TWI653476B - Polyester film for polarizer and polarizing plate using the same - Google Patents

Abstract

An object of the present invention is to provide a polyester film for protecting a polarizer which is a biaxially stretched polyester film and which exhibits no interference color when disposed in a cross Nicol's state and does not exhibit reflection from the surface of the film. The interference fringes caused by the influence of the back reflection have good transparency, are excellent in film properties, and have good adhesion to the adhesive used for the polarizing film and the protective film.

The solution of the present invention is a polyester film for protecting a polarizer, which is a laminated polyester film having a resin layer (X) containing a crosslinked material on both sides of a polyester film, wherein the polyester film has a hysteresis at a wavelength of 590 nm. It is 280 nm or less, and the Young's modulus in the longitudinal direction and the width direction at 25 ° C is 1000 MPa or more and less than 4000 MPa, respectively; it is characterized in that the amplitude ΔR of the vibration waveform derived from the spectral reflection curve of the laminated polyester film is 8 %the following.

Description

Polyester film for polarizer protection and polarizing plate using the same

The present invention relates to a polyester film for polarizer protection.

In recent years, in the field of flat panel displays or touch panels, the demand for various optical films such as a polarizer protective film or a transparent conductive film is increasing. Among them, in the use of a polarizer protective film, a TAC (triethyl fluorene cellulose) film is often used because of its high transparency or optical equivalence. However, TAC films are poor in moisture and heat resistance, are brittle, and have poor handleability. Moreover, the film formation by the solution casting method has a problem that it is difficult to form a film. Therefore, from the viewpoints of cost reduction, thin film formation, and moist heat resistance, the replacement of the biaxially stretched polyester film is being actively reviewed.

However, the biaxially stretched polyester film previously reviewed has birefringence due to the alignment of the polymer during stretching, and the main alignment axis does not exist in a certain direction in the film plane, so it is disposed on the polarizing plate according to the alignment design. In the cross Nicol state, there is a problem that light interference occurs, or sufficient brightness is not obtained due to the angle of the main alignment axis, or interference fringes are observed due to film surface and back reflection. A stronger problem such as lower quality. Further, the polyester film monomer has a problem that "the adhesion to the adhesive for the polarizing film and the protective film is deteriorated". In order to solve these problems, although there is a method of controlling the hysteresis, The degree of hysteresis is still not sufficient (for example, Patent Document 1). Further, although it is proposed to provide an anchor layer for improving adhesion to an adhesive, no specific invention has been disclosed (Patent Documents 2 and 3).

Further, since the hysteresis is proportional to the thickness of the film, it can be controlled by thinning the thickness of the film to a certain number of μm, and the thinning of the film is low, and the glass is not warped in the lamination with the glass when the polarizing plate is formed. It is advantageous in terms of point, but there is a problem that operability and take-up property are lowered.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2011-85725

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2013-200435

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2013-210598

[Summary of the Invention]

The present invention has been made in view of the above problems of the prior art, and has an object of providing a polyester film for protecting a polarizer, which is a biaxially stretched polyester film, and which does not exhibit an interference color when disposed in a crossed Nicols state, and does not exhibit a cause Interference fringes due to the influence of the surface of the film and the reflection of the back surface are excellent in the windability and transparency, and are excellent in adhesion to the adhesive for the polarizing film and the protective film.

In order to solve the above problems, the present invention has the following constitution.

(1) A polyester film for protecting a polarizer, which is a laminated polyester film having a resin layer (X) containing a crosslinked material on both sides of a polyester film, wherein the polyester film has a hysteresis of 280 nm or less at a wavelength of 590 nm. And the Young's modulus in the length direction and the width direction at 25 ° C is 1000 MPa or more and less than 4000 MPa, respectively; characterized by the vibration waveform derived from the spectral reflection curve of the laminated polyester film, the following formula (1) The amplitude ΔR of the vibration waveform shown is 8% or less. The spectroscopic reflection curve is measured by using a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. at an incident angle. = relative reflectance at 10 degrees.

ΔR=(Rmax-Rmin)/2(%) Equation (1)

(Where, the vibration waveform means a spectroscopic reflectance curve obtained by using a wavelength of 1 nm, and a 20-point moving average process is performed for each measurement point, and a 20-point moving average spectral reflectance curve is obtained, and the 20-point moving reflectance curve is obtained. a range of wavelengths of 400 to 700 nm of the curve obtained by the difference between the spectral reflectance curves before and after the moving average processing;

Rmax and Rmin are the maximum and minimum values of the vibration waveform, respectively.

(2) The polarizer-protected polyester film according to (1), wherein the laminated polyester film has a total light transmittance of 85% or more.

(3) The polyester film for protecting a polarizer according to (1) or (2), wherein the resin layer (X) has a refractive index of 1.45 or more and 1.60 or less.

(4) The polyester film resin layer for protecting a polarizer according to any one of (1) to (3), wherein at least one of the resin layer (X) contains 1 The particles having an average particle diameter of 50 nm or more and 1000 nm or less have a static friction coefficient of 0.5 or more and 1.5 or less and a dynamic friction coefficient of 0.3 or more and 1.0 or less on the film surface on one side perpendicular to the film thickness direction and on the film surface on the opposite side.

(5) The polyester film for polarizer protection according to any one of (1) to (4) wherein the haze value is 3.0% or less.

(6) The polyester film for protecting a polarizer according to any one of (1) to (5), wherein the laminated polyester film has a reflection luminance L*(SCI) of 30 or less, and L*(SCE) is satisfied. Equation (2): L*(SCE)≦L*(SCI)/10 Equation (2)

(L* (SCI) and L* (SCE) are the values of the glass surface side of the sample which consists of the polyester film / black ink of a glass / adhesive layer / polarizer protection.

The polyester film for protecting a polarizer according to any one of (1) to (6), wherein the retardation in the thickness direction is 1500 nm or less.

The polyester film for protecting a polarizer according to any one of (1) to (7) wherein the polyester film is a layer containing the thermoplastic resin A (layer A) and a layer containing the thermoplastic resin B. (B layer) A layered body in which at least 11 layers or more are laminated.

(9) The polyester film for protecting a polarizer according to (8), wherein a thickness of each of the A layer and the B layer from the outermost layer to the fourth layer of the polyester film is 55 nm or less.

(10) The polyester film for protecting a polarizer according to any one of (1) to (9), wherein the thickness of the resin layer (X) is not more than 50%.

(11) The polarizer protection according to any one of (1) to (10) A protective polyester film in which the thickness of the resin layer (X) is 20 nm or more and less than 5000 nm.

(12) The polarizer protection according to any one of (1) to (11) The protective polyester film contains at least one of a melamine-based compound, an oxazoline-based compound, and a carbodiimide-based compound.

(13) The polarizer protection according to any one of (1) to (12) A protective polyester film, wherein at least one of the resin layers (X) comprises a water-soluble polyester resin, and the other comprises a water-soluble acrylic modified resin, and a resin layer comprising a water-soluble acrylic modified resin has a refractive index of 1.53 the following.

(14) A polarizing plate in which a PVA film is laminated The polyester film for protecting a polarizer according to any one of (1) to (13).

The present invention provides good adhesion to an adhesive, does not exhibit an interference color when disposed in a crossed Nicols state, does not exhibit interference fringes caused by reflection of the surface of the film, back surface, has good transparency, is a film and is wound up. A polyester film for good polarizer protection.

[Formation of the Invention]

Hereinafter, embodiments of the present invention will be described in detail.

The polyester film for polarizer protection of the present invention is a laminated polyester having a resin layer (X) containing a crosslinked material on both sides of the polyester film. a film, wherein the polyester film has a hysteresis of 280 nm or less at a wavelength of 590 nm, and a Young's modulus of a length and a width direction of 25 ° C of 1000 MPa or more and less than 4000 MPa, respectively; characterized by splitting from the laminated polyester film In the vibration waveform derived from the reflection curve, the amplitude ΔR of the vibration waveform represented by the equation (1) is 8% or less.

ΔR = (Rmax - Rmin) / 2 (%) Formula (1).

The polyester used in the polyester film of the present invention is preferably a polyester obtained by polymerization of a monomer having an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol as a main constituent. Among them, as the aromatic dicarboxylic acid, for example, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6- Naphthalene dicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenyl sulfonium dicarboxylic acid, and the like. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexane dicarboxylic acid, and ester derivatives thereof. Among them, terephthalic acid and 2,6-naphthalenedicarboxylic acid are preferred. These acid components may be used alone or in combination of two or more. Further, a part of the oxo acid such as hydroxybenzoic acid may be copolymerized.

Further, as the diol component, for example, Alcohol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2, 2-bis(4-hydroxyethoxyphenyl)propane, isosorbide, spiroglycerol, and the like. Among them, ethylene glycol is preferred. These diol components may be used alone or in combination of two or more.

Among the above polyesters, it is preferred to use polyparaphenylene Ethylene glycol diester and its polymer, polyethylene naphthalate and its copolymer, polybutylene terephthalate and its copolymer, polybutylene naphthalate and its copolymer, and then poly pairs Hexyl phthalate and its copolymer, polyethylene naphthalate and its copolymers, and the like. Furthermore, various additives such as antioxidants, antistatic agents, crystallization nucleating agents, inorganic particles, organic particles, viscosity reducing agents, thermal stabilizers, lubricants, infrared absorbing agents, ultraviolet absorbing agents may be added to the resin. A dopant, a dopant for adjusting the refractive index, and the like.

Further, the thickness of the polyester film for polarizer protection of the present invention is preferably 5 to 50 μm. In the case where the film thickness is less than 5 μm, in addition to the film formation of the film becoming difficult, there is also a problem that the workability is deteriorated. Moreover, when the thickness is 50 μm or more, the polarizing plate becomes thick, and it is not suitable for cost reduction and thin film formation. More preferably, it is 10 μm or more and less than 25 μm. In this case, operability or mountability is excellent, and it is easy to suppress hysteresis.

