JP2001277455A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film, in which the generation of a coarse projection caused by the deposition of an oligomer and the generation of a stain on a surface are extremely little and heat resistance is excellent. SOLUTION: The laminated polyester film is provided with a heat resistant resin layer on both sides of a polyester film and haze value is <=5%. When heat treatment is performed at 200 deg.C for 6 hours, rise in haze value is <=1%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a projection, which has very little occurrence of coarse projections and surface contamination due to oligomer precipitation.
The present invention relates to a laminated polyester film having excellent heat resistance.

[0002]

2. Description of the Related Art Polyester films, especially polyethylene terephthalate films, are widely used in industrial applications because of their excellent physical and chemical properties. However, a polyester film tends to precipitate a polyester oligomer typified by a cyclic trimer on the surface layer of the film during a high-temperature heat treatment in a processing step, and may cause generation of coarse projections and surface contamination. For example, when used as a film for a magnetic recording medium, as a high-temperature heat treatment in a processing step, a drying step of the applied magnetic layer when a magnetic layer is applied to the film, and a deposition of the magnetic layer when a magnetic layer is deposited. At this time, when the oligomer is precipitated, it becomes a surface defect, which causes output fluctuation when outputting an electric signal. Further, if the surface of the film becomes soiled due to the precipitation of oligomers, it may cause stains of the apparatus in a processing step, and there is also a problem that productivity is reduced. Therefore, methods for reducing the precipitation of oligomers have been studied. For example, a method of laminating a low oligomer resin onto a polyester resin (Japanese Patent Application Laid-Open Nos. 63-197643 and 10-157038) has been proposed as a method for suppressing the precipitation of oligomers of a polyester film by lamination. However, the low oligomer resin of the surface layer used in this method has a small oligomer precipitation amount but cannot completely suppress the oligomer precipitation amount. Therefore, it cannot be said that the oligomer precipitation suppressing effect is sufficient, and the high-temperature heating as described above. When the treatment is performed, there are problems such as generation of coarse projections and surface contamination due to oligomer precipitation.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a laminated polyester film which is excellent in heat resistance and in which generation of coarse projections and surface contamination due to oligomer precipitation is extremely small. Is to do.

[0004]

The laminated polyester film of the present invention which achieves the above object has a heat-resistant resin layer provided on both sides of the polyester film, and has a haze value of 5% or less, and is heat-treated at 200 ° C. for 6 hours. A rise in haze value of not more than 1%.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester in the laminated polyester film of the present invention is not particularly limited, but polyethylene terephthalate, polyethylene naphthalate,
Polypropylene terephthalate, polybutylene terephthalate, polypropylene naphthalate and the like may be used, and a mixture of two or more of these may be used. Further, those obtained by copolymerizing these and other dicarboxylic acid components or diol components may be used. In addition, the inner layer and the surface layer
It may be a composite film having more than two layers. For example, a composite film having substantially no particles in the inner layer portion and having a layer containing particles in the surface layer portion, a laminate having coarse particles in the inner layer portion and containing fine particles in the surface layer portion Examples of the film include a composite film in which the inner layer is a layer containing fine bubbles and the surface layer is substantially free of bubbles.
In the composite film, the inner layer portion and the surface layer portion may be of different polymers or of the same type. When the above-mentioned polyester is used, its intrinsic viscosity (measured in o-chlorophenol at 25 ° C) is from 0.4 to
It is preferably 1.2 dl / g, more preferably 0.5 to 0.8 dl / g.

In the present invention, it is desirable that the polyester film is biaxially oriented with the laminated film provided in view of mechanical strength and dimensional stability. Biaxially oriented means, for example, that the polyester film is stretched about 2.5 to 5 times in the longitudinal direction and the width direction before unstretched, that is, before the crystal orientation is completed, and then the crystal orientation is completed by heat treatment. And shows a biaxially oriented pattern in wide-angle X-ray diffraction. When the polyester film is not biaxially oriented, the dimensional stability of the laminated polyester film, especially, dimensional stability and mechanical strength under high temperature and high humidity is insufficient, or poor flatness Is not preferred.

