JP5385846B2 - Laminated polyester film - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a laminated polyester film, and particularly relates to a laminated film suitable for optical applications where high transparency is required, with emphasis on so-called visibility when transmitting light, for example, for touch panels. It is.

  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, the use of the resistive film type tends to increase by taking advantage of its simple structure and excellent cost performance. The structure of the touch panel using the resistance film method is generally such that a transparent conductive laminate and a glass with a transparent conductive thin film are arranged to face each other via a spacer, and an electric current is passed through the transparent conductive laminate to be transparent. It consists of a structure that measures the voltage in glass with a conductive thin film. Utilizing the principle that when a transparent conductive laminate is brought into contact with a glass with a transparent conductive thin film through a pressing operation with a finger or a pen, the contact portion is energized to detect the position of the contact portion. ing. Moreover, as an example of adopting the resistance film method, an automatic teller machine, a display board of a train ticket machine, and the like are exemplified.

  In the present invention, the transparent conductive laminate is a laminate having a transparent conductive thin film, and the transparent conductive thin film is formed on a film substrate. A transparent conductive laminate is generally provided with a hard coat layer so as to improve transparency and withstand a pressing operation for a touch panel, which contributes to improvement of scratch resistance and the like. ing.

  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 (especially cyclic trimers) contained in the polyester film precipitate and crystallize on the film surface, resulting in the occurrence of coating defects, It may be difficult to obtain a highly accurate transparent conductive thin film.

  As a measure for preventing oligomer precipitation, for example, it has been proposed to provide a curable resin layer made of a crosslinked product of a silicone resin and an isocyanate-based resin on a polyester film (Patent Document 3). However, the curable resin layer is formed by thermosetting, needs high-temperature treatment for dissociation of the blocking agent of the isocyanate resin, and is in a situation where curling and sagging are likely to occur during processing, Care must be taken in handling.

  Further, it is presumed that the conveyance guide roll and the film surface are in contact with and rubbed in the processing step in which the coating layer having the transparent conductive layer is provided on the polyester film. As a result, before processing, even a laminated polyester film having good oligomer sealing performance (for example, Patent Document 4), which is not a problem at all under normal heat treatment conditions (for example, 180 ° C., 10 minutes, etc.), After a long heat treatment such as 150 ° C. for 1 hour or 180 ° C. for 1 hour, the film haze may increase rapidly.

  Moreover, in order to improve the visibility as a base film of a transparent conductive film, it can be achieved by reducing the lubricant particles contained in the film, but if the lubricant particles are reduced too much, the winding workability at the time of film formation and processing is reduced. Decrease and damage to the film surface increase, resulting in a problem that the appearance characteristics are impaired (Patent Document 5).

  Therefore, when taking measures to reduce the amount of oligomer deposited by the coating layer, it should have a higher level of heat resistance than before, and the coating layer itself has good transparency and oligomer sealing performance. The situation is needed.

  In particular, in the touch panel application, the frequency of mounting on communication information devices such as mobile phones and PDAs (Personal Digital Assistance) and game machines has been increasing in recent years. There is a tendency to favor the visibility.

  As a result, in the polyester film used in this field, the visibility deterioration accompanying the increase in film haze after processing has become an increasingly serious problem.

  Therefore, as a polyester film for a touch panel, for example, even after a film is exposed to a high temperature atmosphere such as 150 ° C. for 1 hour or 180 ° C. for 1 hour for a long time and undergoes a severe heat treatment process, It is necessary to maintain the state before processing as much as possible.

JP2007-2000823 JP2007-42473 JP2007-320144 JP2003-237005 JP2009-214360

  The present invention has been made in view of the above circumstances, and the problem to be solved is a useful laminated polyester film that has as little increase in film haze after heat treatment as possible for a long time and is excellent in prevention of scratches, workability, and productivity. Is to provide.

  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 coating layer for a polyester film having a specific configuration can easily solve the above-described problems, and the present invention has been completed. I came to let you.

  That is, the gist of the present invention is to apply a coating solution containing a quaternary ammonium salt-containing polymer, a polyethylene glycol-containing acrylate polymer and a crosslinking agent to one side of a laminated film composed of at least three or more polyester layers, and then dry. The polyester film has the coating layer obtained, has an internal haze of 0.6% or less, and a surface roughness Ra of 9 nm or more.

