JP5048443B2 - Laminated polyester film for antireflection film - Google Patents

Description

  The present invention relates to a laminated polyester film for optics, and for example, a liquid crystal display (hereinafter abbreviated as LCD), a plasma display panel (hereinafter abbreviated as PDP), an organic electroluminescence (hereinafter abbreviated as organic EL). ), Etc., for a laminated polyester film suitable for optical uses such as for display members.

  Conventionally, an optical film having a polyester film as a substrate has been used for various optical applications including display members such as LCD, PDP, and organic EL. These optical films are required to have excellent transparency and visibility.

  As these optical films, those in which surface functional layers such as a hard coat layer and an antireflection layer are laminated on a plastic film are used. As the plastic film, a transparent polyester film is generally used, and in order to improve the adhesion between the polyester film of the base material and the surface functional layer, an easily adhesive coating layer is provided as an intermediate layer between them. Is common.

  As a general antireflection film, a structure in which a high refractive index layer and a low refractive index layer are alternately laminated as a surface functional layer, and antireflection of external light is performed using a light interference phenomenon.

  In applications such as display members such as LCDs and PDPs, the demand for suppression of iris-like colors (non-uniform interference) under fluorescent lamps has increased because of the increased screen size and higher image quality compared to conventional displays. . In addition, fluorescent lamps have become a three-wavelength type for daylight color reproducibility, and interference unevenness is more likely to occur. Furthermore, in recent years, in order to achieve cost reduction and the like, unlike the conventional case, the hard coat layer is made to have a higher refractive index, or the hard coat layer and the antireflection layer are made anti-static, etc. Simplification such as one layer or two layers is being promoted. In order to perform this simplification more easily and effectively, optical design has become important even in a coating layer laminated on a polyester film, and a coating layer having a higher refractive index is required. If the refractive index of the coating layer is low, the occurrence of uneven interference due to reflection of external light may not be sufficiently suppressed. When used as a display member for LCDs, PDPs, organic ELs, etc., various problems due to deterioration in visibility become apparent. Tend to. Therefore, examples in which the refractive index of the coating layer is increased to improve interference unevenness are known (Patent Documents 1 and 2).

  Further, in order to reduce defects on the display screen, it is required to form a more precise surface functional layer. For this reason, in the process of forming the surface functional layer, not only a clean environment with a small amount of dust is required, but also a polyester film serving as a substrate is required to have a small amount of dust. However, the polyester film has the problem that it is easy to generate static electricity as well as the general plastic film, and in the process of forming the surface functional layer such as the hard coat layer on the coating layer, the dust in the process adheres to the coating defect. Occasionally, a surface functional layer with higher accuracy may not be obtained. Therefore, a laminated polyester film imparted with antistatic ability is strongly desired.

There is an example in which thiophene or a derivative thereof is contained in the coating layer in order to impart antistatic properties. However, in the case of this technique, the antireflection performance when the surface functional layer is laminated is low because the coating layer is thin. It becomes worse and interference unevenness is likely to occur. Further, when the film thickness is increased, the production cost tends to increase because the content ratio of thiophene or a derivative thereof is large (Patent Document 3).
Japanese Patent No. 3632044 JP 2004-54161 A JP 2003-157724 A

  The present invention has been made in view of the above circumstances, and its solution is to reduce interference unevenness due to reflection of external light and to prevent the adhesion of dust in the process by providing antistatic properties. Therefore, an object of the present invention is to provide a polyester film for an antireflection film suitable for various optical applications, which can easily perform the process of laminating a surface functional layer.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the above-described problems can be easily solved by using a polyester film having a specific coating layer, and have completed the present invention.

