JP2015232121A - Polyester film for optical use, and polarizing plate and transparent conductive film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film that shows no interference colors when mounted on a display device such as a liquid crystal display and that has excellent dimensional stability and whitening resistance when heated.SOLUTION: The polyester film for an optical use has a polyester-A layer in which a dicarboxylic acid component includes 50 mol% or more and less than 95 mol% of a terephthalic acid component and 5 mol% or more and less than 50 mol% of other dicarboxylic acid components. When a given direction within the film plane is defined as a direction X and a direction orthogonal to the direction X is defined as a direction Y, the film shows a peak temperature of a loss tangent (tanδ) of 60°C or higher and 115°C or lower measured by use of a dynamic viscoelasticity measurement device in the direction X and the direction Y.

Description

  The present invention relates to a polyester film that is particularly suitable for optical use (polarizer protection, transparent conductive film, etc.), and does not exhibit an interference color when mounted on a display device such as a liquid crystal display. The present invention relates to a polyester film having excellent dimensional stability and whitening resistance.

  Thermoplastic resin films, especially biaxially oriented polyester films, have excellent properties such as mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance. It is widely used as a substrate film in the above applications. In recent years, in particular, in the flat panel display and touch panel fields, demand for various optical films such as a polarizer protective film and a transparent conductive film has been increasing. Replacement of a TAC (triacetyl cellulose) film with a biaxially oriented polyester film has been studied. Since biaxially oriented polyester films cause interference color when assembled as a liquid crystal display due to the orientation of the polymer during stretching, studies to make the molecular orientation a specific range to suppress interference color (For example, patent document 1), examination (for example, patent document 2) etc. which make in-plane retardation, a plane orientation degree, etc. into a specific range are performed.

  In both Patent Documents 1 and 2, the interference color when the display is viewed from the front is suppressed, but because the retardation in the thickness direction is high, the interference color suppression when viewed from the oblique direction is insufficient.

  Therefore, in order to suppress the interference color when viewing the display from an oblique direction, there are examples of attempts to increase the copolymerization ratio of the polyester to lower the crystallinity and suppress retardation in the thickness direction. Due to insufficient formation of oriented crystals due to, problems such as an increase in thermal shrinkage and whitening during heating were observed, which were not practical.

  In addition, with transparent conductive films and anti-scattering films used in touch panels, etc., the demand for interference color suppression when assembled on touch panels has increased due to the large screen and simplified structure. (For example, Patent Documents 1 and 2) have insufficient characteristics.

JP 2010-181870 A JP 2013-210598 A

  Therefore, in the present invention, the above-mentioned drawbacks are eliminated, and although it is a biaxially stretched polyester film, it does not exhibit an interference color when mounted on a display device such as a liquid crystal display, and has dimensional stability and whitening resistance during heating. It aims at providing the polyester film which is excellent in.

The present invention for solving the above problems has the following configuration.
(1) A polyester A layer in which 50 mol% or more and less than 95 mol% of the dicarboxylic acid component is a terephthalic acid component, and 5 mol% or more and less than 50 mol% is another dicarboxylic acid component,
The peak temperature of the loss tangent (tan δ) measured by the dynamic viscoelasticity measuring device in the direction X and the direction Y is 60 when any one direction in the film plane is the direction X and the direction orthogonal to the direction X is the direction Y. An optical polyester film having a temperature of not lower than 115 ° C and not higher than 115 ° C.
(2) The optical polyester according to (1), wherein 60 mol% or more and less than 82 mol% of the dicarboxylic acid component of the polyester A layer is a terephthalic acid component, and 18 mol% or more and less than 40 mol% is another dicarboxylic acid component. the film.
(3) The optical polyester film according to (1) or (2), wherein the other dicarboxylic acid component is an isophthalic acid component.
(4) The optical polyester film according to any one of (1) to (3), wherein a retardation with respect to an angle inclined by 50 ° with respect to a plane orthogonal to the light beam incident direction is 1500 nm or less.
(5) One or more selected from the group consisting of hard coat properties, self-repairing properties, antiglare properties, antireflection properties, low reflection properties, and antistatic properties on at least one outermost surface of the optical polyester film The optical polyester film according to any one of (1) to (4), wherein a surface layer exhibiting the above function is laminated.
(6) The optical polyester film according to any one of (1) to (5), which is used for protecting a polarizer.
(7) A polarizing plate comprising a polarizer protective film on both sides of the polarizer, wherein the polarizer protective film on at least one surface is the polarizer protective polyester film according to (6).
(8) A transparent conductive film having the polyester film according to any one of (1) to (5).

  The optical polyester film of the present invention can display a high-quality image without exhibiting an interference color even when mounted on a display device such as a liquid crystal display, and also has excellent whitening resistance during heating. There is an effect.

It is a schematic diagram at the time of measuring retardation with respect to an angle inclined by 50 ° with respect to a plane orthogonal to the light beam incident direction. a indicates a sample stage, which is perpendicular to the direction of incidence of light flux. b is a sample stage inclined by 50 ° with respect to a.

Hereinafter, the optical polyester film of the present invention will be described in detail.
It is important that the optical polyester film of the present invention has a polyester A layer. Polyester A layer important for coexistence of interference color suppression and whitening resistance at the time of heating is important, and the structure of the film has a layer other than the polyester A layer even in the structure of only the polyester A layer. It doesn't matter.

  In the optical polyester film of the present invention, it is important that the polyester A layer is composed of 50 mol% or more and less than 95 mol% of the dicarboxylic acid component and terephthalic acid component, and 5 mol% or more and less than 50 mol% of the other dicarboxylic acid component. It is. About the dicarboxylic acid component of the polyester A layer, the crystallinity of the polyester A layer is lowered by using 50 mol% or more and less than 95 mol% as the terephthalic acid component and 5 mol% or more and less than 50 mol% as the other dicarboxylic acid component. The retardation in the in-plane direction of the film and the retardation in the thickness direction can be reduced, and the interference color when mounted on the display can be suppressed. Regarding the dicarboxylic acid component of the polyester A layer, when the terephthalic acid component is less than 50 mol% and the dicarboxylic acid component other than the terephthalic acid component is 50 mol% or more, it is difficult to produce due to low crystallinity, or the heat shrinkage rate Increases the dimensional stability at high temperatures, resulting in insufficient curling suppression when bonded to the polarizer in polarizer protection applications, or laminating a transparent conductive layer in transparent conductive film applications In some cases, the heat resistance and whitening resistance during the process may be insufficient. On the other hand, if the terephthalic acid component is 95 mol% or more and the dicarboxylic acid component other than terephthalic acid is less than 5 mol%, the retardation in the in-plane direction and the retardation in the thickness direction are high due to high crystallinity, and the display When installed, interference colors may be visible.

  In the polyester A layer, from the viewpoint of interference color suppression and film-forming properties, 60% or more and less than 82 mol% of the dicarboxylic acid component may be terephthalic acid component, and 18 mol% or more and less than 40 mol% may be other dicarboxylic acid component. More preferably, 70 mol% or more and less than 80 mol% of the dicarboxylic acid component is a terephthalic acid component, and more preferably 20 mol% or more and less than 30 mol% is another dicarboxylic acid component.

