JP6029717B2 - Method for producing laminated polyester film - Google Patents

Description

  The present invention relates to a method for producing a laminated polyester film, and particularly relates to a method for producing a laminated polyester film having excellent transparency.

  Because polyester film has excellent transparency and strength, it is used as a base material for touch panels, prism lens films, microlens films, light diffusion films, antireflection films, hard coat films, electromagnetic shielding films, moldings, etc. Yes. In recent years, especially for films used for forming surface functional layers including hard coat layers, such as display members such as touch panels, in-mold transfer films, in-mold label films, etc., more excellent transparency It is being sought.

  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. There was a case where it did.

  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. Until then, the slipperiness was poor and scratches were inevitable.

  In order to impart higher performance, various surface functional layers are usually formed on the polyester film. In recent years, clear hard coat processing has been increasingly performed on members of touch panels and molding members. In order to improve the adhesion between the polyester film and the hard coat layer, an easily adhesive coating layer is generally provided as an intermediate layer. For this reason, interference unevenness occurs unless the refractive index of the three layers of the polyester film, the easily adhesive coating layer, and the hard coat layer is taken into consideration.

  If a film with uneven interference is used for a molding member such as a display such as a touch panel or a casing of a mobile phone that requires a design, the visibility becomes poor and the film becomes difficult to use. Therefore, it is required to take measures against interference unevenness. In general, the refractive index of the coating layer for reducing interference unevenness is considered to be around the geometric mean of the refractive index of the polyester film of the substrate and the refractive index of the hard coat layer, and is adjusted to the refractive index around this. Ideally. Since the refractive index of the polyester film is high, it is generally necessary to design the coating layer with a high refractive index.

JP 2006-169467 A JP 2006-77148 A JP 2000-229355 A

  The present invention has been made in view of the above circumstances, and the solution is to have excellent transparency, good slipperiness, and various surface functional layers such as a hard coat layer have been formed. The object is to provide a polyester film with good visibility.

  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 is coated with a coating solution containing at least one non-crosslinked type non-heat resistant particle selected from acrylic resin, styrene resin, and vinyl resin, and at least The coating layer is formed by stretching in one direction, and has one minimum value in the wavelength range of 400 to 800 nm on the coating layer or on the side opposite to the coating layer. It exists in the manufacturing method of the laminated polyester film characterized by providing the coating layer whose absolute reflectance is 4.0% or more.

  According to the polyester film of the present invention, when various surface functional layers such as a hard coat layer are formed with excellent transparency and slipperiness, it is possible to provide a film with less interference unevenness due to reflection of external light. 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, by using a low-oligomerized polyester film as the surface layer material, various properties can be improved by changing the material of the surface layer and the intermediate layer for the purpose of preventing precipitation of the oligomer on the film surface. In this respect, a three-layer structure can be used.

  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, a titanium compound is preferable from the viewpoint of increasing the brightness of the film.

  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 also about the hardness, specific gravity, a color, etc.
These series of particles may be used in combination of two or more as required.

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

  The polyester film of the present invention may contain an ultraviolet absorber in order to improve the weather resistance of the film, for example, to prevent deterioration of the liquid crystal or the like of a liquid crystal display used for a touch panel or the like. The ultraviolet absorber is not particularly limited as long as it is a compound that absorbs ultraviolet rays and can withstand the heat applied in the production process of the polyester film.

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

  In the polyester film of the present invention, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, etc. may be added to the polyester film in the present invention as necessary in addition to the above-mentioned particles and ultraviolet absorbers. Can do.

