JP2017067822A - Optical polyester film and polarizing plate using the same, and transparent conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film that can suppress an interference color when mounted in a display device including a liquid crystal display, and from which an optical member, such as a polarizing plate and a transparent conductive film can be manufactured with high quality.SOLUTION: There is provided an optical polyester film in which: of the thermal shrinkage at 150°C respectively in a fast axis direction and a slow axis direction, the value of the higher one is 0.1% or more and 5% or less, and the in-plane phase difference of the film is 3000 nm or more and 30000 or less.SELECTED DRAWING: None

Description

  The present invention relates to a polyester film that is particularly suitable for use in optical applications (polarizer protection, transparent conductive film, etc.), and can suppress interference colors when mounted on a display device such as a liquid crystal display, and can be polarized. The present invention relates to a polyester film capable of improving the quality of an optical member such as a 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. 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.

  In addition, studies have been made to reduce the interference color (for example, Patent Documents 3 to 5) by strongly stretching the polyester film in one direction so that the phase difference is in a high specific range. In Patent Documents 3 to 5, although interference color is suppressed, since it is strongly stretched in one direction, the heat shrinkage rate and the balance of heat shrinkage rate are poor, and processing into a polarizing plate, a transparent conductive film, etc. In some cases, defects such as wrinkles and bubbles are likely to occur.

JP 2010-181870 A JP 2013-210598 A International Publication No. 2013-080948 JP 2010-277028 A JP 2011-53271 A

  Accordingly, the present invention provides a polyester film that eliminates the above-described drawbacks, can suppress interference colors when mounted on a display device such as a liquid crystal display, and can improve the quality of optical members such as polarizing plates. The purpose is to do.

The present invention for solving the above problems has the following configuration.
(1) Of the 150 ° C. heat shrinkage in each of the fast axis direction and the slow axis direction, S1 is a polyester film that satisfies the formula (I) when the high value is S1 and the low value is S2. An optical polyester film having an in-plane retardation of 3000 nm or more and 30000 nm or less.
0.1% ≦ S1 ≦ 5% (I)

(2) The optical polyester film according to (1), wherein S2 satisfies the formula (II).
0.1% ≦ S2 ≦ 5% (II)
(3) The optical polyester film according to (1) or (2), which satisfies the following formula (III):
1.05 ≦ S1 / S2 ≦ 4 (III)
(4) When the polyester constituting the film is composed of a dicarboxylic acid component and a diol component, and the total amount of the dicarboxylic acid component and the diol component is 100 mol%, among the most dicarboxylic acid components and the diol components The optical polyester film according to any one of (1) to (3), wherein the sum of the most numerous components is more than 85 mol% and less than 98 mol%.
(5) The polyester constituting the film is composed of a dicarboxylic acid component and a diol component, the most dicarboxylic acid component is terephthalic acid or naphthalene dicarboxylic acid, and the most diol component is ethylene glycol (1) to (4 The optical polyester film as described in any one of 1).
(6) A polyester B layer having a melting point of Tb (° C.) is laminated on at least one surface of a polyester A layer having a melting point of Ta (° C.), and Tb> Ta. The optical polyester film according to any one of (1) to (5).
(7) The optical polyester film according to any one of (1) to (6), which is for protecting a polarizer.
(8) A polarizing plate having a polarizer protective film on both sides of the polarizer, wherein at least one of the polarizer protective films is the optical polyester film according to (7).
(9) A transparent conductive film having the polyester film according to any one of (1) to (6).

  The optical polyester film of the present invention has an effect of enabling high-quality display capable of suppressing interference colors when mounted on a display device such as a liquid crystal display while improving the quality of an optical member such as a polarizing plate. .