The polyester film of the present invention may contain various additives, resin compositions, cross-linking agents, etc. as long as the effects of the present invention are not impaired. For example, antioxidants, heat stabilizers, UV absorbers, organic,
Inorganic particles, pigments, dyes, antistatic agents, nucleating agents, flame retardants,
Acrylic resin, polyester resin, urethane resin, polyolefin resin, polycarbonate resin, alkyd resin, epoxy resin, urea resin, phenol resin, silicone resin, rubber resin, wax composition, melamine crosslinker, oxazoline crosslinker, methylol Alkylolized urea-based crosslinking agents, acrylamide, polyamide, epoxy resins, isocyanate compounds, aziridine compounds, various silane coupling agents, various titanate coupling agents, and the like can be used.

Among these, when inorganic particles such as silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate, barium sulfate, carbon black, zeolite, titanium oxide, and fine metal powder are added. It is preferable because the lubricity and scratch resistance are improved. The average particle size of the inorganic particles is 0.00
5-5 μm is preferable, and more preferably 0.05-1 μm
m. Further, the addition amount is preferably 0.05 to 20 parts by weight, more preferably 0.1 to 10 parts by weight.

The polyester film of the present invention is a laminated polyester film characterized in that the haze value is 5% or less, and the increase in the haze value after heat treatment at 200 ° C. for 6 hours is 1% or less. Has a haze value of 3%
Hereinafter, the haze value when the heat treatment is performed at 200 ° C. for 6 hours is 0.5% or less, more preferably the haze value is 2% or less, and the haze value is increased when the heat treatment is performed at 200 ° C. for 6 hours. 0.3% or less. If the haze value exceeds 5%, the transparency is reduced, so that it cannot be used for applications requiring transparency. If the increase in the haze value after heat treatment at 200 ° C. for 6 hours exceeds 1%, coarse projections are generated due to the precipitation of oligomers, thereby impairing the surface shape of the film or causing surface contamination and processing. This is not preferable because it causes problems such as contamination of the apparatus in the process and reduction in productivity.

Such a laminated polyester film can be obtained by the following method. That is, it is obtained by laminating a heat-resistant resin layer that suppresses oligomer precipitation on both surfaces of the polyester film. It is not preferable to use only the one-layer layer because the effect of suppressing oligomer precipitation is insufficient, and problems such as easy curling of the laminated film occur.

The heat-resistant resin to be laminated has a glass transition point of 170 ° C. or higher due to its heat resistance.
Those having no melting point or decomposition point at 0 ° C. or lower are preferred. The heat-resistant resin selected from the above requirements is not particularly limited as long as the resin satisfies the requirements, but examples thereof include aromatic polyamide resins, aromatic polyimide resins and precursors thereof, and polyethersulfone resins. Resin, polyarylate resin, polyamideimide resin,
Polyetherimide-based resins, polybenzimidazole and its precursors, polybenzoxazole and its precursors, polybenzthiazole and its precursors, polysulfone-based resins, and the like, among which preferred are bipolar non-polar A heat-resistant resin soluble in a proton solvent and / or a heat-resistant resin generated from a precursor resin soluble in a dipolar aprotic solvent, more preferably an aromatic polyamide resin or an aromatic polyimide resin ( A resin formed from the precursor resin), a polyether sulfone resin, and a polyarylate resin, and more preferably, an aromatic polyamide resin and an aromatic polyimide resin (resin formed from the precursor resin). ).

In the present invention, the aromatic polyamide is preferably a repeating unit represented by the following general formula (V) and / or (VI) alone or in a copolymerized form in an amount of 50 mol% or more, more preferably Those containing 70 mol% or more are preferred.

Embedded image

Here, as Ar ₃ , Ar ₄ and Ar ₅ , for example, those represented by the following general formula (III) are used.
X and Y in the general formula (III) are selected from, for example, those shown in the following general formula (IV), but are not limited thereto. Furthermore, some of the hydrogen atoms on these aromatic rings are chlorine,
Halogen groups such as fluorine and bromine (especially chlorine), alkyl groups such as nitro group, methyl group, ethyl group and propyl group (preferably methyl group), and alkoxy groups such as methoxy group, ethoxy group and propoxy group. And those in which the hydrogen in the amide bond constituting the polymer is substituted by another substituent.

