WO2012081438A1

WO2012081438A1 - Layered polyester film

Info

Publication number: WO2012081438A1
Application number: PCT/JP2011/078075
Authority: WO
Inventors: 加藤雄三; 川崎泰史; 藤田真人
Original assignee: 三菱樹脂株式会社
Priority date: 2010-12-15
Filing date: 2011-12-05
Publication date: 2012-06-21

Abstract

Provided is a layered polyester film which, when various functional surface layers including, for example, a hardcoat, are superposed thereon, diminishes unevenness due to interference or the like to attain satisfactory visibility and has excellent adhesion to the functional surface layers. The layered polyester film comprises a polyester film and a coating layer formed on at least one surface thereof from a coating fluid which comprises a polyester resin, titanium oxide particles, and an epoxy compound or isocyanate compound.

Description

Laminated polyester film

The present invention relates to a laminated polyester film, for example, a laminated polyester film that needs to reduce interference unevenness due to reflection of external light, such as a liquid crystal display, a plasma display panel, and organic electroluminescence.

In recent years, polyester films have been used for touch panels, antireflection films, prism sheets, light diffusion sheets, electromagnetic wave shielding films, and the like, which are members of liquid crystal displays and plasma display panels. The base film used for these members is required to have excellent transparency and visibility.

These films are often hard-coated to prevent curling, improve scratch resistance, and improve surface hardness. Moreover, as a base material, the polyester film excellent in transparency and a mechanical characteristic is generally used. In order to improve the adhesion between the polyester film and the hard coat layer, an easy-adhesion coating layer is generally provided as an intermediate layer, but the reflected light at the interface between the hard coat layer and the coating layer, and the coating layer When the reflected light at the interface between the polyester film and the polyester film interferes, rainbow pattern unevenness (interference unevenness) may occur.

If a film with uneven interference is used for a display member such as a touch panel, the visibility is poor and it is difficult to use. For this reason, it is required to produce a film with reduced interference unevenness. The refractive index of the coating layer for reducing the interference unevenness is considered to be around the geometric mean of the refractive index of the biaxially stretched polyester film of the base material and the refractive index of the hard coat layer, and the refractive index around this can be adjusted. Ideal. Since the refractive index of the polyester film is high, it is generally necessary to design the coating layer with a high refractive index.

An example of improving interference unevenness by increasing the refractive index of the coating layer includes, for example, a method of blending a metal chelate compound or metal fine particles having a high refractive index in the coating layer. In the case of chelate compounds, the stability of the coating solution may not be sufficient depending on the combination due to the instability of the metal chelate in the aqueous solution, and there is a possibility of increasing the liquid replacement work when producing for a long time. Yes (Patent Document 1). In addition, an example in which the refractive index is increased by a combination of a polyester resin and metal fine particles is also known, but in this case, there is a case where it is not possible to sufficiently exhibit the strict moist heat-resistant adhesion demanded in recent years (Patent Document). 2, 3).

Furthermore, in addition to the suppression of interference unevenness, there is an increasing need for a coating layer having a high refractive index in order to improve the visibility of the display. For example, in recent years, due to the increase in smartphones and the like, capacitive methods with patterned transparent electrodes are becoming mainstream among touch panels, and the refractive index difference of each layer of the display is reduced for the purpose of further improving the visibility of the display. Processing to make the patterning of the transparent electrode invisible is also required (Patent Documents 4 and 5).

JP 2005-97571 A JP 2004-54161 A JP 2008-169277 A JP 2011-134464 A JP 2011-136562 A

The present case has been made in view of the above circumstances, and the problem to be solved is to reduce interference unevenness when various surface functional layers such as a hard coat are provided, and to have good visibility and surface function. It is providing the laminated polyester film excellent in adhesiveness with a layer.

As a result of intensive studies in view of the above circumstances, the present inventors have found that the use of a laminated polyester film having a specific configuration can easily solve the above-described problems, and have completed the present invention.

That is, the gist of the present invention is a laminated polyester film having a coating layer formed from a coating solution containing a polyester resin, titanium oxide particles, and an epoxy compound or an isocyanate compound on at least one surface of the polyester film. Exist.

According to the laminated polyester film of the present invention, when various surface functional layers such as a hard coat are laminated, visibility is hardly impaired due to interference unevenness and the like, and a film having excellent adhesion to various surface functional layers is provided. And its industrial value is high.

