JP2013095122A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film which has excellent light shielding property, and excellent characteristics for coating, adhering and designing of hard coat material and which can be used for a long period after being processed as a window film.SOLUTION: Coextrusion laminated polyester film is formed of at least three layers and contains dye in an intermediate layer. The film has a primer layer at least on one of the surfaces. An absolute reflectance of the primer layer surface has one minimal value in a wavelength range of 400-800 nm and an absolute reflectance in the minimal value is 4.0% or greater.

Description

  The present invention relates to a laminated polyester film, and is a laminated polyester film suitable for window pasting that is used by laminating to glass such as automobile windows and building windows, and a hard coat layer. The present invention relates to a laminated polyester film that is also suitable for applications that require reduction in interference unevenness due to external light reflection.

  In recent years, films laminated to automobile windows and building windows for the purpose of protecting privacy, design, adjusting sunlight, preventing glass scattering, etc., have transparency, light resistance, water resistance, heat resistance, A polyester film having excellent chemical properties and mechanical strength is often used.

  We have proposed using a composite film containing a dye in the inner layer of three or more layers of laminated polyester film as a polyester film for window pasting having a light shielding property (Patent Document 1).

  By the way, these light-shielding films usually have a layer structure in which a hard coat process is usually applied to one surface, a paste is applied to the opposite surface, and a release film is stuck thereon. When producing this light-shielding film for pasting windows, it is usually necessary to perform solvent-based hard coat processing and paste application processing in order to improve performance such as scratch prevention and surface hardness. At this time, if the interference visually recognized on the hard coat layer surface is strong, visibility and designability are required.

  In order to improve the adhesion between the polyester film used as the substrate and the hard coat layer, an easily adhesive primer 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 easy-adhesion primer layer, and the hard coat layer is taken into consideration.

  If a film with interference unevenness is used, the visibility becomes poor, and it becomes difficult to use or the design is poor. Therefore, it is required to take measures against interference unevenness.

  In general, the refractive index of the primer 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 primer layer with a high refractive index.

  An example of improving interference unevenness by increasing the refractive index of the primer layer is, for example, a method of combining a metal chelate compound having a high refractive index and a resin in the primer 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 when it carries out moisture-proof heat processing (patent document 2). Moreover, since a high refractive index material that is usually used is inferior in adhesion to a surface functional layer such as a hard coat layer, a primer layer that can effectively improve adhesion even in combination with a high refractive index material is required. Yes.

Japanese Patent Laid-Open No. 1-264843 JP 2005-97571 A

  The present invention has been made in view of the above circumstances, and the solution is to have excellent light shielding properties, excellent hard coat material coating properties, adhesion properties, and design properties, for example, processing into a window pasting film. It is to provide a film that can be used for a long time after being applied.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be solved to a high degree according to a polyester film having a specific laminated structure, and have completed the present invention.

  That is, the gist of the present invention is that a primer layer is provided on at least one surface of at least three layers of coextruded laminated polyester film containing a dye in the intermediate layer, and the absolute reflectance of the primer layer surface has a wavelength of 400 to 800 nm. It exists in the laminated polyester film characterized by having one minimum value in the range and having an absolute reflectance of 4.0% or more at the minimum value.

  According to the laminated polyester film of the present invention, it has excellent light-shielding properties, and is excellent in applicability, adhesion, and design properties of a hard coat material. For example, it is used for a long time even after being processed into a window pasting film. Can be provided, and its industrial value is high.

  The biaxially oriented polyester film of the present invention needs to be a film in which at least three or more polyester layers are laminated. More specifically, all the layers are melt-extruded together from an extrusion die, so-called co-polymerization. It is a film extruded by an extrusion method. Further, the film is not an unstretched state or a uniaxially stretched film, but needs to be a film that is stretched and oriented in the biaxial directions of the longitudinal direction and the transverse direction and then heat-set. Such a laminated film has a coextruded surface layer on both sides and a coextruded intermediate layer therebetween, but the coextruded intermediate layer itself may have a laminated structure.

