JP6852770B2 - Laminated polyester film - Google Patents

Description

The present invention relates to a laminated polyester film, and more particularly to a polyester film having less oligomer precipitation on the surface of the polyester film even after being exposed to a high temperature.

Polyester film is excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, etc. , Used in many fields.

However, in recent years, the release film is often exposed to high temperatures as an application. For example, a transparent conductive film provided with an ITO sputtering layer used in a touch panel or the like is subjected to heat of about 150 ° C. for 1 hour or more in the ITO crystallization step (Patent Document 1).

The adhesive layer and the release film for laminating such a transparent conductive film may be laminated on the transparent conductive film before crystallization, and both may undergo a crystallization step. However, as a problem of polyester film, when exposed to such a high temperature treatment, oligomers (low molecular weight components of polyester, particularly cyclic trimer) contained in the film are precipitated from the inside of the film. The oligomers precipitated in this way pass through the release layer and crystallize inside the adhesive layer to become foreign substances, which causes a problem that the visual inspection is hindered.

Further, in recent years, there is a demand for cost reduction in manufacturing a transparent conductive film provided with an ITO sputtered layer used in a touch panel or the like. In order to reduce costs, there is a demand for a manufacturing method in which an adhesive layer and a release film are laminated in advance on a transparent conductive film before the ITO sputtering process. Since the number of heating steps is increased, the problem of oligomers precipitated from the inside of the polyester film is further concerned.

In addition, after processing a release film using a polyester film as a base material and providing a release layer containing a silicone resin or the like as a main component, a roll appearance defect that occurs due to the thickness deviation of the polyester film base material when it is wound up. (Gauge band) tends to be emphasized.

When the transparent conductive laminates are bonded together with this gauge band generated, there is a problem that the appearance (plane shape) of the adhesive layer deteriorates.

Further, the characteristics of the transparent conductive laminate using the release film based on the polyester film are not sufficiently satisfactory.

Therefore, when taking measures to reduce the amount of oligomer precipitation by the undercoat layer, it is required that the undercoat layer itself has an oligomer precipitation prevention property more than before, and the release film roll after the release coating is used. There is a need for polyester films that do not generate gauge bands.

Japanese Unexamined Patent Publication No. 2007-20823

The present invention has been made in view of the above circumstances, and a solution thereof is to provide a polyester film in which a gauge band is not generated on a release film roll wound after release coating, and further, an optical member. It is to provide a release film having excellent optical characteristics and visibility even after being processed as a product for use. Specifically, for example, a long-term heat treatment under 150 ° C. conditions, a sputtering process, and the like. It is an object of the present invention to provide a release film capable of suppressing the formation of foreign substances due to oligomers even after undergoing a process under harsh conditions such as a durability test in a high temperature and high humidity atmosphere.

As a result of diligent studies on the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the polyester film having a specific composition, and have completed the present invention.

That is, the gist of the present invention is that the surface roughness (Ra) of at least one side of the polyester film is 25 to 100 nm, the release agent is contained in at least one side of the polyester film in an amount of 0.01 to 15% by weight, and a cross-linking agent is used. 70 to 99.99% by weight, contains less than 30% by weight of a polymer other than a cross-linking agent and a mold release agent as a non-volatile component, and has a coating layer formed from a coating liquid containing no ammonium group-containing compound. It exists in a laminated polyester film characterized by this.

According to the present invention, in order to prevent highly oligomer precipitation, a polyester layer having a low ester cyclic trimer content and a coating layer having a specific composition are combined to form an extremely ester cyclic trimer. The effect of reducing precipitation can be obtained. Further, by having an appropriate surface roughness, for example, it is possible to provide a base film in which a gauge band is not generated on the release film roll after the release coating, 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, and 1,4-cyclohexyldicarboxylic acid or esters thereof. It is a polyester produced by melt-hypercondensation with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol. The polyester composed of these acid components and glycol components can be produced by using any of the usual methods.

For example, the lower alkyl ester of the aromatic dicarboxylic acid and the glycol are subjected to an ester exchange reaction, or the aromatic dicarboxylic acid and the glycol are directly esterified to substantially bisglycol the aromatic dicarboxylic acid. A method is adopted in which an ester or a low polymer thereof is formed, and then this is heated under reduced pressure to carry out polycondensation. Aliphatic dicarboxylic acids may be copolymerized according to the purpose.

Typical examples of the polyester of the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, etc., but the above-mentioned acid component and glycol component are also used. It may be a polymerized polyester, or may contain other components or additives as required.

The polyester polymerization catalyst is not particularly limited, and conventionally known compounds can be used. Examples thereof include antimony compounds, titanium compounds, germanium compounds, manganese compounds, aluminum compounds, magnesium compounds and calcium compounds. Among these, antimony compounds have the advantages of being inexpensive and having high catalytic activity. Further, the titanium compound and the germanium compound have high catalytic activity, can be polymerized in a small amount, and the amount of metal remaining in the film is small, so that the brightness of the film is high, which is preferable. Further, since the 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 multi-layer structure. In the case of a multi-layer structure, the surface layer and the inner layer, or both surface layers and each layer can be made of different polyesters depending on the purpose.

In the present invention, in order to suppress the precipitation amount of the ester cyclic trimer after the heat treatment, a film may be produced from polyester having a low content of the ester cyclic trimer as a raw material. As a method for producing a polyester having a low content of an ester cyclic trimer, various known methods can be used, and examples thereof include a method of solid-phase polymerization after polyester production.

By forming the polyester film into three or more layers and designing a layer using a polyester raw material having a low content of ester cyclic trimeric as the outermost polyester layer of the polyester film, precipitation of the ester cyclic trimer after heat treatment is performed. 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 the precipitation of the ester cyclic trimer, the content of the ester cyclic trimer is contained. It is preferable to have a polyester layer of 0.7% by weight or less, and more preferably 0.6% by weight or less of the polyester layer. When the polyester layer having an ester cyclic trimer content of 0.7% by weight or less is provided, the effect of preventing precipitation of the ester cyclic trimer on the film surface is particularly highly exhibited.

As the polyester used for forming the film of the polyester layer, it is possible to use a polyester raw material having a low content of the ester cyclic trimer, and the content of the ester cyclic trimer is preferably 0.7% by weight or less. It is more preferably 0.6% by weight or less, and particularly preferably 0.5% by weight or less. When the content of the ester cyclic trimer in the polyester raw material is 0.7% by weight or less, the precipitation amount of the ester cyclic trimer after the heat treatment can be suppressed more effectively.

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, and more preferably 80% by weight or more. When it is composed of 70% by weight or more, it is possible to exert a high degree of effect of preventing precipitation of ester cyclic trimers on the film surface after heat treatment.

When the polyester film has a multi-layer structure, it is preferable 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 from the viewpoint of preventing precipitation of the ester cyclic trimer.

Further, the thicker the thickness of the polyester layer having the ester cyclic trimer content of 0.7% by weight or less in the polyester film, the more effectively the precipitation of the ester cyclic trimer from the polyester film is suppressed. The film thickness of the polyester layer of 0.7% by weight or less 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, it is subjected to a long-term heat treatment under 150 ° C. conditions, a sputtering process under high tension conditions, or under a high temperature and high humidity atmosphere. Even when it is used in a processing process under harsh conditions such as the durability test of the above, the ester cyclic trimer is less likely to precipitate on the surface, and the increase in film haze can be further suppressed.

Particles are added to the layer constituting the surface layer of the polyester film in the present invention mainly for the purpose of forming roughness on the film surface. In this case, the same predetermined surface roughness may be formed on both sides, or the predetermined surface roughness may be formed on only one side. When the specified surface roughness is formed on only one side, the other side is easy to handle, such as unwinding when the film is rolled and running stability when the film is unwound from the film roll. , It is desirable that the surface roughness is lower than the predetermined surface roughness.

