JP2014210422A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for which excellent transparency, slipperiness and adhesiveness are required, and for example, to provide a polyester film capable of suitably being used as a member for protecting a polarizing plate used for a liquid crystal display.SOLUTION: There is provided a laminated polyester film which has a coating layer formed by applying a coating liquid containing non-heat-resistant particles on at least one surface of an unstretched polyester film and then stretching the film in at least one direction and has a coating layer formed from a coating liquid containing a polyvinyl alcohol on the coating layer or on an opposite surface side to the coating layer.

Description

  The present invention relates to a laminated polyester film, and particularly relates to a laminated polyester film that has excellent transparency and is suitably used, for example, as a member for protecting a polarizing plate used in a liquid crystal display.

  Polyester film has excellent transparency, strength, etc., so protective film for polarizing plate, prism lens film, microlens film, light diffusion film, antireflection film, hard coat film, electromagnetic shielding film, touch panel, for molding It is used as a base material. In recent years, more excellent transparency is being demanded especially for films used around liquid crystal displays.

  Conventionally, a technique of incorporating particles into a polyester film for the purpose of easy slipping has been common (Patent Documents 1 and 2). However, in the case of the method of incorporating particles in the polyester film, the haze of the film becomes high and becomes whitish, or when observed under a fluorescent lamp, graininess due to the particles is seen and visibility is deteriorated. In some cases, the brightness decreases due to light scattering by the particles, or when the particles become a foreign substance due to aggregation or the like to form a polarizing plate, or in the inspection process.

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

  The liquid crystal display has a front-side polarizing plate // liquid crystal // rear-side polarizing plate, where the display side is the front side and the opposite side (backlight side) is the rear side. The polarizing plate usually has a configuration in which a protective film or the like is bonded to a polarizing film of a polyvinyl alcohol film which is uniaxially stretched (protective film / polarizing film / protective film). The protective films disposed on the front and rear surfaces of the polarizing film constituting the front polarizing plate are designated as protective film A and protective film B, respectively, and the protective films disposed on the front and rear surfaces of the polarizing film constituting the rear polarizing plate. Assuming that the film is a protective film C and a protective film D, respectively, the overall configuration is as follows: from the front side, protective film A / front side polarizing film / protective film B // liquid crystal // protective film C / rear side polarizing film / protective Film D is obtained.

As the protective film, a triacetyl cellulose film (hereinafter sometimes abbreviated as a TAC film) is often used because it has high transparency and optical isotropy.
However, it is inferior in dimensional stability and heat-and-moisture resistance, and has the disadvantage that the surface must be saponified beforehand with an alkaline solution in order to adhere to the polarizing film. As liquid crystal displays increase in size and quality in recent years, improvement in mechanical strength and stability under high-temperature and high-humidity environments is required. The need to avoid quality degradation has emerged. Further, since the alkali treatment uses a high-concentration alkaline solution, it is not preferable in terms of work safety and environmental protection.

  In order to solve these problems, studies on materials other than TAC films such as norbornene-based films have been conducted (Patent Documents 4 and 5). However, since a film made of another material does not use a general-purpose resin, there is a problem that the cost is high. Then, the method of using the polyester film which is general purpose resin which can ensure dimensional stability, does not require the process of the alkali treatment which has various problems, and also has no problem also in cost is also proposed.

  However, the polyester film alone has a drawback that the adhesiveness between the polarizing film and the adhesive used for bonding the protective film is poor. In order to improve the adhesion of the polyester film, a configuration in which an anchor layer is provided has also been proposed, but there is no specific disclosure, and depending on the adhesive, it is difficult to ensure sufficient adhesion. (Patent Documents 6 to 8).

JP 2006-169467 A JP 2006-77148 A JP 2000-229355 A JP-A-6-511117 JP 2006-227090 A JP 2002-116320 A JP-A-8-271733 JP-A-8-271734

  The present invention has been made in view of the above circumstances, and the solution is to have excellent transparency and slipperiness, and adhesion between the polarizing film and the adhesive used to bond the protective film. Is suitable, for example, as a protective film for the polarizing film, particularly as a protective film on the front side of the front side polarizing plate (the above protective film A) or a protective film on the back side of the rear side polarizing plate (the above protective film D). It is providing the laminated polyester film which can be utilized for.

