JP7261738B2 - Liquid crystal displays, polarizers and protective films for polarizers - Google Patents

Description

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

A polarizing plate used in a liquid crystal display (LCD) generally has a structure in which a polarizer made of polyvinyl alcohol (PVA) dyed with iodine is sandwiched between two polarizer protective films. usually uses a triacetyl cellulose (TAC) film. In recent years, along with the thinning of LCDs, thinning of polarizing plates is required. However, if the thickness of the TAC film used as the protective film is reduced for this reason, there arises a problem that sufficient mechanical strength cannot be obtained and moisture permeability is deteriorated. In addition, TAC film is very expensive, and polyester film has been proposed as an inexpensive alternative material (Patent Documents 1 to 3), but there is a problem that rainbow-like color spots are observed.

When an oriented polyester film having birefringence is arranged on one side of the polarizer, the polarization state of the linearly polarized light emitted from the backlight unit or the polarizer changes when passing through the polyester film. The transmitted light exhibits an interference color characteristic of the retardation, which is the product of the birefringence and thickness of the oriented polyester film. Therefore, when a discontinuous emission spectrum such as a cold-cathode tube or a hot-cathode tube is used as a light source, the transmitted light intensity varies depending on the wavelength, resulting in rainbow-like color spots (Reference: Proceedings of the 15th Micro-Optical Conference, 30-31).

As a means for solving the above problems, it is possible to use a white light source having a continuous and broad emission spectrum such as a white light emitting diode as a backlight source, and use an oriented polyester film having a certain retardation as a polarizer protective film. It has been proposed (Patent Document 4). A white light emitting diode has a continuous and broad emission spectrum in the visible light region. Therefore, focusing on the envelope shape of the interference color spectrum due to the transmitted light that has passed through the birefringent material, 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. It made it possible to suppress iridescence.

JP-A-2002-116320 Japanese Patent Application Laid-Open No. 2004-219620 Japanese Patent Application Laid-Open No. 2004-205773 WO2011/162198

As a backlight source for a liquid crystal display device, a white light-emitting diode (white LED) composed of a light-emitting element combining a blue light-emitting diode and an yttrium-aluminum-garnet-based yellow phosphor (YAG-based yellow phosphor) has been widely used. It is Since the emission spectrum of this white light source has a wide spectrum in the visible light region and is excellent in emission efficiency, it is widely used as a backlight source. However, in a liquid crystal display device using this white LED as a backlight source, only about 20% of the spectrum recognizable by the human eye can be reproduced.

On the other hand, due to the increasing demand for expanding the color gamut in recent years, the emission spectrum of the white light source has a wide color gamut, which has a clear peak shape in each wavelength region of R (red), G (green), and B (blue). A liquid crystal display device corresponding to the new technology has been developed. For example, a white light source using quantum dot technology, a phosphor-type white LED light source using blue LEDs and phosphors that have clear emission peaks in the R (red) and G (green) regions of excitation light, and three wavelengths. Various types of light sources, such as a white LED light source of the system, a white LED light source using a fluoride phosphor (also referred to as “KSF”) having a composition formula of K ₂ SiF ₆ : Mn ⁴ + and a blue LED, etc. , a liquid crystal display device compatible with a wide color gamut has been developed. In the case of such a wide color gamut compatible liquid crystal display device, it is said that colors of 60% or more of the spectrum recognizable by the human eye can be reproduced.

All of these white light sources have a narrow peak half-value width compared to a light source composed of a white light emitting diode using a conventional YAG-based yellow phosphor, and a polyethylene terephthalate-based resin film having retardation is used as a constituent member of the polarizing plate. It was newly found that when used as a certain polarizer protective film, iridescence may occur depending on the type of light source.

In addition, there is a strong demand for further thinning of the polarizer protective film, and even in such a case, a polyethylene terephthalate resin film that can further suppress iridescence when the display screen is observed from an oblique direction. (polarizer protective film) is required.

That is, in the present invention, when a polyethylene terephthalate-based resin film is used as a polarizer protective film, which is a constituent member of the polarizing plate, in a liquid crystal display device compatible with a wide color gamut, or when it is thinned, rainbow spots are formed. An object of the present invention is to provide a liquid crystal display device, a polarizing plate, and a polarizer protective film that can suppress the occurrence of the phenomenon and have improved visibility.

As a result of intensive studies, the present inventors have found that the above problem can be solved by controlling the rigid amorphous fraction to a certain level or more, in addition to the fact that the polyethylene terephthalate-based resin film has a retardation within a specific range. I found

A typical present invention is as follows.
Section 1.
A polarizer protective film made of a polyethylene terephthalate resin film that satisfies the following (1) and (2).
(1) The retardation is 3000 nm or more and 30000 nm or less (2) The rigid amorphous fraction represented by the following formula is 33 wt% or more (rigid amorphous fraction (wt%)) = 100 - (movable amorphous content rate (wt%)) - (mass fraction crystallinity (wt%))
Section 2.
Item 1. The polarizer protective film according to Item 1, wherein the polyethylene terephthalate-based resin film further satisfies the following (3).
(3) The degree of orientation of the (100) plane with respect to the film surface measured by X-ray diffraction is 0.7 or less.
A polarizing plate comprising a polarizer and the polarizer protective film according to Item 1 or 2 laminated on at least one surface of the polarizer.
Section 4.
A liquid crystal display device comprising a backlight source, two polarizing plates, and a liquid crystal cell arranged between the two polarizing plates, wherein at least one of the two polarizing plates is the polarizing plate according to item 3. , liquid crystal display.

According to the present invention, when a polyethylene terephthalate-based resin film is used as a polarizer protective film, which is a constituent member of a polarizing plate, in a liquid crystal display device compatible with a wide color gamut, or when it is thinned, rainbow spots are formed. It is possible to provide a liquid crystal display device, a polarizing plate, and a polarizer protective film that can suppress the generation and have improved visibility.

