JP2014210424A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film which can be suitably used in applications requiring excellent transparency, slipperiness, adhesiveness and the like, and for example, to provide a polyester film which can be suitably used as a member for protecting a polarizing plate used for a liquid crystal display.SOLUTION: There is provided a laminated polyester film which has a coating layer formed from a coating liquid containing non-heat-resistant particles and a (meth)acrylate compound on at least one surface a polyester film.

Description

  The present invention relates to a laminated polyester film, in particular, a laminate having excellent transparency and good adhesion to a surface functional layer such as a prism layer or a microlens layer used in a backlight unit of a liquid crystal display. It relates to a polyester film.

  Since polyester film has excellent transparency, strength, etc., it is used as a base material for prism lens film, microlens film, light diffusion film, antireflection film, hard coat film, electromagnetic wave shield film, touch panel, molding, etc. It has been. In recent years, more excellent transparency is being demanded particularly for films used for forming a surface functional layer, such as a member such as a backlight unit of a liquid crystal display, an in-mold transfer film, and an in-mold label film.

  Conventionally, a technique of incorporating particles into a polyester film for the purpose of easy slipping has been common (Patent Documents 1 and 2). However, in the case of the method of incorporating particles in the polyester film, the haze of the film becomes high and becomes whitish, or when observed under a fluorescent lamp, graininess due to the particles is seen and visibility is deteriorated. In some cases, the luminance may decrease due to light scattering by the particles.

  In order to solve these problems, a film that does not contain particles in a polyester film has also been proposed (Patent Document 3). However, in the case of a film containing no particles, there is a drawback that the slipperiness is poor and the film is easily damaged. A proposal has been made to form a coating layer containing particles on a uniaxially stretched polyester film to impart slipperiness. However, before the coating layer is formed, the slipperiness cannot be improved, and it is applied from film formation by melt extrusion. In the meantime, the slipperiness is poor and scratches are inevitable.

  In order to impart higher performance, various surface functional layers are usually formed on the polyester film. In recent years, liquid crystal displays have been widely used as display devices for televisions, personal computers, digital cameras, mobile phones and the like. Since these liquid crystal displays do not have a light emitting function by a liquid crystal display unit alone, a method of displaying by irradiating light using a backlight from the back side is widespread.

  A prism sheet is used to improve the optical efficiency of the backlight and increase the brightness. As the transparent base film, a polyester film is generally used in consideration of transparency and mechanical properties. In order to improve the adhesion between the base polyester film and the prism layer, these intermediate layers are easily bonded. In general, a conductive coating layer is provided. As an easily adhesive coating layer, for example, polyester resins, acrylic resins, and urethane resins are known (Patent Documents 4 to 6).

  As a method for forming the prism layer, for example, an active energy ray-curable coating material is introduced into a prism type, irradiated with active energy rays while being sandwiched between polyester films, the resin is cured, and the prism type is removed to remove polyester. The method of forming on a film is mentioned. In the case of such a method, it is necessary to use a solventless active energy ray-curable coating material in order to form the prism type with precision. However, solvent-free paints are less likely to penetrate and swell into easily-adhesive coating layers laminated on polyester films and have insufficient adhesion compared to solvent-based paints. A coating layer made of a specific urethane resin has been proposed, and improvement in adhesion has been achieved. However, even with such a coating layer, adhesion has not always been sufficient for solventless resins. (Patent Document 7).

  In order to improve adhesion to a solventless resin, a coating layer mainly composed of a urethane resin and an oxazoline compound has been proposed (Patent Document 8). However, there is a case where the adhesiveness to the prism resin corresponding to the increase in the brightness of the prism derived from the decrease in the number of backlights and the demand for reduction in power consumption, that is, the prism resin having a higher refractive index, is not sufficient.

JP 2006-169467 A JP 2006-77148 A JP 2000-229355 A JP-A-8-281890 Japanese Patent Laid-Open No. 11-286092 JP 2000-229395 A JP-A-2-158633 JP 2010-13550 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is a polyester film having excellent transparency and good adhesion to various surface functional layers such as a prism layer and a microlens layer. Is to provide.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the use of a 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 resides in a laminated polyester film characterized by having a coating layer formed from a coating solution containing non-heat resistant particles and a (meth) acrylate compound on at least one surface of the polyester film.

  According to the polyester film of the present invention, it is possible to provide a film having excellent transparency and excellent adhesion to various surface functional layers such as a prism layer and a microlens layer, and its industrial value is high.

  The polyester film constituting the 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 the gist of the present invention is not exceeded other than the two-layer or three-layer structure. It may be a multilayer and is not particularly limited. For example, it is possible to change the raw material of the surface layer and the intermediate layer into a three-layer structure for the purpose of effectively improving various properties using a polyester film with high functionality as the surface layer raw material.

  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 polyester layer of the film of the present invention, particles can be blended mainly for the purpose of imparting slidability and preventing scratches in each step, but from the viewpoint of transparency, particles are not blended. It is preferable that 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, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, and benzoguanamine resin. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  Moreover, when mix | blending particle | grains, the average particle diameter of particle | grains is 3 micrometers or less normally, Preferably it is the range of 0.01-1.5 micrometers. When the average particle diameter exceeds 3 μm, the film brightness decreases when the transparency of the film deteriorates, when the graininess due to the particles occurs and the visibility deteriorates, or when light scattering by the particles occurs. There is a case.

