JP2004216877A - Laminated polyester film and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated polyester film whose surfaces both have excellent adhesion of a desired level, in particular strong laminating properties and adhesion to various types of coatings, and whose handling properties are excellent due to high solvent resistance. <P>SOLUTION: The film has a polyester layer(A layer) of a melting point of 250°C or lower on one or both sides of a polyester layer(B layer) containing a polyester of a melting point of 250°C or lower and a laminated film layer(C layer) containing a polyester on the side opposite to the A layer or on one side of the A layer. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a laminated polyester film. More specifically, both surfaces of the film have a desired level of excellent adhesive strength (particularly, strong laminating properties and adhesiveness to various coatings), and furthermore, solvent resistance The present invention relates to a laminated polyester film which is excellent in handling properties based on a polyester film.

  Biaxially oriented polyester film has excellent properties such as dimensional stability, mechanical properties, heat resistance, transparency, electrical properties and chemical resistance, so it can be used for various industrial materials, magnetic recording materials, packaging materials, construction materials, etc. It is widely used as a base film for many applications such as materials, electrical insulating materials, various photographic materials and graphic arts materials.

  However, in general, the biaxially oriented polyester film has a disadvantage that the surface is highly crystallographically oriented and has poor adhesion to various coatings. For this reason, conventionally, studies have been made to impart adhesiveness to the surface of the polyester film by various methods.

  As an example of a method for imparting adhesiveness, there is known a method in which various resins such as acrylic resin, polyester resin, urethane resin or polyolefin resin having adhesiveness are provided on a film surface as a primer layer (see Patent Document 1). ). Further, in order to form a surface having good adhesiveness to both the curable ink and the water-soluble resin, a layer in which two kinds of specific polyester resins having different glass transition temperatures are blended may be provided. It has been proposed (see Patent Document 2). Further, it is known that a polyester film obtained by laminating a low-melting polyester as an adhesive layer exhibits, for example, a laminating property with a metal (see Patent Document 3).

JP-A-60-198240 JP-A-2002-337287 JP-A-5-42643

  However, in the above-described conventional technology in which a primer layer and a laminate layer are provided, even if such a primer layer and a laminate layer are provided, the laminating power is insufficient or the laminating property with different materials is poor.

  Also, in practice, when one side of the film is required to have excellent adhesion to various coatings and the other side of the film needs to have strong laminating properties, two types of films having respective functions are used. Although they are sometimes used in a laminated state, there is a problem that they are easily peeled off on the laminated surface, and the intended function is hardly exhibited.

  Furthermore, when the film surface that requires adhesiveness to various coatings becomes dirty during the manufacturing and processing steps, the surface is wiped off with a solvent to clean the surface. In some cases, the adhesive strength did not return to the expected level.

  In view of this situation, the present invention has improved such disadvantages, and each of the two surfaces of the film has a desired level of excellent adhesive strength (particularly, strong laminating properties and adhesiveness to various coatings). Moreover, it is an object of the present invention to provide a laminated polyester film having excellent handling properties based on solvent resistance.

  In order to achieve this object, the laminated polyester film of the present invention comprises a polyester layer having a melting point of 250 ° C. or less (layer A) on one or both sides of a polyester layer (B layer) containing a polyester having a melting point of 250 ° C. or less. ), And a laminated film layer (C layer) containing polyester is provided on the side opposite to the A layer or on one side of the A layer.

  In addition, the method of the present invention for producing the laminated polyester film comprises melting a polyester layer (B layer) containing a polyester having a melting point of 250 ° C. or less and a polyester layer (A layer) having a melting point of 250 ° C. or less. After laminating in the extrusion step, a laminated film layer (C layer) containing polyester is formed on one side of the layer by means of applying a coating liquid, and then heat-treated at a temperature equal to or higher than the melting point of the polyester constituting layer A. Thus, the laminated polyester film is manufactured.

