JP2003268211A - Biaxially oriented polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-quality polyester film which comprises a polyester and a polyimide, has a high dimensional stability, and is produced in an enhanced productivity by reducing the occurrence of defects during the film formation process by preventing problems such as the oxidation degradation of a polymer from arising. <P>SOLUTION: This film, biaxially oriented and essentially comprising a polyester and a polyimide, has a degree of gelation (a degree of formation of o- chlorophenol (OCP) insolubles by a heat treatment at 300°C for 2.5 hr) of 0-15%. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biaxially oriented polyester film in which the quality of a polyester film, in particular, the dimensional stability is greatly improved, and yet the defects in the film production process are reduced and the productivity is greatly improved. Relates to a biaxially oriented polyester film which is improved.

[0002]

2. Description of the Related Art Biaxially oriented polyester films are used in various applications because of their excellent thermal properties, dimensional stability, mechanical properties, and ease of control of surface morphology. In particular, they are used as base films for magnetic tapes. Utility is well known. In recent years, magnetic tapes are required to have high density recording in order to reduce the weight and size of equipment and to record for a long time. For high-density recording, it is effective to shorten the recording wavelength and downsize the recording signal. However, if the recording signal is downsized, there is a problem that the recording track is apt to be displaced due to heat during running of the magnetic tape or thermal deformation during storage of the tape. Therefore, there is an increasing demand for improvements in characteristics such as dimensional stability and storage stability in a tape use environment.

As a base film capable of meeting the above-mentioned dimensional stability requirements, aramid films have been conventionally used for strength,
It is used in terms of dimensional stability. Since aramid film is expensive, it is disadvantageous in terms of cost.
Unlike the conventional polyethylene terephthalate film, it is disadvantageous in that the production efficiency is low because it cannot be formed by melt extrusion, but it is currently used because there is no substitute.

On the other hand, as a technique for improving the dimensional stability of a polyester film, a biaxially oriented polyester film composed of polyethylene terephthalate and polyetherimide (see, for example, Patent Document 1) is known.

However, as a result of diligent studies on the above-mentioned biaxially oriented polyester film, in a polymer alloy film composed of polyester and polyimide, oxidative deterioration of the polyester is apt to be promoted in the film manufacturing process, resulting in many surface defects. Then, it turns out that it has a problem that the productivity of the film decreases.

[0006]

[Patent Document 1] Japanese Patent Laid-Open No. 2000-141475

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the defects in a polymer alloy film composed of polyester and polyimide having excellent dimensional stability by suppressing oxidative deterioration in the manufacturing process, thereby reducing the defects of the film. It is intended to provide a biaxially oriented polyester film having improved productivity, which is suitable as an industrial film for use as a base film for high density magnetic recording tape.

[0008]

The present invention is a polyester film comprising polyester and polyimide as essential components, and the production rate of orthochlorophenol (OCP) insoluble matter in the film when heat-treated at 300 ° C. for 2.5 hours. The biaxially oriented polyester film is characterized in that (hereinafter referred to as gelation rate) is 0 to 15%.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The biaxially oriented polyester film of the present invention is a biaxially oriented film. When the film has a laminated structure of two or more layers, at least one of the film layers constituting the film needs to be biaxially oriented. When all layers are non-oriented or uniaxially oriented, the characteristics of the present invention cannot be satisfied.

The biaxially oriented polyester film of the present invention comprises a polymer alloy containing polyester and polyimide as essential components.

The polymer alloy as referred to in the present invention means a polymer multi-component system, and may be a block copolymer produced by copolymerization or a polymer blend produced by mixing. However, the case where polymer particles such as polystyrene particles and polymethylmethacrylate particles are externally added is excluded.

The term "becomes an essential component" as used herein.
Means that the component accounts for 80% or more of the whole,
For example, in the above case, it means that the total amount of polyester and polyimide occupies 80% by weight or more of the film of the present invention.

The polyester used in the biaxially oriented polyester film of the present invention is a polymer composed of an acid component such as an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol component.

As the aromatic dicarboxylic acid, for example, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid and the like can be used. As the alicyclic dicarboxylic acid, for example, cyclohexanedicarboxylic acid or the like can be used. As the aliphatic dicarboxylic acid, for example, adipic acid, sebacic acid, dodecanedioic acid or the like can be used. Among them, terephthalic acid, 2,6-naphthalenedicarboxylic acid and the like can be preferably used, and terephthalic acid can be particularly preferably used. These acid components may be used alone or in combination of two or more.

As the diol component, for example, ethylene glycol, 1,3-propanediol, 1,4
-Butanediol, 1,5-pentanediol, 1,6
-Hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, 2,2'-bis (4'-β-hydroxyethoxyphenyl) propane and the like can be used, and among them, ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol and the like can be used, and ethylene glycol can be particularly preferably used. These diol components may be used alone or in combination of two or more.

Polyester used in the present invention includes polyethylene terephthalate (PET) and poly (ethylene-2,6-naphthalene dicarboxylate) (PE
N) is particularly preferably exemplified, and from the viewpoint of melt moldability,
Most preferably, polyethylene terephthalate (PE
T).

When the polyester used in the present invention is a polyester having ethylene terephthalate as a main constituent, the polyester may be either a direct weight method or a DMT method. In the DMT method, calcium acetate is used as an ester exchange catalyst. It is preferable to use. Further, in the polymerization stage, although not particularly limited, it is preferable to use a germanium compound as a polymerization catalyst in order to reduce coarse protrusions due to foreign matters. As the germanium catalyst, as is known, (1) amorphous germanium oxide, (2) crystalline germanium oxide of 5 μm or less, (3) germanium oxide in the presence of an alkali metal or an alkaline earth metal or a compound thereof, Solution dissolved in, and
(4) A glycol solution of germanium oxide prepared by dissolving germanium oxide in water, adding glycol to this and distilling off water is used.

Polyesters include polyfunctional compounds such as trimellitic acid, pyromellitic acid, glycerol, pentaerythritol and 2,4-dioxybenzoic acid, monofunctional compounds such as lauryl alcohol and phenyl isocyanate, p-hydroxyl. Benzoic acid, m-hydroxybenzoic acid, aromatic hydroxycarboxylic acid such as 2,6-hydroxynaphthoic acid, or p-aminophenol, p-aminobenzoic acid, etc., as long as the effects of the present invention are not impaired. Further, it may be copolymerized.

The polyimide used in the biaxially oriented polyester film of the present invention is not particularly limited as long as it has a good affinity with polyester and is melt moldable. For example, a structural unit represented by the following general formula The one containing

[0020]

[Chemical 1]

However, R _{1 in} the formula is

[Chemical 2]

[0022]

[Chemical 3]

Represents one or more groups selected from an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and R _{2 in} the formula is

[0024]

[Chemical 4]

And one or more groups selected from aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups.

The good affinity (compatibility) mentioned here
Having, for example, an unstretched or biaxially stretched film is produced using a polymer alloy composed of the polymer 1 and the polymer 2, and the cross section of the film is measured with a transmission electron microscope to obtain 30,000 to
When observed at a magnification of 500,000 times, a structure having a diameter of 200 nm or more that does not originate from additives such as externally added particles (for example,
That is, poorly dispersed polymer domains) are not observed. However, the method of determining the affinity between the polymer 1 and the polymer 2 is not particularly limited to this, and if necessary, a single glass transition point is observed by the temperature modulation type DSC (MDSC). Therefore, it may be determined that there is a good affinity.

The polyimide is a tetracarboxylic acid and / or an acid anhydride thereof, and one or more selected from the group consisting of aliphatic primary monoamines, aromatic primary monoamines, aliphatic primary diamines and aromatic primary diamines. It can be obtained by dehydration condensation of a compound.

From the viewpoints of melt moldability with polyester, handleability, surface protrusion formation, and the like, polyether imides having an ether bond as a polyimide component as represented by the following general formula are particularly preferable.

[0029]

[Chemical 5]

(Wherein R ₃ is a divalent aromatic or aliphatic residue having 6 to 30 carbon atoms, R 3
₄ is a divalent aromatic residue having 6 to 30 carbon atoms, an alkylene group having 2 to 20 carbon atoms, 2 to
It is a divalent organic group selected from the group consisting of a cycloalkylene group having 20 carbon atoms and a polydiorganosiloxane group chain-terminated with an alkylene group having 2 to 8 carbon atoms. )

Examples of R ₃ and R ₄ include aromatic residues represented by the following formula group:

[Chemical 6] Can be mentioned. (N in the formula is an integer of 1 to 5)

In the present invention, from the viewpoints of affinity with polyester, cost, melt moldability, etc., 2,2-bis [4-
A polymer having a repeating unit represented by the following formula, which is a condensation product of (2,3-dicarboxyphenoxy) phenyl] propane dianhydride and m-phenylenediamine or p-phenylenediamine is preferable.

[0033]

[Chemical 7]

Or

[Chemical 8] (N is an integer of 2 or more, preferably 20 to 50)

This polyetherimide is "Ultem"
(Registered trademark), which is available from GE Plastics.

If necessary, a compatibilizing agent may be used in combination with the polymer alloy constituting the biaxially oriented polyester film of the present invention in order to control the dispersion diameter. In this case, the type of the compatibilizer varies depending on the type of the polymer, but the addition amount is preferably 0.01 to 10% by weight.

In the present invention, the polyimide is added to the polyester before the polymerization of the polyester, for example,
It may be added before the esterification reaction or after the polymerization. Also, polyester and polyimide may be mixed and pelletized before melt extrusion.

At the time of pelletizing, the polyimide is once concentrated to a high concentration (for example, 35 to 65% by weight, more preferably 40% by weight).
(~ 60 wt%) is used to prepare a master pellet consisting of polyester and polyimide, and then further diluted with polyester to adjust to a predetermined concentration, the dispersibility of the polymers is improved, A more preferable dispersion state as a polymer alloy is shown.

As another method of adjusting the polymer alloy constituting the layer A of the present invention to a more preferable dispersion state, for example, a method of mixing using a tandem extruder, 2
Method of finely dispersing polyetherimide using more than one kind of polyester, method of pulverizing polyimide after pulverizing with a pulverizer, mixing, method of mixing both by dissolving and coprecipitating in a solvent, one in the solvent A method in which the solution is made into a melted solution and then mixed with the other solution may be mentioned, but the method is not limited to this.

The biaxially oriented polyester film of the present invention is not particularly limited, but when it is used as a magnetic recording medium, a laminated portion (referred to as layer B) is laminated on at least one side of a base layer portion (referred to as layer A). It may be a laminated polyester film having at least two or more film layers. In this case, the layer A is generally the thickest layer in the film, and is mainly used for magnetic recording media and the like, which serves to maintain strength and dimensional stability. In addition, the layer B, which is a laminated portion, is a layer having a thinner film layer than the layer A, and by having a relatively rough surface, the transportability of the film and the winding characteristics are improved,
For magnetic tape applications and the like, good running properties can also be obtained.

