JP2010065144A - Biaxially oriented polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented film excellent in moisture heat resistance and dielectric breakdown characteristics and to provide a biaxially oriented polyester film for obtaining a high-density magnetic recording medium having a less error rate, less chipping of a magnetic head or a magnetic tape, and excellent traveling durability. <P>SOLUTION: The biaxially oriented polyester film includes a polyester (A) having a glass transition temperature of ≥50°C to <130°C, an amorphous polyimide (B) having a glass transition temperature of >210°C to ≤300°C, and an amorphous resin (C) having a glass transition temperature of ≥130°C to ≤210°C, wherein the total content of the polyester (A), the amorphous polyimide (B) and the amorphous resin (C) is ≥80 mass% to ≤100 mass% in the whole film weight; the content ratios by mass of the polyester (A), the amorphous polyimide (B) and the amorphous resin (C) are 70 to 99, 0.1 to 30, and 0.01 to 20, respectively; and the film shows a coefficient of expansion by moisture of 0 to 6.0 ppm/%RH in the film width direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a biaxially oriented polyester film that is particularly excellent in rigidity and dimensional stability, and also excellent in heat and moisture resistance and dielectric breakdown characteristics.

  Polyester film uses excellent mechanical properties, thermal properties, electrical properties, surface properties, dimensional stability, heat resistance, and other properties for magnetic recording media, electrical insulation, capacitors, packaging, and various industrial materials. It is used for various applications. In particular, its usefulness as a support for magnetic recording media is well known.

  Under the high quality in these applications, there is a demand for improvement in dimensional stability, heat resistance, and moist heat resistance under a high temperature environment. However, for example, a polyester film made of ethylene terephthalate alone (hereinafter referred to as PET) may not have sufficient dimensional stability, heat resistance, and moist heat resistance in a high temperature environment.

  In particular, in recent years, magnetic recording media such as magnetic tapes are required to have a thin base film and high density recording in order to reduce the weight, size, and capacity of equipment. For high density recording, it is useful to shorten the recording wavelength and the recording track. However, if the recording track is made small, there is a problem that the recording track is liable to shift due to deformation caused by heat during tape running or temperature and humidity changes during tape storage. Accordingly, there is an increasing demand for improvement in characteristics such as dimensional stability in the usage environment and storage environment of the tape. On the other hand, there is an increasing demand for improvement in running durability when using magnetic tape. However, when the film is thinned, the mechanical strength becomes insufficient and the stiffness of the film becomes weak, and the film tends to stretch in the longitudinal direction and shrink in the width direction. There are problems such as deterioration of electromagnetic conversion characteristics and head and tape scraping.

  In recent years, in order to increase the heat resistance of polyester films, methods such as blending other thermoplastic resins with polyester have been studied.

  About the blend of polyester and polyimide resin, the glass transition temperature which becomes a heat resistant parameter | index may rise with the increase in a polyimide resin fraction (for example, patent document 1).

In addition, in a film made of polyester and a heat-resistant thermoplastic resin other than polyester, by containing polyethylene naphthalate, polyetherimide, polyethersulfone, there is little dropout of particles in the film, and the surface has scratch resistance. An improved film has been proposed (for example, Patent Document 2). However, in the invention of Patent Document 2, there may be insufficient dispersion of each heat-resistant thermoplastic resin in the film, which may not be sufficient for effective molecular chain orientation by stretching or the like. It may not always be sufficient to meet stringent requirements such as dimensional stability against humidity, and in addition, foreign matter due to unmelted heat-resistant thermoplastic resin is likely to be generated in the film and the surface is likely to be rough. There is. In addition, voids are easily formed in the film, and the film forming property may not be stable. Furthermore, a resin composition composed of polyimide and other thermoplastic resins has been proposed (for example, Patent Document 3), but no specific method for applying it to a polyester film is disclosed.
U.S. Pat. No. 4,141,927 JP 2001-323146 A JP 2002-249660 A

  An object of the present invention is to solve the above-described problems and to obtain a biaxially oriented polyester film having particularly excellent rigidity and dimensional stability, and at the same time excellent in moisture and heat resistance and dielectric breakdown characteristics.

  Furthermore, it aims at obtaining the biaxially-oriented polyester film which exhibits the outstanding dimensional stability in a high temperature environment or a high humidity environment, and is excellent in film forming production stability.

  In addition, it can be suitably used for magnetic recording media, electrical insulation, capacitors, circuit materials, solar cell materials, etc. Especially when it is used as a magnetic recording medium, environmental changes in temperature and humidity and dimensional changes due to storage. To provide a biaxially oriented polyester film that can be reduced in size, has a low error rate, and has a low magnetic head and magnetic tape scraping and a high-density magnetic recording medium with excellent running durability. And

  In order to achieve the above object, the present invention has the following features.

  (1) Polyester (A) having a glass transition temperature of 50 ° C. or higher and lower than 130 ° C., Amorphous polyimide (B) having a glass transition temperature higher than 210 ° C. and 300 ° C. or lower, and a glass transition temperature of 130 ° C. or higher and 210 ° C. or lower. Including the amorphous resin (C), the total content of the polyester (A), the amorphous polyimide (B) and the amorphous resin (C) is 80% by mass or more and 100% by mass of the total weight of the film. The content mass ratio of the polyester (A), the amorphous polyimide (B), and the amorphous resin (C) is 70 to 99, 0.1 to 30, 0.01 to 20, respectively, and A biaxially oriented polyester film having a humidity expansion coefficient in the film width direction of 0 to 6.0 ppm /% RH.

(2) A ratio W _C / W _B of a mass W _B of the amorphous polyimide (B) and a mass W _C of the amorphous resin (C) is greater than 0 and 1/3 or less (1 ) Biaxially oriented polyester film.

  (3) The biaxially oriented polyester film according to (1) or (2), wherein the internal haze of the film is 0 to 75%.

  (4) The biaxially oriented polyester film according to any one of (1) to (3), wherein the polyester (A) is polyethylene terephthalate or polyethylene naphthalate.

  (5) The biaxially oriented polyester film according to any one of (1) to (4), wherein the amorphous polyimide (B) is a polyetherimide.

  (6) In the above (1) to (5), the amorphous resin (C) is at least one amorphous resin selected from the group consisting of polysulfone, polyphenylene ether, polycarbonate, polyarylate and cyclic olefin copolymer. The biaxially oriented polyester film according to any one of the above.

  (7) The polyester (A) forms a continuous structure in the film, and the amorphous polyimide (B) and the amorphous resin (C) together form a dispersed phase with respect to the polyester (A). The biaxially oriented polyester film according to any one of (1) to (6), which has a discontinuous structure.

  (8) The biaxially oriented polyester film according to any one of (1) to (7), wherein the temperature expansion coefficient in the film width direction is −6.0 to 6.0 ppm / ° C.

  Since the biaxially oriented film of the present invention has few foreign substances and has excellent rigidity and dimensional stability, excellent moisture and heat resistance and dielectric breakdown properties, it is used for magnetic recording media, electrical insulation, circuit materials, solar cells, The industrial value is extremely high as a film for various industrial materials such as condenser use, packaging use, and ink ribbon use.

  In particular, according to the present invention, when the magnetic recording medium is used, environmental changes in temperature and humidity and dimensional changes due to storage can be reduced, the error rate is low, and the magnetic head and the magnetic tape are less scraped. A biaxially oriented polyester film that can be used as a high-density magnetic recording medium excellent in running durability can be obtained.

  The biaxially oriented polyester film of the present invention (hereinafter sometimes referred to as a biaxially oriented film) is a polyester (A) having a glass transition temperature of 50 ° C. or higher and lower than 130 ° C. (hereinafter sometimes referred to as polyester A), glass Amorphous polyimide (B) having a transition temperature of more than 210 ° C and not more than 300 ° C (hereinafter sometimes referred to as polyimide B), and an amorphous resin (C) having a glass transition temperature of not less than 130 ° C and not more than 210 ° C, ( Hereinafter, the total amount of these resins (the total amount of polyester A, polyimide B, and amorphous resin C) is 80 mass of the total mass of the biaxially oriented polyester film. % Or more and 100% by mass or less.

  When the total amount of the above-described resins is less than 80% by mass, heat resistance and film forming properties tend to be lowered. The total amount of the above-described resins is preferably 85% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, based on the total mass of the biaxially oriented polyester film.

  Moreover, as for the biaxially oriented film of this invention, the content mass ratio of polyester A, polyimide B, and amorphous resin C is 70-99, 0.1-30, 0.01-20 in order. By satisfying such a mass ratio, excellent heat resistance, dielectric breakdown characteristics, rigidity, and dimensional stability can be imparted to the biaxially oriented film. Outside such a mass ratio range, the heat resistance and film-forming properties tend to decrease.

  In the present invention, among the polyester A, the polyimide B and the amorphous resin C contained in the biaxially oriented film, the mass ratio of the polyester A is as high as 70 to 99. If the mass ratio of polyester A is less than 70, mechanical properties, thermal properties, electrical properties, surface properties, heat resistance, and processability tend to be reduced. On the other hand, if it exceeds 99, the dimensional stability, heat resistance and heat-and-moisture resistance are likely to be lowered. The mass ratio of polyester A is preferably 80 to 97, more preferably 85 to 95.

  The resin constituting the biaxially oriented film of the present invention includes particles, a flame retardant, a heat stabilizer, a weathering material, an antioxidant, an ultraviolet absorber, a light stabilizer, a rust inhibitor, depending on the purpose. Various additives such as copper-resistant damage stabilizers, antistatic agents, pigments, plasticizers, endblockers, lubricants, organic lubricants, chlorine scavengers, antiblocking agents, viscosity modifiers, etc., do not impair the purpose of these inventions You may make it contain in the range.

  The “polyester (A) having a glass transition temperature of 50 ° C. or higher and lower than 130 ° C.” as used in the present invention is a polymer having an ester bond in the main chain in the molecular structure of the polymer, and a diol and dicarboxylic acid or an ester thereof. A polymer containing at least 80% by mass of a polymer obtained by condensation polymerization of a forming derivative. Preferred examples thereof include thermoplastic polyesters having an aromatic ring in the chain unit of the polymer. Specifically, usually, an aromatic dicarboxylic acid (or an ester-forming derivative thereof) and a diol (or an ester-forming derivative thereof) and / or Or the polymer or copolymer obtained by the condensation reaction which has hydroxycarboxylic acid as a main component is mentioned.

  Here, the dicarboxylic acid is represented by terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, adipic acid, sebacic acid or ester-forming derivatives thereof. Examples of the ester-forming derivative include dimethyl terephthalate, dimethyl isophthalate, and dimethyl phthalate. Two or more of these dicarboxylic acids can be used in combination. On the other hand, the diol is represented by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexanedimethanol and the like. Two or more of these diols can be used in combination.

  The biaxially oriented polyester film of the present invention includes a polyester (A) having a glass transition temperature of 50 ° C. or higher and lower than 130 ° C., which is excellent in terms of mechanical properties, thermal properties, electrical properties, surface properties, heat resistance, and the like. An axially oriented film can be obtained.

  When the glass transition temperature of the polyester A in the present invention is less than 50 ° C., the film formability and productivity of the biaxially oriented film may be lowered, and the heat resistance of the film may be lowered. On the other hand, when the glass transition temperature of polyester A is 130 ° C. or higher, melt processability is lowered and productivity tends to be inferior.

  Polyester A in the present invention preferably has a glass transition temperature of 60 ° C. or higher and 120 ° C. or lower in order to perform biaxial stretching and to exhibit the effects of the present invention such as dimensional stability. Is 70 ° C. or higher and 110 ° C. or lower.

  From the viewpoint of processability and melt moldability with polyimide B and amorphous resin C, the melting point of polyester A is preferably 200 ° C. or higher and lower than 280 ° C., more preferably 230 ° C. or higher and 270 ° C. or lower.

  The intrinsic viscosity of the polyester A used in the present invention is preferably 0.55 to 2.0 dl / g, more preferably from the viewpoints of melt moldability with polyimide B and amorphous resin C, film-forming property, and melt heat stability. It is 0.6 to 1.4 dl / g, particularly preferably 0.65 to 1.3 dl / g.