  According to the present invention, both surfaces of the film have a desired level of excellent adhesive strength (particularly, strong laminating properties and adhesiveness to various coatings), and also have good handling properties based on solvent resistance. An excellent laminated polyester film can be obtained.

  The laminated polyester film of the present invention includes a polyester layer (B layer) containing a polyester having a melting point of 250 ° C. or less, a polyester layer (A layer) having a melting point of 250 ° C. or less, and a laminated film layer containing the polyester ( C), and the layer configuration is as follows.

  That is, the layer A is laminated on one or both surfaces of the layer B, and when the layer A is provided only on one side of the layer B, the layer C is provided on the side opposite to the layer A. Is on both sides of the layer B, the layered structure has the layer C provided on one side of the layer A. A specific layer configuration including the A to C layers can be represented by a laminated structure of A layer / B layer / C layer and a laminated structure of A layer / B layer / A layer / C layer.

  The polyester used in the present invention is a polymer having an ester bond as a main bonding chain of a main chain, and can be obtained by polycondensation of a dicarboxylic acid and a diol. In this polyester, various additives, for example, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, organic and inorganic particles, pigments, dyes, fillers, antistatic agents and A nucleating agent and the like may be added as long as the effects of the present invention are not impaired.

  Above all, the fact that the organic and inorganic particles are contained in one or more layers of the A to C layers may reduce the slipperiness of the laminated polyester film of the present invention and the blocking resistance when formed into a film roll. It is suitable for improving. As the organic particles, crosslinked polystyrene, crosslinked acrylic resin, melamine resin, benzoguanamine resin, etc., and as the inorganic particles, silica, colloidal silica, beaded silica, alumina, alumina sol, kaolin, talc, mica, clay, calcium carbonate And metal oxides (such as tin oxide) are preferably used. These organic particles and inorganic particles preferably have an average particle diameter of 0.001 to 6 μm, more preferably 0.01 to 5 μm. In each layer containing such particles, two or more kinds of particles can be used in combination.

  The content of the particles is not particularly limited, but is 0.0001 to 30% by weight based on the total amount of the resin forming the A layer when contained in the A layer, and B layer when contained in the B layer. 0.0001 to 50% by weight based on the total amount of the resin forming the C layer, and 0.01 to 30% by weight based on the total amount of the resin forming the C layer when contained in the C layer. it can.

  The total thickness of the laminated polyester film of the present invention is not particularly limited, and is appropriately selected depending on the use in which the film of the present invention is used.However, mechanical strength, handling properties, productivity, etc. , Preferably 100 to 500 µm, more preferably 120 to 400 µm.

  In the present invention, the layer A is a layer laminated on at least one surface of the layer B, and the polyester constituting the layer A has a melting point of 250 ° C. or less. The preferred range of the melting point is 180 to 250 ° C, more preferably 190 to 245 ° C. If the melting point is too low, the surface is easily damaged when handling the film. If it exceeds 250 ° C., the laminating property will be poor.

  The polyester constituting the layer A and having a melting point of 250 ° C. or lower may be used alone or in combination of two or more. And more preferably 90% by weight or more. When the amount of the polyester is small, the laminating property may be poor or the adhesive strength at the interface between the A layer and the B layer may be reduced. The resin constituting the layer A other than the polyester having a melting point of 250 ° C. or less is not particularly limited as long as the effects of the present invention are not impaired, and other polyester resins can be preferably exemplified. Examples include polyethylene terephthalate and waste polyester produced in the process of producing a general polyester film.

  As the polyester having a melting point of 250 ° C. or less for forming the A layer, a copolymerized polyester containing at least one selected from isophthalic acid and 1,4-cyclohexanedimethanol as a copolymerization component is preferable, and particularly contains isophthalic acid. Is preferred. Known dicarboxylic acids and diols can be used as other copolymer components. Examples of known dicarboxylic acids include, for example, terephthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, decanedicarboxylic acid, azelaic acid, dodecadicarboxylic acid, cyclohexanedicarboxylic acid, etc. Examples thereof include, but are not limited to, ethylene glycol, butanediol, hexanediol, neopentyl glycol, decanediol, neopentyl glycol, diethylene glycol, triethylene glycol, and polyethylene glycol.

