JP2014012372A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold release film which is a polyester film substrate material used in manufacturing of a ceramic laminated capacitor, has few surface defects and the like existing on the surface of a polyester film, and does not simultaneously cause defects, such as winding slippage during winding up of the mold release film into a roll shape.SOLUTION: A laminated polyester film has a laminated structure having at least three or more layers, has a surface roughness (Ra) of one surface (smooth surface) of in a range of from 0.001 to 0.005 μm and a surface roughness (Ra) of the other surface in a rage of from 0.010 to 0.030 μm, and has a coating layer, which is formed of a coating liquid containing a mold release component, on the smooth surface.

Description

  The present invention particularly relates to a laminated polyester film used as a release film used as a base material in the production of a ceramic multilayer capacitor.

  In recent years, as the ceramic multilayer capacitor has been reduced in size and capacity, the thickness of the green sheet tends to become thinner. As the green sheet becomes thinner, the influence of the surface properties of the release polyester film, which is the supporting base material, on the properties of the green sheet is increasing. It is in a required situation (Patent Document 1).

  The smoother the surface of the release polyester film used as the base material, the more difficult it is to manufacture the release polyester film, and in particular, the tendency to cause problems such as winding slippage in the roll-up process. There is.

  Polyester film designed so that the surface roughness opposite to the surface on which the green sheet is coated is designed to be a film with a different surface roughness on the front and back sides, in order to suppress the occurrence of winding deviation in the roll winding process. Have also been proposed (Patent Documents 2 and 3).

  However, if the surface roughness of the rough surface is not controlled, the surface protrusions on the rough surface are transferred to the green sheet when rolled up in a roll form, and there is a disadvantage that the quality of the green sheet is deteriorated. When the surface roughness of the rough surface is adjusted and rolled up into a roll form, it is designed that the influence of the rough surface does not reach the smooth surface. It is difficult to prevent the occurrence of surface defects such as scratches.

JP 2003-291291 A JP 11-320764 A JP 2009-143091 A

  The present invention has been made in view of the above circumstances, the solution of the problem is a release polyester film base material used at the time of manufacturing a ceramic multilayer capacitor, there are few surface defects and the like present on the surface of the polyester film, and An object of the present invention is to provide a laminated polyester film that does not cause problems such as winding slip when rolled up.

  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 it has a laminated structure of at least three layers, the surface roughness (Ra) of one surface (smooth surface) is in the range of 0.001 to 0.005 μm, and the other A laminated polyester film having a surface roughness (Ra) of 0.010 to 0.030 μm and a coating layer formed from a coating solution containing a release component on a smooth surface. Exist.

  According to the laminated polyester film of the present invention, it is a release polyester film base material used at the time of producing a ceramic laminated capacitor, has few surface defects present on the surface of the polyester film, and has a winding slip when wound into a roll form. It is possible to provide a release film that does not cause any of the above problems, and its industrial value is high.

  The laminated polyester film of the present invention is required to be a multilayer film having at least 3 layers.

  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 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanone neopentyl glycol, is mentioned. Moreover, polyester of this invention Other thermoplastic resins such as polyethylene naphthalate and polytrimethylene terephthalate can be mixed in the film as long as the effects of the present invention are not impaired. Further, a conductive material, an ultraviolet absorber, an antioxidant, a surfactant, a fluorescent brightening agent, a lubricant, a light shielding agent, a matting agent, and a coloring agent such as a dye or a pigment may be blended. 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. Furthermore, a functional multilayer thin film for the purpose of preventing electric shock due to static electricity, dust adhesion, and electromagnetic wave shielding may be formed thereon.

  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 obtaining an unstretched sheet by cooling and solidifying a molten sheet extruded from a die with a cooling roll using pellets obtained by drying the polyester raw material described above using a single screw extruder 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 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 be adopted for the production of the polyester film constituting the laminated 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 270 ° C. under tension or relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  The total film thickness of the film of the present invention is preferably in the range of 10 to 50 μm. When the total film thickness is less than 10 μm, it may be difficult to handle the polyester film when the green sheet is applied. On the other hand, when the thickness is larger than 50 μm, the absolute value of the thickness unevenness of the film becomes large, and it may be difficult to uniformly coat the green sheet due to this influence.

  In the film of the present invention, the thickness of the outermost layer on the smooth surface side is preferably 1 μm or more, more preferably 2 μm or more. When the thickness of the outermost layer is less than 1 μm, the influence of the inner layer may appear on the surface characteristics of the polyester.

  In the outermost layer on the smooth surface side of the film of the present invention, it is preferable to mix aluminum oxide particles mainly for the purpose of imparting slipperiness and preventing scratches in each step. The average primary particle diameter of the aluminum oxide particles to be added is preferably in the range of 5 to 100 nm, more preferably in the range of 30 to 100 nm. When the average primary particle diameter is less than 5 nm, a fine uneven structure with a smooth surface cannot be expressed. If the average primary particle size exceeds 100 nm, the surface roughness within the scope of the claims of the present invention may not be achieved.

