JP2005103954A - Laminated polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated polyester film excellent in peeling resistance at the interface of film lamination. <P>SOLUTION: In the laminated polyester film, a layer (layer A) of a polyester 250°C or below in melting point is formed on at least one side of a layer (layer B) of a polyester 250°C or below in melting point. Particles are contained in both layers A and B, and the number of the kinds of particles contained in the layer B is greater than that contained in the layer A. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laminated polyester film. More specifically, the present invention relates to a laminated polyester film having excellent peel resistance at the film lamination interface.

  Biaxially oriented polyester film has excellent properties such as dimensional stability, mechanical properties, heat resistance, transparency, electrical properties, and chemical resistance, so various industrial materials, magnetic recording materials, packaging materials, construction 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 defect that its surface is highly crystallized and therefore has poor adhesion to various coatings. For this reason, conventionally, studies have been made to give adhesion 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 an acrylic resin, a polyester resin, a urethane resin, or a polyolefin resin having adhesiveness are provided on the film surface as a primer layer (see Patent Document 1). ). In addition, in order to form a surface having good adhesion to both curable ink and 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). Furthermore, it is known that a polyester film obtained by laminating a low melting point polyester as an adhesive layer exhibits, for example, a laminating property with a metal (see Patent Document 3).
JP-A-60-198240 JP 2002-337287 A JP-A-5-42643

  However, in a laminated polyester provided with a low-melting polyester layer as an adhesive layer, peeling occurs at the laminated interface under a severe environment such as high temperature and high humidity, and there are many cases where a desired function cannot be exhibited.

  In view of this situation, an object of the present invention is to provide a laminated polyester film that improves such drawbacks and has excellent peel resistance at the film lamination interface.

  In order to achieve this object, the laminated polyester film of the present invention has the following constitution. That is, a laminated polyester film in which a polyester layer (A layer) having a melting point of 250 ° C. or lower is provided on one or both sides of a polyester layer (B layer) containing polyester a having a melting point of 250 ° C. or lower, Both the layer and the B layer contain particles, and the number of kinds of particles contained in the B layer is larger than the kind of particles contained in the A layer.

  According to this invention, it can be set as the laminated polyester film which is excellent in the peeling resistance in a film lamination interface.

  The laminated polyester film of the present invention comprises a polyester layer (B layer) containing polyester a having a melting point of 250 ° C. or lower, a polyester layer (layer A) having a melting point of 250 ° C. or lower, and more preferably a laminate containing polyester. It consists of each layer of the film layer (C layer), and the layer structure is as follows.

  That is, the A layer is laminated on the surface of one side or both sides of the B layer. Preferably, when the A layer is only on one side of the B layer, the C layer is provided on the opposite side of the A layer, or A In the case where the layer is on both sides of the B layer, the layered structure is such that the C layer is provided on one side of the A layer. The specific layer structure composed of 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 bond chain, and can be obtained by polycondensation of a dicarboxylic acid and a diol. Known dicarboxylic acid components include, for example, terephthalic acid, isophthalic acid, diphenylcarboxylic acid, diphenylsulfone dicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfoisophthalic acid, aromatic dicarboxylic acid such as phthalic acid, oxalic acid, Succinic acid, eicoic acid, adipic acid, sebacic acid, dimer acid, dodecanedioic acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, cyclohexanedicarboxylic acid and other alicyclic dicarboxylic acids, trimellitic acid, pyromellitic acid, etc. The polyfunctional acid of these can be mentioned. On the other hand, examples of known diol components include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, neopentyl glycol, and triethylene glycol, aromatic glycols such as bisphenol A and bisphenol S, Examples include diethylene glycol and polytetramethylene glycol. In the polyester, various additives such as antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, organic and inorganic particles, pigments, dyes, fillers, antistatic agents and A nucleating agent or the like may be added as long as the effects of the present invention are not impaired. Further, as a polymerization catalyst, a Ti catalyst (as a kind of titanium-based polymerization catalyst, for example, titanium alkoxides such as titanium tetrabutoxide and titanium tetraisopropoxide, composite oxides whose main metal elements are titanium and silicon, titanium complexes, etc. It is preferable to use 0.0005 to 0.15% by weight in terms of titanium atom with respect to the obtained polyester. The polyester thus obtained contains a Ti catalyst, which in some cases may have a deactivated polymerization catalyst function. More organic and more types of particles contained in layer A It is necessary for the purpose of the present invention to contain inorganic particles in the B layer. That is, it is for improving the peel resistance between the A layer and the B layer by roughening the interface between the A layer and the B layer to increase the surface area and increase the adhesion. In addition, inclusion of various types of particles in the B layer can also be achieved by using waste polyester produced in the production process of the polyester-based film containing the particles, which is excellent in terms of economy and productivity. The effect can be demonstrated.

