JP5608199B2 - Laminated polyester film - Google Patents

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 and strength, 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. Yes. 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.

  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 7). 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 2010-13550 A

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

  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 is that at least one surface of an unstretched polyester film has a coating layer formed by stretching a coating solution containing particles and then stretching in at least one direction, on the coating layer or on the coating layer. It has a coating layer formed from a coating solution containing a compound having an acrylate group or a methacrylate group on the side opposite to the layer and having a coating amount of 0.005 to 0.5 g / m ^2. It exists in the laminated polyester film.

  According to the polyester film of the present invention, it is possible to provide a film having excellent transparency and slipperiness, 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 size exceeds 3 μm, the transparency of the film may be deteriorated, or the graininess due to the particles may be generated and the visibility may be deteriorated.

  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). When it exceeds 1000 ppm, transparency may deteriorate, or graininess due to particles may occur and visibility may deteriorate.

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 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 obtaining an unstretched film by cooling and solidifying a molten film extruded from a die with a cooling roll using pellets obtained by drying the polyester raw material described above 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, a coating solution containing 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 particles is applied to the unstretched film, and stretched simultaneously in the machine direction and in the width direction, usually at a temperature of 70 to 120 ° C., preferably 80 to 110 ° C. The draw ratio is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times as the draw ratio. 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, on at least one surface of the unstretched polyester film, a coating layer (hereinafter sometimes abbreviated as a first coating layer) is formed from a coating solution containing particles, and then stretched in at least one direction. A coating layer formed from a coating solution containing a compound having a carbon-carbon double bond on the coating layer and / or on the side opposite to the coating layer (hereinafter sometimes abbreviated as a second coating layer). ) Is an essential requirement.

  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.

  Usually, when particles are present, they appear whitish due to light scattering. However, in the case of particles with a small amount of particles and a small particle size, the scattering of light is suppressed, so it was considered possible to maintain high transparency. When putting particles in the polyester film, the particles are embedded in the polyester film, and there are many particles that cannot be effectively slipped.Therefore, in order to exert slipperiness, a large amount of particles, and Since it is necessary to contain particles having a large particle size, the particles appear whitish. However, since the particles can be arranged only on the outermost surface of the polyester film by containing the particles in a coating layer that is thinner than the film, it is effective with a small amount of particles and a small particle size. The present inventors have considered that slipperiness can be imparted and have reached the present invention.

  The first coating layer (particles) of the present invention is formed at an early stage of the film production process, so that sufficient slipping can be achieved in various processes after the first coating layer is formed on the unstretched film formed after melt extrusion. It is used to ensure the property.

  Formation of the 1st coating layer in the film of this invention can be performed in the arbitrary steps after the unstretched film formed after melt extrusion. 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.

  The first coating layer in the film of the present invention is not limited to the following, for example, in sequential biaxial stretching, after the unstretched film is formed, the first coating layer is formed at an initial stage, and then A more suitable polyester film can be produced by performing the first stretching and then performing the high temperature treatment after the second stretching.

  The first 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 part. Moreover, in the case of both surfaces, the formation location may be simultaneous or different.

  In the film of the present invention, various conventionally known particles can be used as the particles used in the first coating layer. For example, silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate. And inorganic particles such as kaolin, aluminum oxide and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin and benzoguanamine resin. Among these, in order to ensure slipperiness even after production of the polyester film, particles having good heat resistance are preferably used, and inorganic particles and crosslinked organic particles are particularly preferable. Silica particles are more preferable from the viewpoint of transparency and the like.

  Although the average particle diameter of the particles depends on the thickness of the coating layer, it cannot be generally specified, but is preferably in the range of 0.01 to 1 μm, more preferably in the range of 0.02 to 0.5 μm, and still more preferably. The range is from 0.03 to 0.2 μm. When the average particle size is less than 0.01 μm, the slipperiness may not be sufficiently obtained. When the average particle size exceeds 1 μm, whitishness may remain as a film.

