KR20160143648A - Polarizer-protecting polyester film, and polarization plate obtained using same - Google Patents

Abstract

An object of the present invention is to provide a biaxially stretched polyester film which does not show an interference color when arranged in a crossed Nicol state and does not show interference fringes due to the reflection of the surface of the film and the reflection of the back surface, And a polarizer-protective polyester film excellent in adhesiveness to an adhesive used for bonding a polarizing film and a protective film. [MEANS FOR SOLVING PROBLEMS] A polyester film having a retardation at a wavelength of 590 nm of 280 nm or less and a Young's modulus in a longitudinal direction and a width direction at 25 ° C of 1000 MPa or more and less than 4000 MPa, (X), wherein the amplitude? R of the vibration waveform derived from the spectral reflection curve of the laminated polyester film is 8% or less.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a polarizer-protective polyester film, and a polarizer using the polarizer. 2. Description of the Related Art Polarizer-

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

2. Description of the Related Art In recent years, demand for various optical films such as a polarizer protective film and a transparent conductive film has been increasing in the field of flat panel displays and touch panels. Among them, TAC (triacetylcellulose) film has been widely used because of its high transparency and optical isotropy for polarizer protective film applications. However, the TAC film is poor in moisture resistance and heat resistance, and poor in handleability. Further, there is a problem that it is difficult to make a thin film because it is formed by a solution casting method. Therefore, substitution with a biaxially stretched polyester film has been actively studied from the viewpoint of low cost, thinning, and heat and humidity resistance.

However, the biaxially stretched polyester film conventionally investigated has birefringence due to the orientation of the polymer at the time of stretching, and its main orientation axis does not exist in a certain direction in the film plane. Therefore, depending on the orientation design, There is a problem that the light interference color is generated when arranged in the Nicole state or that sufficient brightness can not be obtained depending on the angle of the main alignment axis and that the quality of the interference is reduced due to the reflection of the film surface and back surface there was. In addition, in a single polyester film, there is a problem that adhesiveness with an adhesive used for bonding a polarizing film and a protective film is poor. In order to solve these problems, a method of controlling the retardation has been proposed, but the degree of retardation is still not sufficient (for example, Patent Document 1). Further, a structure for forming an anchor layer in order to improve adhesion with an adhesive has been proposed, but no specific invention has been disclosed (Patent Documents 2 and 3).

Since the retardation is proportional to the film thickness, it can be controlled by thinning the film thickness to a few micrometers. The thinning of the film is caused by the warping of the glass in the lamination with the glass when the retardation is changed and the polarizing plate is used However, there is a problem in that handling and winding property are deteriorated.

Japanese Patent Laid-Open No. 11-85725 Japanese Patent Application Laid-Open No. 2013-200435 Japanese Patent Application Laid-Open No. 2013-210598

DISCLOSURE OF THE INVENTION In view of the problems of the prior art described above, it is an object of the present invention to provide a biaxially stretched polyester film which exhibits no interfering color when placed in a cross-Nicol state and exhibits no winding- And is excellent in adhesion to an adhesive used for bonding a polarizing film and a protective film. It is an object of the present invention to provide a polarizing film for protecting a polarizer.

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

(1) A polyester film having a retardation at a wavelength of 590 nm of 280 nm or less and a Young's modulus in a longitudinal direction and a transverse direction at 25 占 폚 of 1000 MPa or more and less than 4000 MPa, respectively, X), and the relative reflectance at an incident angle? = 10 degrees was measured using a spectrophotometer (U-4100 Spectrophotometer, manufactured by Hitachi, Ltd.) of the laminated polyester film Wherein the amplitude? R of the vibration waveform expressed by the formula (1) in the vibration waveform derived from one spectral reflection curve is 8% or less.

? R = (Rmax-Rmin) / 2 (%)  Equation (1)

(Note that the vibration waveform means a 20-point moving average spectral reflectance curve obtained by performing a 20-point moving average process on each measurement point with respect to a spectral reflectance curve obtained with a wavelength of 1 nm, Quot; refers to a range of a wavelength of a curve of 400 to 700 nm obtained by subtracting the difference of the spectral reflectance curve after that.

Rmax, and Rmin are the maximum value and the minimum value 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 polarizer protection according to (1) or (2), wherein the refractive index of the resin layer (X) is 1.45 or more and 1.60 or less.

(4) A method for producing a laminated film, which comprises at least one particle of an average particle diameter of 50 nm or more and 1000 nm or less on at least one side of the resin layer (X) and has one film surface perpendicular to the film thickness direction, The polyester film for polarizer protection according to any one of (1) to (3), which has a static friction coefficient of the film surface of 0.5 mu d or more and 1.5 mu d or less and a dynamic friction coefficient of 0.3 mu d or more and 1.0 mu d or less.

(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 laminated polyester film according to any one of (1) to (5), wherein the laminate polyester film has a reflection brightness L * (SCI) of 30 or less and L * (SCE) Polarizer protective polyester film.

L * (SCE)? L * (SCI) / 10 Equation (2)

(Where L * (SCI) and L * (SCE) are values obtained by measuring the glass surface side of a sample composed of a glass / adhesive layer / polarizer protective polyester film / black ink)

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

(8) The polyester film according to any one of (1) to (6), wherein the polyester film is a laminate in which at least eleven layers or more of a layer (A layer) containing thermoplastic resin A and a layer (7) The polarizer-protective polyester film described in any one of (1) to (7) above.

(9) The polyester film for polarizer protection according to (8), wherein the 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 polarizer-protective polyester film according to any one of (1) to (9), wherein the thickness unevenness of the resin layer (X) is 50% or less.

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

(12) The polyester film for polarizer protection according to any one of (1) to (11), wherein the crosslinking material contains at least one of a melamine compound, an oxazoline compound and a carbodiimide compound.

(13) The resin composition according to any one of (1) to (3), wherein at least one of the resin layer (X) contains a water-soluble polyester resin and the other contains a water- soluble acrylic- The polyester film for polarizer protection according to any one of (1) to (12).

(14) A polarizer comprising a PVA film laminated on the polarizer-protective polyester film according to any one of (1) to (13).

An object of the present invention is to provide a polarizer which exhibits good adhesion to an adhesive and does not exhibit an interference color when disposed in a crossed Nicol state and which exhibits good transparency without interference fringes due to film surface and back reflection effects, A protective polyester film is provided.

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

The polarizer-protective polyester film of the present invention has a retardation at a wavelength of 590 nm of 280 nm or less and a Young's modulus at 25 ° C in the longitudinal direction and in the transverse direction of 1,000 to 4,000 MPa, (X), wherein the amplitude? R of the vibration waveform represented by the formula (1) in the vibration waveform derived from the spectral reflection curve of the laminated polyester film is 8% or less do.

? R = (Rmax-Rmin) / 2 (%)     Equation (1)

The polyester used in the polyester film of the present invention is preferably a polyester obtained by polymerization from an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a monomer mainly composed of a diol. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, , 4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, and 4,4'-diphenyl sulfone dicarboxylic acid. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimeric acid, dodecanedioic acid, cyclohexanedicarboxylic acid and ester derivatives thereof. Among them, terephthalic acid and 2,6-naphthalene dicarboxylic acid are preferable. These acid components may be used alone, or two or more of them may be used together, and further, oxyacid such as hydroxybenzoic acid may be partially copolymerized.

Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, Cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, Bis (4-hydroxyethoxyphenyl) propane, isosorbate, spiroglycol and the like. Of these, ethylene glycol is preferably used. These diol components may be used alone or in combination of two or more.

Of the above polyesters, polyesters such as polyethylene terephthalate and its polymers, polyethylene naphthalate and its copolymers, polybutylene terephthalate and its copolymers, polybutylene naphthalate and its copolymers, polyhexamethylene terephthalate and its copolymers, Polyhexamethylene naphthalate and copolymers thereof and the like are preferably used. The resin may contain various additives such as antioxidants, antistatic agents, nucleating agents, inorganic particles, organic particles, a viscosity reducing agent, a heat stabilizer, a lubricant, an infrared absorbent, an ultraviolet absorber, And the like may be added.

The thickness of the polarizer-protective polyester film in the present invention is preferably 5 to 50 mu m. When the film thickness is less than 5 占 퐉, there is a problem that the film formation becomes difficult and the handling property is deteriorated. When the thickness is 50 m or more, the polarizing plate becomes thick, which is not suitable for reduction in cost and thickness. More preferably not less than 10 mu m and not more than 25 mu m. In this case, it is easy to suppress the retardation easily while handling and mounting are excellent.

The polyester film of the present invention needs to have a retardation value of 280 nm or less at a wavelength of 590 nm. More preferably 100 nm or less, and further preferably 50 nm or less. Generally, the retardation is calculated from the product of the film thickness and the maximum value of the refractive index difference in the two orthogonal directions in the film plane. In the laminated film, since the refractive index as a film can not be easily measured, the retardation value is calculated by an indirect method and made to be retardation. Specifically, the value measured in the KOBRA series of retardation measuring apparatus for measuring the retardation based on an optical method sold by Oji Paper Co., Ltd. is used. The sample was cut into 3.5 cm x 3.5 cm from the center in the film width direction and installed in the apparatus so that the film width direction was 0 deg. Defined by the present measuring apparatus. The retardation and the retardation at a wavelength of 590 nm And the orientation angle is measured. As the value of the retardation becomes smaller, it is preferable that the interference color when the polarizing plate is mounted on a liquid crystal display is difficult to be produced as a polarizer-protective polyester film. In addition, the lower the Rth, the thickness direction retardation, the lower the interference color is, and the better.