Embedded image _{-O -, - CH 2 -,} - CO -, - SO 2 -, - S -, - C (CH 3) 2 - (IV)

In particular, when a polymer in which the aromatic ring of the above general formula (VI) is bonded at the para position accounts for 50 mol% or more, more preferably 70 mol% or more of the total aromatic ring, the polymer may be used as a laminated film. Is preferred in terms of the effect of inhibiting oligomer precipitation. Suitable aromatic polyamide in the present invention,
The repeating unit represented by the general formula (V) and / or the general formula (VI) is at least 50 mol%, more preferably at least 70 mol%, but less than this may be copolymerized with another compound or other polymer. They may be mixed.

The preferred aromatic polyimide in the present invention means that at least 70 mol%, more preferably at least 90 mol%, of the total unit structure is a unit structure represented by the following general formula (I) and / or (II): It is preferred that

Embedded image

(Ar ₁ and Ar _{2 in the} general formulas (I) and (II)
Is at least one group selected from the following general formula (III),

Embedded image Here, X and Y in the general formula (III) represent the following general formula (IV)
And at least one group selected from _{-O -, - CH 2 -,} - CO -, - SO 2 -, - S -, - C (CH 3) 2 - (IV))

When 70 mol% or more, more preferably 90 mol% or more, of all the unit structures of the aromatic polyimide are the unit structures represented by the above general formulas (I) and / or (II), a laminated film is obtained. It is preferable from the viewpoint of the effect of suppressing the precipitation of oligomers at that time. The aromatic polyimide in the present invention is more preferably an aromatic polyimide having a unit structure represented by the following general formula (VII) of 70 mol% or more, and particularly preferably a unit structure represented by the following general formula (VII) Is an aromatic polyimide having at least 90 mol%, but copolymerization of other compounds with less than this and other polymers may be mixed.

Embedded image

The method for laminating the aromatic polyimide layer on the polyester film in the present invention is not particularly limited, and a film comprising an aromatic polyimide and / or an aromatic polyamic acid which is a precursor of the aromatic polyimide is prepared. A method of bonding through an adhesive layer, a method of applying and drying an aromatic polyamic acid which is a precursor of an aromatic polyimide and / or an aromatic polyimide are optional, and when an aromatic polyamic acid which is a precursor is used, The amide acid component is dehydrated and ring-closed to obtain an aromatic polyimide. The method of dehydration and ring closure is not particularly limited, but a method of dehydration and ring closure by heat treatment at 150 ° C. or higher is preferably used. When the aromatic polyamic acid is subjected to dehydration and ring closure, it is not particularly limited, but may include benzimidazole, imidazole, 1,2,4-triazole, quinoline, isoquinoline, 3-hydroxypyridine, 4-hydroxypyridine, nicotinamide, Nicotinamide, 4-
Addition of a compound selected from hydroxyquinoline, 8-hydroxyquinoline, and the like to the polyamic acid is preferable because the dehydration ring closure is accelerated and the dehydration ring closure time is shortened to increase productivity.

An example of a dipolar aprotic solvent is N 2
-Methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like. In the present invention, the heat-resistant resin used to form the heat-resistant resin layer and / or its precursor resin may be dissolved in these dipolar aprotic solvents,
It has a very important meaning in the adhesion between the polyester film and the heat-resistant resin layer, and it is difficult to obtain the desired interfacial adhesion with other solvents. That is, a solvent that dissolves the heat-resistant resin and / or the precursor resin of the heat-resistant resin and whitens or swells the polyester film before the completion of the crystal orientation is particularly preferable, and among the above, N-methyl-2-pyrrolidone is particularly preferable.

The heat-resistant resin layer may contain various additives, a resin composition, a cross-linking agent and the like as long as the effects of the present invention are not impaired. For example, antioxidants, heat stabilizers,
UV absorbers, organic and inorganic particles, pigments, dyes, antistatic agents, nucleating agents, acrylic resins, polyester resins, urethane resins, polyolefin resins, polycarbonate resins,
Alkyd resin, epoxy resin, urea resin, phenol resin, silicone resin, rubber-based resin, wax composition,
Melamine-based crosslinking agents, oxazoline-based crosslinking agents, methylolated, alkylolated urea-based crosslinking agents, acrylamide, polyamide, epoxy resins, isocyanate compounds, aziridine compounds, various silane coupling agents, various titanate coupling agents, etc. Can be mentioned.

