JP7563025B2 - Laminated Polyester Film - Google Patents

Description

The present invention relates to a laminated polyester film.

Polyester film has excellent properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, and optical properties, and is cost-effective, so it is used for a variety of purposes.

One application for polyester film is as a process protection film that protects other components during the processing of displays and touch panels. However, problems that arise when using polyester film as the base material for a process protection film include the precipitation of oligomers such as ester cyclic trimers from within the film, and the generation of static electricity.

For example, polyester film may be treated at 150°C for 1 hour to reduce thermal shrinkage (Patent Document 1), or heat treated at 150°C to crystallize ITO (Patent Document 2). When such high-temperature treatment is performed for a long period of time, oligomers contained in the polyester film precipitate and crystallize on the film surface. This can cause problems such as reduced visibility due to whitening of the film's exterior, defects during post-processing, and contamination of processes and materials.

In addition, polyester film has a common problem with plastic films in that it easily generates static electricity and becomes charged up, which can cause problems at processing sites due to foreign matter sticking to or getting caught in the film.

For this reason, various antistatic measures have been taken. A common method is to provide a functional layer with antistatic properties on the surface. The main antistatic agents used to coat polyester films are cationic compounds containing cationic groups such as quaternary ammonium groups, and anionic compounds containing anionic groups such as sulfonate and phosphonate groups. However, these are ionically conductive and their antistatic properties are easily affected by ambient humidity and moisture, and they have the disadvantage that their conductivity decreases, especially in low humidity conditions, making it impossible to achieve the desired antistatic properties. This tendency is often more pronounced with anionic antistatic agents.

In recent years, there has been a growing interest in environmental issues and concerns about the impact on other components that are incorporated into the film, leading to a growing demand for the non-use of halogens in polyester films. However, in the case of cationic antistatic agents, compounds in which the counter anion of the quaternary ammonium group is a chloride ion are common. There are also antistatic agents in which the counter anion is a monoalkyl sulfate ion, an alkyl sulfonate ion, etc., but the mobility of the ions is low, resulting in inferior antistatic performance.

Compared with the ionic conductive compounds, electronically conductive compounds can exhibit better antistatic properties and are less susceptible to the effects of humidity. As electronically conductive compounds, various conductive organic polymer compounds have been proposed, including conductive polymer compounds such as polyacetylene, polyphenylene, polyaniline, polypyrrole, polyisothianaphthene, and polythiophene. Polythiophene compounds have excellent conductivity and can exhibit high antistatic properties and transparency when applied to a film (Patent Documents 3 and 4). However, the structure of the antistatic agent of electronically conductive compounds changes when exposed to air, so that the antistatic properties may decrease depending on the usage environment compared to immediately after production (Patent Document 5).

As a method for reducing oligomer precipitation and imparting antistatic properties as described above, a method has been proposed in which an undercoat layer that suppresses oligomer precipitation and an undercoat layer that has antistatic properties are laminated in sequence (Patent Document 6). This method can also impart both properties, but the processing costs are an issue because two layers must be processed.

JP 2007-42473 A JP 2007-200823 A JP 2003-154594 A Japanese Patent Application Publication No. 9-131843 JP 2020-29485 A JP 2016-187866 A

The present invention has been made in consideration of the above-mentioned circumstances, and the problem to be solved is to provide a laminated polyester film that reduces the precipitation of oligomers from the polyester film when treated at high temperatures, thereby preventing problems such as reduced visibility due to whitening of the film's appearance, defects in post-processing, and contamination of the process and parts, and that has good antistatic properties to suppress problems due to adhesion or entrapment of foreign matter, etc.

In view of the above-mentioned circumstances, the inventors conducted extensive research and discovered that the above-mentioned problems could be easily solved by using a laminated polyester film having a specific composition, and thus completed the present invention. That is, the present invention provides the following [1] to [8].

[1] A laminated polyester film having, on at least one surface of a polyester film, a cured resin layer made of a resin composition containing the following compounds (A), (B) and (C):
(A) one or more selected from (a1) a polymer obtained by doping a compound consisting of thiophene or a thiophene derivative with another anionic compound, and (a2) a self-doped polymer having an anionic group in a compound consisting of thiophene or a thiophene derivative; (B) a (meth)acrylic polymer having a styrene structure; (C) one or more compounds or derivatives thereof selected from (c1) polyglycerin and (c2) an alkylene oxide adduct of polyglycerin; [2] The laminated polyester film according to the above item [1], wherein the acrylic structure of the (meth)acrylic polymer is a (meth)acrylic acid structure.
[3] The laminated polyester film according to the above [1] or [2], which has a film haze change (ΔH) of 1.0% or less after heat treatment at 150° C. for 90 minutes.
[4] The laminated polyester film according to any one of the above [1] to [3], wherein the cured resin layer has a surface resistivity of 1×10 ⁸ (Ω/□) or less.
[5] The laminated polyester film according to any one of the above [1] to [4], wherein the resin composition contains at least one crosslinking agent selected from the group consisting of a melamine compound, an epoxy compound, an isocyanate compound, and a carbodiimide compound.
[6] The laminated polyester film according to any one of the above [1] to [5], which is a process protection film.
[7] A film laminate comprising the laminated polyester film according to any one of [1] to [5] above attached to a surface of a metal layer via an adhesive layer.
[8] The film laminate according to the above [7], wherein the metal layer is a patterned metal layer.

According to the present invention, it is possible to provide a laminated polyester film in which the precipitation of oligomers from the polyester film is suppressed even when the film is treated at high temperatures, and in which defects caused by adhesion or entrapment of foreign matter due to static electricity are also suppressed, making the film highly valuable in industrial applications.

