KR20180041712A - Coating film - Google Patents

Abstract

The present invention provides a coating film which suppresses an ester cyclic trimer precipitated in a film when exposed to a high temperature and does not cause problems according to an ester cyclic trimer in film storage, film use, film processing, etc. do. The present invention also relates to a coating film having a coating layer on at least one side of a polyester film, wherein the coating layer contains an addition polymer resin having an acid group.

Description

Coating film

The present invention relates to a coating film in which oligomer (low molecular weight component of polyester, particularly ester cyclic trimer) is less precipitated from a film even after exposure to a high temperature, for example.

The polyester film is excellent in transparency, dimensional stability, mechanical properties, heat resistance and electrical properties and is used in various fields.

Particularly, as a base material of a transparent conductive laminate, which has recently been used for a touch panel or the like, it has been widely used instead of glass. As such a transparent conductive laminate, a polyester film is used as a substrate, and an ITO (indium tin oxide) film is formed on the film directly or through an anchor layer by sputtering. Such a biaxially stretched polyester film is generally subjected to heat processing.

For example, in order to reduce the heat shrinkage, the film is allowed to stand at 150 DEG C for 1 hour (Patent Document 1) or heat treatment is performed at 150 DEG C for crystallization of ITO (Patent Document 2).

However, as a problem of the polyester film, when exposed to such a treatment at a high temperature for a long time, the ester cyclic trimer contained in the film precipitates and crystallizes on the film surface, resulting in deterioration of visibility due to whitening of the appearance of the film, Contamination of the member occurs. For this reason, the characteristics of the transparent conductive laminate based on a polyester film can not be said to be sufficiently satisfactory.

Further, as a measure for preventing the ester cyclic trimer from precipitating, for example, it has been proposed to form a curable resin layer comprising a crosslinking agent of a silicone resin and an isocyanate resin on a polyester film (Patent Document 3). However, since the curable resin layer is formed by thermosetting, it requires a high temperature treatment in order to separate the blocking agent of the isocyanate resin, and it is prone to cause curling or sagging during processing, so care must be taken for handling.

Therefore, when a method for reducing the amount of the ester cyclic trimers by the coating layer is proposed, it is necessary to have a heat resistance far higher than that of the prior art, and to have good ester cyclic trimer sealing performance of the coating layer itself.

Further, for example, a polyester film used for a touch panel often is hard-coated in order to improve performance such as curl prevention, scratch resistance improvement, surface hardness and the like. Therefore, there is a demand for a polyester film having a coating layer excellent in adhesiveness to a hard coat.

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

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

The inventors of the present invention have conducted intensive studies on the above problems, and as a result, they have found that the above problems can be solved by forming a specific coating layer, and have accomplished the present invention.

That is, the gist of the present invention is a coating film having a coating layer on at least one side of a polyester film, wherein the coating layer contains an addition polymer resin having an acid group.

According to the coated film of the present invention, since the precipitation of the ester cyclic trimer on the surface is suppressed even when treated at a high temperature for a long time, it is possible to obtain an excellent appearance product without increase in haze and generation of foreign matter, high.

The polyester film constituting the coated film of the present invention may have a single layer structure or a multi-layer structure, and may be a multi-layer structure of four or more layers, without being limited to a two-layer structure or a three-layer structure, without departing from the gist of the present invention . It is preferable that a multilayer structure of two or more layers is provided, and each layer is characterized to have a multifunctionality.

The polyester may be homopolyester or copolymerized polyester. In the case of homopolyester, it is preferable that the homopolyester is 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, and 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, in the case of the copolyester, the dicarboxylic acid component is preferably a dicarboxylic acid such as isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p- And two or more of them may be enumerated. As the glycol component, ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol, neopentyl glycol and the like may be mentioned.

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 titanium compound and the germanium compound are preferable because they have high catalytic activity, can be polymerized in a small amount, and have a small amount of metal remaining in the film, thereby increasing transparency of the film. Further, the antimony compound is preferable because it is inexpensive.

In the present invention, in order to suppress the precipitation amount of the ester cyclic trimer after the heat treatment, a polyester having a small content of the ester cyclic trimer is preferable. As a method for producing such a polyester, various known methods can be used, and examples thereof include a method of solid-state polymerization after production of a polyester.

A method of suppressing the precipitation amount of the ester cyclic trimer after heat treatment by using a polyester raw material having a polyester film of three or more layers and a low content of an ester cyclic trimer in the outermost layer is also possible.

