JP2003011217A - Biaxially stretched polyester film for processing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially stretched polyester film for processing having stretchability and flexbility, excellent in molding processability and also excellent in heat resistance, vapor deposition properties and surface processing characteristics such as printability or the like. SOLUTION: The biaxially stretched polyester film for processing comprises a polyester with a melting point of 245-270 deg.C and satisfies the formula: (Fa+ Fb)/(Sa+Sb)>=150 [wherein, Fa is elongation at break at 25 deg.C in the arbitrary direction of the film, Fb is elongation at break at 25 deg.C in the direction perpendicular to Fa, Sa is a heat shrinkage factor (%) in the same direction as Fa at 150 deg.C for 30 min and Sb is a heat shrinkage factor (%) in the direction perpendicular to Sa at 150 deg.C for 30 min].

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biaxially stretched polyester film for processing, and particularly to heat resistance, moldability,
The present invention relates to a biaxially stretched polyester film for processing which is excellent in vapor deposition property and printability.

[0002]

2. Description of the Related Art Vinyl chloride films and polyolefin films are generally used as films for processing. However, the vinyl chloride film has problems such as deterioration of various properties depending on the plasticizer used, lack of heat resistance and chemical resistance, and generation of toxic gas during incineration after use. In addition, the heat resistance of polyolefin film,
There is a problem in terms of whitening. On the other hand, polyethylene terephthalate (PE, a typical example of polyester film)
T) Biaxially stretched film has good mechanical strength, thermal properties,
Humidity properties, chemical resistance, and many other excellent properties,
It is used in a wide range of fields such as industrial materials, magnetic recording materials, and packaging materials. However, the polyethylene terephthalate (PET) biaxially stretched film is rarely used as a main constituent material because it lacks in elongation and flexibility in molding processing applications. Since the polyester can be suitably used as a processing film if it is imparted with elongation and flexibility, a technique of introducing a copolymerization component is known as a method of imparting molding processing characteristics to the polyester. In addition, unstretched PET or the like is known as a polyester having good processability.

[0003]

However, the method of introducing the copolymerization component into the polyester has a problem that the melting point is lowered and the heat resistance is deteriorated. In addition, unstretched PET,
In so-called A-PET, etc., the elastic modulus and strength are low,
In addition to not being able to exhibit good flatness characteristics like a biaxially stretched film, it was also unsuitable for molding processing requiring high quality because of poor thermal dimensional properties. In view of such a situation, the present invention provides a biaxially stretched polyester film for processing, which has elongation and processability that conventional PET films do not have, and which is excellent in heat resistance, thermal dimensional stability, printability, and the like. With the goal.

[0004]

Means for Solving the Problems A film of the present invention for this purpose comprises a polyester having a melting point of 245 to 270 ° C. and satisfies the following formula (1). You can get more. (Fa + Fb) / (Sa + Sb) ≧ 150 Formula (1) (where Fa is the elongation at break in the arbitrary direction of the film at 25 ° C., Fb is the elongation at break at 25 ° C. in the direction perpendicular to Fa, and Sa is 150. Heat shrinkage (%) in the same direction as Fa at 30 ° C. for 30 minutes, Sb is 150 in the direction perpendicular to Sa
Shows heat shrinkage (%) at 30 ° C for 30 minutes)

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester used in the present invention exhibits good heat resistance, suppresses change in elongation over time, and prevents adhesion to jigs such as molds during molding.
Alternatively, the melting point is required to be 245 to 270 ° C., preferably 250 ° C. to 265 ° C., from the viewpoint of preventing breakage due to insufficient heat resistance when insert-molded.

The polyester used in the present invention is not particularly limited as long as it has a melting point in the above range, but is preferably a polyester having ethylene terephthalate units and / or ethylene naphthalate units as main constituents.
90 mol% or more is preferably ethylene terephthalate units and / or ethylene naphthalate units,
Further, from the viewpoint of imparting high heat resistance and good thermal dimensional stability, that is, low heat shrinkage, it is more preferably 96 mol% or more, and particularly preferably 98 mol% or more. In applications where moldability and heat resistance are important, it is preferable to include a naphthalene dicarboxylic acid component, and the addition amount thereof is preferably 1 to 10 mol% in the dicarboxylic acid, and further 1 to 4 mol% in terms of productivity and the like. preferable.