An example of an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the embodiment described below, and can be modified as desired without departing from the gist of the present invention.
The laminated polyester film of the present invention has, on at least one surface of the polyester film, a cured resin layer made of a resin composition containing the following compounds (A), (B) and (C).
(A) one or more selected from (a1) a polymer in which a compound consisting of thiophene or a thiophene derivative is doped with another anionic compound, and (a2) a self-doped polymer having an anionic group in a compound consisting of thiophene or a thiophene derivative; (B) a (meth)acrylic polymer having a styrene structure; (C) one or more compounds selected from (c1) polyglycerin, and (c2) an alkylene oxide adduct to polyglycerin, or derivatives thereof.

<Polyester film>
The polyester film (substrate) constituting the laminated polyester film may have a single layer structure or a multi-layer structure. In the case of a multi-layer structure, it may have a two-layer structure, a three-layer structure, or a four-layer structure or more, as long as it does not deviate from the gist of the present invention, and the number of layers is not particularly limited. In addition, as the polyester film, a biaxially oriented polyester film is preferable from the viewpoints of thinning and dimensional stability.

The polyester used may be either a homopolyester or a copolymer polyester. In the case of a homopolyester, it is preferable to use one obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. A representative example of the polyester is polyethylene terephthalate.
On the other hand, examples of the dicarboxylic acid component of the copolymer polyester include one or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid, and examples of the glycol component include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol, and neopentyl glycol.

There are no particular limitations on the polyester polymerization catalyst, and any conventionally known compound can be used, such as titanium compounds, germanium compounds, antimony compounds, manganese compounds, aluminum compounds, magnesium compounds, and calcium compounds.

In order to suppress the amount of oligomer component precipitation, the film may be produced using a polyester with a low content of oligomer components as the raw material. Various known methods can be used to produce polyester with a low content of oligomer components, such as a method of solid-phase polymerization after polyester production. The amount of oligomer component precipitation may also be suppressed by forming a polyester film with a three or more layer structure and using a polyester raw material with a low content of oligomer components as the outermost layer of the polyester film. The polyester may also be obtained by melt polycondensation under reduced pressure at a higher reaction temperature after esterification or ester exchange reaction.

It is possible to incorporate an ultraviolet absorbing agent into the polyester film in order to improve the weather resistance of the film and prevent deterioration of the adherend (e.g. liquid crystal). There are no particular limitations on the ultraviolet absorbing agent, so long as it is a compound that absorbs ultraviolet light and can withstand the heat applied during the polyester film manufacturing process.

There are organic and inorganic ultraviolet absorbers as ultraviolet absorbents, with organic ultraviolet absorbers being preferred from the viewpoint of transparency. There are no particular limitations on organic ultraviolet absorbers, and examples include cyclic imino esters, benzotriazoles, and benzophenones. From the viewpoint of durability, cyclic imino esters and benzotriazoles are more preferred. It is also possible to use two or more types of ultraviolet absorbers in combination.

Particles can be added to the polyester film for the main purpose of imparting slipperiness and preventing scratches during each process. There are no particular limitations on the type of particles added, so long as they are capable of imparting slipperiness. Specific examples include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenolic resin, epoxy resin, and benzoguanamine resin. In addition, precipitated particles formed by precipitating and finely dispersing a portion of a metal compound such as a catalyst during the polyester manufacturing process can also be used.

There is no particular limitation on the shape of the particles used, and any of spherical, blocky, rod-like, flat, etc. may be used. There are also no particular limitations on the hardness, specific gravity, color, etc. of the particles. Two or more types of these particles may be used in combination as necessary.

The average particle size of the particles used is usually 5 μm or less, and preferably in the range of 0.01 to 3 μm. If it is 5 μm or less, the surface roughness of the film will not be too rough, which is preferable since it will not cause problems when forming various surface functional layers in later processes.

Furthermore, the particle content in the polyester film is usually less than 5% by mass, preferably in the range of 0.0003 to 3% by mass. When there are no particles or when there are only a few particles, the transparency of the film is high and a good film is obtained, but the slipperiness may be insufficient, so that it may be necessary to improve the slipperiness by adding particles to the coating layer. Furthermore, when the particle content is less than 5% by mass, the transparency of the film can be sufficiently guaranteed.
When particles are contained, for example, it is preferable to provide a surface layer and an intermediate layer and to contain particles in the surface layer. In this case, it is more preferable to form a multilayer structure having a surface layer containing particles, an intermediate layer, and a surface layer containing particles in this order.

The method of adding particles to a polyester film is not particularly limited, and any conventionally known method can be used. For example, in the case of a multi-layer polyester film, the particles can be added at any stage in the production of the polyester that constitutes each layer, but it is preferable to add the particles after the completion of the esterification or transesterification reaction.

In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, etc. can be added to the polyester film as necessary.

The thickness of the polyester film is not particularly limited as long as it can be formed into a film, but is usually in the range of 10 to 350 μm, preferably 25 to 250 μm, and more preferably 38 to 125 μm.

Next, a specific example of the production of a polyester film will be described, but the production is not limited to the following production example. For example, when producing a biaxially stretched polyester film, a method is preferred in which the dried pellets of the polyester raw material described above are extruded as a molten sheet from a die using an extruder, and then cooled and solidified with a cooling roll to obtain an unstretched sheet. In this case, it is preferred to increase the adhesion between the sheet and the rotating cooling drum in order to improve the flatness of the sheet, and an electrostatic application adhesion method and/or a liquid application adhesion method are preferably used.
Next, the unstretched sheet obtained is stretched in biaxial directions. In this case, the unstretched sheet is first stretched in one direction by a roll or tenter type stretching machine. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the sheet is stretched in a direction perpendicular to the first-stage stretching direction, in which the stretching temperature is usually 70 to 170°C, and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times.
The film is then heat-treated at a temperature of 180 to 270° C. under tension or relaxation of 30% or less to obtain a biaxially oriented film. In the above stretching, a method of stretching in one direction in two or more stages can also be adopted. In that case, it is preferable to perform the stretching so that the final stretch ratios in both directions are each within the above range.