  When the polyester film has a single layer structure, the phenomenon that the added dye springs up to the film surface (bleed out) and the phenomenon that it sublimates easily occur, and this causes contamination of the film forming machine, In many cases, the production itself is not possible, and even if it can be produced, the surface layer contains springs from the inside of the film due to bleed-out, which is not preferable because it often adversely affects post-processing.

  The polyester film of the present invention is obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol with a polyester used for each layer laminated. 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. Representative polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and the like. Among these, PET has a good balance between physical properties and cost, and is the most frequently used polyester.

  The polyester used in the present invention may be a copolymer containing a third component as long as it is generally within 10 mol%, preferably within 5 mol%. Examples of the dicarboxylic acid component of the copolyester include one or two of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (for example, P-oxybenzoic acid). The glycol component includes one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like.

  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. Among these, a titanium compound is preferable from the viewpoint of increasing the brightness of the film.

  The laminated polyester film of the present invention needs to contain a dye in at least one of the coextruded intermediate layers of the laminated structure, and the dye preferably has absorption in the visible light region (380 to 780 nm). By including such a dye, the visible light transmittance of the entire film is preferably in the range of 3 to 70%, more preferably 5 to 50%.

  The dye used in the present invention is preferably substantially dissolved in the polyester. The term “substantially dissolved” as used herein means that when kneaded in the molten state of polyester, it means that the aggregates are not mixed and remain uniformly, and as described later, the film haze after biaxial orientation is reduced. It means 5.0% or less, preferably 4.0% or less. These dyes are preferably those which are less decomposed at the molding temperature of the polyester. Such dyes are preferably anthraquinone, perinone, perylene, azomethine, and heterocyclic dyes in terms of chemical structure, and dispersible dyes and oil-soluble dyes are suitable in terms of dyeing formulation. Moreover, even if it is generally classified as a pigment, it can be used as a dye in the present invention as long as it is soluble in molten polyester as described above. Examples thereof include complex salt dyes with metal ions such as copper, cobalt, nickel, zinc and chromium such as phthalocyanine.

  The above-mentioned dyes are generally used by appropriately selecting and mixing several kinds of dyes, for example, in order to adjust to gray or brown tones. It can be appropriately selected from the range of 01 to 10.0% by weight, preferably 0.05 to 5.0% by weight.

  The laminated polyester film of the present invention is a UV absorber or radical trap capable of withstanding the heat applied in the production process of a known polyester film in order to prevent deterioration due to external light, etc. in addition to the dyes described above in the coextruded intermediate layer. An agent or the like can coexist. However, even if these additives are added, the film haze is preferably within the above-mentioned range without causing turbidity in the 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 laminated polyester film of the present invention, particles can be blended mainly for the purpose of imparting slipperiness and preventing scratches in each step, but blending the particles from the viewpoint of transparency. A small amount is preferred. When the particles are blended, the kind of the particles to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness, and specific examples thereof include, for example, silica, calcium carbonate, magnesium carbonate, barium carbonate, sulfuric acid. Examples thereof include inorganic particles such as calcium, calcium phosphate, magnesium phosphate, 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.

  Moreover, when mix | blending particle | grains, the average particle diameter of particle | grains is 3 micrometers or less normally, Preferably it is the range of 0.01-1.5 micrometers. When the average particle size exceeds 3 μm, the transparency of the film may be deteriorated, or the graininess due to the particles may be generated and the visibility may be deteriorated.

  The content of the particles depends on the average particle size, but in the polyester film layer containing the particles, it is usually in the range of 1000 ppm or less, preferably in the range of 500 ppm or less, more preferably in the range of 50 ppm or less (intentionally contained). Do not). When it exceeds 1000 ppm, transparency may deteriorate, or graininess due to particles may occur and visibility may deteriorate.

  In order to ensure the minimum slipperiness without deteriorating the visibility of the film, the average surface roughness Ra of the film surface is in the range of 0.005 to 0.050 μm by including the above particles. It is preferable to be inside.