  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 to have a coating layer formed on at least one side of an unstretched polyester film by stretching a coating solution containing non-heat-resistant particles and then stretching in at least one direction. Or it exists in the laminated polyester film characterized by having the coating layer formed from the coating liquid containing a polyvinyl alcohol in the opposite surface side from the said coating layer.

  According to the polyester film of the present invention, it is possible to provide a film excellent in transparency and slipperiness, and excellent in adhesiveness with an adhesive or the like used for bonding the polarizing film and the protective film. Value is high.

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

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

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

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

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

  The content of the particles depends on the average particle size, but in the polyester film layer containing the particles, it is usually in the range of 1000 ppm or less, preferably in the range of 500 ppm or less, more preferably in the range of 50 ppm or less (intentionally contained). Do not). If it exceeds 1000 ppm, if the transparency deteriorates, the graininess due to the particles occurs and the visibility deteriorates, or the brightness of the film decreases due to light scattering by the particles, the particles are aggregated and foreign matter There is a concern about the occurrence of defects such as

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 is a range which can be formed into a film as a film, Usually, 10-300 micrometers, Preferably it is the range of 15-250 micrometers.

Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. That is, a method of drying the polyester raw material pellets described above and cooling and solidifying the molten film extruded from the die with a cooling roll using a single screw extruder is preferable. In this case, in order to improve the flatness of the film, it is preferable to improve the adhesion between the film and the rotary cooling drum, and an electrostatic application adhesion method or a liquid application adhesion method is preferably employed. Next, the obtained unstretched film is stretched in the biaxial direction. In that case, first, 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, a coating layer formed from a coating solution containing polyvinyl alcohol (hereinafter sometimes abbreviated as a second coating layer) is formed on the coating layer and / or on the side opposite to the coating layer. Is an essential requirement.

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

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

  The 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 the same or different.

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

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

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

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

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

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

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

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

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

  That is, in the film of the present invention, the best form of the non-heat-resistant particles used for forming the 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, monobutylhydroxyfumarate, mono Various hydroxyl group-containing monomers such as butylhydroxy itaconate; various (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate ) Acrylic esters; Various nitrogen-containing compounds such as meth) acrylamide, diacetone acrylamide, N-methylolacrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, vinyl propionate Various vinyl esters such as: Various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; Phosphorus-containing vinyl monomers; Various such as vinyl chloride and biridene chloride And various conjugated dienes such as butadiene.

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

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

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

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

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

  Examples of the polyisocyanate compound used for obtaining the urethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, α, α, α ′, α ′. -Aliphatic diisocyanates having aromatic rings such as tetramethylxylylene diisocyanate, aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl Methanzi Cyanate, alicyclic diisocyanates such as isopropylidene dicyclohexyl diisocyanates. These may be used alone or in combination.

  A chain extender may be used when synthesizing the urethane resin, and the chain extender is not particularly limited as long as it has two or more active groups that react with an isocyanate group. Alternatively, a chain extender having two amino groups can be mainly used.

  Examples of the chain extender having two hydroxyl groups include aliphatic glycols such as ethylene glycol, propylene glycol and butanediol, aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene, and esters such as neopentyl glycol hydroxypivalate. And glycols such as glycols. Examples of the chain extender having two amino groups include aromatic diamines such as tolylenediamine, xylylenediamine, and diphenylmethanediamine, ethylenediamine, propylenediamine, hexanediamine, 2,2-dimethyl-1,3- Propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10- Aliphatic diamines such as decane diamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, isoprobilitincyclohexyl-4,4′-diamine, 1,4-diaminocyclohexane, 1 , 3-Bisaminomethylcyclohexa And alicyclic diamines such as

The urethane resin in the present invention may use a solvent as a medium, but preferably uses water as a medium. In order to disperse or dissolve the urethane resin in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into the urethane resin, and a water-soluble type. In particular, a self-emulsification type in which an ionic group is introduced into the skeleton of a urethane resin to form an ionomer is preferable because of excellent storage stability of the liquid and water resistance, transparency, and adhesion of the resulting coating layer.
Examples of the ionic group to be introduced include various groups such as a carboxyl group, sulfonic acid, phosphoric acid, phosphonic acid, quaternary ammonium salt, and the like, and a carboxyl group is preferable. As a method for introducing a carboxyl group into a urethane resin, various methods can be taken in each stage of the polymerization reaction. For example, there are a method of using a carboxyl group-containing resin as a copolymer component during prepolymer synthesis, and a method of using a component having a carboxyl group as one component such as polyol, polyisocyanate, and chain extender. In particular, a method in which a desired amount of carboxyl groups is introduced using a carboxyl group-containing diol depending on the amount of this component charged is preferred. For example, dimethylolpropionic acid, dimethylolbutanoic acid, bis- (2-hydroxyethyl) propionic acid, bis- (2-hydroxyethyl) butanoic acid and the like are copolymerized with a diol used for polymerization of a urethane resin. Can do. The carboxyl group is preferably in the form of a salt neutralized with ammonia, amine, alkali metal, inorganic alkali or the like. Particularly preferred are ammonia, trimethylamine and triethylamine. In such a 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. Various known crosslinking agents can be used as the crosslinking agent to be used in combination, and examples thereof include oxazoline compounds, epoxy compounds, melamine compounds, isocyanate compounds, carbodiimide compounds, aziridine compounds, and silane coupling compounds. .

