JP2006016537A - Polyester film for simultaneous molding and transfer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film for simultaneous molding and transfer having excellent moldability and transferability, especially deep drawing properties and follow-up properties to the surface shape of a material to be transferred. <P>SOLUTION: The polyester film for simultaneous molding and transfer is a polyester film comprising a dicarboxylic acid component, an aliphatic or an alicyclic diol component and a polyalkylene ether glycol component having 300-4,000 number-average molecular weight as main constituent components. The polyester film has 0.1-3.5 GPa Young's modulus in the longitudinal and the cross directions and 1.49-1.55 refractive index (nα) in the thickness direction of the film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a molding simultaneous transfer polyester film excellent in moldability and transferability, and particularly to a molding simultaneous transfer polyester film excellent in deep drawability and followability to the surface shape of a transfer target.

  Conventionally, a polyester foil such as polyethylene terephthalate or a film of vinyl chloride resin is used as a base film as a transfer foil for in-mold molding that is transferred simultaneously with molding in injection molding, etc., and a release layer is provided on the surface of the base film. Furthermore, a laminated film having a printed layer applied thereon is used.

  The laminated film used for in-mold molding transfer is separated between the release layer surface and the printing layer surface after the molding transfer. That is, after molding transfer, the printed layer is adhered to the surface of the molded product and taken out as a product, and the release layer is removed after molding in a state of being laminated on the base film.

  Such a transfer method is used for plastic molded products used for household appliances, automobile interior parts, kitchenware, cosmetic containers, toys and the like. In particular, various transfer foils using a polyester film as a base film have been proposed. For example, a polyester film having a molding stress in a specific range (for example, see Patent Document 1), a film obtained by copolymerizing isophthalic acid at a specific ratio (for example, see Patent Literature 2), a polyester film having a specific plane orientation (for example, And Patent Document 3) are known.

  However, in recent years, consumer needs regarding the design properties and comfortability of the plastic molded products have been diversified, and there is a strong tendency that a surface finish with a three-dimensional curved surface structure with a particularly high degree of deep drawing is desired.

  When using a transfer foil for in-mold molding and transfer with polyester as a base film, the polyester film is not sufficiently stretched. Film tears occur frequently in the process, making transfer virtually impossible. Therefore, the transfer foil using a polyester film is currently used only in molding transfer using a mold having a shallow bottom and a simple shape.

  On the other hand, in the case of a transfer foil using a vinyl chloride resin film as a base film, the degree of deep drawing is high, and the moldability for a molded product having a complicated shape is excellent, but the smoothness of the film is better than that of a polyester film. In addition, since there are many coarse foreign substances present on the film surface and inside, there is a drawback that clear transfer printing cannot be performed.

  In addition, the shape of molded products has been diversified in recent years, and the demand for molding transfer that requires the above-described deep drawability is constantly increasing. A film that maintains the smoothness of a polyester film as a base film of a transfer foil and also has the deep drawability of a vinyl chloride resin film is desired.

JP 2000-238070 A Japanese Patent Laid-Open No. 1-40400 JP 7-237283 A

  This invention is made | formed in view of the said situation, Comprising: The solution subject is providing the polyester film for shaping | molding simultaneous transfer excellent in smoothness and deep drawing workability.

  As a result of intensive studies in view of the above situation, the present inventors have found that the film having a specific configuration can easily solve the above situation, and have completed the present invention.

  That is, the gist of the present invention is a polyester film mainly composed of a dicarboxylic acid component, an aliphatic or alicyclic diol component, and a polyalkylene ether glycol component having a number average molecular weight of 300 to 4000. The present invention resides in a polyester film for simultaneous molding, wherein Young's modulus in the vertical and horizontal directions is 0.1 to 3.5 GPa, and the refractive index (nα) in the thickness direction is 1.49 to 1.55.

Hereinafter, the present invention will be described in detail.
The polyester film of the present invention is a polyester film mainly composed of a dicarboxylic acid component, an aliphatic or alicyclic diol component, and a polyalkylene ether glycol having a number average molecular weight of 300 to 4000. The main component mentioned here means that 80% by weight or more is occupied by the above component among all components. Moreover, about a structural component, a polyester film can be decomposed | disassembled with an alkali and it can analyze by chromatography, for example.