It is also possible to incorporate particles into the polyester film for the main purpose of imparting lubricity and preventing scratches 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 impart lubricity, and specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, Inorganic particles such as magnesium, 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. It is also possible to use precipitation particles in which a part of metal compounds such as catalysts are precipitated and finely dispersed in the polyester production process. Of these, silica particles and calcium carbonate particles are particularly preferable in that they are particularly effective in small amounts.

The average particle diameter of the particles is usually 5.0 占 퐉 or less, preferably 0.01 to 3.0 占 퐉. If the average particle diameter exceeds 5.0 탆, the surface roughness of the film becomes too coarse, which may cause problems in various processes in a subsequent step. In addition, the use in the above range can suppress the haze to a small extent and make it easy to ensure transparency as a whole film.

The content of the particles in the polyester film is usually 5 wt% or less, preferably 0.0003 to 1 wt%, and more preferably 0.0005 to 0.5 wt%.

The shape of particles to be used is not particularly limited, and any of spherical, massive, rod-shaped, and flat-shaped particles may be used. There are no particular restrictions on hardness, specific gravity, color, etc. These series of particles may be used in combination of two or more kinds, if necessary.

The method of adding particles to the polyester film is not particularly limited, and conventionally known methods can be used. 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 may be added to the polyester film.

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

As the film forming method of the polyester film, a generally known film forming method can be used, 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, it is preferable to enhance the adhesion between the sheet and the rotary cooling drum in order to improve the planarity of the sheet, and an electrostatic adhesion method or a liquid application adhesion method is preferably used. Then, the obtained non-stretched sheet is stretched in one direction by a roll or tenter 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. Subsequently, the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times, at 70 to 170 캜 in a direction orthogonal to the stretching direction of the first step. Followed by heat treatment at a temperature of 180-270 ° C under relaxation or within 30% relaxation to obtain a biaxially oriented film. In the stretching, a method of performing unidirectional stretching in two or more steps can be used. In this case, it is preferable that the stretching magnifications in the two directions finally become the above ranges.

Further, a simultaneous biaxial stretching method can be used. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is subjected to simultaneous stretching orientation in the machine direction and the width direction at a temperature-controlled state of usually 70 to 120 캜, preferably 80 to 110 캜. As the stretching magnification, 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. Subsequently, the stretched oriented film is obtained by heat treatment at a temperature of 180 to 270 캜 under tension or under relaxation of 30% or less. As the simultaneous biaxial stretching apparatus using the stretching method, a conventionally known stretching method such as a screw method, a pantograph method, and a linear driving method can be used.

Next, the formation of the coating layer constituting the coating film of the present invention will be described. The coating layer may be formed by an in-line coating method in which the film surface is treated during the polyester film forming step, or an off-line coating method which is applied from outside the system onto a film that is once fabricated may be used. Preferably an in-line coating method.

The in-line coating is a method of coating in a production process of a polyester film, specifically, a method in which polyester is melt-extruded, followed by stretching, heat fixation, and winding at an optional step. Generally, it is coated on any of an unstretched sheet obtained by melt quenching and a stretched uniaxially stretched film.

For example, in 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 preferable. According to this method, since the film formation and the coating layer formation can be performed at the same time, there is an advantage in production cost, and since the coating layer is stretched after coating, the thickness of the coating layer can be changed according to the stretching magnification, Can be made easier.

Further, by forming a coating layer on the film before stretching, the coating layer can be stretched together with the base film, and thereby, the coating layer can be strongly adhered to the base film. Further, in the production of a biaxially stretched polyester film, the film can be stretched while grasping the film end by grasping the film end by a clip or the like, and the film can be restrained in the longitudinal direction and the transverse direction, The high temperature can be applied.

Therefore, since the heat treatment performed after the coating can be performed at a high temperature which is not attained by other methods, it is possible to improve the film formability of the coating layer, to firmly adhere the coating layer to the base film, can do.

The coating layer of the present invention contains an addition polymer resin having an acid group as an essential requirement, and as a preferred embodiment, a crosslinking agent is contained. As used herein, the addition polymer resin means a polymer resin produced by opening a double bond of an unsaturated compound having a double bond between carbon atoms and linking an unsaturated compound with a covalent bond, as is well known to those skilled in the art. This addition polymerization technique is a technique that has already been established in the manufacturing industry of polyethylene, polystyrene, polyvinyl chloride, and polymethylmethacrylate.

