JP2013006375A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film that has superior adhesion to a conductive layer, and can be suitably used in applications that is required to have excellent visibility and adhesion with regard to a hard coat layer or the like, for instance, a transparent electrode of a touch panel etc. and a transparent conductive film such as an electromagnetic wave shielding film.SOLUTION: The laminated polyester film has a coating layer formed from the coating liquid containing a polyester resin and an oxazoline compound on one surface of a polyester film and a coating layer formed from a coating liquid containing a metal oxide and at least two types of crosslinking agents on the other surface of the polyester film wherein the absolute reflectance of the surface of the coating layer has one minimum value in the wavelength range of 400-800 nm and the absolute reflectance in the minimum value is ≥4.0%.

Description

  The present invention relates to a laminated polyester film, for example, a laminated polyester film suitable for applications requiring adhesion with a conductive layer and reduction of interference unevenness due to reflection of external light, such as a transparent electrode such as a touch panel and an electromagnetic shielding film. It is about.

  In recent years, polyester films have been used in various optical films and also as substrates for transparent electrodes such as touch panels and transparent conductive films such as electromagnetic wave shielding films. As a transparent conductive film, conventionally, a technique in which ITO (indium tin oxide) or the like is formed by a dry process such as vacuum deposition or sputtering has been the mainstream. However, the dry process needs to be evacuated, and has the disadvantages of low processing speed and low productivity. Moreover, since the ITO film formed by these processes does not have sufficient flexibility, there is a problem that a crack or the like is generated during a post-processing step or a punching step, resulting in a defect in which the surface resistance does not sufficiently occur.

  In order to overcome these drawbacks of the dry process, a method of forming a transparent conductive layer by a wet process (method of applying a conductive material liquid) has been proposed (Patent Document 1). Since the wet process does not need to be evacuated and the processing speed can be increased, productivity can be improved. Moreover, since it is excellent in a flexibility, there also exists an advantage that generation | occurrence | production of a crack etc. is suppressed.

  Examples of the wet process include transparent conductive polymers such as polythiophene (Patent Documents 1 and 2). However, the adhesion with the polyester film may not be sufficient.

  By the way, the side of the transparent conductive film opposite to the side on which the conductive layer is formed is often subjected to hard coat processing in order to improve performance such as scratch prevention and surface hardness. In order to improve the adhesion between the polyester film used as a substrate and the hard coat layer, an easily adhesive coating layer is generally provided as an intermediate layer. For this reason, interference unevenness occurs unless the refractive index of the three layers of the polyester film, the easily adhesive coating layer, and the hard coat layer is taken into consideration.

  When a film with interference unevenness is used for a display such as a touch panel, the visibility becomes poor and it is difficult to use. Therefore, it is required to take measures against interference unevenness. In general, the refractive index of the coating layer for reducing interference unevenness is considered to be around the geometric mean of the refractive index of the polyester film of the substrate and the refractive index of the hard coat layer, and is adjusted to the refractive index around this. Ideally. Since the refractive index of the polyester film is high, it is generally necessary to design the coating layer with a high refractive index.

  An example of improving interference unevenness by increasing the refractive index of the coating layer is, for example, a method of combining a metal chelate compound having a high refractive index and a resin in the coating layer. In this case, the stability of the coating solution may not be sufficient depending on the combination due to the instability of the metal chelate in the aqueous solution, which may lead to an increase in the liquid exchange work when producing for a long time. . Moreover, when using a metal chelate compound, the adhesiveness with a hard-coat layer may fall if it carries out moisture-proof heat processing (patent document 3). Moreover, since a high refractive index material usually used is inferior in adhesion to a surface functional layer such as a hard coat layer, a coating layer that can effectively improve adhesion even when combined with a high refractive index material is required. Yes.

Japanese Patent Laid-Open No. 1-313521 JP 2006-294455 A JP 2005-97571 A

  The present invention has been made in view of the above circumstances, and the solution is to have excellent adhesion to the conductive layer, and to reduce interference unevenness due to external light reflection and various surface functional layers such as a hard coat layer. It is providing the laminated polyester film excellent in adhesiveness.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the use of a laminated polyester film having a specific configuration can easily solve the above-described problems, and have completed the present invention.

  That is, the gist of the present invention is to provide a coating solution having a coating layer formed from a coating solution containing a polyester resin and an oxazoline compound on one surface of a polyester film, and containing a metal oxide and two or more kinds of crosslinking agents. A coating layer formed from the above, wherein the coating layer surface has an absolute reflectance of one minimum value in the wavelength range of 400 to 800 nm, and the absolute reflectance at the minimum value is 4.0% or more. It exists in the laminated polyester film characterized by having a layer in the other surface.

  According to the laminated polyester film of the present invention, the adhesiveness with the conductive layer is excellent, and when various surface functional layers such as a hard coat layer are laminated, there is little interference unevenness due to external light reflection, and For example, a base film for forming a structure of a surface functional layer such as a conductive layer / base film / hard coat layer can be provided, which has high industrial value.

  The polyester film constituting the laminated polyester film in the present invention may have a single layer structure or a multilayer structure, and may have four or more layers as long as it does not exceed the gist of the present invention other than a two-layer or three-layer structure. It may be a multilayer, and is not particularly limited.

