JP6035964B2 - Liquid crystal display device, polarizing plate and polarizer protective film - Google Patents

Description

  The present invention relates to a liquid crystal display device, a polarizing plate and a polarizer protective film. Specifically, the present invention relates to a liquid crystal display device, a polarizing plate, and a polarizer protective film in which generation of rainbow spots is improved.

  A polarizing plate used in a liquid crystal display device (LCD) is usually composed of a polarizer in which iodine is dyed on polyvinyl alcohol (PVA) or the like and sandwiched between two polarizer protective films. In general, a triacetyl cellulose (TAC) film is used. In recent years, with the thinning of LCDs, there has been a demand for thinner polarizing plates. However, if the thickness of the TAC film used as the protective film is reduced for this purpose, sufficient mechanical strength cannot be obtained and moisture permeability deteriorates. Further, TAC films are very expensive, and there is a strong demand for inexpensive alternative materials.

  Therefore, it has been proposed to use a polyester film instead of the TAC film so that the polarizing plate can be made thin so that high durability can be maintained even if the thickness is small as a polarizer protective film (Patent Documents 1 to 3). ).

  The triacetyl cellulose film used as a polarizer protective film is subjected to alkali treatment or the like on its surface, and has an extremely high affinity with a hydrophilic adhesive. Therefore, the protective film made of a triacetyl cellulose film has extremely high adhesiveness with a polarizer coated with a hydrophilic adhesive. However, the polyester film has insufficient adhesion to the hydrophilic adhesive, and this tendency becomes more prominent particularly in the case of a polyester film having orientation by a stretching treatment. Then, in order to improve adhesiveness with a polarizer or the hydrophilic adhesive apply | coated to the polarizer, providing an easily bonding layer in a polyester film is proposed (patent documents 4-7).

  The polyester film is superior to the TAC film in durability, but unlike the TAC film, the polyester film has birefringence. Therefore, when the polyester film is used as a polarizer protective film, there is a problem that the image quality is deteriorated due to optical distortion. That is, since the polyester film having birefringence has a predetermined optical anisotropy (retardation), when used as a polarizer protective film, a rainbow-like color spot is generated when observed from an oblique direction, and the image quality is deteriorated. . Therefore, in patent documents 1-3, the countermeasure which makes retardation small is made by using copolyester as polyester. However, even in that case, the iridescent color spots could not be completely eliminated.

JP 2002-116320 A JP 2004-219620 A JP 2004-205773 A JP-A-8-271733 JP-A-8-271734 JP 2009-157361 A JP 2011-8170 A WO2011-162198

  As a means for solving the above problems, the present inventors have found that a white light emitting diode is used as a backlight light source, and an oriented polyester film having a certain retardation is used as a polarizer protective film (Patent Document 8). . However, the inventors have made further studies on the liquid crystal display device having such a configuration, and even in such an improved liquid crystal display device, polyester as a polarizer protective film is provided on both of the pair of polarizing plates. In the case of using a film, we discovered the existence of a new problem that, when observed from an oblique direction, there may still be rainbow spots depending on the angle.

  Furthermore, the polyester film has a low affinity for water, and this tendency is particularly remarkable in the polyester film having an aromatic dicarboxylic acid as a dicarboxylic acid component. Moreover, the polyester film which has crystal orientation by extending | stretching has a low affinity with water further. On the other hand, the polarizer and the adhesive applied on the polarizer are generally composed mainly of a polyvinyl alcohol resin and have high hydrophilicity. Due to such a difference in properties, the polyester film and the polarizer or the polyvinyl alcohol-based adhesive have low affinity, and it has been difficult to firmly bond the two. Therefore, even if it is a polyester film which has an easily bonding layer disclosed by patent documents 1-3 and 5, compared with a triacetyl cellulose film, sufficient adhesiveness is not yet acquired. Therefore, when a polarizing plate using a conventional polyester film as a protective film is used as a display member for a long time, floating or peeling occurs between the protective film and the polarizer, and the polarization characteristics deteriorate due to a change in the amount of moisture in the polarizer. In addition, the visibility such as white spots may deteriorate.

Therefore, the present invention has been made to solve such a problem, and the purpose thereof is excellent in adhesion between a polyester film and a polyvinyl alcohol resin layer such as a polarizer or an adhesive applied on the polarizer. It is an object of the present invention to suppress the occurrence of rainbow spots when an oriented polyester film is used as a polarizer protective film for both of a pair of polarizing plates of a liquid crystal display device.

  As a result of examining the above problems day and night, the present inventor has controlled the retardation of the oriented polyester film used as the polarizer protective film and the characteristic of the Nz coefficient represented by | ny-nz | / | ny-nx |. The present inventors have found that the occurrence of rainbow spots can be effectively suppressed when a polyester film is used as the polarizer protective film for both of the pair of polarizing plates of the liquid crystal display device.

  Moreover, regarding the polyester film excellent in adhesiveness to the polarizer, the present inventors include a polyester resin having a high affinity with the polyester film and a polyvinyl alcohol resin having a high affinity with the polyvinyl alcohol resin layer. The idea was to provide a layer on the polyester film. However, the present inventors have found that the function of closely adhering the polyester film and the polyvinyl alcohol-based resin layer due to each component cannot be sufficiently exhibited by simply combining these components. Therefore, as a result of repeated day and night studies, the present inventors have controlled the presence of the binder resin in the coating layer provided on the surface of the polyester film in the above concept, and the phase in which the polyester resin is aggregated and the polyvinyl alcohol resin. It has been found that by forming a nanophase separation structure composed of an aggregated phase on the surface of the coating layer, the adhesive action with the polarizer can be more effectively exhibited.

The present invention has been completed as a result of further research and improvement based on such knowledge.

The representative present invention is as follows.
Item 1.
A polarizer protective film having a coating layer on at least one side of an oriented polyester film,
The oriented polyester film is a film having a retardation of 4000 to 30000 nm and an Nz coefficient of 1.70 or less,
The coating layer includes a cross-linking agent;
The crosslinking agent is a melamine crosslinking agent and / or an isocyanate crosslinking agent,
The coating layer includes a polyvinyl alcohol resin and a polyester resin, and a surface of the coating layer has a nanophase separation structure including a phase in which the polyvinyl alcohol resin is aggregated and a phase in which the polyester resin is aggregated. The polarizer protective film whose area ratio of an alcohol phase is 30% or more and less than 99%.
Item 2.
Item 2. The polarizer protective film according to Item 1, wherein the orientation degree of the oriented polyester film is 0.13 or less.
Item 3.
Item 3. The polarizer protective film according to Item 1 or 2, wherein the oriented polyester film comprises at least three layers, an ultraviolet absorber is contained in a layer other than the outermost layer, and the light transmittance at 380 nm is 20% or less.
Item 4.
Item 4. The polarizer protective film according to any one of Items 1 to 3, wherein the saponification degree of the polyvinyl alcohol-based resin is 95% or less.
Item 5.
Item 5. The polarizer protective film according to any one of Items 1 to 4, wherein the polyester-based resin has a glass transition temperature of 25 ° C or higher.
Item 6.
Item 6. The polarizer protective film according to any one of Items 1 to 5, wherein the acid value of the polyester-based resin is 20 KOHmg / g or less.
Item 7 .
Item 7. The polarizer protective film according to any one of Items 1 to 6 , wherein a mass ratio of the polyvinyl alcohol resin (PVA) and the polyester resin (PEs) contained in the coating layer satisfies the following formula.
0.2 ≦ PVA / PEs ≦ 1.25
Item 8.
The compounding ratio ((A) + (B) / (C)) of the polyester resin (A), the polyvinyl alcohol resin (B), and the crosslinking agent (C) contained in the coating layer is 2 to 50 in terms of mass ratio. The polarizer protective film in any one of claim | item 1 -7.
Item 9.
The polarizing plate by which the polarizer protective film in any one of claim | item 1 -8 was laminated | stacked on the at least single side | surface of the polarizer.
Item 10.
A liquid crystal display device having a backlight light source and a liquid crystal cell disposed between two polarizing plates,
The backlight source is a white light source having a continuous emission spectrum;
Item 10. A liquid crystal display device, wherein both the two polarizing plates are the polarizing plates according to Item 9.
Item 11.
The polarizer protective film on the incident light side of the polarizing plate arranged on the incident light side and the polarizer protective film on the outgoing light side of the polarizing plate arranged on the outgoing light side are according to any one of claims 1 to 8. The liquid crystal display device according to claim 10 , which is a polarizer protective film.
Item 12.
Item 12. The liquid crystal display device according to item 10 or 11 , wherein the white light source having a continuous emission spectrum is a white light emitting diode.

The polarizer protective film of the present invention is excellent in adhesion between the polarizer protective film and a polarizer represented by a polyvinyl alcohol-based resin layer or an adhesive applied thereon. Therefore, a polarizing plate using the polarizer protective film of the present invention, the protective film and the floating or peeling hardly occurs between the polarizer, hardly occurs a decrease in polarization characteristics due to a change in water content in the polarizer. Therefore, in the liquid crystal display device using the polarizing plate of the present invention, the deterioration of visibility such as white spots due to the deterioration of the characteristics over time in the conventional polarizing plate is reduced. Moreover, if it is a polarizer protective film of this invention, even if it is a case where an oriented polyester film is used as a polarizer protective film of both of a pair of polarizing plate of a liquid crystal display device, generation | occurrence | production of an rainbow spot is suppressed. it can. That is, the liquid crystal display device produced using the polarizer protective film of the present invention has excellent visibility since the occurrence of rainbow spots is suppressed.

  Although not limited by theory, the polarizer protective film of the present invention is a phase in which a polyester resin is agglomerated on the surface of the coating layer (hereinafter referred to as “PEs phase” as appropriate). ) And a phase in which the polyvinyl alcohol-based resin is aggregated (hereinafter, referred to as “PVA phase” as appropriate) is formed, so that a polarizer caused by the PVA phase or on the polarizer It is considered that strong adhesiveness with the provided adhesive is exhibited.

The nanophase separation structure of the coating layer surface of the polarizer protective film 20 is shown. The scale unit is μm, and the actual size is 1 μm × 1 μm.

1. 2. Liquid Crystal Display Device In general, a liquid crystal display device is composed of a rear module, a liquid crystal cell, and a front module in order from the side facing the backlight light source toward the image display side (viewing side or outgoing light 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, and a polarizing plate disposed on the opposite side. Here, the polarizing plate is disposed on the side facing the backlight light source in the rear module, and is disposed on the image display side (viewing side or outgoing light side) in the front module.

2. Backlight Light Source The liquid crystal display device of the present invention includes at least a backlight light source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates as constituent members. The liquid crystal display device of the present invention may have other constituent members other than these, for example, a color filter, a lens film, a diffusion sheet, an antireflection film and the like as appropriate.

  The configuration of the backlight may be an edge light method using a light guide plate, a reflection plate, or the like as a constituent member, or a direct type. In the present invention, it is preferable to use a white light source having a continuous and broad emission spectrum as the backlight source of the liquid crystal display device. Here, the continuous emission spectrum means an emission spectrum in which there is no wavelength at which the light intensity becomes zero in a wavelength region of at least 450 nm to 650 nm, preferably in the visible light region. As such a white light source having a continuous and broad emission spectrum, for example, a white LED can be exemplified, but the present invention is not limited thereto.

  The white LED usable in the present invention includes a phosphor type, that is, an element that emits white light by combining a light emitting diode that emits blue light or ultraviolet light using a compound semiconductor and a phosphor, or an organic light emitting diode (Organic light diode). -Emitting diode (OLED). Examples of the phosphor include yttrium / aluminum / garnet yellow phosphor and terbium / aluminum / garnet yellow phosphor. Among white LEDs, white light-emitting diodes, consisting of light-emitting elements that combine blue light-emitting diodes using compound semiconductors with yttrium, aluminum, and garnet-based yellow phosphors, have a continuous and broad emission spectrum and have a luminous efficiency. Therefore, it is suitable as the backlight light source of the present invention. Since the white LED has low power consumption, the liquid crystal display device of the present invention using the white LED contributes to energy saving.