  Regarding the dicarboxylic acid component of the polyester A layer, a specific method in which 50 mol% or more and less than 95 mol% is a terephthalic acid component, and 5 mol% or more and less than 50 mol% is another dicarboxylic acid component is as follows. Examples include a known method of reacting a dicarboxylic acid other than an acid, and a method of mixing and melt-extruding two or more polyesters obtained by a known method and having different concentrations of dicarboxylic acid other than terephthalic acid.

  Although it is important that the polyester A layer in the polyester film of the present invention has 50 mol% or more and less than 95 mol% of the dicarboxylic acid component as the terephthalic acid component, and 5 mol% or more and less than 50 mol% as the other dicarboxylic acid component. From the viewpoint of suppressing retardation, the other dicarboxylic acid component is preferably a 2,6-naphthalenedicarboxylic acid component and / or an isophthalic acid component.

  Other examples of the dicarboxylic acid component contained in the polyester film of the present invention include phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4 ′. -Structural units derived from aromatic dicarboxylic acids such as diphenyl ether dicarboxylic acid and 4,4'-diphenylsulfone dicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid and cyclohexanedicarboxylic acid Examples are derived structural units and ester derivatives thereof. These dicarboxylic acid-derived structural units may be used alone or in combination of two or more, and may further partially copolymerize oxyacids such as hydroxybenzoic acid.

  Examples of the diol component contained in the polyester film of the present invention include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2, Examples thereof include 2-bis (4-hydroxyethoxyphenyl) propane, isosorbate, spiroglycol and the like. Among these, neopentyl glycol, diethylene glycol, 1,4-cyclohexanedimethanol, isosorbate, and spiro glycol are preferably used. These diol components may be used alone or in combination of two or more.

  In the optical polyester film of the present invention, from the viewpoint of dimensional stability during heating and whitening resistance, the direction X is the direction X when the direction X is the arbitrary direction in the film plane and the direction Y is the direction orthogonal to the direction X. It is important that the peak temperature of the loss tangent (tan δ) measured by the dynamic viscoelasticity measuring device in Y is 60 ° C. or higher and 115 ° C. or lower. Here, the loss tangent (tan δ) refers to the ratio of the imaginary part to the real part of the complex elastic modulus obtained from the temporal strain and stress observed when a sinusoidal force is applied to the film. . When the loss tangent (tan δ) is observed while changing the temperature, the maximum value or the maximum value is exhibited at a certain temperature. Therefore, in the present invention, the temperature at which the loss tangent (tan δ) exhibits the maximum value or the maximum value is determined. The peak temperature of loss tangent (tan δ) is used. When two or more maximum values and maximum values are observed, the value on the lowest temperature side is adopted.

  Since the peak temperature of the loss tangent (tan δ) of the film is the temperature at which molecular motion begins, in the present invention, if the peak temperature of the loss tangent (tan δ) of the film is less than 60 ° C., the molecular motion of the film is low Since this tends to occur, the molecular motion of the film starts from a low temperature, the thermal shrinkage rate increases, the dimensional stability during heating becomes insufficient, and curling suppression when bonded to the polarizer is inadequate for polarizer protection applications. In some cases, the heat resistance may be insufficient when the transparent conductive layer is laminated in the application of the transparent conductive film. Furthermore, spherulites may be formed by the molecular motion of the film, resulting in whitening of the film.

  On the other hand, if the peak temperature of the loss tangent (tan δ) of the film exceeds 115 ° C., the orientation crystallinity of the film increases, so that retardation increases, and interference colors may be seen when mounted on a display.

  In the optical polyester film of the present invention, the peak temperature of the loss tangent (tan δ) in any one direction X and the direction Y orthogonal to the direction X is a high level of retardation reduction, dimensional stability during heating, and suppression of whitening resistance. From the standpoint of compatibility, it is preferably 65 ° C or higher and 90 ° C or lower, and more preferably 70 ° C or higher and 85 ° C or lower.

  A specific method for setting the peak temperature of loss tangent (tan δ) in the optical polyester film of the present invention to 60 ° C. or more and 115 ° C. or less is not particularly limited, but the dicarboxylic acid component is 50 mol% or more and less than 95 mol%. Examples thereof include a method of suppressing the molecular motion of the film to some extent while having a polyester A layer in which the terephthalic acid component is 5 mol% or more and less than 50 mol% is another dicarboxylic acid component.

  Specifically, after biaxial stretching during the production of polyester and between heat setting, a cooling zone is provided to maintain the orientation, the heat setting temperature is set below the melting point of the polyester layer with the lowest melting point, orientation For example, there is a method in which the obtained crystals are left without melting. The temperature of the cooling zone between biaxial stretching and heat setting is preferably 120 ° C. or lower, more preferably 80 ° C. or lower, and most preferably 10 ° C. or higher and 50 ° C. or lower.

  Moreover, the polyester film for optics of this invention may laminate | stack polyester layers other than the polyester A layer in the range which does not impair the effect of invention. By laminating a polyester layer other than the polyester A layer, the peak temperature of loss tangent (tan δ) may be controlled, or the thermal shrinkage rate may be reduced to improve the dimensional stability during heating.

  When laminating a polyester layer other than the polyester A layer, the number of layers and the layer configuration are not particularly limited, but from the viewpoint of suppressing curling of the film and achieving both reduction in warpage and suppression of interference color when bonded to a polarizer, B layer / A layer / B layer, B layer / A layer / B layer / A layer / B layer (here, a polyester layer other than the polyester A layer is temporarily expressed as B layer), and so on. A configuration that is symmetrical with respect to the thickness direction and that both surface layers are layers other than the polyester A layer is preferable. In applications where it is more important to reduce warpage when bonded to a polarizer, the number of layers to be laminated is preferably 3 to 9, and more preferably 5 to 7. If the number of layers to be laminated is less than 3 layers, warpage reduction at the time of bonding to a polarizer may be insufficient, and if the total number of layers exceeds 9 layers, the laminating properties at the time of film formation become low, and the flow Marks and the like are generated, and the quality of the film may be lowered.

  The optical polyester film of the present invention has an angle inclined by 50 ° with respect to a plane perpendicular to the light incident direction from the viewpoint of interference color suppression when viewed from an oblique direction when mounted on a display device such as a display. It is preferable that retardation is 1500 nm or less. Here, the angle inclined by 50 ° with respect to the plane perpendicular to the light beam incident direction refers to an angle defined in a phase difference measuring apparatus such as “KOBRA” series manufactured by Oji Scientific Instruments Co., Ltd. Indicates an angle obtained by tilting and rotating the 50 ° stage when the angle of the stage of the measurement sample in a state where the light beam is perpendicularly incident on the film is 0 °.

  The retardation with respect to an angle inclined by 50 ° with respect to the plane perpendicular to the light incident direction is preferably 1000 nm or less, more preferably 400 nm or less, more preferably 400 nm or less, particularly from the viewpoint of further suppressing the interference color when viewed from an oblique direction. Preferably it is 300 nm or less. Further, the retardation with respect to the angle inclined by 50 ° with respect to the plane orthogonal to the light incident direction is preferably as low as possible from the viewpoint of suppressing the interference color in the oblique direction, but from the viewpoint of suppression of whitening during heating and dimensional stability. Is preferably 50 nm or more.