The addition polymer resin having an acid group used in the present invention is preferably an addition copolymer resin and is preferably an addition copolymer resin having an addition copolymerization with a monomer composed of an unsaturated compound having no acid group in the molecule and a monomer composed of an unsaturated compound having at least one acid group in the molecule . The monomer composed of an unsaturated compound having no acid group in the molecule is not particularly limited, but a monomer composed of an unsaturated compound having a (meth) acrylic acid ester structure is preferably used. In this case, another monomer may be used as a copolymer component as a monomer composed of an unsaturated compound having no acid group in the molecule.

The (meth) acrylic acid ester structure means a derivative in which a (meth) acrylic acid ester or a (meth) acrylic acid ester is substituted with a substituent, and the term "(meth) acrylic acid" means acrylic acid and methacrylic acid.

Examples of the (meth) acrylic esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, butyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, t-octyl (meth) acrylate, 2-ethylhexyl Cycloalkyl esters having 5 to 12 carbon atoms such as acrylic acid and / or methacrylic acid alkyl esters having 1 to 18 carbon atoms and cyclohexyl acrylate, aralkyl esters having 7 to 12 carbon atoms benzyl acrylate, and the like. Of these, acrylic acid esters and methacrylic acid esters having an alkyl group having 4 or less carbon atoms at the terminal of the ester group are preferably used from the viewpoint of preventing precipitation of an ester cyclic trimer by heat treatment.

As the acid group of the monomer composed of an unsaturated compound having an acid group, a carboxyl group, a sulfonic acid group, a phosphoric acid group and the like can be mentioned, but a carboxyl group is preferable from the viewpoint of the effect of preventing the ester cyclic trimer precipitation by heat treatment. The number of the acid groups may be two or more in the molecule.

Examples of the monomer composed of an unsaturated compound having an acid group include monomers having a carboxylic acid group such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid and itaconic acid; and monomers having carboxylic acid groups such as sulfonic acid, xylene sulfonic acid, mesitylene sulfonic acid and naphthalene sulfonic acid Monomers having sulfonic acid, monomers having phosphoric acid such as phosphoric acid, diphosphoric acid, dimethylphosphoric acid, and dimethylallylphosphoric acid. From the viewpoint of the effect of preventing precipitation of the ester cyclic trimer by heat treatment, it is preferably acrylic acid or methacrylic acid, more preferably methacrylic acid.

Examples of the monomer used as the copolymerization component include various nitrogen-containing compounds such as (meth) acrylamide, diacetone acrylamide, N-methylol acrylamide or (meth) acrylonitrile, vinyl propionate, Various vinyl esters; various silicon-containing polymerizable monomers such as? -methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane and the like; Phosphorus-containing vinyl monomers; Various halogenated vinyls such as vinyl chloride and vinylidene chloride; And various conjugated dienes such as butadiene.

The reactor phase of the addition polymerization is composed of initiation reaction, growth reaction, termination reaction, and chain transfer reaction. In the present invention, the addition polymer resin having an acidic group can be easily produced by already established addition polymerization techniques, for example, radical polymerization using a radical as an active species of the reaction mechanism. Radical polymerization techniques are described in "Encyclopedia of Polymer Science, " John Wiley & Sons, 13, 708 (1988). In general, the radical polymerization is carried out in the presence of a radical initiator by raising the temperature to 50 to 150 DEG C, and reacting the monomer in a solution. Examples of the radical initiator include azobisisobutyronitrile (AIBN), benzoyl peroxide, lauryl peroxide, azobisisocapronitrile, azobisisobalonitrile, t-butyl hydrogen peroxide, and the like.

The ratio of the acid groups in the acid group-containing addition polymer resin is generally 1 mol% or more, and is preferably in the range of 1 mol% or more per one acid group of the unsaturated compound having an acid group. As follows.

That is, the ratio of the acid group-containing monomers to one acid group is usually from 30 to 90 mol%, preferably from 35 to 70 mol%, more preferably from 40 to 60 mol% . When a cross-linking agent is used in combination, it is usually in the range of 10 to 90 mol%, preferably 25 to 70 mol%, and more preferably 40 to 60 mol%. When the proportion of the monomer having an acid group is less than 1 mol%, the precipitation of the ester cyclic trimer by heat treatment can not be effectively suppressed.