  The amount of aluminum oxide particles added is preferably in the range of 1000 to 15000 ppm, and more preferably in the range of 2000 to 5000 ppm. When the added amount of aluminum oxide particles is less than 1000 ppm, not only a fine uneven structure with a smooth surface cannot be expressed, but there is a possibility that sufficient scratch resistance cannot be realized. Moreover, when the addition amount exceeds 15000 ppm, the alumina oxide particles generate aggregates and become surface protrusions on the film surface, which may adversely affect the smoothness of the surface of the green sheet to be applied in a subsequent step.

  The surface roughness (Ra) on the smooth surface side of the film of the present invention is in the range of 0.001 to 0.005 μm as an essential condition. When the surface roughness (Ra) on the smooth surface side is less than 0.001 μm, the film surface is too smooth in the peeling step after the green sheet is coated on the polyester film, so that a peeling failure is likely to occur. When the surface roughness (Ra) on the smooth surface side exceeds 0.005 μm, coating defects are likely to occur during coating of the green sheet slurry.

  Also in the outermost layer on the rough surface side of the film of the present invention, particles capable of imparting slipperiness are added for the main purpose of imparting slipperiness. Examples thereof include particles of silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, titanium oxide, and the like. 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. The average primary particle diameter of the particles to be added is preferably in the range of 5 to 500 nm, more preferably in the range of 30 to 500 nm. If the average primary particle size is less than 5 nm or more than 500 nm, the surface roughness as claimed in the present invention may not be achieved.

  Moreover, the addition amount of the particle added to the rough surface side of the particle is preferably in the range of 1000 to 30000 ppm, and more preferably in the range of 2000 to 10000 ppm. When the added amount of the particles is less than 1000 ppm, there is a possibility that sufficient rollability of the film cannot be realized. Moreover, when the addition amount exceeds 30000 ppm, the particle concentration becomes too high, the particles generate aggregates, and a projection shape is formed on the film surface, which may cause surface defects.

  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.

  The surface roughness (Ra) on the rough surface side of the film of the present invention is in the range of 0.010 to 0.030 μm as an essential condition. When the surface roughness (Ra) on the rough surface side is less than 0.010, the film surface is too smooth during the production of the polyester film and during the processing of the polyester film, and problems such as winding slippage are likely to occur in the winding process. When the surface roughness (Ra) on the rough surface side exceeds 0.030 μm, the smoothness of the green sheet is sufficiently obtained by transferring the projection shape on the rough surface side to the smooth surface side when winding the polyester film. Can't be achieved.

  Moreover, in this invention, it is preferable that content of the calcium compound contained in a polyester film and a silicon compound is 100 ppm or less. These compounds may be detached from the surface of the polyester film during the production process of the polyester film. In particular, when the content is 100 ppm or more, a desorbed product of these compounds may be caught in the film during the production of the laminated polyester film. It occurs frequently and the portion of the polyester film loses its surface smoothness, which may result in defects in products manufactured by processing the film.

  In the present invention, the content of the antimony compound contained in the polyester film is preferably 100 ppm or less. In particular, when the content of the antimony compound exceeds 100 ppm, a protrusion derived from the precipitation of the antimony compound is often formed on the film surface in the polyester film manufacturing process. Conventionally, the protrusions do not cause any problems in general-purpose applications, but are critical in applications that require smoothness at a higher level, such as green sheet molding, as in the present invention. It becomes a problem. For example, in the projection forming portion, there may be a problem such as shape transfer on the green sheet surface after molding.

  Next, formation of the coating layer which comprises the laminated polyester film in this invention is demonstrated. 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 inline 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 offline coating, thin film coating can be performed more easily. That is, a film suitable as a polyester film can be produced by in-line coating, particularly coating before stretching.

  In the present invention, it is an essential requirement to have a coating layer formed from a coating solution containing a release agent on the smooth surface side.

  The coating layer formed on the smooth surface side of the film of the present invention is provided in order to improve the release performance, for example, for a separate film.

  The release agent used for forming the coating layer on the smooth surface side of the film of the present invention is used for improving the release property of the film, and is not particularly limited, and a conventionally known release agent should be used. Examples thereof include long-chain alkyl compounds, waxes, fluorine compounds, and silicone compounds. These release agents may be used alone or in combination.

  The long-chain alkyl compound is a compound having a linear or branched alkyl group having 6 or more, particularly preferably 8 or more carbon atoms. Specific examples include, but are not limited to, long-chain alkyl group-containing polyvinyl resins, long-chain alkyl group-containing acrylic resins, long-chain alkyl group-containing polyester resins, long-chain alkyl group-containing amine compounds, long-chain alkyl groups. And an ether compound, a long-chain alkyl group-containing quaternary ammonium salt, and the like. In view of heat resistance and contamination, a polymer compound is preferable.