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

In the polyester film of the present invention, among the heat shrinkage rates at 150 ° C. in each of the fast axis direction and the slow axis direction, when S1 is a high value and S2 is a low value, S1 satisfies the formula (I) This is very important. 0.1% ≦ S1 ≦ 5% (I)
By making the high value S1 out of the thermal shrinkage at 150 ° C. in each of the fast axis direction and the slow axis direction within the range of the formula (I), that is, 5% or less, for example, polarizing plate production for polarizer protection applications Lamination of a transparent conductive layer (for example, a process of laminating a polyester film of the present invention and a PVA sheet (polarizer) prepared by incorporating iodine in PVA) or the like (for example, In sputtering processing, coating, and the like, it is possible to suppress thermal deformation in the process, and to obtain an optical member (such as a polarizing plate and a transparent conductive film) with less wrinkles and good quality. Further, by setting the high value S1 of the thermal shrinkage at 150 ° C. in each of the fast axis direction and the slow axis direction to be within the range of the formula (I), that is, 0.1% or more, for example, for polarizer protection use In the production of a polarizing plate in (for example, a process of laminating the PVA sheet (polarizer) prepared by containing iodine in PVA and aligning the polyester film of the present invention) or transparent conductive film for transparent conductive film applications In layer lamination (sputtering, coating, etc.), at least one direction of the film is stretched in the process, so that the flatness of the film at the time of processing can be secured, and an optical member with good quality with few bubbles etc. (polarizing plate, transparent conductive material) For example, a conductive film.
Here, the fast axis direction is a direction in which the in-plane refractive index of the film is minimized, and the slow axis direction is a direction in which the in-plane refractive index of the film is maximized. The heat shrinkage rate in the present invention is a sample cut out into a rectangle of 70 mm × width 10 mm. Draw marked lines at intervals of 50 mm on the sample, place a 3 g weight in a hot air oven heated to 190 ° C for 30 minutes, measure the distance between marked lines after heat treatment, and measure the distance between marked lines before and after heating. From this change, the value is calculated as {(distance between marked lines before heat treatment) − (distance between marked lines after heat treatment)} / (distance between marked lines before heat treatment) × 100.

The optical polyester film of the present invention has a high value S1 of 0.2% or more of the thermal shrinkage rate at 150 ° C. in each of the fast axis direction and the slow axis direction from the viewpoint of improving the quality of the optical member. It is preferably 4% or less, more preferably 0.3% or more and 3% or less.
As a specific method for setting the high value S1 of the 150 ° C. heat shrinkage in each of the fast axis direction and the slow axis direction to 0.1% or more and 5% or less, the heat setting temperature after biaxial orientation is set to 170. Examples thereof include a method of performing 2 to 10% relaxation treatment at a temperature of not lower than ° C., a method of increasing the plane orientation by performing longitudinal stretching and / or lateral stretching again after biaxial stretching.

In the polyester film of the present invention, if the higher value S1 satisfies the formula (I) among the thermal shrinkage at 150 ° C. in each of the fast axis direction and the slow axis direction, the lower value S2 is the shrink direction. In the process, from the viewpoint of preventing loosening during polarizing plate production for polarizer protection or lamination of a transparent conductive layer (sputtering, coating, etc.) for use in a transparent conductive film. The film shrinks in both directions, that is, among the heat shrinkage rates at 150 ° C. in each of the fast axis direction and the slow axis direction, when S1 is a high value and S2 is a low value, S2 is (II It is preferable to satisfy the formula.
0.1% ≦ S2 ≦ 5% (II)
Since the refractive index is an index of the orientation of the polymer constituting the film and has a correlation with the mechanical characteristics, it can be considered that the difference in mechanical characteristics is the largest in the fast axis direction and the slow axis direction. Therefore, if the thermal contraction rate is in a specific range in each of the fast axis direction and the slow axis direction, the thermal contraction rate is considered to be in the same range in all directions in the plane of the film. Therefore, setting the mechanical characteristics in the fast axis direction and the slow axis direction within a specific range is effective as an index for confirming the physical properties in all directions of the film.
It is important that the in-plane retardation of the optical polyester film of the present invention is 3000 nm or more and 30000 nm or less. By setting the in-plane phase difference to 3000 nm or more, interference colors can be suppressed when mounted on a display device such as a liquid crystal display. From the standpoint of interference color suppression, the higher the in-plane retardation is, the better, but from the viewpoint of improving the balance between the thermal shrinkage rates of the fast axis and the slow axis and preventing the film from becoming excessively thick. 30000 nm or less is important.
Here, the in-plane retardation refers to a product of the thickness and the birefringence (refractive index difference in the in-plane biaxial direction) by using an Abbe refractometer, the refractive index of any one direction of the film (n _a ), The refractive index (n _b ) in the direction orthogonal to the direction can be measured and calculated from the following formula.
In-plane retardation = | n _a −n _b | × film thickness (nm) (IV)
It is also possible to measure using a phase difference measuring device such as “KOBRA” series manufactured by Oji Scientific Instruments. The in-plane retardation of the present invention was calculated from the above formula (IV).
In the present invention, the in-plane retardation can be set to 3000 nm or more and 30000 nm or less depending on a birefringence control by adjusting a stretching method, a stretching ratio, stretching and heat treatment during film formation, and a thickness setting.