  Fluorescent tubes such as cold-cathode tubes and hot-cathode tubes that have been widely used as backlight light sources have a discontinuous emission spectrum whose emission spectrum has a peak at a specific wavelength. Therefore, since it is difficult to obtain the desired effect of the present invention, it is not preferable as the light source of the liquid crystal display device of the present invention.

3. Polarizer Protective Film The polarizing plate has a configuration in which two polarizer protective films are bonded to a polarizer in which PVA or the like is dyed with iodine. The polarizing plate used in the present invention is an oriented polyester that satisfies at least one of two polarizer protective films with a specific range of retardation and a physical property of Nz coefficient represented by | ny-nz | / | ny-nx |. Use film.

3-1. Retardation It is preferable that the oriented polyester film used for the polarizer protective film used in the present invention has a retardation of 4000 to 30000 nm. This is because when the retardation is less than 4000 nm, an interference color is exhibited when the liquid crystal display device is observed from an oblique direction, so that good visibility cannot always be ensured. The preferred retardation of the oriented polyester film is 4500 nm or more, then preferably 5000 nm or more, more preferably 6000 nm or more, still more preferably 8000 nm or more, and even more preferably 10,000 nm or more.

  The upper limit of the retardation of the oriented polyester film is 30000 nm. Even if an oriented polyester film having a retardation higher than that is used, a further improvement effect of visibility is not substantially obtained, and as the retardation increases, the thickness of the film is considerably increased, and the handleability as an industrial material is improved. It is because it falls.

  The retardation value of the oriented polyester film can be determined by measuring the biaxial refractive index and thickness according to a known method. For example, it can also measure using commercially available automatic birefringence measuring apparatuses, such as KOBRA-21ADH (Oji Scientific Instruments).

  As shown in Patent Document 8, when the oriented polyester film is used as a polarizer protective film for only one of a pair of polarizing plates, the retardation of the oriented polyester film is controlled in the range of 3000 to 30000 nm and is continuously used as a light source. By adopting a white light source having a broad spectrum of emission, the generation of rainbow spots is suppressed. The principle is considered as follows.

That is, when a birefringent or oriented polyester film is disposed on one side of the polarizer, the linearly polarized light emitted from the polarizer is disturbed when passing through the polyester film. And the transmitted light shows the interference color peculiar to the retardation which is the product of the birefringence and the thickness of the polyester film. Therefore, when a light source having a discontinuous emission spectrum, such as a cold cathode tube or a hot cathode tube, is used as the light source, the transmitted light intensity varies depending on the wavelength, and a rainbow-like color spot is exhibited.

  On the other hand, when light having a continuous and broad emission spectrum in a wavelength region of at least 450 nm to 650 nm, preferably in the visible light region, passes through the birefringent body, the interference color spectrum becomes an envelope shape. Therefore, by controlling the retardation of the polyester film, a spectrum similar to the emission spectrum of the light source can be obtained. In this way, by making the emission spectrum of the light source similar to the envelope shape of the interference color spectrum by the transmitted light that has passed through the birefringent body, visibility is not noticeable without rainbow-like color spots. It is thought to improve.

  However, as described above, when the oriented polyester film is used as the polarizer protective film in both of the pair of polarizing plates, rainbow spots may still be observed. Although the present invention makes it possible to suppress the occurrence of such rainbow spots, the principle has not yet been elucidated.

3-2. The oriented polyester film used for the Nz coefficient 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 determined using a molecular orientation meter (manufactured by Oji Scientific Instruments, MOA-6004 type molecular orientation meter), and the biaxial refractive index (ny, nx, However, ny> nx) and the refractive index (nz) in the thickness direction are obtained by an Abbe refractometer (manufactured by Atago Co., Ltd., NAR-4T, measurement wavelength 589 nm). The Nz coefficient can be obtained by substituting nx, ny, and nz obtained in this way into an expression represented by | ny-nz | / | ny-nx |.

If the Nz coefficient of the oriented polyester film exceeds 1.7, rainbow spots may occur depending on the angle when the liquid crystal display device is observed from an oblique direction. The Nz coefficient is more preferably 1.65 or less, and still more preferably 1.63 or less. The lower limit value of the Nz coefficient is 1.20. This is because it is difficult in terms of manufacturing technology to obtain a film of less than 1.20. In order to maintain the mechanical strength of the film, the lower limit value of the Nz coefficient is preferably 1.30 or more, more preferably 1.40 or more, and further preferably 1.45 or more.

3-3. Arrangement of Polarizer Protective Film In the liquid crystal display device of the present invention, the oriented polyester film having the specific retardation and the Nz coefficient is used as both polarizer protective films of a pair of polarizing plates. The pair of polarizing plates means a combination of a polarizing plate disposed on the incident light side with respect to the liquid crystal and a polarizing plate disposed on the outgoing light side with respect to the liquid crystal. That is, the oriented polyester film is used for both a polarizing plate on the incident light side and a polarizing plate on the outgoing light side. The oriented polyester film only needs to be used as at least one of the two polarizer protective films constituting each polarizing plate, and may be used for both.

  In a preferred embodiment, the oriented polyester film is used as a polarizer protective film on the incident light side of the polarizing plate on the incident light side, and as a polarizer protective film on the outgoing light side of the polarizing plate on the outgoing light side. used. When the oriented polyester film is used for only one of the two polarizer protective films constituting the polarizing plate, an arbitrary polarizer protective film (for example, a TAC film) can be used for the other. When the oriented polyester film is used as the polarizer protective film on the liquid crystal cell side of the polarizing plate arranged on the incident light side and the polarizer protective film on the liquid crystal cell side of the polarizing plate arranged on the outgoing light side, the polarization of the liquid crystal cell Since there is a possibility of changing the characteristics, the polarizer protective film at these positions is a polarizer protective film other than the oriented polyester film (for example, a TAC film, an acrylic film, or a norbornene-based film). It is preferable to use a film having no birefringence.

3-4. In addition to controlling the retardation value and Nz coefficient of the plane orientation coefficient oriented polyester film to the above specific range, by making the plane orientation degree represented by (nx + ny) / 2-nz below the specific value, more reliably Iridescents can be completely eliminated when a polyester film is used as a polarizer protective film for both of the pair of polarizing plates. Here, the values of nx, ny, and nz are obtained by the same method as for the Nz coefficient. The degree of plane orientation of the oriented polyester film is preferably 0.13 or less, more preferably 0.125 or less, and still more preferably 0.12 or less. By setting the degree of plane orientation to 0.13 or less, it is possible to completely eliminate rainbow spots observed depending on the angle when the liquid crystal display device is observed from an oblique direction. The plane orientation degree is preferably 0.08 or more, and more preferably 0.10 or more. If the degree of plane orientation is less than 0.08, the thickness of the film varies, and the retardation value may be nonuniform in the film plane.

3-5. Retardation ratio The ratio (Re / Rth) of retardation (Re) and thickness direction retardation (Rth) of the oriented polyester film is preferably 0.2 or more, more preferably 0.5 or more, and still more preferably 0.6. That's it. This is because as the ratio of the retardation to the retardation in the thickness direction (Re / Rth) is larger, the birefringence action is more isotropic, and the occurrence of rainbow-like color spots due to the observation angle is less likely to occur. In a perfect uniaxial (uniaxial symmetry) film, the ratio of the retardation to the retardation in the thickness direction (Re / Rth) is 2.0. However, as will be described later, the mechanical strength in the direction orthogonal to the orientation direction is significantly lowered as the film approaches a complete uniaxial (uniaxial symmetry) film.

  Therefore, the upper limit of the ratio of retardation to retardation in the thickness direction (Re / Rth) is preferably 1.2 or less, and more preferably 1.0 or less. In order to completely suppress the occurrence of rainbow-like color spots due to the observation angle, the ratio of the retardation to the thickness direction retardation (Re / Rth) does not have to be 2.0, and 1.2 or less is sufficient. is there. Even if the ratio is 1.0 or less, it is possible to satisfy the viewing angle characteristics (180 degrees left and right, 120 degrees up and down) required for the liquid crystal display device.

3-6. Thickness unevenness In order to suppress the variation in retardation of the oriented polyester film, it is preferable that the thickness unevenness of the film is small. In this respect, the uneven thickness of the oriented polyester film is preferably 5.0% or less, more preferably 4.5% or less, still more preferably 4.0% or less, and 3.0% % Or less is particularly preferable.

3-7. Thickness The thickness of the oriented polyester film is not particularly limited as long as the effect of the present invention is not hindered, but is usually 15 to 300 μm, preferably 15 to 200 μm. When the film thickness is less than 15 μm, the anisotropy of the mechanical properties of the film becomes remarkable, and tearing, tearing, and the like may occur. A particularly preferable lower limit of the thickness is 25 μm. On the other hand, if the upper limit of the thickness of the polarizer protective film exceeds 300 μm, the thickness of the polarizing plate becomes too thick, which is not preferable. From the viewpoint of practicality as a polarizer protective film, the upper limit of the thickness is preferably 200 μm. A particularly preferable upper limit of the thickness is 100 μm, which is about the same as a general TAC film.

3-8. Polyester resin The oriented polyester film used in the present invention can be obtained from any polyester resin. The type of the polyester resin is not particularly limited, and any polyester resin obtained by condensing dicarboxylic acid and diol can be used.

  Examples of the dicarboxylic acid component that can be used in the production of the polyester resin include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1 , 5-Naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracene dicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid , Hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyl Adipine , Pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, dodecamethylene dicarboxylic acid and the like.

  Examples of the diol component that can be used for the production of the polyester resin include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1 , 3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexadiol, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, etc. Can be mentioned.

  The dicarboxylic acid component and the diol component constituting the polyester resin can be used alone or in combination of two or more. Suitable polyester resins constituting the polyester film include, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and more preferably polyethylene terephthalate and polyethylene naphthalate. Furthermore, other copolymer components may be included. These resins are excellent in transparency and excellent in thermal and mechanical properties, and the retardation can be easily controlled by stretching. In particular, polyethylene terephthalate is the most suitable material because it has a large intrinsic birefringence and a large retardation can be obtained relatively easily even if the film is thin.

3-9. Light Transmittance The oriented polyester film desirably has a light transmittance of 20% or less at a wavelength of 380 nm from the viewpoint of suppressing deterioration of optical functional dyes such as iodine dyes contained in the polarizer. The light transmittance at 380 nm is more preferably 15% or less, further preferably 10% or less, and particularly preferably 5% or less. If the light transmittance is 20% or less, the optical functional dye can be prevented from being deteriorated by ultraviolet rays. The light transmittance is measured by a method perpendicular to the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500 type).

  The transmittance of the oriented polyester film at a wavelength of 380 nm can be controlled to 20% or less by appropriately adjusting the type and concentration of the ultraviolet absorber to be blended and the thickness of the film. As the ultraviolet absorber used in the present invention, a known ultraviolet absorber can be appropriately selected and used. Specific examples of the ultraviolet absorber include an organic ultraviolet absorber and an inorganic ultraviolet absorber, and an organic ultraviolet absorber is preferable from the viewpoint of transparency.

  Examples of the organic ultraviolet absorber include benzotriazole, benzophenone, and cyclic imino ester, and combinations thereof. However, the organic ultraviolet absorber is not particularly limited as long as it is within the absorbance range defined in the present invention. However, from the viewpoint of durability, benzotoazole and cyclic imino ester are particularly preferable. When two or more kinds of ultraviolet absorbers are used in combination, ultraviolet rays having different wavelengths can be absorbed simultaneously, so that the ultraviolet absorption effect can be further improved.

Examples of the benzophenone ultraviolet absorber, benzotriazole ultraviolet absorber, and acrylonitrile ultraviolet absorber 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. Examples of cyclic imino ester UV absorbers include 2,2 ′-(1,4- Phenylene) bis (4H-3,1-benzoxazinon-4-one), 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazin-4-one, 2 -Phenyl-3,1-benzoxazin-4-one, etc. These ultraviolet absorbers may be used alone or in combination of two or more.