Among these, when inorganic particles such as silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate, barium sulfate, carbon black, zeolite, titanium oxide, and fine metal powder are added. Is particularly preferable since the lubricity and scratch resistance are improved. The average particle size of the inorganic particles is 0.
005 to 5 μm, preferably about 0.05 to 1 μm. The amount of addition is desirably 0.05 to 20% by weight, preferably 0.1 to 10% by weight.

The method of laminating the heat-resistant resin layer on the polyester film is not particularly limited, and a method of laminating a film made of the heat-resistant resin and / or a precursor resin of the heat-resistant resin via an adhesive layer is used. The method of applying and drying the heat-resistant resin and / or the precursor resin of the heat-resistant resin is optional. However, in order to more effectively exhibit the effects of the present invention, the heat-resistant resin is applied to both sides of the biaxially oriented polyester film. It is preferable that the resin layers are laminated without substantially interposing the adhesive layer.

Here, the fact that the adhesive layer is not substantially interposed is used.
In the state in which the heat-resistant resin layer is laminated on the polyester film, it means that no layer other than the substrate and the laminated film forming substance is formed at the interface between the substrate and the laminated film, Even when a layer containing a substance other than the laminated film as a main component is present, when the thickness is 10 nm or less, it can be regarded that the layer does not pass through the adhesive layer. However, it is particularly preferable that a mixed layer of a base material and a heat-resistant resin layer is formed at the interface because the adhesiveness is further improved, and this layer is out of the definition of the adhesive layer.

The laminate film and the substrate of the laminate film thus obtained have a peeling stress in a T-shaped peeling of 100 g.
/ 25 mm width or more, preferably 200 g / 25 mm width or more. Peel stress is 100
When the width is less than g / 25 mm, the haze value tends to increase more than 1% when heat treatment is performed at 200 ° C. for 6 hours, which is presumed to be due to the following reasons.
That is, since the adhesion between the substrate and the heat-resistant resin layer is not sufficiently strong, the release of oligomers from the end laminated section increases,
It is thought that the transparency is likely to be reduced because it goes around the film surface, but the details are unknown. Furthermore, if the adhesion between the base material and the heat-resistant resin layer is not sufficiently strong, there may be a problem that the laminated film is peeled off. When the laminated film is peeled off, generation of coarse protrusions and generation of surface contamination due to oligomer precipitation are suppressed. It will be difficult to do.

The upper limit of the peeling stress is not particularly limited. If the peeling stress is sufficiently large, the thermoplastic resin film may break at the time of measuring the peeling stress, making it impossible to measure the peeling stress.
When the width is 25 mm or more, the peeling stress is 100 g / 25.
mm width or more.

The laminated polyester film has a haze value of 5% or less and a rise in the haze value of 1% or less when heat-treated at 200 ° C. for 6 hours. According to the findings of the inventors, 0.05 μ
m to 2 μm, more preferably 0.1 to 2 μm.
07 μm to 0.5 μm, more preferably 0.1 μm to
0.3 μm.

When the thickness is less than 0.05 μm, the effect of suppressing the precipitation of oligomers becomes insufficient, and when the heat treatment is performed at 200 ° C. for 6 hours, the haze value tends to increase more than 1%. This is not preferable because the transparency is lowered and the haze tends to be larger than 5%. Further, a layer thickness greater than that does not significantly improve the effects of the present invention.

Next, a preferred production method for obtaining the laminated polyester film of the present invention will be illustrated below, but is not necessarily limited thereto.