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

In the laminated polyester film of the present invention, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, infrared absorbers and the like as required in addition to the above-mentioned particles. It is also possible to add additives in known amounts.
In the present invention, the method of adding a dye and other additives to the laminated polyester may be a method of adding these powders, pastes, or liquids when melt-forming a film. Considering the ease of switching between brands, it is preferable to prepare a masterbatch such as a dye in advance and add the masterbatch while diluting with a clear resin during melt molding of the film. In addition, it is particularly preferable to use a twin screw extruder in order to carry out these melt moldings while kneading the polyester with good dispersion.

  Further, regarding the laminated thickness structure of the coextruded surface layer and the coextruded intermediate layer, it is preferable that the coextruded surface layer to which fine particles are added is as thin as possible in order to suppress turbidity (film haze) of the entire film. On the other hand, in order to prevent the dye and other additives present in the intermediate layer from bleeding out, the coextruded surface layer is preferably thicker. Taking these into consideration, the thickness of the coextruded surface layer is usually preferably in the range of 0.5 to 5.0 μm on one side regardless of the thickness of the entire film. Moreover, although the thickness of both surface layers may be the same or may differ, it is preferable that both are in said thickness range also in different cases.

  The thickness of the laminated polyester film in the present invention is not particularly limited as long as it can be formed as a film, but is usually in the range of 10 to 300 μm, preferably 15 to 100 μm.

  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 drying the above-described polyester pellet raw material and cooling and solidifying the molten sheet extruded from the multilayer die using a single-screw extruder with a cooling roll 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 270 ° C. under tension or 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 primer layer which comprises the laminated polyester film in this invention is demonstrated. Regarding the primer layer in the present invention, it may be provided by in-line coating, which treats the film surface during the process of forming a polyester film, or may be applied outside the system on the manufactured film, or may employ offline coating. Good. 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 a primer layer is provided on a polyester film by in-line coating, the primer layer can be applied simultaneously with film formation, and the primer layer can be treated at a high temperature in the heat treatment step 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 a primer 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, the absolute reflectance of the primer layer surface 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 is lowered or the design property is lowered.

  In order to form the primer layer in the present invention, it is preferably provided with a primer layer formed from a coating solution containing a metal oxide and two or more kinds of crosslinking agents.

  The metal oxide is mainly used for adjusting the refractive index of the primer layer. In particular, since the refractive index of the resin used in the primer 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.

  Various known resins can be used as the crosslinking agent, and examples thereof include an oxazoline compound, an epoxy compound, a melamine compound, an isocyanate compound, and a carbodiimide compound. In the selection of the two kinds of crosslinking agents, it is particularly preferable from the viewpoint of improving the adhesion with the hard coat layer that a compound derived from an oxazoline compound and a compound derived from an epoxy compound are contained.

  In the present invention, the primer layer preferably contains a compound derived from an oxazoline compound and a compound derived from an epoxy compound, but these improve adhesion with a surface functional layer such as a hard coat layer provided on the primer layer. Can be made. Although it has been found that a compound derived from an oxazoline compound or a compound derived from an epoxy compound alone can improve the adhesion, it is possible to further improve the adhesion by using these two kinds of compounds in combination. It was found that the adhesion after the wet heat test can be improved.

  The compound derived from an oxazoline compound in the present invention is a compound obtained as a result of a reaction between a compound having an oxazoline group in the molecule and an oxazoline group. The compound having an oxazoline group in the molecule is preferably a polymer containing an oxazoline group, and can be prepared by polymerization of an addition polymerizable oxazoline group-containing monomer alone or with another monomer. 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.

  The compound derived from the epoxy compound in the present invention is a compound having an epoxy group in the molecule and a compound obtained as a result of reaction of the epoxy group. Examples of the compound having an epoxy group in the molecule include condensates of epichlorohydrin and ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A and the like with hydroxyl groups and amino groups, such as polyepoxy compounds and diepoxy compounds. 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 compound include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidyl amine compound such as N, N, N ′, N ′,-tetraglycidyl-m-. Examples include xylylenediamine and 1,3-bis (N, N-diglycidylamino) cyclohexane.

