KR101944747B1 - Coating film - Google Patents

Abstract

Provided is a coating film which suppresses an ester cyclic trimer precipitated from a film when exposed to a high temperature and does not cause troubles associated with ester cyclic trimer in film storage, film use, film processing, and the like. A coating film having a coating layer containing a resin having a styrene structure and a (meth) acrylic acid structure on at least one side of a polyester film.

Description

Coating Film {COATING FILM}

The present invention relates to a coating film which is less susceptible to precipitation of oligomers (low molecular weight components of polyester, especially ester cyclic trimer) from a film even after exposure to high temperatures.

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

Particularly in recent years, use in touch panels and the like is increasing, and it is used in place of glass as a base material of a transparent conductive laminate. As such a transparent conductive laminate, an ITO (indium tin oxide) film is formed by sputtering directly on the polyester film as a base or through an anchor layer. The polyester film used in this application is generally subjected to heat processing.

As a specific example of the heat treatment, for example, there is a treatment in which heat treatment is performed at 150 캜 for crystallization of ITO (Patent Document 2) in which the film is allowed to stand at 150 캜 for one hour for low heat shrinkage (Patent Document 1).

However, as a problem peculiar to the polyester film, when the ester cyclic trimer contained in the film is exposed and crystallized on the surface of the film when exposed to such a treatment at a high temperature for a long period of time, the visibility of the appearance of the film, Defects, contamination of the inside of the process, and the like. Therefore, the characteristics of the transparent conductive laminate based on a polyester film can not be said to be sufficiently satisfactory.

It is also proposed to provide a curable resin layer composed of a cross-linked product of a silicone resin and an isocyanate-based resin on a polyester film, for example, as the ester cyclic trimer precipitation preventive measure described above (Patent Document 3). However, since the curable resin layer is formed by thermosetting, a high temperature treatment is required to dissociate the blocking agent of the isocyanate-based resin, and in a situation where curling or sagging is likely to occur during processing, care must be taken in handling Do.

Therefore, when a reduction in the amount of the ester cyclic trimer precipitated by the coating layer is taken, it is necessary that the ester cyclic trimer sealing performance of the coating layer itself is higher than that of the prior art .

Patent Document 1: Japanese Patent Application Laid-Open No. 2007-42473 Patent Document 2: Japanese Patent Application Laid-Open No. 2007-200823 Patent Document 3: Japanese Patent Application Laid-Open No. 2007-320144

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ester cyclic trimer which inhibits the ester cyclic trimer precipitated from a film when exposed to a high temperature, And it is an object of the present invention to provide a coating film which does not cause problems accompanying cyclic trimerization.

The inventors of the present invention have made intensive investigations on the above problems, and as a result, they have found that the above problems can be solved by providing a specific coated layer, and have completed the present invention.

That is, the gist of the present invention resides in a coating film characterized by having a coating layer containing a resin having a styrene structure and a (meth) acrylic acid structure on at least one side of a polyester film.

According to the coated film of the present invention, since the precipitation of the ester cyclic trimer from the surface is suppressed even when the treatment is carried out at a high temperature for a long time, a product having excellent appearance without an increase in haze or generation of foreign matter can be obtained, Industrial use value is high.

Carrying out the invention  Form for

The polyester film constituting the coated film of the present invention may have a single layer structure or a multilayer structure and may have a multilayer structure of four or more layers as long as the present invention does not depart from the gist of the present invention, no.

The polyester may be homopolyester or copolymerized polyester. When a homopolyester is included, it is preferable to be obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol.

 Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid. Examples of the aliphatic glycol include ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol, and the like. Representative polyesters include polyethylene terephthalate and the like.

On the other hand, examples of the dicarboxylic acid component of the copolymerizable polyester include one or two kinds of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid And examples of the glycol component include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol, neopentyl glycol, and the like.