In the optical polyester film of the present invention, the in-plane retardation is preferably 3500 nm or more, more preferably 7000 nm or more, and particularly preferably 10,000 nm or more from the viewpoint of suppressing interference color when mounted on a display device. Further, from the viewpoint of improving the balance of mechanical properties, the in-plane retardation is preferably 21000 nm or less, more preferably 12000 nm or less, and particularly preferably 10,000 nm or less. .
As a specific method for setting the in-plane retardation to 3000 nm or more and 30000 nm or less, a polyester having moderate crystallinity is selected, and the polyester melted by an extruder is cooled by a rotating cast drum. The polyester sheet is stretched in two perpendicular directions in the plane, and the ratio of the stretch ratios in the two directions is set to 2 times or more, so that many polymers are oriented in one direction, and the refractive index in one direction is set to the other direction. The direction in which the refractive index is increased is increased.
In the present invention, it is not easy to simultaneously achieve the heat shrinkage rate and the in-plane phase difference. For example, in order to achieve the heat shrinkage rate in each of the fast axis direction and the slow axis direction, in-plane vertical 2 If both of the directions are stretched in a balanced manner, the orientation of the polymer becomes isotropic, and the in-plane retardation may be lowered. For this reason, it is usually difficult to achieve both thermal shrinkage and in-plane retardation, so as necessary, control of the crystallinity of the polymer, lamination structure of polymers having different properties, stretching ratio, stretching temperature, etc. By combining the manufacturing conditions and the like, it is possible to achieve both a thermal contraction rate and an in-plane retardation.
In the optical polyester film of the present invention, S1 and S2 are the following when S1 is a high value and S2 is a low value of the heat shrinkage at 150 ° C. in each of the fast axis direction and the slow axis direction: It is preferable to satisfy the formula III) from the viewpoint of further suppressing wrinkles and bubble generation of the optical member. 1.05 ≦ S1 / S2 ≦ 4 (III)
When S1 / S2 exceeds 4, thermal deformation in one direction increases, and even when the absolute values of S1 and S2 are small, fine wrinkles may occur when manufacturing an optical member. Further, when heat shrinkage occurs, if there is even a little anisotropy, bubbles are likely to escape in the deformation direction during processing into an optical member, but if S1 / S2 is less than 1.05, the tendency of shrinkage is very high. Since they are close to isotropic, even if the absolute values of S1 and S2 are small, fine bubbles may be generated when the optical member is manufactured.
From the viewpoint of suppressing deformation of wrinkles and bubbles generated during processing, S1 / S2 is more preferably 1.1 or more and 3.7 or less, and particularly preferably 1.5 or more and 3.5 or less.
As a method of controlling S1 / S2 within the range of the formula (III), from the viewpoint of uniformly eliminating the distortion after stretching of the film, the time for the film to cool to room temperature (25) after completion of the heat treatment step after stretching is 10 For example, a method of setting the film winding tension at the time of production to 20 mm or less by converting the film winding tension to 1000 mm width can be used.