A simultaneous biaxial stretching method can also be used to produce a polyester film. In the simultaneous biaxial stretching method, the unstretched sheet is simultaneously stretched and oriented in the machine direction and the width direction under a temperature controlled condition usually at 70 to 120° C., preferably 80 to 110° C., and the stretching ratio is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area ratio.
The film is then subsequently heat-treated under tension or relaxation of 30% or less at a temperature of 170 to 250° C. to obtain a stretched and oriented film. Regarding the simultaneous biaxial stretching device employing the above-mentioned stretching method, any conventionally known stretching method such as a screw method, a pantograph method, or a linear drive method can be employed.

<Resin Composition>
The laminated polyester film of the present invention has an essential requirement that it has a cured resin layer on the surface of a polyester film, and that the cured resin layer is formed from a resin composition containing the following compounds (A), (B), and (C).
(A) one or more selected from (a1) a polymer in which a compound consisting of thiophene or a thiophene derivative is doped with another anionic compound, and (a2) a self-doped polymer having an anionic group in a compound consisting of thiophene or a thiophene derivative; (B) a (meth)acrylic polymer having a styrene structure; (C) one or more compounds selected from (c1) polyglycerin, and (c2) an alkylene oxide adduct of polyglycerin, or a derivative thereof.

(Compound (A))
Compound (A) is (a) a polymer obtained by doping a compound made of thiophene or a thiophene derivative with another anionic compound, or (b) a self-doped polymer having an anionic group in a compound made of thiophene or a thiophene derivative. These substances are preferable because they show excellent electrical conductivity. Compound (A) is, for example, a compound obtained by polymerizing a compound of the following formula (1) or (2) in the presence of a polyanion. Polymer (a) and polymer (b) may be used in combination.

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

In the above formula (2), n represents an integer from 1 to 4.

Examples of polyanions used during polymerization include poly(meth)acrylic acid, polymaleic acid, polystyrene sulfonic acid, and polyvinyl sulfonic acid. Methods for producing such polymers include the method described in JP-A-7-90060.

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

When these polyanions are acidic, they may be partially or completely neutralized. The base used for neutralization is preferably ammonia, organic amines, or alkali metal hydroxides.

(Compound (B))
The compound (B) is a (meth)acrylic polymer having a styrene structure.

The styrene structure refers to styrene and styrene derivatives, and for example, alkyl groups such as methyl and ethyl groups, or phenyl groups may be introduced as substituents into styrene. From the viewpoint of the effect of preventing oligomer precipitation due to heat treatment, styrene substituted with an alkyl group having 4 or less carbon atoms or styrene without any substituents is preferred, and styrene is more preferred.

The (meth)acrylic polymer is a polymer having (meth)acrylic acid or an alkyl (meth)acrylate ester as a constituent unit, and the compound (B) is a copolymer of styrene or a styrene derivative and (meth)acrylic acid or an alkyl (meth)acrylate ester.
In the present invention, the term "(meth)acrylic acid" means either or both of "acrylic acid" and "methacrylic acid". Similarly, "(meth)acrylate" means either or both of "acrylate" and "methacrylate", and "(meth)acryloyl" means either or both of "acryloyl" and "methacryloyl".

Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, etc. Also usable are (meth)acrylic acid alkyl esters containing a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.
These may be used alone or in combination of two or more. Among these, from the viewpoint of the effect of preventing oligomer precipitation by heat treatment, (meth)acrylic acid is preferable, and acrylic acid is more preferable. That is, the acrylic structure of the (meth)acrylic polymer is preferably a (meth)acrylic acid structure.
The (meth)acrylic polymer may have a radically polymerizable double bond.

In addition, (meth)acrylic polymers having a styrene structure can be combined with other polymerizable monomers that are copolymerizable therewith. Examples of copolymerizable monomers include hydroxyl group-containing dibasic acid ester compounds such as monobutyl hydroxy fumarate and monobutyl hydroxy itaconate, various nitrogen-containing compounds such as (meth)acrylamide, diacetone acrylamide, N-methylol acrylamide, and (meth)acrylonitrile, various vinyl esters such as vinyl propionate and vinyl acetate, various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane, phosphorus-containing vinyl monomers, various vinyl halides such as vinyl chloride and vinylidene chloride, and various conjugated dienes such as butadiene.

The proportion of (meth)acrylic acid or (meth)acrylic acid alkyl ester in the (meth)acrylic polymer having a styrene structure is, for example, 3 mol% or more, preferably 5 to 40 mol%, more preferably 10 to 30 mol%, and even more preferably 15 to 25 mol%, based on the total amount of monomers constituting the (meth)acrylic polymer having a styrene structure. When the proportion of (meth)acrylic acid or (meth)acrylic acid alkyl ester is 3 mol% or more, the effect of preventing oligomer precipitation due to heat treatment is exerted. Also, when it is below the upper limit, the proportion of the styrene structure increases, and the durability of the antistatic performance can be ensured.

The ratio of styrene and styrene derivatives in the (meth)acrylic polymer having a styrene structure is, for example, 50 to 97 mol%, preferably 60 to 95 mol%, more preferably 70 to 90 mol%, and even more preferably 75 to 85 mol%, based on the total amount of monomers constituting the (meth)acrylic polymer having a styrene structure. When the ratio of styrene and styrene derivatives is equal to or greater than the lower limit, the durability of antistatic performance is ensured, and when it is equal to or less than the upper limit, the oligomer precipitation effect by heat treatment is ensured.

(Compound (C))
(Compound (C)) is one or more compounds selected from polyglycerin, or alkylene oxide adducts of polyglycerin, or derivatives thereof. Polyglycerin is a compound represented by the following general formula (3).

In the above formula, n is 2 or more, and in the present invention, n in the formula is usually in the range of 2 to 20, preferably 3 to 15, and more preferably 3 to 12.

