WO2016147767A1 - Polyester film for optical use and polarizing plate using same - Google Patents

Abstract

[Problem] The purpose of the present invention is to provide a polyester film that can, although being a biaxially-drawn polyester film, suppress interference colors when the polyester film is installed in a display such as a liquid crystal display and when the display is visually observed, and that is superior in whitening resistance and dimensional stability when being heated. [Solution] A polyester film, for optical use, of which retardation at a 50° tilt angle with respect to the film surface is not larger than 1500 nm, and of which heat of crystallization for temperature-rise (ΔHc) measured by differential scanning calorimetry (DSC) is not more than 15 J/g.

Description

Optical polyester film and polarizing plate using the same

The present invention relates to an optical polyester film and a polarizing plate.

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 particular, in recent years, demand for various optical films such as a polarizer protective film and a transparent conductive film has been increasing in the flat panel display and touch panel fields. Among them, the conventional TAC is used for the purpose of reducing the cost for the polarizer protective film application. Replacement of a (triacetylcellulose) film with a biaxially oriented polyester film has been studied. The biaxially oriented polyester film causes interference color when assembled as a liquid crystal display due to the orientation of the polymer at the time of stretching, so molecular orientation is required to suppress the interference color when viewing the display. Examination (for example, patent documents 1 and 2) etc. which make it a specific range is performed.

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

Moreover, in order to suppress the interference color when viewing the display from an oblique direction, a method of reducing the biaxial orientation of the film by adjusting the polymer composition and manufacturing conditions can be considered, Since the formation of oriented crystals by stretching becomes insufficient, defects such as an increase in the heat shrinkage rate and whitening during heating were observed, which were not practical.

JP 2011-252048 A JP 2014-66942 A

Therefore, in the present invention, the above-described drawbacks are eliminated, and when the film is mounted on a display device such as a liquid crystal display while being a biaxially stretched polyester film, the interference color when the display is visually observed can be suppressed, and the resistance during heating can be suppressed. It aims at providing the polyester film which is excellent in whitening property.

The present invention for solving the above problems has the following configuration.
(1) The retardation with respect to the angle inclined by 50 ° with respect to the film surface is 1500 nm or less,
An optical polyester film having a temperature rising crystallization calorie (ΔHc) of 15 J / g or less by differential scanning calorimetry (DSC).
(2) The optical polyester film according to (1), wherein the rigid amorphous amount by a temperature modulation differential scanning calorimeter (m-DSC) is 20% or more and 30% or less.
(3) The polyester film for optics according to (1) or (2), wherein the temperature rising crystallization heat (ΔHc2) at 2ndRun by a differential scanning calorimeter (DSC) is 5 J / g or more and 30 J / g or less.
(4) 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 on at least one outermost surface of the polyester film The optical polyester film as set forth in any one of (1) to (3), wherein layers showing the above are laminated.
(5) A laminate obtained by laminating a film having an in-plane retardation of 500 nm or less on at least one surface of the optical polyester film according to any one of (1) to (4).
(6) The optical polyester according to any one of (1) to (4), wherein the polarizer has a polarizer protective film on at least one side of the polarizer, and the polarizer protective film on at least one side is A polarizing plate that is a film.

The optical polyester film of the present invention does not exhibit an interference color when mounted on a display device such as a liquid crystal display, and is excellent in resistance to whitening during heating. Therefore, particularly when used for polarizer protection and touch panel applications. In addition, there is an effect that enables high-quality display.

Hereinafter, the optical polyester film of the present invention will be described in detail.

The optical polyester film of the present invention needs to have a retardation of 1500 nm or less with respect to an angle inclined by 50 ° with respect to the film surface. When the retardation with respect to the angle inclined by 50 ° with respect to the film surface is set to 1500 nm or less, the interference color when viewed from an oblique direction can be suppressed when mounted on a display device such as a liquid crystal display.

Here, the angle inclined by 50 ° with respect to the film surface refers to an angle defined in a phase difference measuring device such as “KOBRA” series manufactured by Oji Scientific Instruments Co., Ltd. When the angle of the stage of the measurement sample that is perpendicularly incident on the film is set to 0 °, the angle is obtained by tilting and rotating the 50 ° stage.

The retardation with respect to an angle inclined by 50 ° with respect to the film surface is preferably 1000 nm or less, more preferably 700 nm or less, and particularly preferably 600 nm or less, from the viewpoint of further suppressing the interference color when viewed from an oblique direction. . Further, the retardation with respect to the angle inclined by 50 ° with respect to the film surface is preferably as low as possible from the viewpoint of suppressing the interference color in the oblique direction, but 1 nm or more is preferable from the viewpoint of dimensional stability during heating and whitening resistance. preferable.

As a specific method for setting the retardation with respect to an angle inclined by 50 ° with respect to the film surface to 1500 nm or less, two or more dicarboxylic acid components of the polyester constituting the polyester film of the present invention are used, and the biaxial orientation of the polyester film is set. A method of reducing, a method of reducing the biaxial orientation of the polyester film by adjusting the production conditions, such as setting the draw ratio low or raising the drawing temperature, a method of reducing the film thickness, a polyester layer having a different melting point In the case of a laminated structure having at least two layers, a method of increasing the thickness ratio of the layer having a low melting point may be mentioned.