The polymerization catalyst of the polyester 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 them, the antimony compound is preferable because of its low cost. Further, the titanium compound and the germanium compound have high catalytic activity, can be polymerized in a small amount, and have a small amount of metal remaining in the film, so that transparency of the film is increased, which is preferable.

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

By designing a layer using a polyester film having three or more layers and using a polyester material having a small content of ester cyclic trimer in the outermost polyester layer of the polyester film, it is possible to suppress the amount of the ester cyclic trimer after heat treatment It is also possible to do this.

It is also possible to incorporate particles into the polyester layer of the coating film of the present invention for the main purpose of imparting reactivity and preventing damage in each step. In the case of blending the particles, the type of the blended particles is not particularly limited as long as the particles can be lubricated, and specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, Inorganic particles such as kaolin, aluminum oxide, zirconium oxide and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin and benzoguanamine resin. In the polyester production process, precipitated particles in which a part of metal compounds such as catalysts are precipitated and finely dispersed can be used.

The average particle diameter of the particles is usually 5.0 占 퐉 or less, preferably 0.01 to 3.0 占 퐉. When the average particle diameter exceeds 5.0 탆, the surface roughness of the film becomes excessively coarse, which may cause problems in various processes in a subsequent step. In addition, when used in the above-mentioned range, the haze is suppressed to be low and the transparency of the entire film can be ensured easily.

The content of particles in the polyester layer is usually less than 5% by weight, preferably 0.0003 to 1% by weight, more preferably 0.0005 to 0.5% by weight. In the case where the particles are absent or the content is small, the transparency of the film becomes high, which results in a good film. However, since the slidability becomes insufficient in some cases, it is possible to improve the slidability Research is sometimes required. When the content of the particles is too large, the haze increases and lacks transparency. In such a case, for example, the degree of difficulty in inspecting defects such as foreign matters may be increased during various inspections.

The shape of particles to be used is not particularly limited, and any of spherical, massive, rod-shaped, and flat-shaped shapes may be used. The hardness, specific gravity, color, and the like are not particularly limited. These series of particles may be used in combination of two or more as necessary.

The method of adding particles to the polyester layer is not particularly limited, and conventionally known methods can be employed. For example, it may be added at any stage of producing the polyester constituting each layer, but it is preferably added after completion of the esterification or transesterification reaction.

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

The thickness of the polyester film is not particularly limited as long as the film can be formed into a film, but is usually in the range of 10 to 300 mu m, preferably 20 to 250 mu m.

As a film forming method of a film, a commonly known film forming method can be adopted, and there is no particular limitation. For example, in the case of producing a biaxially stretched polyester film, first, the above-mentioned polyester raw material is melt-extruded from a die using an extruder, and the molten sheet is cooled and solidified by a cooling roll to obtain an unstretched sheet. In this case, in order to improve the planarity of the sheet, it is preferable to enhance the adhesion between the sheet and the rotary cooling drum, and the electrostatic adhesion method or the liquid application adhesion method is preferably employed. Then, the obtained unstretched sheet is stretched in one direction by a roll or tenter type stretching machine. The stretching temperature is usually 70 to 120 占 폚, preferably 80 to 110 占 폚, and the stretching magnification is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the stretching magnification is usually 2.5 to 7 times, preferably 3.0 to 6 times, at 70 to 170 占 폚 in the direction perpendicular to the first stretching direction. Followed by heat treatment at 180 to 270 ° C under relaxation or under 30% relaxation to obtain a biaxially oriented film. In the stretching, a method of performing stretching in one direction in two or more steps can be employed. In this case, it is preferable that the stretching magnifications in the two directions finally fall within the above ranges.

In addition, the simultaneous biaxial stretching method can be employed. The simultaneous biaxial stretching method is a method in which the above unstretched sheet is simultaneously stretched in the machine direction and the width direction under the temperature-controlled state at 70 to 120 캜, preferably 80 to 110 캜, But it is preferably 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in magnification. Subsequently, heat treatment is carried out at a temperature of 180 to 270 DEG C under relaxation or under 30% relaxation to obtain a stretched oriented film. Conventionally known stretching methods such as a screw method, a pantograph method, and a linear driving method can be employed for the simultaneous axial stretching device employing the above-described stretching method.