  The content of the particles depends on the average particle size, but in the polyester film layer containing the particles, it is usually in the range of 1000 ppm or less, preferably in the range of 500 ppm or less, more preferably in the range of 50 ppm or less (intentionally contained). Do not). If it exceeds 1000 ppm, the transparency may deteriorate, the graininess caused by particles may occur and the visibility may deteriorate, or the brightness of the film may decrease due to light scattering by the particles.

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.

  The polyester film of the present invention may contain an ultraviolet absorber in order to improve the weather resistance of the film, for example, to prevent deterioration of the liquid crystal or the like 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.

  As the ultraviolet absorber, there are an organic ultraviolet absorber and an inorganic ultraviolet absorber. From the viewpoint of transparency, 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 film of the present invention, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, etc. may be added to the polyester film in the present invention as necessary in addition to the above-mentioned particles and ultraviolet absorbers. Can do.

  Although the thickness of the polyester film in this invention will not be specifically limited if it can be formed into a film as a film, Usually, 10-300 micrometers, Preferably it is the range of 25-250 micrometers.

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. That is, a method of drying the polyester raw material pellets described above and cooling and solidifying the molten film extruded from the die with a cooling roll using a single screw extruder is preferable. In this case, in order to improve the flatness of the film, it is preferable to improve the adhesion between the film and the rotary cooling drum, and an electrostatic application adhesion method or a liquid application adhesion method is preferably employed. Next, the obtained unstretched film is stretched in the biaxial direction. In that case, first, there is a method in which a coating solution containing non-heat-resistant particles is applied to the unstretched film and dried to form a coating layer. Thereafter, the film is stretched in one direction by a roll or tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. is there. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can be adopted for the production of the polyester film constituting the polyester film. In the simultaneous biaxial stretching method, a coating solution containing non-heat-resistant particles is applied to the unstretched film, and the machine direction and the width direction are usually controlled at 70 to 120 ° C., preferably 80 to 110 ° C. The stretching ratio is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. 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.

  In the present invention, it is an essential requirement to have a coating layer formed from a coating solution containing non-heat resistant particles and a (meth) acrylate compound on at least one surface of the polyester film. In addition, the notation of “(meth) acrylate” in this specification represents “acrylate and methacrylate”.

  The present inventors include particles in a polyester film, and as a method for ensuring transparency and slipperiness, a change in the average particle diameter of the particles, a change in the addition amount of the particles, a layer of the polyester film containing the particles ( In the three-layer structure, only the outermost layer contains particles, and while improving the transparency, the method of changing the thickness of the slippery) has been studied, but both ensure high transparency and sufficient slipperiness. It was a difficult result.

  As one of the objects of the present invention, by forming the coating layer at the initial stage of the film production process, in various processes from the formation of the coating layer on the unstretched film formed after the melt extrusion until before the high temperature treatment. It is used to ensure sufficient slipperiness.

  In addition, usually when particles are present, they appear whitish due to light scattering, but when non-heat-resistant particles are used, they can be melted at a high temperature to reduce the particle size, deform, or be eliminated in a later step. In addition, they found that it was possible to reduce whitishness and realized high transparency.

  The formation of the coating layer in the film of the present invention may be provided by in-line coating, which treats the film surface during the process of forming a polyester film, or is applied off-system on a once produced film. Is also possible. In-line coating is preferred because it can be applied at the same time as film formation and the production cost can be kept low. Among these, in order to heat-treat the non-heat resistant particles and make them highly transparent, it is more preferable to carry out at any stage from after the unstretched film formed after melt extrusion to before high temperature treatment. In particular, in order to prevent damage due to the roll, it is preferable to carry out at an initial stage. Moreover, in the method of extending | stretching by making it contact with films, such as a roll, since the damage to a film becomes large, forming in the step before extending | stretching is preferable.

  Furthermore, in order to increase transparency, it is necessary to treat at a temperature higher than the heat-resistant temperature (temperature at which heat is deformed) in order to reduce, deform, or eliminate the particle size by melting the non-heat-resistant particles in the subsequent process. Is preferable.

  The coating layer in the film of the present invention is not limited to the following. For example, in sequential biaxial stretching, after forming an unstretched film, a coating layer is formed at an initial stage, and then the first stretching is performed. A more suitable polyester film can be manufactured by performing high temperature treatment after performing the second stretching. The place where the coating layer is formed is not limited to the above. For example, in the case of sequential biaxial stretching, the coating layer may be formed at the stage after the first stretching and before the second stretching. Also good.

  The coating layer in the film of the present invention may be formed on only one side of the film or may be formed on both sides in order to overcome, for example, a more easily damaged area. Moreover, in the case of both surfaces, the formation location may be the same or different.

  The non-heat resistant particles used in the present invention are particles having low heat resistance, and the particles are deformed at a high temperature. In particular, in the production process of the polyester film, the particles are deformed or dissolved in a process in which the temperature after film formation is high. However, for example, when selecting a method of stretching in contact with a film such as a roll in the first stretching, it is necessary to maintain a sufficient shape as particles in order to exhibit slipperiness in the stretching process. Some heat resistance is necessary.

  That is, the thermal characteristics required for the non-heat resistant particles are preferably those that do not undergo thermal deformation at a temperature of less than 120 ° C. and that undergo thermal deformation at a temperature of 120 ° C. or higher.

