JP5770066B2 - Laminated polyester film - Google Patents

Description

  The present invention relates to a laminated polyester film, for example, severe conditions such as a long-time heat treatment at 150 ° C., a sputtering process at a high tension, and a durability test in a high-temperature and high-humidity atmosphere. Even after passing through the steps below, the increase in film haze is as small as possible, especially for optical laminated polyester films with excellent optical properties and visibility even after processing as a product for optical members, The present invention relates to a laminated polyester film that is suitable for optical applications where high transparency is required with emphasis on so-called visibility that transmits light, for example, for touch panels.

  Conventionally, in touch panel applications, various methods such as a resistive film method and a capacitance method are employed depending on the position detection method. Among them, there is a tendency to increase the spread of a capacitance method characterized by multipoint detection, high light transmittance, high resolution, and high response speed. There are two types of capacitive touch panels: surface type and projection type. The surface type consists of three layers: a cover, a transparent conductive layer, and a glass substrate. The projection type consists of a glass or plastic film, a transparent electrode layer, and a substrate layer equipped with an IC that performs arithmetic processing. The

  In the manufacturing process of the transparent conductive laminate, it is generally heat-processed. For example, in order to form a transparent conductive film, an ITO film is formed by a sputtering method, and then heat treatment is performed at 150 ° C. for crystallization (Patent Document 1), or in the production of a conductive laminated film. When it is allowed to stand at 150 ° C. for 1 hour for low heat shrinkage treatment (Patent Document 2), or when processing a transparent conductive film, heat treatment at about 150 ° C. may be required to print a silver paste or the like. Yes (Patent Document 3). In the transparent conductive thin film manufacturing process, with heat treatment in a high temperature atmosphere, low molecular weight substances called oligomers contained in the polyester film (especially cyclic trimers) precipitate and crystallize on the film surface, resulting in coating defects, etc. Occurrence of this may make it difficult to obtain a highly accurate transparent conductive thin film.

  In addition, in the touch panel application, in recent years, the frequency of mounting on communication information devices such as mobile phones and PDAs (Personal Digital Assistance), game machines, etc. has been increasing. High visibility tends to be preferred. As a result, in the polyester film used in this field, the visibility degradation accompanying the increase in film haze due to oligomer precipitation after processing is increasingly regarded as a problem.

  A technique for suppressing oligomer precipitation by applying a coating layer on a polyester film substrate has also been proposed (Patent Document 4). However, contact between the conveying guide roll and the polyester film surface in the processing step, peeling of the coating layer due to rubbing, etc. may occur. In such a case, oligomer precipitation of the part cannot be suppressed, and polyester When the amount of oligomer precipitation on the base material itself decreases, the technique for suppressing oligomer precipitation on the polyester film base material itself is stronger because the amount of oligomer precipitation can be further reduced in combination with a coating layer that has the function of suppressing oligomer precipitation. There is also a demanded situation.

JP2007-2000823 JP2007-42473 JP2007-320144 JP2003-237005

  The present invention has been made in view of the above circumstances, and the present invention relates to a laminated polyester film, which is a highly transparent film, for example, a long-time heat treatment under conditions of 150 ° C. and a high tension. Even after going through harsh conditions such as sputtering processes in the process of heat treatment and durability tests in high-temperature and high-humidity atmospheres, the increase in film haze can be suppressed to a small level and processed as a product for optical components. An object of the present invention is to provide an optical laminated polyester film that is excellent in optical properties and visibility even after being applied.

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

That is, the gist of the present invention is that a quaternary ammonium salt-containing polymer is provided on one side of a laminated polyester film having a thickness of 45 to 200 μm, which has a laminated structure of at least three layers, each having a thickness of each outermost layer of 4 μm or more. It has a coating layer formed from a coating solution containing a polyethylene glycol-containing acrylate polymer and a crosslinking agent, the amount of oligomer extracted from the surface of the coating layer is 0.5 mg / m ² or less, and a coating layer is provided The laminated polyester film is characterized in that an ITO film, which is a transparent conductive film, is provided on the opposite surface to the opposite surface .

  According to the laminated polyester film of the present invention, it is a highly transparent film, for example, a long-time heat treatment at 150 ° C., a sputtering process with high tension, and durability under a high-temperature and high-humidity atmosphere. Even after undergoing harsh conditions such as testing, the increase in film haze is kept small, and even after processing as a product for optical members, optical laminated polyester film with excellent optical properties and visibility And its industrial value is high.