When an ultraviolet absorbent is blended in the oriented polyester film, it is preferable that the oriented polyester film has a multilayer structure of three or more layers, and the ultraviolet absorbent is added to a layer other than the outermost layer (ie, the intermediate layer) of the film.

3-10. Other components, etc. In addition to the ultraviolet absorber, it is also preferable to add various additives to the oriented polyester film as long as the effects of the present invention are not hindered. Examples of additives include inorganic particles, heat resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light proofing agents, flame retardants, thermal stabilizers, antioxidants, and antigelling agents. And surfactants. Moreover, in order to show high transparency, it is also preferable that a polyester film does not contain a particle | grain substantially. “Substantially free of particles” means, for example, in the case of inorganic particles, a content that is 50 ppm or less, preferably 10 ppm or less, particularly preferably the detection limit or less when inorganic elements are quantified by fluorescent X-ray analysis. means.

4). Covering layer (adhesive layer)
The polarizer protective film of the present invention has a polyester resin (on at least one surface of a polyester film) in order to improve the adhesion with a polarizer or a polyvinyl alcohol resin layer such as a water-based adhesive provided on one or both surfaces of the polarizer. The easy-adhesion layer (coating layer) which consists of a resin composition containing A) and polyvinyl alcohol-type resin (B) is laminated | stacked. The coating layer is provided on at least one side of the polyester film, and may be provided on both sides. A different kind of resin coating layer may be provided on the other surface. Adhesiveness to the base film is achieved with the polyester resin (A), and adhesion to the polarizer / water-based adhesive is achieved with the polyvinyl alcohol resin (B), thereby favoring the adhesion between these two layers. Can be compatible.

(Coating layer)
In the present invention, the coating layer contains a polyvinyl alcohol resin and a polyester resin as a binder resin, and the surface of the coating layer has a phase in which the polyvinyl alcohol resin is aggregated (PVA phase) and a phase in which the polyester resin is aggregated (PEs phase). A nanophase separation structure. In the present invention, the phrase “the coating layer contains a polyvinyl alcohol resin and a polyester resin” means that the coating layer is a resin layer formed using a polyvinyl alcohol resin and a polyester resin as raw material components. Similarly, when the coating layer contains a component other than these resins (for example, a crosslinking agent), it means that it is a coating layer formed using these resins and other components (for example, a crosslinking agent) as raw materials. To do.

  The nanophase separation structure on the surface of the coating layer refers to two types of nanoscale phases (or regions) of PVA phase and PEs phase that are clearly distinguished by detection of the surface of the coating layer using a scanning probe microscope described later. It means existing on the surface of the coating layer. As described above, the PVA phase is a phase formed by aggregation of polyvinyl alcohol-based resins. Therefore, although the PVA phase is mainly composed of a polyvinyl alcohol-based resin, as long as it can be distinguished from the PEs phase by a scanning probe microscope, the component constituting the other coating layer mixed with aggregation (for example, Crosslinkers and trace amounts of PEs) may be included. Similarly, the PEs phase is a phase formed by aggregating polyester resins. Therefore, the PEs phase is mainly composed of a polyester resin, but as long as it can be distinguished from the PVA phase by a scanning probe microscope, other components (for example, a cross-linking agent and a small amount of PVA) are mixed. You may do it.

  The size and shape of the PVA phase and the PEs phase are not particularly limited as long as the structure satisfies the surface fraction of the PVA phase described later and is recognized as a nanophase separation structure in the technical field. Specific examples of the nanophase separation structure include a sea-island structure, a core / shell structure, and a laminated structure (lamella structure) in which each phase is regularly arranged.

  When forming the nano isolation | separation structure whose coating layer surface is a sea island structure, any of a PVA phase and a PEs phase may form the phase corresponded to an island. As shown in FIG. 1, the sea-island structure may be an independent “island” -like form or may be a form in which “islands” are continuous. The size of the sea-island structure is not particularly limited. For example, the sea-island structure is mainly an island-shaped structure having a width in the minor axis direction of 20 nm to 500 nm at the maximum and a length in the major axis direction exceeding 50 nm. By having such a nano-sized dispersion structure, the properties of both resins can be suitably achieved.

The core-shell structure, which is one of the nanophase separation structures, is a structure in which, for example, the PVA phase is surrounded by the PEs phase, and further, the PEs phase is surrounded by the PVA phase. In any case, on the surface of the coating layer, when measured using a scanning probe microscope, a phase recognized as an aggregate of a polyvinyl alcohol resin and a phase recognized as an aggregate of a polyester resin, It is preferable from the viewpoint of exhibiting excellent adhesiveness that it is dispersed without significant deviation. The coating layer surface having the nanophase separation structure as described above preferably has an area ratio of the PVA phase defined by the following formula of 30% or more and less than 99%.
PVA phase surface fraction (%) = (PVA phase area / measurement area) × 100
The area of the PVA phase is measured by using a phase measurement mode of a scanning probe microscope, which will be described later. In that case, the polyvinyl alcohol phase shows a dark hue in a phase image, for example. Although the measurement area is not particularly limited, for example, it can be performed at 1 μm × 1 μm.

  The PVA surface fraction is preferably 30 to 99%. If it is less than 30%, the surface fraction of the PEs phase on the surface of the coating layer becomes relatively large, and the adhesion to the polarizer / water-based adhesive may decrease. On the other hand, when the PVA surface fraction is 99% or more, the adhesion to the polyester film (base material) may be lowered. The lower limit of the PVA surface fraction on the surface of the coating layer is preferably 30%, more preferably 35%, and even more preferably 40%. On the other hand, the upper limit of the PVA surface fraction is more preferably 99%, further preferably 95%, and still more preferably 90%.

  The PVA surface fraction of the nanophase separation structure can be measured by a paper weight method or an image analysis method described in Examples described later.

  The reason why the adhesion is improved by the nano-separation structure is considered as follows. Polyvinyl alcohol resins are rich in hydrophilicity, and polyester resins are rich in hydrophobicity. For this reason, simply mixing and applying the two resins causes the two resins to be completely separated and cannot exhibit sufficient adhesion. On the other hand, although both resins can be forcibly mixed with a surfactant or the like, sufficient adhesiveness cannot be exhibited in this case because the properties of both resins are impaired. On the other hand, both resins form a nanophase separation structure, and a predetermined proportion of PVA phase is present on the surface of the coating layer, so that adhesion with the polarizer or the adhesive provided thereon is caused by the PVA resin. And the adhesiveness with the polyester film due to the PEs resin can be efficiently exhibited at the same time.

  The nanophase separation structure on the surface of the coating layer can be confirmed by measuring in a phase measurement mode (phase mode) using a scanning probe microscope (SPM). The phase mode is a phase lag measurement mode that is performed simultaneously with surface morphology observation in a normal dynamic force mode (DFM mode; when SII NanoTechnology SPM is used).

  The measurement of the phase separation structure of the coating layer by the phase measurement mode (phase mode) of the scanning probe microscope (SPM) will be described. In the phase mode, the phase delay of the cantilever vibration when the DFM operation is performed is detected. In the DFM operation, the shape is measured by controlling the distance between the probe and the sample so that the vibration amplitude of the resonated cantilever is constant. Here, when the signal that vibrates the bimorph (piezoelectric element) for vibrating the cantilever is called an “input signal”, in the phase measurement mode, the phase delay of the effective cantilever vibration signal with respect to this “input signal” Is detected simultaneously with the vibration amplitude. The phase delay responds sensitively to the influence of surface properties, and the softer the sample surface, the greater the delay. By imaging the magnitude of this phase lag, it becomes possible to observe the distribution of surface physical properties (referred to as phase image or phase image). Thus, by using the phase measurement mode of the scanning probe microscope (SPM), it is possible to measure and confirm a phase separation structure in which a plurality of resin phases having different physical properties exist on the surface.

  The phase separation structure of the coating layer can be evaluated in the surface property distribution evaluation mode using a scanning probe microscope, in addition to the phase measurement mode, it can be performed in other modes such as the friction force measurement mode and viscoelasticity measurement mode. It is preferable to select an observation mode in which the phase separation structure can be evaluated well. In the phase measurement mode, not only the phase lag due to the difference in viscoelasticity of the coating layer but also the phase lag due to the difference in surface physical properties such as the magnitude of the adsorption force can be detected.

  Since the coating layer of the present invention has a nanophase separation structure, it can exhibit high adhesiveness equal to or higher than that of triacetyl cellulose to polarizers and water-based adhesives, particularly polyvinyl alcohol-based polarizers and water-based adhesives. Is possible. Specifically, the coating layer preferably has a residual area after peeling once of 90% or more, more preferably 95% or more, and further preferably 100% in the adhesion test shown in the examples described later. The remaining area after continuous peeling is preferably 75% or more, more preferably 85% or more, further preferably 95% or more, and the remaining area after 10 times continuous peeling is preferably 50% or more, more preferably 80% or more. More preferably, it is 90% or more, still more preferably 93% or more, and particularly preferably 95% or more.

  The phase separation structure as described above can be obtained by controlling the resin concentration, selection of the resin type, drying / heating conditions and the like as described later.

Hereinafter, each composition of the coating layer will be described in detail.
(Polyvinyl alcohol resin)
The polyvinyl alcohol resin used as a component of the coating layer is not particularly limited as long as it is recognized as a polyvinyl alcohol resin. Specific examples thereof include polyvinyl alcohol obtained by saponifying polyvinyl acetate; a derivative thereof; a saponified product of a copolymer of vinyl acetate and a monomer having copolymerizability; Modified polyvinyl alcohol which has been converted to ether, ether, graft, phosphoric ester or the like. Examples of the monomer include unsaturated carboxylic acids such as (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth) acrylic acid, and esters thereof; α-olefins such as ethylene and propylene, (meth) Examples include allyl sulfonic acid (soda), sulfonic acid soda (monoalkyl malate), disulfonic acid soda alkyl maleate, N-methylol acrylamide, acrylamide alkyl sulfonic acid alkali salt, N-vinyl pyrrolidone, N-vinyl pyrrolidone derivatives, and the like. . These polyvinyl alcohol resins may be used alone or in combination of two or more.

  Examples of suitable polyvinyl alcohol resins used in the present invention include vinyl alcohol-vinyl acetate copolymer, vinyl alcohol-vinyl butyral copolymer, and ethylene-vinyl alcohol copolymer. Among these, vinyl alcohol-vinyl acetate copolymer is exemplified. A polymer and an ethylene-vinyl alcohol copolymer are preferred. The degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but the degree of polymerization is preferably 3000 or less from the viewpoint of the coating solution viscosity.

  The copolymerization ratio of vinyl alcohol is represented by the degree of saponification. The degree of saponification of the polyvinyl alcohol resin of the present invention is not particularly limited as long as excellent adhesiveness is exhibited, but it is preferably 60 mol% or more. More preferably, the upper limit of the saponification degree of the polyvinyl alcohol-based resin is 95 mol% or less, and preferably 85 mol% or less. More preferably, the degree of saponification is 65 mol% or more and 83 mol% or less, more preferably 68 mol% or more and 80 mol% or less, still more preferably 70 mol% or more and less than 80 mol%, and 71 mol% or more and 78 mol% or less. % Or less is even more preferable, and 73 mol% or more and 75 mol% or less is particularly preferable. When the degree of saponification of the polyvinyl alcohol-based resin is equal to or higher than the above lower limit, the water-based adhesive or the polarizer is suitably adhered, and the phase separation from the polyester-based resin can be suitably performed. Further, when the degree of saponification of the polyvinyl alcohol-based resin is not more than the above upper limit (or less), a nanophase separation structure can be formed more suitably with the polyester-based resin. The degree of saponification of the vinyl alcohol resin can be determined by alkali consumption required for hydrolysis of copolymer units such as vinyl acetate or composition analysis by NMR.