  Specific examples of polyester A include, for example, polymethylene terephthalate, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene isophthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylenedimethylene. Terephthalate, polyethylene-2,6-naphthalate, or the like can be used.

  Of course, these polyesters may be a homopolymer or a copolymer. In the case of a copolymer, examples of the copolymer component include diol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol, adipic acid, and sebatin. Dicarboxylic acid components such as acid, phthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid, and hydroxycarboxylic acid components such as hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid may be contained.

  The polyester preferably contains polyethylene terephthalate (hereinafter sometimes referred to as PET), polyethylene-2,6-naphthalate (hereinafter sometimes referred to as PEN), a copolymer thereof, or a modified product thereof. Particularly preferred is PET or / and PEN. A film containing PET or PEN or a copolymer or a modified product thereof can be continuously formed using a conventional melt film forming method, and can be manufactured at low cost because productivity can be improved. Moreover, it is also practically suitable to use these polyesters as a mixture according to required properties such as moldability, heat resistance, toughness, and surface properties.

  The biaxially oriented film of the present invention contains an amorphous polyimide (B) having a glass transition temperature of more than 210 ° C. and not more than 300 ° C., so that the glass transition temperature of the film is higher than that of a film composed solely of polyester. Therefore, excellent heat resistance and moisture and heat resistance can be imparted to the film.

  When the glass transition temperature of the amorphous polyimide B in the present invention is 210 ° C. or lower, the glass transition temperature of the film may not be sufficiently high. On the other hand, when the glass transition temperature is higher than 300 ° C., the polyester A, The melt moldability with the amorphous resin C may be lowered, and further, the amorphous polyimide B tends to be a defect of coarse foreign matters in the film.

  From the viewpoint of workability with polyester A and amorphous resin C and melt kneadability, the preferred range of the glass transition temperature of polyimide B is greater than 210 ° C. and 280 ° C. or less, and a more preferred range is greater than 210 ° C. and 270 ° C. It is below ℃.

  The “amorphous polyimide (B) having a glass transition temperature of greater than 210 ° C. and not more than 300 ° C.” of the present invention is an amorphous resin and a melt-formable polymer containing a cyclic imide group. It may be anything that can meet the purpose.

  The term “amorphous (resin)” in the present invention refers to a property in which, when a sample is measured using differential scanning calorimetry (DSC) or the like, only the glass transition temperature is detected and the melting point and melting peak are not detected. (Refers to a resin having such characteristics).

  Polyimide B is compatible with polyester A or dispersed well in polyester A from the viewpoint of making the glass transition temperature single in the polymer alloy with polyester A and improving the glass transition temperature for improving heat resistance. Resins are preferred.

  By making the polyimide B a polymer alloy with the polyester A, it is possible to control the heat resistance (glass transition temperature) of the resin composition and film obtained by the mixing ratio, and to design a polymer in accordance with the use conditions. The mixing ratio of the polymer can be examined using a micro FT-IR method (Fourier transform micro infrared spectroscopy) or an NMR method.

  The biaxially oriented polyester film of the present invention has a polyimide B mass ratio of 0.1 to 30 as described above. If the mass ratio of polyimide B is less than 0.1, the glass transition temperature of the film is not sufficiently increased, so that the heat resistance and the heat and humidity resistance tend to be inferior. On the other hand, when it exceeds 30, the film-forming property of the film deteriorates, the production cost increases, and the dimensional stability of the film tends to decrease. The mass ratio of polyimide B is more preferably 1 to 20, more preferably 2 to 15, and most preferably 3 to 10 from the viewpoints of heat resistance, heat and humidity resistance and cost of the film.

Weight ratio W _B / W _A mass W _B of the mass W _A and the polyimide B of the polyester A contained in the biaxially oriented polyester film of the present invention is preferably in the range of 0.01 to 0.4. By being in the said range, the production cost can be lowered at the same time as imparting excellent heat and moisture resistance to the film.

Polyester A and scope of the mass ratio W _B / W _A polyimide B is more preferably 0.03 or more, more preferably 0.05 or more, and most preferably 0.1 or more.

Range of weight ratio W _B / W _A of the polyester A and the polyimide B is more preferably 0.3 or less, more preferably 0.25 or less, most preferably 0.25 or less.

Range of weight ratio W _B / W _A of the polyester A and the polyimide B is more preferably 0.03 to 0.3, more preferably 0.05 to 0.25, and most preferably 0.1 to 0.2.

  By being in the said range, the production cost can be lowered at the same time as imparting excellent heat and moisture resistance to the film.

  The polyimide B in the present invention preferably has a melt viscosity of 100 to 1,500 (Pa · S) at a temperature of 350 ° C. and a shear rate of 300 (1 / second).

  When the melt viscosity of the polyimide B is 100 to 1,500 (Pa · S), the miscibility and workability with the polyester A and the amorphous resin C are improved. In the finally obtained film, the molecular chains of the polymer can be effectively oriented by stretching or the like, and excellent dimensional stability can be imparted to the film. The melt viscosity of polyimide B is more preferably 150 to 1,000 (Pa · S), and particularly preferably 200 to 800 (Pa · S).

  The melt viscosity [B] at a temperature of 350 ° C. and a shear rate of 300 (1 / second) for polyimide B and the melt viscosity [C] at a temperature of 350 ° C. and a shear rate of 300 (1 / second) for amorphous resin C are as follows: It is preferable to satisfy the relationship.

1/3 ≤ [C] / [B] ≤ 3
More preferably, 2/5 ≦ [C] / [B] ≦ 5/2 is satisfied.

  Most preferably, 1/2 ≦ [C] / [B] ≦ 2 is satisfied.

  When the melt viscosity of the polyimide B and the amorphous resin C satisfies the above relational expression, the miscibility and workability of the polyimide B and the amorphous resin C are improved. Thereby, the foreign material in the film finally obtained can be reduced.

  Polyimide B is preferably a polyetherimide (hereinafter sometimes referred to as PEI) containing, for example, an aliphatic, alicyclic or aromatic ether unit and a cyclic imide group as repeating units. PEI is particularly preferable because it is easy to increase the compatibility with the polyester A and easily controls the glass transition temperature in the polymer alloy with the polyester.

  PEI is a resin containing an ether bond in a polyimide constituent component composed of an imide group.

  Examples of such PEI include, but are not limited to, polymers described in US Pat. No. 4,141,927 and Japanese Patent No. 2622678.

  If the effect of the present invention is not impaired, the main chain of polyimide contains structural units other than cyclic imide and ether units, such as aromatic, aliphatic, alicyclic ester units, oxycarbonyl units, and the like. It does not matter.

  Further, if the effect of the present invention is not inhibited, structural units other than cyclic imide and ether units in the main chain of polyetherimide, for example, aromatic, aliphatic, alicyclic ester units, oxycarbonyl units, etc. It may be contained.

  Specific examples of the polyetherimide that can be preferably used in the present invention include polymers represented by the following general formula.

Wherein R ₁ is a divalent aromatic or aliphatic residue having 6 to 30 carbon atoms, and R ₂ is a divalent aromatic having 6 to 30 carbon atoms. From a residue, an alkylene group having 2 to 20 carbon atoms, a cycloalkylene group having 2 to 20 carbon atoms, and a polydiorganosiloxane group terminated with an alkylene group having 2 to 8 carbon atoms A divalent organic group selected from the group consisting of Examples of R ₁ and R ₂ include aromatic residues represented by the following formula group.

  In the present invention, 2,2-bis [4- (2,2) having a structural unit represented by the following formula from the viewpoints of affinity with polyester A and amorphous resin C described later, cost, melt moldability and the like. Most preferred are condensates of 3-dicarboxyphenoxy) phenyl] propane dianhydride with m-phenylenediamine or p-phenylenediamine, and copolymers and modified products thereof.

Or

(N is an integer of 2 or more, preferably an integer of 20 to 50)
This PEI is available from SABIC Innovative Plastics under the trade name “Ultem” (registered trademark), “Ultem1000”, “Ultem1010”, “Ultem1040”, “Ultem5000”, “Ultem6000” and “UltemXH6050” series And “Extem XH” and “Extem UH” are registered trademark names.

  The biaxially oriented film of the present invention contains an amorphous resin (C) having a glass transition temperature of 130 ° C. or higher and 210 ° C. or lower.

  Since the film contains an amorphous resin (C) having a glass transition temperature of 130 ° C. or higher and 210 ° C. or lower, the amorphous resin C having a glass transition temperature higher than that of the polyester A is a film in a biaxially oriented polyester film. It functions as a point for restraining the polymer molecules in the stretching step, and can enhance the orientation of the polymer molecular chains. When the orientation of the polymer molecular chain is increased, the biaxially oriented film is imparted with excellent mechanical strength and excellent dimensional stability.

  The lower limit of the preferable glass transition temperature of the amorphous resin C is 160 ° C. or higher, and the more preferable glass transition temperature is 170 ° C. or higher. The upper limit of the preferable glass transition temperature of the amorphous resin C is 200 ° C. or less.

  When the glass transition temperature is within the above range, the miscibility and processability of the amorphous resin C, the polyimide B, and the polyester A are improved. In the film finally obtained, by stretching the amorphous resin C in the film to act as a knotting point or restraint point of the polymer molecular chain, the molecular chain of the polymer can be oriented particularly effectively. Particularly excellent dimensional stability can be imparted to the film.

  Amorphous resin C in the present invention has a characteristic that, when the resin (sample) is measured using differential scanning calorimetry (DSC) or the like, only the glass transition temperature is detected and the melting point and melting peak are not detected. It is resin which has.

  Here, the amorphous resin C is a resin different from the polyester A and the polyimide B.

  The amorphous resin in the present invention is a polymer in which no melting peak is observed when the polymer is measured as follows according to JIS K 7121 (1987) using a thermal analyzer RDC220 manufactured by Seiko Instruments. is there.

  The film is charged in an aluminum pan with a mass of 4.5 to 5.5 mg, set in the apparatus, heated from 30 ° C. to 300 ° C. at a rate of 10 ° C./min in a nitrogen atmosphere, and the temperature rise is completed. After waiting at 300 ° C. for 5 minutes, subsequently cooling to 30 ° C. at a rate of 10 ° C./minute, waiting for 30 minutes at 30 ° C. after completion of cooling, and then raising the temperature again to 300 ° C. at a rate of 10 ° C./minute The melting peak is observed in the calorimetric curve obtained in the above.

  In the biaxially oriented film of the present invention, the mass ratio of the amorphous resin C is 0.01 to 20 as described above. When the mass ratio of the amorphous resin C is less than 0.01, the portion that functions as a restraint point during stretching in the polyester A is reduced, so that it may not be sufficient to obtain the effect of high orientation of the present invention. Inferior to the mechanical strength and dimensional stability of the film. On the other hand, if it exceeds 20, the film surface tends to become rough in biaxial stretching of the polyester film, the film-forming property of the film decreases, and the production cost increases. Moreover, it is inferior to the secondary workability of a film. In particular, when the film surface becomes rough, for example, when used for a magnetic recording medium, the electromagnetic conversion characteristics tend to be low, and the effects of the present invention may not be obtained.

  The mass ratio of the amorphous resin C is preferably 0.05 to 15, more preferably 0.1 to 10, and still more preferably 0.5 to 5 from the viewpoints of dimensional stability, film surface roughness, film forming property, and cost.

It weight ratio W _C / W _B of the mass W _C of the mass W _B and the amorphous resin C of polyimide B that are contained in the range of greater than 0 and less than 1/3 the biaxially oriented polyester film of the present invention Is preferred. By being in the said range, workability improves and the foreign material in a film can be reduced. Furthermore, the production cost can be reduced.

Polyimide B mass ratio W _C / W range _B of the amorphous resin C is more preferably 0.01 or more. More preferably, it is 0.03 or more. Most preferably, it is 0.05 or more. Range of the mass ratio W _C / W _B are more preferably 0.25 or less, more preferably 0.2 or less. Mass ratio W _C / W _B are more preferably 0.02 to 0.25, more preferably 0.03 to 0.2, most preferably 0.05 to 0.2. When W _C / W _B is within the above range, it is easy to form a constraining point in the film, and it is possible to effectively orient the molecular chain and at the same time to control the film surface roughness within the scope of the present application. Cost can be lowered.

