JP5730961B2 - Laminated polyester film - Google Patents

Description

  The present invention, for example, has less oligomer precipitation from the film even after being exposed to high temperature, adhesion to a surface functional layer such as a hard coat layer used in a transparent conductive laminate of a touch panel, and external light reflection. It is related with the laminated polyester film suitable for the use where reduction of the interference nonuniformity by is calculated | required.

Polyester films are excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, etc., and are used in various fields.

  In particular, in recent years, it has been increasingly used instead of glass as a base material for a transparent conductive laminate, which is increasingly used for touch panels and the like. As such a transparent conductive laminate, there is one in which a polyester film is used as a base material and an ITO (indium tin oxide) film is formed by sputtering directly or via an anchor layer. Such a polyester film is generally heat-processed.

  For example, there are treatments such as leaving for 1 hour at 150 ° C. for low heat shrinkage (Patent Document 1) and performing heat treatment at 150 ° C. for crystallization of ITO (Patent Document 2).

  However, as a problem of polyester film, when exposed to such high temperature and long time treatment, oligomers (low molecular weight component of polyester, especially ester cyclic trimer) contained in the film are precipitated and crystallized on the film surface. As a result, deterioration of visibility due to whitening of the external appearance of the film, defects in post-processing, contamination of the process and members, and the like occur. Therefore, the characteristics of the transparent conductive laminate based on the polyester film cannot be said to be sufficiently satisfactory.

  Further, as a measure for preventing oligomer precipitation, for example, it has been proposed to provide a curable resin layer made of a crosslinked product of a silicone resin and an isocyanate resin on a polyester film (Patent Document 3). However, the curable resin layer is formed by thermosetting, requires high-temperature treatment for dissociation of the blocking agent of the isocyanate resin, and is in a situation where curling and sagging are likely to occur during processing. Care must be taken in handling.

  Therefore, when taking measures to reduce the amount of oligomer precipitation by the coating layer, it is necessary to have higher heat resistance than before and the oligomer sealing performance of the coating layer itself must be good. is there.

  Furthermore, when used as a base material of a transparent conductive laminate, it is often hard-coated to prevent curling, improve scratch resistance, and improve performance such as surface hardness. In order to improve the adhesion between the polyester film and the hard coat layer, an easy-adhesion coating layer is generally provided as an intermediate layer, but the reflected light on one side of the hard coat layer and the opposite side Interference of the reflected light may cause rainbow pattern unevenness (interference unevenness).

  If a film with interference unevenness is used for a display member such as a touch panel, the visibility is poor and it is difficult to use. For this reason, a film with reduced interference unevenness is desired. In order to reduce interference unevenness, it is considered that the refractive index of the coating layer should be adjusted to the vicinity of the geometric mean of the refractive index of the polyester film of the substrate and the refractive index of the hard coat layer. It is ideal to adjust. 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 includes, for example, a method of blending a metal chelate compound having a high refractive index in the coating layer. However, in the case of chelate compounds, the stability of the coating solution may not be sufficient depending on the combination due to the instability of the metal chelate in an aqueous solution. (Patent Document 4).

JP 2007-42473 A JP 2007-200823 A JP 2007-320144 A JP 2005-97571 A

  The present invention has been made in view of the above circumstances, and its solution is to suppress oligomers precipitated from the film when exposed to high temperatures, for example, during storage of the film, use of the film, processing of the film, etc. It is an object of the present invention to provide a laminated polyester film that does not cause problems associated with, and reduces interference unevenness due to external light after forming a surface functional layer such as a hard coat layer.

  As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by providing a specific coating layer, and have completed the present invention.

  That is, the gist of the present invention is to have a coating layer formed from a coating solution containing a polyvalent aldehyde compound on one surface of a polyester film, and to have a minimum value within a wavelength range of 400 to 800 nm. And having a coating layer having an absolute reflectance of 4.0% or more at the minimum value on the other surface of the polyester film.

  According to the laminated polyester film of the present invention, the amount of oligomer precipitation due to high-temperature and long-time treatment is small, and when various surface functional layers such as a hard coat layer are laminated, there is little interference unevenness due to reflection of external light, and various surfaces A base film excellent in adhesion to the functional layer can be provided, and its industrial utility value is high.

  The base film of the laminated polyester film of the present invention is made of polyester. Such polyesters include dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexyldicarboxylic acid or esters thereof. It is a polyester produced by melt polycondensation with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol. Polyesters composed of these acid components and glycol components can be produced by arbitrarily using a commonly used method.

  For example, a transesterification reaction between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or a direct esterification of an aromatic dicarboxylic acid and a glycol, to form a substantially bisglycol of an aromatic dicarboxylic acid A method is employed in which an ester or a low polymer thereof is formed and then polycondensed by heating under reduced pressure. Depending on the purpose, an aliphatic dicarboxylic acid may be copolymerized.

  Typical examples of the polyester of the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and the like. It may be a polymerized polyester and may contain other components and additives as necessary.

  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, antimony compounds have the advantage of being inexpensive and having high catalytic activity. Titanium compounds and germanium compounds are preferable because they have high catalytic activity and can be polymerized in a small amount, and since the amount of metal remaining in the film is small, the brightness of the film is increased. Furthermore, since a germanium compound is expensive, it is more preferable to use a titanium compound.

  The polyester film in the present invention may have a single layer structure or a multilayer structure. In the case of a multilayer structure, the surface layer and the inner layer, or both the surface layer and each layer can be made of different polyesters depending on purposes.

  In this invention, in order to suppress the precipitation amount of the ester cyclic trimer after heat processing, manufacturing a film from polyester with little content of ester cyclic trimer is mentioned. Various known methods can be used as a method for producing a polyester having a low ester cyclic trimer content. Examples thereof include a method of solid-phase polymerization after polyester production.

  Precipitation of ester cyclic trimer after heat treatment by designing a layer using a polyester raw material with a low content of ester cyclic trimer in the outermost polyester layer of the polyester film, with a polyester film comprising three or more layers A method of reducing the amount is also possible.

  The content of the ester cyclic trimer contained in the polyester film is about 1% by weight in a general production method, but from the viewpoint of preventing precipitation of the ester cyclic trimer, the content of the ester cyclic trimer Is preferably 0.7% by weight or less, more preferably 0.6% by weight or less. When the polyester cyclic trimer content is 0.7% by weight or less, the effect of preventing the precipitation of the ester cyclic trimer on the film surface is particularly high.

  The polyester used for forming the polyester layer can use a polyester raw material with a low ester cyclic trimer content, and the ester cyclic trimer content is preferably 0.7% by weight or less, More preferably, it is 0.6 weight% or less, Most preferably, it is 0.5 weight% or less. When the content of the ester cyclic trimer in the polyester raw material is 0.7% by weight or less, it becomes possible to more effectively suppress the precipitation amount of the ester cyclic trimer after the heat treatment.

  The polyester layer is preferably composed of 70% by weight or more of polyester having an ester cyclic trimer content of 0.7% by weight or less, more preferably 80% by weight or more. When comprised from 70 weight% or more, it becomes possible to exhibit the ester cyclic trimer precipitation prevention effect to the film surface after heat processing highly.