  By containing more particles in the B layer than the types of particles contained in the A layer, it is possible to form a non-uniform laminated interface in which various types of particles are mixed, and the surface area can be increased. Since the A layer is processed at a temperature higher than the melting point in the manufacturing process, the lamination interface tends to be uniformly smooth, and even if various particles are contained in the A layer instead of the B layer, the effect of roughening the lamination interface is small. . Further, even if the B layer contains fewer types of particles than the types of particles contained in the A layer, the particle interface has little variation, so that the lamination interface tends to be uniform, and the effect of increasing the surface area is small.

  Examples of the type of particle include the type of material constituting the particle. Even if the particle size distribution is different even with the same material, the type may be different. As described above, when the types of particles are counted in an integer, the type of particles contained in the B layer needs to be one or more more than the types of particles contained in the A layer. A large amount is preferable. Exceeding the upper limit of the numerical range is not preferable because the extrusion stability of the raw material during film formation is lowered.

  If the particle size distribution is wide, the particle size distribution peaks overlap, are not independent, and it is difficult to count the types of particles in an integer, the standard deviations σA and B of the particle size contained in the A layer What is necessary is just to define by ratio (sigma) B / (sigma) A of the standard deviation (sigma) B of the particle diameter contained in a layer. The ratio σB / σA needs to be 1.5 or more, preferably 1.5 to 200.

  It should be noted that, when enumerating the types of particles, a very small amount (for example, 0.0001% by weight or less) cannot be expected to make a substantial contribution to the effect of the invention. It shall not be counted as the number of types.

  The inclusion of organic and inorganic particles in layer A, more preferably in layer C, is suitable for improving the slipperiness of the laminated polyester film of the present invention and the blocking resistance when used as a film roll. .

  The organic particles contained in the laminated polyester film of the present invention include crosslinked polystyrene, crosslinked acrylic resin, melamine resin, benzoguanamine resin, etc., and the inorganic particles include silica, colloidal silica, beaded silica, alumina, alumina sol, kaolin. , Talc, mica, clay, calcium carbonate, metal oxide (such as tin oxide) and the like are preferably used. These organic particles and inorganic particles preferably have an average particle size (50% cumulative particle size (D50) measured by laser diffraction scattering method) of 0.001 to 6 μm, more preferably 0.01 to 5 μm. It is.

  The content of the particles is not particularly limited, but in the A layer, 0.0001 to 30% by weight based on the total of the resins forming the A layer, and in the B layer, based on the total of the resins forming the B layer. 0.001 to 50% by weight, and in the C layer, 0.0001 to 30% by weight with respect to the total amount of resins forming the C layer can be mentioned as a preferred range.

  The total thickness of the laminated polyester film of the present invention is not particularly limited, and is appropriately selected according to the use for which the film of the present invention is used. From the viewpoint of mechanical strength, handling properties, productivity, and the like. The thickness is preferably 100 to 500 μm, more preferably 120 to 400 μm.