  The wax is a wax selected from natural waxes, synthetic waxes, and blended waxes thereof. Natural waxes are plant waxes, animal waxes, mineral waxes, and petroleum waxes. Examples of plant waxes include candelilla wax, carnauba wax, rice wax, wood wax, and jojoba oil. Animal waxes include beeswax, lanolin, and whale wax. Examples of the mineral wax include montan wax, ozokerite, and ceresin. Examples of petroleum wax include paraffin wax, microcrystalline wax, and petrolatum. Synthetic waxes include synthetic hydrocarbons, modified waxes, hydrogenated waxes, fatty acids, acid amides, amines, imides, esters, and ketones. As synthetic hydrocarbons, Fischer-Tropsch wax (also known as Sazoir wax) and polyethylene wax are famous, but in addition to this, low molecular weight polymers (specifically, polymers having a viscosity number average molecular weight of 500 to 20000) Some of the following polymers are also included. That is, there are polypropylene, ethylene / acrylic acid copolymer, polyethylene glycol, polypropylene glycol, polyethylene glycol and polypropylene glycol block or graft conjugate. Examples of the modified wax include montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives. The derivative herein is a compound obtained by any of purification, oxidation, esterification, saponification treatment, or a combination thereof. Hydrogenated waxes include hardened castor oil and hardened castor oil derivatives. Among these waxes, synthetic hydrocarbons are preferable from the viewpoint of stable performance and easy availability, and oxidized polyethylene wax and oxidized polypropylene wax are more preferable.

  The fluorine compound is a compound containing a fluorine atom in the compound. Organic fluorine compounds are preferably used in terms of the appearance of coating by in-line coating, and examples thereof include perfluoroalkyl group-containing compounds, polymers of olefin compounds containing fluorine atoms, and aromatic fluorine compounds such as fluorobenzene. . In view of heat resistance and contamination, a polymer compound is preferable, and a perfluoroalkyl group-containing compound is preferable in order to effectively improve slipperiness.

The silicone compound is a compound having a silicone structure in the molecule, and examples thereof include silicone emulsion, acrylic graft silicone, silicone graft acrylic, amino-modified silicone, perfluoroalkyl-modified silicone, and alkyl-modified silicone. In view of heat resistance and contamination, it is preferable to contain a curable silicone resin.
As the type of the curable silicone resin, any of the curing reaction types such as an addition type, a condensation type, an ultraviolet curable type, and an electron beam curable type can be used.

These release agents may be used alone or in combination. Among these release agents, it is preferably not a silicone compound in view of process contamination, and more preferably a long-chain alkyl compound or a fluorine compound in view of release performance. In the coating solution to be contained, various polymers and cross-linking agents can be used in combination in order to improve the coating appearance and transparency and to control the releasability.

  Examples of the polymer include polyester resin, acrylic resin, urethane resin, polyvinyl (polyvinyl alcohol, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches, and the like. Can be mentioned. Among these, polyester resin, acrylic resin, and urethane resin are preferable, and polyester resin is more preferable in that it is easy to control releasability.

  Examples of the cross-linking agent include melamine compounds, oxazoline compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, silane coupling compounds, and the like. In particular, in order to strengthen the coating layer and provide stable release properties, melamine It is preferable to use a compound in combination.

  As the melamine compound, for example, an alkylolated melamine derivative, a compound obtained by reacting an alcohol with an alkylolated melamine derivative or partially etherified, and a mixture thereof can be used. As alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. Moreover, as a melamine compound, either a monomer or a multimer more than a dimer may be sufficient, or a mixture thereof may be used. Further, a product obtained by co-condensing urea or the like with a part of melamine can be used, and a catalyst can be used to increase the reactivity of the melamine compound.

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

  As a ratio with respect to all the non-volatile components in the coating liquid containing the release agent in the present invention, the release agent is usually in the range of 5% by weight or more, preferably in the range of 10 to 90% by weight, more preferably in the range of 20 to 85% by weight. % Range. If it is less than 5% by weight, the releasability may not be sufficient.

  As a ratio with respect to all the non-volatile components in the coating liquid containing the release agent in the present invention, the crosslinking agent is usually in the range of 90% by weight or less, preferably in the range of 5 to 80% by weight, more preferably in the range of 10 to 60% by weight. Range. If it is out of the above range, the releasability may not be sufficient.

  Regarding the laminated polyester film in the present invention, the thickness of the coating layer formed from the coating solution containing a release agent is usually 0.001 to 1.0 μm, preferably 0.01 to 0.3 μm, more preferably 0. The range is 0.02 to 0.2 μm. When the film thickness is out of the above range, the releasability and the coating appearance may be deteriorated.

  The polyester film in the present invention has a coating layer formed from a coating solution containing a release agent on the smooth surface side, but is provided with a similar or other coating layer or functional layer on the rough surface side of the film. Is naturally included in the concept of the present invention.