  The polyester film in the present invention may have a single layer structure or a multilayer structure. In the case of a multilayer structure, the surface layer and the inner layer, or both the surface layer and each layer can be made of different polyesters depending on purposes.

  When making a polyester film into a multilayer structure, it is preferable from the viewpoint of preventing ester cyclic trimer precipitation that at least one layer of the polyester film has a polyester layer having an ester cyclic trimer content of 0.7% by weight or less.

  Moreover, precipitation of the ester cyclic trimer from the polyester film is effectively suppressed when the polyester layer having a polyester film having an ester cyclic trimer content of 0.7% by weight or less is thicker. The thickness of the 0.7% by weight or less polyester layer is preferably 1.5 μm or more, more preferably 2.0 μm or more, and particularly preferably 2.5 μm or more. When the film thickness of the polyester layer of 0.7% by weight or less is 1.5 μm or more, the heat treatment for a long time at 150 ° C., the sputtering process under high tension, Even when used in a processing step under severe conditions such as a durability test, it is possible to further suppress an increase in film haze.

  The polyester film in the present invention can contain particles for the purpose of ensuring the film runnability and preventing scratches. Examples of such particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide. Further, organic particles such as crosslinked polymer particles and calcium oxalate, and precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

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

  The particle size and content of the particles to be used are selected according to the use and purpose of the film. The average particle size (d50) is usually 3 μm or less, preferably 0.02 μm to 2.8 μm, more preferably 0.8. It is in the range of 03 μm to 2.5 μm. If the average particle size exceeds 3 μm, the surface roughness of the film becomes too rough, or the particles easily fall off from the film surface.

  About particle | grain content, it is 3 weight% or less normally with respect to the polyester layer containing particle | grains, Preferably it is 0.0003 to 1.0 weight%, More preferably, it is the range of 0.0005 to 0.5 weight%. When there are no or few particles, the transparency of the film becomes high and a good film is obtained, but the slipperiness may be insufficient. In some cases, it is necessary to improve the performance. Further, when the particle content exceeds 3% 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.

  In addition to the above-mentioned particles, conventionally known antioxidants, heat 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 20-250 micrometers.

  As a film forming method of the film of the present invention, a generally known film forming method can be adopted, and there is no particular limitation. For example, a sheet obtained by melt extrusion is first stretched 2 to 6 times at 70 to 145 ° C. by a roll stretching method to obtain a uniaxially stretched polyester film, and then perpendicular to the previous stretching direction in the tenter. A film is obtained by extending | stretching 2 to 6 times at 80-160 degreeC to the direction, and also heat-processing at 150-250 degreeC for 1 to 600 seconds. Further, at this time, it is preferable to perform relaxation within 20% in the longitudinal direction and / or the transverse direction in the heat treatment zone and / or the cooling zone at the heat treatment outlet.

  The coating layer of the film of the present invention can be provided by any of so-called off-line coating, in which a coating layer is provided later on the formed film, and so-called in-line coating, in which a coating layer is provided during film formation. It is preferably provided by in-line coating, particularly by a coating stretching method in which stretching is performed after coating.

  In-line coating is a method of coating within the process of manufacturing a polyester film, and specifically, a method of coating at any stage from melt extrusion of a polyester to heat setting after stretching and winding up. Usually, it is either a substantially amorphous unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat setting, or a film after winding and before winding. Coating. Although not limited to the following, for example, in sequential biaxial stretching, a method of stretching in the transverse direction after coating a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction) is particularly excellent. According to such a method, since film formation and coating layer coating can be performed at the same time, there is a merit in manufacturing cost. Stabilize. Moreover, the polyester film before biaxial stretching is first covered with a resin layer constituting the coating layer, and then the base film and the coating layer are firmly adhered by stretching the film and the coating layer simultaneously. become. In addition, the biaxial stretching of the polyester film is that the film is constrained in the longitudinal / lateral direction by gripping the end of the film with a tenter clip etc. High temperature can be applied while maintaining flatness. Therefore, since the heat treatment performed after coating can be performed at a high temperature that cannot be achieved by other methods, the film forming property of the coating layer is improved, and the coating layer and the polyester film are firmly adhered. As the polyester film provided with the coating layer, the uniformity of the coating layer, the improvement of the film forming property, and the adhesion between the coating layer and the film often produce preferable characteristics.

  In the case of the coating stretching method, the coating solution to be used is preferably an aqueous solution or an aqueous dispersion for safety reasons in terms of handling, working environment, but water is the main medium and does not exceed the gist of the present invention. If so, an organic solvent may be contained.

  In the present invention, the polyester film has a coating layer (hereinafter sometimes abbreviated as a first coating layer) formed from a coating solution containing a polyvalent aldehyde compound on one surface of the polyester film. A coating layer having an absolute reflectance on the surface having a minimum value in the wavelength range of 400 to 800 nm and an absolute reflectance at the minimum value of 4.0% or more (hereinafter abbreviated as a second coating layer). Is an essential requirement.

  The first coating layer of the laminated polyester film of the present invention is for the purpose of reducing the amount of oligomers deposited by heating, for example, reducing the contamination in the heating step and each subsequent step, and suppressing the whitening of the film and maintaining transparency. It is provided for. The coating solution may contain other components.

  The polyvalent aldehyde compound in the present invention is a compound having two or more aldehyde groups or a functional group derived from an aldehyde group in one molecule. For example, glyoxal, glutaraldehyde, terephthalaldehyde, cyclohexane Polyaldehyde aldehyde compounds such as dialdehyde, tricyclodecanedialdehyde, norbornane dialdehyde, suberaldehyde, etc., compounds obtained by reaction (protection) of these aldehyde groups to form acetals, thioacetalized compounds, silyl etherification And nitrogenated compounds such as imine, iminium salts and enamines.

  The polyvalent aldehyde compound may be unstable and is preferably used in a form in which an aldehyde group is reacted (protected). In view of stability and reactivity in coating, a form reacted with a hydroxyl group-containing compound, particularly a polyhydric alcohol compound, is preferable, and among them, a type that forms a cyclic structure when reacted with an aldehyde group is more preferable.

  Examples of the polyhydric alcohol compound include polyhydric alcohols such as ethylene glycol, 1,3-propanediol, and glycerin, and saccharides such as glucose and galactose. Among them, saccharides are preferable in consideration of applicability.

  As the polyhydric aldehyde compound, an aliphatic polyhydric aldehyde compound or a derivative thereof is preferable in consideration of the strength of the coating layer and the coating appearance, and among them, glyoxal that increases the amount of aldehyde functional group is more preferable, in particular, the molecular weight. .

  That is, the most preferable form of the polyhydric aldehyde compound in the present invention is a type in which a polyhydric alcohol compound is reacted with glyoxal, and among them, a compound in which a saccharide is reacted with glyoxal.