That is, the gist of the present invention is a polyester film having a coating layer on at least one side, and the coating layer is obtained by applying a coating solution containing the following (A) to (C), stretching, and drying. The specular reflectance of the coating layer surface is 5.0% or more at an arbitrary wavelength of 400 to 800 nm, and the surface resistivity of the coating layer surface is 1 × 10 ¹² Ω or less. It exists in the polyester film for antireflection films characterized by the above-mentioned.
(A) Compound 0.5 to 10% obtained by polymerizing thiophene or thiophene derivative
(B) One or more compounds selected from the group of polyalkylene oxide, glycerin, polyglycerin, glycerin or alkylene oxide adducts to polyglycerin or derivatives thereof 10 to 80%
(C) 10-80% binder resin

Hereinafter, the present invention will be described in more detail.
The polyester film in the present invention may have a single layer structure or a multilayer structure, and may have a multilayer structure of four layers or more as long as the gist of the present invention is not exceeded other than the two-layer or three-layer structure. Well, not particularly limited.

  The polyester used in the present invention is preferably obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol, and may be a polyester comprising one kind of aromatic dicarboxylic acid and one kind of aliphatic glycol. It may be a copolyester obtained by copolymerizing one or more other components. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyester includes polyethylene terephthalate and the like. On the other hand, examples of the dicarboxylic acid used as a component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, and sebacic acid, and glycol components include ethylene glycol, diethylene glycol, and propylene. Examples include glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like. Oxycarboxylic acids such as p-oxybenzoic acid can also be used.

  Further, in order to improve the weather resistance of the film and prevent the deterioration of the pigment used in the color filter of PDP, an ultraviolet absorber may be contained in the polyester film. The ultraviolet absorber is not particularly limited as long as it is a compound having ultraviolet absorbing ability and can withstand the heat applied in the production process of the polyester film.

  Furthermore, due to the thermal history during film processing, the oligomer contained in the film is deposited on the surface of the film, and may cause deterioration of the visibility of the film due to contamination of the production line or deterioration of the film haze, etc. It is preferable to use low oligomerized polyester for the outermost layer of the multilayer structure film. As a method for reducing the amount of oligomer in the polyester, a solid phase polymerization method or the like can be used.

  In the film of the present invention, it is preferable to blend particles for the main purpose of imparting slipperiness and preventing scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color. Two or more kinds of these particles may be used in combination as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-3 micrometers normally, Preferably it is the range of 0.01-2 micrometers. When the average particle diameter is less than 0.01 μm, the particles are likely to aggregate and dispersibility may be insufficient. On the other hand, when the average particle diameter exceeds 3 μm, the surface roughness of the film becomes too rough and Problems may occur when various surface functional layers are applied in the process.

  Further, the content of particles in the polyester layer is usually in the range of 0.001 to 5% by weight, preferably 0.005 to 3% by weight. When the particle content is less than 0.001% by weight, the slipperiness of the film may be insufficient, while when it exceeds 5% by weight, the transparency of the film may be insufficient.

  The method for adding particles to the polyester is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

  Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, and the like can be added to the polyester film in the present invention as necessary.

  Although the thickness of the polyester film in this invention will not be specifically limited if it can be formed into a film as a film, Usually, 10-300 micrometers, Preferably it is the range of 50-250 micrometers.

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. That is, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. is there. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can also be adopted for the production of the polyester film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is usually stretched and oriented in the machine direction and the width direction at a temperature controlled normally at 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be employed.

  Next, the formation of the coating layer constituting the laminated polyester film in the present invention is provided by coating the film with a coating solution, and is preferably provided by in-line coating performed in the film manufacturing process. An off-line coating that is applied outside the system may be employed.

  Specifically, the in-line coating is a method in which the coating is performed at any stage from melt extrusion of the polyester to stretching, heat setting, and winding. Normally, it is coated on a substantially amorphous unstretched sheet obtained by melting and quenching, followed by a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction), or a biaxially stretched film before heat setting. To do. In these, the method of drying and extending | stretching to a horizontal direction after coating to a uniaxially stretched film, and also heat-processing with a base film is excellent. According to this method, since film formation and coating layer formation can be performed at the same time, there is an advantage in manufacturing cost, and heat treatment applied after coating is so high that it is difficult to achieve with other coatings. Therefore, there is an advantage that the film forming property of the coating layer is improved and the coating layer and the polyester film are firmly adhered.