  As a specific method of setting the retardation with respect to an angle inclined by 50 ° with respect to the plane perpendicular to the light beam incident direction to 1500 nm or less, two or more types of dicarboxylic acid components of the polyester constituting the polyester film of the present invention are used. The method of reducing the biaxial orientation of the polyester film, the method of reducing the biaxial orientation of the polyester film by adjusting the production conditions, such as setting the stretching ratio low or raising the stretching temperature, the method of reducing the film thickness, the melting point And a method of increasing the thickness ratio of a layer having a low melting point (a layer having low crystallinity) in the case of a laminated structure having at least two polyester layers having different from each other.

  From the viewpoint of appearance, the optical polyester film of the present invention preferably has a film haze of 3% or less, more preferably 2.5% or less, and most preferably 0% or more and 2% or less.

  Examples of the method of setting the haze to 3% or less include a method of reducing the concentration of particles to be contained in order to improve the film transportability. The optical polyester film of the present invention can contain particles in the film in order to improve the film transportability. Here, the particles to be used are not particularly limited, but externally added particles are preferably used in terms of transportability and appearance. Examples of the external additive particles include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, and aluminum oxide, and organic particles include styrene, silicone, acrylic acid, methacrylic acid, Particles containing polyesters, divinyl compounds and the like as constituent components can be used. Among them, it is preferable to use inorganic particles such as wet and dry silica and alumina, and particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituent components. Further, these externally added particles may be used in combination of two or more. From the viewpoint of transportability and appearance, the particle content in the film is preferably 0.00001 to 0.02% by mass, more preferably 0.00002 to 0.01% by mass, based on 100% by mass of the entire film. .

  As a method for reducing the particle concentration without reducing the transportability of the film, for example, in the case of a laminated film having at least an A layer and a B layer, a method of adding particles only to the A layer or the B layer can be mentioned. . By adding particles only to the A layer or the B layer, the amount of particles added can be reduced, and haze can be reduced without deteriorating the handleability.

  The optical polyester film of the present invention preferably has a film haze of 5% or less when heat-treated at 130 ° C. for 10 minutes in order to achieve whitening resistance during heating. When the film haze at the time of heat treatment at 130 ° C. for 10 minutes is higher than 5%, it is not preferable because the whitening of the film can be visually confirmed during the heat treatment. The film haze after heat treatment at 130 ° C. for 10 minutes is more preferably 3% or less, and most preferably 2% or less.

Further, the optical polyester film of the present invention is 10 minutes at 130 ° C. from the viewpoint of dimensional stability at the time of heating, assuming that any one direction in the film plane is the direction X and the direction perpendicular to the direction X is the direction Y. It is preferable that the thermal contraction rate in the direction X and the direction Y when the heat treatment is performed is 3% or less.
If the heat shrinkage rate at the time of heat treatment at 130 ° C. for 10 minutes exceeds 3%, the film shrinkage during heating is large, and the yield during the production process of the polarizing plate and the transparent conductive film may be reduced. . The heat shrinkage rate in the direction X and the direction Y when heat treatment is performed at 130 ° C. for 10 minutes is more preferably 2% or less, and most preferably 1% or less.

  In the optical polyester film of the present invention, as a method of setting the thermal shrinkage rate in the direction X and the direction Y when it is heat-treated at 130 ° C. for 10 minutes to 3% or less, in the film manufacturing process, infrared rays during longitudinal stretching are used. A method of increasing the heater strength, a method of relaxing in the width direction during heat setting after biaxial stretching, and the like are preferably used.

  In addition, in order to provide process stabilization in the manufacturing process and durability in the use environment, the optical polyester film of the present invention has hard coat properties, self-repairing properties, antiglare properties, antireflection properties on at least one surface, It is preferable to have a surface layer that exhibits one or more functions selected from the group consisting of low reflectivity, ultraviolet shielding, and antistatic properties.

  The thickness of the surface layer varies depending on its function, but is preferably in the range of 10 nm to 30 μm, and more preferably 50 nm to 20 μm. If it is thinner than this, the effect will be insufficient, and if it is heated, there is a possibility of adversely affecting the optical performance.

Here, the hard coat property is a function of making the surface hard to be damaged by increasing the hardness of the surface. As its function, it is preferably HB or more, more preferably 2H or more, or # 0000 steel wool in the evaluation by scratch hardness (pencil method) described in JIS K-5600-5-4-1999. In the scratch resistance test conducted under the condition of 200 g / cm ^2, a state in which no scratch is made is shown.

  Here, the self-repairing property is a function of making a scratch difficult by repairing the scratch by elastic recovery or the like. The function is preferably when the surface is rubbed with a brass brush under a load of 500 g. Within 3 minutes, more preferably within 1 minute.

  The anti-glare property is a function of improving visibility by suppressing reflection of external light by light scattering on the surface. The function is preferably 2 to 50%, more preferably 2 to 40%, and particularly preferably 2 to 30% in the evaluation based on the method for obtaining haze described in JIS K-7136-2000. It is.

  Antireflection and low reflectivity are functions that improve visibility by reducing the reflectance at the surface due to the interference effect of light. Its function is preferably 2% or less, particularly preferably 1% or less, by reflectance spectroscopy measurement.

The antistatic property is a function of removing triboelectricity generated by peeling from the surface or rubbing on the surface by leaking. As a standard of the function, the surface resistivity described in JIS K-6911-2006 is preferably 10 ¹¹ Ω / □ or less, more preferably 10 ⁹ Ω / □ or less. In addition to a layer containing a known antistatic agent, the antistatic property may be imparted from a layer containing a conductive polymer such as polythiophene, polypyrrole or polyaniline. Hereinafter, the provision of hard coat properties and antiglare properties will be described in more detail.

  The material used for the surface layer imparting the hard coat property (hereinafter, referred to as a hard coat layer) can be a material used for a known hard coat layer, and is not particularly limited, but is dry, heat, chemical reaction Alternatively, a resin compound that polymerizes and / or reacts by irradiation with any of electron beam, radiation, and ultraviolet light can be used. Examples of such a curable resin include melamine-based, acrylic-based, silicon-based, and polyvinyl alcohol-based curable resins, but acrylic resins that are cured by electron beams or ultraviolet rays in terms of obtaining high surface hardness or optical design. A curable resin is preferred.

  An acrylic resin that is cured by an electron beam or ultraviolet ray has an acrylate-based functional group. For example, a relatively low molecular weight polyester resin, polyether resin, acrylic resin, epoxy resin, urethane resin, alkyd resin, spiro resin Acetal resins, polybutadiene resins, polythiol polyene resins, oligomers or prepolymers of polyfunctional compounds such as polyhydric alcohols (meth) acrylates and prepolymers and reactive diluents such as ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methyl Monofunctional monomers such as styrene and N-vinylpyrrolidone as well as polyfunctional monomers such as trimethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate Contains rate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, etc. Things can be used.