  The softening point of the non-heat resistant particles is preferably in the range of 120 to 270 ° C, more preferably in the range of 150 to 250 ° C, and still more preferably in the range of 180 to 230 ° C. When the temperature is lower than 120 ° C., when a method of stretching by contacting with a film such as a roll in the first stretching is selected, depending on the stretching temperature, thermal deformation of the particles may occur, and the slipping property is deteriorated. There are concerns. On the other hand, if the temperature exceeds 270 ° C., the final product may be a film in which the particles are not thermally deformed and remain whitish.

  The non-heat resistant particle is not particularly limited as long as it can maintain the above-mentioned thermal characteristics, but in general, the organic particles, i.e. Heat-resistant organic particles are preferred. In consideration of control of the size and shape of the particles and dispersibility in various solvents including water, the organic particles are more preferably of a high molecular type, that is, non-heat resistant polymer particles.

  As the non-heat-resistant polymer particles, cross-linked or non-cross-linked polymer particles can be used as long as the gist of the present invention is not impaired, but in order to make the thermal characteristics more suitable for the purpose of the present invention. More preferably, it is a non-crosslinked type, that is, a non-heat resistant non-crosslinked polymer particle.

  The non-crosslinking in the non-heat resistant non-crosslinked polymer particles is a polymer particle that does not have a three-dimensional structure or has a small number of heat resistance. For example, in the case of particles made of a polymerizable monomer as described later, the crosslinkable polymerizable monomer is preferably less than 5% by weight of the entire polymerizable monomer, and more preferably in the range of less than 1% by weight.

  As the polymer of the non-heat-resistant non-crosslinked polymer particles, conventionally known compounds can be used. For example, acrylic resin, styrene resin, vinyl resin, epoxy resin, urea resin, phenol resin, polyester resin, polyurethane resin , Polycarbonate resin, polyether resin and the like. Among these polymers, an acrylic resin, a styrene resin, and a vinyl resin formed from a polymerizable monomer having a carbon-carbon double bond are more preferable from the viewpoint that a compound having a desired thermal characteristic can be easily produced. In addition, in the case of these resins, since they are thermally deformed by high-temperature treatment, it is possible to prevent the particles from falling off. Furthermore, not only the function as particles, but also, for example, adhesion to various surface functional layers formed thereon It is also possible to develop other performances such as increasing.

  The polymerizable monomer having a carbon-carbon double bond refers to various carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citraconic acid, and salts thereof; 2 -Various hydroxyl-containing monomers such as hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutylhydroxyfumarate, monobutylhydroxyitaconate; ) Acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, various (meth) acrylic esters such as lauryl (meth) acrylate; (meth) acrylamide, diacetone acrylamide, N- Methylol Various nitrogen-containing compounds such as chloramide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, various vinyl esters such as vinyl propionate; γ-methacrylic Various silicon-containing polymerizable monomers such as loxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; phosphorus-containing vinyl monomers; various vinyl halides such as vinyl fluoride, vinyl chloride, and biridene chloride; butadiene And various conjugated dienes.

  Among these, an acrylic resin obtained by polymerizing a (meth) acrylic polymerizable monomer as a main component is optimal. Also, a styrene / acrylic resin having a (meth) acrylic polymerizable monomer as a main component and copolymerized with a styrene derivative can be suitably used.

  That is, in the film of the present invention, the best form of the non-heat-resistant particles used for forming the coating layer is the non-heat-resistant non-crosslinked acrylic resin particles and the non-heat-resistant non-crosslinked styrene / acrylic resin particles as described above. .

  When non-heat resistant non-crosslinked acrylic resin particles are used, the glass transition point of the resin particles is preferably in the range of 0 to 150 ° C, more preferably in the range of 50 to 120 ° C. When the temperature is lower than 0 ° C, there is a concern that the slipperiness cannot be sufficiently exhibited. When the temperature exceeds 150 ° C, there is a concern that the thermal deformation of the particles is not sufficient.

  The average particle diameter of the non-heat-resistant particles depends on the film thickness and cannot be generally specified, but is preferably in the range of 0.01 to 3 μm, more preferably in the range of 0.03 to 1 μm, and still more preferably 0.00. It is the range of 05-0.5 micrometer. When the average particle size is less than 0.01 μm, the slipperiness may not be sufficiently obtained. When the average particle size exceeds 3 μm, the particles are not sufficiently deformed and a whitish film remains. May end up.

  The present inventors have found out that the adhesiveness with the coating layer is deteriorated when the refractive index of the active energy ray-curable resin layer formed on the coating layer is high, and a conventionally known coating layer (for example, Patent Document 7). And 8) found that sufficient adhesion cannot be obtained. Therefore, the coating layer contains a carbon-carbon double bond, and the double bond and a carbon-carbon double bond of a compound used for forming a prism layer or a microlens layer are reacted at the time of irradiation with active energy rays, We thought that a covalent bond could be formed, thereby improving adhesion. As a result of various investigations, it was found that the adhesion was improved by using the (meth) acrylate compound.

The presumed mechanism for improving the adhesion is that (meth) acrylate (CH ₂ ═CH—COO—R or CH ₂ ═C (CH) contained in the coating layer by ultraviolet rays irradiated when forming the prism layer or the microlens layer. ₃ ) A carbon-carbon double bond in —COO—R) is reacted with a carbon-carbon double bond of a compound used for forming a prism layer or a microlens layer to form a covalent bond. .

  As the carbon-carbon double bond of the (meth) acrylate compound, a conventionally known material may be used as long as it can react with the carbon-carbon double bond contained in the compound forming the prism layer or the microlens layer. Although not particularly limited, for example, monofunctional (meth) acrylate, bifunctional (meth) acrylate, polyfunctional (meth) acrylate, and the like can be given.

