JP6477265B2 - Laminated polyester film - Google Patents

Description

  The present invention suppresses the precipitation of oligomers (low molecular weight components of polyester, particularly ester cyclic trimers) from a film even after being exposed to high temperature, and adhesion to a coating such as a hard coat or ink. It is related with the laminated polyester film which is excellent in.

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

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

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

  However, as a problem of the polyester film, when exposed to such high temperature and long time treatment, the ester cyclic trimer contained in the film precipitates and crystallizes on the film surface. Decrease in visibility, post-processing defects, in-process and member contamination, etc. occur. Therefore, the characteristics of the transparent conductive laminate based on the polyester film cannot be said to be sufficiently satisfactory.

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

  Moreover, when laminating | coating coverings, such as a hard coat, on a polyester film, when adhesiveness with the material to laminate | stack is bad, peeling will generate | occur | produce in a process and it will become difficult to apply to a product.

  In general, in order to improve the adhesion between the polyester film of the base material and the hard coat layer, for example, a urethane resin is known as the coating layer (Patent Document 4). However, when a urethane resin is used, there is a disadvantage that the ester cyclic trimer is likely to precipitate when heat treatment is performed at a high temperature for a long time.

  Therefore, when taking measures to reduce the amount of ester cyclic trimer precipitated by the coating layer, the coating layer itself has higher heat resistance and adhesion to the hard coat, and the coating layer itself seals the ester cyclic trimer. An application layer with good stopping performance has been proposed (Patent Document 5). However, the coating layer is disadvantageous in that it is expensive because it is thick.

  Therefore, when taking measures to reduce the amount of ester cyclic trimer precipitated by the coating layer in consideration of cost, the film thickness is much thinner than before, the adhesion to the hard coat and the ester cyclic trimer of the coating layer itself It is in a situation where a coating layer with good body sealing performance is required.

JP 2007-42473 A JP 2007-200823 A JP 2007-320144 A JP 2000-229395 A JP 2014-46503 A

  The present invention has been made in view of the above circumstances, and its solution is to suppress, for example, an ester cyclic trimer precipitated from a film when exposed to a high temperature, and a coating such as a hard coat or an ink. An object of the present invention is to provide a laminated polyester film having excellent adhesion.

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

That is, the gist of the present invention, on at least one surface of a polyester film, and containing not compound monomer and carbon atoms having a hydroxyl group has a (meth) acrylic acid ester structure having 4 or less of the alkyl group to an ester group terminated as constituents (Meth) acrylic acid, which is a laminated polyester film having a coating layer with a thickness of 74 nm or less, formed from a coating solution containing a resin and a melamine compound, and having an alkyl group with 4 or less carbon atoms at the ester group terminal The ratio of the compound having an ester structure to the total resin is in the range of 50 to 95 mol%, and the melamine compound is 51% by weight or more based on the total nonvolatile components in the coating solution. Be on film.

  According to the laminated polyester film of the present invention, since the precipitation of the ester cyclic trimer from the surface is suppressed even after high-temperature and long-time treatment, an excellent appearance with no haze increase or generation of foreign matters Can be obtained, and its industrial utility value is high.

  The polyester film constituting the laminated polyester film in the present invention may have a single layer structure or a multilayer structure, and may have four or more layers as long as it does not exceed the gist of the present invention other than a two-layer or three-layer structure. It may be a multilayer, and is not particularly limited.

  The base film of the laminated polyester film of the present invention is made of polyester. Such polyester may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. 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. Typical polyester includes polyethylene terephthalate and the like. On the other hand, the dicarboxylic acid component of the copolyester includes isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), etc. 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexane dimethanol, neopentyl glycol, is mentioned.

  There is no restriction | limiting in particular as a polymerization catalyst of polyester, A conventionally well-known compound can be used, For example, an antimony compound, a titanium compound, a germanium compound, a manganese compound, an aluminum compound, a magnesium compound, a calcium compound etc. are mentioned. Among these, an antimony compound is preferable because it is inexpensive. Titanium compounds and germanium compounds are preferable because they have high catalytic activity and can be polymerized in a small amount, and since the amount of metal remaining in the film is small, the transparency of the film becomes high. Furthermore, since a germanium compound is expensive, it is more preferable to use a titanium compound.

