JP5557870B2 - Laminated polyester film - Google Patents

Description

  The present invention relates to a polyester film having a coating layer having excellent adhesion to various topcoats, and in particular, a high-brightness prism sheet having a coating layer having excellent adhesion to an active energy ray-curable resin. And a polyester film suitably used as a substrate for processing microlenses.

  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.

  The backlight system has a structure called an edge light type or a direct type. Recently, there is a tendency to reduce the thickness of liquid crystal displays, and an edge light type is increasingly used. The edge light type is generally configured in the order of a reflection sheet, a light guide plate, a light diffusion sheet, and a prism sheet. As the flow of light, the light incident on the light guide plate from the backlight is reflected by the reflection sheet and emitted from the surface of the light guide plate. The light beam emitted from the light guide plate enters the light diffusion sheet, is diffused and emitted by the light diffusion sheet, and then enters the next existing prism sheet or microlens sheet.

  The prism sheet and the microlens sheet used in this configuration are for improving the optical efficiency of the backlight and improving the luminance. 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 polyurethane resins are known (Patent Documents 1 to 3).

  As a method for forming the prism layer and the microlens layer, for example, an active energy ray-curable coating material is introduced into a mold, irradiated with active energy rays in a state of being sandwiched between polyester films, the resin is cured, and the mold is removed. The method of forming on a polyester 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, solventless paints are less permeable and swellable to the easy-adhesion layer laminated on the polyester film than solvent-based paints, and tend to have insufficient adhesion. A coating layer made of a specific polyurethane resin has been proposed to improve the adhesion, but even with such a coating layer, the adhesion has not always been sufficient for solventless paints. (Patent Document 4).

  In order to improve adhesion to a solventless resin, a coating layer mainly composed of a polyurethane resin and an oxazoline compound has been proposed. (Patent Document 5). However, it is derived from the current decrease in the number of backlights and the demand for lower power consumption, etc., and solvent-free resins corresponding to higher brightness of prism sheets and microlens sheets, that is, resins with a higher refractive index. Adhesion may not be sufficient.

  On the other hand, by providing a back coat on the surface opposite to the prism forming surface, there is a case where the light diffusion function is given and the brightness of the prism sheet is improved. (Patent Documents 6 to 7). However, from the viewpoint of reducing the number of steps and suppressing the manufacturing cost, it is preferable not to provide a back coat, and the polyester film base surface may be used as it is as the opposite surface of the prism forming surface.

  When the back coat is not provided, it is preferable from the viewpoint of manufacturing cost, but there arises a problem that the luminance is lowered when processed into a prism sheet or a micro lens sheet. This is because the polyester film base material has a high refractive index in the in-plane direction, and thus has a high light reflectance at the interface with air, and the total light transmittance is reduced as compared with the case where a back coat is provided.

JP-A-8-281890 Japanese Patent Laid-Open No. 11-286092 JP 2000-229395 A JP-A-2-158633 JP 2010-13550 A JP-A-6-324205 JP-A-10-160914

  The present invention has been made in view of the above circumstances, and the problem to be solved is that the refractive index has been increased for the purpose of increasing the brightness when processed into various topcoats, particularly prisms and microlenses, and more than in the past. Laminating that can be suitably used as a base material for prism sheets and microlens sheets having good adhesiveness even for active energy ray-curable resins with weak adhesiveness and having high brightness even when no backcoat is provided. It is to provide a polyester film.

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

That is, the gist of the present invention is that a polyester film has a coating layer formed from a coating solution containing a polyurethane resin having an acrylate group or a methacrylate group on one surface and a wavelength of 400 to 800 nm on the other surface. In this range, the laminated polyester film has a coating layer having a minimum absolute reflectance of 3.5% or less.

  According to the present invention, it is also possible to increase the refractive index for the purpose of increasing the brightness when processed into various top coats, particularly prisms and microlenses, and to an active energy ray-curable resin having lower adhesion than before. It is possible to provide a laminated polyester film that can be suitably used as a base material for prism sheets and microlens sheets having good adhesion and having high brightness even when no backcoat is provided. Value is high.