Hereinafter, the present invention will be described in more detail.
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 polyester used in the present invention 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, examples of the dicarboxylic acid component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (for example, p-oxybenzoic acid). 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.

The polyester polymerization catalyst is not particularly limited, and a conventionally known compound can be used. Examples thereof include an antimony compound, a titanium compound, a germanium compound, a manganese compound, an aluminum compound, a magnesium compound, and a calcium compound. Among these, a titanium compound is particularly preferable from the viewpoint of increasing the brightness of the film.

In the polyester film of the present invention, an ultraviolet absorber can be contained in order to improve the weather resistance of the film and prevent deterioration of the liquid crystal. The ultraviolet absorber is not particularly limited as long as it is a compound that absorbs ultraviolet rays and can withstand the heat applied in the production process of the polyester film.

As the ultraviolet absorber, there are an organic ultraviolet absorber and an inorganic ultraviolet absorber, and an organic ultraviolet absorber is preferable from the viewpoint of transparency. Although it does not specifically limit as an organic type ultraviolet absorber, For example, a cyclic imino ester type, a benzotriazole type, a benzophenone type etc. are mentioned. From the viewpoint of durability, a cyclic imino ester type and a benzotriazole type are more preferable. It is also possible to use two or more ultraviolet absorbers in combination.

In the polyester layer of the film of the present invention, particles can be blended mainly for the purpose of imparting slipperiness and preventing the occurrence of scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples include inorganic particles such as magnesium, kaolin, aluminum 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.

On the other hand, 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 average particle size of the particles used is usually in the range of 0.01 to 3 μm. If the average particle size is less than 0.01 μm, the slipperiness may not be sufficiently imparted, or the particles may be aggregated to make the dispersibility insufficient, thereby reducing the transparency of the film. On the other hand, when the thickness exceeds 5 μm, the surface roughness of the film becomes too rough, which may cause problems when various surface functional layers such as a hard coat layer are formed in a subsequent process.

Further, the particle content in the polyester layer is less than 5% by weight, preferably in the range of 0.0005 to 3% 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. Further, when the particle content exceeds 5% by weight, the transparency of the film may be insufficient.

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.

Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, and the like can be added to the polyester film in the present invention as necessary. .

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

Next, a production example of the polyester film in the present invention will be specifically described, but is not limited to the following production examples. That is, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. 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 and / or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the 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 stretching direction. In this case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. is there. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or relaxation within 30% to obtain a biaxially oriented film. 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 stretched and oriented simultaneously in the machine direction and the width direction in a state where the temperature is usually controlled 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 170 to 250 ° C. under tension or under 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 constituting the laminated polyester film in the present invention will be described. 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. Since the coating can be performed simultaneously with the film formation, the production can be handled at a low cost, and therefore in-line coating is preferably used.

Although the in-line coating is not limited to the following, for example, in the sequential biaxial stretching, a coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When the coating layer is provided on the polyester film by in-line coating, it is possible to apply at the same time as the film formation, and the coating layer can be processed at a high temperature in the heat treatment process of the polyester film after stretching. Performances such as adhesion to various surface functional layers that can be formed on the layer and heat-and-moisture resistance can be improved. Moreover, when coating before extending | stretching, the thickness of an application layer can also be changed with a draw ratio, and compared with offline coating, thin film coating can be performed more easily. That is, a film suitable as a polyester film can be produced by in-line coating, particularly coating before stretching.

In the present invention, it is an essential requirement to have a coating layer formed of a coating solution containing a polyester resin, titanium oxide particles, and an epoxy compound or an isocyanate compound on at least one surface of the polyester film.

In order to improve the visibility when the surface functional layer such as a hard coat layer is provided, the coating layer of the present invention is obtained by setting the refractive index of the surface functional layer such as the hard coat layer and the refractive index of the coating layer to the biaxially stretched polyester. It is designed to be close to the refractive index of the film. When these refractive indexes are in the vicinity of the same, reflection at each interface can be suppressed, so that interference unevenness is extremely reduced.