Next, the formation of the coating layer constituting the coating film of the present invention will be described. The coating layer may be provided by in-line coating in which the film surface is treated during the film formation process of the polyester film, or off-line coating may be applied outside the system on the film once formed. More preferably, it is formed by in-line coating.

The in-line coating is a method of performing coating in a process of producing a polyester film, specifically, a method in which the polyester is melt-extruded, and then the coating is carried out at any stage from stretching to heat setting and winding. Normally, it is coated on any of an unstretched sheet obtained by melting and quenching and a stretched uniaxially stretched film.

For example, in the case of sequential biaxial stretching, a method of stretching in the transverse direction after coating on a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction) is excellent. According to this method, since the film formation and the coating layer formation can be performed at the same time, there is merit in production cost, and since the drawing is performed after coating, the thickness of the coating layer can be changed by the stretching magnification, The thin film coating can be performed more easily.

The present invention has an essential requirement that a polyester film has a coating layer containing a resin having a styrene structure and a (meth) acrylic acid structure on at least one side. In the present invention, (meth) acrylic acid means methacrylic acid or acrylic acid. The coating liquid may contain other components.

Examples of the styrene structure include styrene and styrene derivatives, and may be introduced as substituents such as an alkyl group such as a methyl group or an ethyl group or a phenyl group in styrene. From the viewpoint of the effect of preventing the ester cyclic trimer from being precipitated by the heat treatment, the alkyl group having 4 or less carbon atoms is preferably substituted styrene or styrene having no substituent, and more preferably styrene.

(Meth) acrylic acid structure is a derivative having a substituent group introduced into (meth) acrylic acid and (meth) acrylic acid. From the viewpoint of the effect of preventing precipitation of the ester cyclic trimer by heat treatment, it is preferably (meth) acrylic acid, more preferably acrylic acid.

The resin having a styrene structure and a (meth) acrylic acid structure may be combined with other polymerizable monomer copolymerizable with a compound having a styrene structure and a (meth) acrylic acid structure. Examples of the copolymerizable monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2- ethylhexyl (meth) (Meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutylhydroxyl Various kinds of nitrogen-containing compounds such as (meth) acrylamide, diacetone acrylamide, N-methylol acrylamide or (meth) acrylonitrile, and the like, Various vinyl esters such as vinyl and vinyl acetate; various silicon-containing polymerizable monomers such as? -methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane and the like; Phosphorus-containing vinyl-based monomers; Various halogenated vinyls such as vinyl chloride and vinylidene chloride; And various conjugated dienes such as butadiene.

The ratio of the styrene structure in the resin having the styrene structure and the (meth) acrylic acid structure is usually in the range of 5 to 95 mol%, preferably 20 to 90 mol%, and more preferably 40 to 85 mol%. The use in the above range can effectively suppress the precipitation of the ester cyclic trimer by the heat treatment.

(Meth) acrylic acid in the resin having a styrene structure and a (meth) acrylic acid structure is usually 3 mol% or more, preferably 5 to 95 mol%, more preferably 10 to 80 mol%, particularly preferably 15 To 40 mol%. When the proportion of the (meth) acrylic acid is less than 3 mol%, precipitation of the ester cyclic trimer by heat treatment can not be effectively suppressed.

For the purpose of forming the coating layer of the coating film of the present invention, a crosslinking agent may be used for the purpose of improving the durability and coating property of the coating layer. As the crosslinking agent, conventionally known crosslinking agents may be used, and examples thereof include melamine compounds, oxazoline compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds and silane coupling compounds. Of these, epoxy compounds, isocyanate compounds and carbodiimide compounds are suitably used from the viewpoint of suppressing the precipitation of ester cyclic trimer. In addition, from the standpoint of suppressing the precipitation of ester cyclic trimer and improving the coating appearance A melamine compound and an oxazoline compound are suitably used, and a melamine compound is particularly suitable. When two or more crosslinking agents are used, a combination of a melamine compound and an oxazoline compound, a melamine compound and an epoxy compound, an oxazoline compound and an epoxy compound are suitably used from the viewpoint of suppressing precipitation of an ester cyclic trimer, Among them, it is more preferable to use a melamine compound in combination.