The type of particles to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness, and specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Inorganic particles such as magnesium silicon oxide, kaolin, aluminum oxide, titanium oxide, talc, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, crosslinked polymer particles, organic particles such as calcium oxalate, and , JP-A-59-5216, JP-A-59-217755, and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resin, thermosetting phenol resin, thermosetting epoxy resin, benzoguanamine resin and the like. Further, during the polyester production process, precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed can also be used.

On the other hand, the shape of the particles to be used is not particularly limited, and any of spherical, lumpy, rod-shaped, flat-shaped and the like may be used. Further, the hardness, specific gravity, color and the like are not particularly limited. Two or more kinds of these series of particles may be used in combination, if necessary.

The average particle size of the particles used is preferably in the range of 0.01 to 6 μm. If the average particle size is less than 0.01 μm, the particles tend to aggregate and the dispersibility may be insufficient, while if the average particle size exceeds 6 μm, the surface roughness of the film becomes rough. Too much, it becomes inferior in transparency. Further, in the film forming process, there may be a problem that the pressure rise of the filter becomes large, the productivity is deteriorated, and the filter is easily broken.

The method of adding the particles to the polyester is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage in the production of polyester, but preferably the polycondensation reaction may proceed at the stage of esterification or after the transesterification reaction is completed. Further, a method of blending a slurry of particles dispersed in ethylene glycol or water with a polyester raw material using a kneading extruder with a vent, or a method of blending dried particles with a polyester raw material using a kneading extruder. It is done by a method or the like.

The particle content in the surface layer of the polyester film is blended so that the surface roughness (Ra) on at least one side is 25 to 100 nm. Ra is more preferably in the range of 35-80 nm. In the present invention, when the surface roughness is lower than 25 nm, a gauge band is generated when the release layer is coated and then wound, and when the surface roughness is higher than 100 nm, the slipperiness of the film is formed. It becomes high, and when it is made into a film roll, it is unwound, and when the film is unwound from the film roll and used, it meanders on the roll in another process, and the running stability is lost, which is preferable. Absent. Further, when the same surface roughness design is performed on both sides, unevenness is generated on the coating surface side of the release layer, and after bonding with the adhesive layer, the unevenness is transferred to the adhesive layer, which deteriorates the appearance, which is preferable. Absent.

Further, regarding the surface roughness on the opposite surface side when only one surface has a predetermined surface roughness design, it is preferable to mix the particles so that the surface roughness (Ra) is in the range of 8 to 100 nm. More preferably, it is in the range of 10 to 25 nm. When the surface roughness is higher than 100 nm, the film may be unwound during transportation or use when it is made into a film roll, and when the film is unwound from the film roll and used, it is preferable from the viewpoint of film handleability such as running stability. If the surface roughness is lower than 8 nm, the film surface tends to be easily scratched during film formation or handling.

In addition to the above-mentioned particles, conventionally known antioxidants, ultraviolet absorbers, heat stabilizers, lubricants, dyes, pigments and the like can be added to the polyester film of the present invention, if necessary.

The thickness of the polyester film in the present invention is not particularly limited as long as it can be formed as a film, but is preferably in the range of 10 to 300 μm, more preferably 15 to 250 μm, and further preferably 20 to 200 μm. is there.

The haze of the laminated polyester film obtained in the present invention is preferably 10% or less. It is more preferably 5% or less, still more preferably 4% or less. If the haze of the laminated polyester film exceeds 10%, it may not be suitable for use in appearance in optical film applications.

The film of the present invention has a laminated structure by using a coextrusion method. At that time, the thickness of the outermost layer is usually 1.5 μm or more and 1/10 or less of the total thickness on only one side. ..
If the thickness is less than 1.5 μm, particles may easily fall off. On the other hand, if it exceeds 1/10, the film tends to curl easily, and the internal haze of the polyester film rises to increase the total haze. In addition, a large amount of particles will be used, which will lead to an increase in cost.

Hereinafter, the method for producing a polyester film of the present invention will be specifically described, but the present invention is not particularly limited to the following examples as long as the gist of the present invention is satisfied.

First, dried or undried polyester chips are supplied to a melt extruder by a known method, and heated to a temperature equal to or higher than the melting point of each polymer to be melted. The molten polymer is then extruded from the die and quenched and solidified on a rotary cooling drum to a temperature below the glass transition temperature to give a substantially amorphous unaligned sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and in the present invention, the electrostatic application adhesion method and / or the liquid coating adhesion method is preferably adopted.

In the present invention, the sheet thus obtained is stretched in the biaxial direction to form a film. Specifically describing the stretching conditions, the unstretched sheet is preferably stretched 2 to 5 times at 70 to 120 ° C. in the longitudinal direction to form a longitudinal uniaxially stretched film, and then at 80 to 160 ° C. in the horizontal direction. It is preferable to perform 2 to 5 times stretching and heat treatment at 200 to 245 ° C. for 10 to 600 seconds. Further, at this time, a method of relaxing by 2 to 20% in the vertical direction and / or the horizontal direction in the maximum temperature zone of the heat treatment and / or the cooling zone of the heat treatment outlet is preferable. It is also possible to add re-longitudinal stretching and re-transverse stretching as needed.

In the present invention, as described above, two or more polyester melt extruders can be used to form a three-layer laminated film by a so-called coextrusion method. As the layer structure, a film having an A / B / A structure can be obtained by using the A raw material and the B raw material. Further, a film having an A / B / C composition can be obtained by using the A raw material, the B raw material, and the C raw material.

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

The in-line coating is a method of coating in the process of manufacturing a polyester film, and specifically, a method of coating at an arbitrary stage from melt extrusion of polyester to heat fixing and winding after stretching. 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 fixing, or a film after heat fixing and before winding. To coat.

Although not limited to the following, for example, in sequential biaxial stretching, a method of coating a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction) and then stretching in the lateral direction is particularly excellent.

According to this method, film formation and coating layer coating can be performed at the same time, which has an advantage in terms of manufacturing cost. Since stretching is performed after coating, the coating layer has characteristics of a thin film and uniform coating. Stabilize.

Further, the polyester film before biaxial stretching is first coated with a resin layer constituting the coating layer, and then the film and the coating layer are simultaneously stretched so that the base film and the coating layer are firmly adhered to each other. become.

Further, in the biaxial stretching of the polyester film, the film is restrained in the longitudinal / lateral direction by stretching in the lateral direction while gripping the end of the film with a tenter clip or the like, and wrinkles or the like do not occur during thermal fixing. High temperature can be applied while maintaining flatness. Therefore, since the heat treatment applied after the coating can be made to a high temperature which 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 to each other. As a polyester film provided with a coating layer, the uniformity of the coating layer, the improvement of film forming property, and the adhesion between the coating layer and the film often produce favorable characteristics.

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

The coating layer of the present invention is a coating formed from a coating liquid containing a cross-linking agent and a mold release agent and a polymer other than the cross-linking agent and the mold release agent in an amount of 30% by weight or less as a non-volatile component on at least one side of the polyester film. Having a layer is an essential requirement. In addition, other components may be contained in the coating liquid.

A coating liquid containing 30% by weight or less of a polymer other than a cross-linking agent and a mold release agent as a non-volatile component means that most of the coating liquid is occupied by other materials, but the cross-linking agent is mainly composed. Is preferable. When the cross-linking agent occupies most of the coating layer, a coating layer cross-linked with high density is formed, and the precipitation of the ester cyclic trimer can be efficiently suppressed.

As the cross-linking agent, various known cross-linking agents can be used, and examples thereof include oxazoline compounds, melamine compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, and silane coupling compounds. Among these, the oxazoline compound is preferably used from the viewpoint of improving the durable adhesion when it is used for providing a functional layer on the coating layer. Further, the melamine compound is preferably used from the viewpoint of preventing the precipitation of the ester cyclic trimer on the film surface by heating and improving the durability and coatability of the coating layer.