The optical polyester film of the present invention needs to have a heat-up crystallization heat (ΔHc) of 15 J / g or less by differential scanning calorimetry (DSC). If the temperature rising crystallization heat (ΔHc) by differential scanning calorimetry (DSC) is 15 J / g or less, the polyester film has been sufficiently crystallized, and when the optical polyester film of the present invention is heated, Dimensional stability and whitening resistance are improved. From the viewpoint of dimensional stability during heating and whitening resistance, the temperature rising crystallization calorie (ΔHc) by differential scanning calorimetry (DSC) is more preferably 10 J / g or less, most preferably 5 J / g or less. preferable.

Here, the temperature rising crystallization calorie (ΔHc) by differential scanning calorimetry (DSC) is the crystallization phenomenon when measuring at a heating rate of 20 ° C./min using a differential scanning calorimeter (DSC). In the case where there are a plurality of temperature rising crystallization peaks, the amount of heat at the temperature at which the absolute value of the heat flow is the largest is defined as the temperature rising crystallization heat amount (ΔHc) in the present invention.
Polyester film is biaxially oriented, and orientational crystallization proceeds, and dimensional stability during heating and whitening resistance are improved. The retardation with respect to the angle is increased, and when used for optical applications, particularly for touch panel applications and polarizer protection applications, an interference color is exhibited and the appearance is deteriorated. On the other hand, in order to reduce the interference color, it is necessary to reduce the biaxial orientation of the polyester film if the surface orientation is to be lowered. Since it becomes insufficient, it has been difficult to control the temperature rising crystallization heat (ΔHc) by differential scanning calorimetry (DSC) to 15 J / g or less.

In order to reduce the interference color, the optical polyester film of the present invention maintains low retardation with respect to an angle inclined by 50 ° with respect to the film surface, in order to achieve both dimensional stability during heating and whitening resistance. It is important that the temperature rise crystallization heat (ΔHc) by differential scanning calorimetry (DSC) of the polyester raw material used when forming the polyester film is 15 J / g or less.

The optical polyester film of the present invention preferably has a heat of crystal fusion (ΔHm) of 25 J / g or more by differential scanning calorimetry (DSC) from the viewpoint of dimensional stability and whitening resistance. More preferably, the heat of crystal fusion (ΔHm) by differential scanning calorimetry (DSC) is 30 J / g or more, and most preferably 35 J / g or more and 50 J / g or less. If the heat of crystal fusion (ΔHm) is 25 J / g or more, the polyester film is sufficiently crystallized and its crystallinity is very high, so that the dimensional stability and whitening resistance are improved. . Here, the crystal melting calorie (ΔHm) by differential scanning calorimetry (DSC) is expressed by the crystal melting phenomenon when measured at a heating rate of 20 ° C./min using a differential scanning calorimeter (DSC). In the case where there are a plurality of differential scanning calorimetry (DSC) crystal melting peaks, the total calorific value is defined as the crystal melting calorie in the present invention.
Furthermore, in order to improve dimensional stability and whitening resistance, the optical polyester film of the present invention has a temperature rising crystallization heat (ΔHc2) at 2ndRun by a differential scanning calorimeter (DSC) of 5 J / g or more and 30 J / g or less. It is preferable that If the temperature rising crystallization heat (ΔHc2) at 2ndRun by differential scanning calorimeter (DSC) is 5 J / g or more and 30 J / g or less, crystallinity can be sufficiently secured as a polyester resin constituting the polyester film, and It becomes easy to control the retardation with respect to the angle inclined by 50 ° with respect to the film surface. For example, when the polyester film has at least two layers having a polyester A layer and a polyester B layer having a melting point lower than that of the polyester A layer, the crystallinity of the polyester B layer is lowered and the film surface is inclined by 50 °. If the retardation with respect to the angle is controlled to be low, it is preferable to achieve both dimensional stability and whitening resistance by increasing the crystallinity of the polyester A layer, and the temperature rise at 2ndRun with a differential scanning calorimeter (DSC) By designing the resin so that the heat of crystallization (ΔHc2) is 5 J / g or more and 30 J / g or less, it is possible to achieve a reduction in interference color, dimensional stability, and whitening resistance at a higher level. . The temperature rising crystallization heat amount (ΔHc2) at 2ndRun by a differential scanning calorimeter (DSC) is more preferably 10 J / g or more and 30 J / g or less, and most preferably 15 J / g or more and 25 J / g or less. Here, the temperature rising crystallization calorie (ΔHc2) in 2ndRun by differential scanning calorimetry (DSC) is a temperature rising to 300 ° C. at a temperature rising rate of 20 ° C./min using a differential scanning calorimeter (DSC). This is an exothermic peak calorific value that appears in the crystallization phenomenon when the temperature is raised again from 25 ° C. at a rate of temperature increase of 20 ° C./min. In the case where there are a plurality of nuclei, the total calorific value is defined as the temperature-rise crystallization calorie (ΔHc2) in the present invention.