Furthermore, in recent years, due to the increase in smartphones and the like, capacitive touch panels with patterned transparent electrodes are becoming mainstream among touch panels, and in order to further improve the visibility of screens, patterning of transparent electrodes has been performed in addition to reducing interference unevenness. The need for invisible processing is increasing. By reducing the refractive index of the coating layer to approximately the same as the refractive index of the surface functional layer such as a hard coat layer and the biaxially stretched polyester film of the base material, interference unevenness is reduced and transparent We thought that it can be used effectively for processing that makes electrode patterning invisible.

The polyester resin used for forming the coating layer of the present invention includes, for example, the following polyvalent carboxylic acid and polyvalent hydroxy compound as main components. That is, as the polyvalent carboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and 2,6 -Naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutar Acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, trimellitic acid monopotassium salt and ester-forming derivatives thereof can be used. In particular, the coating layer has a higher refractive index and hard coating. Surface functional layer such as a layer, and since the interference unevenness can highly inhibited by adjusting the near equivalent polyester film substrate preferably has a naphthalene structure. Examples of the polyvalent hydroxy compound include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2- Methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, ethylene glycol modified bisphenol A, diethylene glycol modified bisphenol A, diethylene glycol, triethylene glycol, polyethylene Glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, dimethylo Or the like can be used potassium Rupuropion acid. One or more of these polyvalent carboxylic acids and polyvalent hydroxy compounds may be appropriately selected, and a polyester resin may be synthesized by a conventional polycondensation reaction.

In the formation of the coating layer in the present invention, a polymer other than the above-described polyester resin is used in order to improve the adhesion with the surface functional layer, the coated surface, and the visibility and transparency when the surface functional layer is formed. It can also be used in combination.

Specific examples of the polymer include acrylic resin, urethane resin, polyvinyl (polyvinyl alcohol, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like. It is done.

The titanium oxide particles used for forming the coating layer of the present invention are mainly used for adjusting the refractive index of the coating layer. Titanium oxide has a high refractive index and can increase the refractive index of the coating layer without impairing the transparency of the film. In particular, since the refractive index of the resin used in the coating layer is low, it is preferable to use titanium oxide particles having a high refractive index, and in order to obtain a coating layer having a refractive index close to that of the polyester film, refraction is required. It is preferable to use a rate of 1.7 or more. If necessary, two or more types of titanium oxide particles may be used in combination.

From the viewpoint of transparency, the average particle size of the titanium oxide particles used for forming the coating layer of the present invention is preferably 100 nm or less, more preferably 50 nm or less, still more preferably 25 nm or less, and particularly preferably 15 nm or less.

Further, in order to improve slipperiness and blocking, particles other than titanium oxide particles may be used in combination for forming the coating layer.

The epoxy compound used for the formation of the coating layer of the present invention is a compound having an epoxy group in the molecule. For example, epichlorohydrin and ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A and other hydroxyl groups such as Examples include condensates with amino groups, such as polyepoxy compounds, diepoxy compounds, monoepoxy compounds, and glycidylamine compounds. 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-. Examples include xylylenediamine, 1,3-bis (N, N-diglycidylamino) cyclohexane, and the reactants thereof. These may be used alone or in combination of two or more.

The isocyanate compound used for forming the coating layer of the present invention is a compound having an isocyanate derivative structure typified by isocyanate or blocked isocyanate. Examples of isocyanates 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 and acetylacetone, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, lactam compounds such as ε-caprolactam and δ-valerolactam , Amine compounds such as diphenylaniline, aniline, ethyleneimine, acetanilide, acid amide compounds of acetic acid amide, formaldehyde, acetal Examples include oxime compounds such as dooxime, 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 as a mixture or combination 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.

Furthermore, various cross-linking agents other than the epoxy compound and the isocyanate compound can be used in combination in forming the coating layer of the present invention within a range not impairing the gist of the invention. As a crosslinking agent other than the epoxy compound and the isocyanate compound, a known crosslinking agent can be used, and examples thereof include oxazoline compounds, melamine compounds, carbodiimide compounds, and silane coupling compounds.