The oxazoline compound is a compound having an oxazoline group in the molecule, and a polymer containing an oxazoline group is particularly preferable, and it can be prepared by polymerization of an addition-polymerizable oxazoline group-containing monomer alone or with another monomer. Additionally 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 suitable 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, and is, for example, an alkyl (meth) acrylate (as an alkyl group, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, etc. (Meta) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene Unsaturated carboxylic acids such as sulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth) acrylamide, N-alkyl ( Meta) acrylamide, N, N-dialkyl (meth) acrylamide, (alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl Unsaturated amides such as groups (groups, cyclohexyl groups, etc.); Vinyl esters such as vinyl acetate and vinyl propionate; Vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; Vinyl chloride and vinylidene chloride , Halogen-containing α, β-unsaturated monomers such as vinyl fluoride; α, β-unsaturated aromatic monomers such as styrene, α-methylstyrene, etc., and one or more of these. Monomer can be used.

The amount of oxazoline groups of the oxazoline compound contained in the coating liquid forming the coating layer forming the laminated polyester film in the present invention is usually 0.5 to 10 mmol / g, preferably 3 to 9 mmol / g, and more preferably 5. It is in the range of ~ 8 mmol / g. By using it in the above range, the durability of the coating film is improved.

The melamine compound is a compound having a melamine structure in the compound, for example, an alkylolated melamine derivative, a compound obtained by reacting an alcoholylated melamine derivative with an alcohol to partially or completely etherify, and these. A mixture can be used. As the alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. Further, the melamine compound may be either a monomer, a multimer of a dimer or more, or a mixture thereof. Further, a melamine in which urea or the like is co-condensed can be used, or a catalyst can be used to increase the reactivity of the melamine compound.

The epoxy compound is a compound having an epoxy group in the molecule, and examples thereof include a condensate of epichlorohydrin and an ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A and other 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, triglycidyltris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, and trimethylolpropane. Examples of the polyglycidyl ether and the 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, Polytetramethylene glycol diglycidyl ether, Monoepoxy compounds include, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenylglycidyl ether, glycidylamine compounds N, N, N', N ′ -Tetraglycidyl-m-xylylene diamine, 1,3-bis (N, N-diglycidylamino) cyclohexane and the like can be mentioned.

The isocyanate-based compound is a compound having an isocyanate derivative structure typified by isocyanate or blocked isocyanate. Examples of the isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylenedi isocyanate and naphthalene diisocyanate, and aromatic rings such as α, α, α'and α'-tetramethylxylylene diisocyanate. Aliphatic isocyanates such as aliphatic isocyanates, methylene diisocyanates, propylene diisocyanates, lysine diisocyanates, trimethylhexamethylene diisocyanates, hexamethylene diisocyanates, cyclohexane diisocyanates, methylcyclohexane diisocyanates, isophorone diisocyanates, methylenebis (4-cyclohexylisocyanates), isopropyridene dicyclohexyldiisocyanates and the like. The alicyclic isocyanate of the above is exemplified. In addition, polymers and derivatives such as burettes, isocyanurates, uretdiones, and carbodiimides of these isocyanates can also be mentioned. These may be used alone or in combination of two or more. 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, phenolic compounds such as heavy sulfites, phenol, cresol and ethylphenol, and alcoholic compounds 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 and dodecyl mercaptan, ε-caprolactam, δ-valerolactam, etc. Examples include lactam compounds, amine compounds such as diphenylaniline, aniline, and ethyleneimine, acid amide compounds of acetoanilide and acetate amide, oxime compounds such as formaldehyde, acetoaldoxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime. These may be used alone or in combination of two or more.

Further, the isocyanate-based compound in the present invention may be used alone, or may be used as a mixture or a bond with various polymers. In terms 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, which is a compound having one or more carbodiimide structures in the molecule, but polycarbodiimide having two or more in the molecule for better adhesion or the like. The system compound is more preferable.

The carbodiimide-based compound can be synthesized by a conventionally known technique, and a condensation reaction of a diisocyanate compound is generally used. The diisocyanate compound is not particularly limited, and either aromatic or aliphatic type can be used. Specifically, toluene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylenedi isocyanate, naphthalene diisocyanate, hexa. Examples thereof include methylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyldiisocyanate, and dicyclohexylmethane diisocyanate.

The content of the carbodiimide group contained in the carbodiimide-based compound is a carbodiimide equivalent (weight [g] of the carbodiimide compound for giving 1 mol of the carbodiimide group), and is usually 100 to 1000, preferably 250 to 700, and more preferably 300. It is in the range of ~ 500. By using it in the above range, the durability of the coating film is improved.

Further, in order to improve the water solubility and water dispersibility of the polycarbodiimide compound within the range where the effect of the present invention is not lost, a surfactant may be added, or a polyalkylene oxide or a quaternary ammonium salt of a dialkylamino alcohol may be added. Hydrophilic monomers such as hydroxyalkyl sulfonate may be added and used.

These cross-linking agents may be used alone or in combination of two or more types, but by combining two or more types, adhesion to the functional layer and precipitation of the ester cyclic trimer after heating are difficult. It was found to improve the preventability. Among them, a combination of an oxazoline compound capable of improving adhesion to the functional layer and a melamine compound having good precipitation-preventing property of the ester cyclic trimer after heating is particularly preferable and preferable.

It was also found that it is effective to combine three kinds of cross-linking agents in order to further improve the adhesion with the functional layer. As a combination of three or more kinds of cross-linking agents, it is optimal to select a melamine compound as one of the cross-linking agents, and as a combination with the melamine compound, an oxazoline compound and an epoxy compound, and a carbodiimide compound and an epoxy compound are used. Especially preferable.

These cross-linking agents are used in a design to improve the performance of the coating layer by reacting them in the drying process and the film forming process. It can be inferred that unreacted products of these cross-linking agents, compounds after the reaction, or mixtures thereof are present in the completed coating layer.

When such a cross-linking component is contained, a component for promoting cross-linking, for example, a cross-linking catalyst can be used in combination at the same time.

In order to form the coating layer of the film of the present invention, it is an indispensable requirement to use a mold release agent in combination from the viewpoint of imparting appropriate water repellency.

The release agent used for forming the coating layer is used to improve the releasability of the film, and there is no particular limitation, and a conventionally known release agent can be used, for example, a long chain. Examples thereof include alkyl compounds, fluorine compounds, waxes and silicone compounds. Among these, long-chain alkyl compounds and fluorine compounds are preferable from the viewpoint of effectively obtaining water repellency even in a small amount, and long-chain alkyl compounds are more preferable from the viewpoint of the appearance of the coating layer. These release agents may be used alone or in a plurality of types.

The long-chain alkyl compound is a compound having a linear or branched alkyl group having 6 or more carbon atoms, preferably 8 or more carbon atoms, and more preferably 12 or more carbon atoms. Examples of the alkyl group include an octyl group, a decyl group, a lauryl group, an octadecyl group, a behenyl group and the like. Examples of the compound having an alkyl group include various long-chain alkyl group-containing polymer compounds, long-chain alkyl group-containing amine compounds, long-chain alkyl group-containing ether compounds, and long-chain alkyl group-containing quaternary ammonium salts. .. Considering heat resistance and stain resistance, a polymer compound is preferable. Further, from the viewpoint that an appropriate water repellency can be effectively obtained with a small content, a polymer compound having a long-chain alkyl group in the side chain is more preferable.

The polymer compound having a long-chain alkyl group in the side chain can be obtained by reacting a polymer having a reactive group with a compound having an alkyl group capable of reacting with the reactive group. Examples of the reactive group include a hydroxyl group, an amino group, a carboxyl group, an acid anhydride and the like.
Examples of the compound having these reactive groups include polyvinyl alcohol, polyethyleneimine, polyethyleneamine, a polyester resin containing a reactive group, a poly (meth) acrylic resin containing a reactive group, and the like. Among these, polyvinyl alcohol is preferable in consideration of releasability and ease of handling.