A sufficiently dried polyester chip is supplied to an extruder, melt-extruded at 280 to 300 ° C., and formed into a sheet on a mirror cooling drum at 20 to 70 ° C. The sheet is stretched in the longitudinal direction at a temperature of 80 to 120 ° C. for 2.5 to
Stretch 4.5 times. Apply a heat-resistant resin dissolved in a solvent to be laminated on both sides of the uniaxially oriented polyester film,
Then, hold both ends of the film with clips and
1. After a preheating step of 20 ° C, at 80 to 120 ° C in the width direction.
Stretch 5 to 4.5 times. 180 to 25 more continuously
Heat fix the polyester film at 0 ° C. Here, in the case of stretching in the width direction, it is preferable that the solvent is stretched together with the base material before being completely dried, and thereafter the solvent is evaporated to complete the crystal orientation of the base material. It is preferable that most of them remain in the preheating step and the stretching step before the stretching and evaporate in the heat treatment step after the stretching in terms of the adhesion to the base material and the transparency in the laminated state.

Further, the laminated polyester film may be further stretched in the longitudinal direction after stretching in the width direction or before or after heat treatment.
Stretching in the width direction is more preferable because the strength and rigidity of the laminated polyester film can be improved.

When re-stretching in the longitudinal or width direction,
The stretching temperature is preferably 150 to 260 ° C., more preferably 200 to 250 ° C., and the stretching ratio is preferably about 1.1 to 2 times in the width direction and the longitudinal direction, respectively. Further, after the re-stretching, it is desirable to heat-set at a temperature of preferably 210 to 280 ° C, more preferably 220 to 260 ° C.

The laminated polyester film thus obtained is excellent in the effect of suppressing oligomer precipitation, has a haze value of 5% or less, and has a haze value increase of 1% or less when heat-treated at 200 ° C. for 6 hours. It is a laminated polyester film characterized by having excellent interfacial adhesion, and is used for magnetic recording media, electrical insulating materials, flexible printed circuit boards, electronic components, label thermal transfer materials, etc. It can be suitably used for various industrial materials and various packaging materials such as a metal plate laminate film which causes a problem due to oligomer precipitation.

[Method of measuring characteristics and method of evaluating effects]
The method for measuring characteristics and the method for evaluating effects in the present invention are as follows.

(1) Thickness of Laminated Film A section was cut out from the laminated polyester film, and the section was observed with a transmission electron microscope to measure the thickness of the laminated film. When there was a mixed phase, the thickness including the mixed phase was defined as the lamination thickness.

(2) Peeling stress Polyurethane ("Takelac" A-385 / "Takenate" A-50) was applied to the laminated surface of the laminated polyester film.
(Used by mixing at a weight ratio of 6/1): Ethyl acetate solution of Takeda Pharmaceutical Co., Ltd.) was applied at a thickness of 3 μm after drying, and dried at 110 ° C. for 1 minute. A 50 μm-thick biaxially oriented polypropylene film that had been subjected to corona discharge treatment was laminated and heat-laminated at 90 ° C. Thereafter, heat treatment was carried out at 45 ° C. for 70 hours, and a strip having a width of 25 mm was sampled. Was. When the peeling stress was 300 g / 25 mm or more and the laminated film did not peel at all, the measurement was not possible.

(3) Haze value before heat treatment The haze value of the heat-set laminated film was determined according to JIS-K-67.
It was determined with an SEP-H-2 turbidimeter (Nihon Seimitsu Kogaku Co., Ltd.) according to 14-58.

(4) Haze increase value after heat treatment The heat-set laminated film was further heat-treated in an oven at 200 ° C. for 6 hours, and the haze value of the sample was measured according to JIS-K-
It was determined with a SEP-H-2 turbidity meter (Nihon Seimitsu Kogaku Co., Ltd.) according to 6714-58. The haze value before heat treatment is A,
Assuming that the haze value after the heat treatment was B, the haze increase value after the heat treatment was determined by the haze increase value after the heat treatment = BA.

(5) Number of oligomers deposited on the surface after heat treatment The heat-set laminated film was further heat-treated in an oven at 200 ° C. for 6 hours, and then platinum palladium was deposited. Observe the surface of the sample with a scanning electron microscope,
The number of the above oligomers was counted. After the number of oligomers was converted to the number per 1 mm ² , evaluation was made according to the following criteria. Grades 1 and 2 are acceptable.