An alkylene oxide adduct of polyglycerin has a structure in which an alkylene oxide is added and polymerized to the hydroxyl group of polyglycerin represented by the general formula (3).

Here, the structure of the alkylene oxide added to each hydroxyl group of the polyglycerin skeleton may be different. Also, it is sufficient that the alkylene oxide or its derivative is added to at least one hydroxyl group in the molecule, and it is not necessary that the alkylene oxide or its derivative is added to all hydroxyl groups.

The alkylene oxide added to polyglycerin is preferably ethylene oxide or propylene oxide. If the alkylene chain of the alkylene oxide is too long, the hydrophobicity becomes strong, the dispersibility in the coating liquid deteriorates, and the antistatic property and transparency of the cured resin layer tend to deteriorate. Ethylene oxide is particularly preferable.
The number of additions is preferably in the range of 200 to 2,000, more preferably 300 to 1,000, and even more preferably 400 to 900, in terms of the number average molecular weight of the final compound.

The above polyglycerols or alkylene oxide adducts of polyglycerols may be used alone or in combination of two or more.

(Crosslinking Agent)
The resin composition according to the present invention may contain a crosslinking agent for the purpose of improving the durability of the cured resin layer, particularly the durability of the antistatic performance.
As the crosslinking agent, various known crosslinking agents can be used, for example, melamine compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, oxazoline compounds, silane coupling compounds, etc. Among these, melamine compounds, epoxy compounds, isocyanate compounds, and carbodiimide compounds are preferred from the viewpoint of suppressing the decrease in antistatic properties after exposure to air, and melamine compounds and carbodiimide compounds are more preferred from the viewpoint of more effectively suppressing oligomer precipitation.

(Melamine compounds)
The melamine compound is a compound having a melamine skeleton in the compound, and for example, an alkylolated melamine derivative, a compound obtained by reacting an alkylolated melamine derivative with an alcohol to partially or completely etherify it, and a mixture thereof can be used. As the alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol, etc. are preferably used. In addition, the melamine compound may be either a monomer or a dimer or higher polymer, or a mixture thereof may be used. Furthermore, a compound obtained by co-condensing a part of melamine with urea or the like can also be used, and a catalyst can also be used to increase the reactivity of the melamine compound.

(Epoxy Compound)
The epoxy compound is a compound having an epoxy group in the molecule, and examples thereof include condensations of epichlorohydrin, ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A, etc. with a hydroxyl group or an amino group, polyepoxy compounds, diepoxy compounds, monoepoxy compounds, and glycidylamine compounds.
Examples of polyepoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris(2-hydroxyethyl)isocyanate, glycerol polyglycidyl ether, and trimethylolpropane polyglycidyl ether. Examples of diepoxy compounds include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, ethylene glycol Examples of the monoepoxy compound include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether. Examples of the glycidylamine compound include N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylamino)cyclohexane. From the viewpoint of improving adhesion, polyether-based epoxy compounds are preferred. In addition, in terms of the amount of epoxy groups, polyepoxy compounds having three or more functionalities are preferred over bifunctional ones.

(Isocyanate Compounds)
The isocyanate compound is a compound having an isocyanate or an isocyanate derivative structure, such as a blocked isocyanate. Examples of the isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate, aliphatic isocyanates having an aromatic ring such as α,α,α',α'-tetramethyl xylylene diisocyanate, aliphatic isocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate, and alicyclic isocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylene bis(4-cyclohexyl isocyanate), and isopropylidenedicyclohexyl diisocyanate. In addition, polymers and derivatives such as biuretized products, isocyanurate products, uretdione products, 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 prevent yellowing due to ultraviolet rays.

When used in the form of a blocked isocyanate, examples of the blocking agent include bisulfites, phenolic compounds such as phenol, cresol, and ethylphenol, alcoholic compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol, active methylene compounds such as isobutanoylmethyl acetate, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, lactam compounds such as ε-caprolactam and δ-valerolactam, amine compounds such as diphenylaniline, aniline, and ethyleneimine, acetanilide, acid amide compounds of acetic acid amide, and oxime compounds such as formaldehyde, acetaldoxime, acetoneoxime, methyl ethyl ketoneoxime, and cyclohexanoneoxime, which may be used alone or in combination of two or more.

The isocyanate compound may be used alone or as a mixture or combination with various polymers. In order to improve the dispersibility and crosslinking properties of the isocyanate compound, it is preferable to use a mixture or combination with a polyester resin or a urethane resin.

(Carbodiimide Compound)
A carbodiimide compound is a compound having a carbodiimide structure, and is a compound having one or more carbodiimide structures in the molecule. For better adhesion and the like, a polycarbodiimide-based compound having two or more carbodiimide structures in the molecule is more preferred.

Carbodiimide compounds can be synthesized by conventional techniques, and generally, a condensation reaction of a diisocyanate compound is used. There are no particular limitations on the diisocyanate compound, and either aromatic or aliphatic compounds can be used. Specific examples include tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate.

The content of carbodiimide groups contained in the carbodiimide compound is, in terms of carbodiimide equivalent (weight [g] of the carbodiimide compound required to give 1 mol of carbodiimide groups), usually in the range of 100 to 1000, preferably 250 to 800, and more preferably 300 to 700. Use within the above range improves the durability of the coating film.

Furthermore, within the scope of the present invention, in order to improve the water solubility or water dispersibility of the polycarbodiimide compound, a surfactant may be added, or a hydrophilic monomer such as a polyalkylene oxide, a quaternary ammonium salt of a dialkylamino alcohol, or a hydroxyalkylsulfonate may be added.