1. Polarizer Protective Film The polyethylene terephthalate-based resin film used for the polarizer protective film of the present invention preferably has a retardation of 3000 nm or more and 30000 nm or less. If the retardation is less than 3000 nm, when used as a polarizer protective film, it exhibits a strong interference color when observed from an oblique direction, and good visibility cannot be ensured. A preferred lower limit of retardation is 4000 nm, and the next preferred lower limit is 5000 nm.

On the other hand, the upper limit of retardation is preferably 30000 nm. Even if a polyethylene terephthalate-based resin film having a higher retardation is used, substantially no further effect of improving visibility can be obtained, and the thickness of the film becomes considerably thicker, resulting in a decrease in handleability as an industrial material. A preferred upper limit is 10000 nm, a more preferred upper limit is 9000 nm, and a still more preferred upper limit is 8000 nm.

The retardation can be obtained by measuring the refractive index in the biaxial direction and the film thickness in the plane of the film, or it can be obtained using a commercially available automatic birefringence measuring device such as KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.). can. The refractive index is measured at a wavelength of 589 nm.

The in-plane refractive index difference (refractive index in the slow axis direction - refractive index in the fast axis direction) of the polyethylene terephthalate-based resin film 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 refractive index difference is preferably 0.15 or less. Strong stretching in one direction and a large refractive index difference in the film plane are preferred from the viewpoint of further suppressing iridescence. The refractive index in the slow axis direction and the refractive index in the fast axis direction are determined by an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd., measuring wavelength 589 nm).

The polyethylene terephthalate-based resin film used for the polarizer protective film of the present invention has a retardation within a specific range and a rigid amorphous fraction of 33 wt% or more, which suppresses iridescence observed from an oblique direction. It is preferable from the viewpoint of The rigid amorphous fraction of the polyethylene terephthalate-based resin film is preferably 33 wt % or more, more preferably 34 wt % or more, still more preferably 35 wt % or more, still more preferably 36 wt % or more. The upper limit is preferably 60 wt%, but about 50 wt% or 45 wt% is also sufficient. Here, the rigid amorphous fraction is represented by the following formula (1).
(Rigid amorphous fraction (wt%)) = 100 - (movable amorphous fraction (wt%)) - (mass fraction crystallinity (wt%)) (1)
In addition, in this specification, wt% is synonymous with mass%.

Conventionally, it has been thought that the higher-order structure of macromolecules is divided into crystalline and amorphous. However, in recent years, the amorphous regions can be further distinguished by the temperature dependence of their molecular motions: mobile amorphous, in which molecular motions are released at the glass transition temperature (Tg), and molecular motions, in which molecular motions are frozen even at temperatures above Tg. It is reported to be divided into rigid amorphous. It is known that, in the case of polyethylene terephthalate, this rigid amorphous state is maintained up to a temperature of around 200°C. Therefore, it is considered that the higher the rigid amorphous fraction is, the more difficult it is for crystallization to proceed during stretching or heat treatment of the film. In a polyethylene terephthalate-based resin film with the same thickness and retardation, the more randomly oriented the benzene rings around the molecular chain axis, the more the iridescence observed from an oblique direction when used as a polarizer protective film. is suppressed. On the other hand, it is known that in a polyethylene terephthalate-based resin film, benzene rings are oriented parallel to the film surface as the film crystallizes. In a polyethylene terephthalate-based resin film produced by a known method, when the refractive index difference in the film plane is increased, the degree of orientation of the benzene rings with respect to the film plane is simultaneously increased, and a sufficient iris suppression effect is obtained. was not possible. As a result of studies by the present inventors, it was found that by controlling the rigid amorphous fraction within the above range, the orientation of benzene rings accompanying crystallization can be effectively suppressed even when the refractive index difference in the film plane is increased. , it was found that the iridescence seen obliquely can be suppressed.

In the above formula (1), the rigid amorphous fraction is obtained indirectly using the values of the mobile amorphous fraction and the mass fraction crystallinity. The movable amorphous fraction is determined from the reversible heat capacity difference ΔCp at Tg of the reversible heat capacity curve obtained by temperature-modulated DSC measurement using a differential scanning calorimeter (Q100, manufactured by TA Instruments). On the other hand, the mass fraction crystallinity is calculated from density values obtained using a density gradient tube according to JIS K7112. Details will be described later in Examples.

The degree of orientation of the benzene rings in the polyethylene terephthalate-based resin film with respect to the film surface can be evaluated using the degree of orientation with respect to the film surface of the (100) plane substantially parallel to the benzene rings as an index. The polyethylene terephthalate-based resin film used for the polarizer protective film of the present invention has a retardation within a specific range, and the degree of orientation of the (100) plane with respect to the film surface measured by X-ray diffraction is 0.7 or less. is preferable from the viewpoint of suppressing iridescence observed from an oblique direction. The degree of orientation of the (100) plane of the polyethylene terephthalate resin film with respect to the film plane is preferably 0.7 or less, more preferably 0.68 or less, more preferably 0.66 or less, and still more preferably 0.64. It is below. The lower limit is preferably 0.40. The degree of orientation of the (100) plane with respect to the film surface is an index indicating the orientation of polyethylene terephthalate crystals around the molecular chain axis, and the lower the value, the more random the orientation around the molecular chain axis. The more random the orientation around the molecular chain axis, the more suppressed iridescence observed from an oblique direction.

In the X-ray diffraction measurement of polymers, the intensity of X-rays scattered by crystals is mainly measured. Intensity is also included in the measurements. In general, the (100) plane refers to a specific crystal plane in the crystal lattice, and the degree of orientation of the (100) plane with respect to the film plane is an index of the degree of orientation of the benzene rings with respect to the film plane in crystals and oriented amorphous. Equivalent to.

