JP5822999B2 - Laminated polyester film - Google Patents

Description

  The present invention relates to a laminated polyester film. For example, in an application for forming a functional layer such as a hard coat layer such as a transparent electrode such as a touch panel or a film for molding, it is easy to distinguish between processing and unprocessed functional layers. Therefore, the present invention relates to a laminated polyester film suitable for the purpose.

  In recent years, polyester films are often used for various optical films and molding films. Transparent electrodes such as touch panels, which are members of various displays, antireflection films, prism sheets, light diffusion sheets, electromagnetic wave shielding films, It is used for applications such as mold transfer films and in-mold label films. The base film used for these members is required to have excellent transparency and visibility.

  Therefore, the film used for these uses generally has high transparency. However, because of its high transparency, it is not easy to distinguish between processed films with various functional layers and unprocessed films before processing. There was a possibility of mistaken goods and raw products.

JP 2005-97571 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is excellent in making it easy to distinguish between processed and unprocessed functional layers in applications where functional layers such as hard coat layers are formed. The object is to provide a laminated polyester film.

  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 that the average particle diameter is in the range of 0.01 to 1.0 μm, where the haze value is reduced by 1.0% or more when a functional layer is formed on one surface of the polyester film. The particles are contained in a range of 3 to 70% by weight as a ratio to the total nonvolatile components in the coating liquid forming the coating layer, and have a coating layer whose thickness is in the range of 0.001 to 1 μm. wherein the surface opposite to the coating layer, have a coating layer containing a polyester resin or an acrylic resin, consists in laminated polyester film characterized in that haze value is 3.0% or more.

  According to the laminated polyester film of the present invention, by forming various functional layers such as a hard coat layer, the base film that can greatly distinguish the processed / unprocessed functional layer by greatly reducing haze The industrial 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 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, 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, titanium compounds and germanium compounds are preferable because they have high catalytic activity, can be polymerized in a small amount, and the amount of metal remaining in the film is small, so that the brightness of the film becomes high. Furthermore, since a germanium compound is expensive, it is more preferable to use a titanium compound.

In the case of polyester using a titanium compound, the titanium element content is preferably 50 ppm or less, more preferably 1 to 20 ppm, and still more preferably 2 to 10 ppm. If the content of the titanium compound is too high, the polyester may be deteriorated in the process of melt-extruding the polyester, resulting in a strong yellowish film. If the content is too low, the polymerization efficiency is poor and the cost is low. In some cases, a film having a sufficient strength or a sufficient strength cannot be obtained. Moreover, when using the polyester by a titanium compound, it is preferable to use a phosphorus compound in order to reduce the activity of a titanium compound for the purpose of suppressing deterioration in the step of melt extrusion. As the phosphorus compound, orthophosphoric acid is preferable in view of the productivity and thermal stability of the polyester. The phosphorus element content is preferably in the range of 1 to 300 ppm, more preferably 3 to 200 ppm, and still more preferably 5 to 100 ppm with respect to the amount of polyester to be melt-extruded. If the content of the phosphorus compound is too large, it may cause gelation or foreign matter. If the content is too small, the activity of the titanium compound cannot be lowered sufficiently, and the yellowish It may be a film.

  The polyester film of the present invention may contain an ultraviolet absorber in order to improve the weather resistance of the film and to prevent deterioration of the liquid crystal of a liquid crystal display used for a touch panel or the like. 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.

  Examples of the ultraviolet absorber include an organic ultraviolet absorber and an inorganic ultraviolet absorber, and an organic ultraviolet absorber is preferable. 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 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. Of these, silica particles are preferred because they are particularly effective in a small amount.

The average particle diameter of the particles is preferably 5 μm or less, more preferably 0.01 to 3 μm. By using the average particle diameter within the above range, an appropriate surface roughness is imparted to the film, and in the case where various functional layers and the like are formed in a subsequent process, problems are unlikely to occur.

Furthermore, the particle content in the polyester layer is preferably less than 5% by weight, more preferably in the range of 0.0003 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. Moreover, when there is too much particle content, even if a functional layer is formed, haze will not fully fall, and transparency of a film may be inadequate.

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 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 it is preferably 10 to 350 μm, more preferably 20 to 300 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 170 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, it is coated on any of an unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat setting, and a film after heat setting and before winding. 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. Further, by providing the coating layer on the film before stretching, the coating layer can be stretched together with the base film, whereby the coating layer can be firmly adhered to the base film. Furthermore, in the production of a biaxially stretched polyester film, the film can be restrained in the longitudinal and lateral directions by stretching while gripping the film end with a clip, etc. High temperature can be applied while maintaining the properties. Therefore, since the heat treatment performed after coating can be performed at a high temperature that cannot be achieved by other methods, the film forming property of the coating layer can be improved, and the coating layer and the base film can be more firmly adhered to each other. Furthermore, it can be set as a firm coating layer, and performances such as adhesion to various functional layers that can be formed on the coating layer and wet heat resistance can be improved.

  In the present invention, when a functional layer is formed on one surface of the polyester film, it has a coating layer in which haze is reduced by 1.0% or more (hereinafter sometimes referred to as a first coating layer), It is an essential requirement to have a coating layer containing a polyester resin or an acrylic resin (hereinafter sometimes referred to as a second coating layer) on the surface of the polyester film opposite to the coating layer. .

  The film of the present invention is designed to facilitate the distinction between processing and unprocessed functional layers by reducing haze after forming a functional layer such as a hard coat layer.

