JP2002120280A - Biaxially stretched polyester film for molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially stretched polyester film for molding showing excellent environmental resistance, transparency, printability, moldability and beautifulness. SOLUTION: A biaxially stretched polyester film for molding has an ethyleneterephthalate unit and/or an ethylenenaphthalate unit as a major component wherein the polyester film shows a melting point of not lower than 245 deg.C and has a face orientation coefficient (fn), a heat shrinkage SrMD(%)} in the lengthwise direction at 190 deg.C and a heat shrinkage SrTD(%)} in the widthwise direction at 190 deg.C each within a specific range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to metal, wood, paper,
The present invention relates to a polyester film suitably used as a processing sheet to be adhered to a surface of an article (a molded article) made of a resin or the like. More specifically, the present invention relates to a biaxially oriented polyester film for molding suitable as a surface material for furniture, building materials (such as wall materials), home appliances, home appliances, and electronic devices, and as a printing substrate.

[0002]

2. Description of the Related Art As a conventional sheet for processing, a polyvinyl chloride film is typical and has been preferably used because of its excellent workability. On the other hand, a polyvinyl chloride film has problems such as generation of toxic gas when the film is burned due to a fire or the like, and bleed-out of a plasticizer, and new materials have been demanded in recent years due to the need for environmental resistance.

[0003] In order to solve these requirements, a method using a transparent polyester film is effective. However, in the case of a conventional polyester film, the heat resistance is good, but the elongation required for the forming process is insufficient, so that the forming process is insufficient. It is not suitable for processing applications and has been desired to be improved.

In Japanese Patent Publication No. 6-4276, for example, a membrane switch film using a polyethylene naphthalate film has been proposed, and a film having good dimensional stability has been obtained. However, these techniques have insufficient molding workability, and are not suitable for a switch having a so-called click feeling that requires a pressing depth.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the problems of the prior art and not only to improve the environmental performance but also to improve the moldability such as in-mold molding and emboss molding. An object of the present invention is to provide a biaxially oriented polyester film for molding which is excellent and has excellent dimensional stability at high temperatures.

[0006]

The object of the present invention is to provide a polyester film comprising a polyester having an ethylene terephthalate unit and / or an ethylene naphthalate unit as a main component, wherein the polyester film has a melting point of 245 ° C. or more, Plane orientation coefficient (fn), heat shrinkage at 190 ° C in the longitudinal direction of film {SrMD (%)},
And a biaxially stretched polyester film for molding having a 190 ° C. heat shrinkage {SrTD (%)} in the width direction that simultaneously satisfies the following formulas I to III. 0.02 ≦ fn ≦ 0.15 Formula I 0 ≦ SrMD ≦ 3 Formula II 0 ≦ SrTD ≦ 3 Formula III

The biaxially oriented polyester film for molding of the present invention preferably satisfies the following conditions. (A) Stress at 100% elongation in the film longitudinal direction at 25 ° C. {F100MD (MPa)}, 100% in the film width direction
The stress at extension {F100TD (MPa)} and the film thickness {d (μm)} simultaneously satisfy the following formulas IV to VII. F100MD ≦ 150 Formula IV F100TD ≦ 150 Formula V 6000 ≦ F100MD × d ≦ 25000 Formula VI 6000 ≦ F100TD × d ≦ 25000 Formula VII

(B) The breaking elongation in the longitudinal direction of the film and the breaking elongation in the width direction of the film at 25 ° C. are both 170%.
That is all. (C) Heat set temperature (Tmeta) is 180 to 240 ° C
That.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail.

[0010] The polyester in the present invention is a generic term for a high molecular weight compound constituted by an ester bond.

As the dicarboxylic acid component used for the ester bond, for example, terephthalic acid, isophthalic acid,
Naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfondicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfoisophthalic acid, aromatic dicarboxylic acids such as phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, Aliphatic dicarboxylic acids such as maleic acid and fumaric acid, alicyclic dicarboxylic acids such as cyclohexyne dicarboxylic acid, and oxycarboxylic acids such as p-oxybenzoic acid can be used. Among them, in the polyester of the present invention, the ratio of terephthalic acid and naphthalenedicarboxylic acid is preferably 95 mol% or more from the viewpoint of heat resistance and productivity.

