JP2015150796A - laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film which has various functional layers such as a hard coat layer formed therein, and thereby greatly reduces a haze and can be suitably used for an application to easily discriminate whether the functional layers are processed or unprocessed; and for instance, can be suitably used for a member such as a backlight unit of a liquid crystal display, a hard coat layer, a sticking prevention layer, a prism layer, a microlens layer, and a light diffusion layer.SOLUTION: A laminated polyester film has coating layers on both surfaces thereof. An absolute value of a difference between haze reduction amounts when functional layers are formed on each of the coating layers is 1.0% or more.

Description

  The present invention relates to a laminated polyester film, for example, in an application for forming a functional layer such as a backlight unit of a liquid crystal display, a prism layer, a microlens layer, a hard coat layer, a sticking prevention layer, a light diffusion layer, etc. The present invention relates to a laminated polyester film suitable for easily distinguishing between processing and unprocessed functional layers.

  In recent years, polyester films have been used in various applications such as liquid crystal display members such as prism sheets, microlens sheets, hard coat films, antireflection films, light diffusion sheets, and electromagnetic wave shielding 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.

  Furthermore, when the transparency of the film is high, when the functional layer is processed on both sides, it becomes difficult to distinguish which side is processed, and there is a possibility that the surface is mistaken.

  As a transparent base film for forming various functional layers such as a prism layer, a hard coat layer and a light diffusion layer, a polyester film is generally used in consideration of transparency and mechanical properties. In order to improve adhesion to various functional layers, an easily adhesive coating layer is generally provided as the intermediate layer.

JP 2007-55222 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is, for example, in an application of forming a functional layer such as a hard coat layer, an anti-sticking layer, a prism layer, a microlens layer, and a light diffusion layer. An object of the present invention is to provide an excellent laminated polyester film in order to easily distinguish between functional and processed layers.

  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 polyester film has a coating layer on both surfaces, and the absolute value of the difference in haze reduction when the functional layer is formed on each coating layer is 1.0% or more. The feature resides in a laminated polyester film.

  According to the laminated polyester film of the present invention, by forming various functional layers such as a hard coat layer, an anti-sticking layer, a prism layer, a microlens layer, a light diffusion layer, the haze is greatly reduced, It is possible to provide a base film capable of easily distinguishing the raw material, and to provide a base film capable of discriminating on which side the functional layer is provided. 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, it is essential that the absolute value of the difference in haze reduction amount is 1.0% or more when the polyester film has a coating layer on both surfaces and a functional layer is formed on each coating layer. It is what. Hereinafter, unless otherwise specified, the case where the haze reduction amount when the functional layer is formed is referred to as the first coating layer, and the case where the haze reduction amount when the functional layer is formed is referred to as the second coating layer. There is.

  The coating layer of the present invention distinguishes between processed and unprocessed functional layers by reducing the haze after forming functional layers such as hard coat layers, anti-sticking layers, prism layers, microlens layers, and light diffusion layers. It is designed to make it easier. In the present invention, it has a coating layer on both sides of the polyester film, but by adjusting the haze reduction amount when a functional layer is formed on the coating layer, it functions on either side. It is possible to determine whether a layer is provided. It has been found that if the absolute value of the difference in haze reduction amount is 1.0% or more, the film can be distinguished.

  In order to reduce the haze 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. In addition, a metal oxide is also preferable in that it has a large refractive index difference from the polymer used to hold the particles in the coating layer, thereby increasing light scattering and increasing haze.

  The average particle size of the particles used in the coating layer cannot be generally described because it depends on the thickness of the coating layer, but is generally 0.01 to 1.0 μm, preferably 0.05 to 0.8 μm. More preferably, it is 0.1-0.7 micrometer, Most preferably, it is the range of 0.2-0.5 micrometer. In particular, it is preferable that the average particle size of the particles used in the first coating layer is larger than the average particle size of the particles used in the second coating layer. Among the ranges described above, the range of 0.3 to 0.5 μm is particularly preferable. On the other hand, the average particle size of the particles used for the second coating layer is particularly preferably in the range of 0.05 to 0.2 μm, within the above-mentioned range.

