JP2012250447A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film that shows an excellent adhesion to various top coat agents.SOLUTION: The polyester film has a coating layer, and the coating layer is formed by the coating liquid containing the polyurethane and the carbodiimide crosslinking agent. In the laminated polyester film, the polyurethane has the polycarbonate polyol which is obtained by copolymerizing two kinds of carbonate polyols different in the main chain structure as the constituent, and the polyisocyanate which is the constituent of the polyurethane is aliphatic family or alicyclic family.

Description

  The present invention relates to a polyester film having a coating layer excellent in adhesion to various topcoats.

  Biaxially stretched polyester film excels in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, gas barrier properties, chemical resistance, etc., packaging materials, plate making materials, display materials, transfer materials, window stickers In addition to materials, it is widely used for antireflection films used for membrane switches and flat displays, optical films such as diffusion sheets and prism sheets, and transparent touch panels. However, in such an application, when another material is applied and laminated on the polyester film, there is a drawback that the adhesiveness is poor depending on the material used.

  In order to cope with these problems, the resin to be applied and laminated on the polyester film is selected according to the material used and the required adhesiveness, and the combination of the resins and the resin ratio are optimized. For example, as a method for improving adhesion, there are a method of laminating a coating layer made of a polyurethane resin on the surface of a polyester film, a method of laminating a coating layer made of an acrylic resin, a method of laminating a coating layer made of polyolefin and polyester, etc. is there.

  Although it is possible to form an appropriate laminate by properly using the material to be laminated with respect to the material of the adherend surface, the current issue is to develop adhesion to a wide range of materials with a laminate containing a specific material It is mentioned as.

JP-A-8-281890 Japanese Patent Laid-Open No. 11-286092

  This invention is made | formed in view of the said situation, The subject to solve is to provide the polyester film which shows favorable adhesiveness with respect to various topcoats.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problem can be easily solved by adopting a specific configuration, and the present invention has been completed.

  That is, the gist of the present invention is a polyester film having a coating layer, wherein the coating layer is formed from a coating solution containing polyurethane and a carbodiimide-based crosslinking agent, and the polyurethane has two types having different main chain structures. The present invention resides in a laminated polyester film characterized in that a polycarbonate polyol copolymerized with a carbonate polyol is used as a constituent component, and the polyisocyanate as a constituent component of the polyurethane is aliphatic or alicyclic.

  According to this invention, the polyester film which shows favorable adhesiveness with respect to various topcoats can be provided, and the industrial value of this invention is high.

  The base film of the coated film of the present invention is made of polyester. Such polyesters include dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexyldicarboxylic acid or esters thereof. Polyester produced by melt polycondensation with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol. Polyesters composed of these acid components and glycol components can be produced by arbitrarily using a commonly used method.

  For example, a transesterification reaction between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or a direct esterification of an aromatic dicarboxylic acid and a glycol, to form a substantially bisglycol of an aromatic dicarboxylic acid A method is employed in which an ester or a low polymer thereof is formed and then polycondensed by heating under reduced pressure. Depending on the purpose, an aliphatic dicarboxylic acid may be copolymerized.

  Typical examples of the polyester of the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and the like. It may be a polymerized polyester and may contain other components and additives as necessary.

  The polyester film in the present invention can contain particles for the purpose of ensuring the film runnability and preventing scratches. Examples of such particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide. Further, organic particles such as crosslinked polymer particles and calcium oxalate, and precipitated particles during the polyester production process can be used.

  The particle size and content of the particles to be used are selected according to the use and purpose of the film, but the average particle size (d50) is usually 0.01 μm to 3 μm, preferably 0.02 μm to 2.5 μm, more preferably Is in the range of 0.03 μm to 2 μm. If the average particle size exceeds 3.0 μm, the surface roughness of the film may become too rough, or the particles may easily fall off from the film surface. When the average particle size is less than 0.01 μm, the surface roughness is too small and sufficient slipperiness may not be obtained.