(Oxazoline Compounds)
The oxazoline compound is a compound having an oxazoline group in the molecule, and in particular a polymer containing an oxazoline group is preferred. The oxazoline compound can be prepared by polymerization of an addition-polymerizable oxazoline group-containing monomer alone or with other monomers. Examples of the addition-polymerizable oxazoline group-containing monomer 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, and 2-isopropenyl-5-ethyl-2-oxazoline, and one or a mixture of two or more of these 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 the addition-polymerizable oxazoline group-containing monomer, and examples thereof include (meth)acrylic acid esters such as alkyl(meth)acrylates (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl groups); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid, and salts thereof (sodium salts, potassium salts, ammonium salts, tertiary amine salts, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)acrylamide, N-alkyl(meth)acrylates, etc. Examples of the monomer include unsaturated amides such as N,N-dialkyl(meth)acrylamide and N,N-dialkyl(meth)acrylamide (the alkyl group may be, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, or a cyclohexyl group); 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; halogen-containing α,β-unsaturated monomers such as vinyl chloride and vinylidene chloride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene. One or more of these monomers may be used. From the viewpoint of improving adhesion, the amount of oxazoline groups in the oxazoline compound is preferably in the range of 0.5 to 10 mmol/g, more preferably 1 to 9 mmol/g, even more preferably 3 to 8 mmol/g, and particularly preferably 4 to 6 mmol/g.

(Silane coupling compound)
A silane coupling compound is an organosilicon compound having an organic functional group and a hydrolyzable group such as an alkoxy group in one molecule. For example, epoxy group-containing compounds such as 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; vinyl group-containing compounds such as vinyltrimethoxysilane and vinyltriethoxysilane; styryl group-containing compounds such as p-styryltrimethoxysilane and p-styryltriethoxysilane; (meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; (meth)acryl group-containing compounds such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)- Amino group-containing compounds such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltriethoxysilane; isocyanurate group-containing compounds such as tris(trimethoxysilylpropyl)isocyanurate and tris(triethoxysilylpropyl)isocyanurate; mercapto group-containing compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane.

(Other ingredients)
In forming the cured resin layer, various conventionally known polymers such as polyester resins, acrylic resins, urethane resins, etc. may be used in combination as a binder in order to improve the coating appearance and transparency, etc. Furthermore, particles may be used in combination for the purpose of improving blocking properties and slip properties, etc., within the scope of the present invention.

The proportion of compound (A) in the total non-volatile components in the resin composition is usually 2 to 30 mass%, more preferably 3 to 15 mass%, and even more preferably 5 to 12 mass%. When the proportion of compound (A) is equal to or less than the upper limit, the strength and transparency of the cured resin layer are good.
On the other hand, when the ratio of the compound (A) is equal to or more than the lower limit, sufficient antistatic performance is obtained, and the antistatic property is not decreased after exposure to air.

The proportion of compound (B) in the total non-volatile components in the resin composition is usually in the range of 5 to 80 mass%, preferably 10 to 50 mass%, and more preferably 15 to 40 mass%. If the proportion of compound (B) is below the upper limit, the proportions of other components are high, so that sufficient antistatic properties are obtained and the coating appearance is not insufficient. On the other hand, if the proportion of compound (B) is above the lower limit, precipitation of oligomers can be sufficiently suppressed, sufficient film-forming properties can be ensured, and a uniform coating film can be obtained.

The proportion of compound (C) in the total non-volatile components in the resin composition is usually in the range of 10 to 85 mass%, preferably 40 to 70 mass%, and more preferably 45 to 65 mass%. If the proportion of compound (C) is below the upper limit, the proportions of other components are high, resulting in sufficient antistatic properties and film-forming properties. On the other hand, if the proportion of compound (C) is above the lower limit, the transparency of the cured resin layer is good.

When a crosslinking agent is used in combination, its proportion of the total non-volatile components in the resin composition is usually 30% by mass or less, preferably 1 to 25% by mass, and more preferably 3 to 20% by mass. By using a crosslinking agent in this range, sufficient antistatic performance is obtained, deterioration of antistatic properties after exposure to air can be suppressed, and the strength of the cured resin layer is improved.

<Cured Resin Layer>
The cured resin layer according to the present invention is formed from the above-mentioned resin composition.
The thickness of the cured resin layer is preferably 0.002 μm to 1.0 μm, more preferably 0.005 μm to 0.25 μm, and even more preferably 0.02 μm to 0.10 μm. If the thickness of the cured resin layer is within the above range, precipitation of oligomer components can be suppressed and good antistatic properties can be imparted.
It can be assumed that the cured resin layer contains unreacted compounds of the various compounds in the resin composition, reacted compounds, or a mixture thereof.

<Method of forming cured resin layer>
Next, a method for forming the cured resin layer constituting the laminated polyester film will be described.
The method for forming the cured resin layer is not particularly limited, and any conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, etc. can be used.
The cured resin layer can be formed by in-line coating or off-line coating. The drying and curing conditions are not particularly limited, and when the cured resin layer is formed by off-line coating, the heat treatment is usually performed at 80 to 200°C for 3 to 40 seconds, preferably at 100 to 180°C for 3 to 40 seconds.
On the other hand, when the cured resin layer is provided by in-line coating, it is usually preferable to carry out heat treatment at 70 to 280° C. for 3 to 200 seconds.

In the present invention, it is preferable to form the protective layer by in-line coating, which is a method of treating the surface of a polyester film during the film-forming process.
In-line coating is a method of coating within the polyester film production process, specifically, a method of coating at any stage from melt extrusion of polyester to stretching, heat setting and winding up. Usually, coating is performed on any of the following: an unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat setting, and a film after heat setting and before winding up. 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 transverse direction is particularly excellent. According to this method, film formation and cured resin layer formation can be performed simultaneously, which is advantageous in terms of production costs, and also. Since stretching is performed after coating, the thickness of the cured resin layer can be changed by the stretching ratio, and thin film coating can be performed more easily than with offline coating films. In addition, by providing a cured resin layer on the film before stretching, the cured resin layer can be stretched together with the polyester film, and the cured resin layer can be firmly attached to the polyester film. Furthermore, in the production of a biaxially stretched polyester film, by stretching the film while holding the ends with clips or the like, the film can be restrained in the longitudinal and lateral directions, and in the heat setting step, a high temperature can be applied while maintaining flatness and without wrinkles, etc. 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 properties of the cured resin layer are improved, the cured resin layer and the polyester film can be more firmly adhered to each other, and further, a strong cured resin layer can be formed, and performance such as adhesion to various functional layers that can be formed on the cured resin layer and resistance to moisture and heat can be improved.