  Although it does not specifically limit as monofunctional (meth) acrylate, For example, methyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meta) ) Acrylate, cyclohexyl (meth) acrylate, alkyl (meth) acrylate such as isobornyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate such as hydroxyalkyl (meth) acrylate, Alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, ethoxypropyl (meth) acrylate, etc. Relate, aromatic (meth) acrylates such as benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, amino group-containing (meth) acrylates such as diaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, methoxyethylene glycol ( (Meth) acrylate, phenoxypolyethyleneglycol (meth) acrylate, ethylene oxide modified (meth) acrylate such as phenylphenol ethylene oxide modified (meth) acrylate, glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, (meth) acrylic An acid etc. are mentioned.

  Although it does not specifically limit as bifunctional (meth) acrylate, For example, 1, 4- butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 6-hexanediol di (meth) Alkanediol di (meth) acrylate such as acrylate, 1,9-nonanediol di (meth) acrylate, tricyclodecane dimethylol di (meth) acrylate, bisphenol A ethylene oxide modified di (meth) acrylate, bisphenol F ethylene oxide modified Bisphenol-modified di (meth) acrylate such as di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, urethane di (meth) acrylate, epoxy di (meth) acrylate Examples include chlorate.

  The polyfunctional (meth) acrylate is not particularly limited. For example, dipentaerythritol hexa (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) ) Isocyanurates such as acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethaneethylene oxide modified tetra (meth) acrylate, isocyanuric acid ethylene oxide modified tri (meth) acrylate, ε-caprolactone modified tris (acryloxyethyl) isocyanurate Acid-modified tri (meth) acrylate, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol Triacrylate toluene diisocyanate urethane prepolymer, urethane acrylates such as dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, and the like.

  These compounds may be used alone or in combination as a mixture. Moreover, from a viewpoint of adhesive improvement, Preferably bifunctional (meth) acrylate and polyfunctional (meth) acrylate, More preferably, polyfunctional (meth) acrylate is good.

  Further, the ratio of the carbon-carbon double bond part to the (meth) acrylate compound is preferably 3% by weight or more in consideration of adhesion to the prism layer and the microlens layer, particularly adhesion to a resin having a high refractive index. More preferably, it is 5% by weight or more. The upper limit is usually 40% by weight.

  For the formation of the coating layer, it is preferable to use a crosslinking agent together in order to strengthen the coating film of the coating layer and improve the adhesion, moist heat resistance and the like after forming the surface functional layer such as the prism layer and the microlens layer. . Examples of the crosslinking agent include the oxazoline compounds, isocyanate compounds, melamine compounds, epoxy compounds, carbodiimide compounds, aziridine compounds, silane coupling compounds, and the like that can be used in the formation of the first coating layer. Among them, oxazoline compounds, isocyanate compounds, and melamine compounds are preferable from the viewpoint of improving adhesion, and when used in combination with oxazoline compounds and isocyanate compounds, the adhesion is remarkably improved, and it is also used for applications that require more stringent quality. be able to. In particular, in the case of an isocyanate compound, there is a feature that the adhesion performance is easily maintained even when the coating film thickness is thin, and it is more preferably used. Moreover, it is also possible to use two or more types of crosslinking agents together in order to further improve the adhesion.

  The isocyanate compound is a compound having an isocyanate derivative structure typified by isocyanate or blocked isocyanate. Examples of 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.

  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. Moreover, it may be more suitable that it is a combined material with a urethane resin or a polyester resin from a viewpoint of an adhesive improvement.

  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 surface 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.

  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.

  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.

  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.

  For the formation of the coating layer, various polymers are used in combination to improve the coating appearance and improve the visibility and transparency when various prism layers, microlens layers, etc. are formed on the coating surface. Is also possible. As the polymer, it is possible to use a conventionally known polymer, and among these, urethane resin, polyester resin, and acrylic resin are preferable from the viewpoint of adhesion with a surface functional layer such as a prism layer or a microlens layer, A urethane resin is particularly preferable.

  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.

  In order to improve the adhesion to various topcoat layers, among the polyols, a urethane resin having a polycarbonate structure or a polyester structure using polycarbonate polyols and polyester polyols is preferable. Moreover, the urethane resin which has a polyester structure is preferable from a viewpoint that adhesiveness improves even when not using a crosslinking agent together.

  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 skeleton 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.

  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 having a carbon-carbon double bond, as typified by acrylic and methacrylic monomers. These may be either a homopolymer or a copolymer. 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 having a carbon-carbon double bond in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or polyurethane dispersion is also included. Similarly, a polymer obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion (in some cases, a polymer mixture) is also included. Moreover, in order to improve adhesiveness, it is also possible to contain a hydroxyl group and an amino group.

  The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but particularly representative compounds include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citracone. Various carboxyl group-containing monomers such as acids, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutylhydroxyfumarate, mono Various hydroxyl group-containing monomers such as butylhydroxy itaconate; various (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate ) Acrylic esters; Various nitrogen-containing compounds such as meth) acrylamide, diacetone acrylamide, N-methylolacrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, vinyl propionate Various vinyl esters such as: Various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; Phosphorus-containing vinyl monomers; Various such as vinyl chloride and biridene chloride And various conjugated dienes such as butadiene.

