JP2000186161A - Polyester film for laminating use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject film with ethylene terephthalate unit as the main constitutive component, having specific physical properties, excellent in taste-affording characteristics, laminating character and heat resistance, capable of laminating at relatively row temperatures, and excellent in forming processability as well, therefore useful as an inner surface coating film for metallic cans for foods. SOLUTION: This film for laminating use is such one as to consist mainly of ethylene terephtalate unit as constitutive component and have the difference between the refractive index in the longitudinal direction (nX) and that in the cross direction (nY) (birefringence: Δn=nX-nY) of -0.001 to -0.050 and have a melting point of pref. >=246 deg.C; furthermore for this film, it is preferable that the ratio of the thermal shrinkage stress in the cross direction to that in the longitudinal direction is >=1.3, the refractive index in the cross direction is 1.650-1.675, and the endothermic peak temperature associated with heat treatment using differential scanning calorimetry is 120-230 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polyester film for lamination. More specifically, it is a biaxially stretched polyester film that is used after being subjected to molding processing after being laminated on a metal plate, etc., and has good adhesion to metal plates and the like even after molding processing, and is suitable for containers such as metal cans. The present invention relates to a polyester film for lamination that is easy to form and has excellent taste characteristics.

[0002]

2. Description of the Related Art Conventionally, the inner and outer surfaces of metal cans are coated with various thermosetting resins, such as epoxy and phenolic resins, dissolved or dispersed in a solvent to prevent corrosion. That was widely done. However, such a method of coating the thermosetting resin requires a long time for drying the paint, and has unfavorable problems such as a decrease in productivity and environmental pollution due to a large amount of an organic solvent.

As a method for solving these problems, there is a method of laminating a film on a steel plate, an aluminum plate, or a metal plate which has been subjected to various surface treatments such as plating on the metal plate as a material of the metal can. When a metal can is manufactured by drawing or ironing a laminated metal plate of a film, the film is required to have the following characteristics.

(1) It has excellent laminating properties on a metal plate. In particular, if the laminating temperature exceeds 270 ° C., there is a concern that the film may stick to the rubber roll used for laminating, causing problems such as scratches and winding, so that laminating at a temperature of 270 ° C. or less is possible. .

(2) Excellent adhesion to a metal plate.

(3) It is excellent in moldability and does not cause defects such as pinholes after molding.

(4) The polyester film does not peel off, crack or pinhole due to impact on the metal can.

(5) The scent component of the contents of the can is not adsorbed on the film, or the flavor of the contents is not impaired by the eluate from the film (hereinafter referred to as taste characteristics).

A number of proposals have been made to solve these requirements. For example, Japanese Patent Publication No. 64-22530 discloses a polyester film having a specific density and plane orientation coefficient. 2-573
No. 39 discloses a copolyester film having specific crystallinity. However, these proposals do not necessarily satisfy the above-mentioned various required properties comprehensively, and it has been difficult to achieve both laminating properties and moldability in applications where particularly strict taste characteristics are required. .

[0010]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention can be laminated at 270 ° C. or lower while exhibiting excellent taste characteristics and laminating properties, particularly high heat resistance. An object of the present invention is to provide a polyester film for lamination having excellent moldability.

[0011]

The present invention employs the following means to solve the above-mentioned problems. That is, the polyester film for lamination of the present invention is a polyester film containing an ethylene terephthalate unit as a main component, and has a refractive index (n _X ) in the longitudinal direction and a refractive index (n _Y ) in the width direction of the film. the difference (birefringence: Δn = n _X -n _Y) is -0.001～-0.
050.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The present invention addresses this problem, namely,
The polyester film for lamination, which is excellent in taste characteristics and can be laminated at 270 ° C. or less while exhibiting laminating properties, particularly high heat resistance, and also excellent in moldability, was eagerly studied. Between the refractive index of the surface and the refractive index in the width direction (birefringence)
Only those within a certain range have been determined to solve such a problem at once.