When forming a cured resin layer by in-line coating, it is preferable to manufacture a laminated polyester film by coating a polyester film with a cured resin layer composition prepared by preparing an aqueous solution or aqueous dispersion of the above-mentioned series of compounds so that the solids concentration (total non-volatile components) is adjusted to approximately 0.1 to 50% by mass.

Regardless of whether off-line coating or in-line coating is used, heat treatment and irradiation with active energy rays such as ultraviolet light may be used in combination as necessary. The polyester film constituting the laminated polyester film of the present invention may be previously subjected to a surface treatment such as a corona treatment or a plasma treatment.

<Physical properties of laminated polyester film>
The laminated polyester film of the present invention preferably has a film haze change (ΔH) of 1.0% or less, more preferably 0.5% or less, before and after heat treatment (150° C., 90 minutes). It is known that the film haze of a polyester film increases due to the precipitation of oligomer components on the film surface by heat treatment, and ΔH is an index showing the precipitation of oligomer components on the film surface before and after heat treatment.
When the film haze change (ΔH) is 1.0% or less, it can be said that contamination due to precipitation of oligomer components is suppressed.

The antistatic property of the laminated polyester film of the present invention can be evaluated by the surface resistivity measured on the surface of the cured resin layer. The lower the surface resistivity of the cured resin layer, the better the antistatic property. If the surface resistivity is 1×10 ¹² Ω/□ or less, it can be said to have antistatic properties, if it is 1×10 ⁸ Ω/□ or less, it can be said to have good antistatic properties, and if it is 1×10 ⁶ Ω/□ or less, it can be said to have very good antistatic performance, which is preferable. There is no particular lower limit for the surface resistivity, but it is preferably 1×10 ⁴ Ω/□ or more in consideration of the cost of the conductive agent.

Analysis of the various components in the cured resin layer can be performed, for example, by TOF-SIMS, ESCA, X-ray fluorescence, etc.

The mechanism by which the precipitation of oligomer components contained in polyester film is suppressed is presumed to be as follows. When a polyester film is heated above its glass transition point, oligomer components precipitate on its surface. However, by forming a cured resin layer made of a resin composition using a (meth)acrylic polymer with a styrene structure on the polyester film, the aromatic rings contained in the styrene are stacked in parallel with the film, forming a structure that prevents the precipitation of oligomer components.

The mechanism by which deterioration of antistatic properties after exposure to air is suppressed even in the case of a cured resin layer containing an antistatic agent of an electronically conductive compound is believed to be as follows: As described in Patent Document 5, it is known that the antistatic properties of a cured resin layer containing an antistatic agent of an electronically conductive compound deteriorate when exposed to air for several days after production.
The electronically conductive compound in the present invention is a polymer in which a compound made of thiophene or a thiophene derivative is doped with another anionic compound, or a self-doped polymer having an anionic group in a compound made of thiophene or a thiophene derivative, and this polythiophene is oxidized by oxygen in the air, causing deterioration of antistatic properties. Although the mechanism by which good antistatic performance is exhibited is only a matter of speculation, it is believed that the use of a (meth)acrylic polymer having a styrene structure suppresses contact between the polythiophene and oxygen in the air, thereby suppressing the deterioration of antistatic properties.

The laminated polyester film of the present invention has good antistatic properties while reducing oligomer precipitation from the polyester film when treated at high temperatures, and can be suitably used, for example, as a process protection film, which is attached to another member such as a film to protect the other member.
In particular, it is suitable for use in a film laminate structure in which the film is attached to the surface of a metal layer via an adhesive layer. Here, the metal layer may be patterned.
Specifically, in the manufacturing process in which an ITO layer is sputtered onto a base film, the laminated polyester film of the present invention is bonded via an adhesive layer, and even if the film passes through a crystallization process of ITO (e.g., exposure to a high-temperature atmosphere of 150° C. for 90 minutes or more), the transparency and antistatic properties of the film are maintained, and it is also possible to inspect the ITO layer with the film still bonded.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples within the scope of the gist of the invention. The measurement and evaluation methods used in the present invention are as follows.

(1) Intrinsic Viscosity of Polyester 1 g of polyester from which components incompatible with the polyester had been removed was precisely weighed, dissolved in 100 ml of a mixed solvent of phenol/tetrachloroethane = 50/50 (mass ratio), and measured at 30°C.

(2) Average particle size
The polyester film was observed using a TEM (Hitachi H-7650, accelerating voltage 100 V), and the average particle size of 10 particles was determined as the average particle size.

(3) Film Thickness of Cured Resin Layer The surface of the cured resin layer was stained with _RuO4 and embedded in epoxy resin. Then, a section prepared by ultrathin sectioning was stained with _RuO4 , and the cross section of the cured resin layer was measured using a transmission electron microscope (TEM) (Hitachi High-Technologies Corporation, H-7650, accelerating voltage 100 kV).

(4) Haze measurement method: Measured according to JIS K 7136 using a haze meter "HM-150" manufactured by Murakami Color Research Laboratory.