The polyester film of the present invention must have a hysteresis value at a wavelength of 590 nm of 280 nm or less. More preferably, it is 100 nm or less, and still more preferably 50 nm or less. In general, the hysteresis is calculated from the product of the maximum value of the refractive index difference between the two directions perpendicular to the inside of the film surface and the film thickness. In the laminated film, since the refractive index of the film cannot be easily measured, the hysteresis value calculated by the indirect method is used as the hysteresis. Specifically, the value measured by the KOBRA series of the phase difference measuring device sold by Oji Scientific Instruments Co., Ltd. is used, and the phase difference measuring device KOBRA series measures the hysteresis optically. This value is a sample of 3.5 cm × 3.5 cm cut out from the center of the film width direction (the film width direction is defined as an angle of 0° in the apparatus), and is measured at an incident angle of 0°. Hysteresis at a wavelength of 590 nm and the value of its alignment angle. When the value of the hysteresis is small, when it is mounted on a liquid crystal display as a polyester film for polarizer protection, interference color is less likely to occur, which is preferable. Further, as the thickness direction phase difference Rth is also lower, the interference color is less likely to occur, which is preferable.

Moreover, the polyester film of the present invention is yang under 25 ° C The modulus is preferably 1000 MPa or more and less than 4000 MPa in both the longitudinal direction and the width direction of the film. More preferably, it is 2000 MPa or more and 3800 MPa or less. In this case, in the manufacturing step of using the polarizer protective film, it is preferable that the warpage of the glass does not easily occur when laminated with the glass. When the Young's modulus is less than 1000 MPa, the rigidity of the film becomes too weak, the workability is poor, and the winding at the time of film formation is difficult, which is not preferable. Here, the longitudinal direction of the film means that when the laminated film on the roller is used, the winding direction of the roller is the longitudinal direction of the film, and the width direction of the roller corresponds to the width direction of the film. On the other hand, in the case of cutting into a sheet shape, the hysteresis is measured at both ends of the longitudinal direction of the film and the direction perpendicular to the longitudinal direction, and the difference from the center of the film is large as the present invention. Film width direction.

Polyester film for polarizer protection of the present invention, in polyester Both sides of the film must have a resin layer (X) containing a crosslinked material. As the resin layer (X), a water-soluble polyester resin, a water-soluble acrylic resin, an acrylic modified polyester resin or the like is preferable.

For the carboxylic acid component constituting the polyester resin, it can be used. An aromatic, aliphatic, alicyclic dicarboxylic acid or a trivalent or higher polycarboxylic acid. For aromatic dicarboxylic acids, terephthalic acid, isophthalic acid, phthalic acid, citric acid, 2,5-dimethylterephthalic acid, 5-sulfonic acid can be used. Sodium isophthalate (5-sodium sulfoisophtahlate), 1,4-naphthalenedicarboxylic acid, diphenyl phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bisphenoxyethane-p-, p-dicarboxylic acid And phenyl decane dicarboxylic acid, and the like, and ester-forming derivatives thereof.

For the glycol component of the polyester resin, B can be used. Glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, and the like.

Also, a polyester resin is used as a coating liquid for a water-based resin In order to improve the adhesion of the polyester resin or to easily water-soluble the polyester resin, it is preferred to copolymerize the sulfonate group-containing compound or the carboxylate group-containing compound.

For compounds containing a sulfonate group, for example, Sulfonic acid terephthalic acid, 5-sulfoisophthalic acid, 4-sulfonic acid isophthalic acid, 4-sulfonic acid naphthalene-2,7-dicarboxylic acid, sulfonic acid-p-anthracene An alcohol, 2-sulfonic acid-1,4-bis(hydroxyethoxy)benzene or the like or an alkali metal salt, an alkaline earth metal salt or an ammonium salt, which is not limited thereto.

For compounds containing a carboxylate group, for example, Trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, 4-methylcyclohexene-1,2,3-tricarboxylic acid, symmetric benzenetricarboxylic acid, 1,2,3,4- Butane tetracarboxylic acid, 1,2,3,4-pentanetetracarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 5-(2,5-di-oxytetrahydroindenyl) 3-methyl-3-cyclohexene-1,2-dicarboxylic acid, 5-(2,5-di-oxytetrahydroindenyl)-3-cyclohexene-1,2-dicarboxylic acid, ring Pentanetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, ethylene glycol trimellitate, 2,2',3,3'-di Phenyltetracarboxylic acid, thiophene-2,3,4,5-tetracarboxylic acid, ethylidenetetracarboxylic acid, etc. or alkali metal salts thereof, Alkaline earth metal salts, ammonium salts, however, are not limited thereto.

For the glycol component of the polyester resin, B can be used. Glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1, 6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-nonanediol, 2,4-dimethyl-2-ethyl Hexa-1,3-diol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 3-methyl Base-1,5-pentanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1, 4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 4,4'-thiodiphenol, bisphenol A, 4,4'-methylene Diphenol, 4,4'-(2-norbornylidene) diphenol, 4,4'-dihydroxybiphenol, o-, m-, and p-dihydroxybenzene, 4,4' - isopropylidene phenol, 4,4'-isopropylidene glycol, cyclopenta-1,2-diol, cyclohex-1,2-diol, cyclohexyl-1,4-diol, double Phenol A and the like.

For the polyester resin used in the present invention, it can also be used The modified polyester copolymer is, for example, a block copolymer modified with acrylic acid, urethane, epoxy or the like, a graft copolymer or the like.

For the acrylic resin component, methacrylic acid can be used. The acid alkyl ester and/or the alkyl acrylate are, in particular, preferably methacrylic acid, methyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, A N-hexyl acrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, acrylic acid, methyl acrylate, isopropyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate Ester, n-hexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, and the like. These can be used 1 or 2 More than one species.

a polyester tree constituting an acrylic modified polyester resin The lipid component is an ester bond in the main chain or the side chain, and is composed of a dicarboxylic acid component and a glycol component.

Moreover, the cross-linking material used in the present invention is only required to be The compound which causes the crosslinking reaction is not particularly limited, and a urea-based, melamine-based, urethane-based, acrylamide-based, polyamidiamine-based or cyclic-based hydroxymethylated or hydroxyalkylated group can be used. An oxygen compound, an isocyanate compound, an oxazoline compound, a carbodiimide compound, an aziridine compound, various decane coupling agents, various titanate coupling agents, and the like.

There is no particular limitation on the method of setting the resin layer (X). However, in terms of cost and environment, an in-line coating method in which crystal alignment is completed by coating, stretching, and heat treatment of a polyester film before completion of crystal alignment is suitable. As the coating method, for example, a reverse coating method, a spray coating method, a bar coating method, a gravure coating method, a bar coating method, a die coating method, or the like can be used. The thickness of the resin layer can be adjusted depending on the concentration or coating amount of the coating liquid.

Moreover, the polyester film for polarizer protection of the present invention is In the vibration waveform derived from the spectral reflection curve, the amplitude ΔR of the vibration waveform represented by the equation (1) must be 8% or less: ΔR = (Rmax - Rmin) / 2 (%) Formula (1).

Vibration derived from the spectral reflectance curve of the present invention Waveform means numerically processing by using a spectral reflectance curve obtained by using a well-known spectrophotometer at intervals of 1 nm wavelength. A plot of the resulting wavelength versus amplitude R.

Numerical processing means the division of wavelengths per 1 nm The light reflectance curve is subjected to a 20-point moving average process, and the curve of the amplitude R per 1 nm in the range of 400 nm to 700 nm obtained by subtracting the spectral reflectance curve after the 20-point moving average process is subtracted from the original spectral reflectance curve.

Among them, the moving average processing means that the continuous 20 will be calculated. The operation of point averaging is performed on the wavelength and reflectance by shifting at a wavelength of 1 nm. The reason why the 20-point moving average processing is used is that when the periodicity of the wavelength of the short-period vibration waveform that affects the interference fringe (that is, the subject of the present invention) is observed, it is found that there is one cycle of at least 20 nm or less. By averaging the one-period portion, a waveform free from vibration, that is, a curve in which the vibration element is removed and which can be referred to as a prototype of the spectral reflectance curve can be obtained. Since the spectral reflectance curve used in the present invention is data per 1 nm, a 20-point moving average process has been employed. For every 2 nm wavelength data, a 10-point moving average process can also be used.

If the amplitude of the vibration waveform in the wavelength range of 400~700nm ΔR is 8% or less, and the main cause of the light source side which exhibits the equal inclination angle interference fringe, that is, the bright line spectrum of the light source, has the effect of weakening the contrast shading contrast, which is based on the incident angle of the light. The light path is created. More preferably, it is 6% or less, and even more preferably 4% or less. The amplitude of the reflectance of the spectral reflectance curve is generated in a short period of a wavelength interval of less than 1 nm, and is highly likely to be affected by the slit condition of the spectrophotometer used for the measurement. The measurement of the width is preferably 5 nm or more and 8 nm or less. . If the slit width is less than 5 nm, even if the air measurement of the test object is not provided, the amplitude of the reflectance can be shorter than the short period of the wavelength interval of 1 nm to obtain a vibration waveform, which is mixed with the vibration waveform of the laminated film. In addition, when the slit width is 8 nm or more, the effect of the moving average is exerted, and the vibration waveform itself originally contained in the test subject disappears, and the characteristics of the test subject cannot be accurately measured.

The polyester film for polarizer protection of the present invention preferably has a total light transmittance of 85% or more from the viewpoint of high transparency. More preferably, it is 87%, more preferably 90% or more, and most preferably 93% or more. In the case where the transparency is high, it is preferable because it has image sharpness of the screen of the liquid crystal display device.

In the polyester film for polarizer protection of the present invention, the refractive index of the resin layer (X) is preferably 1.45 or more and 1.60 or less. More preferably, it is 1.45 or more and less than 1.58. When the resin having a low refractive index on the surface layer of the polyester film is used, the surface reflectance is lowered. As a result, the vibration waveform ΔR of the spectral reflectance curve is lowered, and the interference fringes are less likely to be seen.

The polyester film for polarizer protection of the present invention preferably contains one or more kinds of particles having a number average particle diameter of 50 nm or more and 1000 nm or less in at least one of the resin layers (X), and a film on one side perpendicular to the thickness direction of the film. The static friction coefficient of the surface of the film on the opposite side of the surface is 0.5 or more and 1.5 or less, and the dynamic friction coefficient is 0.3 or more and 1.0 or less.

The particles used in the present invention are not particularly limited, and examples thereof include inorganic particles such as colloidal cerium oxide, titanium oxide, aluminum oxide, zirconium oxide, calcium carbonate, carbon black, and zeolite particles; or acrylic particles and polyfluorene. Organic particles such as oxygen particles, polyimide particles, Teflon (registered trademark) particles, crosslinked polyester particles, crosslinked polystyrene particles, crosslinked polymer particles, core-shell particles, etc. Use any of these particles, or use multiples in combination. More preferably, particles having a refractive index close to that of the resin layer (X) are used. In this case, since the diffusion by the particles is minimized, the transparency can be maintained.