The polyester film of the present invention preferably has a Young's modulus in a longitudinal direction and a width direction of 1000 MPa or more and less than 4000 MPa in an atmosphere at 25 캜. More preferably from 2000 MPa to 3800 MPa. In this case, it is preferable that glass is not warped when laminated with glass in a manufacturing process for use as a polarizer protective film. When the Young's modulus is less than 1000 MPa, the strength of the film is too weak to handle, which is not preferable because it is difficult to wind the film at the time of film formation.

Here, the film longitudinal direction is a laminated film on a roll, and the winding direction of the roll is referred to as the film longitudinal direction, and the width direction of the roll corresponds to the film width direction. On the other hand, in the case of a cut sheet, retardation is measured at both ends in the direction perpendicular to the long side direction and the long side direction of the film, and the direction in which the difference from the center of the film is large is referred to as the film width direction in the present invention .

The polarizer-protective polyester film of the present invention needs to have a resin layer (X) containing a crosslinking agent on both sides of the polyester film. As the resin layer (X), a water-soluble polyester resin, a water-soluble acrylic resin, and an acrylic-modified polyester resin are preferable.

As the carboxylic acid component constituting the polyester resin, an aromatic, aliphatic or alicyclic dicarboxylic acid or a trivalent or higher polyvalent carboxylic acid can be used. Examples of the aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, 5-sodium sulfoisophthalic acid, 1,4-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, 6-naphthalene dicarboxylic acid, 1,2-bisphenoxyethane-p, p-dicarboxylic acid, phenylindanedicarboxylic acid, and ester-forming derivatives thereof.

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

When a coating solution containing a polyester resin as an aqueous resin is used, in order to improve the adhesiveness of the polyester resin or to facilitate the water-solubilization of the polyester resin, a compound containing a sulfonic acid group or a carboxylic acid It is preferable to copolymerize a compound containing a base.

Examples of the compound containing a sulfonic acid base include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, sulfo-p-xylylene glycol , 2-sulfo-1,4-bis (hydroxyethoxy) benzene, and alkali metal salts, alkaline earth metal salts and ammonium salts thereof, but are not limited thereto.

Examples of the compound containing a carboxylic acid base include trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, 4-methylcyclohexene-1,2,3-tricarboxylic acid, Acid, 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-pentanetetracarboxylic acid, 3,3 ', 4,4'-benzophenonetetracarboxylic acid, 5- ( Cyclohexene-1,2-dicarboxylic acid, 5- (2,5-dioxotetrahydrofurfuryl) -3-cyclohexene- 1,2-dicarboxylic acid, cyclopentanetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, ethylene glycol bistrimellitate , 2,2 ', 3,3'-diphenyltetracarboxylic acid, thiophene-2,3,4,5-tetracarboxylic acid, ethylenetetracarboxylic acid, or an alkali metal salt, an alkaline earth metal salt, Ammonium salts may be used, but are not limited thereto .

Examples of the diol component of the polyester resin include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, , 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 2,4-dimethyl- Diol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl- , 2,4-trimethyl-1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4- Methylene-1,3-cyclobutanediol, 4,4'-thiodiphenol, bisphenol A, 4,4'-methylenediphenol, 4,4 '- (2-norbornylidene) Dihydroxybiphenol, o-, m-, and p-dihydroxybenzene, 4,4'-isopropylidene phenol, 4,4'-isopropylidenibindiol, cyclopentane-1,2-diol , Cyclohexane-1,2-di And cyclohexane-1,4-diol, it may be used a bisphenol A or the like.

As the polyester resin used in the present invention, it is also possible to use a modified polyester copolymer, for example, a block copolymer or graft copolymer modified with acrylic, urethane, epoxy or the like.

As the acrylic resin component, alkyl methacrylate and / or alkyl acrylate is used, and specific examples thereof include methacrylic acid, methyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacryl Acrylic acid, methyl acrylate, isopropyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, n-hexyl acrylate, n- Hexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate and the like are preferably used. These may be used alone or in combination of two or more.

The polyester resin component constituting the acrylic-modified polyester resin is composed of a dicarboxylic acid component and a diol component having an ester bond in the main chain or side chain.

The crosslinking agent used in the present invention is not particularly limited as long as it is a compound capable of causing a crosslinking reaction. Examples of the crosslinking agent include methylol or alkylol urea type, melamine type, urethane type, acrylamide type, polyamide type, epoxy compound, isocyanate compound, oxazoline Based compounds, carbodiimide compounds, aziridine compounds, various silane coupling agents, and various titanate-based coupling agents.

The method of setting the resin layer (X) is not particularly limited, but an in-line coating method in which the composition is applied to a polyester film before crystal orientation is completed and crystal orientation is completed by stretching and heat treatment is suitably used in terms of cost and environment have. As a coating method, for example, a reverse coating method, a spray coating method, a bar coating method, a gravure coating method, a rod coating method, a die coating method and the like can be used. The thickness of the resin layer can be adjusted by the concentration or application amount of the coating.

In the polarizing-protective polyester film of the present invention, it is necessary that the amplitude? R of the vibration waveform expressed by the formula (1) in the vibration waveform derived from the spectral reflection curve is 8% or less.

? R = (Rmax-Rmin) / 2 (%)  Equation (1)

The vibration waveform derived from the spectral reflectance curve of the present invention is a curve showing the relationship between the wavelength and the amplitude R obtained by performing numerical processing on the spectral reflectance curve obtained at a wavelength interval of 1 nm by a known spectrophotometer.

The numerical processing refers to a process of calculating a spectral reflectance curve having a wavelength of 400 nm to 700 nm obtained by performing a 20 point moving average process on a spectral reflectance curve for each wavelength interval of 1 nm and subtracting the spectral reflectance curve after the 20 point moving average process from the original spectral reflectance curve Is the curve of the amplitude R per 1 nm of the range.

The moving average process here is to perform an operation of calculating an average of 20 consecutive points with respect to wavelength and reflectance by shifting every 1 nm of wavelength. The reason why the 20-point moving average process is adopted is that when the periodicity with respect to the wavelength of the short-period vibration waveform affecting the interference fringe, which is a problem of the present invention, is observed, it has been found that there is one cycle of at least 20 nm to be. This is because a curve that should be a circular shape of a spectral reflectance curve from which a vibration-free waveform, that is, a vibrating element is removed is obtained by averaging the one cycle. Since the spectral reflectance curve used in the present invention is data for every 1 nm, 20-point moving average processing is employed. A 10-point moving average process may be employed as long as it is wavelength data for every 2 nm.

When the amplitude? R of the vibration waveform at a wavelength of 400 to 700 nm is 8% or less, the light line spectrum of the light source which is the main light source side that produces the isosceles (tilt angle) And has an effect of weakening the contrast of contrast based on the interference fringes. , More preferably not more than 6%, still more preferably not more than 4%. In the case where the amplitude of the reflectance of the spectral reflectance curve occurs in a short period shorter than the wavelength of 1 nm, it is highly likely that the amplitude is dependent on the slit condition of the spectrophotometer used for measurement. Therefore, Is preferably measured at 5 nm or more and 8 nm or less. When the slit width is less than 5 nm, even in the air measurement in which the test subject is not provided, the amplitude of the reflectance has a short-period vibration waveform at a wavelength of less than 1 nm, which is confused with the vibration waveform of the laminated film. Further, when the slit width is 8 nm or more, a moving average effect is exerted, and the vibration waveform itself inherent to the object to be tested is lost, so that the characteristics of the object can not be accurately measured.

The polarizer-protective polyester film of the present invention preferably has a total light transmittance of 85% or more from the viewpoint of having high transparency. , More preferably not less than 87%, more preferably not less than 90%, and most preferably not less than 93%. When the transparency is high, it is preferable because the sharpness of the screen of the liquid crystal display device is increased.

In the polarizer-protective polyester film 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 not less than 1.45 and less than 1.58. The surface reflectance is lowered by laminating a resin having a low refractive index on the surface of the polyester film. As a result, the oscillation waveform? R of the spectral reflectance curve is lowered and interference fringes are less likely to be seen.

The polarizer-protective polyester film of the present invention is characterized in that at least one side of the resin film (X) contains one or more particles having a number average particle diameter of 50 nm or more and 1000 nm or less, , And the coefficient of static friction of the film surface located on the opposite side thereof is 0.5 mu d or more and 1.5 mu d or less, and the coefficient of dynamic friction is 0.3 mu d or more and 1.0 mu d or less.

The particles used in the present invention are not particularly limited, but may be inorganic particles such as colloidal silica, titanium oxide, aluminum oxide, zirconium oxide, calcium carbonate, carbon black and zeolite particles, acrylic particles, silicone particles, polyimide particles, Teflon Crosslinked polyester particles, crosslinked polystyrene particles, crosslinked polymer particles, and core shell particles, and any of these particles may be used, or a plurality of kinds may be used in combination. It is more preferable to use particles having a refractive index close to that of the resin layer (X). In this case, since the diffusion by the particles is minimized, transparency can be maintained.