  The polyester used in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. 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, the dicarboxylic acid component of the copolyester includes isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), etc. 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexane dimethanol, neopentyl glycol, is mentioned.

  There is no restriction | limiting in particular as a polymerization catalyst of polyester, A conventionally well-known compound can be used, For example, an antimony compound, a titanium compound, a germanium compound, a manganese compound, an aluminum compound, a magnesium compound, a calcium compound etc. are mentioned.

  The polyester film of the present invention may contain an ultraviolet absorber in order to improve the weather resistance of the film and to prevent deterioration of the liquid crystal of a liquid crystal display used for a touch panel or the like. The ultraviolet absorber is not particularly limited as long as it is a compound that absorbs ultraviolet rays and can withstand the heat applied in the production process of the polyester film.

  As the ultraviolet absorber, there are an organic ultraviolet absorber and an inorganic ultraviolet absorber. From the viewpoint of transparency, an organic ultraviolet absorber is preferable. Although it does not specifically limit as an organic type ultraviolet absorber, For example, a cyclic imino ester type, a benzotriazole type, a benzophenone type etc. are mentioned. From the viewpoint of durability, a cyclic imino ester type and a benzotriazole type are more preferable. It is also possible to use two or more ultraviolet absorbers in combination.

  In the polyester layer of the film of the present invention, it is preferable to blend particles mainly for the 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 include inorganic particles such as magnesium, kaolin, aluminum oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, and benzoguanamine resin. 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.

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, etc.
These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of particle | grains is 0.01-5 micrometers normally, Preferably it is the range of 0.01-3 micrometers. If the average particle size is less than 0.01 μm, the slipperiness may not be sufficiently imparted, or the particles may be aggregated to make the dispersibility insufficient, thereby reducing the transparency of the film. On the other hand, when it exceeds 5 μm, the surface roughness of the film becomes too rough, and there may be a problem when various surface functional layers and the like are applied in a subsequent process.

  Further, the content of particles in the polyester layer is usually less than 5% by weight, preferably in the range of 0.0003 to 3% by weight. When there are no or few particles, the transparency of the film becomes high and the film becomes a good film, but the slipperiness may be insufficient. There are cases where improvement is required. Further, when the particle content exceeds 5% by weight, the transparency of the film may be insufficient.

  The method for adding particles to the polyester layer 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 25-250 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 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 be adopted for the production of the polyester film constituting the laminated 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, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  Next, formation of the coating layer which comprises the laminated polyester film in this invention is demonstrated. Regarding the coating layer, it may be provided by in-line coating which treats the film surface during the process of forming a polyester film, or offline coating which is applied outside the system on a once produced film may be adopted. Since the coating can be performed simultaneously with the film formation, the production can be handled at a low cost, and therefore in-line coating is preferably used.

  The in-line coating is not limited to the following, but for example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When the coating layer is provided on the polyester film by in-line coating, it is possible to apply at the same time as the film formation, and the coating layer can be processed at a high temperature in the heat treatment process of the polyester film after stretching. Performances such as adhesion to various surface functional layers that can be formed on the layer and heat-and-moisture resistance can be improved. Moreover, when coating before extending | stretching, the thickness of an application layer can also be changed with a draw ratio, and compared with offline coating, thin film coating can be performed more easily. That is, a film suitable as a polyester film can be produced by in-line coating, particularly coating before stretching.

  In the present invention, a coating layer (hereinafter sometimes abbreviated as a first coating layer) formed from a coating solution containing a polyester resin and an oxazoline compound is provided on one surface of the polyester film, and a metal oxide and A coating formed from a coating solution containing two or more kinds of crosslinking agents, having an absolute reflectance of one minimum value in the wavelength range of 400 to 800 nm, and having an absolute reflectance of 4.0% or more at the minimum value. A laminated polyester film having a layer (hereinafter sometimes abbreviated as a second coating layer) on the other surface

  The first coating layer of the film of the present invention is a coating layer for improving adhesion with a conductive layer, and can be used particularly for improving adhesion with a conductive polymer such as polythiophene or polyaniline. .

  The present inventors have found out that the untreated polyester film has poor adhesion to the conductive polymer, and studied various resin layers by coating in order to improve the adhesion. Adhesion could be improved by laminating the resin layer, but it turned out that whitening that increases haze may occur due to the heating process after forming the transparent conductive layer or moisture-resistant heat treatment, and improvement is necessary. . Various studies were conducted to clear the two characteristics of improving adhesion and suppressing haze rise by heat treatment, and found that the problem could be solved by combining polyester resin and oxazoline compound.

  The polyester resin used for forming the first coating layer of the film of the present invention includes, for example, those composed of the following polyvalent carboxylic acid and polyvalent hydroxy compound as main constituent components. That is, as the polyvalent carboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and 2,6 -Naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutar Acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, trimellitic acid monopotassium salt and ester-forming derivatives thereof can be used. As the polyvalent hydroxy compound, ethylene Recall, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,5-pentanediol , Neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol Polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolpropionate, and the like can be used. One or more compounds may be appropriately selected from these compounds, and a polyester resin may be synthesized by a conventional polycondensation reaction.