The melamine compound is a compound having a melamine skeleton in the compound, for example, a compound obtained by partially or completely etherifying an alkylated melamine derivative or an alkylated melamine derivative by an alcohol, and a mixture thereof can be used. As the alcohol used in the etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are suitably used. As the melamine compound, any of a monomer, a dimer or the like having a dimer or more may be used, or a mixture thereof may be used. It is also possible to use a catalyst in which a urea or the like is co-condensed with a part of melamine, and a catalyst may be used to enhance the reactivity of the melamine compound.

The oxazoline compound is a compound having an oxazoline group in the molecule, particularly a polymer containing an oxazoline group, and may be prepared by polymerization with an addition-polymerizable oxazoline group-containing monomer or other monomer. The addition-polymerizable oxazoline group-containing monomer may be at least one selected from the group consisting of 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, Isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like, and one kind or a mixture of two or more thereof Can be used. Of these, 2-isopropenyl-2-oxazoline is industrially readily available and therefore suitable. The other monomer is not particularly limited as long as it is a monomer copolymerizable with the addition-polymerizable oxazoline group-containing monomer, and examples thereof include alkyl (meth) acrylates (examples of the alkyl group include a methyl group, ethyl group, n-propyl group, isopropyl group, Butyl group, t-butyl group, 2-ethylhexyl group, and cyclohexyl group); Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt and the like); Unsaturated nitriles such as acrylonitrile and methacrylonitrile; (Meth) acrylamide, N-alkyl (meth) acrylamide and N, N-dialkyl (meth) acrylamide. Examples of the alkyl group include a methyl group, ethyl group, n-propyl group, Butyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.); Vinyl esters such as vinyl acetate and vinyl propionate; Vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; ? -Olefins such as ethylene and propylene; Halogen-substituted?,? - unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride; And?,? - unsaturated aromatic monomers such as styrene,? -Methylstyrene, and the like, and one kind or two or more kinds of these monomers can be used.

The oxazoline group of the oxazoline compound is usually in the range of 0.5 to 10 mmol / g, preferably 3 to 9 mmol / g, and more preferably 5 to 8 mmol / g. The use in the above range improves the durability of the coating film and is effective to prevent precipitation of the ester cyclic trimer on the film surface by heating.

The epoxy compound is a compound having an epoxy group in the molecule and includes, for example, a condensation product of epichlorohydrin with a hydroxyl group or an amino group such as ethylene glycol, polyethylene glycol, glycerin, polyglycerin and bisphenol A, and a polyepoxy compound , Diepoxy compounds, monoepoxy compounds, glycidyl amine compounds, and the like. Examples of the polyepoxy compound include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) Examples of the isocyanate, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether and diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, Polyglycoldiglycidyl ether, polytetramethylene glycol diglycidyl ether, monoepoxy compound, polyglycidyl ether, polyglycerol diglycidyl ether, polyglycerol diglycidyl ether, Include, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, glycidyl Examples of the nitrogen-containing compound include N, N, N ', N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis (N, N-diglycidylamino) cyclohexane.