  The melt viscosity of the amorphous resin C of the present invention is based on the miscibility between the amorphous resin C and polyimide B and polyester A, and the workability, at a temperature of 350 ° C. and at a shear rate of 300 (1 / sec). Therefore, it is preferably in the range of 50 to 1,500 Pa · S, more preferably in the range of 100 to 1,000 Pa · S. Most preferably, it is in the range of 200 to 800 Pa · S.

  Amorphous resin C has a glass transition temperature higher than that of polyester A, and amorphous resin C tends to have a higher melt viscosity than polyester A. Therefore, in the biaxially oriented polyester film of the present invention, It becomes an unmelted product, and foreign matters are likely to be generated in the finally obtained film. Therefore, it is preferable that the amorphous resin C is not directly mixed with the polyester A, but the polyimide B and the amorphous resin C are mixed in advance and the mixed resin is mixed with the polyester A.

  Furthermore, in the biaxially oriented polyester film of the present invention, when the polyimide B and the amorphous resin C are blended with the polyester A, it is more preferable to blend a block copolymer composed of the polyimide B and the amorphous resin C together. Due to the presence of this block copolymer, the processability when mixing the mixed resin of polyimide B and amorphous resin C into polyester A is dramatically improved, and foreign matters in the finally obtained film are reduced, Furthermore, the film surface roughness can be controlled within a preferable range.

  In order to derive a block copolymer composed of polyimide B and amorphous resin C, the molecular chain terminal of polyimide B and the molecular chain of amorphous resin C are blended when polyimide B and amorphous resin C are blended by melt kneading. A method of adding a compound that reacts with the terminal and chemically bonds the amorphous resin B and the amorphous resin C (hereinafter referred to as a chain linking agent) can be exemplified.

  In other words, the raw material used when manufacturing the biaxially oriented film of the present invention is the chain binder used for the polyimide B and the amorphous resin C when the resin used as the raw material of the biaxially oriented film of the present invention is manufactured. It is preferable to use a resin kneaded in advance.

  From the viewpoint of forming a block copolymer as described above, the end of the polymer molecular chain of polyimide B and / or amorphous resin C has a highly reactive end group, specifically -COOH (carboxyl group) or- It preferably has a functional group as exemplified by OH (hydroxyl group).

  When the polyimide B and / or the amorphous resin C has a reactive functional group at the terminal of the polymer structure, a block copolymer can be formed more efficiently.

  The presence of such a block copolymer can be confirmed using a spectroscopic technique such as a microscopic FT-IR method (Fourier transform microscopic infrared spectroscopy) or an NMR method.

  In the present invention, as described above, by forming a block copolymer of polyimide B and amorphous resin C using a chain linking agent, processability can be improved, and coarse foreign matter in the film is reduced, The film surface roughness can be easily controlled within the preferred range of the present application.

  As such a chain linking agent, a compound having at least one functional group selected from an epoxy group, an amino group, an isocyanate group, a hydroxyl group, a mercapto group, and a ureido group in the molecular formula and molecular structure of the compound is preferable. . These functional groups react with polyimide B or amorphous resin C selectively and with high yield.

  Examples of the chain linking agent in the present invention include alkoxysilanes having one or more functional groups selected from an epoxy group, an amino group, and an isocyanate group. Specific examples of such compounds include epoxy group-containing alkoxysilanes such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. Compounds, ureido group-containing alkoxysilane compounds such as γ-ureidopropyltriethoxysilane, γ-ureidopropyltrimethoxysilane, γ- (2-ureidoethyl) aminopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane Γ-isocyanate-propyltrimethoxysilane, γ-isocyanate-propylmethyldimethoxysilane, γ-isocyanate-propylmethyldiethoxysilane, γ-isocyanate-propylethyldimethoxysilane, γ-isocyanatopropylethyldi Ethoxysilane, γ- Isocyanate group-containing alkoxysilane compounds such as cyanoocyanatopropyltrichlorosilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ-aminopropyltri Examples thereof include amino group-containing alkoxysilane compounds such as methoxysilane. Among them, epoxy group-containing alkoxysilane compounds and isocyanate group-containing alkoxysilane compounds are PEI used as polyimide B, polysulfone (hereinafter sometimes referred to as PSU) used as amorphous resin C, polyphenylene ether (hereinafter referred to as PPE). ), Polycarbonate (hereinafter sometimes referred to as PC), polyarylate (hereinafter sometimes referred to as PAR), and cyclic olefin copolymer (hereinafter sometimes referred to as COC), which are preferable. In particular, an isocyanate group-containing alkoxysilane is most preferred. Examples include γ-isocyanatopropyltriethoxysilane, γ-isocyanatopropyltrimethoxysilane, γ-isocyanatopropylmethyldimethoxysilane, γ-isocyanatopropylmethyldiethoxysilane, γ-isocyanate. Examples thereof include propylethyldimethoxysilane, γ-isocyanatopropylethyldiethoxysilane, and γ-isocyananetopropyltrichlorosilane.

  As a specific chain linking agent, for example, “KBE-9007” (product name) 3-isocyanatopropyltriethoxysilane, which is commercially available from Shin-Etsu Chemical Co., Ltd. and is available as a silane coupling agent, KBM-303 ”(product name) 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and the like.

  The content of the chain linking agent preferably contained in the present invention is 100 parts by mass of the total of polyester A, polyimide B, and amorphous resin C in the film from the viewpoint of processability of amorphous resin C and polyimide B. It is preferable that it is 0.01-3 mass parts. More preferably, it is 0.1-2 mass parts, Most preferably, it is 0.2-1.5 mass parts.

  In the present invention, when alkoxysilane is used as the chain linking agent, alcohol derived from alkoxysilane may be generated during kneading or extrusion. In order to obtain a resin composition with a small amount of alcohol generated as a raw material for film formation, using a twin-screw extruder having at least two kneading parts, once the amorphous resin C, the polyimide B, and the chain A preferred method is to melt and knead the coupling agent and then melt and knead it once more. Further, in the second and subsequent melt-kneading, it is preferable to add 0.02 parts by mass or more, more preferably 0.1 to 5 parts by mass of water with respect to 100 parts by mass in total of the amorphous resin C and the polyimide B. By this method, hydrolysis of the alkoxysilane compound is promoted, and the amount of alcohol generated from the resulting resin composition can be reduced. In order to stabilize the film formation, it is possible to remove impurities, oligomers, and alcohol generated from the reaction of the chain linking agent in the amorphous resin C and polyimide B as much as possible from the raw material chips for film formation obtained by kneading. For this purpose, it is preferable to provide a vacuum vent after the kneading zone of the extruder during melt kneading. The method of adding water is not particularly limited, but a method of side-feeding water using a liquid feeding device such as a gear pump or a plunger pump from the middle of the extruder, or once melting and kneading and further melting once or more. When kneading, a preferable method is to mix water or side feed from the middle of the extruder.

  When the biaxially oriented polyester film of the present invention is observed with an electron microscope, polyester A forms a continuous phase in the resin phase separation structure, and polyimide B and amorphous resin C are dispersed with respect to polyester A in the film, respectively. A phase is formed and a discontinuous structure is preferable.

  In the final film, when polyimide B and amorphous resin C are dispersed with respect to polyester A, the polymer molecular chains can be effectively aligned by stretching, etc., and the film has excellent mechanical properties. And excellent dimensional stability can be imparted, coarse foreign matters in the film can be reduced, and the film surface roughness can be controlled within an appropriate range.

  When polyimide B and amorphous resin C form a dispersed phase in the film, the average dispersion diameter of the dispersion domain of polyimide B is in the range of 1 to 500 nm from the viewpoint of orienting the molecular chains of the polymer effectively during film stretching. Preferably there is.

  When the average dispersion diameter of the polyimide B is within the above range, the glass transition temperature (Tg) of the polyester film of the present invention can be sufficiently increased, and excellent heat resistance and moist heat resistance can be imparted to the film. it can.

  The average dispersion diameter of the dispersion domain of the amorphous resin C is preferably in the range of 50 to 500 nm.

  When the average dispersion diameter of the dispersion domains of the polyimide B and the amorphous resin C is within the above range, the dispersion state of the polyimide B and the amorphous resin C with respect to the polyester A can be improved in the finally obtained film. Therefore, the molecular chain of the polyester A can be particularly effectively oriented by stretching or the like, and particularly excellent dimensional stability can be imparted to the film. The average dispersion diameter of polyimide B in the film is preferably 1 to 400 nm. More preferably, it is 5-300 nm. The average dispersion diameter of the amorphous resin C in the film is preferably 50 nm or more, and more preferably 100 nm or more. The average dispersion diameter of the amorphous resin C is preferably 300 nm or less. More preferably, it is 200 nm or less.

  When the average dispersion diameter of the polyimide B is within the above range, the film forming property is more stable.

  When the average dispersion diameter of the polyimide B and the amorphous resin C is within the above range, the amorphous resin C effectively functions as a knotting point and a constraint point of the molecular chain of the polyester A when the film is stretched. Excellent film forming properties, mechanical strength, heat and humidity resistance, and dielectric breakdown characteristics can be imparted.

  Here, the average dispersion diameter is an average of circle equivalent diameters of dispersion domains obtained on a plurality of observation surfaces.

  The average dispersion diameter of the dispersion domains of the polyimide B and the amorphous resin C in the film of the present invention was determined by first observing the cut surface of the film using a transmission electron microscope under a pressure of 100 kV. Take a photo at double. Next, the obtained photograph was taken into an image analyzer as an image, 100 arbitrary dispersed phases were selected, and image processing was performed as necessary to obtain a dispersion diameter, and a number average thereof was obtained. Details of the measurement method will be described later.

  In addition, among dispersed domains formed in polyester, in a polymer forming a domain by energy dispersive X-ray spectroscopy (TEM-EDX method) using a field emission electron microscope (TEM-EDX method) (energy dispersive X-ray spectroscopy) It was decided to detect the atoms contained in and identify the polymer.

  From the viewpoint of controlling the average dispersion diameter of the amorphous resin C in the film, the amorphous resin C is preferably not nanocompatible with the polyimide B.

  Here, whether the polyimide B and the amorphous resin C are nano-compatible can be determined by the following method.

  First, polyimide B and amorphous resin C are blended by a melt kneading method with a twin screw extruder at an arbitrary ratio of mass ratio of 100/0 to 0/100. Use an extruder equipped with a triple-screw type screw. In the kneading part of the extruder, the resin temperature is set to 330 to 380 ° C., and the residence time during kneading is set to a range of 1 to 5 minutes. The screw speed is 300 rpm. Further, the ratio of (screw shaft length / screw shaft diameter) of the twin screw extruder is 40. Further, the twin screw has a screw shape with two kneading portions. At this time, in the mixing order of the raw materials, all the raw materials are blended and then melt-kneaded by the above method.

  When the obtained blend is observed with a transmission electron microscope (TEM), the dispersion domain diameter is 100 nm or more at any mass ratio of polyimide B and amorphous resin C. It is said that the crystalline resin C is a combination that is not nano-compatible. Here, the dispersion domain diameter is an average equivalent circle diameter obtained in a plurality of observation planes.

  It can also be determined whether or not the polyimide B and the amorphous resin C are nanocompatible with each other by examining whether or not the blend has a single glass transition temperature.

  More preferably, the amorphous resin C in the film forms a dispersion domain of the amorphous resin C in a part of the dispersed phase of the polyimide B formed in the polyester A. That is, polyimide B forms a dispersed phase with respect to polyester A that forms a continuous phase. It is preferable that the amorphous resin C is dispersed in a part of the dispersion domain of the polyimide B, and all the amorphous resin C is present in any dispersion domain of the polyimide B.

  In the finally obtained film, when the amorphous resin C is dispersed in the dispersion domain of the polyimide B, the molecular chain can be effectively oriented by stretching or the like, and the film has particularly excellent mechanical properties and particularly excellent Dimensional stability can be imparted. Moreover, the coarse foreign material in a film can be reduced and film surface roughness can be controlled within an appropriate range. In addition, the amorphous resin C forms a dispersed phase in the polyester A, that is, the pores formed in the film as compared with the case where the amorphous resin C is dispersed in the polyester A without the polyimide B being interposed. The number can be reduced, and the film forming property and productivity are excellent.

  In the film, the average dispersion diameter of the polyimide B containing the dispersion domain of the amorphous resin C is preferably 100 to 500 nm, more preferably 100 to 400 nm, and most preferably 100 to 300 nm.