The average number of primary particles of these particles is 0.05 A range of ~1.0 μm is preferred. Here, the average primary particle diameter refers to an average value of particle diameters of primary particles in JIS-H7008 (2002), and the primary particles are defined as particles generated by growth of a single crystal nucleus. The particle diameter of the particles again (hereinafter referred to as primary particle diameter) means the average of the long diameter and the short diameter. For the measurement of such an average primary particle diameter, the sample can be observed at a magnification of 50,000 times using a scanning electron microscope (SEM) in accordance with JIS-H7804 (2005), and the long diameter and the short diameter of each primary particle are measured using a photograph to average The primary particle diameter was determined, and the same primary particle diameter measurement was further performed for 100 primary particles, and the average primary particle diameter was obtained from the average value thereof. When the average primary particle diameter of the particles is less than 0.05 μm, there is a possibility that the particles are agglomerated and the haze is deteriorated. Conversely, when the particles exceed 1.0 μm, it is difficult to obtain an easy sliding or anti-sticking degree of the added amount (blocking). The effect of the resistance) is that there is a possibility that the particles fall off depending on the thickness of the resin layer. Further, as the particles, monodisperse particles may be used, and agglomerated particles in which a plurality of kinds of particles are agglomerated may be used. Further, a plurality of kinds of particles having an average primary particle diameter different may be used in combination as the case may be. Further, the amount of the particles to be added can be appropriately adjusted in accordance with the thickness of the resin layer (X) or the resin composition, the average primary particle diameter, the desired slidability, use, and the like. In the present invention, It is preferable to suppress the interference fringes caused by the reflection of the surface and the back surface of the film, and to form the optical thickness of the resin layer (X) to be λ/4. In the case of a film comprising a layer of the thermoplastic resin A (layer A) and a layer containing the layer of the thermoplastic resin B (layer B) having a total thickness of about 12 μm, the film having an average thickness of about 50 nm, the resin layer (X) The thickness is preferably in the range of 70 to 110 nm. The particles to be added to the resin layer (X) have an average particle diameter of 200 to 400 nm and 100 to 200 nm, respectively, from the viewpoint of film take-up property and transparency, using an average primary particle diameter larger than the thickness of the resin layer. The two component particles are preferred.

Further, it is preferable that the surface of the film on one side perpendicular to the thickness direction of the film and the surface of the film on the opposite side thereof have a static friction coefficient of 0.5 or more and 1.5 or less, and a dynamic friction coefficient of 0.3 or more and 1.0 or less. More preferably, the static friction coefficient is 0.5 or more and 1.2 or less, and the dynamic friction coefficient is 0.3 or more and 0.8 or less. In this case, since the slidability of the film becomes good, even in the winding step of the film forming step, the winding wrinkles do not enter, and therefore it is good.

The polyester film for polarizer protection of the present invention preferably has a haze value of 3.0% or less. It is more preferably 2% or less, and still more preferably 1% or less. When the haze value is 3.0% or more, the transparency of the film is lowered, and when used as a polyester film for polarizer protection, there is a problem that image sharpness is deteriorated.

The polyester film for polarizer protection of the present invention preferably has a reflection luminance L* (SCI) of 30 or less from the viewpoint of appearance, and L*(SCE) satisfies the formula (1).

L*(SCE)≦L*(SCI)/10 (1) (L*(SCI) and L*(SCE) represent the values when measuring the glass surface of a sample which is similar to the actual display, which is a glass/adhesive layer/polarizer protective polyester film/black ink The black ink is a liquid crystal of a black screen because the transmittance or reflectance is minimized when no voltage is applied, so in the present case, black acrylic varnish spray H62-8014 (ROCK PAINT) is used. (share) system)). Among them, SCI and SCE mean the measurement method of the brightness of the reflected light. The method of measuring the color with the light trap on the detection side and removing the specular reflected light is called SCE (excluding the regular reflection) method, and the method of measuring the color of all the reflection without removing the light reflected and removing the regular reflection light is called SCI. (including regular reflection) mode.

If L*(SCI) exceeds 30, the surface reflection is high, Glare and interference fringes are clearly visible, and the original color of the image cannot be obtained when actually mounted on the display, which is not preferable. Further, it is preferable that L*(SCE) satisfies the formula (1). In the case where the formula (1) is not satisfied, the diffused reflected light becomes an advantage compared with the specular reflected light, and it feels whitish when visually observed, so that the appearance is not good.

In order to satisfy this requirement, it is added to the resin layer (X). The particles are preferably colloidal cerium oxide particles having a refractive index close to that of the resin layer, and the particle diameter is preferably less than 4 times the thickness of the resin layer (X). Further, in order to have both slidability and transparency, it is preferred to add particles in which two or more kinds of particle diameters are different.

Regarding L* (SCI) and L* (SCE), in accordance with the following The value determined by the law.

Use black on one side of the polyester film for polarizer protection Color acrylic varnish spray H62-8034 (manufactured by ROCK PAINT Co., Ltd.) was applied in black, and the surface opposite to the surface was bonded to the surface of the surface by the adhesive sheet SK-1478 (manufactured by Amika Chemical Co., Ltd.), and the thickness was 0.55. Corning (R) Gorilla (R) Glass (manufactured by Corning Incorporated) of mm was laminated so as not to sandwich air bubbles, and a glass laminated sample was prepared. Furthermore, after applying black, the sample was lifted once toward the fluorescent lamp to confirm that the light was not transmitted.

The glass surface of the glass laminated sample to be prepared was measured using CM-3600d manufactured by KONICA MINOLTA Co., Ltd. Under the condition of 8 mm target mask (CM-A106), the L value was measured by SCI method including specular reflection and SCE method for removing specular reflection, and the average value of n number 3 was obtained. Furthermore, the white calibration plate uses CM-A103, the zero correction box uses CM-A104, and the light source is D65.

Thickness of polyester film for polarizer protection of the present invention The direction retardation is preferably 1500 nm or less. It is more preferably 1200 nm or less. The term "delay in the thickness direction" means that the vertical direction of the surface of the polyester film for polarizer protection is regarded as 0°, and the hysteresis at the position of the viewing angle of 50°. In the case where the retardation in the thickness direction is 1500 nm or less, it is preferable because the rainbow spot is not seen even when the display is viewed from the front side and from the oblique direction. Further, from the viewpoint that the interference color observed in the crossed Nicols state of the polarizer is close to colorless, it is more preferably 600 nm or less. It is more preferably 400 nm or less. When the orthogonal Nicols system indicates that the absorption axis of the polarizer is arranged in a vertical relationship, when the lower side covers the light such as the backlight, it becomes a matte state.

The polyester film for polarizer protection of the present invention is preferably A layered body in which at least 11 layers of the layer (layer A) containing the thermoplastic resin A and the layer (layer B) containing the thermoplastic resin B are alternately laminated.

The above thermoplastic resin A, thermoplastic resin B In particular, a polyester obtained by polymerization of a monomer having an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol as a main constituent component is preferred. Among them, as the aromatic dicarboxylic acid, for example, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6- Naphthalene dicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenyl sulfonium dicarboxylic acid, and the like. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexane dicarboxylic acid, and ester derivatives thereof. Among them, terephthalic acid and 2,6-naphthalenedicarboxylic acid which exhibit a high refractive index are preferred. These acid components may be used alone or in combination of two or more. Further, a part of the oxo acid such as hydroxybenzoic acid may be copolymerized.

Further, as the diol component, for example, Alcohol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2, 2-bis(4-hydroxyethoxyphenyl)propane, isosorbide, spiroglycerol, and the like. Among them, ethylene glycol is preferred. These diol components may be used alone or in combination of two or more.

Among the above polyesters, it is preferred to use polyparaphenylene Ethylene glycol diester and its polymer, polyethylene naphthalate and its copolymer, polybutylene terephthalate and its copolymer, polybutylene naphthalate and its copolymer, and then poly pairs Hexyl phthalate and its copolymer, polynaphthalene Hexyl dicarboxylate and copolymers thereof.

Combination of thermoplastic resin A and thermoplastic resin B From the viewpoint of reducing the lamination failure in the step of forming the laminated structure, it is important to use a combination of resins having good compatibility. In the step of forming the laminated structure, it is difficult to form a laminar flow in the polymer flow path, causing lamination failure such as flow marks, resulting in uneven buildup, that is, damage to the thickness uniformity of each layer. In the case of the combination index of the resin, it is preferred to use a resin having a similar compatibility parameter δ, and it is preferable that the difference between the absolute values of the compatibility parameter δ is 2 or less. More preferably, the difference between the absolute values of the compatibility parameters δ is 1 or less.

The combination of the resins to choose to use contains common basics The resin of the skeleton is preferred. The term "basic skeleton" as used herein means a repeating unit constituting a resin. For example, in the case where the resin on one side is polyethylene terephthalate, the ethylene terephthalate unit is a basic skeleton. In this case, in the case of a resin having a common basic skeleton, a copolymer of a repeating unit of an ethylene terephthalate unit and another ester is exemplified. When a resin containing a common basic skeleton is used, it is possible to suppress not only lamination failure such as flow marks but also problems such as peeling between layers after molding. From the viewpoint that it is difficult to cause lamination failure, it is preferred that the A layer is polyethylene terephthalate and the B layer is a combination of copolymers. Preferably, the copolymer is: polyethylene terephthalate copolymerized with 5 to 40 mol% of cyclohexane dimethanol; and 5 to 40 mol% of cyclohexane dicarboxylic acid. Or polyethylene terephthalate copolymerized with 5 to 40 mole % of the spirulina component. Further, from the viewpoint that it is difficult to cause lamination failure, it is preferred that the layer B is a mixture of polyethylene terephthalate and a copolymer thereof. This is by The same resin as the layer A is added to the layer B, and the affinity with the interface of the layer A is further increased.

