JP2008248027A - Optical laminated polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a useful film which reduces curling due to the thermal history undergone in the annealing treatment and processing steps for improving antistatic properties, the prevention of dust and the like from attaching thereto, and dimensional stability and excels in workability and the adhesion to a hard coat layer. <P>SOLUTION: The optical laminated polyester film has a film haze of 2.0% or less, both values of the thermal shrinkage ratio in the lengthwise and crosswise directions of the film after the treatment at 150°C for 30 minutes in the range of 1.5-0.5%, and a difference in the values of the thermal shrinkage ratio between the lengthwise and crosswise directions of not greater than 0.5% and a coated layer on both surfaces of the film provided in the process of preparing the film, respectively, and contains an antistatic agent in at least one of the coated layers. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical laminated polyester film, and in particular, has antistatic properties, less curling due to annealing treatment and thermal history during processing after providing a hard coat layer, prevention of contamination due to adhesion of dust, The present invention relates to an optical laminated polyester film excellent in prevention of scratches, workability, productivity, and adhesion to a hard coat layer.

  Biaxially stretched polyester film is excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, chemical resistance, etc., packaging materials, electrical insulation materials, metal deposition materials, plate making materials, magnetic recording materials, It is used in many applications such as display materials, transfer materials, and window paste materials.

  Especially recently, for anti-static, anti-reflective, and electromagnetic shielding for pasting the front panel glass surface of so-called flat displays such as base films for prismatic sheets used in transparent touch panels and liquid crystal display devices, cathode ray tubes, LCDs and PDPs. It is widely used in various optical applications such as a protective film for a base film provided with a functional layer. However, since the polyester film is easily scratched, there is a drawback that the appearance and optical characteristics are easily impaired. In order to prevent damage to the surface, the polyester film is generally used with a hard coat layer.

  However, the hard coat film is inferior in antistatic property, and adhesion of dust, dust, and the like due to charging has become a cause of optical defects in post-processing, and has been a cause of lowering the yield. In addition, in portable information terminals, mobile phones, and portable game machines, for which demand has been increasing recently, the precision of conductive circuits has been remarkably improved in order to achieve both light weight, small size, and high functionality. It is a strict requirement.

  Conventionally, as a measure for improving the dimensional stability in the circuit forming process, a technique (Patent Document 1) in which a polyester film serving as a base is subjected to low thermal shrinkage by annealing treatment or the like has been used. However, in recent years, with the demand for improving the surface hardness of the hard coat layer, the hard coat layer itself has been changed to a resin composition of a type having a large heat shrinkage rate. Dimensional stability is no longer maintained.

  Therefore, recently, not only the polyester film as a base is annealed independently, but also after the hard coat layer coating, before the circuit formation process, or when the dimensional stability is improved by the annealing process during the formation process Is increasing. In this case, depending on the heat treatment conditions, curling resulting from the difference in thermal shrinkage between the active energy ray-curable resin layer and the base polyester film may cause a decrease in workability and productivity. .

Japanese Patent Laid-Open No. 3-104623

  The present invention has been made in view of the above-mentioned circumstances, and the problem to be solved is the anti-static property, the adhesion prevention of dust and the like, the annealing treatment for improving the dimensional stability and the curl due to the thermal history received during the processing step. It is an object of the present invention to provide a useful film that is small, excellent in workability, and excellent in adhesion to a hard coat layer.

  As a result of intensive studies in view of the above circumstances, the present inventor has found that the above problem can be easily solved by a polyester film having a specific configuration, and has completed the present invention.

  That is, the gist of the present invention is that the film haze is 2.0% or less, and the heat shrinkage rate values in the film longitudinal direction and the transverse direction after treatment at 150 ° C. for 30 minutes are both 1.5 to 0.5%. And the difference in thermal shrinkage value between the vertical direction and the horizontal direction is 0.5% or less, and has a coating layer provided in the film forming process on both sides of the film, and in at least one coating layer It contains an antistatic agent in the laminated polyester film for optics.