The oxazoline compound used in the formation of the coating layer of the present invention is a compound having an oxazoline group in the molecule, and a polymer containing an oxazoline group is particularly preferred, and an addition-polymerizable oxazoline group-containing monomer alone or another monomer Can be made by polymerization with. 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, Examples thereof include 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like, and one or a mixture of two or more thereof can be used. Of these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not particularly limited as long as it is a monomer copolymerizable with an addition polymerizable oxazoline group-containing monomer. For example, alkyl (meth) acrylate (alkyl groups include methyl, ethyl, n-propyl, isopropyl, (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, Examples of the alkyl group include unsaturated amides such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, cyclohexyl, etc .; 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 melamine compound used for forming the coating layer of the present invention is a compound having a melamine structure in the compound. For example, an alcohol is reacted with an alkylolated melamine derivative or an alkylolated melamine derivative to partially Alternatively, 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.

The carbodiimide compound used for the formation of the coating layer of the present invention is a compound having a carbodiimide structure, and is a compound having one or more carbodiimide structures in the molecule, for better adhesion and the like. Further, a polycarbodiimide compound having two or more in the molecule is more preferable.

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.

Furthermore, in order not to lose the effect of the present invention, in order to improve the water solubility and water dispersibility of the polycarbodiimide compound, adding a surfactant, polyalkylene oxide, quaternary ammonium salt of dialkylamino alcohol, You may add and use hydrophilic monomers, such as a hydroxyalkyl sulfonate.

These cross-linking agents are used in a design that improves the performance of the coating layer by reacting in the drying process or film forming process. It can be inferred that unreacted products of these crosslinking agents, compounds after the reaction, or mixtures thereof exist in the finished coating layer.

Furthermore, as long as it does not impair the gist of the present invention, the coating layer has an antifoaming agent, a coating property improving agent, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, an antioxidant, foaming as necessary. Agents, dyes, pigments and the like may be contained.

The ratio of the polyester resin is usually in the range of 10 to 90% by weight, more preferably in the range of 40 to 85% by weight, based on the total amount of non-volatile components in the coating solution forming the coating layer constituting the laminated polyester film in the present invention. . By using in this range, the refractive index of the coating layer can be easily adjusted, and interference unevenness can be easily suppressed when a surface functional layer such as a hard coat layer is provided. Moreover, when it uses outside this range, adhesiveness with a surface functional layer may fall.

In the present invention, the content of titanium oxide particles is usually 5 to 60% by weight, preferably 8 to 50% by weight, and more preferably, as a ratio to the total nonvolatile components in the coating solution forming the coating layer constituting the laminated polyester film. It is in the range of 20 to 40% by weight. When the content of the titanium oxide particles is less than 5% by weight, the refractive index of the coating layer does not increase, so that interference unevenness may not be reduced, and when it exceeds 60% by weight, the haze of the coating layer may deteriorate.

As a ratio with respect to all nonvolatile components in the coating solution for forming the coating layer constituting the laminated polyester film in the present invention, the content of the epoxy compound is usually in the range of 1 to 50% by weight, preferably in the range of 5 to 30% by weight. More preferably, it is in the range of 10 to 20% by weight. When the amount is less than 1% by weight, there is a concern that the adhesion to a surface functional layer such as a hard coat layer may be lowered. When the amount exceeds 50% by weight, the haze of the coating layer may be deteriorated.

In the present invention, the content of the compound derived from the isocyanate compound is usually in the range of 1 to 50% by weight, preferably 5 to 30% by weight, based on the total amount of non-volatile components in the coating solution forming the coating layer constituting the laminated polyester film. More preferably, it is in the range of 10 to 20% by weight. When the amount is less than 1% by weight, there is a concern that the adhesion to a surface functional layer such as a hard coat layer may be lowered. When the amount exceeds 50% by weight, the haze of the coating layer may be deteriorated.

The analysis of various components in the coating layer can be performed by analysis of TOF-SIMS, ESCA, fluorescent X-rays, and the like.

When providing a coating layer by in-line coating, apply the above-mentioned series of compounds as an aqueous solution or water dispersion on a polyester film with a coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight. It is preferable to produce a laminated polyester film. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

Regarding the laminated polyester film in the present invention, the thickness of the coating layer provided on the polyester film is in the range of 0.01 to 0.20 μm, more preferably 0.02 to 0.10 μm. If the coating amount is less than 0.01 μm, sufficient adhesion may not be obtained, and if it exceeds 0.20 μm, the appearance, transparency, and film blocking properties may be deteriorated.

In the present invention, as a method of providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating or the like can be used.

In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, usually at 80 to 200 ° C. for 3 to 40 seconds. The heat treatment is preferably performed at 100 to 180 ° C. for 3 to 40 seconds as a guide.