  The dicarboxylic acid component is preferably 50 mol% or more of terephthalic acid, but may be copolymerized with other dicarboxylic acid components. Specific examples of the dicarboxylic acid component other than terephthalic acid include, for example, isophthalic acid, orthophthalic acid, phenylenedioxydiacetic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenoxyethanedicarboxylic acid, 4 , 4′-diphenyl ether carboxylic acid, 4,4′-diphenyl carboxylic acid, 1,5-naphthalenedicarboxylic acid, aromatic dicarboxylic acid such as 2,6-naphthalenedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4 -Aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, aliphatic dicarboxylic acids such as malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, etc., among them, isophthalic acid, 2,6-naphthalenedicarboxylic One or more selected from acids and cyclohexanedicarboxylic acids are preferred.

  In the present invention, the dicarboxylic acid component includes an ester-forming derivative such as an alkyl ester having about 1 to 4 carbon atoms at the raw material stage.

  As the aliphatic or alicyclic diol (excluding the polyalkylene ether glycol component described below), 50 mol% or more is preferably ethylene glycol, but other aliphatic or alicyclic diol components are commonly used. It may be polymerized. Specific examples of aliphatic and / or alicyclic diol components other than ethylene glycol include 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, and 1,4-butane. Diols, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 2,2-dimethyl-1,3-propanediol, aliphatic diols such as diethylene glycol, 1,1-cyclohexanedimethanol Alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, etc. 1,4-butanediol, diethylene glycol, 1,4-cyclohexane Methanol, one or more selected from 2,2-dimethyl-1,3-propanediol are preferred.

  In the present invention, the aliphatic or alicyclic diol component other than ethylene glycol is usually 30 mol% or less, preferably 5 to 30 mol%, more preferably 10 to 20 mol% of the total diol component. is there. By copolymerizing aliphatic or cycloaliphatic diol components other than ethylene glycol, flexibility and transparency may be improved, but depending on the amount of copolymerization, the mechanical properties of the resulting copolymerized polyester film The characteristics may be inferior.

  In the polyester film of the present invention, for example, 4,4-dihydroxybiphenyl, 2,2-bis (4′-hydroxyphenyl) propane, 2,2 may be used as long as the effects of the present invention are not impaired. -Aromatic diols such as bis (4'-β-hydroxyethoxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, bis (4-β-hydroxyethoxyphenyl) sulfonic acid, glycolic acid, p-hydroxybenzoic acid, Monofunctional components such as hydroxycarboxylic acids such as p-β-hydroxyethoxybenzoic acid, alkoxycarboxylic acids, stearic acid, stearyl alcohol, benzyl alcohol, benzoic acid, t-butylbenzoic acid, benzoylbenzoic acid, tricarballylic acid, hexane Tricarboxylic acid, trimellitic acid, trimesic acid, pyromellitic , Benzophenonetetracarboxylic acid, naphthalenetetracarboxylic acid, 1,2,6-hexanetriol, gallic acid, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, sorbitol, trimethylolpropane, glycerol, pentaerythritol, sorbitol, di A polyfunctional component having three or more functional groups such as pentaerythritol and polyglycerol may be copolymerized.

  In the present invention, the polyester film needs to contain polyalkylene ether glycol as a constituent component, and the number average molecular weight of the glycol component is in the range of 300 to 4000, preferably 400 to 3000, and more preferably 500 to 2000. . When the number average molecular weight is less than 300, thermal stability is inferior or low molecular weight substances are precipitated. On the other hand, when the number average molecular weight exceeds 4000, the transparency of the film is inferior, so that it is difficult to observe complicated patterns and characters through the film.

  Examples of the polyalkylene ether glycol include polyethylene glycol, polypropylene glycol, polytrimethylene glycol, polytetramethylene glycol, polyhexamethylene glycol, a block or random copolymer of ethylene oxide and propylene oxide, and among these, Polytetramethylene ether glycol is preferred.

  A plurality of polyalkylene ether glycols having different number average molecular weights can be used in combination. When using together, the value measured by mixing uniformly should just be the said range. Here, the number average molecular weight of the polyalkylene ether glycol can be measured by a general method such as gel permeation chromatography.