  Further, the thickness of the layer A is preferably from 1 to 30 μm, more preferably from 3 to 25 μm. If the thickness is too small, the laminability may be poor, and if it is too thick, economic efficiency, productivity, and blocking resistance when formed into a film roll may be poor.

  Further, the plane orientation coefficient measured from the layer A surface side of the laminated polyester film of the present invention is preferably in a range of 0.04 or more and 0.13 or less, more preferably in a range of 0.05 or more and 0.12 or less. Can be. When the plane orientation coefficient exceeds 0.13, the laminating property may be poor, and when it is less than 0.04, the productivity and the blocking resistance when formed into a film roll may be poor. The value of the plane orientation coefficient can be controlled by the temperature of the heat treatment performed after the formation of the laminated film layer (C layer) in the production process of the laminated polyester film of the present invention, and generally, the temperature of the heat treatment is increased. By doing so, the value of the plane orientation coefficient can be reduced. Further, it can be controlled by changing the stretching ratio in the direction of film advance and in the width direction in the production process of the laminated polyester film of the present invention.

  The layer B of the laminated polyester film of the present invention contains a polyester having a melting point of 250 ° C. or less. The polyester having a melting point of 250 ° C. or less contained in the layer B may be used alone or in combination of two or more. Preferably, there is. By containing the same type of polyester as the polyester forming the A layer in the B layer, the adhesive force at the interface between the A layer and the B layer can be significantly improved.

  The content of the polyester having a melting point of 250 ° C. or less contained in the B layer is preferably 0.1% by weight or more, more preferably 0.1 to 20% by weight, based on the total amount of the polyester forming the B layer. %, Most preferably 0.1 to 15% by weight. If the content is too small, the adhesive force at the interface between the layer A and the layer B may decrease, and if it is too large, the economic efficiency and productivity may deteriorate.

  The polyester constituting the layer B other than the polyester having a melting point of 250 ° C. or lower is not particularly limited, but preferably includes, for example, polyethylene terephthalate and waste polyester produced in a general polyester film manufacturing process. Can be. In forming the layer B, the total of the polyester having a melting point of 250 ° C. or less and the other polyester is preferably 80% by weight or more, more preferably 85% by weight or more, based on the total of the resin forming the layer B. The resin other than the polyester resin constituting the layer B is not particularly limited as long as the effects of the present invention are not impaired. For example, acrylic resin, urethane resin, epoxy resin, silicone resin, urea resin And a phenol resin.

  In the laminated polyester film of the present invention, the base film portion composed of the layer B and the layer A is preferably biaxially oriented. A biaxially oriented polyester film is generally obtained by stretching an unstretched polyester sheet or film by about 2.5 to 5 times each in the longitudinal direction and the width direction, and then performing a heat treatment to complete the crystal orientation. Which indicates a biaxially oriented pattern in wide-angle X-ray diffraction.

  The laminated film layer (C layer) in the present invention is provided on one surface of the base film composed of the B layer and the A layer. In the case of the A layer / B layer in which the A layer is on only one side of the B layer, the C layer is provided on the surface opposite to the A layer, and the A layer is provided on both sides of the B layer. In the case of layer / layer B / layer A, layer C is provided on one surface of layer A.

  The C layer is preferably a coating layer formed by applying an aqueous coating solution and stretching in at least one direction after application of the aqueous coating solution from the viewpoints of environmental pollution prevention and explosion proof during film production. It is preferably performed in a manufacturing process. The timing of the stretching is not particularly limited, but a method of applying a water-based coating solution and then biaxially stretching, or a method of applying a water-based coating solution after stretching vertically (in the direction of film movement) and then horizontally stretching is preferably used. As the method for applying the aqueous coating liquid, various coating methods, for example, a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a die coating method, a spray coating method, and the like can be used.