  In the case of an electron beam or ultraviolet curable resin, as a photopolymerization initiator in the above-mentioned resin, acetophenones, benzophenones, Michler benzoylbenzoate, α-amyloxime ester, tetramethyltyramium monosulfide, thioxanthones, As a photosensitizer, n-butylamine, triethylamine, tri-n-butylphosphine and the like can be mixed and used. It is preferable that the addition amount of the said photoinitiator is 0.1-10 mass parts with respect to 100 mass parts of electron beam ultraviolet curable resins.

  Although it does not specifically limit as a hardening method of the said coating film, It is preferable to carry out by ultraviolet irradiation. When curing by ultraviolet rays, it is preferable to use ultraviolet rays having a wavelength range of 190 to 380 nm. Curing with ultraviolet rays can be performed, for example, with a metal halide lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a carbon arc lamp, a black light fluorescent lamp, or the like. Specific examples of the electron beam source include various electron beam accelerators such as a cockcroft-wald type, a bandegraft type, a resonant transformer type, an insulating core transformer type, a linear type, a dynamitron type, and a high frequency type.

  Siloxane-based thermosetting resins are also useful as the resin for the hard coat layer, and can be produced by hydrolyzing and condensing the organosilane compound alone or in combination of two or more under an acid or base catalyst.

  The film thickness of the hard coat layer is preferably 0.5 μm to 20 μm, more preferably 1 μm to 20 μm, and even more preferably 1 μm to 15 μm.

  As the resin used for the surface layer imparting the antiglare property (hereinafter referred to as the antiglare layer), the same resin as the electron beam or ultraviolet curable resin described above can be used. One or two or more of the above-mentioned resins can be mixed and used. Further, in order to adjust physical properties such as plasticity and surface hardness, a resin that is not cured by an electron beam or ultraviolet rays can be mixed. Examples of resins that are not cured by electron beams or ultraviolet rays include polyurethane, cellulose derivatives, polyesters, acrylic resins, polyvinyl butyral, polyvinyl alcohol, polyvinyl chloride, polyvinyl acetate, polycarbonate, and polyamide.

Specific examples of the particles used in the antiglare layer include, for example, particles of inorganic compounds such as silica particles, alumina particles, TiO ₂ particles, or polymethyl methacrylate particles, acrylic-styrene copolymer particles, crosslinked acrylic particles, melamine particles. Preferred are resin particles such as crosslinked melamine particles, polycarbonate particles, polyvinyl chloride particles, benzoguanamine particles, crosslinked benzoguanamine particles, polystyrene particles, and crosslinked polystyrene particles. As the shape, spherical particles having a uniform surface protrusion shape are preferably used, but indefinite shapes such as layered inorganic compounds such as talc and bentonite can also be used. Two or more different kinds of particles may be used in combination. Even if there are two or more kinds of material and two or more kinds of particle sizes, there is no limitation.

The particle size of the particles used in the antiglare layer is 0.5 to 10 μm, more preferably 0.5 to 5 μm, further preferably 0.5 to 3 μm, and still more preferably 0.5 to 1.5 μm. The content of the particles is 1 to 50% by weight, more preferably 2 to 30% by weight, based on the resin.
The film thickness of the antiglare layer is preferably 0.5 μm to 20 μm, more preferably 1 μm to 20 μm, and further preferably 1 μm to 10 μm. Here, the average particle diameter in the present invention refers to a number average diameter D represented by D = ΣDi / N (Di: equivalent circle diameter of particles, N: number of particles).

  As the antiglare layer used in the present invention, JP-A-6-18706, JP-A-10-20103, JP-A-2009-227735, JP-A-2009-86361, JP-A-2009-80256 are disclosed. JP, 2011-81217, JP 2010-204479, JP 2010-181898, JP 2011-197329, JP 2011-197330, JP 2011-215393, etc. The described antiglare layer can also be suitably used.

The surface layer may contain other components in addition to those described above as long as the effects of the invention are not lost. Other components include, but are not limited to, for example, inorganic or organic pigments, polymers, polymerization initiators, polymerization inhibitors, antioxidants, dispersants, surfactants, light stabilizers, leveling agents, An antistatic agent, an ultraviolet absorber, a catalyst, an infrared absorber, a flame retardant, an antifoaming agent, conductive fine particles, a conductive resin, and the like can be added.
The optical film of the present invention enables high-quality display when mounted on a display device such as a liquid crystal display, and thus can be suitably used for various optical applications. It can be suitably used for polarizer protection applications, transparent conductive film applications, glass scattering prevention film applications, and the like.

  The polarizing plate of this invention is a polarizing plate which has a polarizer protective film on both surfaces of a polarizer, Comprising: It is preferable that the polarizer protective film of at least one surface is the said polyester film for optics. The other polarizer protective film may be the optical polyester film of the present invention, or a film having no birefringence such as a triacetyl cellulose film, an acrylic film, or a norbornene film is preferably used.

  Examples of the polarizer include a polyvinyl alcohol film containing a dichroic material such as iodine. The polarizer protective film is bonded to the polarizer directly or via an adhesive layer, but is preferably bonded via an adhesive from the viewpoint of improving the adhesiveness. As a preferable polarizer for bonding the polyester film of the present invention, for example, iodine or dichroic material is dyed and adsorbed on a polyvinyl alcohol film, uniaxially stretched in a boric acid aqueous solution, and the stretched state is maintained. The polarizer obtained by performing washing | cleaning and drying is mentioned. The draw ratio of uniaxial stretching is usually about 4 to 8 times. Polyvinyl alcohol is preferred as the polyvinyl alcohol film. “Kuraray Vinylon” (manufactured by Kuraray Co., Ltd.), “Tosero Vinylon” (manufactured by Tosero Co., Ltd.), “Nippon Synthetic Chemical Co., Ltd.” (Commercially available) can be used. Examples of the dichroic material include iodine, a disazo compound, and a polymethine dye.

  The transparent conductive film of the present invention is a film in which a transparent conductive layer is laminated directly or via an easy adhesion layer on the optical polyester film of the present invention. The transparent conductive layer is not particularly limited as long as a transparent conductive film can be formed. For example, indium oxide containing tin oxide (ITO), tin oxide containing antimony (ATO), zinc oxide, zinc-aluminum composite oxide And thin films of indium-zinc composite oxide, CNT, silver, copper and the like. These compounds can achieve both transparency and conductivity by selecting appropriate production conditions.

As a method for forming a transparent conductive layer, a vacuum deposition method, a sputtering method, a CVD method, an ion plating method, a spray method, a method of coating a coating liquid containing a conductive material, and the like are known. An appropriate method can be selected and used depending on the required film thickness. For example, in the case of a sputtering method, normal sputtering using a compound target, reactive sputtering using a metal target, or the like is used. At this time, a reactive gas such as oxygen, nitrogen or water vapor can be introduced, or means such as addition of ozone or ion assist can be used in combination.
Next, the preferable manufacturing method of the optical polyester film of this invention is demonstrated below. The present invention should not be construed as being limited to such examples.