  A melamine compound as another crosslinking agent is a compound having a melamine skeleton in the compound. For example, an alkylolated melamine derivative, a compound partially or completely etherified by reacting an alcohol with an alkylolated melamine derivative, and a mixture thereof 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 the 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 and 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 used for improving adhesion with a surface functional layer such as a hard coat layer that can be formed on a coating layer, and for improving wet heat resistance of the coating layer. It is The carbodiimide compound is a compound having one or more carbodiimide or carbodiimide derivative structures in the molecule, but a polycarbodiimide compound having two or more in the molecule is more preferable for better adhesion and the like.

  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 of the present invention, for improving the coated surface, reducing interference unevenness when various surface functional layers such as a hard coat layer are laminated on the coated surface, improving transparency and adhesion, etc. It is preferable to use various polymers.

  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.

  In order to make it easier to adjust the refractive index of the primer layer, it is preferable to use a compound having a condensed polycyclic aromatic structure as exemplified by the following formula.

  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 primer 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 primer layer and good 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, and amide groups may be introduced from the viewpoints of coatability and adhesion.

  In the present invention, the primer layer may contain particles other than the above-described metal oxides for the purpose of improving adhesion (blocking) and slipperiness. 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 primer layer may be provided with an antifoaming agent, a coating property improver, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, an antioxidant, a foam as necessary. Agents, dyes, pigments and the like may be contained.

  The ratio of the metal oxide used in the primer layer of the present invention is usually in the range of 3 to 70% by weight, preferably 5 to 50% by weight, more preferably 5 to 40% by weight, particularly preferably 8 to It is in the range of 30% by weight. When the amount of the metal oxide is less than 3% by weight, the refractive index of the primer layer cannot be made sufficiently high, so that interference unevenness may not be reduced. When it exceeds 70% by weight, the primer layer is transparent. Sexuality may worsen.

  The ratio of the crosslinking agent used in the primer layer of the present invention is generally in the range of 1 to 70% by weight, more preferably 1 to 50% by weight, and further preferably 3 to 40% by weight in total of the crosslinking agents. 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 reduced. If the amount exceeds 70% by weight, the refractive index of the primer 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.

  The proportion of the compound derived from the oxazoline compound used in the primer layer of the present invention is in the range of 1 to 50% by weight, more preferably 1 to 30% by weight, still more preferably 3 to 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 the hard coat layer may be reduced. If the amount exceeds 50% by weight, the refractive index of the primer 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.

  The proportion of the compound derived from the epoxy compound used in the primer layer of the present invention is usually in the range of 1 to 50% by weight, more preferably in the range of 3 to 30% by weight, still more preferably in the range of 5 to 20% by weight. It is a range. When 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 coated surface state may be deteriorated.

  In the compound having a condensed polycyclic aromatic that can be used in the primer 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 proportion of the compound having a condensed polycyclic aromatic in the entire primer 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 primer 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, for example, by dissolving and extracting the primer 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.

  In the polyester film of the present invention, a primer layer can also be provided on the surface opposite to the surface on which the primer layer is provided. For example, when forming a functional layer such as a microlens layer, a prism layer, an anti-sticking layer, a light diffusion layer, a hard coat layer, an adhesive layer, or a print layer on the opposite side of forming a surface functional layer such as a hard coat layer, Adhesion with the functional layer can be improved. A conventionally well-known thing can be used as a component of the primer layer formed in the surface on the opposite side. Examples thereof include binder polymers such as polyester resins, acrylic resins and urethane resins, cross-linking agents such as oxazoline compounds, epoxy compounds, melamine compounds, isocyanate compounds and carbodiimide compounds, and these materials may be used alone. A plurality of types may be used in combination. Further, it may be a primer layer (a primer layer having the same surface on both sides of a polyester film) containing a metal oxide, a compound derived from an oxazoline compound, and a compound derived from an epoxy compound as described above.

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

  When providing a primer layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or water dispersion, and a coating solution prepared by adjusting the solid content concentration to about 0.1 to 50% by weight as a guide is applied to 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 primer 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, the primer layer may be provided by a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating or the like.