The degree of orientation of the (100) plane with respect to the film surface is the half width of the diffraction intensity profile of the (100) plane obtained by wide-angle X-ray diffraction measurement using an X-ray diffractometer (RINT2100PC manufactured by Rigaku Co., Ltd.). is a parameter defined by the following formula. Details will be described later in Examples.
(100) orientation degree with respect to the film plane = (180-half width) / 180

The polyethylene terephthalate-based resin film, which is the protective film of the present invention, can be manufactured using a general polyester film manufacturing method. For example, a non-oriented polyethylene terephthalate resin melted and extruded into a sheet is stretched in the longitudinal direction using the speed difference between the rolls at a temperature above the glass transition temperature, and then stretched horizontally by a tenter. A method in which the film is stretched in the direction and subjected to heat treatment can be mentioned.

Specifically, the film-forming conditions for the polyethylene terephthalate-based resin film are as follows: longitudinal stretching temperature and 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 draw ratio is preferably 0.7 to 1.5 times, particularly preferably 0.7 to 1.0 times. Moreover, from the viewpoint of suppressing the relaxation of the amorphous molecular chains during stretching and increasing the rigid amorphous fraction, it is preferable to increase the lateral stretching ratio. The lower limit of the transverse draw ratio is preferably 4.5 times, more preferably 4.7 times, and particularly preferably 5.0 times. On the other hand, if the transverse draw ratio exceeds 7.0 times, the film tends to tear in the transverse direction, resulting in a decrease in productivity. Therefore, the upper limit of the transverse draw ratio is preferably 7.0 times, more preferably 6.5 times, particularly preferably 6.0 times, and most preferably 5.5 times.

On the other hand, when producing a film having a slow axis in the longitudinal direction (MD direction) of the film, the transverse draw ratio is preferably 1.0 to 3.0 times, more preferably 2.0 to 3.0 times. be. From the viewpoint of suppressing the relaxation of amorphous molecular chains during stretching and increasing the rigid amorphous fraction, it is preferable to increase the longitudinal draw ratio. The lower limit of the longitudinal draw ratio is preferably 4.5 times, more preferably 4.7 times, and particularly preferably 5.0 times. If the longitudinal draw ratio exceeds 7.0 times, the film tends to tear in the longitudinal direction and the productivity decreases, so the upper limit of the longitudinal draw ratio is preferably 7.0 times, more preferably 6.5 times, particularly Preferably, it is 6.0 times.

In order to control the retardation within the above range, it is preferable to control the ratio of the longitudinal draw ratio to the transverse draw ratio, the drawing temperature, and the thickness of the film. If the difference in stretch ratio in the vertical and horizontal directions is too small, it is difficult to increase the retardation, which is not preferable.

In order to suppress the orientation of the benzene rings with respect to the film surface due to crystallization during heat treatment, it is preferable to increase the rigid amorphous fraction. Specifically, it is preferable to suppress the relaxation of amorphous molecular chains during stretching, and it is preferable to increase the strain rate in stretching the film in the slow axis direction. The strain rate is preferably 13%/sec or higher, more preferably 15%/sec or higher, and particularly preferably 17%/sec or higher. From the viewpoint of film formability, the upper limit of the strain rate is preferably 60%/sec. Here, the strain rate is the amount represented by (nominal strain (%) in stretching in the slow axis direction) / (required time in stretching in the slow axis direction (sec)), and the nominal strain (%) is obtained by ((deformation amount (mm))/(initial length (mm)))×100.

In the subsequent heat treatment, the lower limit of the heat treatment temperature is preferably 150.degree. C., more preferably 160.degree. C., particularly preferably 170.degree. C., and most preferably 180.degree. On the other hand, the upper limit of the heat treatment temperature is preferably 220° C., more preferably 210° C., and particularly preferably 200° C., from the viewpoint of preventing crystallization of the rigid amorphous and lowering the degree of orientation of the (100) plane of the crystal with respect to the film plane. °C.

In the polyethylene terephthalate-based resin constituting the polyethylene terephthalate-based resin film, 85 mol % or more of the monomer units is preferably ethylene terephthalate. The ethylene terephthalate unit is preferably at least 90 mol %, more preferably at least 95 mol %. In addition, as a copolymerization component, a well-known acid component and a glycol component may be included. A particularly preferred polyethylene terephthalate-based resin is polyethylene terephthalate, which is a homopolymer.

These resins are excellent in transparency as well as in thermal and mechanical properties, and their retardation can be easily controlled by stretching. Polyethylene terephthalate has a large intrinsic birefringence and can relatively easily obtain a large retardation even if the film is thin, and is the most suitable material.

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, even more preferably 10% or less, and particularly preferably 5% or less. If the light transmittance is 20% or less, deterioration of the optical functional dye due to ultraviolet rays can be suppressed. The transmittance in the present invention is measured perpendicularly to the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500).

In order to set the transmittance of the protective film of the present invention at a wavelength of 380 nm to 20% or less, it is desirable to appropriately adjust the type and concentration of the ultraviolet absorbent and the thickness of the film. The ultraviolet absorbers used in the present invention are known substances. Examples of the UV absorber include organic UV absorbers and inorganic UV absorbers, but organic UV absorbers are preferred from the viewpoint of transparency. Examples of organic UV absorbers include benzotriazole-based, benzophenone-based, cyclic iminoester-based, and combinations thereof, but are not particularly limited as long as the absorbance is within the range defined by the present invention. 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, ultraviolet rays of different wavelengths can be absorbed at the same time, so that the ultraviolet absorption effect can be further improved.

Examples of benzophenone UV absorbers, benzotriazole UV absorbers, and acrylonitrile UV absorbers include 2-[2'-hydroxy-5'-(methacryloyloxymethyl)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-( tert-butyl)phenol, 2,2′-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol, etc. Cyclic iminoesters Examples of UV absorbers include 2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazinone-4-one) and 2-methyl-3,1-benzoxazin-4-one. , 2-butyl-3,1-benzoxazin-4-one, 2-phenyl-3,1-benzoxazin-4-one, etc., but are not particularly limited thereto.