The isocyanate compound is a compound having an isocyanate derivative structure represented by isocyanate or block isocyanate. Examples of the isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate and naphthalene diisocyanate, and aromatic isocyanates such as α, α, α'-tetramethylxylylene Aliphatic isocyanates having an aromatic ring such as diisocyanate and the like, aliphatic isocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate and hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, iso And alicyclic isocyanates such as methylenebis (4-cyclohexylisocyanate), isopropylidene dicyclohexyl diisocyanate, and the like. Also included are polymers and derivatives of these isocyanates such as burette, isocyanurate, uretdionate and carbodiimide modified products. These may be used alone or in combination of two or more. Among the 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 block isocyanate state, examples of the blocking agent include phenol compounds such as a bisulfate, phenol, cresol and ethylphenol, alcohol compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol and ethanol , Active methylene compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate and acetylacetone, mercapane compounds such as butyl mercaptan and dodecyl mercaptan, ε-caprolactam, δ-valero Lactam compounds such as lactam, amine compounds such as diphenyl aniline, aniline and ethylene imine, acid amide compounds of acetanilide and acetic amide, formaldehyde, acetal aldehyde, acetone oxime, methyl ethyl ketone oxime, cyclohexanone oxime , Etc. These may be used singly or in combination of two or more.

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

The carbodiimide compound is a compound having a carbodiimide structure and can be used for improving the adhesion to various surface functional layers that can be formed on the coating layer and for improving the heat and humidity resistance of the coating layer . The carbodiimide compound can be synthesized by a conventionally known technique, and in general, a condensation reaction of a diisocyanate compound can be used. The diisocyanate compound is not particularly limited and any of aromatic and aliphatic diisocyanate compounds may be used. Specific examples thereof include tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate Isocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, dicyclohexylmethane diisocyanate, and the like.

The content of the carbodiimide group contained in the carbodiimide-based compound is the carbodiimide equivalent (weight [g] of the carbodiimide compound for imparting 1 mol of the carbodiimide group), usually 100 to 1000, Is in the range of 250 to 800, more preferably 300 to 650. [ Use in the above range improves the durability of the coating film.

Further, in order to form a coating layer, it is also possible to use a polymer in combination to improve the outer appearance of the applied coating and to improve adhesion when various surface functional layers are formed in the coating layer. However, if the amount is too large, the precipitation of the ester cyclic trimer by heat treatment may not be effectively suppressed.

Specific examples of the polymer include polyester resin, urethane resin, polyvinyl (polyvinyl alcohol, etc.), conductive polymer, polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxyethylcellulose, and the like.

In order to form a coating layer, it is also possible to use particles together for the purpose of improving blocking and sliding properties. From the viewpoint of transparency of the film, the average particle diameter thereof is usually in the range of 1.0 μm or less, preferably 0.5 μm or less, and more preferably 0.2 μm or less. The lower limit is usually in the range of not less than 0.01 탆, preferably not less than 0.03 탆, more preferably not more than the film thickness of the coating layer, in order to improve the sliding property more effectively. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, and organic particles. Among them, silica is preferable from the viewpoint of transparency.

In order to form the coating layer, a combination of a defoaming agent, a coating improver, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, an antioxidant, a foaming agent, a dye, It is also possible to do.

The resin having a styrene structure and a (meth) acrylic acid structure is usually at least 1% by weight, preferably from 10 to 99% by weight, more preferably from 20 to 80% by weight, particularly preferably from 30 to 80% by weight, 60% by weight. The use in the above range makes it possible to suppress the precipitation of the ester cyclic trimer on the film surface by the heat treatment.

When a crosslinking agent is added, the proportion thereof is usually in the range of 10 to 99% by weight, preferably 20 to 80% by weight, more preferably 40 to 70% by weight, in the coating layer. The use in the above range makes it possible to suppress the precipitation of the ester cyclic trimer on the film surface by the heat treatment. When a melamine compound is used as a crosslinking agent, it is preferably in the range of 45 to 70% by weight.

The thickness of the coating layer is usually from 0.003 to 1 mu m, preferably from 0.005 to 0.5 mu m, more preferably from 0.01 to 0.20 mu m, particularly preferably from 0.04 to 0.5 mu m, 0.15 mu m. The use in the above-mentioned range can effectively suppress the precipitation of the ester cyclic trimer by the heat treatment, and the coated appearance and blocking resistance are good.