  In the formation of the first coating layer in the film of the present invention, it is preferable to use various polymers and adhesive compounds in combination in order to hold the particles on the film. In particular, it is preferable to use a polymer in combination for the purpose of improving the appearance of coating, improving the transparency, and further improving the adhesion with various layers provided on the coating layer.

  Specific examples of the polymer include polyester resin, acrylic resin, urethane resin, polyvinyl (polyvinyl alcohol, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, and starches. Among these, it is preferable to use a polyester resin, an acrylic resin, or a urethane resin from the viewpoint of particle retention and adhesion. Moreover, when considering familiarity with a polyester film, a polyester resin is optimal.

  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, urethane, etc.) is also contained. 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 obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a urethane solution or a urethane dispersion (in some cases, a mixture of polymers) 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, monobutyl hydroxyl fumarate, Various hydroxyl group-containing monomers such as monobutylhydroxy itaconate; various monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate ( (Meth) acrylic acid 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; And various conjugated dienes such as butadiene.

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

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

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

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

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

  Moreover, in the 1st application layer in this invention, in order to improve an intensity | strength, you may use a crosslinking agent together. As the crosslinking agent used in combination, various known crosslinking agents can be used, and examples thereof include an oxazoline compound, an epoxy compound, a melamine compound, an isocyanate compound, a carbodiimide compound, and a silane coupling compound.

  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 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 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 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.

  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 for improving adhesion with a surface functional layer such as a hard coat layer that can be formed on a coating layer, and for improving wet heat resistance of the coating layer. It is what 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.

  Regarding the formation of the first coating layer in the film of the present invention, a coating solution prepared by adjusting the solid content concentration to about 0.1 to 80% by weight using the above-described series of compounds as a solution or a dispersion of a solvent is used as an unstretched polyester. It is preferable to produce a polyester film in the manner of application on the film. 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.

If the objective is achieved, the quantity of the particle | grains which comprise the 1st application layer in the film of this invention will not be specifically limited. Moreover, since it depends on the size of the particles to be used and the film thickness of the first coating layer, it cannot be said unconditionally, but as an amount only on one side, it is a film after drying (before stretching), preferably 0.01 to 100 mg. / M ² , more preferably 0.1 to 50 mg / m ² , and even more preferably 1 to 30 mg / m ² .

Moreover, since the coating amount of the first coating layer (after drying and before stretching) depends on the size of the particles, the stretching ratio, etc., it cannot be generally stated, but is preferably 0.001 to 5 g / m ² or less. The range is more preferably in the range of 0.01 to 3 g / m ² , still more preferably in the range of 0.05 to 1 g / m ² , and most preferably in the range of 0.1 to 0.7 g / 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 first coating layer, for example, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, spray coating or the like is used. be able to.

  Moreover, when forming a 1st application layer in a film, you may perform surface treatments, such as a corona treatment and a plasma treatment, as needed.

  Moreover, in this invention, after forming a 1st coating layer and extending | stretching at least to one direction, a 2nd coating layer is formed in order to provide various performances. The second coating layer may be formed on the surface side on which the first coating layer is formed, or may be formed on the opposite surface side of the first coating layer. Further, it may be formed only on one side of the film or on both sides. Regarding the second coating layer, it may be provided by in-line coating, which treats the film surface during the process of forming a polyester film, or may be applied off-system on a once produced film. . Since the coating can be performed simultaneously with the film formation, the production can be handled at a low cost, and therefore in-line coating is preferably used.

  The in-line coating in the formation of the second coating layer is not limited to the following. For example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When the second coating layer is provided on the polyester film by in-line coating, coating can be performed simultaneously with film formation, and the coating layer can be processed at a high temperature in the heat treatment step of the stretched polyester film. The properties such as adhesion to various surface functional layers that can be formed on the coating layer and heat-and-moisture resistance can be improved. Further, when coating is performed before transverse stretching, the thickness of the coating layer can be changed by the stretching ratio, and thin film coating can be performed more easily than offline coating. That is, a film suitable as a polyester film can be produced by in-line coating, particularly coating before stretching.