Among the above-mentioned definitions concerning the ratio of the acid groups, "the ratio of monomers per one acid group" means that one molecule of monocarboxylic acid is one molecule as it is, while one molecule of dicarboxylic acid means two molecules. Accordingly, each numerical range defined by the above-mentioned mol% is a rule for a monocarboxylic acid, and in the case of a dicarboxylic acid, it is a numerical value of 1/2 thereof.

In a preferred embodiment of the present invention, when the addition polymer resin has an acid group and a (meth) acrylic acid ester structure, the proportion of the (meth) acrylic acid ester structure is preferably such that the ratio of the monomer composed of the unsaturated compound having a Generally 1 mol% or more, and the appropriate range is the case where the coating layer is not used in combination with a cross-linking agent.

That is, in the case where the crosslinking agent is not used in combination, the amount is usually in the range of 5 to 70 mol%, preferably 10 to 70 mol%, and more preferably 25 to 40 mol%. When a crosslinking agent is used in combination, Mol%, preferably 10 to 70 mol%, and more preferably 25 to 40 mol%.

In the present invention, it is preferable to use a cross-linking agent for the purpose of improving the durability and coatability of the coating layer. As the crosslinking agent, various known crosslinking agents can be used, and examples thereof include melamine compounds, oxazoline compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds and silane coupling compounds. Of these, a melamine compound is preferably used from the viewpoint of an effect of preventing precipitation of an ester cyclic trimer by heat treatment. In addition, an oxazoline compound, an epoxy compound, an isocyanate compound and a carbodiimide compound are preferably used from the viewpoint of improving adhesion with the upper layer in the case of forming an upper layer such as a hard coat layer, , An isocyanate compound, and a carbodiimide compound are particularly preferably used. When two or more crosslinking agents are used, a combination of a melamine compound and an oxazoline compound or a combination of a melamine compound and an epoxy compound is preferably used from the viewpoint of further suppressing the precipitation of the ester cyclic trimer.

The melamine compound is a compound having a melamine skeleton in the compound. For example, an alkylated melamine derivative, an alkylated melamine derivative may be reacted with an alcohol to form a partially or fully etherified compound and a mixture thereof. As the alcohol used for the etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. The melamine compound may be either a monomer or a multimer of dimers or more, or a mixture thereof. Also, a co-condensation of urea or the like with a part of melamine may be used, 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 produced by polymerization with addition polymerizable oxazoline group-containing monomers alone or with other monomers. The addition polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2- 2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline and 2-isopropenyl-5-ethyl-2-oxazoline. Can be used. Of these, 2-isopropenyl-2-oxazoline is preferable 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. Examples of the alkyl (meth) acrylate (the alkyl group includes methyl, ethyl, (Meth) acrylic acid esters such as 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 salt, potassium salt, ammonium salt and tertiary amine salt); Unsaturated nitriles such as acrylonitrile and methacrylonitrile; (Meth) acrylamide, N-alkyl (meth) acrylamide, N, N-dialkyl (meth) acrylamide 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 amount of the oxazoline group of the oxazoline compound is usually 0.5 to 10 mmol / g, preferably 2 to 9 mmol / g, and more preferably 4 to 7 mmol / g. The use in the above range improves the adhesion to the upper layer such as the hard coat layer and is also 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 examples thereof include condensates of epichlorohydrin with hydroxyl groups and amino groups such as ethylene glycol, polyethylene glycol, glycerin, polyglycerin and bisphenol A, and polyepoxy compounds, Diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like. As the polyepoxy compound, for example, 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 compounds include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol But are not limited to, diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, Examples of the epoxy compound include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, Sidil amine compounds there may be mentioned N, N, N ', N'- tetraglycidyl -m- xylylenediamine, 1,3-bis (N, N- diglycidyl-amino) cyclohexane and the like.

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 ', α'- Alicyclic diisocyanates such as methylene diisocyanate, propylene diisocyanate, lidine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate , Isophorone diisocyanate, methylene bis (4-cyclohexyl isocyanate), and isopropylidene dicyclohexyl diisocyanate. Also included are polymers or derivatives of these isocyanates such as biuret compounds, isocyanurate, uretdiones, and carbodiimide-modified products. These may be used alone or in combination. Among the isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferable than aromatic isocyanates in order to prevent yellowing by ultraviolet rays.