  When polyalkylene ether glycol is blended in the copolymerized polyester film in an amount of 5 to 35% by weight, more preferably 10 to 30% by weight, a three-dimensional curved surface structure having a high deep drawing ratio (drawing ratio of 0.2 or more) is formed. It is preferable because deep drawing workability in the body is excellent. The drawing ratio in the present invention is the minimum depth of the molded body opening in the molded body having a three-dimensional structure at the time of in-mold molding transfer. For example, the molded body opening is rectangular. In this case, the value obtained by dividing the drawing depth of the molded body by the minimum length of the vertical and horizontal lengths of the molded body, or if the molded body opening is circular, the drawing depth of the molded body is It is a value divided by the diameter of the molded body. When the content of the polyalkylene ether glycol is less than 5% by weight, flexibility tends to be inferior, so that the molding followability and the film may be broken during molding, particularly during deep drawing. On the other hand, if it exceeds 35% by weight, although it is excellent in flexibility, the transparency of the film tends to be inferior, so that it may be difficult to observe complicated pictures and characters through the film.

  The polyester resin constituting the film of the present invention is basically divided into batches by a conventional production method of a polyester resin using a dicarboxylic acid component, a diol component, and a polyalkylene ether glycol, that is, a direct polymerization method or a transesterification method. Or manufactured continuously. Here, the polyalkylene ether glycol and the optional copolymerization component can be added at any stage of the polycondensation reaction process. Furthermore, the polyester of the present invention is obtained by preparing an oligomer having a low polymerization degree composed of a dicarboxylic acid and an aliphatic and / or alicyclic diol component in advance, and polycondensing the oligomer with a polyalkylene ether glycol. You can also.

  The resin obtained by the polycondensation reaction is usually extracted in the form of a strand from an extraction port provided at the bottom of the polycondensation reaction tank, and is cut with a cutter while cooling with water or with water, and is formed into a pellet. Furthermore, by subjecting the pellets after polycondensation to solid phase polycondensation by heat treatment, the degree of polymerization can be further increased, and reaction by-products such as acetaldehyde and low-molecular oligomers can be reduced.

  In the above production method, the esterification reaction is performed in the presence of an esterification catalyst such as an organic acid salt or an organic metal compound such as antimony trioxide, antimony, titanium, magnesium, or calcium, if necessary. The exchange reaction is performed in the presence of an ester exchange catalyst such as an organic acid salt or an organic metal compound such as lithium, potassium, sodium, magnesium, calcium, manganese, titanium, or zinc, if necessary.

  The polycondensation reaction is carried out in the presence of phosphorus compounds such as orthophosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid and their esters and organic acid salts, and, for example, antimony trioxide, germanium dioxide, tetraoxide. It is carried out in the presence of a metal compound such as germanium, or a polycondensation catalyst such as an organic acid salt such as antimony, germanium, zinc, titanium, or cobalt, or an organic metal compound. Among these polycondensation catalysts, one or more selected from tetrabutoxy titanate, antimony trioxide, and germanium dioxide are preferably used.

  The intrinsic viscosity of the polyester resin constituting the film of the present invention is usually 0.4 to 1.5 dl / g, preferably 0.5 to 1.2 dl / g, more preferably 0.6 to 1.0 dl / g. It is a range. If the intrinsic viscosity is less than 0.4 dl / g, the moldability tends to deteriorate. On the other hand, when the intrinsic viscosity exceeds 1.5 dl / g, the film-forming property of the film may be deteriorated, and the thickness unevenness of the film may occur.

  The glass transition temperature (Tg) of the polyester resin constituting the film of the present invention is usually 20 to 60 ° C., preferably 25 to 50 ° C., more preferably 25 to 40 ° C. When the glass transition temperature is less than 20 ° C., the heat-resistant dimensional stability is deteriorated, film transport and local tarmi may occur, and chip fusion may occur during storage. On the other hand, when the glass transition temperature exceeds 60 ° C., the flexibility tends to be inferior, and the moldability tends to deteriorate.

  The melting point (Tm) of the film is usually 200 to 260 ° C, preferably 210 to 250 ° C. If it is less than 200 degreeC, there exists a tendency for the heat resistance in the case of shaping | molding to be inferior. On the other hand, when it exceeds 260 ° C., the molding followability tends to decrease particularly during deep drawing.