  The polyester film constituting the laminated polyester film in the present invention may have a single layer structure or a multilayer structure, and may have four or more layers as long as it does not exceed the gist of the present invention other than a two-layer or three-layer structure. It may be a multilayer, and is not particularly limited.

  The polyester used in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyester includes polyethylene terephthalate and the like. On the other hand, the dicarboxylic acid component of the copolyester includes isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), etc. 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexane dimethanol, neopentyl glycol, is mentioned.

  There is no restriction | limiting in particular as a polymerization catalyst of polyester, A conventionally well-known compound can be used, For example, an antimony compound, a titanium compound, a germanium compound, a manganese compound, an aluminum compound, a magnesium compound, a calcium compound etc. are mentioned. Among these, titanium compounds and germanium compounds are preferable because they have high catalytic activity, can be polymerized in a small amount, and the amount of metal remaining in the film is small, so that the brightness of the film becomes high. Furthermore, since a germanium compound is expensive, it is more preferable to use a titanium compound.

  The polyester film of the present invention may contain an ultraviolet absorber for improving the weather resistance of the film and preventing deterioration of the liquid crystal. The ultraviolet absorber is not particularly limited as long as it is a compound that absorbs ultraviolet rays and can withstand the heat applied in the production process of the polyester film.

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

  In the polyester layer of the film of the present invention, particles can be blended mainly for the purpose of imparting slipperiness and preventing scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples include inorganic particles such as magnesium, kaolin, aluminum oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, and benzoguanamine resin. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 5 micrometers or less normally, Preferably it is the range of 0.01-3 micrometers. When the thickness exceeds 5 μm, the surface roughness of the film becomes too rough, which may cause problems when various surface functional layers such as a hard coat layer are formed in a subsequent process.

Further, the content of particles in the polyester layer is usually less than 5% by weight, preferably in the range of 0.0003 to 3% by weight. When there are no or few particles, the transparency of the film becomes high and the film becomes a good film, but the slipperiness may be insufficient. There are cases where improvement is required. Further, when the particle content exceeds 5% by weight, the transparency of the film may be insufficient.
The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

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

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

  Next, 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 is preferred in which pellets obtained by drying the polyester raw material described above are extruded as a molten sheet from a die using a single screw extruder, and cooled and solidified with a cooling roll to obtain an unstretched sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In 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 laminated polyester film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is usually stretched and oriented in the machine direction and the width direction at a temperature controlled normally at 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  Next, formation of the coating layer which comprises the laminated polyester film in this invention is demonstrated. Regarding the coating layer, it may be provided by in-line coating which treats the film surface during the process of forming a polyester film, or offline coating which is applied outside the system on a once produced film may be adopted. Since the coating can be performed simultaneously with the film formation, the production can be handled at a low cost, and therefore inline coating is preferably used. The in-line coating is not limited to the following, but 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 coating layer is provided on the polyester film by in-line coating, it is possible to apply at the same time as the film formation, and the coating layer can be processed at a high temperature in the heat treatment process of the polyester film after stretching. Performances such as adhesion to various surface functional layers that can be formed on the layer and heat-and-moisture resistance can be improved. Moreover, when coating before extending | stretching, the thickness of an application layer can also be changed with a draw ratio, and compared with offline coating, thin film coating can be performed more easily. That is, a film suitable as a polyester film can be produced by in-line coating, particularly coating before stretching.

  In the present invention, a coating layer (hereinafter sometimes abbreviated as a first coating layer) formed from a coating solution containing a polyurethane resin containing a carbon-carbon double bond on one surface of a polyester film. And having a coating layer having a minimum absolute reflectance of 3.5% or less (hereinafter sometimes abbreviated as a second coating layer) on the other surface in a wavelength range of 400 to 800 nm. Is an essential requirement.