In the optical polyester film of the present invention, the polyester constituting the film is composed of a dicarboxylic acid component and a diol component, and the most of the dicarboxylic acid components when the total amount of the dicarboxylic acid component and the diol component is 100 mol%. The sum of the most numerous components among the components and the diol component is more than 85 mol% and less than 98 mol% in that both the quality of optical members such as polarizing plates and transparent conductive films and interference color suppression can be achieved. preferable. When the total amount of the dicarboxylic acid component and the diol component is 100 mol%, the total of the most dicarboxylic acid component and the most diol component among the dicarboxylic acid components is a value exceeding 85 mol%. Shows moderate crystallinity, the polymer is oriented during stretching and the dimensional stability is improved. Further, when the total amount of the dicarboxylic acid component and the diol component is 100 mol%, the total of the most dicarboxylic acid component and the most diol component among the dicarboxylic acid components is less than 98 mol%. Crystallinity is suppressed, excessive orientation of the polymer in the in-plane direction when the film is stretched is suppressed, and the refractive index in the thickness direction is maintained even after stretching. This makes it possible to suppress interference colors when viewed from an oblique direction when mounted on a display device. In addition, when trying to make the thermal shrinkage ratio of the optical polyester film in a good range in both the fast axis and slow axis directions, for example, the ratio of longitudinal stretching and transverse stretching is made close so that the balance is as good as possible On the other hand, when trying to make the phase difference high and in a good range, for example, manufacturing conditions having different balance as much as possible by increasing the difference in magnification between the longitudinal stretching and the lateral stretching are preferable. To do. Here, when the total amount of the dicarboxylic acid component and the diol component is 100 mol%, the sum of the most dicarboxylic acid component and the most diol component is less than 98 mol%, and the crystallinity of the polymer By making the polymer in an appropriate range, the polymer is oriented in two directions of the film so that the heat shrinkage ratio is in a good range, and the crystallinity is lower than that of the homopolymer. Since the difference in ease increases, the in-plane refractive index difference between the direction with a small stretch ratio and the direction with a large stretch ratio increases, and the in-plane phase difference can be kept high.
When the total amount of the dicarboxylic acid component and the diol component is 100 mol%, the sum of the most abundant component of the dicarboxylic acid component and the most abundant component of the diol component is that of an optical member such as a polarizing plate or a transparent conductive film. From the viewpoint of achieving both quality and interference color suppression, it is more preferably more than 88 mol% and less than 97 mol%, particularly preferably more than 90 mol% and less than 96 mol%.
Among the polyesters used in the optical polyester film of the present invention, examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and 2,6. -Aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid, adipic acid, suberic acid, sebacic acid, dimer acid Aliphatic dicarboxylic acids such as dodecanedioic acid and cyclohexanedicarboxylic acid, and various aromatic dicarboxylic acids and ester derivatives with aliphatic dicarboxylic acids are preferably used. Among these, terephthalic acid and naphthalenedicarboxylic acid (1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, etc.) are used from the viewpoints of mechanical properties, optical properties, and productivity. Is more preferable.
Among the polyesters used in the optical polyester film of the present invention, examples of the diol component 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, Examples include polyalkylene glycol, 2,2-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. Among these, ethylene glycol is more preferable from the viewpoints of mechanical properties, optical properties, and productivity.

The polyester film for optics of the present invention is a polyester having at least two layers and a melting point of Ta (° C.) from the viewpoint of achieving both workability during production of a polarizing plate and a transparent conductive film and interference color suppression. It is preferable that a polyester B layer having a melting point of Tb (° C.) is laminated on at least one surface of the A layer and that Tb> Ta. By laminating layers with different melting points, for example, the crystal structure is maintained with a high melting point layer to improve workability, and the low melting point layer increases the refractive index difference in two directions during stretching to suppress interference color. It is possible to make it easy to achieve both functions such as improving the function. In addition, by stacking layers having different crystal states, it is possible to increase the difference in characteristics at the interface and to easily control the heat shrinkage rate.
From the viewpoint of workability and interference color suppression, Tb is preferably 5 ° C. higher than Ta. On the other hand, from the viewpoint of co-stretchability of the A layer and the B layer, Tb is preferably 15 ° C. or less higher than Ta.
As a specific method for satisfying Tb> Ta, when the total amount of the dicarboxylic acid component and the diol component is set to 100 mol% in the polyester constituting the A layer, compared to the polyester constituting the B layer, A method of reducing the crystallinity of the polyester and lowering the melting point by reducing the sum of the most abundant components of the acid components and the most abundant components of the diol components can be mentioned.
The layer structure of the optical polyester film of the present invention is 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 / The film is preferably symmetrical with respect to the thickness direction, such as B layer, B layer / A layer / B layer / A layer / B layer. 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 a hard coat property, self-repairing property and anti-glare property on at least one surface in order to stabilize the process in the production process of the polarizing plate and the transparent conductive film and to provide durability in the use environment. It is preferable to have a surface layer exhibiting one or more functions selected from the group consisting of properties, antireflection properties, low reflection properties, ultraviolet shielding properties, 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 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. 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 the scratch difficult to be repaired by repairing the scratch by elastic recovery or the like, and the function is preferably when the surface is rubbed with a brass brush loaded with 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%, particularly preferably 2 to 30% in the evaluation based on the method of obtaining haze described in JIS K-7136-2000. is there.
Antireflection and low reflectivity are functions that improve visibility by reducing the reflectance at the surface due to the interference effect of light. As its function, the reflectance 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. 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).