  In order to reduce the haze by 1.0% or more when the functional layer is formed on the coating layer, it is preferable to set the haze of the laminated polyester film having the coating layer before forming the functional layer high. It is possible to adjust both from the haze of the polyester film of the substrate and the haze of the coating layer. In order to increase the haze, for example, there is a method in which particles are contained in a substrate or a coating layer to diffuse light. Since it depends on the refractive index of the particles, it cannot be generally stated, but in general, the larger the particle size and the larger the amount, the higher the haze tends to be. Therefore, it is possible to adjust the haze by changing the particle size or amount according to the purpose.

  In order to reduce haze when a functional layer is formed on the coating layer, a technique of reducing the surface irregularities formed by the polyester film or coating layer of the substrate by forming the functional layer is effective. . Surface irregularities can be formed from both the design of the polyester film of the substrate and the design of the coating layer, as in the adjustment of the film haze. When adjusting with the design of the polyester film of the base material, for example, a method of incorporating particles in the outermost polyester film layer on the coating layer side (side on which the functional layer is formed) rather than the intermediate layer of the polyester film in a multilayer configuration However, it is preferable because surface irregularities are easily formed. In addition, the method of forming the surface irregularities mainly by adjusting the design of the coating layer that is in direct contact with the functional layer, that is, the outermost layer of the laminated polyester film of the present invention, by adjusting the design of the base material formed the functional layer. It is more preferable because the haze reduction at that time becomes efficient. In addition, the adjustment by the design of the coating layer is preferable from the viewpoint of increasing the degree of freedom in adjusting the haze because it is easy to design independently on both sides.

  Examples of the method for forming the surface unevenness in which the haze is lowered by the functional layer include a method of containing particles and a method of forming unevenness on the coating layer itself. As a method for forming irregularities on the coating layer itself, a method of forming a coating layer by mixing and mixing polymers having poor stability, or a film stretching process by coating a polymer having poor stretching followability The method of forming a coating layer through this is mentioned. Considering the stability of the haze value due to production, the liquid stability of the coating solution, etc., a method of incorporating particles in the coating layer is preferable. In particular, the method of incorporating particles in the coating layer is preferable because blocking and slipperiness can be improved. In addition, an increase in the surface area of the coating layer has an effect of contributing to an improvement in adhesion to the functional layer.

  As the particles to be contained in the coating layer, various conventionally known particles can be used. For example, silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, Examples include inorganic particles such as zirconium oxide and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, and benzoguanamine resin. Among them, inorganic particles are preferable in that hardness can be imparted, and silica particles are more preferable in consideration of stability in the state of the coating liquid.

  The average particle size of the particles used in the first coating layer cannot be generally described because it depends on the film thickness of the coating layer, but is generally 0.01 to 1.0 μm, preferably 0.05 to 0.00. It is 8 μm, more preferably 0.1 to 0.7 μm, particularly preferably 0.2 to 0.5 μm.

  In order to hold the particles in the first coating layer, it is preferable to use various polymers for forming the coating layer. A conventionally well-known polymer can be used as a polymer. Specific examples of the polymer include polyester resin, acrylic resin, urethane resin, polyvinyl (polyvinyl alcohol, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like. . Among these, it is preferable to use a polyester resin, an acrylic resin, or a urethane resin from the viewpoint of improving adhesion with a functional layer such as a hard coat layer and improving the appearance of coating. In view of compatibility with the polyester film of the substrate, a polyester resin is more preferable, and an acrylic resin is preferably used from the viewpoint of improving the adhesion with a functional layer such as a hard coat layer.

  The polyester resin includes, for example, those composed of the following polyvalent carboxylic acid and polyvalent hydroxy compound as main constituent 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. As the polyvalent hydroxy compound, ethylene Recall, 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, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol Polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolpropionate, and the like can be used. One or more compounds may be appropriately selected from these compounds, and a polyester resin may be synthesized by a conventional polycondensation reaction.

  The acrylic resin is a polymer composed of a polymerizable monomer including acrylic and methacrylic monomers. These may be either homopolymers or copolymers, and copolymers with polymerizable monomers other than acrylic and methacrylic monomers. Moreover, the copolymer of these polymers and other polymers (for example, polyester, polyurethane, etc.) is also included. For example, a block copolymer or a graft copolymer. Alternatively, a polymer (possibly a mixture of polymers) obtained by polymerizing a polymerizable monomer in a polyester solution or a polyester dispersion is also included. Similarly, a polymer obtained by polymerizing a polymerizable monomer in a polyurethane solution or a polyurethane dispersion (sometimes a mixture of polymers) is also included. Similarly, a polymer (in some cases, a polymer mixture) obtained by polymerizing a polymerizable monomer in another polymer solution or dispersion is also included. Moreover, in order to improve adhesiveness more, it is also possible to contain a hydroxyl group and an amino group.

  The polymerizable monomer is not particularly limited, but particularly representative compounds include, for example, various carboxyl groups such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citraconic acid. Monomers, and salts thereof; such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutyl hydroxyl fumarate, monobutyl hydroxy itaconate Various hydroxyl group-containing monomers; various (meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate; (Meth) acrylamide, Various nitrogen-containing compounds such as acetone acrylamide, N-methylol acrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, and various vinyls such as vinyl propionate Esters; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; phosphorus-containing vinyl monomers; various vinyl halides such as vinyl chloride and biridene chloride Various conjugated dienes such as butadiene.