  For application as an aqueous coating liquid, the polyester contained in the layer C is preferably a copolymerized polyester containing a compound containing a sulfonic acid group or a compound containing a carboxylic acid group as a copolymerization component. Examples of the compound containing a sulfonic acid group include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and the like, or an alkali metal salt or an alkaline earth metal thereof. Salts and ammonium salts can be used, but are not limited thereto. Examples of the compound containing a carboxylate group include trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, 4-methylcyclohexene-1,2,3-tricarboxylic acid, trimesic acid, 1,2,3 , 4-butanetetracarboxylic acid, 5- (2,5-dioxotetrahydrofurfuryl) -3-cyclohexene-1,2-dicarboxylic acid, cyclopentanetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid Acid, 1,2,5,6-naphthalenetetracarboxylic acid, ethylene glycol bistrimellitate, 2,2 ′, 3,3′-diphenyltetracarboxylic acid, thiophene-2,3,4,5-tetracarboxylic acid, Use of ethylene tetracarboxylic acid, etc. or their alkali metal salts, alkaline earth metal salts, and ammonium salts Although it is not intended to be limited thereto.

  The polyester contained in the layer C is preferably a copolymer polyester containing isophthalic acid and diethylene glycol as copolymer components. By using this component as a copolymer component, the solvent resistance of the layer C to alcohol in particular can be improved, and when the layer A or the layer B contains a polyester containing isophthalic acid as a copolymer component, the layer A and the layer A can be used. The adhesive strength at the interface between the C layers or between the B layers and the C layers can be improved. The amount of isophthalic acid as the copolymer component is preferably from 65 to 95 mol%, more preferably from 70 to 95 mol%. The amount of diethylene glycol as the copolymer component is preferably 50 to 95 mol%, more preferably 60 to 90 mol%. As other copolymerization components, known dicarboxylic acids and diols can be used, and examples thereof include the above-mentioned dicarboxylic acids and diols, but are not limited thereto. Further, a compound containing a sulfonic acid group or a compound containing a carboxylic acid group described above can be contained as a copolymerization component. The glass transition point of the copolymerized polyester is preferably in the range of 0 to 60C, more preferably 10 to 45C.

  The content of the copolymerized polyester containing isophthalic acid and diethylene glycol as a copolymerization component is preferably from 10 to 60% by weight, more preferably from 20 to 50% by weight, based on the total amount of the resin forming the C layer. If the content is too small, the solvent resistance and the adhesive strength to the layer A and the layer B may be poor. If the content is too large, the blocking resistance when formed into a film roll may be poor.

  The resin other than the copolyester having isophthalic acid and diethylene glycol as the copolymer component forming the C layer is not particularly limited as long as the effects of the present invention are not impaired. For example, other polyester resins and acrylic resins , A urethane resin, an epoxy resin, a silicone resin, a urea resin, a phenol resin, and the like. Among them, other polyester resins are particularly preferable. The glass transition temperature of the polyester resin is preferably from 60 to 100C, more preferably from 70 to 90C.

  The thickness of the C layer is preferably from 0.01 to 2 μm, more preferably from 0.05 to 1 μm. If the thickness of the C layer is too small, the adhesion to various coatings and the solvent resistance may be insufficient, and if it is too large, the slipperiness and the blocking resistance when formed into a film roll may decrease.