  The film of the present invention has a specific coating layer, and the coating layer is (A) a compound obtained by polymerizing thiophene or a thiophene derivative, (B) polyalkylene oxide, glycerin, polyglycerin, glycerin or polyglycerin. It is necessary to contain at least one compound selected from the group of alkylene oxide adducts or derivatives thereof, and (C) a binder resin.

  The compound (A) obtained by polymerizing thiophene or a thiophene derivative used in the present invention is a polymer obtained by singly or copolymerizing a thiophene or thiophene derivative. Those doped with an anionic compound of the above or those self-doped with an anionic group in the compound exhibit excellent conductivity and are preferred. Examples of the compound (A) include those obtained by polymerizing a compound of the following formula (1) or (2) in the presence of a polyanion.

In the above formula (1), R ¹ and R ² each independently represent hydrogen, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, an aromatic hydrocarbon group, or the like.

  In said formula (2), n represents the integer of 1-4.

  Examples of the polyanion used at the time of polymerization include poly (meth) acrylic acid, polymaleic acid, polystyrene sulfonic acid and the like. These acids may be partially or completely neutralized. In addition, as a manufacturing method of this polymer, the method as shown, for example in patent 7-90060 is employable.

  In the present invention, a particularly preferable embodiment is one in which n = 2 in the compound of the above formula (2) and polystyrene sulfonic acid is used as a polyanion.

  In addition, one or more compounds selected from the group of polyalkylene oxide, glycerin, polyglycerin, glycerin or alkylene oxide adducts to polyglycerin or derivatives thereof can further reduce the surface resistivity by assisting the conduction mechanism. To be contained.

  Preferable polyalkylene oxide or its derivative is a structure having an ethylene oxide or propylene oxide skeleton. If the alkyl group in the alkylene oxide structure is too long, the hydrophobicity becomes strong, the uniform dispersibility in the coating solution tends to deteriorate, and the antistatic property tends to deteriorate. Particularly preferred is ethylene oxide.

  Glycerin and polyglycerin are compounds represented by the following formula (3).

  In the above formula (3), the compound in which n is 1 is glycerol, and the compound in which n is 2 or more is polyglycerol. In the present invention, n in the formula is preferably in the range of 1-20, more preferably in the range of 2-20. When glycerin is used, transparency may be slightly inferior.

  The alkylene oxide adduct to glycerin or polyglycerin has a structure in which alkylene oxide or a derivative thereof is added to the hydroxyl group of glycerin or polyglycerin represented by the formula (3).

  Here, the structure of the alkylene oxide to be added or a derivative thereof may be different for each hydroxyl group of the glycerin or polyglycerin skeleton. Moreover, it is sufficient that it is added to at least one hydroxyl group in the molecule, and alkylene oxide or a derivative thereof need not be added to all hydroxyl groups.

  Moreover, what is preferable as an alkylene oxide or its derivative added to glycerol or polyglycerol is a structure which has ethylene oxide or a propylene oxide frame | skeleton. If the alkyl chain in the alkylene oxide structure becomes too long, the hydrophobicity becomes strong, the uniform dispersibility in the coating solution tends to deteriorate, and the antistatic property tends to deteriorate. Particularly preferred is ethylene oxide.

  In the present invention, as a particularly preferable form as the compound (B), polyglycerol and an alkylene oxide adduct to glycerol or polyglycerol can be mentioned. When polyalkylene oxide or glycerin is used, the appearance of the resulting coating layer may be slightly inferior. As the polyglycerin, in the compound of the above formula (3), those having n of 2 to 20 are particularly preferable. Further, as the alkylene oxide adduct to glycerin or polyglycerin, a compound having a structure in which ethylene oxide or polyethylene oxide is added to the compound of formula (3) wherein n is 2, the addition number is A compound having a weight average molecular weight of 300 to 2000 as a final compound is particularly preferable.

  In addition, in the alkylene oxide adduct to glycerin or polyglycerin, the copolymerization ratio of alkylene oxide or its derivative to the glycerin or polyglycerin skeleton is not particularly limited, but when the glycerin or polyglycerin moiety is 1 in terms of molecular weight ratio The alkylene oxide moiety is preferably 20 or less, more preferably 10 or less. If the ratio of alkylene oxide or its derivative to glycerin or polyglycerin skeleton is larger than this range, it will be close to the characteristics when ordinary polyalkylene oxide is used. It may be slightly inferior.