Examples of the method of applying the coating liquid to the polyester film include air doctor coats, blade coats, rod coats, bar coats, knife coats, squeeze coats, impregnated coats, reverse roll coats, transfer roll coats, gravure coats, , A cast coat, a spray coat, a curtain coat, a calender coat, and an extrusion coat.

The film may be subjected to a chemical treatment, a corona discharge treatment, a plasma treatment, or the like before application to improve the coatability and adhesiveness of the coating agent to the film.

With respect to the coated film of the present invention, a high degree of transparency may be required even after exposure in a high-temperature atmosphere for a long time, such as for a touch panel.

From this point of view, in order to cope with high transparency, the film haze change amount in the heat treatment (at 150 DEG C for 90 minutes) is usually not more than 1.0%, more preferably not more than 0.7%, still more preferably not more than 0.5%. When the film haze variation is more than 1.0%, the visibility is lowered due to the increase of the film haze due to the precipitation of the ester cyclic trimer, and for example, it is unsuitable for applications requiring high visibility such as for a touch panel .

From the viewpoint of the precipitation amount of the ester cyclic trimer, the amount of the ester cyclic trimer extracted from the film surface by the dimethylformamide from the film surface by the heat treatment (150 ° C, 90 minutes) of the coated film of the present invention is usually 1.5 mg / m ² or less, preferably 0.9 mg / m ² or less, more preferably 0.5 mg / m ² or less, particularly preferably 0.2 mg / m ² or less. If it exceeds 1.5 mg / m ² , the amount of the ester cyclic trimer precipitated increases in the post-process, for example, at 150 ° C. for 90 minutes, and the transparency of the film decreases There is a possibility of process contamination.

Example

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 without departing from the gist thereof. The evaluation methods in Examples and Comparative Examples are as follows.

(1) Method of measuring intrinsic viscosity of polyester:

1 g of a polyester obtained by removing the other polymer component and pigment from the polyester was dissolved and dissolved in 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) and measured at 30 캜.

(2) Method of measuring average particle diameter (d50: 占 퐉)

The value of 50% of the total (based on weight) in the distribution of the type of furniture measured using a centrifugal sediment type particle size distribution measuring apparatus (SA-CP3 manufactured by Shimadzu Corporation) was taken as the average particle size.

(3) Method of measuring film thickness of coating layer:

The surface of the coating layer was dyed with RuO ₄ and embedded in an epoxy resin. Subsequently, the slice prepared by the ultra slice slice method was dyed with RuO ₄ , and the cross section of the applied layer was measured using TEM (H-7650, manufactured by Hitachi High Technologies Co., Ltd., acceleration voltage: 100 V).

(4) Heat treatment method of film:

The sample is placed in a state in which the measuring surface of the sample is exposed, and the sample is fixed with the Kent paper. The sample is left to stand at 150 DEG C for 90 minutes in a nitrogen atmosphere.

(5) Measurement method of film haze:

The film haze was measured by a haze meter " HM-150 " manufactured by Murakami Color Research Laboratory Co., Ltd. according to JIS-K-7136.

(6) Method of measuring film haze change amount by heat treatment:

80 parts by weight of dipentaerythritol hexaacrylate, 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, 20 parts by weight of a photopolymerization initiator ( 5 parts by weight of Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) and 200 parts by weight of methyl ethyl ketone were coated so as to have a dry film thickness of 3 탆 and cured by irradiation with ultraviolet rays to form a hard coat layer . The haze of the film formed with the hard coat layer was measured by the method (5). Then, after heating by the method of (4), the haze was measured by the method of (5). The difference between the haze after the heat treatment and the haze before the heat treatment was calculated and used as the film haze variation. The smaller the change in the film haze, the smaller the precipitation of the ester cyclic trimer due to the high-temperature treatment was, and the better.