  The content of the polyvinyl alcohol resin is preferably 10% by mass or more and 60% by mass or less, more preferably 15% by mass or more and 55% by mass or less, and further preferably 20% by mass or more and 50% by mass or less in the coating layer. When the content of the polyvinyl alcohol-based resin is equal to or more than the above lower limit, the PVA surface fraction increases, which is suitable for adhesiveness with a polarizer / water-based resin. On the other hand, it is suitable for adhesiveness with a polyester film base material that it is below the upper limit.

(Polyester resin)
The polyester resin used in the coating layer of the present invention is a copolymer formed by polycondensation of a dicarboxylic acid component and a diol component, and the dicarboxylic acid component and the diol component are described as a polyester film used as the above-mentioned substrate. Can be used. From the viewpoint of improving the adhesion to the polyester film substrate, it is preferable to use a dicarboxylic acid component having the same or similar structure and properties as the dicarboxylic acid component in the polyester film as the dicarboxylic acid component of the polyester resin. Therefore, for example, when an aromatic dicarboxylic acid is employed as the dicarboxylic acid component of the polyester film, it is preferable to use the aromatic dicarboxylic acid as the dicarboxylic acid component of the polyester resin. As such an aromatic dicarboxylic acid component, terephthalic acid and isophthalic acid are most preferred. For example, another aromatic dicarboxylic acid may be added and copolymerized within a range of 10 mol% or less with respect to the total dicarboxylic acid component.

  From the viewpoint of blocking resistance, the glass transition temperature of the polyester-based resin is preferably 25 ° C or higher, more preferably 30 ° C or higher, and further preferably 35 ° C or higher. Furthermore, the upper limit of the glass transition temperature is preferably 110 ° C. or less, more preferably 100 ° C. or less, and further preferably 90 ° C. or less. When the upper limit of the glass transition temperature is not more than the above, it becomes easy to suitably form phase separation by heat treatment described later. The glass transition temperature of the polyester-based resin can be controlled by introducing a copolymer component, particularly a branched glycol component, as will be described later.

  As the glycol component of the polyester-based resin, ethylene glycol and branched glycol are preferably used as constituent components. By having a branched structure, it is considered that it contributes to stress relaxation in the coating layer, and can suitably exhibit adhesiveness. Examples of the branched glycol component include 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, and 2-methyl-2-butyl-1,3. -Propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3-propanediol 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2, Such as 2-di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, and 2,2-di-n-hexyl-1,3-propanediol. And the like.

  The molar ratio of the branched glycol component is preferably 10 mol%, particularly preferably 20 mol%, based on the total glycol component. On the other hand, the upper limit is preferably 80 mol%, more preferably 70 mol%, and particularly preferably 60 mol%. If necessary, diethylene glycol, propylene glycol, butanediol, hexanediol, 1,4-cyclohexanedimethanol or the like may be used in combination.

  The polyester resin used as a component of the coating layer in the present invention is preferably a water-soluble or water-dispersible resin from the viewpoint of forming a suitable nanophase separation structure with the polyvinyl alcohol resin. In order to make the polyester resin water-soluble or water-dispersed, it is preferable to copolymerize a compound containing a hydrophilic group such as a sulfonate group or a carboxylate group. Among these, a dicarboxylic acid component having a sulfonate group is preferable from the viewpoint of imparting hydrophilicity while maintaining a low acid value of the polyester-based resin and controlling the reactivity with the crosslinking agent. Examples of the dicarboxylic acid component having a sulfonate group include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfonaphthaleneisophthalic acid-2,7-dicarboxylic acid, and 5- (4-sulfophenoxy) isophthalic acid or an alkali thereof. Examples of the metal salt include 5-sulfoisophthalic acid.

  1-15 mol% is preferable in the dicarboxylic acid component of a polyester resin, as for the dicarboxylic acid component which has a sulfonate group, 1.5-12 mol% is more preferable, and 2-10 mol% is further more preferable. When the dicarboxylic acid component having a sulfonate group is at least the above lower limit, it is suitable for water-solubilization or water-dispersion of the polyester resin. Moreover, when the dicarboxylic acid component which has a sulfonate group is below the said upper limit, it is suitable for adhesiveness with a polyester film base material.

  When a crosslinking agent is used in combination as described later, it is preferable that the polyester resin has few carboxylic acid groups which are reactive groups with the crosslinking agent, from the viewpoint of forming a suitable phase separation structure. By reducing the number of carboxyl groups that have reactivity with the cross-linking agent, the reactivity with the cross-linking agent decreases, and as a result, the cross-linked polyvinyl alcohol resin does not completely mix with the polyvinyl alcohol resin. It is believed that the phase separation structure can be suitably maintained. From such a viewpoint, the acid value of the polyester-based resin is preferably 20 KOHmg / g or less, more preferably 15 KOHmg / g or less, further preferably 10 KOHmg / g or less, still more preferably 8 KOHmg / g or less, and even more preferably. Is 5 KOHmg / g or less. The acid value of the polyester resin can be theoretically determined from the result of component analysis by titration method described later or NMR.

  In order to control the acid value of the polyester-based resin within the above range, the introduction amount of the carboxylic acid base for water solubilization or water dispersion is reduced, or a hydrophilic group other than the carboxylic acid base is employed, It is preferable to lower the carboxylic acid terminal concentration of the polyester resin. As a method for lowering the carboxylic acid terminal concentration of the polyester resin, it is preferable to employ a polyester resin in which the carboxylic acid terminal group is modified, or a polyester resin having a large number average molecular weight of the polyester resin. For this reason, the number average molecular weight of the polyester-based resin is preferably 5000 or more, more preferably 6000 or more, and further preferably 10,000 or more. Moreover, it is preferable to make low content of the acid component which has a polyester-type resin as a structural component and has three or more carboxyl groups.

  The content of the polyester resin in the coating layer is preferably 40% by mass or more and 90% by mass or less, more preferably 45% by mass or more and 85% by mass or less, and further preferably 50% by mass or more and 80% by mass or less. When the content of the polyester resin is not less than the above lower limit, it is suitable for adhesiveness with a polyester film substrate, and when it is not more than the above upper limit, it is suitable for adhesiveness with a polarizer or a water-based adhesive provided thereon. is there.

(Crosslinking agent)
A nanophase separation structure can be more suitably formed by using a crosslinking agent in the coating layer. This is considered to be because the polyvinyl alcohol-based resin easily aggregates due to crosslinking of the hydroxyl groups of the polyvinyl alcohol-based resin, and as a result, a suitable separation structure is formed. Although it will not specifically limit as a crosslinking agent if it has a hydroxyl group and crosslinking property, Compounds, such as a melamine type, an isocyanate type, a carbodiimide type, an oxazoline type, an epoxy type, are mentioned. Melamine-based, isocyanate-based, carbodiimide-based, and oxazoline-based compounds are preferable from the viewpoint of the temporal stability of the coating solution. Further, the crosslinking agent is preferably a melamine compound or an isocyanate compound that suitably cross-links with the hydroxyl group of the polyvinyl alcohol resin. This is because a carbodiimide-based crosslinking agent reacts with a carboxyl group, whereas a melamine-based compound or an isocyanate-based compound reacts with a hydroxyl group, and thus forms a crosslinked structure more suitably with a polyvinyl alcohol-based resin having a hydroxyl group as a functional group. This is probably because of this. Furthermore, when a melamine compound or an isocyanate compound is used, the polyvinyl alcohol in the coating layer suitably forms a cross-linked structure, and easily moves to the surface opposite to the polyester film, so that the surface fraction of PVA is increased. This makes it possible to form a suitable sea-island structure. Especially, it is especially preferable to use an isocyanate type compound from a viewpoint that it forms a crosslinking reaction suitably with the hydroxyl group of polyvinyl alcohol-type resin, and is excellent in transparency. Moreover, in order to promote a crosslinking reaction, you may use a catalyst etc. suitably as needed.

  As the isocyanate compound, a low molecular or high molecular diisocyanate or a trivalent or higher polyisocyanate can be used. For example, the isocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 1, 5-naphthylene diisocyanate, 1,4-naphthylene diisocyanate, phenylene diisocyanate, tetramethylxylylene diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane -4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, 3,3'-dimethoxydi Aromatic diisocyanates such as phenyl-4,4'-diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, etc. Examples thereof include aliphatic diisocyanates such as alicyclic diisocyanates, hexamethylene diisocyanate, and 2,2,4-trimethylhexamethylene diisocyanate, and trimers of these isocyanate compounds. Furthermore, an excess amount of these isocyanate compounds and low molecular active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, or polyester polyols, poly Mention may be made of a polymer containing a terminal isocyanate group of a polymer obtained by reacting a polymer active hydrogen compound such as ether polyols and polyamides.

  As the crosslinking agent used in the present invention, a blocked isocyanate compound is also preferable. By adding the blocked isocyanate compound, it is possible to more suitably improve the temporal stability of the coating solution.

  The blocked isocyanate compound can be prepared by subjecting the isocyanate compound and the blocking agent to an addition reaction by a conventionally known method. Examples of the isocyanate blocking agent include phenols such as phenol, cresol, xylenol, resorcinol, nitrophenol, and chlorophenol; thiophenols such as thiophenol and methylthiophenol; oximes such as acetoxime, methyl etiketooxime, and cyclohexanone oxime. Alcohols such as methanol, ethanol, propanol and butanol; halogen-substituted alcohols such as ethylene chlorohydrin and 1,3-dichloro-2-propanol; tertiary alcohols such as t-butanol and t-pentanol Pyrazole compounds such as 3,5-dimethylpyrazole, 3-methylpyrazole, 4-bromo-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole; ε- Lactams such as prolactam, δ-valerolactam, γ-butyrolactam, β-propyllactam; aromatic amines; imides; acetylacetone, acetoacetate, malonic acid ethyl ester, malonic acid diester (dimethyl malonate, malonic acid Active methylene compounds such as diethyl, di-n-butyl malonate, di-2-ethylhexyl malonate); triazole compounds such as 1,2,4-triazole; mercaptans; imines; ureas; diaryl compounds; sodium bisulfite; And so on.

  As the melamine compound, a melamine compound substituted with a substituent — (CH 2) n —O—R (wherein n is an integer of 1 to 3 and R is an alkyl group having 1 to 4 carbon atoms). R in the above formula is preferably methyl. The number of the substituents that one melamine structure has is preferably 3 to 6. Specific examples of melamine compounds include M-3, MK, M-6, M-100, MC, etc. of Sumitomo Chemical Co., Ltd. Sumitex Resin series and methylated melamine resin MW-22, MX manufactured by Sanwa Chemical Co., Ltd. -706, MX-042 and the like.

  A melamine compound and an epoxy compound or an oxazoline compound may be used in combination, but the content of the epoxy compound or oxazoline compound in that case is preferably less than 10% by weight, more preferably less than 5% by weight, More preferably, it is less than 2% by weight, particularly preferably less than 1% by weight. If the content of the epoxy compound or oxazoline compound is larger than the above upper limit, depending on the ratio of polyester and polyvinyl alcohol in the coating layer, the PVA surface fraction cannot be kept high, and the adhesiveness may be inferior. .

  Further, an isocyanate compound and an epoxy compound or an oxazoline compound may be used in combination, but the content of the epoxy compound or oxazoline compound in that case is preferably less than 10% by weight, more preferably less than 5% by weight. Even more preferably, it is desired to be less than 2% by weight, particularly preferably less than 1% by weight. If the content of the epoxy compound or oxazoline compound is larger than the above upper limit, depending on the ratio of polyester and polyvinyl alcohol in the coating layer, the PVA surface fraction cannot be kept high, and the adhesiveness may be inferior. .

  As content of a crosslinking agent, 2 mass% or more and 50 mass% or less are preferable in a coating layer, 5 mass% or more and 40% mass% or less are more preferable, and 8 mass% or more and 30 mass% or less are more preferable. When the content of the cross-linking agent is not less than the above lower limit, it is suitable for forming a cross-linked polyvinyl alcohol resin, and when it is not more than the above upper limit, it is suitable for the expression of the adhesive effect by the binder resin.