On the other hand, when the coating layer is provided by in-line coating, it is usually preferable to perform heat treatment at 70 to 280 ° C. for 3 to 200 seconds as a guide.

In addition, regardless of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as necessary. The polyester film constituting the laminated polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

The coating layer in the present invention has a refractive index adjusted to be around the same as that of the base polyester film in order to suppress interference unevenness to a higher degree. The absolute reflectance of the coating layer is in the range of 5.5 to 6.5%, preferably in the range of 5.6 to 6.4%, more preferably 5.7 at an arbitrary wavelength of 400 to 800 nm. It is in the range of ˜6.3%. When the reflectance is out of this range, interference unevenness is increased when a surface functional layer such as a hard coat is provided on the coating layer, and the visibility may be lowered.

The polyester film of the present invention is generally provided with a surface functional layer such as a hard coat layer on the coating layer. Although it does not specifically limit as a material used for a hard-coat layer, For example, hardened | cured materials, such as reactive silicon compounds, such as monofunctional (meth) acrylate, polyfunctional (meth) acrylate, and tetraethoxysilane, are mentioned. Among these, from the viewpoint of achieving both productivity and hardness, a polymerization cured product of a composition containing an ultraviolet curable polyfunctional (meth) acrylate is particularly preferable.

The composition containing an ultraviolet curable polyfunctional (meth) acrylate is not particularly limited. For example, a mixture of one or more known ultraviolet curable polyfunctional (meth) acrylates, a commercially available UV curable hard coating agent, or other than these, in the range not impairing the purpose of the present embodiment, What added the other component further can be used.

The UV-curable polyfunctional (meth) acrylate is not particularly limited. For example, dipentaerythritol hexa (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, tetramethylolmethanetri (meth) acrylate, (Meth) acryl derivatives of polyfunctional alcohols such as trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,6-bis (3-acryloyloxy-2-hydroxypropyloxy) hexane And polyethylene glycol di (meth) acrylate and polyurethane (meth) acrylate.

Other components contained in the composition containing an ultraviolet curable polyfunctional (meth) acrylate are not particularly limited. Examples thereof include inorganic or organic fine particles, polymerization initiators, polymerization inhibitors, antioxidants, antistatic agents, dispersants, surfactants, light stabilizers and leveling agents. Moreover, when making it dry after film forming in the wet-coating method, arbitrary amounts of solvents can be added.

As a method for forming the hard coat layer, when an organic material is used, a general wet coat method such as a roll coat method or a die coat method is employed. The formed hard coat layer can be subjected to a curing reaction by heating, irradiation with active energy rays such as ultraviolet rays and electron beams as necessary.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples without departing from the scope of the present invention. The measurement method and evaluation method used in the present invention are as follows.

(1) Measurement of intrinsic viscosity of polyester:
1 g of polyester from which other polymer components and pigments incompatible with polyester were removed was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and measurement was performed at 30 ° C.

(2) Measurement of average particle size:
The coating layer was observed using TEM (Hitachi H-7650, acceleration voltage 100 V), and the average value of the particle diameter of 10 particles was defined as the average particle diameter.

(3) Measurement of coating layer thickness:
The surface of the coating layer was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the section prepared by the ultrathin section method was stained with RuO _4, and the cross section of the coating layer was measured using TEM (H-7650 manufactured by Hitachi, accelerating voltage 100 V).

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

(5) Measurement of absolute reflectance from one coating layer surface in polyester film:
In advance, a black tape (vinyl tape VT-50, manufactured by Nichiban Co., Ltd.) is pasted on the measurement back surface of the polyester film. ARM-500N) using synchronous mode, incident angle 5 °, N polarization, response Fast, data collection interval 1.0 nm, bandwidth 10 nm, scanning speed 1000 nm / min. The reflectance was measured.

(6) Evaluation of interference unevenness of coating layer:
On the coating layer side of the polyester film, 60 parts by weight of dipentaerythritol acrylate, 15 parts by weight of 1,6-hexanediol acrylate, 25 parts by weight of antimony pentoxide, photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals) A mixed coating solution of 1 part by weight and 200 parts by weight of methyl ethyl ketone was applied so as to have a dry film thickness of 5 μm and cured by irradiating with ultraviolet rays to form a hard coat layer having a refractive index equivalent to that of a polyester film. The obtained film is visually observed under the three-wavelength type fluorescent lamp for interference unevenness on the coating layer side, ◎ when the interference unevenness cannot be confirmed, ◎ when thin and sparse interference unevenness is confirmed ○, thin Indicates that a linear interference unevenness can be confirmed, and Δ indicates that a clear interference unevenness is confirmed.