The optical polyester film of the present invention has both a retardation of 1500 nm or less with respect to an angle inclined by 50 ° with respect to the film surface and a temperature rising crystallization heat amount (ΔHc) by differential scanning calorimetry (DSC) of 15 J / g or less. In addition, it is preferable to have at least two layers having a polyester A layer and a polyester B layer having a melting point lower than that of the polyester A layer. By setting it as a laminated structure, the design which controls the retardation of a polyester B layer low and provides a handleability with a polyester A layer, for example becomes possible.

As long as the optical polyester film of the present invention has at least two layers, the number of layers and the layer structure are not particularly limited. However, from the viewpoint of curling of the film, reduction of warpage, and handling properties, A layer / B layer / A A configuration in which the film is symmetrical with respect to the thickness direction, and the both surface layers are polyester A layers, such as a layer, A layer / B layer / A layer / B layer / A layer, is preferable.

As a method for lowering the melting point of the polyester B layer than that of the polyester A layer, a method of lowering the melting point of the polyester resin constituting the polyester B layer can be mentioned. As a specific method, the method is derived from the diol constituting the polyester B layer. A method of increasing the other components with respect to the most numerous components among the diol component which is a structural unit of the dicarboxylic acid component and the dicarboxylic acid component which is the structural unit derived from the dicarboxylic acid constituting the B layer.

For example, in the case where the structural unit derived from ethylene glycol is the most as the structural unit derived from diol constituting the B layer, and the most terephthalic acid is included as the structural unit derived from dicarboxylic acid, the proportion of diol components other than ethylene glycol, The melting point of the polyester B layer can be lowered by increasing the proportion of the dicarboxylic acid component other than the acid.

Here, as diol components other than ethylene glycol, for example, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5- Pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis ( 4-hydroxyethoxyphenyl) propane, isosorbate, spiroglycol and the like. Of 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 addition to ethylene glycol.
Among them, from the viewpoint of reducing retardation for an angle inclined by 50 ° with respect to the film surface and suppressing interference color when viewed from an oblique direction, 1,4-cyclohexanedimethanol, neopentyl glycol, isosorbate, spiroglycol Is preferred.

Examples of dicarboxylic acid components other than terephthalic acid include, for example, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-diphenyl. Dicarboxylic acids, 4,4'-diphenyl ether dicarboxylic acids, aromatic dicarboxylic acids such as 4,4'-diphenylsulfone dicarboxylic acid, fats such as adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid An aromatic dicarboxylic acid, various aromatic dicarboxylic acids, and ester derivatives with aliphatic dicarboxylic acids.

Among them, isophthalic acid and 2,6-naphthalenedicarboxylic acid are preferable from the viewpoint of reducing retardation with respect to an angle inclined by 50 ° with respect to the film surface and suppressing interference color when viewed from an oblique direction.

In the polyester B layer constituting the optical polyester film of the present invention, 60 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 40 mol% is another dicarboxylic acid component. preferable. When 95 mol% or more of the dicarboxylic acid component is a terephthalic acid component and less than 5% is another dicarboxylic acid component, the retardation with respect to an angle inclined by 50 ° with respect to the film surface is increased, and interference when viewed from an oblique direction. Color may occur. Further, when less than 60 mol% of the dicarboxylic acid component is a terephthalic component and 40 mol% or more is another dicarboxylic acid component, the crystallinity of the polyester is lowered, resulting in increased thickness unevenness during production, or during polarizing plate production. In some cases, cracks at the edges and cracks at the edge portions are likely to occur. From the viewpoint of coexistence of interference color suppression when viewed from an oblique direction and handleability during processing, the polyester B layer has a terephthalic acid component of 84 mol% or more and less than 92 mol% of the dicarboxylic acid component, and 8 mol% or more and 16 mol%. It is preferable that less than mol% is other dicarboxylic acid components.

That is, in the polyester B layer in the present invention, 84 to 92 mol% of the dicarboxylic acid component is terephthalic acid component, and 8 to 16 mol% is diphthalic acid component other than terephthalic acid and / or isophthalic acid and / or It is a particularly preferable embodiment that 2,6-naphthalenedicarboxylic acid is contained in an amount of 8 mol% or more and less than 16 mol%.

The optical polyester film of the present invention has both a retardation of 1500 nm or less with respect to an angle inclined by 50 ° with respect to the film surface and a temperature rising crystallization heat amount (ΔHc) by differential scanning calorimetry (DSC) of 15 J / g or less. In addition, there is a method in which the heat treatment temperature after stretching during film production is set in the range from the melting point of -5 ° C. to the melting point of the polyester layer having the lowest melting point, and the oriented crystals remain without melting. Further, in order to control the retardation with respect to the angle inclined by 50 ° with respect to the film surface as low as 1500 nm or less, it is preferable to increase the heat treatment time, but on the other hand, the temperature rising crystallization heat by differential scanning calorimetry (DSC) In order to maintain high crystallinity (ΔHc) of 15 J / g or less, it is preferable that the heat treatment time near the melting point is short. For this reason, as a heat treatment condition, a method of increasing the heat treatment temperature stepwise is also very effective. In this case, the temperature of the first stage of the heat treatment is the melting point of the polyester layer with the lowest melting point—80 ° C. to melting point—30 ° C. (the polyester layer with the lowest melting point has low crystallinity. If the measurement is difficult, for example, 120 ° C. to 170 ° C., and the temperature of the second stage of the heat treatment is in the range of -5 ° C. to −1 ° C. of the polyester layer with the lowest melting point (the crystal of the polyester layer with the lowest melting point) When the melting point is difficult to measure by ordinary differential scanning calorimeter measurement, it is preferably set to 200 ° C. or less.