  The blending ratio (B) / (A) of the polyester-based resin (A) and the polyvinyl alcohol-based resin (B) is preferably 0.2 to 1.25 in terms of mass ratio, and preferably 0.25 to 1. More preferably, it is more preferably 0.25 to 0.5, and particularly preferably 0.25 to 0.45. When (B) / (A) is at least the above lower limit, it is suitable for adhesion to a polyester film substrate, and when it is at most the above upper limit, it is suitable for adhesion to a polarizer / water-based resin.

  The blending ratio ((A) + (B)) / (C) of the polyester resin (A) and the polyvinyl alcohol resin (B) and the crosslinking agent (C) is preferably 2 to 50 in terms of mass ratio. More preferably, it is -40, and it is further more preferable that it is 8-30. When ((A) + (B)) / (C) is not less than the above lower limit, it is suitable for expression of the adhesive effect by the binder resin component, and when it is not more than the above upper limit, it is suitable for the adhesive effect by phase separation. .

(Additive)
In the coating layer constituting the polarizer protective film of the present invention, known additives such as surfactants, antioxidants, catalysts, heat stabilizers, weathering stabilizers, ultraviolet absorbers are used as long as the effects of the present invention are not impaired. Agents, organic lubricants, pigments, dyes, organic or inorganic particles, antistatic agents, nucleating agents, and the like may be added.

  In the present invention, in order to further improve the blocking resistance of the coating layer, it is also a preferred embodiment to add particles to the coating layer. Examples of the particles to be contained in the coating layer in the present invention include titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay and the like, or a mixture thereof. Inorganic particles such as calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride, etc., and inorganic particles such as styrene, acrylic, melamine, benzoguanamine, and silicone Examples thereof include polymer-based particles.

  The average particle size of the particles in the coating layer (number average particle size based on SEM; the same applies hereinafter) is preferably 0.04 to 2.0 μm, more preferably 0.1 to 1.0 μm. When the average particle size of the inert particles is less than 0.04 μm, the formation of irregularities on the film surface becomes insufficient, so that the handling properties such as the slipping property and the winding property of the film are deteriorated and the film is stuck. The workability at the time of alignment may deteriorate. On the other hand, if it exceeds 2.0 μm, the particles are likely to fall off, which is not preferable. The particle concentration in the coating layer is preferably 1 to 20% by mass, more preferably 5 to 15% by mass in the solid component.

  In the present invention, the thickness of the coating layer can be appropriately set in the range of 0.01 to 2 μm, but in order to achieve both workability and adhesiveness, the range of 0.03 to 0.25 μm is preferable. Preferably it is 0.05-0.25 micrometer, More preferably, it is 0.05-0.2 micrometer. Adhesiveness will become inadequate that the thickness of a coating layer is less than 0.03 micrometer. When the thickness of the coating layer exceeds 0.25 μm, blocking may occur.

5. Polarizer Examples of the polarizer include, for example, a polyvinyl alcohol film containing a dichroic material such as iodine. The polarizer protective film is bonded to the polarizer directly or via an adhesive layer, but is preferably bonded via an adhesive from the viewpoint of improving the adhesiveness. In that case, it is preferable to arrange | position the coating layer which comprises the polarizer protective film of this invention to the surface which contact | connects a polarizer or an adhesive bond layer. As a preferable polarizer for bonding the polyester film of the present invention, for example, iodine or dichroic material is dyed and adsorbed on a polyvinyl alcohol film, uniaxially stretched in a boric acid aqueous solution, and the stretched state is maintained. The polarizer obtained by performing washing | cleaning and drying is mentioned. The draw ratio of uniaxial stretching is usually about 4 to 8 times. Polyvinyl alcohol is suitable as the polyvinyl alcohol film. “Kuraray Vinylon” [manufactured by Kuraray Co., Ltd.], “Tosero Vinylon” [manufactured by Tosero Co., Ltd.], “Nippon Vinylon” [Nippon Synthetic Chemical Co., Ltd.] Commercial products such as “made” can be used. Examples of the dichroic material include iodine, a disazo compound, and a polymethine dye.

  From the viewpoint of thinning the adhesive layer, the adhesive applied to the polarizer is preferably an aqueous one, that is, an adhesive component dissolved in water or dispersed in water. For example, a polyvinyl alcohol resin, a urethane resin, or the like is used as a main component, and a composition containing an isocyanate compound, an epoxy compound, or the like can be used as necessary in order to improve adhesiveness. The thickness of the adhesive layer is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less.

  When using polyvinyl alcohol resin as the main component of the adhesive, in addition to partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, amino group-modified A modified polyvinyl alcohol resin such as polyvinyl alcohol may be used. 1-10 mass% is preferable and, as for the density | concentration of the polyvinyl alcohol-type resin in an adhesive agent, 2-7 mass% is more preferable.

6). Functional layer The polarizing plate used in the present invention has various functional layers, that is, a hard coat layer, an antiglare layer, an antireflection layer, a low reflection layer, a low reflection layer, for the purpose of preventing reflection, suppressing glare, suppressing scratches, and the like. It is also preferable to provide one or more functional layers selected from the group consisting of an anti-reflection layer and an anti-reflection anti-glare layer on the oriented polyester surface. When providing various functional layers, the oriented polyester film preferably has an easy adhesion layer on the surface thereof. At that time, from the viewpoint of suppressing interference due to reflected light, it is preferable to adjust the refractive index of the easy-adhesion layer so that it is close to the geometric mean of the refractive index of the functional layer and the refractive index of the oriented polyester film. The refractive index of the easy-adhesion layer can be adjusted by a known method. For example, the refractive index of the easy-adhesion layer can be easily adjusted by adding titanium, zirconium, or other metal species to the binder resin.

7). The manufacturing method of an oriented polyester film The oriented polyester film which is a protective film of this invention can be manufactured in accordance with the manufacturing method of a general polyester film. For example, the polyester resin is melted and the non-oriented polyester extruded and formed into a sheet shape is stretched in the longitudinal direction by utilizing the speed difference of the roll at a temperature equal to or higher than the glass transition temperature, and then stretched in the transverse direction by a tenter. The method of performing heat processing is mentioned.

  The oriented polyester film of the present invention may be a uniaxially stretched film or a biaxially stretched film, but when the biaxially stretched film is used as a polarizer protective film, even if observed from directly above the film surface, rainbow-like color spots are observed. Although it is not seen, it should be noted that rainbow-like color spots may be observed when observed from an oblique direction.

  This phenomenon is that a biaxially stretched film is composed of refractive index ellipsoids having different refractive indexes in the running direction, width direction, and thickness direction, and the retardation becomes zero depending on the light transmission direction inside the film (refractive index ellipse). This is because there is a direction in which the body appears to be a perfect circle. Therefore, when the liquid crystal display screen is observed from a specific oblique direction, a point where the retardation becomes zero may be generated, and a rainbow-like color spot is generated concentrically around that point. When the angle from the position directly above the film surface (normal direction) to the position where the rainbow-like color spots are visible is θ, the angle θ increases as the birefringence in the film increases, and the rainbow-like color increases. Spots are difficult to see. The biaxially stretched film tends to reduce the angle θ, and therefore the uniaxially stretched film is more preferable because rainbow-like color spots are less visible.

  However, a perfect uniaxial (uniaxial symmetry) film is not preferable because the mechanical strength in the direction orthogonal to the orientation direction is significantly reduced. The present invention has biaxiality (biaxiality) in a range that does not substantially cause rainbow-like color spots or a range that does not cause rainbow-like color spots in the viewing angle range required for a liquid crystal display screen. It is preferable. Such biaxial objectivity is obtained by producing an oriented polyester film under the following conditions.

  The oriented polyester film having the specific retardation and Nz coefficient described above can be obtained by adjusting the conditions during film formation (for example, the draw ratio, the draw temperature, the film thickness, etc.). For example, the higher the stretching ratio, the lower the stretching temperature, and the thicker the film, the higher the retardation. On the other hand, the lower the stretching ratio, the higher the stretching temperature, and the thinner the film, the lower the retardation.

  As specific film forming conditions, for example, the longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 145 ° C, and particularly preferably 90 to 140 ° C. The longitudinal draw ratio is preferably 1.0 to 3.5 times, particularly preferably 1.0 to 3.0 times. The transverse draw ratio is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times.

In order to control the retardation within the specific range described above, it is preferable to control the ratio of the longitudinal draw ratio and the transverse draw ratio. If the difference between the vertical and horizontal draw ratios is too small, it is difficult to increase the retardation, which is not preferable. It is also preferable to set the stretching temperature low in order to increase the retardation. The temperature of the subsequent heat treatment is preferably 140 to 240 ° C, particularly preferably 180 to 240 ° C.

  In order to set the Nz coefficient to the above-described specific value, it is preferable to control the ratio of the longitudinal draw ratio and the transverse draw ratio, and most preferably a uniaxially stretched film. In order to reduce the Nz coefficient, it is also preferable to add a copolymer component in order to increase the molecular weight of the polymer and to decrease the crystallinity. Furthermore, in order to control the Nz coefficient of the film within a specific range, the total stretching ratio and the stretching temperature can be appropriately set. For example, the lower the total draw ratio and the higher the drawing temperature, the lower the Nz coefficient can be obtained.

In order to set the degree of plane orientation to the above specific value, it is preferable to control the total draw ratio. If the total draw ratio is too high, the degree of plane orientation becomes too high, which is not preferable. It is also preferable to control the stretching temperature in order to reduce the degree of plane orientation. By increasing the difference between the longitudinal draw ratio and the transverse draw ratio, setting the total draw ratio low, and setting the draw temperature high, the Nz coefficient and the degree of plane orientation can be made to be below specific values.

  Since the stretching temperature and the stretching ratio have a great influence on the thickness unevenness of the film, it is preferable to optimize the film forming conditions from the viewpoint of the thickness unevenness. In particular, if the longitudinal stretching ratio is lowered to increase the retardation, the longitudinal thickness unevenness may be deteriorated. Since there is a region where the vertical thickness unevenness becomes very bad in a specific range of the draw ratio, it is desirable to set the film forming conditions outside this range.

  A coating layer can be provided after manufacture of a film or in a manufacturing process. In particular, from the viewpoint of productivity, it is preferable to apply a coating solution to at least one side of a PET film after unstretched or uniaxially stretched in the film production process to form a coating layer.

  Any known method can be used as a method for applying the coating solution to the PET film. For example, reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method, etc. It is done. These methods are applied alone or in combination.

In the present invention, the finally obtained coating layer preferably has a thickness of 0.04 to 0.33 g / m ² . If it is less than 0.04 g / m ² , the adhesiveness is lowered, and if it is thicker than 0.33 g / m ² , the blocking property and the slipping property are lowered, which is not preferable.

  After coating of the coating solution, it is preferable to dry in a drying furnace. The temperature of the drying air hitting the coated surface is preferably 80 ° C. or higher and lower than 150 ° C. The wind speed is preferably 30 m / second or more. A more preferable drying temperature is 100 ° C. or higher and lower than 150 ° C. After drying the coating film at a temperature of 80 ° C. or higher and lower than 150 ° C. in the drying furnace, it is preferable to immediately cool the laminated film having the coating layer to near room temperature. By passing through the drying step, the fluidity of the coating liquid can be reduced, and a phase separation structure can be suitably performed.

  In the method for producing a laminated polyester film of the present invention, it is preferable to perform a heat setting treatment at 140 ° C. or higher. In the heat setting treatment step, a suitable phase separation state can be formed by temporarily improving the flow state of the binder in the coating layer. The reason is that by improving the flow state of the binder, a polyester resin with a lot of hydrophobic groups and a polyvinyl alcohol resin with a lot of hydrophilic groups are aggregated in a self-organized manner to form a suitable phase separation state. I think so. It is also considered that the cross-linking reaction of the cross-linking agent proceeds and the phase separation state can be accelerated. The temperature in each heat setting zone in the heat setting treatment step is slightly different depending on the type of the constituent resin of the thermoplastic resin film of the base material, but is within the temperature range of 140 to 240 ° C, more preferably 180 to 240 ° C. What is necessary is just to set suitably.