  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.

  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 polarizer protective polyester film. 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 is preferably bonded 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 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. When the polyester A layer and the polyester B layer having a higher melting point than the polyester A layer are laminated, the polyester A used for the polyester A layer and the polyester B used for the polyester B layer are supplied to separate vent type twin screw extruders. Melt extrusion. Hereinafter, the polyester A layer and the polyester B layer having a higher melting point than the polyester A layer will be described. 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, 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 a draw ratio in such a drawing method, 1.1 times to 2.5 times, preferably 1.5 times to 2 times is preferably used 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. The stretching ratio in the width direction is preferably 3.5 times or more and 6 times or less, more preferably 4 times or more and 5.5 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.

  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 B layer). In general, the heat treatment temperature is set as high as possible.

  Furthermore, in order to improve the adhesive force with a polarizer or a transparent conductive layer, 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. 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 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 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 polyester film for protecting a polarizer 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.

  The characteristic measuring method and the effect evaluating method in the present invention are as follows.

(1) Polyester composition 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) Film thickness, 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.

(3) Measurement and analysis were performed in accordance with JIS K-7121-1987 and JIS K-7122-1987 using a melting point differential scanning calorimeter (Seiko Denshi Kogyo's RDC220). 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 (2), each layer was scraped off with a cutter, the melting point of each layer was measured, and the low melting point layer was designated as the polyester A layer and the high layer as the polyester B layer. When the melting point is not observed, “ND” is indicated in the table.

(4) Refractive index Sodium D-line (wavelength 589 nm) was used as a light source, and the refractive index in the in-plane direction of the film was measured using an Abbe refractometer.

(5) Microwave molecular orientation meter MOA-2001A (manufactured by KS Systems (currently Oji Scientific Instruments)) cut out a sample with dimensions of 100 mm × 100 mm at any point on the fast axis, slow axis, and in-plane retardation film. The frequency of 4 GHz) was used to determine the in-plane main orientation axis of the polyester film, the Y direction, and the direction perpendicular to the Y direction was the X direction. In the present invention, the X direction is the fast axis. Then, using a sodium D line (wavelength 589 nm) as a light source, using methylene iodide as a mounting liquid, and using an Abbe refractometer at 25 ° C., the refractive indices in the X direction, Y direction, and Z direction (thickness direction) (respectively, nx, ny, nz), and the in-plane phase difference was calculated from the following equation (V).
In-plane retardation = | nx−ny | × film thickness (nm) (V)
(6) After obtaining the fast axis and the slow axis by the method of thermal contraction rate (5), the sample was cut into a rectangle of length 70 mm × width 10 mm (fast axis × slow axis). Marks were drawn on the sample at intervals of 50 mm, and a heat treatment was performed by placing in a hot air oven heated to 150 ° C. with a 3 g weight suspended for 30 minutes. The distance between marked lines after the heat treatment was measured, and the thermal contraction rate of the fast axis was calculated from the change in the distance between marked lines before and after heating by the following formula. For each film, three samples were measured in the X direction and the Y direction for each film, and the average value was evaluated. The slow axis was evaluated in the same manner.
Thermal shrinkage (%) = {(distance between marked lines before heat treatment) − (distance between marked lines after heat treatment)} / (distance between marked lines before heat treatment) × 100.