  In the present invention, the drying and curing conditions for forming the primer layer on the polyester film are not particularly limited. For example, when the primer layer is provided by off-line coating, it is usually 3 to 40 at 80 to 200 ° C. The heat treatment may be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when providing a primer layer by in-line coating, it is usually preferable to perform heat treatment 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 primer layer in the present invention has a refractive index adjusted in order to suppress the occurrence of interference unevenness, and the refractive index is in the vicinity of the geometric mean of the surface functional layer such as the polyester film of the substrate and the hard coat layer. Designed. The refractive index of the primer layer and the reflectance of the primer layer are closely related.

  In the polyester film of the present invention, a surface functional layer such as a hard coat layer is generally provided on the primer 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 active energy ray-curable polyfunctional (meth) acrylate is particularly preferable.

  It does not specifically limit as a composition containing active energy ray-curable polyfunctional (meth) acrylate. For example, a mixture of one or more known active energy ray-curable polyfunctional (meth) acrylates, a commercially available active energy ray-curable hard coat material, or other than these, the purpose of the present embodiment is impaired. As long as there are no other components, those further added with other components can be used.

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

  The other component contained in the composition containing active energy ray-curable polyfunctional (meth) acrylate is 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. In the examples and comparative examples, “parts” means “parts by weight”. The measuring method used in the present invention is as follows.

(1) Measuring method of 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 primer layer was observed using TEM (H-7650 manufactured by Hitachi, Ltd., acceleration voltage 100 V), 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 primer layer The surface of the primer layer was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the section prepared by ultramicrotomy stained with RuO _4, was measured using a primer layer sectional TEM (manufactured by Hitachi, Ltd. H-7650, accelerating voltage 100 V).

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

(5) Interference unevenness evaluation method On the primer 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, a photopolymerization initiator ( (Product name: Irgacure 184, manufactured by Ciba Specialty Chemicals) 1 part by weight of a mixed coating solution of 200 parts by weight of methyl ethyl ketone was applied to a dry film thickness of 5 μm and cured by irradiating with ultraviolet rays to form a hard coat layer. . The obtained film was visually observed for interference unevenness under a three-wavelength light region type fluorescent lamp, and ranked as follows.
◎: Interference unevenness cannot be confirmed ○: Thin and sparse interference unevenness is confirmed △: Thin but linear interference unevenness can be confirmed ×: Clear interference unevenness is confirmed

(6) Hard coat layer adhesion evaluation method In order to perform a more stringent evaluation of adhesion, examination was performed with materials obtained by removing antimony pentoxide from the hard coat solution used in the evaluation of (5) above. 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 as to have a dry film thickness of 5 μm, and cured by irradiation 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 a 18 mm wide tape (Cello Tape (registered trademark) CT-Nichiban Co., Ltd.) 18) was affixed, the peeled surface after being peeled off rapidly at a peel angle of 180 degrees was observed, and the rank evaluation was performed based on the peeled area as follows.
◎ Peeling area: less than 3% ○: Peeling area: 3% or more and less than 10% △: Peeling area: 10% or more and less than 50% ×: Peeling area: 50% or more

(7) Visible light transmittance The light transmittance of each wavelength was measured with a D65 light source using a spectrocolorimeter SE-2000 (manufactured by Nippon Denshoku), and the visible light transmittance was calculated according to JIS-S3107.

(8) Turbidity of film (film haze)
According to JIS-K7105, the turbidity (haze) of the film was measured using a turbidimeter NDH300A (manufactured by Nippon Denshoku).

(9) Pencil hardness on the surface of the hard coat layer The pencil hardness on the surface of the hard coat layer was displayed according to JIS-K5401.