The polyester used in the present invention may be copolymerized with a dicarboxylic acid component other than terephthalic acid and / or naphthalene dicarboxylic acid, such as isophthalic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethane. Aromatic dicarboxylic acids such as dicarboxylic acid, 5-sodium sulfoisophthalic acid, phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, cyclohexyne dicarboxylic acid Alicyclic dicarboxylic acids such as acids and oxycarboxylic acids such as p-oxybenzoic acid can be used. Further, the polyester used in the present invention may be copolymerized with a glycol component other than ethylene glycol, for example, propanediol, butanediol, pentanediol, hexanediol, neopentyl glycol. And the like, alicyclic glycols such as cyclohexanedimethanol, aromatic glycols such as bisphenol A and bisphenol S, and diethylene glycol can be used. Two or more of these dicarboxylic acid components and glycol components may be used in combination.

In addition, a polyfunctional compound such as trimellitic acid, trimesic acid and trimethylolpropane can be copolymerized with the polyester used in the present invention, as long as the effects of the present invention are not impaired. In the present invention, butanediol, diethylene glycol, polyethylene glycol, cyclohexanedimethanol, sebacic acid, dimer acid, isophthalic acid and the like can be mentioned as the component which is preferably copolymerized in a small amount.

In the present invention, it is necessary to biaxially stretch the polyester in terms of heat resistance and chemical resistance. As a method of biaxial stretching, simultaneous biaxial stretching, sequential biaxial stretching,
Although it may be any of tubular stretching, as a result of diligent examination of the production conditions for the biaxially stretched film, simultaneous biaxial stretching or sequential biaxial stretching in which longitudinal and transverse stretching are performed in order is preferably used.

The biaxially stretched polyester film for processing of the present invention has a ratio of (Fa + Fb) / (Sa + Sb) of 150 from the viewpoint of satisfying both heat resistance, dimensional stability, printability and moldability.
Or more, preferably 200 or more,
Particularly preferably, it is 250 or more. Where Fa is 25 ° C
In the film, the elongation at break in any direction, Fb is the elongation at break at 25 ° C. in the direction perpendicular to Fa, Sa is 150 ° C.,
Heat shrinkage (%) in the same direction as Fa at 30 minutes, and Sb shows heat shrinkage (%) at 150 ° C. and 30 minutes in the direction perpendicular to Sa.

Further, (Fa + Fb) is preferably 350% or more, particularly preferably 380% to 600.
%. Here, the method for controlling the elongation at break within this range is not particularly limited, but the preheating temperature in the longitudinal stretching step is 1 to 1 at a glass transition temperature (Tg) + 30 ° C. to Tg + 70 ° C.
A method for 10 seconds is preferably used.

Further, in order to make the moldability uniform and good in each direction, the absolute value of the difference between Fa and Fb is preferably 0 to 50%, more preferably 0 to 40%.

In the film of the present invention, both Sa and Sb are 1.5 in view of suppressing thermal dimensional change during processing, proper self-tension load, and suppressing pitch deviation during printing.
% Or less, and more preferably -1 to 1%. The method of controlling the heat shrinkage ratio at 150 ° C. as described above is not particularly limited, but for example, a method of performing heat treatment after stretching the film at two or more stages at different temperatures is preferably used. In this case, the difference between the heat treatment temperatures is preferably 20 to 120 ° C.
It is more preferable to include a treatment step of -240 ° C and 120-170 ° C. By the multi-step heat treatment, it is possible to achieve a low heat shrinkability at 150 ° C while maintaining a high breaking elongation at 25 ° C.

The refractive index in the thickness direction of the biaxially stretched polyester film for processing of the present invention is 1.50 from the viewpoint of improving moldability and impact resistance when processed in the thickness direction.
It is preferably 1.54, more preferably 1.5
It is 1 to 1.53.

The film of the present invention has a polyester intrinsic viscosity of 0.5 to 5 in view of heat resistance, productivity and low elution property.
1 dl / g is preferable, more preferably 0.55
It is 0.7 dl / g.