  The polyester film of the present invention preferably contains inert fine particles in order to impart blocking resistance, slipperiness, etc., and the content thereof is usually 0.01 to 1.0 with respect to the film. % By weight, preferably 0.05 to 0.5% by weight, more preferably 0.1 to 0.3% by weight. When the particle content is less than 0.01% by weight, the transparency is excellent, but the slipperiness and the handleability of the film may be inferior. On the other hand, if the particle content exceeds 1.0% by weight, the slipperiness is excellent, but the transparency is inferior, so that it may be difficult to observe complicated patterns and characters through the film. .

  As the inert fine particles used in the present invention, inorganic particles such as calcium carbonate, silica, calcium phosphate, kaolin, talc, titanium oxide, alumina, barium sulfate, lithium fluoride, zeolite, molybdenum sulfide, calcium oxalate, and crosslinked polymer particles Examples of the organic particles include, but are not limited to these.

  The average particle size of the inert part particles is usually in the range of 0.1 to 5.0 μm, preferably 0.2 to 4.0 μm, and more preferably 0.3 to 3.0 μm. When the average particle size is less than 0.1 μm, the transparency is excellent, but the slipperiness and the handleability of the film may be inferior. On the other hand, if the thickness exceeds 5.0 μm, the slipperiness is excellent, but a flaw-like defect is generated, and the surface of the molded product may be defective.

  As a method of causing the polyester constituting the film of the present invention to contain particles in the resin, a known method can be adopted. For example, it can be added at any stage for producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or after the end of the transesterification reaction and before the start of the polycondensation reaction. Then, the polycondensation reaction may proceed. In addition, a method of blending a slurry of particles dispersed in water or an organic solvent having a boiling point of 200 ° C. or less and a polyester raw material using an extruder with a vent, or a particle and polyester dried using a kneading extruder It is performed by a method of blending with raw materials. The particles to be added may be subjected to a treatment such as pulverization, dispersion, classification, and filtration in advance as necessary.

  The polyester film of the present invention needs to have a Young's modulus in the longitudinal and lateral directions in the range of 0.1 to 3.5 GPa, and the Young's modulus is preferably 0.1 to 3.0 GPa, more preferably 0.2. It is in the range of ~ 2.5 GPa. If the Young's modulus is less than 0.1 GPa, distortion is likely to occur in the pattern of the molded product that is the product, which is not preferable. On the other hand, if the Young's modulus exceeds 3.5 GPa, the elongation at the time of molding becomes low, and a problem that sufficient moldability cannot be obtained at the time of deep drawing is likely to occur.

  Further, the refractive index (nα) in the thickness direction of the film needs to be in the range of 1.49 to 1.55, preferably 1.49 to 1.54, more preferably 1.495 to 1.535. It is a range. If the refractive index (nα) in the thickness direction is less than 1.49, the elongation at the time of molding becomes low, and a problem that sufficient moldability cannot be obtained at the time of deep drawing is likely to occur. On the other hand, if the refractive index (nα) in the thickness direction exceeds 1.55, it is not preferable because distortion tends to occur in the pattern of the molded product.

  The polyester film of the present invention may be provided with a coating layer in order to impart adhesion, antistatic properties, and slipperiness. Examples of components constituting the coating layer include polyester, polyamide, polystyrene, polyacrylate, polycarbonate, polyarylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyvinyl alcohol, polyurethane, and the like, and the weight of these resins. Examples include coalescence. You may contain 1 type or 2 or more types of resin of this resin simultaneously.

  Examples of the method for applying the coating solution to the film include a forward rotation roll coater, a reverse roll coater, a gravure coater, a knife coater, a blade coater, a rod coater, an air doctor coater, a curtain coater, a fountain coater, a kiss coater and a kiss roll. A coating apparatus such as a coater, a bead coater, or a dip coater, a screen coating, a cast coating, an impregnation machine, or a coating method such as an LB method can be employed, but is not limited thereto. The coating layer may be provided within the film production process, or may be applied after the film production. The method of apply | coating in a film manufacturing process is especially preferable at the point of the uniformity of a coating layer and production efficiency.