The manufacturing method of the polyester raw material used in the following examples and comparative examples is as follows.
<Polyester A>
100 parts of dimethyl terephthalate, 60 parts of ethylene glycol, and 0.09 part of magnesium acetate tetrahydrate are placed in a reactor, and the temperature is raised while heating, the methanol is distilled off, a transesterification reaction is performed, and it takes 4 hours from the start of the reaction. The temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, 0.04 part of ethyl acid phosphate and 0.04 part of antimony trioxide were added, and then the temperature was 280 ° C. and the pressure was 15 mmHg in 100 minutes. The pressure was gradually reduced thereafter, and finally 0.3 mmHg It was. After 4 hours, the system was returned to normal pressure to obtain polyester A substantially free of fine particles. The intrinsic viscosity of this polyester was 0.70.

<Polyester B>
100 parts of dimethyl terephthalate, 60 parts of ethylene glycol, and 0.09 part of magnesium acetate tetrahydrate are placed in a reactor, and the temperature is raised while heating, the methanol is distilled off, a transesterification reaction is performed, and it takes 4 hours from the start of the reaction. The temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, an ethylene glycol slurry containing 2.0 parts of silica particles having an average particle diameter of 1.4 μm was added to the reaction system, and further 0.04 parts of ethyl acid phosphate and 0.04 parts of antimony trioxide were added. In 100 minutes, the temperature was 280 ° C. and the pressure was 15 mmHg, and thereafter the pressure was gradually reduced to finally 0.3 mmHg. After 4 hours, the system was returned to normal pressure to obtain polyester B. The resulting polyester B had a silica particle content of 1.0% by weight. The intrinsic viscosity of this polyester was 0.70.

<Polyester C>
Polyester A is subjected to a twin screw extruder with a vent to have a concentration of 3.0% by weight of Mitsubishi Chemical's Dial Resin Red HS, 5.5% by weight of Blue H3G, and 1.5% by weight of Yellow F, respectively. Thus, the mixture was added and melt-kneaded to form chips to prepare a dye master batch polyester C.

Examples of compounds constituting the primer layer are as follows.
(Example compounds)
・ Metal oxide: (1A)
Zirconium oxide particles / metal oxide with an average particle size of 15 nm: (1B)
Titanium oxide particles with an average particle size of 15 nm

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

・ Epoxy compounds: (3A)
Denacol EX-521 (manufactured by Nagase ChemteX Corporation), which is polyglycerol polyglycidyl ether.
・ Epoxy compounds: (3B)
Denacol EX-1410 (manufactured by Nagase ChemteX Corporation), which is an epoxy resin.

・ Polyester resin having condensed polycyclic aromatic: (4A)
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: (4B)
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: (4C)
Aqueous dispersion of acrylic resin polymerized with the following composition: Emulsion polymer of ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (% by weight) (emulsifier: Anionic surfactant)
・ Urethane resin (4D)
Hydran AP-40 (manufactured by DIC), which is a carboxylic acid water-dispersed polyester polyurethane resin

・ Hexamethoxymethylmelamine (5)
-Particles: (6A) Silica particles with an average particle size of 0.07 [mu] m-Particles: (6B) Silica particles with an average particle size of 0.12 [mu] m

Examples of compounds constituting the hard coat layer are as follows.
・ Hard coat material: (mixed coating liquid)
Dipentaerythritol hexaacrylate 72 parts by weight 2-hydroxy-3-phenoxypropyl acrylate 18 parts by weight Antimony pentoxide 10 parts by weight Photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals) 1 part by weight Methyl ethyl ketone 200 parts by weight