The number average primary particle diameter of these particles is preferably in the range of 0.05 to 1.0 占 퐉. Here, the average primary particle diameter is an average of the particle diameters of primary particles defined as particles generated by the growth of a single crystal nucleus in JIS-H7008 (2002). The particle diameter of the primary particles (hereinafter referred to as the primary particle diameter) is an average value of the long diameter and the short diameter. With respect to the measurement of the average primary particle diameter, a sample was observed at a magnification of 50,000 times using a scanning electron microscope (SEM) according to JIS-H7804 (2005), and the diameter of each primary particle And the short diameter are measured, the primary particle diameter is determined by the average thereof, and the same primary particle diameter is measured for 100 primary particles, and the average primary particle diameter can be obtained from the number average value thereof. If the average primary particle diameter of the particles is less than 0.05 탆, the particles may agglomerate to aggravate the haze. On the other hand, if the average primary particle diameter exceeds 1.0 탆, the effect of easy addition or blocking resistance is not obtained as much as the addition amount, There is also a possibility that the particles may fall off depending on the thickness of the resin layer. The particles may be monodisperse particles or aggregated particles in which a plurality of particles are aggregated. In some cases, plural kinds of particles having different primary diameters may be used in combination. The addition amount of the particles is appropriately controlled and designed in accordance with the thickness of the resin layer (X), the resin composition, the average primary particle diameter, the required lubricity, and the application. In the present invention, in order to suppress interference fringes due to film surface and back reflection, it is preferable that the optical thickness of the resin layer (X) is set to? / 4. In the case of a film having an average thickness of about 50 nm for each layer of a layer (A layer) containing a thermoplastic resin A and a layer (B layer) containing a thermoplastic resin B with a total film thickness of about 12 μm, ) Is preferably in the range of 70 to 110 nm. Particles to be added to the resin layer (X) preferably use two-component particles having an average primary particle diameter of 200 to 400 nm and an average particle diameter of 100 to 200 nm, which are larger in average primary particle diameter than the resin layer thickness, from the viewpoints of film winding property and transparency Do.

It is also preferable that the coefficient of static friction between one film surface perpendicular to the film thickness direction and the film surface opposite to the film thickness direction is 0.5 mu d or more and 1.5 mu d or less and the coefficient of dynamic friction is 0.3 mu d or more and 1.0 mu d or less. More preferably, the static friction coefficient is not less than 0.5 mu d and not more than 1.2 mu d, and the dynamic friction coefficient is not less than 0.3 mu d and not more than 0.8 mu d. In this case, the slipperiness of the film becomes favorable, so that even when the film is wound in the film-forming step, the film is not wound.

The polarizer-protective polyester film of the present invention preferably has a haze value of 3.0% or less. , More preferably not more than 2%, further preferably not more than 1%. When the haze value is 3.0% or more, there is a problem that the transparency of the film is deteriorated and the sharpness is deteriorated when it is used as a polarizer-protective polyester film.

It is preferable from the viewpoint of appearance that the polarizer protective polyester film of the present invention has a reflection lightness L * (SCI) of 30 or less and L * (SCE) satisfies the formula (1).

L * (SCE)? L * (SCI) / 10 Equation (1)

(L * (SCI) and L * (SCE) represent numerical values obtained by measuring the glass surface of a sample composed of a glass / adhesive layer / polarizer protective polyester film / black ink close to the actual display configuration. The acrylic lacquer spray H62-8014 (manufactured by Rock Paint Co., Ltd.) was used in the present invention in order to fabricate a liquid crystal having a black screen with a minimum transmittance or reflectance when no voltage was applied )

Here, SCI and SCE refer to a measurement method of light intensity for reflected light. SCE (Regular Reflection Removal) is a method to measure color by removing regularly reflected light because there is a light trap on the detection side. SCI ) Method.

When L * (SCI) is more than 30, surface reflection is high, glare occurs, or interference fringes appear to be prominent, so that the original color of the image can not be obtained when it is actually mounted on a display. It is also preferable that L * (SCE) satisfies the formula (1). When the formula (1) is not satisfied, the diffuse reflection light becomes dominant compared with the regular reflection light, and the white reflection is felt in the case of naked eyes, which is not preferable in appearance.

In order to satisfy this requirement, the particles to be added to the resin layer (X) are preferably colloidal silica particles which are close to the refractive index of the resin layer, and the particle diameter is preferably less than four times the thickness of the resin layer (X). In order to achieve both slidability and transparency, it is preferable to add two or more kinds of additive particles different in particle diameter.

L * (SCI) and L * (SCE) are values measured by the following methods.

One side of the polarizer-protective polyester film was coated with black using an acrylic lacquer spray H62-8034 (manufactured by Rock Paint Co., Ltd.), and a pressure-sensitive adhesive sheet SK-1478 (manufactured by Soken Chemical & ) Was laminated so as to prevent air bubbles from entering into the glass laminate sample by Corning® Gorilla® Glass (manufactured by Corning Incorporated) having a thickness of 10 cm and a thickness of 0.55 mm. Further, after applying the black color, the sample is checked once with a fluorescent lamp to confirm that no light is transmitted.

The glass surface of the prepared glass laminate sample was subjected to the SCI method including the regularly reflected light under the condition of a target mask (CM-A106) having a measuring diameter of 8 mm using CM-3600d manufactured by Konica Minolta Co., L value is measured, and an average value of n number 3 is obtained. The white calibration plate is CM-A103, the zero calibration box is CM-A104, and the light source is D65.

The retardation in the thickness direction of the polarizer-protective polyester film of the present invention is preferably 1500 nm or less. More preferably, it is 1200 nm or less. The term "retardation in the thickness direction" as used herein means retardation at a viewing angle of 50 ° in the direction perpendicular to the surface of the polarizer-protective polyester film. When the retardation in the thickness direction is 1500 nm or less, it is preferable not to show iridescence even when the display is viewed from the oblique direction as well as from the front. Further, from the viewpoint that the interference color observed in the cross-Nicol state of the polarizer is nearly colorless, it is more preferable that it is not more than 600 nm. More preferably, it is 400 nm or less. Cross-Nicol refers to the case where the absorption axes of the polarizers are arranged in an orthogonal relationship, and when the light such as a backlight is illuminated on the lower side thereof, it is in a quenched state.

The polarizer-protective polyester film of the present invention is preferably a laminate in which at least eleven layers or more of a layer (A layer) containing thermoplastic resin A and a layer (B layer) containing thermoplastic resin B are alternately laminated.

As the thermoplastic resin A and the thermoplastic resin B, a polyester obtained by polymerization from an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a monomer mainly composed of a diol is preferable. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, , 4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, and 4,4'-diphenyl sulfone dicarboxylic acid. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimeric acid, dodecanedioic acid, cyclohexanedicarboxylic acid and ester derivatives thereof. Among them, terephthalic acid and 2,6-naphthalene dicarboxylic acid which exhibit a high refractive index are preferable. These acid components may be used alone, or two or more of them may be used together, and further, oxyacid such as hydroxybenzoic acid may be partially copolymerized.

Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, Cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, Bis (4-hydroxyethoxyphenyl) propane, isosorbate, spiroglycol and the like. Of these, ethylene glycol is preferably used. These diol components may be used alone or in combination of two or more.

Of the above polyesters, polyesters such as polyethylene terephthalate and its polymers, polyethylene naphthalate and its copolymers, polybutylene terephthalate and its copolymers, polybutylene naphthalate and its copolymers, polyhexamethylene terephthalate and its copolymers, Polyhexamethylene naphthalate and copolymers thereof and the like are preferably used.

The combination of the thermoplastic resin A and the thermoplastic resin B is important from the viewpoint of reducing the defective lamination in the step of forming the laminated structure. In the combination of resins having poor compatibility, it is difficult to form laminar flow in the polymer flow path in the step of forming a laminated structure, thereby causing poor lamination of flow marks and the like, and occurrence of lamination unevenness, The uniformity may be impaired. As the index of the combination of the resins, it is preferable to use a resin having a compatibility parameter δ close to that, and in particular, the difference in absolute value of the compatibility parameter δ is preferably 2 or less. More preferably, the difference in the absolute value of the compatibility parameter delta is 1 or less.

It is preferable that a resin containing a common basic skeleton is selected and used for the combination of these resins. The basic skeleton referred to herein is a repeating unit constituting the resin. For example, when one resin is polyethylene terephthalate, the ethylene terephthalate unit is a basic skeleton. In this case, as a resin having a common basic skeleton, a copolymer of an ethylene terephthalate unit and a repeating unit of another ester is a typical example. When a resin including a common basic skeleton is used, it is possible not only to suppress lamination defects such as flow marks, but also to make it difficult to cause problems such as peeling between layers after molding. The combination of polyethylene terephthalate for the A layer and a copolymer thereof for the B layer is most preferable in view of difficulty in occurrence of lamination failure. The copolymer thereof includes polyethylene terephthalate copolymerized with 5 to 40 mol% of cyclohexane dimethanol component, polyethylene terephthalate copolymerized with 5 to 40 mol% of cyclohexanedicarboxylic acid component and 5 to 40 mol% of spiroglycol component Is preferably used. From the viewpoint of making it difficult to cause lamination failure, it is preferable that the B layer is a mixture of polyethylene terephthalate and a copolymer thereof. This is because when the same resin as the A layer is added to the B layer, the affinity at the interface with the A layer increases.

It is also preferable that the thermoplastic resin B is a crystalline resin having a melting point lower than the melting point of the crystalline polyester by 20 占 폚 or more. In this case, the heat treatment is performed between the melting point of the thermoplastic resin B and the melting point of the crystalline polyester in the heat treatment step described later, so that the orientation of the thermoplastic resin B alone can be relaxed and retardation can be easily suppressed, Since the stiffness of the film is lowered by the relaxation, the film-forming residual stress generated when the film is laminated with the glass is low, and the warp of the glass is less likely to occur. Preferably, the difference in melting point is 40 DEG C or higher. In this case, since the range of the temperature in the heat treatment step is widened, promotion of the orientation relaxation of the thermoplastic resin B and control of the orientation of the crystalline polyester can be facilitated . It is also preferable that the thermoplastic resin B contains an amorphous resin. Compared with the crystalline resin, the amorphous resin is less likely to generate orientation when the biaxially oriented film is produced, so that an increase in retardation can be suppressed, and further it is easy to suppress retardation unevenness of the laminated film .