  In order to retain particles in the 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 or a prism layer and improving the appearance of coating. In view of compatibility with the polyester film of the base material, a polyester resin is more preferable, and from the viewpoint that adhesion with a functional layer such as a hard coat layer or a prism layer is further improved, an acrylic resin or a urethane resin is used. In particular, urethane resin is preferable.

  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, and is usually produced by a reaction between a polyol and an isocyanate. Examples of the polyol include polyester polyols, polycarbonate polyols, polyether polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

  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.) and those having derivative units of lactone compounds such as polycaprolactone.

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.

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

  Among the above polyols, polyester polyols and polycarbonate polyols are more preferably used in order to improve the adhesion to various functional layers.

  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 urethane resin, the 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.

  In the coating layer of the present invention, a polymer containing a carbon-carbon double bond can be used in order to further improve the adhesion with various functional layers that can be formed on the coating layer. From the viewpoint of improving adhesion, examples of the polymer containing a carbon-carbon double bond include a urethane resin, an acrylic resin, and a polyester resin. Further, from the viewpoint of introducing a stable carbon-carbon double bond, a urethane resin is more preferable, and among them, a polyester-based urethane resin formed from a polyester polyol and a polycarbonate-based urethane resin formed from a polycarbonate polyol are particularly preferable. Is preferred. The effect is particularly great when the functional layer is active energy ray curable. The coating layer contains a carbon-carbon double bond, and the carbon-carbon double bond of the compound used for forming the prism layer, the microlens layer, the hard coat layer, or the like is irradiated with active energy rays. It can be reacted to form a covalent bond, thereby improving adhesion.

  The coating layer formed from the polymer containing a carbon-carbon double bond is usually a solvent-free active energy ray-curable composition, such as a prism layer or a microlens layer, among functional layers. It is optimal for improving the adhesion with a functional layer that is generally formed from Particularly in recent years, there is a trend toward lower power consumption, and it is necessary to improve the brightness of the prism sheet and microlens sheet as compared with the prior art. Therefore, the materials used for the prism layer and microlens layer are made to have a higher refractive index. There is a tendency. In order to increase the refractive index of these functional layers, a technique using a compound containing a large amount of aromatics has been taken. However, on the other hand, when the aromatic content is increased, there is a problem that the adhesiveness with the coating layer is lowered due to the small interaction. Therefore, there is a demand for a laminated polyester film having a coating layer that can sufficiently ensure adhesion even in a design with a high aromatic content, a high refractive index, that is, a high brightness.

  The urethane resin containing a carbon-carbon double bond is one having a carbon-carbon double bond in a urethane resin, and contained in a compound that forms a prism layer, a microlens layer, a hard coat layer, or the like. Any conventionally known material can be used as long as it reacts with a carbon-carbon double bond. For example, introduction into a urethane resin in the form of an acrylate group, a methacrylate group, a vinyl group, an allyl group or the like can be mentioned.

  Various substituents can be introduced into the carbon-carbon double bond, such as an alkyl group such as a methyl group or an ethyl group, a phenyl group, a halogen group, an ester group, an amide group, or a conjugated double bond. You may have such a structure. Further, the amount of the substituent is not particularly limited, and any of a 1-substituted product, a 2-substituted product, a 3-substituted product, or a 4-substituted product can be used. A 2-substituted product is preferable, and a 1-substituted product is more preferable.

  Considering the ease of introduction into the urethane resin and the reactivity with the carbon-carbon double bond contained in the compound forming the prism layer, microlens layer, hard coat layer, etc., an acrylate group or a methacrylate group is preferable, An acrylate group and a methacrylate group having no group are more preferable, and an acrylate group having no substituent is particularly preferable.

  The ratio of the carbon-carbon double bond part (C = C part, molecular weight 24) to the whole urethane resin is preferably 0.5% by weight or more, more preferably 1.0% by weight or more, and further preferably 1 .5% by weight or more. When the ratio of the carbon-carbon double bond portion to the entire resin is 0.5% by weight or more, adhesion to a prism resin, a microlens resin, a hard coat resin, or the like is effectively improved.