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

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. That is, a method of 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 non-heat-resistant particles is applied to the unstretched film and dried to form a coating layer. Thereafter, the film is stretched in one direction by a roll or tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. is there. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can be adopted for the production of the polyester film constituting the polyester film. In the simultaneous biaxial stretching method, a coating solution containing non-heat-resistant particles is applied to the unstretched film, and the machine direction and the width direction are usually controlled at 70 to 120 ° C., preferably 80 to 110 ° C. The stretching ratio is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. Subsequently, heat treatment is performed at a temperature of 170 to 270 ° C. under tension or relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

In the present invention, a coating layer (hereinafter sometimes abbreviated as a first coating layer) is formed from a coating solution containing non-heat-resistant particles on at least one surface of an unstretched polyester film, and then at least in one direction. After stretching, the absolute reflectance has one minimum value in the wavelength range of 400 to 800 nm on the coating layer and / or on the side opposite to the coating layer, and the absolute reflectance at the minimum value is 4.0. It is an essential requirement to have a coating layer (hereinafter sometimes abbreviated as a second coating layer) that is at least%.

  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.

  The first coating layer (non-heat-resistant particles) of the present invention is formed at the initial stage of the film production process, so that the first coating layer is formed on the unstretched film formed after melt extrusion and before the high temperature treatment. In these various processes, it is used to ensure sufficient slipperiness.

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

The formation of the first coating layer in the film of the present invention can be carried out at any stage from after the unstretched film formed after melt extrusion to before high temperature treatment. In particular, in order to prevent damage due to the roll, it is preferable to carry out at an initial stage. Moreover, in the method of extending | stretching by making it contact with films, such as a roll, since the damage to a film becomes large, forming in the step before extending | stretching is preferable.

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

  The 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.

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

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

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

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

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

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

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

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

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

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

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

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

  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, polyurethane, etc.) is also included. For example, a block copolymer or a graft copolymer. Alternatively, a polymer (possibly a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or polyurethane dispersion is also included. Similarly, a polymer obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion (in some cases, a polymer mixture) is also included. Moreover, in order to improve adhesiveness, it is also possible to contain a hydroxyl group and an amino group.

  The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but particularly representative compounds include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citracone. Various carboxyl group-containing monomers such as acids, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 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; Various such as vinyl chloride and biridene chloride 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 the polycarbonate-based 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 polyurethane resin, a carboxyl group from which the neutralizing agent has been removed in the drying step after coating can be used as a crosslinking reaction point by another crosslinking agent. Thereby, it is possible to further improve the durability, solvent resistance, water resistance, blocking resistance, and the like of the obtained coating layer, as well as excellent stability in a liquid state before coating.

  Moreover, in 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, 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.

The amount of the non-heat-resistant particles constituting the first coating layer in the film of the present invention is not particularly limited as long as the object is achieved. Further, since it depends on the thermal characteristics and size of the particles to be used and the film thickness of the first coating layer, it cannot be generally stated. However, the amount of only one side is a film after drying (before stretching), preferably 0. range 01~200mg / ^{m 2,} more preferably from 0.1~150mg / ^{m 2,} more preferably in the range of 1~70mg / ^{m 2.}

  In addition, the film thickness of the first coating layer (after drying and before stretching) depends on the size of the particles, the stretching ratio, etc., so it cannot be generally stated, but is preferably in the range of 0.001 to 5 μm or less. Preferably it is the range of 0.01-3 micrometers, More preferably, it is the range of 0.05-1 micrometer, Most preferably, it is the range of 0.1-0.7 micrometer. When the film thickness is out of the above range, there is a concern about blocking, deterioration of the coating appearance, and dropout of particles. In addition, when the second coating layer is formed on the first coating layer and interference unevenness due to reflection of external light after various surface functional layers are formed is reduced, the first coating is applied in the range where the film thickness is thin. It was found that there is almost no influence of the layer and it is determined by the design of the second coating layer, but if the film thickness is too thick, the influence of the first coating layer becomes strong, and there is a concern that the design for reducing interference unevenness becomes difficult. There is.

  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 provided for improving adhesion with various surface functional layers such as a hard coat layer, reducing interference unevenness due to external light reflection, and the like.

  For the formation of the second coating layer, various polymers used in the formation of the first coating layer, as described above, in order to improve the adhesion with various surface functional layers and the coating appearance, It is possible to use a crosslinking agent or the like.