  The first coating layer in the film of the present invention is an active energy having a high refractive index, which has been used for the purpose of increasing brightness in recent years, which has been difficult to improve various adhesives, in particular, adhesion. It is designed to improve the adhesion to the linear curable resin, and for example, a prism layer, a microlens layer, or the like can be formed on the coating layer.

  The polyurethane resin containing a carbon-carbon double bond used for forming the first coating layer in the film of the present invention has a carbon-carbon double bond in the polyurethane resin. Any conventionally known material can be used as long as it reacts with the carbon-carbon double bond contained in the compound forming the microlens layer. For example, the method of introducing into a polyurethane resin in the form of an acrylate group, a methacrylate group, a vinyl group, an allyl group or the like can be mentioned.

  Various substituents can be introduced into the carbon-carbon double bond used to form the first coating layer in the film of the present invention, for example, an alkyl group such as a methyl group or an ethyl group, a phenyl group, It may have a structure such as a halogen group, an ester group, an amide group, or a conjugated double bond. Further, the amount of the substituent is not particularly limited, and any one monosubstituted, disubstituted, trisubstituted or tetrasubstituted can be used. In consideration of reactivity, the monosubstituted or disubstituted Body is preferable, and mono-substituted body is more preferable.

  Considering the ease of introduction into the polyurethane resin and the reactivity with the carbon-carbon double bond contained in the compound that forms 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.

  Further, the ratio of the carbon-carbon double bond part to the whole resin is preferably 0.5% by weight or more, more preferably 1.0% by weight or more, and further preferably 1.5% by weight or more. When the ratio of the carbon-carbon double bond part to the entire resin is 0.5% by weight or more, the adhesion to the prism resin and the microlens resin is effectively improved, particularly the adhesion to the resin having a high refractive index. improves.

  The polyurethane resin used for forming the first coating layer in the film of the present invention is a polymer compound having a urethane bond in the molecule, and is usually prepared by a reaction between a polyol and an isocyanate. Examples of the polyol include polyester polyols, polycarbonate polyols, polyether polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

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

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

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

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

  Examples of the polyisocyanates constituting the polyurethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, α, α, α ′, α′-tetra. Aliphatic diisocyanates having an aromatic ring such as methylxylylene diisocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, aliphatic diisocyanates such as trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylene bis (4 -Cyclohexyl Isocyanate), dicyclohexylmethane diisocyanate, alicyclic diisocyanates such as isopropylidene dicyclohexyl diisocyanates. These may be used alone or in combination. These polyisocyanate compounds may be a dimer, a trimer represented by an isocyanuric ring, or a higher polymer.

A chain extender may be used when synthesizing the polyurethane 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, butanediol and pentanediol, aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene, neopentyl glycol and neopentyl. Examples include glycols such as ester glycols such as glycol hydroxypivalate. 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 Alicyclic diamines such as isophorone diamine.

  The polyurethane resin in the film of the present invention may use a solvent as a medium, but preferably uses water as a medium. In order to disperse or dissolve the polyurethane 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 polyurethane resin, and a water-soluble type. In particular, a self-emulsification type in which an ionic group is introduced into a skeleton of a polyurethane 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, and quaternary ammonium salt, and a carboxyl group is preferred. As a method for introducing a carboxyl group into a polyurethane 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, dimethylolpropanoic 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 polyurethane resin. Can do. The carboxyl group is preferably in the form of a salt neutralized with ammonia, amine, alkali metal, inorganic alkali or the like. Particularly preferred are ammonia, trimethylamine and triethylamine. In such a polyurethane resin, a carboxyl group from which the neutralizing agent has been removed in the drying step after coating can be used as a crosslinking reaction point by another crosslinking agent. Thereby, it is possible to further improve the durability, solvent resistance, water resistance, blocking resistance, and the like of the obtained coating layer, as well as excellent stability in a liquid state before coating.

  For the formation of the first coating layer in the film of the present invention, in order to improve the appearance of the coating layer and the adhesion to various prism layers, microlens layers, etc., other than polyurethane resin having a carbon-carbon double bond These polymers can also be used in combination.