In addition to the ultraviolet absorber, it is also a preferred embodiment to contain various additives other than the catalyst 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, light stabilizers, flame retardants, heat stabilizers, antioxidants, and anti-gelling agents. , surfactants, and the like. Moreover, in order to exhibit high transparency, it is also preferable that the polyethylene terephthalate-based resin film contains substantially no particles. The term "substantially contains no particles" means, for example, in the case of inorganic particles, a content of 50 ppm or less, preferably 10 ppm or less, particularly preferably a detection limit or less when an inorganic element is quantified by fluorescence X-ray analysis. means.

In addition, as a method for blending the ultraviolet absorber with the polyethylene terephthalate-based resin film in the present invention, a combination of known methods can be employed. are blended to prepare a masterbatch, and the predetermined masterbatch and the polymer raw material are mixed at the time of film formation.

At this time, the concentration of the UV absorber in the masterbatch is preferably 5 to 30% by weight in order to uniformly disperse the UV absorber and to blend it economically. As conditions for preparing the masterbatch, a kneading extruder is preferably used, and the extrusion temperature is preferably the melting point of the polyethylene terephthalate-based raw material or higher and 290° C. or lower for 1 to 15 minutes. At 290° C. or higher, the weight loss of the ultraviolet absorber is large, and the viscosity of the masterbatch is greatly lowered. If the extrusion time is less than 1 minute, it becomes difficult to uniformly mix the ultraviolet absorber. At this time, a stabilizer, a color tone adjusting agent, and an antistatic agent may be added as necessary.

Moreover, in the present invention, it is preferable that the film has a multi-layered structure of at least three layers, and an ultraviolet absorber is added to an intermediate layer of the film. Specifically, a three-layer film containing an ultraviolet absorber in the intermediate layer can be produced as follows. Polyethylene terephthalate-based resin pellets alone for the outer layer, and a masterbatch containing an ultraviolet absorber and polyethylene terephthalate-based resin pellets for the intermediate layer are mixed in a predetermined ratio, dried, and then extruded into a known melt lamination extruder. It is supplied, extruded into a sheet form through a slit-shaped die, and cooled and solidified on a casting roll to produce an unstretched film. That is, using two or more extruders, a three-layer manifold or a confluence block (for example, a confluence block having a square confluence portion), the film layers constituting both outer layers and the film layers constituting the intermediate layer are laminated, A three-layer sheet is extruded through a die and cooled on casting rolls to form an unstretched film. In addition, in the present invention, in order to remove foreign substances contained in the raw polyethylene terephthalate-based resin, which cause optical defects, it is preferable to perform high-precision filtration during melt extrusion. The filtration particle size (initial filtration efficiency of 95%) of the filter medium used for high-precision filtration of molten resin is preferably 15 μm or less. If the filtration particle size of the filter medium exceeds 15 μm, the removal of foreign matter with a size of 20 μm or more tends to be insufficient.

Furthermore, the polyethylene terephthalate-based resin film of the present invention may be subjected to corona treatment, coating treatment, flame treatment, or the like in order to improve adhesion to the polarizer.

In the present invention, in order to improve the adhesion to the polarizer, at least one surface of the film of the present invention has an easy-adhesion layer containing at least one of polyester resin, polyurethane resin or polyacrylic resin as a main component. is preferred. Here, the "main component" refers to a component that accounts for 50% by mass or more of the solid components that constitute the easy-adhesion layer. The coating liquid used for forming the easy-adhesion 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 these coating liquids include water-soluble or water-dispersible coating liquids disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191 and Japanese Patent No. 4150982. A polymerized polyester resin solution, an acrylic resin solution, a polyurethane resin solution and the like can be used.

The easy-adhesion layer can be obtained by applying the above-described coating liquid to one or both sides of a uniaxially stretched film in the longitudinal direction, drying it at 100 to 150° C., and stretching it in the transverse direction. It is preferable to control the final coating amount of the easy-adhesion layer to 0.05 to 0.2 g/m ² . If the coating amount is significantly less than 0.05 g/m ² , the resulting adhesiveness to the polarizer may be insufficient. On the other hand, if the coating amount significantly exceeds 0.2 g/m ² , blocking resistance may deteriorate. When the easy-adhesion layer is provided on both sides of the polyethylene terephthalate-based resin film, the coating amount of the easy-adhesion layer on both sides may be the same or different, and each can be independently set within the above range. .

Particles are preferably added to the easy-adhesion layer to impart lubricity. It is preferable to use particles having an average particle size of 2 μm or less. If the average particle size of the particles significantly exceeds 2 μm, the particles tend to fall off from the coating layer. Particles contained in the easy-adhesion layer include, for example, titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, Examples include inorganic particles such as calcium fluoride, and organic polymer particles such as styrene, acrylic, melamine, benzoguanamine, and silicone particles. These may be added to the easy-adhesion layer singly, or two or more of them may be added in combination.

Moreover, a well-known method can be used as a method of apply|coating 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., and these methods can be used alone. Or it can be performed in combination.

The average particle size of the above particles is measured by the following method. The particles are photographed with a scanning electron microscope (SEM) and the largest diameter of 300-500 particles (between the two furthest Distance) is measured, and the average value is taken as the average particle size.

Although the thickness of the polyethylene terephthalate-based resin film of the present invention is arbitrary, it is preferably in the range of 30 to 300 μm, more preferably in the range of 40 to 200 μm. In principle, it is possible to obtain a retardation of 3000 nm or more even with a film having a thickness of less than 30 μm. However, in this case, the anisotropy of the mechanical properties of the film becomes conspicuous, and the film is likely to tear, tear, etc., and the practicality as an industrial material is remarkably lowered. A particularly preferable lower limit of the 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 120 μm, more preferably 100 μm or less, even more preferably 80 μm or less, even more preferably 65 μm or less, even more preferably 60 μm or less, and even more preferably 60 μm or less. is 55 μm or less. In general, from the viewpoint of thinning, the thickness of the polarizer protective film is preferably in the range of 30 to 65 μm.