As an example of a combination of resins for satisfying the above conditions, it is preferable that the thermoplastic resin A comprises polyethylene terephthalate or polyethylene naphthalate and the thermoplastic resin B is a polyester comprising spiroglycol. The polyester comprising spiroglycol refers to a copolyester or homopolyester copolymerized with spiroglycol, or a polyester blended therewith. Polyesters containing spiroglycols are preferred because of the small glass transition temperature difference between polyethylene terephthalate and polyethylene naphthalate, because they are difficult to be stretched at the time of molding and are difficult to be delaminated. More preferably, the crystalline polyester is composed of polyethylene terephthalate or polyethylene naphthalate, and the thermoplastic resin B is a polyester comprising spiroglycol and cyclohexanedicarboxylic acid. If the polyester is composed of spiroglycol and cyclohexanedicarboxylic acid, crystallinity can be lowered, and retardation can be easily suppressed. Further, since the difference in the glass transition temperature between polyethylene terephthalate and polyethylene naphthalate is small and the adhesive property is excellent, it is hard to be stretched at the time of molding, and also the delamination between layers is difficult.

A laminate in which a layer (A layer) containing thermoplastic resin A and a layer (B layer) containing thermoplastic resin B are alternately laminated refers to a laminated structure in which layer A and layer B are regularly laminated in the thickness direction It is defined that a part exists. That is, it is preferable that the sequence of arrangement in the thickness direction of the A layer and the B layer in the film of the present invention is not in a random state, and with respect to the third layer other than the A layer and the B layer, And is not particularly limited. For example, in the case of having a C layer including an A layer, a B layer and a resin C, it is more preferable to laminate with a regular permutation such as A (BCA) n, A (BCBA) n and A (BABCBA) n . Herein, n is the number of repeating units. For example, when n = 3 in A (BCA) n, it means that the film is laminated with a permutation of ABCABCABCA in the thickness direction.

By alternately laminating the resins having different thermal properties in this way, it is possible to highly control the orientation state of each layer when manufacturing the biaxially oriented film, and further to suppress the retardation. When the number of layers to be laminated is 10 or less, influence on various physical properties such as film formability and mechanical properties becomes remarkable depending on the characteristics of the resin and the composition of the layer thickness of the resin in which the resins having different thermal properties are laminated, For example, it may be difficult to produce a biaxially stretched film, or a problem may occur when the film is combined with a polarizing plate. On the other hand, in the case of a film in which 11 or more layers are alternately laminated, it is possible to control each thermoplastic resin so as to be easily and homogeneously arranged in the thickness direction, thereby stabilizing film formability and mechanical properties. In addition, as the number of layers increases, the growth of orientation in each layer tends to be suppressed, and it becomes easy to control the retardation, and when the glass is laminated for use as a polarizer protective film by lowering the Young's modulus , So that warpage of the glass is less likely to occur. More preferably 100 layers or more, and even more preferably 200 layers or more. In addition, although there is no upper limit on the number of layers, as the number of layers increases, the effect of thinning due to an increase in production cost accompanied with the enlargement of the manufacturing apparatus and the thickening of the film thickness is lost. .

The thickness of each layer of the layer (A layer) including the thermoplastic resin A from the outermost surface to the fourth thermoplastic resin A and the layer (B layer) including the thermoplastic resin B of the polarizer-protective polyester film containing the laminate was 55 Nm or less. The term from the outermost layer to the forth layer means a layer structure of A / B / A / B or B / A / B / A, for example, and all layers preferably have a thickness of 55 nm or less. In this case, since the amplitude of the vibration waveform at a wavelength of 400 to 700 nm, which is a visible light region, becomes small, interference fringes become difficult to see and it is preferable. In addition, the total light transmittance is also increased by decreasing the amplitude, which is more preferable. More preferably, it is 45 nm or less. More preferably, it is 40 nm or less. On the other hand, if it exceeds 55 nm, it becomes possible to interfere with the light reflected at the interface of the resin layer, and the amplitude of the vibration waveform becomes large, and the interference fringe appears clearly. The layer thickness of the four layers from the outermost layer of the front and back surfaces can be made 55 nm or less by adjusting the flow rate of each slit in the laminating apparatus.

It is preferable that the thickness unevenness of the resin layer (X) of the present invention is 50% or less. , More preferably not more than 40%, further preferably not more than 30%. It is possible to prevent the particles from falling off from the resin layer and to obtain a uniform adhesion property by suppressing the thickness unevenness of the resin layer and applying it with a certain thickness. In addition, it is preferable because unevenness of surface reflection due to thickness irregularity of the resin layer can be suppressed, and fluctuation of the total light transmittance can be suppressed.

The thickness unevenness referred to herein was measured by a spectrophotometer (U-4100 Spectrophotometer, manufactured by Hitachi, Ltd.) at a distance of 10 cm in the longitudinal direction of the film, and the thickness of the resin layer was calculated from the spectral transmittance, Respectively.

In the polarizer-protective polyester film of the present invention, the thickness of the resin layer (X) is preferably from 20 nm to less than 5000 nm, more preferably from 20 to 2000 nm, and still more preferably from 40 to less than 500 nm. If the thickness of the resin layer (X) is too thin, there is a possibility that the adhesiveness with the adhesive material is poor and the additive particles are dropped off.

It is preferable that the crosslinking material contained in the resin layer (X) of the polarizer-protective polyester film of the present invention contains at least one of a melamine compound, an oxazoline compound and a carbodiimide compound. In this case, it is preferable because improvement in anti-wet heat adhesion is seen. The content of the melamine-based compound, oxazoline-based compound, or carbodiimide-based compound is not particularly limited, and two or more crosslinking materials may be contained.

The melamine-based crosslinking agent used in the present invention is not particularly limited, but it may be a melamine, a methylol melamine derivative obtained by condensing melamine and formaldehyde, a compound partially or fully etherified by reacting methylol melamine with a lower alcohol, Etc. may be used. As the melamine-based crosslinking agent, any of condensates containing monomers and dimers of dimer or higher may be used, or a mixture thereof may be used. As the lower alcohol used in the etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like can be used. As the functional group, an imino group, a methylol group, or an alkoxymethyl group such as a methoxymethyl group or a butoxymethyl group may be contained in one molecule, and examples thereof include an imino group type methylated melamine resin, a methylol group type melamine resin, a methylol group type methylated melamine resin, Type methylated melamine resin. Among them, a methylol melamine resin is most preferable. Further, in order to accelerate the thermosetting of the melamine crosslinking agent, for example, an acidic catalyst such as p-toluenesulfonic acid may be used.

The oxazoline 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. However, it may contain at least one oxazoline group-containing monomer, And an oxazoline group-containing copolymer obtained by copolymerizing monomers.

Examples of the monomer containing an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2- 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like can be used. It is possible. Among them, 2-isopropenyl-2-oxazoline is preferable because it is easily available industrially.

In the oxazoline crosslinking agent, at least one other monomer used for the monomer containing an oxazoline group is not particularly limited as long as it is a monomer copolymerizable with the monomer containing the oxazoline group, and examples thereof include methyl acrylate, methacrylate Acrylic acid esters or methacrylic acid esters such as methyl acrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate and 2-ethylhexyl methacrylate, Unsaturated carboxylic acids such as acrylic acid, itaconic acid and maleic acid, unsaturated nitriles such as acrylonitrile and methacrylonitrile, acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide and the like Unsaturated amides, vinyl esters such as vinyl acetate and vinyl propionate, vinyl ethers such as methyl vinyl ether and ethyl vinyl ether, , Alpha, beta -unsaturated monomers such as olefins such as ethylene and propylene, halogen-containing vinyl esters such as vinyl chloride, vinylidene chloride and vinyl fluoride, and alpha, beta -unsaturated aromatic monomers such as styrene and alpha -methylstyrene These may be used alone or in a mixture of two or more.

The carbodiimide crosslinking agent used in the present invention is a compound having a carbodiimide group as a functional group in the compound or a compound having one or more cyanoamide groups in the molecule in relation to tautomerism, It is not. Specific examples of such carbodiimide compounds include dicyclohexylmethanecarbodiimide, dicyclohexylcarbodiimide, tetramethylxsilylenecarbodiimide and urea-modified carbodiimide. These compounds may be used alone or in combination of two or more. The above mixture may also be used.

The polarizer-protected polyester film of the present invention is characterized in that at least one of the constituent resin layers (X) comprises a water-soluble polyester resin and the other comprises a water-soluble acrylic-modified resin, and the resin layer The refractive index is preferably 1.53 or less. In this case, the resin layer containing the water-soluble polyester resin has improved adhesion to PVA, and the other water-soluble acrylic-modified resin layer has a refractive index of 1.53 or less, thereby reducing the reflectance of the film surface and suppressing interference fringes . The refractive index of the resin layer containing the water-soluble acrylic-modified resin is more preferably 1.52 or less. In order to achieve the present refractive index, it is preferable that the water-soluble resin has a low polarization ratio.

Next, a preferred method for producing the laminated film of the present invention will be described below. Of course, the present invention is not limited to these examples.

First, a specific method for producing a general polyester film will be described. First, regarding the polyester resin A (corresponding to the resin A) and the polyester resin B (corresponding to the resin A) used in the biaxial oriented film used in the present invention, commercially available polyethylene terephthalate resin or polybutylene terephthalate A phthalate resin, or polycondensed by a known method. For example, in the case of a polyethylene terephthalate resin, polymerization can be carried out as follows. Magnesium acetate and antimony trioxide are added to a mixture of dimethyl terephthalate and ethylene glycol, the temperature is gradually raised, and finally the ester exchange reaction is carried out while distilling methanol at 220 占 폚. Subsequently, an 85% aqueous solution of phosphoric acid is added to the transesterification reaction product, and then the reaction mixture is transferred to a polycondensation reaction kettle. The reaction system is gradually depressurized while heating and heating in a polymerization kettle, and a polycondensation reaction is carried out at 290 占 폚 under a reduced pressure of 1 hPa to obtain a desired polyethylene terephthalate resin having an intrinsic viscosity. In the case of adding particles, it is preferable to add a slurry in which particles are dispersed in ethylene glycol to a polymerization reaction kettle so as to have a predetermined particle concentration to carry out polymerization.