Hereinafter, the present invention will be described in detail.
The laminated polyester film for optics of the present invention may be a single layer or a multilayer of 3 or more layers. The laminated polyester film for optics referred to in the present invention is a polyester film extruded by a so-called extrusion method that is melt-extruded from an extrusion die, and is oriented in the biaxial direction of the vertical direction and the horizontal direction as necessary. Film.

  In the present invention, the polyester is obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. 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 polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN) and the like.

  The polyester used in the present invention may be a homopolyester or a copolyester. In the case of a copolyester, it is a copolymer containing 30 mol% or less of the third component. Examples of the dicarboxylic acid component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acids (for example, P-oxybenzoic acid). Or 2 or more types are mentioned, As a glycol component, 1 type, or 2 or more types, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanol, neopentyl glycol, are mentioned.

  The film of the present invention has a film haze of 2.0% or less, preferably 1.5% or less, more preferably 1.0% or less. The film of the present invention is widely used for optical applications because of its excellent transparency. However, when the film haze exceeds 2.0%, it becomes inappropriate for optical use.

  The total film thickness of the film of the present invention is usually 50 to 300 μm or more, preferably 75 to 250 μm. If the total film thickness is less than 50 μm, the film is weak, so after punching into a single sheet, the workability at the time of final inspection performed for each sheet or sticking to a display tends to be worse, from 300 μm If it is thick, workability may deteriorate due to its rigidity.

The film of the present invention preferably has an oligomer precipitation amount of 15.0 mg / m ² or less on the film surface in order to improve the durable adhesion of the hard coat layer.

  In order to make the oligomer precipitation amount on the film surface by heat processing into said range, the method of using polyester with little oligomer content is mentioned. Moreover, in the case of the laminated film by coextrusion, the oligomer precipitation amount on the film surface after heat processing can be suppressed to said range by using polyester with little oligomer content for outermost layer. Specifically, by setting the amount of oligomer contained in the polyester film to 5000 ppm or less, further 4000 ppm, particularly 3000 ppm or less, oligomers that deposit on the film surface when heated can be prevented.

  It is known that the oligomer in the polymer increases due to the melting step in film formation, and the increase is strongly influenced by the water content in the polymer, the temperature at the time of melting, the residence time, etc. It is considered to increase by about ˜5000 ppm.

  In order to obtain the amount of oligomer contained in the film, the amount of oligomer in the polyester raw material is preferably 4000 ppm or less, more preferably 3000 ppm or less, and particularly preferably 2500 ppm or less in consideration of an increase in the melting step.

  As a method for reducing the amount of oligomer in the polyester, conventionally known solid phase polymerization can be used.

  In the case of a film having a laminated structure, the outermost layer thickness is a thickness on one side only, usually 3 μm or more, and preferably ¼ or less of the total thickness. If the thickness is less than 3 μm, the oligomer (cyclic trimer) contained in the inner layer may be deposited on the film surface due to heat history during processing, etc., and production line contamination and film haze may deteriorate. If the thickness is more than 1/4 of the thickness, the haze value (particularly the internal haze value) due to the lubricant particles blended in the outermost layer film is increased to improve the winding property of the film, and the transparency of the film is deteriorated. Tend.

  In the polyester layer of the film of the present invention, it is preferable to blend particles mainly for the purpose of imparting slipperiness and preventing scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

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

  The average particle size of the particles to be blended in the polyester film is not particularly limited, but is usually in the range of 0.02 to 3 μm, preferably 0.02 to 2.5 μm, more preferably 0.02 to 2 μm. It is. When particles having an average particle size of less than 0.02 μm are used, sufficient slipperiness cannot be imparted, so that the winding characteristics in the film production process tend to be inferior. On the other hand, when the average particle diameter exceeds 3 μm, the degree of roughening of the film surface becomes too large and the film may become hazy.

    Further, the content of particles in the polyester layer is usually in the range of 0.001 to 5% by weight, preferably 0.005 to 3% by weight. When the particle content is less than 0.001% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by weight, the transparency of the film is insufficient. There is.