  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 isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate, and aromatic rings such as α, α, α ′, α′-tetramethylxylylene diisocyanate. Aliphatic isocyanates such as aliphatic isocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylene bis (4-cyclohexyl isocyanate), isopropylidene dicyclohexyl diisocyanate Ne Alicyclic isocyanates such as bets are exemplified. Further, polymers and derivatives such as burettes, isocyanurates, uretdiones, and carbodiimide modified products of these isocyanates are also included. These may be used alone or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferable than aromatic isocyanates in order to avoid yellowing due to ultraviolet rays.

  When used in the state of blocked isocyanate, the blocking agent includes, for example, bisulfites, phenolic compounds such as phenol, cresol, and ethylphenol, and alcohols such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol. Compounds, active methylene compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate and acetylacetone, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, lactam compounds such as ε-caprolactam and δ-valerolactam , Amine compounds such as diphenylaniline, aniline, ethyleneimine, acetanilide, acid amide compounds of acetic acid amide, formaldehyde, acetoald Examples include oxime compounds such as oxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime, and these may be used alone or in combination of two or more.

  In addition, the isocyanate compound in the present invention may be used alone, or may be used as a mixture or bond with various polymers. In the sense of improving the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or a bond with a polyester resin or a urethane resin.

  A carbodiimide-based compound is a compound having a carbodiimide structure, and is used to improve adhesion with various surface functional layers that can be formed on a coating layer and to improve the heat and humidity resistance of the coating layer. is there. The carbodiimide compound is a compound having one or more carbodiimide or carbodiimide derivative structures in the molecule, but a polycarbodiimide compound having two or more in the molecule is more preferable for better adhesion and the like.

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

  Furthermore, in order not to lose the effect of the present invention, in order to improve the water solubility and water dispersibility of the polycarbodiimide compound, adding a surfactant, polyalkylene oxide, quaternary ammonium salt of dialkylamino alcohol, You may add and use hydrophilic monomers, such as a hydroxyalkyl sulfonate.

  These cross-linking agents are used in a design that improves the performance of the coating layer by reacting in the drying process or film forming process. It can be inferred that unreacted products of these crosslinking agents, compounds after the reaction, or mixtures thereof exist in the finished coating layer.

  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 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.}

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

  In the film of the present invention, the first coating layer may be formed by, for example, gravure coating, reverse roll coating, die coating, air doctor coating, blade coating, rod coating, bar coating, curtain coating, knife coating, transfer roll coating. Conventionally known coating methods such as squeeze coating, impregnation coating, kiss coating, spray coating, calendar coating, extrusion coating, and the like can be used.

  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. Moreover, you may form only in the single side | surface side of a film, and may form in both surfaces. 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 2nd application layer in the film of the present invention is an application layer for improving adhesiveness with various functional layers, for example, various adhesion used for pasting together a polarizing film and a lamination polyester film of the present invention. It is provided in order to improve the adhesiveness with the agent.

  The polyvinyl alcohol used for the formation of the second coating layer has a polyvinyl alcohol moiety. For example, polyvinyl alcohol including a modified compound partially acetalized or butyralized with respect to polyvinyl alcohol is known. Alcohol can be used. The degree of polymerization of polyvinyl alcohol is not particularly limited, but is usually 100 or more, preferably 300 to 40,000. When the degree of polymerization is less than 100, the water resistance of the coating layer may decrease. Further, the saponification degree of polyvinyl alcohol is not particularly limited, but it is preferably a saponified polyvinyl acetate having a range of 70 mol% or more, more preferably 80 to 99 mol%, and still more preferably 86 to 97 mol%.