(5) Precipitation of Oligomers by Heating A mixed coating solution of 80 parts by mass of dipentaerythritol hexaacrylate, 20 parts by mass of 2-hydroxy-3-phenoxypropyl acrylate, 5 parts by mass of a photopolymerization initiator (product name: Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.), and 200 parts by mass of methyl ethyl ketone was applied to the surface of the sample film opposite to the surface on which the cured resin layer was formed, so that the dry film thickness was 3 μm, and the coating was cured by irradiation with ultraviolet light (cumulative light amount of 200 mJ/cm ² ) to form a hard coat layer. The film haze of the obtained sample film with the hard coat layer was measured by the method described in (4) above.
Next, the film sample with the hard coat layer was fixed by overlapping Kent paper with the surface of the cured resin layer exposed, and was left to stand at 150°C for 90 minutes in a nitrogen atmosphere for heat treatment, after which the film haze was measured by the method described in (4) above.
The difference between the film haze after the heat treatment and the film haze before the heat treatment was calculated and defined as the film haze change (ΔH).
A lower change in film haze indicates less precipitation of oligomer components (ester cyclic trimer components) due to heat treatment.

(6) Surface resistivity Using a low resistivity meter: Loresta GP MCP-T600 manufactured by Mitsubishi Chemical Corporation, the surface resistivity was measured after conditioning the sample for 30 minutes in a measurement atmosphere at a temperature of 23° C. and a relative humidity of 50%. If the resistance value exceeded the upper limit of the measurable range, it was deemed unmeasurable.

(7) Durability of surface resistivity A sample film was attached to the wall of a constant temperature and humidity chamber adjusted to a temperature of 23°C and a relative humidity of 50%, with the measurement surface facing away from the wall (indoor side), and treated by exposing it to indoor light for 14 consecutive days. After that, the surface resistivity was measured in the same manner as in (6) above and compared with that before the attachment. This wall was not exposed to outdoor light, but was illuminated by white fluorescent lamps at about 500 lux.
◎: The increase in surface resistivity after treatment is less than 10 times. ◯: The increase in surface resistivity after treatment is 10 times or more but less than 50 times. △: The increase in surface resistivity after treatment is 50 times or more. ×: The resistance value after treatment exceeds the upper limit of the measurable range and cannot be measured.

The polyester raw materials used in the examples and comparative examples are as follows:

<Production method of polyester (1)>
100 parts by mass of dimethyl terephthalate and 55 parts by mass of ethylene glycol were used as starting materials, and 0.04 parts by mass of magnesium acetate tetrahydrate was added to the reactor as a catalyst. The reaction was started at 150°C, and the reaction temperature was gradually increased with the distillation of methanol, and reached 230°C after 3 hours. After 4 hours, the transesterification reaction was essentially completed. 0.02 parts by mass of ethyl acid phosphate was added to the reaction mixture, and then 0.04 parts by mass of antimony trioxide was added to carry out a polycondensation reaction for 4 hours. That is, the temperature was gradually increased from 230°C to 280°C. Meanwhile, the pressure was gradually reduced from normal pressure, and finally reached 0.3 mmHg. After the start of the reaction, the reaction was stopped at a point corresponding to an intrinsic viscosity of 0.65 due to a change in the stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester (1) having an intrinsic viscosity of 0.65.

<Production method of polyester (2)>
100 parts by mass of dimethyl terephthalate and 45 parts by mass of ethylene glycol were used as starting materials, and 0.06 parts by mass of magnesium acetate tetrahydrate was added to the reactor as a catalyst. The reaction was started at 150°C, and the reaction temperature was gradually increased with the distillation of methanol, and reached 230°C after 3 hours. After 4 hours, the transesterification reaction was essentially completed. After adding 0.03 parts by mass of ethyl acid phosphate to this reaction mixture, 0.3 parts by mass of silica particles having an average particle size of 2.7 μm dispersed in ethylene glycol and 0.03 parts by mass of antimony trioxide were added, and the polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually increased from 230°C to 280°C. Meanwhile, the pressure was gradually reduced from normal pressure, and finally reached 0.3 mmHg. After the start of the reaction, the reaction was stopped at a point corresponding to an intrinsic viscosity of 0.65 due to a change in the stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester (2) having an intrinsic viscosity of 0.65.

The following resin composition was used for forming the cured resin layer.
(Compound (A))
(A1): Conductive agent consisting of polyethylenedioxythiophene and polystyrenesulfonic acid (Orgacon ICP1010 manufactured by Agfa-Gevaert) neutralized with concentrated aqueous ammonia to pH=9; non-volatile component: 1.2% by mass; solvent: water

(Compound (B))
(B1): Aqueous dispersion of acrylic resin polymerized with the following composition: Styrene/acrylic acid=85/15 (mass%), non-volatile component: 30 mass%
(B2): Water dispersion of acrylic resin polymerized with the following composition (comparative compound)
Ethyl acrylate/n-butyl acrylate/methyl methacrylate/N-methylol acrylamide/acrylic acid=65/21/10/2/2 (mass%)

(Compound (C))
(C1): Polyglycerin having an average of n=4 in the formula (3) (C2): Polyglycerin having an average of n=10 in the formula (3) (C3): A compound having an average of 4 polyethylene oxide molecules added to a polyglycerin skeleton having an average of n=4 in the formula (3)

(Crosslinking Agent)
(D1): Melamine compound Hexamethoxymethylolmelamine (D2) Epoxy compound Water-soluble polyglycerol polyglycidyl ether (D3): Carbodiimide compound Polycarbodiimide compound Carbodilite SV-02 (carbodiimide equivalent: 430) (manufactured by Nisshinbo Co., Ltd.)
(D4): Isocyanate compound Blocked polyisocyanate prepared by the following method 1000 parts by mass of hexamethylene diisocyanate was stirred at 60 ° C., and 0.1 parts by mass of tetramethylammonium caprylate was added as a catalyst. After 4 hours, 0.2 parts by mass of phosphoric acid was added to stop the reaction, and an isocyanurate-type polyisocyanate composition was obtained. 100 parts by mass of the obtained isocyanurate-type polyisocyanate composition, 42.3 parts by mass of methoxypolyethylene glycol having a number average molecular weight of 400, and 29.5 parts by mass of propylene glycol monomethyl ether acetate were charged and held at 80 ° C. for 7 hours. Thereafter, the reaction liquid temperature was held at 60 ° C., and 35.8 parts by mass of methyl isobutanoyl acetate, 32.2 parts by mass of diethyl malonate, and 0.88 parts by mass of a 28% methanol solution of sodium methoxide were added, and the mixture was held for 4 hours. 58.9 parts by mass of n-butanol was added, and the reaction liquid temperature was maintained at 80° C. for 2 hours, after which 0.86 parts by mass of 2-ethylhexyl acid phosphate was added to obtain a blocked polyisocyanate.