  The above-mentioned laminated polyester film of the present invention was obtained by laminating a polyester layer (B layer) containing a polyester having a melting point of 250 ° C. or less and a polyester layer (A layer) having a melting point of 250 ° C. or less in a melt extrusion step. Thereafter, a laminated film layer (C layer) containing polyester is formed by means of applying a coating liquid on one side thereof, and further subjected to uniaxial stretching or biaxial stretching as necessary, followed by heat treatment. However, it is necessary to perform the heat treatment at a temperature equal to or higher than the melting point of the polyester constituting the layer A in order to achieve the object of the present invention. That is, by performing the heat treatment at the temperature, the laminating property can be greatly improved. The means for performing the heat treatment at this specific temperature is not particularly limited as long as the effect of the present invention can be achieved by partially breaking the crystal orientation of the surface of the layer A. For example, in a manufacturing process of biaxially orienting a film, a method of performing heat treatment subsequent to stretching in the vertical and horizontal directions can be cited as a preferable method in terms of economy and productivity. It is also possible to use a method in which the biaxially oriented film is wound and then heat-treated again. Further, by performing the heat treatment at such a specific temperature, the plane orientation coefficient measured from the surface side of the layer A can be controlled in a range of 0.04 or more and 0.13 or less.

  Next, the method for producing a laminated polyester film of the present invention will be described in more detail, but the present invention is not limited thereto.

  The polyester pellets for the layer A and the polyester pellets for the layer B prepared in advance so as to have a predetermined polymer composition are vacuum-dried, respectively, and then supplied to two extruders for the layer A and the layer B. Melting at ℃, layer A is laminated on one or both sides of layer B, then extruded in a molten state from a T-shaped die in the form of a sheet, and a mirror surface casting at a surface temperature of 10 to 60 ° C. using an electrostatic application casting method. It is wound around a drum and cooled and solidified to produce an unstretched polyester film. Subsequently, the unstretched film is stretched 2.5 to 5 times in the longitudinal direction (the traveling direction of the film) between rolls heated to 60 to 120 ° C. Subsequently, on one side of the film (that is, when the layer A is on only one side of the layer B, on the surface opposite to the layer A, and when the layer A is on both sides of the layer B, A corona discharge treatment is applied to one surface of the layer A, and an aqueous coating liquid for forming the layer C is applied. Subsequently, the coated film is gripped with a clip, guided to a hot air zone heated to 70 to 150 ° C., dried, stretched 2.5 to 5 times in the width direction, and subsequently, an A layer is formed. To the heat treatment zone at a temperature equal to or higher than the melting point of the polyester to be heat-treated for 1 to 30 seconds. During this heat treatment step, a 3 to 12% relaxation treatment may be performed in the width direction or the longitudinal direction as necessary. In addition, biaxial stretching may be performed by simultaneous biaxial stretching in addition to the above-described longitudinal and transverse sequential stretching, and may be performed by a method of longitudinally or transversely stretching, and then re-stretching in any of longitudinal or transverse directions. Is also good.

  In the method of the present invention, the heat treatment performed after the biaxial stretching is, for example, when a copolymer polyester having a melting point of 240 ° C. is used for the A layer, at a temperature of 240 ° C. or higher corresponding to the melting point or higher. However, it is preferable to carry out the reaction at a temperature higher than the melting point by about 5 ° C. The upper limit of the heat treatment temperature is appropriately determined depending on the relationship with the heat treatment time, but in practice it is about 255 ° C. at the highest.

  Next, the present invention will be described based on examples, but the present invention is not limited thereto.

[Method of measuring characteristics and evaluating effect]
The method for measuring characteristics and the method for evaluating effects in the present invention are as follows.
(1) Melting Point and Glass Transition Point of Polyester Measurement was performed by connecting an SSC5200 disk station (manufactured by Seiko Instruments Inc.) to a robot DSC (differential scanning calorimeter) RDC220 (manufactured by Seiko Instruments Inc.). After adjusting a sample (10 mg) in an aluminum pan, the sample was set in a DSC device (reference: an aluminum pan of the same type without a sample), heated at 300 ° C. for 5 minutes, and quenched using a liquid nitrogen atmosphere. . The sample was measured for DSC while heating at a rate of 10 ° C./min. From the obtained DSC chart, the melting point was determined from the peak temperature based on the crystal melting, and the glass transition was determined based on the temperature based on the transition from the glassy state to the rubbery state. I read the points.