  For the formation of the first coating layer of the film of the present invention, an ammonium group-containing compound or polyvinyl alcohol is used from the viewpoint of preventing precipitation of the ester cyclic trimer on the film surface by heating, and improving the durability and coating properties of the coating layer. It is preferable to use a crosslinking agent in combination. Among these, from the viewpoint of preventing precipitation of the ester cyclic trimer on the film surface by heating, it is more preferable to use an ammonium group-containing compound or a crosslinking agent, and it is more preferable to use an ammonium group-containing compound in combination.

  That is, a more preferable embodiment of the present invention has a coating layer formed from a coating liquid containing a polyvalent aldehyde compound and at least one compound selected from the group consisting of an ammonium group-containing compound, a crosslinking agent, and polyvinyl alcohol. It is a laminated polyester film.

  The ammonium group-containing compound refers to a polymer compound having an ammonium group in the molecule. For example, a polymer containing a monomer having an ammonium group and an unsaturated double bond as a component can be used.

  Specific examples of such a polymer include a polymer having a constituent represented by the following formula (1) or the following formula (2) as a repeating unit. These homopolymers and copolymers, and other plural components may be copolymerized.

In the above formula (1), R ² is —O— or —NH—, R ³ is an alkylene group, or other structure capable of forming the structure of formula (2), R ¹ , R ⁴ , R ⁵ , R ⁶ Are each a hydrogen atom, an alkyl group, a phenyl group or the like, and these alkyl group and phenyl group may be substituted with the following groups. Substitutable groups include, for example, hydroxy group, amide group, ester group, alkoxy group, phenoxy group, naphthoxy group, thioalkoxy group, thiophenoxy group, cycloalkyl group, trialkylammonium alkyl group, cyano group, halogen, etc. is there.

In said formula (2), R < ¹ >, R < ² > is respectively independently a hydrogen atom, an alkyl group, a phenyl group, etc., These alkyl groups and a phenyl group may be substituted by the group shown below. Substitutable groups include, for example, hydroxyl group, amide group, ester group, alkoxy group, phenoxy group, naphthoxy group, thioalkoxy group, thiophenoxy group, cycloalkyl group, trialkylammonium alkyl group, cyano group, halogen, etc. is there. R ¹ and R ² may be chemically bonded. For example, — (CH ₂ ) _m — (m is an integer of 2 to 5), —CH (CH ₃ ) CH (CH ₃ ) —, -CH = CH-CH = CH - , - CH = CH-CH = N -, - CH = CH-N = C -, - CH 2 OCH 2 -, - (CH 2) 2 O (CH 2) 2 - Etc.

X ⁻ in the above formulas (1) and (2) can be appropriately selected within a range not impairing the gist of the present invention. Examples include halogen ions, sulfonates, phosphates, nitrates, alkyl sulfonates, and carboxylates.

A polymer having a component represented by the above formula (1) is preferable because of excellent transparency of the resulting coating layer. However, in the coating stretching method, heat resistance may be inferior, and when used in the coating stretching method, X ⁻ is preferably not a halogen.

  A compound represented by the above formula (2) or other ammonium base in the polymer skeleton is excellent in heat resistance and is preferable.

  In addition, the polymer in which the constituents represented by the above formulas (1) and (2) and the polyethylene glycol-containing (meth) acrylate are copolymerized has a flexible structure, and is uniform during coating and stretching. An excellent coating layer is obtained and preferable.

  Alternatively, a coating layer having excellent uniformity can also be obtained by coating a polyethylene glycol-containing (meth) acrylate polymer in a coating solution.

  Specific examples of the polyethylene glycol-containing (meth) acrylate include polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, polyethylene glycol diacrylate (the polymerization degree of polyethylene glycol units is preferably in the range of 4 to 14), and polypropylene glycol diacrylate. Acrylate, polytetramethylene glycol diacrylate, poly (ethylene glycol-tetramethylene glycol) diacrylate, poly (propylene glycol-tetramethylene glycol) diacrylate, polyethylene glycol-polypropylene glycol-polyethylene glycol diacrylate, polypropylene glycol-polybutylene glycol Monomethacrylate, methoxypolyethylene glycol Methacrylate, methoxy polyethylene glycol monoacrylate, octoxy polyethylene glycol-polypropylene glycol monomethacrylate, octoxy polyethylene glycol-polypropylene glycol monoacrylate, lauroxy polyethylene glycol monomethacrylate, lauroxy polyethylene glycol monoacrylate, stearoxy polyethylene glycol monomethacrylate, steer Examples include polymers starting from loxypolyethylene glycol monoacrylate, allyloxypolyethylene glycol monomethacrylate, allyloxypolyethylene glycol monoacrylate and the like.

  The number average molecular weight of the ammonium group-containing compound is 1000 to 500000, preferably 2000 to 350,000, and more preferably 5000 to 200000. When the molecular weight is less than 1000, the strength of the coating film may be weak or the heat resistance stability may be poor. On the other hand, when the molecular weight exceeds 500,000, the viscosity of the coating solution increases, and the handleability and applicability may deteriorate.

  Various known crosslinking agents can be used as the crosslinking agent, and examples thereof include melamine compounds, oxazoline compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, and silane coupling compounds. Moreover, a melamine compound is used suitably from a viewpoint of prevention of precipitation of the ester cyclic trimer on the film surface by heating and improvement of durability and applicability of the coating layer.

  The melamine compound is a compound having a melamine structure 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 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 oxazoline compound is a compound having an oxazoline group in the molecule, and a polymer containing an oxazoline group is particularly preferable, 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 amount of the oxazoline group of the oxazoline compound contained in the first coating layer constituting the laminated polyester film in the present invention is usually 0.5 to 10 mmol / g, preferably 3 to 9 mmol / g, more preferably 5 to 8 mmol / g. The range of g. By using it in the above range, the durability of the coating film is improved.

  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 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 methyl isobutanoyl acetate, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, mercaptan compounds such as butyl mercaptan, dodecyl mercaptan, ε-caprolactam, δ-valerolactam, etc. Lactam compounds, amine compounds such as diphenylaniline, aniline, ethyleneimine, acetanilide, acid amide compounds of acetic acid amide, Examples include oxime compounds such as maldehyde, acetoald 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.

  The content of the carbodiimide group contained in the carbodiimide-based compound is a carbodiimide equivalent (weight of the carbodiimide compound to give 1 mol of carbodiimide group [g]) and is usually 100 to 1000, preferably 250 to 800, more preferably 300. It is in the range of ~ 700. By using it in the above range, the durability of the coating film is improved.

  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.

  When such a crosslinking component is contained, a component for accelerating crosslinking, for example, a crosslinking catalyst can be used in combination.

  Polyvinyl alcohol is a compound having a polyvinyl alcohol moiety. For example, conventionally known polyvinyl alcohols including modified compounds partially acetalized or butyralized with respect to polyvinyl alcohol can be used. The degree of polymerization of polyvinyl alcohol is not particularly limited, but is usually 100 or more, preferably in the range of 300 to 40,000. When the degree of polymerization is less than 100, the water resistance of the coating layer may decrease. The saponification degree of polyvinyl alcohol is not particularly limited, but is usually 70 mol% or more, preferably in the range of 70 to 99.9 mol%, more preferably 80 to 97 mol%, and particularly preferably 86 to 97 mol%. A saponified polyvinyl acetate of 95 mol% is practically used.