  The urethane resin is a polymer compound having a urethane bond in the molecule. Usually, urethane resin is prepared by reaction of polyol and isocyanate. Examples of the polyol include polycarbonate polyols, polyester polyols, polyether polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

  Polycarbonate polyols are obtained from a polyhydric alcohol and a carbonate compound by a dealcoholization reaction. Examples of the polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentane. Diol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decane Diol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylol heptane and the like can be mentioned. Examples of the carbonate compound include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, and ethylene carbonate. Examples of polycarbonate polyols obtained from these reactions include poly (1,6-hexylene) carbonate, poly (3- And methyl-1,5-pentylene) carbonate.

  Polyester polyols include polycarboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides. Product and polyhydric alcohol (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol 2-methyl-2-propyl-1 3-propanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexane Diol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyl dialkanolamine, lactone diol, etc.).

  Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, and the like.

  Examples of the polyisocyanate compound used for obtaining the urethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, α, α, α ′, α ′. -Aliphatic diisocyanates having aromatic rings such as tetramethylxylylene diisocyanate, aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl Methanzi Cyanate, alicyclic diisocyanates such as isopropylidene dicyclohexyl diisocyanates. These may be used alone or in combination.

  A chain extender may be used when synthesizing the urethane resin, and the chain extender is not particularly limited as long as it has two or more active groups that react with an isocyanate group. Alternatively, a chain extender having two amino groups can be mainly used.

  Examples of the chain extender having two hydroxyl groups include aliphatic glycols such as ethylene glycol, propylene glycol and butanediol, aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene, and esters such as neopentyl glycol hydroxypivalate. And glycols such as glycols. Examples of the chain extender having two amino groups include aromatic diamines such as tolylenediamine, xylylenediamine, and diphenylmethanediamine, ethylenediamine, propylenediamine, hexanediamine, 2,2-dimethyl-1,3- Propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10- Aliphatic diamines such as decane diamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, isoprobilitincyclohexyl-4,4′-diamine, 1,4-diaminocyclohexane, 1 , 3-Bisaminomethylcyclohexa And alicyclic diamines such as

  The urethane resin in the present invention may use a solvent as a medium, but preferably uses water as a medium. In order to disperse or dissolve the urethane resin in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into the urethane resin, and a water-soluble type. In particular, a self-emulsification type in which an ionic group is introduced into the structure of a urethane resin to form an ionomer is preferable because of excellent storage stability of the liquid and water resistance, transparency, and adhesion of the resulting coating layer.

Examples of the ionic group to be introduced include various groups such as a carboxyl group, sulfonic acid, phosphoric acid, phosphonic acid, quaternary ammonium salt, and the like, and a carboxyl group is preferable. As a method for introducing a carboxyl group into a urethane resin, various methods can be taken in each stage of the polymerization reaction. For example, there are a method of using a carboxyl group-containing resin as a copolymer component during prepolymer synthesis, and a method of using a component having a carboxyl group as one component such as polyol, polyisocyanate, and chain extender. In particular, a method in which a desired amount of carboxyl groups is introduced using a carboxyl group-containing diol depending on the amount of this component charged is preferred.
For example, dimethylolpropionic acid, dimethylolbutanoic acid, bis- (2-hydroxyethyl) propionic acid, bis- (2-hydroxyethyl) butanoic acid and the like are copolymerized with a diol used for polymerization of a urethane resin. Can do. The carboxyl group is preferably in the form of a salt neutralized with ammonia, amine, alkali metal, inorganic alkali or the like. Particularly preferred are ammonia, trimethylamine and triethylamine. In such a polyurethane resin, a carboxyl group from which the neutralizing agent has been removed in the drying step after coating can be used as a crosslinking reaction point by another crosslinking agent. Thereby, it is possible to further improve the durability, solvent resistance, water resistance, blocking resistance, and the like of the obtained coating layer, as well as excellent stability in a liquid state before coating.

  Moreover, in order to improve the intensity | strength of an application layer, it is preferable to use a crosslinking agent together. A conventionally well-known material can be used with a crosslinking agent, For example, an oxazoline compound, an epoxy compound, an isocyanate type compound, a carbodiimide type compound, a melamine compound, a silane coupling compound etc. are mentioned. In order to further improve the adhesion with the functional layer, it is preferable to use two or more kinds of crosslinking agents in combination. Among the above, in terms of good adhesion, oxazoline compounds, epoxy compounds, isocyanate compounds, and carbodiimide compounds are more preferable. Particularly, oxazoline compounds and epoxy compounds, oxazoline compounds and isocyanate compounds, oxazoline compounds and carbodiimide compounds. It has been found that the adhesion is remarkably improved when used in combination. In addition, in terms of increasing the strength of the coating layer, it has also been found that it is more preferable to use a melamine compound in combination, especially when the average particle size exceeds 0.2 μm and the particle content exceeds 10% by weight. Proved to be very effective.

  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 content of the oxazoline group contained in the oxazoline compound is usually 0.5 to 10 mmol / g, preferably 1 to 9 mmol / g, more preferably 3 to 8 mmol / g, and further preferably 4 to 6 mmol in terms of the amount of the oxazoline group. / G. Use within the above range is preferable because adhesion to various functional layers is improved.

  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 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, 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. Among these, an active methylene compound is preferable from the viewpoint that adhesion with the functional layer is easily improved.

  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.

  The carbodiimide-based compound is a compound having a carbodiimide structure, and is used for improving adhesion with various functional layers that can be formed on the coating layer and for improving the heat and humidity resistance of the coating layer. . The carbodiimide compound is a compound having one or more carbodiimide or carbodiimide derivative structures in the molecule, but a polycarbodiimide compound having two or more in the molecule is more preferable for better adhesion and the like.