  That is, as one of the preferable production methods in the present invention, for example, an unstretched film is formed after melt extrusion, and then a first coating layer is formed and then longitudinal stretching is performed to further form a second coating layer, Then, it is the method of processing at high temperature, after performing horizontal extending | stretching.

  The second coating layer in the film of the present invention is improved in adhesion with various surface functional layers such as a prism layer and a microlens layer, particularly with a coating layer aimed at a high-brightness prism layer and a microlens layer. It is provided for the purpose of improving the adhesion with a prism layer or microlens layer having a high refractive index that tends to lower the adhesion.

  In the formation of the second coating layer, a compound having a carbon-carbon double bond is used. This is due to the active energy rays irradiated when forming the prism layer and the microlens layer, in the coating layer of the film of the present invention. This is because the carbon-carbon double bond and the carbon-carbon double bond of the compound used for forming the prism layer or the microlens layer are reacted to form a covalent bond, thereby improving the adhesion.

  As the carbon-carbon double bond, conventionally known materials can be used as long as they react with the carbon-carbon double bond contained in the compound forming the prism layer or the microlens layer. Among them, it may be a polymer containing a carbon-carbon double bond for the purpose of strengthening the overall adhesion including the adhesion with the polyester film substrate and the covalent bond with various surface functional layers. Preferable examples include a polymer having a carbon-carbon double bond in the form of an acrylate group, a methacrylate group, a vinyl group, an allyl group, or the like.

  Examples of the polymer having a carbon-carbon double bond include urethane resins, acrylic resins, and polyester resins. Among them, urethane resins are preferable from the viewpoint of adhesion to the prism layer and the microlens layer. More preferred. Among urethane resins, a urethane resin having a polyester structure or a polycarbonate structure is more preferable.

  The ratio of the carbon-carbon double bond part (C = C part, molecular weight 24) to the entire compound having a carbon-carbon double bond used for forming the second coating layer is preferably 0.5% by weight. More preferably, it is in the range of 1.0% by weight or more, more preferably 1.5% by weight or more. When the ratio of the carbon-carbon double bond portion to the whole resin is 0.5% by weight or more, the adhesion to the prism resin and the microlens resin can be effectively maintained even with a resin having a particularly high refractive index. Can be useful.

  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 various polymers and the reactivity with the carbon-carbon double bond contained in the compound forming the prism layer or the microlens layer, an acrylate group or a methacrylate group having no substituent is preferable. An acrylate group having no substituent is more preferable.

  For the formation of the second coating layer, the carbon-carbon described above is used in order to improve the coating appearance and to improve the visibility and transparency when various prism layers and microlens layers are formed on the coating surface. Various polymers having no double bond can be used in combination. As the polymer, it is possible to use the above-described polymers that can be used in the formation of the first coating layer, and among these, from the viewpoint of adhesion to a surface functional layer such as a prism layer or a microlens layer, a polyester resin An acrylic resin and a urethane resin are preferable. Among them, a urethane resin, particularly a urethane resin having a polycarbonate structure or a polyester structure is preferable, and a urethane resin having a polycarbonate structure is more preferable.

  In forming the second coating layer, it is preferable to use a crosslinking agent together in order to strengthen the coating layer of the coating layer and improve the heat and heat resistance after the formation of the surface functional layer such as the prism layer and the microlens layer. Examples of the crosslinking agent include the oxazoline compounds, epoxy compounds, melamine compounds, isocyanate compounds, carbodiimide compounds, silane coupling compounds, and the like that can be used in the formation of the first coating layer. Among them, an oxazoline compound and an epoxy compound are preferable from the viewpoint of improving the adhesion, and in particular, the combined use of the oxazoline compound and the epoxy compound is preferable because the adhesion is significantly improved.