  In order to improve the adhesiveness with various functional layers and improve the coating appearance, it is preferable to use various polymers other than polyvinyl alcohol in combination for forming the second coating layer. As the polymer, various polymers used in the formation of the first coating layer can be used, and among them, a polyester resin, an acrylic resin, and a urethane resin are preferable, and a polyester resin is more preferable from the viewpoint of improving adhesiveness. preferable.

  When the polyester resin is used after being dispersed in water, a hydrophilic functional group is generally contained in the polyester resin. Examples of the hydrophilic functional group include a carboxylic acid group and a sulfonic acid group. A dispersion with a carboxylic acid group is preferable in terms of improving adhesiveness.

  Moreover, in order to strengthen the coating film of the coating layer and improve various adhesive properties, it is preferable to use a crosslinking agent in combination in forming the second coating layer. Examples of the crosslinking agent include the oxazoline compounds, carbodiimide compounds, epoxy compounds, melamine compounds, isocyanate compounds, aziridine compounds, silane coupling compounds, and the like that can be used in the formation of the first coating layer. Among these, from the viewpoint of improving adhesiveness, oxazoline compounds, isocyanate compounds, carbodiimide compounds and epoxy compounds are preferable, and oxazoline compounds are particularly preferable.

  The content of the oxazoline group contained in the oxazoline compound is usually 0.5 to 10 mmol / g, preferably 1 to 9 mmol / g, more preferably 3 to 8 mmol / g in terms of the amount of oxazoline group. Use within the above range is preferable because the adhesion to various surface functional layers is improved.

  As the isocyanate compound, aliphatic isocyanate and its block, alicyclic isocyanate and its block are preferable from the viewpoint of improving adhesiveness. Moreover, it is effective for the improvement of adhesiveness that it is a combined material with a urethane resin or a polyester resin.

  The content of the carbodiimide group contained in the carbodiimide-based compound is a carbodiimide equivalent (weight of the carbodiimide compound to give 1 mol of carbodiimide group [g]) and is usually 100 to 1000, preferably 250 to 800, more preferably 300. It is -700, More preferably, it is the range of 350-650. Use within the above range is preferable because the adhesion to various surface functional layers is improved.

  In the film of the present invention, particles can be used in combination with the formation of the second coating layer for the purpose of blocking the coating layer and improving the slipperiness. The average particle size is preferably in the range of 1.0 μm or less, more preferably 0.5 μm or less, particularly preferably 0.2 μm or less from the viewpoint of the transparency of the film. Moreover, when it is necessary to raise the effect of improving slipperiness, it is preferable to use particles having an average particle size larger than the film thickness of the coating layer. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, heat-resistant organic particles, and the like.

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

  As a ratio with respect to all the non-volatile components in the coating liquid forming the second coating layer, the polyvinyl alcohol is usually 10% by weight or more, preferably 15 to 70% by weight, more preferably 20 to 50% by weight. . If it is less than 10% by weight, the adhesion may not be sufficient.

As a ratio with respect to the total nonvolatile components in the coating liquid for forming the second coating layer, the polymer other than polyvinyl alcohol is usually 80% by weight or less, preferably in the range of 10 to 70% by weight, more preferably in the range of 20 to 50% by weight. It is a range. Adhesiveness can be improved by using in the said range.

  As a ratio with respect to the total nonvolatile components in the coating liquid for forming the second coating layer, the crosslinking agent is usually in the range of 80% by weight or less, preferably in the range of 10 to 70% by weight, more preferably in the range of 20 to 50% by weight. It is. Adhesiveness can be improved by using in the said range.

  When two or more types of crosslinking agents are used in combination as the formation of the second coating layer, the adhesion may be improved without using a polymer other than polyvinyl alcohol. For example, the combined use of an oxazoline compound and an isocyanate compound and the combined use of an oxazoline compound and a carbodiimide compound are effective, and in particular, the combined use of an oxazoline compound and an isocyanate compound is highly effective. In the above case, the oxazoline compound is generally in the range of 80% by weight or less, preferably in the range of 10 to 70% by weight, more preferably in the range of 20 to 50%, as a ratio with respect to the total nonvolatile components in the coating liquid for forming the second coating layer. The isocyanate compound or carbodiimide compound is usually in the range of 80% by weight or less, preferably in the range of 10 to 70% by weight, more preferably in the range of 20 to 50% by weight. Adhesiveness can be improved by using in the said range.