  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.

  The content of the carbodiimide group contained in the carbodiimide-based compound is a carbodiimide equivalent (weight of the carbodiimide compound to give 1 mol of carbodiimide group [g]) and is usually 100 to 1000, preferably 250 to 800, more preferably 300. It is -700, More preferably, it is the range of 350-650. Use within the above range is preferable because adhesion to various functional layers is improved.

  The melamine compound is a compound having a melamine skeleton in the compound. For example, an alkylolized melamine derivative, a compound partially or completely etherified by reacting an alcohol with an alkylolated melamine derivative, and these Mixtures 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.

  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.

  The second coating layer of the present invention contains a polyester resin or an acrylic resin, and is provided for improving the adhesion to various functional layers that can be formed on the second coating layer. As the polyester resin or acrylic resin used for forming the second coating layer, the same resin as that of the first coating layer can be used. It is also possible to use a polymer such as urethane resin in combination. Furthermore, it is preferable to use a cross-linking agent in combination with the first coating layer in order to improve strength and adhesion. In view of good adhesion, the cross-linking agent used in combination is more preferably an oxazoline compound, an epoxy compound, an isocyanate compound, or a carbodiimide compound, and for further improving the adhesion with the functional layer, etc. It is more preferable to use two or more kinds of cross-linking agents in combination, and it has been found that adhesion is particularly improved when used in combination with an oxazoline compound and an epoxy compound, an oxazoline compound and an isocyanate compound, or an oxazoline compound and a carbodiimide compound. .

  In the present invention, when a functional layer having high transparency such as a hard coat layer is provided on the second coating layer, when used for an application that needs to reduce interference unevenness due to reflection of external light, It is preferable to increase the refractive index of the coating layer. In order to increase the refractive index of the coating layer, it can be solved by using a material having a high refractive index for forming the coating layer. As a material having a high refractive index, a conventionally known material can be used. For example, an aromatic-containing compound such as a benzene structure, a bisphenol A structure, a melamine structure, a fluorene structure, or a high refractive index among aromatics. Examples thereof include condensed polycyclic aromatic compounds such as naphthalene structures considered as materials, metal-containing compounds such as metal oxides, compounds containing sulfur elements, and compounds containing halogen elements.

  Among these high refractive index materials, aromatic compounds that can contain a large amount of various compounds such as polyester resins are preferable from the viewpoint of maintaining adhesion to various functional layers such as a hard coat layer. In order to increase the refractive index more effectively, a condensed polycyclic aromatic compound is more preferable. From the viewpoint of increasing the refractive index while increasing the strength of the coating layer, a melamine compound is also preferably used. Furthermore, it is possible to use a metal-containing compound such as a metal oxide in order to increase the refractive index more effectively than the aromatic compound.

  Considering the applicability on the polyester film, the aromatic compound is preferably a polymer compound such as a polyester resin, an acrylic resin, or a urethane resin. In particular, it is more preferable from the viewpoint that more aromatic compounds can be introduced into the polyester resin, thereby increasing the refractive index.

  Among the aromatic compounds, the condensed polycyclic aromatic compound having a higher refractive index is, for example, naphthalene, anthracene, phenanthrene, naphthacene, benzo [a] anthracene, benzo [a] phenanthrene, pyrene, benzo [c] phenanthrene. And compounds having a structure such as perylene.

  As a method of incorporating the condensed polycyclic aromatic into the polyester resin, for example, two or more hydroxyl groups are introduced into the condensed polycyclic aromatic as a substituent to form a diol component or a polyvalent hydroxyl component, or There is a method in which two or more acid groups are introduced to prepare a dicarboxylic acid component or a polyvalent carboxylic acid component.

  In the laminated polyester film manufacturing process, the condensed polycyclic aromatic used for forming the coating layer is preferably a compound having a naphthalene structure in that it is difficult to be colored. In addition, a resin in which a naphthalene skeleton is incorporated as a polyester component is preferably used in terms of good adhesion to various functional layers formed on the coating layer and transparency. Representative examples of the naphthalene skeleton include 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and the like.

  In addition to the hydroxyl group and the carboxylic acid group, the condensed polycyclic aromatic has a refractive index of a refractive index by introducing a substituent containing a sulfur element, an aromatic substituent such as a phenyl group, a halogen element group, and the like. Improvements can be expected, and substituents such as alkyl groups, ester groups, amide groups, sulfonic acid groups, carboxylic acid groups, and hydroxyl groups may be introduced from the viewpoint of coating properties and adhesion.

  Further, as a metal-containing compound that can be expected as a material capable of effectively increasing the refractive index of the coating layer, a metal oxide having a high refractive index is preferably used, and a refractive index of 1.7 or more is used. Is preferred. Specific examples include, for example, zirconium oxide, titanium oxide, zinc oxide, tin oxide, antimony oxide, yttrium oxide, indium oxide, cerium oxide, ATO (antimony tin oxide), ITO (indium tin oxide), and the like. A metal oxide is mentioned. These may be used alone or in combination of two or more. Among these, zirconium oxide and titanium oxide are more preferably used. In particular, zirconium oxide is more preferably used from the viewpoint of weather resistance.

  The metal oxide is preferably used in the form of particles because there is a concern that the adhesion may be lowered depending on the use form, and the average particle size is preferably 100 nm or less from the viewpoint of coating appearance and transparency, More preferably, it is 50 nm or less, More preferably, it is the range of 25 nm or less.