  About particle | grain content, it is 0.0003 to 1.0 weight% normally with respect to polyester, Preferably it is the range of 0.0005 to 0.5 weight%. When the particle content is less than 0.0003% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 1.0% by weight, the transparency of the film is poor. It may be enough. In addition, when it is particularly desired to ensure the transparency and smoothness of the film, the film may be substantially free of particles. Further, various stabilizers, lubricants, antistatic agents and the like can be appropriately added to the film.

  As a film forming method of the film of the present invention, a generally known film forming method can be adopted, and there is no particular limitation. For example, a sheet obtained by melt extrusion is first stretched 2 to 6 times at 70 to 145 ° C. by a roll stretching method to obtain a uniaxially stretched polyester film, and then perpendicular to the previous stretching direction in the tenter. A film is obtained by extending | stretching 2 to 6 times at 80-160 degreeC to the direction, and also heat-processing at 150-250 degreeC for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the heat treatment zone and / or the cooling zone at the heat treatment outlet is preferable.

  The polyester film in the present invention has a single layer or multilayer structure. In the case of a multilayer structure, the surface layer and the inner layer, or both the surface layer and each layer can be made of different polyesters depending on the purpose.

  The polyester film of the present invention has a coating layer on at least one surface, but even if a similar or other coating layer or functional layer is provided on the opposite surface of the film, it is naturally included in the concept of the present invention.

  The coating layer of the present invention is obtained by coating a coating composition on a polyester film. Various methods can be applied to the coating, but a so-called in-line coating in which a coating layer is provided during film formation, particularly a coating stretching method in which stretching is performed after coating is preferably used.

  In-line coating is a method of coating within the process of manufacturing a polyester film. Specifically, it is a method of coating at any stage from melt extrusion of polyester to biaxial stretching and then heat setting and winding. is there. Normally, it is coated on either a substantially amorphous unstretched sheet obtained by melting and quenching, then a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction), or a biaxially stretched film before heat setting. To do. In particular, as a coating stretching method, a method of stretching in the transverse direction after coating on a uniaxially stretched film is excellent.

  According to such a method, since film formation and coating layer coating can be performed simultaneously, there is an advantage in manufacturing cost, and since stretching is performed after coating, a uniform coating with a thin film is achieved, so that adhesion performance is stabilized. . Moreover, the polyester film before biaxially stretching is first covered with an easy-adhesive resin layer, and then the film and the coating layer are stretched simultaneously, whereby the base film and the coating layer are firmly adhered. In addition, biaxial stretching of the polyester film is achieved by stretching the film in the lateral direction while holding the film edge with a tenter, so that the film is constrained in the longitudinal / lateral direction, so that it is flat without wrinkles or the like in heat setting. High temperature can be applied while maintaining Therefore, since the heat treatment performed after coating can be performed at a high temperature that cannot be achieved by other methods, the film forming property of the coating layer is improved, and the coating layer and the polyester film are firmly adhered. For example, as an easily-adhesive polyester film, the uniformity of the coating layer, the improvement of the film-forming property, and the adhesion between the coating layer and the film often produce favorable characteristics.

  In this case, the coating solution to be used is preferably an aqueous solution or an aqueous dispersion for safety reasons in terms of handling, working environment, and water as the main medium, as long as it does not exceed the gist of the present invention. An organic solvent may be contained.

  Next, the coating layer provided on the film in the present invention will be described.

  The coating layer of this invention can be obtained by apply | coating the coating liquid containing a polyurethane and a carbodiimide type crosslinking agent to a film, drying and hardening.

  The combined use of the crosslinking agent is sometimes used to increase the hardness of the coating layer or improve the water resistance, but a hard coating layer usually tends to have poor adhesion. However, in the present invention, it was possible to obtain extremely excellent adhesiveness by using together a polyurethane having a specific structure and a carbodiimide-based crosslinking agent.

  The polyurethane contained in the coating solution for forming the coating layer of the present invention is a polyurethane having as a constituent component a copolymerized polycarbonate polyol having a structure in which two types of carbonate diols having different main chain structures are copolymerized. is there.