  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, especially oxazoline compounds and epoxy compounds, oxazoline compounds and isocyanate compounds, oxazoline compounds and carbodiimide compounds, It has been found that the adhesion is markedly improved when used in combination with an isocyanate compound and a carbodiimide compound. 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.

  A carbodiimide-based compound is a compound having a carbodiimide structure, and is used to improve adhesion with various surface functional layers that can be formed on a coating layer and to improve the heat and humidity resistance of the coating layer. is there. The carbodiimide compound 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.

  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. Moreover, when using the method containing particle | grains in a 2nd application layer, as a ratio with respect to all the non-volatile components in the coating liquid which forms an application layer, particle | grains are 3 to 70 weight% normally, Preferably it is 5 to 50 weight%. More preferably, it is in the range of 10 to 40% by weight.

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

  As a ratio with respect to all the non-volatile components in the coating liquid which forms the 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%, More preferably It is in the range of 10 to 50% by weight. Use within the above range is effective in improving the appearance of a good coating and improving adhesion with a strong coating layer or functional 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.

  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. By using the film thickness within the above range, good coating appearance and adhesion with the functional layer can be ensured.

  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, the heat treatment is usually performed at 70 to 270 ° C. for 3 to 200 seconds. good.

  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 absolute value of the difference in haze reduction when the functional layer is formed on each coating layer of the polyester film of the present invention must be 1.0% or more, preferably 3.0% or more. Preferably it is 5.0% or more, More preferably, it is 8.0% or more, Most preferably, it is 10% or more of range. By setting the above range, it becomes easy to distinguish whether the functional layer is formed on which side of the first coating layer or the second coating layer.

  The amount of haze reduction by forming a functional layer on the first coating layer of the polyester film of the present invention is 1.0% or more, preferably 3.0% or more, more preferably 5.0% or more, Preferably it is 8.0% or more, Especially preferably, it is 10% or more of range. 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 the functional layer, for example, a hard coat layer, an anti-sticking layer, a light diffusion layer, a prism layer, a microlens layer, an ink layer, a pressure-sensitive adhesive layer, an adhesive layer, and the like are provided for imparting various functions. That is. The functional layer is not particularly limited as long as the haze is lowered when it is formed on the first coating layer. Usually, the haze is preferably not so high, and the haze of only the functional layer is preferably 8. It is 0% or less, more preferably 3.0% or less, still more preferably 1.0% or less, and particularly preferably 0.5% or less. 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.

  In the present invention, as one of the preferred forms of film use, for example, the functional layer formed on the first coating layer having a large amount of haze reduction due to the functional layer formation is relatively hard, such as a hard coat layer or an anti-sticking layer. The functional layer formed on the second coating layer, which is a highly transparent functional layer and has a relatively small haze reduction amount due to the functional layer formation, is usually more difficult to ensure adhesion, such as a prism layer or a microlens layer. And a solvent-free active energy ray-curable resin layer used in the above. By adopting such a configuration, for example, the first coating layer side is specialized to be a high haze coating layer in order to place importance on processed / unprocessed discrimination, and the second coating layer side is closely attached. It is possible to specialize in forming a coating layer that improves adhesion to a functional layer for which it is difficult to ensure the properties, and a film with higher performance and efficiency can be obtained.

  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 aromatic (meth) acrylates such as coxyalkyl (meth) acrylate, benzyl (meth) acrylate, 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.

  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.

  In addition, as an example of a solventless active energy ray-curable resin layer that is a functional layer, a prism layer has recently been proposed in various shapes in order to efficiently improve luminance. Is a parallel arrangement of prism rows having a triangular cross section. Similarly, various shapes of the microlens layer have been proposed, but in general, a large number of hemispherical convex lenses are provided on the film. Any layer can have a conventionally known shape.