  In the final film, heat-resistant particles can be used in combination for the purpose of blocking and improving slipperiness. The average particle size is preferably in the range of 1.0 μm or less, more preferably 0.5 μm or less, particularly preferably 0.2 μm or less from the viewpoint of the transparency of the film. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, heat-resistant organic particles, and the like.

  Regarding the formation of a coating layer in the film of the present invention, a coating solution prepared by adjusting the above-described series of compounds as a solution or solvent dispersion to a solid content concentration of about 0.1 to 80% by weight as a guide is applied to an unstretched polyester film. It is preferable to produce a polyester film in the manner of application to the substrate. In consideration of being inline in particular, it is more preferable that the solution is an aqueous solution or a water dispersion, but the coating solution contains a small amount of an organic solvent for the purpose of improving the dispersibility in water and improving the film forming property. You may do it. Moreover, only one type of organic solvent may be used, and two or more types may be used as appropriate.

The amount of the non-heat resistant particles constituting the coating layer in the film of the present invention is not particularly limited as long as the object is achieved. Moreover, since it depends on the thermal characteristics, size, and coating layer thickness of the particles to be used, it cannot be said unconditionally, but as a quantity on only one side, it is a film after drying (before stretching), preferably 0.01 to range of 200 mg / ^{m 2,} more preferably from 0.1~150mg / ^{m 2,} more preferably in the range of 1~70mg / ^{m 2.}

Also, the coating amount of the coating layer (after drying and before stretching) depends on the size of the particles, the stretching ratio, etc., so it cannot be generally stated, but only on one side, preferably 0.001 to 5 g / m. ² or less, more preferably in the range of 0.01 to 3 g / ^{m 2,} more preferably 0.05 to 1 g / ^{m 2} range, and most preferably in the range of 0.1~0.7g / ^{m 2} . When the coating amount is out of the above range, there are concerns about blocking, deterioration of the coating appearance, and dropout of particles.

  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.

  Moreover, when forming a coating layer in a film, you may perform surface treatments, such as a corona treatment and a plasma treatment, as needed.

  Moreover, in this invention, it is also possible to form a coating layer (2 layer structure) further on the coating layer of the film of this invention. For example, after forming the coating layer of the film of the present invention and stretching in at least one direction, the second coating layer can be formed in order to impart various performances. Further, the second coating layer can be formed on the side opposite to the surface on which the coating layer of the film of the present invention is formed. Moreover, you may form only in the single side | surface side of a film, and may form in both surfaces. Furthermore, the second coating layer can be the coating layer of the present invention.

  Furthermore, within the range not impairing the gist of the present invention, the above-mentioned coating layer is formed with heat-resistant particles, antifoaming agent, coating property improving agent, thickener, organic lubricant, antistatic agent, ultraviolet ray as necessary. Absorbers, antioxidants, foaming agents, dyes, pigments and the like can be used.

As a ratio with respect to the total non-volatile components in the coating solution for forming the coating layer, the non-heat-resistant particles cannot be generally described because they depend on the particle size and film thickness, but are usually in the range of 0.1 to 80% by weight, Preferably it is the range of 0.5 to 40 weight%, More preferably, it is the range of 1 to 25 weight%. When it is out of the above range, there is a concern that the sliding property is not sufficient or the transparency is not sufficient.

  As a ratio with respect to all the non-volatile components in the coating liquid for forming the coating layer, the (meth) acrylate compound is usually in the range of 5 to 99.9% by weight, preferably in the range of 10 to 80% by weight, more preferably in the range of 20 to 70%. It is in the range of wt%. If it is out of the above range, the adhesion may not be sufficient.

  The ratio of the carbon-carbon double bond part of the (meth) acrylate compound is preferably 0.2% by weight or more, more preferably 0. 0% by weight as a ratio with respect to all nonvolatile components in the coating liquid forming the coating layer in the film of the present invention. It is 4% by weight or more, more preferably 0.8% by weight or more. When it is out of the above range, the adhesion after the heat-resistant heat treatment with the prism layer or the microlens layer may not be sufficient. The upper limit is usually 28% by weight.

  Moreover, as a ratio with respect to all the non-volatile components in the coating liquid which forms the coating layer in the film of this invention, a crosslinking agent is 95 weight% or less normally, Preferably it is 5-85 weight%, More preferably, it is 10-75 weight%. It is a range. By using in this range, adhesiveness and coating film strength can be improved.

  Analysis of the final form of the non-heat-resistant particles used for forming the coating layer and other components in the coating layer can be performed by, for example, TOF-SIMS, ESCA, fluorescent X-ray, various surface / cross-sectional observations, and the like. it can.

  The polyester film in the present invention can be used for applications requiring excellent transparency, and its internal haze is preferably in the range of 0.0 to 1.0%, more preferably 0.0 to 0.5%. More preferably, it is 0.0 to 0.3% of range. When the internal haze exceeds 1.0%, even if various surface functional layers are provided on the film, the haze cannot be sufficiently lowered, and the whitish color remains as a film. Cannot be achieved.

  The haze of the polyester film in the present invention cannot be generally stated when various surface functional layers are provided on the film because the surface haze can be lowered, but is preferably in the range of 0.0 to 2.0%, more preferably. Is in the range of 0.0 to 1.5%, more preferably in the range of 0.0 to 1.0%. If it exceeds 2.0%, the appearance of the film may be poor, or even if various surface functional layers are provided, the haze cannot be lowered sufficiently, and the visibility may be insufficient.