When the biaxially oriented polyester film of the present invention is used in a laminated constitution of two or more layers, at least one layer is
The polyester film layer may include polyester and polyimide as essential components, but from the viewpoint of improving dimensional stability, the base layer portion (A layer) is preferably the above film layer.

In this case, the kind of polymer used in the film layers other than the above film layer is not particularly limited, but when the same polymer alloy made of polyester and polyimide as used in the above film layer is used, the base layer portion and the laminated portion are used. This is preferable because a difference in melt viscosity is unlikely to occur, and troubles in the production process such as stacking spots and die lines are unlikely to occur. Most preferably, all the film layers are made of a polymer alloy containing polyester and polyimide as essential components, and the weight ratio of polyester and polyimide is the same in all the film layers.

The conventional film made of polyester and polyimide has a problem of low productivity during film production. However, gelation rate (300
The biaxially oriented polyester film of the present invention, which has a orthochlorophenol insoluble matter production rate of 0 to 15% after heat treatment at 2.5 ° C. for 2.5 hours, has the above problems even if it is a film containing polyester and polyimide. It can be resolved.

The gelation rate of the biaxially oriented polyester film of the present invention (generation rate of orthochlorophenol-insoluble matter in heat treatment at 300 ° C. for 2.5 hours) is 0 to 15%, preferably 0 to 10%. Preferably 0-5%
Is. The gelation rate means that after freeze-grinding the film into a powder form, it is heat-treated in the atmosphere at 300 ° C. for 2.5 hours, then dissolved in orthochlorophenol (OCP), and a glass filter is used. It is the weight fraction of the filter residue when filtered.

When the gelation rate of the film is high, defects are likely to occur on the film surface, and the film productivity is lowered. That is, a high gelation rate indicates that the polymer in the film is susceptible to oxidative deterioration, and in the steps such as filtration and extrusion during film production, oxidative deterioration of the polyester progresses and many crosslinked structures are formed. It will be an indicator that it will be included.

As will be described later, the film of the present invention having a low gelation rate is to reduce the amount of magnesium present in the film, contain an antioxidant, reduce the amount of amide end groups in the polyimide, etc. It can be manufactured by taking at least one of the above means.

For example, magnesium present in the polyester derived from a transesterification catalyst or the like at the time of polymerization acts specifically in the system containing the polyester and the polyimide to promote the oxidative deterioration of the polyester, Since a gel-like crosslinked structure is generated in the polymer, it is effective to sufficiently reduce the amount of magnesium present in the film containing polyester and polyimide.

Although not particularly limited, the biaxially oriented polyester film of the present invention preferably contains an antioxidant in the film in order to suppress oxidative deterioration of the polyester. Above all, it is particularly preferable to contain a phenolic antioxidant or a phosphorus antioxidant. Further, from the viewpoint of the effect of suppressing oxidative deterioration and the castability (electrostatic application property) of the polymer, the most preferable antioxidant is a phenolic antioxidant.

The type of the phenolic antioxidant depends on the type of polyester and the polyimide and is not particularly limited, but is not limited to pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxy). Phenyl) propionate], 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4)
-Hydroxybenzyl) benzene, 3,9-bis [2-
[3- (3-t-Butyl-4-hydroxy-5-methylphenyl) -propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro-
[5.5] Undecane, triethylene glycol-bis
[3- (3-t-Butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate ], 2,4-bis- (n
-Octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine,
2,2-thio-diethylenebis [3- (3,5-di-t
-Butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-
4-hydroxyphenyl) propionate, N, N'-
Hexamethylene bis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, bis (3,5 -Ethyl di-t-butyl-4-hydroxybenzylphosphonate), tris (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, octylated diphenylamine, 2,4-bis [( Preferable examples include octylthio) methyl] -o-cresol and isooctyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate.

Among them, pentaerythrityl tetrakis [3- (3,5-di-t-] represented by the following chemical formula, from the viewpoint of affinity with polyester and effect of suppressing oxidative deterioration.
Butyl-4-hydroxyphenyl) propionate]
(This material is available from Ciba Specialty Chemicals under the tradename "Irganox 1010" (R)),

[0051]

[Chemical 9]

Alternatively, 1,3,5 represented by the following chemical formula
-Trimethyl-2,4,6-tris (3,5-di-t-
Butyl-4-hydroxybenzyl) benzene (this material is available from Ciba Specialty Chemicals under the trade name "Irganox 1330" (R)),

[0053]

[Chemical 10]

Alternatively, 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5) represented by the following chemical formula:
-Methylphenyl) -propionyloxy] -1,1-
Dimethylethyl] -2,4,8,10-tetraoxaspiro- [5.5] undecane (This material is a product name of "Adeka Stab A0-80" (registered trademark) from Asahi Denka Kogyo Co., Ltd., or It is available from Sumitomo Chemical Co., Ltd. under the trade name of "Sumilyzer GA-80" (registered trademark).)

[0055]

[Chemical 11]

Is preferably exemplified. Among them, 1, 3,
5-trimethyl-2,4,6-tris (3,5-di-t
-Butyl-4-hydroxybenzyl) benzene is most preferable because it has a particularly large effect of suppressing the oxidative deterioration of the polyester.

The content of the phenolic antioxidant is
Although not particularly limited, it is preferably 0.01 to 2% by weight, and more preferably 0.05 to 1% by weight from the viewpoint of the effect of suppressing oxidative deterioration, the formation of craters, the suppression of bleed-out on the film surface, and the like. The amount of antioxidant added is 0.
When it is less than 01% by weight, it is difficult to uniformly disperse the antioxidant, and the effect of suppressing oxidative deterioration is small. On the other hand, if it exceeds 2% by weight, a crater may be formed on the film, causing breakage of the film, resulting in a decrease in productivity, or blade-out on the surface of the film to deteriorate the performance of the film.

The type of the phosphorus-based antioxidant varies depending on the type of polyester and polyimide,
Although not particularly limited, tris (2,4-di-t-butylphenyl) phosphite, tetrakis (2,4-di-t)
-Butylphenyl) -4,4'-biphenylenediphosphonite, tetrakis (2,4-di-t-butyl-5-methylphenyl-4,4'-biphenylenediphosphonite, bis (2,4-di-) t-butylphenyl) pentaerythritol diphosphite, bis (2,6-di-t-
Butylphenyl) pentaerythritol diphosphite, 2,2'-methylenebis (4,6-di-t-butylphenyl) -2-ethylhexylphosphite, bis (2,6-di-t-butyl-6-methylphenyl) ) Ethylphosphite, 2,2 ', 2''-nitrilo [triethyltris (3,3', 5,5'-tetra-t-butyl-1,1'-biphenyl-2,2'-diyl) phosphine Fight], 6- [3- (3-t-butyl-4-hydroxy-
5-Methylphenyl) propoxy] -2,4,8,10
-Tetra-t-butyldibenzo [d, f] [1,3,2] dioxaphosphepine, 2-[[2,4,8,10-tetrakis (1,1-dimethylether) dibenzo [d, f]
[1,3,2] Dioxaphosphepin 6-yl] oxy]
-N, N-bis [2-[[2,4,8,10-tetrakis (1,1dimethylethyl) dibenzo [d, f] [1,3
Preferable examples include 2] dioxaphosphepin-6-yl] oxy] -ethyl] ethanamine, cyclic neopentanetetraylbis (2,6-di-t-butyl-methylphenyl) phosphite and the like.

Among them, tris (2,4-di-t-butylphenyl) phosphite, or cyclic neopentanetetraylbis (2,6-) represented by the following chemical formula
Di-t-butyl-methylphenyl) phosphite (this substance is available from Asahi Denka Kogyo Co., Ltd. under the trade name of "ADEKA STAB PEP-36" (registered trademark)) is particularly preferably exemplified.

[0060]

[Chemical 12]

The content of the above-mentioned phosphorus-based antioxidant is not particularly limited, but from the viewpoint of the effect of suppressing oxidative deterioration and the formation of craters, the content is preferably 0.01 to 2% by weight, more preferably 0.05 to 1%. % By weight. When the amount of the antioxidant added is less than 0.01% by weight, it is difficult to uniformly disperse the antioxidant, and the effect of suppressing oxidative deterioration is small. On the other hand, if it exceeds 2% by weight, craters may be formed on the film, which may cause film breakage and reduce productivity.

However, when a phosphorus antioxidant is used,
In some cases, the metal component in the polymer is deactivated, the melt specific resistance of the polymer increases, and the castability (electrostatic application property) decreases.

If desired, a lactone type antioxidant may be added. As the lactone antioxidant,
For example, 5,7-di-t-butyl-3- (3,4-di-methylphenyl) -3H-benzofuran-2-one represented by the following chemical formula (this substance is "HP-136")
(Registered trademark), available from Ciba Specialty Chemicals. ) Is preferably exemplified.

[0064]

[Chemical 13]

The content of the lactone-based antioxidant is not particularly limited, but is preferably 0.01 to 2% by weight, more preferably 0.05 to 1% by weight from the viewpoint of the effect of suppressing oxidative deterioration and the formation of craters. %. When the amount of the antioxidant added is less than 0.01% by weight, it is difficult to uniformly disperse the antioxidant, and the effect of suppressing oxidative deterioration is small. On the other hand, if it exceeds 2% by weight, craters may be formed on the film, which may cause film breakage and reduce productivity.

These antioxidants may be used alone or in combination of two or more. Although not particularly limited, it is preferable to include both a phenol-based antioxidant and a phosphorus-based antioxidant because the effect of preventing oxidative deterioration is enhanced. In this case, the total amount of antioxidants added is preferably 0.01 to 2% by weight from the viewpoint of the effect of suppressing oxidative deterioration and the formation of craters. If the total amount of antioxidant added is less than 0.01% by weight, it is difficult to uniformly disperse the antioxidant, and the effect of suppressing oxidative deterioration is small. On the other hand, if it exceeds 2% by weight, craters may be formed on the film, which may cause film breakage and reduce productivity.

As the method of adding the above-mentioned antioxidant to the polymer, a method of adding and mixing at the time of polymerization of polyester, a conventionally used mixer or kneader,
For example, a method of adding and mixing in a polymer alloy production step or a melt extrusion step using a uniaxial or biaxial extruder type kneader and the like can be mentioned. However, when added at the time of polymerization, craters may be generated in the film due to the effect of the defoaming agent, and film breakage may occur frequently, resulting in a decrease in productivity. The method of mixing is preferable.

The biaxially oriented polyester film of the present invention is not particularly limited, but the amount of magnesium derived from the transesterification catalyst in the film is 0 to 500 p.
It is preferably pm. More preferably, 0-20
0 ppm, most preferably 0 to 100 ppm.