(2) Thickness of Each Layer of Laminated Film The thickness was determined from a photograph obtained by observing a cross section of the laminated polyester film using a transmission electron microscope, model H-7100FA (manufactured by Hitachi, Ltd.). The thickness was an average value of five points in the measurement visual field.

(3) Laminating property on the surface of the laminated film A urethane-based adhesive (KU2NA / KU662 = 100/5; manufactured by Konishi Co., Ltd.) is applied to the surface of the layer A of the laminated polyester film to a thickness of about 10 μm, and the coating is applied at 40 ° C. for 1 minute. I left it. Thereafter, a biaxially stretched polypropylene film (about 150 μm thick) is laminated on the urethane-based adhesive using a laminating machine (Lamipacker LPP650, manufactured by Fuji Plastic Machinery CO. LTD.) Passing through a roll at 80 ° C., and a laminated polyester film is laminated. And a polypropylene film were stuck together and left in an atmosphere of 40 ° C. for 3 days. The adhesive strength (lamination property) between the laminated films was measured with "Tensilon" RTA-100 type (manufactured by Orientec Co., Ltd.). Further, the quality of the obtained adhesive force was determined. The criteria are a: 5 or more (kg / 25 mm), b: 3 or more and less than 5 (kg / 25 mm), c: 2 or more and less than 3 (kg / 25 mm), d: 1 or more and less than 2 (kg / 25 mm), e: 0 to less than 1 (kg / 25 mm), and a to c were good.

(4) Adhesion of Solvent on Laminated Film Surface After Solvent Treatment The surface of layer C of the laminated polyester film was subjected to a load of about 100 g using a gauze impregnated with isopropyl alcohol ("Benlyse" manufactured by Asahi Kasei Corporation). Rubbed three round trips. Next, “Dicure” RT-8 black (manufactured by Dainippon Ink and Chemicals, Inc.) was used as an ultraviolet-curable ink, and applied to the alcohol-treated laminated polyester film to a thickness of about 1 μm on the C layer. Thereafter, an ultraviolet lamp having an irradiation intensity of 80 W / cm was irradiated for 5 seconds at an irradiation distance (distance between the lamp and the ink surface) of 12 cm to form a printed layer. After humidity control at 23 ° C. and 65% RH for 1 day, 100 crosscuts of 1 mm ² were put in the print layer, Nichiban Co., Ltd. cellophane tape was stuck thereon, and pressed with a rubber roller. It peeled off sharply in the 90 degree direction. The adhesiveness (solvent resistance) after the solvent treatment was evaluated based on the number of remaining print layers. The evaluation criteria were a: 100, b: 80 to 99, c: 50 to 79, and d: 0 to 49, and a and b had good adhesion.

(5) Plane orientation coefficient Using an Abbe refractometer (using a sodium D line (589 nm) and a mounting liquid as methylene iodide), the maximum value nx of the refractive index in the film plane and the refractive index in a direction perpendicular thereto. ny and the refractive index nz in the thickness direction of the film were measured from the surface of the layer A of the laminated polyester film (23 ° C., 65% RH). The plane orientation coefficient was calculated by the following equation.
Plane orientation coefficient = {(nx + ny) / 2} -nz

[Polyester used in Examples and Comparative Examples]
As the polyester, a copolyester having the following composition or polyethylene terephthalate (composition) was prepared by an ordinary method. The following acrylic resin and particles were used. In addition, about the composition for C layers which combined c1-c7 suitably, it was used for C layer formation as the aqueous coating liquid (water dispersion) containing the composition as an active ingredient.