  For example, a coating layer formed from a coating solution containing a release agent is provided on the smooth surface side of a polyester film, and the antistatic performance and the performance of sealing the precipitation of ester cyclic trimer are provided on the rough surface side. Thus, it is preferable to provide a coating layer formed from a coating solution containing a quaternary ammonium group-containing polymer and a polyvalent aldehyde compound. The coating liquid containing the quaternary ammonium group-containing polymer and the polyvalent aldehyde compound may contain other components.

  The quaternary ammonium group-containing polymer here refers to a polymer compound having a quaternized ammonium group in the molecule.

  In a coating layer formed from a coating solution containing a quaternary ammonium group-containing polymer and a polyvalent aldehyde compound, for example, a polymer containing as a component a monomer having a quaternary ammonium group and an unsaturated double bond is used. be able to.

  Specific examples of such a polymer include a polymer having a constituent represented by the following formula 1 or 2 as a repeating unit. These homopolymers and copolymers, and other plural components may be copolymerized.

In the above formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ² is —O— or —NH—, R ³ is an alkylene group having 1 to 6 carbon atoms or the structure of formula 1 Other possible structures, R ¹ , R ² and R ³ are each a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and X ⁻ is a monovalent anion.

In the above formula, R ¹ and R ² are each a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and X ⁻ is a monovalent anion.

A polymer having a component represented by Formula 1 is preferable because of excellent transparency of the resulting coating layer. However, in the coating stretching method, heat resistance may be inferior, and when used in the coating stretching method, X ⁻ is preferably not a halogen.

  The compound represented by Formula 2 and other compounds having a quaternary ammonium base in the polymer skeleton are excellent in heat resistance, and antistatic properties are easily obtained even in a coating stretching method.

  In addition, the polymer in which the component represented by the formulas 1 and 2 and the polyethylene glycol-containing (meth) acrylate are copolymerized has a flexible structure, and has a uniform coating layer during coating and stretching. Is preferable.

  Alternatively, a coating layer having excellent uniformity can also be obtained by coating a polyethylene glycol-containing (meth) acrylate polymer in a coating solution.

  Specific examples of the polyethylene glycol-containing (meth) acrylate include 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), and polypropylene glycol diacrylate. Acrylate, 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 Methacrylate, 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, steer Examples include polymers starting from loxypolyethylene glycol monoacrylate, allyloxypolyethylene glycol monomethacrylate, allyloxypolyethylene glycol monoacrylate and the like.

  The ratio of the quaternary ammonium group-containing polymer to the entire nonvolatile content in the coating solution is usually 10% by weight or more, preferably 15% by weight or more, and more preferably 20% by weight or more. When the content is less than this, the antistatic performance may be insufficient. On the other hand, the upper limit is usually 90% by weight, preferably 80% by weight or less, more preferably 60% by weight or less. When there is more content than this, the uniformity and external appearance of the coating film obtained may be inferior.

  Examples of the polyvalent aldehyde compound in the coating solution containing a quaternary ammonium group-containing polymer and a polyvalent aldehyde compound include glyoxal, glutaraldehyde, terephthalaldehyde, cyclohexanedialdehyde, tricyclodecanedialdehyde, norbornanedialdehyde, Examples include aldehydes. Further, those obtained by reacting these aldehyde groups with glycol or amide can also be used. In particular, a product obtained by reacting glyoxal with a polyhydric alcohol such as ethylene glycol or glycerin, a monosaccharide such as glucose or galactose, or a cyclic amide can be preferably used. These reactants suppress the reactivity of polyaldehyde at room temperature, and after coating and drying, glycols such as ethylene glycol and cyclic amides are removed, and the reaction of aldehyde starts in the coating layer, making it easy to handle. In addition, once the glycols such as ethylene glycol and the cyclic amide are removed, there are fewer free reactive residues due to their high reactivity, and there are advantages in terms of performance stability over time and safety and health.

  The coating solution containing the quaternary ammonium group-containing polymer and the polyvalent aldehyde compound preferably contains polyvinyl alcohol. When the polyester film having the coating layer thus obtained is heated, precipitation of the ester cyclic trimer component from the film surface tends to be further suppressed.

  Polyvinyl alcohol blended in a coating solution containing a quaternary ammonium group-containing polymer and a polyvalent aldehyde compound can be synthesized by a normal polymerization reaction and is preferably water-soluble.

  The degree of polymerization of polyvinyl alcohol is not particularly limited, but is usually 100 or more, preferably 300 to 40,000. When the degree of polymerization is 100 or less, the water resistance of the coating layer tends to decrease. The saponification degree of polyvinyl alcohol is not particularly limited, but a polyvinyl acetate saponified product that is usually 70 mol% or more, preferably 80 mol% or more and 99.9 mol% or less is practically used.