  In addition, particles can be used in combination for the purpose of blocking and improving slipperiness in the formation of the first coating layer. The average particle diameter is preferably 1.0 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.2 μm or less from the viewpoint of transparency of the film. The lower limit is preferably in the range of 0.005 μm or more, more preferably 0.01 μm or more, and particularly preferably larger than the film thickness of the coating layer in order to improve the slipperiness more effectively. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, and organic particles. Among these, silica is preferable from the viewpoint of transparency.

  In addition, the formation of the first coating layer of the film of the present invention includes a second coating layer which will be described later for the purpose of improving the coating appearance and improving the adhesion when various surface functional layers are formed in the coating layer. It is also possible to use various polymers such as those used in the formation of

  In the present invention, the second coating layer has a refractive index adjusted to suppress the occurrence of interference unevenness after the surface functional layer is formed, and its refractive index (1.55 to 1.65). Is designed around the geometric mean of the refractive index (1.45-1.65) of the surface functional layer such as the hard coat layer and the polyester film (1.60-1.70) as the base material. The refractive index of the coating layer and the reflectance of the coating layer are closely related. The absolute reflectance of the second coating layer of the laminated polyester film of the present invention is a graph showing the wavelength on the horizontal axis and the reflectance on the vertical axis, and the minimum value of the reflectance is one in the wavelength range of 400 to 800 nm. The minimum value 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.

  The second coating layer in the film of the present invention needs to be designed with a high refractive index in order to reduce interference unevenness, and therefore it is necessary to use a material with a high refractive index. As the material having a high refractive index, a conventionally known material can be used. For example, an aromatic compound such as a benzene structure, a bisphenol A structure, a melamine structure, or a higher refractive index material among aromatics. Conceivable examples include condensed polycyclic aromatic compounds such as naphthalene structures, metal-containing compounds such as metal oxides and metal chelate compounds, compounds containing sulfur elements, and compounds containing halogen elements.

  Among these high refractive index materials, aromatic compounds that can contain a large amount of various compounds such as polyester resins from the viewpoint of maintaining adhesion to various functional surface layers such as a hard coat layer. In order to increase the refractive index more effectively, a condensed polycyclic aromatic compound is more preferable. Furthermore, in order to increase the refractive index more effectively than the aromatic compound, metal-containing compounds such as metal oxides and metal chelate compounds are preferable, and metal oxides are more preferable from the viewpoint of the stability of the coating solution.

  The second coating layer of the present invention preferably uses a metal oxide 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. Or two or more types may be used. Among these, zirconium oxide and titanium oxide are more preferably used.

  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.

  Considering the applicability on the polyester film, the aromatic compound is preferably a polymer compound such as a polyester resin, an acrylic resin, or a urethane resin. In particular, it is more preferable because more aromatics can be introduced into the polyester resin.

  Among the aromatic compounds, the condensed polycyclic aromatic compound having a higher refractive index is, for example, naphthalene, anthracene, phenanthrene, naphthacene, benzo [a] anthracene, benzo [a] phenanthrene, pyrene, benzo [c] phenanthrene. And compounds having a structure such as perylene.

  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 manufacturing process, the condensed polycyclic aromatic used for forming the coating layer is preferably a compound having a naphthalene structure 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, 2,7-naphthalenedicarboxylic acid, and the like.

  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.

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

  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.

  The polyester resin 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 acrylic resin is a polymer composed of a polymerizable monomer having a carbon-carbon double bond, as typified by acrylic and methacrylic monomers. These may be either a homopolymer or a copolymer. Moreover, the copolymer of these polymers and other polymers (for example, polyester, polyurethane, etc.) is also included. For example, a block copolymer or a graft copolymer. Alternatively, a polymer (possibly a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or polyurethane dispersion is also included. Similarly, a polymer obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion (in some cases, a polymer mixture) is also included. Moreover, in order to improve adhesiveness, it is also possible to contain a hydroxyl group and an amino group.

  The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but particularly representative compounds include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citracone. Various carboxyl group-containing monomers such as acids, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutyl hydroxyl fumarate, Various hydroxyl group-containing monomers such as monobutylhydroxy itaconate; various monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate ( (Meth) acrylic acid esters; Various nitrogen-containing compounds such as meth) acrylamide, diacetone acrylamide, N-methylolacrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, vinyl propionate Various vinyl esters such as: Various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; Phosphorus-containing vinyl monomers; Various such as vinyl chloride and biridene chloride And various conjugated dienes such as butadiene.

  The urethane resin is a polymer compound having a urethane bond in the molecule. Usually, urethane resin is prepared by reaction of polyol and isocyanate. Examples of the polyol include polycarbonate polyols, polyester polyols, polyether polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

  Polycarbonate polyols are obtained from a polyhydric alcohol and a carbonate compound by a dealcoholization reaction. Examples of the polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentane. Diol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decane Diol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylol heptane and the like can be mentioned. Examples of the carbonate compound include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, and ethylene carbonate. Examples of polycarbonate polyols obtained from these reactions include poly (1,6-hexylene) carbonate, poly (3- And methyl-1,5-pentylene) carbonate.

  Polyester polyols include polycarboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides. Product and polyhydric alcohol (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol 2-methyl-2-propyl-1 3-propanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexane Diol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyl dialkanolamine, lactone diol, etc.).

  Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, and the like.

  Among the above polyols, polycarbonate polyols and polyester polyols are more preferably used in order to improve adhesion to various topcoat layers.

  Examples of the polyisocyanate compound used for obtaining the urethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, α, α, α ′, α ′. -Aliphatic diisocyanates having aromatic rings such as tetramethylxylylene diisocyanate, aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl Methanzi Cyanate, alicyclic diisocyanates such as isopropylidene dicyclohexyl diisocyanates. These may be used alone or in combination.

  A chain extender may be used when synthesizing the urethane resin, and the chain extender is not particularly limited as long as it has two or more active groups that react with an isocyanate group. Alternatively, a chain extender having two amino groups can be mainly used.