  According to the laminated polyester film of the present invention, for example, the film is exposed to a high temperature atmosphere for a long time, such as 150 ° C., 1 hour, or 180 ° C., 1 hour, and the transport roll and the coating layer are rubbed. Even after undergoing a harsh heat treatment step, the increase in film haze is as small as possible, and a laminated polyester film excellent in damage prevention, workability and productivity can be provided, 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 film of the present invention needs to have an internal haze of 0.6% or less. The film of the present invention is widely used in optical applications because of its excellent transparency. However, when the internal haze exceeds 0.6%, the transparency as an optical display member is impaired due to poor transparency. It is.

  The total film thickness of the film of the present invention is usually in the range of 12 to 75 μm. If the total film thickness is less than 12 μm, wrinkles may occur during bonding. On the other hand, if it is thicker than 75 μm, the writing taste due to the cushioning effect of the adhesive tends to be lowered.

  Particles are blended in the polyester layer of the film of the present invention 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 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 polyester film of the present invention must have a surface roughness Ra of 9 nm or more, and preferably has a surface roughness Ra of 11 nm or more. If the surface roughness Ra is lower than 9 nm, the slipping property is likely to be damaged by the transport roll of the film forming process line, and when it is wound up in a roll shape, a pyramidal micro-planar defect is likely to occur. It is not preferable.

  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 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 in order to reduce the amount of oligomer precipitation due to thermal damage to the coating layer from the outside. It 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 amount of the quaternary ammonium base-containing polymer in the coating layer is preferably in the range of 20 to 70% by weight, more preferably in the range of 40 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, containing a polyethylene glycol-containing polymer constituting the coating layer for the purpose of improving the stretch followability at the time of forming the coating layer by ensuring higher coating properties than before. It is essential to do. 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 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 and the polyethylene glycol-containing polymer may be a mixture or may be copolymerized in advance, and does not impair the gist of the present invention. If it is a range, it will not specifically limit. Moreover, when making it copolymerize, a conventionally well-known manufacturing method can be used.

  In the coating layer constituting the laminated polyester film in the present invention, a crosslinking agent needs to be used in combination for the purpose of further improving the durability of the 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, melamine cross-linking agents are preferable in terms of good coating properties and durable adhesion particularly in 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, an acidic catalyst such as p-toluenesulfonic acid can be used in combination for the purpose of promoting thermal curing of the melamine crosslinking agent.

  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 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, 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. 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 in 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 to 0. The range is 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 viewpoint, in order to correspond as a member for a touch panel, the film haze change rate (ΔH) before and after heat treatment (180 ° C., 1 hour) is preferably 0.5% or less, more preferably 0.3%. Hereinafter, 0.1% or less is most preferable. When ΔH exceeds 0.5%, the visibility decreases as the film haze increases, and may be inappropriate for applications that require high visibility, such as for touch panels.

The amount (OL) of oligomer (cyclic trimer) extracted with dimethylformamide from the surface of the coating layer before and after heat treatment (180 ° C., 1 hour) of the laminated polyester film of the present invention is usually 0.5 mg / m ² or less. Yes, preferably 0.2 mg / m ² or less, more preferably 0.1 mg / m ² or less. When OL exceeds 0.5 mg / m ² , in post-processing, for example, 180 ° C., 1 hour, etc., in a high temperature atmosphere, the amount of oligomer precipitation increases and the transparency of the film decreases. There is a case.

  In addition, when the polyester film of the present invention is used for optics, a colorant, a conductive material, etc. may be added, and further, reflection of external light, electric shock due to static electricity, prevention of dust adhesion, and further electromagnetic wave shielding. An intended 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) Measuring method of oligomer amount (OL) extracted from the coating layer surface which comprises a laminated polyester film An untreated laminated polyester film is previously heated at 180 degreeC for 1 hour in air. 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 depends on the standard sample peak area and the measured sample peak.

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

(4) Measurement of film haze (H0) The film haze of the sample film was measured with a haze meter “HM-150” manufactured by Murakami Color Research Laboratory according to JIS-K-7136.

(5) Measurement of film haze (H1) after heat treatment In the sample film, a coating agent having the following coating agent composition is applied to the surface opposite to the surface provided with the coating layer. Thereafter, the obtained film was treated under predetermined heat treatment conditions (180 ° C., 1 hour), and then the film haze was measured in the same manner as in the item (4).
<< Coating composition >>
Colcoat P
Bar used: # 3 bar Drying conditions: 100 ° C for 1 minute

(6) Internal haze According to JIS-K-7136, the internal haze of the sample film was measured with a haze meter “HM-150” manufactured by Murakami Color Research Laboratory. In addition, it measured in the quartz cell by using ethanol as a rough surface compensation solvent.