  The binder resin in the present invention is contained in order to improve antireflection performance and transparency when various surface functional layers are laminated on the coated surface, and to improve adhesion to various surface functional layers. Specific examples thereof include polyester resin, acrylic resin, urethane resin, polyvinyl, polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like. From the viewpoint of improving the adhesion with the surface functional layer, polyester resin, acrylic resin, and urethane resin are more preferably used.

  The film of the present invention is required to have a specular reflectance of 5.0% or more at an arbitrary wavelength of 400 to 800 nm in the wavelength range of 400 to 800 nm on the surface of the coating layer, and is minimal in the wavelength range. Preferably it has a value. In order to form a coating layer having a specular reflectance of 5.0% or more at an arbitrary wavelength in the wavelength range of 400 to 800 nm, it can be realized, for example, by including a high refractive index material in the coating layer. Examples of the material having a high refractive index include metal compounds and aromatic-containing organic compounds, but are not limited to these compounds.

  Examples of the metal compound include titanium oxide, zinc oxide, tin oxide, antimony oxide, yttrium oxide, zirconium oxide, indium oxide, cerium oxide, ATO (antimony / tin oxide), and ITO (indium / tin oxide). Aluminum such as metal oxide, aluminum acetylacetonate, hydroxyaluminum diacetate, dihydroxyaluminum acetate; tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, tetramethyl titanate, titanium acetylacetate Nato, titanium tetraacetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamine Titanium such as iron acetate and titanium ethyl acetoacetate; Iron such as iron acetylacetonate and iron acetate; Cobalt such as cobalt acetylacetonate; Copper acetate, copper acetate monohydrate, copper acetate multihydrate, copper acetyl Coppers such as acetonate; zincs such as zinc acetate, zinc acetate dihydrate, zinc acetylacetonate hydrate; zirconium acetate, zirconium normal propylate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetate Examples thereof include organic compounds having a metal element such as zirconium and zirconium compounds such as narate and zirconium bisacetylacetonate. These may be used alone or in combination of two or more.

  Among the above metal compounds, an organic compound having a titanium element or a zirconium element is preferable in terms of particularly good coatability and transparency, and more preferably a water-soluble titanium chelate compound when considering application to in-line coating, A water-soluble zirconium chelate compound or the like is preferably used.

  Examples of aromatic-containing organic compounds include compounds having a high proportion of benzene rings such as condensed polycyclic aromatic compounds, bisphenol A compounds, biphenyl compounds, and fluorene compounds, which can be exemplified by naphthalene rings and anthracene rings. Examples thereof include compounds, ultraviolet absorber-containing compounds such as benzophenone and benzotriazole, and various heteroaromatic compounds such as melamine. These may be used alone or in combination of two or more.

  In particular, if an aromatic compound is contained in the binder resin (C) to increase the refractive index, it is effective because the blending species of the coating liquid can be reduced. Among the binder resins (C), in the case of a polyester resin, an aromatic compound such as a benzene ring can be more effectively introduced. Among polyester resins, a polyester resin containing a naphthalene ring is more preferably used in that the refractive index can be increased and the appearance of the coating layer is good.

  The content ratio of the coating layer (A) constituting the coating layer of the present invention is usually 0.3 to 20% by weight, preferably 0.5 to 10%. When the content ratio of (A) is less than 0.3%, the antistatic property may not be sufficient, and when it exceeds 20%, the appearance / transparency of the coating layer may deteriorate, and the cost increases. It is not preferable because it is easy to invite.

  Further, the content ratio of (B) is usually in the range of 10 to 80%, more preferably 20 to 50% by weight. Outside this range, the antistatic property and the appearance of the coating layer may deteriorate.

  The content ratio of (C) is usually in the range of 10 to 80%, more preferably 20 to 70% by weight. Outside this range, the appearance of the coating layer and the adhesion with the surface functional layer may deteriorate.