a1: Copolyester having a copolymer composition of terephthalic acid / isophthalic acid // diethylene glycol (molar ratio 90/10 // 100) (melting point 240 ° C.).
a2: Copolyester having a copolymer composition of terephthalic acid / isophthalic acid // diethylene glycol (molar ratio 80/20 // 100) (melting point: 213 ° C.).
a3: Copolyester having a copolymer composition of terephthalic acid // ethylene glycol / 1,4-cyclohexanedimethanol (molar ratio: 100 // 75/25) (melting point: 202 ° C).
b1: Polyethylene terephthalate (melting point: 255 ° C.)
b2: A polyester composition in which colloidal silica (average particle size: 0.4 μm) is contained in the polyester of b1 in an amount of 1% by weight.
b3: A polyester composition in which the polyester of the above b1 contains 1% by weight of colloidal silica (average particle size: 1.5 μm).
b4: Recycled polyester obtained by collecting the laminated polyester film of Example 3.

c1: Copolyester having a copolymer composition of isophthalic acid / 5-sodium sulfoisophthalic acid // ethylene glycol / diethylene glycol (molar ratio 93/7/10/10/90) (glass transition point: 18 ° C).
c2: Copolyester having a copolymer composition of isophthalic acid / 5-sodium sulfoisophthalic acid // ethylene glycol / diethylene glycol / cyclohexanedimethanol (molar ratio: 91/9 // 5/80/15) (glass transition point: 38 ° C) ).
c3: Copolyester having a copolymer composition of terephthalic acid / trimellitic acid // ethylene glycol / neopentyl glycol / diethylene glycol (molar ratio 80/20 // 40/40/20) (glass transition point 75 ° C).
c4: an acrylic resin having a copolymer composition of methyl methacrylate / ethyl acrylate / acrylic acid (molar ratio 60/37/3).
c5: Crosslinked acrylic particles (average particle diameter 5 μm).
c6: Colloidal silica (average particle size 0.3 μm).
c7: Colloidal silica (average particle size 0.08 μm).

(Examples 1 to 6)
When a pellet having a composition of a mixture of polyester and particles is used as the polyester for the A layer and the polyester for the B layer, the polyester pellets are usually made of a predetermined polyester or the like so as to have the composition described in Table 1, respectively. It was produced by a method of melt-mixing and pelletizing according to the method described above.

  After each of the pellets for the A layer and the pellets for the B layer are vacuum-dried, they are supplied to two extruders for the A layer and the B layer and melted, and A / B / A or , A / B, and a layered sheet-like melt composed of an A layer and a B layer is extruded from a T-shaped die, and a surface temperature of 20 ° C. is applied by using an electrostatic application casting method. It was wound around a mirror casting drum and cooled and solidified to obtain an unstretched film.

  This unstretched film was heated to 75 ° C. and stretched 3.3 times in the longitudinal direction to obtain a uniaxially stretched film. The surface of the film on which the C layer was to be formed was subjected to a corona discharge treatment in air, and an aqueous coating solution for forming the C layer was applied. As this aqueous coating liquid, an aqueous dispersion having a concentration of about 5% by weight containing the resins and particles described in the column of the resin composition of the layer C in Table 1 as an active ingredient was used. The uniaxially stretched film coated with the aqueous coating solution is guided into a preheating zone while being gripped with a clip, dried at 90 ° C., and then continuously stretched 3.3 times in a width direction in a 100 ° C. heating zone. Then, a heat treatment was performed at the temperature shown in Table 1 to produce a laminated polyester film.

  In addition, Table 1 shows the conditions of the layer structure of the laminated film, the heat treatment temperature, the type of polyester used for each layer, and the thickness of each layer. Table 2 shows the evaluation results of the obtained laminated film.

(Comparative Examples 1 to 3)
The resin composition of the pellets for the A layer, the resin composition of the pellets for the B layer, the effective component composition in the aqueous coating solution for the C layer, the layer composition of the laminated film, and the heat treatment temperature were changed as shown in Table 1, respectively. A laminated polyester film was produced in the same manner as in the above example, except for the above.