Moreover, the thermoplastic resin B has a specific crystalline polyester A crystalline resin having a melting point lower than a melting point of 20 ° C or higher is preferred. In this case, in the heat treatment step to be described later, by performing heat treatment between the melting point of the thermoplastic resin B and the melting point of the crystalline polyester, only the thermoplastic resin B can be relaxed, and it is easy to suppress the hysteresis, By the relaxation of the alignment, the rigidity of the film is lowered, and there is an effect that "the residual stress of the film formed when the glass is laminated is low, and the warpage of the glass is less likely to occur". The melting point difference is preferably 40 ° C or more. In this case, since the temperature selection range in the heat treatment step is widened, the promotion of the relaxation of the thermoplastic resin B or the alignment control of the crystalline polyester can be facilitated. Further, the thermoplastic resin B is preferably made of an amorphous resin. Compared with the crystalline resin, the amorphous resin is less likely to cause alignment when the biaxially stretched film is produced, and the increase in hysteresis can be suppressed, and the hysteresis unevenness of the laminated film can be suppressed.

One of the combinations of resins used to satisfy the above conditions For example, the polyester is preferably a thermoplastic resin A containing polyethylene terephthalate or polyethylene naphthalate, and a thermoplastic resin B containing spiro glycerol. A polyester comprising spiro glycerol means a copolyester or a homopolyester in which spiro glycerol is copolymerized, or a polyester blended therewith. A polyester comprising spiro glycerol is preferred because it has a small difference in glass transition temperature from polyethylene terephthalate or polyethylene naphthalate, is not easily extended during forming, and is not easily peeled off between layers. . More preferably, the following polyester is preferred: the crystalline polyester comprises polyethylene terephthalate The ester or polyethylene naphthalate is formed, and the thermoplastic resin B is composed of spiro glycerol and cyclohexane dicarboxylic acid. When it is a polyester which consists of spiro glycerol and cyclohexane dicarboxylic acid, since a crystallinity fall, it is easy to suppress a hysteresis. Further, since the difference in glass transition temperature from polyethylene terephthalate or polyethylene naphthalate is small, the adhesion is also excellent, so that it is not easily excessively stretched during molding, and interlayer peeling is not easily obtained.

Further, a layer (layer A) containing thermoplastic resin A and containing The layered body formed by alternately laminating the layers of the thermoplastic resin B (layer B) is defined as a portion having a structure in which the layers A and B are regularly laminated in the thickness direction. That is, in the film of the present invention, the sequence in which the layer A and the layer B are arranged in the thickness direction is preferably not in an irregular state, and the sequence of the third layer or the layer other than the layer A and the layer B is arranged. There is no special limit. For example, in the case of having the A layer, the B layer, and the C layer containing the resin C, it is more preferable to laminate the layers in the order of A(BCA)n, A(BCBA)n, A(BABCBA)n or the like. Where n is the number of repeating units, for example, in the case where n=3 in A(BCA)n, it means that the layer is laminated in the order of ABCABCABCA in the thickness direction.

As described above, by alternately laminating the resins having different thermal characteristics, when the biaxially stretched film is produced, the alignment state of each layer can be highly controlled, and the hysteresis can be suppressed. In addition, when the number of laminated layers is 10 or less, the influence of the properties of the resin laminated resin having different thermal characteristics or the thickness of the layer thickness on the physical properties such as film forming properties and mechanical properties becomes remarkable, for example, The production of the biaxially stretched film becomes difficult, or there is a possibility of occurrence of defects when combined with a polarizing plate, and thus it is not suitable. On the other hand, in the case of a film in which 11 or more layers are alternately laminated, each layer of heat can be used. The plastic resin can be controlled to be easily disposed homogeneously in the thickness direction, and the film forming property or the mechanical property can be stabilized. In addition, as the number of layers increases, there is a tendency to suppress the growth of the alignment of the respective layers. In addition to the easy control of the hysteresis, the Young's modulus is lowered and used as a polarizer protective film to laminate with the glass. Warpage is not easy to produce, so it is preferable. More preferably, it is 100 or more layers, and more preferably 200 or more layers. In addition, there is no upper limit on the number of layers, but as the number of layers increases, the manufacturing cost increases due to the increase in the size of the manufacturing apparatus, and the thickness of the film is thickened, so that the thin film effect of the object is lost. Therefore, in reality, it is less than 10,000 layers. For practical use.

Further, from the polarizer protective polycondenser comprising the above laminated body The thickness of each layer including the layer of the thermoplastic resin A (layer A) and the layer containing the thermoplastic resin B (layer B) from the outermost surface of the ester film to the fourth layer is preferably 55 nm or less. From the outermost layer to the fourth layer, it means a layer structure of, for example, A/B/A/B or B/A/B/A, and all of the layers are preferably 55 nm or less. In this case, since the amplitude of the vibration waveform in the wavelength range of 400 to 700 nm in the visible light region is small, interference fringes are less likely to be seen, which is preferable. Further, since the amplitude is small, the total light transmittance is also improved, which is preferable. More preferably, it is 45 nm or less. More preferably, it is 40 nm or less. On the other hand, when it exceeds 55 nm, since the light reflected by the interface with the resin layer becomes correlated, the amplitude of the vibration waveform becomes large, and the interference fringe is clearly visible, which is a problem in appearance. The thickness of the layer from the outermost layer to the fourth layer on the front and back sides can be made 55 nm or less by adjusting the flow rate of each slit of the layering device.

The thickness of the resin layer (X) of the present invention is not uniform, and is 50% The next is better. More preferably, it is 40% or less, and even more preferably 30% or less. By suppressing uneven thickness of the resin layer and coating it at a certain thickness, particles can be prevented from being The resin layer peeled off and a uniform adhesiveness was obtained. Further, it is preferable because the surface reflection unevenness caused by the thickness unevenness of the resin layer can be suppressed, and the dispersion of the total light transmittance can be suppressed.

The so-called thickness unevenness means the length direction of the film. The measurement of the spectral transmittance was performed using a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd., and the thickness of the resin layer was calculated from the spectral transmittance to calculate the thickness unevenness.

Polyester film for polarizer protection of the present invention, resin layer The thickness of (X) is preferably 20 nm or more and less than 5000 nm, more preferably 20 nm or more and less than 2000 nm, and still more preferably 40 nm or more and less than 500 nm. When the thickness of the resin layer (X) is too small, there is a possibility that the adhesion to the adhesive material is poor or the added particles fall off.

The resin layer of the polyester film for polarizer protection of the present invention The crosslinked material contained in (X) preferably contains at least one of a melamine-based compound, an oxazoline-based compound, and a carbodiimide-based compound. In this case, since it is seen that the heat-and-moisture resistance is improved, it is preferable. Further, the content of the melamine-based compound, the oxazoline-based compound, and the carbodiimide-based compound is not particularly limited, and two or more kinds of crosslinked materials may be contained.

The melamine crosslinking agent used in the present invention has no special Further, however, a methylolated melamine derivative obtained by condensing melamine, melamine and formaldehyde, a compound partially or completely etherified by reacting methylolated melamine with a lower alcohol, and the like may be used. Further, the melamine-based crosslinking agent may be either a monomer or a condensate containing a polymer of a dimer or more, or a mixture thereof. For the lower alcohol used in etherification, methanol and ethanol can be used. , isopropanol, n-butanol, isobutanol, and the like. The functional group is an imido group methylated melamine resin having an imido group, a methylol group, or an alkoxymethyl group such as a methoxymethyl group or a butoxymethyl group in one molecule. A methylol type melamine resin, a methylol type methylated melamine resin, a completely alkyl type methylated melamine resin, or the like. Among them, a hydroxymethylated melamine resin is preferred. Further, in order to promote thermal hardening of the melamine-based crosslinking agent, an acidic catalyst such as p-toluenesulfonic acid may also be used. In addition, the oxazoline-based crosslinking agent used in the present invention is not particularly limited as long as it has an oxazoline group as a functional group in the compound, and is preferably a copolymer containing an oxazoline group. The oxazoline group-containing copolymer contains at least one or more oxazoline group-containing monomers and is obtained by copolymerizing at least one other monomer.

For monomers containing oxazoline groups, 2-ethylene can be used. 2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazole For the porphyrin, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, etc., one or more of these may be used. mixture. Among them, 2-isopropenyl-2-oxazoline is preferred in the industry and is preferred.

In the oxazoline crosslinking agent, it is relative to the oxazole The other monomer which is used for the monomer of the morphyl group is not particularly limited as long as it is a monomer copolymerizable with the monomer containing the oxazoline group, but for example, acrylic acid can be used. Ester, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, etc. Or methacrylates; acrylic acid, methacrylic acid, clothing Unsaturated carboxylic acids such as benzamic acid and maleic acid; unsaturated nitriles such as acrylonitrile and methacrylonitrile; acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methyl Unsaturated guanamines such as acrylamide; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; olefins such as ethylene and propylene; , halogen-containing α,β-unsaturated monomers such as vinylidene chloride and vinyl fluoride; α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene; etc. One type or a mixture of two or more types.

Further, the carbodiimide cross-linking used in the present invention The compound is not particularly limited as long as it is a compound having one or two or more carbodiimide groups in the molecule or a cyanamide group having a mutually deformable relationship as a functional group. Specific examples of such a carbodiimide compound include dicyclohexylmethane carbodiimide, dicyclohexylcarbodiimide, tetramethylphosphonium carbodiimide, urea modified carbodiimide, and the like. It is also possible to use one or a mixture of two or more of these.

The polarizer of the present invention protects the polyester film to constitute At least one of the resin layers (X) contains a water-soluble polyester resin, and the other contains a water-soluble acrylic modified resin, and a resin layer containing a water-soluble acrylic modified resin has a refractive index of 1.53 or less. In this case, the adhesion between the resin layer containing the water-soluble polyester resin and PVA is improved, and the water-soluble acrylic modified resin layer on the other side has a refractive index of 1.53 or less, thereby lowering the reflectance of the surface of the film. It has the effect of suppressing interference fringes. The refractive index of the resin layer containing the water-soluble acrylic modified resin is preferably 1.52 or less. In order to achieve the refractive index, the water-soluble resin is preferably low in polarizability. Next, a preferred method for producing the laminated film of the present invention will be described below. Of course, the invention is not limited to the related examples and explained.