The compounds having an alkyl group capable of reacting with the above-mentioned reactive groups include, for example, long-chain alkyl group-containing isocyanates such as octyl isocyanate, decyl isocyanate, lauryl isocyanate, octadecyl isocyanate, and behenyl isocyanate, octyl chloride, decyl chloride, and lauryl chloride. , Octadecyl chloride, long-chain alkyl group-containing acid chlorides such as behenyl chloride, long-chain alkyl group-containing amines, long-chain alkyl group-containing alcohols and the like. Among these, long-chain alkyl group-containing isocyanates are preferable, and octadecyl isocyanates are particularly preferable, in consideration of releasability and ease of handling.

Further, the polymer compound having a long-chain alkyl group in the side chain can also be obtained by copolymerizing a polymer of a long-chain alkyl (meth) acrylate or a long-chain alkyl (meth) acrylate with another vinyl group-containing monomer. .. Examples of the long-chain alkyl (meth) acrylate include octyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, octadecyl (meth) acrylate, and behenyl (meth) acrylate.

The fluorine compound is a compound containing a fluorine atom in the compound. Organic fluorine compounds are preferably used in terms of coating appearance by in-line coating, and examples thereof include perfluoroalkyl group-containing compounds, polymers of olefin compounds containing fluorine atoms, and aromatic fluorine compounds such as fluorobenzene. .. A compound having a perfluoroalkyl group is preferable from the viewpoint that appropriate water repellency can be obtained with a small content. Further, as the fluorine compound, a compound containing a long-chain alkyl compound as described later can also be used.

Compounds having a perfluoroalkyl group include, for example, perfluoroalkyl (meth) acrylate, perfluoroalkylmethyl (meth) acrylate, 2-perfluoroalkylethyl (meth) acrylate, and 3-perfluoroalkylpropyl (meth) acrylate. , 3-Perfluoroalkyl-1-methylpropyl (meth) acrylate, 3-perfluoroalkyl-2-propenyl (meth) acrylate and other perfluoroalkyl group-containing (meth) acrylates and polymers thereof, perfluoroalkylmethylvinyl ether , 2-Perfluoroalkyl ethyl vinyl ether, 3-perfluoropropyl vinyl ether, 3-perfluoroalkyl-1-methylpropyl vinyl ether, 3-perfluoroalkyl-2-propenyl vinyl ether and other perfluoroalkyl group-containing vinyl ethers and polymers thereof. And so on. A polymer is preferable in consideration of heat resistance and stain resistance. The polymer may be a single compound alone or a polymer of a plurality of compounds. Further, the perfluoroalkyl group preferably has 3 to 11 carbon atoms from the viewpoint that residual water on the film can be suppressed with a small content. Further, it may be a polymer with a compound containing a long-chain alkyl compound as described later. Further, from the viewpoint of adhesion to the base material, a polymer with vinyl chloride is more preferable.

The wax is a wax selected from natural waxes, synthetic waxes, and waxes containing them. Natural waxes are plant-based waxes, animal-based waxes, mineral-based waxes, and petroleum-based waxes. Examples of the plant wax include candelilla wax, carnauba wax, rice wax, wood wax and jojoba oil. Examples of animal waxes include mitsuro, lanolin, and whale wax. Examples of mineral waxes include montan wax, ozokerite, and selecin. Examples of petroleum wax include paraffin wax, microcrystalline wax, and petrolatum. Examples of synthetic waxes include synthetic hydrocarbons, modified waxes, hydrogenated waxes, fatty acids, acid amides, amines, imides, esters and ketones. Fisher Tropsch wax (also known as Sazoir wax) and polyethylene wax are well-known synthetic hydrocarbons, but other low molecular weight polymers (specifically, polymers with a viscosity number average molecular weight of 500 to 20000) are used. The following polymers are also included. That is, there are polypropylene, ethylene / acrylic acid copolymers, polyethylene glycol, polypropylene glycol, block or graft conjugates of polyethylene glycol and polypropylene glycol. Examples of the modified wax include a montan wax derivative, a paraffin wax derivative, and a microcrystalline wax derivative. The derivative here is a compound obtained by any treatment of purification, oxidation, esterification, saponification, or a combination thereof. Examples of the hydrogenated wax include hardened castor oil and hardened castor oil derivatives. Among these waxes, synthetic hydrocarbon waxes are preferable from the viewpoint of stable performance and easy availability, and polyethylene oxide wax and polypropylene oxide wax are more preferable.

The silicone compound is a compound having a silicone structure in the molecule, and examples thereof include silicone emulsion, acrylic graft silicone, silicone graft acrylic, amino-modified silicone, perfluoroalkyl-modified silicone, and alkyl-modified silicone. Considering heat resistance and stain resistance, it is preferable to contain a curable silicone resin.
As the type of the curable silicone resin, any curing reaction type such as addition type, condensation type, ultraviolet curable type, and electron beam curable type can be used.

Further, in forming the coating layer of the film of the present invention, it is also possible to use a polymer in combination for improving the coating appearance, improving the adhesion when the functional layer is formed on the coating layer, and the like. However, if the content is large, the precipitation prevention property of the ester cyclic trimer after heating may be deteriorated.

Specific examples of the polymer include polyester resin, acrylic resin, urethane resin, polyvinyl (polyvinyl alcohol and the like), polyalkylene glycol, polyalkyleneimine, methyl cellulose, hiroxycellulose, starches and the like. Among these, polyester resin, acrylic resin, and urethane resin are preferably used from the viewpoint of improving adhesion to various surface functional layers.

Examples of the polyester resin include those composed of the following polyvalent carboxylic acids and polyvalent hydroxy compounds as main constituents. 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, glutaru Acids, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, monopotassium trimellitic acid and their ester-forming derivatives can be used. As polyvalent hydroxy compounds, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanedioyl, 2 -Methyl-1,5-pentandiol, neopentylglycol, 1,4-cyclohexanedimethanol, p-xylyleneglycol, bisphenol A-ethyleneglycol adduct, diethyleneglycol, triethyleneglycol , Polyethylene glycol, Polypropylene glycol, Polytetramethylene glycol, Polytetramethylene oxide glycol, Dimethylolpropionic acid, Glycerin, Trimethylolpropane, Sodium dimethylolethylsulfonate, Dimethylolpropion Potassium acid or the like can be used. One or more of these compounds may be appropriately selected, and a polyester resin may be synthesized by a conventional polycondensation reaction.

The acrylic resin is a polymer composed of a polymerizable monomer containing an acrylic-based or methacrylic-based monomer. These may be homopolymers or copolymers, and may be copolymers with polymerizable monomers other than acrylic and methacrylic monomers. Also included are copolymers of these polymers with other polymers (eg polyester, polyurethane, etc.). For example, block copolymers and graft copolymers. Alternatively, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer 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 in a polyurethane solution or a polyurethane dispersion is also included. Similarly, a polymer (in some cases, a polymer mixture) obtained by polymerizing a polymerizable monomer in another polymer solution or dispersion is also included. It is also possible to contain a hydroxyl group and an amino group in order to further improve the adhesion.

The polymerizable monomer is not particularly limited, but as a particularly representative compound, it contains various carboxyl groups such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citraconic acid. Monomers and salts thereof; such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutylhydroquilfumarate, monobutylhydroxyitaconate. Various hydroxyl group-containing monomers; various (meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and lauryl (meth) acrylate; Various nitrogen-containing compounds such as meta) acrylamide, diacetone acrylamide, N-methylol acrylamide 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-based monomers; various types such as vinyl chloride, billidene chloride. Vinyl halides; various conjugated dienes such as butadiene can be mentioned.

The urethane resin is a polymer compound having a urethane bond in the molecule. Urethane resins are usually made by the reaction of polyol and isocyanate. Examples of the polyol include polycarbonate polyols, polyester polyols, polyether polyols, polyolefin polyols, and acrylic polyols, and these compounds may be used alone or in a plurality of types.