  The second coating layer in the film of the present invention needs to be designed with a high refractive index in order to reduce interference unevenness, and therefore it is necessary to use a material with a high refractive index. As the material having a high refractive index, a conventionally known material can be used. For example, an aromatic compound such as a benzene structure, a bisphenol A structure, a melamine structure, or a higher refractive index material among aromatics. Conceivable examples include condensed polycyclic aromatic compounds such as naphthalene structures, metal-containing compounds such as metal oxides and metal chelate compounds, compounds containing sulfur elements, and compounds containing halogen elements.

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

  Considering the applicability on the polyester film, the aromatic compound is preferably a polymer compound such as a polyester resin, an acrylic resin, or a urethane resin. In particular, it is more preferable because more aromatics can be introduced into the polyester resin.

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

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

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

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

  As a metal-containing compound that can be expected as a material capable of effectively increasing the refractive index of the coating layer, for example, titanium oxide, zinc oxide, tin oxide, antimony oxide, yttrium oxide, zirconium oxide, indium oxide, cerium oxide, ATO ( Antimony / tin oxide), metal oxides such as ITO (indium / tin oxide), aluminum such as aluminum acetylacetonate, hydroxyaluminum diacetate, dihydroxyaluminum acetate; tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate Dimer, tetra (2-ethylhexyl) titanate, tetramethyl titanate, titanium acetylacetonate, titanium tetraacetylacetonate, polytitanium acetylacetonate, titanium octoate Trens such as lenglycolate, titanium lactate, titanium triethanolamate, titanium ethyl acetoacetate; irons such as iron acetylacetonate and iron acetate; cobalts such as cobalt acetylacetonate; copper acetate, copper acetate monohydride Rate, copper acetate multihydrate, copper such as copper acetylacetonate; zinc such as zinc acetate, zinc acetate dihydrate, zinc acetylacetonate hydrate; zirconium acetate, zirconium normal propylate, zirconium normal butyrate, Examples thereof include organic compounds having metal elements such as zirconium such as zirconium tetraacetylacetonate, zirconium monoacetylacetonate, and zirconium bisacetylacetonate. These may be used alone or in combination of two or more.

  Among the above-mentioned metal compounds, metal chelate compounds are particularly preferable in terms of good coating appearance and transparency, and when considering application to in-line coating, water-soluble titanium chelate compounds, water-soluble zirconium chelate compounds are more preferable, From the viewpoint of the stability of the coating solution when used in an aqueous system, titanium triethanolamate and titanium lactate are more preferable.

  In consideration of the stability of the coating solution and the coating appearance, it is preferable to use two or more metal chelate compounds in combination, and particularly preferable to use two types of titanium chelate compounds in combination. That is, when the metal chelate compound is used for forming the second coating layer, the optimum form is to use titanium triethanolamate and titanium lactate in combination.

Moreover, it is also possible to use particles in the above-mentioned second coating layer for the purpose of blocking and improving slipperiness. The average particle size is preferably in the range of 1.0 μm or less, more preferably 0.5 μm or less, particularly preferably 0.2 μm or less from the viewpoint of the transparency of the film. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, heat-resistant organic particles, and the like. Among these, silica is preferable from the viewpoint of transparency.

  Further, in the range not impairing the gist of the present invention, the above-mentioned coating layer may include an antifoaming agent, a coating property improving agent, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, and an antioxidant as necessary. , Foaming agents, dyes, pigments and the like may be contained.

  Analysis of the final form of the non-heat-resistant particles used for forming the first coating layer, and other components in the first and second coating layers, for example, TOF-SIMS, ESCA, fluorescent X-rays, various surfaces, It can be performed by cross-sectional observation or the like.

  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.

  Regarding the polyester film in the present invention, the film thickness of the second coating layer provided on the polyester film is usually in the range of 0.05 to 0.16 μm, preferably 0.07 to 0.13 μm, as a film after drying and stretching. Range. When the film thickness is out of the above range, visibility may deteriorate due to interference unevenness after the surface functional layer is laminated.

  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 may 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.