The production of polybutylene terephthalate resin can be carried out, for example, as follows. The mixture of terephthalic acid and 1,4-butanediol is heated to 140 DEG C under a nitrogen atmosphere to obtain a homogeneous solution, and then the esterification reaction is carried out by adding tetra-n-butyl orthotitanate and monohydroxybutyltin oxide. Subsequently, tetra-n-butyl orthotitanate is added and a polycondensation reaction is carried out under reduced pressure to obtain a desired polybutylene terephthalate resin having an intrinsic viscosity.

A preferable method for producing the laminated polyester film of the present invention and the multilayer laminated polyester film laminated by 11 or more layers using the polyester resin thus obtained will be described in detail.

First, when the polyester resin to be used is mixed, the mixture is metered and mixed at a predetermined ratio. Subsequently, the substrate is dried in a nitrogen atmosphere, a vacuum atmosphere or the like at 150 DEG C for 5 hours, for example, so that the moisture content in the polyester resin is preferably 50 ppm or less. Thereafter, the mixture is supplied to an extruder and melt-extruded. In the case of melt extrusion using a vented twin-screw extruder, the step of drying the resin may be omitted. Subsequently, foreign matters are removed and the amount of extrusion is homogenized through a filter or a gear pump, and discharged from the T-die onto the cooling drum in a sheet form. In this case, for example, a method of applying an electric charge using a wire-shaped electrode or a tape-shaped electrode, a casting method in which a water film is provided between a casting drum and an extruded polymer sheet, a casting drum temperature, The glass transition point is -20 占 폚), or a method in which a plurality of these methods are combined, the sheet-like polymer is brought into close contact with the casting drum and cooled and solidified to obtain an unstretched film. Among these casting methods, when polyester is used, a method of applying an electric charge is preferably used from the viewpoints of productivity and planarity.

Subsequently, this unstretched film is stretched in the longitudinal direction, then stretched in the width direction, or stretched in the width direction, and then stretched in the longitudinal direction, or by a sequential biaxial stretching method in which the longitudinal direction, width direction Are stretched by a simultaneous biaxial stretching method or the like.

The stretching magnification in this stretching method is preferably 2.5 to 3.5 times, more preferably 2.8 to 3.5 times, particularly preferably 3 to 3.4 times in each direction. The stretching speed is preferably 1,000 to 200,000% / minute. The stretching temperature is preferably in the range of from the glass transition point to (glass transition point + 50 占 폚), more preferably 90 to 130 占 폚, still more preferably 100 to 120 占 폚 in the longitudinal direction, The temperature is preferably 90 to 110 占 폚. The stretching may be performed plural times in each direction.

In the laminated film of the present invention, it is preferable to set a difference in transverse stretching speed in order to suppress variations in retardation and orientation angle in the film width direction. Specifically, when the transverse stretching section is divided into two, It is preferable that the stretching amount of the film at the midpoint of the transverse stretching section (film width at the measuring point-film width before stretching) is 60% or more of the stretching amount at the end of the transverse stretching section. More preferably, it is 70% or more. By changing the stretching ratio in the transverse stretching section as described above, fluctuations in the retardation and the orientation angle in the film width direction can be suppressed, and further, a high-quality liquid crystal display device having no coloring and no reduction in luminance when mounted on a liquid crystal display It becomes possible to make a display.

Further, in the laminated film of the present invention, it is also preferable to change the temperature at the transverse stretching step by step. More specifically, when the transverse stretching section is divided into two, a difference of not less than 20 占 폚 is given to the atmospheric temperature in the first half and the second half of the stretching section from the midpoint of the transverse stretching section. Here, the atmospheric temperature means that there is a portion satisfying the above condition at a temperature of a part of the first half and a part of the second half of the transverse stretching section. Preferably 40 DEG C or more. By changing the stretching temperature in the transverse stretching section stepwise in this manner, variations in retardation and orientation angle in the film width direction can be suppressed, and furthermore, a high-quality Of the liquid crystal display.

It is preferable that the biaxially stretched film is subjected to heat treatment in order to impart planarity and dimensional stability. The heat treatment can be carried out by any conventionally known method such as in an oven and on a heated roll. This heat treatment is carried out at a temperature of not less than 120 캜 and not higher than the melting point of the polyester, but is preferably a heat treatment temperature of 200 to 240 캜. From the viewpoint of film transparency and dimensional stability, it is more preferable that the temperature is 210 to 235 占 폚. The heat treatment time can be arbitrarily set within a range that does not deteriorate the characteristic, and is preferably 1 to 60 seconds, and 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.

In order to improve the adhesion to the ink printing layer, the adhesive, and the vapor deposition layer before the transverse stretching step, at least one surface is subjected to corona discharge treatment so that the wet tension of the surface is 47 mN / m or more, Thereby forming the resin layer (X) of the present invention. For the formation, known coating means such as roll coater, gravure coater, micro gravure coater, bar coater, die coater, dip coater and the like can be used.

The case of simultaneous biaxial stretching will be described below. In the case of the simultaneous biaxial stretching, the obtained cast film was subjected to corona discharge treatment on one side of the film as in the case of the sequential biaxial stretching, thereby forming a water-soluble resin layer. Subsequently, the cast film is guided by a simultaneous biaxial tenter, and both ends of the film are held while being gripped by a clip, and are simultaneously and / or sequentially stretched in the longitudinal direction and the width direction. The simultaneous biaxial stretching machine includes a pantograph system, a screw system, a drive motor system, and a linear motor system. However, a drive motor system or a linear motor system capable of arbitrarily changing the stretching magnification and performing relaxation processing at an arbitrary position is preferable Do. The stretching magnification varies depending on the type of the resin, but is usually 6 to 50 times as an area multiplication factor, and when polyethylene terephthalate is used as any of the resins constituting the laminated film, the area ratio is preferably 8 to 30 times, Is used. Particularly, in the case of simultaneous biaxial stretching, it is preferable to make the stretching magnifications in the longitudinal direction and the transverse direction the same and to make the stretching speed almost equal in order to suppress the in-plane orientation difference. The stretching temperature is preferably from the glass transition temperature to the glass transition temperature + 120 占 폚 of the resin constituting the laminated film.

In order to impart planarity and dimensional stability to the biaxially stretched film in this way, it is preferable that the film is subsequently subjected to a heat treatment at a stretching temperature or higher and a melting point or lower in the tenter. In order to suppress the distribution of the main orientation axis in the width direction at the time of this heat treatment, it is preferable to relax the film in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone. After such heat treatment, the mixture is uniformly and slowly cooled, cooled to room temperature, and wound. If necessary, relaxation treatment may be performed in the longitudinal direction and / or the width direction at the time of the heat treatment to the gradual cooling. Immediately before and / or immediately after entering the heat treatment zone, relaxation is performed in the longitudinal direction at an instant.

A preferable method for producing the multi-layer laminated film having 11 or more layers can be easily realized by the same method as described in paragraphs [0053] to [0063] of Japanese Patent Application Laid-Open No. 2007-307893. The thermoplastic resin is prepared in the form of pellets or the like. The pellets, if necessary, are dried in hot air or under vacuum and then fed to a separate extruder. In the extruder, the resin melted by heating at a temperature higher than the melting point is made uniform in the amount of extrusion of the resin by a gear pump or the like, and foreign matters or denatured resin are removed through a filter or the like. These resins are molded into a desired shape on a die and then discharged. Then, the multilayered sheet discharged from the die is extruded onto a cooling body such as a casting drum, cooled and solidified to obtain a casting film. At this time, it is preferable to use an electrode such as a wire, a tape, a needle, or a knife to closely contact a cooling body such as a casting drum by an electrostatic force to quench and solidify it. It is also preferable to spray air from a slit, spot, or plane device to adhere to a cooling body such as a casting drum to rapidly quench or solidify it, or to adhere to a cooling body with a nip roll to quench and solidify.

Further, the thermoplastic resin used for the layer A and a plurality of resins of the thermoplastic resin B different therefrom are sent out from different flow paths by using two or more extruders, and are fed into the multi-layer lamination apparatus. As the multilayer lamination device, a multi-manifold die, a feed block, a static mixer or the like can be used. In order to efficiently obtain the constitution of the present invention, it is preferable to use a feed block having 11 or more fine slits. When such a feed block is used, since the apparatus does not become extremely large, foreign matters due to thermal degradation are few, and even when the number of layers is extremely large, high-precision lamination is possible. In addition, the stacking accuracy in the width direction is remarkably improved as compared with the conventional technique. Further, in this apparatus, since the thickness of each layer can be adjusted by the shape (length, width) of the slit, it is possible to achieve an arbitrary layer thickness.

The molten multi-layer laminate thus formed with the desired layer structure is led to a die to obtain a casting film as described above. The cast film thus obtained is likewise made into a desired film by sequential biaxial stretching or simultaneous biaxial stretching.

The laminated film thus obtained is bonded to PVA produced by orienting the PVA containing commercially available iodine and used as a polarizing plate.

Example

Methods for evaluating the physical properties used in the present invention are described.