  In the present invention, the method of blending the particles with the polyester is not particularly limited, and a known method can be adopted. For example, it can be added at any stage of producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or before the start of the polycondensation reaction after completion of the transesterification reaction, The polycondensation reaction may proceed. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  Hereinafter, although the manufacturing method of the film of this invention is demonstrated concretely, as long as the summary of this invention is satisfied, this invention is not specifically limited to the following illustrations.

  Polyester chips dried by a known method are supplied to a melt extrusion apparatus and heated to a temperature equal to or higher than the melting point of each polymer to melt. Next, the molten polymer is extruded from a die and rapidly cooled and solidified on a rotary cooling drum so that the temperature is equal to or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed.

  In the present invention, the sheet thus obtained is stretched biaxially to form a film. Specifically describing the stretching conditions, the unstretched sheet is preferably stretched 2 to 6 times at 70 to 145 ° C. in the longitudinal direction to form a longitudinal uniaxially stretched film, and then 2 to 90 to 160 ° C. in the lateral direction. It is preferable to perform ~ 6 times stretching and heat treatment at 150 to 240 ° C for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary.

  The polyester film of the present invention is used with a hard coat layer provided for improving the surface hardness. In this case, since the polyester film is generally inactive, the adhesiveness is poor, and in order to improve the adhesiveness with the hard coat layer, it is necessary to provide a coating layer for improving the adhesiveness in advance. is there.

  As a method for forming such a coating layer, a so-called in-line coating method in which coating is performed before the tenter entrance (before completion of orientation crystallization) and drying is performed in the tenter is employed. The coating layer for improving the adhesiveness with the hard coat layer is not particularly limited as long as it improves the adhesiveness, but a binder resin as described in JP-A-2003-201357. A combination of and a crosslinking agent is preferred.

  In the present invention, it is preferable to contain inorganic particles or organic particles in the coating layer in order to further improve the slipperiness, adhesion and the like. The amount of the particles in the coating agent is usually 0.5 to 10% by weight, preferably 1 to 5% by weight. When the blending amount is less than 0.5% by weight, the blocking resistance may be insufficient. When the blending amount exceeds 10% by weight, the transparency of the film is hindered and the sharpness of the image tends to be lowered.

  Examples of the inorganic particles include silicon dioxide, alumina, zirconium oxide, kaolin, talc, calcium carbonate, titanium oxide, barium oxide, carbon black, molybdenum sulfide, and antimony oxide. Among these, silicon dioxide is easy to use because it is inexpensive and has various particle sizes.

  Examples of the organic particles include polystyrene or polyacrylate polymethacrylate in which a crosslinked structure is achieved by a compound (for example, divinylbenzene) containing two or more carbon-carbon double bonds in one molecule.

  The above inorganic particles and organic particles may be surface-treated. Examples of the surface treatment agent include a surfactant, a polymer as a dispersant, a silane coupling agent, a titanium coupling agent, and the like. The content of the particles in the coating layer is preferably 10% by weight or less, more preferably 5% by weight or less as an appropriate addition amount that does not impair the transparency.

  The coating layer may contain an antifoaming agent, a coating property improving agent, a thickener, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment, and the like.

  As long as water is the main medium, the coating agent may contain a small amount of an organic solvent for the purpose of improving dispersion in water or improving the film-forming performance. It is necessary to use the organic solvent as long as it is soluble in water. Examples of the organic solvent include aliphatic or alicyclic alcohols such as n-butyl alcohol, n-propyl alcohol, isopropyl alcohol, ethyl alcohol, and methyl alcohol, glycols such as propylene glycol, ethylene glycol, and diethylene glycol, n-butyl cellosolve, Glycol derivatives such as ethyl cellosolve, methyl cellosolve, propylene glycol monomethyl ether, ethers such as dioxane and tetrahydrofuran, esters such as ethyl acetate and amyl acetate, ketones such as methyl ethyl ketone and acetone, amides such as N-methylpyrrolidone Can be mentioned. These organic solvents may be used in combination of two or more as required.