  Examples of the shape of the prism layer include a triangular cross section having a thickness of 10 to 500 μm, a pitch of prism rows of 10 to 500 μm, and an apex angle of 40 ° to 100 °. Examples of the shape of the microlens layer include a hemispherical shape having a thickness of 10 to 500 μm and a diameter of 10 to 500 μm, but may have a shape such as a cone or a polygonal pyramid.

  The prism layer and the microlens layer are generally composed of an active energy ray-curable compound that is solvent-free (the solvent content is 5% by weight or less, more preferably 3% by weight or less, and even more preferably no solvent is contained). It is formed. The hard coat layer is generally formed from a solvent-based active energy ray-curable compound.

  Examples of the compound that forms the prism layer and the microlens layer include the compounds used in the formation of the hard coat layer described above. Furthermore, in order to increase the brightness, it is preferable to use a material that can increase the refractive index.

  The refractive index of the prism layer and the microlens layer for increasing the brightness is preferably 1.57 or more. In the laminated polyester film of the present invention, the higher the refractive index, the more the luminance tends to improve. In the present invention, the refractive index of the polyester film is around 1.65. Therefore, the refractive index range of the active energy ray-curable resin layer such as the prism layer or the microlens layer is usually 1.57 to 1.65, Preferably it is 1.58-1.64, More preferably, it is the range of 1.59-1.63. By setting it within the above range, the luminance can be increased.

  In order to make the refractive index within the above range, a method using a compound having a large aromatic structure, a sulfur atom, a halogen atom, or a metal compound in addition to the general compound described above can be used. Among them, a method using a compound having a large aromatic structure or a sulfur atom is particularly preferable from the viewpoint of the environment because the refractive index of the prism layer and the microlens layer can be made uniform.

  Examples of the compound having a large aromatic structure include condensed polycyclic aromatic structures such as naphthalene, anthracene, phenanthrene, naphthacene, benzo [a] anthracene, benzo [a] phenanthrene, pyrene, benzo [c] phenanthrene, and perylene. , A compound having a biphenyl structure, a compound having a fluorene structure, and the like.

  Various substituents may be introduced into the condensed polycyclic aromatic structure, biphenyl structure, and fluorene structure. Particularly, those having a benzene ring-containing substituent such as a phenyl group have a higher refractive index. Since it can be made high, it is preferable. It is also possible to introduce atoms that increase the refractive index, such as sulfur atoms and halogen atoms. Furthermore, various functional groups such as an ester group, an amide group, a hydroxyl group, an amino group, and an ether group can be introduced in order to improve the adhesion with the coating layer.

  The total of the condensed polycyclic aromatic structure, the biphenyl structure, the fluorene structure and the aromatic compound substituted in these structures in the active energy ray-curable resin layer in the film of the present invention is the type and amount of other structures, or Since it depends on the curing condition, it cannot be generally stated, but it is preferably 20 to 80% by weight, more preferably 25 to 70% by weight, still more preferably 30 to 60% by weight, based on the entire ultraviolet curable resin layer. It is a range. By using in the above range, it is possible to form a functional layer with high luminance.

  The ratio of the compound having a condensed polycyclic aromatic structure, biphenyl structure, and fluorene structure forming the active energy ray-curable resin layer in the film of the present invention is the total nonvolatile content of the compound composition forming the active energy ray-curable resin layer. As a ratio with respect to a component, it is 10 weight% or more normally, Preferably it is 20 to 90 weight%, More preferably, it is the range of 25 to 80 weight%. By using in the above range, it is possible to form a functional layer with high luminance.

  As an example of the functional layer, the anti-sticking layer and the light diffusion layer contain particles and a binder. The anti-sticking layer contains the same binder and particles as the light diffusion layer, and the content of the particles is not intended to be light diffusive. Therefore, a method of containing a smaller amount with a smaller particle size is generally used. It is.