[0013] The polyester constituting the polyester film of the present invention is a generic name of polymers having a main bond in the main chain as an ester bond, and is usually obtained by a polycondensation reaction between a dicarboxylic acid component and a glycol component. be able to. Here, as the dicarboxylic acid component, for example, aromatic dicarboxylic acids such as terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenyldicane carboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodiumsulfonedicarboxylic acid, and phthalic acid , Oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, aliphatic dicarboxylic acids such as fumaric acid, alicyclic dicarboxylic acids such as cyclohexyne dicarboxylic acid, and oxycarboxylic acids such as paraoxybenzoic acid. Can be used. Examples of the glycol component include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and neopentyl glycol; polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, and polypropylene glycol; and cyclohexanedimethanol. And aromatic glycols such as bisphenol A and bisphenol S are used.

In the present invention, among such polyesters, it is important to use those having ethylene terephthalate unit as a main component, from the viewpoint of improving taste characteristics after heat treatment such as retort treatment. is there.
The term "main component" as used herein means that the polyester has preferably at least 80 mol%, more preferably at least 93 mol%, particularly preferably at least 95 mol%, of the ethylene terephthalate unit. Is what you do. Further, among such polyesters, the melting point is preferably 246 ° C. or higher, more preferably 250 ° C. or higher and 275 from the viewpoint of taste characteristics and heat resistance.
Those having the property of not more than ℃ are preferably used.

On the other hand, a glycol component may be copolymerized with another dicarboxylic acid component as long as the taste characteristics are not impaired. The dicarboxylic acid component and the glycol component include those described above. In addition, two or more of these dicarboxylic acid components and glycol components may be used in combination. From the viewpoint of taste characteristics, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, and 5-sodium sulfonedicarboxylic acid are preferred.
Further, as long as the effects of the present invention are not impaired, a polyester obtained by copolymerizing a polyester with a polyfunctional compound such as trimellitic acid, trimesic acid, or trimethylolpropane may be used.

In producing the polyester of the present invention, conventionally known reaction catalysts and coloring inhibitors can be used. Examples of the reaction catalyst include an alkali metal compound,
Alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and the like. As a coloring inhibitor, for example, a phosphorus compound can be used. It is not something to be done.

In general, it is preferable to add an antimony compound, a germanium compound, or a titanium compound as a polymerization catalyst at any stage before the production of the polyester is completed. Such methods include, for example,
Taking a germanium compound as an example, a method in which a germanium compound powder is added as it is,
As described in Japanese Patent No. 22234, a method in which a germanium compound is dissolved and added to a glycol component which is a starting material of a polyester can be used.

Such germanium compounds include, for example, germanium dioxide, germanium hydroxide hydrate,
Or germanium tetramethoxide, germanium tetraethoxide, germanium tetrabutoxide, germanium alkoxide compounds such as germanium ethylene glycolide, germanium phenolate, germanium phenoxide compounds such as germanium β-naphthalate, germanium phosphate, germanium phosphite and the like A phosphoric acid-containing germanium compound, germanium acetate, or the like can be used. Among them, germanium dioxide is preferably used.

The antimony compound is not particularly restricted but includes, for example, oxides such as antimony trioxide,
Antimony acetate or the like is used. The titanium compound is not particularly limited, but an alkyl titanate such as tetraethyl titanate or tetrabutyl titanate is preferably used.

The polyester of the present invention is produced as described above, and will be further described with specific examples. For example, when producing polyethylene terephthalate, when germanium dioxide is added as a germanium compound, a transesterification or esterification reaction between a terephthalic acid component and an ethylene glycol component is performed, and then germanium dioxide and a phosphorus compound are added, followed by high temperature. A method is preferably employed in which a polycondensation reaction is carried out under reduced pressure until the content of diethylene glycol reaches a certain value, thereby obtaining a germanium element-containing polymer. As a more preferred method, the obtained polymer is subjected to a solid-phase polymerization reaction under reduced pressure or an inert gas atmosphere at a temperature equal to or lower than its melting point, to reduce the content of acetaldehyde, and obtain a predetermined intrinsic viscosity and a carboxy terminal group. Methods and the like are used.