Polycarbonate polyols are obtained from polyhydric alcohols and carbonate compounds by a dealcohol reaction. Examples of polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 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 Examples thereof include diol, neopentyl glycol, 3-methyl-1,5-pentanediol, and 3,3-dimethylol heptane. Examples of the carbonate compound include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate and the like, and examples of the polycarbonate-based polyols obtained from these reactions include poly (1,6-hexylene) carbonate and poly (3-). Methyl-1,5-pentylene) carbonate and the like can be mentioned.

Polypolypolyols include polyvalent carboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimeric acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides. Products and polyhydric alcohols (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-Diol-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, cyclohexanediol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyldialkanolamine, lactonediol, etc.) can be mentioned.

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

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

Examples of the polyisocyanate compound used to obtain a urethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylenedi isocyanate, naphthalene diisocyanate, and trizine diisocyanate, α, α, α', and α'. -Adiocyanate having an aromatic ring such as tetramethylxylylene diisocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate and other aliphatic diisocyanates, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl Examples thereof include alicyclic diisocyanates such as methane diisocyanate and isopropyridene dicyclohexyldiisocyanate. These may be used alone or in combination of two or more.

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 the isocyanate group, and is generally a hydroxyl 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. Examples of glycols such as glycols can be mentioned. Examples of the chain extender having two amino groups include aromatic diamines such as tolylene diamine, xylylene diamine, 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 decanediamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, isoprovilitincyclohexyl-4,4'-diamine, 1,4-diaminocyclohexane, 1 , 3-Bisaminomethylcyclohexane and other alicyclic diamines and the like.

The urethane resin in the present invention may use a solvent as a medium, but is preferably 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, a water-soluble type, and the like. In particular, a self-emulsifying type in which an ionic group is introduced into the structure of a urethane resin to form an ionomer is preferable because it is excellent in storage stability of the liquid and the water resistance, transparency, and adhesion of the obtained coating layer.

Examples of the ionic group to be introduced include various types such as a carboxyl group, a sulfonic acid, a phosphoric acid, a phosphonic acid, and a quaternary ammonium salt, and a carboxyl group is preferable. As a method for introducing a carboxyl group into the urethane resin, various methods can be taken in each stage of the polymerization reaction.

For example, there are a method of using a resin having a carboxyl group as a copolymerization component and a method of using a component having a carboxyl group as one component of a polyol, a polyisocyanate, a chain extender, etc. at the time of prepolymer synthesis. In particular, a method of using a carboxyl group-containing diol and introducing a desired amount of carboxyl groups according to the amount of this component charged is preferable. For example, copolymerizing dimethylolpropionic acid, dimethylolbutanoic acid, bis- (2-hydroxyethyl) propionic acid, bis- (2-hydroxyethyl) butanoic acid, etc. with the diol used for polymerizing the urethane resin. Can be done. Further, this carboxyl group is preferably in the form of a salt neutralized with ammonia, amines, alkali metals, inorganic alkalis and the like. Particularly preferred are ammonia, trimethylamine and triethylamine. In such a polyurethane resin, the carboxyl group from which the neutralizing agent has been removed in the drying step after coating can be used as a cross-linking reaction point by another cross-linking agent. As a result, the stability of the liquid before coating is excellent, and the durability, solvent resistance, water resistance, blocking resistance, etc. of the obtained coating layer can be further improved.

Among the above-mentioned polymers, acrylic resin is particularly preferable from the viewpoint of suppressing the precipitation of the ester cyclic trimer and achieving both high adhesion.

Further, it is also possible to use particles in combination for the purpose of blocking and improving slipperiness in forming the coating layer. The average particle size 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 film transparency. Further, the lower limit is preferably 0.005 μm or more, more preferably 0.01 μm or more in order to more effectively improve the slipperiness. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, organic particles and the like. Among them, silica is preferable from the viewpoint of transparency.

Further, as long as the gist of the present invention is not impaired, a defoaming agent, a coating property improving agent, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, and an antioxidant are necessary for forming the coating layer. , Foaming agents, dyes, pigments and the like can also be used in combination.

The ratio of the cross-linking agent to the total non-volatile components in the coating liquid forming the coating layer forming the laminated polyester film in the present invention is preferably in the range of 70 to 99.99% by weight, more preferably 80 to 99. It is in the range of 5% by weight, more preferably 90 to 99% by weight. When the ratio is less than the above range, the precipitation of the ester cyclic trimer after heating may not be effectively suppressed, or the adhesion may be deteriorated.

The ratio of the release agent to the total non-volatile components in the coating liquid forming the coating layer forming the laminated polyester film in the present invention is preferably in the range of 0.01 to 30% by weight, more preferably 0.5. It is in the range of ~ 15% by weight, more preferably 1-5% by weight. If the ratio is less than the above range, the water repellency may not be sufficient. Further, when the ratio is more than the above range, the adhesion with various topcoating agents may not be sufficient.

As a ratio to all non-volatile components in the coating liquid forming the coating layer forming the laminated polyester film in the present invention, the ratio of the polymer other than the cross-linking agent and the release agent is usually less than 30% by weight, preferably less than 20% by weight. , More preferably less than 10% by weight, still more preferably less than 3% by weight, and particularly preferably not contained. When the ratio is more than the above range, it may not be possible to effectively suppress the precipitation of the ester cyclic trimer after heating.

When a melamine compound is selected as one of the cross-linking agents from the viewpoint of preventing the precipitation of the ester cyclic trimer after heating, the ratio of the melamine compound to the total non-volatile components in the coating liquid forming the coating layer is determined. It is preferably in the range of 5 to 95% by weight, more preferably in the range of 10 to 90% by weight, and even more preferably in the range of 30 to 85% by weight. When the ratio is within the above range, precipitation of the ester cyclic trimer after heating can be effectively suppressed.

When an oxazoline compound is selected as one of the cross-linking agents from the viewpoint of coating appearance and adhesion, the ratio of the oxazoline compound to the total non-volatile components in the coating liquid forming the coating layer is preferably 5 to 95 weight by weight. %, More preferably 10-80% by weight, even more preferably 20-70% by weight. When the ratio is within the above range, excellent results can be obtained in terms of coating appearance and adhesion when combined with other cross-linking agents.

The thickness of the coating layer is usually in the range of 0.003 to 1 μm, preferably 0.005 to 0.6 μm, and more preferably 0. It is in the range of 01 to 0.4 μm. When the thickness is thinner than 0.003 μm, the amount of ester cyclic trimer precipitated from the film may not be sufficiently reduced. If it is thicker than 1 μm, problems such as deterioration of the appearance of the coating layer and easy blocking may occur.

Examples of the method of applying the coating liquid to the polyester film include air doctor coat, blade coat, rod coat, bar coat, knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat, gravure coat, and kiss roll coat. , Cast coat, spray coat, curtain coat, calender coat, extrusion coat and the like, conventionally known coating methods can be used.

In order to improve the coatability 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.

The laminated polyester film in the present invention may be required to have a high degree of transparency even after being exposed to a high temperature atmosphere for a long time, for example, for a touch panel. From this point of view, in order to cope with a high degree of transparency, the amount of change in film haze (ΔH) during heat treatment (180 ° C., 30 minutes) is preferably 1.0% or less, more preferably 0.5% or less. More preferably, it is 0.3% or less. When ΔH exceeds 1.0%, the visibility is lowered due to the increase in film haze due to the precipitation of the ester cyclic trimer, which is not suitable for applications requiring high visibility such as for touch panels. It may be appropriate.