In the biaxially stretched polyester film for processing of the present invention, having a plane orientation coefficient of 0.11 to 0.15 is excellent in moldability, prevention of whitening during bending and prevention of loosening during high temperature molding. From the viewpoint, it is preferably 0.12 to 0.145.

The film of the present invention preferably has a modulus of elasticity at 25 ° C. of 2.5 to 3.5 GPa, particularly preferably 3 to 3 from the viewpoints of conformability during molding, uniform moldability and the like. It is 0.5 GPa.

Next, a method for producing the polyester used in the present invention will be described. When producing the polyester used in the present invention, a reaction catalyst, a color preventive agent can be used, and examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, A cobalt compound, an aluminum compound, an antimony compound, a titanium compound, or the like, and a coloring compound such as a phosphorus compound can be used. Preferably, antimony is used as a polymerization catalyst in any stage before the polymerization of the polyester is usually completed. It is preferable to add a compound, a germanium compound, or a titanium compound. As such a method, for example, when a germanium compound is taken as an example, a method of adding a germanium compound powder as it is, or JP-B-54-2223.
As described in JP-A-4, a method in which a germanium compound is dissolved in a glycol component which is a starting material of polyester and then added can be mentioned. Examples of the germanium compound include germanium dioxide, germanium hydroxide containing water of crystallization, or germanium tetramethoxide, germanium tetraethoxide, germanium tetrabutoxide, germanium alkoxide compounds such as germanium ethylene glycoloxide, germanium phenolate, germanium β- A germanium phenoxide compound such as naphtholate, a phosphorus-containing germanium compound such as germanium phosphate and germanium phosphite, and germanium acetate can be used. Of these, germanium dioxide is preferable. As the antimony compound, for example, antimony oxide such as antimony trioxide, antimony acetate or the like can be used. As the titanium compound, alkyl titanate compounds such as tetraethyl titanate and tetrabutyl titanate are preferably used.

For example, in the case of producing polyethylene terephthalate as the polyester used in the present invention, the case of adding germanium dioxide as the germanium compound will be described in more detail. Transesterify or esterify the terephthalic acid component and ethylene glycol, then add germanium dioxide and phosphorus compound,
Subsequently, polycondensation reaction is carried out at a high temperature under reduced pressure until the content of diethylene glycol becomes constant to obtain a germanium element-containing polymer. Further, preferably, the obtained polymer is subjected to a solid-state polymerization reaction under a reduced pressure or in an inert gas atmosphere at a temperature below its melting point to reduce the content of acetadeldide to obtain a desired intrinsic viscosity and a carboxyl terminal group. Etc. can be mentioned.

The polyester used in the present invention preferably has a diethylene glycol component content of 0.01 to 4% by weight, more preferably 0.01 to 3% by weight, and particularly preferably 0.01 to 2% by weight. is there. Controlling the amount of the diethylene glycol component is desirable from the standpoint of maintaining hygiene and good hygiene even when subjected to heat history after aging or during processing. The timing of addition of diethylene glycol is not particularly limited, but it may be added during the polymerization of polyester, for example. Further, the polyester used in the present invention,
You may add 0.0001 to 1 weight% of antioxidant.

In the biaxially stretched polyester film for processing of the present invention, the content of acetaldehyde in the film is preferably 30 ppm or less, more preferably 25 ppm or less, particularly preferably 20 ppm or less in order to improve hygiene. . The method for controlling the acetaldehyde content in the film to 30 pm or less is not particularly limited, but for example, as a method for removing acetaldehyde generated by thermal decomposition when the polyester is produced by a polycondensation reaction or the like, the polyester is depressurized or inert. In a gas atmosphere, a method of heat-treating at a temperature below the melting point of polyester, preferably a method of solid-phase polymerizing polyester at a temperature below 150 ° C. and below the melting point under reduced pressure or in an inert gas atmosphere, a vacuum vented extruder Method of melt extrusion using, extruding temperature when melt extruding polyester is within melting point of high melting point polyester + 30 ° C, preferably within melting point + 25 ° C, for short time, preferably within 1 hour of average residence time The method and the like are preferably used.