On the other hand, as the glycol component, for example, ethylene glycol, propanediol, butanediol,
Aliphatic glycols such as pentanediol, hexanediol and neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, aromatic glycols such as bisphenol A and bisphenol S, and diethylene glycol can be used. In addition, two or more of these dicarboxylic acid components and glycol components may be used in combination.

Further, as long as the effects of the present invention are not impaired, those obtained by copolymerizing a polyfunctional compound such as trimellitic acid, trimesic acid, and trimethylolpropane with a copolymerized polyester can be used.

It is preferable to use a blend of two or more of the above polymers in order to improve processability. Among them, a polyester containing a polyethylene terephthalate unit and / or an ethylene naphthalate unit as a main component is particularly preferable from the viewpoint of heat resistance and workability.

The melting point of the polyester film in the present invention is preferably 245 ° C. or more, more preferably 245 ° -270 ° C., and particularly preferably 248 ° C.-270 ° C. from the viewpoint of heat resistance and workability. In particular, when the melting point is less than the above range, heat resistance is inferior, so that when exposed to a high temperature in a processing step or during use, a problem may occur, which is not preferable. Here, the melting point of the polyester film is defined as the primary temperature rise (1st temperature) of the so-called differential scanning calorimetry (DSC).
Run) is the endothermic peak temperature at the time of polymer melting detected during Run).

The polyester film of the present invention is desirably biaxially stretched from the viewpoint of heat resistance, dimensional stability, scratch resistance and stain resistance. Such a biaxial stretching method may be any of simultaneous biaxial stretching and sequential biaxial stretching. At this time, simultaneous biaxial stretching is particularly preferable from the viewpoint of suppressing uneven thickness.

The polyester film of the present invention can be prepared by using different kinds of polyesters, for example, as disclosed in JP-A-9-245.
No. 88, it can be a laminated structure. The form of the laminated film is not particularly limited, and examples thereof include A / B, B / A / B, and C / A / B lamination.

The total thickness of the biaxially stretched polyester film for molding of the present invention is preferably from 10 to 500 μm from the viewpoints of moldability, coatability to a substrate, protection of the surface of the substrate, and design. It is preferably from 20 to 300 μm, particularly preferably from 20 to 200 μm.

In the present invention, from the viewpoint of improving moldability, printability, aesthetics, and dimensional stability, the plane orientation coefficient (f
n), heat shrinkage at 190 ° C. in the longitudinal direction of the film ｛SrMD
(%)｝ And heat shrinkage at 190 ° C in the width direction ｛SrTD
(%)｝ Must simultaneously satisfy the following formulas I to III.

0.02 ≦ fn ≦ 0.15 Formula I 0 ≦ SrMD ≦ 3 Formula II 0 ≦ SrTD ≦ 3 Formula III In Formula I, the plane orientation coefficient is considered from the viewpoint of moldability. The range of (fn) is preferably 0.05 to 0.15, particularly preferably 0.10 to 0.15. The plane orientation coefficient (fn) is calculated from the following equation based on the refractive index in the longitudinal direction (Nx), the refractive index in the width direction (Ny), and the refractive index in the thickness direction (Nz) of a film measured using an Abbe refractometer or the like. Value.

Fn = (Nx + Ny) / 2-Nz If the longitudinal direction and the width direction of the film are not clear at this time, the refractive index in the direction of the principal axis of the orientation, the direction perpendicular to the direction of the principal axis of the orientation, and the thickness direction are respectively determined. Nx, Ny, N
The plane orientation coefficient can be obtained as z.

In the formulas II and III, the heat shrinkage at 190 ° C. (SrMD) in the longitudinal direction of the film, and
The range of 0 ° C. heat shrinkage (SrTD) is preferably from 0 to 2
%, Particularly preferably 0 to 1%. Outside the above range, problems such as deformation of the printed pattern after molding occur, which is not preferable in terms of dimensional stability.