  The optical laminated polyester film of the present invention is required to be a multilayer film having at least 3 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 dimethanone neopentyl glycol, is mentioned.

  The polyester used for the outermost layer in the present invention preferably has an oligomer (cyclic trimer) content of 0.5% by weight or less. When a polyester with an oligomer content exceeding 0.5% is used, the resulting laminated polyester is heat-treated for a long time at 150 ° C, a sputtering process with high tension, and in a high-temperature, high-humidity atmosphere. When used in processing processes under harsh conditions such as durability tests at high temperatures, the film haze increases, and after processing as a product, it may not be suitable for optical members in terms of optical properties and visibility .

  In the film of the present invention, the thickness of both outermost layers is 4 μm or more, preferably 6 μm or more, and more preferably 7 μm or more. When the thickness of the outermost layer is less than 4 μm, the oligomer precipitation sealing effect of the outermost layer with a low oligomer (cyclic trimer) content is diminished.

  The film of the present invention preferably has a haze of 1.3% or less. More preferably, it is 1.1% or less. The film of the present invention is widely used in optical applications because of its excellent transparency. However, when the haze exceeds 1.3%, the transparency as an optical display member is impaired due to poor transparency. May end up.

  The total film thickness of the film of the present invention is in the range of 45 to 200 μm. When the total film thickness is less than 45 μm, after forming a transparent conductive film on the film, when forming a transparent conductive film sheet (laminated transparent conductive film) formed by laminating the film and film, wrinkles are formed on the film. It arises and a transparent conductive film sheet cannot be formed appropriately. Also, when the thickness exceeds 200 μm, after forming a transparent conductive film on the film, the sheet flexibility of the sheet forming the transparent conductive film sheet (laminated transparent conductive film) formed by laminating the film-film (flexibility) ) Will be damaged.

  In the polyester layer of the film of the present invention, particles may be blended mainly for the purpose of imparting slipperiness and preventing scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples 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 μm to 3 μm, preferably 0.02 μm to 2.5 μm, more preferably 0.02 μm 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.

  Furthermore, the particle content in the polyester layer is usually in the range of 0.0005 to 0.5% by weight, preferably 0.001 to 0.3% by weight. When the particle content is less than 0.0005% by weight, the slipperiness of the film may be insufficient, resulting in poor appearance such as scratches during film processing. On the other hand, when adding over 0.5 weight%, the transparency of a film may be inadequate.

  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, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary.

  In the laminated polyester film of the present invention, a coating layer may be provided for the purpose of improving adhesion with a layer processed thereon, improving slipperiness during processing, and the like.

  Regarding the coating layer, it may be provided by in-line coating which treats the film surface during the process of forming a polyester film, or offline coating which is applied outside the system on a once produced film may be adopted. Since the coating can be performed simultaneously with the film formation, the production can be handled at a low cost, and therefore in-line coating is preferably used.

  The in-line coating is not limited to the following, but for example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When the coating layer is provided on the polyester film by in-line coating, it is possible to apply at the same time as the film formation, and the coating layer can be processed at a high temperature in the heat treatment process of the polyester film after stretching. Performances such as adhesion to various surface functional layers that can be formed on the layer and heat-and-moisture resistance can be improved. Moreover, when coating before extending | stretching, the thickness of an application layer can also be changed with a draw ratio, and compared with off-line coating, uniform coating can be performed with a thin film. That is, a film suitable as a polyester film can be produced by in-line coating, particularly coating before stretching.

  Moreover, the coating layer of the film of the present invention comprises a surfactant, an antifoaming agent, a coating property improving agent, a thickener, an organic lubricant, organic particles, inorganic particles, an antioxidant, an ultraviolet absorber, a foaming agent, It may contain additives such as dyes and pigments. In the present invention, as a component constituting the coating layer provided on the film, a compound having a quaternary ammonium base (essential) and polyvinyl alcohol are preferably used.

  In this invention, the coating layer which shows the performance which seals precipitation of an oligomer is provided in the polyester film. In the present invention, as a component constituting the coating layer provided on the film, a compound having a quaternary ammonia base or polyvinyl alcohol is preferably used.

  Further, a so-called coating stretching method (in-line coating) in which the film surface is treated during the stretching process of the laminated polyester film described above can be applied. When a coating layer is provided on a laminated polyester film by a coating stretching method, it can be applied simultaneously with stretching and the thickness of the coating layer can be reduced according to the stretching ratio, and is a film suitable as a laminated polyester film. Can be manufactured.