From the viewpoint of the amount of precipitation of the ester cyclic trimer, the ester cyclic trimeric amount extracted from the film surface by dimethylformamide by heat treatment (180 ° C., 30 minutes) of the laminated polyester film in the present invention is preferable. It is 1.3 mg / m ² or less, more preferably 0.8 mg / m ² or less, still more preferably 0.6 mg / m ² or less. When it exceeds 1.3 mg / m ² , the precipitation amount of the ester cyclic trimer increases in the subsequent step with a long-term heat treatment in a high temperature atmosphere such as 180 ° C. for 30 minutes, and the film becomes transparent. There is a concern that the property may deteriorate or that the process may be contaminated.

Regarding the laminated polyester film in the present invention, for example, in the case of a touch panel, it is necessary to suppress residual water on the film in the cleaning step for removing the photoresist after laminating the photoresist and patterning the ITO layer. is there. From this point of view, the water droplet contact angle is preferably 55 degrees or more, more preferably 65 degrees or more, still more preferably 70 degrees or more in order to cope with appropriate water repellency. If the water droplet contact angle is less than 55 degrees, the residual water on the film cannot be effectively suppressed in the cleaning step, which may be inappropriate.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The evaluation methods in Examples and Comparative Examples are as follows.

(1) Method for measuring 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 carried out at 30 ° C.

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

(3) Method for measuring the contained ester cyclic trimer contained in the polyester raw material:
Approximately 200 mg of the polyester raw material is weighed and dissolved in 2 ml of a mixed solvent having a chloroform / HFIP (hexafluoro-2-isopropanol) ratio of 3: 2. After dissolution, 20 ml of chloroform is added, and then 10 ml of methanol is added little by little. The precipitate is removed by filtration, and the precipitate is washed with a mixed solvent having a chloroform / methanol ratio of 2: 1 to collect the filtrate and washing liquid, concentrated by an evaporator, and then dried. After dissolving the dry matter in 25 ml of DMF (dimethylformamide), this solution is supplied to liquid chromatography (“LC-7A” manufactured by Shimadzu Corporation) to determine the amount of ester cyclic trimer in DMF. The value is divided by the amount of the polyester raw material dissolved in the chloroform / HFIP mixed solvent to obtain the amount of the contained ester cyclic trimer (% by weight). The amount of the ester cyclic trimer in the DMF was determined from the peak area ratio of 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-prepared ester cyclic trimer and dissolving it in the accurately weighed DMF.

The conditions of the liquid chromatograph were as follows.
Mobile phase A: Acetonitrile Mobile phase B: 2% aqueous acetic acid solution Column: "MCI GEL ODS 1HU" manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow velocity: 1 ml / min Detection wavelength: 254 nm

(4) Method for calculating ester cyclic trimer contained in polyester film:
It was calculated based on the amount of the ester cyclic trimer contained in the polyester raw material obtained by the method (3).

(5) Coating layer thickness The film was fixed with an embedding resin, the cross section was cut with a microtome, and the sample was prepared by staining with 2% osmium 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 the average of 9 points excluding 3 points from the larger value and 3 points from the smaller value is taken as the coating layer thickness.

(6) Method of heat-treating the film The sample is fixed on top of Kent paper with the measurement surface exposed, and left at 180 ° C. for 30 minutes in a nitrogen atmosphere for heat treatment.

(7) Measurement of film haze The sample film was measured according to JIS-K-7136 with a haze meter "HM-150" manufactured by Murakami Color Technology Laboratory Co., Ltd.

(8) Measurement of film haze rise (ΔH) by heat treatment First, the haze of the sample film was measured by the method of item (7) (haze 1).
Then, after heating by the method of item (6), the haze was measured by the method of (7) (haze 2).
ΔH = (Haze 2)-(Haze 1)
The lower the ΔH, the smaller the precipitation of oligomers due to the high temperature treatment, which is good.

(9) Measurement of Precipitation of Ester Cyclic Trimer Precipitated on the Surface of Laminated Polyester Film The polyester film is heated in air at 180 ° C. for 30 minutes. Then, the heat-treated film is formed into a box shape with the measurement surface (coating layer) as the inner surface so that the film has an open top of 10 cm in length and width and 3 cm in height. Next, 4 ml of DMF (dimethylsulfoamide) is placed in the box prepared by the above method and left for 3 minutes, and then the DMF is collected. The recovered DMF was supplied to liquid chromatography (manufactured by Shimadzu Corporation: LC-7A) to determine the amount of ester cyclic trimer in the DMF, and this value was divided by the area of the film in contact with the DMF. The amount of ester cyclic trimer precipitated on the film surface was determined to be (mg / m ² ). The amount of the ester cyclic trimer in the DMF was calculated according to the absolute calibration curve method described in (3) The method for measuring the amount of oligomers contained in the polyester raw material.

(10) Adhesion Evaluation Method An active energy ray-curable resin composed of the following coating agent composition is applied to the coating film-forming surface of the polyester film, dried at 80 ° C. for 1 minute to remove the solvent, and then subjected to an ultraviolet irradiation machine. ^{Ultraviolet rays were irradiated at 180 mJ / cm 2} with a metal halide lamp 120 W to form a hard coat layer having a thickness of 5 μm. 100 square-shaped cuts were made on the obtained film using a cutter guide with a gap spacing of 1 mm. Next, an 18 mm wide tape (Cellotape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) was attached to the cut surface on the square, and a 2.0 kg roller was reciprocated 20 times to completely adhere the tape, and then 180 degrees. Observe the peeled surface after abrupt peeling at the peeling angle, and if the peeled area is less than 5%, ◎, if 5% or more and less than 20%, ○, if 20% or more and less than 50%, △, if 50% or more, ×. did.
<< Composition of active energy ray-curable resin >>
A mixed coating solution of 72 parts by weight of dipentaerythritol acrylate, 18 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, 1 part by weight of a photopolymerization initiator (Irgacare 651, manufactured by Ciba Specialty Chemicals Co., Ltd.), and 200 parts by weight of methyl ethyl ketone.

(11) Water Drop Contact Angle The contact angle was determined by the sessile drop method using a contact angle meter CA-DA type manufactured by Kyowa Interface Science Co., Ltd. The water used was pure water purified by a MILLI-Q REAGEENT-WATER-SYSTEM device manufactured by Nippon Millipore Co., Ltd. The time from dropping the droplet to the measurement was about 30 seconds. It was measured 6 times and the average value was adopted.

(12) Surface roughness (Ra)
The measurement was performed using a three-dimensional non-contact / surface shape measurement system Micromap (MM537N-M100, manufactured by Ryoka System Co., Ltd.). The optical system used was a Milow-type two-luminous flux interference objective lens (20 times) and a zoom lens (BodyTube 1.0 times), and the wavelength filter used was 530 White, and the light was received by a 2/3 inch CCD camera. The measurement was performed in the wave mode, and the roughness (Ra) of the film surface was measured for the observation region of 433 μmx 323 μm. 10 points were arbitrarily measured and the average value was calculated.

(13) Appearance evaluation of release film roll For product rolls slit from the master roll to a winding length of 1000 m with a width of 1000 mm, both sides, in the case of a predetermined surface roughness, from either side to one side, one side, a predetermined surface roughness In the case of the case, a release coating was applied to the opposite side surface, and a release film roll was prepared by applying a release coating to one side. The appearance inspection of the obtained release film roll was performed under a fluorescent lamp, the generation of gauge bands was comprehensively evaluated, and the following judgment was made.
A: No gauge band is generated B: Slight gauge band is generated C: Gauge band is generated

(14) Adhesive Appearance Evaluation Acrylic adhesive Corponil N-2233 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) is applied to the release surface of the release film prepared in (13) so that it is 3 μm after drying. , An adhesive layer was provided. After the release film was attached to the glass plate via this adhesive layer, it was left at 150 ° C. for 1 hour in a nitrogen atmosphere to perform heat treatment. Then, the release film was peeled off, the appearance of the adhesive layer was observed, and the judgment was made according to the following criteria.
◯: Adhesive layer is uniformly coated and there is no problem in appearance Level △: Fine unevenness is seen, there is no major problem in appearance Level ×: Large unevenness in the adhesive layer or missing of the adhesive layer is seen , Level with appearance problems

The polyesters used in Examples and Comparative Examples were prepared as follows.
<Manufacturing method of 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 was taken in a reactor as a catalyst, the reaction start temperature was set to 150 ° C., and gradually with the distillation of methanol. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially completed. 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 the normal pressure to finally reach 0.3 mmHg. After the reaction was started, the reaction was stopped at a time corresponding to the ultimate viscosity of 0.63 due to a change in the stirring power of the reaction tank, and the polymer was discharged under nitrogen pressurization. The obtained polyester (A) had an ultimate viscosity of 0.63 and a cyclic trimer content of 0.97% by weight.