  The oxazoline compound used for forming the first coating layer of the film of the present invention is a compound having an oxazoline group in the molecule, and in particular, a polymer containing an oxazoline group is preferred, and an addition polymerizable oxazoline group-containing monomer alone or It can be made by polymerization with other monomers. Addition polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like can be mentioned, and one or a mixture of two or more thereof can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with an addition polymerizable oxazoline group-containing monomer. For example, alkyl (meth) acrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, (meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene Unsaturated carboxylic acids such as sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Unsaturated nitriles such as acrylonitrile, methacrylonitrile; (meth) acrylamide, N-alkyl ( (Meth) acrylamide, N, N-dialkyl (meth) acrylamide, As the alkyl group, unsaturated amides such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group); vinyl acetate Vinyl esters such as vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α, β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride And α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene, and the like, and one or more of these monomers can be used.

  Furthermore, in order to further improve the adhesion of the first coating layer of the film of the present invention, and to achieve good transparency and coating appearance, a polymer other than a polyester resin or a compound other than an oxazoline compound may be used without departing from the gist of the present invention. It is also possible to use a crosslinking agent in combination. Specific examples of the polymer include acrylic resin, polyurethane resin, polyalkylene glycol, polyalkyleneimine, cellulose, and starches. Moreover, as a crosslinking agent, an epoxy compound, a melamine compound, an isocyanate type compound, a carbodiimide type compound, a silane coupling compound, etc. are mentioned. Among these, an epoxy compound is preferably used from the viewpoint that adhesion is further improved.

  Moreover, in the range which does not impair the main point of this invention, it is also possible to use a particle | grain together for the formation of the 1st application layer of the film of this invention for the purpose of the adhesiveness of an application layer, and slipperiness improvement.

  The second coating layer of the film of the present invention is designed to reduce interference unevenness due to external light after the surface functional layer such as a hard coat layer is formed, and is provided to improve adhesion with the surface functional layer. is there.

  The metal oxide used for forming the second coating layer of the film of the present invention is mainly used for adjusting the refractive index of the coating layer. In particular, since the refractive index of the resin used in the coating layer is low, it is preferable to use a metal oxide having a high refractive index, and it is preferable to use a refractive index of 1.7 or more. Specific examples of the metal oxide include, for example, zirconium oxide, titanium oxide, tin oxide, yttrium oxide, antimony oxide, indium oxide, zinc oxide, antimontin oxide, indium tin oxide, and the like. You may use 2 or more types. Among these, zirconium oxide and titanium oxide are more preferably used. In particular, zirconium oxide is more preferably used from the viewpoint of weather resistance.

  The metal oxide is preferably used in the form of particles because there is a concern that the adhesion may be lowered depending on the use form, and the average particle size is preferably 100 nm or less, more preferably from the viewpoint of transparency. It is 50 nm or less, more preferably 25 nm or less.

  In the present invention, the coating liquid for forming the second coating layer contains two or more types of crosslinking agents, but these are in close contact with a surface functional layer such as a hard coat layer provided on the coating layer. Can be improved. We have found that even one type of cross-linking agent can improve the adhesion, but by using two or more types of cross-linking agents together, the adhesion can be further improved, especially the adhesion after the wet heat test. I found what I could do.

  Examples of the crosslinking agent used for forming the second coating layer of the film of the present invention include oxazoline compounds, epoxy compounds, melamine compounds, isocyanate compounds, carbodiimide compounds, and silane coupling compounds. Among these crosslinking agents, from the viewpoint of good adhesion, it is particularly preferable to use an oxazoline compound or an epoxy compound, and it is more preferable to use an oxazoline compound and an epoxy compound in combination.

  As the oxazoline compound, the same compound as that used for the first coating layer can be used.

  The epoxy compound is a compound having an epoxy group in the molecule, and examples thereof include condensates of epichlorohydrin with ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A and the like hydroxyl groups and amino groups, There are polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like. Examples of the polyepoxy compound include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylolpropane. Examples of the polyglycidyl ether and diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and propylene glycol diglycidyl ether. , Polypropylene glycol diglycidyl ether, poly Examples of tetramethylene glycol diglycidyl ether and monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidyl amine compounds such as N, N, N ′, N′-tetraglycidyl-m-xylyl. Examples include range amine and 1,3-bis (N, N-diglycidylamino) cyclohexane.

  The melamine compound is a compound having a melamine skeleton in the compound. For example, an alkylolized melamine derivative, a compound partially or completely etherified by reacting an alcohol with an alkylolated melamine derivative, and these Mixtures can be used. As alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. Moreover, as a melamine compound, either a monomer or a multimer more than a dimer may be sufficient, or a mixture thereof may be used. Further, a product obtained by co-condensing urea or the like with a part of melamine can be used, and a catalyst can be used to increase the reactivity of the melamine compound.