(7) Surface roughness (Ra)
The center line average roughness Ra (nm) is defined as the surface roughness. It calculated | required as follows using the Kosaka Laboratory Co., Ltd. surface roughness measuring machine (SE-3F). That is, a portion having a reference length L (2.5 mm) is extracted from the film cross-sectional curve in the direction of the center line, the roughness line y = f with the center line of the extracted portion as the x axis and the direction of the vertical magnification as the y axis. When represented by (x), the value given by the following equation is represented by [nm]. The center line average roughness was represented by the average value of the center line average roughness of the extracted portion obtained from 10 cross section curves obtained from the sample film surface. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.
Ra = (1 / L) ∫ L 0 | f (x) | dx

(8) Evaluation method of 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) having a thickness of 25 nm 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>
A: Transparency / visibility, particularly good (practical problem-free level)
○: Transparency / Visibility is good (practically acceptable level)
×: Transparency / visibility poor (practical problem level)

(9) Productivity The obtained film surface was visually observed under a three-wavelength fluorescent lamp, and judged according to the following criteria.
○: good with almost no visible scratches ×: many optically visible scratches and poor as an optical film

(10) 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.

<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)]
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)

Example 1:
A mixture of the above polyesters (A) and (B) at a ratio of 75% and 25% is used as the raw material for the A layer, and 100% of the polyester (A) is used as the 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 co-extrusion and cooling and solidification so that the thickness composition ratio was A: B: A = 2.5: 20: 2.5. Next, the film is stretched 3.4 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating amount after transverse stretching and drying is 0.020 g / m ^{2 on} one side of the machined film. After coating the coating solution 1, the film was guided to a tenter, stretched 4.3 times at 120 ° C in the transverse direction, and heat treated at 225 ° C, and then the film was wound on a roll and had a coating layer on one side with a thickness of 25 µm. A laminated polyester film having an internal haze of 0.5% was obtained. The properties of the obtained film are shown in Table 2 below.

Example 2:
A polyester film was obtained in the same manner as in Example 1 except that the coating liquid 1 was changed to the coating liquid 2 in Example 1. The characteristics of the obtained laminated polyester film are shown in Table 2 below.

Comparative Example 1:
A polyester film was obtained in the same manner as in Example 1, except that the coating liquid 1 was changed to the coating liquid 3 in Example 1. The characteristics of the obtained laminated polyester film are shown in Table 2 below.

Comparative Example 2:
A polyester film was obtained in the same manner as in Example 1, except that the coating liquid 1 was changed to the coating liquid 4 in Example 1. 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 coating layer was not provided. The characteristics of the obtained laminated polyester film are shown in Table 2 below.

Comparative Example 4:
In Example 1, the polyester film was obtained by the same method as Example 1 except having made the raw material of A layer into polyester (A) / polyester (B) = 85/15. The characteristics of the obtained laminated polyester film are shown in Table 2 below.

Comparative Example 5:
A mixed raw material in which the polyesters (A) and (B) are mixed at a ratio of 90% and 10%, respectively, is used as a raw material for the B layer, and is melted at 285 ° C. and then cooled to 40 ° C. in a single layer configuration. A laminated polyester film was obtained in the same manner as in Example 1 except that a non-oriented sheet was obtained by extrusion cooling and solidification. The characteristics of the obtained laminated polyester film are shown in Table 2 below.

Comparative Example 6:
A laminated polyester film was obtained in the same manner as in Comparative Example 5, except that a mixed raw material in which the polyesters (A) and (B) were mixed at a ratio of 97% and 3%, respectively, was used as the raw material for the B layer. The characteristics of the obtained laminated polyester film are shown in Table 2 below.

  The film of the present invention can be suitably used for optical applications where high transparency is required, for example, for touch panels.

Claims (1)

It has a coating layer obtained by applying and drying a coating solution containing a quaternary ammonium salt-containing polymer, a polyethylene glycol-containing acrylate polymer and a crosslinking agent on one side of a laminated film comprising at least three polyester layers. A polyester film having an internal haze of 0.6% or less and a surface roughness Ra of 9 nm or more.