  Specific examples of the polymer include polyurethane resin having no carbon-carbon double bond, polyester resin, acrylic resin, polyvinyl (polyvinyl alcohol, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkylene. Examples include imine, methylcellulose, hydroxycellulose, and starches. Among these, from the viewpoint of adhesion with the surface functional layer such as a prism layer and a microlens layer, a polyester resin, an acrylic resin, and a polyurethane resin are preferable, and among them, a polyurethane resin, particularly a polycarbonate-based polyurethane resin and a polyester-based polyurethane resin are preferable. Furthermore, a polycarbonate-type polyurethane resin is preferable.

  In addition, in the formation of the first coating layer in the film of the present invention, a crosslinking agent is used to strengthen the coating film of the coating layer, and to improve the sufficient adhesion and wet heat resistance characteristics with the prism layer and the microlens layer. It is preferable to use together.

  Examples of the crosslinking agent include oxazoline compounds, epoxy compounds, melamine compounds, isocyanate compounds, carbodiimide compounds, silane coupling agents, and the like. 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.

  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 and vinylidene chloride; styrene, An α, β-unsaturated aromatic monomer such as α-methylstyrene can be used, 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 bonded product with a polyester resin or a polyurethane resin.

  A carbodiimide-based compound is a compound having a carbodiimide structure, and is a compound having one or more carbodiimide structures in the molecule, but for better adhesion, etc., the polycarbodiimide having two or more in the molecule More preferred are system compounds.

  The carbodiimide compound can be synthesized by a conventionally known technique, and generally a condensation reaction of a diisocyanate compound is used. The diisocyanate compound is not particularly limited, and any of aromatic and aliphatic compounds can be used. Specifically, tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexa Examples include methylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate.

Furthermore, in order not to lose the effect of the present invention, in order to improve the water solubility and water dispersibility of the polycarbodiimide compound, adding a surfactant, polyalkylene oxide, quaternary ammonium salt of dialkylamino alcohol, You may add and use hydrophilic monomers, such as a hydroxyalkyl sulfonate.
The second coating layer in the film of the present invention is designed to have a low reflectance when coated on a polyester film substrate. The prism sheet or microlens is formed with the second coating layer side as the rear surface side. When a sheet is prepared, a suitable luminance can be obtained even when a back coat is not provided.

  As a result of various studies to consider the optical characteristics of only the second coating layer, it has been found that it is important to consider the absolute reflectance of only the second coating layer. It has been noted that the reflectance and the transmittance are mutually related characteristics, and in general, a high transparency shows a low reflectance in a polyester film that absorbs less visible light and has high transparency.

  The second coating layer in the film of the present invention is a coating layer having a minimum absolute reflectance of 3.5% or less in the wavelength range of 400 to 800 nm in order to improve the luminance when processed into a prism sheet. It is essential to have. A more preferable condition for the wavelength having the minimum value is in the range of 400 to 700 nm, and more preferably in the range of 450 to 650 nm. Furthermore, the minimum value is preferably 3.0% or less, more preferably 2.5% or less.

  When the absolute reflectance of the second coating layer does not satisfy the above conditions, the total light transmittance of the laminated polyester film of the present invention is lowered, and there is a concern that the luminance when processed into a prism sheet is lowered.

  Since acrylic resin, urethane resin, and fluorine-containing resin generally have a low refractive index, they are suitable materials for achieving the absolute reflectance as described above, and are effective for forming the second coating layer in the present invention. Material.

  In the film of the present invention, the acrylic resin that can be used for forming the second coating layer is a polymer made of a polymerizable monomer having a carbon-carbon double bond, as represented by an acrylic or methacrylic monomer. It is a coalescence. 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 polysynthetic 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.