  The polycarbonate polyol can be obtained, for example, by a reaction from diphenyl carbonate and diol, a reaction from dialkyl carbonate and diol, or a reaction from alkylene carbonate and diol.

  For example, the diol component used in the above reaction includes the following. 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol 1,10-decanediol, neopentyl glycol, cyclohexanediol and the like.

  The copolymerized polycarbonate polyol in the present invention is formed by, for example, adding carbonate to these diol components to form a monomer unit having carbonate at the terminal, and copolymerizing two or more of these monomer units, or two or more of these monomer units. It can be obtained by a method such as copolymerization while adding carbonate to the diol component. These copolymer polycarbonate polyols are used as a polyol component of polyurethane.

  The copolymer polycarbonate polyol constituting the copolymer polycarbonate polyurethane has a number average molecular weight (Mn) in terms of polystyrene by gel permeation chromatography (GPC), and is preferably from 100 to 3000. More preferably, it is 200-2500, More preferably, it is 400-2000. When it is larger than this range, the blocking resistance is deteriorated, and when it is smaller than this range, the adhesion may be inferior.

  Further, the structure of these copolymers is not particularly limited, such as random copolymerization, graft copolymerization, and block copolymerization.

  As long as it contains said copolymerization polycarbonate polyol as polyurethane in the present invention, other polyols (for example, polyether diol, polyester diol, etc.) may be contained.

  The polyisocyanate component of the polyurethane comprising the copolymer polycarbonate polyol in the present invention is composed of an aliphatic group or an alicyclic group. Specifically, it is preferable that 50 mol% or more of all the polyisocyanate components is an aliphatic or alicyclic polyisocyanate.

  Examples of polyisocyanate components include isophorone diisocyanate, 1,6 hexamethylene diisocyanate, triene diisocyanate, hydrogenated diphenylmethane diisocyanate, trans-1,4-cyclohexylene diisocyanate, 4,7-dimer acid diisocyanate, lysine diisocyanate, 1,6 -Diisocyanato-2,2,4-trimethylhexane, cyclohexane-1,3-diyl diisocyanate, cyclohexane-1,4-diyl diisocyanate, cyclohexane-1,3-diylbis (methyl isocyanate), 1-methylcyclohexane-2,4 -Diyl diisocyanate, methyl 2,6-diisocyanatohexanoate, tetramethylene diisocyanate and the like.

  When 50 mol% or more of all the polyisocyanate components is an aromatic polyisocyanate, the adhesiveness, appearance, and transparency are inferior.

  The polyurethane having the copolymerized polycarbonate as a constituent component in the present invention may be one using a solvent as a medium, but is preferably one containing water as a medium. In order to disperse or dissolve polyurethane in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into a polyurethane resin, and a water-soluble type. In particular, the self-emulsification type in which a hydrophilic group is introduced into the skeleton of the polyurethane resin is preferable because of excellent storage stability of the liquid and water resistance and transparency of the resulting coating layer.

  Examples of the hydrophilic group to be introduced include various groups such as a carboxyl group, a sulfone group, phosphoric acid, phosphonic acid, quaternary ammonium, and polyethylene glycol.

  The amount of hydrophilic groups in the polyurethane is preferably 0.05% by weight to 8% by weight. When the amount of the hydrophilic group is small, the water-solubility or water dispersibility of the polyurethane is poor, and when the amount of the hydrophilic group is large, the water resistance of the coating layer after coating is poor or the film tends to stick to each other due to moisture absorption. Because.

  The amount of polyurethane contained in the nonvolatile component of the coating solution is usually 40 to 95% by weight, preferably 40 to 90% by weight, and more preferably 50 to 80% by weight. When outside this range, the appearance and adhesion of the coating layer obtained may be inferior.

  The carbodiimide crosslinking agent in the present invention is a compound having a carbodiimide group in the molecule. In particular, polycarbodiimide compounds having two or more carbodiimide groups in the molecule are suitable. For example, as shown in JP-A-10-316930 and JP-A-11-140164, organic polyisocyanates are particularly preferable. Is produced using organic diisocyanate as the main synthetic raw material.