(7) Evaluation of adhesion of coating layer:
In order to evaluate the adhesion, examination was made on materials obtained by removing antimony pentoxide from the hard coat solution used in the evaluation of (6) above. That is, a mixed coating solution of 80 parts by weight of dipentaerythritol acrylate, 20 parts by weight of 1,6-hexanediol acrylate, 5 parts by weight of a photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals), and 200 parts by weight of methyl ethyl ketone. It was applied so that the dry film thickness was 5 μm, and cured by irradiation with ultraviolet rays to form a hard coat layer. The obtained film was subjected to 10 × 10 cross-cut after 100 hours in an environment of 60 ° C. and 90% RH, and a 18 mm wide tape (Cello Tape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) was used. When the peeled area is less than 3%, ◎ if the peeled area is less than 3%, ◯ if it is 3% or more but less than 10%, Δ if the peeled area is less than 3%, 50 If it is more than%, it was marked as x.

The polyester used in the examples and comparative examples was prepared as follows.

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (A)>
100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, 30 ppm of ethyl acid phosphate with respect to the produced polyester, and 100 ppm with respect to the produced polyester of magnesium acetate tetrahydrate as the catalyst at 260 ° C. in a nitrogen atmosphere. The reaction was allowed to proceed. Subsequently, 50 ppm of tetrabutyl titanate was added to the resulting polyester, the temperature was raised to 280 ° C. over 2 hours and 30 minutes, the pressure was reduced to an absolute pressure of 0.3 kPa, and melt polycondensation was further carried out for 80 minutes. 0.63 polyester (A) was obtained.

<Method for producing polyester (B)>
100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, and magnesium acetate tetrahydrate as a catalyst were subjected to an esterification reaction at 225 ° C. in a nitrogen atmosphere at 900 ppm with respect to the produced polyester. Subsequently, 3500 ppm of orthophosphoric acid was added to the produced polyester, and 70 ppm of germanium dioxide was added to the produced polyester. The temperature was raised to 280 ° C. over 2 hours and 30 minutes, and the pressure was reduced to an absolute pressure of 0.4 kPa. After 85 minutes of melt polycondensation, polyester (B) having an intrinsic viscosity of 0.64 was obtained.

<Method for producing polyester (C)>
Using 100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol and 2 parts by weight of diethylene glycol as starting materials, antimony trioxide as a catalyst is taken into the reactor, the reaction start temperature is 150 ° C., and the reaction temperature is gradually increased with the distillation of methanol. Was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially completed, and then a polycondensation reaction was performed 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 obtained chip was preliminarily crystallized at 160 ° C., and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 220 ° C. to obtain a polyester (C) having an intrinsic viscosity of 0.85.

<Method for producing polyester (D)>
In the production method of polyester (A), polyester (D) is obtained using the same method as the production method of polyester (A) except that 0.3 part by weight of silica particles having an average particle diameter of 2 μm is added before melt polymerization. It was.

Examples of compounds constituting the coating layer are as follows.
(Compound example)
・ Polyester resin (E1)
Water dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / 1,4-butanediol / diethylene glycol = 56/40/4 // 70/20/10 (mol%)

・ Polyester resin having condensed polycyclic aromatic (E2)
Water dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / diethylene glycol = 92/8 / / 80/20 (mol%)

・ Epoxy compounds (C1A)
Denacol EX-521 (manufactured by Nagase ChemteX Corporation), a polyglycerol polyglycidyl ether
・ Epoxy compounds (C1B)
Denacol EX-1410 (manufactured by Nagase ChemteX Corporation), an epoxy resin
・ Epoxy compounds (C1C)
Denacol EX-1610 (manufactured by Nagase ChemteX Corporation), an epoxy resin

・ Isocyanate compounds (C2A)
Obtained by blocking 200 parts of a polyester having an average molecular weight of 1000 consisting of an ethylene oxide 2 mol adduct of bisphenol A and maleic acid, and 84 parts of sodium bisulfite with a polyisocyanate consisting of 33.6 parts of hexamethylene diisocyanate, Polyester resin-containing blocked isocyanate compound.