(7) Measurement of the amount of ester cyclic trimers deposited on the surface of the coating film:

The polyester film is heated in air at 150 캜 for 90 minutes. Thereafter, the film subjected to the heat treatment is formed into a box-like shape with the measurement surface (coated layer) as the inner surface so that the upper surface is open 10 cm in height and 3 cm in height. Then, 4 ml of DMF (dimethylsulfoamide) was placed in the box prepared by the above method, and the mixture was allowed to stand for 3 minutes. DMF was recovered and purified by liquid chromatography (LC-7A mobile phase A: acetonitrile, mobile phase B: , The amount of ester cyclic trimer in DMF was obtained, and the amount of the ester cyclic trimer in DMF was determined. The amount of ester cyclic trimer in DMF was determined by the following equation: " 2% acetic acid aqueous solution, column: MCI GEL ODS 1HU manufactured by Mitsubishi Kagaku KK; column temperature: 40 ° C; flow rate: 1 ml / min; detection wavelength: Value was divided by the area of the film in contact with DMF to obtain the amount of ester cyclic trimer on the surface of the film (mg / m < ² >). The ester cyclic trimer in DMF was determined from the standard sample peak area and the measured sample peak area ratio (absolute calibration curve method). A standard sample was prepared by precisely weighing an ester cyclic trimer obtained in advance and dissolving it in accurately weighed DMF.

The polyester used in Examples and Comparative Examples was prepared as follows.

≪ Production method of polyester (A)

100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol were used as a starting material and 0.09 part by weight of magnesium acetate quaternary salt as a catalyst was added to the reactor. The reaction was started at a temperature of 150 ° C and distilled off (distillation) The temperature was raised to 230 deg. C after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. To this reaction mixture, 0.04 parts by weight of ethyl acid phosphate was added, and then 0.04 part by weight of antimony trioxide was added thereto, followed by conducting a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 占 폚 to 280 占 폚. On the other hand, the pressure was gradually decreased from the atmospheric pressure, and was finally set to 0.3 mmHg. After the initiation of the reaction, the reaction was stopped at the point of time when the intrinsic viscosity reached 0.63 due to the change in stirring power of the reaction tank, and nitrogen was pressed to discharge the polymer. The obtained polyester (A) had an intrinsic viscosity of 0.63.

≪ Production method of polyester (B)

In the production process of the polyester (A), 0.04 parts by weight of ethyl acetate phosphate was added, and then 0.2 part by weight of silica particles having an average particle size of 2 탆 and 0.04 part by weight of antimony trioxide were added to obtain a polycondensation reaction at an intrinsic viscosity of 0.65 The polyester (B) was obtained in the same manner as in the production of the polyester (A) except that the polyester (B) was stopped. The obtained polyester (B) had an intrinsic viscosity of 0.65.

Examples of the compound constituting the coating layer are as follows.

Styrene acrylic copolymer (IA): Styrene acrylic copolymer copolymerized with styrene / acrylic acid = 80/20 (mol%)

Styrene acrylic copolymer (IB): Styrene acrylic copolymer copolymerized with styrene / acrylic acid / hydroxyethyl acrylamide = 70/20/10 (mol%)

Melamine compound (IIA): Hexamethoxymethylol melamine

Oxazoline compound (IIB): Acrylic polymer epoxhose (oxazoline group amount = 4.5 mmol / g, manufactured by Nippon Shokubai Co., Ltd.) having an oxazoline group and a polyalkylene oxide chain.

(Oxazoline group amount = 7.7 mmol / g, manufactured by Nihon Shokubai Co., Ltd.)

Epoxy compounds (IID): Polyglycerol polyglycidyl ether

Isocyanate compound (IIE): The block polyisocyanate obtained by the following process

And 1000 parts of hexamethylene diisocyanate were stirred at 60 캜, and 0.1 part of tetramethylammonium caprylate was added as a catalyst. After 4 hours, 0.2 part of phosphoric acid was added to terminate 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 kept at 80 DEG C for 7 hours. Thereafter, the temperature of the reaction solution was maintained at 60 占 폚, and 35.8 parts of methyl isophanoylacetate, 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. 58.9 parts of n-butanol was added and the reaction solution temperature was maintained at 80 占 폚 for 2 hours. Then, 0.86 part of 2-ethylhexyl acid phosphate was added to obtain a block polyisocyanate.