In the biaxially oriented polyester film for molding of the present invention, from the viewpoint of moldability, the stress at 25 ° C. at the time of 100% elongation in the longitudinal direction of the film {F100MD (MPa)} and the stress at the time of 100% elongation in the film width direction. ｛F100TD (MP
a) and the film thickness {d (μm)} are represented by the following formula IV
It is preferable to satisfy the following conditions at the same time. F100MD ≦ 150 Formula IV F100TD ≦ 150 Formula V 6000 ≦ F100MD × d ≦ 25000 Formula VI 6000 ≦ F100TD × d ≦ 25000 Formula VII

More preferably, F100MD of formula IV, formula V
Has a F100TD of 140 MPa or less, particularly preferably 130 MPa or less. Also more preferably, the formula
F100MD × d of VI and F100MD × d of formula VII are 7000 to
20,000, particularly preferably 8,000 to 1,
It is in the range of 8000.

From the viewpoint of moldability, the elongation at break in the longitudinal direction and the elongation in the width direction at 25 ° C. are preferably 170% or more, more preferably 200% or more.
It is particularly preferably at least 250%. Elongation at break 170
%, It is not preferable because molding tends to cause insufficient molding due to insufficient elongation and peeling of the film.

Further, the heat setting temperature (T
meta) is preferably in the range of 180 to 240 ° C. Particularly preferably, it is 200 to 240 ° C. If the heat setting temperature is lower than the above range, the dimensional stability tends to deteriorate, and if the heat setting temperature is higher than the above range, the film is likely to be broken, which is not preferable from the viewpoint of productivity. Heat set temperature (Tme
ta) is an endothermic melting curve detected at the time of the first heating (1st Run) of the differential scanning calorimeter measurement method (DSC),
This is the temperature of the sub-endothermic peak existing near the peak temperature (melting point) due to the heat treatment.

The thickness unevenness of the film is preferably 15
%, Particularly preferably 10%,
It is preferable from the viewpoint of workability and the like.

The film of the present invention has a surface wetting tension of 50 from the viewpoints of printability, processability, adhesion and the like on the film.
It is preferably at least mN / m, more preferably at least 56 mN / m.

A film having a wet surface tension of 50 mN / m or more can be achieved by performing an appropriate surface treatment, for example, a corona discharge treatment, a plasma treatment, a flame treatment, or the like.
It can be achieved by a surface treatment such as an ultraviolet irradiation treatment, an electron beam irradiation treatment, a chemical treatment, a physical roughening treatment, and a surface coating treatment, but any surface treatment can be achieved as long as the effects of the present invention are not impaired. Is not particularly limited. Among them, corona discharge treatment is preferable because it is a simple and effective method.

The film of the present invention may be coated with various coatings.
There is no particular limitation as long as the effects of the present invention are not impaired.

In the present invention, from the viewpoint of beauty after printing, the 60-degree specular gloss of the film is preferably 60% or more,
Particularly preferably, it is 90% or more.

The film of the present invention has a carboxyl terminal group content of preferably 20 to 60 equivalents / ton, more preferably 30 to 50 equivalents / ton, from the viewpoint of improving the adhesiveness and processability between the film and the substrate. Is better.

In the present invention, the intrinsic viscosity of the polyester is preferably 0.50 dl / g or more, more preferably 0.55 d / g, in order to further improve the adhesive property and the stability of film formation.
Those having a l / g or more, particularly preferably 0.60 dl / g or more, are used. If the intrinsic viscosity is less than 0.50 dl / g, the adhesiveness is undesirably reduced.

The catalyst for producing the polyester used in the present invention is not particularly limited, but may be an alkaline earth metal compound, a manganese compound, a cobalt compound, an aluminum compound, an antimony compound, a titanium compound, a titanium compound.
Silicon composite oxides, germanium compounds and the like can be used. Among them, titanium compounds, titanium / silicon composite oxides,
Germanium compounds are preferred for optimizing catalytic activity, taste characteristics, and the amount of the catalytic metal.

For example, when a titanium / silicon catalyst is added as a catalyst in a polymerization process for producing a polyester, a terephthalic acid component and an ethylene glycol component are reacted, and then a titanium / silicon composite oxide and a phosphorus compound are added. Then, a method in which a polycondensation reaction is continuously performed at a high temperature under reduced pressure until the content of diethylene glycol reaches a certain value to obtain a polyester having a specific catalytic metal content and a specific phosphorus content is preferably employed.

The phosphorus compound added as a heat stabilizer is not particularly limited, but phosphoric acid, phosphorous acid and the like are preferable.