  On the coated layer of the laminated polyester film of the present invention, a prism layer or a microlens layer, which is an active energy ray-curable resin layer, is generally provided in order to improve luminance, and particularly adhesion is ensured. It is difficult to provide a resin layer having a high refractive index necessary for increasing the brightness. In recent years, various shapes have been proposed for the prism layer in order to improve the luminance efficiently. Generally, prism layers are formed by arranging prism rows having a triangular cross section in parallel. 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.

As a material used for the active energy ray-curable resin layer, conventionally known materials can be used, and examples thereof include those made of an active energy ray-curable resin, such as monofunctional (meth) acrylate, bifunctional. Examples include (meth) acrylates, polyfunctional (meth) acrylates, polyester resins, epoxy resins, polyester (meth) acrylates, epoxy (meth) acrylates, urethane (meth) acrylates, and other (meth) acrylate resins.

  The composition containing the active energy ray-curable (meth) acrylate is not particularly limited. For example, known active energy ray curable monofunctional (meth) acrylate, bifunctional (meth) acrylate, polyfunctional (meth) acrylate mixed one or more types, active energy ray curable prism and resin for microlenses What is marketed as a material, or what added the other component in the range which does not impair the objective of this embodiment other than these can be used.

  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.

The higher the refractive index of the active energy ray-curable resin layer is, the higher the luminance tends to improve, and it is usually 1.56 to 1.65, preferably 1.57 to 1.64, more preferably 1.58. It is in the range of ~ 1.63. If it is out of the above range, the luminance may not be sufficiently increased.

  Examples of the prescription for increasing the refractive index for increasing the brightness include a method using a compound having a large aromatic structure, a sulfur atom, a halogen atom, and a metal compound in addition to the above general compound. Among them, a method using a compound having a large aromatic structure and 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 biphenyl structure, fluorene structure, and condensed polycyclic aromatic structure, and those having a benzene ring-containing substituent such as a phenyl group have a refractive index. Since it can be made higher, 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 biphenyl structure, fluorene structure, condensed polycyclic aromatic structure and aromatic compounds substituted for these structures in the active energy ray-curable resin layer depends on the type and amount of other structures or the curing conditions. Therefore, although it cannot be generally stated, it is preferably in the range of 20 to 80% by weight, more preferably 25 to 70% by weight, and further preferably 30 to 60% by weight with respect to the entire active energy ray-curable resin layer. . If it is out of the above range, the luminance may decrease or the active energy ray-curable resin layer may not be formed successfully.

  The proportion of the compound having a biphenyl structure, a fluorene structure, or a condensed polycyclic aromatic structure forming the active energy ray-curable resin layer in the film of the present invention is the total non-volatile content of the compound composition forming the active energy ray-curable resin layer. As a ratio with respect to a component, Preferably it is 5 weight% or more, More preferably, it is 10 to 90 weight%, More preferably, it is the range of 20 to 80 weight%. By using in this range, a refractive index becomes high and it becomes easy to obtain high luminance.

  Other components contained in the composition containing the active energy ray-curable compound 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.

  Analysis of the components of the active energy ray-curable resin 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 of particles The film was observed using an electron microscope (S-4500 manufactured by HITACHI), and the average value of the particle diameters of 10 particles was defined as the average particle diameter. The non-heat resistant particles were observed on the film before the high temperature process, that is, after the longitudinal stretching and before the transverse stretching.

(3) Measuring method of internal haze Using haze meter HZ-2 manufactured by Suga Test Instruments Co., Ltd., the film was immersed in ethanol and measured according to JIS K 7136.

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

(5) Film surface roughness (Sa)
Using a three-dimensional non-contact surface shape measurement system (MN537N-M100, manufactured by Ryoka System Co., Ltd.), the roughness Sa of the film on the cooled and solidified surface side before the high-temperature process, that is, after the longitudinal stretching and before the transverse stretching is determined. It was measured. When the Sa is less than 5 nm, the slipperiness is poor, and there is a concern that scratches may occur when coming into contact with a roll or the like in a stretching process or the like. A more preferable form is 5 nm or more.

(6) Transparency evaluation method When the film is visually observed under a three-wavelength light region type fluorescent lamp, the particle feeling (dots due to particles in the film) is not observed and there is a clear feeling. The case where there was a particle feeling or the case where whitishness was observed was taken as x.

(7) Evaluation method of adhesion of coating layer In order to form a prism layer, 30 parts by weight of 2-biphenoxyethyl acrylate was added to a mold member in which a large number of prism rows having a pitch of 50 μm and an apex angle of 65 ° were arranged in parallel. 17 parts by weight of 4 ′-(9-fluorenylidene) bis (2-phenoxyethyl acrylate), 40 parts by weight of ethylene glycol-modified bisphenol A acrylate (ethylene glycol chain = 8), 10 parts by weight of trimethylolpropane triacrylate, diphenyl (2, A composition comprising 3 parts by weight of 4,6-trimethylbenzoyl) phosphine oxide is placed, and a laminated polyester film is stacked thereon so that the coating layer is in contact with the resin, and the composition is uniformly stretched by a roller, and an ultraviolet irradiation device The resin was cured by irradiating with ultraviolet rays. Subsequently, the film was peeled off from the mold member to obtain a film on which a prism layer (refractive index = 1.59) was formed. The prism layer of the film immediately after (adhesion 1) and after treatment for 24 hours in an environment of 60 ° C. and 90% RH (adhesion 2, evaluation for applications requiring higher adhesion) A 24 mm wide tape (Cello Tape (registered trademark) CT-24 manufactured by Nichiban Co., Ltd.) was applied to the surface with a cutter knife, and was peeled off rapidly at a peeling angle of 180 degrees. The peeled surface was observed. If the peeled area was 10% or less, ◎ if it exceeded 10% and 20% or less, ○, if it exceeded 20% and 40% or less, Δ, and if it exceeded 40%, it was ×.