Magnesium is usually contained in the polyester because it is often used as a transesterification catalyst in the polymerization of polyester and is often contained in the polyester for the purpose of improving electrostatic application. However, when magnesium is present in the film containing polyester and polyimide, oxidative deterioration of the polyester is particularly promoted. Therefore, in the present invention, it is effective to reduce the amount of magnesium present in the film as much as possible. On the other hand, the oxidative deterioration is not promoted in the system containing only polyester and magnesium, and the oxidative deterioration is not promoted also in the system containing polyester and polyimide in the absence of magnesium. Furthermore, oxidative deterioration is not promoted even with a polyimide alone or a system containing only polyimide and magnesium. Thus, the oxidative deterioration promoting action of magnesium is a unique phenomenon that occurs only in a system in which polyester, polyimide and magnesium coexist.

That is, if the amount of magnesium present in the film containing polyester and polyimide deviates from the above range, the production of oxidative deterioration products of polyester is easily promoted, which is not preferable. However, when magnesium is deactivated by a phosphorus compound or the like, the production of oxidative deterioration products is suppressed, so it is also effective to deactivate the magnesium instead of or together with the reduction. If the amount of magnesium present is too small, the electrostatic applicability may be reduced. In that case, by containing cobalt or the like, both the oxidative decomposition-inhibiting property and the electrostatic application property can be improved.

In order to reduce the amount of magnesium present in the biaxially oriented polyester film of the present invention to the above-mentioned preferable level, the amount of magnesium catalyst added in the polymerization stage for producing the polyester used as the film raw material is reduced. By taking the means of
The amount of magnesium in the polyester may be appropriately controlled to a desired level.

The biaxially oriented polyester film of the present invention is not particularly limited, but the amount of amino terminal groups in the film is preferably 0 to 20 × 10 ^-6 mol / g.
More preferably, it is 0 to 10 × 10 ⁻⁶ mol / g. If the amount of amino terminal groups in the film is out of this range, the production of oxidatively deteriorated polyester may be accelerated.

The biaxially oriented polyester film of the present invention is not particularly limited, but the transportability in the film forming / processing step of the film, the running property and running durability of the magnetic tape when used as a magnetic recording medium application. Inert particles may be contained for the purpose of improving. The inert particles referred to in the present invention are inorganic or organic particles having an average particle size of about 1 nm to 5 μm, which cause a chemical reaction in the polymer used in the present invention or adversely affect magnetic recording due to electromagnetic influence. Say what you don't As the inert particles, titanium oxide, calcium carbonate, kaolin, talc, wet or dry silica, colloidal silica, calcium phosphate, barium sulfate, inorganic particles such as alumina and zirconia, acrylic acid, styrene, silicone, imide, etc. And organic particles, particles (so-called internal particles) precipitated by a catalyst added during the polyester polymerization reaction, and a surfactant.

The average particle size and content of the inert particles contained in the biaxially oriented polyester film of the present invention vary greatly depending on the film application and the laminated structure. In particular, when used for magnetic recording media such as magnetic tapes, the front and back surfaces have smooth surfaces for obtaining excellent electromagnetic conversion characteristics, transport in film forming / processing steps, and magnetic tape runnability. In order to impart running durability, a surface morphology having different roughness, that is, a relatively rough surface is required. For this reason, it is common to have a laminated structure of two or more layers, in which one film layer contains particles with a small particle size and the opposite film layer contains particles with a relatively large particle size. is there.

For example, when the film of the present invention is used as a magnetic recording medium in an A / B two-layer laminated structure, the average particle size of the inert particles contained in the A layer is such as electromagnetic conversion characteristics and running property with a magnetic head. From the viewpoint of 0.005 to 0.5
μm is preferable, and more preferably 0.01 to 0.3 μm.
The content of the inert particles is, from the viewpoint of electromagnetic conversion characteristics, generation of coarse projections due to particle aggregation, scraping of projections, etc.,
0.01 to 1% by weight is preferable, and 0.0 is more preferable.
It is 2 to 0.05% by weight. The average particle diameter of the inert particles added to the layer B is preferably 0.01 to 2 μm, more preferably 0.01 to 1 μm from the viewpoints of running property, running durability and show-through of the magnetic tape. Content is 0.00
It is 1 to 3% by weight, preferably 0.005 to 1% by weight. One type of inert particles may be contained in each film layer, but two or more types may be used in combination.

When the biaxially oriented polyester film of the present invention is used in a laminated constitution, the laminated thickness is not particularly limited, but if it is 20% or less of the total thickness of the film, the film forming property is good and it is preferable. It is more preferably 15% or less, and particularly preferably 10% or less of the total thickness of the film.
In addition, the laminated thickness is 0.1 to 10 of the average particle diameter of the inert particles contained in the laminated portion, from the viewpoint of the protrusion forming property of the laminated portion.
It is preferably double, and more preferably 0.2 to 5 times.

The surface roughness of the surface of the biaxially oriented polyester film of the present invention varies greatly depending on the intended use of the film. For example, when used as a magnetic recording medium, the surface roughness Ra is preferably 3 to 30 nm. ,
30 to 120 nm when used as a capacitor
Is preferred. In particular, when used as a magnetic recording medium such as a magnetic tape, the front and back surfaces of the film are required to have a flat surface on which magnetic recording is applied and a relatively rough surface for tape running property. It is preferable that the heights are different. For example, in the case of using an A / B two-layer laminated structure as a magnetic recording medium application, the surface roughness of the surface on the A layer side is 3 from the viewpoint of electromagnetic conversion characteristics and the like.
~ 15 nm is preferable, and more preferably 5-10 nm.
The surface roughness of the layer B side is preferably 5 to 30 nm, more preferably 7 to 15 nm, from the viewpoint of magnetic tape running properties.

The number of coarse projections of the biaxially oriented polyester film of the present invention is not particularly limited, but when used as a magnetic recording medium, from the viewpoint of electromagnetic conversion characteristics, running durability, etc., the number of coarse projections H1 (height 0 The number of protrusions of 0.28 μm or more) is preferably 100 / cm ² or less, and more preferably 50 / cm ² or less. Similarly, the number of large protrusions H2
The number of protrusions having a height of 0.56 μm or more is preferably 10 / cm ² or less, more preferably 5 / cm ² or less.
When used in an A / B two-layer laminated structure, it is preferable that the number of coarse protrusions on the surface of the A layer is within the above range.

The content of the polyimide in the biaxially oriented polyester film of the present invention is 1 to 30 in the polymer alloy.
It is preferably in the range of% by weight. It is more preferably 5 to 20% by weight, and particularly preferably 8 to 15% by weight. Generally, polyesters and polyimides have large melt viscosities, so if the content of polyimide is less than 1% by weight, it may be difficult to finely disperse in the extruder, and the polyimide domains are coarse. Therefore, the surface protrusions may become coarse. Further, the effect of improving the thermal dimensional stability cannot be obtained. Further, when the content of the polyimide is more than 30% by weight, it becomes difficult to carry out extrusion molding processing or stretching processing, which may cause film formation or processing troubles such as film tearing and die streak during extrusion. In some cases, the voids formed around the particles become large and the voids cannot be controlled within the scope of the present invention.

The biaxially oriented polyester film of the present invention is an organic compound such as a heat stabilizer, an ultraviolet absorber, an antistatic agent, a flame retardant, a pigment, a dye, a fatty acid ester, a wax, etc. within a range that does not impair the effects of the present invention. A lubricant or the like may be added.

The Young's modulus of the biaxially oriented polyester film of the present invention varies greatly depending on the intended use of the film. For example, when used as a magnetic recording medium, the sum of the Young's modulus in the longitudinal direction and the Young's modulus in the width direction is: From the viewpoint of elongation and deformation of the magnetic tape, the range is preferably 9 to 25 GPa, more preferably 11 to 22 GPa,
More preferably, it is 14 to 20 GPa. The Young's modulus in the longitudinal direction is preferably 4.5 GPa or more, more preferably 5 GPa or more, and most preferably 6.5 GPa or more from the viewpoint of head contact with the magnetic head. The Young's modulus in the width direction is preferably 4.5 GPa or more, more preferably 5 GPa or more, and most preferably 5.5 GPa or more from the viewpoint of tape edge damage and the like.

The heat shrinkage rate of the biaxially oriented polyester film of the present invention varies greatly depending on the intended use of the film. For example, when used as a magnetic recording medium application, the heat shrinkage rate at a temperature of 100 ° C. in the longitudinal direction for 30 minutes is: From the viewpoint of dimensional stability, tape elongation deformation and storage stability,
It is preferably 1.2% or less. More preferably,
It is 1% or less. The thermal shrinkage at a temperature of 80 ° C. for 30 minutes in the longitudinal direction is preferably 0.3% or less from the viewpoint of elongation deformation property and storability of the tape. More preferably, it is 0.25% or less. Temperature in the width direction 100 ℃,
The heat shrinkage rate after 30 minutes is preferably 0.5% or less from the viewpoint of elongation deformation and storage stability of the tape. More preferably, it is 0.3% or less. The heat shrinkage at a temperature of 80 ° C. for 30 minutes in the width direction is preferably 0.1% or less from the viewpoint of elongation deformation property and storage stability of the tape. More preferably, it is 0.05% or less.

When the biaxially oriented polyester film of the present invention is used as a magnetic recording medium, it is at 60 ° C. and 80% R
Under the condition of H, with a load of 26 MPa applied in the longitudinal direction, when left for 72 hours, the dimensional change rate in the width direction is -0.4 to 0% from the viewpoint of track deviation and elongation deformation of the tape. It is preferably in the range of. More preferably, it is −0.3 to 0%.

The extrapolated glass transition _onset temperature (Tg _onset ) of the polymer of the biaxially oriented polyester film of the present invention is
Although not particularly limited, it is preferably 90 to 150 ° C, more preferably 95 to 130 ° C, and further preferably 98 to 120 ° C.

The intrinsic viscosity of the polymer alloy which constitutes the biaxially oriented polyester film of the present invention is 0. 0 from the viewpoint of stability of film forming process and miscibility with a thermoplastic resin.
The range is preferably 55 to 3.0 (dl / g), more preferably 0.60 to 2.0 (dl / g).
Is. In addition, the intrinsic viscosity of the film after film formation is from 0. 0 from the viewpoint of stability of film forming process and dimensional stability.
The range is preferably 50 to 2.0 (dl / g), and more preferably 0.55 to 1.0 (dl / g).

The use of the biaxially oriented polyester film of the present invention is not particularly limited, but it is used for a base film for magnetic recording media, a capacitor, a heat-sensitive transfer ribbon, a heat-sensitive stencil, an optical material and the like. Above all, it is preferably used for a magnetic recording medium such as a base film for data storage or a digital video tape having a vapor-deposited magnetic layer, which requires a uniform and fine surface morphology and high dimensional stability. Of these, particularly preferred is a film suitable for a base film for data storage for high-density magnetic recording. The data recording capacity of the data storage is preferably 30 GB (gigabytes) or more, more preferably 70 GB.
It is GB or more, more preferably 100 GB or more.