The polyester film of the present invention can be used to improve the aesthetics, weather resistance and discoloration resistance of a printed product to an extremely high level. It is preferable that the relationship of the residual amount (P: unit mmol%) satisfies the following expression. 0.3 ≦ M / P ≦
5 Further, when the value of M / P is 3 or less, both the productivity and the thermal stability of the film are improved, which is particularly preferable.

The method for producing the polyester film of the present invention is not particularly limited. For example, after drying the polyester as required, it is supplied to a known melt extruder and extruded from a slit die into a sheet. This is a method in which the unstretched sheet is stretched after being brought into close contact with the casting drum by a method such as electrostatic application, cooled and solidified to obtain an unstretched sheet. Such a stretching method may be any of simultaneous biaxial stretching and sequential biaxial stretching. In short, the unstretched sheet is stretched in the longitudinal direction and the width direction of the film, and heat-treated to obtain a film having a desired plane orientation degree. The method is adopted. Among these methods, preferably, in terms of film quality, a tenter method is preferable, and after stretching in the longitudinal direction, a sequential biaxial stretching method of stretching in the width direction, after stretching in the width direction, in the longitudinal direction. A sequential biaxial stretching method in which stretching is performed, or a simultaneous biaxial stretching method in which stretching is performed substantially simultaneously in the longitudinal direction and the width direction is desirable.

The stretching ratio of the biaxial stretching is 1.6 to 4.2 times, preferably 1.7 to 4.2 times in each direction.
It is 4.0 times. In this case, the stretching ratio in the longitudinal direction or the width direction may be increased, and may be the same. The stretching speed is desirably 1000% / min to 200,000% / min, and the stretching temperature can be any temperature as long as it is equal to or higher than the glass transition temperature of the polyester and equal to or lower than [glass transition temperature + 100 ° C.]. , Preferably 80
Stretching is preferably performed at a temperature in the range of 170 to 170C. Further, the film is subjected to a heat treatment after the biaxial stretching, and this heat treatment can be carried out by any conventionally known method such as in an oven or on a heated roll. Heat treatment temperature is 120
The temperature can be set to an arbitrary temperature of not lower than 245 ° C. and preferably from 120 to 240 ° C. Further, the heat treatment time can be arbitrarily set, but is preferably 1 to 60 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction. Further, re-stretching may be performed once or more in each direction, and then heat treatment may be performed.

The polyester has an average particle size of 0.0
Particles arbitrarily selected from known internal particles of 1 to 10 μm, external particles such as inorganic particles and / or organic particles can be contained. Here, the average particle diameter is 10
Use of particles having a particle size exceeding μm tends to cause defects in the film, which is not preferable in terms of transparency and design. Examples of such particles include inorganic particles such as wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay, and hydroxyapatite, and styrene, silicone, and acrylic acids. And the like. Organic particles containing as a constituent component can be used. Of these, inorganic particles such as dry, wet and dry colloidal silica and alumina, and organic particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituents are preferably used. Two or more of these internal particles, inorganic particles and / or organic particles may be used in combination as long as the properties are not impaired.

Further, the addition amount of these particles is preferably in the range of 0.01% by weight to 50% by weight. 0.01
If it is less than 10% by weight, film winding becomes difficult, which is not preferable in handling. On the other hand, if it exceeds 50% by weight, it is not preferable because it causes coarse projections and deterioration of transparency and film forming property.

The biaxially stretched polyester film for molding of the present invention is used as a film that is in close contact with a material such as a resin when the material is molded, that is, used as a film for molding. For this molding, for example, applications such as metal, wood, paper, resin and other materials that are in close contact with each other, or applications that are placed in a mold during injection molding and bonded to the surface during injection molding Specific examples include those for injection molding and transfer in-mold molding.

In some cases, a film molded together with a material such as a resin is commercialized while being adhered to the surface of a molded product made of a resin or the like, and a film is used as a release material or a transfer material. It may be peeled off before being commercialized. In the latter case, for example, after laminating the material on the printing surface side of the film printed with ink and integrally molding, curing the ink by UV irradiation or the like and transferring the print to the material molded product side, There is a method of peeling the film to obtain a product. As the transfer in-mold molding, for example, a resin is poured onto a sheet processed into a film / release layer / top layer (hard coat layer) / printing layer / adhesive layer, and the sheet is closely adhered. A method of producing a printed molded article by simultaneously performing printing and member molding by peeling the film / release layer after the article is produced.