(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. 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. In the same manner, a test piece in which a 30 cm square film was bonded was prepared and evaluated in the same manner.
A: In the evaluation of 10 cm square, no interference color is seen. In the 30 cm square evaluation, no interference color is seen or 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) Optical member quality (i)
In the same manner as in (7), 10 test pieces bonded to a polarizer were prepared, and then evaluated according to the following criteria.
A: None of the test pieces having air bubbles that can be visually confirmed were found in any of the 10 cm square and 30 cm square test pieces.
B: For 10 cm square test pieces, no test piece having air bubbles that can be visually confirmed was found, but for 30 cm square test pieces, one or more test pieces having air bubbles that can be visually confirmed were found. Less than 3 were seen.
C: One to three test pieces having air bubbles that can be visually confirmed for 10 cm square test pieces, and one to 10 test pieces having air bubbles that can be visually confirmed for 30 cm square test pieces 10 Less than one was seen.
D: 4 to 10 test pieces having air bubbles that can be visually confirmed for 10 cm square test pieces, and 1 to 10 test pieces having air bubbles that can be visually confirmed for 30 cm square test pieces Less than one was seen.
(9) Optical member quality (ii)
In the same manner as in (7), a 30 cm square test piece bonded to a polarizer was further evaluated on the following criteria for a sample that was further heat treated in a 100 ° C. oven for 24 hours.
A: No wrinkles were found on the test piece.
B: A fine wrinkle portion having a longest diameter of 1 cm or less was observed.
C: Wrinkles having a longest diameter of 1 cm or more were observed.
D: Wrinkles were observed on the entire test piece.
(Manufacture of polyester)
The polyester resin used for film formation was prepared as follows.

(Polyester A)
Isophthalic acid copolymerized polyethylene terephthalate containing 44 mol% of terephthalic acid and 6 mol% of isophthalic acid as dicarboxylic acid components and 50 mol% of ethylene glycol as glycol components with respect to 100 mol% of the total amount of dicarboxylic acid component and diol component Resin (intrinsic viscosity 0.7).

(Polyester B)
Cyclohexanedimethanol copolymer with 50 mol% of terephthalic acid as dicarboxylic acid component, 35 mol% of ethylene glycol and 15 mol% of cyclohexanedimethanol as dicarboxylic acid component, based on 100 mol% of total amount of dicarboxylic acid component and diol component Polyethylene terephthalate resin (intrinsic viscosity 0.75).
(Polyester C)
Cyclohexanedimethanol copolymer with 50 mol% of terephthalic acid as dicarboxylic acid component, 35 mol% of ethylene glycol and 15 mol% of cyclohexanedimethanol as dicarboxylic acid component, based on 100 mol% of total amount of dicarboxylic acid component and diol component Polyethylene terephthalate resin (intrinsic viscosity 0.75).
(Polyester D)
Cyclohexanedimethanol copolymer containing 50 mol% of terephthalic acid as the dicarboxylic acid component, 34 mol% of ethylene glycol as the glycol component, and 16 mol% of cyclohexanedimethanol with respect to 100 mol% of the total amount of the dicarboxylic acid component and the diol component. Polyethylene terephthalate resin (intrinsic viscosity 0.75).

(Polyester E)
Polyethylene terephthalate resin (inherent viscosity 0.7) having 50 mol% of terephthalic acid as the dicarboxylic acid component and 50 mol% of ethylene glycol as the glycol component with respect to 100 mol% of the total amount of the dicarboxylic acid component and the diol component.

(Particle Master 1)
A polyester master containing agglomerated silica particles having a number average particle size of 2.2 μm in polyester A at a particle concentration of 2% by mass.

(Particle Master 2)
A polyester master containing agglomerated silica particles having a number average particle size of 2.2 μm in polyester B at a particle concentration of 2% by mass.

(Particle Master 3)
A polyester master containing agglomerated silica particles having a number average particle size of 2.2 μm in polyester C at a particle concentration of 2% by mass.

(Particle Master 4)
A polyester master containing agglomerated silica particles having a number average particle size of 2.2 μm in polyester D at a particle concentration of 2% by mass.

(Particle Master 5)
A polyester master containing agglomerated silica particles having a number average particle size of 2.2 μm in polyester E at a particle concentration of 2 mass%.