  The isocyanate compound is a compound having an isocyanate derivative structure typified by isocyanate or blocked isocyanate. Examples of isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate, and aromatic rings such as α, α, α ′, α′-tetramethylxylylene diisocyanate. Aliphatic isocyanates such as aliphatic isocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylene bis (4-cyclohexyl isocyanate), isopropylidene dicyclohexyl diisocyanate Ne Alicyclic isocyanates such as bets are exemplified. Further, polymers and derivatives such as burettes, isocyanurates, uretdiones, and carbodiimide modified products of these isocyanates are also included. These may be used alone or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferable than aromatic isocyanates in order to avoid yellowing due to ultraviolet rays.

  When used in the state of blocked isocyanate, the blocking agent includes, for example, bisulfites, phenolic compounds such as phenol, cresol, and ethylphenol, and alcohols such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol. Compounds, active methylene compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, lactam compounds such as ε-caprolactam and δ-valerolactam , Amine compounds such as diphenylaniline, aniline, ethyleneimine, acetanilide, acid amide compounds of acetic acid amide, formaldehyde, acetoald Examples include oxime compounds such as oxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime, and these may be used alone or in combination of two or more.

  In addition, the isocyanate compound in the present invention may be used alone, or may be used as a mixture or bond with various polymers. In the sense of improving the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or a bond with a polyester resin or a urethane resin.

  A carbodiimide-based compound is a compound having a carbodiimide structure, and is a compound having one or more carbodiimide structures in the molecule, but for better adhesion, etc., the polycarbodiimide having two or more in the molecule More preferred are system compounds.

  The carbodiimide compound can be synthesized by a conventionally known technique, and generally a condensation reaction of a diisocyanate compound is used. The diisocyanate compound is not particularly limited, and any of aromatic and aliphatic compounds can be used. Specifically, tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexa Examples include methylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate.

  Furthermore, in order not to lose the effect of the present invention, in order to improve the water solubility and water dispersibility of the polycarbodiimide compound, adding a surfactant, polyalkylene oxide, quaternary ammonium salt of dialkylamino alcohol, You may add and use hydrophilic monomers, such as a hydroxyalkyl sulfonate.

  These cross-linking agents are used in a design that improves the performance of the coating layer by reacting in the drying process or film forming process. It can be inferred that unreacted products of these crosslinking agents, compounds after the reaction, or mixtures thereof exist in the finished coating layer.

  In the laminated polyester film in the second coating layer of the present invention, the coating appearance is improved, interference unevenness is reduced when various surface functional layers such as a hard coat layer are laminated on the coating surface, and transparency and adhesion are improved. It is preferable to use various polymers for such as.

  Specific examples of the polymer include polyester resin, acrylic resin, urethane resin, polyvinyl (polyvinyl alcohol, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches. Etc. Among these, it is preferable to use a polyester resin, an acrylic resin, or a urethane resin from the viewpoint of improving adhesion with a surface functional layer such as a hard coat layer and improving the appearance of coating. In addition, a polyester resin is particularly preferable from the viewpoint that a large number of aromatic compounds such as a benzene ring can be contained in the molecule, thereby increasing the refractive index.

  Further, in order to make it easier to adjust the refractive index of the coating layer, naphthalene, anthracene, phenanthrene, naphthacene, benzo [a] anthracene, benzo [a] phenanthrene, pyrene, benzo [c It is preferable to use a compound having a condensed polycyclic aromatic structure such as phenanthrene or perylene.

  In consideration of applicability on the polyester film, the compound having a condensed polycyclic aromatic is preferably a polymer compound such as a polyester resin, an acrylic resin, or a urethane resin. In particular, polyester resins are more preferable because more condensed polycyclic aromatics can be introduced.

  As a method of incorporating the condensed polycyclic aromatic into the polyester resin, for example, two or more hydroxyl groups are introduced into the condensed polycyclic aromatic as a substituent to form a diol component or a polyvalent hydroxyl component, or There is a method in which two or more acid groups are introduced to prepare a dicarboxylic acid component or a polyvalent carboxylic acid component.

  In the laminated polyester film production process, the condensed polycyclic aromatic contained in the coating layer is preferably a compound having a naphthalene skeleton in that it is difficult to be colored. In addition, a resin in which a naphthalene skeleton is incorporated as a polyester component is suitably used in terms of good adhesion to various surface functional layers formed on the coating layer and transparency. Representative examples of the naphthalene skeleton include 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid.

  In addition to the hydroxyl group and the carboxylic acid group, the condensed polycyclic aromatic has a refractive index of a refractive index by introducing a substituent containing a sulfur element, an aromatic substituent such as a phenyl group, a halogen element group, and the like. Improvements can be expected, and substituents such as alkyl groups, ester groups, amide groups, sulfonic acid groups, carboxylic acid groups, and hydroxyl groups may be introduced from the viewpoint of coating properties and adhesion.

  Moreover, this invention may contain particle | grains other than the above-mentioned metal oxide in the 2nd application layer for the purpose of the adhesiveness and slipperiness improvement of an application layer. The average particle size is preferably in the range of 1.0 μm or less, more preferably 0.5 μm or less, particularly preferably 0.2 μm or less from the viewpoint of the transparency of the film. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, and organic particles.

  Furthermore, as long as the gist of the present invention is not impaired, the first coating layer and the second coating layer have an antifoaming agent, coating property improving agent, thickening agent, organic lubricant, antistatic agent, ultraviolet absorption as necessary. Agents, antioxidants, foaming agents, dyes, pigments and the like may be contained.