In order to suppress variations in retardation, it is preferable that the thickness unevenness of the film is small. Since the stretching temperature and the stretching ratio have a great effect on the thickness unevenness of the film, it is necessary to optimize the film-forming conditions also from the viewpoint of the thickness unevenness. In particular, if the longitudinal draw ratio is lowered in order to increase the retardation, longitudinal thickness unevenness may become worse. Since there is a region in which the longitudinal thickness unevenness becomes extremely poor within a certain range of the draw ratio, it is desirable to set the film-forming conditions outside this range.

The thickness unevenness of the film of the present invention is preferably 5.0% or less, more preferably 4.5% or less, even more preferably 4.0% or less, and 3.0% or less. It is particularly preferred to have

The polyethylene terephthalate-based resin film used for the polarizer protective film preferably has an Nz coefficient represented by |ny-nz|/|ny-nx| of 1.7 or less. The Nz coefficient can be obtained as follows. The orientation axis direction of the film is obtained using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Keisoku Co., Ltd.), and the biaxial refractive indices (ny, nx, ny>nx) and the refractive index (nz) in the thickness direction are determined by an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd., measurement wavelength 589 nm). The Nz coefficient can be obtained by substituting nx, ny, and nz obtained in this way into the expression represented by |ny-nz|/|ny-nx|. The Nz coefficient is more preferably 1.65 or less, still more preferably 1.63 or less. The lower limit of the Nz coefficient is 1.2. In order to maintain the mechanical strength of the film, the lower limit of the Nz coefficient is preferably 1.3 or more, more preferably 1.4 or more, and still more preferably 1.45 or more.

The polyethylene terephthalate resin film has a retardation (Re) to thickness retardation (Rth) ratio (Re/Rth) of preferably 0.2 or more, more preferably 0.5 or more, and still more preferably 0.6. That's it. The larger the ratio (Re/Rth), the better. The upper limit is preferably 2.0 or less, more preferably 1.8 or less. The retardation in the thickness direction refers to the two birefringences ΔNxz (=|nx-nz|) and ΔNyz (=|ny-nz|) when viewed from the cross section in the film thickness direction, and the film thickness d is a parameter indicating the average retardation obtained by multiplying by . nx, ny, nz and film thickness d (nm) are obtained, and the average value of (ΔNxz×d) and (ΔNyz×d) is calculated to obtain thickness direction retardation (Rth). Note that nx, ny, and nz are determined by an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd., measuring wavelength 589 nm).

2. Polarizing Plate The polarizing plate of the present invention has a structure in which a polarizer protective film is attached to at least one surface of a polarizer made by dyeing polyvinyl alcohol (PVA) or the like with iodine. is preferably the polarizer protective film of the present invention described above. As the other polarizer protective film, it is preferable to use a non-birefringent film such as a TAC film, an acrylic film, or a norbornene film. Also, the other polarizer protective film does not necessarily have to be present. It is also preferable to apply various hard coats on the surface of the polarizing plate used in the present invention for the purpose of preventing reflection, suppressing glare, and suppressing scratches.

3. Liquid Crystal Display Device In general, a liquid crystal panel is composed of a rear module, a liquid crystal cell, and a front module in order from the side facing the backlight source toward the image display side (viewing side). The rear module and the front module are generally composed of a transparent substrate, a transparent conductive film formed on the liquid crystal cell side surface of the substrate, and a polarizing plate disposed 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 image display side (viewing side) in the front module.

The liquid crystal display device of the present invention includes at least a backlight source and a liquid crystal cell disposed between two polarizing plates as constituent members. In addition, other structures other than these, such as a color filter, a lens film, a diffusion sheet, an antireflection film, and the like, may be provided as appropriate. At least one of the two polarizing plates is preferably the polarizing plate of the present invention described above.

The configuration of the backlight may be an edge-light type in which a light guide plate, a reflector, or the like is used as constituent members, or a direct type.

The backlight source of the liquid crystal display device is not particularly limited, but a phosphor type white LED is preferable. That is, it is an element that emits white light by combining a light-emitting diode that emits blue light or ultraviolet light using a compound semiconductor with a phosphor. Examples of phosphors include yttrium-aluminum-garnet-based yellow phosphors and terbium-aluminum-garnet-based yellow phosphors.

As the backlight light source, a white light source having emission spectrum peak tops 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 is also preferable. For example, a white light source using quantum dot technology, a phosphor-type white LED light source using a blue LED and a phosphor having emission peaks in the R (red) and G (green) regions of excitation light, and a three-wavelength method. , a white LED light source combining a red laser, and a white LED using a blue LED and a fluoride phosphor (also referred to as “KSF”) having a composition formula of K ₂ SiF ₆ : Mn ⁴ + A light source etc. are mentioned. These are attracting attention as backlight sources for liquid crystal display devices compatible with 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. side), the polarizer protective film on the incident light side of the polarizing plate arranged on the incident light side, and / or the polarizing plate arranged on the outgoing light side It is preferable that the polarizer protective film on the exiting light side is a polarizer protective film made of a polyethylene terephthalate-based resin film having the specific retardation. A particularly preferred embodiment is one in which the polyethylene terephthalate-based resin film having the specific retardation is used as the polarizer protective film on the exit light side of the polarizing plate arranged on the exit light side. If the polyethylene terephthalate-based resin film is arranged at a position other than the above, the polarization characteristics of the liquid crystal cell may be changed. Since it is not preferable to use the polymer film of the present invention where polarizing properties are required, it is preferably used as a protective film for the polarizing plate at such a specific position.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and can be carried out with appropriate modifications within the scope of the gist of the present invention. It is also possible, and all of them are included in the technical scope of the present invention. Methods for evaluating physical properties in the following examples are as follows.