  Moreover, it is preferable to add a thermosetting crosslinking component to a coating solution containing a quaternary ammonium group-containing polymer and a polyvalent aldehyde compound because the durability of the resulting coating layer is improved. Examples of such cross-linking components include amino resin-based, isocyanate-based, oxazoline-based, and epoxy-based components. Also included are polymer-type cross-linking reactive compounds having reactive groups in other polymer skeletons. As a particularly preferred embodiment in the present invention, an amino resin-based crosslinking agent can be exemplified. Examples of amino resin-based crosslinking agents include alkylolized melamine-based, benzoguanamine-based, and urea-based agents. In particular, a laminated polyester film in which an amino group is methylolated and a part of the methylol group is methylated is a water-soluble, easy to handle, highly reactive, and less precipitated ester cyclic trimer from the film. can get.

  When such a crosslinking component is contained, a component for accelerating crosslinking, for example, a crosslinking catalyst can be used in combination.

  Moreover, the thickness of the coating layer formed from the coating solution containing the quaternary ammonium group-containing polymer and the polyvalent aldehyde compound is usually in the range of 0.003 μm to 1 μm as the film thickness on the finally obtained film. Preferably, it is in the range of 0.005 μm to 0.5 μm, more preferably 0.01 μm to 0.2 μm. When the thickness is smaller than this, the amount of ester cyclic trimer precipitated from the film may not be sufficiently reduced. On the other hand, if it is thicker than this, problems such as deterioration of the appearance of the coating layer and easy blocking may occur.

  In the film of the present invention, the thickness of the coating layer is determined by dyeing the coating film with a heavy metal such as a ruthenium compound or an osmium compound, adjusting the cross section of the coating film by an ultrathin section method, and then using a transmission electron microscope. This can be confirmed by observing a plurality of coating layers on the cross section of the coating film and averaging the measured values.

  In the film of the present invention, analysis of components in the coating layer can be performed by analysis of TOF-SIMS, ESCA, fluorescent X-rays, and the like.

  In the film of the present invention, the coating layer can be formed by 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.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, it is usually 3 to 40 at 80 to 200 ° C. The heat treatment may be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when the coating layer is provided by in-line coating, heat treatment is usually performed at 70 to 270 ° C. for 3 to 200 seconds as a guide.

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

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

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

  In addition, inorganic particles and organic particles may be contained in the coating layer in order to further improve the slipperiness and adhesion within the range not impairing the gist of the present invention.

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

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

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

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

The amount of the ester cyclic trimer that is extracted from the smooth surface of the film after heat treatment (180 ° C., 10 minutes) in the present invention with dimethylformamide is preferably 10 mg / m ² or less, and Preferably it is 1 m ² or less. When the amount of the ester cyclic trimer exceeds 10 mg / m ² , the precipitated ester cyclic trimer is transferred to the green sheet and mixed into the wiring board, resulting in a loss of electrical characteristics or an electrical defect. There is a fear. In addition, the processing apparatus may be contaminated by the precipitated ester cyclic trimer, and the productivity may be reduced.

The amount of the ester cyclic trimer extracted from the rough film surface by dimethylformamide after heat treatment (180 ° C., 10 minutes) of the laminated polyester film in the present invention is preferably 10 mg / m ² or less. Preferably it is 1 mg / m ² or less, particularly preferably 0.5 mg / m ² or less. When the amount of the ester cyclic trimer exceeds 15 mg / m ² , the precipitated cyclic ester trimer may contaminate the processing apparatus or reduce the productivity.

The surface specific resistance value on the rough surface side of the laminated polyester film in the present invention is preferably 1 × 10 ¹⁴ Ω or less, more preferably 1 × 10 ¹³ Ω or less. When the surface specific resistance value on the rough surface side exceeds 1 × 10 ¹⁴ Ω, there is a possibility that the film is charged by static electricity during film processing and attracts surrounding dust and the like.

  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) Surface roughness (Ra) of laminated polyester film
It measured according to JIS-B-0601-1994 using the surface roughness measuring machine "SE-3500" by Kosaka Laboratory. When the extracted portion is sandwiched by two parallel straight lines to the average line of the portion (hereinafter referred to as the extracted portion) extracted by the reference length (2.5 mm) from the obtained cross-sectional curve, the interval between the two straight lines is defined as the cross-sectional curve. The value measured in the direction of the vertical magnification and the value expressed in units of micrometers (μm) was taken as the maximum height of the extracted portion. The maximum height was expressed as an average value of the maximum heights of the extracted portions obtained from 10 cross-sectional curves obtained from the sample film surface. The radius of the stylus used at this time was 2.0 μm, the load was 30 mg, and the cutoff value was 0.08 mm.