  As a ratio with respect to all the non-volatile components in the coating liquid which forms the 1st coating layer which comprises the laminated polyester film in this invention, a polyester resin is the range of 50 to 99 weight% normally, Preferably it is the range of 60 to 97 weight%, More preferably, it is the range of 70 to 95 weight%. When the amount of the polyester resin is out of the above range, the haze may be increased by heat-resistant heat treatment when the adhesion is not sufficient, the transparency or the appearance of the coating is deteriorated.

  As a ratio with respect to all the non-volatile components in the coating liquid forming the first coating layer constituting the laminated polyester film in the present invention, the oxazoline compound is usually in the range of 1 to 50% by weight, preferably in the range of 3 to 20% by weight, More preferably, it is 5 to 15% by weight. When the amount of the oxazoline compound is less than 1% by weight, the adhesion may not be sufficient, and when it exceeds 50% by weight, there is a concern that the haze is increased by the heat-resistant heat treatment.

  As a ratio with respect to all the non-volatile components in the coating liquid which forms the 2nd coating layer which comprises the laminated polyester film in this invention, a metal oxide is the range of 3-70 weight% normally, Preferably it is the range of 5-50 weight%. More preferably, it is in the range of 5 to 40% by weight, particularly preferably in the range of 8 to 30% by weight. When the amount of the metal oxide is less than 3% by weight, the refractive index of the coating layer cannot be made sufficiently high, so that interference unevenness may not be reduced. When it exceeds 70% by weight, the coating layer is transparent. Sexuality may worsen.

  As a ratio with respect to all the non-volatile components in the coating liquid which forms the 2nd coating layer which comprises the laminated polyester film in this invention, 2 or more types of crosslinking agents are 2-80 weight% normally, More preferably, it is 4-60. It is in the range of wt%, more preferably in the range of 10-40 wt%. If it is out of these ranges, there is a concern that the adhesion with the surface functional layer such as the hard coat layer may be lowered, if the coating appearance deteriorates, interference after the formation of the surface functional layer such as the hard coat layer The visibility may not be good due to unevenness.

  When an oxazoline compound is used as a crosslinking agent, the content of the oxazoline compound is usually in the range of 1 to 50% by weight, more preferably 1 to 30 as a ratio to the total nonvolatile components in the coating liquid for forming the second coating layer. % By weight, more preferably in the range of 3-20% by weight. If the amount is less than 1% by weight, there is a concern that the adhesion to the surface functional layer such as a hard coat layer may be lowered. If the amount exceeds 50% by weight, the refractive index of the coating layer is lowered, thereby causing a hard coat layer or the like. Visibility may not be good due to interference unevenness after the surface functional layer is formed.

  When using an epoxy compound as a crosslinking agent, the content of the epoxy compound is usually in the range of 1 to 50% by weight, more preferably 3 to 30 as a ratio to the total nonvolatile components in the coating liquid for forming the second coating layer. It is in the range of wt%, more preferably in the range of 5-20 wt%. If it is out of these ranges, there is a possibility that the adhesion with the surface functional layer such as the hard coat layer may be lowered, or the coating appearance may be deteriorated.

  In the compound having a condensed polycyclic aromatic that can be used in the coating layer constituting the laminated polyester film in the present invention, the proportion of the condensed polycyclic aromatic in the compound is preferably in the range of 5 to 80% by weight. More preferably, it is in the range of 10 to 60% by weight. The content of the compound having a condensed polycyclic aromatic in the coating layer is preferably in the range of 80% by weight or less, more preferably in the range of 5 to 70% by weight, and still more preferably in the range of 10 to 50% by weight. It is. By using within these ranges, the refractive index of the coating layer can be easily adjusted, and interference unevenness after forming a surface functional layer such as a hard coat layer can be easily reduced. The ratio of the condensed polycyclic aromatic can be determined by, for example, dissolving and extracting the coating layer with an appropriate solvent or warm water, separating by chromatography, analyzing the structure by NMR or IR, and further pyrolyzing GC-MS (gas It can be determined by analyzing by chromatography mass spectrometry) or optical analysis.

  Analysis of the components in the coating layer can be performed by analysis of TOF-SIMS, ESCA, fluorescent X-rays, and the like, for example.

  When providing a coating layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or dispersion, and the coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight as a guide is applied onto the polyester film. It is preferable to produce a laminated polyester film. 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.

  Regarding the laminated polyester film in the present invention, the thickness of the first coating layer provided on the polyester film is usually 0.002 to 1.0 μm, preferably 0.03 to 0.3 μm, more preferably 0.05 to 0. .2 μm range. When the film thickness is out of the above range, the adhesion and the coating appearance may be deteriorated.

  Regarding the laminated polyester film in the present invention, the thickness of the second coating layer provided on the polyester film is usually in the range of 0.04 to 0.20 μm, preferably 0.07 to 0.15 μm. When the film thickness is out of the above range, visibility may deteriorate due to interference unevenness after the surface functional layer is laminated.