  First, a polyester raw material is supplied to a vent type twin screw extruder and melt extruded. Separate vented twin-screw extruders for polyester A used for the polyester A layer and, if necessary, polyesters (hereinafter referred to as polyester B) used for polyester layers other than the polyester A layer (hereinafter referred to as polyester B layer). To be melt extruded. Hereinafter, a description will be given of a configuration in which a polyester A layer and a polyester B layer are laminated. At this time, it is preferable to control the resin temperature to 265 ° C. to 295 ° C. under an atmosphere of flowing nitrogen in the extruder, with an oxygen concentration of 0.7% by volume or less. Next, the foreign matter is removed and the amount of extrusion is leveled through a filter and a gear pump, the polyester A layer and the polyester B layer are merged, and then discharged from the T die onto a cooling drum in a sheet form. At that time, an electrostatic application method in which a cooling drum and the resin are brought into close contact with each other by static electricity using an electrode applied with a high voltage, a casting method in which a water film is provided between the casting drum and the extruded polymer sheet, and the casting drum temperature is set to be equal to that of the polyester resin. The sheet-like polymer is brought into close contact with the casting drum, cooled and solidified by a method of sticking the extruded polymer at a glass transition point to (glass transition point−20 ° C.) or a combination of these methods, and unstretched. Get a film. Among these casting methods, when using polyester, a method of applying an electrostatic force is preferably used from the viewpoint of productivity and flatness.

  The optical polyester film of the present invention is preferably a biaxially oriented film from the viewpoints of heat resistance and dimensional stability. The biaxially oriented film is obtained by stretching an unstretched film in the longitudinal direction and then stretching in the width direction, or by stretching in the width direction and then stretching in the longitudinal direction, or by the longitudinal direction of the film. It can be obtained by stretching by a simultaneous biaxial stretching method in which the width direction is stretched almost simultaneously.

  As the draw ratio in such a drawing method, preferably 2.8 times or more and 3.5 times or less, more preferably 3 times or more and 3.3 times or less in the longitudinal direction. The stretching speed is preferably 1,000% / min or more and 200,000% / min or less. The stretching temperature in the longitudinal direction is preferably 95 ° C. or higher and 130 ° C. or lower, and it is preferable to preheat at 85 ° C. for 1 second or longer before stretching. Further, the stretching ratio in the width direction is preferably 2.8 times or more and 3.5 times or less, more preferably 3 times or more and 3.5 times or less, and it is preferable to match the stretching ratio in the longitudinal direction. The stretching speed in the width direction is desirably 1,000% / min or more and 200,000% / min or less.

  Further, the film is heat-treated after biaxial stretching. In order to control the peak temperature of loss tangent (tan δ) to 60 ° C. or higher and 115 ° C. or lower, 120 ° C. between the stretching step in the width direction and the heat treatment step. It is preferable to provide the following cooling zones. The heat treatment can be performed by any conventionally known method such as in an oven or on a heated roll. The purpose of this heat treatment is to grow oriented crystals after biaxial stretching to improve thermal dimensionality, so that it is within the range below the melting point of the polyester layer with the highest melting point (in this configuration, the polyester A layer). In general, the heat treatment temperature is set as high as possible.

  However, the optical polyester film of the present invention has a polyester A layer composed of two or more kinds of dicarboxylic acid components to reduce crystallinity in order to suppress interference color when mounted on a display, Under general heat treatment conditions, not only does the growth of oriented crystals proceed, but heat above the melting point is applied to the polyester A layer, and the oriented crystals melt and disappear. As a result of the melting of the oriented crystals in the polyester A layer, the amorphous portion having high molecular mobility increases at low temperatures, and spherulites grow and whitening occurs during the reliability test. In some cases, the dimensional stability in the case becomes insufficient. Therefore, when manufacturing the optical polyester film of this invention, it is preferable to heat-process at temperature lower than the polyester layer with the lowest melting | fusing point.

  Also, if the polyester A layer has very low crystallinity and it is difficult to measure the melting point by ordinary differential scanning calorimetry, it is assumed that the temperature at which the melting point of the polyester becomes difficult to observe is around 200 ° C. Thus, the heat treatment temperature is preferably set to less than 200 ° C.

  In addition, the temperature of heat processing shows the temperature which becomes the highest among the heat processing temperatures performed after biaxial stretching. The heat treatment time can be arbitrarily set within a range not deteriorating the characteristics, and is preferably 5 seconds to 60 seconds, more preferably 10 seconds to 40 seconds, and most preferably 15 seconds to 30 seconds. Good.

  Furthermore, in order to improve the adhesive strength with the polarizer, at least one surface can be subjected to corona treatment or can be coated with an easy adhesion layer. As a method of providing the coating layer in-line in the film manufacturing process, at least uniaxially stretched film with a coating layer composition dispersed in water is uniformly applied using a metalling ring bar or gravure roll. Then, a method of drying the coating while stretching is preferable, and in this case, the thickness of the easy adhesion layer is preferably 0.01 μm or more and 1 μm or less. Also, various additives such as antioxidants, heat stabilizers, ultraviolet absorbers, infrared absorbers, pigments, dyes, organic or inorganic particles, antistatic agents, nucleating agents, etc. may be added to the easy-adhesion layer. Good. The resin preferably used for the easy-adhesion layer is preferably at least one resin selected from an acrylic resin, a polyester resin, and a urethane resin from the viewpoint of adhesiveness and handleability. Furthermore, off-annealing at 90 to 200 ° C. is also preferably used.

  In the optical polyester film of the present invention, a surface layer is laminated on the outermost surface in order to provide functions such as hard coat property, self-repairing property, antiglare property, antireflection property, low reflection property, and antistatic property. For this, it is preferable to use a production method in which the aforementioned coating composition is formed by coating, drying and curing.

  The method for producing the surface layer by coating is not particularly limited, but the coating composition is supported by a dip coating method, a roller coating method, a wire bar coating method, a gravure coating method, a die coating method (US Pat. No. 2,681,294), or the like. It is preferable to form the surface layer by applying to a material or the like. Further, among these coating methods, the gravure coating method or the die coating method is more preferable as the coating method.

  Next, in order to completely remove the solvent by drying the applied liquid film, it is preferable that the liquid film is heated in the drying step. Examples of the drying method include heat transfer drying (adherence to a high-temperature object), convection heat transfer (hot air), radiant heat transfer (infrared ray), and others (microwave, induction heating). Among these, a method using convective heat transfer or radiant heat transfer is preferable because it is necessary to make the drying speed uniform even in the width direction.

  Furthermore, you may perform the further hardening operation (hardening process) by irradiating a heat | fever or an energy ray. In the curing step, when cured with heat, the temperature is preferably from room temperature to 200 ° C, more preferably from 100 ° C to 200 ° C from the viewpoint of the activation energy of the curing reaction, and from 130 ° C to 200 ° C. More preferably.