The film of the present invention can be used in either a single layer or a laminate. The thickness of the biaxially stretched film of the present invention can be set to any thickness, but it is 3 to 5 from the viewpoint of followability.
It is preferably 00 μm, more preferably 10
To 200 μm, particularly preferably 30 to 150 μm
Is. When used in lamination, a polymer such as a thermoplastic polymer or a thermosetting polymer may be laminated, and particularly from the viewpoint of adhesiveness and followability, the film of the present invention has a melting point of 180 to 260 ° C on at least one side. Polyester B (described below) is preferably laminated, and particularly has a melting point of 190 to 2
The polyester B of 40 ° C. is preferable from the viewpoint of softening the stiffness of the film (stiffness) and adhesiveness. Here, as the polyester B to be laminated, for example, high-molecular-weight polyethylene terephthalate, isophthalic acid copolymerized polyethylene terephthalate, butanediol, copolymerized polyethylene terephthalate having an isophthalic acid residue skeleton, and polyester to which diethylene glycol is further added or copolymerized are preferable. Can be used. The layered structure may be a two-layered structure in which the B layer is laminated on one side, a three-layered structure in which both layers are laminated, or a three- or more-layered structure in which the polyester C or the like is laminated in addition to the polyester B. Here, the laminated thickness of the polyester B layer is preferably 1 to 30 μm in total of only the polyester B layer from the viewpoint of adhesiveness and the like,
More preferably, it is 2 to 20 μm.

As the method for producing the biaxially stretched film in the present invention, for example, each polyester is dried if necessary, then fed to a known melt extruder, extruded into a sheet form from a slit die, and electrostatically applied. And the like, and then adhered to the casting drum to be cooled and solidified to obtain an unstretched sheet. The unstretched sheet is stretched in the longitudinal direction and the width direction of the film and heat-treated to obtain a target biaxially stretched film. The stretching method may be either simultaneous biaxial or sequential biaxial stretching, but a tenter method is preferable in terms of the quality of the film, and after stretching in the longitudinal direction, a sequential biaxial stretching method of stretching in the width direction, longitudinal A simultaneous biaxial stretching method in which stretching in the machine direction and the width direction is performed almost simultaneously is preferably used.
The stretching ratio is 1.5 to 4.0 times, preferably 1.8 to 4.0 times in each of the longitudinal direction and the width direction. Either the stretching ratio in the longitudinal direction or the stretching ratio in the width direction may be increased or may be the same. The stretching speed is 1000
% / Min to 200,000% / min. The stretching temperature may be any temperature as long as it is not less than the glass transition temperature of the polyester and not more than the glass transition temperature + 80 ° C., but is usually preferably 80 to 150 ° C. . The film is heat-treated after the biaxial stretching, and this heat treatment can be performed by any conventionally known method such as in an oven or on a heated roll. Heat treatment temperature is 120 ° C or higher and 245 ° C
The temperature can be any of the following, but preferably 1
20-240 degreeC. The heat treatment time may be arbitrary, but it is usually preferably 1 to 60 seconds. The heat treatment may be performed while relaxing the film in its longitudinal direction and / or width direction. Furthermore, re-stretching may be performed once or more in each direction, and then heat treatment may be performed.

The film of the present invention contains internal particles having an average particle diameter of 0.01 to 5 μm and external particles such as inorganic particles and / or organic particles in order to achieve both handling and processability of the film and surface haze. It is preferable that the particles arbitrarily selected from the above are contained in an amount of 0.01 to 10% by weight. In particular, it is preferable that 0.01 to 0.2% by weight of internal particles having an average particle diameter of 0.1 to 5 μm, inorganic particles and / or organic particles are contained. The use of particles having an average particle size of more than 5 μm tends to cause film defects. Here, as a method of depositing the internal particles, for example, JP-A-48-61556 and JP-A-51-1286 are available.
0, JP-A-53-41355, JP-A-54
The technique described in Japanese Patent Publication No. 90397 or the like can be used. Further, it can be used in combination with other particles described in JP-A-55-20496 and JP-A-59-204617. Examples of the inorganic particles and / or organic particles include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay and the like, and styrene.
Examples thereof include organic particles containing silicon, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituent components. Of these, inorganic particles such as wet and dry colloidal silica and alumina, and organic particles including styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like are preferably used. Two or more kinds of these internal particles, inorganic particles and / or organic particles may be used in combination. From the viewpoint of controlling the surface haze, spherical particles are preferable, and silica and alumina are particularly preferable.