(3) Abrasion resistance Using a RUBING TESTER manufactured by Taihei Rika Kogyo Co., Ltd., the sample surface was rubbed back and forth 10 times with a special felt at a load of 200 g. The surface after rubbing was visually observed, and scratch resistance was evaluated according to the following evaluation criteria.
○: Scratches cannot be confirmed △: Scratches can be confirmed a little ×: Many scratches can be confirmed

(4) Rollability The roll rollability of the film at the time of manufacturing the polyester film was evaluated according to the following evaluation criteria.
○: Winding property is good △: Film slipping property is slightly insufficient, winding property is somewhat inferior ×: Film slipping property is insufficient, winding misalignment and the like occur, and there is a problem in winding property

(5) Measurement of content of silicon compound, calcium compound and antimony compound A single piece by a film FP method (Fundamental Parameter Method) using a fluorescent X-ray analyzer (model “XRF-1500” manufactured by Shimadzu Corporation) The amount of element in the film was determined by measurement, and the detection limit in this method is usually about 1 ppm.

(6) Coating property of green sheet slurry Barium titanate (manufactured by Fuji Titanium Industry Co., Ltd .: average) on the smooth surface of the polyester film (surface having a coating layer formed from a coating solution containing a release component) 100 parts of particle size 0.7 μm), 30 parts of polyvinyl butyral resin (“S-REC BM-S” manufactured by Sekisui Chemical Co., Ltd.), 5 parts of plasticizer (dioctyl phthalate), toluene / ethanol mixed solvent (mixing ratio: 6: 4) A ceramic slurry composed of 200 parts was applied, and applied so that the application amount after drying was 1.0 g / m ² to obtain a green sheet. At this time, the coating property of the green sheet was evaluated according to the following evaluation criteria.
○: Slurry repelling and coating unevenness do not occur Δ: Fine slurry repelling and coating unevenness occur ×: Slurry repelling and coating unevenness remarkably occur

(7) Green sheet peelability The peelability of the green sheet obtained by the method described in (7) above from the release film was evaluated according to the following evaluation criteria.
○: The green sheet can be peeled off from the release film without problems. ×: The green sheet is not peeled off from the release film, and the green sheet fragments remain on the release film side.

(8) Smoothness evaluation of the green sheet surface The surface (measuring area: 100 cm ² ) of the green sheet obtained by the method described in (7) above is the surface by a scanning laser microscope (manufactured by Lasertec Corporation). Observation was performed and the determination was made according to the following criteria.
◯: One or less dents having a depth of 0.2 μm or more on the surface of the green sheet / 100 cm ²
Δ: 1 or more and less than 5 dents having a depth of 0.2 μm or more on the surface of the green sheet / 100 cm ²
×: 5 or more dents having a depth of 0.2 μm or more on the surface of the green sheet / 100 cm ²

(9) Measuring method of average particle size of particles in coating layer The coating layer was observed using TEM (H-7650, Hitachi High-Technologies Corporation, acceleration voltage 100V), and the average value of the particle size of 10 particles. Was the average particle size.

(10) Method for measuring film thickness of coating layer The surface of the coating layer was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the section prepared by ultramicrotomy stained with RuO _4, a coating layer cross-section was measured by using a TEM (Hitachi High Technologies Corporation H-7650, accelerating voltage 100 V).

(11) Specific surface resistance value Using a high resistance measuring instrument manufactured by Hewlett-Packard Japan: HP4339B and measuring electrode: HP16008B, the sample was sufficiently conditioned in a measurement atmosphere of 23 ° C. and 50% RH, and then 1 at an applied voltage of 100V. The surface specific resistance value of the coating layer on the rough surface side after minutes was measured.

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

(13) Method for measuring the amount of ester cyclic trimer extracted from the surface of the laminated polyester film In advance, the 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 an upper portion of 10 cm in length and width of 3 cm and a height of 3 cm to form a box shape. At this time, the measurement surface is set inside. Next, 4 ml of DMF is placed in the box prepared by the above method and left for 3 minutes, and then DMF is recovered. The recovered DMF is supplied to liquid chromatography (manufactured by Shimadzu Corporation: LC-7A) to determine the amount of ester cyclic trimer in DMF, and this value is divided by the film area in contact with DMF to obtain the film surface. The amount of ester cyclic trimer (mg / m ² ) was used.

Examples of compounds contained in the coating solution for forming the coating layer on the smooth surface side are as follows.
(Example compounds)
・ Release agent (long chain alkyl compound): (1)
To a four-necked flask, 200 parts of xylene and 600 parts of octadecyl isocyanate were added and heated with stirring. From the time when xylene began to reflux, 100 parts of polyvinyl alcohol having an average degree of polymerization of 500 and a degree of saponification of 88 mol% was added in small portions over a period of about 2 hours. After the addition of polyvinyl alcohol, the reaction was completed by further refluxing for 2 hours. When the reaction mixture was cooled to about 80 ° C. and added to methanol, the reaction product was precipitated as a white precipitate. This precipitate was filtered off, added with 140 parts of xylene, and heated to dissolve completely. After repeating the operation of adding methanol again to precipitate several times, the precipitate was washed with methanol and dried and ground.