First grade 0 Second grade 0 to less than 50 Third grade 50 to less than 100 Quaternary 100 or more

[0040]

Next, the present invention will be described with reference to examples, but is not necessarily limited thereto.

<Coating Liquid 1 for Forming Laminated Film> Biaxially stretched para-aromatic polyamide film having substantially no glass transition point and melting point (registered trademark: Microtron (Toray Industries, Ltd.)
Was dissolved at 60 ° C. in N-methyl-2-pyrrolidone so as to have a solid concentration of 5% by weight, and then cooled to room temperature to prepare a coating solution having a viscosity of 55 poise. This coating solution was appropriately diluted with N-methyl-2-pyrrolidone according to the thickness of the laminated film and used.

<Coating Liquid 2 for Forming a Laminated Film> A weighed amount of 4,4'-diaminodiphenyl ether was added to a dried flask together with N-methyl-2-pyrrolidone, and the mixture was stirred to dissolve. Next, pyromellitic dianhydride was added to this solution in an amount of 100 mol per 100 mol of 4,4′-diaminodiphenyl ether so that the reaction temperature was 60 ° C. or lower. Thereafter, when the viscosity became constant, the polymerization was terminated, and the polymerization was terminated. Thus, a polymerization solution of an aromatic polyamic acid as a precursor of an aromatic polyimide having a unit structure represented by the following general formula (VIII) was obtained. This coating solution was appropriately diluted with N-methyl-2-pyrrolidone according to the thickness of the laminated film and used.

Embedded image

Comparative Example 1 0.015% by weight of colloidal silica having an average particle diameter of 0.4 μm and 0.05% by weight of colloidal silica having an average particle diameter of 1.5 μm
A polyethylene terephthalate (hereinafter referred to as PET) containing 0.05% by weight (intrinsic viscosity: 0.63 dl / g) chips were sufficiently vacuum-dried at 180 ° C., fed to an extruder, melted at 285 ° C., and then T-shaped. The sheet was extruded from a die into a sheet, wound around a mirror-surface cast drum having a surface temperature of 20 ° C. using an electrostatic application casting method, and cooled and solidified. This unstretched sheet is stretched 3.5 times in the longitudinal direction by a group of rolls heated to 95 ° C. to obtain a uniaxially stretched film. Then, while holding both ends of the film with clips, a preheating zone at 100 ° C. Then, the film was stretched 3.5 times in the width direction in a heating zone at 110 ° C. Further, a heat treatment was continuously performed in a heat treatment zone at 230 ° C. for 5 seconds to thermally fix the base film. This laminated film had a thickness of 20 μm, excellent transparency, and a haze value of 0.8%.

The haze value of a film obtained by heat-treating this film in an oven at 200 ° C. for 6 hours was 1.8% higher than that of the film before the heat treatment.

Example 1 In the production of the film of Comparative Example 1, a coating liquid 1 for forming a laminated film (5% by weight liquid) was applied to both surfaces of the film after stretching in the longitudinal direction (before stretching in the width direction). A film was obtained in the same manner as in Comparative Example 1 except that the film was applied by a die coating method so that the final lamination thickness per side was 0.2 μm.

This laminated film had a thickness of 20 μm, a laminated thickness on one side of 0.2 μm, and was excellent in transparency, and the haze value was 1.1%.

A film obtained by heat-treating this film in an oven at 200 ° C. for 6 hours was also excellent in transparency, and the rise in haze from the film before heat treatment was 0%.

Example 2 In the production of the film of Comparative Example 1, after the film was stretched in the longitudinal direction (before stretching in the width direction), a coating liquid 2 for forming a laminated film (5% by weight solution) was applied to both surfaces of the film. A film was obtained in the same manner as in Comparative Example 1 except that the film was applied by a die coating method so that the final lamination thickness per side was 0.2 μm.

This laminated film had a thickness of 20 μm, a laminated thickness on one side of 0.2 μm, excellent transparency, and a haze value of 0.9%.

A film obtained by heat-treating this film in an oven at 200 ° C. for 6 hours was also excellent in transparency, and the rise in haze from the film before the heat treatment was 0%.