The polysynthetic monomer having a carbon-carbon double bond is not particularly limited, but as typical compounds, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, Various carboxyl group-containing monomers such as citraconic acid, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutylhydroxyl 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 ester Various nitrogen-containing compounds such as (meth) acrylamide, diacetone acrylamide, N-methylol acrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, propionic acid Various vinyl esters such as vinyl; various silicon-containing polysynthetic monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; phosphorus-containing vinyl monomers; such as vinyl chloride and biliden chloride Various vinyl halides; various conjugated dienes such as butadiene.
The polyurethane resin that can be used for forming the second coating layer of the present invention can be the same compound as that of the first coating layer, and can be obtained by reaction of various polyols with isocyanate.

  Examples of the fluorine-containing resin that can be used for forming the second coating layer of the present invention include a copolymer of a fluoroolefin and an alkyl vinyl ether, a polymer containing a polyfluoroalkyl group, and the like. For example, polytetrafluoroethylene, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / ethylene copolymer, copolymer of tetrafluoroethylene and heterocyclic fluorine-containing monomer. Polymer, polychlorotrifluoroethylene, fluoroalkyl (meth) acrylate polymer, fluoroalkyl (meth) acrylate and other alkyl (meth) acrylate copolymer, vinylidene fluoride, vinylidene fluoride and tetrafluoroethylene copolymer, And vinylidene fluoride and perfluoroalkyl vinyl ether copolymers.

  In forming the second coating layer in the film of the present invention, it is possible to use a polymer other than an acrylic resin, a polyurethane resin, or a fluorine-containing resin in order to improve the appearance and transparency of the coating layer.

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

  Furthermore, a crosslinking agent can be used in combination with the second coating layer as long as the gist of the present invention is not impaired. By using a cross-linking agent, the coating film becomes stronger, and the heat and moisture resistance and scratch resistance may be improved. Examples of the crosslinking agent include compounds similar to those in the first coating layer, such as an oxazoline compound, an epoxy compound, a melamine compound, an isocyanate compound, a carbodiimide compound, and a silane coupling agent.

  The crosslinking agent used for forming the first coating layer and the second coating layer in the film of the present invention is used in a design that improves the performance of the coating layer by reacting in the drying process or the 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.

  In forming the first coating layer and the second coating layer in the film of the present invention, it is preferable to use particles as a constituent component of the coating layer in order to improve slipperiness and blocking. The content of particles is preferably in the range of 0.3 to 25%, more preferably in the range of 0.4 to 15%, and more preferably in the range of 0.5 to 10% by weight ratio of the entire coating layer. More preferably, it is the range. If it is less than 0.3%, the effect of imparting slipperiness or preventing blocking may be insufficient. On the other hand, if it exceeds 25%, the transparency of the coating layer may be lowered, the coating film strength may be lowered due to the loss of the continuity of the coating layer, or the easy adhesion may be lowered.

  The average particle diameter of the particles used is preferably in the range of 1.0 μm or less, more preferably 0.5 μm or less, and 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, and organic particles.

  Furthermore, as long as the gist of the present invention is not impaired, the first coating layer and the second coating layer have an antifoaming agent, coating property improving agent, thickening agent, organic lubricant, antistatic agent, ultraviolet absorption as necessary. Agents, antioxidants, foaming agents, dyes, pigments and the like may be contained.

  The polyurethane resin containing a carbon-carbon double bond is usually 20 to 90% by weight, preferably 30 to 85% by weight as a proportion of the total nonvolatile components in the coating liquid formed by the first coating layer of the film of the present invention. More preferably, it is in the range of 45 to 80% by weight. However, when used in combination with other polymers, it is possible to make it less than the above range, and the ratio in that case is generally 20 to 90% by weight, preferably 30 to 85% by weight in total with other polymers, More preferably, it is in the range of 45 to 80% by weight, in which the proportion of the polyurethane resin containing a carbon-carbon double bond is 5 to 80% by weight, preferably 10 to 70% by weight, more preferably 15%. It is in the range of ˜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 1st coating layer of the film of this invention, a crosslinking agent is 80 weight% or less normally, Preferably it is 10 to 60 weight%, More preferably, it is 20 to 50 weight%. % Range. When outside the above range, the heat and moisture resistance and adhesion may not be sufficient.