  Furthermore, a crosslinking agent may be used in the coating layer as long as the gist of the present invention is not impaired, and various known resins can be used, and examples thereof include melamine compounds, epoxy compounds, oxazoline compounds, and isocyanate compounds. These cross-linking agents may be used alone or in combination of two or more. Furthermore, it is more preferable to use a material containing (poly) alkylene oxide, (poly) glycerin, or a derivative thereof in the structure because the antistatic property of the resulting coating layer is not impaired.

  Further, for the purpose of improving the adhesion and slipperiness of the coating layer, inert particles may be included in the coating layer, and specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, organic particles, and the like. It is done.

  Furthermore, as long as the gist of the present invention is not impaired, the coating layer contains an antifoaming agent, surfactant, thickener, organic lubricant, antioxidant, ultraviolet absorber, foaming agent, dye, etc. as necessary. May be. It is more preferable to use (poly) alkylene oxide, (poly) glycerin, or a derivative thereof in the structure because the antistatic property of the resulting coating layer is not impaired.

  In the case of in-line coating, the above-described series of compounds is prepared as an aqueous solution or water dispersion, and the coating liquid prepared with a solid content concentration adjusted to about 0.1 to 50% by weight as a guide is applied on the polyester film. Is preferred. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

  In the present invention, as a method for providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, spray coating or the like can be used. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by in-line coating, it is usually 3 to 70 to 280 ° C. Heat treatment should be performed with 200 seconds as a guide.

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film constituting the laminated polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  The specular reflectance on the surface of the coating layer is required to be 5.0% or more at an arbitrary wavelength of 400 to 800 nm, and the specular reflectance is preferably 5.5% or more, It is preferable that it is less than the specular reflectance of the polyester film which is not provided. When the specular reflectance is less than 5.0%, the antireflection performance deteriorates when a surface functional layer such as a hard coat layer or an antireflection layer is laminated on the coating layer of the film. It becomes stronger and visibility decreases.

  Moreover, it is preferable that the minimum value of a specular reflectance exists in the wavelength range of 400-800 nm, More preferably, it exists in the range of wavelength 500-700 nm, and these can be achieved by adjusting the film thickness of a coating layer. The thickness of the coating layer is usually 0.05 to 0.25 μm, preferably 0.07 to 0.18 μm. When the coating layer is incorporated into a design that provides antireflection performance by using the interference caused by external light reflection of each layer in the same manner as the surface functional layer, in order to achieve better antireflection performance, not only the refractive index but also the minimum It is preferable to adjust the wavelength range (film thickness) of the value. When there is no minimum value of the specular reflectance in the wavelength range of 400 to 800 nm, depending on the refractive index of the surface functional layer to be used, the optical characteristics may not match, and interference unevenness may occur.

The surface specific resistance in the coating layer of the film of the present invention is 1 × 10 ¹² Ω or less, preferably 1 × 10 ¹⁰ Ω or less, more preferably 1 × 10 ⁸ Ω or less. When the surface specific resistance is higher than 1 × 10 ¹² Ω, when various surface functional layers are laminated on the coated surface, the prevention of adhering foreign matter such as dust and handling properties are deteriorated, and a more sophisticated lamination is sufficiently performed. It may not be possible.

  According to the laminated polyester film for optics of the present invention, it is possible to provide an optical film excellent in antireflection performance when various surface functional layers are laminated, and its industrial value is high.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement method and evaluation method used in the present invention are as follows.

(1) Measurement of Intrinsic Viscosity of Polyester 1 g of polyester was accurately weighed and dissolved by adding 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio), and measured at 30 ° C.

(2) Measurement of average particle diameter (d ₅₀ : μm) Integration (weight basis) 50% in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) Was the average particle size.