  Next, the formation of the coating layer constituting the laminated polyester film in the present invention is provided by coating the film with a coating solution, and even if it is provided by in-line coating performed in the film manufacturing process, So-called off-line coating that is applied outside the system may be employed.

  In the present invention, the coating layer constituting the laminated polyester film contains a quaternary ammonium base-containing polymer (A) in order to reduce the amount of oligomer precipitation due to thermal damage to the coating layer from the outside. Doing so is an essential requirement.

  Moreover, in the range which does not impair the main point of this invention, the compound which has a quaternary ammonium base can be used together in the coating layer which comprises a laminated polyester film.

  Regarding the compound having a quaternary ammonium base used in the present invention, those having a constituent element containing a quaternary ammonium base in the main chain or side chain in the molecule are targeted. Specific examples include pyrrolidinium ring, quaternized alkylamine, copolymerized with acrylic acid or methacrylic acid, quaternized N-alkylaminoacrylamide, vinylbenzyltrimethylammonium salt, 2-hydroxy-3- And methacryloxypropyltrimethylammonium salt. Furthermore, these may be combined or copolymerized with other binder polymers. In addition, examples of anions that serve as counter ions of these quaternary ammonium salts include ions such as halogen, alkyl sulfate, alkyl sulfonate, and nitric acid. Among these, counterions other than halogen are preferable in that heat resistance is particularly good.

  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 and the performance may deteriorate over time, or problems such as blocking of the coating layer may occur. Moreover, when the molecular weight is low, the heat resistance stability may be inferior. From this viewpoint, the number average molecular weight of the compound having a quaternary ammonium base is usually 1000 or more, preferably 2000 or more, and more preferably 5000 or more. On the other hand, when the number average molecular weight is too high, problems such as the viscosity of the coating solution becoming too high may occur. From this viewpoint, it is preferable that the upper limit of the number average molecular weight is 500,000 or less. Moreover, these compounds may be used independently and may be used in combination of 2 or more types.

  The blending amount of the quaternary ammonium base-containing polymer (A) in the coating layer is preferably in the range of 20% by weight to 70% by weight, and more preferably in the range of 40% by weight to 70% by weight. When it is out of the range, it may be difficult to obtain a desired oligomer sealing effect.

  In the laminated polyester film of the present invention, the polyethylene glycol-containing polymer (B) constituting the coating layer is used for the purpose of improving the stretch followability at the time of forming the coating layer by ensuring higher coating properties than before. ) Is essential. Specifically, polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, polyethylene glycol diacrylate (the polymerization degree of polyethylene glycol units is preferably in the range of 4 to 14), polypropylene glycol diacrylate, polytetramethylene glycol diacrylate, poly (Ethylene glycol-tetramethylene glycol) diacrylate, poly (propylene glycol-tetramethylene glycol) diacrylate, polyethylene glycol-polypropylene glycol-polyethylene glycol diacrylate, polypropylene glycol-polybutylene glycol monomethacrylate, methoxypolyethylene glycol monomethacrylate, methoxy Polyethylene glycol monoacrylate , Octoxy polyethylene glycol-polypropylene glycol monomethacrylate, octoxy polyethylene glycol-polypropylene glycol monoacrylate, lauroxy polyethylene glycol monomethacrylate, lauroxy polyethylene glycol monoacrylate, stearoxy polyethylene glycol monomethacrylate, stearoxy polyethylene glycol monoacrylate, Examples include polymers starting from allyloxy polyethylene glycol monomethacrylate, allyloxy polyethylene glycol monoacrylate, and the like.

  The number average molecular weight of the polyethylene glycol-containing polymer (B) in the present invention is usually 1000 or more, preferably 2000 or more, and more preferably 5000 or more. On the other hand, when the number average molecular weight is too high, problems such as the viscosity of the coating solution becoming too high may occur. From this viewpoint, it is preferable that the upper limit of the number average molecular weight is 500,000 or less. Moreover, these compounds may be used independently and may be used in combination of 2 or more types.

  In the coating layer constituting the laminated polyester film in the present invention, a polyethylene glycol-containing alkyl acrylate polymer is preferably used in order to further improve stretchability. The chain length of the alkyl chain is not particularly limited as long as it is in a range that can be polymerized as a polymer. About content of the polyethyleneglycol containing polymer (B) which comprises the coating layer in this invention, the range of 5 to 40 weight% is preferable in order to make stretch followability favorable. When it is out of the range, problems such as insufficient stretch followability when forming the coating layer may occur.