  As particles to be included in the anti-sticking layer and the light diffusion layer, conventionally known particles can be used. Organic particles such as acrylic resin, acrylic urethane resin, urethane resin, polyester resin, and polyvinyl resin, silica, metal oxide And inorganic particles such as barium sulfate can be used. Of these, acrylic resins and acrylic urethane resins having good transparency are preferably used. The particle size of these particles is not particularly limited, but is 1 to 50 μm, more preferably 1 to 10 μm as an average particle size.

  The binder contained in the anti-sticking layer or the light diffusion layer is used to fix the particles. For example, polyester resin, acrylic resin, polyurethane resin, fluororesin, silicone resin, epoxy resin, the above-described hard coat layer Examples thereof include active energy ray-curable resins similar to those used for the formation of. In consideration of processability, a polyol compound is preferably used, and examples thereof include acrylic polyol and polyester polyol.

  When a polyol compound is used as a binder, it is preferable to contain isocyanate as a curing agent. By containing isocyanate, a stronger crosslinked structure can be formed, and the physical properties as a functional layer are improved. Further, when an ultraviolet curable resin is used as the binder, an acrylate resin is preferable, which can be used for improving the hardness of the functional layer.

  If necessary, the anti-sticking layer and the light diffusion layer may contain a surfactant, a fine inorganic filler, a plasticizer, a curing agent, an antioxidant, an ultraviolet absorber, a rust inhibitor, and the like.

  The mixing ratio of the binder and the particles in the anti-sticking layer and the light diffusion layer can be appropriately set depending on the characteristics to be obtained, and is not particularly limited. For example, the binder / particles are 0.1 to 50 by weight ratio. The range is more preferably 0.5 to 20.

  Examples of the method for forming the anti-sticking layer and the light diffusion layer include a method in which a coating liquid containing a binder and particles is prepared, applied and dried. As a coating method, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, spray coating, spin coating or the like can be used. The thickness of the anti-sticking layer or the light diffusion layer is not particularly limited, but it is in the range of 1 to 100 μm, more preferably in the range of 1 to 30 μm in consideration of light diffusibility, film strength, and the like.

  Analysis of the components of the functional layer can be performed by analysis such as TOF-SIMS, ESCA, fluorescent X-ray, and NMR.

  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) Weight of carbon-carbon bond part in polymer After drying the polymer under reduced pressure, each peak of ¹ H and ¹³ C was assigned using NMR (AVANCE III600 manufactured by Bruker Biospin) and obtained by calculation.

(4) 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.

(5) Refractive Index Measurement Method An active energy ray-curable composition used for forming the functional layer of (11) below is placed flat on the coating layer side with a film thickness of 10 μm, cured with ultraviolet rays, and flat active energy. A line curable resin layer was formed. The refractive index on the active energy ray-curable resin layer side was measured using a refractometer (SL-NA-B manufactured by Atago Co., Ltd.).

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

(7) Method for measuring haze reduction when functional layer is formed on first coating layer As functional layer, resin (Nippon Catalysts Hals Hybrid UV-G301) 100 parts by mass, isocyanate (manufactured by Sumika Bayer Urethane, Desmodule N-3200) 10 parts by mass, 3 parts by mass of acrylic resin particles (MBX-15 manufactured by Sekisui Plastics Co., Ltd.) having an average particle size of 5 μm, 100 parts by mass of toluene, and 100 parts by mass of methyl ethyl ketone are prepared and applied and heat cured. As a result, a film on which a sticking prevention layer having a thickness of 3 μm (the haze of the layer is 0.4%) was obtained. The haze was measured by the method according to (6), and the difference from the haze of the laminated polyester film before forming the functional layer was calculated.

(8) Discriminability evaluation method before and after functional layer processing on first coating layer (discriminability 1)
The difference between the 20 cm × 20 cm film before and after forming the functional layer (7) 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.

(9) Method for evaluating adhesion of first coating layer A 10 × 10 cross-cut is made on the film on which the functional layer of (7) is formed, and then a 18 mm wide tape (Nichiban Co., Ltd.) Cellophane tape (registered trademark) CT-18) was affixed and peeled off rapidly at a peeling angle of 180 degrees. The peeled surface was observed. If the peeled area was less than 10%, it was evaluated as ◯ if it was 10% or more but less than 30%, and × if it was more than 30%.