(3) Method of measuring the minimum reflectance value from the surface of one layer of the polyester film In advance, a black tape (vinyl tape VT-50 manufactured by Nichiban Co., Ltd.) is pasted on the back surface of the polyester film, and a spectrophotometer (Shimadzu Corporation) If the coating layer is present at an incident angle of 8 ° using a UV-3100PC type manufactured by Seisakusho Co., Ltd., the surface of the coating layer has a specular reflection with a wavelength range of 400 to 800 nm, a sampling pitch of 1 nm, a slit width of 20 nm, and a medium scanning speed. The rate was measured and the minimum value was evaluated. In addition, the minimum wavelength at that time was read.

(4) Method for Measuring Surface Specific Resistance of Laminated Polyester Film Based on the following method (4-1), the surface specific resistance of the film coating layer was measured. In the method (4-1), since the surface resistivity higher than 1 × 10 ⁸ Ω cannot be measured, the method (4-2) was used for the sample that could not be measured in (4-1).
(4-1) Low resistivity meter manufactured by Mitsubishi Chemical Co., Ltd .: Loresta GP MCP-T600 was used, the sample was conditioned for 30 minutes in a measurement atmosphere of 23 ° C. and 50% RH, and then the surface resistivity value was measured.
(4-2) Using a high resistance measuring instrument manufactured by Nippon Bullet Packard: HP4339B and measuring electrode: HP16008B, adjusting the sample for 30 minutes in a measurement atmosphere of 23 ° C. and 50% RH, and then determining the surface resistivity value. It was measured. It can be said that the lower the surface resistivity, the better the antistatic property. If the surface resistivity is 1 × 10 ¹² Ω or less, it can be said that there is no problem with antistatic properties, and if it is 1 × 10 ⁸ Ω or less, it can be said that the antistatic properties are extremely good.

(5) Evaluation method of antireflection ability On a polyester film (when a coating layer is laminated, the coating layer side), KAYARAD (registered trademark) manufactured by Nippon Kayaku Co., Ltd. and purple light (registered trademark) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. ) 3: 2 mixture was applied and dried at 80 ° C. for 1 minute to remove the solvent. Next, while the film was run at a feeding speed of 10 m / min, ultraviolet rays were irradiated using a mercury lamp under the conditions of irradiation energy of 120 W / cm and irradiation distance of 10 cm to obtain a film having a surface functional layer having a thickness of 5 μm. . The obtained film was visually observed under a three-wavelength light region type fluorescent lamp, and interference unevenness was observed.

(6) Dust adhesion evaluation method of laminated polyester film After the humidity of the polyester film is sufficiently adjusted in a measurement atmosphere of 23 ° C. and 50% RH, the coated layer is rubbed 10 times with a cotton cloth. This was brought close to the finely crushed cigarette ash and the ash adhesion was evaluated according to the following criteria.
○: Even if the film is brought close to ash, it is not attached.

(7) Thickness measurement of polyester layer After fixing a small piece of film with an epoxy resin, it cut | disconnected with the microtome, and observed the cross section of the film with the transmission electron micrograph. Two of the cross-sections are observed in parallel with the film surface, and the interface is observed by light and dark. The distance between the two interfaces and the film surface was measured from 10 photographs, and the average value was defined as the layer thickness.

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (I)>
100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol are used as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is gradually distilled off. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part of ethyl acid phosphate to this reaction mixture, 0.04 part of antimony trioxide was added, and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (I) was 0.63.

<Method for producing polyester (II)>
Polyester (I) was pre-crystallized in advance at 160 ° C. and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 220 ° C. to obtain an intrinsic viscosity 0.75 polyester (II).

<Method for producing polyester (III)>
In the process for producing polyester (I), after adding 0.04 part of ethyl acid phosphate, 0.2 part of silica particles having an average particle diameter of 1.6 μm dispersed in ethylene glycol and 0.04 part of antimony trioxide are added. In addition, polyester (III) was obtained using the same method as the production method of polyester (I) except that the polycondensation reaction was stopped at a time corresponding to an intrinsic viscosity of 0.65. The obtained polyester (III) had an intrinsic viscosity of 0.65.