Improving the adhesiveness by subjecting the film of the present invention to a surface treatment such as corona discharge treatment
It is preferable in that it improves the film characteristics. Preferably 5~50W · min / m ² as a processing intensity of the corona discharge, more preferably 10~45W · min / m ^2.

The polyester film of the present invention contains additives such as an antistatic agent, a heat stabilizer, an antioxidant, a crystal nucleating agent, a weathering agent, an ultraviolet absorber, a pigment and a dye, which does not impair the purpose of the present invention. It can be added in a range. If necessary, surface irregularity processing such as embossing or sand matting, or surface treatment such as plasma treatment or alkali treatment may be performed. Furthermore, the film of the present invention may be provided with an easily adhesive treating agent, an antistatic agent, a water vapor / gas barrier agent (such as polyvinylidene chloride), a release agent, an adhesive, an adhesive, a flame retardant, an ultraviolet absorber, a matting agent, and a pigment. , Dyes, etc. may be added and / or coated and / or printed.

The film of the present invention may be vacuum-deposited with a metal such as aluminum, aluminum oxide, silicon oxide or palladium or a compound thereof for the purpose of light shielding, water vapor / gas barrier, surface conductivity, infrared reflection and the like.

The biaxially stretched polyester film for processing of the present invention is used for processing applications. The processing method is not particularly limited, and examples thereof include surface processing of the above-mentioned film, embossing, and molding processing such as sand matting.

[Measurement of Physical Properties and Properties, Evaluation Method]
Each physical property used in the present invention, the measurement of the characteristics, and the evaluation method will be described.

(1) Melting point (Tm), glass transition temperature (T
g) Measurement was performed using a differential scanning calorimeter DSC2 (manufactured by Perkin Elmer). 28 mg of 10 mg sample under nitrogen stream
It was kept melted at 0 ° C. for 5 minutes, and then quenched 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 was read, and this temperature was taken as the glass transition temperature (Tg), and the endothermic peak due to crystal melting The temperature was taken as the melting point (Tm).

(2) Elastic Modulus For the elastic modulus, ASTM-D-882-81 (method A)
The average value in the longitudinal direction and the width direction was calculated.

(3) Elongation The elongation was measured according to ASTM-D-882-81 (method A).

(4) Heat Shrinkage The film sample is set to 200 mm between the marked lines, the film is cut to a width of 10 mm, the film sample is hung in the length direction, a load of 1 g is applied in the length direction, and hot air at 150 ° C. is applied. After heating for 30 minutes using, measure the length between the marked lines,
The amount of shrinkage of the film was expressed as a percentage as a ratio to the original size.

(5) Refractive Index The refractive index (Nz) in the thickness direction was measured using an Abbe refractometer with sodium D ray as a light source.

(6) Molding processability The mold was heated to 150 ° C. and then pushed into the film, and the drawing ratio was reduced to 0.
Molding was carried out in No. 6 and judged as follows. Grade B and above are acceptable. Grade A: Uniformly molded, and the molded body has no slack. Class B: There is a part with uneven thickness, but it is molded uniformly as a whole, and there is no slack after molding. Class C: Clearly non-uniform molding, and surface roughness is observed.

(7) Printing workability Transfer in-mold molding was performed with a height of 25 mm, a width of 200 mm and a length of 180 mm, and the following judgment was made. Grade B and above are acceptable. Grade A: The printed surface is clear and good with no spots. Class B: There are some printing spots but there is no problem. Class C: Rupture is recognized, printing spots are remarkable, and it cannot be used practically.

(8) Vacuum Formability After the film of the present invention and a polystyrene sheet having a thickness of 1.5 mm were laminated by dry lamination, plug-assisted vacuum forming was performed in a cup shape at 150 ° C. with a drawing ratio of 0.5. It was judged as follows. Grade B and above are acceptable. Class A: Formed uniformly, followed by corner formation. Class B: Some parts have uneven thickness, but they are formed uniformly as a whole. Class C: Molding is impossible or apparently non-uniform molding.