First, a specific manufacturing method of a general polyester film will be described. First, as the polyester resin A (corresponding to the resin A) and the polyester resin B (corresponding to the resin B) used for the biaxial alignment film used in the present invention, commercially available polyethylene terephthalate resin or The polybutylene terephthalate resin is obtained by polycondensation according to a known method. However, for example, in the case of a polyethylene terephthalate resin, it can be polymerized as follows. Magnesium acetate and antimony trioxide were added to a mixture of dimethyl terephthalate and ethylene glycol, and the temperature was gradually raised. Finally, methanol was distilled off at 220 ° C, and a transesterification reaction was carried out. Then, an 85% phosphoric acid aqueous solution was added to the transesterification reaction product, and then transferred to a polycondensation reaction vessel. The temperature was raised by heating in a polymerization vessel, and the reaction system was gradually depressurized, and a polycondensation reaction was carried out at 290 ° C under a reduced pressure of 1 hPa to obtain a polyethylene terephthalate resin having a desired ultimate viscosity. In the case of adding particles, it is preferred to add a slurry in which ethylene glycol is dispersed in ethylene glycol so as to be a set particle concentration, and to carry out polymerization.

Further, the production of the polybutylene terephthalate resin can be carried out, for example, in the following manner. The mixture of terephthalic acid and 1,4-butanediol is heated to 140 ° C under nitrogen atmosphere to form a homogeneous solution, and then tetra-n-butyl phthalate and mono-butyl butyl oxide are added for esterification. reaction. Then, tetra-n-butyl phthalate is added, and a polycondensation reaction is carried out under reduced pressure to obtain a polybutylene terephthalate resin having a desired ultimate viscosity.

For the use of the polyester resin obtained in the above manner A preferred method for producing the laminated polyester film of the present invention and the multilayered polyester film having 11 or more layers is specifically described below.

First, in the case where the polyester resin to be used is mixed, It is measured and mixed in such a manner as to be a set ratio. Then, for example, drying at 150 ° C for 5 hours is carried out under nitrogen atmosphere, vacuum gas, or the like, so that the water content in the polyester resin is preferably 50 ppm or less. Thereafter, it is supplied to an extruder for melting and extruding. Further, in the case where the venting type two-axis extruder is used for melt extrusion, the drying step of the resin can be omitted. Then, the foreign matter is removed by the filter or the gear pump, and the amount of the extrusion is equalized, and is discharged from the T die to the cooling drum in a sheet form. At this time, the sheet-like polymer is bonded to the casting drum by, for example, the following method, and is solidified by cooling to obtain an unstretched film: a method of applying static electricity using a wire electrode or a strip electrode, and a polymerization in the casting drum and the extrusion. a method of casting a water film between the sheets, a method of setting the temperature of the casting drum to a glass transition point of the polyester resin (glass transition point -20 ° C) to adhere the extruded polymer, or a plurality of methods of the method The method of combination. Among these casting methods, in the case of using a polyester, it is preferred to use a method of applying static electricity from the viewpoint of productivity or planarity.

Then, by extending the unstretched film along the length After stretching, extending in the width direction, or extending in the width direction, a sequential biaxial stretching method extending in the longitudinal direction, or extending by a simultaneous biaxial stretching method in which the longitudinal direction and the width direction of the film are almost simultaneously extended .

In terms of the stretching ratio in the extension method, in each The direction is preferably 2.5 to 3.5 times, more preferably 2.8 to 3.5 times. It is especially suitable for 3~3.4 times. Further, the stretching speed is preferably from 1,000 to 200,000%/min. Further, although the extension temperature is a temperature at which the glass transition point is ~ (glass transition point + 50 ° C), it is preferably 90 to 130 ° C, and particularly preferably the extension temperature in the longitudinal direction is 100 to 120 ° C, and the extension temperature in the width direction. It is preferably 90 to 110 ° C. Moreover, the extension can also be performed multiple times in each direction.

Furthermore, in the laminated film of the present invention, in order to suppress thin The hysteresis in the film width direction or the dispersion angle of the alignment angle is preferably set to have a difference in the lateral stretching speed. Specifically, in the case where the laterally extending region 2 is divided, the film is extended at the intermediate point of the laterally extending region ( The width of the film at the measurement site - the width of the film before stretching is preferably 60% or more of the elongation at the end of the lateral extension. More preferably 70% or more. By thus changing the elongation ratio of the laterally extending regions, the retardation of the film width direction or the dispersion of the alignment angle can be suppressed, and then a high-quality liquid crystal display having no coloring or no brightness reduction when the liquid crystal display is mounted can be produced.

Furthermore, the laminated film of the present invention is used to make a lateral extension The temperature is sometimes changed stepwise to be preferred. Specifically, in the case where the laterally extending region 2 is divided, the intermediate point of the laterally extending portion is used as a base point, and the ambient temperature of the extending portion of the first half and the second half is set to have a difference of 20 ° C or more. Here, the term "air-conditioning temperature" may be such that the temperature of one of the first half portion and one of the second half portion of the laterally extending portion satisfies the above-described portion. It is preferable to provide a difference of 40 ° C or more. By gradually changing the extension temperature of such a laterally extending region, it is possible to suppress the retardation in the film width direction or the dispersion angle of the alignment angle, and then to form a high-quality liquid crystal display which is not colored or has no brightness reduction when mounted on a liquid crystal display.

The film that is biaxially stretched in this way is to give a plane The stability and dimensional stability are preferably performed by heat treatment. The heat treatment can be carried out by any method previously known in an oven, on a heated roller, or the like. This heat treatment is carried out at a temperature lower than the melting point of the polyester of 120 ° C or higher, but a heat treatment temperature of 200 to 240 ° C is preferred. From the viewpoint of transparency and dimensional stability of the film, it is preferably 210 to 235 ° C. Further, the heat treatment time can be arbitrarily selected within a range in which the characteristics are not deteriorated, and it is preferably 1 to 60 seconds, more preferably 1 to 30 seconds. Further, the heat treatment may be performed by relaxing the film in the longitudinal direction and/or the width direction.

Furthermore, before the horizontal stretching step, in order to make ink marks The adhesion of the brush layer, the adhesive agent, and the vapor deposition layer is increased, and at least one surface is subjected to corona discharge treatment, and the wet tension of the surface is made 47 mN/m or more, and the resin layer (X) of the present invention is formed on the treated surface. In the present formation, a known coating tool such as a roller coater, a gravure coater, a dicavity applicator, a bar coater, a die coater, or a dip coater can be used.

The case of simultaneous two-axis extension is explained below. in At the same time, in the case of biaxial stretching, on the obtained cast film, a single surface of the film was subjected to corona discharge treatment in the same manner as in the case of successive biaxial stretching to form a water-soluble resin layer. Then, the cast film is guided to a simultaneous two-axis tenter, and both sides of the film are held by a jig while being conveyed, and simultaneously and/or stepwise extending in the longitudinal direction and the width direction. In the case of the simultaneous two-axis extension machine, there are a pan/tilt method, a screw method, a drive motor method, and a linear motor method. However, the drive motor method or the linear motor method in which the relaxation ratio can be arbitrarily changed at any position can be changed. good. In terms of the stretching ratio, it varies depending on the type of resin, however Generally, in terms of area magnification, it is preferably 6 to 50 times, and in the case of using polyethylene terephthalate in any of the resins constituting the laminated film, in terms of area magnification, it is 8 to 30 times. good. In particular, in the case of simultaneous biaxial stretching, in order to suppress the misalignment in the plane, it is preferable to make the stretching ratios in the longitudinal direction and the width direction the same, and the elongation speed is almost equal. Further, in terms of the elongation temperature, the glass transition temperature to the glass transition temperature + 120 ° C of the resin constituting the laminated film is preferable.

Such a biaxially stretched film, in order to impart planarity, The dimensional stability is preferably followed by heat treatment in the tenter at a temperature above the melting point. At the time of this heat treatment, in order to suppress the distribution of the main alignment axis in the width direction, it is preferable to perform the relaxation treatment in the longitudinal direction immediately before entering the heat treatment zone and/or immediately after entering the heat treatment zone. After heat treatment in this manner, it was uniformly cooled slowly, cooled to room temperature, and then taken up. Further, if necessary, the relaxation treatment may be carried out in the longitudinal direction and/or the width direction from the heat treatment to the cold cooling. The relaxation treatment is instantaneously performed in the longitudinal direction immediately before entering the heat treatment zone and/or immediately after entering the heat treatment zone.

Preferred manufacturer of multi-layer laminated film of 11 layers or more The method can be easily carried out in the same manner as described in paragraphs [0053] to [0063] of JP-A-2007-307893. The thermoplastic resin is prepared in the form of pellets or the like. The granules can be supplied to individual extruders as needed, after drying in hot air or under vacuum. In the extruder, the resin is heated and melted to a temperature higher than the melting point, and the amount of the resin is equalized by a gear pump or the like, and the foreign matter or the modified resin or the like is removed through a filter or the like. These resins are formed into a desired shape by a die and then discharged. then, The laminate which is discharged from the die is a multi-layered sheet which is extruded onto a cooling body such as a casting drum to be cooled and solidified to obtain a cast film. In this case, it is preferable to use an electrode such as a wire, a belt, a needle, or a knife to be cooled and solidified by being bonded to a cooling body such as a casting drum by an electrostatic force. Further, it is also preferred that air is blown from a slit-like, dot-like or planar device to be adhered to a cooling body such as a casting drum to be quenched and solidified, or adhered to a cooling body by a nip roll to be quenched and solidified. Methods.

Moreover, the thermoplastic resin used in the layer A and its phase A plurality of resins of different thermoplastic resin B are output from a different flow path using two or more extruders and transported to a multilayer laminating apparatus. As the multilayer laminating apparatus, a multi-manifold die, a feed member, a static mixer or the like can be used, but in particular, in order to obtain the constitution of the present invention efficiently, a feed member having 11 or more fine slits is used. good. When such a feed member is used, since the apparatus does not become extremely large, the amount of foreign matter due to thermal deterioration is small, and even when the number of layers is extremely large, a high-precision laminate is possible. Further, the stacking accuracy in the width direction is also greatly improved as compared with the prior art. Moreover, since the thickness of each layer can be adjusted by the shape (length, width) of the slit, the thickness of the layer can be achieved.

In this way, the melt will be formed into the desired layer. A molten multilayer laminate is introduced into the die to obtain a cast film as described above. The obtained cast film is formed into a desired film by the same biaxial stretching or simultaneous biaxial stretching as described above.

The laminated film obtained as described above is Commercially available PVA contains iodine and is formulated to form a PVA fit. Use with polarizing plates.

[Examples]

The evaluation method of the physical property value used in the present invention is described.

[Evaluation method of physical property]

The evaluation method of the physical property value and the evaluation method of the effect are as follows.