  When the maximum temperature in the heat setting treatment step is less than 140 ° C., the fluidity of the binder resin is insufficient and it is difficult to form a nanophase separation structure in the coating layer. Furthermore, the thermal contraction rate of the obtained laminated film becomes large, which is not preferable.

  The time required to reach the maximum temperature of the heat setting treatment from the temperature at which the phase separation of the coating layer starts to proceed remarkably is preferably 3 seconds or more and less than 20 seconds, and particularly preferably 4 seconds or more and less than 15 seconds.

  The blending of the ultraviolet absorber into the oriented polyester film can be carried out by combining known methods. For example, using a kneading extruder, the dried UV absorber and polymer raw material are blended to prepare a master batch in advance, and blended by a method of mixing the predetermined master batch and polymer raw material during film formation. be able to.

  The concentration of the UV absorber in the star batch is preferably 5 to 30% by mass in order to uniformly disperse the UV absorber and economically blend it. As conditions for producing the master batch, a kneading extruder is used, and the extrusion temperature is preferably from 1 to 15 minutes at a temperature not lower than the melting point of the polyester raw material and not higher than 290 ° C. Above 290 ° C, the weight loss of the UV absorber is large, and the viscosity of the master batch is greatly reduced. Extrusion for 1 minute or less makes it difficult to uniformly mix the UV absorber. At this time, if necessary, a stabilizer, a color tone adjusting agent, and an antistatic agent may be added.

  The blending of the ultraviolet absorber into the intermediate layer of the oriented polyester film having a multilayer structure of three or more layers can be carried out by the following method. Polyester pellets alone for the outer layer, master batches containing UV absorbers for the intermediate layer and polyester pellets are mixed at a predetermined ratio, dried, and then supplied to a known melt laminating extruder, which is slit-shaped. Extruded into a sheet form from a die and cooled and solidified on a casting roll to make an unstretched film. That is, using two or more extruders, a three-layer manifold or a merging block (for example, a merging block having a square merging portion), a film layer constituting both outer layers and a film layer constituting an intermediate layer are laminated, An unstretched film is formed by extruding a three-layer sheet from the die and cooling with a casting roll.

In order to remove foreign substances contained in the raw material polyester, which cause optical defects, it is preferable to perform high-precision filtration during melt extrusion in the process of producing an oriented polyester film. The filter particle size (initial filtration efficiency 95%) of the filter medium used for high-precision filtration of the molten resin is preferably 15 μm or less. When the filter particle size of the filter medium exceeds 15 μm, removal of foreign matters of 20 μm or more tends to be insufficient.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and may be implemented with appropriate modifications within a scope that can meet the gist of the present invention. These are all possible and are within the scope of the present invention.

  The physical property evaluation methods in the examples are as follows.

(1) PVA surface fraction (1-1) Evaluation of phase separation structure The phase separation structure of the coating layer was evaluated using a scanning probe microscope (NaIINavi system / SPA300, manufactured by SII Nanotechnology). The mode (phase mode) was performed. In the phase image, the larger the phase lag, the brighter the color image, and the smaller the phase lag, the darker the image. A small phase lag means that it is hard or has a relatively low adsorption force compared to other phases. In the coating layer of the easily adhesive polyester film of the present invention, the dark hue is the polyvinyl alcohol layer β, and the light hue is the polyester layer α.

  The measurement principle of the phase measurement mode in the scanning probe microscope is described on the website of SII Nanotechnology Inc. (http://www.siint.com/products/spm/tec_mode/1_pm.html).

  As the cantilever used for measurement, DF3 (spring constant: about 1.6 N / m) was mainly used, and a new one was always used in order to prevent a decrease in sensitivity and resolution due to probe contamination. The scanner used was FS-20A. The observation was performed with a resolution of 512 × 512 pixels or more, and the observation field of view was 1 μm × 1 μm. The measurement parameters such as the amplitude attenuation rate of the cantilever, the scanning speed, and the scanning frequency at the time of measurement were subjected to line scanning, and conditions were set so that observation can be performed with the highest sensitivity and resolution.

  The phase mode image (bitmap format, 512 × 512 pixels) obtained as described above is read into image processing software (manufactured by Adobe, Photoshop ver. 7.0) and displayed on the display so that the image size is 205 mm × 205 mm. Displayed. Next, a black line was drawn at the boundary between the light hue and the dark hue with the pencil tool (master diameter: 3 px) of the same software to clarify the boundary between both phases. Furthermore, using the paint tool of the same software, the dark hue was painted black and the light hue was painted white to binarize.

(1-2) Measurement of PVA surface fraction (1-2-1) Paper weight method PVA surface fraction was measured by the following procedure.

  The phase mode image obtained by the above method (1-1) was stored as a digital image in a bitmap format. Next, this image was printed out on A4 size fine paper with a printer (manufactured by Xerox, Doccentre Color a250). For the output image (200 mm × 200 mm), the boundary between the light hue and the dark hue in the image was clarified with a 4B pencil in a bright room under 500 lux illumination by visual confirmation. At this time, since the dark hue having a diameter of 0.1 μm or less existing in the bright hue is confirmed to be particles contained in the coating layer unevenly distributed in the bright hue, no boundary line is drawn. , Included in light hue. After that, the boundary line that clarifies the light hue and the dark hue is divided by cutting with a cutter knife, and the mass of the paper of the light hue (polyester phase α) and the dark hue (polyvinyl alcohol phase β) is measured. The ratio of the mass of the dark hue (polyvinyl alcohol phase β) to the total mass of the dark hue paper was determined in units of%. This measurement operation was carried out with measurement samples taken from five different locations, and the average value was taken as the PVA surface fraction. In addition, when the phase separation did not occur, it described as x.

In addition to the paper weight method, the PVA surface fraction can also be measured using the following image analysis method.
(1-2-2) Image analysis method The binarized image is displayed with the same software, and a histogram with luminance (black, white) as the horizontal axis and frequency as the vertical axis is displayed to determine the area ratio of the black part. . This measurement operation is carried out with measurement samples taken from five different locations, and the average value is taken as the PVA surface fraction. In addition, when nanophase separation has not occurred, it is described as x.

(2) Glass transition temperature In accordance with JIS K7121, using a differential scanning calorimeter (Seiko Instruments, DSC6200), 10 mg of a resin sample was heated at a rate of 20 ° C / min over a temperature range of 25 to 300 ° C, and DSC The extrapolated glass transition start temperature obtained from the curve was defined as the glass transition temperature.

(3) Number average molecular weight 0.03 g of resin was dissolved in 10 ml of tetrahydrofuran, and a GPC-LALLS apparatus low-angle light scattering photometer LS-8000 (manufactured by Tosoh Corporation, tetrahydrofuran solvent, reference: polystyrene) was used at a column temperature of 30 ° C. The number average molecular weight was measured using a flow rate of 1 ml / min and a column (showex KF-802, 804, 806 manufactured by Showa Denko KK).

(4) Resin composition The resin is dissolved in deuterated chloroform, 1H-NMR analysis is performed using a nuclear magnetic resonance analyzer (NMR) Gemini-200 manufactured by Varian, and the mol% ratio of each composition is determined from the integration ratio. did.

(5) Acid value 1 g (solid content) of a sample was dissolved in 30 ml of chloroform or dimethylformamide, and titrated with 0.1 N potassium hydroxide ethanol solution using phenolphthalein as an indicator to determine the carboxyl groups per gram of the sample. The amount (mg) of KOH required for neutralization was determined as the acid value.

(6) Saponification degree Residual acetate groups (mol%) of the polyvinyl alcohol resin were quantified using sodium hydroxide according to JIS-K6726, and the value was defined as the saponification degree (mol%). The same sample was measured three times, and the average value was defined as the saponification degree (mol%).

(7) PVA adhesion On the surface of the coating layer of the polarizer protective film, a polyvinyl alcohol aqueous solution (PVA117 made by Kuraray) adjusted to a solid content concentration of 5% by mass is dried so that the polyvinyl alcohol resin layer has a thickness of 2 μm. The film was coated with a wire bar and dried at 70 ° C. for 5 minutes. As the polyvinyl alcohol aqueous solution, a solution in which a red dye was added so as to facilitate the determination was used. The prepared evaluation target film was attached to a glass plate having a thickness of 5 mm to which a double-sided tape was attached, and the opposite surface of the evaluation target laminated film on which the polyvinyl alcohol resin layer was formed was attached to the double-sided tape. Next, 100 grid-like cuts that penetrated through the polyvinyl alcohol resin layer and reached the base film were made using a cutter guide with a gap interval of 2 mm. Next, an adhesive tape (Cello Tape (registered trademark) CT-24; 24 mm width, manufactured by Nichiban Co., Ltd.) was attached to the grid-shaped cut surface. The air remaining at the interface at the time of pasting was pressed with an eraser to bring it into close contact, and then the work of peeling off the adhesive tape vigorously vertically was performed once, five times and ten times. The number of squares on which the polyvinyl alcohol resin layer was not peeled was counted to determine PVA adhesion. That is, when the PVA layer was not peeled off at all, the PVA adhesion rate was 100, and when all the PVA layer was peeled off, the PVA adhesion rate was 0. In addition, what was partially peeled within one square was also included in the number of peeled.

(8) PVA coating property A polyvinyl alcohol aqueous solution (PVA117 manufactured by Kuraray Co., Ltd.) adjusted to a solid content concentration of 5% by mass on the coating layer surface of the polarizer protective film has a thickness of 2 μm after drying. Thus, the coating condition of the polyvinyl alcohol resin layer after apply | coating with a wire bar and drying for 5 minutes at 70 degreeC was evaluated on the following references | standards.

◎: The coated whole surface is neatly applied without repelling. ○: The coated whole surface is completely repelled without repelling. △: The coated portion is repelled.
X: It almost repels the whole coated surface.

(9) Retardation (Re)
Retardation is a parameter defined by the product (ΔNxy × d) of the biaxial refractive index anisotropy (ΔNxy = | nx−ny |) and the film thickness d (nm) on the film. Yes, a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was determined by the following method. Using a molecular orientation meter (MOA-6004 type molecular orientation meter, manufactured by Oji Scientific Instruments Co., Ltd.), the orientation axis direction of the film is obtained, and a rectangle of 4 cm × 2 cm is cut and measured so that the orientation axis direction becomes the long side. A sample was used. With respect to this sample, the biaxial refractive index (nx, ny) perpendicular to each other and the refractive index (nz) in the thickness direction were measured using an Abbe refractometer (NAR-4T, measurement wavelength 589 nm, manufactured by Atago Co., Ltd.). The absolute value (| nx−ny |) of the difference between the biaxial refractive indexes was defined as the refractive index anisotropy (ΔNxy). The thickness d (nm) of the film was measured using an electric micrometer (manufactured by Fine Reef, Millitron 1245D), and the unit was converted to nm. Retardation (Re) was determined from the product (ΔNxy × d) of refractive index anisotropy (ΔNxy) and film thickness d (nm).

(10) Nz coefficient | ny-nz | / | ny-nx | However, the values of ny and nx were selected so that ny> nx.

(11) Degree of plane orientation (ΔP)
The value obtained by (nx + ny) / 2−nz was defined as the degree of plane orientation (ΔP).

(12) Thickness direction retardation (Rth)
Thickness direction retardation is obtained by multiplying two birefringences ΔNxz (= | nx−nz |) and ΔNyz (= | ny-nz |) by film thickness d when viewed from the cross section in the film thickness direction. It is a parameter which shows the average of retardation obtained. Thickness direction retardation (Rth) is calculated by calculating nx, ny, nz and film thickness d (nm) in the same manner as the retardation measurement, and calculating an average value of (ΔNxz × d) and (ΔNyz × d). )

(13) Light transmittance at a wavelength of 380 nm Using a spectrophotometer (manufactured by Hitachi, U-3500 type), the light transmittance in the wavelength region of 300 to 500 nm of each film is measured using the air layer as a standard, and the light beam at a wavelength of 380 nm. The transmittance was determined.