When used in the form of a block isocyanate, examples of the blocking agent include phenol compounds such as bisulfates, phenol, cresol, and ethylphenol, propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, Alcohol compounds, active methylene compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate and acetylacetone, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, ε-caprolactam, δ - lactam compounds such as valerolactam, amine compounds such as diphenyl aniline, aniline and ethylene imine, acid amide compounds of acetanilide and acetic acid amide, formaldehyde, acetal aldehyde, acetone oxime, methyl ethyl ketone oxime, cyclo Hexanone oxime, and the like. These may be used alone or in combination of two or more.

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

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

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

The content of the carbodiimide group in the carbodiimide compound is usually from 100 to 1,000, preferably from 250 to 1,000, in terms of carbodiimide equivalent (weight [g] of the carbodiimide compound for providing 1 mole of carbodiimide group) To 800, and more preferably in the range of 300 to 650. Use in the above range improves the durability of the coating film.

In forming the coating layer of the present invention, a polymer may be used in combination for improving the appearance of the applied coating, improving the adhesion when various surface functional layers are formed in the coating layer, and the like. However, in the case of using in combination, if the amount is too large, precipitation of the ester cyclic trimer by heat treatment may not be effectively suppressed.

Specific examples of the polymer include a resin containing a (meth) acrylic acid ester structure composed of a monomer having no acid group, a polyester resin, a urethane resin, polyvinyl (polyvinyl alcohol etc.), a conductive polymer, a polyalkylene glycol, , Methylcellulose, hydroxyethylcellulose, and the like.

In forming the coating layer, it is also possible to use particles in combination for the purpose of improving the blocking property and the sliding property. The average particle diameter is usually in the range of 1.0 占 퐉 or less, preferably 0.5 占 퐉 or less, more preferably 0.2 占 퐉 or less, from the viewpoint of film transparency. 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 slidability more effectively. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, organic particles and the like. Among them, silica is preferable from the viewpoint of transparency.

In order to form the coating layer within the range not impairing the object of the present invention, the coating layer may be formed by using 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.

The ratio of the addition polymer resin having an acid group in the coating layer is generally 1% by weight or more, but the appropriate range is the same as in the case where the coating layer is not used in combination with a crosslinking agent.

That is, in the case where the crosslinking agent is not used in combination, the amount is usually 1% by weight or more, preferably 40 to 100% by weight, more preferably 70 to 100% by weight, Preferably from 10 to 70% by weight, and more preferably from 20 to 45% by weight.

The proportion of the crosslinking agent in the coating layer is usually in the range of 5 to 95% by weight, preferably 30 to 90% by weight, and more preferably 55 to 80% by weight. When two or more crosslinking agents are used and one of them is an oxazoline compound or an epoxy compound, the proportion of the oxazoline compound or the epoxy compound is usually 5 to 90% by weight, preferably 10 to 70% More preferably 10 to 40% by weight. When two or more crosslinking agents are used and one of them is a melamine compound, the proportion thereof is usually in the range of 5 to 90% by weight, preferably 10 to 70% by weight, more preferably 20 to 50% by weight to be.

The thickness of the coating layer is generally in the range of 0.003 to 1 mu m, preferably 0.005 to 0.5 mu m, more preferably 0.01 to 0.2 mu m, Mu] m, and particularly preferably in the range of 0.01 [mu] m to 0.08 [mu] m. When a cross-linking agent is used in combination, it is preferably 0.005 mu m to 0.5 mu m, more preferably 0.01 mu m to 0.2 mu m, particularly preferably 0.04 mu m to 0.09 mu m. When the thickness is thinner than 0.003 탆, the amount of the ester cyclic trimer precipitated in the film may not be sufficiently reduced. If it is thicker than 1 占 퐉, problems such as deterioration of appearance of the coating layer and easy blocking may occur.

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

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

With respect to the coated film of the present invention, for example, even after exposure to a high-temperature atmosphere for a long time such as a touch panel, high transparency is sometimes required. The initial film haze is usually 5.0% or less, preferably 3.0% or less, more preferably 1.8% or less. When the initial film haze exceeds 5.0%, the visibility is poor and may be inappropriate for applications requiring high visibility, 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 (150 DEG C, 90 minutes) is usually 1.0% or less, preferably 0.7% or less, more preferably 0.0 to 0.5%. When the amount of change in the film haze exceeds 1.0%, the visibility is lowered due to the increase of the film haze due to precipitation of the ester cyclic trimer, which may be inappropriate for applications requiring high visibility such as 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 DEG C, 90 minutes) of the coated film of the present invention is usually 2.5 mg / m ² or less, preferably 2.0 mg / m ² or less, more preferably 1.5 mg / m ² or less, and particularly preferably 0.0 to 0.5 mg / m ² . If it exceeds 2.5 mg / m ² , the precipitation amount of the ester cyclic trimer increases in the subsequent step of heat treatment at a high temperature atmosphere, for example, at 150 ° C. for 90 minutes in the subsequent step, There is a fear of contamination.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it departs 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 the other polymer component which is incompatible with the polyester and 1 g of the polyester from which the pigment has been removed are precisely weighed and dissolved in 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) and measured at 30 ° C.