  Examples of the chain extender having two hydroxyl groups include aliphatic glycols such as ethylene glycol, propylene glycol and butanediol, aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene, and esters such as neopentyl glycol hydroxypivalate. And glycols such as glycols. Examples of the chain extender having two amino groups include aromatic diamines such as tolylenediamine, xylylenediamine, and diphenylmethanediamine, ethylenediamine, propylenediamine, hexanediamine, 2,2-dimethyl-1,3- Propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10- Aliphatic diamines such as decane diamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, isoprobilitincyclohexyl-4,4′-diamine, 1,4-diaminocyclohexane, 1 , 3-Bisaminomethylcyclohexa And alicyclic diamines such as

The urethane resin in the present invention may use a solvent as a medium, but preferably uses water as a medium. In order to disperse or dissolve the urethane resin in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into the urethane resin, and a water-soluble type. In particular, a self-emulsification type in which an ionic group is introduced into the structure of a urethane resin to form an ionomer is preferable because of excellent storage stability of the liquid and water resistance, transparency, and adhesion of the resulting coating layer.
Examples of the ionic group to be introduced include various groups such as a carboxyl group, sulfonic acid, phosphoric acid, phosphonic acid, quaternary ammonium salt, and the like, and a carboxyl group is preferable. As a method for introducing a carboxyl group into a urethane resin, various methods can be taken in each stage of the polymerization reaction. For example, there are a method of using a carboxyl group-containing resin as a copolymer component during prepolymer synthesis, and a method of using a component having a carboxyl group as one component such as polyol, polyisocyanate, and chain extender. In particular, a method in which a desired amount of carboxyl groups is introduced using a carboxyl group-containing diol depending on the amount of this component charged is preferred. For example, dimethylolpropionic acid, dimethylolbutanoic acid, bis- (2-hydroxyethyl) propionic acid, bis- (2-hydroxyethyl) butanoic acid and the like are copolymerized with a diol used for polymerization of a urethane resin. Can do. The carboxyl group is preferably in the form of a salt neutralized with ammonia, amine, alkali metal, inorganic alkali or the like. Particularly preferred are ammonia, trimethylamine and triethylamine. In such a polyurethane resin, a carboxyl group from which the neutralizing agent has been removed in the drying step after coating can be used as a crosslinking reaction point by another crosslinking agent. Thereby, it is possible to further improve the durability, solvent resistance, water resistance, blocking resistance, and the like of the obtained coating layer, as well as excellent stability in a liquid state before coating.

  Among the above-mentioned polymers, polyester resins are particularly preferable from the viewpoint that a large number of aromatic compounds such as benzene rings can be contained in the molecule, thereby increasing the refractive index.

  The coating solution for forming the second coating layer of the film of the present invention preferably contains a crosslinking agent. These can improve adhesion to a surface functional layer such as a hard coat layer provided on the coating layer.

  As the crosslinking agent used for forming the second coating layer of the film of the present invention, various crosslinking agents described in the first coating layer can be used. From the viewpoint of good adhesion among the crosslinking agents, oxazoline compounds, epoxy compounds, isocyanate compounds, and carbodiimide compounds are particularly preferable, and it is more preferable to use two or more crosslinking agents in combination. In particular, from the viewpoint of improving the adhesion after the wet heat test, the combination includes, for example, an oxazoline compound and an epoxy compound, an oxazoline compound and an isocyanate compound, an oxazoline compound and a carbodiimide compound, an epoxy compound and an isocyanate compound, and an epoxy compound. And carbodiimide compounds. Among these, the combination of an oxazoline compound and an epoxy compound is particularly preferable. By combining the above crosslinking agents, adhesion is highly expressed. From the viewpoint of increasing the refractive index while increasing the strength of the coating layer, a melamine compound is preferably used.

  Further, when oxazoline is used for forming the second coating layer, the amount of oxazoline group of the oxazoline compound contained in the second coating layer is usually 0.5 to 10 mmol / g, preferably 3 to 9 mmol / g. Preferably it is the range of 4-8 mmol / g. By using in the said range, adhesiveness with a surface functional layer etc. improves.

  In the present invention, particles other than the metal oxides described above may be used in the formation of the second coating layer for the purpose of improving the adhesion and slipperiness of the coating layer. The average particle diameter is preferably in the range of less than 1.0 μm, more preferably in the range of less than 0.50 μm, and particularly preferably in the range of less than 0.20 μm from the viewpoint of the transparency of the film. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, and organic particles.

  Furthermore, in the range that does not impair the gist of the present invention, the formation of the first coating layer and the second coating layer, if necessary, defoaming agent, coating property improver, thickener, organic lubricant, antistatic agent, It is also possible to use ultraviolet absorbers, antioxidants, foaming agents, dyes, pigments and the like in combination.

  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, the ratio of a polyvalent aldehyde type compound is the range of 0.01 to 99 weight% normally, Preferably it is 1. It is in the range of ˜50% by weight, more preferably in the range of 3 to 30%. When the ratio is out of the above range, precipitation of the ester cyclic trimer after heating cannot be effectively suppressed or the appearance of coating may be deteriorated.

  From the viewpoint of preventing precipitation of the ester cyclic trimer after heating, when using the ammonium group-containing compound that forms the first coating layer, the ratio of the ammonium group-containing compound as the ratio to the total nonvolatile components in the coating liquid is: Usually, it is 1 to 99% by weight, preferably 10 to 80% by weight, more preferably 20 to 70% by weight or more. When the ratio is within the above range, precipitation of the ester cyclic trimer after heating can be effectively suppressed.

  From the viewpoint of durability of the coating film and prevention of precipitation of the ester cyclic trimer after heating, when a crosslinking agent is used in the coating solution for forming the first coating layer, crosslinking is performed as a ratio to the total nonvolatile components in the coating solution. The proportion of the agent is usually in the range of 1 to 99% by weight, preferably in the range of 2 to 95% by weight, more preferably in the range of 5 to 90% by weight. When the ratio is within the above range, the durability of the coating film is improved, and the prevention of precipitation of the ester cyclic trimer after heating is also effectively exhibited.

  From the viewpoint of coating appearance and prevention of precipitation of the ester cyclic trimer after heating, when polyvinyl alcohol is used in the coating liquid for forming the first coating layer, the ratio of polyvinyl alcohol as the ratio to the total nonvolatile components in the coating liquid Is usually in the range of 1 to 99% by weight, preferably in the range of 5 to 90% by weight, more preferably in the range of 10 to 85% by weight. When the ratio is within the above range, a good coating appearance can be obtained, and precipitation of the ester cyclic trimer after heating can be effectively suppressed.

  From the viewpoint of reducing interference unevenness, when a metal oxide is used in the coating liquid for forming the second coating layer, the metal oxide is usually in the range of 3 to 70% by weight as a ratio to the total nonvolatile components in the coating liquid. The range is preferably 5 to 50% by weight, more preferably 5 to 40% by weight, and particularly preferably 8 to 30% by weight. When the amount of the metal oxide is within the above range, the refractive index of the coating layer is sufficiently adjusted, the interference unevenness after coating the surface functional layer such as the hard coat layer is reduced, and the visibility is easily improved. .

  In the case of using a compound containing a condensed polycyclic aromatic in the coating solution for forming the second coating layer from the viewpoint of reducing interference unevenness, the compound having the condensed polycyclic aromatic is condensed polycyclic in the compound. The proportion of aromatics is preferably in the range of 5 to 80% by weight, more preferably in the range of 10 to 60% by weight. Further, the content of the compound having a condensed polycyclic aromatic in all the non-volatile components in the coating liquid forming 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, More preferably, it is the range of 10-50 weight%. 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.