  Examples of these diisocyanates include 1,4-phenylene diisocyanate, 1,3-phenylene diisocyanate, 1-methylphenylene-2,4-diisocyanate, 1-methoxyphenylene-2,4-diisocyanate, and 2,4-tolylene diene. Isocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, biphenylene-4,4′-diisocyanate, 3,3′-dimethoxybiphenylene-4,4′-diisocyanate, 3,3′-dimethylbiphenylene-4,4′-diisocyanate, diphenylmethane-2,4′-diisocyanate, diphenylmethane-4,4′-diisocyanate, 3,3′-dimethoxydiphenylmethane-4,4′-diisocyanate 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, naphthylene-1,5-diisocyanate, cyclobutylene-1,3-diisocyanate, cyclopentylene-1,3-diisocyanate, cyclohexylene-1, 3-diisocyanate, cyclohexylene-1,4-diisocyanate, 1-methylcyclohexylene-2,4-diisocyanate, 1-methylcyclohexylene-2,6-diisocyanate, 1-isocyanate-3,3,5-trimethyl-5 -Isocyanatomethylcyclohexane, cyclohexane-1,3-bis (methylisocyanate), cyclohexane-1,4-bis (methylisocyanate), isophorone diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, di Chlohexylmethane-4,4′-diisocyanate, ethylene diisocyanate, 2,6-diisopropylphenyl isocyanate, tetramethylene-1,4-diisocyanate, hexamethylene diisocyanate, dodecamethylene-1,12-diisocyanate, lysine diisocyanate methyl ester, 1 , 5-naphthalene diisocyanate and the like.

  In the production of polycarbodiimide, one or a mixture of two or more of these organic diisocyanates can be used. Moreover, organic polyisocyanate other than diisocyanate can also be used. Furthermore, monomers other than these may be included as a copolymerization component in the molecule.

The amount of the carbodiimide-based crosslinking agent contained in the non-volatile component of the coating solution is usually 5 to 60% by weight, preferably 10 to 60% by weight, and more preferably 20 to 50% by weight. When outside this range, the appearance and adhesion of the coating layer obtained may be inferior.

  When each component has not reacted, the obtained coating layer contains both unreacted products and reaction products of each component.

  In the coating liquid for providing the coating layer which is excellent in easy-adhesiveness, components other than those described above can be included as necessary. For example, surfactants, other binders, crosslinking agents, antifoaming agents, coatability improvers, thickeners, antioxidants, ultraviolet absorbers, foaming agents, dyes, pigments and the like. These additives may be used alone or in combination of two or more as necessary.

  In the present invention, particles may be contained in the coating layer in order to give film slidability or reduce blocking. If the content of the particles is too large, the transparency of the coating layer may decrease, the continuity of the coating layer may be impaired, and the coating strength may decrease, or the easy adhesion may decrease. In the non-volatile component of the coating solution, usually 15% by weight or less and 10% by weight or less are suitable. Moreover, there is no limitation in particular about the minimum of particle content.

  As the particles, for example, inorganic particles such as silica, alumina, and metal oxide, or organic particles such as crosslinked polymer particles can be used. In particular, silica particles are preferred from the viewpoint of dispersibility in the coating layer and transparency of the resulting coating film.

  If the particle diameter is too small, the effect of reducing blocking is difficult to obtain, and if it is too large, the coating film easily falls off. The average particle size is preferably about 1/2 to 10 times the thickness of the coating layer. Furthermore, if the particle size is too large, the transparency of the coating layer may be inferior, so the average particle size is preferably 300 nm or less, and more preferably 150 nm or less. The average particle diameter of the particles described here can be obtained by measuring the 50% average diameter of the number average of the particle dispersion with Microtrac UPA (Nikkiso Co., Ltd.).

  As a method for applying the coating solution to the polyester film, for example, a coating technique as shown in “Coating system” published by Yuji Harasaki, Tsuji Shoten, published in 1979 can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater And techniques such as an extrusion coater and a bar coater.

  In addition, in order to improve the applicability of the coating agent to the film, the film may be subjected to chemical treatment, corona discharge treatment, plasma treatment or the like before coating.