(10) Method for evaluating strength of first coating layer The surface of the coating layer was rubbed three times with a finger pad wrapped with ERIEL (registered trademark) Pro Wipe Soft Micro Wiper S220 manufactured by Daio Paper Co., Ltd., 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 ×.

(11) Method for measuring haze reduction amount when functional layer is formed on second coating layer As a functional layer, a flat metal plate, 30 parts by weight of 2-biphenoxyethyl acrylate, 4,4 ′-(9 -Fluorenylidene) bis (2-phenoxyethyl acrylate) 17 parts by weight, ethylene glycol modified bisphenol A acrylate (ethylene glycol chain = 8) 40 parts by weight, trimethylolpropane triacrylate 10 parts by weight, diphenyl (2,4,6-trimethyl) A composition consisting of 3 parts by weight of benzoyl) phosphine oxide is placed, and a laminated polyester film is stacked thereon in such a direction that the coating layer comes into contact with the resin, and the composition is uniformly stretched by a roller and irradiated with ultraviolet rays from an ultraviolet irradiation device. The resin was cured. Next, the film was peeled off from the metal plate to obtain a film on which a functional layer having a thickness of 2 μm (the refractive index of the layer was 1.59 and haze was 0.1%) was formed. The haze was measured by the method according to (6), and the difference from the haze of the laminated polyester film before forming the functional layer was calculated.

(12) Discriminability evaluation method before and after functional layer processing on second coating layer (discriminability 1)
The difference between the 20 cm × 20 cm film before and after the functional layer (11) was formed 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.

(13) Evaluation method of absolute value of difference in haze reduction amount when functional layer is formed on first coating layer and second coating layer Haze reduction amount by measurement of (7) and haze reduction by (11) The absolute value of the amount difference was calculated.

(14) Discriminability evaluation method for functional layer processed surface (discriminability 2)
The difference between the 20 cm × 20 cm film in which the functional layer (7) was provided only on the first coating layer and the 20 cm × 20 cm film in which the functional layer (11) was provided only on the second coating layer were observed. Take both hands and observe both films. If it is easy to determine whether the functional layer is formed on the first coating layer side or the second coating layer side according to the condition of haze, it can be determined. The case where it was not possible to discriminate without carefully observing from an oblique angle was marked with Δ, and the case where it could not be discriminated was marked with ×.

(15) Evaluation method of adhesion of second coating layer
With respect to the film on which the functional layer of (11) is formed, the functional layer of the film after being treated for 24 hours in an environment of 60 ° C. and 90% RH is scratched at intervals of 5 mm with a cutter knife, and the width is 18 mm. A tape (cello tape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) was applied and peeled off rapidly at a peeling angle of 180 degrees. The peeled surface was observed. If the peeled area was less than 5%, ◎ was marked if it was 5% or more but less than 20%, Δ if it was 20% or more and less than 50%, and x if it was 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 the polyester (A), the polyester (C) is produced using the same method as the production method of the polyester (A) except that 0.3 part by weight of silica particles having an average particle diameter of 2.7 μm is added before the melt polymerization. Got.

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 0.20 μm Particles: (IC) Silica particles with an average particle size of 0.30 μm Particles: (ID ) Silica particles with an average particle size of 0.45 μm

・ Polyester urethane resin (IIA)
Water of polyester urethane resin formed from isophorone diisocyanate unit: terephthalic acid unit: isophthalic acid unit: ethylene glycol unit: diethylene glycol unit: dimethylolpropanoic acid unit = 12: 19: 18: 21: 25: 5 (mol%) Dispersion.

・ Polycarbonate urethane resin: (IIB)
80 parts by weight of polycarbonate polyol consisting of 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 2000, 4 parts by weight of polyethylene glycol having a number average molecular weight of 400, 12 parts by weight of methylenebis (4-cyclohexylisocyanate), dimethylolbutanoic acid 4 An aqueous dispersion obtained by neutralizing a urethane resin consisting of parts by weight with triethylamine.