  Further, from the viewpoint of moldability with polyimide B or polyester A, amorphous resin C is particularly polysulfone (PSU), polyphenylene ether (PPE), polycarbonate (PC), polyarylate (PAR), cyclic olefin copolymer ( COC).

  When the biaxially oriented film of the present invention is produced using a resin obtained by kneading polyimide B and amorphous resin C in advance using a chain linking agent as a raw material, selected from an epoxy group, an amino group, and an isocyanate group When an alkoxysilane having one or more functional groups is used as a chain linking agent, a siloxane bond is easily formed between the polyimide B and the amorphous resin C. Thereby, a siloxane bond tends to exist in the vicinity of the interface of the dispersed phase of the amorphous resin C. Silicon atoms can be detected near the interface of the dispersed phase using the TEM-EDX method. In the present invention, from the viewpoint of processability of the polyimide B and the amorphous resin C and the viewpoint of improving productivity, the interface of the dispersed phase composed of the amorphous resin C contains silicon atoms (Si) due to siloxane bonds. It is preferable.

  The biaxially oriented polyester film of the present invention preferably has a pore area ratio (R) of 30% or less centering on the amorphous resin C. By using the mixed resin prepared as described above as a raw material for the biaxially oriented film, it becomes difficult to generate pores having the amorphous resin C as a nucleus in the film. By suppressing the formation of pores with amorphous resin C as the core, when the biaxially oriented film of the present invention is continuously formed by the melt film forming method, the film formation is stable and the productivity is very high. improves.

  Here, the “hole having the amorphous resin C as a nucleus” in the present invention refers to a hole in which the amorphous resin C is recognized inside the hole when the hole is observed. Further, even when it is unclear whether or not the amorphous resin C exists in the inside of the hole, it may be recognized that the hole is formed due to the amorphous resin C. It is considered to be a “hole having a crystalline resin C as a nucleus”.

  Such a hole having the amorphous resin C as a nucleus is usually located inside the hole when an ultrathin section of the film is observed under a specific condition using a transmission electron microscope (TEM), as will be described later. Amorphous resin C is observed as a nucleus. On the other hand, in the present invention, the holes that do not correspond to the holes having the amorphous resin C as a nucleus have a spherical shape, a fibrous shape, an indeterminate shape, or other shapes in the hole in the TEM observation image. Even if there are nuclei, the nuclei are pores composed of a substance other than the amorphous resin C. Of course, preferably, the hole itself is not observed in the observed image.

  The biaxially oriented film of the present invention preferably has an internal haze of 0 to 75%. When the internal haze is within the above range, the biaxially oriented film of the present invention can be used for a wider range of applications such as a display-related film such as an optical film. The internal haze was measured using a haze meter (HZ-2 manufactured by Suga Test Instruments Co., Ltd.) based on JIS K 7105 (1985). Moreover, the internal haze except a film surface haze was measured by putting the film into the quartz cell for liquid measurement, filling liquid paraffin, and performing the measurement. The internal haze of the biaxially oriented film of the present invention is more preferably 0 to 50%, most preferably 0 to 30%.

  When producing the biaxially oriented film of the present invention, a mixed resin D obtained by blending polyester A and polyimide B in advance, and a mixed resin E obtained by blending polyimide B and amorphous resin C are prepared in advance. Each is prepared individually, and then a mixed resin F obtained by further kneading polyester A ′ with the mixed resin E is prepared. It is preferable to produce a film using this mixed resin F, mixed resin D and polyester A and / or A 'as raw materials.

  Here, polyester A ′ refers to a polyester resin different from polyester A. The melt viscosity [A ′] of the polyester A ′ is preferably larger than the melt viscosity [A] of the polyester A. For example, specific examples of the polyester A 'when the polyester A is PET having an intrinsic viscosity of 0.65 include PET having an intrinsic viscosity of 1.1, PEN having an intrinsic viscosity of 0.65, and PEN having an intrinsic viscosity of 1.1. Polyester A ′ is preferably PET having an intrinsic viscosity of 1.1 and a PEN having an intrinsic viscosity of 1.1, which have a higher melt viscosity than polyester A.

  However, when the resin G obtained by simply mixing a substance containing polyester A, polyimide B and amorphous resin C at a time is used as a raw material, the intrinsic viscosity (IV) of a large film during melt extrusion during film formation. In some cases, the film deteriorates to reduce the heat and moisture resistance of the film, or unmelted matter is generated as coarse foreign matter in the film, thereby reducing mechanical strength, dimensional stability, and dielectric breakdown characteristics. Moreover, compared with the film formed using this resin G, the film manufactured using said mixed resin D and mixed resin F has the outstanding film forming property.

At this time, the melt viscosity [A ′] of polyester A ′ at a temperature of 315 ° C. and a shear rate of 300 (1 / sec) is the same as that of mixed resin E at a temperature of 315 ° C. and a shear rate of 300 (1 / sec). And the melt viscosity [E]
1/4 ≤ [A '] / [E] ≤ 4
It is important to meet.

Furthermore, the following formula
1/3 ≤ [A '] / [E] ≤ 3
It is more preferable to satisfy.

The melt viscosity [A] of polyester A at a temperature of 300 ° C. and a shear rate of 300 (1 / sec) is the melt viscosity [A] of the mixed resin F at a temperature of 300 ° C. and a shear rate of 300 (1 / sec). Between the viscosity [F] and the following formula
1/4 ≤ [A] / [F] ≤ 4
It is important to meet.

Furthermore, the following formula
1/3 ≤ [A] / [F] ≤ 3
It is more preferable to satisfy.

  In order to obtain the biaxially oriented film of the present invention, a resin E in which polyimide B and amorphous resin C are kneaded is prepared, and then the resin E and polyester A are kneaded. It is important to use a mixed resin prepared separately for the film material.

  In the present invention, in order to prepare a polyimide B-amorphous resin C mixed resin from polyimide B and amorphous resin C, a method of kneading using a high shear mixer with shear stress such as a twin screw extruder is used. preferable. In that case, it is important to prepare a mixed resin having a mass fraction of polyimide B and amorphous resin C of 99/1 to 50/50. Particularly preferably, the mass fraction of polyimide B and amorphous resin C is 95/5 to 70/30.

  By setting the mass ratio of the kneading of the polyimide B and the amorphous resin C within the above range, the dispersion of the amorphous resin C in the film becomes good, and the molecular chains are more easily oriented. Furthermore, it becomes easy to control the amorphous resin C content in the film within the range of the present invention. From the viewpoint of controlling the amorphous resin C content in the finally obtained film, the mass ratio is more preferably 90/10 to 80/20.

  The raw material for forming the biaxially oriented film of the present invention is preferably thermally stable. The thermal stability of the film forming raw material is evaluated by the average dispersed diameter of the dispersed phase. The method is as follows.

  The biaxially oriented film of the present invention is the highest melting point or glass transition temperature to melting point or glass transition temperature of the resin polyester A, polyimide B, amorphous resin C constituting the film, and / or glass transition temperature. Regarding the dispersed phase in the resin composition melted and retained for 5 minutes at a temperature of 30 ° C. and cooled in a water bath, the average dispersed particle size of the polyimide B in the polyester A is 1 to 100 nm, and the amorphous resin C in the polyester A The average dispersed particle size is preferably 100 to 800 nm. The lower limit of the average dispersed particle size of polyimide B after 5 minutes of melt residence is preferably 2 nm or more, more preferably 3 nm or more, and the upper limit is preferably 70 nm or less, more preferably 40 nm or less. The lower limit of the average dispersed particle size of the amorphous resin C after being melted for 5 minutes is preferably 150 nm or more, more preferably 200 nm or more, and the upper limit is preferably 750 nm or less, more preferably 700 nm or less. When the raw material for forming the biaxially oriented film of the present invention has such thermal stability, continuous film formation for a long time becomes stable, and the cost of the biaxially oriented film of the present invention can be reduced. Moreover, it becomes easy to keep the quality of the film uniform.

  The dispersion particle size of the dispersed phase after melt residence is measured by charging a thermoplastic resin composition that has been dried at 130 ° C for 3 hours into a Toyo Seiki melt indexer. Samples cooled with a water bath were cut from an 80 nm thick piece from the center and observed with a transmission electron microscope. Image software `` Scion Image '' (Scion Corporation) The average value is obtained by measuring the maximum diameter and the minimum diameter of each particle using a product manufactured by the company, and then the number average value (average particle diameter) of the 100 average values is obtained.

  The biaxially oriented polyester film of the present invention preferably has a 10-point average roughness Rz of 50 to 300 nm on at least one side.

  If Rz is less than 50 nm, the friction coefficient with the transport rolls and the like may increase in film production and processing processes, causing process troubles. In particular, when the biaxially oriented polyester film of the present invention is used as a magnetic recording medium, the friction with the magnetic head is increased and the magnetic tape characteristics are deteriorated, so that the effects of the present invention may not be obtained.

  On the other hand, when Rz is larger than 300 nm, when the biaxially oriented polyester film of the present invention is used as a magnetic recording medium, the electromagnetic conversion characteristics deteriorate, so the effects of the present invention may not be obtained.

  The lower limit of the surface roughness Rz of at least one surface of the biaxially oriented polyester film of the present invention is more preferably 75 nm, still more preferably 100 nm, and the upper limit is 250 nm, more preferably 200 nm. A more preferable range of Rz is 75 to 250 nm, and a more preferable range is 100 to 200 nm.

  The biaxially oriented polyester film of the present invention preferably has a center line average roughness Ra of at least one surface of 0.5 to 20 nm.

  When the center line average roughness Ra of at least one surface of the biaxially oriented polyester film of the present invention is within the above range, friction with a transport roll or the like in film production or processing of the biaxially oriented polyester film of the present invention. The coefficient becomes smaller and process trouble is reduced. In particular, when the biaxially oriented polyester film of the present invention is used as a magnetic recording medium, friction with the magnetic head can be reduced, magnetic tape characteristics and electromagnetic conversion characteristics can be improved, and the effects of the present invention can be easily obtained.

  On the other hand, when the centerline average roughness Ra of one surface of the biaxially oriented polyester film of the present invention is 0.5 to 20 nm, the centerline average roughness Ra of the surface of the other surface (hereinafter referred to as the opposite surface) Is preferably 3 to 30 nm.

  When Ra on the opposite surface is within the above range, in the film production, processing process, etc., process trouble due to friction with the transport roll, etc. is reduced, and when used as a magnetic tape, the friction with the guide roll is reduced, Excellent tape runnability can be imparted. Moreover, when storing the biaxially oriented polyester film of the present invention as a film roll or pancake, it is possible to suppress a decrease in electromagnetic conversion characteristics caused by transfer of surface protrusions to the opposite surface.

  When the center line average roughness Ra of one surface of the biaxially oriented polyester film of the present invention is 0.5 to 20 nm, the lower limit of Ra on the opposite surface is more preferably 5 nm, more preferably 7 nm, and the upper limit. Is 20 nm, more preferably 15 nm. A more preferable range is 5 to 20 nm, and a further preferable range is 7 to 15 nm.

  The biaxially oriented polyester film of the present invention preferably has a temperature expansion coefficient in the width direction of −6.0 to 6.0 ppm / ° C. The temperature expansion coefficient being within the above range is, for example, from the viewpoint of dimensional stability due to temperature change during recording and reproduction of the magnetic recording medium and dimensional stability after storage under high temperature conditions when used for a magnetic recording medium. preferable. The upper limit of the temperature expansion coefficient in the width direction is preferably 5.5 ppm / ° C, more preferably 5.0 ppm / ° C, and the lower limit is preferably -3.0 ppm / ° C, more preferably 0 ppm / ° C. In order to make the lower limit of the temperature expansion coefficient in the width direction smaller than −6.0 ppm / ° C., it is necessary to considerably increase the orientation in the width direction, and it may be difficult to obtain a biaxially oriented polyester film substantially. . A more preferable range is -3.0 to 5.5 ppm / ° C, and a further preferable range is 0 to 5.0 ppm / ° C.