(8) Method for measuring softening point Using a flow tester CFT-500D manufactured by Shimadzu Corporation, the temperature at which half of the non-heat-resistant particles flow out was measured as the softening point. 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. 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 same method as the production method of the polyester (A) is used except that 0.5% by weight of silica particles having an average particle size of 0.1 μm is added to the produced polyester before melt polymerization. Thus, polyester (C) was obtained.

<Method for producing polyester (D)>
In the production method of polyester (A), the same method as the production method of polyester (A) is used except that 0.5% by weight of silica particles having an average particle diameter of 3.2 μm is added to the produced polyester before melt polymerization. Thus, polyester (D) was obtained.

Examples of compounds constituting each coating layer are as follows.
(Example compounds)
Non-heat-resistant particles: (IA) Non-heat-resistant non-crosslinked styrene / acrylic resin having an average particle size of 0.37 μm, a softening point of 220 ° C. and a glass transition point of 110 ° C., copolymerized with a composition of methyl methacrylate / styrene = 70/30 Particles / Non-heat-resistant particles: (IB) Non-heat-resistant, non-crosslinked acrylic particles having an average particle size of 0.09 μm, a softening point of 210 ° C., and a glass transition point of 60 ° C., copolymerized with a composition of methyl methacrylate / butyl acrylate = 80/20 Silica particles: (IC) Silica particles having an average particle size of 0.07 μm Silica particles: (ID) Silica particles having an average particle size of 0.30 μm

・ (Meth) acrylate compounds: (IIA)
Tetramethylol methane ethylene oxide modified tetraacrylate (total ethylene glycol chain = 35). A tetrafunctional acrylate that can be developed in an aqueous system having a carbon-carbon double bond ratio of 5% by weight based on the whole.
・ (Meth) acrylate compounds: (IIB)
Biscoat # 1000 (manufactured by Osaka Organic Chemical Industry Co., Ltd.), which is a hyperbranched polymer having dipentaerythritol as a core and a polyfunctional acrylate having a carbon-carbon double bond ratio of 5% by weight or more based on the whole. In addition, when this material was used, the coating liquid was created using methanol.

・ Polyester resin: (IIIA)
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: (IIIB) 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)

-Urethane resin: (IIIC)
Tolylene diisocyanate unit: terephthalic acid unit: isophthalic acid unit: ethylene glycol unit: neopentyl glycol unit: dimethylolpropanoic acid unit = 14: 17: 17: 23: 24: 5 (mol%) polyester-based polyurethane Water dispersion of resin.

-Urethane resin: (IIID)
Polycarbonate polyol unit comprising 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 2000: Polycarbonate formed from methylenebis (4-cyclohexylisocyanate) unit: dimethylolpropanoic acid unit = 45: 50: 5 (mol%) An aqueous dispersion of polyurethane resin.

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

・ Isocyanate compounds: (IVB)
Hexamethylene diisocyanate trimer unit: methoxypolyethylene glycol unit having a number average molecular weight of 1400: methyl ethyl ketone oxime unit = 30: 2: 68 (mol%), a number consisting of 1,6-hexanediol and diethyl carbonate Polyethylene polyol unit having an average molecular weight of 2000: isophorone diisocyanate unit: trimethylolpropane unit: dimethylolpropionic acid unit = 24: 55: 3: 18 (mol%) neutralized with triethylamine to diethylenetriamine An aqueous blocked isocyanate compound containing a urethane resin obtained by chain extension at

・ Isocyanate compounds: (IVC)
Trimethylolpropane adduct unit of tolylene diisocyanate (tolylene diisocyanate: trimethylolpropane = 3: 1 (mol%)): methoxypolyethylene glycol unit having a number average molecular weight of 2000: N, N, N ′, N′-tetrakis An aqueous block polyisocyanate compound formed from (2-hydroxyethyl) ethylenediamine unit: methyl ethyl ketone oxime unit = 33: 2: 55: 10 (mol%).

Melamine compound: (IVD) hexamethoxymethylol melamine

Example 1:
A mixed raw material in which polyesters (A) and (B) are mixed at a ratio of 97% and 3%, respectively, is used as a raw material for the outermost layer (surface layer), and polyesters (A) and (B) are respectively at a ratio of 97% and 3%. Each of the mixed raw materials is fed to two extruders as a raw material for the intermediate layer, melted at 285 ° C., and then two types and three layers (surface layer / intermediate layer / Coextruded and cooled and solidified with a layer structure of (surface layer = 1: 18: 1 discharge amount) to obtain an unstretched film. Thereafter, an aqueous coating solution A1 shown in Table 1 below was applied to both sides of the unstretched film and dried to obtain a film having a coating layer with a coating amount (after drying) of 0.8 g / m ^{2 on} one side. Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the roll peripheral speed difference, then led to a tenter, stretched 4.0 times at 120 ° C. in the transverse direction, and heat-treated at 230 ° C. Thereafter, the film was relaxed by 2% in the transverse direction to obtain a polyester film having a thickness of 125 μm. When the obtained polyester film was evaluated, the roughness of the film after longitudinal stretching was sufficient, the transparency was good, and the adhesion was good. The properties of this film are shown in Table 3 below.