  In the present invention, the A layer is a layer laminated on at least one side of the B layer, and the polyester constituting the A layer has a melting point of 250 ° C. or lower. The preferable range of the melting point is 160 to 250 ° C, more preferably 170 to 245 ° C. If the melting point is too low, the polymer tends to stick and handleability is lowered, and the surface of the film is easily scratched. When the melting point exceeds 250 ° C., the adhesion during lamination becomes poor.

  The polyester a having a melting point of 250 ° C. or lower constituting the A layer may be used alone or in combination of two or more, but 85% by weight or more is based on the total of the resins constituting the A layer. Polyester is preferable, and 90% by weight or more is more preferable. When the amount of the polyester is small, the laminating property may be inferior or the adhesive force at the interface between the A layer and the B layer may be reduced. The resin constituting the A layer other than the polyester a having a melting point of 250 ° C. or lower is not particularly limited as long as the effects of the present invention are not impaired, and other polyester resins can be preferably used. Examples thereof include polyethylene terephthalate and waste polyester produced in the production process of a general polyester film.

  As polyester a having a melting point of 250 ° C. or lower, as copolymerization components, isophthalic acid, 1,4-cyclohexanedimethanol, terephthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, decanedicarboxylic acid , A copolyester containing at least one selected from azelaic acid, dodecadicarboxylic acid and cyclohexanedicarboxylic acid is preferable, and a copolyester containing isophthalic acid or 1,4-cyclohexanedimethanol is particularly economical and has performance. To preferred. As other copolymerization components, known dicarboxylic acids and diols can be used. Examples of known diols include, but are not limited to, ethylene glycol, butanediol, hexanediol, neopentyl glycol, decanediol, neopentyl glycol, diethylene glycol, triethylene glycol, and polyethylene glycol. is not.

  Furthermore, the thickness of the A layer is preferably 1 to 30 μm, and more preferably 3 to 25 μm. If the thickness is too thin, the laminating property may be inferior, and if it is too thick, the economy and productivity may be inferior, the film may be easily curled, or may be blocked when formed into a film roll.

  The layer B of the laminated polyester film of the present invention contains polyester a having a melting point of 250 ° C. or lower. The polyester a having a melting point of 250 ° C. or lower contained in the B layer may be used alone or in combination of two or more, but the polyester a having a melting point of 250 ° C. or lower forming the A layer The same kind is preferable. 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 improved.

  The content of the polyester a 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% by weight or more based on the total of all the polyesters forming the B layer. 50% by weight, most preferably 0.1-30% by weight. If the content is too small, the adhesive force at the interface between the A layer and the B layer may be lowered, and if it is too much, the economy and productivity may be inferior. Moreover, as a method of making the B layer contain polyester a having a melting point of 250 ° C. or less, it may be copolymerized or blended.

  The polyester constituting the B layer other than the polyester a having a melting point of 250 ° C. or lower is not particularly limited, but preferably includes, for example, waste polyester produced in the production process of polyethylene terephthalate or a general polyester film. Can do. In forming the B layer, the total of the polyester a 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 resins forming the B layer. The resin other than the polyester resin constituting the B layer 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 phenol resin.

  It is preferable that melting | fusing point of resin other than the polyester a in B layer is 250-280 degreeC. When the value is below the lower limit of the numerical range, the surface of the film tends to be scratched, which is not preferable. On the other hand, when the value exceeds the upper limit, the film-forming stability is lowered, which is not preferable.

  In the laminated polyester film of the present invention, the base film portion composed of the B layer and the A layer is preferably biaxially oriented. The biaxially oriented polyester film is generally an unstretched polyester sheet or film that is stretched about 2.5 to 5 times in the longitudinal direction (longitudinal direction) and in the direction perpendicular to the longitudinal direction (transverse direction). In this case, the crystal orientation is completed by heat treatment, and a biaxial orientation pattern is shown by wide-angle X-ray diffraction.