(1) Retardation (Re)
The retardation is a parameter defined by the product (ΔNxy×d) of the anisotropy of the biaxial refractive index on the film (ΔNxy=|nx-ny|) and the film thickness d (nm). It is a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was obtained by the following method. Using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Keisoku Co., Ltd.), the slow axis direction of the film was determined, and the slow axis direction was 4 cm so that it was parallel to the long side of the sample for measurement. A 2 cm x 2 cm rectangle was cut out and used as a measurement sample. For this sample, the refractive index in the biaxial direction perpendicular to each other (refractive index in the slow axis direction: ny, refractive index in the direction perpendicular to the slow axis direction: nx) and the refractive index in the thickness direction (nz) were measured by Abbe refracting The absolute value of the biaxial refractive index difference (|nx−ny|) was defined as the anisotropy of the refractive index (ΔNxy) by using an index meter (NAR-4T manufactured by Atago Co., measuring wavelength 589 nm). The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D, manufactured by Finereuf Co.) and converted into nm. The retardation (Re) was obtained from the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy) and the film thickness d (nm).

(2) Rigid Amorphous Fraction The rigid amorphous fraction is represented by the above formula (1) and is indirectly calculated from the values of the mobile amorphous fraction and the mass fraction crystallinity.
The movable amorphous fraction is obtained by measuring the reversible heat capacity curve ΔCp (J/(g K)) at Tg of the reversible heat capacity curve obtained by temperature-modulated DSC measurement using a differential scanning calorimeter (Q100, manufactured by TA Instruments). is a parameter defined by the following formula using
Movable amorphous fraction = ((ΔCp of sample) / (ΔCp of completely amorphous)) × 100 (wt%)
In the case of polyethylene terephthalate, completely amorphous ΔCp=0.4052 (J/(g·K)). A sample of 2.0±0.2 mg was weighed into an aluminum pan and measured in MDSC (registered trademark) heat-only mode with an average heating rate of 5.0° C./min and a modulation period of 60 sec. Measurement data were collected at a sampling frequency of 5 Hz. Also, indium was used for calibration of temperature and calorie, and sapphire was used for calibration of specific heat.

Methods for calculating Tg and ΔCp are shown below. First, plot the first derivative F′(T) of the temperature T of the reversible heat capacity curve F(T), take the moving average for every 2401 points and perform smoothing, and then calculate the temperature value at the peak top. The Tg was determined by reading. Next, a straight line G(T) passing through two points, point A (Tg-15, F(Tg-15)) and point B (Tg+15, F(Tg+15)), was determined. Subsequently, the temperature at which F(T)-G(T) was minimized was defined as T1, and the temperature at which F(T)-G(T) was maximized was defined as T2 in the range of Tg-15≤T≤Tg+15. Since T1 corresponds to the start temperature of glass transition and T2 corresponds to the end temperature of glass transition, the value of ΔCp was obtained from ΔCp=F(T2)−F(T1).

The mass fraction crystallinity χ was calculated by the following formula using the density value d (g/cm ³ ) obtained using a water/calcium nitrate density gradient tube according to JIS K7112.
χ = (dc/d) x ((d-da)/(d-dc)) x 100 (wt%)
However, dc: density of perfect crystal, da: density of perfect amorphous In the case of polyethylene terephthalate, dc=1.498 (g/cm ³ ) and da=1.335 (g/cm ³ ).

(3) Orientation degree of the (100) plane with respect to the film surface The degree of orientation of the (100) plane with respect to the film surface is obtained by wide-angle X-ray diffraction measurement using an X-ray diffractometer (manufactured by Rigaku Co., Ltd., RINT2100PC). It is a parameter defined by the following formula using the half width of the diffraction intensity profile of the (100) plane.
(100) orientation degree with respect to the film plane = (180-half width) / 180
The measurement was carried out by the Schulz reflection method with a RINT2000 goniometer that can be attached to the RINT2100PC and a multi-purpose sample stand for poles. The sample was cut into a circular shape with a diameter of 5 cm and mounted on a sample stage so that the slow axis direction coincided with the β=90 and 270 degree directions. The details of the measurement conditions are as follows: tube voltage = 40 kV, tube current = 40 mA, 2θ fixed angle = 25.830 degrees, vertical divergence limit = 1.2 mm, divergence slit = 1 degree, scattering slit = 1 degree, receiving slit 0.30 mm. with β=0 and 180 degrees respectively, the object to be controlled is reflection α, measurement method=FT, start position=15.000 degrees, end position=90.000 degrees, step width=0. Measurement was performed at 500 degrees and counting time = 2.0 sec.

A method for calculating the degree of orientation of the (100) plane with respect to the film surface will be described below. First, the diffraction intensity profile I(α) (15≦α≦90) at β=0 and 180 degrees is corrected for incident X-ray absorption by the following equation, and the diffraction intensity profile J(α) ( 15≦α≦90).
J(α)=I(α)×(1−exp(−2μt/sinθ))/(1−exp(−2μt/(sinθcos(90−α))))
Here, μ is the linear absorption coefficient of CuKα rays, μ=9.02 (/cm) in the case of polyethylene terephthalate, t is the sample thickness (cm), and θ is the half of the 2θ fixed angle during measurement. .915 degrees. Regarding the obtained J (α) (15 ≤ α ≤ 90), the horizontal axis is α'(α' = α when β = 0 degrees, and α' = 180-α when β = 180 degrees), and the vertical axis is By setting the diffraction intensity at each α', the diffraction intensity profiles at β=0 and 180 degrees were connected to obtain a diffraction intensity profile J(α') (15≤α'≤165). However, for the diffraction intensity at α′=90 degrees, the average value of the value at β=0 degrees and the value at β=180 degrees was used. Subsequently, by fitting J(α') (15≦α'≦165) with a pseudo Voigt function, a diffraction intensity profile K(α') for all α's was obtained. Subtract a straight line connecting the diffraction intensity at α' = 0 and 180 degrees from K(α') as a baseline, and use the half-value width of the obtained diffraction intensity profile L(α') to obtain (180-half-value width) The degree of orientation of the (100) plane with respect to the film surface was calculated by /180.