  The coating layer design with a high refractive index for reducing interference unevenness due to reflection of external light after the above functional layer is formed is used not only for the second coating layer but also for the first coating layer. Can be incorporated into the design accordingly.

  When the second coating layer is used for an application where it is desired to reduce the occurrence of interference unevenness due to reflection of external light after the functional layer is formed, the refractive index is preferably adjusted. 55 to 1.65) is designed around the geometric mean of the refractive index of the base polyester film (1.60 to 1.70) and the refractive index of the functional layer such as the hard coat layer (1.45 to 1.65). Ideally. The refractive index of the coating layer and the reflectance of the coating layer are closely related. The absolute reflectivity on the second coating layer side when used for an application where it is desired to reduce the occurrence of interference unevenness, draws a graph showing the wavelength on the horizontal axis and the reflectivity on the vertical axis, and the minimum value of the reflectivity is 400 to 800 nm. Preferably, the minimum value is 4.0% or more. In the range of the absolute reflectance of the present invention, if the minimum value appears at the same wavelength, the reflectance of the minimum value is a high value when the refractive index is high, and a low value when the refractive index is low.

  The absolute reflectance described above preferably has one minimum value in the wavelength range of 400 to 800 nm, more preferably one minimum value in the wavelength range of 500 to 700 nm. The minimum value is preferably in the range of 4.0 to 6.5%, more preferably 4.5 to 6.2%. By designing within these ranges, interference unevenness after forming a functional layer such as a hard coat layer can be reduced, and the visibility of the film is improved.

  Moreover, various particles can also be used in the second coating layer of the present invention in order to impart slipperiness and prevent blocking. As the particles, in order to more effectively prevent slipping and blocking, it is preferable to use particles having an average particle size larger than the thickness of the coating layer.

  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.

  In the configuration of the laminated polyester film in the present invention, when using a technique containing particles in the first coating layer, the particles are usually 3 to 70% by weight as a ratio to the total nonvolatile components in the coating liquid forming the coating layer. The range is preferably 10 to 60% by weight, more preferably 15 to 50% by weight, still more preferably 20 to 40% by weight, and particularly preferably 30 to 40% by weight. By using in the above range, it is possible to effectively adjust the haze.

  As a ratio with respect to all the non-volatile components in the coating liquid which forms the 1st coating layer which comprises the laminated polyester film in this invention, Preferably a polymer is 10-90 weight%, More preferably, it is 15-80 weight%, More preferably It is in the range of 30 to 70% by weight. By using it in the above range, it is effective for good coating appearance and prevention of falling off of particles.

  As a ratio with respect to all the non-volatile components in the coating liquid which forms the 1st coating layer which comprises the laminated polyester film in this invention, Preferably a crosslinking agent is 80 weight% or less, More preferably, it is the range of 5-70 weight%, Furthermore, Preferably it is the range of 10 to 50 weight%. By using in the said range, it becomes a favorable application | coating external appearance and a firm coating layer. In particular, when it is desired to strengthen the coating layer, it is preferable to use a melamine compound in combination, and a preferable range thereof is 3 to 30% by weight, and more preferably 5 to 20% by weight.

  As a ratio with respect to all the non-volatile components in the coating liquid which forms the 2nd coating layer which comprises the laminated polyester film in this invention, Preferably a polyester resin or an acrylic resin is 10 weight% or more, More preferably, it is 15 to 95 weight%. The range is more preferably 30 to 90% by weight. By using in the said range, adhesiveness with a functional layer will become favorable. However, since acrylic resin generally has a low refractive index, acrylic resin is preferably in the range of 30% by weight or less, more preferably in the range of 20% by weight or less in applications where it is desired to reduce the occurrence of interference unevenness. .

  When used in applications where it is desired to reduce the occurrence of interference unevenness, the compound having a condensed polycyclic aromatic that can be used in the coating layer is preferably 5 to 80% by weight of the condensed polycyclic aromatic in the compound. %, More preferably in the range of 10 to 60% by weight. Further, the content of the compound having a condensed polycyclic aromatic is preferably in the range of 5 to 90% by weight, more preferably in the range of 10 to 80 as a ratio with respect to all the non-volatile components in the coating liquid for forming the second coating layer. It is in the range of wt%, more preferably in the range of 10 to 70 wt%. By using within these ranges, the refractive index of the coating layer can be easily adjusted, and interference unevenness after forming a functional layer such as a hard coat layer can be easily reduced. The ratio of the condensed polycyclic aromatic can be determined by, for example, dissolving and extracting the coating layer with an appropriate solvent or warm water, separating by chromatography, analyzing the structure by NMR or IR, and further pyrolyzing GC-MS (gas It can be determined by analyzing by chromatography mass spectrometry) or optical analysis.

  When used in applications where it is desired to reduce the occurrence of interference unevenness, the metal oxide is preferably in the range of 3 to 70% by weight, more preferably 5 to 5% as a ratio to the total nonvolatile components in the coating liquid for forming the second coating layer. It is in the range of 50% by weight, more preferably in the range of 8-40% by weight. By using within these ranges, the refractive index of the coating layer can be easily adjusted, and interference unevenness after forming a functional layer such as a hard coat layer can be easily reduced.