  The laminated film layer (C layer) in the present invention is preferably provided on one surface of the base film composed of the B layer and the A layer. More specifically, a laminated film layer (C layer) containing polyester is provided on one side of the laminated polyester film, and at least an A layer is provided on the opposite side of the B layer from the surface on which the C layer is provided. It is preferable. That is, in the case of the A layer / B layer where the A layer is only on one side of the B layer, the C layer is provided on the surface opposite to the A layer, and the A layer is on both sides of the B layer. In the case of A layer / B layer / A layer, a C layer is provided on one surface of the A layer.

  The layer C is preferably a coating layer formed by stretching in at least one direction after applying the aqueous coating liquid from the viewpoint of preventing environmental pollution and explosion-proofing during film production, and biaxially orienting the base film. It is preferable to be performed within the manufacturing process. Although the timing of the stretching is not particularly limited, a method of biaxial stretching after applying the aqueous coating liquid, or a method of applying the aqueous coating liquid after longitudinal (longitudinal direction of the film) and further laterally stretching is preferably used. As the coating method of the aqueous coating liquid, various coating methods such as reverse coating method, gravure coating method, rod coating method, bar coating method, die coating method, spray coating method and the like can be preferably used. Is not to be done.

  In order to apply as an aqueous coating liquid, the polyester contained in the C layer is preferably a copolymer polyester containing a compound containing a sulfonate group or a compound containing a carboxylate group as a copolymer component. Examples of the compound containing a sulfonate group include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and alkali metal salts and alkaline earth metals thereof. Although a salt and an ammonium salt can be used, it is not limited to these. 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, 1,2,5,6-naphthalenetetracarboxylic acid, ethylene glycol bistrimellitate, 2,2 ′, 3,3′-diphenyltetracarboxylic acid, thiophene-2,3,4,5-tetracarboxylic acid, Ethylene tetracarboxylic acid, or alkali metal salts, alkaline earth metal salts, ammonium salts, etc. You can have, but is not limited thereto.

  The polyester contained in the C layer is preferably a copolymer polyester containing isophthalic acid and diethylene glycol as copolymer components. By using the component as a copolymer component, the solvent resistance of the C layer, particularly with respect to alcohol, can be improved, and when the A layer or the B layer contains polyester having a copolymer component of isophthalic acid, The adhesive force at the C layer or at the interface between the B layer and the C layer can be improved. The amount of isophthalic acid as the copolymer component is preferably 65 to 95 mol%, more preferably 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. Examples thereof include, but are not limited to, the dicarboxylic acids and diols described above. Moreover, the compound containing an above described sulfonate group and the compound containing a carboxylate group can also be included as a copolymerization component. The range of the preferable glass transition point of this copolyester is 0-60 degreeC, More preferably, it is 10-45 degreeC.

  The content of the copolyester containing isophthalic acid and diethylene glycol as a copolymerization component is preferably 10 to 60% by weight, more preferably 20 to 50% by weight, based on the total of the resins forming the C layer. If the content is too small, the solvent resistance and the adhesive strength with the A layer and the B layer may be inferior. If the content is too large, the blocking resistance may be inferior when used as a film roll.

  The resin other than the copolymerized polyester having isophthalic acid and diethylene glycol as the copolymerization 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, acrylic resins , Urethane resin, epoxy resin, silicone resin, urea resin, phenol resin, and the like, and other polyester resins are particularly preferable.

  The thickness of the C layer is preferably 0.01 to 2 μm, more preferably 0.05 to 1 μm. If the thickness of the C layer is too thin, adhesion to various coatings and solvent resistance may be insufficient, and if it is too thick, the slip resistance and blocking resistance when used as a film roll may be reduced.