(1) The layer thickness, the number of layers, and the structure of the laminated structure layer were obtained by observing a sample by a transmission electron microscope (TEM) on a sample obtained by cutting a cross section using a microtome. Specifically, a transmission electron microscope model H-7100FA (manufactured by Hitachi, Ltd.) was used to observe a section of the film at an acceleration voltage of 75 kV for 40,000 times, and a cross-sectional photograph was taken to measure the layer constitution and the thickness of each layer. Further, in order to improve the contrast, a dyeing technique using well-known RuO ₄ or OsO ₄ or the like is employed as appropriate.

(2) Calculation method of layer thickness The 40,000-fold TEM photograph image obtained in the above item (1) was captured with an image size of 720 dpi using a Canon Scan D123U. Save the image in a bitmap file (BMP) or compressed image file (JPEG) on your PC, and then use the image processing software Image-Pro Plus ver.4 (seller Planetron) to open the file for image analysis. . The image analysis process is in a vertical thick profile mode and a low-pass filter is used as needed. Furthermore, the low pass filter has a maximum of 10 x 10. Then, the relationship between the "thickness direction position" and the "average brightness of the area sandwiched between the two lines in the width direction" is read as numerical data. Use the table to calculate the software, using position (nm) and brightness data. Furthermore, the data of the periodic brightness change obtained by the differential is differentiated, and the maximum value and the minimum value of the differential curve are read by a VBA (Visual Basic for Applications) program, and the interval between the adjacent layers is used as a layer of 1 layer. The layer thickness was calculated from the thickness. Do this for each photo and calculate the layer thickness for all layers.

Further, the contact surface with the casting drum at the time of film formation is regarded as the first layer, and the number of layers is specified so as to be referred to as the second layer and the third layer in the thickness direction. The first layer thereof means a layer which is melted and extruded, and is different from a resin layer provided by coating or the like.

(3) Glass transition temperature (Tg) ‧ melting point (Tm) The melt-kneaded polyester sheet which was cooled by cold water of 10 ° C or less immediately after the discharge was subjected to differential calorimetry (DSC), and was heated from 25 ° C at 5 ° C / min. At 290 ° C, the transfer point occurring at this time was measured and calculated in accordance with JIS-K-7122 (1987).

Device: SEIKO Electronics industrial (share) "Robot DSC-RDC220"

Data analysis "Disk Session SSC/5200"

Sample quality: 5 mg.

(4) Intrinsic viscosity (IV) was calculated from the solution viscosity measured at 25 ° C in o-chlorophenol. Further, the solution viscosity was measured using an Ostwald viscometer. The unit is expressed in [dl/g]. Furthermore, the number of n is 3, and the average value thereof is used.

(5) Measurement of spectral reflectance For a 5 cm square sample of a laminated film, an incident angle was measured using a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. = 10 degree relative reflectivity. The inner wall of the attached integrating sphere is barium sulfate, and the standard plate is alumina. The measurement wavelength was set to be 250 nm to 1200 nm, the interval was 5 nm (visible light)/10 nm (infrared light), the gain was set to 2, and the measurement was performed at a scan speed of 1 nm and a scan speed of 600 nm/min. In order to eliminate interference caused by reflection from the back side of the sample, the back side of the sample was attached to a Vinyl Tape (registered trademark) manufactured by Nitto Denko Corporation. Furthermore, the switching wavelength of the detector of visible light and infrared light is 850 nm.

(6) The amplitude of the vibration waveform △R

The data of the spectral reflectance curve (curve A) on the 1 nm scale obtained by the measurement of the item (5) was subjected to a 20-point moving average process as the reflectance data with respect to the wavelength. Then, by linearly interpolating the data per 1 nm of the obtained wavelength range of 259.5 to 1190.5 nm, the data is converted into data of 1 nm in the range of 260 to 1190 nm, and a 20-point moving average spectral reflectance curve (curve B) is obtained. . In the wavelength range of 400 to 700 nm, the difference between the curve A and the curve B (the reflectance in the curve A - the reflectance in the curve B) is taken to obtain a vibration waveform. From the vibration waveform, the maximum value Rmax and the minimum value Rmin of the reflectance difference are obtained, and ΔR is calculated by the equation (1).

(7) Refractive index of the resin layer (X)

A film having a film thickness of about 1 mm obtained by drying or curing the resin to be used was measured using an Abbe refractometer manufactured by Atago Co., Ltd. according to JIS-K-7105 (1981). That is, a sodium lamp (Na-D line) is used as a light source, and a mounting liquid is measured by using diiodomethane at 23 ° C and a relative humidity of 65% to measure the birefringence in two perpendicular directions. As the refractive index.

(8) Hysteresis and thickness lag A phase difference measuring device (KOBRA-21ADH) manufactured by a prince measuring machine (stock) was used. The sample was cut out from the center of the film width direction by 3.5 cm × 3.5 cm, and the film width direction was set to 0° as defined by the measuring device, and the incident angle was set to 0° in the slow phase mode. Hysteresis at a wavelength of 590 nm. Further, with respect to the retardation in the thickness direction, the retardation at a wavelength of 590 nm at which the incident angle was set to 50° was measured in the refractive index mode.

(9) Young's modulus The measurement was carried out using an Instron type tensile tester in accordance with the method specified in JIS-K7127 (1999). The measurement was carried out under the following conditions.

Measuring device: "Tensilon AMF/RTA-100" automatic measuring device for film elongation of Orientec Co., Ltd.

Sample size: width 10mm × gauge length 50mm

Stretching speed: 300mm/min

Measurement environment: temperature 23 ° C, humidity 65% RH.

(10) Static friction coefficient (μs), dynamic friction coefficient (μd) according to ASTM-D-1894, after sliding by a sliding tester at a sliding speed of 150 mm/min and a load of 200 g, based on the resistance strain gauge The stress (resistance value) is calculated by the formula (2). Further, the static friction coefficient is a friction coefficient obtained from the resistance value immediately after the slip, and the dynamic friction coefficient is the resistance value of the stable region after the slip.

Friction coefficient = resistance value (G) / load (G)

(11) Haze

The measurement was carried out in accordance with JIS K 7105 using a direct reading haze meter HGM-2DP (manufactured by Suga Test Equipment Co., Ltd.). Haze (%) is calculated by dividing the diffuse transmittance by the total light transmittance and multiplying by 100.

(12) Adhesiveness

First, PVA having a different degree of saponification was dissolved in water to prepare four kinds of PVA solutions having a solid concentration of 5%. The PVA used in the four PVA solutions is shown below.

PVAa: Completely saponified PVA (saponification degree: 98 to 99 mol%) "PVA-117" (Kuraray Co., Ltd.)

PVAb: quasi-fully saponified PVA (saponification degree: 91 to 94 mol%) "AL-06" (manufactured by Japan Synthetic Chemical Industry Co., Ltd.)

PVAc: Ethyl-based modified PVA (saponification degree: 92-94% by mole) "Z-320" (manufactured by Japan Synthetic Chemical Industry Co., Ltd.)

PVAd: Partially saponified PVA (saponification degree: 78 to 82 mol%) "KL-06" (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)

Then, on the resin layer (X)-2 of the polyester film, four kinds of PVA solutions were respectively applied using a bar coater (manufactured by Matsuo Co., Ltd., No. 4, wet thickness: about 8 μm), using a hot air oven. "HIGH-TEMP-OVEN PHH-200 (manufactured by Espec)" was dried at 100 ° C for 1 minute to obtain four films for evaluation of adhesion. On the obtained sample for evaluation of adhesion, 25 grids of 5 × 5 were cut out at a cutting interval of 2 mm in accordance with JIS 5600-5-6 (developed in 1999). Then, in the section where the grid is placed, Nichiban 18mm Cellotape (registered trademark) (item number: CT-118S) is used to wipe the Cellotape (registered trademark) with a finger in a manner to see the grid. Then, the Cellotape is peeled off instantaneously at an angle of about 60° to the resin layer. Trademark). Calculate the number of peels in the grid. The number of evaluations was 5, and the average value was obtained. The evaluation criteria are as follows. The evaluation criteria "A" and "B" were judged to be good adhesion.

A: The number of peelings of the grid is less than 1 grid.

B: The number of peelings of the grid is less than 3 grids

C: The number of peelings of the grid is 4 or more and 5 or less.

D: the number of peelings of the grid is 6 or more

(13) Visibility test (interference color)

In the PVA, the surface on one side of the polarizing plate in which the iodine was adsorbed and aligned was 99.9%, and a sample having a width direction of 420 mm and a length of 310 mm cut out from the central portion in the film width direction was bonded to each other to prepare a test piece. The prepared test piece and the polarizing plate to which the film was not attached were overlapped in the arrangement of crossed Nicols, and the visibility of the case where it was placed on the LED light source (A3-101 by Trytec) was confirmed.

◎: Almost no interference color was observed.

○: I saw some interference colors, but there was no problem in practical use.

×: It is not suitable for display use because the interference color is clearly visible or the image becomes unclear.

(14) Take-up

When the film to be produced was taken up in a roll shape by a winder, the film condition during the winding and after winding was confirmed.

◎: The reel after winding and the film unwound from the reel have no wrinkles, and almost no occurrence of winding deviation or protrusion occurs.

○: When the film is taken out from the roll after winding, the wrinkles on the film are visually observed, but the same method as the above (13) visibility test is confirmed. When the visibility was recognized, wrinkles, streaks, and protrusions occurred during the winding were not observed.

X: Many wrinkles were observed on the reel after winding, and wrinkles, streaks, and protrusions were observed when the visibility was confirmed in the same manner as the above (13) visibility test. Further, winding deviation occurred during winding, and the end deviation in the width direction of the web film was 3 cm or more.

(15) L* (SCI) and L* (SCE)

A black acrylic varnish spray H62-8034 (manufactured by ROCK PAINT Co., Ltd.) was applied to black on one side of the polyester film for polarizer protection, and the adhesive sheet SK-1478 was passed on the opposite side of the surface. Corning (R) Gorilla (R) Glass (manufactured by Corning Incorporated) having a thickness of 0.5 cm and a thickness of 0.55 mm was laminated without being surrounded by bubbles to prepare a glass laminated sample. Furthermore, after being applied in black, the sample was once directed toward the fluorescent lamp to confirm opacity.

The glass surface of the prepared glass laminate sample was measured using CM-3600d manufactured by KONICA MINOLTA Co., Ltd. Under the condition of 8 mm target mask (CM-A106), the L value was measured by SCI method including specular reflection and SCE method for removing specular reflection, and the average value of n number 3 was obtained. Furthermore, the white calibration plate uses CM-A103, the zero correction box uses CM-A104, and the light source is D65.