  The biaxially oriented polyester film of the present invention preferably has a humidity expansion coefficient in the width direction of 0 to 6.0 ppm /% RH. The humidity expansion coefficient being within the above range means that, for example, when used for a magnetic recording medium, dimensional stability due to humidity change during recording / reproduction of the magnetic recording medium and dimensional stability after storage under high humidity conditions To preferred. The upper limit of the humidity expansion coefficient in the width direction is preferably 5.5 ppm /% RH, more preferably 5.0 ppm /% RH. In order to make the lower limit of the humidity expansion coefficient in the width direction smaller than 0 ppm /% RH, it is necessary to considerably increase the orientation in the width direction, and it may be difficult to obtain a biaxially oriented polyester film substantially. A more preferred range is 0 to 5.5 ppm /% RH, and a further preferred range is 0 to 5.0 ppm /% RH.

  Furthermore, the biaxially oriented polyester film of the present invention preferably has a sum of Young's modulus in the longitudinal direction and Young's modulus in the width direction of 11 to 20 GPa. A preferable range of the sum of Young's moduli is 12 to 19 GPa, and a more preferable range is 13 to 18 GPa. When the sum of Young's moduli is less than 11 GPa, for example, when used for magnetic recording media, the Young's modulus in the longitudinal direction and the width direction is insufficient, as will be described later. Problems such as recording track misalignment and edge damage are likely to occur. Also, if the sum of Young's moduli is greater than 20 GPa, for example, it is necessary to increase the draw ratio and make it extremely oriented, resulting in frequent film breakage and decreased productivity, and the break elongation becomes small and breaks easily. Sometimes.

  In order to set the sum of the Young's modulus in the longitudinal direction and the Young's modulus in the width direction within the above range, the Young's modulus in the longitudinal direction of the biaxially oriented polyester film is preferably set to 4.5 to 12 GPa. When the Young's modulus in the longitudinal direction is smaller than 4.5 GPa, the film stretches in the longitudinal direction due to the tension in the longitudinal direction in the tape drive, and contracts in the width direction due to the elongation deformation, so that a problem of recording track deviation is likely to occur. The lower limit of the Young's modulus in the longitudinal direction is more preferably 5.0 GPa, still more preferably 5.5 GPa. On the other hand, when the Young's modulus in the longitudinal direction is larger than 12 GPa, it is difficult to control the Young's modulus in the width direction within a preferable range, and the Young's modulus in the width direction is insufficient, which tends to cause edge damage. The upper limit of the Young's modulus in the longitudinal direction is more preferably 11 GPa, still more preferably 10 GPa. A more preferable range is 5.0 to 11 GPa, and a further preferable range is 5.5 to 10 GPa.

  In the biaxially oriented polyester film of the present invention, the ratio Em / Et of Young's modulus Em in the longitudinal direction and Young's modulus Et in the width direction is preferably in the range of 0.50 to 0.95, and in the range of 0.60 to 0.90. More preferably, it is most preferably in the range of 0.60 to 0.80. In particular, when the Young's modulus in the width direction is larger than the Young's modulus in the longitudinal direction, it is easier to control the temperature expansion coefficient and humidity expansion coefficient in the width direction within the scope of the present invention.

  The Young's modulus in the width direction is preferably in the range of 5 to 12 GPa. If the Young's modulus in the width direction is less than 5 GPa, it may cause edge damage. The lower limit of the Young's modulus in the width direction is more preferably 6 GPa. On the other hand, when the Young's modulus in the width direction is larger than 12 GPa, it is difficult to control the Young's modulus in the longitudinal direction within a preferable range, and it may be easily deformed by the tension in the longitudinal direction or the slit property may be deteriorated. . The upper limit of the Young's modulus in the width direction is more preferably 11 GPa, still more preferably 10 GPa. A more preferable range is 5.5 to 11 GPa, and a further preferable range is 6 to 10 GPa.

  The biaxially oriented film of the present invention has moisture and heat resistance. As a method for defining the heat and moisture resistance, there is an elongation half-life by film elongation retention (defined by the following formula) before and after the moisture heat treatment.

Elongation retention (%) =
(Break elongation of sample after treatment) / (Break elongation of sample before treatment)
The processing time until the elongation retention reaches 50% is defined as the elongation half-life. The elongation half-life of the present invention is preferably 20 hours or more and 80 hours or less. The larger the elongation half-life of the biaxially oriented film of the present invention in the moist heat test (wet heat treatment), the more the film corresponds to being less likely to deteriorate under high temperature and high humidity.

  The biaxially oriented film of the present invention provides excellent dielectric breakdown characteristics, excellent mechanical strength, and excellent dimensional stability by having an elongation half-life of 20 to 80 hours according to a moist heat test. Furthermore, when the film of the present invention is used for industrial materials, for example, electrical insulation, a long life can be imparted to the member.

  In the biaxially oriented film of the present invention, it is often difficult for the elongation half-life to exceed 80 hours. On the other hand, in the biaxially oriented film of the present invention, when the elongation half-life is less than 20 hours, the film may not substantially have moisture and heat resistance.

  In order to obtain a biaxially oriented film having an elongation half-life of 20 hours or more and 80 hours or less, it can be easily obtained by favorably dispersing polyimide B and amorphous resin C in the polyester. Preferably, it is preferable that the polyimide B is dispersed in the dispersion domain of the amorphous resin C as described above using the more preferable chain linking agent described above. The smaller the average dispersion diameter of the dispersion domain of the amorphous resin C formed in the polyester A, the better the biaxially oriented film of the present invention is. The elongation half life of the biaxially oriented film of the present invention is preferably 25 hours to 75 hours, more preferably 30 hours to 70 hours.

  Moreover, the biaxially oriented film of the present invention may be a single layer or a laminated structure of at least two layers. When taking a laminated structure, the film layer of the present invention may be used as a base layer part or a laminated part, but at least one surface layer is preferably composed of the film layer of the present invention.

  When the polyester film of the present invention is used as a magnetic recording medium, it is preferably a laminated structure of two or more layers. At this time, one surface is required to have smoothness to obtain excellent electromagnetic conversion characteristics, and the other surface is transportable in the film forming / processing process, and the running performance and running durability of the magnetic tape. Roughness for imparting is required. Therefore, it is preferable that the polyester film has a laminated structure of two or more layers.

  A metal layer may be formed on at least one side of the biaxially oriented film of the present invention. Moreover, you may perform arbitrary processes, such as heat processing, shaping | molding, surface treatment, metal vapor deposition to the film surface, formation of a metal layer by sputtering, lamination, coating, printing, embossing, and etching.

  The thickness of the biaxially oriented polyester film of the present invention is not particularly limited, but is preferably 1,000 μm or less, and more preferably in the range of 2 to 300 μm, and more preferably in the range of 3 to 200 μm, from the viewpoint of thin film use and workability. It is. In particular, the magnetic recording medium is suitable for a high density magnetic recording tape, for example, a base film for data storage. The film thickness is usually in the range of 1-15 μm for magnetic recording materials, 2-10 μm for coated magnetic recording media for data or digital video, and 3-9 μm for vapor-deposited magnetic recording media for data or digital video. Is preferred. Further, a film having a thickness of 0.5 to 15 μm is preferably used for the capacitor, and the dielectric breakdown voltage and the stability of the dielectric characteristics are excellent. A film having a thickness of 1 to 6 μm is preferably applied to the thermal transfer ribbon application, so that high-definition printing can be performed without causing wrinkles during printing and without causing printing unevenness and ink overtransfer. For heat-sensitive stencil paper use, a film of 0.5 to 5 μm is preferably applied, and it has excellent perforation property at low energy. The perforation diameter can be changed according to the energy level. It is also excellent in printability such as when performing.

  When used for electrical insulation, it is preferably 1,000 μm or less. More preferably, it is the range of 0.5-500 micrometers, More preferably, it is 5-300 micrometers. Although it can be appropriately determined according to the detailed application and purpose, the range of 10 to 200 μm is most preferable from the viewpoint of workability.

  Next, PET is used as polyester A, PEI “Ultem” (registered trademark of SABIC Innovative Plastics) is used as polyimide B, and PAR polymer U-100 ”(manufactured by Unitika) is used as amorphous resin C. Although the preferable manufacturing method of the biaxially oriented film of this invention is demonstrated, this invention is not limited to the following manufacturing method.

  First, magnesium acetate is added to a mixture of dimethyl terephthalate and ethylene glycol, and the mixture is heated to raise the ester exchange reaction. Next, after adding trimethyl phosphate to the transesterification reaction product, germanium oxide is added to move to the polycondensation reaction layer. Next, the reaction system is gradually depressurized while the temperature is raised, and the polymerization reaction proceeds at 290 ° C. under a reduced pressure of 1 mmHg or less. Here, a polyester having an intrinsic viscosity of about 0.6 is obtained. In addition, as a method of incorporating the particles into the polyester constituting the film, a method of dispersing particles in ethylene glycol in a predetermined ratio in the form of a slurry, mixing the ethylene glycol slurry and the polyester, or adding them during the polyester manufacturing process. Is preferred.

  When adding the particles, for example, it is preferable to add the water sol or alcohol sol obtained at the time of synthesis without drying, since the dispersibility of the particles is good. It is also effective to mix a water slurry of particles directly with predetermined polyester pellets and knead them into polyester using a vented twin-screw kneading extruder. As a method for adjusting the content and number of particles, a master of high-concentration particles is prepared by the above-mentioned method, and it is diluted with a polyester that does not substantially contain particles during film formation to reduce the content of particles. The method of adjusting is effective.

  When mixing PET, PEI, and PAR, a preferred example is a method of pre-melting and kneading (pelletizing) a mixture of PET and PEI, PEI and PAR, and a chain binder, respectively, into a master pellet before melt extrusion. The

In the present invention, first, the PET pellets and PEI pellets are mixed at a mass ratio of 20/80 to 80/20 and fed to a vented twin-screw kneading extruder heated to 270 to 320 ° C. And melt extrusion. The shear rate at this time is preferably 50 to 2,000 sec ⁻¹ , more preferably 100 to 1,800 sec ⁻¹ , and the residence time is preferably 0.5 to 10 minutes, more preferably 1 to 5 minutes. Furthermore, when it is desired to further reduce the average dispersion diameter of PEI dispersion in PET, the obtained chips may be put into the twin screw extruder again and extrusion may be repeated until they are compatible.

  In the present invention, when a PEI-PAR mixed resin is produced from PAR and PEI, a method of kneading using a high shear mixer with shear stress such as a twin screw extruder is preferable. In that case, it is important to prepare a mixed resin having a mass fraction of PEI, PAR, and chain linking agent of 99/1 / 0.001 to 50/50/3. Particularly preferably, the mass fraction of PEI, PAR and chain linking agent is 95/5 / 0.1 to 70/30 / 2.0.

  PAR having a glass transition temperature higher than that of polyester A and having a high melt viscosity may become an unmelted coarse foreign substance in the film, resulting in a decrease in film formability or an increase in the surface roughness of the finally obtained film. . By setting the mass ratio of the PEI and PAR kneading within the above range, it becomes easy to control the dispersibility of the PAR during processing, and further to control the PEEK content in the film within the range of the present invention. The mass ratio is more preferably 90/10 / 0.1 to 80/20 / 1.5.

  When mixing with a twin-screw extruder, from the viewpoint of reducing poor dispersion, it is preferable to equip a three- or two-screw type screw, and the kneading part has a PAR resin processing temperature of 300 to 380 ° C. The resin temperature range is preferred. A more preferable temperature range is 310 to 370 ° C, and a more preferable temperature range is 320 to 365 ° C. Setting the temperature range of the kneading part to a preferable range makes it easy to increase the shear stress, increases the effect of reducing defective dispersion, and makes it easy to control the surface roughness of the film within the preferable range of the present invention. The residence time at that time is preferably in the range of 1 to 5 minutes. Moreover, it is preferable that screw rotation speed shall be 100-500 rotation / min, More preferably, it is the range of 200-400 rotation / min. By setting the screw rotation speed within a preferable range, high shear stress is easily added, and the dispersion diameter of the dispersed phase can be controlled within the preferable range of the present invention. The ratio of (screw shaft length / screw shaft diameter) of the twin screw extruder is preferably in the range of 20 to 60, more preferably in the range of 30 to 50. Further, in the twin screw, it is preferable to provide a kneading part by a kneading paddle or the like in order to increase the kneading force, and the kneading part is preferably formed in a screw shape having two or more, more preferably three or more. At this time, the mixing order of the raw materials is not particularly limited, and a method in which all raw materials are blended and then melt-kneaded by the above method, a part of the raw materials are blended and then melt-kneaded by the above method, and the remaining raw materials are blended Any method may be used such as a method of melt-kneading, or a method of mixing a part of raw materials and mixing the remaining raw materials using a side feeder during melt-kneading with a single-screw or twin-screw extruder. Further, a method using a supercritical fluid described in Journal of Plastics Processing Society of Japan, “Molding”, Vol. 15, No. 6, pages 382 to 385 (2003) can be preferably exemplified.