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

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

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

  In the polyester layer of the film of the present invention, particles can be blended mainly for the purpose of imparting slipperiness and preventing scratches in each step. When the particles are blended, the kind of the particles to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness, and specific examples thereof include, for example, silica, calcium carbonate, magnesium carbonate, barium carbonate, sulfuric acid. Examples thereof include inorganic particles such as calcium, calcium phosphate, magnesium phosphate, 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. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  Moreover, the average particle diameter of the particles is preferably 5.0 μm or less, and more preferably in the range of 0.01 to 3.0 μm. When the average particle diameter exceeds 5.0 μm, the surface roughness of the film becomes too rough, and problems may occur in various processes in the subsequent steps. Moreover, by using in the said range, haze is restrained low and it is easy to ensure transparency as the whole film.

  Further, the particle content in the polyester layer is preferably less than 5% by weight, more preferably in the range of 0.0003 to 1% by weight, and still more preferably in the range of 0.0005 to 0.5% by weight. When there are no or few particles, the transparency of the film becomes high and the film becomes a good film, but the slipperiness may be insufficient. There are cases where improvement is required. In addition, when the particle content is high, haze increases and lacks transparency. For example, during various inspections, defects such as difficulty of defect inspection for foreign matters may occur.

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

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

  In addition to the above-mentioned particles, conventionally known UV absorbers, antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, etc. may be added to the polyester film in the present invention as necessary. Can do.

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

  As a film forming method of the film of the present invention, a generally known film forming method can be adopted, and there is no particular limitation. For example, when producing a biaxially stretched polyester film, the polyester raw material described above is first melt-extruded from a die using an extruder, and the molten sheet is cooled and solidified with a cooling roll to obtain an unstretched sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in one direction by a roll or a 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 film is stretched in the direction perpendicular to the first-stage stretching direction at usually 70 to 170 ° C. and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Subsequently, a method of obtaining a biaxially oriented film by performing heat treatment at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% can be mentioned. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can be adopted for the production of the polyester film constituting the laminated polyester film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is usually stretched and oriented in the machine direction and the width direction at a temperature controlled normally at 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  Next, formation of the coating layer which comprises the laminated polyester film in this invention is demonstrated. Regarding the coating layer, it may be provided by in-line coating which treats the film surface during the process of forming a polyester film, or offline coating which is applied outside the system on a once produced film may be adopted. More preferably, it is formed by in-line coating.

  In-line coating is a method of coating within the process of manufacturing a polyester film, and specifically, a method of coating at any stage from melt extrusion of a polyester to heat setting after stretching and winding up. Usually, coating is performed on either an unstretched sheet obtained by melting and rapid cooling, or a stretched uniaxially stretched film.

  Although not limited to the following, for example, in sequential biaxial stretching, a method of stretching in the transverse direction after coating a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction) is particularly excellent. According to such a method, film formation and coating layer formation can be performed at the same time, so there is an advantage in manufacturing cost. In addition, in order to perform stretching after coating, the thickness of the coating layer can be changed by the stretching ratio. Compared to offline coating, thin film coating can be performed more easily.

  The coating layer of the present invention has a coating layer formed from a coating liquid containing a resin having a hydroxyl group and a (meth) acrylic acid ester structure and a melamine compound, and the coating layer having a thickness of 74 nm or less is made of a polyester film. It is an essential requirement to have at least one side. The coating solution may contain other components.