  Regarding the coating layer constituting the laminated polyester film in the present invention, the quaternary ammonium base-containing polymer (A) and the polyethylene glycol-containing polymer (B) may be a mixture or copolymerized in advance. There is no particular limitation as long as the gist of the invention is not impaired. Moreover, when making it copolymerize, a conventionally well-known manufacturing method can be used.

  In the coating layer which comprises the laminated polyester film in this invention, it is necessary to use a crosslinking agent (C) together for the purpose of the further durable improvement of a coating layer. Specific examples include methylolated or alkylolized urea, melamine, guanamine, acrylamide, polyamide compound, epoxy compound, aziridine compound, block polyisocyanate, titanium coupling agent, zirco-aluminate coupling agent, polycarbodiimide and the like. It is done.

  Among the cross-linking agents (C), a melamine cross-linking agent is preferable in that the coating property and the durable adhesion are particularly good for the use of the present invention. The melamine crosslinking agent is not particularly limited, but melamine, a methylolated melamine derivative obtained by condensing melamine and formaldehyde, a compound partially or completely etherified by reacting methylolated melamine with a lower alcohol, And a mixture thereof can be used.

  The melamine crosslinking agent may be either a monomer or a condensate composed of a dimer or higher multimer, or a mixture thereof. As the lower alcohol used for the etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like can be preferably used. The functional group has an imino group, a methylol group, or an alkoxymethyl group such as a methoxymethyl group or a butoxymethyl group in one molecule, and an imino group type methylated melamine, a methylol group type melamine, or a methylol group type methylated group. Melamine, fully alkyl methylated melamine and the like can be used. Of these, methylolated melamine is most preferred. Furthermore, for the purpose of promoting thermal curing of the melamine crosslinking agent, for example, an acidic catalyst such as p-toluenesulfonic acid can be used in combination.

  The compounding quantity of the melamine crosslinking agent contained in the coating layer which comprises the laminated polyester film in this invention is 1 to 50 weight% normally, Preferably it is the range of 5 to 30 weight%. When it is out of the range, the durability adhesion of the coating layer may be insufficient.

  Furthermore, it is preferable to contain particles (D) for the purpose of improving the adhesion and slipperiness of the coating layer. Specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, barium salt and the like.

  The compounding amount of the particles in the coating layer 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. On the other hand, when it exceeds 10% by weight, the transparency of the film may be lowered.

  Further, as long as it does not impair the gist of the present invention, an antifoaming agent, a coating property improver, a thickener, an organic lubricant, organic polymer particles, an antioxidant, an ultraviolet ray may be included in the coating layer as necessary. Absorbent blowing agents, dyes and the like may be contained.

  In the case of the coating stretching method (in-line coating), a coating solution in which the above-mentioned series of compounds is used as an aqueous solution or water dispersion and the solid content concentration is adjusted to about 0.1 wt% to 50 wt% as a guide is applied onto the polyester film. It is preferable to produce a laminated polyester film in the manner of application.

  In addition, a small amount of an organic solvent may be contained in the coating solution for the purpose of improving the dispersibility in water, improving the film forming property, and the like within a range not exceeding the gist of the present invention. 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, Examples include 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, and amides such as N-methylpyrrolidone. Can be mentioned. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

The coating amount (after drying) of the coating layer provided on the polyester film of the present invention is usually 0.005 to 1 g / m ² , preferably 0.005 to 0.5 g / m ² , more preferably 0.005. The range is 0.1 g / m ² . When the coating amount is less than 0.005 g / m ² , the uniformity of coating thickness may be insufficient, and the amount of oligomer deposited from the coating layer surface after heat treatment may increase. On the other hand, when the coating is applied in excess of 1 g / m ² , problems such as a decrease in slipperiness may occur.

  In the laminated polyester film of the present invention, a binder polymer such as a polyester resin, an acrylic resin, a polyurethane resin, or polyvinyl alcohol is used within the range not impairing the gist of the present invention for the purpose of improving the coating appearance and improving the oligomer precipitation preventing property. It can also be used in combination.

  In the present invention, as a method for providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, spray coating or the like can be used. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

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

  For the laminated polyester film in the present invention, for example, for a touch panel or the like, high transparency may be required even after being exposed to a high temperature atmosphere for a long time. From this point of view, in order to correspond as a member for a touch panel, the visibility is lowered in a heat treatment (150 ° C., 90 minutes), and is unsuitable for applications requiring high visibility such as for a touch panel. There is a case.