<Manufacturing method of polyester (B)>
The polyester (A) was pre-crystallized at 160 ° C. and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 220 ° C. to have an intrinsic viscosity of 0.75 and an ester cyclic trimer content of 0.46% by weight. Polyester (B) was obtained.

<Manufacturing method of polyester (C)>
Ester 100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, 30 ppm of ethyl acid phosphate with respect to the produced polyester, and 100 ppm of magnesium acetate / tetrahydrate as a catalyst with respect to the produced polyester in a nitrogen atmosphere at 260 ° C. A chemical reaction was allowed. Subsequently, 50 ppm of tetrabutyl titanate was added to the produced polyester, the temperature was raised to 280 ° C. over 2 hours and 30 minutes, the pressure was reduced to an absolute pressure of 0.3 kPa, and the melt polycondensation was carried out for another 80 minutes to obtain the ultimate viscosity. A polyester (C) having a content of 0.61 polyester (A) ester cyclic trimer of 1.02% by weight was obtained.

<Manufacturing method of polyester (D)>
The polyester (C) was pre-crystallized at 160 ° C. and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 210 ° C. to have an intrinsic viscosity of 0.72 and an ester cyclic trimer content of 0.50% by weight. Polyester (D) was obtained.

<Manufacturing method of polyester (E)>
In the method for producing polyester (A), 0.8 parts of silica particles having an average particle diameter (d50) of 2.2 μm dispersed in ethylene glycol after adding 0.04 part of ethyl acid phosphate, 0 part of antimony trioxide. A polyester (E) was obtained using the same method as that for producing the polyester (A) except that the polycondensation reaction was stopped at a time corresponding to the ultimate viscosity of 0.64 by adding .04 parts. The obtained polyester (E) had an intrinsic viscosity of 0.64 and an ester cyclic trimer content of 0.82% by weight.

Moreover, the following was used as the composition contained in the coating liquid.
(A1): Hexamethoxymethylol melamine (A2): Epocross (manufactured by Nippon Shokubai Co., Ltd.), which is an oxazoline compound, has an oxazoline group amount of 7.7 mmol / g.
(A3): Epocross (manufactured by Nippon Shokubai Co., Ltd.), which is an oxazoline compound, has an oxazoline group amount of 4.5 mmol / g.
(A4): Polyglycerol polyglycidyl ether

(A5): 1000 parts of blocked polyisocyanate hexamethylene diisocyanate synthesized by the following method was stirred at 60 ° C., and 0.1 part of tetramethylammonium capriate was added as a catalyst. After 4 hours, 0.2 part of phosphoric acid was added to stop the reaction to obtain an isocyanurate-type polyisocyanate composition. 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 held at 80 ° C. for 7 hours. Then, the temperature of the reaction solution was maintained at 60 ° C., 35.8 parts of methyl isobutanoyl acetate, 32.2 parts of diethyl malonate, and 0.88 parts of a 28% methanol solution of sodium methoxide were added and kept for 4 hours. Block polyisocyanate obtained by adding 58.9 parts of n-butanol, holding at a reaction solution temperature of 80 ° C. for 2 hours, and then adding 0.86 parts of 2-ethylhexyl acid phosphate.

(A6): Carbodilite (manufactured by Nisshinbo Chemical Co., Ltd.), which is a polycarbodiimide-based compound. Carbodiimide equivalent 340.

(B1): 200 parts of xylene and 600 parts of octadecyl isocyanate were added to a four-necked flask and heated under stirring. From the time when xylene began to reflux, 100 parts of polyvinyl alcohol having an average degree of polymerization of 500 and a saponification degree of 88 mol% was added little by little at 10-minute intervals for about 2 hours. After the addition of polyvinyl alcohol was completed, reflux was carried out for another 2 hours to complete the reaction. When the reaction mixture was cooled to about 80 ° C. and then added to methanol, the reaction product precipitated as a white precipitate. This precipitate was filtered off, 140 parts of xylene was added, and the mixture was heated to completely dissolve it. After that, the operation of adding methanol again to precipitate the precipitate was repeated several times, and then the precipitate was washed with methanol and dried and pulverized to obtain a long-chain alkyl compound.

(B2): Hydrodisperse of fluorine compound polymerized with the following composition Octadecyl acrylate / perfluorohexyl ethyl methacrylate / vinyl chloride = 66/17/17 (% by weight)

(B3): 300 g of polyethylene oxide wax having a melting point of 105 ° C., oxidation of 16 mgKOH / g, density of 0.93 g / mL, average molecular weight of 5000, ion exchange in an emulsification facility having an internal volume of 1.5 L equipped with a stirrer, a thermometer and a temperature controller. 650 g of water, 50 g of decaglycerin monooleate surfactant, 10 g of 48% potassium hydroxide aqueous solution were added, replaced with nitrogen, sealed, stirred at 150 ° C. for 1 hour at high speed, cooled to 130 ° C., and high-pressure homogenizer. A wax emulsion cooled to 40 ° C.

(C1): Acrylic resin polymerized with the following composition Emulsified weight of ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (% by weight) Combined (emulsifier: anionic surfactant)

(C2): Isophorone diisocyanate: Terephthalic acid: Isophthalic acid: Ethylene glycol: Diethylene glycol: Dimethylolpropaneic acid = 12: 19: 18: 21: 25: 5 (mol%) An aqueous dispersion of a polyester-based urethane resin formed from ..
(D1): 2-amino-2-methylpropanol hydrochloride (E1), which is a melamine cross-linking catalyst: silica particles having an average particle size of 0.07 μm.

Example 1:
A layer in which polyesters (B) and (E) are blended at a weight ratio of 93/7, a layer in which only polyester (A) is blended at a weight ratio of 93/7, and polyesters (B) and (E) at a weight ratio of 50/50. The blended material is used as the raw material for the C layer, and each of them is supplied to three vent type twin-screw extruders, heated and melted at 285 ° C., and then the A layer and the C layer are the outermost layer (surface layer) and the B layer is the intermediate layer. Coextruded so that the thickness composition ratio is A / B / C = 7.5 / 110 / 7.5 with 3 types and 3 layers (A / B / C), and the surface temperature is 45 ° C. using the electrostatic adhesion method. An unstretched polyethylene terephthalate film was prepared by cooling and solidifying the film while keeping it in close contact with the mirror surface cooling drum. While passing this film through a group of heated rolls at 85 ° C., the film was stretched 3.1 times in the vertical direction by utilizing the difference in peripheral speed of the rolls, and then the aqueous coating liquid shown in Table 1 below was applied to both sides of the vertically stretched film. 1 is applied, guided to a tenter stretching machine, stretched 4.3 times in the lateral direction at 100 ° C., further heat-treated at 230 ° C., and then subjected to a relaxation treatment of 8% in the lateral direction to obtain a film thickness of the coating layer. A biaxially oriented polyethylene terephthalate film having a coating layer (after drying) of 0.04 μm and a film thickness of 125 μm was obtained.

The film haze increase value (ΔH) due to the heat treatment of the obtained polyester film was small, and the amount of precipitation of the ester cyclic trimer was also small, which was good. In addition, the adhesion was also good.
Furthermore, the water droplet contact angle was also high, showing appropriate water repellency. Further, no gauge band was generated on the release film roll, and the appearance of the adhesive layer was also good.
The characteristics of this film are shown in Table 3 below.