  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 laminated polyester film in the present invention, the coating amount of the second coating layer provided on the polyester film is usually 0.002 to 1.0 g / m ² , more preferably 0.01 to 0.5 g on one side only. / M ² , more preferably in the range of 0.04 to 0.2 g / m ² . If the coating amount is less than 0.002 g / m ^2, sufficient adhesiveness may not be obtained, and if it exceeds 1.0 g / m ² , the appearance, transparency, and film blocking properties may be deteriorated. There is sex.

  In the present invention, as the method for forming the second coating layer, for example, gravure coating, reverse roll coating, die coating, air doctor coating, blade coating, rod coating, bar coating, curtain coating, knife coating, transfer roll coating, squeeze Conventionally known coating methods such as coating, impregnation coating, kiss coating, spray coating, calendar coating, extrusion coating, etc. can be used.

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

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

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

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

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

  For example, when the laminated polyester film of the present invention is used as a protective film for a polarizing film in a polarizing plate, for example, the polarizing film is generally bonded to the second coating layer side through an adhesive for adhering the polarizing film. . As the adhesive, conventionally known ones can be used, for example, acrylic compounds such as polyvinyl alcohol, polyvinyl butyral and polybutyl acrylate, and epoxy having an alicyclic epoxy group exemplified by glycidyl group and epoxycyclohexane. System compounds and the like.

  On the prepared adhesive layer, for example, polyvinyl alcohol that is uniaxially stretched and dyed with iodine or the like is bonded as a polarizing film. A protective film, a retardation film, or the like can be bonded to the opposite side of the polarizing film to form a polarizing plate.

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

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

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

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

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

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

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

(7) Adhesive evaluation method A 5% by weight aqueous solution of polyvinyl alcohol having a polymerization degree of 1000 and a saponification degree of 98.5 mol% as an adhesive was applied to the first coated layer surface of the laminated polyester film so that the dry film thickness was 2 μm. It dried and it was set as the adhesive bond layer. After affixing an 18 mm width tape (Cellotape (registered trademark), Elpac (registered trademark) LP-18) manufactured by Nichiban Co., Ltd.) to this adhesive layer and peeling it off at a 180 degree peeling angle ( Adhesiveness 1), and 10 × 10 crosscut for the adhesive layer, 24 mm wide tape (Cellotape (registered trademark), Elpac (registered trademark) LP-24 manufactured by Nichiban Co., Ltd.) After peeling and abruptly peeling off at a 180 degree peel angle (Evaluation for applications requiring adhesion 2 and higher adhesiveness), if the peel area is 5% or less, ◎, If it exceeded 5% and 20% or less, it was evaluated as ◯, if it exceeded 20% and 50% or less, Δ, and if it exceeded 50%, it was rated as x.

(8) Measuring method of softening point Using a flow tester CFT-500D manufactured by Shimadzu Corporation, the temperature at which half of the non-heat-resistant particles flowed out was measured as the softening point.

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

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

<Method for producing polyester (C)>
In the production method of the polyester (A), the same method as the production method of the polyester (A) is used except that 0.5% by weight of silica particles having an average particle size of 0.1 μm is added to the produced polyester before melt polymerization. Thus, polyester (C) was obtained.

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

Examples of compounds constituting each coating layer are as follows.
(Example compounds)
Non-heat-resistant particles: (IA) Non-heat-resistant non-crosslinked 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 particles 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 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

・ Polyvinyl alcohol: (II)
Polyvinyl alcohol having a saponification degree of 88 mol% and a polymerization degree of 500

・ Polyester resin: (IIIA)
Carboxylic acid aqueous dispersion monomer composition of polyester resin copolymerized with the following composition: (acid component) isophthalic acid / trimellitic acid // (diol component) diethylene glycol / neopentyl glycol = 96/4 // 80/20 (mol %)
・ Polyester resin: (IIIB)
Carboxylic acid aqueous dispersion monomer composition of polyester resin copolymerized with the following composition: (acid component) terephthalic acid / isophthalic acid // (diol component) ethylene glycol / diethylene glycol / neopentyl glycol / dimethylolpropionic acid = 20/80 /// 16/64/12/8 (mol%)

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

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

・ Oxazoline compounds: (IVB)
Oxazoline group-containing acrylic polymer Epocross (registered trademark) (Oxazoline group amount = 7.7 mmol / g, manufactured by Nippon Shokubai Co., Ltd.)