  Regarding the film of the present invention, the total light transmittance of the film is preferably 90% or more, more preferably 91% or more, and further preferably 91.5% or more. When the total light transmittance of the film is less than 90%, there is a concern that sufficient luminance cannot be obtained when a prism or a microlens is processed on the first coating layer.

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

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

  In the film of the present invention, the thickness of the first coating layer provided on the polyester film is usually 0.002 to 1.0 μm, preferably 0.005 to 0.5 μm, more preferably 0.01 to 0.2 μm. Especially preferably, it is the range of 0.01-0.1 micrometer. When the film thickness is out of the above range, adhesion, coating appearance, and blocking characteristics may be deteriorated.

  Regarding the film of the present invention, the coating thickness of the second coating layer provided on the polyester film is usually in the range of 0.04 to 0.15 μm, preferably 0.07 to 0.13 μm. Although affected by the refractive index of the coating layer, when the coating thickness is out of this range, the reflectance increases and a film having sufficient transmittance may not be obtained, or the blocking characteristics may be deteriorated.

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

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

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

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

  In general, a prism layer, a microlens layer, or the like is provided on the first coating layer in the film of the present invention. In recent years, various shapes have been proposed in order to efficiently improve the luminance of the prism layer. Generally, prism rows having a triangular cross section are arranged 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, 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. ( Examples include meth) acrylate compounds.

  In recent years, in order to increase the brightness of prism sheets and microlens sheets, materials having a high refractive index are sometimes used. Examples of materials include benzene rings and naphthalene rings in addition to the above-mentioned general compounds. Examples thereof include compounds having many aromatic structures such as sulfur atoms, halogen atoms, and metal compounds. Among them, a method using a compound having an aromatic structure or a sulfur atom is 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 an 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.
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 the material used for the microlens layer, conventionally known materials can be used as in the prism layer, and examples thereof include an active energy ray curable resin.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example in the range which does not exceed the summary. The measurement method and evaluation method used in the present invention are as follows.

(1) Measuring method of intrinsic viscosity of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added. And dissolved at 30 ° C.

(2) Measuring method of average particle diameter The coating layer was observed using TEM (H-7650 made by Hitachi, acceleration voltage 100V), and the average value of the particle diameters of 10 particles was defined as the average particle diameter.

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

(4) Adhesion evaluation method of first coating layer (adhesion 1)
In order to form a prism layer, 50 parts by weight of ethylene glycol-modified bisphenol A acrylate (ethylene glycol chain = 8), 4,4 ′-( A composition comprising 27 parts by weight of 9-fluorenylidene) bis (2-phenoxyethyl acrylate), 20 parts by weight of 2-biphenoxyethyl acrylate, and 3 parts by weight of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide; 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 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.

(5) Evaluation method of absolute reflectance from one coating layer surface in polyester film A black tape (manufactured by Nichiban Co., Ltd., vinyl tape VT-50) is previously pasted on the measurement back surface of the polyester film, and a spectrophotometer (JASCO) Co., Ltd., UV-visible spectrophotometer V-570 and automatic absolute reflection measuring device ARM-500N), synchronous mode, incident angle 5 °, N-polarized light, response Fast, data collection interval 1.0 nm, band The absolute reflectance of the coated layer surface in the wavelength range of 400 to 800 nm was measured at a width of 10 nm and a scanning speed of 1000 nm / min, and the wavelength (bottom wavelength) and reflectance at the minimum value were evaluated.

(6) Measuring method of total light transmittance It measured by JIS K 7361 using Murakami Color Research Laboratory make haze meter HM-150.