The polyester in the present invention preferably has a diethylene glycol content of 0.01 to 3.5% by weight, more preferably 0.01 to 2.5% by weight, particularly preferably 0.01 to 2.0% by weight. Is desirable in order to maintain excellent taste characteristics even when subjected to many heat histories such as heat treatment in a can making process and retort treatment after can making. This is considered to be because the oxidation resistance at 200 ° C. or higher is improved.
It may be added in an amount of from 01 to 1% by weight. Further, diethylene glycol may be added during the production of the polymer as long as the properties are not impaired.

In order to improve the taste characteristics, the content of acetaldehyde in the film is preferably 25 ppm.
Below, it is more desirable to make it 20 ppm or less. When the content of acetaldehyde exceeds 25 ppm, the taste characteristics are inferior.

The method for reducing the content of acetaldehyde in the film to 25 ppm or less is not particularly limited. For example, in order to remove acetaldehyde generated by thermal decomposition when producing a polyester by a polycondensation reaction or the like, a polyester is used. Heat treatment at a temperature not higher than the melting point of the polyester under reduced pressure or an inert gas atmosphere, preferably a method of solid-phase polymerization of the polyester at a temperature of 155 ° C. or higher and a melting point or lower under a reduced pressure or an inert gas atmosphere, a vent method A method of melt-extrusion using an extruder. When melt-extruding a polymer, set the extrusion temperature within 30 ° C. of the melting point of the high-melting polymer side, preferably + 25 ° C.
A method of extruding within a short period of time, preferably within one hour of the average residence time can be used.

The thickness of the polyester film of the present invention is as follows:
In terms of moldability after lamination to metal, coatability to metal, impact resistance and taste characteristics, preferably 3 to 50 μm
m, more preferably 5 to 35 μm, particularly preferably 8
It is preferable to use one having a thickness of 30 μm.

In the present invention, the polyester film
Is the refractive index in the longitudinal direction of the film (n _X) And bending in the width direction
Folding rate (n_Y) (Birefringence: Δn = n)_X-N_Y) Is-
It is necessary to be 0.001--0.050. Or
In this range, the refraction in the longitudinal direction is greater than that in the width direction.
Low compression rate, tensile strength of crimping force during thermal lamination
Excellent laminating properties due to contraction in the width direction acting as force
Can be obtained. From the viewpoint of film handling
Means that the birefringence (Δn) is −0.001 to −0.040.
More preferably, Δn is −0.010−−
When it is in the range of 0.040, particularly excellent laminating property is obtained.
Can be

In the present invention, when the refractive index (n _Y ) in the width direction of the film is in the range of 1.650 to 1.675,
It is preferable because not only the lamination property but also the moldability is good. If the refractive index in the width direction is smaller than this range, wrinkles may be formed in the film during thermal lamination, and if it is larger than this range, moldability is deteriorated, which is not preferable. From the viewpoint of moldability, the range of n _Y is 1.650 to
More preferably, it is 1.665.

In the present invention, the plane orientation coefficient (fn) of the polyester film is preferably 0.080 to 0.1.
45, more preferably 0.08 to 0.135, from the viewpoint of improving laminating properties, moldability and impact resistance. If the plane orientation coefficient is too high, not only the lamination property but also the moldability may be deteriorated. On the other hand, if the plane orientation coefficient is too low, the uniformity of the film may decrease.

The method for setting n _X , n _Y , Δn and fn of the film within the above ranges is not particularly limited, but for example, the stretching ratio and / or the stretching temperature in the longitudinal and width directions of the film. This can be achieved by adjusting, adjusting the temperature and / or time of the heat treatment.

The polyester film of the present invention has a heat shrinkage in the width direction with respect to a peak value (TMD) of a heat shrinkage stress in a longitudinal direction of the film from the viewpoint of moldability and impact resistance after lamination due to structural change during lamination. It is preferable that the ratio (TTD / TMD) of the stress peak value (TTD) is 1.3 or more. More preferably, 1.5 to
3.0, and 1.7 to 3.0 are particularly preferable because excellent impact resistance can be obtained. Conversely, TMD /
If the TTD is less than 1.3, the film may be poor in impact resistance and cracks may occur in the film. The method for setting the ratio of the heat shrinkage stress to 1.3 or more is not particularly limited, and the stretching ratio in the longitudinal direction and the width direction of the film, the relaxation rate during heat treatment after stretching, and the like are adjusted. This can be achieved by:

The method for producing the polyester film in the present invention is not particularly limited. For example, after drying the polyester as required, it is supplied to a known melt extruder, melted, and then cut out of a slit die into a sheet or It is extruded into a tube, and in the former, it is brought into close contact with a casting drum by a method such as electrostatic application, and cooled and solidified to obtain an unstretched sheet. As a method of forming a film using such an unstretched sheet, there are a tubular method, a tenter method and the like, but a tenter method is preferable in terms of film quality, and after stretching in the longitudinal direction, stretching in the width direction,
Alternatively, a sequential biaxial stretching method in which the film is stretched in the width direction and then in the longitudinal direction, or a simultaneous biaxial stretching method in which the film is stretched almost simultaneously in the longitudinal direction and the width direction is desirable.

In such a stretching method, the stretching ratio employed in each direction is preferably 1.6 to 1.6.
The ratio is 4.2 times, and more preferably 1.7 to 4.0 times.
The stretching speed is desirably 1000 to 200,000% / min. The stretching temperature can be any temperature as long as it is equal to or higher than the glass transition point of the polyester and equal to or lower than the glass transition point + 100 ° C. 80-170
° C, particularly preferably, the longitudinal stretching temperature is 90 to 150 ° C and the transverse stretching temperature is 80 to 150 ° C.

After the biaxial stretching, the film is subjected to heat treatment. This heat treatment can be carried out by any conventionally known method such as in an oven or on a heated roll. The heat treatment temperature can be any temperature from 120 ° C. to the melting point of the polyester, but from the viewpoint of moldability, the endothermic peak temperature (Ts) accompanying heat treatment appearing on a differential scanning calorimeter (DSC) is 120. A heat treatment temperature in the range of up to 230 ° C is preferred. Furthermore, Ts is 15
The range of 0 to 220 ° C is more preferable because the impact resistance after molding is improved, and the range of Ts in the range of 170 to 210 ° C is still more preferable. Although the heat treatment time can be arbitrarily set, it is usually preferable to perform the heat treatment for 1 to 60 seconds. Such heat treatment causes the film to move in its longitudinal direction and / or
Alternatively, it may be performed by relaxing in the width direction. Further, re-stretching may be performed once or more in each direction.

Further, in order to improve the handleability and processability of the film of the present invention, the average particle size is 0.01 to 10 μm.
It is preferable to contain 0.01 to 50% by weight of particles arbitrarily selected from among known external particles such as internal particles, inorganic particles, and organic particles. In particular, the average particle size is 0.1 to
It is preferable that the film used for the inner surface of the can contain 0.01 to 3% by weight of 5 μm internal particles, inorganic particles and / or organic particles. As a method for depositing internal particles, known techniques can be employed. For example, JP-A-48-61556, JP-A-51-12860, JP-A-53-41355, and JP-A-54-41355 −90
The technology described in, for example, Japanese Patent No. 397 can be adopted. JP-A-55-20496 and JP-A-59-20496
Other particles such as JP-204617 can also be used in combination. It should be noted that use of particles having an average particle size exceeding 10 μm may cause defects in the film.

Examples of such inorganic 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. Organic particles include styrene, silicone, and the like. Acrylic acids,
Particles composed of methacrylic acids, polyesters, divinylbenzene, and the like can be used. Among these, inorganic particles such as wet and dry colloidal silica and alumina, and particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene, and the like as constituent components can be preferably used. Two or more of these internal particles, inorganic particles, and organic particles may be used in combination.

Further, it is preferable to further improve the adhesiveness by subjecting the film surface to a surface treatment such as a corona discharge treatment from the viewpoint of improving the characteristics. At this time, the E value is preferably 5 to 50, more preferably 10 to 50.
~ 45 can be adopted. Here, the E value is the intensity of the corona discharge treatment, and is a function of the applied voltage (Vp), the applied current (Ip), the processing speed (S), and the processing width (Wt), and E = Vp × Ip / S × Wt.

The film of the present invention may be coated with various coatings, and the coating compound, method, and thickness are not particularly limited as long as the effects of the present invention are not impaired.