The amount (OL) of oligomer (cyclic trimer) extracted from the surface of the coating layer by the dimethylformamide before and after heat treatment (150 ° C., 90 minutes) of the laminated polyester film in the present invention is 0.5 mg / m ² or less. , Preferably 0.4 mg / m ² or less. When OL exceeds 0.5 mg / m ² , in post-processing, for example, 180 ° C., 90 minutes, etc., the amount of oligomer precipitation increases with heat treatment for a long time in a high temperature atmosphere, and the transparency of the film decreases. To do.

  When the polyester film of the present invention is used for optics, a colorant, a conductive material or the like may be added, and on top of that, reflection of external light, electrostatic shock, prevention of dust adhesion, and further electromagnetic shielding A functional multilayer thin film may be formed.

  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.

  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) 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.

(4) Method for measuring oligomer amount (OL) extracted from the surface of the laminated polyester film In advance, an untreated laminated polyester film is heated in air at 150 ° C. for 90 minutes. Thereafter, the heat-treated film is brought into close contact with the inner surface of a box having a top and width of 10 cm and a height of 3 cm with the top open to obtain a box shape. When the coating layer is provided, the coating layer surface is set to the inside. Next, 4 ml of DMF (dimethylformamide) is placed in the box prepared by the above method and left for 3 minutes, and then DMF is recovered. The recovered DMF was supplied to liquid chromatography (manufactured by Shimadzu Corporation: LC-7A) to determine the amount of oligomer in DMF, and this value was divided by the film area in contact with DMF to obtain the amount of film surface oligomer (mg / M ² ). The amount of oligomer in DMF 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 the oligomer (cyclic trimer) collected in advance and dissolving it in DMF accurately measured. The concentration of the standard sample is preferably in the range of 0.001 to 0.01 mg / ml.

The conditions for 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

(5) Measuring method of film haze Film haze was measured for the sample film according to JIS-K-7136 with a haze meter “HM-150” manufactured by Murakami Color Research Laboratory.

(6) Method for evaluating film visibility after lamination of transparent conductive film (practical property substitution evaluation)
In the laminated polyester film, a sintered body of 95% indium oxide and 5% by weight tin oxide on the surface opposite to the coating layer in an atmosphere of 0.4 Pa composed of 95% argon gas and 5% oxygen gas. An ITO film (transparent conductive thin film) was formed by a reactive sputtering method using the material. The ITO film was crystallized by heat treatment at 150 ° C. for 1 hour.
The transparency and visibility of the obtained film were determined according to the following criteria.
<Criteria>
○: Transparency / Visibility is good (practically acceptable level)
×: Transparency / visibility poor (practical problem level)

(7) Film-film bonding property evaluation method (practical property substitution evaluation)
A coreless double-sided adhesive was applied to a film heated at 150 ° C. for 2 hours, and the film was attached to the opposite surface for determination. In addition, the roller was used at the time of bonding.
<Criteria>
○: Wrinkle-free and particularly good. (Practical, no problem level)
X: Wrinkles entered and defective. (Practical problem level)

(8) Film-film sheet flexibility evaluation method (practical property substitution evaluation)
The A4 cut size film sample was bent into a loop shape, and the strength of the stiffness was evaluated by loading when the diameter direction of the loop was crushed.
○: The stiffness of the film is weak and the sheet flexibility is good. (Practical, no problem level)
X: The stiffness of the film is strong and the sheet flexibility is poor. (Practical problem level)

<Manufacture of polyester>
[Production method of polyester (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 obtained polyester (A) had an intrinsic viscosity of 0.65 and an oligomer (cyclic trimer) content of 0.97% by weight.