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

The value of 50% of the cumulative total (equivalent weight) of the equivalent spherical distribution measured by a centrifugal sedimentation type particle size distribution measuring apparatus (SA-CP3, manufactured by Shimadzu Seisakusho Co., Ltd.) was taken as the average particle diameter.

(3) Method of measuring the coating layer thickness:

The surface of the coating layer was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the slice prepared by the ultra thin film slicing 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, Ltd., acceleration voltage: 100 kV).

(4) Heat treatment method of film:

The measurement surface of the sample is placed in a state of being exposed and fixed with the Kent paper, and the sample is allowed to stand at 150 DEG C for 90 minutes in a nitrogen atmosphere to perform heat treatment.

(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 (trade name: : Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) and 200 parts by weight of methyl ethyl ketone were coated to a dry film thickness of 3 탆, irradiated with ultraviolet rays and cured 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 less the precipitation of the ester cyclic trimer due to the high temperature treatment means, which is good.

(7) Measurement of the amount of the ester cyclic trimer precipitated on the surface of the laminated polyester film:

The polyester film is heated in the air at 150 캜 for 90 minutes. Thereafter, the heat-treated film is formed into a box-like shape with the measurement surface (coated layer) as the inner surface so that the upper surface is 10 cm in width and 3 cm in height. Subsequently, 4 ml of DMF (dimethylsulfoamide) was placed in the box prepared as described above, and the mixture was allowed to stand for 3 minutes. DMF was recovered and purified by liquid chromatography (LC-7A mobile phase A: acetonitrile, , The amount of the ester cyclic trimer in DMF was obtained by feeding the reaction mixture to a mobile phase B: 2% acetic acid aqueous solution, column: "MCI GEL ODS 1HU" manufactured by Mitsubishi Chemical Corporation, column temperature: 40 ° C, flow rate: 1 ml / min, detection wavelength: 254 nm) , And this 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 by the peak area ratio of the standard sample peak area and the measured sample peak area (absolute calibration curve method). The preparation of the standard sample was carried out by accurately weighing the ester cyclic trimer obtained in advance and dissolving it in precisely weighed DMF.

The polyesters used in Examples and Comparative Examples were 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 4 hydrate as a catalyst was added to the reactor to set the reaction start temperature to 150 ° C and the reaction temperature was gradually raised at the same time as the methanol was suspended, After 230 hours. After 4 hours, the transesterification reaction was substantially terminated. 0.04 parts by weight of ethyl acetate phosphate was added to the reaction mixture, and then 0.04 part by weight of antimony trioxide was added thereto, and polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised at 230 캜 to 280 캜. On the other hand, the pressure was gradually reduced from the normal pressure and finally to 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time point when the intrinsic viscosity reached 0.63 due to the change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The obtained polyester (A) had an intrinsic viscosity of 0.63.

≪ Production method of polyester (B)

After adding 0.04 parts by weight of ethyl acetate phosphate, 0.2 part by weight of silica particles having an average particle size of 2 占 퐉 and 0.04 part by weight of antimony trioxide were added to the polyester (A), and at the time when the intrinsic viscosity reached 0.65 Polyester (B) was obtained in the same manner as in the production of polyester (A) except that the polycondensation reaction was stopped. The obtained polyester (B) had an intrinsic viscosity of 0.65.