  In the film of the present invention, particles can be used in combination with the formation of the second coating layer for the purpose of blocking the coating layer and improving the 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. Moreover, when it is necessary to raise the effect of improving slipperiness, it is preferable to use particles having an average particle size larger than the film thickness of the coating layer. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, heat-resistant organic particles, and the like.

  Further, in the range not impairing the gist of the present invention, the above-mentioned coating layer is formed with an antifoaming agent, a coating property improving agent, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, an oxidation as necessary. Inhibitors, foaming agents, dyes, pigments and the like can be used.

  As a ratio with respect to all the non-volatile components in the coating liquid for forming the second coating layer, the compound having a carbon-carbon double bond is usually 20 to 90% by weight, preferably 30 to 85% by weight, more preferably 45 to 80%. It is in the range of wt%. However, when used in combination with other polymers having no carbon-carbon double bond, it is possible to make the amount less than the above range, and the ratio in that case is usually 20 to 90 weights in total with other polymers. %, Preferably 30 to 85% by weight, more preferably 45 to 80% by weight, in which the proportion of the compound having a carbon-carbon double bond is 5 to 80% by weight, preferably 10 to 10% by weight. It is in the range of 70% by weight, more preferably 15-60% by weight. When it is out of the above range, the adhesion with the prism layer or the microlens layer may not be sufficient.

  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 80 weight% or less normally, Preferably it is 10-60 weight%, More preferably, it is 20-50 weight%. It is a range. When outside the above range, the heat and moisture resistance and adhesion may not be sufficient.

  Analysis of particles used for forming the first coating layer and other components in the first and second coating layers should be performed, for example, by TOF-SIMS, ESCA, fluorescent X-ray, various surface / cross-sectional observations, etc. Can do.

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

Respect laminated polyester film of the present invention, the coating amount of the second coating layer provided on the polyester film is usually 0.002~1.0g / ^{m 2,} more preferably 0.005 to 0.5 / ^{m 2,} further preferably 0.01~0.2g / ^{m 2,} particularly preferably in the range of 0.01 to 0.1 g / ^{m 2.} If the coating amount is less than 0.002 g / m ^2, sufficient adhesion may not be obtained, and if it exceeds 1.0 g / m ² , the appearance, transparency, and film blocking properties may be deteriorated. There is sex.

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

  In the present invention, the drying and curing conditions for forming the second coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, it is usually 3 at 80 to 250 ° C. The heat treatment should be performed for ˜40 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when forming a 2nd application layer by in-line coating, it is good to heat-process normally for 3 to 200 seconds at 70-270 degreeC.

  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 polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  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 second coating layer of the laminated polyester film of the present invention, it is common to provide a prism layer, a microlens layer, or the like, which is an active energy ray-curable resin layer, in order to improve luminance. It is possible to provide a resin layer having a high refractive index which is difficult to ensure and is necessary for high luminance. 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 °. As the material used for the prism layer, conventionally known materials can be used, and examples thereof include materials made of an active energy ray-curable resin, and (meth) acrylate-based resins are typical examples.
As a constituent compound of the resin layer, generally, for example, it has a polyhydric alcohol component such as ethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, bisphenol A structure, urethane structure, polyester structure, epoxy structure, etc. (Meth) acrylate compounds may be mentioned.

  The refractive index of the active energy ray-curable resin layer is preferably higher because the luminance tends to be improved, and considering that the refractive index of the polyester film in the present invention is 1.65, it is usually 1.57. ˜1.65, preferably 1.58 to 1.64, more preferably 1.59 to 1.63. If it is out of the above range, the luminance may not be sufficiently increased.