Similarly, it is also suitable for molding applications such as injection mold decoration. Here, as a resin used for transfer in-mold or injection mold decoration, a resin such as ABS, acrylic, or polycarbonate is preferably used because of good adhesion and adhesion to a film.

In the case of producing a molded article having a pattern layer or a colored layer (referred to as a printed layer) provided on the surface by printing or the like, the printed layer is formed on the molded article side and then a film is laminated. Alternatively, they may be bonded after forming a printing layer on the film side. The bonding may be heat bonding or bonding via an adhesive.

Examples of the adhesive used here include a urea resin adhesive, a melamine resin adhesive, a phenol resin adhesive, an α-olefin resin adhesive, a polyester adhesive, and a mixture of an aqueous polymer and an isocyanate. Adhesive, epoxy adhesive, solution type vinyl acetate resin adhesive, emulsion type vinyl acetate resin adhesive, acrylic emulsion adhesive, hot melt adhesive, cyanoacrylate adhesive, polyurethane adhesive, chloroprene Rubber adhesive, nitrile rubber adhesive, SBR
Adhesives, modified rubber emulsion adhesives, ethylene copolymer resin adhesives, resorcinol adhesives, natural rubber adhesives, cellulose adhesives, starch pastes, dextrins and the like.

The biaxially stretched polyester film for molding of the present invention can be used for molding after performing various surface treatments such as embossing and printing. For example, after printing on a film, it is bonded to a steel plate and bent. It can be suitably used as a transparent surface material for furniture, building materials (such as wall materials), home appliances, home electric appliances, and electronic appliances, and as a printing substrate, by performing molding according to the purpose such as compression.

[0048]

EXAMPLES Next, the effects of the present invention will be described with reference to examples, but the present invention is not limited to these examples. First, a method for measuring and evaluating a characteristic value will be described below.

[Method of Measuring and Evaluating Characteristic Value] The characteristic value in the present invention is determined by the following measuring method.

(1) Melting point (Tm), heat setting temperature (Tmeta) Differential scanning calorimeter DS manufactured by Seiko Instrument Inc.
Using type CII, 5 mg of sample was heated from room temperature at a rate of 10 ° C /
The peak temperature of the endothermic melting curve when the temperature was raised in minutes was defined as the melting point (Tm). The sub-endothermic peak temperature caused by the heat treatment was defined as a heat set temperature (Tmeta).

(2) Intrinsic viscosity Polyester is dissolved in orthochlorophenol,
Measured in ° C.

(3) Plane Orientation Coefficient (fn) Using a Abbe refractometer manufactured by Atago Co., Ltd., the refractive index of the film was measured using a sodium D line (wavelength: 589 nm) as a light source. Refractive index nγ in the longitudinal direction in the film plane,
The refractive index nβ in the horizontal direction and the refractive index nα in the thickness direction, which are perpendicular thereto, were determined, and the plane orientation coefficient (fn) was determined by the following equation: fn = (nγ + nβ) / nα.

(4) Heat Shrinkage Ratio (Sr) A sample having a distance between marker lines of 200 mm in the film longitudinal direction (MD) and a sample having a marker line distance of 200 mm in the film width direction (TD) were prepared. Each was cut into elongated film samples 10 m wide. The film sample was hung in its length direction, a load of 1 g was applied in the length direction, and
After heating using hot air at 30 ° C. for 30 minutes, the length between the marked lines was measured, and the shrinkage of the film was determined as a percentage (%) of the original size. When the film is stretched, it is indicated by minus (-), and the heat shrinkage in the MD direction is SrMD,
The heat shrinkage in the TD direction was defined as SrTD.

(5) Stress at 100% elongation and elongation at break A sample having a length of 150 mm and a width of 10 mm (sample length direction is the film length direction or width direction) is cut out from the biaxially stretched film, and this sample is orientec Using a tensile tester, initial length 50 mm, tensile speed 300 mm / min, 25 ° C
Was measured under the following conditions. From the obtained load-strain curve, 1
The stress at 00% elongation and the elongation at break were determined.