Example 1
The composition is as shown in the table, and the raw material is supplied to a vented co-directional twin-screw extruder with an oxygen concentration of 0.2% by volume, the A-layer extruder cylinder temperature is set to 280 ° C., and the raw material is melted. The sheet was discharged in the form of a sheet on 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, preheating was performed for 1.5 seconds at a preheating temperature of 85 ° C. in the longitudinal direction, the film was stretched 1.5 times in the longitudinal direction, 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 95 ° C. with a tenter-type transverse stretching machine, and the film is stretched 4.5 times in the width direction, and the heat treatment is performed at 200 ° C. for 15 seconds in the tenter as it is. Heat treatment was performed while relaxing 3% in the direction to obtain a biaxially oriented polyester film having a thickness of 85 μm. In addition, when the temperature change of the film was observed about the film after heat processing using the infrared thermography (875-1 / 875i by Testo Co., Ltd.), and the film center part became room temperature (25 degreeC), it was 8 seconds. Met. The winding tension was 50 N in terms of 1000 mm width.
(Examples 2, 3, 5, 6)
The raw material composition and manufacturing conditions were changed as shown in the table, a heating zone of 100 ° C was provided after heat treatment, the time when the center of the film reached room temperature (25 ° C) was 11 seconds, and the winding tension was converted to 1000 mm A polyester film was obtained in the same manner as in Example 1 except that 18N was obtained.

(Examples 4 and 7)
A polyester film was obtained in the same manner as in Example 1 except that the raw material composition and production conditions were changed as shown in the table.
(Example 8)
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 cylinder temperature is 280 ° C. for both the A-layer extruder and the B-layer extruder. Set and melt the raw materials and merge them into a three-layer structure of B layer / A layer / B layer in the feed block, and the short tube temperature and base temperature after merging are 280 ° C and 25 ° C from the T-die The sheet was discharged in a sheet form on a temperature-controlled cooling drum. Thereafter, a polyester film was obtained in the same manner as in Example 1 under the production conditions shown in the table.

Example 9
A polyester film was obtained in the same manner as in Example 8 except that the raw material composition and production conditions were changed as shown in the table.
(Comparative Examples 1 and 2)
A polyester film was obtained in the same manner as in Example 1 except that the raw material composition and production conditions were changed as shown in the table.

  The present invention relates to a polyester film that is particularly suitable for optical applications (polarizer protection, transparent conductive film, etc.), and can suppress interference color when mounted on a display device such as a liquid crystal display, and a polarizing plate. Since the quality of an optical member such as a transparent conductive film can be improved, it is bonded to a PVA sheet (polarizer) prepared by containing iodine in PVA and oriented as a polarizing plate, or a transparent conductive layer Is preferably used as a transparent conductive film in which is laminated, and a touch panel member using the transparent conductive film.

Claims (9)

Of the 150 ° C. heat shrinkage in each of the fast axis direction and the slow axis direction, S1 is a polyester film satisfying the formula (I) where S1 is a high value and S2 is a low value. An optical polyester film having an internal retardation of 3000 nm or more and 30000 nm or less.
0.1% ≦ S1 ≦ 5% (I) The optical polyester film according to claim 1, wherein S2 satisfies the formula (II).
0.1% ≦ S2 ≦ 5% (II) The optical polyester film according to claim 1 or 2, which satisfies the following formula (III).
1.05 ≦ S1 / S2 ≦ 4 (III)   The polyester constituting the film is composed of a dicarboxylic acid component and a diol component, and when the total amount of the dicarboxylic acid component and the diol component is 100 mol%, the most component of the dicarboxylic acid component and the most component of the diol component The optical polyester film according to any one of claims 1 to 3, wherein the total of is more than 85 mol% and less than 98 mol%.   The polyester constituting the film is composed of a dicarboxylic acid component and a diol component, the most dicarboxylic acid component is terephthalic acid or naphthalene dicarboxylic acid, and the most diol component is ethylene glycol. The optical polyester film described.   A polyester B layer having a melting point of Tb (° C.) is laminated on at least one surface of a polyester A layer having a melting point of Ta (° C.), and Tb> Ta. The optical polyester film in any one of claim | item 1 -5.   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, wherein at least one of the polarizer protective films is the optical polyester film according to claim 7. A transparent conductive film comprising the polyester film according to claim 1.