  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 or the like can be used.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. The heat treatment may be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when the coating layer is provided by in-line coating, heat treatment is usually performed at 70 to 280 ° C. for 3 to 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 second coating layer in the present invention has a refractive index adjusted in order to suppress the occurrence of interference unevenness, and the refractive index is a geometric mean of the surface functional layer such as the polyester film of the substrate and the hard coat layer. It is designed in the vicinity. The refractive index of the coating layer and the reflectance of the coating layer are closely related. The absolute reflectance of the film of the present invention is a graph in which the horizontal axis indicates the wavelength and the vertical axis indicates the reflectance, and the minimum value of the reflectance needs to be one in the wavelength range of 400 to 800 nm. Is 4.0% or more. In the range of the absolute reflectance of the present invention, if the minimum value appears at the same wavelength, the reflectance of the minimum value is a high value when the refractive index is high, and a low value when the refractive index is low.

  In the present invention, the absolute reflectance of the second coating layer has one minimum value in the wavelength range of 400 to 800 nm, more preferably one minimum value in the wavelength range of 500 to 700 nm. The minimum value is preferably in the range of 4.0 to 6.5%, more preferably 4.5 to 6.2%. If the minimum value in the wavelength range of 400 to 800 nm is not one, and if the absolute reflectance of the minimum value deviates from the above value, interference unevenness occurs after the surface functional layer such as a hard coat layer is formed. The visibility of the film may be reduced.

The polyester film of the present invention is generally provided with a conductive layer, particularly a conductive polymer, on the first coating layer. Although it does not specifically limit as a conductive polymer, For example, polythiophene, polyaniline, polypyrrole, etc. are mentioned, for example, polythiophene type which uses poly (3,4-ethylenedioxythiophene) together with polystyrene sulfonic acid among them is mentioned, for example. Preferably used.

  The polyester film of the present invention is generally provided with a surface functional layer such as a hard coat layer on the second coating layer. Although it does not specifically limit as a material used for a hard-coat layer, For example, hardened | cured materials, such as reactive silicon compounds, such as monofunctional (meth) acrylate, polyfunctional (meth) acrylate, and tetraethoxysilane, are mentioned. Among these, from the viewpoint of achieving both productivity and hardness, a polymerization cured product of a composition containing an ultraviolet curable polyfunctional (meth) acrylate is particularly preferable.

  It does not specifically limit as a composition containing a ultraviolet curable polyfunctional (meth) acrylate. For example, a mixture of one or more known ultraviolet curable polyfunctional (meth) acrylates, those commercially available as ultraviolet curable hard coat materials, or the range that does not impair the purpose of this embodiment other than these, What added the other component further can be used.

  The UV-curable polyfunctional (meth) acrylate is not particularly limited. For example, dipentaerythritol hexa (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, tetramethylolmethanetri (meth) acrylate, (Meth) acryl derivatives of polyfunctional alcohols such as trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,6-bis (3-acryloyloxy-2-hydroxypropyloxy) hexane And polyethylene glycol di (meth) acrylate and polyurethane (meth) acrylate.

  Other components contained in the composition containing an ultraviolet curable polyfunctional (meth) acrylate are not particularly limited. Examples thereof include inorganic or organic fine particles, polymerization initiators, polymerization inhibitors, antioxidants, antistatic agents, dispersants, surfactants, light stabilizers, and leveling agents. In addition, when the film is dried after film formation in the wet coating method, an arbitrary amount of solvent can be added.

  As a method for forming the hard coat layer, when an organic material is used, a general wet coat method such as a roll coat method or a die coat method is employed. The formed hard coat layer can be subjected to a curing reaction by heating, irradiation with active energy rays such as ultraviolet rays and electron beams as necessary.

  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) Method for measuring the intrinsic viscosity of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added. And dissolved at 30 ° C.

(2) Measuring method of average particle diameter The coating layer was observed using TEM (H-7650 manufactured by Hitachi High-Technologies Corporation, acceleration voltage 100V), and the average value of the particle diameters of 10 particles was defined as the average particle diameter. .

(3) Method for measuring film thickness of coating layer The surface of the coating layer was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the section prepared by ultramicrotomy stained with RuO _4, a coating layer cross-section was measured by using a TEM (Hitachi High Technologies Corporation H-7650, accelerating voltage 100 V).

(4) Adhesion evaluation method of first coating layer (adhesion 1)
A mixture of poly (3,4-ethylenedioxythiophene) and polystyrene sulfonic acid (CELVIOS PH500 manufactured by HC Starck Co., Ltd.), which is a conductive polymer, is applied to the first coating layer side of the polyester film and dried at 100 ° C. A conductive layer was formed. The obtained film was treated for 10 days in an environment of 85 ° C. and 85% RH, and a 18 mm width tape (Cello Tape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) was applied, and the film was peeled off by 180 degrees. The peeled surface after sharply peeling at an angle was observed. If the peeled area was less than 10%, it was evaluated as ◯ if it was 10% or more and less than 50%, and × if it was 50% or more.