Carbodiimide compound (IIF): polycarbodiimide compound carboditrite (carbodiimide equivalent = 600, manufactured by Nisshinbo)

Particles (III): Silica particles having an average particle diameter of 0.07 mu m

Melamine crosslinking catalyst (IV): 2-Amino-2-methylpropanol hydrochloride

Acrylic resin (VA): Acrylic resin copolymerized with ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2

Styrene-vinyl acetate copolymer (VB): A styrene-vinyl acetate copolymer copolymerized with styrene / vinyl acetate / 2,2'-azobisisobutyronitrile = 65/35/1 (mol%

Styrene-vinyl acetate copolymer (VC): styrene-vinyl acetate copolymer copolymerized with styrene / vinyl acetate / acrylic acid / 2,2'-azobisisobutyronitrile = 65/33/2/1 (mol%

Example 1:

A mixed raw material in which the polyester (A) and the polyester (B) were mixed at a ratio of 90% and 10%, respectively, was used as the raw material of the outermost layer (surface layer) Extruded on a cooling roll set at 40 占 폚 in a layer configuration of two kinds of three layers (surface layer / intermediate layer / surface layer = 1: 8: 1 discharge volume) and cooled and solidified To obtain an unoriented sheet. Subsequently, the film was stretched 3.4 times in the transverse direction at a film temperature of 85 占 폚 using a roll speed gauge. The coating liquid 1 shown in Table 1 was applied to one side of the longitudinal stretched film, ° C and annealed at 235 ° C and relaxed by 2% in the transverse direction to obtain a polyester film having a thickness of 50 탆 and a coating layer having a film thickness (after drying) of 0.05 탆.

The amount of change in film haze obtained by the heat treatment of the obtained polyester film was as small as 0.1%, and the amount of the ester cyclic trimer precipitated was also at least good. The properties of this film are shown in Table 2 below.

Examples 2 to 23:

A polyester film was prepared in the same manner as in Example 1, except that the coating composition was changed to the coating composition shown in Table 1 in Example 1. As shown in Table 2, the obtained coating film had a small amount of film haze change due to heat treatment and a small amount of ester cyclic trimer deposition.

Comparative Example 1:

In Example 1, a polyester film was obtained in the same manner as in Example 1, except that a coating layer was not provided. Evaluation of the obtained coated film revealed that the haze of the film due to the heat treatment was greatly increased as shown in Table 2, and the ester cyclic trimer was precipitated much.

Comparative Examples 2 to 6:

A polyester film was prepared in the same manner as in Example 1, except that the coating composition was changed to the coating composition shown in Table 1 in Example 1. Evaluation of the obtained coating film revealed that the film haze was high, the film haze was greatly increased by the heat treatment, and the ester cyclic trimer was precipitated many times. Thus, there was concern about contamination of the process and deterioration of visibility due to whitening after heating.

[Table 1]

[Table 2]

Industrial availability

The coating film of the present invention can be used in applications requiring extremely low increase in film haze and little precipitation of an ester cyclic trimer even after a severe heat treatment process in which the film is exposed for a long time under a high temperature atmosphere, Can be suitably used as a base material of a laminate.

Claims (4)

A polyester film comprising a coating layer containing a resin having a styrene structure and a (meth) acrylic acid structure on at least one side of the polyester film and having a proportion of a (meth) acrylic acid structure in the resin of 10 mol% to 95 mol% And the deposition amount is 1.5 mg / m ² or less. The coating film according to claim 1, wherein the proportion of the (meth) acrylic acid structure in the resin is from 10 mol% to 40 mol%, and the styrene structure is from 40 mol% to 90 mol%. The coating film according to claim 1, wherein the coating layer contains a crosslinking agent. delete