(16) Uneven thickness of the resin layer (X)

The length of the polyester film for polarizer protection was 2 m every 10 cm in the longitudinal direction, and the spectral transmittance was measured, and the thickness of the resin layer was calculated from the obtained spectral characteristics, and the thickness unevenness was calculated. Spectroscopic transmittance was measured for a 5 cm square sample of a polyester film for polarizer protection using a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. 0.02 degree transmittance. The inner wall of the attached integrating sphere is barium sulfate, and the standard plate is alumina. The measurement wavelength was set to be 250 nm to 1200 nm, the interval was 5 nm (visible light)/10 nm (infrared light), the gain was set to 2, and the measurement was performed at a scan speed of 1 nm and a scan speed of 600 nm/min. For the determination of the thickness unevenness, the transmittance of the observation wavelength of 400 to 500 nm is varied in the longitudinal direction, and the following criteria are used.

Thickness unevenness of 20% or less: transmittance change is 5% or less

Uneven thickness 40~20%: change in transmittance is 5~10%

Uneven thickness 50~40%: change in transmittance is 20% or more

(17) Visibility test (interference fringe)

The visibility when the glass surface side of the glass laminated sample produced in the above (15) was placed under a F10 light source fluorescent lamp (diffused light) was confirmed. Furthermore, the fluorescent lamp used was in the form of FPL27EX-N, and the distance between the sample and the fluorescent lamp was 33 cm.

◎: There was almost no interference fringe.

○: Some interference fringes are visible, but there is no problem in practical use.

△: Interference fringes are visible, but practically applicable.

×: Interference fringes and coloring are clearly visible and are not suitable for display use.

[resin]

For the resin of the laminated film, the following are prepared.

<Resin A>

In 100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol In the mixture, 0.09 part by weight of magnesium acetate and 0.03 part by weight of antimony trioxide were added to the amount of dimethyl terephthalate, and the transesterification reaction was carried out by heating at a normal temperature. Then, in the transesterification reaction product, 0.020 parts by weight of an 85% phosphoric acid aqueous solution was added to the amount of dimethyl terephthalate, and then transferred to a polycondensation reaction layer. Further, while heating and heating, the reaction system was gradually depressurized, and a polycondensation reaction was carried out in accordance with a usual method under a reduced pressure of 1 mmHg at 290 ° C to obtain polyethylene terephthalate having an IV of 0.63.

On the other hand, as for the resin B, the following are prepared.

<Resin B-1>

IV = 0.74, polyethylene terephthalate copolymerized with (30 mol% cyclohexane dimethanol).

<Resin B-2>

IV = 0.55, polyethylene terephthalate copolymerized with (20 mol% spiroglycerol component, 30 mol% cyclohexanedicarboxylic acid component).

[Resin method of resin layer (X)]

The method of blending the resin layers used is as follows.

<Resin B-3>

IV = 0.6, and 15 wt% of Resin A was kneaded in polyethylene terephthalate copolymerized with (20 mol% of spiroglycerol component and 30 mol% of cyclohexanedicarboxylic acid component).

<Resin B-4>

IV = 0.7, polyethylene terephthalate copolymerized with (25 mol% isophthalic acid (IPA)).

<Resin layer O>

Resin solution (a): contains methyl methacrylate (62 mol%), ethyl acrylate (30 mol%), acrylic acid (2 mol%), N-methylol acrylamide (1 mol%) ), the ethylene oxide repeating unit is 16 polyethylene glycol monomethacrylate (3 mole %), acrylic acid 2-sulfonate ethyl ester (2 mole %) acrylic resin solution

Crosslinking agent (b): hydroxymethyl type melamine crosslinking agent

Particle (c): an aqueous dispersion of colloidal cerium oxide particles having a particle diameter of 80 nm.

Fluorine-based surfactant (d): such that the solid component weight ratio (a) / (b) / (c) / (d) = 30 parts by weight / 8 parts by weight / 2 parts by weight / 0.6 parts by weight mixing.

<Resin layer P>

Resin solution (e): 70 parts by weight of a water-soluble coating liquid of a polyester resin containing an acid component and a glycol component [wherein the acid component is terephthalic acid (88 mol%), 5-sulfonate-based benzene) Sodium diformate (12 mol%), glycol component (ethylene glycol (100 mol%)], and 30 parts by weight of an aqueous dispersion of a polyester resin containing an acid component and a glycol component [wherein the acid component It is terephthalic acid (50 mol%), isophthalic acid (49 mol%), sodium 5-sulfonate isophthalate (1 mol%), and the glycol component is ethylene glycol (55 mol) A solution of a mixture of %), neopentyl glycol (44 mol%), and polyethylene glycol (molecular weight: 4000) (1 mol%).

Crosslinking agent (b): hydroxymethyl type melamine crosslinking agent

Crosslinking agent (f): crosslinker containing oxazoline group

Particle (g): aqueous dispersion of colloidal cerium oxide particles having a particle diameter of 140 nm

Particle (h): aqueous dispersion of colloidal cerium oxide particles having a particle diameter of 300 nm

Fluorine surfactant (d):-

The solid content by weight ratio (e) / (b) / (f) / (g) / (h) / (d) = 47 parts by weight / 19 parts by weight / 4.9 parts by weight / 0.7 parts by weight / 0.1 weight Mix the way.

<Resin layer Q>

(b) to (h) used for the resin layer P as a solid content by weight ratio (e) / (b) / (f) / (g) / (h) / (d) = 47 parts by weight / 19 parts by weight / Mixed in a manner of 4.9 parts by weight / 5.0 parts by weight / 0.4 parts by weight.

<Resin layer R>

(b) to (h) used for the resin layer P as a solid content by weight ratio (e) / (b) / (f) / (g) / (h) / (d) = 47 parts by weight / 19 parts by weight / Mixed in a manner of 4.9 parts by weight / 1.1 parts by weight / 1.0 parts by weight.

<Resin layer S>

(b) to (h) used for the resin layer P as a solid content by weight ratio (e) / (b) / (f) / (g) / (h) / (d) = 47 parts by weight / 19 parts by weight / Mixed in a manner of 4.9 parts by weight / 1.1 parts by weight / 0.4 parts by weight.

<Resin layer T>

(b) to (h) used for the resin layer P as a solid content by weight ratio (e) / (b) / (f) / (g) / (h) / (d) = 47 parts by weight / 19 parts by weight / It was mixed in such a manner as to be 4.9 parts by weight / 7.0 parts by weight / 1.0 part by weight.

<Resin layer U>

(b) to (h) used for the resin layer P as a solid content by weight ratio (e) / (b) / (f) / (g) / (h) / (d) = 47 parts by weight / 19 parts by weight / It was mixed in the form of 2.5 parts by weight / 0.4 parts by weight / 0.1 parts by weight.

<Resin layer V>

For the resin layer O used for (a), (b), (d) and water-soluble resin P (g), (h) in terms of solid content by weight (a) / (b) / (g) / (h) / (d) = 25 parts by weight / 6 parts by weight / 0.3 parts by weight / 0.1 parts by weight / 0.3 Mix by weight.

(Example 1)

After the resin A was vacuum dried at 180 degrees for 3 hours, the resin B-1 was vacuum dried at 150 degrees for 3 hours, and then placed in two two-axis extruders and melt-kneaded at 280 degrees. Furthermore, the lower part of the hopper is flushed with nitrogen. Then, after passing through five leaf disk filters of FSS (Fiber Sintered Stereo) type, the discharge ratio was made of resin A/resin B-1=1.1/1 by a gear pump. In this manner, the measurement is simultaneously merged into a slit laminating device having a number of slits of 251, and a laminated body in which 251 layers are alternately laminated in the thickness direction is formed. The method of forming a laminate is carried out in accordance with the description of paragraphs [0053] to [0056] of JP-A-2007-307893. The length and interval of the gap are all fixed. The obtained laminate had a laminated structure in which 126 layers of a resin layer containing a resin A and 125 layers of a resin layer containing a resin B were laminated in the thickness direction. Further, the enlargement ratio inside the nozzle, that is, the length in the film width direction of the lip portion is divided by the value in the film width direction of the nozzle inlet portion, and is set to 2.5. The thus obtained laminated body containing a total of 251 layers was supplied to a multi-manifold die, and after molding in a sheet shape, static electricity of 8 kV was applied by a wire, and it was rapidly solidified on a casting drum having a surface temperature of 25 ° C. The obtained cast film was heated by a roller group set at 75 ° C, and rapidly heated from both sides of the film by an electric radiant heater in an extension of 100 mm in length, while extending 3.3 times in the longitudinal direction, and then cooled once. Next, on both sides of the uniaxially stretched film, corona discharge treatment was performed in the air, and the wetting tension of the base film was adjusted to 55 mN/m, respectively, using a metering rod (meter Bar) #4 is coated with a resin layer O on the surface of the film on one side perpendicular to the film thickness direction of the film, and a resin layer Q is applied on the surface of the film on the side opposite to the film surface.

The uniaxially stretched film was guided to a tenter, and after preheating at 105 ° C hot air, it was extended 4.3 times in the transverse direction at a temperature of 140 ° C. The stretched film was heat treated by hot air at 225 ° C in the tenter as it is, and then subjected to a relaxation treatment of 2% in the width direction at the same temperature, and further, after quenching to 100 ° C, 1% relaxation was performed in the width direction. After treatment, a wound laminated film is obtained. The obtained film showed physical properties as shown in Table 1, and was a film having low haze, good windability, and no interference color.

(Example 2)

Except that the layering apparatus used in Example 1 was changed to a device having a number of slits of 491, the resin B-2 was changed to the layer B, and the resin B-2 was dried under nitrogen at 100 ° C to carry out Example 1 gave a film in the same manner. The obtained film showed the physical properties as shown in Table 1, and even if the film thickness was 30 μm, it was a film having low haze, good windability, and no interference fringe.

(Example 3)

The same procedure as in Example 2 except that the resin layer (X)-2 in Example 2 was changed to the resin layer P, and the discharge ratio of the A layer and the B layer was changed to Resin A/resin B-2 = 1.0/2.0. The way to get the film. The obtained film showed physical properties as shown in Table 1, and was a film having low haze and no interference color. Although the film was weak in rigidity, it was excellent in the windability.