Further, in the optical polyester film of the present invention, a retardation of 1500 nm or less with respect to an angle inclined by 50 ° with respect to the film surface and a temperature rising crystallization heat (ΔHc) by differential scanning calorimetry (DSC) of 15 J / g or less are compatible. In order to increase the crystallization speed, the dicarboxylic acid component of the polyester B layer should be 84 to 92 mol% terephthalic acid, and 8 to 16 mol% dicarboxylic acid component other than terephthalic acid. preferable. Specifically, it is preferable to control the temperature of the crystallization temperature (Tcr) to 170 ° C. or less by controlling the catalyst type and the amount of the polyester raw material used for the production of the film. Furthermore, the amount of diethylene glycol in the polyester raw material is preferably 1.2 mol% or less, more preferably 0.8 mol% or more and 1.2 mol% or less.

The optical polyester film of the present invention preferably has a rigid amorphous amount of 20% or more and 30% or less by a temperature modulation differential scanning calorimeter (m-DSC). By setting the rigid amorphous amount to 20% or more and 30% or less, it becomes possible to achieve both dimensional stability and whitening resistance during high-temperature heating while suppressing interference colors when viewed from an oblique direction. From the viewpoint of dimensional stability and whitening resistance during high-temperature heating, the rigid amorphous amount is more preferably 25% or more and 30% or less.

In the optical polyester film of the present invention, as a method for setting the rigid amorphous amount by a temperature modulation differential scanning calorimeter (m-DSC) to 20% or more and 30% or less, there is a method of increasing the draw ratio during biaxial stretching. Preferably used. The optical polyester film of the present invention preferably has a polyester B layer in which 80 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 20 mol% is another dicarboxylic acid component. However, as the structure, by increasing the draw ratio, the amount of rigid amorphous can be controlled to 20% or more and 30% or less, and the dimensional stability and whitening resistance particularly at high temperature heating are improved. The specific draw ratio is preferably 13 times or more in terms of surface magnification, and particularly preferably the draw ratio in the width direction is 3.7 times or more.

In addition, the optical polyester film of the present invention has a hard coat property, self-healing property, antiglare property, and antireflection property on at least one outermost surface in order to provide process stabilization in the production process and durability in the use environment. It is preferable to have a surface layer exhibiting 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, more preferably 50 nm to 20 μm. If it is thinner than this, the effect is insufficient, and if it is thicker, there is a possibility of adversely affecting optical performance and the like.

Here, the hard coat property is a function of making the surface hard to be damaged by increasing the hardness of the surface. Its function is preferably HB or higher, more preferably 2H or higher, or # 0000 steel wool as evaluated 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 that makes it difficult to be damaged by repairing the wound 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 from 2 to 50%, more preferably from 2 to 40%, particularly preferably from 2 to 30%, based on the evaluation based on the method for obtaining haze described in JIS K-7136-2000. It is.

Anti-reflective properties and low-reflective properties are functions that improve visibility by reducing the reflectance at the surface due to light interference effects. Its function is preferably 2% or less, particularly preferably 1% or less, by reflectance spectroscopy measurement.

UV blocking property is a function of improving light resistance by selectively blocking the wavelength in the ultraviolet region (wavelength 200 to 400 nm). There is no problem in either the method of reflecting the ultraviolet ray or the method of absorbing the ultraviolet ray as a method for expressing the ultraviolet blocking property, and as its function, the transmittance at a wavelength of 380 nm is preferably 30% or less, more preferably 25. % Or less, particularly preferably 0.1% or more and 20% or less.

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 and polyfunctional monomers such as styrene and N-vinylpyrrolidone such as trimethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) a Contains relate, 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. The addition amount of the photopolymerization initiator is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the electron beam ultraviolet curable resin.

The method for curing the coating film is not particularly limited, but is preferably performed 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.

A siloxane-based thermosetting resin is also useful as a resin for the hard coat layer, and can be produced by hydrolyzing and condensing a single or two or more organosilane compounds in the presence of 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 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 with respect to the resin, and more preferably 2 to 30% by weight.

The film thickness of the antiglare layer is preferably 0.5 μm to 20 μm, more preferably 1 μm to 20 μm, and even more preferably 1 μm to 10 μm.
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, JP-A-2011-81217, JP-A-20102010. -204479, JP-A 2010-181898, JP-A 2011-197329, JP-A 2011-197330, JP-A 2011-215393, and the like can also be suitably used.

The surface layer may contain other components in addition to those described above as long as they do not lose the effects of the invention. 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.

Next, a preferred method for producing the optical polyester film of the present invention will be described below. The present invention should not be construed as being limited to such examples.