(14) Iridescent observation A polyester film prepared by the method described later is attached to one side of a polarizer composed of PVA and iodine so that the polarization axis of the polarizer and the orientation main axis of the polyester film are perpendicular to each other, and the opposite surface A TAC film (manufactured by FUJIFILM Corporation, thickness 80 μm) was attached to the substrate to prepare a polarizing plate. The obtained polarizing plate was placed on both sides of the liquid crystal so that each polarizing plate was in a crossed Nicols condition to produce a liquid crystal display device. Each polarizing plate was arrange | positioned so that the said polyester film might be on the opposite side (distal) from a liquid crystal. As a light source of the liquid crystal display device, a white LED composed of a light emitting element in which a blue light emitting diode and a yttrium / aluminum / garnet yellow phosphor were combined was used as a light source (Nichia Chemical, NSPW500CS). Visual observation was performed from the front and oblique directions of the polarizing plate of such a liquid crystal display device, and the presence or absence of rainbow spots was determined as follows.

A: No iridescence from any direction.
A ′: When observed from an oblique direction, very thin rainbow spots are observed depending on the angle.
B: When observed from an oblique direction, thin rainbow spots can be observed depending on the angle.
C: Iris can be observed when observed from an oblique direction.
D: Iris can be observed when observed from the front and diagonal directions.

(15) Tear strength The tear strength of each film was measured in accordance with JIS P-8116 using an Elmendorf tear tester manufactured by Toyo Seiki Seisakusho. The tearing direction was performed so as to be parallel to the orientation main axis direction of the film, and was determined as follows. In addition, the measurement of the orientation main axis direction was measured with a molecular orientation meter (manufactured by Oji Scientific Instruments Co., Ltd., MOA-6004 type molecular orientation meter).
○: Tear strength is 50 mN or more ×: Tear strength is less than 50 mN

(Polyester resin polymerization)
In a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser, 194.2 parts by mass of dimethyl terephthalate, 184.5 parts by mass of dimethyl isophthalate, and 14.8 parts by mass of dimethyl-5-sodium sulfoisophthalate Then, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate were charged, and a transesterification reaction was performed at a temperature of 160 ° C. to 220 ° C. over 4 hours. Next, the temperature was raised to 255 ° C., and the pressure of the reaction system was gradually reduced, followed by reaction for 1 hour 30 minutes under a reduced pressure of 30 Pa to obtain a copolymerized polyester resin (A-1). The obtained copolyester resin (A-1) was light yellow and transparent. It was 0.70 dl / g when the reduced viscosity of copolyester resin (A-1) was measured. The glass transition temperature by DSC was 40 ° C.

In the same manner, copolymer polyester resins (A-2) to (A-5) having different compositions were obtained. Table 1 shows the composition (mole% ratio) and other characteristics measured by ¹ H-NMR for these copolymer polyester resins.

(Adjustment of polyester aqueous dispersion)
30 parts by mass of polyester resin (A-1) and 15 parts by mass of ethylene glycol n-butyl ether were placed in a reactor equipped with a stirrer, a thermometer and a reflux device, and heated and stirred at 110 ° C. to dissolve the resin. After the resin was completely dissolved, 55 parts by mass of water was gradually added to the polyester solution while stirring. After the addition, the solution was cooled to room temperature while stirring to prepare a milky white polyester aqueous dispersion (Aw-1) having a solid content of 30% by mass. Similarly, using the polyester resins (A-2) to (A-5) instead of the polyester resin (A-1), water dispersions are prepared, and the polyester water dispersions (Aw-2) to (Aw) are respectively produced. -5).

(Preparation of aqueous polyvinyl alcohol solution)
In a container equipped with a stirrer and a thermometer, 90 parts by mass of water was added, and 10 parts by mass of polyvinyl alcohol resin (manufactured by Kuraray) (B-1) having a polymerization degree of 500 was gradually added while stirring. After the addition, the solution was heated to 95 ° C. while stirring to dissolve the resin. After dissolution, the mixture was cooled to room temperature with stirring to prepare a polyvinyl alcohol aqueous solution (Bw-1) having a solid content of 10% by mass. Similarly, polyvinyl alcohol resins (B-2) to (B-8) were used instead of the polyvinyl alcohol resin (B-1) to prepare aqueous solutions, which were designated as (Bw-2) to (Bw-8), respectively. . Table 2 shows the degree of saponification of the polyvinyl alcohol resins (B-1) to (B-8).

(Polymerization of block polyisocyanate crosslinking agent C-1)
In a flask equipped with a stirrer, thermometer and reflux condenser, 100 parts by mass of a polyisocyanate compound having an isocyanurate structure using hexamethylene diisocyanate as a raw material (manufactured by Asahi Kasei Chemicals, Duranate TPA), 55 parts by mass of propylene glycol monomethyl ether acetate, polyethylene 30 parts by mass of glycol monomethyl ether (average molecular weight 750) was charged, and kept at 70 ° C. for 4 hours under a nitrogen atmosphere. Thereafter, the reaction solution temperature was lowered to 50 ° C., and 47 parts by mass of methyl ethyl ketoxime was added dropwise. The infrared spectrum of the reaction solution was measured to confirm that the absorption of the isocyanate group had disappeared, and a block polyisocyanate aqueous dispersion (C-1) having a solid content of 75% by mass was obtained.

(Production Example 1-Polyester X)
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 while stirring. 0.064 parts by mass of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were charged. Next, the pressure was raised and the pressure esterification reaction was carried out under the conditions of gauge pressure 0.34 MPa and 240 ° C., then the esterification reaction can was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Furthermore, it heated up to 260 degreeC over 15 minutes, and 0.012 mass part of trimethyl phosphate was added. Then, after 15 minutes, dispersion treatment was performed with a high-pressure disperser, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction can and subjected to polycondensation reaction at 280 ° C. under reduced pressure.

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

(Production Example 2-Polyester Y)
10 parts by weight of a dried ultraviolet absorber (2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazinon-4-one), PET (X) containing no particles (inherent viscosity Was 0.62 dl / g) and 90 parts by mass were mixed, and a polyethylene terephthalate resin (Y) containing an ultraviolet absorber was obtained using a kneading extruder (hereinafter abbreviated as PET (Y)).

(Polarizer protective film 1)
The following coating agent was mixed and the coating liquid from which the mass ratio of polyester-type resin (A) / polyvinyl alcohol-type resin (B) became 70/30 was created. The polyester aqueous dispersion uses an aqueous dispersion (Aw-1) in which a polyester resin having an acid value of 2 KOH mg / g is dispersed, and the polyvinyl alcohol aqueous solution is an aqueous solution in which polyvinyl alcohol having a saponification degree of 74 mol% is dissolved. (Bw-4) was used.
Water 40.61 mass%
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 11.67 mass%
Polyvinyl alcohol aqueous solution (Bw-4) 15.00 mass%
Block isocyanate-based crosslinking agent (C-1) 0.67% by mass
1.25% by mass of particles
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound, solid content concentration 14% by mass) 0.3% by mass
Surfactant 0.5% by mass
(Silicone, solid content concentration 10% by mass)

  After drying 90 parts by mass of PET (X) resin pellets containing no particles as a raw material for the base film intermediate layer and 10 parts by mass of PET (Y) resin pellets containing an ultraviolet absorber at 135 ° C. for 6 hours under reduced pressure (1 Torr) , And supplied to the extruder 2 (for the intermediate layer II layer), and PET (X) was dried by a conventional method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), respectively, and dissolved at 285 ° C. . After filtering these two kinds of polymers with a filter medium made of a sintered stainless steel (nominal filtration accuracy of 10 μm particles 95% cut), laminating them in a two-kind / three-layer confluence block, and extruding them into a sheet form from a die, The film was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and then cooled and solidified to produce an unstretched film. At this time, the discharge amount 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, after applying the above-mentioned adhesive property-modifying coating solution on the both sides of this unstretched PET film by a reverse roll method so that the coating amount after drying is 0.15 g / m ² , it is dried at 80 ° C. for 15 seconds. Thus, a coating layer was formed.

  The unstretched film on which the coating layer was formed was guided to a tenter stretching machine, guided to a hot air zone at a temperature of 125 ° C. while being gripped by a clip, and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, heat treatment was performed at a temperature of 230 ° C. for 0.5 seconds, and further, a relaxation treatment in the width direction of 3% was performed at 230 ° C. for 10 seconds, and the film thickness was about 50 μm. An oriented PET film was obtained.

(Polarizer protective film 2)
By changing the thickness of the unstretched film, a uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 1 except that the thickness was about 100 μm.

(Polarizer protective film 3)
An unstretched film produced by the same method as that for the polarizer protective film 1 is heated to 105 ° C. using a heated roll group and an infrared heater, and then 1.5 rolls in the traveling direction with a roll group having a difference in peripheral speed. After being double-stretched, the film was stretched 4.0 times in the width direction in the same manner as the polarizer protective film 1 to obtain a biaxially oriented PET film having a film thickness of about 50 μm.

(Polarizer protective film 4)
In the same manner as for the polarizer protective film 3, the film was stretched 2.0 times in the running direction and 4.0 times in the width direction to obtain a biaxially oriented PET film having a film thickness of about 50 μm.

(Polarizer protective film 5)
A uniaxially oriented PET film having a film thickness of 50 μm was obtained in the same manner as in the polarizer protective film 1 without using a PET resin (B) containing an ultraviolet absorber in the intermediate layer.

(Polarizer protective film 6)
In the same manner as the polarizer protective film 3, the film was stretched 4.0 times in the running direction and 1.0 times in the width direction to obtain a uniaxially oriented PET film having a film thickness of about 100 μm.

(Polarizer protective film 7)
In the same manner as for the polarizer protective film 1, the film was stretched 1.0 times in the running direction and 3.5 times in the width direction to obtain a uniaxially oriented PET film having a film thickness of about 75 μm.

(Polarizer protective film 8)
Using the same method as for the polarizer protective film 1, the thickness of the unstretched film was changed, the transverse stretch ratio was 3.8 times, the stretch temperature was 135 ° C., and a uniaxially oriented PET film having a thickness of about 100 μm was obtained.

(Polarizer protective film 9)
A method similar to that for the polarizer protective film 1 was used to obtain a uniaxially oriented PET film having a thickness of about 50 μm at a lateral stretching ratio of 3.8 times and a stretching temperature of 135 ° C.

(Polarizer protective film 10)
A method similar to that for the polarizer protective film 1 was used, and the transverse stretch ratio was 3.8 times to obtain a uniaxially oriented PET film having a thickness of 50 μm.

(Polarizer protective film 11)
A method similar to that for the polarizer protective film 1 was used, and a lateral stretching ratio of 4.2 times and a stretching temperature of 135 ° C. were obtained to obtain a uniaxially oriented PET film having a thickness of about 50 μm.

(Polarizer protective film 12)
Using the same method as for the polarizer protective film 1, the thickness of the unstretched film was changed, and the lateral stretch ratio was changed to 3.8 times to obtain a uniaxially oriented PET film having a thickness of 38 μm.

(Polarizer protective film 13)
Using a method similar to that for the polarizer protective film 1 and changing the thickness of the unstretched film, a uniaxially oriented PET film having a thickness of 38 μm was obtained.

(Polarizer protective film 14)
In the same manner as for the polarizer protective film 3, the film was stretched 1.8 times in the running direction and 2.0 times in the width direction to obtain a biaxially oriented PET film having a film thickness of about 275 μm.

(Polarizer protective film 15)
In the same manner as for the polarizer protective film 3, the film was stretched 3.6 times in the running direction and 4.0 times in the width direction to obtain a biaxially oriented PET film having a film thickness of about 38 μm.

(Polarizer protective film 16)
A uniaxially oriented PET film having a thickness of about 10 μm was obtained by changing the thickness of the unstretched film using the same method as for the polarizer protective film 1.