  As a method of coating in the film manufacturing process, a coating solution is applied to an unstretched sheet, biaxially stretched sequentially or simultaneously, applied to a uniaxially stretched film, and further in a direction perpendicular to the previous uniaxially stretched direction. There are a method of stretching, a method of applying to a biaxially stretched film, and a method of stretching in the transverse and / or longitudinal direction.

  The thickness of the coating layer is usually in the range of 0.005 to 1.0 μm, and preferably in the range of 0.01 to 0.5 μm. If the coating thickness is less than 0.005 μm, coating leakage and coating spots are likely to occur. On the other hand, if the coating thickness exceeds 1.0 μm, the continuity during film production may deteriorate.

  Such a coating layer may be provided on only one side of the film, but is preferably provided on both sides. Moreover, when apply | coating only to one side, the application layer other than the application layer in this invention can be formed in the opposite surface as needed, and another characteristic can also be provided to the film of this invention.

  In addition, in order to improve the applicability | paintability to the film of a coating agent and adhesiveness, you may perform a chemical process and an electrical discharge process to a film before application | coating. From the viewpoint of processing efficiency, cost, and ease of processing, it is preferable to perform corona discharge processing. Moreover, in order to improve the adhesiveness, applicability, etc. of the coating layer in the film of the present invention, the coating layer can be subjected to a discharge treatment after the coating layer is formed.

  Next, although the manufacturing method of the polyester film of this invention is demonstrated concretely, as long as the structural requirements of this invention are satisfied, it is not specifically limited to the following illustrations.

  That is, the above-described polyester raw material is supplied to an extruder, heated to a temperature equal to or higher than the melting point of the polyester and melted to extrude the molten sheet from the die, and cooled and solidified with a cooling roll to obtain an unstretched sheet. In this case, in order to improve the flatness of the sheet, it is necessary to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed.

  Next, the obtained unstretched sheet is stretched biaxially and biaxially oriented. That is, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 20 to 100 ° C., preferably 30 to 80 ° C., and the stretching ratio is usually 2.0 to 6.0 times, preferably 2.5 to 4.5 times. Next, stretching is performed in a direction perpendicular to the first stage direction. The stretching temperature is usually 30 to 100 ° C., preferably 40 to 90 ° C., and the stretching ratio is usually 3.0 to 6.0 times, preferably 3.5 to 4.5 times. In addition, although the method of extending | stretching one direction in two steps or more can also be used, it is desirable for the final draw ratio to enter into the above-mentioned range also in that case. Further, the unstretched sheet can be simultaneously biaxially stretched so that the area magnification is 10 to 40 times.

  The film thus obtained is preferably heat-treated at 150 to 210 ° C. for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal and / or transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary.

  According to the present invention, it is possible to provide a polyester film for simultaneous molding and transfer that is excellent in moldability and transferability, particularly excellent in deep drawability and surface shape of a transfer object, and has high industrial value.

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

(1) Average particle diameter (μm)
The diameter (particle diameter) of the integrated volume fraction of 50% in an equivalent spherical distribution measured with a centrifugal sedimentation type particle size distribution measuring apparatus (SP-CP3 type) manufactured by Shimadzu Corporation was used.

(2) Glass transition temperature [Tg (° C.)], melting point [Tm (° C.)]
It measured using the differential calorimeter (DSC-2920 type | mold) made from TA Instrument. The DSC measurement conditions are as follows. That is, 10 mg of a sample was melted and held at 280 ° C. for 5 minutes under a nitrogen stream, and then rapidly cooled with liquid nitrogen. In the process of raising the temperature of the obtained sample at a rate of 10 ° C./min, the specific heat change based on the transition from the glass state to the rubber state is read, and this temperature is defined as the glass transition temperature (Tg), and the endothermic peak temperature based on crystal melting. Was the melting point (Tm).

(3) Intrinsic viscosity of polymer (dl / g)
1 g of the polymer was dissolved in 100 ml of a mixed solvent of phenol / tetrachloroethane (50/50 (weight ratio)) and measured at 30 ° C. with an Ubbelohde viscometer.