・ Releasing agent (fluorine compound): (2)
In a glass reaction vessel, perfluoroalkyl group-containing acrylate CF ₃ (CF ₂ ) _n CH ₂ CH ₂ OCOCH═CH ₂ (n = 5 to 11, n average = 9) 80.0 g, acetoacetoxyethyl 20.0 g of methacrylate, 0.8 g of dodecyl mercaptan, 354.7 g of deoxygenated pure water, 40.0 g of acetone, 1.0 g of C ₁₆ H ₃₃ N (CH ₃ ) ₃ Cl and C ₈ H ₁₇ C ₆ H ₄ O (CH ₂ CH ₂ O) nH (n = 8) (3.0 g) was added, 0.5 g of azobisisobutylamidine dihydrochloride was added, and a copolymerization reaction was carried out at 60 ° C. for 10 hours with stirring under a nitrogen atmosphere. A coalescence emulsion was obtained.

・ Crosslinking agent (hexamethoxymethylmelamine): (3)

・ Polyester resin: (4)
Water dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / 1,4-butanediol / diethylene glycol = 56/40/4 // 70/20/10 (mol%)

-Particles: (5) Silica particles having an average particle size of 0.07 μm Examples of compounds contained in the coating solution for forming the coating layer on the rough surface side are as follows.
Copolymer having a weight ratio of 2- (trimethylamino) ethyl methacrylate / ethyl methacrylate / butyl methacrylate / polyethylene glycol-containing monoacrylate of 75/12/15/30, wherein the counter ion is methyl sulfonate: (6)

2-hydroxy 3-methacryloxypropyltrimethylammonium salt polymer in which the counter ion is methylsulfonate: (7)

A high molecular compound having a number average molecular weight of 20000 obtained by copolymerizing a structural unit of the following formula 1-1 and a structural unit of the following formula 1-2 at a weight ratio of 95/5: (8)

・ Polyhydric aldehyde compound obtained by reacting glyoxal with anhydrous glucose: (9)
Polyethylene glycol-containing monoacrylate polymer having a number average molecular weight of 20000: (10)

Polyvinyl alcohol having a saponification degree of 88 mol% and a polymerization degree of 500: (11)
Hexamethyl-toximethylolated melamine in which the imino group / methylol group / methoxy group has a molar ratio of 1.5 / 2 / 2.5: (12)
-Surface alumina coated silica sol, average particle size 15 nm by BET method: (13)

<Manufacture of polyester>
[Production method of polyester (A0)]
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 (A0) was 0.65.

[Method for producing polyester (A1)]
In the production method of polyester (A0), after adding 0.04 part of ethyl acid phosphate, the content of silica particles dispersed in ethylene glycol having an average particle diameter of 1.6 μm is 0.6% by weight based on the polyester. And a polycondensation reaction was performed for 4 hours to obtain a polyester (A1).

[Production method of polyester (A2)]
In the production method of polyester (A1), polyester (A1) is used except that the particle type to be added is calcium carbonate particles dispersed in ethylene glycol having an average particle diameter of 0.7 μm and the content thereof is 2.0% by weight. ) To obtain polyester (A2) by the same method.

[Polyester (B0)]
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, adding tetrabutoxy titanate as a catalyst to the reactor, setting the reaction start temperature to 150 ° C., and gradually increasing the reaction temperature as methanol is distilled off. It was 230 degreeC after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. This reaction mixture was transferred to a polycondensation tank and subjected to a polycondensation reaction for 4 hours. After 4 hours, the transesterification reaction was substantially terminated. Ethyl acid phosphate was added to the reaction mixture, which was then transferred to a polycondensation tank and subjected to a polycondensation reaction 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 0.55 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester chip. The intrinsic viscosity was 0.55. The obtained polyester chip was subjected to solid phase polymerization at 220 ° C. to obtain a polyester (B0) having an intrinsic viscosity of 0.65.

[Method for producing polyester (B1)]
In the method for producing polyester (B0), the content of aluminum oxide particles dispersed in ethylene glycol having an average particle diameter of 60 nm after addition of 0.04 part of ethyl acid phosphate is 1.5% by weight with respect to polyester. And a polycondensation reaction was carried out for 4 hours to obtain polyester (B1).

[Production method of polyester (B2)]
In the production method of polyester (B1), the production method of polyester (B1) is the same except that the particle type to be added is divinylbenzene-crosslinked polystyrene particles having an average particle size of 0.4 μm and the content to the polyester is 0.5% by weight. Polyester (B2) was obtained by the same method as that described above.