Examples 2-25:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. As shown in Table 3 below, the finished polyester film had sufficient film roughness after longitudinal stretching, good transparency, and good adhesion.

Example 26:
A mixed raw material in which polyesters (A), (B), and (C) were mixed at a ratio of 96%, 3%, and 1%, 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 film. Thereafter, an aqueous coating solution A1 shown in Table 1 below was applied to both sides of the unstretched film and dried to obtain a film having a coating layer with a coating amount (after drying) of 0.8 g / m ^{2 on} one side. Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the roll peripheral speed difference, then led to a tenter, stretched 4.0 times at 120 ° C. in the transverse direction, and heat-treated at 230 ° C. Thereafter, the film was relaxed by 2% in the transverse direction to obtain a polyester film having a thickness of 125 μm. When the obtained polyester film was evaluated, the roughness of the film after longitudinal stretching was sufficient, the transparency was good, and the adhesion was good. The properties of this film are shown in Table 3 below.

Example 27:
A mixed raw material in which polyesters (A) and (B) are mixed at a ratio of 97% and 3%, respectively, is used as a raw material for the outermost layer (surface layer), and polyesters (A) and (B) are respectively at a ratio of 97% and 3%. Each of the mixed raw materials is fed to two extruders as a raw material for the intermediate layer, melted at 285 ° C., and then two types and three layers (surface layer / intermediate layer / Coextruded and cooled and solidified with a layer structure of (surface layer = 1: 18: 1 discharge amount) to obtain an unstretched film. Thereafter, an aqueous coating solution B1 shown in Table 2 below was applied to both sides of the unstretched film and dried to obtain a film having a coating layer with a coating amount (after drying) of 0.2 g / m ^{2 on} one side. 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 aqueous coating solution A1 shown in Table 1 below was applied to both sides of the longitudinally stretched film. Then, the film was stretched 4.0 times at 120 ° C. in the transverse direction and heat-treated at 230 ° C., and then relaxed by 2% in the transverse direction. The coating amount of the coating layer (after drying and stretching) was 0.06 g / side. A polyester film with a thickness of 125 μm having a second coating layer of m ² was obtained. When the obtained polyester film was evaluated, the roughness of the film after longitudinal stretching was sufficient, the transparency was good, and the adhesion was good. The properties of this film are shown in Table 3 below.

Example 28:
In Example 27, a polyester film was obtained in the same manner as in Example 27 except that the coating composition of the second coating layer was changed to coating solution A2 shown in Table 1. As shown in Table 3 below, the finished polyester film had sufficient film roughness after longitudinal stretching, good transparency, and good adhesion.

Example 29:
In Example 27, a polyester film was obtained in the same manner as in Example 27 except that the coating composition of the second coating layer was changed to coating solution A3 shown in Table 1. As shown in Table 3 below, the finished polyester film had sufficient film roughness after longitudinal stretching, good transparency, and good adhesion.

Example 30:
In Example 27, the coating agent composition of the second coating layer was changed to coating solution A9 shown in Table 1, and the coating layer coating amount (after drying and stretching) was changed to 0.15 g / m ² on one side. In the same manner as in Example 27, a polyester film was obtained. As shown in Table 3 below, the finished polyester film had sufficient film roughness after longitudinal stretching, good transparency, and good adhesion.

Example 31:
In Example 27, the coating composition of the second coating layer was changed to coating solution A12 shown in Table 1, and the coating layer coating amount (after drying and stretching) was changed to 0.15 g / m ² on one side. In the same manner as in Example 27, a polyester film was obtained. As shown in Table 3 below, the finished polyester film had sufficient film roughness after longitudinal stretching, good transparency, and good adhesion.

Comparative Example 1:
In Example 1, it manufactured like Example 1 except not providing an application layer, and obtained the polyester film. When the finished polyester film was evaluated, as shown in Table 4 below, the roughness of the film after longitudinal stretching was small, there was a concern that scratches would easily occur, and the adhesion was poor.

Comparative Examples 2 to 10:
In Example 1, it manufactured like Example 1 except changing a coating agent composition into the coating agent composition shown in following Table 2, and obtained the polyester film. As shown in Table 4, the finished polyester film has a high haze and is a whitish film, or when the film after longitudinal stretching is not sufficiently rough, there are cases where the adhesion is weak. It was.

Comparative Example 11:
A mixed raw material in which polyesters (A), (B), and (D) were mixed at a ratio of 92%, 3%, and 5%, 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 film. Then, the aqueous coating liquid B3 shown in the following Table 2 was applied to both sides of the unstretched film and dried to obtain a film having a coating amount of 0.8 g / m ^{2 on} one side and a coating amount (after drying). Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the roll peripheral speed difference, then led to a tenter, stretched 4.0 times at 120 ° C. in the transverse direction, and heat-treated at 230 ° C. Thereafter, the film was relaxed by 2% in the transverse direction to obtain a polyester film having a thickness of 125 μm. When the obtained polyester film was evaluated, a particle feeling was observed and the film was whitish. The properties of this film are shown in Table 4 below.

  The film of the present invention has excellent transparency, and is suitable, for example, for applications that require adhesion to a surface functional layer such as a prism layer or a microlens layer used in a backlight unit of a liquid crystal display. Can be used.

Claims (1)

A laminated polyester film comprising a coating layer formed from a coating solution containing non-heat resistant particles and a (meth) acrylate compound on at least one side of the polyester film.