(5) Evaluation method of haze increase value of first coating layer The polyester film was treated for 10 days in an environment of 85 ° C. and 85% RH. Thereafter, 80 parts by weight of dipentaerythritol hexaacrylate, 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, a photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) 5 on the second coating layer side A mixed coating solution of 200 parts by weight of methyl ethyl ketone is applied so that the dry film thickness is 5 μm, and a hard coat layer cured by irradiating with ultraviolet rays is provided, and similarly on the second coating layer side of the film before processing The haze value when the hard coat layer was provided was compared, and the haze increase value after the treatment was evaluated. The haze was measured according to JIS K 7136 using a haze meter HM-150 manufactured by Murakami Color Research Laboratory. The haze increase value is preferably 1.5% or less, more preferably 1.0% or less, and particularly preferably 0.5% or less. Within this range, the heating step after the formation of the conductive layer or wet heat treatment may be used. , Whitening is suppressed, and the film has good visibility.

(6) Whitening Evaluation Method A conductive layer was formed on the first coating layer side of the polyester film in the same manner as in the evaluation of (4) above, and the treatment was performed for 10 days in an environment of 85 ° C. and 85% RH. The surface of the conductive layer was visually observed, and the case where whitening was not confirmed was evaluated as “◯” and the case where whitening was confirmed as “X”.

(7) Evaluation method of absolute reflectance from the surface of the second coating layer in the polyester film In advance, a black tape (vinyl tape VT-50 manufactured by Nichiban Co., Ltd.) is pasted on the measurement back surface of the polyester film, and a spectrophotometer (JASCO Corporation) Using UV-Vis spectrophotometer V-570 and automatic absolute reflectance measuring device ARM-500N), synchronous mode, incident angle 5 °, N-polarized light, response Fast, data collection interval 1.0 nm, bandwidth 10 nm The absolute reflectance of the coating layer surface in the wavelength range of 300 to 800 nm was measured at a scanning speed of 1000 m / min, and the wavelength (bottom wavelength) and reflectance at the minimum value were evaluated.

(8) Interference unevenness evaluation method On the second coating layer side of the polyester film, 72 parts by weight of dipentaerythritol hexaacrylate, 18 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, 10 parts by weight of antimony pentoxide, photopolymerization start Apply a mixed coating solution of 1 part by weight of agent (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) and 200 parts by weight of methyl ethyl ketone so that the dry film thickness is 5 μm, and cure by irradiating with ultraviolet rays to hard coat layer Formed. The obtained film is visually observed under a three-wavelength fluorescent lamp, and interference unevenness is observed. If the interference unevenness is not confirmed, ◎, thin sparse interference unevenness is confirmed, thin, linear The case where the interference unevenness was confirmed was indicated by Δ, and the case where clear interference unevenness was confirmed was indicated by ×.

(9) Adhesion evaluation method of second coating layer (adhesion 2)
In order to evaluate the tighter adhesion, the material obtained by removing antimony pentoxide from the hard coat solution used in the evaluation of the above (8) was examined. That is, 80 parts by weight of dipentaerythritol hexaacrylate, 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, 5 parts by weight of a photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals), 200 parts by weight of methyl ethyl ketone The mixed coating solution was applied so that the dry film thickness was 5 μm, and cured by irradiating with ultraviolet rays to form a hard coat layer. The obtained film was subjected to 10 × 10 cross-cut after 100 hours in an environment of 80 ° C. and 90% RH, and then a 18 mm wide tape (cello tape (registered trademark) CT manufactured by Nichiban Co., Ltd.). -18) is pasted and the peeled surface is observed after being peeled off rapidly at a peeling angle of 180 °. If the peeled area is less than 3%, ◎ if it is 3% or more and less than 10%, or 10% or more and 50% If it was less than △, it was marked as x if it was 50% or more.

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (A)>
100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, 30 ppm of ethyl acid phosphate with respect to the resulting polyester, and 100 ppm of magnesium acetate tetrahydrate with respect to the resulting polyester as the catalyst at 260 ° C. in a nitrogen atmosphere at 260 ° C. The reaction was allowed to proceed. Subsequently, 50 ppm of tetrabutyl titanate was added to the resulting polyester, the temperature was raised to 280 ° C. over 2 hours and 30 minutes, the pressure was reduced to 0.3 kPa in absolute pressure, and melt polycondensation was further carried out for 80 minutes. 0.63 polyester (A) was obtained.

<Method for producing polyester (B)>
100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, and magnesium acetate tetrahydrate as a catalyst were subjected to an esterification reaction at 225 ° C. in a nitrogen atmosphere at 900 ppm with respect to the produced polyester. Subsequently, 3500 ppm of orthophosphoric acid was added to the produced polyester, and 70 ppm of germanium dioxide was added to the produced polyester. The temperature was raised to 280 ° C. over 2 hours and 30 minutes, and the pressure was reduced to an absolute pressure of 0.4 kPa. After 85 minutes of melt polycondensation, polyester (B) having an intrinsic viscosity of 0.64 was obtained.

<Method for producing polyester (C)>
In the production method of polyester (A), polyester (C) is obtained using the same method as the production method of polyester (A), except that 0.3 part by weight of silica particles having an average particle diameter of 2 μm is added before melt polymerization. It was.