PEI pellets, PAR pellets and chain linking agent are mixed at the above-mentioned mass ratio, supplied to a bent type twin-screw kneading extruder heated to 300 to 380 ° C., and melt extruded. Shear rate is preferably 50～3,000Sec ^-1 in this case, more preferably 100～2,000Sec ^-1, residence time is preferably 0.5 to 10 minutes, more preferably a condition of 1-5 minutes.

  Next, the pellets made of PET and PEI, the pellets made of PEI, PAR, and a chain linking agent and the PET pellets were dried under reduced pressure at 150 to 180 ° C. for 3 hours or more, and nitrogen was added so that the intrinsic viscosity did not decrease. A biaxially oriented film is produced by supplying to an extruder heated to 270 to 320 ° C. under an air flow or under reduced pressure.

  According to the purpose, the resin constituting the biaxially oriented polyester film of the present invention includes a flame retardant, a heat stabilizer, a weathering material, an antioxidant, an ultraviolet absorber, a light stabilizer, a rust inhibitor, and a copper-resistant damage. Various additives such as stabilizers, antistatic agents, pigments, plasticizers, endblockers, lubricants, organic lubricants, chlorine scavengers, antiblocking agents, viscosity modifiers, and the like are added within a range that does not impair the purpose of the present invention. It doesn't matter.

  Examples of the antioxidant include 2,6-di-tert-butyl-p-cresol (BHT); 3,3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-tert-butyl-a, a ', a' '-(mesitylene-2,4,6-triyl) tri-p-cresol (for example, IRGANOX1330 manufactured by Ciba Specialty Chemicals Co., Ltd.); Pentaeryst reel Tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate] (for example, IRGANOX 1010 manufactured by Ciba Specialty Chemicals Co., Ltd.) and the like.

  Examples of the heat stabilizer include tris (2,4-di-tert-butylphenyl) phosphite (for example, IRGAFOS168 manufactured by Ciba Specialty Chemicals Co., Ltd.); 3-hydroxy-5,7-di-tert- Examples include a reaction product of butyl-furan-2-one and o-xylene (for example, HP-136 manufactured by Ciba Specialty Chemicals Co., Ltd.).

  However, antioxidants and heat stabilizers are not limited to the above examples.

  It is preferable that content of the said antioxidant and a heat stabilizer is 0.03-1 mass part with respect to 100 mass parts of film total mass, respectively. When the content of each of the antioxidant and the heat stabilizer is less than the above range, it is inferior in long-term heat resistance and heat-and-moisture resistance in the production process until the biaxially oriented polyester film is obtained from the initial raw material and in the subsequent secondary processing process. There is a case. In addition, when the content of each of the antioxidant and the heat stabilizer exceeds the above range, the long-term heat resistance and heat-and-moisture resistance of the biaxially oriented polyester film obtained by adding more than this range is not improved and the economy is inferior. There is. The content of each of the antioxidant and the heat stabilizer is more preferably 0.05 to 0.9 parts by mass, and still more preferably 0.1 to 0.8 parts by mass with respect to 100 parts by mass of the total film mass.

  In the biaxially oriented film of the present invention, other components such as an organic lubricant such as an ultraviolet absorber, an antistatic agent, a flame retardant, a pigment, a dye, a fatty acid ester, and a wax are added within a range that does not impair the effects of the present invention. May be. In addition, inorganic particles, organic particles, and the like can be added to impart easy slipping, abrasion resistance, scratch resistance, and the like to the film surface.

  Examples of such additives include clay, mica, titanium oxide, calcium carbonate, kaolin, talc, wet or dry silica, colloidal silica, calcium phosphate, barium sulfate, alumina, zirconia, and other inorganic particles, acrylic acids, styrene And so-called internal particles, surfactants, and the like which are precipitated by a catalyst added during the polymerization reaction of polyester or polyphenylene sulfide.

  Moreover, it is preferable to use various types of filters, for example, filters made of materials such as sintered metal, porous ceramics, sand, and wire mesh, in order to remove foreign substances and denatured polymers. Moreover, you may provide a gear pump as needed in order to improve fixed_quantity | feed_rate supply property. Using an extruder, a molten sheet of PET, PEI, and PAR mixture is extruded from a slit die and cooled on a casting roll to produce an unstretched film.

  When the biaxially oriented polyester film of the present invention is continuously formed by a melting method, it is important to stretch at least once at the glass transition temperature of the amorphous resin C or less. By stretching below the glass transition temperature of the amorphous resin C, the amorphous resin C in the film does not deform due to stretching stress, and restrains the molecular chain of the polyester A entangled with the amorphous resin C. Demonstrate. By stretching the film at least once below the glass transition temperature of the amorphous resin C, the molecular chain of the polyester A can be effectively tensioned and the orientation of the film can be effectively enhanced. By increasing the orientation of the film, the humidity expansion coefficient may be easily controlled within the range of the present invention. Most preferably, all the stretching steps are performed at a temperature equal to or lower than the glass transition temperature of the amorphous resin C.

  Next, the obtained unstretched film is stretched in the longitudinal direction (longitudinal direction), then stretched in the width direction (transverse direction), or stretched in the width direction (transverse direction) and then stretched in the longitudinal direction (longitudinal direction). Biaxial orientation is imparted to the film by the sequential biaxial stretching method or the simultaneous biaxial stretching method. Although the specific example by the sequential biaxial stretching method used most generally is shown below, this invention is not limited to the following description.

  First, a film heated by a plurality of roll groups is not less than the glass transition temperature of the polyester A and not more than the glass transition temperature of the amorphous resin C. The magnification is 2 to 5 times, preferably 2.5 to 4.5 times, more preferably 3 to The film is stretched in the longitudinal direction (longitudinal direction) in one step or two or more steps at a magnification of 4 times. Further, the film is held by a clip and guided to a tenter. Below the glass transition temperature of C, the film is stretched in the width direction (lateral direction) at a magnification of 2 to 6 times, preferably 2.5 to 5.5 times, and more preferably 3 to 4.5 times. Under the present circumstances, you may perform extending | stretching 1.01-2.5 times further in a longitudinal direction and / or the width direction as needed.

  In the present invention, the heat treatment temperature after stretching is preferably a temperature not higher than the melting point of the polyester A, more preferably a temperature of 190 to 245 ° C., more preferably 200, from the viewpoints of dimensional stability, heat resistance, and heat and humidity resistance. It is preferably a temperature of ˜230 ° C. and is preferably heat treated for 1 to 30 seconds. The biaxially oriented film of the present invention is preferably subjected to intermediate cooling at 100 to 160 ° C. after the heat treatment step from the viewpoint of easily obtaining toughness, preferably a relaxation treatment, and in the width direction and / or the longitudinal direction. The relaxation treatment is preferably performed at a rate of 2 to 10%, more preferably 4 to 9%.

  In this way, a biaxially oriented film having excellent heat and heat resistance can be obtained.

  In addition, specific examples in the case of producing a film for magnetic recording media, for example, when the simultaneous biaxial stretching method is used are shown below.

  This biaxial stretching can be performed by a simultaneous biaxial stretching method in which stretching is performed simultaneously in the longitudinal direction and the width direction using a simultaneous biaxial tenter. The stretching temperature varies depending on the structural component of the polyester and the constituent components of the lamination, but a case where a single layer is mainly composed of PET and PEI is used as polyimide B will be described as an example. An unstretched film is guided to a linear motor type simultaneous biaxially stretched tenter by gripping both ends of the film with clips, and in the preheating zone, the glass transition temperature (Tg) of PET to the glass transition temperature of amorphous resin C Hereinafter, for example, the film is heated to 85 to 90 ° C., and stretched in multiple stages of one or two or more stages 4.5 to 10 times simultaneously in both the longitudinal direction and the width direction. The draw ratio may be different between the longitudinal direction and the width direction. In either case, the temperature of the clip for gripping the film end is preferably set in the temperature range of (PT Tg) to (PET Tg + 120) ° C. The stretching temperature in the stretching process is preferably maintained within the temperature range between (Tg of PET) and (Tg of amorphous resin C), but once cooled, the film is stretched while suppressing crystallization of the film. It doesn't matter.

  More preferably, the film is stretched between (Tg of PET) to (Tg-30 of amorphous resin C) ° C., most preferably from (Tg of PET) to (Tg-50 of amorphous resin C) ° C.

  Since the stretching temperature of the film is lower than the Tg of the amorphous resin C, the amorphous resin C acts as a knotting point or restraint point of the polymer molecular chain, which is extremely effective for high orientation of the film.

  In the case of a raw material having a high molecular weight or a material that is difficult to crystallize, it is preferable that the stretching temperature is increased to 200 ° C. In the latter half of the stretching process, it is preferable to stretch while gradually increasing the stretching temperature in two or more stages.

  Subsequently, from the viewpoint of manifesting the effects of the present invention, the biaxially stretched polyester film is subjected to (PET melting point Tm-70) ° C. to (Tm) ° C., more preferably (PT Tm-50) ° C. to (PET Tm-10) Perform heat setting in the range of ° C. Furthermore, a limited shrinkage of 0.5 to 5%, more preferably 1 to 3% is given in the longitudinal and width directions at the heat setting temperature (hereinafter referred to as relaxation heat treatment I), and then in the cooling process (Tg of PET) ° C. to ( PET Tm-50) ° C, more preferably (PET Tg + 10) ° C to (PET Tm-80) ° C in the temperature range of 1 to 7%, more preferably 2 to 6% in the longitudinal and width directions Provides limited shrinkage in the range (hereinafter referred to as relaxation heat treatment II). The relaxation heat treatment may be performed with different limiting shrinkage rates in the longitudinal direction and the width direction. In particular, it is preferable to perform relaxation heat treatment II in the cooling process after performing relaxation heat treatment I at the heat setting temperature in order to further enhance the effects of the present invention. The relaxation heat treatment II is preferably performed in two or more stages by changing the temperature. Then, the target biaxially oriented polyester film is obtained by cooling the film to room temperature, removing the film edge and winding up.

  The glass transition temperature Tg referred to in the present invention is a value determined according to JIS-K7121 (1987) from the heat flux gap at the time of temperature increase in differential scanning calorimetry. When it is difficult to make a determination only by a method based on differential scanning calorimetry, a morphological method such as dynamic viscoelasticity measurement or microscopic observation may be used in combination. When determining the glass transition temperature by differential scanning calorimetry, it is also effective to use a temperature modulation method or a high sensitivity method. The melting point Tm in the present invention is a value determined according to JIS-K7122 (1987).

[Measurement method of physical properties]
(1) Measurement of content of each resin in film After weighing the film, it is dissolved in hexafluoroisopropanol (HFIP). When the amorphous resin C is insoluble, the insoluble component is separated by centrifugation, then the mass is measured, and the structure and mass fraction of the amorphous resin C are measured by elemental analysis, FT-IR, and NMR methods. Measure. If the supernatant component is similarly analyzed, the mass fraction and the structure of the polyester A component and the polyimide B component can be specified. Specifically, the NMR spectrum of ¹ H nucleus is measured for this supernatant component. In the spectrum obtained, the peak areas of absorption specific to polyester A and polyimide B (for example, the aromatic proton of terephthalic acid if polyester A is PET and the aromatic proton of bisphenol A if polyimide B is PEI) The strength is obtained, and the molar ratio of the blend is calculated from the ratio and the number of protons. Further, the mass ratio is calculated from the formula amount corresponding to the unit unit of the polymer. In this way, the mass fraction and structure of the polyester A component and the polyimide B component can be specified.

(2) Intrinsic viscosity (IV)
Dissolve the sample in orthochlorophenol. The portion that does not dissolve is removed, and the portion that dissolves is measured. The value calculated from the following equation from the solution viscosity measured at 25 ° C. in orthochlorophenol was used.