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

  Regarding the formation of the coating layer, the above-described series of compounds is used as a solution or solvent dispersion, and the coating solution adjusted with a solid content concentration of about 0.1 to 80% by weight as a guide is laminated on the polyester film. It is preferred to produce a polyester film. In particular, when the coating layer is provided by in-line coating, an aqueous solution or a water dispersion is more preferable, but a small amount of an organic solvent is added to the coating solution for the purpose of improving the dispersibility in water and improving the film forming property. You may contain. Moreover, only one type of organic solvent may be used, and 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 usually in the range of 0.001 to 1 μm, preferably 0.01 to 0.5 μm, more preferably 0.03 to 0.2 μm. Among them, in the case of the first coating layer, it is more preferably 0.08 to 0.2 μm, particularly preferably 0.10 to 0.20 μm. When the film thickness is out of the above range, the coating appearance may deteriorate and the adhesion with the functional layer may deteriorate. Moreover, when using for the use which wants to reduce generation | occurrence | production of interference nonuniformity, the film thickness of a 2nd application layer becomes like this. Preferably it is 0.05-0.20 micrometers, More preferably, it is the range of 0.07-0.15 micrometer.

  In the case of the method of forming surface irregularities on the coating layer using particles, the relationship between the average particle diameter of the particles and the film thickness of the coating layer is preferably 1.0 as the average particle diameter / film thickness of the coating layer. The above range, more preferably in the range of 1.2 to 20, more preferably in the range of 1.5 to 15, particularly preferably in the range of 1.7 to 10. By using in the said range, it can increase in haze as a laminated polyester film provided with the coating layer, and haze reduction after providing a functional layer can be performed effectively. In addition, it is possible to contribute to preventing the particles from falling off the coating layer.

  In the film of the present invention, as a method for forming the coating layer, for example, gravure coating, reverse roll coating, die coating, air doctor coating, blade coating, rod coating, bar coating, curtain coating, knife coating, transfer roll coating, squeeze Conventionally known coating methods such as coating, impregnation coating, kiss coating, spray coating, calendar coating, extrusion coating, etc. 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, it is usually 3 to 40 at 80 to 200 ° C. The heat treatment may be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when the coating layer is provided by in-line coating, heat treatment is usually performed at 70 to 270 ° C. for 3 to 200 seconds as a guide.

  Further, irrespective 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 required. 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 haze reduction amount by forming the functional layer on the first coating layer of the polyester film of the present invention is essential to be 1.0% or more, preferably 3.0% or more, more preferably 5. The range is 0% or more, more preferably 8.0% or more, and particularly preferably 10% or more. By setting the above range, it becomes easy to distinguish between processing / unprocessed functional layers according to various places such as a conference room, a work room, an inspection room, and a film view.

  The haze of the polyester film of the present invention is not particularly limited, but is preferably 3.0% or more. When adjusting the haze with particles, the appearance of the film depends on the type and size of the particles used and the state of the substrate, so it cannot be said unconditionally, but the distinction between processed and unprocessed functional layers can be made. In order to make it easier to apply, it is preferably more than 5.0%, more preferably more than 10%, and still more preferably more than 15%. In the scope of the present invention, it has been found that even if the haze value is the same, the smaller the average particle diameter of the particles, the more apparent haze value becomes whitish, and the distinction between functional layer processing and unprocessed I found that is easier to put.

  In the polyester film of the present invention, a functional layer is generally formed on the coating layer. As a functional layer, it is a layer provided in order to provide various functions, such as a hard-coat layer, a light-diffusion layer, a prism layer, a micro lens layer, an ink layer, an adhesive layer, an adhesive bond layer, for example. The functional layer is not particularly limited as long as the haze is lowered when formed on the coating layer, but usually the haze is preferably not so high, and the haze of only the functional layer is preferably 8.0% or less, More preferably, it is 3.0% or less, More preferably, it is 1.0% or less, Most preferably, it is 0.5% or less of range. Similarly, the thickness of the functional layer is not particularly limited as long as the haze decreases when formed on the coating layer, but is preferably 0.1 to 50 μm, more preferably 1 to 15 μm, and still more preferably 1 to 1 μm. The range is 8 μm.

  As an example of the functional layer, for example, in the case of a hard coat layer, the material to be used is not particularly limited. For example, reactive silicon compounds such as monofunctional (meth) acrylate, polyfunctional (meth) acrylate, and tetraethoxysilane And the like. Among these, from the viewpoint of achieving both productivity and hardness, a polymerization cured product of a composition containing an active energy ray-curable (meth) acrylate is particularly preferable.

  The composition containing the active energy ray-curable (meth) acrylate is not particularly limited. For example, a mixture of one or more known active energy ray-curable monofunctional (meth) acrylates, bifunctional (meth) acrylates, polyfunctional (meth) acrylates, and commercially available as an active energy ray-curable hard coat resin material In addition, those other than these may be used as long as the object of the present embodiment is not impaired.

  The active energy ray-curable monofunctional (meth) acrylate is not particularly limited. For example, methyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) ) Acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, alkyl (meth) acrylate such as isobornyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, etc. Alkyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, ethoxypropyl (meth) acrylate, etc. Amino group-containing (meth) acrylates such as xylalkyl (meth) acrylate, benzyl (meth) acrylate, aromatic (meth) acrylate such as phenoxyethyl (meth) acrylate, diaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, Methoxyethylene glycol (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, ethylene oxide modified (meth) acrylate such as phenylphenol ethylene oxide modified (meth) acrylate, glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, Examples include (meth) acrylic acid.

  The active energy ray-curable difunctional (meth) acrylate is not particularly limited, and for example, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6- Hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, alkanediol di (meth) acrylate such as tricyclodecane dimethylol di (meth) acrylate, bisphenol A ethylene oxide modified di (meth) acrylate Bisphenol F ethylene oxide modified di (meth) acrylate and other bisphenol modified di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, urethane di (meth) acrylate And epoxy di (meth) acrylate.