[Evaluation method of physical properties]

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

(1) layer thickness, number of layers, layered structure

The layer composition was obtained by observing a transmission electron microscope (TEM) of a sample cut from a cross section using a microtome. That is, the cross section of the film was magnified at 40000 magnification under the condition of an accelerating voltage of 75 kV using a transmission electron microscope H-7100FA type (manufactured by Hitachi Seisakusho Co., Ltd.) The thickness was measured. In some cases, in order to obtain a high contrast, a known dyeing technique using RuO ₄ or OsO ₄ is used.

(2) Calculation method of layer thickness

The TEM photograph image of 40,000 times obtained in the above item (1) was acquired using CanonScanD123U at an image size of 720 dpi. The image is saved in the personal computer as a bitmap file (BMP) or a compressed image file (JPEG), and then this file is opened using the image processing software Image-Pro Plus ver.4 Image analysis was performed. In the image analysis processing, a low-pass filter was applied as necessary in the vertical seek profile mode. In addition, the low-pass filter was set at a maximum of 10 x 10. Next, the relationship between the position in the thickness direction and the average brightness of the region sandwiched between the two lines in the width direction was read as numerical data. Using table calculation software, position (nm) and brightness data were employed. The data obtained by periodically varying the brightness 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 intervals between adjacent ones are set as one layer thickness The layer thickness was calculated. This operation was performed for each photograph to calculate the layer thicknesses of all the layers.

In addition, the contact surface with the casting drum at the time of film formation was designated as the first layer, and the number of layers was specified as the second and third layers in the thickness direction. Here, the first layer means a melt-extruded layer and is different from a resin layer provided by coating or the like.

(3) Glass transition temperature (Tg) and melting point (Tm)

Using a differential scanning calorimeter (DSC), the melt-kneaded polyester chips cooled by cold water immediately after being discharged were heated from 25 占 폚 to 290 占 폚 at a rate of 5 占 폚 / min. -K-7122 (1987).

Device: "Robot DSC-RDC220" manufactured by Seiko Denshi Kogyo Co.,

 Data Interpretation "Disk Session SSC / 5200"

Sample mass: 5 mg

(4) Intrinsic viscosity (IV)

Was calculated from the solution viscosity measured at 25 占 폚 in orthochlorophenol. The solution viscosity was also measured using an Ostwald viscometer. The unit was expressed in [dl / g]. In addition, the number of n is 3, and the average value is adopted.

(5) Measurement of spectral reflectance

Relative reflectance at an incident angle? = 10 degrees was measured for a sample of 5 cm in each side of the laminated film using a spectrophotometer (U-4100 Spectrophotometer, manufactured by Hitachi, Ltd.). The inner wall of the integrating sphere is barium sulfate, and the standard plate is aluminum oxide. The measurement wavelength was set to 250 nm to 1200 nm, the slit was set to 5 nm (visible) / 10 nm (infrared), the gain was set to 2, and the scanning speed was measured at 1 nm to 600 nm / min. At the time of sample measurement, a black vinyl tape (registered trademark) manufactured by Nitto Denko Co., Ltd. was bonded on the back surface of the sample in order to eliminate interference due to reflection from the back surface of the sample. The switching wavelength of the detector for the visible light and the infrared light is 850 nm.

(6) Amplitude of the vibration waveform ΔR

A 20-point moving average process was performed with the data of the spectral reflectance curve (curve A) at 1 nm unit obtained by the measurement of the above expression (5) as the reflectance data with respect to the wavelength. Next, data obtained per 1 nm in the range of the obtained wavelength of 259.5 to 1190.5 nm was linearly interpolated and converted into data per 1 nm in the range of 260 to 1190 nm to obtain a 20-point moving average spectral reflectance curve (curve B) . At the wavelength range of 400 to 700 nm, the difference between the curves A and B (reflectance in curve A - reflectance in curve B) was taken to obtain a vibration waveform. The maximum value Rmax and the minimum value Rmin of the difference in reflectance from the vibration waveform were determined, and the value of DELTA R was calculated using the equation (1).

(7) The refractive index of the resin layer (X)

The film having a thickness of about 1 mm obtained by dry-solidifying or activating the resin to be used was measured according to JIS-K-7105 (1981) using an Abbe's refractometer manufactured by Atago Corporation. That is, birefringence in two directions orthogonal to each other was measured using a sodium lamp (Na-D line) as a light source and methylene iodide at 23 DEG C and a relative humidity of 65% .

(8) Retardation and thickness direction retardation

A phase difference measuring apparatus (KOBRA-21ADH) manufactured by Oji Chemical Co., Ltd. was used. The sample was cut into 3.5 cm x 3.5 cm from the center in the film width direction and installed in the apparatus so that the film width direction became 0 deg. Defined by the present measuring apparatus. The incident angle was set to 0 deg. In the slow axis mode The retardation at a wavelength of 590 nm was measured.

For retardation in the thickness direction, the retardation at a wavelength of 590 nm was measured at a setting of an incident angle of 50 degrees in a refractive index mode.

(9) Young's modulus

Was measured using an Instron type tensile tester according to the method specified in JIS-K7127 (1999). The measurement was performed under the following conditions.

Measuring apparatus: manufactured by Orientech Co., Ltd. Automatic film thickness measuring apparatus "Tensilon AMF / RTA-100"

Sample size: 10 mm width × 50 mm between test lengths

Tensile speed: 300 mm / min

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

(10) Static friction coefficient (μs), dynamic friction coefficient (μd)

(2) on the basis of the stress (resistance value) detected in the electric resistance strain meter after starting to slip under the condition of a slip speed of 150 mm / min and a load of 200 g with a slip tester according to ASTM-D-1894 . The static friction coefficient is a friction coefficient obtained from the resistance value immediately after slipping, and the dynamic friction coefficient is a resistance value in the stable region after slipping out.

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

(11) Hayes

Measurement was carried out according to JIS K 7105 using a direct-action type haze meter HGM-2DP (manufactured by Suga Shikibiki Seisakusho). The haze (%) was 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, and four kinds of PVA solutions having a solid content concentration of 5% were adjusted. The PVA used for the four types of PVA solutions is shown below.

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

PVAb: semi-fully saponified PVA (saponification degree: 91 to 94 mol%) "AL-06" (manufactured by NIPPON KOGYO KAGAKUCHOKU Co., Ltd.)

PVAc: acetyl group-modified PVA (saponification degree: 92 to 94 mol%) "Z-320" (manufactured by NIPPON KOGYO CHEMICALS CO., LTD.)

PVAd: partially saponified PVA (saponification degree: 78 to 82 mol%) "KL-06" (manufactured by NIPPON KOGYO KAGAKUCHOKU Co., Ltd.)

Subsequently, four types of PVA solutions were applied on the resin layer (X) -2 of the polyester film using a bar coater (Matsuo Sanboshi Co., Ltd., number 4: wet thickness: about 8 μm) And then dried at 100 DEG C for 1 minute by using a hot air oven " HIGH-TEMP-OVEN PHH-200 (manufactured by Espec Co., Ltd.) " In accordance with JIS 5600-5-6 (established in 1999), a 25-piece perforated line of 5 × 5 at a cut interval of 2 mm was placed in the obtained sample for evaluation of adhesion. Next, a cellulose tape (registered trademark) was rubbed with a finger firmly to the perforated line, so that the perforated line was visible with a Nichiban 18 mm cellotape (registered trademark) (product number: CT-118S). Cellotape (registered trademark) is momentarily removed at an angle of about 60 DEG with respect to the resin layer. Count the number of peels in the piece. The number of evaluations is 5, and the average value is obtained. The evaluation criteria are set as follows. The evaluation standards " A " and " B " are determined as good adhesion.

A: No more than 1 piece of stripping

B: No more than 3 pieces of strips

C: The number of pieces to be peeled is 4 pieces or more and 5 pieces or less

D: 6 pieces or more of pieces to be peeled off

(13) Visibility test (interference color)

The sample was cut into a size of 420 mm in the width direction and 310 mm in the longitudinal direction from the widthwise center portion of the film on one side of the polarizing plate having a polarization degree of 99.9% produced by adsorption / orientation of iodine in the PVA to prepare a test piece. The prepared test piece and a polarizing plate to which no film was attached were superimposed by the arrangement of Cross-Nicols, and visibility was confirmed when they were placed on an LED light source (Trialte A3-101).

⊚: Interference color is hardly seen.

○: Although the interference color is slightly visible, there is no problem in practical use.

X: The interference color is clearly seen or the image becomes unclear, which is not suitable for display use.

(14) Writability

The state of the film during winding and after winding was confirmed when the formed film was rolled up into rollers by a winder.

?: There is no wrinkle on the film wound from the roll after the winding and the roll, and the occurrence of the winding displacement or the bump is hardly seen.

A: When the film was taken out from the roll after winding, a wrinkle mark was visible to the naked eye. However, when the visibility was confirmed in the same manner as in the above-mentioned (13) visibility test, the wrinkles, streaks,

X: A lot of wrinkles were observed on the roll after being wound, and wrinkles, streaks, and nodules were seen when the visibility was confirmed in the same manner as in the above (13) visibility test. Further, winding displacement occurs during winding, and the end in the width direction of the roll film is displaced by 3 cm or more.

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

One side of the polarizer-protective polyester film was coated with black using an acrylic lacquer spray H62-8034 (manufactured by Rock Paint Co., Ltd.), and a pressure-sensitive adhesive sheet SK-1478 (manufactured by Soken Chemical & ) Was laminated so that bubbles would not enter the Corning® Gorilla® Glass (manufactured by Corning Incorporated) having a thickness of 10 cm and a thickness of 0.55 mm to prepare a glass laminate sample. Further, after applying the black color, the sample is checked once with a fluorescent lamp to confirm that no light is transmitted.