  Moreover, you may perform various coatings by offline coating after manufacture of a film as needed. Such a coat may be either single-sided or double-sided. The coating material may be either water-based and / or solvent-based for off-line coating, but is preferably water-based or water-dispersed for in-line coating.

  In addition, when the polyester film of the present invention is used for optics, an antistatic agent, a colorant, a conductive material, etc. may be added for the purpose of imparting other functionality to the hard coat layer provided for improving the surface hardness. In addition, a functional multilayer thin film may be formed thereon for the purpose of reflection of external light, electric shock due to static electricity, dust adhesion prevention, and electromagnetic wave shielding.

  The coating layer is formed on both sides of the polyester film, but a coating layer containing an antistatic agent is formed on the back surface of the surface on which the hard coat layer is provided.

  As a component constituting the coating layer containing the antistatic agent on the back side of the surface on which the hard coat layer is provided, a compound having a quaternary ammonium base or polyvinyl alcohol is preferably used.

  The compound having a quaternary ammonium base refers to a compound having a component containing a quaternary ammonium base in the main chain or side chain in the molecule. Examples of such constituents include pyrrolidinium ring, quaternized alkylamine, copolymerized with acrylic acid or methacrylic acid, quaternized N-alkylaminoacrylamide, vinylbenzyltrimethylammonium salt, 2 -Hydroxy 3-methacryloxypropyltrimethylammonium salt etc. can be mentioned. Further, these may be combined or copolymerized with other resins. In addition, examples of anions that serve as counter ions for these quaternary ammonium salts include ions such as halogen, alkyl sulfate, alkyl sulfonate, and nitric acid.

  In the present invention, the compound having a quaternary ammonium base is preferably a polymer compound. If the molecular weight is too low, it may be easily removed from the coating layer, causing deterioration in performance over time, or the coating layer becoming sticky. Moreover, when the molecular weight is low, the heat resistance stability may be inferior. In order not to cause such a problem, it is desirable that the number average molecular weight of the compound having a quaternary ammonium base is usually 1000 or more, more preferably 2000 or more, particularly 5000 or more. On the other hand, when such a compound has a molecular weight that is too high, problems such as excessively high viscosity of the coating solution may occur. In order not to cause such a problem, the number average molecular weight is preferably 500,000 or less.

  The polyvinyl alcohol used in the present invention can be synthesized by a normal polymerization reaction and is preferably water-soluble.

  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 100 or less, the water resistance of the coating layer tends to decrease. The degree of saponification of polyvinyl alcohol is not particularly limited, but a polyvinyl acetate saponified product that is usually 70 mol% or more, preferably 80 mol% or more and 99.9 mol% or less is practically used.

  Furthermore, in the coating layer containing an antistatic agent, one or more water-soluble or water-dispersible binder resins other than those described above can be used in combination, if necessary. Examples of the binder resin include polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, amide resin, and the like. In these, each skeleton structure may have a composite structure substantially by copolymerization or the like. Examples of the binder resin having a composite structure include acrylic resin graft polyester, acrylic resin graft polyurethane, vinyl resin graft polyester, and vinyl resin graft polyurethane.

  Further, it may contain a crosslinking reactive compound as required. The crosslinking reactive compound can improve the cohesiveness, surface hardness, scratch resistance, solvent resistance, and water resistance of the coating layer mainly by crosslinking reaction with the functional group contained in the coating layer component. preferable.

  Coating layers containing antistatic agents are surfactants, antifoaming agents, coatability improvers, thickeners, organic lubricants, organic particles, inorganic particles, antioxidants, UV absorbers, foaming agents, dyes In addition, additives such as pigments may be contained. These additives may be used alone or in combination of two or more as necessary.

  The ratio of the compound having a quaternary ammonium base in the coating layer constituting component is usually 10 to 99% by weight, preferably 20 to 95% by weight. If the ratio is too high or too low, the desired antistatic performance and oligomer precipitation prevention performance may not be obtained.

  The coating liquid used in the present invention is preferably an aqueous solution or an aqueous dispersion in terms of handling and working environment, but contains water as the main medium and contains an organic solvent as long as it does not exceed the gist of the present invention. You may do it.