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
Metal oxide: (IA) Zirconium oxide particles having an average particle diameter of 15 nm Metal oxide: (IB) Titanium oxide particles having an average particle diameter of 15 nm

・ Oxazoline compounds: (IIA)
Acrylic polymer having an oxazoline group and a polyalkylene oxide chain Epocros WS-500 (manufactured by Nippon Shokubai Co., Ltd., containing about 38% by weight of 1-methoxy-2-propanol solvent)
・ Oxazoline compounds: (IIB)
Acrylic polymer having oxazoline group and polyalkylene oxide chain Epocros WS-700 (Nippon Shokubai Co., Ltd., VOC free type)

Epoxy compound: (IIIA) Denacol EX-521 (manufactured by Nagase ChemteX Corporation), which is polyglycerol polyglycidyl ether.
Epoxy compound: (IIIB) Denacol EX-1410 (manufactured by Nagase ChemteX Corporation), which is an epoxy resin.

・ Condensed polycyclic aromatic polyester resin: (IVA)
Water dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / diethylene glycol = 92/8 // 80/20 (mol%)

・ Polyester resin: (IVB)
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%)

Acrylic resin: (IVC) Aqueous dispersion of acrylic resin polymerized with the following composition: ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (% by weight) Emulsion polymer (emulsifier: anionic surfactant)

-Urethane resin: (IVD)
400 parts of polycarbonate polyol composed of 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 2000, 10.4 parts of neopentyl glycol, 58.4 parts of isophorone diisocyanate, and 74.3 parts of dimethylolbutanoic acid. An aqueous dispersion of urethane resin obtained by neutralizing a prepolymer with triethylamine and extending the chain with isophoronediamine.

・ Urethane resin (IVE)
Hydran AP-40 (manufactured by DIC Corporation), which is a carboxylic acid water-dispersed polyester polyurethane resin

・ Hexamethoxymethylmelamine (V)

・ Particles: (VIA) Silica particles with an average particle size of 0.07 μm ・ Particles: (VIB) Silica particles with an average particle size of 0.15 μm

Example 1:
A mixed raw material in which polyesters (A) and (B) are mixed at a ratio of 95% and 5%, respectively, is used as a raw material for the outermost layer (surface layer), and polyesters (A), (B), and (C) are 89% and 5%, respectively. % And 6% mixed raw materials were used as intermediate layer raw materials, each was supplied to two extruders, melted at 285 ° C., and then on a cooling roll set at 40 ° C. Coextruded with a layer structure of layers (surface layer / intermediate layer / surface layer = 1: 18: 1 discharge amount) and cooled and solidified to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid A1 shown in Table 1 below was applied to one side of the longitudinally stretched film (first coating layer). The coating liquid B3 shown in Table 2 below is applied to the opposite surface (formation of the second coating layer), led to a tenter, stretched 4.0 times at 120 ° C in the transverse direction, and heat-treated at 225 ° C. Thereafter, the film is relaxed by 2% in the lateral direction, and the thickness of the first coating layer (after drying) is 0.05 μm, and the thickness of the second coating layer (after drying) is 0.10 μm. A polyester film was obtained.

  When the obtained polyester film was evaluated, the adhesion with the conductive layer was good, the haze increase value was low, and no whitening was observed, which was a good result. Further, when the absolute reflectance of the second coating layer was measured, the minimum value was 600 nm, the reflectance was 5.0%, and there was no clear interference unevenness in the film after forming the hard coat layer. Adhesion was also good. The properties of this film are shown in Tables 3 and 4 below.

Examples 2-33:
In Example 1, it manufactured like Example 1 except having changed the coating composition into the coating composition shown in Table 1 and Table 2, and obtained the polyester film. As shown in Tables 3 and 4, the finished polyester film had good adhesion between the first coating layer and the second coating layer, the second coating layer had high reflectance, and the interference unevenness level was also good. It was.

Comparative Examples 1-9:
In Example 1, it manufactured like Example 1 except having changed the coating composition into the coating composition shown in Table 1 and Table 2, and obtained the polyester film. When the finished laminated polyester film was evaluated, as shown in Tables 5 and 6 below, when the adhesiveness was poor, the haze increase value was high, and clear interference unevenness could be observed.

  The film of the present invention is suitably used for applications that place importance on adhesion with a conductive layer, adhesion with a surface functional layer such as a hard coat layer, and visibility, such as a transparent electrode such as a touch panel or an electromagnetic shielding film. be able to.

Claims (4)

A coating layer formed from a coating solution containing a polyester resin and an oxazoline compound on one surface of a polyester film, and formed from a coating solution containing a metal oxide and two or more crosslinking agents. Then, the absolute reflectance of the coating layer surface has one minimum value in the wavelength range of 400 to 800 nm, and the other surface has a coating layer whose absolute reflectance at the minimum value is 4.0% or more. A laminated polyester film characterized by that. The laminated polyester film according to claim 1, wherein the metal oxide is zirconium oxide or titanium oxide. The laminated polyester film according to claim 1 or 2, comprising a condensed polycyclic aromatic compound in a coating layer formed from a coating solution containing a metal oxide and two or more kinds of crosslinking agents. The laminated polyester film according to any one of claims 1 to 3, wherein the crosslinking agent is a compound selected from an oxazoline compound or an epoxy compound.