ηsp / C = [η] + K [η] ² · C
Here, ηsp = (solution viscosity / solvent viscosity) −1, C is the weight of dissolved polymer per 100 ml of solvent (g / 100 ml, usually 1.2), and K is the Huggins constant (assumed to be 0.343). Further, the solution viscosity and the solvent viscosity were measured using an Ostwald viscometer.

(3) Glass transition temperature (Tg)
The specific heat is measured with the following equipment and conditions, and determined according to JIS K7121 (1987).
・ Equipment: Temperature modulation DSC manufactured by TA Instrument
·Measurement condition :
・ Heating temperature: 270-570K (RCS cooling method)
・ Temperature calibration: Melting point of high purity indium and tin ・ Temperature modulation amplitude: ± 1K
・ Temperature modulation period: 60 seconds ・ Temperature increase step: 5K
・ Sample weight: 5mg
・ Sample container: Aluminum open container (22mg)
・ Reference container: Aluminum open container (18mg)
The glass transition temperature (Tg) is calculated by the following formula.

Glass transition temperature = (extrapolated glass transition start temperature + extrapolated glass transition end temperature) / 2
(4) Melting point (Tm)
The peak temperature of the endothermic peak of melting was measured according to JIS-K7122 (1987) as the melting point (Tm).

  Using a Seiko Instruments DSC (RDC220) as a differential scanning calorimeter and a company's disk station (SSC / 5200) as a data analyzer, 5 mg of the sample was melted and held at 300 ° C. for 5 minutes on an aluminum pan and rapidly solidified. Thereafter, the temperature is raised from room temperature at a heating rate of 20 ° C./min. At that time, the peak temperature of the endothermic peak of melting observed is defined as the melting point (Tm). The melting point of polyester A can be detected by the above method.

  As a method for detecting the melting point of the amorphous resin C, a micro thermal analyzer (“μ-TA device” manufactured by T.A. Instruments) was used. The sensor of this device is provided with a detection unit made of a wire whose tip is folded back in a V shape. For measurement, the substrate film is exposed by slant cutting, etc., and the V-shaped detection part of the sensor is brought into contact, and the temperature rises from room temperature to 400 ° C under the conditions of a heating rate of 10 ° C / second and an indentation strength of 20nA. I did it.

(5) Average domain diameter of dispersed phase The biaxially oriented polyester film of the present invention is (a) a direction parallel to the longitudinal direction and perpendicular to the film surface, (a) a direction parallel to the width direction and perpendicular to the film surface, ) The sample was cut in a direction parallel to the film surface, and a sample was prepared by an ultrathin section method. In order to clarify the contrast of the dispersed phase, it may be stained with osmic acid, ruthenic acid, phosphotungstic acid, or the like. The cut surface was observed using a transmission electron microscope (H-7100FA, manufactured by Hitachi) under the condition of an applied voltage of 100 kV, and a photograph was taken at 20,000 times. The obtained photograph is taken into an image analyzer as an image, 100 arbitrary dispersed phases are selected, and image processing is performed as necessary, thereby obtaining the size of the dispersed phase as shown below. It was. The maximum length (la) and the maximum length (lb) in the film thickness direction of each dispersed phase appearing on the cut surface in (a), and the maximum thickness in the longitudinal direction (lb), The maximum length (lc), the maximum length in the width direction (ld), the maximum length in the film longitudinal direction (le) and the maximum length in the width direction (lf) of each dispersed phase appearing on the cut surface of (c) Asked. Next, the shape index I of the dispersed phase I = (number average value of lb + number average value of le) / 2, shape index J = (number average value of ld + number average value of lf) / 2, shape index K = (of la Number average value + number average value of lc) / 2, the average dispersion diameter of the dispersed phase was set to (I + J + K) / 3. Further, from I, J, and K, the maximum value was determined as the average major axis L, and the minimum value was determined as the average minor axis D.

A method for performing image analysis will be described. Transmission electron micrographs of each sample were taken into a computer with a scanner. Thereafter, image analysis was performed with dedicated software (Image Pro Plus Ver. 4.0, manufactured by Planetron). Adjust the brightness and contrast by manipulating the tone curve, and then randomly observe 100 circle-equivalent diameters of the high-contrast component of the image obtained using the Gaussian filter. did. Here, when using a negative photograph of a transmission electron microscope photograph, Leafscan 45 Plug-In manufactured by Nihon Cytex is used as the scanner, and when using a transmission electron microscope positive, the scanner is used as the scanner. A Seiko Epson GT-7600S is used, but an equivalent value can be obtained with either of them. Image processing procedures and parameters:
Once flattened Contrast +30
Gauss once Contrast +30, Brightness -10
1 Gauss flattening filter: background (black), object width (20 pix)
Gaussian filter: size (7), strength (10)
(6) Detection of Si atom at interface of dispersion diameter The film was cut in a direction parallel to the longitudinal direction and perpendicular to the film surface, and a sample was prepared by an ultrathin section method. In order to clarify the contrast of the dispersed phase, it may be stained with osmic acid, ruthenic acid, phosphotungstic acid, or the like. Using a field emission electron microscope (JEOL JEM2100F, EDX (JEOL JED-2300T)), the cut surface was subjected to a pressurization voltage of 200 kV, a sample absorption current of 10 ⁻⁹ A, an EDX ray analysis of 20 seconds / point, and a beam diameter of 1 nm. The interface of the dispersed phase was evaluated by the TEM-EDX method under the conditions described above. Arbitrary evaluation was made on 10 dispersed phases, and the case where Si element was detected by 0.2 atomic% or more was indicated as ◯, and the case where it was not possible was indicated as X.

(7) Confirmation that pores having amorphous resin C as a nucleus do not exist In order to confirm that pores having amorphous resin C as a nucleus do not exist, the following method was used.

  An ultrathin slice having a cross section in the transverse direction-thickness direction of the biaxially oriented film or polyester film composite of the present invention was collected by an ultramicrotome by a resin embedding method using an epoxy resin. The section of the collected slice was observed using a transmission electron microscope (TEM) under the following conditions.

・ Device: Transmission electron microscope (TEM) H-7100FA manufactured by Hitachi, Ltd.
・ Acceleration voltage: 100kV
Observation magnification: 40,000 times Collect an image observed continuously from one surface of the film to the other surface so that one side of the image is parallel to the lateral direction of the film and parallel to the thickness direction. At this time, the size of each image is adjusted so that one side parallel to the horizontal direction is 5 μm as the actual size of the film.
An OHP sheet (Seiko Epson Co., Ltd. EPSON-dedicated OHP sheet) was placed on the obtained images. Next, among the observed holes, if there was a crystalline thermoplastic resin C observed as a nucleus inside the hole, it was painted black with a magic pen on the OHP sheet of the hole having the amorphous resin C as a nucleus. . The obtained OHP sheet image was read under the following conditions.

・ Scanner: Seiko Epson GT-7600U
・ Software: EPSON TWAIN ver. 4.20J
・ Image type: Line drawing ・ Resolution: 600dpi
The obtained image was subjected to image analysis using Image-Pro Plus, Ver.40 for Windows (registered trademark) manufactured by Planetron Co., Ltd. At this time, spatial calibration was performed using the scale of the captured cross-sectional image. The measurement conditions were set as follows.

-Fill the outline format in the display option settings in the count / size option.

  -Set the object extraction option to None on the boundary.

  ・ Automatic extraction of dark objects for the brightness range selection setting during measurement.

  Under the above conditions, the total area of the film, that is, the transverse direction × thickness direction = 5 μm × film thickness (measured in the following (9)) as the object of measurement, pores with amorphous resin C as the core (filled in black) The area ratio was calculated as a percentage and used as the area ratio (R) of the pores (unit:%). Accordingly, when the ratio of the pores having the amorphous resin C as a nucleus to the total area of the film is 0% or more and 30% or less, the film has no pores having the amorphous resin C as a nucleus. Defined.

  The case where the ratio of the pores having the amorphous resin C as the core to the total film area is 0% or more and less than 3% is ◎, the case where it is 3% or more and less than 5% is ○, and the ratio is 5% or more and 10% or less The case was marked △. Moreover, since the film with the said ratio R larger than 30 has the hole which has the amorphous resin C as a nucleus, it was set as x.

(8) Film-forming stability The number of film tears when a film was wound up to a width of 5 m and a length of 10,000 m was determined. In addition, film formation stability was evaluated from the number of film breaks as follows.

  A: When there was no film tearing.

  ○: When the film was torn once or twice.

  Δ: When the film was broken 3 or 4 times.

  X: When the film was broken 5 times or more.

(9) Film thickness Using an electronic micrometer (K-312A type) manufactured by Anritsu Corporation under an atmosphere of 23 ° C. and 65% RH, the film thickness was measured at a needle pressure of 30 g.

(10) Centerline average roughness Ra, 10-point average roughness Rz
Using an atomic force microscope, 20 fields of view were measured at different locations. Ra and Rz were determined according to JIS-B0601 (1994). With respect to the obtained image, the three-dimensional surface roughness was calculated by Roughness Analysis of the Off-Line function, and the center line average roughness Ra and the 10-point average roughness Rz were measured.

Measuring device: NanoScope III AFM (manufactured by Digital Instruments)
Cantilever: Silicon single crystal Scanning mode: Tapping mode Scanning range: 30μm
Scanning speed: 0.5 Hz
Flatten Auto: Order 3
(11) Temperature expansion coefficient The biaxially oriented polyester film of the present invention is measured in the width direction under the following conditions, and the average value of three measurement results is defined as the temperature expansion coefficient in the present invention.

・ Measuring device: Thermomechanical analyzer TMA-50 manufactured by Shimadzu Corporation
Sample size: 10 mm in the film longitudinal direction x 12.6 mm in the film width direction
・ Load: 0.5g
-Number of measurements: 3 times-Measurement temperature: Temperature is raised from a temperature of 25 ° C to a temperature of 50 ° C at a rate of temperature rise of 2 ° C / min in a nitrogen flow state, held for 5 minutes, and then a temperature drop rate of 2 to 25 ° C. The temperature is lowered at ° C./min, and the dimensional change ΔL (mm) in the film width direction at a temperature of 40 to 30 ° C. is measured. The temperature expansion coefficient (ppm / ° C.) is calculated from the following formula.

・ Temperature expansion coefficient (ppm / ° C.) = 10 ⁶ × {(ΔL / 12.6) / (40-30)}
(12) Humidity expansion coefficient The film is measured under the following conditions in the width direction of the film, and the average value of three measurement results is defined as the humidity expansion coefficient in the present invention.

Measuring device: Thermomechanical analyzer TMA-50 manufactured by Shimadzu (humidity generator: humidity control device HC-1 manufactured by ULVAC-RIKO)
Sample size: 10 mm in the film longitudinal direction x 12.6 mm in the film width direction
・ Load: 0.5g
・ Number of measurements: 3 times ・ Measurement temperature: 30 ° C.
・ Measurement humidity: Measured dimensions by holding at 40% RH for 6 hours, increasing the humidity to 80% RH in 40 minutes and holding at 80% RH for 6 hours, and then measuring the dimensional change ΔL (mm) in the width direction of the support. taking measurement. The humidity expansion coefficient (ppm /% RH) is calculated from the following equation.

Humidity expansion coefficient (ppm /% RH) = 10 ⁶ × {(ΔL / 12.6) / (80-40)}
(13) Breaking strength, breaking elongation: Measured using an Instron type tensile tester according to the method defined in JIS K7127 (1989). The measurement was performed under the following conditions, and the sample was changed 20 times. The average value was obtained by measuring each sample.

Measuring device: Orientec Co., Ltd. film strong elongation automatic measuring device "Tensilon AMF / RTA-100"
Sample size: width 10 mm x test length 200 mm (in the film longitudinal direction)
Sample shape: Strip shape Pulling speed: 300 m / min Measurement environment: Temperature 25 ° C., humidity 65% RH
The distance between the initial pull chucks is 100 mm.
(14) Young's modulus The Young's modulus of the biaxially oriented polyester film of the present invention is measured according to ASTM-D882 (1997). Instron type tensile tester is used and the conditions are as follows. The average value of the five measurement results is defined as the Young's modulus in the present invention.