[Production method of polyester (B)]
Polyester (A) was 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 0.46% 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)
(Example compounds)
-Quaternary ammonium base-containing polymer (A):
2-hydroxy-3-methacryloxypropyltrimethylammonium salt polymer Counter ion: methyl sulfonate Number average molecular weight: 30000
-Polyethylene glycol-containing acrylate polymer (B):
Polyethylene glycol-containing monoacrylate polymer Number average molecular weight: 20000
・ Crosslinking agent (C):
Melamine crosslinking agent (DIC Corporation: Becamine “MAS”)
-Particle (D):
Alumina surface modified colloidal silica (average particle size: 50 nm)
-Binder (E):
Polyvinyl alcohol (saponification degree 88 mol%, polymerization degree 500)
The coating agents (A) to (E) were used as coating solutions at the following mixing ratio.
(A) / (B) / (C) / (D) / (E) = 30/10/40/10/10

Example 1:
A mixture raw material in which the polyesters (B) and (C) are mixed at a ratio of 84% and 16%, respectively, is used as a raw material for the A layer, and a raw material of 100% polyester (A) is used as a raw material for the B layer. Each was supplied to the machine and melted at 285 ° C., then the A layer was the outermost layer (surface layer), the B layer was the intermediate layer, and on the casting drum cooled to 40 ° C., two types and three layers (ABA), A non-oriented sheet was obtained by coextrusion and cooling and solidification so that the thickness composition ratio was A: B: A = 4.0: 42: 4.0. Next, after stretching in the machine direction using the roll peripheral speed difference, a coating solution is applied to one side of this machined stretch film so that the coating amount after transverse stretching and drying is 0.020 g / m ² , The film was guided to a tenter, stretched in the transverse direction, and heat treated, and then the film was wound on a roll to obtain a laminated polyester film. The characteristics of the obtained film are shown in Tables 1 and 2 below.

Example 2:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coextrusion was changed so that the thickness ratio was A: B: A = 6.0: 38: 6.0. It was. The characteristics of the obtained laminated polyester film are shown in Tables 1 and 2 below.

Example 3:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coextrusion was changed so that the thickness composition ratio was A: B: A = 7.0: 36: 7.0. It was. The characteristics of the obtained laminated polyester film are shown in Tables 1 and 2 below.

Example 4:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coextrusion was changed so that the thickness composition ratio was A: B: A = 7.0: 86: 7.0. It was. The characteristics of the obtained laminated polyester film are shown in Tables 1 and 2 below.

Example 5:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coextrusion was changed so that the thickness ratio was A: B: A = 7.0: 111: 7.0. It was. The characteristics of the obtained laminated polyester film are shown in Tables 1 and 2 below.

Example 6:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coextrusion was changed so that the thickness composition ratio was A: B: A = 7.0: 174: 7.0. It was. The characteristics of the obtained laminated polyester film are shown in Tables 1 and 2 below.

Comparative Example 1:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coextrusion was changed so that the thickness ratio was A: B: A = 2.5: 45: 2.5. It was. The characteristics of the obtained laminated polyester film are shown in Tables 1 and 2 below.

Comparative Example 2:
In Example 1, the mixed raw materials obtained by mixing the polyesters (A) and (C) at a ratio of 84% and 16%, respectively, are used as the raw material of the A layer, and the thickness composition ratio is A: B: A = 2.5: A polyester film was obtained in the same manner as in Example 1 except that the coextrusion was changed to 45: 2.5. The characteristics of the obtained laminated polyester film are shown in Table 2 below.

Comparative Example 3:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coextrusion was changed so that the thickness ratio was A: B: A = 5.0: 13: 5.0. It was. The characteristics of the obtained laminated polyester film are shown in Tables 1 and 2 below.

Comparative Example 4:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coextrusion was changed so that the thickness composition ratio was A: B: A = 7.0: 236: 7.0. It was. The characteristics of the obtained laminated polyester film are shown in Tables 1 and 2 below.

Comparative Example 5:
In Example 1, the film was stretched in the longitudinal direction using the roll peripheral speed difference, then led to a tenter, stretched in the lateral direction, and heat treated, and then the film was wound on a roll to obtain a laminated polyester film. A polyester film was obtained in the same manner as in Example 1 except that the change was made. The characteristics of the obtained laminated polyester film are shown in Tables 1 and 2 below.

  The film of this invention can be utilized suitably for the electrostatic capacitance type touch panel use which bonded the transparent conductive film-film, for example.

Claims (1)

A quaternary ammonium salt-containing polymer, a polyethylene glycol-containing acrylate polymer, and a crosslink are formed on one side of a laminated polyester film having a thickness of 45 to 200 μm, which has a laminated structure of at least three layers, and each of the outermost layers has a thickness of 4 μm or more. Having a coating layer formed from a coating solution containing an agent, the amount of oligomer extracted from the coating layer surface is 0.5 mg / m ² or less, and is transparent on the surface opposite to the surface on which the coating layer is provided A laminated polyester film comprising an ITO film which is a conductive film.