Moreover, when hardening with an active energy ray, it is preferable that it is an electron beam (EB ray) and / or an ultraviolet-ray (UV ray) from a versatility point. In the case of curing with ultraviolet rays, the oxygen concentration is preferably as low as possible because oxygen inhibition can be prevented, and curing in a nitrogen atmosphere (nitrogen purge) is more preferable. When the oxygen concentration is high, the hardening of the outermost surface is inhibited, and the surface hardening may be insufficient. Examples of the ultraviolet lamp used when irradiating ultraviolet rays include a discharge lamp method, a flash method, a laser method, and an electrodeless lamp method. Case of UV cured using a high pressure mercury lamp is a discharge lamp type, illuminance of ultraviolet rays 100~3,000mW / cm ^2, preferably 200~2,000mW / cm ^2, more preferably 300~1,500mW / cm ² conditions it is preferable to perform the UV irradiation, the integrated light quantity of ultraviolet 100~3,000mJ / cm ^2, which is a preferably 200~2,000mJ / cm ^2, more preferably 300~1,500mJ / cm ² under the condition that the More preferably, UV irradiation is performed.
Here, the illuminance of ultraviolet rays is the irradiation intensity received per unit area, and changes depending on the lamp output, the emission spectrum efficiency, the diameter of the light emission bulb, the design of the reflector, and the light source distance to the irradiated object. However, the illuminance does not change depending on the conveyance speed. Further, the UV integrated light amount is irradiation energy received per unit area, and is the total amount of photons reaching the surface. The integrated light quantity is inversely proportional to the irradiation speed passing under the light source, and is proportional to the number of irradiations and the number of lamps.
The optical polyester film of the present invention is preferably used as a polarizing plate by being bonded to a PVA sheet (polarizer) prepared by containing iodine in PVA and being oriented.

(Characteristic measurement method and effect evaluation method)
The characteristic measuring method and the effect evaluating method in the present invention are as follows.

(1) Composition of polyester A polyester resin and a film are dissolved in hexafluoroisopropanol (HFIP), and the content of each monomer residue component and by-product diethylene glycol can be quantified using ¹ H-NMR and ¹³ C-NMR. it can. In the case of a laminated film, the components constituting each layer can be collected and evaluated by scraping off each layer of the film according to the laminated thickness. In addition, about the film of this invention, the composition was computed by calculation from the mixing ratio at the time of film manufacture.

(2) Intrinsic viscosity of polyester The intrinsic viscosity of the polyester resin and the film was measured at 25 ° C. using an Ostwald viscometer after dissolving the polyester in orthochlorophenol. In the case of a laminated film, the intrinsic viscosity of each layer can be evaluated by scraping each layer of the film according to the laminated thickness.

(3) Film thickness and layer thickness The film was embedded in an epoxy resin, and the film cross section was cut out with a microtome. The cross section was observed with a transmission electron microscope (TEM H7100, manufactured by Hitachi, Ltd.) at a magnification of 5000 times to determine the film thickness and the thickness of the polyester layer.

(4) Using a melting point differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., RDC220), measurement and analysis were performed in accordance with JIS K-7121-1987 and JIS K-7122-1987. Using 5 mg of a polyester film as a sample, the temperature at the apex of the endothermic peak obtained from the DSC curve when the temperature was raised from 25 ° C. to 300 ° C. at 20 ° C./min was defined as the melting point. In the case of a laminated film, the melting point of each layer was measured by scraping each layer of the film according to the laminated thickness. When the laminated structure was confirmed in the cross-sectional observation of (3), in the present invention, each layer was scraped with a cutter and the melting point of each layer was measured. When the melting point is not observed, “ND” is indicated in the table.

(5) Retardation at an angle inclined by 50 ° with respect to a plane perpendicular to the incident direction of the light beam (Re (50))
Measurement was performed using a phase difference measuring device (KOBRA-21ADH) manufactured by Oji Scientific Instruments. A sample of 30 mm × 50 mm (direction X × direction Y) was cut out with an arbitrary one direction in the film plane as direction X and a direction orthogonal to direction X as direction Y, and placed in a phase difference measuring apparatus. When the angle of the measurement sample stage (FIG. 1a) perpendicular to the incident direction of the light beam is 0 °, the sample stage is tilted (FIG. 1b) so that the angle formed by this 0 ° surface and the measurement sample stage is 50 °. The retardation at a wavelength of 590 nm was measured.

(6) Loss Tangent (tan δ) Peak Temperature A sample of 60 mm × 5 mm (direction X × direction Y) was cut out with an arbitrary direction in the film surface as direction X and a direction orthogonal to direction X as direction Y. Using a dynamic viscoelasticity measuring apparatus (DMS6100, manufactured by Seiko Instruments Inc.), viscoelasticity was measured under the following conditions, and the peak temperature of loss tangent (tan δ) in direction X was determined. A sample of 60 mm × 5 mm (direction Y × direction X) was cut out, and the loss tangent (tan δ) in direction Y was determined in the same manner.

Frequency: 10 Hz, test length (distance between chucks): 20 mm, displacement amplitude: 10 μm
Measurement temperature range: 25 ° C. to 200 ° C., heating rate: 5 ° C./min.

(7) A 130 ° C. heat shrinkage film was cut into a rectangular shape having a length of 150 mm and a width of 10 mm in an arbitrary direction X and a direction Y orthogonal to the X direction, and used as samples. Marks were drawn on the sample at intervals of 100 mm, and a heat treatment was performed by placing in a hot air oven heated to 130 ° C. by hanging a 3 g weight for 10 minutes. The distance between the marked lines after the heat treatment was measured, and the thermal contraction rate was calculated from the change in the distance between the marked lines before and after heating by the following formula. For each film, five samples were measured in the X direction and Y direction, and the average value was evaluated.
Thermal shrinkage (%) = {(distance between marked lines before heat treatment) − (distance between marked lines after heat treatment)} / (distance between marked lines before heat treatment) × 100.

(8) Haze Based on JIS K-7105-1985, the haze was measured using a haze meter (HGM-2GP manufactured by Suga Test Instruments Co., Ltd.). In addition, about the haze at the time of heat-processing for 10 minutes at 130 degreeC, the haze after throwing a 100 mm x 100 mm square film sample into a 130 degreeC hot air oven and hold | maintaining for 10 minutes was measured similarly to the above. . The measurement was performed at 10 arbitrary locations, and the average value was adopted.

(9) Visibility test (i)
The film haze value after heat treatment at 130 ° C. for 10 minutes was evaluated according to the following criteria.
A: Film haze was 2% or less.
B: The film haze was higher than 2% and 3% or lower.
C: Film haze was higher than 3% and 5% or lower.
D: Film haze was higher than 5%.

(10) Visibility test (ii)
A test piece was prepared by laminating a 10 cm square film on one surface of a polarizer having a polarization degree of 99.9% prepared by adsorbing and orienting iodine in PVA. In addition, the laminator roll set to 85 degreeC was used for bonding. 50 with respect to the normal direction of the plane of the test piece when the prepared test piece and the polarizing plate on which no film is attached are placed on an LED light source (Tritech A3-101) in a crossed Nicol arrangement. Visibility from an angle of ° was confirmed. Similarly, a test piece in which a 30 cm square film was bonded was prepared, the visibility was similarly confirmed, and the evaluation was performed according to the following criteria.
S: No interference color is observed in any of the evaluations of 10 cm square and 30 cm square.
A: In the evaluation of 10 cm square, no interference color is seen. In the evaluation of 30 cm square, a slight interference color is seen, but there is no practical problem.
B: In both the 10 cm square and 30 cm square evaluations, a slight interference color is observed, but it is acceptable.
C: In the evaluation of 10 cm square, a slight interference color is seen, but it is acceptable. In any evaluation of 30 cm square, interference color is seen, so it is not suitable for large screen display applications.
D: In any evaluation of 10 cm square or 30 cm square, an interference color is clearly seen, so that it is not suitable for display applications.
S to C are acceptable levels.
(11) Visibility test (iii)
An ITO film having a thickness of 30 nm was formed as a transparent conductive layer on the film by sputtering in a 150 ° C. atmosphere to produce a transparent conductive film. Measure the haze before and after the ITO film formation, determine the change in haze in the ITO film formation (the value obtained by subtracting the haze before the ITO film formation from the haze after the ITO film formation), and evaluate it according to the following criteria went.
A: The change value of haze was 3% or less.
B: The change value of haze was 5% or less.
C: The change value of haze was higher than 5%.