[0038]

The present invention will be described below with reference to examples.

Example 1 One chip of polyethylene terephthalate (antimony catalyst, intrinsic viscosity 0.64) containing 0.05% by weight of silica particles having an average particle size of 0.4 μm as polyester was used.
It was vacuum dried at 80 ° C. for 3 hours, supplied to a single-screw extruder, discharged from a normal die, and then cooled and solidified by a mirror-cooling drum while applying static electricity (7 kv) to obtain an unstretched film. This unstretched film is Tg + 4 with a non-adhesive silicone roll.
After preheating at 0 ° C. for 4 seconds, the roll was stretched at a stretching temperature of 105 ° C. for a total of 3.4 times in the longitudinal direction, then cooled to 25 ° C., and further preheated at a temperature of 95 ° C. for 4 seconds and then at 120 ° C. 3.2 times multi-stage stretching, then after treatment at 130 ℃ for 2 seconds,
The film was heat-treated at 238 ° C. in the width direction for 5% for 5 seconds to give a biaxially stretched polyester film having a thickness of 45 μm. The obtained film showed excellent properties as shown in Table 1.

Example 2 Polyethylene terephthalate (antimony catalyst, intrinsic viscosity 0.64) containing 0.012% by weight of spherical silica particles having an average particle diameter of 0.8 μm as polyester and polybutylene terephthalate (titanium catalyst, intrinsic viscosity 0) .9)
Blended in a ratio of 97/3% by weight to obtain 150
After vacuum drying at 5 ° C. for 5 hours, it was supplied to a single-screw extruder, discharged from an ordinary die, and then cooled and solidified by a mirror cooling drum while applying electrostatic (7 kv) to obtain an unstretched film. This unstretched film is Tg + 40 ° C with a non-adhesive silicone roll
After preheating for 3 seconds, the rolls are simultaneously biaxially stretched at a stretching temperature of 110 ° C. in the longitudinal and width directions by 3.2 times, and relaxed at 232 ° C. in both the longitudinal direction and the width direction at 4% and 155 ° C. at 1%.
% For 3 seconds each to obtain a biaxially stretched polyester film having a thickness of 45 μm. The films obtained are shown in Table 1.
As shown in, excellent properties were exhibited.

Example 3 A polyethylene terephthalate (amorphous germanium catalyst, intrinsic viscosity 0.67) chip containing 0.012% by weight of silica particles having an average particle size of 1.5 μm as polyester was vacuum dried at 180 ° C. for 3 hours. Supplied to a single-screw extruder,
After being discharged from a normal die, an unstretched film was obtained by cooling and solidifying with a mirror cooling drum while applying static electricity (8 kv).
Tg of this unstretched film with a non-adhesive silicone roll
After preheating at + 40 ° C for 7 seconds, the silicone roll stretches 3.1 times in the longitudinal direction at a stretching temperature of 100 ° C, cools to 50 ° C, preheats at 95 ° C for 5 seconds, and then at 120 ° C in the width direction.
After stretching 9 times in multiple stages, relax in the width direction at 235 ° C 4
% For 5 seconds to obtain a biaxially stretched polyester film having a thickness of 45 μm. The obtained film showed excellent properties as shown in Table 1.

EXAMPLE 4 Polyethylene terephthalate (antimony catalyst, intrinsic viscosity 0.64) and polypropylene terephthalate (titanium-based catalyst, intrinsic viscosity 0. 4) containing 0.012% by weight of spherical silica particles having an average particle diameter of 0.8 μm as polyester.
Blend the chips of 9) at a ratio of 97/3% by weight, and
After vacuum drying at 50 ° C. for 5 hours, it was supplied to a single-screw extruder, discharged from a normal die, and then cooled and solidified with a mirror cooling drum while applying electrostatic (7 kv) to obtain an unstretched film. This unstretched film is preheated with a non-adhesive silicone roll Tg
After preheating at + 40 ° C. for 5 seconds, the silicone roll was simultaneously biaxially stretched at a stretching temperature of 110 ° C. in the longitudinal and width directions by 3.2 times, and relaxed at 229 ° C. in both the longitudinal direction and the width direction.
%, 1% at 155 ° C. for 3 seconds each to obtain a biaxially stretched polyester film having a thickness of 45 μm. The obtained film showed excellent properties as shown in Table 1.