  Although there is no restriction | limiting in particular in the solid content density | concentration of a coating liquid, Usually, 0.3 to 65 weight%, Preferably it is 0.5 to 30 weight%, More preferably, it is 1 to 20 weight%. When the concentration is too high or too low than these ranges, it may be difficult to provide a coating layer having a thickness necessary for fully expressing the function.

  The thickness of a coating layer is dry thickness, and is 0.003-1.5 micrometers normally, Preferably it is 0.01-0.5 micrometer, More preferably, it is 0.01-0.3 micrometer. If the thickness of the coating layer is less than 0.003 μm, sufficient performance may not be obtained, and if it exceeds 1.5 μm, blocking between films tends to occur.

  As a coating method of the coating agent, for example, a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, or a coating apparatus other than these as shown in Yuji Harasaki, Tsuji Shoten, published in 1979, “Coating Method” Can be used.

  The polyester film of the present invention can be mixed with other thermoplastic resins such as polyethylene naphthalate and polytrimethylene terephthalate as long as the effects of the present invention are not impaired. Moreover, you may mix | blend coloring agents, such as a ultraviolet absorber, antioxidant, surfactant, a fluorescent whitening agent, a lubricant agent, a light-shielding agent, a matting agent, and a dye, a pigment. In addition, for the purpose of improving the slipperiness and abrasion resistance of the film, inert inorganic or organic fine particles can be blended with the polyester as necessary.

  In the optical polyester film of the present invention, the biaxially stretched polyester film having a coating layer has a heat shrinkage value of 1.5 to 0.5% in both the longitudinal direction and the transverse direction at 150 ° C. for 30 minutes, and is longitudinal. The difference in transverse heat shrinkage value should be 0.5% or less. When the thermal shrinkage rate is greater than 1.5%, the annealing treatment after providing the hard coat layer produces a curl larger than 10 mm on the polyester film surface, and when the thermal shrinkage rate value is less than 0.5%, Curls larger than 10 mm are generated on the hard coat layer surface. Further, when the difference between the heat shrinkage rates in the vertical and horizontal directions is 0.5% or more, a curl larger than 10 mm is generated even within the range of the above heat shrinkage rate values. The heat shrinkage rate in the vertical and horizontal directions is preferably 1.3 to 0.9%, and the difference between the heat shrinkage values in the vertical and horizontal directions is preferably within 0.3%.

  The optical polyester film of the present invention is used by forming a hard coat layer on a coating layer of a biaxially stretched polyester film.

  In the present invention, an unsaturated polyester resin system, an acrylic system, an addition polymerization system, a thiol / acrylic hybrid system, a cationic polymerization system, a hybrid system of cationic polymerization and radical polymerization, and the like are used as the hard coat layer curing component. Can do. Among these, acrylic curing components are preferable from the viewpoints of curability, scratch resistance, surface hardness, flexibility, durability, and the like.

  The acrylic curing component contains an acrylic oligomer as a hard coat layer polymerization component and a reactive diluent. And a photoinitiator, a photosensitizer, and a modifier are contained as needed.

  Typical examples of the acrylic oligomer include an oligomer in which a reactive acryloyl group or methacryloyl group is bonded to an acrylic resin skeleton. Examples of other acrylic oligomers include polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, polyether (meth) acrylate, silicone (meth) acrylate, polybutadiene (meth) acrylate, and the like. Furthermore, an oligomer in which an acryloyl group or a methacryloyl group is bonded to a rigid skeleton such as melamine, isocyanuric acid, and cyclic phosphazene can be given.

  The reactive diluent serves as a solvent for the coating process as a coating medium, and has a group that itself reacts with a polyfunctional or monofunctional acrylic oligomer. It becomes. Specific examples of reactive diluents include pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) ) Acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene glycol (meth) acrylate, propylene glycol di (meth) acrylate, (meth) acryloyloxypropyltriethoxysilane, (meth) acryloyl Examples include oxypropyltrimethoxysilane.