Examples 2-7:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coating agent composition was changed to the coating agent compositions shown in Tables 1 and 2. The obtained polyester film had the characteristics shown in Table 3, the amount of precipitation of the ester cyclic trimer by the heat treatment was small, and the adhesion was also good. In addition, the water droplet contact angle was high, showing appropriate water repellency. Further, no gauge band was generated on the release film roll, and the appearance of the adhesive layer was also good.

Example 8:
A layer in which polyesters (D) and (E) are blended at a weight ratio of 93/7, a layer in which only polyester (C) is blended at a weight ratio of 93/7, and polyesters (D) and (E) at a weight ratio of 50/50. The blended material is used as the raw material for the C layer, and each of them is supplied to three vent type twin-screw extruders, heated and melted at 285 ° C., and then the A layer and the C layer are the outermost layer (surface layer) and the B layer is the intermediate layer. Co-extruded so that the thickness composition ratio is A / B / A = 5/115/5 with 3 types and 3 layers (A / B / C), and a mirror cooling drum with a surface temperature of 45 ° C. using the electrostatic adhesion method. An unstretched polyethylene terephthalate film was prepared by cooling and solidifying the film while keeping it in close contact with the film. While passing this film through a group of heated rolls at 85 ° C., the film was stretched 3.1 times in the vertical direction by utilizing the difference in peripheral speed of the rolls, and then the aqueous coating liquid shown in Table 1 below was applied to both sides of the vertically stretched film. 6 is applied, guided to a tenter stretching machine, stretched 4.3 times in the lateral direction at 100 ° C., further heat-treated at 230 ° C., and then subjected to a relaxation treatment of 8% in the lateral direction to obtain a film thickness of the coating layer. A biaxially oriented polyethylene terephthalate film having a coating layer (after drying) of 0.04 μm and a film thickness of 125 μm was obtained.

The film haze increase value (ΔH) due to the heat treatment of the obtained polyester film was small, the amount of precipitation of the ester cyclic trimer was small and good, and the adhesion was also good. In addition, the water droplet contact angle was high, and the water repellency was appropriate, which was good. Further, no gauge band was generated on the release film roll, and the appearance of the adhesive layer was also good. The characteristics of this film are shown in Table 3 below.

Example 9:
In Example 6, a polyester film was obtained in the same manner as in Example 6 except that a polyester (B) and (E) blended at a weight ratio of 80/20 was used as a raw material for the C layer.
The characteristics of the obtained polyester film are shown in Table 3.

Example 10:
In Example 6, a polyester film was obtained in the same manner as in Example 6 except that a polyester (B) and (E) blended at a weight ratio of 30/70 was used as a raw material for the C layer.
The characteristics of the obtained polyester film are shown in Table 3.

Example 11:
A blend of polyester (B) and (E) at a weight ratio of 80/20 is used as a raw material for the surface layer, and a material containing only polyester (A) is used as a raw material for the intermediate layer. After heating and melting, the A layer is the outermost layer (surface layer), the B layer is the intermediate layer, and the thickness composition ratio is A / B / A = 7.5 / 110/7 with 2 types and 3 layers (A / B / A). An unstretched polyethylene terephthalate film was prepared by co-extruding so as to be .5 and cooling and solidifying the film by using an electrostatic contact method while keeping the film in close contact with a mirror cooling drum having a surface temperature of 45 ° C. While passing this film through a group of heated rolls at 85 ° C., the film was stretched 3.1 times in the vertical direction by utilizing the difference in peripheral speed of the rolls, and then the aqueous coating liquid shown in Table 1 below was applied to both sides of the vertically stretched film. 1 is applied, guided to a tenter stretching machine, stretched 4.3 times in the lateral direction at 100 ° C., further heat-treated at 230 ° C., and then subjected to a relaxation treatment of 8% in the lateral direction to obtain a film thickness of the coating layer. A biaxially oriented polyethylene terephthalate film having a coating layer (after drying) of 0.04 μm and a film thickness of 125 μm was obtained.
The characteristics of the obtained polyester film are shown in Table 3.

Comparative Example 1:
In Example 11, a polyester film was obtained in the same manner as in Example 10 except that a polyester (B) and (E) blended at a weight ratio of 93/7 was used as a raw material for the A layer. When the finished laminated polyester film was evaluated, as shown in Table 3, a gauge band was generated on the release film roll, and the appearance of the adhesive layer was also poor.

Comparative Example 2:
In Example 6, a polyester film was obtained in the same manner as in Example 6 except that a polyester (E) blended at a weight ratio of 100 was used as a raw material for the C layer. When the finished laminated polyester film was evaluated, as shown in Table 3, the appearance of the adhesive layer was poor due to the influence of the high surface roughness.

Comparative Examples 3 to 6:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coating agent composition was changed to the coating agent composition shown in Table 1. When the finished laminated polyester film was evaluated, as shown in Table 3, in Comparative Examples 3, 5 and 6, the film haze due to the heat treatment was greatly increased, the ester cyclic trimer was often precipitated, and the adhesion was poor. It was. Comparative Example 4 had a low water droplet contact angle and did not show appropriate water repellency. None of them could achieve both performance.

Comparative Example 7:
In Example 1, a polyester film was obtained by producing in the same manner as in Example 1 except that the coating layer was not provided. When the finished laminated polyester film was evaluated, the film haze due to heat treatment increased significantly and the ester cyclic trimer was often precipitated, and there was concern about contamination of the process and deterioration of visibility due to whitening after heating. It was a thing. In addition, the adhesion was also poor.

Since the film of the present invention has an appropriate surface roughness, for example, a gauge band is not generated on the release film roll after the release coating, so that the appearance of the adhesive layer is impaired when the film is bonded to the adhesive layer. Even after undergoing a harsh heat treatment process in which the film is exposed to a high temperature atmosphere for a long period of time, there is little precipitation of the ester cyclic trimer, and the film has appropriate water repellency and various topcoat agents. It can be suitably used as a laminated polyester film having excellent adhesion, for example, as a base material of a transparent conductive laminated body.

Claims (9)

The surface roughness (Ra) of at least one side of the polyester film is 35 to 80 nm.
At least one side of the polyester film contains 0.5 to 15% by weight of a release agent, 80 to 99.5% by weight of a cross-linking agent, and a polymer other than the cross-linking agent and the release agent as a non-volatile component ratio of 10. containing less than wt%, have a coating layer formed from a coating solution containing no ammonium group-containing compound,
The cross-linking agent is a combination of two or more kinds containing an oxazoline compound and a melamine compound.
A laminated polyester film characterized in that the oxazoline compound is 5 to 80% by weight and the melamine compound is 10 to 90% by weight as a ratio to the total non-volatile components in the coating liquid. The laminated polyester film according to claim 1, wherein the water-picking contact angle is 55 degrees or more. The laminated polyester film according to claim 1 or 2, wherein the release agent is a polymer compound having a long-chain alkyl group in a side chain. The laminated polyester film according to any one of claims 1 to 3, wherein the cross-linking agent is a combination of three or more kinds. The laminated polyester film according to claim 4 , wherein the cross-linking agent is a combination of three or more kinds containing an oxazoline compound, an epoxy compound and a melamine compound, or an oxazoline compound , an isocyanate compound and a melamine compound. The laminated polyester film according to any one of claims 1 to 5 , wherein the polyester film contains 0.7% by weight or less of an ester cyclic trimer. The laminated polyester film according to claim 6 , wherein the polyester film has a structure of three or more layers. The aspect according to any one of claims 1 to 7 , wherein the surface roughness (Ra) of one side of the polyester film is 25 nm to 100 nm, and the surface roughness (Ra) of the opposite side is 8 to 25 nm. Laminated polyester film. A release film obtained by subjecting the surface of the laminated polyester film according to any one of claims 1 to 8 to a release coating.