(4) Observation of iridescence A polyethylene terephthalate-based resin film prepared by the method described later is attached to one side of a polarizer made of PVA and iodine so that the absorption axis of the polarizer and the main orientation axis of the film are perpendicular, and the other side is attached. A commercially available TAC film was adhered to the surface to prepare a polarizing plate. The resulting polarizing plate was used to replace the polarizing plate on the outgoing light side originally present in a commercially available liquid crystal display (REGZA 43J10X manufactured by Toshiba Corporation). The polarizing plate was replaced so that the polyethylene terephthalate-based resin film was on the viewing side so that the absorption axis of the polarizing plate coincided with the direction of the absorption axis of the polarizing plate originally attached to the liquid crystal display device. The liquid crystal display device has a light source for emitting excitation light and a backlight source containing a KSF phosphor. When the emission spectrum of the backlight source of this liquid crystal display device was measured using a multichannel spectrometer PMA-12 manufactured by Hamamatsu Photonics, an emission spectrum having peak tops near 448 nm, 533 nm, and 630 nm was observed, and each peak top was 2 nm to 49 nm. The exposure time for spectrum measurement was 20 msec. A white image was displayed on the thus-fabricated liquid crystal display device, and visual observation was performed from the front and oblique directions of the display to determine the occurrence of iridescence as follows. The viewing angle was defined as the angle formed by a line drawn in the normal direction (perpendicular) from the center of the screen of the display and a line connecting the center of the display and the eye position during viewing.
A: No iridescence was observed within the observation angle range of 0 to 60 degrees.
◯: Partially thin iridescence was observed in the observation angle range of 0 to 60 degrees.
x: Iridescent spots were clearly observed in the observation angle range of 0 to 60 degrees.

(Production Example 1-Polyester A)
When the temperature of the esterification reactor was raised to 200° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged, and 0.017 parts by mass of antimony trioxide as a catalyst was added while stirring. 0.064 parts by mass of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were charged. Then, the temperature was increased under pressure to carry out a pressure esterification reaction under conditions of a gauge pressure of 0.34 MPa and 240° C., after which the pressure in the esterification reactor was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Furthermore, the temperature was raised to 260° C. over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. After 15 minutes, dispersion treatment was performed with a high-pressure disperser. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reactor, and polycondensation reaction was performed at 280°C under reduced pressure.

After the completion of the polycondensation reaction, it is filtered through a NASLON filter with a 95% cut diameter of 5 μm, extruded from a nozzle in the form of a strand, and cooled and solidified using cooling water that has been previously filtered (pore size: 1 μm or less). , cut into pellets. The resulting polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl/g and contained substantially no inert particles or internal precipitated particles. (Hereinafter abbreviated as PET (A).)

(Production Example 2-Polyester B)
10 parts by weight of dried UV absorber (2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazinone-4-one), particle-free PET (A) (intrinsic viscosity is 0.62 dl/g), and a kneading extruder was used to obtain a polyethylene terephthalate resin (B) containing an ultraviolet absorber (hereinafter abbreviated as PET (B)).

(Production Example 3-Adhesion-improving coating liquid preparation)
A transesterification reaction and a polycondensation reaction were carried out by a conventional method to obtain 46 mol % of terephthalic acid, 46 mol % of isophthalic acid and 8 mol % of sodium 5-sulfonatoisophthalate as dicarboxylic acid components (relative to the total dicarboxylic acid components). A water-dispersible sulfonic acid metal group-containing copolymer polyester resin was prepared having a composition of 50 mol % ethylene glycol and 50 mol % neopentyl glycol as the glycol component (relative to the total glycol component). Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, and 0.06 parts by mass of a nonionic surfactant are mixed and then heated and stirred. After adding 5 parts by mass of a water-dispersible sulfonic acid metal group-containing copolymerized polyester resin and continuing to stir until the lumps of the resin disappear, the resin aqueous dispersion was cooled to room temperature to obtain a solid content concentration of 5.0% by mass. A homogeneous water-dispersible copolyester resin liquid was obtained. Furthermore, after dispersing 3 parts by mass of aggregated silica particles (manufactured by Fuji Silysia Co., Ltd., Silysia 310) in 50 parts by mass of water, Silysia 310 was added to 99.46 parts by mass of the water-dispersible copolymer polyester resin liquid. 0.54 parts by mass of the aqueous dispersion was added, and 20 parts by mass of water was added while stirring to obtain an adhesion-improving coating liquid.

(Example 1)
After drying under reduced pressure (1 Torr) at 135° C. for 6 hours, 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 base film intermediate layer. , supplied to extruder 2 (for intermediate layer II layer), and PET (A) was dried by a conventional method, supplied to extruder 1 (for outer layer I layer and outer layer III), and melted at 285 ° C. . These two types of polymers are each filtered with a stainless sintered filter material (nominal filtration accuracy: 10 μm, 95% cut of particles), laminated in a two-type, three-layer confluence block, extruded in a sheet form from a nozzle, An unstretched film was produced by winding the film around a casting drum having a surface temperature of 30° C. and solidifying it by cooling using an electrostatic casting method. At this time, the discharge rate of each extruder was adjusted so that the thickness ratio of the I layer, the II layer, and the III layer was 10:80:10.

Next, the adhesion-improving coating solution was applied to both sides of the unstretched PET film by a reverse roll method so that the coating amount after drying was 0.08 g/m ² , and then dried at 80°C for 20 seconds. .

The unstretched film with the coating layer formed thereon is guided to a tenter stretching machine, and while holding the ends of the film with clips, it is guided to a hot air zone at a temperature of 130 ° C., and the strain rate is 13 so that it becomes 5.5 times in the width direction. It was stretched at .8%/sec. Next, while maintaining the stretched width in the width direction, the film was heat treated in a hot air zone at a temperature of 180° C. and further subjected to a 3% relaxation treatment in the width direction to obtain a uniaxially oriented PET film with a film thickness of about 60 μm.