  The second coating layer in the present invention has a refractive index adjusted in order to suppress the occurrence of interference unevenness, and the refractive index is a geometric mean of the surface functional layer such as the polyester film of the substrate and the hard coat layer. It is designed in the vicinity. The refractive index of the coating layer and the reflectance of the coating layer are closely related. The absolute reflectance of the second coating layer of the film of the present invention is a graph showing the wavelength on the horizontal axis and the reflectance on the vertical axis, and the minimum value of the reflectance needs to be one in the wavelength range of 400 to 800 nm. There is a minimum value of 4.0% or more. In the range of the absolute reflectance of the present invention, if the minimum value appears at the same wavelength, the reflectance of the minimum value is a high value when the refractive index is high, and a low value when the refractive index is low.

  In the present invention, the absolute reflectance of the second coating layer has one minimum value in the wavelength range of 400 to 800 nm, more preferably one minimum value in the wavelength range of 500 to 700 nm. The minimum value is preferably in the range of 4.0 to 6.5%, more preferably 4.5 to 6.2%. If the minimum value in the wavelength range of 400 to 800 nm is not one, and if the absolute reflectance of the minimum value deviates from the above value, interference unevenness occurs after the surface functional layer such as a hard coat layer is formed. The visibility of the film may be reduced.

  The polyester film of the present invention is generally provided with a surface functional layer such as a hard coat layer on the second coating layer. Although it does not specifically limit as a material used for a hard-coat layer, For example, hardened | cured materials, such as reactive silicon compounds, such as monofunctional (meth) acrylate, polyfunctional (meth) acrylate, and tetraethoxysilane, are mentioned. Among these, from the viewpoint of achieving both productivity and hardness, a polymerization cured product of a composition containing an active energy ray-curable (meth) acrylate is particularly preferable.

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

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

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

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

  Other components contained in the composition containing the active energy ray-curable (meth) acrylate are not particularly limited. Examples thereof include inorganic or organic fine particles, a polymerization initiator, a polymerization inhibitor, an antioxidant, an antistatic agent, a dispersant, a surfactant, a light stabilizer and a leveling agent. In addition, when the film is dried after film formation in the wet coating method, an arbitrary amount of solvent can be added.

  As a method for forming the hard coat layer, when an organic material is used, a general wet coat method such as a roll coat method or a die coat method is employed. The formed hard coat layer can be subjected to a curing reaction by heating, irradiation with active energy rays such as ultraviolet rays and electron beams as necessary.

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

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

(2) Measuring method of average particle diameter of particles The film was observed using an electron microscope (S-4500 manufactured by HITACHI), and the average value of the particle diameters of 10 particles was defined as the average particle diameter. The non-heat resistant particles were observed on the film before the high temperature process, that is, after the longitudinal stretching and before the transverse stretching.
(3) Method for measuring film thickness of coating layer The surface of the coating layer was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the section prepared by ultramicrotomy stained with RuO _4, a coating layer cross-section was measured by using a TEM (Hitachi High Technologies Corporation H-7650, accelerating voltage 100 V).

(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 K7136.

(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 measuring system (MN537N-M100, manufactured by Ryoka System Co., Ltd.) 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) Evaluation method of absolute reflectance from the surface of the second coating layer in the polyester film In advance, a black tape (vinyl tape VT-50 manufactured by Nichiban Co., Ltd.) is pasted on the measurement back surface of the polyester film, and a spectrophotometer (JASCO Corporation) Using UV-Vis spectrophotometer V-570 and automatic absolute reflectance measuring device ARM-500N), synchronous mode, incident angle 5 °, N-polarized light, response Fast, data collection interval 1.0 nm, bandwidth 10 nm The absolute reflectance in the wavelength range of 400 to 800 nm was measured on the coating layer surface at a scanning speed of 1000 m / min, and the wavelength (bottom wavelength) and reflectance at the minimum value were evaluated.