(6) Dimensional stability Judgment was made from the above (4) values of heat shrinkage in the MD and TD directions at 190 ° C. for 30 minutes according to the following criteria (O, Δ:
Pass, ×: fail, the same applies to the following evaluations). ：: SrMD, SrTD, both values ± 2% or less. Δ: Any of SrMD and SrTD is -2% ≦ SrMD ≦ 2%,
-2% ≦ SrTD ≦ 2%. ×: Any of SrMD and SrTD exceeds ± 3%.

(7) Printability After the film was heat-treated at 100 ° C. for 30 minutes, four-color silk printing was performed. After printing of each color, drying was performed at 80 ° C. × 30 minutes. Based on the printing accuracy and sharpness at this time, printability was determined based on the following criteria. ：: Vivid, no print misregistration of each color observed at visual level. Δ: At a level where the eyes were brought close to a distance of about 20 cm and visually observed, slight printing deviations and the like were observed.
The appearance is generally good at a level observed at a distance of not less than cm. ×: Printing deviation in each color is observed, and unevenness is observed in printing, and the appearance is extremely poor.

(8) Formability After printing on one side of the film, the film was subjected to 245 ° C.
The heated ABS resin was poured into the mold (injection molding) to prepare a key top having a height of 2 mm and a surface covered with a film. At this time, the molded state of the film was visually observed, and a judgment was made based on the following criteria. ：: The appearance is extremely good. Δ: Some wrinkles can be observed, but at a level that does not cause any practical problem. X: Breaking is observed in the film. Alternatively, large wrinkles occur and the appearance is remarkably poor.

(9) Comprehensive evaluation Regarding the dimensional stability, printability and moldability, the practicality of the film as a molding film was evaluated as follows: ○: excellent, slightly poor: Δ,
Poor was evaluated as x.

Next, the effects of the present invention will be described with reference to examples.

Example 1 As a polymerization catalyst, a magnesium compound and an antimony compound were used, and phosphoric acid and silicon oxide particles (0.08% by weight) having a particle size of 1.0 μm were added thereto, and polyethylene terephthalate (having an intrinsic viscosity of 0.1%) was used. 65dl
/ G, melting point 257 ° C). The obtained polyester was dried under reduced pressure at 180 ° C. for 4 hours. After drying, it was supplied to a melt extruder. The polyester was extruded into a sheet from a slit-shaped die, brought into close contact with a mirror cooling drum by applying static electricity (3.0 kV), and solidified by cooling to obtain an unstretched sheet. This unstretched sheet is first preheated at 105 ° C. for 7 seconds, stretched 2.8 times in the longitudinal direction by a roll heated at 115 ° C., and further preheated at a temperature of 95 ° C. for 6 seconds.
After stretching 2.9 times in the width direction in the 0 ° C. heating zone, 245
At 5 ° C., 5% relaxation in the width direction, heat treatment for 5 seconds,
A 100 μm thick biaxially oriented polyester film for molding was obtained. One side of the obtained film was subjected to corona discharge treatment and evaluated.

(Example 2) The same polyethylene terephthalate (50 parts by weight) and polyethylene naphthalate (magnesium compound and antimony compound as catalysts) were added as phosphoric acid and polymerized to give an intrinsic viscosity of 0.69 d as in Example 1.
1 / g, melting point 270 ° C.), dried and supplied to an extruder to form a film. Example 1 was repeated except that the film was preheated at 110 ° C. for 6 seconds, stretched in the longitudinal direction by a factor of 2.5 at 120 ° C., preheated at 100 ° C. for 6 seconds, and then stretched by a factor of 2.9 in the transverse direction at 130 ° C. Similarly, a biaxially oriented polyester film for molding having a thickness of 50 μm was obtained.

Example 3 The same thickness as in Example 1 was used, except that the same polyethylene terephthalate as in Example 1 was preheated at 97 ° C. for 4 seconds, and then stretched 3.0 times at 98 ° C. in the longitudinal direction. A 25 μm biaxially oriented polyester film for molding was obtained.

Example 4 80 parts by weight of polyethylene terephthalate and polypropylene terephthalate used in Example 1 (polymerization by adding phosphoric acid using a titanium compound as a catalyst, intrinsic viscosity 0.9 dl / g, carboxyl end group 1
0 equivalents / ton, M / P = 5) 20 parts by weight were blended, dried under reduced pressure at 150 ° C. for 5 hours, and supplied to an extruder to form a film. After preheating at 85 ° C. for 4 seconds, 3.1% at 85 ° C. in the longitudinal direction.
Except that stretching was performed twice, the thickness was 50
A μm biaxially stretched polyester film for molding was obtained.