・ Isocyanate compounds (C2B)
A blocked isocyanate obtained by blocking an isocyanate group of polyisocyanate comprising 158 parts of hexamethylene diisocyanate trimer and 26 parts of methoxypolyethylene glycol having a number average molecular weight of 1400 with 66 parts of methyl ethyl ketone oxime, 1,6-hexanediol and diethyl carbonate A urethane obtained by neutralizing a prepolymer comprising 115 parts of a polycarbonate polyol having a number average molecular weight of 2000, 1 part of trimethylolpropane, 40 parts of isophorone diisocyanate and 8 parts of dimethylolpropionic acid with triethylamine and extending the chain with diethylenetriamine. An aqueous blocked isocyanate compound containing a resin.

・ Oxazoline compounds (C3)
Acrylic polymer having oxazoline group and polyalkylene oxide chain, Epocros WS-500 (manufactured by Nippon Shokubai Co., Ltd., containing about 38% 1-methoxy-2-propanol solvent)

・ Hexamethoxymethylmelamine (C4)

-Titanium oxide particles (F1) with an average particle size of 15 nm

Example 1:
A mixed raw material in which the polyesters (A) and (B) are mixed at a ratio of 95% and 5%, respectively, is used as a raw material for the intermediate layer, and the polyester (C) and (D) are mixed at a ratio of 90% and 10%, respectively Using the raw material as the raw material for the outermost layer (surface layer), each was supplied to two extruders, melted at 290 ° C., respectively, and then on the cooling roll set at 40 ° C., two types and three layers (surface layer / intermediate layer / A non-stretched sheet was obtained by coextrusion and cooling and solidification with a layer structure of (surface layer = 1/38/1 discharge amount). 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 liquid 1 shown in Table 1 below was applied to both sides of the longitudinally stretched film, and led to a tenter. Thickness having a coating layer in which the film is stretched 4.0 times at 120 ° C. in the transverse direction and heat-treated at 225 ° C. and then relaxed by 2% in the transverse direction and the coating layer thickness (after drying) is 0.10 μm. A 125 μm polyester film was obtained.

When the absolute reflectance of the obtained polyester film was measured, the minimum reflectance at an arbitrary wavelength of 400 to 800 nm of the coating layer was 5.5%. Clear interference unevenness was observed on the film after laminating the hard coat layer. The adhesion was also good. Also, the haze was low and the transparency was good. The properties of this film are shown in Table 2 below.

Examples 2 to 26:
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. The finished polyester film had a high reflectance as shown in Table 2, and had good interference unevenness and adhesion.

Comparative Examples 1-7:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition of an application layer into the coating agent composition shown in Table 1, and obtained the polyester film. As shown in Table 3, the finished laminated polyester film had poor interference unevenness and poor adhesion to the hard coat.

Comparative Example 8:
In Example 1, it manufactured similarly to Example 1 except having not provided the application layer, and obtained the polyester film. The finished laminated polyester film was inferior in adhesion to the hard coat as shown in Table 3.

The film of the present invention can be suitably used for, for example, various optical films that are members of liquid crystals, plasma displays, and the like, and applications that place importance on adhesion and visibility with a surface functional layer such as a hard coat layer. .

Claims

A laminated polyester film comprising a coating layer formed of a coating solution containing a polyester resin, titanium oxide particles, and an epoxy compound or an isocyanate compound on at least one side of the polyester film.
The ratio of the polyester resin content is 10 to 90% by weight, the titanium oxide particle content is 5 to 60% by weight, the epoxy compound or isocyanate compound content is 1 to The laminated polyester film according to claim 1, which is 50% by weight.
The laminated polyester film according to claim 1 or 2, wherein the coating layer has a thickness of 0.01 to 0.20 µm.
The laminated polyester film according to any one of claims 1 to 3, wherein the minimum absolute reflectance of the coating layer is in the range of 5.5 to 6.5% at an arbitrary wavelength of 400 to 800 nm.
The laminated polyester film according to any one of claims 1 to 4, which is used in a mode in which an ultraviolet curable resin layer is formed on at least one surface of the coating layer.