  In order to increase the refractive index of the active energy ray-curable resin layer, a compound having a high refractive index structure such as an aromatic compound is used. Specific examples include a compound having a biphenyl structure, a compound having a fluorene structure, naphthalene, anthracene, phenanthrene, naphthacene, benzo [a] anthracene, benzo [a] phenanthrene, pyrene, benzo [c] phenanthrene, and perylene. Examples thereof include compounds having a cyclic aromatic structure.

  Various substituents may be introduced into the biphenyl structure, the fluorene structure, and the condensed polycyclic aromatic structure, and 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 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, 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%. If it is less than 10% by weight, the refractive index may be low, and the luminance may not be sufficient.

  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 microlens layer, the same material as that of the prism layer can be used.

  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 diameter of 10 particles was defined as the average particle diameter.

(3) Weight of carbon-carbon bond part in urethane resin After the urethane resin was dried 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) 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.

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

(6) 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.

(7) Evaluation method of transparency When the film is visually observed under a three-wavelength 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.

(8) Refractive Index Measuring Method An active energy ray-curable resin compound was placed flat on the coating layer side with a thickness of 10 μm and cured with ultraviolet rays to form a flat active energy ray-curable resin layer. 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.).

(9) Adhesion evaluation method In order to form a prism layer, an ethylene glycol-modified bisphenol A acrylate (ethylene glycol chain = 8) 50 wt. Parts, 4,4 ′-(9-fluorenylidene) bis (2-phenoxyethyl acrylate) 27 parts by weight, 2-biphenoxyethyl acrylate 20 parts by weight, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide 3 parts by weight The laminated polyester film was laminated in such a direction that the coating layer was in contact with the resin, and the composition was uniformly stretched by a roller, and the resin was cured by irradiating ultraviolet rays from an ultraviolet irradiation device. Subsequently, the film was peeled off from the mold member to obtain a film on which a prism layer (refractive index 1.60) was formed. The obtained film was treated in an environment of 60 ° C. and 90% RH for 24 hours, and then the prism layer was subjected to 10 × 10 cross-cut, and then a 18 mm wide tape (cello tape manufactured by Nichiban Co., Ltd.) (Registered Trademark) CT-18) is attached, and the peeled surface is peeled off rapidly at a peel angle of 180 degrees. If the peeled area is less than 5%, ◎, if it is less than 5% and less than 20%, If it was 20% or more and less than 50%, it was evaluated as Δ.

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 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)
Silica particles: (IA) Silica particles having an average particle size of 0.07 μm Silica particles: (IB) Silica particles having an average particle size of 0.15 μm Silica particles: (IC) Silica particles having an average particle size of 0.30 μm Particle: (ID) Silica particle having an average particle diameter of 0.45 μm

・ Polyester resin: (IIA)
Water dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / 1,4-butanediol / diethylene glycol = 56/40/4 // 70/20/10 (mol%)

Acrylic resin: (IIB) 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 (IIC)
Hydran AP-40 (manufactured by DIC Corporation), which is a carboxylic acid water-dispersed polyester polyurethane resin

・ 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 = 18: 12: 22: 26: 18: 4 (mol%) Urethane resin having a carbon-carbon double bond weight of 2.0% by weight

-Urethane resin having a carbon-carbon double bond: (IIE)
Hydroxyethyl acrylate unit: dicyclohexylmethane diisocyanate unit: hexamethylene diisocyanate trimer unit: caprolactone unit: ethylene glycol unit: dimethylolpropanoic acid unit = 23: 12: 22: 24: 15: 4 (mol%) Urethane resin having a carbon-carbon double bond weight of 2.6% by weight

-Urethane resin having a carbon-carbon double bond: (IIF)
Hydroxyethyl acrylate unit: dicyclohexylmethane diisocyanate unit: hexamethylene diisocyanate trimer unit: caprolactone unit: ethylene glycol unit: dimethylolpropanoic acid unit = 8: 10: 20: 38: 20: 4 (mol%) Urethane resin having a carbon-carbon double bond weight of 1.0% by weight