Although the metal plate of the present invention is not particularly limited,
A metal plate made of iron, aluminum, or the like is preferable in terms of molding. Furthermore, in the case of a metal plate made of iron, an inorganic oxide coating layer which improves adhesion and corrosion resistance on the surface thereof, for example, chromic acid treatment, phosphoric acid treatment, chromic acid / phosphoric acid treatment, electrolytic chromic acid treatment, A chemical conversion coating layer represented by chromate treatment, chromium chromate treatment, or the like may be provided. In particular, 6.5 to 1 as chromium in terms of metal chrome.
A chromium hydrated oxide of 50 mg / m ² is preferred, and a spreadable metal plating layer such as nickel, tin, zinc,
Aluminum, gunmetal, brass or the like may be provided. It is preferable that tin plating has a plating amount of 0.5 to 15 mg / m ² , and nickel or aluminum has a plating amount of 1.8 to 20 g / m ² .

The polyester film for lamination of the present invention can be suitably used for the inner surface coating of a two-piece metal can, particularly a metal can for food, produced by drawing or ironing. Also, for the lid part of a two-piece can, or for coating the body, lid, and bottom of a three-piece can,
It can be preferably used because it has good laminating properties, metal adhesive properties, moldability and taste characteristics.

[0039]

The present invention will be described in detail with reference to the following examples. The characteristics were measured and evaluated by the following methods.

(1) Melting Point (Tm) of Polyester, Endothermic Peak (Ts) Associated with Heat Treatment Polyester is crystallized and heated at a rate of 10 ° C./min by a differential scanning calorimeter (DSC2, manufactured by Perkin-Elmer). The peak temperature of melting was taken as the melting point (Tm).
Further, the peak temperature of the peak accompanying the endotherm appearing as a sub-peak on the lower side of the melting point is determined as the endothermic peak (T
s).

(2) Refractive Index, Plane Orientation Coefficient (fn), Birefringence (Δn) Using a sodium D line (wavelength 589 nm) as a light source, a refractive index (longitudinal direction, width direction, thickness direction) using an Abbe refractometer. NX, nY, nZ) were measured. Plane orientation coefficient (fn) was determined by calculating the _{fn = (n X + n Y} ) / 2-n Z. Further, the birefringence (Δn) was obtained by calculating Δn = n _X −n _Y.

(3) Thermal Shrinkage Stress Thermomechanical analyzer (TMA / S manufactured by Seiko Denshi Kogyo KK)
S6100) was used at a heating rate of 10 ° C./min. At that time, the sample length was set to 20 mm and the sample width was set to 4 mm, and constant length measurement was performed.

(4) Laminating property A tin-free steel metal plate having a thickness of 0.20 mm is heated at a temperature range of + 5 ° C. to 270 ° C. at intervals of 3 ° C., bonded to the film, and rapidly cooled. Then, the plane orientation coefficient of the film after being laminated on the metal plate is measured. At a temperature at which the plane orientation coefficient after lamination was closest to 0.04, 15 samples of a laminated film were prepared, and the laminability was evaluated based on the following criteria based on the difference between the maximum and minimum values of the plane orientation coefficient. . The measurement of the plane orientation coefficient after lamination was performed on the non-laminated surface side of the film.

Class A: less than 0.01 Class B: 0.01 or more and less than 0.02 Class C: 0.02 or more (5) Formability Tin-free steel metal with a film heated to 150 to 280 ° C. at 70 m / min. After laminating a plate (heat 0.24 mm), quenching, and forming with a draw forming machine [forming at a forming ratio (maximum thickness / minimum thickness) of 1.9 at a moldable temperature range of 80 to 100 ° C] for food I got a can. A 1% aqueous solution of sodium chloride was placed in the obtained can and left for 1 day. A voltage of 6 V was applied to the electrode and the metal can in the aqueous solution of sodium chloride, and the current value was read 3 seconds later. The value was determined.

Class A: less than 0.001 mA Class B: 0.001 mA or more and less than 0.01 mA Class C: 0.05 mA or more (6) Impact Resistance A can made in the same manner as described above is filled with water and heated to 5 ° C. After cooling,
It was dropped on a vinyl chloride tile floor from a height of 1.2 m. After leaving at 35 ° C. for 2 weeks, the state of the bottom of the can was observed with the naked eye and an optical microscope, and evaluated according to the following criteria.