  Examples of the monomer having a hydroxyl group and a hydroxyl group in a resin having a (meth) acrylate structure include alcohols and the like, but a compound containing a vinyl group or other carbon-carbon double bond from the viewpoint of ease of polymerization. It is preferable that

  Examples of the compound having a hydroxyl group and containing a carbon-carbon double bond include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl ( (Meth) acrylate, 3-hydroxybutyl (meth) acrylate, hydroxyalkyl ester of (meth) acrylic acid such as 4-hydroxybutyl (meth) acrylate, di-2-hydroxyethyl fumarate, mono-2-hydroxyethyl monobutyl (Poly) oxyethylene (meth) acrylate having 1 to 100 ethylene oxide groups such as fumarate, ethylene glycol (meth) acrylate, diethylene glycol (meth) acrylate, tetraethylene glycol (meth) acrylate, ( Meta) (Poly) oxypropylene monohydric acid having 1 to 100 propion oxide groups such as propylene glycol laurate, propylene glycol methoxy (meth) acrylate, dipropylene glycol (meth) acrylate and tetrapropylene glycol (meth) acrylate Examples include (meth) acrylate.

  The (meth) acrylic acid ester is a derivative in which a substituent is introduced into (meth) acrylic acid ester and (meth) acrylic acid ester.

  Examples of (meth) acrylic acid esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, and n-acrylate. -Octyl, i-octyl acrylate, t-octyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, methacryl C1-C1 of acrylic acid and / or methacrylic acid such as i-butyl acid, t-butyl methacrylate, n-octyl methacrylate, i-octyl methacrylate, t-octyl methacrylate, 2-ethylhexyl methacrylate 18 alkyl esters and others, cyclohexyl acrylate Cycloalkyl esters of cycloalkyl carbon atoms 5-12 etc., and the like aralkyl ester of acrylic acid benzyl having 7 to 12 carbon atoms. Among these, from the viewpoint of improving the adhesion to the hard coat, acrylic acid esters and methacrylic acid esters having 4 or less carbon atoms are preferably used.

  The resin having a hydroxyl group and a (meth) acrylate structure can be combined with another polymerizable monomer copolymerizable with a compound having a hydroxyl group and a (meth) acrylate structure. Examples of the copolymerizable monomer include various nitrogen-containing compounds such as (meth) acrylamide, diacetone acrylamide, N-methylol acrylamide or (meth) acrylonitrile, and various vinyls such as vinyl propionate and vinyl acetate. Esters; 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 ratio of the monomer having a hydroxyl group in the resin having a hydroxyl group and a (meth) acrylic acid ester structure is usually 1 to 49 mol%, preferably 3 to 30 mol%, more preferably 5 to 15 mol%. By using in the said range, the adhesiveness with respect to a hard coat etc. is obtained and precipitation of the ester cyclic trimer by heat processing can be suppressed effectively.

  The proportion of the compound having a (meth) acrylate structure in the resin having a hydroxyl group and a (meth) acrylate structure is usually 1 to 98 mol%, more preferably 50 to 95 mol%, and still more preferably 70 to 85. It is in the range of mol%. By using in the said range, the adhesiveness with respect to a hard coat etc. is obtained and precipitation of the ester cyclic trimer by heat processing can be suppressed effectively.

  The melamine compound used for forming the coating layer of the film of the present invention is a compound having a melamine skeleton in the compound. For example, an alcohol is reacted with an alkylolated melamine derivative or an alkylolated melamine derivative. Or fully etherified compounds, and mixtures thereof can be used. As alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. Moreover, as a melamine compound, either a monomer or a multimer more than a dimer may be sufficient, or a mixture thereof may be used. Further, a product obtained by co-condensing urea or the like with a part of melamine can be used, and a catalyst can be used to increase the reactivity of the melamine compound.

  For the formation of the coating layer of the film of the present invention, various known cross-linking agents other than the melamine compound can be used in combination for improving the coating appearance and adhesion, rather than using the melamine compound alone. When used together, the adhesion may be significantly improved. Known cross-linking agents include oxazoline compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, silane coupling compounds, and the like. Among these, an oxazoline compound, an epoxy compound, and an isocyanate compound are preferably used from the viewpoint of suppressing precipitation of an ester cyclic trimer, and an oxazoline compound and an isocyanate compound are preferably used from the viewpoint of improving adhesiveness. In addition, an oxazoline compound is preferably used from the viewpoint of improving the coating appearance. However, when a large amount of a crosslinking agent other than the melamine compound is used in combination, there is a concern that precipitation of the ester cyclic trimer cannot be effectively suppressed.