(12) About a 10 cm square test piece obtained by curl property (10), place it on a horizontal glass plate, measure the amount of lifting at the four corners in the vertical direction from the glass plate surface, the maximum of the four corners The height was evaluated as the curl height according to the following criteria.

  A: The curl height is less than 5 mm.

  B: The curl height is 5 mm or more and less than 10 mm.

C: The curl height is 10 mm or more.
(13) Curl property (ii)
The transparent conductive film obtained in (11) was cut out in 10 cm square and then evaluated in the same manner as (11).

(14) About the test piece obtained by pencil hardness (10), evaluation by the scratch hardness (pencil method) as described in JIS K5600-5-4 (1999) was performed, and H or more was set as the pass.
(15) Steel wool scratch resistance test (steel wool resistance)
The test piece obtained in (10) was subjected to a rubbing test under the following conditions using a rubbing tester to obtain an index of scratch resistance.

Evaluation environmental conditions: 25 ° C., 60% RH
Rubbing material: Steel wool (Nippon Steel Wool Co., Ltd., gelled No. 0000)
Wrap around the tip (1cm x 1cm) of the scraper of the tester that comes into contact with the sample and fix the band.

Travel distance (one way): 13cm
Rubbing speed: 13 cm / second,
Load: 500 g / cm ²
Tip contact area: 1 cm × 1 cm, rubbing frequency: 10 reciprocations.

  An oil-based black ink was applied to the back side of the rubbed sample, and scratches on the rubbed portion were visually observed with reflected light, and evaluated according to the following criteria. For the evaluation, the above test was repeated three times, and the average was evaluated in five stages.

    A: No scratches are visible.

    B: Slight scratches are visible.

    C: There is a scratch that can be seen at first glance.

(Manufacture of polyester)
The polyester resin used for film formation was prepared as follows.

(Polyester A)
Polyethylene terephthalate resin (intrinsic viscosity 0.65) in which the terephthalic acid component is 100 mol% as the dicarboxylic acid component and the ethylene glycol component is 100 mol% as the glycol component.

(Polyester B)
An isophthalic acid copolymerized polyethylene terephthalate resin (inherent viscosity 0.7) having 96 mol% of terephthalic acid component as dicarboxylic acid component, 4 mol% of isophthalic acid component, and 100 mol% of ethylene glycol component as glycol component.
(Polyester C)
An isophthalic acid copolymerized polyethylene terephthalate resin (inherent viscosity 0.7) having 88 mol% of terephthalic acid component as dicarboxylic acid component, 12 mol% of isophthalic acid component, and 100 mol% of ethylene glycol component as glycol component.
(Polyester D)
Copolymer polyester (GN001 manufactured by Eastman Chemical Co.) having 67 mol% ethylene glycol component and 33 mol% 1,4-cyclohexanedimethanol as glycol component is used as 1,4-cyclohexanedimethanol copolymerized polyethylene terephthalate. Used (intrinsic viscosity 0.75).
(Polyester E)
An isophthalic acid copolymerized polyethylene terephthalate resin (inherent viscosity 0.7) having 83 mol% of terephthalic acid component as dicarboxylic acid component, 17 mol% of isophthalic acid component, and 100 mol% of ethylene glycol component as glycol component.
(Polyester F)
An isophthalic acid copolymerized polyethylene terephthalate resin (inherent viscosity 0.7) having 82 mol% of terephthalic acid component as dicarboxylic acid component, 18 mol% of isophthalic acid component, and 100 mol% of ethylene glycol component as glycol component.
(Polyester G)
An isophthalic acid copolymerized polyethylene terephthalate resin (inherent viscosity 0.7) having a terephthalic acid component of 80 mol% as a dicarboxylic acid component, an isophthalic acid component of 20 mol%, and an ethylene glycol component as a glycol component of 100 mol%.
(Polyester H)
An isophthalic acid copolymerized polyethylene terephthalate resin (inherent viscosity 0.7) having 75 mol% of terephthalic acid component as dicarboxylic acid component, 25 mol% of isophthalic acid component, and 100 mol% of ethylene glycol component as glycol component.
(Polyester I)
An isophthalic acid copolymerized polyethylene terephthalate resin (inherent viscosity 0.7) having 49% by mole of terephthalic acid component as the dicarboxylic acid component, 51% of isophthalic acid component, and 100% by mole of ethylene glycol component as the glycol component.

(Particle Master 1)
Polyethylene terephthalate particle master (intrinsic viscosity 0.65) containing agglomerated silica particles having a number average particle size of 2.2 μm in polyester A at a particle concentration of 2 mass%.
(Particle Master 2)
Polyethylene terephthalate particle master (intrinsic viscosity 0.7) containing agglomerated silica particles having a number average particle size of 2.2 μm in polyester C at a particle concentration of 2 mass%.
(Particle Master 3)
Polyethylene terephthalate particle master (intrinsic viscosity 0.7) containing agglomerated silica particles having a number average particle size of 2.2 μm in polyester I at a particle concentration of 2% by mass.
(Coating composition for forming hard coat layer)
The following materials were mixed and diluted with methyl ethyl ketone to obtain a coating composition for forming a hard coat layer having a solid concentration of 40% by mass.
Toluene 30 parts by mass Polyfunctional urethane acrylate 25 parts by mass (KRM 8655 manufactured by Daicel Ornex Co., Ltd.)
25 parts by mass of pentaerythritol triacrylate mixture (PET30 manufactured by Nippon Kayaku Co., Ltd.)
1 part by mass of polyfunctional silicone acrylate (EBECRYL1360, manufactured by Daicel Ornex Co., Ltd.)
3 parts by mass of photopolymerization initiator (Irgacure 184, manufactured by Ciba Specialty Chemicals)
(Anti-glare layer forming coating composition)
The following materials were mixed and diluted with methyl ethyl ketone to obtain a coating composition for forming an antiglare layer having a solid content of 40% by mass.
Toluene 30 parts by mass Pentaerythritol triacrylate 50 parts by mass
(Nippon Kayaku Co., Ltd. PET30)
Silica dispersion (number average particle size 1 μm) 12 parts by mass
1 part by mass of polyfunctional silicone acrylate (EBECRYL1360, manufactured by Daicel Ornex Co., Ltd.)
3 parts by mass of photopolymerization initiator (Irgacure 184, manufactured by Ciba Specialty Chemicals)
(Example 1)
The composition is as shown in the table, and the raw materials are supplied to separate bent co-directional twin-screw extruders each having an oxygen concentration of 0.2% by volume, the A-layer extruder cylinder temperature is 270 ° C., and layers other than the polyester A layer ( (Hereinafter referred to as B layer) The extruder cylinder temperature is melted at 280 ° C. and merged into a B layer / A layer / B layer configuration in the feed block, and the short tube temperature after merging is 275 ° C. The die temperature was 280 ° C., and the sheet was discharged from a T-die onto a cooling drum whose temperature was controlled to 25 ° C. At that time, a wire electrode having a diameter of 0.1 mm was applied electrostatically and adhered to the cooling drum to obtain an unstretched sheet. Next, a metal roll which was preheated at a preheating temperature of 85 ° C. for 1.5 seconds in the longitudinal direction, stretched 3.3 times in the longitudinal direction at a stretching temperature of 115 ° C. and an infrared heater strength of 5 kW, and immediately temperature controlled to 40 ° C. It was cooled with. Next, preheating is performed for 1.5 seconds at a preheating temperature of 85 ° C. using a tenter type horizontal stretching machine, and the film is stretched 3.3 times in the width direction at a stretching first half temperature of 115 ° C., a stretching middle temperature of 135 ° C. After cooling in a cooling zone of 30 ° C., heat treatment was performed at a heat treatment temperature of 220 ° C. while relaxing 3% in the width direction to obtain a biaxially oriented polyester film having a film thickness of 30 μm.