  Examples of the photopolymerization initiator include 2,2-ethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, dibenzoyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, p -Chlorobenzophenone, p-methoxybenzophenone, Michler ketone, acetophenone, 2-chlorothioxanthone, anthraquinone, phenyl disulfide, 2-methyl- [4- (methylthio) phenyl] -2-morpholino-1-propanone and the like.

  Examples of the photosensitizer include tertiary amines such as triethylamine, triethanolamine and 2-dimethylaminoethanol, alkylphosphine such as triphenylphosphine, and thioethers such as β-thiodiglycol.

  Examples of the modifier include a coating property improver, an antifoaming agent, a thickener, inorganic particles, organic particles, a lubricant, an organic polymer, a dye, a pigment, and a stabilizer. These are used within a range that does not inhibit the reaction by active energy rays, and the characteristics of the hard coat layer can be improved according to the application. An organic solvent can be added to the composition of the hard coat layer in order to improve workability during coating and control the coating thickness.

  The hard coat layer is formed by applying a curing resin composition to the surface of the coating layer and then irradiating with an active energy ray to cause crosslinking and curing. As active energy rays, ultraviolet rays, visible rays, electron beams, X-rays, α rays, β rays, and γ rays can be used. Irradiation of active energy rays is usually performed from the coating layer side, but may be performed from the film surface side in order to improve adhesion to the film, and further, a reflection plate capable of reflecting active energy rays is provided on the film surface side. May be provided.

  The thickness of the hard coat layer is usually in the range of 0.5 to 15 μm, preferably 1 to 10 μm. When the thickness of the cured resin layer is less than 0.5 μm, the surface hardness may be insufficient. When the thickness exceeds 15 μm, the cured resin layer has a large cure shrinkage and the film curls toward the cured resin layer. There are things to do. In the present invention, the surface hardness of the cured resin layer side is usually H or higher, preferably 2H or higher. If it is less than H, the scratch resistance is insufficient.

  According to the polyester film of the invention, it is possible to provide a useful film that is excellent in workability with less curling due to heat history during annealing and processing to improve antistatic properties and dimensional stability. Target value is high.

  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. In the examples and comparative examples, “parts” means “parts by weight”. The measuring method used in the present invention is as follows.

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

(2) Average particle diameter (d50)
The particle size was measured by a sedimentation method based on Stokes' resistance law using a centrifugal sedimentation type particle size distribution analyzer SA-CP3 manufactured by Shimadzu Corporation.

(3) Content of oligomer (cyclic trimer) in polyester After a predetermined amount of polyester raw material or polyester film was dissolved in o-chlorophenol, it was reprecipitated with tetrahydrofuran and filtered to remove linear polyethylene terephthalate. After that, the filtrate obtained was supplied to liquid chromatography (Shimadzu LC-7A) to determine the amount of oligomer (cyclic trimer) contained in the polyester, and this value was divided by the amount of polyester used for the measurement. The amount of oligomer contained in the polyester (cyclic trimer). The amount of oligomer (cyclic trimer) determined by liquid chromatography was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method). The standard sample was prepared by accurately weighing an oligomer (cyclic trimer) collected in advance and dissolving it in DMF (dimethylformamide) accurately measured. The conditions of the liquid chromatograph were as follows.

Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: MCI GEL ODS 1HU manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(4) Thickness of Laminated Polyester Layer After fixing a small piece of film with an epoxy resin, it was cut with a microtome, and the cross section of the film was observed with a transmission electron micrograph. Two of the cross-sections are observed in parallel with the film surface, and the interface is observed by light and dark. The distance between the two interfaces and the film surface was measured from 10 photographs, and the average value was defined as the laminated thickness.

