JP5236586B2 - Laminated polyester film - Google Patents

Description

  The present invention relates to a laminated polyester film. For example, the film is exposed to a high temperature atmosphere for a long time such as 150 ° C. for 1 hour or 180 ° C. for 1 hour, and the transport roll and the coating layer are rubbed multiple times. It is related to a film having a feature that the increase in film haze is as small as possible even after undergoing such a severe heat treatment process, and particularly with respect to the so-called visibility that transmits light, The present invention relates to a film suitable for optical applications requiring transparency, 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, 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 is comprised from the structure etc. which measure the voltage in glass with an electroconductive 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 vending 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.

  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.

JP 2007-200823 A JP 2007-42473 A JP 2007-320144 A JP 2003-237005 A

  The present invention has been made in view of the above circumstances, and its solution is mainly due to insufficient heat resistance of the coating film in a high-temperature atmosphere such as heat treatment at 180 ° C. for 1 hour in the heat treatment step. It has been found that this is the main factor causing the film haze after heat treatment to increase rapidly, and it is to provide a laminated polyester film in which the increase in film haze after heat treatment for a long time is as small as possible.

  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 using a polyester film having a specific coating layer, and have completed the present invention.

  That is, the gist of the present invention is to have a coating layer obtained by coating a coating liquid containing a quaternary ammonium base-containing polymer, a polyethylene glycol-containing acrylate polymer and a crosslinking agent on at least one polyester film surface and drying. It exists in the laminated polyester film characterized by this.

  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, it is possible to provide a laminated polyester film having as little increase in film haze as possible, and its industrial value is high.

  Hereinafter, the present invention will be described in more detail.

  The polyester film in the present invention may have a single layer structure or a multilayer structure, and may have a multilayer structure of four layers or more as long as the gist of the present invention is not exceeded other than the two-layer or three-layer structure. Well, not particularly limited.

  The polyester used in the present invention is preferably obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol, and may be a polyester comprising one kind of aromatic dicarboxylic acid and one kind of aliphatic glycol. It may be a copolyester obtained by copolymerizing one or more other components. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyester includes polyethylene terephthalate and the like. On the other hand, examples of the dicarboxylic acid used as a component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, and sebacic acid, and glycol components include ethylene glycol, diethylene glycol, and propylene. Examples include glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like. Oxycarboxylic acids such as p-oxybenzoic acid can also be used.

  In addition, in the laminated polyester film of the present invention, in order to reduce the amount of oligomers contained in the film precipitated and crystallized on the surface of the film due to the thermal history during film processing, etc. It is also possible to use a low oligomerized polyester for the outer layer. As a method for reducing the amount of oligomer in the polyester, for example, a solid phase polymerization method or the like can be used.

  In the laminated polyester film of the present invention, it is necessary to blend particles for the main 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. Two or more kinds of these particles may be used in combination as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-3 micrometers normally, Preferably it is the range of 0.01-2 micrometers. When the average particle diameter is less than 0.01 μm, the particles are likely to aggregate and dispersibility may be insufficient. On the other hand, when the average particle diameter exceeds 3 μm, the surface roughness of the film becomes too rough and Problems may occur when various surface functional layers are applied in the process.

  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, while when it exceeds 5% by weight, the transparency of the film may be insufficient.

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

  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.

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

  Although the thickness of the polyester film in this invention will not be specifically limited if it can be formed into a film as a film, Usually, 9-250 micrometers, Preferably it is the range of 12-188 micrometers.

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. That is, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. 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, and an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. is there. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can also be adopted for the production of the polyester film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is usually stretched and oriented in the machine direction and the width direction at a temperature controlled normally at 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be employed.

  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 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, a polyethylene glycol-containing polymer constituting the coating layer for the purpose of improving the stretch following property at the time of forming the coating layer by ensuring higher coating properties than the conventional one. It is essential to contain. 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, 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 can be polymerized as a polymer. About content of the polyethyleneglycol containing polymer which comprises the coating layer in this invention, the range of 5 to 40 weight% is preferable in order to make stretching 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 methylation. 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 on 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 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 with an increase in film haze, and may be unsuitable 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 in 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.