First, the polyester raw material is supplied to a vent type twin screw extruder and melt extruded. When laminating the polyester A layer and the polyester B layer having a melting point lower than that of the polyester A layer, the polyester A used for the polyester A layer and the polyester B used for the polyester B layer are respectively supplied to separate vent type twin screw extruders. Melt extrusion. In this case, the polyester resin used for the polyester B layer is 84 mol% or more and less than 92 mol% of the dicarboxylic acid component is terephthalic acid, and 8 mol% or more and less than 16 mol% is a dicarboxylic acid component other than terephthalic acid. The warm crystallization temperature (Tcr) is preferably 170 ° C. or less, and the diethylene glycol amount is preferably 1.2 mol% or less. Hereinafter, the polyester A layer and the polyester B layer having a melting point lower than that of the polyester A layer will be described. At this time, it is preferable to control the resin temperature to 250 ° C. to 275 ° 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, Adhere the extruded polymer from the glass transition point to (glass transition point-20 ° C), or a combination of these methods, the sheet polymer is brought into close contact with the casting drum, cooled and solidified, 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 stretching ratio in such a stretching method, preferably 2.8 times or more and 3.5 times or less is employed 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 85 ° C. or higher and 100 ° C. or lower, and it is preferable to preheat at 80 ° C. or higher for 1 second or longer before stretching. The stretching ratio in the width direction is preferably 3.7 times or more and 4.5 times or less, more preferably 3.8 times or more and 4.2 times or less, and the stretching ratio in the longitudinal direction and the width direction is multiplied. The surface magnification is preferably 13 times or more. The stretching speed in the width direction is desirably 1,000% / min or more and 200,000% / min or less.

Furthermore, the film is heat-treated after biaxial stretching. 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.

The optical polyester film of the present invention has a retardation with respect to an angle inclined by 50 ° with respect to the film surface of 1500 nm or less, and a temperature rising crystallization heat (ΔHc) by differential scanning calorimetry (DSC) of 15 J / g or less. In addition, the first heat treatment temperature is the melting point of the polyester B layer −80 ° C. to the melting point −30 ° C. (If the polyester B layer has low crystallinity and it is difficult to measure the melting point by ordinary differential scanning calorimetry, For example, the temperature of the second stage of heat setting is in the range of the melting point of the polyester B layer from -5 ° C. to the melting point of −1 ° C. (The crystallinity of the polyester B layer is low. When it is difficult to measure the melting point, for example, it is preferably set to 200 ° C. or lower.

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 between the polarizer and various functional layers, at least one surface can be subjected to corona treatment or an easy-adhesion layer can be coated. 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. Further, off-annealing at 90 to 200 ° C. is also preferably used.

In the optical polyester film of the present invention, a surface layer is provided on the outermost surface in order to impart functions such as hard coat properties, self-repair properties, antiglare properties, antireflection properties, low reflection properties, ultraviolet ray blocking properties, and antistatic properties. In the case of laminating, it is preferable to use a production method in which the above-mentioned coating composition is formed by coating-drying-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 or a die coating method (US Pat. No. 2,681,294). 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 drying process is accompanied by heating of the liquid film. 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, a further curing operation (curing step) by irradiating heat or energy rays may be performed. 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. When UV curing is performed using a high-pressure mercury lamp that is a discharge lamp method, the illuminance of UV is 100 to 3,000 mW / cm ² , preferably 200 to 2,000 mW / cm ² , more preferably 300 to 1,500 mW / cm ^2. It is preferable to perform ultraviolet irradiation under the following conditions: the condition that the cumulative amount of ultraviolet light is 100 to 3,000 mJ / cm ² , preferably 200 to 2,000 mJ / cm ² , more preferably 300 to 1,500 mJ / cm ^2. 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.
In the optical polyester film of the present invention, the retardation with respect to an angle inclined by 50 ° with respect to the film surface is 1500 nm or less, and the temperature rising crystallization heat (ΔHc) by differential scanning calorimetry (DSC) is 15 J / g or less. Therefore, when mounted on a display device such as a liquid crystal display, interference color when viewed from an oblique direction can be suppressed, and dimensional stability during heating and whitening resistance are excellent, so that in-plane retardation is 500 nm or less. It is preferable to be used by being laminated on a low retardation film. By being laminated on a low retardation film having an in-plane retardation of 500 nm or less, an interference color reducing effect as a laminate is exhibited. Specifically, it is a method for laminating as a protective film for a cyclic olefin film, an acrylic film, a TAC (triacetyl cellulose) film, which is an optical film having a low in-plane retardation, and various coating layers having a low in-plane retardation. And a method used as a support for the above.
In addition, the optical polyester film of the present invention has a retardation with respect to an angle inclined by 50 ° with respect to the film surface of 1500 nm or less, and a temperature-programmed crystallization heat (ΔHc) by differential scanning calorimetry (DSC) of 15 J / g or less. Therefore, when mounted on a display device such as a liquid crystal display, interference colors when viewed from an oblique direction can be suppressed, and since dimensional stability during heating and whitening resistance are excellent, iodine in PVA It is preferably used as a polarizing plate by being bonded to a PVA sheet (polarizer) prepared by containing and aligning.