The glass surface of the prepared glass laminate sample was subjected to the SCI method including the regularly reflected light under the condition of a target mask (CM-A106) having a measuring diameter of 8 mm using CM-3600d manufactured by Konica Minolta Co., L value was measured, and an average value of n number 3 was obtained. The white calibration plate was CM-A103, the zero calibration box was CM-A104, and the light source was D65.

(16) Thickness variation of the resin layer (X)

Polarizer Protecting Polyester Film The spectral transmittance was measured at intervals of 10 cm in the longitudinal direction, and the thickness of the resin layer was calculated from the obtained spectral characteristics to calculate thickness irregularities. As for the spectral transmittance, the transmittance at an incident angle? = 0 degree was measured using a spectrophotometer (manufactured by Hitachi, Ltd., U-4100 Spectrophotometer) with respect to a sample of 5 cm square of the polarizer protective polyester film. The inner wall of the integrating sphere is barium sulfate, and the standard plate is aluminum oxide. The measurement wavelength was set to 250 nm to 1200 nm, the slit was set to 5 nm (visible) / 10 nm (infrared), the gain was set to 2, and the scanning speed was measured at 1 nm to 600 nm / min. In determining the thickness unevenness, the variation in the longitudinal direction of the transmittance at a wavelength of 400 to 500 nm was observed, and the following criteria were adopted.

Thickness variation less than 20%: Transmittance variation less than 5%

Thickness unevenness 40 to 20%: variation in transmittance is 5 to 10%

Thickness unevenness 50 to 40%: variation of transmittance is not less than 20%

(17) Visibility test (interference stripes)

The visibility when the glass surface side of the glass laminate sample prepared in (15) above was placed under an F10 light source fluorescent lamp (diffusion light) was confirmed. The fluorescent lamp used was model: FPL27EX-N, and the distance between the sample and the fluorescent lamp was 33 cm.

◎: Interference stripes are hardly visible.

○: Although interference fringes are slightly visible, there is no problem in practical use.

△: Appearance of interference stripes, but practical application range.

X: Interference streaks and coloring are clearly visible and not suitable for display applications.

[Suzy]

The following resins were prepared as the resin of the laminated film.

<Resin A>

0.09 part by weight of magnesium acetate and 0.03 part by weight of antimony trioxide are added to a mixture of 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, and the temperature is elevated by heating in the usual manner to effect transesterification. Subsequently, 0.020 part by weight of a 85% aqueous solution of phosphoric acid is added to the transesterification reaction product to the amount of dimethyl terephthalate, and the transition to the polycondensation reaction layer is carried out. The reaction system was gradually depressurized while heating and heating, and polycondensation reaction was carried out at 290 占 폚 under a reduced pressure of 1 mmHg by a conventional method to obtain polyethylene terephthalate with IV = 0.63.

On the other hand, the resin B was prepared as follows.

<Resin B-1>

IV = 0.74 (30 mol% of cyclohexanedimethanol) was copolymerized with polyethylene terephthalate.

<Resin B-2>

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

[Combination method of resin layer (X)] [

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

<Resin B-3>

A resin A compounded with 15 wt% of polyethylene terephthalate copolymerized with IV = 0.6 (20 mol% of spiroglycol component and 30 mol% of cyclohexanedicarboxylic acid component).

<Resin B-4>

Polyethylene terephthalate copolymerized with IV = 0.7 (25 mol% of isophthalic acid (IPA)).

<Resin Layer O>

Resin solution (a): methyl methacrylate (62mol%), ethyl acrylate (30mol%), acrylic acid (2mol%), N-methylol acrylamide (1mol%), polyethylene glycol having an ethylene oxide repeating unit of 16 An acrylic resin solution containing monomethacrylate (3 mol%) and 2-sulfoethyl acrylate (2 mol%)

Crosslinking agent (b): methylol group type melamine crosslinking agent

Particle (c): An aqueous dispersion of colloidal silica particles having a particle diameter of 80 nm.

Fluorine Surfactant (d):

(A) / (b) / (c) / (d) = 30 parts by weight / 8 parts by weight / 2 parts by weight / 0.6 parts by weight in terms of solid content.

<Resin Layer P>

Resin solution (e): Water solubility of a polyester resin containing an acid component of terephthalic acid (88 mol%), 5-sodium sulfoisophthalic acid (12 mol%) and ethylene glycol (100 mol% 70 mol% of terephthalic acid (50 mol%), isophthalic acid (49 mol%), 5 mol of sodium sulfoisophthalic acid (1 mol%), ethylene glycol (55 mol%) of diol component and neopentyl glycol %), Polyethylene glycol (molecular weight: 4000) (1 mol%) and 30 parts by weight of an aqueous dispersion of a polyester resin containing a diol component.

Crosslinking agent (b): methylol group type melamine crosslinking agent

Crosslinking agent (f): An oxazoline group-containing crosslinking agent

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

Particles (h): An aqueous dispersion of colloidal silica particles having a particle diameter of 300 nm

Fluorine surfactant (d): -

These were mixed in a weight ratio of (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 part by weight.

<Resin Layer Q>

(B) to (h) used in the resin layer P were changed to 47 parts by weight / 19 parts by weight / 4.9 weight parts (e) / (b) / (f) / 5.0 parts by weight / 0.4 parts by weight.

<Resin Layer R>

(B) to (h) used in the resin layer P were changed to 47 parts by weight / 19 parts by weight / 4.9 weight parts (e) / (b) / (f) / 1.1 parts by weight / 1.0 part by weight.

<Resin Layer S>

(B) to (h) used in the resin layer P were changed to 47 parts by weight / 19 parts by weight / 4.9 weight parts (e) / (b) / (f) / 1.1 parts by weight / 0.4 parts by weight.

<Resin layer T>

(B) to (h) used in the resin layer P were changed to 47 parts by weight / 19 parts by weight / 4.9 weight parts (e) / (b) / (f) / Part / 7.0 parts by weight / 1.0 part by weight.

<Resin Layer U>

(B) to (h) used in the resin layer P were changed to 47 parts by weight / 19 parts by weight / 2.5 weight parts (e) / (b) / (f) / 0.4 parts by weight / 0.1 part by weight.

<Resin Layer V>

(A), (b), (g), (h) and (d) used in the resin layer O and the components (g) and (h) used in the water- d) = 25 parts by weight / 6 parts by weight / 0.3 parts by weight / 0.1 parts by weight / 0.3 parts by weight.

(Example 1)

Resin A was vacuum dried at 180 deg. C for 3 hours, and resin B-1 was vacuum dried at 150 deg. C for 3 hours. Then, each resin was put into two twin-screw extruders and melted at 280 degrees and kneaded. The lower portion of the hopper was subjected to nitrogen purge. Subsequently, five leaf disc filters of the FSS (Fiber Sintered Stereo) type were interposed and weighed so as to have a discharge ratio of resin A / resin B-1 = 1.1 / 1 with a gear pump, And 251 layers were alternately laminated in the thickness direction. A method of forming a laminate was carried out according to the description in paragraphs [0053] to [0056] of Japanese Patent Application Laid-Open No. 2007-307893. In this case, the lengths and intervals of the slits were made constant. The resultant laminate had a laminate structure in which the resin layer containing the resin A had 126 layers and the resin layer including the resin B had 125 layers and alternately laminated in the thickness direction. The value obtained by dividing the length in the film width direction of the perimeter lips, which is the width expansion ratio in the interior of the housing, by the length in the film width direction at the inlet opening of the housing was 2.5. The thus obtained laminate of 251 layers in total was supplied to a multi-manifold die, molded into a sheet, and quenched and solidified on a casting drum maintained at a surface temperature of 25 占 폚 by electrostatic charging of 8 kV with a wire. The obtained cast film was heated in a roll set at 75 占 폚 and stretched 3.3 times in the longitudinal direction while being rapidly heated from both sides of the film by a radial heater at a stretching section length of 100 mm and then cooled . Subsequently, corona discharge treatment was performed on both surfaces of the uniaxially stretched film in the air to adjust the wet tension of the base film to 55 mN / m, and the surface of one film perpendicular to the film thickness direction of the film was coated with a resin layer O , And the resin layer Q was applied to the surface of the film located on the opposite side of the film surface using Meta-Bar # 4.

The uniaxially stretched film was led into a tenter, preheated by hot air at 105 占 폚, and stretched 4.3 times in the transverse direction at a temperature of 140 占 폚. The stretched film was subjected to a heat treatment in a tenter by hot air at 225 캜, followed by 2% relaxation treatment in the width direction at the same temperature, followed by quenching to 100 캜, followed by 1% relaxation treatment in the width direction , And then a rolled laminated film was obtained. The obtained film exhibited the physical properties as shown in Table 1, and was a film having low haze, good windability, and no interference color.

(Example 2)

In Example 1, an apparatus having a slit count of 491 was used as the lamination apparatus to be used, and resin B-2 was used as the B-layer. Resin B-2 was dried under nitrogen at 100 ° C. A film was obtained in the same manner as in Example 1 except for these. The obtained film exhibited physical properties as shown in Table 1, and even if the film thickness was 30 占 퐉, the film had low haze, good winding property, and no interference streaks.

(Example 3)

A film was obtained in the same manner as in Example 2 except that the resin layer (P) -2 was used as the resin layer P and the discharge ratio between the A layer and the B layer was set to 1.0 (resin A / resin B-2) . The obtained film exhibited the physical properties as shown in Table 1, and the film had low haze and no interference color, and the film had good windability in spite of its low viscosity.

(Example 4)

A film was obtained in the same manner as in Example 2 except that the resin layer (S) -2 was used as the resin layer (X) -2 in Example 2. The obtained film exhibited the physical properties as shown in Table 1, and the film had low haze and no interference color, and was good in winding property.

