a hot air zone with a temperature of 200°C and a wind speed of 10 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is carried out in the width direction to obtain A uniaxially aligned PET film with a film thickness of about 80 μm was produced.

(Example 3) The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and while clamping the ends of the film with clips, it was guided to a temperature of 120° C. and a wind speed of a hot air outlet of 12 m/sec. The hot air zone of the bell is stretched so that it becomes 4.5 times in the width direction. Next, heat treatment is carried out in a hot air zone with a temperature of 200°C and a wind speed of 10 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is carried out in the width direction to obtain A uniaxially aligned PET film with a film thickness of about 100 μm was produced.

(Example 4) The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and while clamping the ends of the film with clips, it was guided to a temperature of 130° C. and a wind speed of a hot air outlet of 9 m/sec. The hot air zone of the bell is stretched so that it becomes 5.5 times in the width direction. Next, heat treatment is carried out in a hot air zone with a temperature of 200°C and a wind speed of 10 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is carried out in the width direction to obtain A uniaxially aligned PET film with a film thickness of about 60 μm was produced.

(Example 5) The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and while clamping the ends of the film with clips, it was guided to a temperature of 125° C. and a wind speed of a hot air outlet of 10 m/sec. The hot air zone of the bell is stretched so that it becomes 5.0 times in the width direction and 0.9 times in the flow direction. Next, heat treatment is carried out in a hot air zone with a temperature of 200°C and a wind speed of 10 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is carried out in the width direction to obtain A uniaxially aligned PET film with a film thickness of about 60 μm was produced.

(Example 6) The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and while clamping the ends of the film with clips, it was guided to a temperature of 120° C. and a wind speed of a hot air outlet of 10 m/sec. The hot air zone of the bell is stretched to 5.0 times in the width direction. Next, heat treatment is carried out in a hot air zone with a temperature of 200°C and a wind speed of 10 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is carried out in the width direction to obtain A uniaxially aligned PET film with a film thickness of about 40 μm was produced.

(Example 7) The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and while clamping the ends of the film with clips, it was guided to a temperature of 110° C. and a wind speed of a hot air outlet of 12 m/sec. The hot air zone of the bell is stretched so that it becomes 4.5 times in the width direction. Next, heat treatment is carried out in a hot air zone with a temperature of 200°C and a wind speed of 10 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is carried out in the width direction to obtain A uniaxially aligned PET film with a film thickness of about 125 μm was produced.

(Embodiment 8) The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and while clamping the ends of the film with clips, it was guided to a temperature of 115° C. and a wind speed of a hot air outlet of 10 m/sec. The hot air zone of the bell is stretched so that it becomes 4.5 times in the width direction. Next, heat treatment is carried out in a hot air zone with a temperature of 200°C and a wind speed of 10 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is carried out in the width direction to obtain A uniaxially aligned PET film with a film thickness of about 60 μm was produced.

(Example 9) The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and while clamping the ends of the film with clips, it was guided to a temperature of 120° C. and a wind speed of a hot air outlet of 12 m/sec. The hot air zone of the bell is stretched to 5.0 times in the width direction. Next, heat treatment is carried out in a hot air zone with a temperature of 130° C. and a wind speed of 10 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is performed in the width direction to obtain A uniaxially aligned PET film with a film thickness of about 50 μm was produced.

(comparative example 1) The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and while clamping the ends of the film with clips, it was guided to a temperature of 125° C. and a wind speed of a hot air outlet of 5 m/sec. The hot air zone of the bell is stretched to 4.0 times in the width direction. Next, heat treatment is carried out in a hot air zone with a temperature of 225°C and a wind speed of 5 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is carried out in the width direction to obtain A uniaxially aligned PET film with a film thickness of about 50 μm was produced.

(comparative example 2) The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and while clamping the ends of the film with clips, it was guided to a temperature of 95° C. and a wind speed of a hot air outlet of 10 m/sec. The hot air zone of the bell is stretched to 4.0 times in the width direction. Next, heat treatment is carried out in a hot air zone with a temperature of 150° C. and a wind speed of 10 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is performed in the width direction to obtain A uniaxially aligned PET film with a film thickness of about 60 μm was produced.

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

(comparative example 4) The unstretched film produced by the same method as in Example 1 was guided to a tenter stretching machine, and while clamping the ends of the film with clips, it was guided to a temperature of 90° C. and a wind speed of a hot air outlet of 10 m/sec. The hot air zone of the bell is stretched to 4.0 times in the width direction. Next, heat treatment is carried out in a hot air zone with a temperature of 200°C and a wind speed of 10 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is carried out in the width direction to obtain A uniaxially aligned PET film with a film thickness of about 50 μm was produced.