(5) Adhesion of hard coat Immediately after the hard coat layer is formed, a cross cut is made on the hard coat layer so that there are 100 grids in a 1-inch width, and immediately, three times of tape tape (registered trademark) rapid peeling at the same location. A test was performed and evaluated by the peeled area. The judgment criteria are as follows.
A: Number of cross-cuts = 0
○: 1 ≦ Number of cross cuts ≦ 10
Δ: 11 ≦ number of cross-cuts ≦ 20
×: 21 <Number of cross-cuts peeled

(6) Heat shrinkage rate Using a hot air circulating furnace (manufactured by Taibai Seisakusho), in a 150 ° C atmosphere, the film was heat-treated for 30 minutes in a tensionless state, and the length of the sample before and after that was measured. Calculated with
Thermal contraction rate (%) = (L0−L1) × 100 / L0
(In the above formula, L0 means the sample length (mm) before heat treatment, and L1 means the sample length (mm) after heat treatment)

(7) Film haze Turbidity was measured with an integrating sphere turbidimeter NDH manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS K 7136.

(8) Amount of heated curl The hard coat layer coated product is cut into a 10 cm square size, left to stand in a hot air circulation oven at 150 ° C. for 30 minutes, heat treated, left to cool at room temperature for 30 minutes and then placed on a glass plate. The amount of lifting at the four corners from the glass surface was measured and the maximum value was taken as the curl value. Recessed curls were indicated positively on the active energy ray-curable resin layer surface side, concave curls were indicated negatively on the polyester film surface side, and the following ranking was performed with the maximum absolute value of curl value.
◎: Curling amount is less than 5 mm ○: Curling amount is 5 to 10 mm
X: Curling amount is larger than 10 mm

(9) Surface resistivity value Using “Hiresta-UP MCP-HT450” manufactured by Dia Instruments Co., Ltd., placing the sample in an atmosphere of 23 ° C./50% RH, applying a voltage of 500 V, and charging for 1 minute (Voltage application time 1 minute), the surface resistance (Ω) of the coating layer was measured. The type of electrode used here is a concentric electrode having an outer diameter of 16 mm for the main electrode and an inner diameter of 40 mm for the counter electrode.

(10) Dust adhesion evaluation (ash test)
The polyester film is sufficiently conditioned in a measurement atmosphere of 23 ° C. and 50% RH, and the coated layer is rubbed 10 times with a cotton cloth. This was brought close to the finely crushed cigarette ash and the ash adhesion was evaluated according to the following criteria.
○: Even if the film is brought into contact with ash, it does not adhere. Δ: When the film is brought into contact with ash, it adheres a little.

(11) Appropriateness for optics Appropriateness for optical applications such as touch panels is given based on characteristics such as haze, curling after heat treatment of hard coat layer coated products, adhesion of hard coat, and ease of dust adhesion. Judgment was made based on criteria shown in
○: Low haze value, good adhesion, little curling after processing, suitable for optical applications, little dust adhesion due to charging, high productivity ×: Haze value, adhesion, due to curling and charging after heat treatment There is a problem such as dust adhesion and is not suitable for optical applications.

The production method of the polyester used in the following examples and comparative examples is as follows.
<Manufacture of polyester>
[Method for producing ester (A)]
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part of ethyl acid phosphate to this reaction mixture, 0.04 part of antimony trioxide was added, and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (A) was 0.63, and the content of the oligomer (cyclic trimer) was 0.83% by weight.

[Production method of polyester (B)]
Polyester (A) is pre-crystallized at 160 ° C. in advance, and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 220 ° C., limiting viscosity 0.75, oligomer (cyclic trimer) content 0.24% by weight. Polyester (B) was obtained.

[Production method of polyester (C)]
In the method for producing polyester (A), after adding 0.04 part of ethyl acid phosphate, 0.2 part of silica particles dispersed in ethylene glycol having an average particle diameter of 1.6 μm and 0.04 part of antimony trioxide are added. In addition, polyester (C) was obtained using the same method as the production method of polyester (A) except that the polycondensation reaction was stopped at the time corresponding to the intrinsic viscosity of 0.65. The obtained polyester (C) had an intrinsic viscosity of 0.65 and an oligomer (cyclic trimer) content of 0.82% by weight.