Class A: No defects such as cracks were observed in the film.

Class B: Fine cracks were observed in the film, but there was no abnormality in the can.

Grade C: Cracks of the film were observed with the naked eye, and rust was generated.

(7) Taste characteristics A can made in the same manner as described above was subjected to pressurized steam treatment at 125 ° C. × 35 minutes, filled with water at pH 5, sealed at 38 ° C., and sealed.
It was left for a week, then opened, and the change in odor was evaluated by a sensory test according to the following criteria.

Class A: No change in odor is observed.

Class B: Almost no change in odor.

Class C: Slight change in odor is observed.

Class D: Rust is generated in the can, and the odor is greatly changed. Example 1 Using the polyester and film forming conditions shown in Table 1,
That is, polyethylene terephthalate (hereinafter referred to as PET) is vacuum-dried at 180 ° C., supplied to an extruder, discharged from a T-die, cast on a cooling drum, and obtained as an unstretched film. Is stretched longitudinally (magnification 3.0 times, stretching temperature 110 ° C.), and laterally stretched (magnification 3.4).
And a stretching temperature of 120 ° C.), and then heat-treated (temperature: 200 ° C., relaxation rate: 0%) to obtain a 20 μm biaxially stretched film.

When the film thus obtained was evaluated, it showed excellent characteristics as shown in Table 2. Examples 2-5, Comparative Examples 1-2 In Examples 2-5 and Comparative Examples 1-2, Example 1
The polyester used and the film forming conditions were changed as shown in Table 1 to obtain a biaxially stretched film.

The properties of the obtained film are as shown in Table 2, and as is clear from Table 2, Examples 2 to
Film No. 5 showed good laminating properties and moldability.
On the other hand, the characteristics of the films of Comparative Examples 1 and 2 were inferior.

[0056]

[Table 1]

[0057]

[Table 2]

The abbreviations in the table are as follows. Ts: Endothermic peak temperature due to heat treatment in differential scanning calorimeter TMD: Peak value of heat shrinkage stress in film longitudinal direction TTD: Peak value of heat shrinkage stress in film width direction PET: Polyethylene terephthalate PET / I ^* : Isophthalic acid copolymer PET / N ^* : 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate (the number * is the copolymer mole%)
Is)

[0059]

According to the present invention, it is possible to easily and stably provide a polyester film for lamination having both laminability, moldability and taste characteristics.

Claims (8)

[Claims] (1) An ethylene terephthalate unit having a main constituent
A polyester film,
The refractive index in the longitudinal direction (n_X) And the refractive index in the width direction (n _Y)of
Difference (birefringence: Δn = n_X-N_Y) Is -0.001-
Polyester for lamination characterized by being 0.050
Steal film. 2. The polyester film for lamination according to claim 1, wherein the melting point of the film is 246 ° C. or higher. 3. The ratio (TTD / TMD) of the peak value (TTD) of the thermal shrinkage stress in the width direction to the peak value (TMD) of the thermal shrinkage stress in the longitudinal direction of the film is 1.3 or more. The polyester film for lamination according to any one of claims 1 to 3. 4. The film has a refractive index (n _Y ) in a width direction thereof.
The polyester film for lamination according to any one of claims 1 to 3, which has a molecular weight of 1.650 to 1.675. 5. The endothermic peak temperature (Ts) of the film due to heat treatment in a differential scanning calorimeter is 120 to 230 ° C.
The polyester film for lamination according to any one of claims 1 to 4, wherein 6. The film has a plane orientation coefficient (fn) of 0.
The polyester film for lamination according to any one of claims 1 to 5, wherein the number is from 080 to 0.145. 7. The polyester film for lamination,
2. The method according to claim 1, wherein the metal sheet is used after being laminated on a metal plate.
7. The polyester film for lamination according to any one of items 6 to 6. 8. The polyester film for lamination according to claim 1,
The polyester film for lamination according to any one of claims 1 to 6, which is used by being laminated on an inner surface and / or an outer surface of a metal can for food.