Example 1:
A mixed raw material in which the polyesters (B0) and (B1) are mixed at a ratio of 80.0% by weight and 20.0% by weight is used as the raw material for the a layer, and the raw material of 100% polyester (B0) is used as the raw material for the b layer. Polyesters (B0) and (B2) mixed at a ratio of 50.0% by weight and 50.0% by weight, respectively, were used as c layer raw materials, and each was supplied to three extruders at 285 ° C. After being melted at, the a layer, the c layer as the outermost layer (surface layer), the b layer as the intermediate layer, and on the casting drum cooled to 40 ° C., three types and three layers (abc) with a thickness composition ratio of a: b : C = 2: 27: 2 was coextruded and cooled and solidified to obtain a non-oriented sheet. Next, the film was 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 solution 1 shown in Table 1 below was dried on the a-layer side surface (smooth surface) of the longitudinally stretched film. The film was applied so that the post film thickness was 0.1 μm, and the coating liquid 9 shown in Table 2 below was applied to the c-layer side surface (rough surface) so that the film thickness after drying was 0.03 μm. The film was guided to a tenter, stretched 4.3 times in the transverse direction at 120 ° C., and heat treated at 225 ° C., and then the film was wound on a roll to obtain a laminated polyester film having a thickness of 31 μm. The characteristics of the obtained film are shown in Tables 3 and 4 below.

Example 2:
In Example 1, polyesters (A0) and (B1) were mixed at a ratio of 80.0 wt% and 20.0 wt%, respectively, as the raw material for the a layer, and the polyester (A0) was used as the raw material for the b layer, A polyester film was obtained in the same manner as in Example 1 except that the polyesters (A0) and (B2) were mixed at a ratio of 50.0 wt% and 50.0 wt%, respectively, as the raw material for the c layer. . The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Example 3:
In Example 1, polyester (B0) and (B1) were mixed in the proportions of 30.0% by weight and 70.0% by weight, respectively, as the raw material for layer a. A film was obtained. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Example 4:
In Example 1, except that polyester polyesters (B0) and (B2) were mixed in the proportions of 30.0% by weight and 70.0% by weight as raw materials for the c layer, respectively, in the same manner as in Example 1, A polyester film was obtained. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Example 5:
In Example 1, it is the same method as Example 1 except having mixed polyester polyester (B0) and (A0) in the ratio of 70.0 weight% and 30.0 weight% as a raw material of b layer, A polyester film was obtained. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Examples 6-12:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent 1 apply | coated to a smooth surface into the coating liquids 2-6 shown in Table 1, and obtained the polyester film. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Example 13:
In Example 1, it manufactured like Example 1 except not applying a coating liquid to a rough surface, and obtained the polyester film. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Examples 14-21:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent 9 apply | coated to a rough surface into the coating liquids 10-20 shown in Table 2, and obtained the polyester film. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Comparative Example 1:
Example 1 is the same as Example 1 except that a mixed raw material in which polyesters (B0) and (B1) are mixed at a ratio of 96.0% by weight and 4.0% by weight, respectively, is used as the raw material for the a layer. In this way, a polyester film was obtained. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Comparative Example 2:
Example 1 is the same as Example 1 except that a mixed raw material in which polyesters (B0) and (B1) are mixed at a ratio of 80.0% by weight and 20.0% by weight, respectively, is used as the raw material for the c layer. In this way, a polyester film was obtained. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Comparative Example 3:
In Example 1, the same material as Example 1 was used, except that a mixed raw material in which polyesters (B0) and (A1) were mixed at a ratio of 50.0% by weight and 50.0% by weight was used as the raw material for the c layer. By the method, a polyester film was obtained. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Comparative Example 4:
In Example 2, a mixed raw material in which polyesters (A0) and (A2) were mixed at a ratio of 70.0 wt% and 30.0 wt%, respectively, was used as the raw material for the a layer, and the polyester (A0) was used as the raw material for the c layer. ) And (A2) were used in the same manner as in Example 1 except that a mixed raw material in which 70.0% by weight and 30.0% by weight were mixed was used to obtain a polyester film. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Comparative Example 5:
In Example 2, a mixed raw material in which polyesters (A0) and (A1) were mixed at a ratio of 70.0 wt% and 30.0 wt%, respectively, was used as the raw material for the a layer, and the polyester (A0) was used as the raw material for the c layer. ) And (A1) were obtained in the same manner as in Example 1 except that mixed raw materials were mixed at a ratio of 70.0% by weight and 30.0% by weight, respectively, to obtain a polyester film. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Comparative Example 6:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coating solution was not applied to the smooth surface. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

Comparative Examples 7 and 8:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent 1 apply | coated to a smooth surface into the coating liquids 7 and 8 shown in Table 1, and obtained the polyester film. The characteristics of the obtained laminated polyester film are shown in Tables 3 and 4 below.

  The film of the present invention can be suitably used particularly as a base material for producing a ceramic multilayer capacitor.

Claims (1)

It has a laminated structure of at least three layers, the surface roughness (Ra) of one surface (smooth surface) is in the range of 0.001 to 0.005 μm, and the surface roughness (Ra) of the other surface Has a coating layer formed from a coating solution containing a release component on a smooth surface, wherein the laminated polyester film has a thickness of 0.010 to 0.030 μm.