(Coating agent adjustment)
・ Aqueous coating solution a
(Terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid / ethylene glycol / 1,4-butanediol / diethylene glycol = polyester dispersion at 28/20/2/35/10/5 molar ratio) / (methyl methacrylate / Emulsion polymer of ethyl acrylate / acrylonitrile / N-methylol methacrylamide = 45/45/5/5 molar ratio [emulsifier = anionic surfactant] / hexamethoxymethylmelamine / silica sol having an average particle size of 0.08 μm as a solid content Aqueous coating solution containing 47/20/30/3 in terms of weight ratio in terms of weight

・ Water-based coating solution b
(Charol DC-303P manufactured by Daiichi Kogyo Seiyaku Co., Ltd., which is a polymer having a pyrrolidinium ring in the main chain) / (polyvinyl alcohol having a degree of saponification = 88 mol% and a degree of polymerization = 500) / (hexamethoxymelamine) / (average particle size) An aqueous coating solution containing silica sol having a diameter of 0.05 μm in a weight composition ratio of 40/20/35/5 in terms of solid content.

Example 1:
Two extruders using a mixed raw material in which the polyesters (B) and (C) are mixed at a ratio of 90% and 10%, respectively, as a raw material for the A layer and a raw material of 100% polyester (A) as the raw material for the B layer Each was supplied to each and melted at 285 ° C., then the A layer was the outermost layer (surface layer), the B layer was the intermediate layer, and the two layers and three layers (ABA) were formed on a casting drum cooled to 40 ° C. A non-oriented sheet was obtained by coextrusion and cooling and solidification so that the composition ratio was A: B: A = 5: 90: 5. Next, the film is stretched 3.1 times in the machine direction at a film temperature of 81 ° C. using the difference in peripheral speed of the roll, and then the coating amount after transverse stretching and drying is 0.1 g / m ^{2 on} one side of the longitudinally stretched film. The aqueous coating agent “a” whose concentration was adjusted was applied to the back surface thereof, and the aqueous coating solution “b” whose concentration was adjusted so that the coating amount after transverse stretching and drying was 0.05 g / m ² was applied to the tenter. The film is stretched 3.6 times at 120 ° C in the direction, heat-treated at 230 ° C, and then the film is rolled at a production rate of 40 m / min. And a laminated polyester film having a thickness of 125 μm and an intrinsic viscosity of 0.62 having coating layers on both sides was obtained. Next, a hard coat resin was applied on the coating layer of the obtained film so that the thickness after curing was 3 μm, and irradiation was performed for about 15 seconds at an irradiation distance of 150 mm using a 120 W / cm energy high pressure mercury lamp. And the polyester film of this invention was obtained on the conditions which a curl does not produce in the state of a coated product. As the hard coat layer resin, a composition comprising 30 parts of dipentaerythritol hexaacrylate, 40 parts of tetrafunctional urethane acrylate, 27 parts of bisphenol A type epoxy acrylate and 3 parts of 1-hydroxycyclohexyl phenyl ketone was used. The evaluation results are shown in Table 1 below.

Examples 2, 3 and Comparative Examples 1-6
In Example 1, the heat setting temperature at which the heat shrinkage rate value after processing at 150 ° C. for 30 minutes becomes a predetermined value, the lateral relaxation rate after heat setting, and the rail width until winding on the master roll The polyester film was obtained by the same method as Example 1 except having changed. (However, only in Comparative Example 1, a predetermined sample was obtained by setting the raw material composition of the intermediate layer (B layer) to polyester (A) / polyester (C) = 97/3)

Comparative Example 7
In Example 1, the sample which only applied the coating liquid a to one side was obtained.

  The film of the present invention can be suitably used as an optical film, for example.

Claims (1)

The film has a haze of 2.0% or less, the heat shrinkage value in the machine direction and the transverse direction after treatment at 150 ° C. for 30 minutes is in the range of 1.5 to 0.5%, and the machine direction and the transverse direction. The difference in heat shrinkage value with respect to the direction is 0.5% or less, the coating layer is provided on both sides of the film in the film forming process, and an antistatic agent is contained in at least one coating layer An optical laminated polyester film characterized by