The coating amount of the coating layer provided on the polyester film is usually 0.002 to 1.0 g / m ² , preferably 0.005 to 0.5 g / m as the final coating (as dry solid content). ² and more preferably 0.01 to 0.2 g / m ² . If the coating amount is less than 0.002 g / m ^2, sufficient adhesion performance may not be obtained. If the coating layer exceeds 1.0 g / m ² , the appearance / transparency deteriorates, film blocking, Cost may increase.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method in an Example and a comparative example is as follows.

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

(2) Average particle size of particles added to the polyester film (d50)
The particle size was measured by a sedimentation method based on Stokes' resistance law using a Shimadzu centrifugal sedimentation type particle size distribution analyzer SA-CP3 type.

(3) Adhesive properties Three types of top coats having different characteristics shown below were applied on the polyester film coating layer to form a laminated film. After making a laminated film, the adhesiveness evaluation with respect to various topcoats was performed.

・ Adhesion 1
On the polyester film coating layer, an acrylic HC adjustment liquid was applied to evaluate the adhesion. About adjustment of acrylic HC, it mix | blends by the weight ratio of Karayad DPHA (made by Nippon Kayaku Co., Ltd.) / Karayad R-128H (made by Nippon Kayaku Co., Ltd.) / Irgacure 651 (made by Ciba Specialty Chemicals) = 80/20/5, and toluene. To 30% solution. This coating solution was applied using an automatic coater (PI1210) manufactured by Tester Sangyo Co., Ltd. so that the dry film thickness was 5 μm. The coated film was dried at 80 ° C. for 1 minute and then cured using a 120 W / cm metal halide lamp to prepare a laminated film. The integrated light quantity of the active energy ray applied when curing was 220 mJ / cm ² .

・ Adhesion 2
On the polyester film coating layer, UV curing ink FD Carton X Black M and FD Carton X Indigo M manufactured by Toyo Ink Manufacturing Co., Ltd. are applied with an RI tester which is an offset printing tester manufactured by IHI Machine Systems. Then, a coating thickness of 1 μm was provided, the ink was cured using a 160 W / cm metal halide lamp, and a laminated film was prepared. The integrated light quantity of the active energy ray applied when curing was 90 mJ / cm ² .

・ Adhesion 3
Diamond beam UR-6530 (Mitsubishi Rayon Co., Ltd.), which is an active energy ray curable resin, is dropped on a flat SUS plate, and the evaluation surface of the polyester film is stacked on the flat SUS plate so that the active energy ray curable resin is in contact with it. Using a 160 kg / cm high-pressure mercury lamp, the ink was cured by using a roller having a load of 4 kg and a width of 50 mm so that the thickness after curing was 15 μm, and a laminated film was prepared. The integrated light quantity of the active energy ray applied when curing was 160 mJ / cm ² .

For each of the above adhesive properties 1 to 3, the top coat layer of the obtained laminated film is cross-cut so that there are 100 grids in a 1-inch width, and a quick peel test with cello tape (registered trademark) is performed to peel off The adhesion was evaluated by area. The judgment criteria are as follows.
A: Number of cross-cuts = 0
○: 1 ≦ number of cross-cuts ≦ 10
Δ: 11 ≦ number of cross-cuts ≦ 20
×: 21 ≦ Number of cross-cuts peeled ××: Whole surface peeled

The polyester raw materials used in Examples and Comparative Examples are as follows.
(Polyester 1): Polyethylene terephthalate having an intrinsic viscosity of 0.66 that does not substantially contain particles (Polyester 2): containing 0.3% by weight of amorphous silica having an average particle diameter (d50) of 1.6 μm, Polyethylene terephthalate with intrinsic viscosity of 0.65

  Moreover, the following was used as a coating composition. However, “part” in the text represents the weight ratio of the active ingredient.