  The oxazoline compound is a compound having an oxazoline group in the molecule, and a polymer containing an oxazoline group is particularly preferable, and can be prepared by polymerization of an addition polymerizable oxazoline group-containing monomer alone or with another monomer. Addition polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like can be mentioned, and one or a mixture of two or more thereof can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with an addition polymerizable oxazoline group-containing monomer. For example, alkyl (meth) acrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, (meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene Unsaturated carboxylic acids such as sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Unsaturated nitriles such as acrylonitrile, methacrylonitrile; (meth) acrylamide, N-alkyl ( (Meth) acrylamide, N, N-dialkyl (meth) acrylamide, As the alkyl group, unsaturated amides such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group); vinyl acetate Vinyl esters such as vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α, β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride And α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene, and the like, and one or more of these monomers can be used.

  The amount of the oxazoline group of the oxazoline compound contained in the coating solution forming the coating layer constituting the laminated polyester film in the present invention is usually 0.5 to 10 mmol / g, preferably 2 to 9 mmol / g, more preferably 3 It is in the range of ˜7 mmol / g. By using in the said range, the adhesiveness with respect to a hard-coat etc. improves and it is effective also in precipitation prevention of the ester cyclic | annular trimer to 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 ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A and the like hydroxyl groups and amino groups, There are polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like. Examples of the polyepoxy compound include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylolpropane. Examples of the polyglycidyl ether and diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and propylene glycol diglycidyl ether. , Polypropylene glycol diglycidyl ether, poly Examples of tetramethylene glycol diglycidyl ether and monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidyl amine compounds such as N, N, N ′, N′-tetraglycidyl-m-xylyl. Examples include range amine and 1,3-bis (N, N-diglycidylamino) cyclohexane.

  The isocyanate compound is a compound having an isocyanate derivative structure typified by isocyanate or blocked isocyanate. Examples of the isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate, and aromatic rings such as α, α, α ′, α′-tetramethylxylylene diisocyanate. Aliphatic isocyanates such as aliphatic isocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylene bis (4-cyclohexyl isocyanate), isopropylidene dicyclohexyl diisocyanate Ne Alicyclic isocyanates such as bets are exemplified. Further, polymers and derivatives such as burettes, isocyanurates, uretdiones, and carbodiimide modified products of these isocyanates are also included. These may be used alone or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferable than aromatic isocyanates in order to avoid yellowing due to ultraviolet rays.

  When used in the state of blocked isocyanate, the blocking agent includes, for example, bisulfites, phenolic compounds such as phenol, cresol, and ethylphenol, and alcohols such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol. Compounds, active methylene compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, 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, ethyleneimine, acetanilide, acid amide compounds of acetic acid amide, formaldehyde, acetoald Examples include oxime compounds such as oxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime, and these may be used alone or in combination of two or more.

  In addition, the isocyanate compound in the present invention may be used alone, or may be used as a mixture or bond with various polymers. In the sense of improving the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or a bond with a polyester resin or a urethane resin.

  A carbodiimide-based compound is a compound having a carbodiimide structure, and is used to improve adhesion with various surface functional layers that can be formed on a coating layer and to improve the heat and humidity resistance of the coating layer. is there. The carbodiimide compound can be synthesized by a conventionally known technique, and generally a condensation reaction of a diisocyanate compound is used. The diisocyanate compound is not particularly limited, and any of aromatic and aliphatic compounds can be used. Specifically, tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexa Examples include methylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate.