(9) Interference unevenness evaluation method On the second coating layer side of the polyester film, 72 parts by weight of dipentaerythritol hexaacrylate, 18 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, 10 parts by weight of antimony pentoxide, photopolymerization start Apply a mixed coating solution of 1 part by weight of agent (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) and 200 parts by weight of methyl ethyl ketone so that the dry film thickness is 5 μm, and cure by irradiating with ultraviolet rays to hard coat layer Formed. The obtained film is visually observed under a three-wavelength fluorescent lamp, and interference unevenness is observed. If the interference unevenness is not confirmed, ◎, thin sparse interference unevenness is confirmed, thin, linear The case where the interference unevenness was confirmed was indicated by Δ, and the case where clear interference unevenness was confirmed was indicated by ×.

(10) Method for evaluating adhesion of second coating layer 10 × 10 cross cut is performed on the film on which the hard coat layer obtained in the evaluation of (9) is formed, and 18 mm wide is formed thereon. Tape (Nichiban Co., Ltd. Cellotape (registered trademark) CT-18) was applied and the peeled surface was observed after abrupt peeling at a 180 degree peel angle. If the peeled area was less than 10%, 10% If less than 50%, Δ, and if more than 50%, ×.

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

・ Condensed polycyclic aromatic polyester resin: (IID)
Water dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / diethylene glycol = 92/8 // 80/20 (mol%)

・ 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.

・ Organic compound with metal element: (IVA) Titanium triethanolamate ・ Organic compound with metal element: (IVB) Titanium lactate

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 thickness (after drying) of 0.2 μm. 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, heat-treated at 230 ° C., then relaxed 2% in the transverse direction, and the coating layer thickness (after drying / stretching) was 0.10 μm. A polyester film having a coating layer and a thickness of 125 μm 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 4 below.

Examples 2 to 22:
In Example 1, it manufactured like Example 1 except having changed an application agent composition into an application agent composition shown in Tables 1-3, and obtained a polyester film. As shown in Table 4, the finished polyester film had good transparency, sufficient roughness of the film after longitudinal stretching, and the interference unevenness level of the film after forming the hard coat layer was also good.

Example 23:
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 thickness (after drying) of 0.2 μm. 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, heat-treated at 230 ° C., then relaxed 2% in the transverse direction, and the coating layer thickness (after drying / stretching) was 0.10 μm. A polyester film having a coating layer and a thickness of 125 μm 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 4 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 4, the roughness of the film after longitudinal stretching was small, and there was a concern that scratches would easily occur.

Comparative Examples 2-4:
In Example 1, it manufactured like Example 1 except having changed an application agent composition into an application agent composition shown in Tables 1-3, and obtained a polyester film. As shown in Table 4, the finished polyester film has a high haze and is whitish as a film, or when the film is not sufficiently rough after longitudinal stretching, or clear interference unevenness can be observed. A case was seen.

Comparative Example 5:
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. Guide, stretched 4.0 times at 120 ° C in the transverse direction, heat treated at 230 ° C, relaxed 2% in the transverse direction, and the coating layer thickness (after drying and stretching) is 0.10 µm 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 properties of this film are shown in Table 4 below.

  The film of the present invention can be suitably used for applications that require excellent transparency, such as a film member for transparent electrodes such as a touch panel and a film for molding.

Claims (4)

At least one surface of the unstretched polyester film is coated with a coating solution containing at least one non -crosslinking type non-heat resistant particle selected from acrylic resin, styrene resin, and vinyl resin, and then stretched in at least one direction to be a coating layer And has one absolute value in the wavelength range of 400 to 800 nm on the coating layer or on the side opposite to the coating layer, and the absolute reflectance at the minimum value is 4.0%. The manufacturing method of the laminated polyester film characterized by providing the application layer which is the above. The method for producing a laminated polyester film according to claim 1, wherein the internal haze is 0.0 to 1.0%. The lamination according to claim 1 or 2, wherein the coating film containing non-heat-resistant particles is longitudinally stretched, and the film (Sa) on the cooled and solidified surface before lateral stretching is 5 nm or more. A method for producing a polyester film. The method for producing a laminated polyester film according to any one of claims 1 to 3, wherein the polyester polymerization catalyst is a titanium compound.