(Example 5)

A film was obtained in the same manner as in Example 1 except that the resin layer (R) was used as the resin layer (X) -2 in Example 1. The obtained film exhibited the physical properties shown in Table 1, and the haze was somewhat increased in the resin layer R, and although the clarity was poor, there was no problem and the film was excellent in winding property.

(Example 6)

A film was obtained in the same manner as in Example 1 except that the resin layer (T) was used instead of the resin layer (X) -2 in Example 1. The obtained film exhibited the physical properties as shown in Table 1, and the film made of the resin layer T had a better winding property as compared with Example 1.

(Example 7)

Example 1 was repeated except that the resin layer (P) and the resin layer (X) -2 were used as the resin layer (P) in the lamination apparatus used in Example 1, Similarly, a film was obtained. The obtained film exhibited the physical properties as shown in Table 1, and although a little in comparison with Example 1, interference fringes due to surface reflection were visible, but there was no problem, and the film was low in haze and excellent in winding property.

(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 was changed to 200 nm. The resultant film exhibits physical properties as shown in Table 1. The thickness of the resin layer (X) -1 is thicker than that of Example 7, and although the haze value is slightly high, there is no problem, The interference color was also good.

(Example 9)

A film was obtained in the same manner as in Example 3 except that only the layer A was used. The obtained film exhibited the physical properties as shown in Table 1, and became a film with low haze and good winding property.

(Comparative Example 1)

In Example 7, stretching was carried out at a temperature of 120 캜 after leaving the remaining heat in hot air at 100 캜 in a tenter. A film was obtained in the same manner as in Example 7 except that the stretched film was subjected to heat treatment in a tenter at 230 占 폚 with hot air, followed by quenching by 5% relaxation treatment in the width direction at the same temperature. The resulting film had a high retardation of 310 nm and an interference color, which was not suitable for display purposes.

(Comparative Example 2)

A film was obtained in the same manner as in Example 2 except that the discharge ratio of Resin A and Resin B in Example 3 was changed to Resin A / Resin B-2 = 1.0 / 3.0. The resulting film had poor Young's modulus and poor viscoelasticity and thus had a poor winding property. In addition, film thickness unevenness occurred at the time of stretching, which was not suitable for display use.

(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 was changed to 50 nm in Example 7. The resulting film showed strong interference fringes and a high ΔR of 9%, which was not suitable for display applications.

(Comparative Example 4)

In Example 7, stretching was performed at a stretching ratio of 3.8 times in the machine direction, while the film was rapidly heated from both sides of the film by a radia- tion heater within a stretching section length of 100 mm in the longitudinal direction of the film. Further, in the tenter, after being heated by hot air at 110 캜, stretched at a temperature of 140 캜. A film was obtained in the same manner as in Example 7 except that the stretched film was subjected to heat treatment in a tenter at 230 占 폚 with hot air, followed by quenching by 5% relaxation treatment in the width direction at the same temperature. The resultant film had a high Young's modulus in the film width direction of 4102 MPa and was laminated with a gorilla glass having a thickness of 0.55 mm, which resulted in warping of the glass and was not suitable for display applications.

(Example 10)

In Example 1, a device having 260 slits was used as the lamination apparatus to be used, and resin B-3 was used as resin B. A film was obtained in the same manner as in Example 1 except that the thickness of the resin layer (X) -1 was 50 nm. The obtained film exhibited the physical properties shown in Table 1, and was a film having low haze, good winding property, and no interference color.

(Example 11)

(X) -1 was changed to resin layer V and the resin layer (X) -2 was changed to resin layer P in Example 10, the resin B was changed to resin B-1 and the resin layer A film was obtained. The obtained film shows physical properties as shown in Table 1. Though the phase difference was slightly higher than that in Example 10, interference fringes and interference colors were not seen, and there was no problem in visibility when mounted on a display.

(Example 12)

A film was obtained in the same manner as in Example 11 except that the resin B-3 was used as the resin B in Example 11. The film thus obtained exhibited physical properties as shown in Table 1, had a low L * (SCE) value, was also good in winding property, and had no interference stripes or interference colors.

(Example 13)

A film was obtained in the same manner as in Example 11, except that the resin B-4 was used as the resin B in Example 11. The obtained film exhibited the physical properties shown in Table 1, and became a film with low haze and good phase difference.

(Example 14)

A film was obtained in the same manner as in Example 12 except that the resin layer (X) -1 was used as the resin layer O and the thickness of the resin layer O was set to 50 nm. The obtained film exhibited the physical properties as shown in Table 1, and although slightly interference fringes were seen as compared with Example 12, there was no problem even when mounted on a display.

(Example 15)

In Example 12, a film was obtained in the same manner as in Example 10, except that the lamination apparatus was used with 260 slits and a small manifold. The thicknesses of the respective layers of the A layer and the B layer from the outermost layer to the fourth layer of the obtained film were 55 nm or less. As in Example 12, no interference fringes were observed, and the film had a high total light transmittance.

(Example 16)

A film was obtained in the same manner as in Example 15 except that the transverse stretching method was an onion stretching. The resulting film had a small retardation, and was very visibly good.

(Example 17)

A film was obtained in the same manner as in Example 16 except that the resin layer (X) -1 was used as the resin layer O in Example 16. The obtained film exhibited the physical properties as shown in Table 1, and became a film with low haze and good winding property.

(Example 18)

A film was obtained in the same manner as in Example 16 except that the resin layer (X) -1 was used as the resin layer V and the resin layer (X) -2 was used as the resin layer R in Example 16. The resulting film had good windability and good visibility.

(Example 19)

A film was obtained in the same manner as in Example 7 except that the lamination device used in Example 7 was a device having three slits and the resin B-4 was used in the B-layer. The obtained film had a high degree of haze although it had a good winding property, but was in a range in which there was no problem in visibility when mounted on a display.

It can be used as a polarizer protective polyester film which is a biaxially stretched polyester film and does not show an interference color and has good winding property and good adhesion to an adhesive used for bonding a polarizing film and a protective film. Specifically, it can be applied to a polarizing plate, a circular polarizing plate, and a touch panel base film.

Claims (14)

A resin layer X containing a cross-linking agent was coated on both sides of a polyester film having a retardation of 590 nm and a Young's modulus of 280 nm or less at a wavelength of 590 nm and a Young's modulus in a longitudinal direction and a transverse direction at 25 ° C of 1000 MPa or more and 4000 MPa or less, (U-4100 Spectrophotometer) manufactured by Hitachi Seisakusho Co., Ltd. was used to measure the relative reflectance of the laminated polyester film at the incident angle of 10 = Wherein the amplitude? R of the vibration waveform expressed by the formula (1) in the vibration waveform derived from the curve is 8% or less.
DELTA R = (Rmax-Rmin) / 2 (%) (1)
(Note that the vibration waveform means a 20-point moving average spectral reflectance curve obtained by performing a 20-point moving average process on each measurement point with respect to a spectral reflectance curve obtained with a wavelength of 1 nm, Quot; refers to a range of a wavelength of a curve of 400 to 700 nm obtained by subtracting the difference of the spectral reflectance curve after that.
Rmax, and Rmin are the maximum value and the minimum value of the vibration waveform, respectively) The polarizer-protected polyester film according to claim 1, wherein the laminated polyester film has a total light transmittance of 85% or more. The polarizing plate according to claim 1 or 2, wherein the refractive index of the resin layer (X) is 1.45 or more and 1.60 or less. The image forming apparatus according to any one of claims 1 to 3, wherein at least one of the resin layers (X) contains one or more particles having an average particle diameter of 50 nm or more and 1000 nm or less, Wherein the coefficient of static friction between the film surface and the film surface located on the opposite side of the film surface is not less than 0.5 mu d and not more than 1.5 mu d and the coefficient of dynamic friction is not less than 0.3 mu d and not more than 1.0 mu d. The polarizing plate protective polyester film according to any one of claims 1 to 4, wherein the haze value is 3.0% or less. The polarizing plate according to any one of claims 1 to 5, wherein the laminated polyester film has a reflectance L * (SCI) of 30 or less and L * (SCE) satisfies the formula (2) Protective polyester film.
L * (SCE)? L * (SCI) / 10 (2)
(Where L * (SCI) and L * (SCE) are values obtained by measuring the glass surface side of a sample composed of a glass / adhesive layer / polarizer protective polyester film / black ink) 7. The polarizer-protective polyester film according to any one of claims 1 to 6, wherein the retardation in the thickness direction is 1500 nm or less. The polyester film according to any one of claims 1 to 7, wherein at least eleven layers or more of a layer (A layer) containing a thermoplastic resin A and a layer (B layer) containing a thermoplastic resin B are alternately laminated Wherein the polarizing plate is a laminate comprising a polarizing plate and a polarizing plate. The polarizer protecting polyester film according to claim 8, wherein each layer thickness 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. The polarizing plate according to any one of claims 1 to 9, wherein the thickness unevenness of the resin layer (X) is 50% or less. 11. The polarizing film protection polyester film according to any one of claims 1 to 10, wherein the resin layer (X) has a thickness of 20 nm or more and less than 5000 nm. The polarizing plate according to any one of claims 1 to 11, wherein the crosslinking material contains at least one of a melamine compound, an oxazoline compound and a carbodiimide compound. 13. The resin composition according to any one of claims 1 to 12, wherein at least one of the resin layers (X) comprises a water-soluble polyester resin and the other contains a water-soluble acrylic-modified resin, Wherein the refractive index of the layer is 1.53 or less. A polarizing plate comprising a PVA film laminated on the polarizer-protective polyester film according to any one of claims 1 to 13.