  In addition, in the formation of the coating layer of the film of the present invention, it is also possible to use a polymer in combination for the purpose of improving the coating appearance and improving the adhesion when various surface functional layers are formed in the coating layer. is there. However, when used 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 polyester resin, urethane resin, polyvinyl (polyvinyl alcohol, etc.), conductive polymer, polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like.

In addition, particles can be used in combination for the purpose of blocking and improving slipperiness in forming the coating layer. The average particle size is preferably 1 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.2 μm or less from the viewpoint of film transparency. Further, the lower limit is preferably 0.01 μm or more, more preferably 0.03 μm or more, and particularly preferably a range larger than the film thickness of the coating layer in order to improve the slipperiness more effectively. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, and organic particles.
Among these, silica is preferable from the viewpoint of transparency.

  Further, in the range not impairing the gist of the present invention, an antifoaming agent, a coating property improver, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, and an antioxidant are formed as necessary for forming the coating layer. It is also possible to use a foaming agent, a dye, a pigment and the like in combination.

  As a ratio in the coating layer constituting the laminated polyester film in the present invention, the resin having a hydroxyl group and a (meth) acrylate structure is usually 1 to 50% by weight, preferably 10 to 45% by weight, more preferably 20 to 20%. It is in the range of 40% by weight. By using in the said range, precipitation of the ester cyclic | annular trimer on the film surface by heat processing can be suppressed.

  In the present invention, the ratio of the melamine compound to the non-volatile component in the coating solution is usually 51 to 99% by weight, preferably 55 to 90% by weight, more preferably 60 to 80% by weight. If it is less than 51% by weight, precipitation of the ester cyclic trimer by heat treatment may not be effectively suppressed. If it is 99% by weight or more, adhesion to a hard coat may not be obtained. By using in the said range, precipitation of ester cyclic trimer to the film surface by heat processing can be suppressed more highly.

  The thickness of the coating layer is usually in the range of 0.003 μm to 0.074 μm, more preferably 0.005 μm to 0.07 μm, even more preferably as the thickness of the coating layer on the finally obtained film. Is in the range of 0.01 μm to 0.060 μm. When it is less than 0.005 μm, adhesion to a hard coat may not be obtained. When it is 0.074 μm or more, the appearance of the coating is deteriorated, and precipitation of the ester cyclic trimer due to the heat treatment may not be effectively suppressed. By using in the said range, precipitation of the ester cyclic | annular trimer by heat processing can be suppressed more effectively, and an application | coating external appearance and blocking resistance will become still better.

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

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

  For the laminated polyester film in the present invention, for example, for a touch panel, a high degree of transparency may be required even after being exposed to a high temperature atmosphere for a long time. From this viewpoint, in order to cope with a high degree of transparency, the amount of change in film haze during heat treatment (150 ° C., 90 minutes) is preferably 0.5% or less, more preferably 0.3% or less. When the amount of change in film haze exceeds 0.5%, the visibility decreases as the film haze increases due to precipitation of the ester cyclic trimer. For example, for a touch panel, high visibility is required. It may be inappropriate for the application.

Further, from the viewpoint of the precipitation amount of the ester cyclic trimer, the amount of the ester cyclic trimer extracted from the film surface by dimethylformamide by heat treatment (150 ° C., 90 minutes) of the laminated polyester film in the present invention is preferably 1.4 mg / ^{m 2} or less, more preferably 1.2 mg / ^{m 2,} more preferably not more than 0.9 mg / ^{m 2.} If it exceeds 1.4 mg / m ² , the amount of ester cyclic trimer deposited increases in the subsequent process, for example, with heat treatment for a long time in a high-temperature atmosphere such as 150 ° C. for 90 minutes. There is a concern that the performance may deteriorate or contamination of the process.

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

(1) Method for measuring the intrinsic viscosity of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added. And dissolved at 30 ° C.

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

(3) Measuring method of film thickness of coating layer The surface of the coating layer was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the section prepared by ultramicrotomy stained with RuO _4, a coating layer cross-section was measured by using a TEM (Hitachi High Technologies Corporation H-7650, accelerating voltage 100 V).