(Example 2)
A biaxially oriented polyester film having a thickness of 30 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 3)
A biaxially oriented polyester film having a thickness of 30 μm was obtained in the same manner as in Example 1 except that the cylinder temperature of the A layer extruder was 260 ° C. and the composition and heat treatment temperature were changed as shown in the table.

Example 4
A biaxially oriented polyester film having a thickness of 30 μm was obtained in the same manner as in Example 3 except that the composition was changed as shown in the table.

(Example 5)
A biaxially oriented polyester film having a thickness of 30 μm was obtained in the same manner as in Example 3 except that the composition was changed as shown in the table.

(Example 6)
A biaxially oriented polyester film having a thickness of 30 μm was obtained in the same manner as in Example 3 except that the composition and heat treatment temperature were changed as shown in the table.

(Example 7)
The thickness was 30 μm in the same manner as in Example 3 except that the composition and heat treatment temperature were changed as shown, the infrared heater strength during longitudinal stretching was 8 kW, and the widthwise relaxation rate during heat treatment after biaxial stretching was 5%. A biaxially oriented polyester film was obtained.

(Example 8)
A biaxially oriented polyester film having a thickness of 30 μm was obtained in the same manner as in Example 3 except that the composition and heat treatment temperature were changed as shown in the table.

Example 9
A biaxially oriented polyester film having a thickness of 30 μm was obtained in the same manner as in Example 3 except that the composition and heat treatment temperature were changed as shown in the table.

(Example 10)
A biaxially oriented polyester film having a thickness of 30 μm was obtained in the same manner as in Example 3 except that the lamination ratio was changed as shown in the table.

(Example 11)
A biaxially oriented polyester film having a thickness of 30 μm was obtained in the same manner as in Example 3 except that only a single film configuration of the extruder A layer was used.

(Example 12)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the thickness was 40 μm.

(Example 13)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the thickness was 20 μm.

(Example 14)
A biaxially oriented polyester film was obtained in the same manner as in Example 3 except that the draw ratio was changed as shown in the table.

(Example 15)
A biaxially oriented polyester film was obtained in the same manner as in Example 3 except that the draw ratio was changed as shown in the table.

(Example 15-2)
The biaxially oriented polyester film obtained in Example 15 was coated with the above-described coating liquid for forming a hard coat layer using a slot die coater while controlling the flow rate so that the thickness after drying was 5 μm. Dry at 1 ° C. for 1 minute to remove the solvent. Next, the film coated with the hard coat layer was irradiated with 300 mJ / cm ² of ultraviolet light using a high pressure mercury lamp to obtain an optical polyester film on which the hard coat layer was laminated.

(Example 15-3)
On the biaxially oriented polyester film obtained in Example 15, the above-mentioned coating solution for forming an antiglare layer was applied using a slot die coater and dried at 100 ° C. for 1 minute to remove the solvent. Next, the film coated with the antiglare layer was irradiated with 300 mJ / cm ² of ultraviolet light using a high pressure mercury lamp to obtain an optical polyester film in which a hard coat layer having a thickness of 5 μm was laminated.

(Comparative Example 1)
A biaxially oriented polyester film having a thickness of 30 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Comparative Example 2)
A biaxially oriented polyester film having a thickness of 30 μm was obtained in the same manner as in Example 3 except that the heat treatment temperature was changed as shown in the table.

(Comparative Example 3)
Except for changing the composition, magnification, and heat treatment temperature with a single film configuration of only the extruder B layer, an attempt was made to obtain a biaxially oriented polyester film having a thickness of 30 μm in the same manner as in Example 3. Film tearing occurred frequently during transverse stretching, and it was difficult to collect the film.

  The present invention relates to a polyester film that is particularly suitable for optical use (polarizer protection, transparent conductive film, etc.), and does not exhibit an interference color when mounted on a display device such as a liquid crystal display, and is heated. Since it is excellent in dimensional stability at the time and whitening resistance, it is preferably used as a polarizing plate by being bonded to a PVA sheet (polarizer) prepared by incorporating iodine in PVA and aligning it.

DESCRIPTION OF SYMBOLS 1 Light beam irradiation apparatus 2 Light beam incident direction 3 Light receiver

Claims (8)

A polyester A layer in which 50 mol% or more and less than 95 mol% of the dicarboxylic acid component is a terephthalic acid component, and 5 mol% or more and less than 50 mol% is another dicarboxylic acid component;
The peak temperature of the loss tangent (tan δ) measured by the dynamic viscoelasticity measuring device in the direction X and the direction Y is 60 when any one direction in the film plane is the direction X and the direction orthogonal to the direction X is the direction Y. An optical polyester film having a temperature of not lower than 115 ° C and not higher than 115 ° C. The optical polyester film according to claim 1, wherein 60 mol% or more and less than 82 mol% of the dicarboxylic acid component of the polyester A layer is a terephthalic acid component, and 18 mol% or more and less than 40 mol% is another dicarboxylic acid component. The optical polyester film according to claim 1 or 2, wherein the other dicarboxylic acid component is an isophthalic acid component. The optical polyester film according to any one of claims 1 to 3, wherein a retardation with respect to an angle inclined by 50 ° with respect to a plane perpendicular to the light incident direction is 1500 nm or less. One or more functions selected from the group consisting of hard coat properties, self-healing properties, antiglare properties, antireflection properties, low reflection properties, and antistatic properties are provided on at least one outermost surface of the optical polyester film. The optical polyester film according to claim 1, wherein the surface layer to be shown is laminated.
  The optical polyester film according to claim 1, which is used for protecting a polarizer. The polarizing plate which has a polarizer protective film on both surfaces of a polarizer, Comprising: The polarizer protective film of the at least one surface is a polarizing plate polyester film for polarizer protection of Claim 6. A transparent conductive film comprising the polyester film according to claim 1.

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