Example 1:
The chips of polyesters A and C were charged into the intermediate layer extruder at a ratio of 78.0: 22.0, respectively, as an intermediate layer resin. Separately, each chip of polyester A and B was put into a surface layer extruder as a surface layer resin at a ratio of 93.0: 7.0. Each of the extruders was a bi-directional extruder with a vent, and the resin was extruded at a melting temperature of 290 ° C. without drying, and then the molten polymers were merged in a feed block and laminated. Thereafter, it was cooled and solidified on a cooling roll whose surface temperature was set to 40 ° C. using an electrostatic application adhesion method, to obtain a laminated unstretched sheet having a three-layer structure. The obtained sheet was stretched 3.6 times in the longitudinal direction at 83 ° C. Here, a water-dispersible coating agent having a solid content weight ratio shown in the coating solution 1 of Table 1 below was uniformly applied to both surfaces of the uniaxially stretched film so that the thickness after film formation was 0.10 μm. Next, the film was guided to a tenter, dried and preheated at 93 ° C., stretched 3.8 times in the transverse direction, and heat fixed at 225 ° C. Further, a 5% relaxation treatment was performed in the width direction at 185 ° C., and after cooling, a roll of a biaxially oriented film was prepared by winding. The thickness of each layer of this film was 2/21/2 μm, and the total thickness was 25 μm. The properties of this film are shown in Table 2 below. The obtained film roll was subjected to a slitter and slit into a predetermined width to create a film roll. The film roll was set on a coater, the hard coat material having the above composition was applied, dried at 90 ° C., and then cured under a predetermined condition with a high-pressure mercury lamp to form a 5 μm hard coat layer. The obtained laminated polyester film has no clear interference unevenness in the film after laminating the hard coat layer, and has good adhesion. The properties of this film are shown in Table 2 below.

Examples 2-25:
In Example 1, it manufactured like Example 1 except having changed an application agent composition into the application agent composition shown in Table 1, respectively, and obtained the laminated polyester film. The properties of this film are shown in Table 2. This film roll was subjected to the same slitter as in Example 1 and slit to a predetermined width to prepare a film roll. As shown in Table 2, the finished polyester film had a high reflectance, and the interference unevenness level after laminating the hard coat layer was good. As for adhesion, a film using coating solutions 1 to 19 in which two kinds of crosslinking agents were used in combination was good. In the case of one kind of the crosslinking agent, the film using oxazoline in the coating solution 22 was relatively good, but in the coating solutions 21, 23, and 24, the adhesion was inferior.

Example 26:
In Example 1, each of the chips of polyester A and C was added to the intermediate layer extruder at a ratio of 95.5: 4.5 as an intermediate layer resin, and the coating composition was changed to the coating solution 3. Was produced in the same manner as in Example 1 to obtain a laminated polyester film. The properties of this film are shown in Table 2. This film roll was subjected to the same slitter as in Example 1 and slit to a predetermined width to prepare a film roll. As shown in Table 2, the finished polyester film had high reflectivity, good interference unevenness level after laminating the hard coat layer, and good adhesion.

Comparative Example 1:
In Example 1, it manufactured like Example 1 except having changed an application agent composition into the application agent composition shown in Table 1, respectively, and obtained the laminated polyester film. The properties of this film are shown in Table 2. This film roll was subjected to the same slitter as in Example 1 and slit to a predetermined width to prepare a film roll. When the finished laminated polyester film was evaluated, as shown in Table 2, clear interference unevenness could not be observed after laminating the hard coat layer. Adhesion was good.

Comparative Example 2:
In Example 1, 100% of polyester A was used as the intermediate layer resin, and the surface layer resin was manufactured in the same manner as in Example 1 except that the same resin as in Example 1 was used to obtain a polyester film. The properties of this film are shown in Table 2. This film roll was subjected to the same slitter as in Example 1 and slit to a predetermined width to prepare a film roll.
However, since no dye is added to the intermediate layer of this film, there is no light shielding property, which is outside the scope of the present invention.

  In Table 2 above, film haze 1 is the film haze up to the primer layer, and film haze 2 is the film haze up to the hard coat layer.

  The film of the present invention can be suitably used as, for example, a window pasting film.

Claims (3)

A primer layer is provided on at least one surface of at least three coextruded laminated polyester films containing a dye in the intermediate layer, and the absolute reflectance of the primer layer surface has one minimum value in the wavelength range of 400 to 800 nm. And the absolute reflectance in the said minimum value is 4.0% or more, The laminated polyester film characterized by the above-mentioned. The laminated polyester film according to claim 1, wherein the primer layer is a primer layer formed from a coating solution containing a metal oxide and two or more kinds of crosslinking agents. The film for window sticking which consists of a laminated polyester film of Claim 1 or 2 whose haze of the whole laminated polyester film is 5.0% or less and whose visible light transmittance is 3 to 70%.