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

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

(6) Method for measuring change in film haze by heat treatment On the surface of the polyester film opposite to the surface provided with the coating layer to be measured, 80 parts by weight of dipentaerythritol hexaacrylate, 2-hydroxy-3-phenoxy A mixed coating solution of 20 parts by weight of propyl acrylate, 5 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 was applied so that the dry film thickness was 3 μm. And cured to form a hard coat layer. The haze of the film on which the hard coat layer was formed was measured by the method (5). Subsequently, after heating by the method of (4) term, 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 amount of change in film haze.
The lower the film haze change amount, the less the ester cyclic trimer is precipitated by the high temperature treatment, which is better.

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

(8) Adhesion evaluation method 80 parts by weight of dipentaerythritol hexaacrylate, 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, photopolymerization initiator (trade name: Irgacure 184, Ciba (Specialty Chemicals Co., Ltd.) 5 parts by weight and 200 parts by weight of methyl ethyl ketone were applied, dried at 80 ° C. for 1 minute to remove the solvent, and then irradiated with UV light from a UV irradiation machine at 180 mJ / cm ² with a metal halide lamp 120W. Then, a hard coat layer having a thickness of 5 μm was formed. 100 square cuts were made on the obtained film using a cutter guide having a gap interval of 1 mm. Next, an 18 mm width tape (Cello Tape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) was attached to the cut surface on the mesh, and a 2.0 cm roller of 4.0 cm width was reciprocated 20 times to completely adhere. After observing the peeled surface after being peeled off rapidly at a peeling angle of 180 degrees, ◎ if the number of remaining cells is 95 or more, ○ if it is 80 or more and less than 95, if it is 50 or more and less than 80 Δ, x if less than 50.

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

<Method for producing polyester (B)>
In the polyester (A) production method, after adding 0.04 part by weight of ethyl acid phosphate, 0.2 part by weight of silica particles having an average particle diameter of 2 μm and 0.04 part by weight of antimony trioxide are added to obtain the intrinsic viscosity. A polyester (B) was obtained using the same method as the production method of the polyester (A) except that the polycondensation reaction was stopped at a time corresponding to 0.65. The obtained polyester (B) had an intrinsic viscosity of 0.65.

Examples of compounds constituting the coating layer are as follows.
Resin having a hydroxyl group and (meth) acrylic ester structure (IA):
An acrylic resin copolymerized with methyl methacrylate / ethyl methacrylate / 2-hydroxyethyl methacrylate / polyethylene glycol = 50/15/20/15 (mol%).
Resin (IB) having hydroxyl group and (meth) acrylic ester structure:
An acrylic resin copolymerized with methyl methacrylate / i-butyl acrylate / 2-hydroxyethyl methacrylate / methacrylic acid = 50/30/10/10 (mol%).
Resin having a hydroxyl group and (meth) acrylate structure (IC):
An acrylic resin copolymerized with methyl methacrylate / ethyl methacrylate / ethylene glycol acrylate / polyethylene glycol = 40/10/20/30 (mol%).

Melamine compound (II): Hexamethoxymethylol melamine.
Oxazoline compound (IIIA): an acrylic polymer having an oxazoline group. Epocross (Oxazoline group amount = 4.5 mmol / g, manufactured by Nippon Shokubai Co., Ltd.)
Oxazoline compound (IIB): acrylic polymer having an oxazoline group and a polyalkylene oxide chain Epocross (Oxazoline group amount = 7.7 mmol / g, manufactured by Nippon Shokubai Co., Ltd.)
Epoxy compound (IIIC): polyglycerol polyglycidyl ether.