In the polarizing plate of the present invention, the optical polyester film is preferably used as a polarizer protective film on at least one surface. The other polarizer protective film may be the polarizer protective polyester film of the present invention, or a film having no birefringence such as a triacetyl cellulose film, an acrylic film, or a norbornene-based 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 it is preferable to bond the polarizer protective film via an adhesive from the viewpoint of improving 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 stretching 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 characteristics measurement method and effect evaluation method in the present invention are as follows.

(1) Composition of polyester The polyester resin and film were dissolved in hexafluoroisopropanol (HFIP), and the content of each monomer residue component and by-product diethylene glycol was quantified using ¹ H-NMR and ¹³ C-NMR. In the case of a laminated film, each layer of the film was scraped off in accordance with the laminated thickness to collect and evaluate the components constituting each single layer. 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 was 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) Temperature rising crystallization temperature, temperature rising crystallization calorie, melting point, crystal melting calorie, differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., RDC220), conforming to JIS K-7121-1987 and JIS K-7122-1987 Then, measurement and analysis were performed. The polyester film was measured using a 5 mg film sample, and the temperature at the top of the exothermic 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 temperature rise crystallization temperature (Tc). The amount of heat per unit mass obtained from the exothermic peak area was defined as the heat-up crystallization heat amount (ΔHc). Further, the temperature at the apex of the endothermic peak obtained from the DSC curve was defined as the melting point, and the amount of heat per unit mass obtained from the endothermic peak area was defined as the heat of crystal melting (ΔHm). Further, after heating to 300 ° C., holding for 5 minutes, then rapidly cooling to 25 ° C., holding for 5 minutes, and then generating heat due to crystallization phenomenon when the temperature is raised again from 25 ° C. at a heating rate of 20 ° C./min. The temperature at the peak apex was defined as the temperature rising crystallization temperature (Tc2), and the amount of heat per unit mass obtained from the exothermic peak area was defined as the temperature rising crystallization heat (ΔHc2). 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), each layer was scraped off with a cutter and the melting point of each layer was measured, and the higher melting point layer was designated as the polyester A layer, and the lower layer was designated as the polyester B layer. When the melting point is not observed, “ND” is indicated in the table. Further, regarding the measurement of the polyester resin raw material, in order to remove the influence of crystallization during pelletizing, the sample was heated from 25 ° C. to 300 ° C. at 20 ° C./min, and then the sample was held at 300 ° C. for 5 minutes, and then 25 ° C. The sample was taken out under an atmosphere and rapidly cooled to an amorphous state. After storage at 25 ° C. for 5 minutes, the temperature at the top of the exothermic peak when the temperature was raised from 25 ° C. to 300 ° C. at 2 ° Run as 2nd Run was defined as the temperature rise crystallization temperature (Tc) of 2nd Run. In the present invention, when there are a plurality of temperature rising crystallization peaks of the film, temperature rising crystallization peaks of the polyester resin raw material, and melting peaks, the temperature with the highest absolute value of the heat flow is adopted, and the melting peak of the film, 2ndRun As for the temperature rising crystallization peak of the film, the total amount of heat was adopted.

(5) Retardation for an angle inclined by 50 ° with respect to the film surface (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. Set the measurement conditions so that measurement is performed with the angle of the stage tilted 50 °, and the phase difference (retardation) is obtained when the angle of the stage of the measurement sample in the state where the light beam is perpendicularly incident on the film is 0 °. It was.

(6) Rigid amorphous amount Measured with Q100 manufactured by TA Instruments. A film sample of 5 mg was held at 0 ° C. for 5 minutes in a nitrogen atmosphere and then 10 ° C./min. It measured to 300 degreeC with the temperature increase rate of. From this DSC curve, the temperature of the extreme point (minimum point or maximum point depending on how to determine the sign) was taken as the melting point, and the peak area was taken as the heat of fusion. In addition, 2 ° C./min. From 0 ° C. to 150 ° C. using the temperature modulation DSC method. Temperature rise rate, temperature modulation amplitude ± 1 ° C., temperature modulation period 60 seconds. Find the specific heat difference at the glass transition temperature, as below, to determine the crystallinity, the amount of movable amorphous,
Crystallinity (%) = (heat of fusion) / (theoretical value of heat of fusion of polyester complete crystal) × 100
Movable amorphous amount (%) = (specific heat difference) / (theoretical value of specific heat difference of polyester completely amorphous) × 100
The rigid amorphous amount was calculated from the following formula.
Rigid amorphous amount (%) = 100− (crystallinity + movable amorphous amount).
Indium was used for temperature and calorie calibration, and sapphire was used for specific heat calibration.
(7) Visibility evaluation 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. When the prepared test piece and the polarizing plate with no film attached are placed on an LED light source (Tritech A3-101) in a crossed Nicol arrangement from an angle of 50 ° to the test piece plane The visibility of was confirmed. In the same manner, a test piece in which a 30 cm square film was bonded was prepared and evaluated in the same manner.
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.