  The active energy ray-curable polyfunctional (meth) acrylate is not particularly limited, and examples thereof include dipentaerythritol hexa (meth) acrylate, pentaerythritol tetra (meth) acrylate, and ditrimethylolpropane tetra (meth) acrylate. , Pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, isocyanuric acid ethylene oxide modified tri (meth) acrylate, ε-caprolactone modified tris (acryloxyethyl) isocyanurate Acrylate, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urea Down prepolymers, urethane acrylates such as dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, and the like.

  In addition, since the functional layer such as the hard coat layer has a high refractive index of the polyester film serving as the base material, it may be preferable to design it high in order to reduce interference unevenness in some cases. In the present invention, it is suitable for making a functional layer such as a hard coat layer formed on the second coating layer a layer having a higher refractive index than on the first coating layer because of the design for reducing interference unevenness. Yes. One method for increasing the refractive index is to use a metal oxide. As the metal oxide, a conventionally known metal oxide can be used. For example, zirconium oxide, titanium oxide, tin oxide, acid value yttrium, antimony oxide, indium oxide, zinc oxide, antimontin oxide, indium tin oxide Etc. Among these, zirconium oxide is preferable in consideration of environmental aspects, weather resistance, and price.

  Other components contained in the composition containing the active energy ray-curable (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. In addition, when the film is dried after film formation in the wet coating method, an arbitrary amount of solvent can be added.

  As a method for forming a functional layer such as a hard coat layer, a general wet coat method such as a roll coat method or a die coat method is employed when an organic material is used. 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. The refractive index of the functional layer formed on the coating layer is generally 1.45 to 1.65 as described above.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement method and evaluation method used in the present invention are 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 diameter The coating layer was observed using TEM (H-7650 manufactured by Hitachi High-Technologies Corporation, acceleration voltage 100V), and the average value of the particle diameters of 10 particles was defined as the average particle diameter. .

(3) Method for measuring 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). The film thickness was measured at a location not including the particle portion.

(4) Measuring method of haze It measured by JISK7136 using the haze meter HM-150 by Murakami Color Research Laboratory.

(5) Method for measuring haze reduction when functional layer is formed on first coating layer As functional layer, 80 parts by weight of dipentaerythritol hexaacrylate, 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, light A mixed coating solution of 5 parts by weight of a polymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) and 200 parts by weight of methyl ethyl ketone was applied on the first coating layer so as to have a dry film thickness of 2 μm. Is applied to form a hard coat layer (the haze of the layer is 0.1%), the haze is measured by the method according to (4), and from the haze of the laminated polyester film before forming the functional layer The difference was calculated.

(6) Discrimination evaluation method before and after functional layer processing The difference between the 20 cm × 20 cm film before and after forming the functional layer of (5) was observed. As a method of observation, assuming a conference room, work room, and inspection room, a film and a functional layer on which a functional layer is not formed are formed on a white desk, a green cutter mat, and a black desk, respectively. The difference was observed when the film was placed and observed from directly above and from a location 1 m away at an angle of 30 degrees. 5 points if the difference can be discriminated instantaneously, 4 points if it can be easily discriminated by observation for 3 seconds, 3 points if it can be discriminated if you look carefully, 2 points if it is difficult to discriminate, 1 point if it cannot be discriminated did. A higher score is preferable, and it is ideal that there are three or more points when observed from right above or obliquely under any of the three conditions.

(7) Method for evaluating adhesion of first coating layer 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.) A mixed coating solution of 5 parts by weight and 200 parts by weight of methyl ethyl ketone was applied so as to have a dry film thickness of 2 μm, and cured by irradiating with ultraviolet rays to form a hard coat layer. The obtained film was subjected to 10 × 10 cross-cut after 50 hours in an environment of 80 ° C. and 90% RH, and a tape of 18 mm width (cello tape (registered trademark) CT manufactured by Nichiban Co., Ltd.) was formed thereon. -18) is attached and the peeled surface is observed after abrupt peeling at a 180 ° peel angle. If the peeled area is less than 5%, ◎ if it is 5% or more but less than 10%, ○, 10% or more and 50%. If it was less than △, it was marked as x if it was 50% or more.

(8) Evaluation method of strength of first coating layer The surface of the coating layer was rubbed three times with a finger pad around which AELIEL (registered trademark) soft wipe S220 manufactured by Daio Paper Co., Ltd. was wound, and the surface was observed. The case where the scraped area of the coating layer was less than 10% was evaluated as ◯, the case where it was 10% or more and less than 50% was evaluated as Δ, and the case where it was 50% or more was evaluated as ×.

(9) Evaluation method of absolute reflectance from the surface of the second coating layer in the 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, and a spectrophotometer (JASCO Corporation) Using UV-Vis spectrophotometer V-570 and automatic absolute reflectance measuring device ARM-500N), synchronous mode, incident angle 5 °, N-polarized light, response Fast, data collection interval 1.0 nm, bandwidth 10 nm The absolute reflectance in the wavelength range of 400 to 800 nm was measured on the coating layer surface at a scanning speed of 1000 m / min, and the wavelength (bottom wavelength) and reflectance at the minimum value were evaluated.

(10) Interference unevenness evaluation method On the second coating layer of the polyester film, as a functional layer, 77 parts by weight of dipentaerythritol hexaacrylate, 18 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, 5 parts by weight of zirconium oxide, A mixed coating solution of 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 is applied so as to have a dry film thickness of 2 μm, and cured by irradiation with ultraviolet rays. A hard coat layer (the haze of the layer is 0.2%) was formed. The obtained film is visually observed under a three-wavelength fluorescent lamp, and interference unevenness is observed. If the interference unevenness is not confirmed, ◎, thin sparse interference unevenness is confirmed, thin, linear The case where the interference unevenness was confirmed was indicated by Δ, and the case where clear interference unevenness was confirmed was indicated by ×.