(U1) F2967D (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), which is a polyurethane mainly comprising an alicyclic polyisocyanate as a polyisocyanate component, having a copolymerized polycarbonate polyol as a constituent component

(U2) 202 parts of polycarbonate diol having a number average molecular weight of about 1000, obtained by copolymerizing the structures of the following formulas (1) and (3) at a ratio of 70 mol% / 30 mol%, and hydrogenated diphenylmethane diisocyanate An aqueous dispersion of a urethane resin obtained by neutralizing a prepolymer comprising 78.6 parts of styrene and 6.7 parts of dimethylolpropionic acid with triethylamine and extending the chain with 6.5 parts of dipropylenetriamine

(U3) 160 parts of a polycarbonate diol having a number average molecular weight of about 800 obtained by copolymerizing the structures of the following formulas (2) and (3) at a ratio of 50 mol% / 50 mol%, and hydrogenated diphenylmethane diisocyanate An aqueous dispersion of a urethane resin obtained by neutralizing a prepolymer comprising 78.6 parts of styrene and 6.7 parts of dimethylolpropionic acid with triethylamine and extending the chain with 8.4 parts of isophoronediamine.

(C1): Carbodiimide group-containing crosslinking agent: Carbodilite V02 (Nisshinbo Co., Ltd.)
(C2): Carbodiimide group-containing crosslinking agent: Carbodilite E02 (Nisshinbo Co., Ltd.)
(C3): Melamine group-containing cross-linking agent: Becamine MAS (manufactured by Dainippon Ink & Chemicals, Inc.)
(C4): Isocyanate group-containing crosslinking agent: Elastolon MF25K (Daiichi Kogyo Seiyaku Co., Ltd.)

Comparative Example 1:
A blend of polyester 1 and polyester 2 at a weight ratio of 92/8 was used as the raw material for layer A, and polyester 1 alone was used as the raw material for layer B. To the outer layer (surface layer) and the B layer as an intermediate layer, and coextruded in a layer configuration of two types and three layers (A / B / A) using an electrostatic adhesion method. The film was cooled and solidified while being in close contact with a mirror surface cooling drum having a surface temperature of 40 to 50 ° C., and an unstretched polyethylene terephthalate film having a thickness composition ratio of A / B / A = 3/94/3 was prepared. This film was stretched 3.7 times in the longitudinal direction while passing through a heating roll group at 85 ° C. to obtain a uniaxially oriented film. Next, this film was guided to a tenter stretching machine, stretched 4.0 times in the width direction at 100 ° C., further heat treated at 230 ° C., and then subjected to a relaxation treatment of 2% in the width direction. An axially oriented polyethylene terephthalate film was obtained. The characteristics of this film are shown in Table 1 below.

Comparative Example 2:
The coating composition as shown in Table 1 was applied to one side of the obtained uniaxially oriented film. Next, the film was guided to a tenter stretching machine, and the coating composition was dried using the heat. Thereafter, in the same process as in Comparative Example 1, the film thickness was 100 μm on a biaxially oriented film as shown in Table 1. A laminated polyester film provided with the coating layer shown was obtained. The properties of this film are shown in Table 1.

Comparative Examples 3 and 4:
In the same process as Comparative Example 2, a laminated polyester film was obtained in which the coating layer shown in Table 1 was provided on a base film having a film thickness of 100 μm. Sufficient adhesion could not be obtained with the combined use of a melamine crosslinking agent and an isocyanate crosslinking agent.

Examples 1-7:
In the same process as Comparative Example 2, a laminated polyester film was obtained in which the coating layer shown in Table 1 was provided on a base film having a film thickness of 100 μm. Adequate adhesion could be obtained by using in combination with a carbodiimide-based crosslinking agent.

  The film of the present invention exhibits excellent adhesion with various topcoats, and can be suitably used as a biaxially stretched polyester film in applications that require adhesion.

Claims (1)

A polycarbonate film having a coating layer, wherein the coating layer is formed from a coating solution containing polyurethane and a carbodiimide-based crosslinking agent, and the polyurethane is a copolymer of two types of carbonate polyols having different main chain structures A laminated polyester film comprising a polyol as a constituent component and the polyisocyanate as a constituent component of the polyurethane is aliphatic or alicyclic.