(Comparative Example 1) A thickness of 50 μm was obtained in the same manner as in Example 1 except that the stretching conditions were changed as shown in Table 2.
Was obtained.

Comparative Example 2 Using a magnesium compound and an antimony compound as catalysts, phosphoric acid and silicon oxide particles (0.2% by weight) were added and isophthalic acid 11 mol% copolymerized polyethylene terephthalate (intrinsic viscosity 0.62 dl)
/ g, carboxyl end group 25 equivalents / ton, M / P = 6)
Was polymerized. The obtained polyester was dried and supplied to an extruder to form a film. After preheating at 90 ° C for 6 seconds, 9
The film was stretched 3.3 times at 5 ° C., preheated at 110 ° C. for 6 seconds, stretched 3.4 times at 125 ° C. in the width direction, and then heated at 195 ° C.
Except for 3% relaxation in the width direction and heat treatment for 5 seconds,
In the same manner as in Example 1, a biaxially stretched polyester film having a thickness of 50 μm was obtained.

Tables 1 and 2 summarize the quality evaluation results of the biaxially oriented polyester film for molding described above.

[0067]

[Table 1]

[0068]

[Table 2] The symbols in the table are as follows. PET: polyethylene terephthalate PEN: polyethylene naphthalate PPT: polypropylene terephthalate TPA: terephthalic acid NPA: naphthalenedicarboxylic acid IPA: isophthalic acid EG: ethylene glycol PG: 1,3-propanediol Tmeta: heat setting temperature F100 stress: 100% elongation Stress (25 ° C) MD: Film longitudinal direction TD: Film width direction

As can be seen from the results in Table 1, Examples 1 to
The biaxially oriented polyester film for molding obtained in 4 is
The film had excellent environmental resistance, dimensional stability, printability, and moldability. On the other hand, the polyester films obtained in Comparative Examples 1 and 2 are waviness and misalignment of printed matter when formed into a molded product, and are films having poor moldability. Both films are used as biaxially stretched polyester films for molding. Was not preferred.

[0070]

The biaxially oriented polyester film for molding of the present invention has excellent environmental resistance, dimensional stability, printability and moldability, and is suitable as a biaxially oriented polyester film for molding.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F071 AA45 AA46 AA84 AF15Y AF21Y AF59Y AF61Y BB08 BC01 BC12 4F210 AA24 AA26 AG01 QA03 QC05 QC06 QD16 QG01 QG18 QW12

Claims (4)

[Claims] 1. A polyester film comprising a polyester having an ethylene terephthalate unit and / or an ethylene naphthalate unit as a main component,
The melting point of the polyester film is 245 ° C. or more, the plane orientation coefficient (fn), 190 ° C. in the longitudinal direction of the film.
A biaxially oriented polyester film for molding, wherein a heat shrinkage {SrMD (%)} and a heat shrinkage at 190 ° C in the width direction {SrTD (%)} simultaneously satisfy the following formulas I to III. 0.02 ≦ fn ≦ 0.15 Formula I 0 ≦ SrMD ≦ 3 Formula II 0 ≦ SrTD ≦ 3 Formula III 2. 100% of the film longitudinal direction at 25 ° C.
2. The stress according to claim 1, wherein the stress at extension {F100MD (MPa)}, the stress at 100% extension in the film width direction {F100TD (MPa)} and the film thickness {d (μm)} simultaneously satisfy the following formulas IV to VII. Biaxially oriented polyester film for molding. F100MD ≦ 150 Formula IV F100TD ≦ 150 Formula V 6000 ≦ F100MD × d ≦ 25000 Formula VI 6000 ≦ F100TD × d ≦ 25000 Formula VII 3. The biaxially stretched polyester film for molding according to claim 1, wherein both the elongation at break in the longitudinal direction of the film and the elongation at break in the width direction of the film at 25 ° C. are 170% or more. 4. A heat setting temperature (Tmeta) of 180 to
The biaxially stretched polyester film for molding according to any one of claims 1 to 3, which is at 240C.