(11) Evaluation Method of Adhesion of Second Coating Layer After 50 hours in an environment of 80 ° C. and 90% RH with respect to the film on which the hard coat layer obtained by the evaluation of (10) is formed, 10 × 10 crosscuts, 18mm wide tape (Cellotape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) is applied on it, and the peeled surface is observed after abrupt peeling at a 180 degree peel angle. When the peeled area is less than 5%, ◎ is 5% or more and less than 10%, ◯ is 10% or more and less than 50%, and Δ is 50% or more.

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 resulting polyester, and 100 ppm of magnesium acetate tetrahydrate with respect to the resulting polyester as the catalyst at 260 ° C. in a nitrogen atmosphere at 260 ° C. 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 0.3 kPa in absolute pressure, 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)>
In the production method of polyester (A), polyester (C) 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.
(Example compounds)
・ Particles: (IA) Silica particles with an average particle size of 0.15 μm ・ Particles: (IB) Silica particles with an average particle size of 0.30 μm ・ Particles: (IC) Silica particles with an average particle size of 0.45 μm

・ Polyester resin: (IIA)
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: (IIB)
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%)

Acrylic resin: (IIC) Aqueous dispersion of acrylic resin polymerized with the following composition: ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (% by weight) Emulsion polymer (emulsifier: anionic surfactant)

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

Epoxy compound: (IIIB) polyglycerol polyglycidyl ether

・ Isocyanate compounds: (IIIC)
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.

・ Carbodiimide compounds: (IIID)
Polycarbodiimide compound Carbodilite (carbodiimide equivalent = 600, manufactured by Nisshinbo Co., Ltd.)

Melamine compound: (IIIE) hexamethoxymethylol melamine

Metal oxide: (IV) Zirconium oxide particles with an average particle size of 15 nm

Example 1:
A mixed raw material in which polyesters (A), (B), and (C) were mixed in proportions of 91%, 3%, and 6%, respectively, was used as a raw material for the outermost layer (surface layer), and polyesters (A) and (B) were each 97 %, 3% of the mixed raw material is used as an intermediate layer raw material, each is supplied to two extruders, melted at 285 ° C., and then on a cooling roll set at 40 ° C. Coextruded with a layer structure of layers (surface layer / intermediate layer / surface layer = 1: 18: 1 discharge amount) and cooled and solidified to obtain an unstretched sheet.
Next, the film was stretched 3.4 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating solution A1 shown in Table 1 below was applied to one side of the longitudinally stretched film with the film thickness (dried) (After) is applied so as to be 0.11 μm (first coating layer), and coating liquid B1 is applied to the opposite surface so that the thickness of the coating layer (after drying) is 0.10 μm (second) The coated layer was led to a tenter, stretched 4.0 times in the transverse direction at 120 ° C., heat treated at 225 ° C., and then relaxed 2% in the transverse direction to obtain a polyester film having a thickness of 125 μm.

  When the obtained polyester film was evaluated, the haze was as high as 9.1%, the haze reduction amount of the first coating layer was 8.2%, and a film having no functional layer and a functional layer were formed. The distinguishability from the film was good. Moreover, the adhesiveness of the 2nd application layer was also favorable. The properties of this film are shown in Tables 2 and 3 below.

Examples 2-128:
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 Tables 2 to 9, the finished polyester film had good discrimination between the film in which the functional layer was not formed and the film in which the functional layer was formed, and the adhesiveness of the second coating layer was also good.

Comparative Example 1:
In Example 1, it manufactured similarly to Example 1 except having not provided the application layer, and obtained the polyester film. When the completed polyester film was evaluated, as shown in Tables 10 and 11 below, the results were inferior in discriminability between the film in which the functional layer was not formed and the film in which the functional layer was formed. Also, the adhesion was a bad result.

Comparative Examples 2-4:
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 completed polyester film was evaluated, as shown in Tables 10 and 11 below, the discriminability between the film in which the functional layer was not formed and the film in which the functional layer was formed was not sufficient.

  The film of the present invention is suitably used for applications where it is desired to easily distinguish between processed and unprocessed functional layers in applications that form functional layers such as hard coat layers such as transparent electrodes such as touch panels and molding films. can do.

Claims (4)

When the functional layer is formed on one surface of the polyester film, the coating layer is formed with particles having an average particle size of 0.01 to 1.0 μm, the haze value being decreased by 1.0% or more. It has a coating layer that is contained in the range of 3 to 70% by weight as a ratio to the total nonvolatile components in the coating solution, and the film thickness is in the range of 0.001 to 1 μm, on the side opposite to the coating layer of the polyester film. the surface, the laminated polyester film have a coating layer containing a polyester resin or an acrylic resin, wherein the haze value is 3.0% or more. The laminated polyester film according to claim 1, wherein the haze value of the functional layer is 8.0% or less. The absolute reflectance of the coating layer containing the polyester resin or acrylic resin has one minimum value in the wavelength range of 400 to 800 nm, and the absolute reflectance at the minimum value is in the range of 4.0 to 6.5%. The laminated polyester film according to claim 1 or 2 . The laminated polyester film according to any one of claims 1 to 3 , further comprising a metal oxide in a coating layer containing a polyester resin or an acrylic resin.