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

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

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

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
Polyurethane resin having a carbon-carbon double bond: (U1)
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%) Polyurethane resin having a carbon-carbon double bond weight of 2.0% by weight

Polyurethane resin having a carbon-carbon double bond: (U2)
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%) Polyurethane resin having a carbon-carbon double bond weight of 2.6% by weight

Polyurethane resin having a carbon-carbon double bond: (U3)
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%) Polyurethane resin having a carbon-carbon double bond weight of 1.0% by weight

Polyurethane resin having a carbon-carbon double bond: (U4)
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%) Polyurethane resin having a carbon-carbon double bond weight of 0.7% by weight

Polyurethane resin having no carbon-carbon double bond: (U5)
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.

Acrylic resin: (A1)
Aqueous dispersion of acrylic resin polymerized with the following composition: Monomer composition: Emulsion weight of ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (% by weight) Combined (emulsifier: anionic surfactant)

Polyester resin (E1)
Aqueous 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%)

Epoxy compound (C1)
Denacol EX-521 (manufactured by Nagase ChemteX Corporation), which is polyglycerol polyglycidyl ether

Oxazoline compound (C2)
Acrylic polymer having oxazoline group and polyalkylene oxide chain, Epocros WS-500 (manufactured by Nippon Shokubai Co., Ltd., containing about 38% 1-methoxy-2-propanol solvent)

Hexamethoxymethylmelamine (C3)
Silica particles (F1) with an average particle size of 0.07 μm
Silica particles (F2) with an average particle size of 0.15 μm

Example 1:
A mixed raw material in which polyesters (A), (B), and (C) are mixed at a ratio of 89%, 5%, and 6%, respectively, is used as a raw material for the outermost layer (surface layer), and polyesters (A) and (B) are each 95 %, 5% mixed raw materials were used as intermediate layer raw materials, each was supplied to two extruders, melted at 285 ° C., and then on a cooling roll set at 40 ° C. Coextruded with a layer structure of layers (surface layer / intermediate layer / surface layer = 1: 18: 1 discharge amount) and cooled and solidified to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid A1 shown in Table 1 below was applied to one side of the longitudinally stretched film (first coating layer). The coating liquid B1 shown in Table 2 below is applied to the opposite surface (formation of the second coating layer), led to a tenter, stretched 4.0 times at 120 ° C. in the transverse direction, and heat-treated at 225 ° C. After that, the thickness is relaxed by 2% in the lateral direction, and has a coating layer in which the thickness of the first coating layer (after drying) is 0.03 μm and the thickness of the second coating layer (after drying) is 0.10 μm. A 125 μm polyester film was obtained. When the obtained polyester film was evaluated, the adhesion between the first coating layer and the prism layer was good, and the minimum absolute reflectance of the second coating layer was kept as low as 2.3%. The total light transmittance was 92.0%. The properties of this film are shown in Table 3 below.

Examples 2-25:
In Example 1, it manufactured like Example 1 except having changed the 1st application layer into the composition shown in Table 1, and the 2nd application layer in Table 2, and obtained the polyester film. The performance of the obtained polyester film is shown in Table 3.

Comparative Examples 1-3:
A polyester film was obtained in the same manner as in Example 1 except that the coating agent composition was changed to the compositions shown in Tables 1 and 2. The evaluation results of the obtained polyester film are as shown in Table 4, and the adhesion with the top coat resin was poor, or the absolute reflectance was high and there was a concern that the luminance would be lowered.

  The film of the present invention can be suitably used for applications that require adhesion and visibility with various surface functional layers, such as liquid crystal and plasma display members.

Claims (4)

One side of the polyester film has a coating layer formed from a coating solution containing a polyurethane resin having an acrylate group or a methacrylate group , and the other side has an absolute reflectance in a wavelength range of 400 to 800 nm. A laminated polyester film having a coating layer having a minimum value of 3.5% or less. The laminated polyester film according to claim 1, wherein the total light transmittance is 90% or more. The laminated polyester film according to claim 1 or 2, comprising an active energy ray-curable resin on a coating layer formed from a coating solution containing a polyurethane resin having an acrylate group or a methacrylate group . The laminated polyester film according to any one of claims 1 to 3, wherein the active energy ray-curable resin contains at least one structure selected from an aromatic compound, a biphenyl structure, and a fluorene structure.