(8) Heat resistance (i)
Film samples (100 mm × 100 mm square) and haze after heat treatment of the film samples at 120 ° C. for 1 hour are measured with a haze meter (HGM-2GP manufactured by Suga Test Instruments Co., Ltd.) based on JIS K 7105 (1985). Measurements were made and evaluated as follows. As a heat treatment method at 100 ° C. for 12 hours, a 100 mm × 100 mm square film sample is hung in a tree shape in a hot air oven at a temperature of 100 ° C. so as not to contact the top, bottom, left and right walls of the oven and stored for 12 hours. Carried out.
S: Δhaze value after heat treatment at 120 ° C. for 1 hour is less than 0.5%.
A: Δhaze value after heat treatment at 120 ° C. for 1 hour is 0.5% or more and less than 1%.
B: Δhaze value after heat treatment at 120 ° C. for 1 hour is 1% or more and less than 1.5%.
C: Δhaze value after heat treatment at 120 ° C. for 1 hour is 1.5% or more and less than 2%.
D: Δhaze value after heat treatment at 120 ° C. for 1 hour is 2% or more.
S to C are acceptable levels.

(9) Heat resistance (ii)
Film samples (100 mm × 100 mm square) and haze after heat treatment of the film samples at 150 ° C. for 1 hour were measured with a haze meter (HGM-2GP manufactured by Suga Test Instruments Co., Ltd.) based on JIS K 7105 (1985). Measurements were made and evaluated as follows. As a method of heat treatment at 150 ° C. for 1 hour, a 100 mm × 100 mm square film sample is suspended in a hot air oven at a temperature of 150 ° C. in a tree shape so as not to contact the top, bottom, left and right walls of the oven and stored for 1 hour. Carried out.
S: Δhaze value after heat treatment at 150 ° C. for 1 hour is less than 0.5%.
A: Δhaze value after heat treatment at 150 ° C. for 1 hour is 0.5% or more and less than 1%.
B: Δhaze value after heat treatment at 150 ° C. for 12 hours is 1% or more and less than 1.5%.
C: Δhaze value after heat treatment at 150 ° C. for 12 hours is 1.5% or more and less than 2%.
D: Δhaze value after heat treatment at 150 ° C. for 12 hours is 2% or more.

(10) Scratch resistance The test piece obtained in (7) 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: A flaw is not visually recognized.
B: A flaw is visually recognized.

(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)
Isophthalic acid copolymer polyethylene terephthalate resin (inherent viscosity 0.7, melting point 230 ° C., 90 mol% terephthalic acid component as dicarboxylic acid component, 10 mol% isophthalic acid component, and 100 mol% ethylene glycol component as glycol component) Temperature rising crystallization temperature (Tcr) 160 ° C., diethylene glycol (0.85 mol%)).

(Polyester C)
Isophthalic acid copolymer polyethylene terephthalate resin (inherent viscosity 0.7, melting point 230 ° C., 90 mol% terephthalic acid component as dicarboxylic acid component, 10 mol% isophthalic acid component, and 100 mol% ethylene glycol component as glycol component) Temperature rising crystallization temperature (Tcr) 172 ° C., diethylene glycol (1.25 mol%)).

(Polyester D)
Isophthalic acid copolymerized polyethylene terephthalate resin (inherent viscosity 0.7, melting point 230 ° C., 88 mol% dicarboxylic acid component, 12 mol% isophthalic acid component, and 100 mol% ethylene glycol component as glycol component) Temperature rising crystallization temperature (Tcr) 168 ° C., diethylene glycol (1.15 mol%)).
(Intrinsic viscosity 0.75).

(Polyester E)
An isophthalic acid copolymerized polyethylene terephthalate resin (inherent viscosity 0.7, melting point 225 ° C., 88 mol% terephthalic acid component as dicarboxylic acid component, 12 mol% isophthalic acid component, and 100 mol% ethylene glycol component as glycol component) Temperature rising crystallization temperature (Tcr) 178 ° C., diethylene glycol (1.3 mol%)).

(Polyester F)
Isophthalic acid copolymerized polyethylene terephthalate resin (inherent viscosity 0.7, melting point 212 ° C., 82 mol% terephthalic acid component as dicarboxylic acid component, 18 mol% isophthalic acid component, and 100 mol% ethylene glycol component as glycol component) Temperature rising crystallization temperature (Tcr) 185 ° C., diethylene glycol (1.0 mol%)).

(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%.

(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 were 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 was 280 ° C., and the B-layer extruder cylinder temperature was 265 Melt at ℃, and merge in feed block to form A layer / B layer / A layer, short tube temperature after merging is 270 ℃, die temperature is 275 ℃, T die is 25 ℃ The sheet was discharged in a sheet form on a temperature-controlled cooling drum. 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, preheating was performed for 1.5 seconds at a preheating temperature of 85 ° C. in the longitudinal direction, the film was stretched 3.3 times in the longitudinal direction at a stretching temperature of 90 ° C., and immediately cooled with a metal roll whose temperature was controlled at 40 ° C. Next, preheating is performed for 1.5 seconds at a preheating temperature of 85 ° C. with a tenter type horizontal stretching machine, and the film is stretched 3.5 times in the width direction at a stretching temperature of 120 ° C. The heat treatment was performed at a second-stage heat treatment temperature of 230 ° C., and under the second-stage heat treatment conditions, the heat treatment was performed while relaxing 5% in the width direction to obtain a biaxially oriented polyester film having a film thickness of 25 μm.