  From the viewpoint of adhesion to a surface functional layer such as a hard coat, when the coating solution for forming the second coating layer contains a crosslinking agent, the crosslinking agent is usually 2 to 80 as a ratio to the total nonvolatile components in the coating solution. It is in the range of wt%, more preferably in the range of 4 to 60 wt%, still more preferably in the range of 10 to 40 wt%. Within these ranges, it becomes easy to obtain strong adhesion with a surface functional layer such as a hard coat layer.

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

  The thickness of the first coating layer is usually in the range of 0.003 μm to 1 μm, preferably 0.005 μm to 0.5 μm, more preferably as the thickness of the coating layer on the finally obtained film. It is in the range of 0.01 to 0.2 μm. When the thickness is smaller than this, the amount of oligomers precipitated from the film may not be sufficiently reduced. On the other hand, if it is thicker than this, problems such as deterioration of the appearance of the coating layer and easy blocking may occur.

  The thickness of the second coating layer is usually in the range of 0.04 to 0.20 μm, preferably 0.05 to 0.17 μm, as the thickness of the coating layer on the finally obtained film. Preferably it is the range of 0.07-0.15 micrometer. When the thickness is out of the above range, visibility may deteriorate due to interference unevenness after the surface functional layer is laminated.

  Examples of methods for applying a coating solution to a polyester film include air doctor coating, blade coating, rod coating, bar coating, knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, and kiss roll coating. Conventional coating methods such as cast coating, spray coating, curtain coating, calendar coating, and extrusion coating can be used.

  In order to improve the applicability and adhesion of the coating agent to the film, the film may be subjected to chemical treatment, corona discharge treatment, plasma treatment or the like before coating.

  For the laminated polyester film in the present invention, for example, for a touch panel, a high degree of transparency may be required even after being exposed to a high temperature atmosphere for a long time. From this viewpoint, in order to cope with a high degree of transparency, the film haze change amount (ΔH) in the heat treatment (150 ° C., 90 minutes) is preferably 1% or less, more preferably 0.7% or less, and still more preferably. Is 0.5% or less. When ΔH exceeds 1%, the visibility decreases as the film haze increases due to precipitation of the ester cyclic trimer, and it is inappropriate for applications requiring high visibility, such as for touch panels. There is a case.

Further, from the viewpoint of the precipitation amount of the ester cyclic trimer, the amount of the ester cyclic trimer extracted from the film surface by dimethylformamide by heat treatment (150 ° C., 90 minutes) of the laminated polyester film in the present invention is preferably 1 mg / m ² or less, more preferably 0.7 mg / m ² or less, and still more preferably 0.4 mg / m ² or less. In the case of exceeding 1 mg / m ² , the amount of ester cyclic trimer deposited increases in the subsequent process, for example, in a high temperature atmosphere such as 150 ° C. for 90 minutes, and the transparency of the film increases. There is a concern that it may decrease or contamination of the process.

  The second coating layer in the present invention has a refractive index adjusted in order to suppress the occurrence of uneven interference due to reflection of external light, and the refractive index is a surface functional layer such as a polyester film and a hard coat layer as a base material. In the vicinity of the geometric mean, specifically, the refractive index is designed to be in the range of 1.55 to 1.65. 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 of the reflectance is preferably in the range of 4.0 to 6.5%, more preferably 4.5 to 6.2%. When the minimum value in the wavelength range of 400 to 800 nm is not one, and when the absolute reflectance minimum value deviates from the above value, interference unevenness occurs after the surface functional layer such as the 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 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 active energy ray-curable (meth) acrylate is particularly preferable.

  The composition containing the active energy ray-curable (meth) acrylate is not particularly limited. For example, a mixture of one or more known active energy ray-curable monofunctional (meth) acrylates, bifunctional (meth) acrylates, polyfunctional (meth) acrylates, and commercially available as an active energy ray-curable hard coat resin material In addition, those other than these may be used as long as the object of the present embodiment is not impaired.

  The active energy ray-curable monofunctional (meth) acrylate is not particularly limited. For example, methyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) ) Acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, alkyl (meth) acrylate such as isobornyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, etc. Alkyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, ethoxypropyl (meth) acrylate, etc. Amino group-containing (meth) acrylates such as xylalkyl (meth) acrylate, benzyl (meth) acrylate, aromatic (meth) acrylate such as phenoxyethyl (meth) acrylate, diaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, Methoxyethylene glycol (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, ethylene oxide modified (meth) acrylate such as phenylphenol ethylene oxide modified (meth) acrylate, glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, Examples include (meth) acrylic acid.

  The active energy ray-curable difunctional (meth) acrylate is not particularly limited, and for example, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6- Hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, alkanediol di (meth) acrylate such as tricyclodecane dimethylol di (meth) acrylate, bisphenol A ethylene oxide modified di (meth) acrylate Bisphenol F ethylene oxide modified di (meth) acrylate and other bisphenol modified di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, urethane di (meth) acrylate And epoxy di (meth) acrylate.

  The active energy ray-curable polyfunctional (meth) acrylate is not particularly limited, and examples thereof include dipentaerythritol hexa (meth) acrylate, pentaerythritol tetra (meth) acrylate, and ditrimethylolpropane tetra (meth) acrylate. , Pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, isocyanuric acid ethylene oxide modified tri (meth) acrylate, ε-caprolactone modified tris (acryloxyethyl) isocyanurate Acrylate, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urea Down prepolymers, urethane acrylates such as dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, and the like.

In addition, since the surface functional layer such as the hard coat layer has a high refractive index of the polyester film serving as the base material, it may be preferable to design it high particularly in order to reduce interference unevenness.
One method for increasing the refractive index is to use a metal oxide. As the metal oxide, a conventionally known metal oxide can be used. For example, zirconium oxide, titanium oxide, tin oxide, acid value yttrium, antimony oxide, indium oxide, zinc oxide, antimontin oxide, indium tin oxide Etc. Among these, zirconium oxide is preferable in consideration of environmental aspects, weather resistance, and price.

  Other components contained in the composition containing the active energy ray-curable (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 a surface functional layer such as a hard coat layer, a general wet coat method such as a roll coat method or a die coat method is employed when an organic material is used. 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. The refractive index of the surface functional layer formed on the coating layer is generally 1.45 to 1.65 as described above.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method in an Example and a comparative example is as follows.

(1) Measuring method of intrinsic viscosity of polyester 1 g of polyester was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and the measurement was performed at 30 ° C.

(2) Measuring method of average particle size (d50: μm) Integration (weight basis) 50% in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) Was the average particle size.

(3) Coating layer thickness A film was fixed with an embedding resin, a cross section was cut with a microtome, and a sample was prepared by staining with 2% osmic acid at 60 ° C. for 2 hours. The obtained sample was observed with a transmission electron microscope (JEM2010 manufactured by JEOL Ltd.), and the thickness of the coating layer was measured. A total of 15 points on the film are measured, and an average of 9 points excluding 3 points from the larger value and 3 points from the smaller value is defined as the coating layer thickness.