上記式（４）中のｍ、ｎはエチレンオキサイドの付加モル数を示す整数であり、ここではｍ＋ｎ＝１０となるもの使用した。 Examples of compounds constituting the coating layer are as follows.
(Example compounds)
(A): Thiophene-based polymer, Baytron P AG manufactured by Starck Co., Ltd.
(B): Polyethylene oxide adduct to the polyglycerol skeleton where n = 2 in the formula (3). Average molecular weight 350.
(C-1): Water dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid / isophthalic acid / 5-sodiumsulfoisophthalic acid // (diol component) ethylene Glycol / diethylene glycol = 75/13/12 // 80/20 (mol%)
(C-2): Water dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / 1,4 -Butanediol / diethylene glycol = 56/40/4 // 70/20/10 (mol%)
(C-3): Methyl methacrylate / ethyl methacrylate = 1: 1 molar ratio acrylic resin (emulsifier: polyethylene glycol alkyl ether)
(D): Nonionic surfactant having a structure having polyethylene oxide in the side chain, represented by the following formula (4)

In the above formula (4), m and n are integers indicating the number of moles of ethylene oxide added, and here m + n = 10 was used.

Example 1:
A mixed raw material in which polyesters (II) and (III) are mixed at a ratio of 90% and 10%, respectively, is used as a raw material for the outermost layer (surface layer), and polyester (I) is used as a raw material for the intermediate layer. Each was melted at 285 ° C. and then coextruded in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer) on a cooling roll set to 40 ° C. to obtain an unstretched sheet. . Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the difference in peripheral speed of the roll, and then the coating liquid 1 shown in Table 1 below was applied to both sides of the longitudinally stretched film, and led to a tenter. The film is stretched 3.9 times at 120 ° C. in the transverse direction, heat treated at 225 ° C., relaxed by 2% in the transverse direction, and has a coating thickness of 100 μm with a coating layer (after drying) of 0.12 μm ( A polyester film having a surface layer of 5 μm and an intermediate layer of 90 μm was obtained.

When the specular reflectance of the finished polyester film was measured in the wavelength range of 400 to 800 nm, the minimum value was 6.1%. The surface resistivity was 2 × 10 ⁴ Ω. When the antireflection ability after laminating the surface functional layer was evaluated, the visibility was good. Moreover, when dust adhesion was evaluated, adhesion of ash was not seen and it was good. The properties of this film are shown in Table 2 below.

  Since the compound (B) does not contain an aromatic group such as a benzene ring in the molecule and does not contain an element having a high refractive index, it is not considered to be a compound having a high refractive index. When the coating solution contained 50%, it was considered difficult to achieve a high specular reflectance. However, in actuality, the specular reflectance was as high as 6.1% at the minimum value. It is presumed that this is because the compound (B) is an aliphatic ether compound that is rich in flexibility, flexibly follows the stretching after in-line coating, and assists the orientation of the compound in the coating layer.

Examples 2-4:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. The properties of the obtained polyester film are shown in Table 2 below.

Comparative Examples 1-3:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. The properties of the obtained polyester film are shown in Table 2 below.
Comparative Example 4:
In Example 1, it manufactured similarly to Example 1 except having not provided the application layer, and obtained the polyester film. The properties of the obtained polyester film are shown in Table 2 below.

なお、上記塗布液の濃度はいずれも１０重量％とした。

The concentration of the coating solution was 10% by weight.

  The film of the present invention can be suitably used for, for example, LCDs, PDPs, organic ELs, and other optical uses for display members, as well as uses that place importance on visibility and antistatic properties.

Claims (1)

A polyester film having a coating layer on at least one surface, the coating layer is obtained by applying a coating solution containing the following (A) to (C), stretching, and drying, and applying the coating The specular reflectance of the layer surface is 5.0% or more at an arbitrary wavelength of 400 to 800 nm, and the surface specific resistance of the coating layer surface is 1 × 10 ¹² Ω or less. Polyester film.
(A) Compound 0.5 to 10% obtained by polymerizing thiophene or thiophene derivative
(B) One or more compounds selected from the group of polyalkylene oxide, glycerin, polyglycerin, glycerin or alkylene oxide adducts to polyglycerin or derivatives thereof 10 to 80%
(C) 10-80% binder resin