The thickness of the biaxially oriented polyester film of the present invention can be appropriately determined according to the use, but for example, usually 1 to 15 μm is preferable for magnetic recording medium use, and excellent dielectric breakdown voltage and dielectric property for capacitor use. From the viewpoint of stability and the like, 0.5 to 15 μm is applied, and from 1 to 6 μm is preferably used from the viewpoint of not causing “wrinkles” or printing unevenness at the time of printing and excessive transfer of ink in the use of a thermal transfer ribbon. For atomic use, a thickness of 0.5 to 5 μm is preferably used from the viewpoint of piercing property and printability. Among them, in the case of high density magnetic recording medium use, it is preferably 3 to 8 μm, more preferably 4 to 7 μm, and most preferably 4.5 to 6.5 μm. If the thickness is less than 3 μm, the tape loses its rigidity and the electromagnetic conversion characteristics may deteriorate. If the thickness is more than 8 μm, the tape length per tape becomes short, and the magnetic tape is downsized. It may be difficult to increase the capacity.

The biaxially oriented polyester film of the present invention has a further polymer layer such as polyolefin,
Polyamide, polyvinylidene chloride and acrylic polymer may be laminated directly or via a layer such as an adhesive.

The biaxially oriented polyester film of the present invention may be subjected to any processing such as heat treatment, molding, surface treatment, laminating, coating, printing, embossing and etching, if necessary.

By providing a magnetic layer on at least one side of the biaxially oriented polyester film of the present invention, it can be used as a magnetic recording medium. The surface on which the magnetic layer is provided may be either surface of the film or both surfaces. For example, when a film having an A / B two-layer laminated structure is used, the magnetic layer is provided on the base layer (A layer) side. It is preferable.

Suitable examples of the magnetic layer include a magnetic layer formed by dispersing a ferromagnetic metal thin film or fine ferromagnetic metal powder in a binder, a magnetic layer formed by coating a metal oxide, and the like.
The metal used for the ferromagnetic metal thin film is preferably iron, cobalt, nickel, or an alloy thereof. As the ferromagnetic metal fine powder used in the magnetic layer obtained by dispersing the ferromagnetic metal fine powder in the binder, ferromagnetic hexagonal ferrite fine powder, iron, cobalt, nickel or a powder thereof or an alloy thereof is used. preferable. The binder is preferably a thermoplastic resin, a thermosetting resin, a reactive resin or a mixture thereof.

As the method for forming the magnetic layer, a magnetic powder is kneaded with a binder such as a thermosetting resin, a thermoplastic resin, or a radiation curable composition, and coating and drying are performed, or a metal or alloy is vapor-deposited. Any method of a dry method in which a magnetic metal thin film layer is directly formed on a substrate film by sputtering, ion plating method or the like can be adopted.

In the magnetic recording medium of the present invention, a protective film may be provided on the magnetic layer. This protective film can further improve running durability and corrosion resistance.
As the protective film, oxide protective films such as silica, alumina, titania, zirconia, cobalt oxide, and nickel oxide, nitride protective films such as titanium nitride, silicon nitride, and boron nitride, silicon carbide, chromium carbide, boron carbide, etc. Examples thereof include a carbide protective film, a carbon protective film made of carbon such as graphite and amorphous carbon.

The carbon protective film is a carbon film made of an amorphous, graphite, diamond structure, or a mixture thereof prepared by a plasma CVD method, a sputtering method or the like, particularly preferably a hard carbon film generally called diamond-like carbon. is there.

The surface of the hard carbon protective film may be surface-treated with plasma of an oxidizing gas or an inert gas for the purpose of further improving the adhesion with the lubricant applied on the hard carbon protective film.

In the present invention, in order to improve running durability and corrosion resistance of the magnetic recording medium, it is preferable to add a lubricant or a rust preventive agent on the magnetic layer or the protective film.

In producing the biaxially oriented polyester film of the present invention, generally, a polymer alloy of polyester and polyimide is prepared by a method such as using a master pellet containing a high concentration of polyimide, and the polymer alloy is extruded. The polymer is discharged from the die by melt extrusion using, and the molten polymer is cooled and solidified to be molded into a sheet to obtain an unstretched sheet, which is stretched and heat treated.

When the biaxially oriented polyester film of the present invention is produced, the maximum temperature of the polymer in the extruder during melt extrusion is preferably 260 to 300 ° C, more preferably 270 to 285 ° C. . If the maximum temperature of the polymer in the extruder is higher than 300 ° C, oxidative deterioration may be accelerated, and if it is lower than 260 ° C, the viscosity of the polymer may be high and the melt extrudability may be lowered. is there.

In the case of producing the biaxially oriented polyester film of the present invention, the oxygen concentration in the portion where the polymer is put into the extruder at the time of melt extrusion is preferably 0.01 to 1 mol%, more preferably 0.1 to 0. It is 0.5 mol%. If the oxygen concentration is higher than 1 mol%, oxidative deterioration may be accelerated. On the other hand, if it is less than 0.01 mol%, it is difficult to manufacture and the apparatus cost may be high.

In the melt extrusion, filtration of the polymer with a fiber sintered stainless metal filter having a cut of 1.2 μm or less is preferably exemplified as a method for removing the unmelted material in the polymer alloy. More preferably,
Filter with a filter having a cut of 0.8 μm or less. Further, if necessary, it is preferable to pass through two or more filter parts and to filter in two or more stages, because contaminants, unmelted substances, and gel-like foreign substances can be removed more effectively. The 1.2 μm cut filter referred to here means that the filtration accuracy is 1.2 μm, and the filtration accuracy is JIS-
It means the maximum particle size of glass beads that has permeated the filter media by the method of B8356.

As a method for producing master pellets composed of polyester and polyimide, a method of melt-kneading polyester and polyimide pellets with an extruder and a method of copolymerizing polyimide in the polyester polymerization stage are preferably exemplified. . In this case, the copolymerization is less likely to cause poor dispersion, but the crystallinity of the final film may be lowered, and the film strength may be lowered.

When polyester and polyimide pellets are melt-kneaded in an extruder to prepare master pellets, the polyimide concentration is preferably 35 to 65% by weight,
More preferably, it is 40 to 60% by weight. If the concentration of the polyimide is out of the above range, coarse domains may be generated in the polymer due to phase separation or poor dispersion. The extruder used for melt-kneading is preferably a vent type twin-screw kneading extruder from the viewpoint of kneading properties. The residence time at this time is preferably 30 to 600 seconds, more preferably 60 to 300 seconds, and most preferably 180 to 300 seconds.
It is 300 seconds. If the residence time is less than 30 seconds, a coarse dispersion may be generated without sufficient kneading, and if the residence time exceeds 600 seconds, the composition is exposed to a melting temperature for a long time, and thus a thermal deterioration product is generated. When formed into a film, it may become a coarse protrusion. The master pellet produced by melt-kneading has a structure (for example, a polymer domain) which is not caused by additives such as externally added particles and has a diameter of 500 nm or less when observed with a transmission electron microscope at a magnification of 30,000 to 500,000 times. It is preferable that it is recognized that the polymers are easily dispersed in the subsequent dilution step. When a structure having a size of more than 500 nm is present, it may not be sufficiently dispersed in the diluting step and may form coarse protrusions in the film.

A biaxially oriented polyester film is produced by biaxially stretching a melt-extruded, cooled and solidified molded product biaxially in the longitudinal direction and the width direction, and then heat-treating it. The stretching in the direction may be performed step by step, or may be performed in two or more steps depending on the intended use of the film. Further, re-longitudinal and horizontal re-stretching may be performed.

The biaxially oriented polyester film of the present invention may be stretched in a sequential biaxial stretching method such as stretching in the longitudinal direction and then in the transverse direction, or by using a simultaneous biaxial tenter or the like. A simultaneous biaxial stretching method in which the directions are simultaneously stretched, a method in which a sequential biaxial stretching method and a simultaneous biaxial stretching method are combined, and the like are used.

The total stretching ratio in the longitudinal direction at the time of producing the biaxially oriented polyester film of the present invention is not particularly limited, but is preferably 2.5 to 10 times, more preferably 4.
5 to 7 times. If the total stretching ratio in the longitudinal direction is less than 2.5 times, the elastic modulus in the longitudinal direction is lowered, so that when used as a magnetic recording medium, the electromagnetic conversion characteristics may be deteriorated. If it is larger than 10 times, the film breakage may increase, the productivity may be reduced, or the voids around the particles may become large, and the particles may easily fall off.

The biaxially oriented polyester film of the present invention may be subjected to re-longitudinal stretching when it is used for applications requiring a high elastic modulus such as magnetic recording media. In this case, it is preferable that the re-longitudinal stretching ratio is 25% or less of the total longitudinal stretching ratio because the film breakage is reduced. When the longitudinal re-stretching is performed, the stretching ratio of the first longitudinal stretching is preferably 2.5 to 4.0 times, and the longitudinal re-stretching ratio is preferably 1.2 to 2.3 times.

The total stretching ratio in the width direction when producing the biaxially oriented polyester film of the present invention is not particularly limited, but is preferably 3 to 8 times, more preferably 3.5 to 6 times. If the total draw ratio in the width direction is less than 3 times,
When it is used as a magnetic recording medium, track deviation easily occurs. When the total stretching ratio in the width direction exceeds 6 times, the film may be broken to lower the productivity.

The biaxially oriented polyester film of the present invention may be subjected to transverse re-stretching when it is used in applications such as magnetic recording media which require a high elastic modulus. In this case, it is preferable that the transverse re-stretch ratio is 20% or more of the total transverse stretch ratio because the film breakage is reduced. When the transverse re-stretching is performed, the stretching ratio of the first transverse stretching is preferably 3.0 to 4.5 times, and the longitudinal re-stretching ratio is preferably 1.2 to 2 times.

The stretching temperature in the longitudinal direction in producing the biaxially oriented polyester film of the present invention is not particularly limited, but the glass transition temperature Tg of the polymer (in the case of the laminated constitution, the polymer of the base layer (A layer)) When the temperature is within the range of Tg + 50 ° C., the stretchability becomes good, which is preferable. When the longitudinal re-stretching is performed, the longitudinal re-stretching temperature is Tg + 30 ° C. to Tg + 80 ° C.
Is preferred.

The stretching temperature in the width direction at the time of producing the biaxially oriented polyester film of the present invention is not particularly limited, but it is Tg to Tg + 50 ° C. of the polymer (in the case of the laminated constitution, the polymer of the base layer part (A layer)). Ranges are preferred. When the transverse re-stretching is performed, the transverse re-stretching temperature is Tg + 50 ° C. to Tg + 1.
50 ° C is preferred.

The stretching speed in the longitudinal direction at the time of producing the biaxially oriented polyester film of the present invention is not particularly limited, but it is preferably in the range of 5,000 to 200,000% / min. The speed is preferably in the range of 30,000 to 200,000% / minute.

The stretching speed in the width direction at the time of producing the biaxially oriented polyester film of the present invention is not particularly limited, but it is preferably in the range of 1000 to 10000% / min. Is 1000 to 2000
0% / min is preferred.