Epoxy compound: (IVC) polyglycerol polyglycidyl ether

・ Isocyanate compounds: (IVD)
158 parts by weight of hexamethylene diisocyanate trimer, 26 parts by weight of methoxypolyethylene glycol (OH value = 81 mg KOH / g), 27.8 parts by weight of diethyl diethylene glycol and 0.001 part by weight of dioctyltin laurate were reacted at 85 ° C. Thereafter, the mixture was allowed to cool, and 66 parts by weight of methyl ethyl ketone oxime was added dropwise to react. Subsequently, 115 parts by weight of 1,6-hexamethylenediol-based polycarbonate diol (OH value = 56 mgKOH / g), 1.2 parts by weight of trimethylolpropane (OH value = 1254 mgKOH / g), dimethylolpropionic acid (OH value = 837 mgKOH) / G) 7.6 parts by weight and 50 parts by weight of dimethyldipropylene glycol were added, and after stirring, 40.3 parts by weight of isophorone diisocyanate was added and reacted. After allowing to cool, 8.2 parts by weight of hexamethylene diisocyanate trimer was added, and after stirring, 5.8 parts by weight of triethylamine was added and stirred. A block isocyanate compound obtained by dropping 450 parts by weight of water into this mixed solution and dropping and stirring 21 parts by weight of a 15% aqueous diethylenetriamine solution.

・ Carbodiimide compounds: (IVE)
Polycarbodiimide compound Carbodilite (registered trademark) (carbodiimide equivalent = 600, manufactured by Nisshinbo Co., Ltd.)

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: 5: 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 with a coating amount (after drying) of 0.2 g / m ^{2 on} one side. . Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the aqueous coating solution B1 shown in Table 2 below was applied to both surfaces of the longitudinally stretched film. Then, the film was stretched 4.0 times at 120 ° C. in the transverse direction and heat-treated at 230 ° C., and then relaxed by 2% in the transverse direction. The coating amount of the coating layer (after drying and stretching) was 0.06 g / side. A polyester film having a thickness of 38 μm and having a second coating layer of m ² 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 adhesiveness was also good. The properties of this film are shown in Table 5 below.

Examples 2-33:
In Example 1, it manufactured like Example 1 except having changed into the coating agent composition and application quantity which are shown to Tables 1-3, and obtained the polyester film. As shown in Table 5 below, the finished polyester film had good transparency, sufficient film roughness after longitudinal stretching, and good adhesion.

Example 34:
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. The film was coextruded and cooled and solidified with a layer structure of layers (surface layer / intermediate layer / surface layer = 1: 5: 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 with a coating amount (after drying) of 0.2 g / m ^{2 on} one side. . Next, the film was stretched 3.4 times in the 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., and then relaxed by 2% in the transverse direction. The coating amount of the coating layer (after drying / stretching) A polyester film having a thickness of 38 μm and having a second coating layer of m ² 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 adhesiveness was also good. The properties of this film are shown in Table 5 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 6 below, the film after longitudinal stretching had a small roughness and was likely to be damaged.

Comparative Examples 2-6:
In Example 1, it manufactured like Example 1 except having changed into the coating agent composition and application quantity which are shown in following Table 1, 2, and 4, and obtained the polyester film. As shown in Table 6, the finished polyester film has a high haze and a whitish film, a case where the film is not sufficiently rough after longitudinal stretching, and a case where the adhesiveness is poor. It was.

Comparative Example 7:
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. The film was coextruded and cooled and solidified with a layer structure of layers (surface layer / intermediate layer / surface layer = 1: 5: 1 discharge amount) to obtain an unstretched film. Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the aqueous coating solution B1 shown in Table 2 below was applied to both surfaces of the longitudinally stretched film. Then, the film was stretched 4.0 times at 120 ° C. in the transverse direction and heat-treated at 230 ° C., and then relaxed by 2% in the transverse direction. The coating amount of the coating layer (after drying and stretching) was 0.06 g / side. A 38 μm-thick polyester film having a coating layer of m ² 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 6 below.

  The film of this invention has the outstanding transparency and slipperiness, for example, can be utilized suitably as a member which protects the polarizing plate used for a liquid crystal display.

Claims (1)

After having applied a coating solution containing non-heat-resistant particles on at least one side of an unstretched polyester film, it has a coating layer formed by stretching in at least one direction, on the coating layer or on the opposite side of the coating layer A laminated polyester film comprising a coating layer formed from a coating solution containing polyvinyl alcohol on the side.