・ Urethane resin with carbon-carbon double bond: (IIC)
Hydroxyethyl acrylate unit: dicyclohexylmethane diisocyanate unit: hexamethylene diisocyanate trimer unit: caprolactone unit: ethylene glycol unit: dimethylolpropanoic acid unit = 18: 12: 22: 26: 18: 4 (mol%) A urethane resin having a carbon-carbon double bond weight of 2.0% by weight.

-Urethane resin with carbon-carbon double bond: (IID)
Hydroxyethyl acrylate unit: dicyclohexylmethane diisocyanate unit: hexamethylene diisocyanate trimer unit: caprolactone unit: ethylene glycol unit: dimethylolpropanoic acid unit = 6: 10: 20: 38: 22: 4 (mol%) A urethane resin having a carbon-carbon double bond weight of 0.7% by weight.

・ Polyester resin: (IIE)
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%)

Acrylic resin: (IIF) 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

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: 14: 1 discharge amount) and cooled and solidified to obtain an unstretched sheet.
Next, the film was stretched 3.3 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid A1 shown in Table 1 below was applied on one side of the longitudinally stretched film to the thickness of the coating layer (dried) (After) is applied to be 0.11 μm (first coating layer), and coating liquid B1 is applied to the opposite surface so that the film thickness (after drying) of the coating layer is 0.04 μm (second). The coated layer was led to a tenter, stretched 3.9 times at 120 ° C. in the transverse direction, heat treated at 225 ° C., and relaxed 2% in the transverse direction to obtain a polyester film having a thickness of 250 μm.

  When the obtained polyester film was evaluated, the haze was as high as 12.0%, the haze reduction amount of the first coating layer was 7.8%, and a film having no functional layer and a functional layer were formed. The distinguishability from the film was good. Further, the haze reduction amount of the second coating layer was 2.9%, and it was possible to discriminate between a film in which the functional layer was not formed and a film in which the functional layer was formed. Furthermore, the absolute value of the difference between the haze reduction amount of the first coating layer and the haze reduction amount of the second coating layer was 4.9%, and the discrimination on which side the surface was processed was also good. The properties of this film are shown in Tables 2 and 3 below.

Examples 2-102:
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 2-7, the finished polyester film has a large absolute value of the difference between the haze reduction amount of the first coating layer and the haze reduction amount of the second coating layer, and the discriminability of which side is processed is determined. It was 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 finished polyester film was evaluated, as shown in Tables 8 and 9 below, it was the result that the discriminability between the film in which the functional layer was not formed and the film in which the functional layer was formed was inferior, and the processed film was processed on either side. It was not possible to determine whether or not the adhesiveness was poor.

Comparative Examples 2-6:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. When the finished polyester film was evaluated, as shown in Tables 8 and 9 below, it was impossible to determine which side was processed. In Table 8, for convenience, there is also a description that the amount of decrease in haze is smaller in the first coating layer than in the second coating layer.

  The film of the present invention can be used to form a functional layer such as a backlight unit of a liquid crystal display, a hard coat layer, an anti-sticking layer, a prism layer, a microlens layer, a light diffusion layer, etc. It can be suitably used for applications where it is desired to easily distinguish between processes.

That is, the gist of the present invention is that particles having an average particle diameter in the range of 0.01 to 1.0 μm on both sides of a polyester film are used in a proportion of 3 to 70 as a ratio to the total nonvolatile components in the coating solution forming the coating layer. The absolute value of the difference in the amount of haze reduction when a functional layer is formed on each coating layer having a coating layer that is contained in the range of% by weight and whose film thickness is in the range of 0.03 to 1 μm. It exists in the laminated polyester film characterized by being 0% or more.

Claims (2)

A laminated polyester film having a coating layer on both sides of a polyester film, wherein the absolute value of the difference in haze reduction when a functional layer is formed on each coating layer is 1.0% or more. The laminated polyester film according to claim 1, wherein the haze of one of the functional layers formed on the coating is 8.0% or less.