The heat treatment for producing the biaxially oriented polyester film of the present invention is Tg + 50 ° C. to Tg + 150 ° C.
In order to obtain the effect of the present invention, it is preferable to carry out the treatment in the range of 0.2 to 10 seconds.

Examples of the method for producing the biaxially oriented polyester film of the present invention will be described below, but the invention is not limited thereto. Here, polyethylene terephthalate is used as the polyester, and as the polyimide,
An example of a film using the polyetherimide "Ultem" is shown. In addition, in this example, an example of a strengthened film that has been subjected to re-longitudinal and transverse re-stretching is shown. In addition, the manufacturing conditions differ depending on the polyester and polyimide used or the laminated structure.

First, bis-β-hydroxyethyl terephthalate (BHT) is obtained by esterification of terephthalic acid and ethylene glycol or by transesterification of dimethyl terephthalate and ethylene glycol according to a conventional method. Next, this BHT is transferred to a polymerization tank and heated to 280 ° C. under vacuum to advance the polymerization reaction. Here, a polyester having an intrinsic viscosity of about 0.5 is obtained. The polyester obtained is pelletized and placed under reduced pressure for solid phase polymerization. In the case of solid-phase polymerization, pelletized polyester is preliminarily crystallized at a temperature of 180 ° C. or lower and then solid-state polymerized at 190 to 250 ° C. under a reduced pressure of about 1 mmHg for 10 to 50 hours.

In the obtained polyester, generally,
Magnesium exists due to a transesterification catalyst at the stage of polyester polymerization and a magnesium catalyst added for the purpose of improving electrostatic application. Therefore, in order to produce a polyester in which the amount of magnesium present is reduced for the film of the present invention, the magnesium-based transesterification catalyst is changed to a catalyst such as germanium or cobalt, and the addition amount of phosphorus in PET is changed. By reducing
The amount of magnesium added may be reduced. That is, the amount of magnesium in the polyester can be set to a desired level by appropriately controlling the amount of magnesium catalyst added in the polyester polymerization step.

When the polyester constituting the film contains inactive particles, the inactive particles are dispersed in ethylene glycol in a predetermined ratio in the form of a slurry.
A method of adding this ethylene glycol during polymerization is preferable. When adding the inert particles, for example, the dispersibility of the particles is good if the water sol or alcohol sol obtained during the synthesis of the inert particles is added without being once dried. Also effective is a method in which a water slurry of inert particles is directly mixed with polyester pellets and kneaded into polyester using a vent type twin-screw kneading extruder. As a method for adjusting the content of the inert particles, a master pellet containing a high concentration of the inert particles is prepared by the above method, and it is diluted with a polyester that does not substantially contain the inert particles during film formation. A method of adjusting the content of the inert particles is effective.

Next, the polyethylene terephthalate pellets and the polyetherimide pellets were mixed at a predetermined ratio and fed to a vent type twin-screw kneading extruder heated to 270 to 300 ° C. to perform melt extrusion. To do. The residence time at this time is preferably 30 to 600 seconds, more preferably 60 to 300 seconds. Furthermore, when the two do not become compatible under the above conditions, the obtained chips may be put into the twin-screw extruder again and the extrusion may be repeated until they become compatible. When an antioxidant is contained, the antioxidant may be mixed in a predetermined ratio in addition to the polyethylene terephthalate pellets and the polyetherimide pellets at the stage of producing the pellets.

The obtained polyetherimide-containing polyester pellets were vacuum dried at 180 ° C. for 3 hours or more, and then heated to 260 to 300 ° C. under a nitrogen stream or under vacuum so that the intrinsic viscosity would not decrease. The film is supplied to an extruder, extruded from a slit die, and cooled on a casting roll to obtain an unstretched film. At this time, it is preferable to use various filters, for example, filters made of materials such as sintered metal, porous ceramics, sand, and wire mesh in order to remove foreign matters and denatured polymers. Particularly preferred is a method in which a sand filter and a fiber-sintered stainless metal filter with a 1.2 μm cut or a 0.8 μm cut are used in this order and filtration is carried out in two stages. Further, if necessary, a gear pump may be provided to improve the quantitative supply property. When laminating films, two or more extruders and manifolds or confluence blocks may be used to melt laminate a plurality of different polymers. When an antioxidant having high sublimability and volatility is used, the antioxidant may be added to the extruder during the melt extrusion.

Next, this unstretched film was biaxially stretched,
Orient biaxially. As a stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. Here, a sequential biaxial stretching method is used in which stretching is first performed in the longitudinal direction and then in the width direction. The stretching temperature will be described, for example, in the case where the layers A and B each have a two-layer structure and are made of a mixed polymer of polyethylene terephthalate and polyetherimide (mixing weight ratio 9: 1). Unstretched film 70-170 ℃
Of the heating roll group, and is stretched in the longitudinal direction by 2.5 to 10 times (2.5 to 4 times in the case of re-longitudinal stretching) in one stage or in multiple stages, and in a cooling roll group of 20 to 50 ° C. Cooling. The longitudinal stretching speed is preferably 5000-200000% / min. Subsequently, stretching in the width direction is performed. As a stretching method in the width direction, for example, a method using a tenter is generally used. The stretching ratio in the width direction is 3 to 8 times (3 to 4.5 times in the case of performing transverse stretching again), and the stretching speed is 1.
The temperature is preferably 000 to 10000% / min, and the temperature is preferably 95 to 160 ° C. Further, if necessary, longitudinal re-stretching and / or transverse re-stretching are performed. As the stretching conditions in that case, the stretching in the longitudinal direction is preferably a heating roll group at a temperature of 80 to 170 ° C., the stretching ratio is 1.2 to 2.3 times, and the stretching method in the width direction is preferably a tenter. Temperature 15
It is preferable to carry out at 0 to 250 ° C. and a draw ratio of 1.2 to 2 times. Subsequently, this stretched film is heat-treated under tension or while relaxing in the width direction. The heat treatment temperature in this case is 15
It is preferable to carry out at 0 to 250 ° C., preferably 170 to 220 ° C., and for a time in the range of 0.2 to 10 seconds.

(Physical property measuring method and effect evaluating method) The characteristic value measuring method and effect evaluating method in the present invention are as follows.

(1) Gelation rate 1 g of the film is freeze-pulverized to form a powder having a diameter of 300 μm or less and vacuum dried. This sample is heat-treated in an oven at 300 ° C. for 2.5 hours in the atmosphere. This is 50m
80 to 15 in 1 orthochlorophenol (OCP)
Dissolve for 0.5 hours at a temperature of 0 ° C. Subsequently, a Buchner-type glass filter (G3: maximum pore size of 20 to 30 μm)
m), wash and vacuum dry. The weight of OCP insoluble matter remaining in the filter was calculated from the increase in the weight of the filter before and after filtration, and the film weight of OCP unnecessary substances (1 g)
The weight fraction was calculated as the gelation rate (%).

(2) Magnesium abundance Rigaku Denki KK fluorescent X-ray analyzer (model number: 3270)
Was quantified by the usual method.

(3) Amount of amino end group in polyimide 1 g of polyimide was added to 18 ml of phenol / 2 m of methanol.
1 / chloroform 20ml / 5ml water mixed solvent, automatic potentiometric titrator (Mitsubishi Chemical GT-05 type)
Is used for potentiometric titration with HCl (0.01 normal) to determine the amine value.

(4) Average Particle Diameter of Inert Particles When determining the average particle diameter of the inert particles in the film: The cross section of the film is observed with a transmission electron microscope (TEM) at a magnification of 10,000 times or more. . The section thickness of the TEM is about 100 nm, and the location is changed to measure 100 fields or more. The weight average of the measured equivalent circle diameters is defined as the average particle diameter d of the inert particles. When two or more kinds of particles having different particle diameters are present in the film, the number distribution of equivalent circle equivalent diameters has a distribution having two or more kinds of peaks, and therefore the average particle diameter is calculated separately for each of them. To do.

(5) Content of Polyester, Polyimide, and Inert Particles When determining the respective contents from the film: Dissolve both polyester and polyimide in a suitable solvent to dissolve the ¹ H nucleus (NMR). Resonance) spectrum is measured. The appropriate solvent depends on the type of polymer,
For example, hexafluoroisopropanol (HFIP)
/ Deuterated chloroform is used. In the obtained spectrum, the peak area intensity of absorption peculiar to polyester and polyimide (for example, absorption of terephthalic acid aromatic proton for PET, absorption of bisphenol A aromatic proton for PEI) is obtained, and The molar ratio of polyester and polyimide is calculated from the ratio and the number of protons. Furthermore, the weight ratio is calculated from the formula weight corresponding to the unit unit of each polymer. The measurement conditions are, for example, the following conditions, but they are not limited to these, because they differ depending on the type of polymer.

Apparatus: BRUKER DRX-500 (Bruker) Solvent: HFIP / deuterated chloroform Observation frequency: 499.8 MHz Reference: TMS (tetramethylsilane) (0 pp
m) Measurement temperature: 30 ° C. Observation width: 10 KHz Data point: 64 K acquisiton time: 4.952 seconds pulse delay time: 3.048 seconds Integration times: 256 times

If necessary, the composition may be analyzed by the microscopic FT-IR method (Fourier transform microscopic infrared spectroscopy). In that case, it is determined from the ratio of the peak due to the carbonyl group of the polyester to the peak due to other substances. In order to convert the peak height ratio to the weight ratio,
A calibration curve is prepared in advance using a sample with a known weight ratio, and the polyester ratio relative to the total amount of polyester and other substances is determined. From this and the content of inert particles, PE
Find the I ratio. Moreover, you may use together an X-ray microanalyzer as needed. Regarding the content of the inactive particles, polyester, a solvent that does not dissolve the inactive particles but the polyester is selected, the polyester,
The polyimide is dissolved, the inert particles are centrifuged, the weight of the inert particles is determined, and the weight percentage is calculated.

(6) Laminated thickness Using a transmission electron microscope (H-600 type manufactured by Hitachi), the film cross section was subjected to an ultrathin section method (R) at an acceleration voltage of 100 kV.
uO ₄ stain). The thickness of each layer is obtained from the observation result of the interface. An appropriate magnification is selected according to the layer thickness to be determined, but 10,000 to 100,000 times is appropriate.

A secondary ion mass spectrometer (SIM
S), which can be measured using S).
The concentration ratio (M ⁺ / C ⁺ ) of the element due to the highest concentration of inactive particles (or PEI) in the film in the range of 0 nm to the carbon element of polyester (M ⁺ / C ⁺ ) is increased from the surface to a depth of 3000 nm. SIMS analysis in the vertical direction.
In the surface layer, the element concentration due to the inert particles (or PEI) is low, and the element concentration due to the inert particles (or PEI) increases as the distance from the surface increases. In the case of the film of the present invention, the element concentration due to the inactive particles (or PEI) once reaching the maximum value starts to decrease again.
In this concentration distribution curve, inert particles (or PE
The depth at which the element concentration due to I) is reduced to 1/2 of the maximum value is taken as the stack thickness. The conditions are as follows.