(Polarizer protective film 17)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the temperature of the heat treatment and relaxation treatment after the tenter stretching was changed to 180 ° C.

(Polarizer protective film 18)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the temperature of the heat treatment and relaxation treatment after tenter stretching was changed to 140 ° C.

(Polarizer protective film 19)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the following coating agent was mixed and the mass ratio of polyester resin / polyvinyl alcohol resin was changed to 60/40.
Water 37.28% by mass
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 10.00 mass%
Polyvinyl alcohol aqueous solution (Bw-4) 20.00 mass%
Block isocyanate-based crosslinking agent (C-1) 0.67% by mass
1.25% by mass of particles
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound, solid content concentration 14% by mass) 0.3% by mass
Surfactant 0.5% by mass
(Silicone, solid content concentration 10% by mass)

(Polarizer protective film 20)
Uniaxially oriented PET film in the same manner as the polarizer protective film 7 except that the following coating agent was mixed and the mass ratio of polyester resin (A) / polyvinyl alcohol resin (B) was changed to 80/20. Got.
43.95% by weight of water
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 13.33 mass%
Polyvinyl alcohol aqueous solution (Bw-4) 10.00 mass%
Block isocyanate-based crosslinking agent (C-1) 0.67% by mass
1.25% by mass of particles
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound, solid content concentration 14% by mass) 0.3% by mass
Surfactant 0.5% by mass
(Silicone, solid content concentration 10% by mass)

(Polarizer protective film 21)
Uniaxially oriented PET in the same manner as the polarizer protective film 7 except that the following coating agent was mixed and the mass ratio of the polyester resin (A) / polyvinyl alcohol resin (B) was changed to 50/50. A film was obtained.
Water 33.95% by mass
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 8.33 mass%
Polyvinyl alcohol aqueous solution (Bw-4) 25.00% by mass
Block isocyanate-based crosslinking agent (C-1) 0.67% by mass
1.25% by mass of particles
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound, solid content concentration 14% by mass) 0.3% by mass
Surfactant 0.5% by mass
(Silicone, solid content concentration 10% by mass)

(Polarizer protective film 22)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the polyester aqueous dispersion was changed to an aqueous dispersion (Aw-2) in which a polyester resin having an acid value of 4 KOHmg / g was dispersed.

(Polarizer protective film 23)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the polyester aqueous dispersion was changed to an aqueous dispersion (Aw-3) in which a polyester resin having an acid value of 6 KOHmg / g was dispersed.

(Polarizer protective film 24)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the polyester aqueous dispersion was changed to an aqueous dispersion (Aw-5) in which a polyester resin having an acid value of 10 KOHmg / g was dispersed.

(Polarizer protective film 25)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the aqueous polyvinyl alcohol solution was changed to an aqueous solution (Bw-6) in which polyvinyl alcohol having a saponification degree of polyvinyl alcohol of 67 mol% was dissolved. .

(Polarizer protective film 26)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the polyvinyl alcohol aqueous solution was changed to an aqueous solution (Bw-5) in which polyvinyl alcohol having a saponification degree of polyvinyl alcohol of 70 mol% was dissolved. .

(Polarizer protective film 27)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the polyvinyl alcohol aqueous solution was changed to a polyvinyl alcohol aqueous solution (Bw-3) having a saponification degree of polyvinyl alcohol of 79 mol%.

(Polarizer protective film 28)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the polyvinyl alcohol aqueous solution (Bw-2) had a saponification degree of polyvinyl alcohol of 83 mol%.

(Polarizer protective film 29)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7, except that the aqueous polyvinyl alcohol solution was changed to an aqueous solution (Bw-1) in which polyvinyl alcohol having a saponification degree of 88 mol% was dissolved.

(Polarizer protective film 30)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the composition of the coating solution was changed as follows.
40.87% by mass of water
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 11.67 mass%
Polyvinyl alcohol aqueous solution (Bw-4) 15.00 mass%
Melamine type crosslinking agent (C-2) 0.71 mass%
(Nikarak MX-042, manufactured by Sanwa Chemical Co., Ltd., solid content 70%)
1.25% by mass of particles
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Surfactant 0.5% by mass
(Silicone, solid content concentration 10% by mass)

(Polarizer protective film 31)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the composition of the coating solution was changed as follows.
40.33% by mass of water
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 11.67 mass%
Polyvinyl alcohol aqueous solution (Bw-2) 15.00 mass%
Oxazoline-based crosslinking agent (C-3) 1.25% by mass
(Epocross WS-500, manufactured by Nippon Shokubai, solid concentration 40% by mass)
1.25% by mass of particles
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Surfactant 0.5% by mass
(Silicone, solid content concentration 10% by mass)

(Polarizer protective film 32)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the composition of the coating solution was changed as follows.
40.58% by mass of water
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 11.67 mass%
Polyvinyl alcohol aqueous solution (Bw-2) 15.00 mass%
Epoxy crosslinking agent (C-4) 1.00% by mass
(Adeka Resin EM-051R ADEKA solid content 50% by mass)
1.25% by mass of particles
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Surfactant 0.5% by mass
(Silicone, solid content concentration 10% by mass)

(Polarizer protection film 33)
Uniaxially oriented PET in the same manner as the polarizer protective film 7 except that the following coating agent was mixed and the mass ratio of polyester resin (A) / polyvinyl alcohol resin (B) was changed to 100/0. A film was obtained.
Water 50.62% by mass
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 16.66 mass%
Block isocyanate-based crosslinking agent (C-1) 0.67% by mass
1.25% by mass of particles
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound, solid content concentration 14% by mass) 0.3% by mass
Surfactant 0.5% by mass
(Silicone, solid content concentration 10% by mass)

(Polarizer protective film 34)
Uniaxially oriented PET in the same manner as the polarizer protective film 7 except that the following coating agent is mixed and the mass ratio of polyester resin (A) / polyvinyl alcohol resin (B) is changed to 0/100. A film was obtained.
17.28% by mass of water
Isopropanol 30.00% by mass
Polyvinyl alcohol aqueous solution (Bw-4) 50.00 mass%
Block isocyanate-based crosslinking agent (C-1) 0.67% by mass
1.25% by mass of particles
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound, solid content concentration 14% by mass) 0.3% by mass
Surfactant 0.5% by mass
(Silicone, solid content concentration 10% by mass)

(Polarizer protective film 35)
Uniaxially oriented PET in the same manner as the polarizer protective film 7 except that the following coating agent was mixed and the mass ratio of polyester resin (A) / polyvinyl alcohol resin (B) was changed to 90/10. A film was obtained.
Water 47.28% by mass
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 15.00 mass%
Polyvinyl alcohol aqueous solution (Bw-4) 5.00% by mass
Block isocyanate-based crosslinking agent (C-1) 0.67% by mass
1.25% by mass of particles
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound, solid content concentration 14% by mass) 0.3% by mass
Surfactant 0.5% by mass
(Silicone, solid content concentration 10% by mass)

(Polarizer protective film 36)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the temperature of the heat treatment and relaxation treatment after tenter stretching was changed to 100 ° C.

(Polarizer protective film 37)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7, except that the aqueous polyvinyl alcohol solution was changed to an aqueous solution (Bw-8) in which polyvinyl alcohol having a saponification degree of 99 mol% was dissolved.

(Polarizer protective film 38)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the aqueous polyvinyl alcohol solution was changed to an aqueous solution (Bw-7) in which polyvinyl alcohol having a saponification degree of 40 mol% was dissolved.

(Polarizer protective film 39)
A uniaxially oriented PET film was obtained in the same manner as the polarizer protective film 7 except that the polyester aqueous dispersion was changed to an aqueous dispersion (Aw-4) in which a polyester resin having an acid value of 25 KOH mg / g was dispersed.

Reference example 1
Using the TAC film (manufactured by FUJIFILM Corporation, thickness 80 μm, saponified) as the polarizer protective film, the adhesion test was performed.

  Table 3.4 below shows the results of rainbow spot observation and tear strength measurement performed on the liquid crystal display device manufactured as described above using the polarizer protective films 1 to 39.

In Table 3, polarizer protective film No. 7 * shows the case where the polarizer protective film 7 is used as the polarizer protective film and the organic light emitting diode (OLED) is used as the light source. Also,
In Table 3, polarizer protective film No. 7 ** shows the case where the polarizer protective film 7 is used as the polarizer protective film and the cold cathode tube is used as the light source.

From the results shown in Tables 3 and 4, it is shown that when the retardation of the oriented polyester film is 4000 or more and the Nz coefficient is 1.7 or less, the generation of rainbow spots is remarkably suppressed. It was done. In addition to this condition, it has been shown that by controlling the degree of plane orientation of the oriented polyester film to 0.13 or less, it is possible to more effectively suppress the occurrence of rainbow spots.

  Polarizer protective film No. 1 to 32, nanophase separation structures were observed in all. As a reference, a phase contrast micrograph of the surface of the coating layer of the polarizer protective film 20 is shown in FIG. Polarizer protective film No. whose surface fraction of the PVA phase is 30% or more. Nos. 1 to 32 showed no problem in coatability, and showed excellent adhesion to a PVA film that can be evaluated as equivalent to a TAC film in a single peel test.

  By using the liquid crystal display device, polarizing plate and polarizer protective film of the present invention, it has excellent adhesion and contributes to thinning and cost reduction of LCD without reducing visibility due to iridescent color spots. Is possible. Therefore, the industrial applicability of the present invention is extremely high.

Claims (12)

A polarizer protective film having a coating layer on at least one side of an oriented polyester film,
The oriented polyester film is a film having a retardation of 4000 to 30000 nm and an Nz coefficient of 1.70 or less,
The coating layer includes a polyvinyl alcohol resin and a polyester resin,
The coating layer includes a cross-linking agent;
The crosslinking agent is a melamine crosslinking agent and / or an isocyanate crosslinking agent,
The surface of the coating layer has a nanophase separation structure composed of a phase in which a polyvinyl alcohol resin is aggregated and a phase in which a polyester resin is aggregated, and the area ratio of the polyvinyl alcohol phase is 30% or more and less than 99%. Polarizer protective film.   The polarizer protective film according to claim 1, wherein a degree of planar orientation of the oriented polyester film is 0.13 or less.   The polarizer protective film according to claim 1, wherein the oriented polyester film comprises at least three layers, contains an ultraviolet absorber in a layer other than the outermost layer, and has a light transmittance of 380 nm of 20% or less.   The polarizer protective film in any one of Claims 1-3 whose saponification degree of the said polyvinyl alcohol-type resin is 95% or less.   The polarizer protective film in any one of Claims 1-4 whose glass transition temperature of the said polyester-type resin is 25 degreeC or more. The polarizer protective film in any one of Claims 1-5 whose acid value of polyester-type resin is 20 KOHmg / g or less. The polarizer protective film according to any one of claims 1 to 6 , wherein a mass ratio of the polyvinyl alcohol resin (PVA) and the polyester resin (PEs) contained in the coating layer satisfies the following formula.
0.2 ≦ PVA / PEs ≦ 1.25 The compounding ratio ((A) + (B) / (C)) of the polyester resin (A), the polyvinyl alcohol resin (B), and the crosslinking agent (C) contained in the coating layer is 2 to 50 in terms of mass ratio. The polarizer protective film in any one of Claims 1-7.   The polarizing plate by which the polarizer protective film in any one of Claims 1-8 was laminated | stacked on the at least single side | surface of the polarizer. A liquid crystal display device having a backlight light source and a liquid crystal cell disposed between two polarizing plates,
The backlight source is a white light source having a continuous emission spectrum;
A liquid crystal display device, wherein both of the two polarizing plates are the polarizing plates according to claim 9. The polarizer protective film on the incident light side of the polarizing plate arranged on the incident light side and the polarizer protective film on the outgoing light side of the polarizing plate arranged on the outgoing light side are according to any one of claims 1 to 8 . The liquid crystal display device according to claim 10, which is a polarizer protective film. The liquid crystal display device according to claim 10 or 11 , wherein the white light source having the continuous emission spectrum is a white light emitting diode.