(comparative example 5) The unstretched film produced by the same method as in Example 1 was heated to 105°C using a heated roller group and an infrared heater, and then stretched 3.5 times in the traveling direction with a roller group having a peripheral speed difference. , guided to a tenter stretching machine, while clamping the end of the film with a clamp, guided to a hot air zone with a temperature of 130 ° C and a wind speed of 10 m/s at the hot air outlet, and stretched, so that in the width direction Become 4.0 times. Next, heat treatment is carried out in a hot air zone with a temperature of 220° C. and a wind speed of 10 m/s at the hot air outlet while maintaining the width stretched in the width direction, and further 3% relaxation treatment is carried out in the width direction to obtain A biaxially aligned PET film with a film thickness of about 100 μm was produced.

Table 1 below shows the results of various physical properties, X-ray structure analysis, and rainbow spot observation for the PET films of Examples 1 to 9 and Comparative Examples 1 to 5. Moreover, the PET film system Re/Rth obtained in Examples 2-4, 6-9 was less than 1, and the planarity of a film was excellent.

Table 1 Film thickness (μm) Retardation (nm) (100) plane orientation (-105) plane crystal size (Å) In-plane refractive index difference ny-nx Rainbow Spot Observation Results Example 1 50 5850 0.49 39.8 0.117 ◎ Example 2 80 8530 0.58 40.1 0.107 ◎ Example 3 100 11230 0.64 39.8 0.112 ◎ Example 4 60 7220 0.58 42.8 0.120 ◎ Example 5 60 7280 0.53 41.1 0.121 ◎ Example 6 40 4860 0.61 40.6 0.122 ◎ Example 7 125 13240 0.69 38.3 0.106 ◎ Example 8 60 6240 0.61 37.2 0.104 ◎ Example 9 50 4670 0.51 33.6 0.093 ○ Comparative example 1 50 5177 0.71 45.0 0.104 x Comparative example 2 60 6048 0.74 39.5 0.101 x Comparative example 3 50 3900 0.80 38.7 0.078 x Comparative example 4 50 5335 0.72 51.6 0.107 x Comparative Example 5 100 2900 0.90 60.4 0.029 x [Possibility of industrial use]

In the case of the liquid crystal display device, polarizing plate, and polarizer protective film of the present invention, even in a liquid crystal display that uses a polyethylene terephthalate-based resin film as a polarizer protective film to support wide color gamut, Even in the case of a device, or in the case of thinning it, it is possible to suppress the occurrence of rainbow spots observed on a display screen.

none.

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Claims (13)

A polyethylene terephthalate-based resin film characterized by satisfying the following (1) and (2): (1) have a hysteresis of not less than 3000nm and not more than 30000nm; (2) The degree of orientation of the (100) plane of the crystal relative to the film plane measured by X-ray diffraction is 0.70 or less. The polyethylene terephthalate resin film according to claim 1, wherein the crystal size of the (-105) plane of the crystal measured in the direction of the slow axis is 36 Å or more. The polyethylene terephthalate resin film according to claim 1 or 2, which has a retardation of 6000 nm or more and less than 10000 nm. The polyethylene terephthalate resin film according to claim 1 or 2, wherein the degree of orientation of the (100) plane of the crystal relative to the film plane as measured by X-ray diffraction is 0.65 or less. The polyethylene terephthalate resin film according to claim 1 or 2, wherein the degree of orientation of the (100) plane of the crystal relative to the film plane as measured by X-ray diffraction is 0.61 or less. The polyethylene terephthalate resin film according to claim 1 or 2, wherein the refractive index difference in the film surface (refractive index in the slow axis direction-refractive index in the fast axis direction) is 0.08 to 0.15. The polyethylene terephthalate resin film according to claim 1 or 2, wherein the ratio (Re/Rth) of the retardation (Re) to the thickness direction retardation (Rth) is 0.6 or more and less than 1.0. The polyethylene terephthalate resin film according to claim 1 or 2, which has an easy-adhesive layer on at least one surface. The polyethylene terephthalate resin film according to claim 7, wherein the coating weight of the easy-adhesive layer after drying is 0.05-0.20 g/m ² . A polarizing plate comprising the polyethylene terephthalate resin film according to claim 1 or 2 and a polarizer. A liquid crystal display device having the polarizing plate according to claim 10. The liquid crystal display device according to claim 11, wherein the liquid crystal display device has a backlight light source, and the backlight light source has peaks of emission spectra in the wavelength regions of 400nm to less than 495nm, 495nm to 600nm, and 600nm to 780nm Top white light source. The liquid crystal display device according to claim 12, wherein the backlight source of the liquid crystal display device is at least one of the following (a) to (e): (a) A white light source utilizing quantum dot technology; (b) A white light source in the form of a phosphor and a blue LED that have light emitting peaks in the R (red) and G (green) regions by excitation light; (c) 3-wavelength white LED light source; (d) a white LED light source combined with a red laser; (e) A white light source using a fluoride phosphor and a blue LED.