I) Measuring device Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany ii) Measuring conditions Primary ion species: O ₂ ⁺ primary ion accelerating voltage: 12 KV primary ion current: 200 nA raster Area: 400 μm □ Analysis area: Gate 30% Measurement vacuum degree: 5.0 × 10 ⁻⁹ Torr E-GUN: 0.5 KV-3.0A

If the inert particles contained most in the depth of 3000 nm from the surface layer are organic polymer particles, it is difficult to measure by SIMS. Therefore, while etching from the surface, XPS (X-ray photoelectron spectroscopy), IR The depth profile similar to the above may be measured by (infrared spectroscopy) or the like to obtain the laminated thickness.

(7) Young's Modulus It was measured using an Instron type tensile tester according to the method specified in ASTM-D882. The measurement was performed under the following conditions. Measuring device: Orientec Co., Ltd. automatic film strength / extension measuring device "Tensilon AMF / RTA-100" Sample size: width 10 mm x test length 100 mm, pulling speed: 200 mm / min Measuring environment: temperature 23 ° C, humidity 65 % RH

(8) Heat shrinkage ratio Measured according to JIS C2318. Sample size: width 10 mm, marked line interval 200 mm Measurement conditions: temperature 80 ° C., 100 ° C., treatment time 30 minutes, no-load state heat shrinkage was calculated from the following formula. Thermal contraction rate (%) = [(L ₀ −L) / L ₀ ] × 100 L ₀ : Mark interval before heat treatment L: Mark interval after heat treatment

(9) Surface Roughness Ra The center line average roughness Ra was measured using a high precision thin film step measuring instrument ET-10 manufactured by Kosaka Laboratory. The conditions are as follows, and the average value obtained by scanning 20 times in the film width direction and measuring 20 times was taken as the value.・ Stylus tip radius: 0.5 μm ・ Stylus load: 5 mg ・ Measuring length: 1 mm ・ Cutoff value: 0.08 mm

(10) Number of Coarse Protrusions H1 and H2 ^Two measurement surfaces (100 cm ² ) were superposed on each other and brought into close contact with each other by electrostatic force (applied voltage 5.4 kv). The height of the coarse protrusions was determined from the Newton's ring caused by the interference of 1), and the number of coarse protrusions of a single ring or more was set to H1, and the number of coarse protrusions of a double ring or more was set to H2. The light source used was a halogen lamp with a 564 nm bandpass filter.

When the measurement by the above method is difficult, a three-dimensional roughness meter (SE-3AK manufactured by Kosaka Laboratory: scanning in the film width direction is performed 50 times under the following conditions. Using a tip radius of 2 μm, a stylus load of 0.07 g, a measurement area width of 0.5 mm x length of 15 mm (pitch 0.1 mm, cutoff value of 0.08 mm), and a number of protrusions with a height of 0.28 μm or more and a height of 0.28 μm or more. By measuring the number of protrusions of 0.56 μm or more and converting it to 100 cm ² , H1 and H2
May be asked. Furthermore, if necessary, a known method for measuring the number of protrusions on the film surface such as an atomic force microscope (AFM) or a four-detection SEM may be used in combination.

(11) Dimensional change rate (%) in width direction under load Sample size is 100 mm in longitudinal direction and 30 mm in width direction
The film sample, which is a sample, is subjected to humidity control for 24 hours under the conditions of 23 ° C., 65% RH and no load, and then the sample is electrostatically attached onto a chrome mask manufactured by Dai Nippon Printing Co., Ltd. Width in the width direction (L0 _W ) using a microscope
To measure. Then, it was left for 72 hours under the condition of 60 ° C. and 80% RH with a load of 32 MPa applied in the longitudinal direction. After 72 hours, release the load, 23 ℃, 65% R
After controlling the humidity for 24 hours under the condition of H and no load, the length in the width direction (L1 _W ) was measured. The dimensional change rate was obtained by the following formula. Dimensional change rate _{(%) = [(L1 W} -L0 W) / L0 W] × 1
00

(12) Intrinsic viscosity Calculated from the following formula from the solution viscosity measured in orthochlorophenol at 25 ° C. η _sp / C = [η] + K [η] ² · C where η _sp = (solution viscosity / solvent viscosity) -1, C is the weight of dissolved polymer per 100 ml of solvent (g / 100 m)
1, usually 1.2), and K is a Huggins constant (assumed to be 0.343). The solution viscosity and the solvent viscosity were measured using an Ostwald viscometer.

(13) Extrapolation glass transition start temperature (Tg
_onset ), glass transition temperature (Tg) The specific heat was measured with the following equipment and conditions, and JIS K71
21.

Equipment: Temperature modulation DSC manufactured by TA Instrument Co., Ltd. Measurement conditions: Heating temperature: 270 to 570K (RCS cooling method) Temperature calibration: Melting temperature of high-purity indium and tin Temperature modulation amplitude: ± 1K Temperature modulation cycle: 60 second temperature rise Step: 5K Sample weight: 5 mg Sample container: Aluminum open container (22 mg) Reference container: Aluminum open container (18 mg) The glass transition temperature was calculated by the following formula. Glass transition temperature = (extrapolated glass transition start temperature + extrapolated glass transition end temperature) / 2

(14) Number of defects on the film surface The polarized light was passed through the surface of the film having a length of 5 m and a width of 1 m obtained at the time of film formation for a certain period of time, and the defects having a size of 5 to 10 mm in the longitudinal direction were visually observed. Observe 10 fields of view. Judgment was made according to the following criteria from the total number of defects (per 50 m ² ). Among the above-mentioned defects, the defect that occurs periodically in the longitudinal direction is caused by scratches on the roll and so is excluded from the number of defects. A: The number of film surface defects is less than 10 even if the film formation is performed for more than 170 hours. ⊚: The number of film surface defects is less than 10 even after film formation for 150 hours or more and 170 hours. ◯: Film surface defects are less than 10 until 100 hours, but film surface defects are 10 or more during 100 to 150 hours. X: The number of film defects is 10 or more by 100 hours in film formation time.

[0143]

EXAMPLES The embodiments of the present invention will be described based on the following examples.

Example 1 50 parts by weight of pellets of polyethylene terephthalate (PET) having an intrinsic viscosity of 0.85 (Tg 80 ° C., magnesium content 170 ppm) obtained by a conventional method and Gener
Intrinsic viscosity 0.6 manufactured by al Electric (GE)
50 parts by weight of "Ultem" 1010 (Tg216 ° C) of No. 8 was fed to a co-rotating vent type twin-screw kneading extruder heated to 290 ° C, and a PET / PEI blend containing 50% by weight of PEI. A chip was made.

Next, a film was formed using two extruders. Extruder A heated to 295 ° C (base layer part: layer A)
(Oxygen concentration: 1.5 mol%), 20 parts by weight of the PET / PEI blend chip produced by the pelletizing operation and an intrinsic viscosity of 0.62 substantially containing no inert particles.
Polyethylene terephthalate (PET) pellets 57
3 parts by weight of polyethylene terephthalate (PET) pellets (magnesium content 170 ppm) having an intrinsic viscosity of 0.62 containing 2% by weight of crosslinked divinylbenzene particles having an average particle size of 0.17 μm and an average particle size of 0.025 μm
Intrinsic viscosity 0.6 containing 2% by weight of γ-alumina particles
The mixed raw material (A1) with 20 parts by weight of polyethylene terephthalate (PET) pellets of No. 2 was vacuum dried at 180 ° C. for 3 hours and then supplied. At the same time, the amount of “Irga” corresponding to 0.5% by weight based on the above polymer alloy.
Nox 1330 ″ (indicated as IR1330 in Table 1) was supplied while being weighed by a weighing machine.

Further, in the extruder B (laminated portion: B layer) (oxygen concentration: 1.5 mol%) heated to 295 ° C., 20 parts by weight of the blended chips obtained by the pelletizing operation and substantially inert particles were added. 67 parts by weight of polyethylene terephthalate (PET) pellets having an intrinsic viscosity of 0.62 and 12 parts by weight of polyethylene terephthalate (PET) pellets having an intrinsic viscosity of 0.62 containing 2% by weight of spherical silica particles having an average particle size of 0.17 μm And average particle size 0.75 μm
The mixed raw material (B1) with 1 part by weight of polyethylene terephthalate (PET) pellets having an intrinsic viscosity of 0.62 containing 1% by weight of the crosslinked divinylbenzene particles in (1) was vacuum dried at 180 ° C. for 3 hours and then supplied. At the same time, the amount of "I" corresponding to 0.5% by weight based on the polymer alloy is
rganox 1330 ″ (denoted as IR1330) was supplied while being weighed with a weighing machine.

Subsequently, the mixed raw material A1 was filtered in two steps in the order of a sand filter and a 1.2 μm cut fiber sintered stainless metal filter, and the mixed raw material B1 was filtered with a sand filter and 3 μm cut fiber sintered stainless metal. After filtering in two stages in the order of filters, they are merged in a T-die, discharged from a die, and cooled and solidified while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. to form a two-layer laminated unstretched film (laminated thickness). The ratio A / B = 11/1) was produced.

This unstretched film was stretched in two stages in a longitudinal direction by a roll-type stretching machine at a speed of 20000% / min and a temperature of 115.
The film was stretched at a temperature of 108 ° C. by 3.0 times and further stretched by a tenter at a speed of 3000% / min at a temperature of 108 ° C. by a draw ratio of 3.4 times in a width direction. Then, it was re-stretched 1.4 times at a temperature of 150 ° C. in one step in the longitudinal direction with a roll type stretching machine, and 1.9 times at a temperature of 185 ° C. in the width direction using a tenter. After heat treatment for 8 seconds at a temperature of 200 ° C. under a constant length, a relaxation treatment of 5% was performed in the width direction to produce a laminated polyester film having a thickness of about 6 μm. The film thickness of each layer was A layer of 5.5 μm and B layer of 0.5 μm. Young's modulus in the longitudinal direction is 6.5 GP
a, Young's modulus in the width direction was 4.5 GPa. Also,
Surface roughness Ra on the A layer and B layer sides is 7 nm and 9 nm, respectively.
And the number of coarse projections H1 on the surface of the A layer is 40/10
0 cm ² and H2 were 2 pieces / cm ² .

As shown in Table 1, this laminated polyester film had a low gelation rate, had few defects even during long-term film formation, and had excellent productivity. Furthermore, stable production was possible without film breakage due to craters. Also, as shown in Table 2, this polyester film had a small thermal shrinkage and a small dimensional change in the width direction under load, and had excellent dimensional stability as a magnetic recording medium.

Example 2 As shown in Table 1, the ratio of PET to PEI was changed to 85:15 for both the polymer of Extruder A and the polymer of Extruder B, and the antioxidant was "Irganox 1010" (IR).
Notated as 1010) 0.3% by weight and "ADK STAB PEP
A two-layer laminated unstretched film (laminated thickness ratio A / B = 11/1) was produced in the same manner as in Example 1 except that the content was changed to −36 ″ (denoted as PEP-36) 0.5% by weight. .