(Example 2)
An unstretched film produced by the same method as in Example 1 is guided to a tenter stretching machine, and while holding the ends of the film with clips, it is guided to a hot air zone at a temperature of 120 ° C. so that it is 5.5 times in the width direction. , and stretched at a strain rate of 18.3%/sec. Next, while maintaining the stretched width in the width direction, the film was heat treated in a hot air zone at a temperature of 180° C. and further subjected to a 3% relaxation treatment in the width direction to obtain a uniaxially oriented PET film with a film thickness of about 60 μm.

(Example 3)
An unstretched film produced by the same method as in Example 1 is guided to a tenter stretching machine, and while holding the ends of the film with clips, it is guided to a hot air zone at a temperature of 118 ° C. so that it becomes 5.0 times in the width direction. , at a strain rate of 34.6%/sec. Next, while maintaining the stretched width in the width direction, the film was heat treated in a hot air zone at a temperature of 180° C. and further subjected to a 3% relaxation treatment in the width direction to obtain a uniaxially oriented PET film with a film thickness of about 60 μm.

(Example 4)
An unstretched film produced by the same method as in Example 1 is guided to a tenter stretching machine, and while holding the ends of the film with clips, it is guided to a hot air zone at a temperature of 107 ° C. so that it becomes 5.0 times in the width direction. , at a strain rate of 34.6%/sec. Next, while maintaining the stretched width in the width direction, the film was heat treated in a hot air zone at a temperature of 180° C. and further subjected to a 3% relaxation treatment in the width direction to obtain a uniaxially oriented PET film with a film thickness of about 60 μm.

(Example 5)
An unstretched film produced in the same manner as in Example 1 except that the thickness was changed was guided to a tenter stretching machine, and while holding the end of the film with a clip, was guided to a hot air zone at a temperature of 125 ° C., and stretched 5 in the width direction. It was stretched at a strain rate of 18.3%/sec so as to be 0.5 times. Next, while maintaining the stretched width in the width direction, the film was heat-treated in a hot air zone at a temperature of 180° C. and further subjected to a relaxation treatment of 3% in the width direction to obtain a uniaxially oriented PET film with a film thickness of about 50 μm.

(Example 6)
An unstretched film produced by the same method as in Example 1 is guided to a tenter stretching machine, and while holding the ends of the film with clips, it is guided to a hot air zone at a temperature of 130 ° C. so that it becomes 5.5 times in the width direction. , and stretched at a strain rate of 13.8%/sec. Next, while maintaining the stretched width in the width direction, the film was heat-treated in a hot air zone at a temperature of 200° C. and further subjected to a relaxation treatment of 3% in the width direction to obtain a uniaxially oriented PET film with a film thickness of about 60 μm.

(Example 7)
An unstretched film produced by the same method as in Example 1 is guided to a tenter stretching machine, and while holding the ends of the film with clips, it is guided to a hot air zone at a temperature of 120 ° C. so that it becomes 6.0 times in the width direction. , and stretched at a strain rate of 20.8%/sec. Next, while maintaining the stretched width in the width direction, the film was heat-treated in a hot air zone at a temperature of 180° C. and further subjected to a relaxation treatment of 3% in the width direction to obtain a uniaxially oriented PET film with a film thickness of about 50 μm.

(Comparative example 1)
An unstretched film produced by the same method as in Example 1 is guided to a tenter stretching machine, and while holding the ends of the film with clips, it is guided to a hot air zone at a temperature of 90 ° C. so that it becomes 4.0 times in the width direction. , and stretched at a strain rate of 12.5%/sec. Next, while maintaining the stretched width in the width direction, the film was heat treated in a hot air zone at a temperature of 180° C. and further subjected to a 3% relaxation treatment in the width direction to obtain a uniaxially oriented PET film with a film thickness of about 60 μm.

(Comparative example 2)
An unstretched film produced by the same method as in Example 1 is guided to a tenter stretching machine, and while holding the ends of the film with clips, it is guided to a hot air zone at a temperature of 130 ° C. so that it becomes 5.5 times in the width direction. , and stretched at a strain rate of 13.8%/sec. Next, while maintaining the stretched width in the width direction, the film was heat treated in a hot air zone at a temperature of 240° C. and further subjected to a relaxation treatment of 3% in the width direction to obtain a uniaxially oriented PET film with a film thickness of about 60 μm.

Table 1 shows the results of measurement of the PET films obtained in Examples and Comparative Examples.

With the liquid crystal display device, the polarizing plate, and the polarizer protective film of the present invention, even when the wavelength spectrum of the backlight source is diversified due to the widening of the color gamut of the liquid crystal display device or the thickness of the polarizer protective film is reduced, the rainbow It can suppress spots.

Claims (4)

A polarizer protective film made of a polyethylene terephthalate resin film that satisfies the following (1) and (2).
(1) The retardation is 3000 nm or more and 30000 nm or less (2) The rigid amorphous fraction represented by the following formula is 33 wt% or more (rigid amorphous fraction (wt%)) = 100 - (movable amorphous content rate (wt%)) - (mass fraction crystallinity (wt%)) The polarizer protective film according to claim 1, wherein the polyethylene terephthalate-based resin film further satisfies (3) below.
(3) The degree of orientation of the (100) plane with respect to the film surface measured by X-ray diffraction is 0.7 or less A polarizing plate comprising a polarizer and the polarizer protective film according to claim 1 laminated on at least one surface of the polarizer. A liquid crystal display device comprising a backlight source, two polarizing plates, and a liquid crystal cell arranged between the two polarizing plates,
A liquid crystal display device, wherein at least one of the two polarizing plates is the polarizing plate according to claim 3 .