(Example 4)

In addition to changing the resin layer (X)-2 in Example 2 to the resin layer S A film was obtained in the same manner as in Example 2. The obtained film showed physical properties as shown in Table 1, and was a film having low haze and no interference color, and the windability was also good.

(Example 5)

A film was obtained in the same manner as in Example 1 except that the resin layer (X)-2 in Example 1 was changed to the resin layer R. The obtained film showed the physical properties as shown in Table 1. By forming the resin layer R, although the haze was slightly increased, the image sharpness was deteriorated, but it was still in the range of no problem, and it was a film having good windability.

(Example 6)

A film was obtained in the same manner as in Example 1 except that the resin layer (X)-2 in Example 1 was changed to the resin layer T. The obtained film showed the physical properties as shown in Table 1, and the resin layer T was formed to have a film having a good take-up property as compared with Example 1.

(Example 7)

In addition to changing the number of slitting devices used in the first embodiment to 201, the resin layer (X)-1 was changed to the resin layer P, and the resin layer (X)-2 was changed to the resin layer P to A film was obtained in the same manner as in Example 1. The obtained film showed physical properties as shown in Table 1. Compared with Example 1, although some interference fringes due to surface reflection were observed, there was no problem, and the film was excellent in low haze and windability.

(Example 8)

A film was obtained in the same manner as in Example 7 except that the thickness of the resin layer of the resin layer (X)-1 in Example 7 was changed to 200 nm. The obtained film showed the physical properties as shown in Table 2, by thickening the resin layer (X)-1 Although the degree of haze was somewhat higher than that of Example 7, it was a film which was excellent in the properties of the coiling property and the interference color.

(Example 9)

A film was obtained in the same manner as in Example 3 except that only the A layer was used in Example 3. The obtained film showed physical properties as shown in Table 2, and was a film having low haze and good windability.

(Comparative Example 1)

Except in Example 7, it was changed to: after preheating by a tenter at a hot air of 100 ° C, and then extending at a temperature of 120 ° C, the stretched film was placed in a tenter and heat-treated at a hot air of 230 ° C. Then, a film was obtained in the same manner as in Example 7 except that 5% relaxation treatment was carried out in the width direction with the same temperature and quenching. The obtained film has a hysteresis of up to 310 nm, and an interference color can be seen, which is not suitable for display use.

(Comparative Example 2)

A film was obtained in the same manner as in Example 2 except that the discharge ratio of the resin A to the resin B in Example 3 was changed to Resin A/Resin B-2 = 1.0/3.0. The obtained film has a low Young's modulus and a low rigidity, so that the filming property is poor. Moreover, uneven film thickness occurs during stretching, which is not suitable for display applications.

(Comparative Example 3)

A film was obtained in the same manner as in Example 7 except that the layer thickness of the resin layer (X)-2 in Example 7 was changed to 50 nm. The obtained film was found to have strong interference fringes, and the ΔR was as high as 9%, which was not suitable for display use.

(Comparative Example 4)

Except for Example 7, changed to: film length direction of 100 mm in length In the extension zone, the electric heating heater is rapidly heated from both sides of the film while extending 3.8 times in the longitudinal direction; and, after being preheated by a tenter at a hot air of 110 ° C, it is extended at a temperature of 140 ° C, and The stretched film was heat-treated in a tenter at a hot air of 230 ° C, and then subjected to a relaxation treatment of 5% in the width direction at the same temperature and quenched, and a film was obtained in the same manner as in Example 7. The obtained film had a Young's modulus of 4,102 MPa in the width direction of the film, and when laminated with 0.55 mm of Gorilla Glass, it warped in the glass and was not suitable for display use.

(Embodiment 10)

Except that the layering apparatus used in Example 1 was changed to a device using a slit number of 260, the resin B-3 was used for the resin B, and the thickness of the resin layer (X)-1 was changed to 50 nm, in addition to the examples. 1 A film was obtained in the same manner. The obtained film showed physical properties as shown in Table 2, and was a film having low haze, good windability, and no interference color.

(Example 11)

The resin layer (X)-1 was changed to the resin layer V, the resin layer (X)-1 was changed to the resin layer V, and the resin layer (X)-2 was changed to the resin layer P except that the resin B in the example 10 was changed to the resin B-1. The way to get the film. The obtained film showed physical properties as shown in Table 3. If the phase difference is slightly higher than that of the embodiment 10, the interference fringes and the interference color are not present, and the range is not problematic in terms of visibility when mounted on the display.

(Embodiment 12)

A film was obtained in the same manner as in Example 11 except that the layer B in Example 11 was changed to the resin B-3. The obtained film showed physical properties as shown in Table 3, and the L*(SCE) value was also low, and the take-up property was also good, and no A film that interferes with streaks and interference colors.

(Example 13)

A film was obtained in the same manner as in Example 11 except that the layer B in Example 11 was changed to the resin B-4. The obtained film showed physical properties as shown in Table 3, and was a film having low haze and good phase difference.

(Example 14)

In Example 12, a film was obtained in the same manner as in Example 12 except that the resin layer (X)-1 was changed to the resin layer O and the thickness of the resin layer O was changed to 50 nm. The obtained film showed physical properties as shown in Table 3. When compared with Example 12, some interference fringes were observed, but even if it was mounted on a display, there was no problem.

(Example 15)

A film was obtained in the same manner as in Example 10 except that the layering apparatus in Example 12 was changed to use 260 slits and the manifold was small. The thickness of each layer from the outermost layer of the obtained film to the layer A and the layer B of the fourth layer was 55 nm or less, and a film having no interference fringe and high total light transmittance was obtained as in the case of Example 12.

(Embodiment 16)

A film was obtained in the same manner as in Example 15 except that the lateral stretching method in Example 15 was changed to Onion stretching. The obtained film has a small phase difference and a very good visibility.

(Example 17)

A film was obtained in the same manner as in Example 16 except that the resin layer (X)-1 in Example 16 was changed to the resin layer O. The obtained film showed physical properties as shown in Table 3, and was a film having low haze and good windability.

(Embodiment 18)

A film was obtained in the same manner as in Example 16 except that the resin layer (X)-1 in Example 16 was changed to the resin layer V, and the resin layer (X)-2 was changed to the resin layer R. The obtained film was excellent in rollability and good in visibility.

(Embodiment 19)

A film was obtained in the same manner as in Example 7 except that the layering apparatus used in Example 7 was changed to a device using three slits, and the resin B-4 was used in the layer B. The obtained film was excellent in the coilability but slightly higher in haze, but the visibility when mounted on the display was in the range of no problem.

[Industrial availability]

It can be used as a polyester film for polarizer protection, which is a biaxially stretched polyester film, which does not exhibit interference color, has good windability, and is followed by an adhesive for bonding the polarizing film and the protective film. Good sex. Specifically, it can be suitably used as a polarizing plate, a circular polarizing plate, and a touch panel base film.

Claims (14)

A polyester film for protecting a polarizer, which is a laminated polyester film having a resin layer (X) containing a crosslinked material on both sides of a polyester film, wherein the polyester film has a hysteresis of 280 nm or less at a wavelength of 590 nm, and The Young's modulus in the longitudinal direction and the width direction of 25 ° C is 1000 MPa or more and less than 4000 MPa, respectively, and is characterized by the vibration shown by the following formula (1) in the vibration waveform derived from the spectral reflection curve of the laminated polyester film. The amplitude ΔR of the waveform was 8% or less, and the spectral reflection curve was measured at an incident angle by using a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. ΔR = (Rmax - Rmin) / 2 (%) Equation (1) (wherein the vibration waveform means the spectral reflectance curve obtained for the wavelength of 1 nm scale, The 20-point moving average processing is performed for each measurement point, and the 20-point moving average spectral reflectance curve is obtained, and the wavelength of the curve obtained by the difference between the 20-point moving average processing and the processed spectral reflectance curve is obtained. To the range of 700 nm; Rmax and Rmin are the maximum and minimum values of the vibration waveform, respectively). The polarizer of claim 1 protects the polyester film, wherein the laminated polyester film has a total light transmittance of 85% or more. The polyester film for protecting a polarizer according to claim 1 or 2, wherein the resin layer (X) has a refractive index of 1.45 or more and 1.60 or less. The polyester film for protecting a polarizer according to claim 1 or 2, wherein at least one of the resin layers (X) contains one or more kinds of particles having an average particle diameter of 50 nm or more and 1000 nm or less, which is thinner than one side perpendicular to the thickness direction of the film. The surface of the film and the surface of the film on the opposite side thereof have a static friction coefficient of 0.5 or more and 1.5 or less, and a dynamic friction coefficient of 0.3 or more and 1.0 or less. The polyester film for protecting a polarizer according to claim 1 or 2, wherein the haze value is 3.0% or less. The polyester film for protecting a polarizer according to claim 1 or 2, wherein the laminated polyester film has a reflection brightness L*(SCI) of 30 or less, and L*(SCE) satisfies the formula (2): L*(SCE) ≦L*(SCI)/10 (2) (wherein L*(SCI) and L*(SCE) represent glass for measuring a sample composed of a polyester film/black ink for glass/adhesive layer/polarizer protection The value on the face side). The polyester film for protecting a polarizer according to claim 1 or 2, wherein the retardation in the thickness direction is 1500 nm or less. The polyester film for protecting a polarizer according to claim 1 or 2, wherein the polyester film comprises at least 11 layers of a layer of the thermoplastic resin A (layer A) and a layer containing the thermoplastic resin B (layer B). a layered body. The polyester film for protecting a polarizer according to claim 8, wherein each of the layers A and B from the outermost layer to the fourth layer of the polyester film has a thickness of 55 nm or less. The polyester film for protecting a polarizer according to claim 1 or 2, wherein the resin layer (X) has a thickness unevenness of 50% or less. The polyester film for protecting a polarizer according to claim 1 or 2, wherein the resin layer (X) has a thickness of 20 nm or more and less than 5000 nm. The polyester film for protecting a polarizer according to claim 1 or 2, wherein the crosslinked material contains a melamine compound, an oxazoline compound, and carbonization. At least one or more kinds of carbodiimide compounds. The polyester film for protecting a polarizer according to claim 1 or 2, wherein at least one of the resin layers (X) comprises a water-soluble polyester resin, and the other comprises a water-soluble acrylic modified resin comprising a water-soluble acrylic acid modified product. The resin layer of the resin has a refractive index of 1.53 or less. A polarizing plate obtained by laminating a PVA film on a polyester film for protecting a polarizer according to any one of claims 1 to 13.