(4) Heat treatment method of the film The sample is measured with the measurement surface exposed, and is overlapped with the Kent paper and fixed, and left in a nitrogen atmosphere at 150 ° C. for 90 minutes for heat treatment.

(5) Measurement of film haze Film haze was measured for the sample film according to JIS-K-7136 with a haze meter “HM-150” manufactured by Murakami Color Research Laboratory.

(6) Measurement of film haze increase (ΔH) by heat treatment First, the following composition (a) of the sample film was applied to the second coating layer of the present invention so as to have a dry film thickness of 5 μm and irradiated with ultraviolet rays. And cured to obtain a laminated film provided with a hard coat layer.
<< (a): Hard coat layer composition >>
72 parts by weight of dipentaerythritol hexaacrylate, 18 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, 10 parts by weight of zirconium oxide, 1 part by weight of a photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals) A mixed coating solution of 200 parts by weight of methyl ethyl ketone.
The haze of the obtained sample was measured by the method of item (5) (haze 1).
Next, using the surface opposite to the active energy ray-curable resin layer of the sample as the measurement surface, the sample was heated by the method of (4), and then the haze was measured by the method of (5) (haze 2).
ΔH = (haze 2) − (haze 1)
The lower ΔH, the lower the amount of oligomer precipitation due to the high temperature treatment, and the better.

(7) Measurement of amount of ester cyclic trimer deposited on the surface of the laminated polyester film The polyester film is heated in air at 150 ° C. for 90 minutes. Thereafter, the heat-treated film is formed into a box shape with the measurement surface (coating layer) as the inner surface so that the upper part is 10 cm in length and width and the height is 3 cm. Next, 4 ml of DMF (dimethylsulfoamide) was placed in the box prepared by the above method and allowed to stand for 3 minutes, and then DMF was recovered and subjected to liquid chromatography (manufactured by Shimadzu Corporation: LC-7A, mobile phase A: Acetonitrile, mobile phase B: 2% aqueous acetic acid, column: “MCI GEL ODS 1HU” manufactured by Mitsubishi Chemical Corporation, column temperature: 40 ° C., flow rate: 1 ml / min, detection wavelength: 254 nm) The amount of oligomer was determined, and this value was divided by the film area with which DMF was contacted to obtain the amount of oligomer on the film surface (mg / m ² ). The ester cyclic trimer in DMF was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method). The standard sample was prepared by accurately weighing the pre-sorted ester cyclic trimer and dissolving it in accurately measured DMF.

(8) Measurement of absolute reflectance from one coating layer surface in polyester film A black tape (made by Nichiban Co., Ltd., vinyl tape VT-50) was previously applied to the measurement back surface of the polyester film, and a spectrophotometer (JASCO Corporation) Using company-made UV-visible spectrophotometer V-570 and automatic absolute reflection measuring device ARM-500N), synchronous mode, incident angle 5 °, N-polarized light, response Fast, data collection interval 1.0 nm, bandwidth The absolute reflectance of the coating layer surface in the wavelength range of 400 to 800 nm was measured at 10 nm and a scanning speed of 1000 nm / min.

(9) Evaluation of interference unevenness of second coating layer On the second coating layer of the polyester film, (a) is coated so that the dry film thickness is 5 μm, and cured by irradiation with ultraviolet rays to form a hard coat layer. did. 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 ×.

(10) Evaluation of adhesion of second coating layer In order to evaluate adhesion, the film obtained in the evaluation of (9) above, after 100 hours in an environment of 60 ° C. and 90% RH, 10 × 10 cross cut, 18mm wide tape (Cello Tape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) was applied, and the peeled surface was peeled off sharply at a 180 ° peel angle. If the area is less than 3%, ◎ if it is 3% or more and less than 10%, ◯ if it is 10% or more and less than 50%, and x if it is 50% or more.

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (A)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part of ethyl acid phosphate to this reaction mixture, 0.04 part of antimony trioxide was added, and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The obtained polyester (A) had an intrinsic viscosity of 0.63 and an ester cyclic trimer content of 0.97% by weight.

<Method for producing polyester (B)>
Polyester (A) is pre-crystallized at 160 ° C. in advance, and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 220 ° C., with an intrinsic viscosity of 0.75 and an ester cyclic trimer content of 0.46% by weight. Polyester (B) was obtained.

<Method for producing polyester (C)>
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. A polyester (C) having 0.61 and an ester cyclic trimer content of 1.02% by weight was obtained.

<Method for producing polyester (D)>
Polyester (C) was pre-crystallized at 160 ° C. in advance, and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 210 ° C., with an intrinsic viscosity of 0.72 and an ester cyclic trimer content of 0.50% by weight. Polyester (D) was obtained.

<Method for producing polyester (E)>
In the production method of polyester 1, after adding 0.04 part of ethyl acid phosphate, 0.5 part of silica particles having an average particle diameter (d50) of 1.6 μm dispersed in ethylene glycol and 0.04 of antimony trioxide are added. Polyester (E) was obtained using the same method as the production method of polyester 1 except that the polycondensation reaction was stopped at the time corresponding to the intrinsic viscosity of 0.65. The obtained polyester (E) had an intrinsic viscosity of 0.65 and an ester cyclic trimer content of 0.82% by weight.

Moreover, the following was used as a composition contained in a coating liquid.
(A1): A polyvalent aldehyde compound obtained by reacting glyoxal with anhydrous glucose.
(B1): Polyvinyl alcohol having a saponification degree of 88 mol% and a polymerization degree of 500.
(E1): Copolymer having a weight ratio of 75/12/15/30 of 2- (trimethylamino) ethyl methacrylate / ethyl methacrylate / butyl methacrylate / polyethylene glycol-containing monoacrylate whose counter ion is methyl sulfonate.

(C1): Hexamethoxymethylol melamine.
(C2): Epocros (made by Nippon Shokubai Co., Ltd.) which is an oxazoline compound. Oxazoline group amount 7.7 mmol / g.
(C3): Epocros (made by Nippon Shokubai Co., Ltd.), which is an oxazoline compound. Oxazoline group amount 4.5 mmol / g.
(C4): Epocros (made by Nippon Shokubai Co., Ltd.) which is an oxazoline compound. Oxazoline group amount 4.5 mmol / g. VOC free type.
(C5): Polyglycerol polyglycidyl ether.

(C6): Block polyisocyanate synthesized by the following method.
1000 parts of hexamethylene diisocyanate was stirred at 60 ° C., and 0.1 part of tetramethylammonium capryate was added as a catalyst. After 4 hours, 0.2 part of phosphoric acid was added to stop the reaction, and an isocyanurate type polyisocyanate composition was obtained. 100 parts of the obtained isocyanurate type polyisocyanate composition, 42.3 parts of methoxypolyethylene glycol having a number average molecular weight of 400, and 29.5 parts of propylene glycol monomethyl ether acetate were charged and maintained at 80 ° C. for 7 hours. Thereafter, the reaction solution temperature was kept at 60 ° C., 35.8 parts of methyl isobutanoyl acetate, 32.2 parts of diethyl malonate, and 0.88 part of 28% methanol solution of sodium methoxide were added and kept for 4 hours. Block polyisocyanate obtained by adding 58.9 parts of n-butanol, maintaining the reaction solution temperature at 80 ° C. for 2 hours, and then adding 0.86 part of 2-ethylhexyl acid phosphate.
(C7): Carbodilite (manufactured by Nisshinbo Chemical Co., Ltd.), which is a polycarbodiimide-based compound. Carbodiimide equivalent 340.
(C8): Carbodilite (manufactured by Nisshinbo Chemical Co., Ltd.), which is a polycarbodiimide compound. Carbodiimide equivalent 430.