This unstretched film was longitudinally stretched in two stages with a roll-type stretching machine at a speed of 62000% / min and a temperature of 125.
The film was stretched 3.1 times at a temperature of 130 ° C. and further stretched 3.6 times at a temperature of 130 ° C. at a speed of 3300% / min in the width direction using a tenter. Then, it was re-stretched by a roll-type stretching machine in the longitudinal direction at one stage at a temperature of 145 ° C. by 1.5 times, and by using a tenter at a temperature of 200 ° C. at a temperature of 1.9 times. After heat treatment for 8 seconds at a temperature of 220 ° C. under a constant length, a relaxation treatment of 5% was performed in the width direction to produce a laminated polyester film having a thickness of about 6 μm.

The film thickness of each layer is A layer of 5.5 μm,
The layer B had a thickness of 0.5 μm. Young's modulus in the longitudinal direction is 6.2
GPa and Young's modulus in the width direction were 5.1 GPa. 100 ° C heat shrinkage in the longitudinal direction is 0.65%, 10 in the width direction
0 ° C heat shrinkage rate is 0%, width direction dimensional change rate under load is −
It was 0.32%. Also, the surface roughness R on the A layer and B layer side
a is 8 nm and 10 nm, respectively, and the number of coarse protrusions H1 on the surface of the A layer side is 45/100 cm ² , and H2 is 3 /
It was cm ² .

As shown in Table 1, this laminated polyester film had an extremely low gelation rate, no defect was observed even during long-term film formation, and had excellent productivity. Furthermore, stable production was possible without film breakage due to craters. However, the electrostatic applicability was inferior to that of Example 1, and electrostatic application unevenness was observed at the edge portion of the unstretched film.

Example 3 As shown in Table 1, a two-layer laminated unstretched film (in the same manner as in Example 1) was used except that PET containing no magnesium was used as polyester and no antioxidant was contained. A laminated thickness ratio A / B = 11/1) was produced.

This unstretched film was stretched in the longitudinal direction by a roll-type stretching machine at a speed of 10000% / min at a temperature of 115 ° C. for 3.5 times, and further, using a tenter, a speed of 2500% / min in the width direction. The film was stretched 4.8 times at a temperature of 105 ° C. After heat-treating at a temperature of 215 ° C. for 9 seconds under a fixed length, a relaxation treatment of 3% was performed in the width direction to produce a laminated polyester film having a thickness of about 6 μm. The film thickness of each layer was A layer of 5.5 μm and B layer of 0.5 μm. Young's modulus in the longitudinal direction is 4.8 GPa, Young's modulus in the width direction is 6.2 GPa
Met. The heat shrinkage rate at 100 ° C. and the widthwise dimensional change rate under load were the same as in Example 1. The surface roughness Ra on the A layer side and the B layer side are 7 nm and 9 nm, respectively, and the number of coarse protrusions H1 on the surface on the A layer side is 10/100 cm ² , H2.
Was 0 / cm ² .

As shown in Table 1, this laminated polyester film had an extremely low gelation rate, no defect was observed even during long-term film formation, and had excellent productivity. Furthermore, stable production was possible without film breakage due to craters. However, the electrostatic applicability was inferior to that of Example 1, and electrostatic application unevenness was observed at the edge portion of the unstretched film.

Example 4 As shown in Table 1, the weight ratio of PET to PEI was changed to 80:20, and the polyester was used in an amount of magnesium of 560 pp.
m in the same manner as in Example 3 except that the PET was changed to
A laminated polyester film having a thickness of about 6 μm was produced.
The film thickness of each layer is A layer 5.5 μm, B layer 0.5 μm
It was m. The Young's modulus in the longitudinal direction was 4.5 GPa, and the Young's modulus in the width direction was 5.9 GPa. 10 in the longitudinal direction
The 0 ° C. heat shrinkage was 0.55%, the widthwise 100 ° C. heat shrinkage was 0%, and the widthwise dimensional change under load was −0.29%. The surface roughness Ra on the A layer side and the B layer side are 9 nm and 11 nm, respectively, and the number of large protrusions H on the surface on the A layer side is H.
1 was 50/100 cm ² , and H2 was 3 / cm ² .

As shown in Table 1, this laminated polyester film had a relatively low gelation rate, had few defects even during long-term film formation, and had good productivity. Furthermore, stable production was possible without film breakage due to craters.

Example 5 As shown in Table 1, polyimide was used in which the amount of amino end groups was 17 × 1.
2-layer laminated unstretched in the same manner as in Example 1 except that the PEI was changed to 0 ^-6 mol / g, the weight ratio of PET to PEI was changed to 95: 5, and no antioxidant was added. A film (lamination thickness ratio A / B = 11/1) was produced.

The unstretched film was stretched in two stages in the longitudinal direction by a roll stretching machine at a speed of 60000% / min and a temperature of 105.
The film was stretched at a temperature of 108 ° C. by 3.0 times and further stretched by a tenter at a speed of 3000% / min at a temperature of 108 ° C. by a draw ratio of 3.4 times in a width direction. Subsequently, it was re-stretched 1.4 times at a temperature of 150 ° C. in a single stage in the longitudinal direction with a roll-type stretching machine, and re-stretched 1.9 times at a temperature of 195 ° C. in the width direction using a tenter. After heat treatment for 8 seconds at a temperature of 210 ° C. under a fixed length, a relaxation treatment of 5% was performed in the width direction to produce a laminated polyester film having a thickness of about 6 μm. The film thickness of each layer was A layer of 5.5 μm and B layer of 0.5 μm. Young's modulus in the longitudinal direction is 6.2 GP
a, Young's modulus in the width direction was 5.2 GPa. 100 ° C heat shrinkage in the longitudinal direction is 0.85%, 100 ° C in the width direction
The heat shrinkage was 0.05%, and the width-direction dimensional change rate under load was -0.34%. Further, the surface roughness Ra on the A layer side and the B layer side are 7.5 nm and 8.5 nm, respectively, and the number of coarse projections H1 on the surface on the A layer side is 15/100 cm ² , H2.
Was 0 / cm ² .

As shown in Table 1, this laminated polyester film had a relatively low gelation rate, few defects during long-term film formation, and had good productivity. Furthermore, stable production was possible without film breakage due to craters.

Example 6 Only one extruder was used, and the extruder heated to 300 ° C. had an intrinsic viscosity of 0.65 substantially containing no inert particles.
78 parts by weight of polyethylene (2.6-naphthalene dicarboxylate) (PEN) pellets having a weight average particle diameter of 0.
2 parts by weight of polyethylene (2.6-naphthalene dicarboxylate) (PEN) pellets containing 2% by weight of 5 μm crosslinked divinylbenzene and having an intrinsic viscosity of 0.65, and PEN / PEI prepared in the same manner as in Example 1 A mixed raw material of 20 parts by weight of a blend chip (weight ratio of 50:50) was vacuum dried at 180 ° C. for 3 hours and then supplied, and as an antioxidant, “Sumilyzer GA-80” (SLG
An unstretched film was prepared in the same manner as in Example 1 by adding (A-80) and measuring 1% by weight.
However, a single layer structure is used without stacking.

This unstretched film was stretched in two stages in the longitudinal direction by a roll-type stretching machine at a speed of 60000% / min and a temperature of 135.
It was stretched 4.2 times at a temperature of 140 ° C. and further stretched 3.0 times at a temperature of 140 ° C. at a speed of 3000% / min in the width direction using a tenter. After heat treatment for 8 seconds at a temperature of 220 ° C. under a fixed length, a relaxation treatment of 2% was performed in the width direction to produce a polyester film having a thickness of about 6 μm. Young's modulus in the longitudinal direction is 6.5 GP
a, Young's modulus in the width direction was 5.2 GPa. Also,
The number of coarse protrusions H1 on the surface of layer A is 15 / 100c
m ² and H 2 were 0 / cm ² .

As shown in Table 1, this polyester film had an extremely low gelation rate, had few defects even during long-term film formation, and had excellent productivity. Further, as shown in Table 2, this polyester film has a small heat shrinkage ratio and a small dimensional change in the width direction under load,
It had excellent dimensional stability as a magnetic recording medium. Furthermore, stable production was possible without film breakage due to craters.

Example 7 The antioxidant added was "Irganox 1330".
(Expressed as IR1330) 2.3 wt% and "HP-36"
(Indicated as HP-36) A polyester film was produced in exactly the same manner as in Example 1 except that the content was changed to 0.2% by weight.

As shown in Table 1, this laminated polyester film had an extremely low gelation rate, no defect was observed even during long-term film formation, and had excellent productivity. However, when the film surface was observed with a differential interference microscope, craters (recesses) were observed. Further, although it is considered that this is due to the crater, the film formation breakage increased and the film formation stability was inferior as compared with Example 1.

Example 8 The starting materials used were exactly the same as in Example 5, except that the polymer temperature in extruders A and B was changed to 280 ° C.
By introducing nitrogen into the extruder, the oxygen concentration in the raw material charging part of the extruder was changed to 0.2 mol% to prepare an unstretched film. Then, stretching, heat treatment and relaxation treatment were performed in exactly the same manner as in Example 5 to produce a laminated polyester film having the same layer structure as in Example 5.

As a result of changing the extrusion conditions in this way, as shown in Table 1, the gelation rate of the obtained polyester film was at the same level as in Example 5, but the occurrence of defects in long-term film formation was found in Example 5. Compared with the others, it showed excellent productivity. Furthermore, stable production was possible without film breakage due to craters.

Example 9 As shown in Table 1, the content of the antioxidant, the amount of magnesium present (in this example, cobalt is contained at 50 ppm in order to supplement the electrostatic application property), polyimide content By changing the amount of amino terminal groups, changing the polymer temperature in extruders A and B to 280 ° C., and introducing nitrogen into the extruder, the oxygen concentration in the raw material charging part of the extruder was changed to 0.2 m.
Except that it was changed to ol%, in the same manner as in Example 1,
A laminated polyester film having a thickness of about 6 μm was produced.
The film thickness of each layer is A layer 5.5 μm, B layer 0.5 μm
It was m. The Young's modulus in the longitudinal direction was 6.5 GPa and the Young's modulus in the width direction was 4.5 GPa. Also, layer A, B
The surface roughness Ra on the layer side is 7 nm and 9 nm, respectively,
The number of coarse projections H1 on the surface of layer A is 25 / 100c
m ² and H 2 were 0 / cm ² .

As shown in Table 1, this polyester film had an extremely low gelation rate, and no defect was observed even when the film formation was continued for a long period of time up to 250 hours, resulting in excellent productivity. Had. Further, the electrostatic applicability was good, and stable production was possible without breakage of the film due to the generation of craters.