  The laminated polyester film of the present invention is obtained by laminating a polyester layer (B layer) containing polyester a 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. A laminated film layer (C layer) containing polyester is formed by means of applying a coating solution on one side, and further, it is manufactured by a method of performing uniaxial stretching or biaxial stretching as necessary and then heat-treating. However, by performing the heat treatment at a temperature equal to or higher than the melting point of the polyester constituting the A layer, the laminating property can be greatly improved. The means for performing the heat treatment at the specific temperature is not particularly limited as long as the crystal orientation on the surface of the A layer is partially broken to achieve the effect of the present invention. For example, in a production process in which a film is biaxially oriented, a method in which heat treatment is performed subsequent to stretching in the vertical and horizontal directions can be mentioned as a preferable method in terms of economy and productivity. Moreover, after winding up a biaxially oriented film, the method of heat-processing again is also possible.

  Next, although the manufacturing method of the laminated polyester film of this invention is demonstrated in detail, this invention method is not limited to this.

  The polyester pellets for layer A and the polyester pellets for layer B prepared in advance so as to have a predetermined polymer composition are vacuum-dried, respectively, and then supplied to two extruders for layer A and layer B. 200 to 300 After melting at ℃ and laminating the A layer on one or both sides of the B layer, it is extruded in a molten form from a T-shaped die and wound around a casting drum having a surface temperature of 10 to 60 ℃ using the electrostatic charge method Then, it is cooled and solidified to produce an unstretched polyester film. Subsequently, this unstretched film is stretched 2.5 to 5 times in the longitudinal direction (longitudinal direction) of the film between rolls heated to 60 to 120 ° C. Subsequently, on one side of the film (that is, when the A layer is only on one side of the B layer, on the surface opposite to the A layer, and when the A layer is on both sides of the B layer) A corona discharge treatment is performed on one surface of the A layer, and an aqueous coating liquid for forming the C layer is applied. Subsequently, the coated film is held with a clip, guided to a hot air zone heated to 70 to 150 ° C., dried, and then stretched 2.5 to 5 times in a direction perpendicular to the longitudinal direction (lateral direction). Then, it is led to a heat treatment zone having a temperature equal to or higher than the melting point of the polyester constituting the A layer, and heat treatment is performed for 1 to 30 seconds. In this heat treatment step, a relaxation treatment of 3 to 12% may be performed in the width direction or the longitudinal direction as necessary. 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 re-stretching in either the longitudinal or transverse direction after longitudinal and transverse stretching. Also good.

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

  The use of the laminated polyester film of the present invention is not particularly limited as long as it is used by adhering other materials to both surfaces of the film. For example, for cards, labels, photographs, OHP, thermal transfer, ink jet, offset printing Can be used for receiving sheet substrates such as, hard coat films, packaging, magnetic recording media, various industrial materials, flooring, wallpaper, and car window advertisements.

[Characteristic measurement method and effect evaluation method]
The characteristics measurement method and effect evaluation method in the present invention are as follows.
(1) Melting point of polyester, glass transition point It was measured by connecting an SSC 5200 disk station (manufactured by Seiko Electronics Industry) to a robot DSC (differential scanning calorimeter) RDC220 (manufactured by Seiko Electronics Industry). 10 mg of the sample was adjusted to an aluminum pan, set in a DSC apparatus (reference: aluminum pan of the same type without a sample), heated at a temperature of 300 ° C. for 5 minutes, and then rapidly cooled using a liquid nitrogen atmosphere . DSC measurement was performed while heating the sample at 10 ° C./min. From the obtained DSC chart, the melting point was changed from the peak temperature based on crystal melting, and the temperature was changed from the temperature based on the transition from the glass state to the rubber state. I read the points.
(2) Thickness of each layer of laminated film Using a transmission electron microscope H-7100FA type (manufactured by Hitachi, Ltd.), the thickness was obtained from a photograph observing the cross section of the laminated polyester film. The thickness was an average value of 5 points in the measurement visual field.
(3) Peeling resistance at the interface of the laminated film An adhesive layer is applied on the A layer, a base film that strongly adheres to the adhesive layer is bonded to the other layer, cut into 25 mm × 200 mm, and further 80 ° C. The sample was allowed to stand for 7 days. This sample was forcibly peeled off at a 180 ° angle and a peeling speed of 0.3 m / min using a tensile tester. The force required for peeling is 75N / 25mm or more, ◎, 65N / 25mm or more, less than 75N / 25mm, ○, 55N / 25mm or more, less than 65N / 25mm, △, 45N / 25mm or more, 55N / 25mm Those less than 45 N / 25 mm were judged as xx.