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

Addition copolymer resin (IA) having an acid group:

Acrylic copolymer was copolymerized with methacrylic acid / n-butyl acrylate / n-butyl methacrylate / ethyl acrylate / ethyl methacrylate = 49/14/9/24/4 (mol%

Addition copolymer resin (IB) having an acid group:

Acrylic copolymer (meth) acrylate / ethyl acrylate / ethyl methacrylate / isobutyl methacrylate = 37/43/7/13 (mol%)

Addition copolymer resin (IC) having an acid group:

Acrylate / ethyl acrylate / ethyl methacrylate / n-butyl methacrylate = 20/36/26/18 (mol%

Addition copolymer resin having an acid group (ID):

Acrylic copolymer was copolymerized with methacrylic acid / ethyl acrylate / n-butyl methacrylate / isobutyl methacrylate = 3/25/32/30 (mol%

Melamine compound (II): Hexamethoxymethylol melamine

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

Epoxy compound (IIIB): polyglycerol polyglycidyl ether.

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

And 1,000 parts of hexamethylene diisocyanate were stirred at 60 占 폚, 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 added, and the mixture was maintained at 80 DEG C for 7 hours. Thereafter, 35.8 parts of isobutanol methyl acetate, 32.2 parts of diethyl malonate and 0.88 parts of a 28% methanol solution of sodium methoxide were added, and the mixture was maintained for 4 hours. 58.9 parts of n-butanol was added and the mixture was maintained at a temperature of 80 DEG C for 2 hours. Then, 0.86 part of 2-ethylhexyl acid phosphate was added to obtain a block polyisocyanate.

Carbodiimide compound (IIID): Polycarbodiimide compound Carbodite (carbodiimide equivalent = 600, manufactured by Nisshinbo K.K.)

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

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

Acrylic resin (VI): Acrylic resin copolymerized with n-butyl acrylate / n-butyl methacrylate / ethyl acrylate / ethyl methacrylate = 20/26/40/14 (mol%

Example 1 :

(A) and polyester (B) were mixed in a ratio of 90% and 10%, respectively, as raw materials for the outermost layer (surface layer), and only polyester (A) was used as a raw material for the intermediate layer. Extruded, cooled and solidified in a layer configuration of two kinds of three layers (surface layer / intermediate layer / surface layer = 1: 8: 1 discharge amount) on a cooling roll set at 40 占 폚, . Subsequently, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 DEG C using a roll speed gauge. Then, the coating liquid 1 shown in Table 1 was applied to one side of the longitudinally stretched film, and the film was led into a tenter, ° C. and heat-treated at 235 ° C. to obtain a polyester film having a thickness of 50 μm having a coating layer having a film thickness (after drying) of 0.05 μm, relaxed by 2% in the transverse direction.

The coating film thus obtained had a small amount of change in film haze due to the heat treatment, and the amount of the ester cyclic trimer precipitated was small. The properties of this film are shown in Table 2 below.

Examples 2 to 38 :

A coating film was obtained in the same manner as in Example 1 except that the coating composition of Example 1 was changed to the coating composition shown in Table 1. [ As shown in Table 2, the obtained film had no increase in film haze by heat treatment, and the amount of the ester cyclic trimer precipitated was good.

Comparative Example 1 :

A polyester film was obtained in the same manner as in Example 1 except that the application layer was not formed in Example 1. As a result of evaluating the obtained polyester film, as shown in Table 2, the film haze by the heat treatment was greatly increased and precipitation of the ester cyclic trimer was also increased.

Comparative Examples 2 to 5 :

Was prepared in the same manner as in Example 1 to obtain a polyester film. As a result of evaluating the obtained laminated polyester film, the film haze was high, the ester cyclic trimer was precipitated by heat treatment in a large amount, and the process was contaminated.

[Table 1]

[Table 2]

Industrial availability

The coating film of the present invention exhibits extremely low increase in film haze and low precipitation of ester cyclic trimer even after a severe heat treatment step in which the film is exposed for a long time under a high temperature atmosphere. Therefore, for example, it can be preferably used as a base material of a transparent conductive laminate.

Claims (7)

A coating film comprising a polyester film and a coating layer on at least one side of the polyester film, wherein the coating layer contains an addition polymer resin having an acid group. The coating film according to claim 1, wherein the addition polymer resin has an acid group and a (meth) acrylic acid ester structure. The coating film according to any one of claims 1 to 3, wherein the proportion of the acid groups in the addition polymer resin is 1 mol% or more per one acid group of monomers composed of unsaturated compounds having an acid group. The coated film according to any one of claims 1 to 3, wherein the acid group in the addition polymer resin is a carboxyl group. The coated film according to any one of claims 1 to 4, wherein the coating layer contains a crosslinking agent. The application film according to claim 5, wherein the cross-linking agent is a melamine compound. The coated film according to any one of claims 1 to 6, wherein the haze is 5.0% or less.