-Urethane resin having a carbon-carbon double bond: (IIG)
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%) Urethane resin having a carbon-carbon double bond weight of 0.7% by weight

・ Urethane resin without carbon-carbon double bond: (IIH)
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 Water dispersion obtained by neutralizing urethane resin consisting of parts by weight with triethylamine

・ Hexamethoxymethylmelamine (IIIA)

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

Epoxy compound: (IIIC) Denacol EX-521 (manufactured by Nagase ChemteX Corporation), which is polyglycerol polyglycidyl ether

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 first coating layer having a film thickness (after drying) of 0.2 g / m ² . 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, and then the aqueous coating solution B1 shown in Table 2 below was applied to both surfaces 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 layer thickness (after drying and stretching) was 0.03 g / m ^2. A polyester film having a thickness of 125 μm and having a second coating layer was obtained. When the obtained polyester film was evaluated, the transparency was good, the roughness of the film after longitudinal stretching was sufficient, and the interference unevenness level of the film after forming the hard coat layer was also good. The properties of this film are shown in Table 6 below.

Examples 2-29:
In Example 1, it manufactured like Example 1 except having changed an application agent composition into an application agent composition shown in Tables 1-4, and obtained a polyester film. As shown in Tables 6 and 7, the finished polyester film had good transparency, sufficient roughness of the film after longitudinal stretching, and good interference unevenness level of the film after forming the hard coat layer. .

Example 30:
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 first coating layer having a film thickness (after drying) of 0.2 g / m ² . 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, and then the aqueous coating solution B1 shown in Table 2 below was applied to both surfaces 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 layer thickness (after drying and stretching) was 0.03 g / m ^2. A polyester film having a thickness of 125 μm and having a second coating layer was obtained. When the obtained polyester film was evaluated, the transparency was good, the roughness of the film after longitudinal stretching was sufficient, and the interference unevenness level of the film after forming the hard coat layer was also good. The properties of this film are shown in Table 7 below.

Comparative Example 1:
In Example 1, it manufactured like Example 1 except not providing a 1st coating layer in an unstretched film, and obtained the polyester film. When the finished polyester film was evaluated, as shown in Table 8, the roughness of the film after longitudinal stretching was small, and there was a concern that scratches would easily occur.

Comparative Examples 2-5:
In Example 1, it manufactured like Example 1 except having changed an application agent composition into an application agent composition shown in Table 1, Table 2, and Table 5, and obtained a polyester film. As shown in Table 8, the finished polyester film had insufficient film roughness after longitudinal stretching, and clear interference unevenness could be observed.

Comparative Example 6:
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. 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, and then the aqueous coating solution B1 shown in Table 2 below was applied to both surfaces 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 layer thickness (after drying and stretching) was 0.03 g / m ^2. A polyester film having a thickness of 125 μm was obtained. When the obtained polyester film was evaluated, a particle feeling was observed and the film was whitish. The characteristics of this film are shown in Table 8 below.

  The film of the present invention has excellent transparency and slipperiness, for example, applications that require adhesion with surface functional layers such as prism layers and microlens layers used in backlight units of liquid crystal displays, etc. Can be suitably used.

Claims (3)

After having applied a coating solution containing particles on at least one side of an unstretched polyester film, it has a coating layer formed by stretching in at least one direction, on the coating layer or on the side opposite to the coating layer, A laminated polyester film having a coating layer formed from a coating solution containing a compound having an acrylate group or a methacrylate group and having a coating amount of 0.005 to 0.5 g / m ² . The laminated polyester film according to claim 1, further comprising a coating layer formed by stretching a coating solution containing particles on at least one side of the unstretched polyester film and then stretching in two directions. The laminated polyester film according to claim 1 or 2, further comprising an active energy ray-curable resin layer on a coating layer formed from a coating solution containing a compound having an acrylate group or a methacrylate group.