(4) Young's modulus of film (GPa)
Using an Intesco Corporation tensile tester (2001 type), a sample film having a length (between chucks) of 300 mm and a width of 20 mm is 10% / min in a room adjusted to a temperature of 23 ° C. and a humidity of 50% RH. Was calculated by the following formula using the initial linear portion of the tensile stress-strain curve.
E = Δσ / Δε
(Where E is Young's modulus (GPa), Δσ is the stress difference (GPa) due to the original average cross-sectional area between the two points on the straight line, Δε is the strain difference between the two points / initial length (−) Represents

(5) Refractive index in the film thickness direction (nα)
Using an Atago Co., Ltd. Abbe refractometer 4T, a polarizing plate was attached to the eyepiece, the direction of the polarizing plate and the direction of the film were adjusted, and the refractive index (nα) in the thickness direction of the film was measured. In addition, iodomethane was used as an intermediate solution.

(6) Suitability as a transfer film A release layer, a printing layer, and an adhesive layer were formed on a polyester film, and preformed by vacuum or pressure forming inside a mold having a length of 50 mm, a width of 50 mm, and a maximum depth of 15 mm. . The moldability was evaluated according to the following criteria based on the frequency of film breakage caused by molding.
○: Molded to a uniform thickness without film breakage, cracks, etc. Δ: No film breakage, but there is a locally very thin film ×: Film breaks frequently

For the printing evaluation, after performing the above-described pre-molding, the resin was injected, the molding transfer was performed, and the state of missing or distortion of the printed pattern on the obtained molded product was evaluated as follows.
○: No printing, no distortion △: No printing, almost no distortion ×: Printing, no distortion

  52 parts of terephthalic acid, 18 parts of ethylene glycol, 30 parts of polytetramethylene ether glycol, as catalyst and cocatalyst, 0.009 part of tetrabutoxy titanate, 0.025 part of ethyl acid phosphate, 0.05 part of cobalt acetate Further, 1 part of amorphous fine silica particles having an average particle size of 2.4 μm was taken as an ethylene glycol slurry in a reactor to obtain a polyester resin by a direct polymerization method at 270 ° C. and 400 Pa. The polyester resin was extracted in the form of a strand from the polymerization tank, cooled, and then cut in a pelletizer by cutting with a pelletizer. The obtained polyester resin pellets had a glass transition temperature (Tg) of 40 ° C., a melting point (Tm) of 244 ° C., and an intrinsic viscosity of 0.79. This pellet is air-dried and supplied to a vented twin-screw extruder, melted and kneaded under a reduced pressure of 250 ° C. and 100 KPa, and formed into a sheet on a rotary cooling roll at 20 ° C. from a slit die. Extrusion and quenching with a rotating cooling roll using an electrostatic application cooling method to obtain an unstretched sheet, and then the unstretched sheet is 3.5 times at 50 ° C. in the longitudinal direction and 3.70 ° C. in the lateral direction. Stretched 5 times. The obtained film was heat-treated at 200 ° C. for 3 seconds to obtain a biaxially stretched polyester film having a thickness of 35 μm. The following properties of the obtained film are shown in Table 1.

(Examples 2 and 3)
A biaxially stretched polyester film having a film thickness of 35 μm was obtained in the same manner as in Example 1 except that terephthalic acid, ethylene glycol, and polytetramethylene ether glycol were used in the composition ratios shown in Table 1 below. The properties of the obtained film are shown in Table 1.

(Comparative Examples 1 and 2)
In Example 1, a biaxially stretched polyester film having a film thickness of 35 μm was obtained in the same manner as in Example 1 except that the number average molecular weight of polytetramethylene ether glycol was set in Table 1. The properties of the obtained film are shown in Table 1.

(Comparative Examples 3 and 4)
In Example 1, the film thickness was 35 μm as in Example 1, except that the stretching conditions were changed so that the refractive index (nα) and Young's modulus in the thickness direction of the film were outside the scope of the present invention. An axially stretched polyester film was obtained. The properties of the obtained film are shown in Table 1.

The film of the present invention can be suitably used as a film for simultaneous molding and transfer, for example.

Claims (1)

A polyester film mainly composed of a dicarboxylic acid component, an aliphatic or alicyclic diol component, and a polyalkylene ether glycol component having a number average molecular weight of 300 to 4000, and has a Young's modulus in the vertical and horizontal directions of the film. A polyester film for simultaneous molding transfer, which has a refractive index (nα) of 0.1 to 3.5 GPa and a thickness direction of 1.49 to 1.55.