(D1): 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%)
(D2): A water dispersion of a polyester resin having a condensed polycyclic structure copolymerized with the following composition: Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid / 5-sodium sulfoisophthalic acid // (diol Ingredient) Ethylene glycol / diethylene glycol = 92/8 // 80/20 (mol%)

(F1): Silica particles having an average particle size of 0.07 μm.
(F2): Alumina-modified silica particles having an average particle size of 0.02 μm.
(F3): Titanium oxide particles having an average particle diameter of 15 nm (F4): Zirconium oxide particles having an average particle diameter of 15 nm (F5): Silica particles having an average particle diameter of 0.15 μm

Example 1:
Polyesters (B) and (E) blended at a weight ratio of 80/20 as the surface layer and polyester (A) alone as the raw material for the intermediate layer were each fed to two extruders and heated to 285 ° C. After heating and melting, the layer A is the outermost layer (surface layer), the layer B is the intermediate layer, and the thickness composition ratio is A / B / A = 2.5 / 45/2 with two types and three layers (A / B / A). The film was coextruded so as to be .5 and cooled and solidified while being closely adhered to a mirror surface cooling drum having a surface temperature of 40 to 50 ° C. by using an electrostatic adhesion method, thereby preparing an unstretched polyethylene terephthalate film. The film was stretched 3.4 times in the longitudinal direction using the difference in peripheral speed of the roll while passing through a heated roll group at 85 ° C., and then the aqueous coating solution shown in Table 1 below was formed on one side of the longitudinally stretched film. A1 is applied (formation of the first application layer), and an aqueous coating solution B2 shown in Table 2 below is applied to the opposite surface (formation of the second application layer), and is guided to a tenter stretching machine, at 100 ° C. in the lateral direction. After 4.0 times stretching and heat treatment at 230 ° C., a 2% relaxation treatment is performed in the transverse direction, the film thickness of the first coating layer (after drying) is 0.02 μm, and the film of the second coating layer A biaxially oriented polyethylene terephthalate film having a thickness of 50 μm and a coating layer having a thickness (after drying) of 0.10 μm was obtained.

  The film haze increase value (ΔH) by heat treatment of the obtained polyester film was small, and the precipitation amount of the ester cyclic trimer was small and good. 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 Table 4 below.

Examples 2-25:
In Example 1, it manufactured like Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, Table 2, and Table 3, and obtained the polyester film. As shown in Table 4, the finished polyester film had good film haze increase value (ΔH) by heat treatment and precipitation amount of ester cyclic trimer. The interference unevenness level of the second coating layer was also good.

Example 26:
Polyester (D) and (E) blended at a weight ratio of 80/20 as the surface layer and polyester (D) alone as the raw material for the intermediate layer were fed to the two extruders, respectively, at 285 ° C. After heating and melting, the layer A is the outermost layer (surface layer), the layer B is the intermediate layer, and the thickness composition ratio is A / B / A = 2.5 / 45/2 with two types and three layers (A / B / A). The film was coextruded so as to be .5 and cooled and solidified while being closely adhered to a mirror surface cooling drum having a surface temperature of 40 to 50 ° C. by using an electrostatic adhesion method, thereby preparing an unstretched polyethylene terephthalate film. The film was stretched 3.4 times in the longitudinal direction using the difference in peripheral speed of the roll while passing through a heated roll group at 85 ° C., and then the aqueous coating solution shown in Table 1 below was formed on one side of the longitudinally stretched film. A2 is applied (formation of the first application layer), and an aqueous coating solution B2 shown in Table 2 below is applied to the opposite surface (formation of the second application layer), and is led to a tenter stretching machine in the transverse direction at 100 ° C. After 4.0 times stretching and heat treatment at 230 ° C., a 2% relaxation treatment is performed in the transverse direction, the film thickness of the first coating layer (after drying) is 0.02 μm, and the film of the second coating layer A biaxially oriented polyethylene terephthalate film having a thickness of 50 μm and a coating layer having a thickness (after drying) of 0.10 μm was obtained.

  The film haze increase value (ΔH) by heat treatment of the obtained polyester film was small, and the precipitation amount of the ester cyclic trimer was small and good. 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 Table 4 below.

Examples 27-31:
In Example 18, it manufactured like Example 1 except having changed a coating agent composition into the coating agent composition shown to the following Tables 1-4, and obtained the polyester film. As shown in Table 4, the finished polyester film had good film haze increase value (ΔH) by heat treatment and precipitation amount of ester cyclic trimer. Further, the adhesion of the second coating layer was good, and the interference unevenness level was also good.

Comparative Examples 1-6:
In Example 1, it manufactured like Example 1 except having changed an application agent composition into an application agent composition shown in the following Table 1, Table 2, and Table 5, and obtained a polyester film. When the finished laminated polyester film was evaluated, as shown in Table 4, the film haze by heat treatment was greatly increased, the precipitation of the ester cyclic trimer was much, the interference unevenness of the second coating layer was poor, and the hard coat Adhesiveness to was poor.

Comparative Example 7:
In Example 1, it manufactured similarly to Example 1 except not providing a 1st coating layer, and obtained the polyester film. When the finished laminated polyester film was evaluated, the film haze due to heat treatment was greatly increased, and the precipitation of ester cyclic trimers was also large, and there was a concern about deterioration of visibility due to process contamination and whitening after heating. It was a thing.

  The film of the present invention has a film haze increase that is as small as possible even after a harsh heat treatment process in which the film is exposed to a high temperature atmosphere for a long time, and has good adhesion and visibility with a surface functional layer such as a hard coat layer As a laminated polyester film in an important application, for example, it can be suitably used as a base material of a transparent conductive laminate.

Claims (3)

Having a coating layer formed from a coating solution containing a polyvalent aldehyde compound on one surface of the polyester film, the absolute reflectance has one minimum value in the wavelength range of 400 to 800 nm, and at the minimum value A laminated polyester film comprising an application layer having an absolute reflectance of 4.0% or more on the other surface of the polyester film. The laminated polyester film according to claim 1, wherein the coating liquid containing a polyvalent aldehyde compound contains at least one compound selected from the group consisting of an ammonium group-containing compound, a crosslinking agent, and polyvinyl alcohol. The laminate according to claim 1, wherein the absolute reflectance has one minimum value in the wavelength range of 400 to 800 nm, and the hard coat layer is provided on the coating layer having the absolute reflectance at the minimum value of 4.0% or more. the film.