COMPARATIVE EXAMPLE 2 One side of the biaxially oriented PET film having a thickness of 20 μm obtained in Comparative Example 1 was coated with the same coating liquid 1 for forming a laminated film as in Example 1.
Was applied so that the final laminated thickness became 0.2 μm, and dried at 150 ° C. for 20 minutes to obtain a laminated film. The same operation was performed on the opposite surface of the film to obtain a double-sided laminated film having a final laminated thickness of 0.2 μm per one surface.

Although the haze value of this film was 1.1%, this film was inferior in adhesiveness, and the haze value after heat treatment in an oven at 200 ° C. for 6 hours was 1.2% higher than that before heat treatment. Rose.

Examples 3 to 6 and Comparative Example 3 In Example 1, the lamination thickness was 0.01 μm per side.
(Comparative Example 3), 0.05 μm (Example 3), 0.1 μm
(Example 4) A laminated polyester film having a thickness of 0.5 μm (Example 5) and a thickness of 1 μm (Example 6) was formed on both sides with the same thickness.

When the lamination was too thin, the haze value after the heat treatment increased more than 1%, but good characteristics were exhibited above a specific thickness.

Examples 7 and 8 In Example 2, the thickness of the laminate was 0.05 μm per side.
(Example 7) A laminated polyester film having a thickness of 1 μm (Example 8) and having the same thickness laminated on both surfaces was produced. These films exhibited good properties.

Comparative Example 4 A laminated polyester film having a thickness of 0.2 μm on only one side was produced in the same manner as in Example 1. The haze value of the laminated film after the heat treatment was increased by 1.7%, and the precipitation of the oligomer could not be suppressed.

The results of the above Examples and Comparative Examples are summarized in Table 1.

[0058]

[Table 1]

[0059]

According to the present invention, it is possible to obtain a laminated polyester film excellent in heat resistance, in which generation of coarse projections and surface contamination due to oligomer precipitation are extremely small.

 ────────────────────────────────────────────────── ─── Continuing on the front page F term (reference) 4F100 AK01B AK01C AK41A AK43B AK43C AK46B AK46C AK47B AK47C AK49B AK49C AK54B AK54C AK55B AK55C BA03 BA06 BA10B BA10C GB41 JJ03A01 A30 J01 A30 J01 QW31

Claims (9)

[Claims] 1. A heat-resistant resin layer is provided on both surfaces of a polyester film, the haze value is 5% or less, and the increase in haze value when heat treatment is performed at 200 ° C. for 6 hours is 1% or less. Laminated polyester film. 2. The laminated polyester film according to claim 1, wherein the polyester film is a biaxially oriented polyester film. 3. The heat-resistant resin layer has a thickness of 0.05 μm or more,
The laminated polyester film according to claim 1 or 2, which has a thickness of 2 µm or less. 4. The heat-resistant resin layer is composed of a heat-resistant resin soluble in a dipolar aprotic solvent and / or a heat-resistant resin formed from a precursor resin soluble in a dipolar aprotic solvent. The laminated polyester film according to any one of claims 1 to 3. 5. The laminated polyester film according to claim 1, wherein the heat-resistant resin is at least one selected from the group consisting of aromatic polyamide, aromatic polyimide, polyether sulfone, and polyarylate. 6. The laminated polyester film according to claim 1, wherein the heat-resistant resin is an aromatic polyamide and / or an aromatic polyimide. 7. The laminated polyester film according to claim 6, wherein the aromatic polyamide is a para-aromatic polyamide. 8. An aromatic polyimide having a total unit structure of 70%
The laminated polyester film according to claim 6, wherein at least mol% is an aromatic polyimide having a unit structure represented by the following general formulas (I) and / or (II). Embedded image (Ar ₁ and Ar _{2 in the} general formulas (I) and (II) are at least one group selected from the following general formulas (III). Here, X and Y in the general formula (III) represent the following general formula (IV)
And at least one group selected from _{-O -, - CH 2 -,} - CO -, - SO 2 -, - S -, - C (CH 3) 2 - (IV)) 9. The peeling stress between the polyester film and the heat-resistant resin layer is 100 g / 25 mm or more in width.
8. The laminated polyester film according to any one of 8.