(4) Content ratio of polyester a Measured using a nuclear magnetic resonance spectrometer (NMR) UNITYplus 500 (manufactured by varian). About 50 mg of a sample is dissolved in a solution of deuterated chloroform / HFIP (1/1), adjusted to a sample tube, set in an NMR apparatus and measured, and is a low melting point polyester from the peak area of the obtained 1H-NMR spectrum. The content ratio of various monomers corresponding to polyester a and PET was determined. When measured by the above-mentioned method in each example, it was confirmed that it was in agreement with the charged molar ratio.

(Example)
The present invention will be described based on the following examples, but the present invention is not limited thereto.

  The laminated polyester sheet which consists of A and B layers was obtained using the composite film forming apparatus which has an extruder (A), an extruder (B), and a T-die composite die.

  First, in order to form the A layer, silica having an average particle diameter of 4.0 μm was obtained from 0.05% by weight, and isophthalic acid as a copolymer component was obtained from 17.5% by weight (the polymerization catalyst was a citrate chelate titanium compound). Polyethylene terephthalate (melting point: 216 ° C., polyester a in the present invention, ethylene glycol slurry was used so as to be 0.01% by weight in terms of titanium atom with respect to the obtained polyester). After being vacuum-dried, it was supplied to the extruder (A) side, melted at 280 ° C. by a conventional method, and introduced into the T-die composite die.

  On the other hand, in order to form the B layer, 6.0% by weight of the low melting point polyester (1) and polyethylene terephthalate (melting point: 255 ° C., hereinafter abbreviated as PET) 62. 0% by weight, 2.0% by weight of PET containing 2.0% by weight of silica having an average particle size of 2.6 μm, and 30.0% by weight of PET containing 3.0% by weight of alumina having an average particle size of 3.0 μm The contained raw material was vacuum-dried, then supplied to the extruder (B) side, melted at 280 ° C. by a conventional method, and introduced into the T-die composite die.

  Next, the polyester layer (A) was merged so as to be laminated on one side of the polyester layer (B) in the die, and then co-extruded into a sheet to obtain a melt-laminated sheet. Then, the laminated sheet was closely cooled and solidified by an electrostatic charge method on a casting drum maintained at a surface temperature of 22 ° C. to obtain an unstretched laminated film. Subsequently, the unstretched laminated film was preheated in a roll group heated at 78 ° C. according to a conventional method, and then stretched 2.8 times in the longitudinal direction (longitudinal direction) using a 95 ° C. heated roll, and a 21 ° C. roll. The film was cooled to obtain a uniaxially stretched film. Subsequently, the surface opposite to the laminated surface of the uniaxially stretched laminated film is subjected to corona discharge treatment in air, and the following C layer forming coating solution is applied to the treated surface by a bar coating method using a metalling bar. Coating was performed to form a C layer. While holding both ends of the uniaxially stretched film coated with this coating layer forming coating solution with clips, the film is guided to a preheating zone at 130 ° C. in the tenter, and continuously in a heating zone at 135 ° C. in a direction perpendicular to the longitudinal direction (lateral Direction) was stretched 3.2 times. Subsequently, a heat treatment zone of 223 ° C. was applied in the heat treatment zone in the tenter, and after 2% relaxation treatment at 220 ° C., 2% relaxation treatment was further conducted at 150 ° C. Rolled up to obtain a laminated polyester film.

  The properties of the laminated polyester film thus obtained are as shown in Table 1, and it can be seen that the peel resistance is excellent.

[Prescription of C layer forming coating liquid]
It is formed from (α) to (δ) shown below.