(Example 2)
A biaxially oriented polyester film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 3)
Example 1 except that the draw ratio in the longitudinal direction was 3.5 times, the draw ratio in the width direction was 3.8 times, the first stage heat treatment temperature was 190 ° C., and the second stage heat treatment temperature was 228 ° C. Thus, a biaxially oriented polyester film having a thickness of 25 μm was obtained.

Example 4
A biaxially oriented polyester film having a thickness of 25 μm was obtained in the same manner as in Example 3 except that the composition was as shown in the table and the first-stage heat treatment temperature was 180 ° C. and the second-stage heat treatment temperature was 223 ° C.

(Example 5)
A biaxially oriented polyester film having a thickness of 25 μm was obtained in the same manner as in Example 3 except that the composition was as shown in the table and the first stage heat treatment temperature was 180 ° C. and the second stage heat treatment temperature was 225 ° C.

(Example 6)
A biaxially oriented polyester film having a thickness of 25 μm was obtained in the same manner as in Example 3 except that the composition was as shown in the table and the first-stage heat treatment temperature was 180 ° C. and the second-stage heat treatment temperature was 223 ° C.

(Example 7)
A biaxially oriented polyester film having a thickness of 25 μm was obtained in the same manner as in Example 3 except that the composition was as shown in the table and the first-stage heat treatment temperature was 180 ° C. and the second-stage heat treatment temperature was 223 ° C.

(Example 8)
A biaxially oriented polyester film having a thickness of 20 μm was obtained in the same manner as in Example 3 except that the composition was as shown in the table and the first stage heat treatment temperature was 190 ° C. and the second stage heat treatment temperature was 223 ° C.

Example 9
A biaxially oriented polyester film having a film thickness of 40 μm was obtained in the same manner as in Example 8 except that the thickness of layer B was as shown in the table.

(Example 10)
A biaxially oriented polyester film having a thickness of 40 μm was obtained in the same manner as in Example 9 except that the composition was as shown in the table and the first stage heat treatment temperature was 200 ° C. and the second stage heat treatment temperature was 225 ° C. (Example 4-2)
The biaxially oriented polyester film obtained in Example 4 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 ultraviolet rays using a high-pressure mercury lamp to obtain a biaxially oriented polyester film on which the hard coat layer was laminated.

(Example 4-3)
On the biaxially oriented polyester film obtained in Example 4, 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 ultraviolet rays using a high pressure mercury lamp to obtain a biaxially oriented polyester film in which the antiglare layer having a thickness of 5 μm was laminated.

(Comparative Example 1)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Example 1 except that the first stage heat treatment temperature was 170 ° C. and the second stage heat treatment temperature was 210 ° C.

(Comparative Example 2)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Comparative Example 1 except that the composition was as shown in the table and the first-stage heat treatment temperature was 190 ° C. and the second-stage heat treatment temperature was 230 ° C.

(Comparative Example 3)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Comparative Example 1 except that the composition was as shown in the table and the first stage heat treatment temperature was 225 ° C. and the second stage heat treatment temperature was 225 ° C.

(Comparative Example 4)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Comparative Example 1 except that the composition was as shown in the table and the first-stage heat treatment temperature was 190 ° C. and the second-stage heat treatment temperature was 215 ° C.

(Comparative Example 5)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Comparative Example 3 except that the composition was as shown in the table and the first stage heat treatment temperature was 225 ° C. and the second stage heat treatment temperature was 230 ° C.

The present invention relates to an optical polyester film, and since the retardation with respect to an angle inclined by 50 ° with respect to the film surface is 1500 nm or less, it does not exhibit an interference color and is further increased by differential scanning calorimetry (DSC). Since the warm crystallization calorie (ΔHc) is 15 J / g or less, it is excellent in dimensional stability and whitening resistance during heating, and thus is preferably used for touch panel applications, polarizer protection applications, and the like.

Claims (6)

1. Retardation with respect to an angle inclined by 50 ° with respect to the film surface is 1500 nm or less,
   An optical polyester film having a temperature rising crystallization calorie (ΔHc) of 15 J / g or less by differential scanning calorimetry (DSC).
2. 2. The optical polyester film according to claim 1, wherein the rigid amorphous amount by a temperature modulation differential scanning calorimeter (m-DSC) is 20% or more and 30% or less.
3. 3. The optical polyester film according to claim 1, wherein a temperature rising crystallization heat amount (ΔHc2) at 2ndRun by a differential scanning calorimeter (DSC) is 5 J / g or more and 30 J / g or less.
4. On the outermost surface of at least one of the polyester films, at least one selected from the group consisting of hard coat properties, self-repair properties, antiglare properties, antireflection properties, low reflection properties, ultraviolet blocking properties, and antistatic properties The optical polyester film according to any one of claims 1 to 3, wherein a layer exhibiting a function is laminated.
5. A laminate in which a film having an in-plane retardation of 500 nm or less is laminated on at least one side of the optical polyester film according to any one of claims 1 to 4.
6. A polarizing plate comprising a polarizer protective film on at least one surface of a polarizer, wherein the polarizer protective film on at least one surface is the optical polyester film according to any one of claims 1 to 4. .