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

(1) Measuring method of intrinsic viscosity of polyester 1 g of polyester was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and the measurement was performed at 30 ° C.

(2) Measuring method of average particle size (d ₅₀ : μm) Integration (weight basis) 50 in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) % Was defined as the average particle size.
(3) Amount of oligomer extracted from the surface of the coating layer constituting the laminated polyester film

(OL) Measuring Method An untreated laminated polyester film is heated in air at 180 ° C. for 1 hour in advance. 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 an oligomer (cyclic trimer) collected in advance and dissolving it in accurately measured DMF. 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) 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) 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)

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (I)>
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 (I) was 0.63.

<Method for producing polyester (II)>
In the method for producing polyester (I), after adding 0.04 part of ethyl acid phosphate, 0.3 part of silica particles having an average particle diameter of 1.6 μm dispersed in ethylene glycol and 0.04 part of antimony trioxide are added. In addition, polyester (II) was obtained using the same method as the production method of polyester (I) except that the polycondensation reaction was stopped at the time corresponding to the intrinsic viscosity of 0.65. The obtained polyester (II) had an intrinsic viscosity of 0.65.

Example 1:
The mixed raw materials obtained by mixing polyester (I) and (II) at a ratio of 90% and 10%, respectively, were used as the outermost layer (surface layer) raw material, and the polyester (I) was used as the intermediate layer raw material in two extruders. Are melted at 285 ° C., and then coextruded in a layer configuration of two types and two layers (surface layer / intermediate layer / surface layer) on a cooling roll set at 40 ° C., and cooled and solidified to form an unstretched sheet Obtained. 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 drying the coating layer composed of the following coating agent composition becomes 0.020 g / m ^2. After coating, the film was led to a tenter, stretched 4.3 times at 120 ° C in the transverse direction, heat treated at 225 ° C, relaxed in the transverse direction, and a thickness of 25 µm (surface layer 2.5 µm, intermediate layer 20 µm). ) Polyester film was obtained. Then, on the film surface opposite to the side having the coating layer, 100 parts of acrylic / urethane resin (“Unidic 17-806” manufactured by Dainippon Ink & Chemicals, Inc., hydroxycyclohexyl phenyl ketone as a photopolymerization initiator) ("Irgacure 184" manufactured by Ciba Japan Co., Ltd.) Add 5 parts, apply a toluene solution diluted to a concentration of 50% by weight, dry at 80 ° C, and then irradiate with ultraviolet light to harden 5μm thick A laminated polyester film having a coating layer was obtained, and the obtained laminated polyester film had a small amount of oligomer precipitation by heat treatment, and the characteristics of this film are shown in Table 2 below.

In addition, the example of a compound which comprises an application layer is as follows.
(Example compounds)
-Quaternary ammonium base-containing polymer (A1):
2-hydroxy-3-methacryloxypropyltrimethylammonium salt polymer Counter ion: methyl sulfonate Number average molecular weight: 30000
-Polyethylene glycol-containing acrylate polymer (B1):
Polyethylene glycol-containing monoacrylate polymer Number average molecular weight: 20000
-Polyethylene glycol-containing acrylate polymer (B2):
Octoxy polyethylene glycol-polypropylene glycol monoacrylate polymer Number average molecular weight: 32000
・ 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 2 to Example 5:
In Example 1, it manufactured similarly to Example 1 except having changed the coating layer into the coating agent composition shown in following Table 1, and obtained the laminated polyester film. The characteristics of the obtained laminated polyester film are shown in Table 2 below.

Comparative Example 1:
In Example 1, it manufactured like Example 1 except not providing an application layer, and obtained the lamination polyester film. The characteristics of the obtained laminated polyester film are shown in Table 2 below.

Comparative Examples 2-4:
In Example 1, it manufactured like Example 1 except changing an application layer composition, and obtained a lamination polyester film. 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 in which visibility is important and high transparency is required, for example, for touch panels.

Claims (1)

A laminated polyester film comprising a coating layer obtained by coating a coating liquid containing a quaternary ammonium base-containing polymer, a polyethylene glycol-containing acrylate polymer and a crosslinking agent on at least one polyester film surface and drying.