(Α) Fluorosurfactant (β) Colloidal silica (average particle size 1.0 μm)
(Γ) Copolyester having a copolymer composition of terephthalic acid / 5-sodium sulfoisophthalic acid // ethylene glycol (molar ratio 87.5 / 12.5 // 100) (glass transition point 40 ° C.)
(Δ) Copolyester having a copolymer composition of isophthalic acid / 5-sodium sulfoisophthalic acid // ethylene glycol / diethylene glycol (molar ratio 93/7 // 10/90) (glass transition point 18 ° C.)
C layer forming coating solution is prepared by mixing the above (γ) / (δ) at a solid content weight ratio of 70/30 and diluting with water to a solid content concentration of 4% by weight. 0.0003 wt% with respect to the coating solution, and (β) is added in an amount of 0.006 wt% with respect to the entire coating solution.

  A laminated polyester film was obtained in the same manner as in Example 1 according to the composition and conditions shown in Table 1. The part which is not mentioned is implementing the method similar to Example 1. FIG. The characteristics of the obtained laminated polyester film are as shown in Table 1, and it can be seen that it has excellent peel resistance. The low melting point polyester (2) which is the polyester a of the present invention is a polyethylene containing 0.05% by weight of silica having an average particle size of 4.0 μm and 17.5% by weight of 1,4-cyclohexanedimethanol as a copolymer component. It is terephthalate (melting point: 218 ° C.). The low melting point polyester (3), which is the polyester a of the present invention, has a polyethylene terephthalate (melting point: 245) containing 0.05% by weight of silica having an average particle size of 4.0 μm and 4.5% by weight of isophthalic acid as a copolymerization component. ° C).

(Comparative Examples 1-4)
A laminated polyester film was obtained in the same manner as in Example 1 according to the composition and conditions shown in Table 1. The part which is not mentioned is implementing the method similar to Example 1. FIG. The characteristics of the obtained laminated polyester film are as shown in Table 1, and the level of peel resistance was not achieved in order to exhibit a desired function.

Claims (10)

A laminated polyester film comprising a polyester layer (A layer) having a melting point of 250 ° C. or lower on one or both sides of a polyester layer (B layer) containing a polyester a having a melting point of 250 ° C. or lower, the A layer, A laminated polyester film characterized in that both B layers contain particles, and the number of types of particles contained in the B layer is larger than the types of particles contained in the A layer. 2. The laminated polyester film according to claim 1, wherein the polyester a having a melting point of 250 ° C. or less contained in the A layer and the B layer contains at least one of the copolymerization components in common. The polyester a having a melting point of 250 ° C. or less contained in the A layer and the B layer is a copolymerized polyester containing at least one of isophthalic acid and 1,4-cyclohexanedimethanol as a copolymerization component. The laminated polyester film according to 1 or 2. The content of the polyester a having a melting point contained in the B layer of 250 ° C or lower is 0.1% by weight or more based on the total of the polyesters forming the B layer. The laminated polyester film of crab. A laminated film layer (C layer) containing polyester is provided on one side of the laminated polyester film, and at least the B layer has an A layer on the opposite side of the surface on which the C layer is provided. The laminated polyester film according to any one of claims 1 to 4, wherein: The laminated polyester film according to any one of claims 1 to 5, wherein the polyester contained in the C layer is a copolyester having isophthalic acid and diethylene glycol as copolymerization components. 7. The laminated polyester film according to claim 1, wherein the content of the polyester contained in the C layer is 10 to 60% by weight based on the total amount of resins forming the C layer. The layer C is a coating layer formed of a component capable of being applied with an aqueous coating liquid and stretched in at least one direction, and the thickness of the layer is 0.01 to 2 μm. The laminated polyester film according to any one of 7 above. The laminated polyester film according to any one of claims 1 to 8, wherein the laminated polyester film has a total thickness of 100 to 500 µm. The laminated polyester film according to claim 1, comprising a Ti-based polymerization catalyst.