Comparative Example 1 One chip of polyethylene terephthalate (antimony catalyst, intrinsic viscosity 0.59) having 0.03% by weight of agglomerated silica particles having an average particle size of 1.5 μm as polyester was used.
It was vacuum dried at 80 ° C. for 3 hours, supplied to a single-screw extruder, discharged from a normal die, and then cooled and solidified by a mirror-cooling drum while applying static electricity (7 kv) to obtain an unstretched film. This unstretched film is Tg +
After preheating at 10 ° C for 3 seconds, stretch temperature 9 with a ceramic roll
It was stretched 3.7 times in the longitudinal direction at 0 ° C., cooled to 60 ° C., preheated at 95 ° C. for 5 seconds, then stretched at 110 ° C. in the width direction 3.7 times, and then at 200 ° C. in the width direction. Relax 4
% For 5 seconds to obtain a biaxially stretched polyester film having a thickness of 45 μm. (Fa + Fb) / (Sa +
The comparative example in which the value of Sb) was outside the range of the present invention was inferior in workability and moldability.

Comparative Example 2 17 mol of isophthalic acid copolymerized polyethylene terephthalate (antimony catalyst, containing 0.1% by weight of calcium carbonate particles having an average particle diameter of 1.5 μm as polyester)
Chips with an intrinsic viscosity of 0.62) were vacuum dried at 150 ° C for 3 hours, supplied to a single-screw extruder, discharged from a normal die, and then cooled and solidified by a mirror-cooling drum while applying static electricity (7 kv). A stretched film was obtained. This unstretched film is Tg +
After preheating at 15 ° C for 3 seconds, a polytetrafluoroethylene roll was stretched at a stretching temperature of 95 ° C in the longitudinal direction by 3.6 times,
After cooling to 50 ° C, preheating at 96 ° C for 3 seconds, and then stretching 3.4 times in the width direction at 115 ° C, relaxing at 190 ° C in the width direction for 5% for 5 seconds, and biaxially stretching the thickness. 38
A polyester film of μm was obtained. The comparative example in which the melting point of the polyester was low and the value of (Fa + Fb) / (Sa + Sb) was outside the range of the present invention was inferior in processability and moldability.

[0045]

[Table 1]

[0046]

EFFECTS OF THE INVENTION According to the present invention, there are two types of processing materials, which have excellent elongation and flexibility and molding processability, which are not found in conventional PET films, and also have excellent surface processing characteristics such as heat resistance, vapor deposition property and printability. An axially stretched polyester film can be provided.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F071 AA45 AA46 AA84 AF21Y                       AF31Y AF61Y BB08 BC01                       BC10                 4F210 AA24 AG01 QA02 QA03 QC06                       QC14 QG01 QG18

Claims (4)

[Claims] 1. A biaxially stretched polyester film for processing, comprising a polyester having a melting point of 245 to 270 ° C. and satisfying the following formula (1). (Fa + Fb) / (Sa + Sb) ≧ 150 Equation (1) (where Fa is the elongation at break at 25 ° C. in any direction of the film, Fb is the elongation at break at 25 ° C. in the direction perpendicular to Fa, and Sa is 150. Heat shrinkage (%) in the same direction as Fa at 30 ° C. for 30 minutes, Sb is 150 in the direction perpendicular to Sa
Shows heat shrinkage (%) at 30 ° C for 30 minutes) 2. 90% by mole or more of the constituent units of the polyester are ethylene terephthalate units and / or ethylene naphthalate units.
The biaxially stretched polyester film for processing described in 1. 3. The refractive index in the film thickness direction is 1.50.
It is 1.54, The biaxially stretched polyester film for processing in any one of Claims 1-2. 4. The biaxially stretched polyester film for processing according to claim 1, wherein both Sa and Sb are 1.5% or less.