Isocyanate compound (IIID): 1000 parts of hexamethylene diisocyanate was stirred at 60 ° C., and 0.1 part of tetramethylammonium capryate was added as a catalyst. After 4 hours, 0.2 part of phosphoric acid was added to stop the reaction, and an isocyanurate type polyisocyanate composition was obtained. 100 parts of the obtained isocyanurate type polyisocyanate composition, 42.3 parts of methoxypolyethylene glycol having a number average molecular weight of 400, and 29.5 parts of propylene glycol monomethyl ether acetate were charged and maintained at 80 ° C. for 7 hours. Thereafter, the reaction solution temperature was kept at 60 ° C., 35.8 parts of methyl isobutanoyl acetate, 32.2 parts of diethyl malonate, and 0.88 part of 28% methanol solution of sodium methoxide were added and kept for 4 hours. Block polyisocyanate obtained by adding 58.9 parts of n-butanol, maintaining the reaction solution temperature at 80 ° C. for 2 hours, and then adding 0.86 part of 2-ethylhexyl acid phosphate.
Particle (IV): Silica particles having an average particle diameter of 0.07 μm.

Example 1:
The mixed raw materials obtained by mixing the polyesters (A) and (B) at a ratio of 90% and 10%, respectively, are used as the outermost layer (surface layer) raw material, and only the polyester (A) is used as the intermediate layer raw material in two extruders. Each is supplied, melted at 285 ° C., and then coextruded in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer = 1: 8: 1 discharge amount) on a cooling roll set at 40 ° C. Cooled and solidified to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the difference in peripheral speed of the roll, and then the coating solution 1 shown in Table 1 below was applied to one side of the longitudinally stretched film, which was led to a tenter. Polyester having a thickness of 50 μm having a coating layer having a thickness of 0.05 μm after being stretched 4.3 times at 110 ° C. in the transverse direction and heat-treated at 235 ° C. and then 2% relaxed in the transverse direction. A film was obtained.

  The amount of change in film haze due to heat treatment of the obtained polyester film was as small as 0.1%, and the amount of precipitation of the ester cyclic trimer was small and good. The properties of this film are shown in Table 2 below.

Examples 2-15:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. As shown in Table 2, the finished laminated polyester film had a small amount of change in film haze due to the heat treatment, and the amount of precipitation of the ester cyclic trimer was small.

Comparative Example 1:
In Example 1, it manufactured like Example 1 except not providing an application layer, and obtained the polyester film. When the completed laminated polyester film was evaluated, as shown in Table 2, the film haze by heat treatment was greatly increased, and precipitation of the ester cyclic trimer was also large.

Comparative Examples 2-11:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. When the finished laminated polyester film was evaluated, the film haze was high, the film haze increased significantly due to heat treatment, and many ester cyclic trimers were precipitated, and contamination due to process and visual recognition due to whitening after heating There was concern about the deterioration of sex.

  The film of the present invention is less exposed to ester cyclic trimer and has excellent adhesion to a coating such as a hard coat even after a severe heat treatment process in which the film is exposed to a high temperature atmosphere for a long time. As a laminated polyester film, it can utilize suitably as a base material of a transparent conductive laminated body, for example.

Claims (5)

On at least one surface of the polyester film, containing monomers and the number of carbon atoms having a hydroxyl group has 4 an alkyl group to an ester group-terminated (meth) containing a resin as a constituent a compound having an acrylic acid ester structure, and a melamine compound The resin of a compound having a (meth) acrylic acid ester structure, which is a laminated polyester film having a coating layer having a thickness of 74 nm or less, formed from a coating solution and having an alkyl group having 4 or less carbon atoms at the ester group terminal. A laminated polyester film characterized in that the ratio relative to the whole is in the range of 50 to 95 mol%, and the melamine compound is 51% by weight or more based on the total nonvolatile components in the coating solution . The laminated polyester film according to claim 1, wherein a ratio of the monomer having a hydroxyl group to the whole resin is in a range of 3 to 49 mol%. The laminated polyester film according to claim 1 or 2, wherein the resin is in the range of 1 to 45% by weight as a ratio in the coating layer. The laminated polyester film according to any one of claims 1 to 3, further comprising a hard coat layer on the coating layer. The transparent conductive laminated body which uses the laminated polyester film in any one of Claims 1-4 as a base material.