Example 1
A blend of polyester (1) and polyester (2) in a mass ratio of 82/18 was used as the raw material for layer A, and polyester (1) alone was used as the raw material for layer B, which were fed into an extruder, heated and melted at 285°C, and co-extruded to a thickness composition ratio of A/B/A=5/90/5 under extrusion conditions, with layer A being the outermost layer (surface layer) and layer B being the middle layer, and cooled and solidified while being in close contact with a mirror-finished cooling drum with a surface temperature of 40-50°C, to prepare an unstretched polyethylene terephthalate film. This film was stretched 3.7 times in the longitudinal direction while passing through a group of heating rolls at 85°C, to obtain a uniaxially oriented film. Resin composition 1 (coating solution 1, non-volatile component concentration: 3.0% by mass) shown in Table 1 was applied to one side of this uniaxially stretched film, and then this film was introduced into a tenter stretching machine, stretched 4.3 times in the width direction at 100°C, and further heat-treated at 230°C, followed by 2% relaxation treatment in the width direction to obtain a biaxially oriented polyester film having a thickness of 50 μm and a cured resin layer having a thickness (after drying) of 0.03 μm. The haze of the obtained laminated polyester film after heat treatment and the film haze change amount (ΔH) before heat treatment were 0.1%, the surface resistivity was 3×10 ⁴ (Ω/□), and the increase in surface resistivity after treatment with indoor light for 14 consecutive days was 10 times or more but less than 50 times. The properties of this film are shown in Table 2 below.

Examples 2 to 18
A laminated polyester film was obtained in the same manner as in Example 1, except that the cured resin layer composition was changed to the composition shown in Table 1. The results are shown in Table 2.

Comparative Examples 1 to 5
The same procedure as in Example 1 was carried out except that the cured resin layer composition was changed to the composition shown in Table 1, to obtain a laminated polyester film.

Comparative Example 6
A polyester film was obtained in the same manner as in Example 1, except that no cured resin layer was provided. The results are shown in Table 2.

As is clear from the results shown in Table 2, the laminated polyester film of the present invention has low haze and high transparency. In addition, the surface resistivity is 1 x 10 ⁸ (Ω/□) or less, indicating excellent antistatic performance. Furthermore, the change in film haze (ΔH) between the haze after heat treatment and before heat treatment is 1.0% or less, indicating that the film haze does not deteriorate even by heat treatment. It was also revealed that the durability of the surface resistivity is high.
On the other hand, in Comparative Examples 1 and 3, the surface resistivity exceeded the upper limit of the measurable range (Table 2 indicates "unmeasurable"), and in Comparative Examples 4 and 5, the change in film haze (ΔH) between before and after heat treatment exceeded 1.0%, confirming the precipitation of oligomers by heat treatment. Furthermore, in Comparative Example 2, the film-forming properties were poor and a uniform coating film could not be obtained (Table 2 indicates "coating unfeasible" in the haze column).
In addition, as shown in Table 2, the polyester film obtained in Comparative Example 6, which did not have a cured resin layer of the present invention, had a film haze increase (ΔH) due to heat treatment of 1.5%, and the surface resistance value exceeded the upper limit of the measurable range.

Claims (10)

A laminated polyester film having a cured resin layer made of a resin composition containing the following compounds (A), (B), and (C) on at least one surface of a polyester film, the resin composition containing the following compound (A) in an amount of 2 to 30 mass %, the following compound (B) in an amount of 5 to 50 mass %, and the following compound (C) in an amount of 15 to 85 mass %, based on the total non-volatile components of the resin composition.
(A) one or more selected from (a1) a polymer in which a compound consisting of thiophene or a thiophene derivative is doped with another anionic compound, and (a2) a self-doped polymer having an anionic group in a compound consisting of thiophene or a thiophene derivative; (B) a (meth)acrylic polymer having a styrene structure; (C) one or more compounds selected from (c1) polyglycerin, and (c2) an alkylene oxide adduct of polyglycerin, or a derivative thereof. The laminated polyester film according to claim 1, wherein the acrylic structure of the (meth)acrylic polymer is a (meth)acrylic acid structure. The laminated polyester film according to claim 1 or 2, in which the film haze change (ΔH) after heat treatment at 150°C for 90 minutes is 1.0% or less. 4. The laminated polyester film according to claim 1, wherein the cured resin layer has a surface resistivity of 1×10 ⁸ (Ω/□) or less. The laminated polyester film according to any one of claims 1 to 4, wherein the resin composition contains at least one crosslinking agent selected from a melamine compound, an epoxy compound, an isocyanate compound, and a carbodiimide compound. The laminated polyester film according to any one of claims 1 to 5, wherein the compound (A) accounts for 2 to 15 mass% of the total non-volatile components in the resin composition. The laminated polyester film according to any one of claims 1 to 6, wherein the compound (C) is a compound represented by the following general formula (3), and n in the following general formula (3) is 3 or more:
The laminated polyester film according to any one of claims 1 to 7 , which is a process protection film. A film laminate comprising the laminated polyester film according to any one of claims 1 to 7 attached to a surface of an ITO layer via an adhesive layer. 10. The film stack of claim 9 , wherein the ITO layer is a patterned ITO layer.