Comparative Example 1 The thickness was the same as in Example 1 except that the amount of magnesium in the PET chip was adjusted so that the amount of magnesium present in the film was 550 ppm and no antioxidant was added. A laminated polyester film of about 6 μm was produced. The film thickness of each layer was A layer of 5.5 μm and B layer of 0.5 μm. Young's modulus in the longitudinal direction is 6.5 GP
a, Young's modulus in the width direction was 4.5 GPa. The heat shrinkage rate, the dimensional change rate in the width direction under load, the surface roughness, the number of coarse projections, etc. were the same as in Example 1.

As shown in Table 1, this laminated polyester film had many defects and was inferior in productivity.

Comparative Example 2 Polyimide having an amino end group content of 23 × 10 ⁻⁶ mol / g
A laminated polyester film having a thickness of about 6 μm was prepared in exactly the same manner as in Example 1 except that the PEI was changed to PEI and the antioxidant was not added. The film thickness of each layer was A layer of 5.5 μm and B layer of 0.5 μm. The Young's modulus in the longitudinal direction is 6.5 GPa, and the Young's modulus in the width direction is 4.
It was 5 GPa. The heat shrinkage rate, the dimensional change rate in the width direction under load, the surface roughness, the number of coarse projections, etc. were the same as in Example 1.

As shown in Table 1, this laminated polyester film had many defects and was inferior in productivity.

Comparative Example 3 The thickness was the same as in Example 1 except that the amount of magnesium present in the film, the amount of amino end groups in PEI, and the type of antioxidant were changed as shown in Table 1. About 6 μm
To produce a laminated polyester film. The film thickness of each layer was A layer of 5.5 μm and B layer of 0.5 μm.
The Young's modulus in the longitudinal direction was 6.5 GPa and the Young's modulus in the width direction was 4.5 GPa. The heat shrinkage rate, the dimensional change rate in the width direction under load, the surface roughness, the number of coarse projections, etc. were the same as in Example 1.

As shown in Table 1, this laminated polyester film had many defects and was inferior in productivity.

Comparative Example 4 The procedure of Example 1 was repeated, except that the amount of magnesium present in the film and the amount of amino terminal groups in PEI were changed as shown in Table 1 and no antioxidant was added. Thickness about 6
A laminated polyester film having a thickness of μm was produced. The film thickness of each layer was A layer of 5.5 μm and B layer of 0.5 μm. The Young's modulus in the longitudinal direction was 6.5 GPa and the Young's modulus in the width direction was 4.5 GPa. The heat shrinkage rate, the dimensional change rate in the width direction under load, the surface roughness, the number of coarse projections, etc. were the same as in Example 1.

As shown in Table 1, this laminated polyester film had many defects and was inferior in productivity.

Comparative Example 5 As shown in Table 1, the amount of antioxidant added, the amount of magnesium present, and the amount of amino end groups in the polyimide were changed, and in the same manner as in Example 1, a laminated polyester film of about 6 μm was prepared. Was produced.

As shown in Table 1, this laminated polyester film had many defects and was inferior in productivity.

[0181]

[Table 1]

Comparative Example 6 The procedure of Example 1 was repeated, except that PET chips were used instead of the PET / PEI blend chips and no antioxidant was added.

That is, in the extruder A (for the base layer portion) heated to 295 ° C., 77 parts by weight of polyethylene terephthalate (PET) pellets having an intrinsic viscosity of 0.62 substantially containing no inert particles and an average particle diameter were used. 3 parts by weight of polyethylene terephthalate (PET) pellets having an intrinsic viscosity of 0.62 containing 2% by weight of crosslinked divinylbenzene particles of 0.17 μm and an intrinsic viscosity of 2% by weight of γ-alumina particles having an average particle size of 0.025 μm .62 polyethylene terephthalate (PET) pellets 20 parts by weight mixed raw material (A
2) was vacuum dried at 180 ° C. for 3 hours and then supplied. No antioxidant was added.

Further, in the extruder B (for the laminating section) heated to 295 ° C., 87 parts by weight of polyethylene terephthalate (PET) pellets having an intrinsic viscosity of 0.62 substantially containing no inert particles and an average particle diameter were used. 12 parts by weight of polyethylene terephthalate (PET) pellets having an intrinsic viscosity of 0.62 containing 2% by weight of spherical silica particles of 0.17 μm and 1% by weight of a crosslinked divinylbenzene particle having an average particle size of 0.75 μm, an intrinsic viscosity of 0. 62 parts of polyethylene terephthalate (PET) pellets 1 part by weight of mixed raw material (B2)
Was vacuum dried at 180 ° C. for 3 hours and then fed. No antioxidant was added.

Subsequently, the mixed raw material A2 was filtered in two steps in the order of a sand filter and a 1.2 μm cut fiber-sintered stainless metal filter.
2 was filtered in two steps in the order of a sand filter and a 3 μm cut fiber sintered stainless metal filter, then merged in a T-die and discharged from a die, while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. Adhesion cooling and solidification, two-layer laminated unstretched film (laminated thickness ratio A / B = 11
/ 1) was produced.

This unstretched film was stretched in two stages in the longitudinal direction by a roll-type stretching machine at a speed of 20000% / min and a temperature of 105.
The film was stretched at a temperature of 100 ° C. by a factor of 3.0 and further stretched by a tenter at a speed of 3000% / min at a temperature of 100 ° C. by a factor of 3.4. Then, it was re-stretched 1.4 times at a temperature of 155 [deg.] C. in a longitudinal direction with a roll-type stretching machine, and re-stretched 1.9 times at a temperature of 195 [deg.] C. in the width direction using a tenter. After heat treatment for 8 seconds at a temperature of 210 ° C. under a fixed length, a relaxation treatment of 5% was performed in the width direction to produce a laminated polyester film having a thickness of about 6 μm. The film thickness of each layer was A layer of 5.5 μm and B layer of 0.5 μm. Young's modulus in the longitudinal direction is 6.7 GP
a, Young's modulus in the width direction was 4.9 GPa. The heat shrinkage rate, the dimensional change rate in the width direction under load, the surface roughness, the number of coarse projections, etc. were the same as in Example 1.

As shown in Table 2, this laminated polyester film did not cause the problem of film defects, but was inferior in heat shrinkage ratio to the polyester film of the present invention (Example 1) and was used as a magnetic recording medium. Had inferior properties.

Comparative Example 7 The procedure of Example 6 was repeated except that PEN chips were used instead of the PEN / PEI blend chips and no antioxidant was added.

That is, using only one extruder, polyethylene (2.6-naphthalene dicarboxylate) (intrinsic viscosity 0.65) containing essentially no inert particles was added to the extruder heated to 300.degree. PEN) 98 parts by weight of pellets and 2% by weight of cross-linked divinylbenzene particles having a weight average particle diameter of 0.5 μm, polyethylene (2.6-naphthalene dicarboxylate) (PEN) having an intrinsic viscosity of 0.65.
A mixed raw material with 2 parts by weight of pellets was vacuum dried at 180 ° C. for 3 hours and then supplied, and an unstretched film having a single-layer structure was produced in the same manner as in Example 6 without adding an antioxidant.

This unstretched film was stretched in two stages in the longitudinal direction by a roll-type stretching machine at a speed of 60000% / min and a temperature of 130.
The film was stretched 4.2 times at ℃ and further stretched 3.0 times at a temperature of 135 ° C. at a speed of 3000% / min in the width direction using a tenter. After heat treatment for 8 seconds at a temperature of 215 ° C. under a fixed length, a relaxation treatment of 2% in the width direction was performed to obtain a polyester film having a thickness of about 6 μm. Young's modulus in the longitudinal direction is 6.7 GPa,
The Young's modulus in the width direction was 5.3 GPa.

As shown in Table 2, this polyester film did not cause the problem of film defects, but was inferior to the polyester film of the present invention (Example 6) in the dimensional change rate in the width direction and was used for magnetic recording media. As a result, the characteristics were inferior.

[0192]

[Table 2]

[0193]

EFFECTS OF THE INVENTION According to the present invention, it is possible to suppress problems such as oxidative deterioration in a manufacturing process in a film made of polyester and polyimide and having good dimensional stability, and to have high dimensional stability. In addition, a polyester film having high productivity can be obtained.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 5/73 G11B 5/73 F term (reference) 4F100 AK41A AK41B AK49A AR00C BA02 BA03 BA07 BA10A BA10B BA10C BA15 EJ38A EJ38B GB41 JG06C JL02 JL04 4J002 CF061 CM042 EJ066 EW067 FD076 FD077 GS01 5D006 CB01 CB02 CB05 CB07 FA00

Claims (14)

[Claims] 1. A polyester film comprising polyester and polyimide as essential components, the film comprising:
A biaxially oriented polyester film having a production rate of orthochlorophenol (OCP) insoluble matter of 0 to 15% after heat treatment at 00 ° C for 2.5 hours. 2. The polyester film according to claim 1, which contains 0.01 to 2% by weight of an antioxidant.
Axial oriented polyester film. 3. The biaxially oriented polyester film according to claim 1, wherein the polyester film contains 0.01 to 2% by weight of a phenolic antioxidant. 4. The phenolic antioxidant is pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate],
1,3,5-Trimethyl-2,4,6-tris (3,5
-Di-t-butyl-4-hydroxybenzyl) benzene, 3,9-bis [2- [3- (3-t-butyl-4-
Hydroxy-5-methylphenyl) -propionyloxy] -1,1-dimethylethyl] -2,4,8,10-
The biaxially oriented polyester film according to claim 3, which is one or more of tetraoxaspiro- [5.5] undecane. 5. The polyester film contains 0.01 to 2% by weight of a phosphorus-based antioxidant.
The biaxially oriented polyester film according to any one of 1. 6. The biaxially oriented polyester film according to claim 1, wherein the amount of magnesium present in the polyester film is 0 to 500 ppm. 7. The amount of amino terminal groups in the polyimide is 0.
The biaxially oriented polyester film according to any one of claims 1 to 6, wherein the biaxially oriented polyester film has a concentration of from 20 to ^10-6 mol / g. 8. The biaxially oriented polyester film according to claim 1, wherein the polyimide is polyetherimide. 9. The biaxially oriented polyester film according to claim 1, wherein the polyester has an ethylene terephthalate unit as a main component. 10. The biaxially oriented polyester film according to claim 1, wherein the film contains 1 to 30% by weight of polyimide. 11. A laminated film for a magnetic recording medium, wherein a film layer (layer B) containing polyester as an essential component is laminated on at least one side of a polyester film layer (layer A) containing polyester and polyimide as essential components. And the total thickness is 3 to 8 μm, and the biaxially oriented polyester film according to claim 1. 12. The method according to any one of claims 1 to 11.
A magnetic recording medium comprising a magnetic layer provided on at least one surface of an axially oriented polyester film. 13. The magnetic recording medium according to claim 12, wherein the magnetic layer is a ferromagnetic metal thin film or a magnetic layer formed by dispersing ferromagnetic hexagonal ferrite fine powder in a binder. 14. A digital recording type cassette tape comprising the magnetic recording medium according to claim 12.