The laminated polyester film obtained in Comparative Example 1 was inferior in laminating properties as shown in Table 2 since neither polyester having a melting point of 250 ° C. or less was used in both the A layer and the B layer.
The laminated polyester film obtained in Comparative Example 2 did not contain a polyester having a melting point of 250 ° C. or less in the B layer and did not contain the polyester in the C layer. Adhesion (solvent resistance) afterwards was poor.

  Further, the laminated polyester film obtained in Comparative Example 3 was evaluated for laminability on the surface of the C layer because the C layer was provided on both sides of the film, but was inferior in laminability as shown in Table 2. . In Comparative Example 3, since the layer A was not present on the outermost surface, the measurement of the plane orientation coefficient was not performed.

(Comparative Example 4)
A laminated polyester film having an A / B layer configuration was produced in the same manner as in Example 3, except that the application of the coating liquid for the C layer was not performed. The obtained laminated film was a two-layer (A / B) laminated film without the C layer, and the adhesiveness (solvent resistance) after the solvent treatment was evaluated on the surface of the B layer. Solvent resistance).

  The use of the laminated polyester film of the present invention is not particularly limited as long as it is a use in which another material is adhered to both surfaces of the film, and for example, for card, label, photograph, OHP, thermal transfer, ink jet, offset printing Such as a receiving sheet substrate, a hard coat film, packaging, a magnetic recording medium, various industrial materials, a building material, and the like.

Claims (12)

A polyester layer (Layer A) having a melting point of 250 ° C. or less is provided on one or both sides of a polyester layer (Layer B) containing a polyester having a melting point of 250 ° C. or less, and on the opposite side or the A layer. Characterized in that a laminated film layer (C layer) containing polyester is provided on one side of the laminated polyester film. 2. The laminated polyester film according to claim 1, wherein the plane orientation coefficient of the laminated polyester film measured from the layer A surface side is 0.04 or more and 0.13 or less. The polyester having a melting point of 250 ° C. or less contained in the A layer and the B layer is a copolymer polyester containing at least one selected from isophthalic acid and 1,4-cyclohexanedimethanol as a copolymer component. The laminated polyester film according to claim 1 or 2, wherein: The laminated polyester film according to any one of claims 1 to 3, wherein the polyesters having a melting point of 250 ° C or less contained in the A layer and the B layer are of the same type. The laminated polyester film according to any one of claims 1 to 4, wherein the layer A has a thickness of 1 to 30 µm. The polyester according to any one of claims 1 to 5, wherein the content of the polyester having a melting point of 250 ° C or less contained in the B layer is 0.1% by weight or more based on the total amount of the polyester forming the B layer. 3. The laminated polyester film according to item 1. The laminated polyester film according to any one of claims 1 to 6, wherein the polyester contained in the C layer is a copolymer polyester having isophthalic acid and diethylene glycol as a copolymer component. The laminated polyester film according to any one of claims 1 to 7, wherein the content of the polyester contained in the C layer is 10 to 60% by weight based on the total amount of the resin forming the C layer. The C layer is a coating layer formed by stretching in at least one direction after applying the aqueous coating liquid, and the thickness of the layer is 0.01 to 2 μm. 9. The laminated polyester film according to any one of items 1 to 8. The laminated polyester film according to any one of claims 1 to 9, wherein the particles are contained in one or more of the A layer, the B layer, and the C layer. The total thickness of a laminated polyester film is 100-500 micrometers, The laminated polyester film in any one of Claims 1-10 characterized by the above-mentioned. After laminating a polyester layer (layer B) containing polyester having a melting point of 250 ° C. or less and a polyester layer (layer A) having a melting point of 250 ° C. or less in a melt extrusion step, a coating liquid is applied to one surface thereof. The laminated polyester film according to any one of claims 1 to 11, wherein a polyester-containing laminated film layer (C layer) is formed by means, and then heat-treated at a temperature equal to or higher than the melting point of the polyester constituting the A layer. And a method for producing a laminated polyester film.