・ Measuring device: Model 5848, an ultra-precision material testing machine manufactured by Instron
・ Sample size:
When measuring Young's modulus in the film width direction Film length direction 2 mm x film width direction 12.6 mm
(The gripping distance is 8mm in the film width direction)
When measuring Young's modulus in the longitudinal direction of the film 2 mm in the film width direction × 12.6 mm in the film longitudinal direction
(Grip interval is 8mm in the longitudinal direction of the film)
・ Tensile speed: 1 mm / min ・ Measurement environment: Temperature 23 ° C., humidity 65% RH
-Number of measurements: Measured 5 times and calculated from the average value.

(15) Moisture and heat resistance (half-life of elongation at break)
A strip-shaped sample having a length of 200 mm and a width of 10 mm was cut out and used in the longitudinal direction of the film. According to the method defined in JIS K-7127 (1989), the elongation at break was measured at 25 ° C. and 65% RH using a tensile tester. The distance between the initial pull chucks was 100 mm, and the pull speed was 300 m / min. The measurement was performed 20 times by changing the sample, and the average value (X) of the elongation at break was determined. In addition, a strip-shaped sample having a length of 200 mm and a width of 10 mm in the longitudinal direction of the film is 2 kg / cm 2 using a highly accelerated life tester (unsaturated super accelerated life test apparatus model PC-304R8D manufactured by Hirayama Seisakusho Co., Ltd.). The sample was allowed to stand under an atmosphere of 140 ° C. and 80% RH under natural pressure, and then naturally cooled. The sample was subjected to a tensile test under the same conditions as described above 20 times, and the average value (Y) of the breaking elongation was obtained. It was. From the average values (X) and (Y) of the obtained elongation at break, the elongation retention was determined by the following equation. The treatment time until the elongation retention was 50% or less was defined as the half time of elongation at break.

Elongation retention (%) = (Y / X) × 100
The heat treatment time until the elongation retention was 50% or less was defined as the half-life of elongation at break. Wet heat resistance was evaluated according to the following criteria. ○ is a pass.

  ○: Elongation half-life is 20 hours or more.

  X: The elongation half-life is less than 20 hours.

(16) Dielectric breakdown characteristics 100μm thick, 10cm square aluminum foil electrode is used for the cathode, 25mmφ, 500g brass electrode is used for the anode, a film is sandwiched between them, and the voltage boosting rate is 100V / sec using Kasuga high voltage DC power supply When a current of 10 mA or more flows, the dielectric breakdown is assumed, and the voltage value at this time is measured. 200V / μ or more was rated as ◯, and less than 200V / μ was rated as x.

(17) Measurement of width dimension A film slit to a width of 1 m is transported with a tension of 200 N, and a magnetic coating and a non-magnetic coating of the following composition are applied to one surface (A) of the support by an extrusion coater (the upper layer is The magnetic coating is applied with a coating thickness of 0.2 μm, the lower layer is a nonmagnetic coating with a coating thickness of 0.9 μm), magnetically oriented, and dried at a drying temperature of 100 ° C. Next, a back coat having the following composition was applied to the opposite surface (B), and then calendered with a small test calender (steel / nylon roll, 5 steps) at a temperature of 85 ° C. and a linear pressure of 2.0 × 105 N / m. And then take up. The original tape is slit to a width of 1/2 inch (12.65 mm) to make a pancake. Next, a length of 200 m from this pancake is incorporated into a cassette to form a cassette tape.
(Composition of magnetic paint)
Ferromagnetic metal powder: 100 parts by mass [Fe: Co: Ni: Al: Y: Ca = 70: 24: 1: 2: 2: 1 (mass ratio)]
[Long axis length: 0.09 μm, axial ratio: 6, coercive force: 153 kA / m (1,922 Oe), saturation magnetization: 146 Am ² / kg (146 emu / g), BET specific surface area: 53 m ² / g, X-ray Particle size: 15 nm]
-Modified vinyl chloride copolymer (binder): 10 parts by mass (average polymerization degree: 280, epoxy group content: 3.1% by mass, sulfonic acid group content: 8 × 10 ⁻⁵ equivalent / g)
Modified polyurethane (binder): 10 parts by mass (number average molecular weight: 25,000, sulfonic acid group content: 1.2 × 10 ⁻⁴ equivalent / g, glass transition point: 45 ° C.)
Polyisocyanate (curing agent): 5 parts by mass (Coronate L (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd.)
2-ethylhexyl oleate (lubricant): 1.5 parts by mass Palmitic acid (lubricant): 1 part by mass Carbon black (antistatic agent): 1 part by mass (average primary particle size: 0.018 μm)
Alumina (abrasive): 10 parts by mass (α alumina, average particle size: 0.18 μm)
-Methyl ethyl ketone: 75 parts by mass-Cyclohexanone: 75 parts by mass-Toluene: 75 parts by mass (composition of non-magnetic paint)
Modified polyurethane: 10 parts by mass (number average molecular weight: 25,000, sulfonic acid group content: 1.2 × 10 ⁻⁴ equivalent / g, glass transition point: 45 ° C.)
-Modified vinyl chloride copolymer: 10 parts by mass (average polymerization degree: 280, epoxy group content: 3.1% by mass, sulfonic acid group content: 8 × 10 ⁻⁵ equivalent / g)
-Methyl ethyl ketone: 75 parts by mass-Cyclohexanone: 75 parts by mass-Toluene: 75 parts by mass-Polyisocyanate: 5 parts by mass (Coronate L (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd.)
・ 2-Ethylhexyl oleate (lubricant): 1.5 parts by mass Palmitic acid (lubricant): 1 part by mass (backcoat composition)
Carbon black: 95 parts by mass (antistatic agent, average primary particle size 0.018 μm)
Carbon black: 10 parts by mass (antistatic agent, average primary particle size 0.3 μm)
Alumina: 0.1 part by mass (α alumina, average particle size: 0.18 μm)
Modified polyurethane: 20 parts by mass (number average molecular weight: 25,000, sulfonic acid group content: 1.2 × 10 ⁻⁴ equivalent / g, glass transition point: 45 ° C.)
-Modified vinyl chloride copolymer: 30 parts by mass (average polymerization degree: 280, epoxy group content: 3.1% by mass, sulfonic acid group content: 8 × 10 ⁻⁵ equivalent / g)
• Cyclohexanone: 200 parts by mass • Methyl ethyl ketone: 300 parts by mass • Toluene: 100 parts by mass Take out the tape from the cassette tape cartridge, put the sheet width measuring device prepared as shown in FIG. Measure. The sheet width measuring device shown in FIG. 1 is a device that measures the width dimension using a laser, and fixes the magnetic tape 9 to the load detector 3 while setting it on the free rolls 5 to 8, and the end portion A weight 4 serving as a load is hung on. When this magnetic tape 9 is irradiated with the laser beam 10, the laser beam 10 oscillated linearly in the width direction from the laser oscillator 1 is blocked only by the portion of the magnetic tape 9, enters the light receiving unit 2, and the blocked laser beam The width is measured as the width of the magnetic tape. The average value of the three measurement results is defined as the width in the present invention.

・ Measuring device: Sheet width measuring device manufactured by Ayaha Engineering Co., Ltd. ・ Laser oscillator 1, light receiving unit 2: Laser dimension measuring device LS-5040 manufactured by Keyence Corporation
-Load detector 3: Load cell CBE1-10K manufactured by NMB
・ Constant temperature and humidity chamber: SE-25VL-A manufactured by Kato Corporation
・ Load 4: Weight (longitudinal direction)
・ Sample size: width 1/2 inch x length 250 mm
-Holding time: 5 hours-Number of measurements: Measure 3 times.

(Width dimensional change rate: dimensional stability)
The width dimension (1A, 1B) is measured under two conditions, and the dimensional change rate is calculated by the following equation. Specifically, dimensional stability is evaluated according to the following criteria.

  The lA is measured after 24 hours under the A condition, and then the lB is measured after 24 hours under the B condition. Three points were measured: a sample cut from the 30 m point from the beginning of the tape cartridge, a sample cut from the 100 m point, and a sample cut from the 170 m point. X is rejected.

A condition: 10 ° C, 10% RH, tension 0.85N
B condition: 29 ° C, 80% RH, tension 0.55N
Width change rate (ppm) = 10 ⁶ × ((1B-1A) / 1A)
A: Maximum width change rate is less than 500 (ppm) ○: Maximum width change rate is 500 (ppm) or more and less than 600 (ppm) Δ: Maximum width change rate is 600 (ppm) or more Less than 700 (ppm) ×: The maximum value of the width dimensional change rate is 700 (ppm) or more.
(18) Storage stability As in (17) above, remove the tape from the cassette tape cartridge that was produced, measure the width dimension (1C, 1D) under the following two conditions, and use the following formula to determine the dimensional change rate. Is calculated.
Specifically, dimensional stability is evaluated according to the following criteria.

  After 24 hours at 23 ° C. and 65% RH, 1C is measured. After storing the cartridge for 10 days in an environment of 40 ° C. and 20% RH, 1D is measured after 24 hours at 23 ° C. and 65% RH. Three points were measured: a sample cut from the 30 m point from the beginning of the tape cartridge, a sample cut from the 100 m point, and a sample cut from the 170 m point. X is rejected.

Width dimensional change rate (ppm) = 10 ⁶ × (| lC−lD | / lC)
○: Maximum value of width dimension change rate is less than 100 (ppm) Δ: Maximum value of width dimension change rate is 100 (ppm) or more and less than 150 (ppm) ×: Maximum value of width dimension change rate is 150 (ppm) or more
(19) Running durability A cassette tape is prepared in the same manner as in (17) above, and evaluated by running 300 times in an environment of 23 ° C. and 65% RH using a commercially available LTO drive 3580-L11 manufactured by IBM. The error rate is calculated from the error information (number of error bits) output from the drive by the following formula. X is rejected.

Error rate = (number of error bits) / (number of write tribits)
A: Error rate is less than 1.0 × 10 ^{−6 B} : Error rate is 1.0 × 10 ⁻⁶ or more, less than 1.0 × 10 ⁻⁵ Δ: Error rate is 1.0 × 10 ⁻⁵ or more, 1 Less than 0 × 10 ⁻⁴ ×: Error rate is 1.0 × 10 ⁻⁴ or more
(20) Electromagnetic conversion characteristics A cassette tape was prepared in the same manner as in the above (17), and a C / N measurement was performed using a reel-to-reel tester and a commercially available MR head mounted under the following conditions.

Relative speed: 2m / sec
Recording track width: 18 μm
Playback track width: 10μm
Distance between shields: 0.27 μm
Recording signal generator: HP 8118A
Reproduction signal processing: spectrum analyzer When this C / N was compared with a commercially available LTO4 tape (manufactured by Fuji Film Co., Ltd.), -1 dB or more was judged as ◯, -2 or more and less than -1 dB was judged as Δ, and less than -2 dB was judged as ×. ○ is desirable, but Δ can be used practically.

(21) Internal haze of film It was measured using a haze meter (HZ-2 manufactured by Suga Test Instruments Co., Ltd.) based on JIS K 7105 (1985). Moreover, the internal haze except a film surface haze was measured by putting the film into the quartz cell for liquid measurement, filling liquid paraffin, and performing the measurement.

  The present invention will be described based on examples.

(Reference Example 1)
Production of polyethylene terephthalate (PET) (X-1) polymer pellets:
To a mixture of 100 parts by mass of dimethyl terephthalate and 60 parts by mass of ethylene glycol, 0.04 part by mass of magnesium acetate was added with respect to the amount of dimethyl terephthalate, and the mixture was heated to increase the ester exchange reaction. Next, 0.02 parts by mass of trimethyl phosphate was added to the transesterification product with respect to the amount of dimethyl terephthalate, and then 0.02 parts by mass of germanium oxide was added, followed by transition to a polycondensation reaction layer. Subsequently, the reaction system was gradually depressurized while being heated and heated, and polymerization was performed at 290 ° C. under a reduced pressure of 1 mmHg or less by a conventional method to obtain PET (X-1) pellets having an intrinsic viscosity [η] = 0.65. The obtained PET had a melt viscosity of 90 Pa · S at 300 ° C. and 300 sec ^{−1 and} 40 Pa · S at 315 ° C. and 300 sec ⁻¹ .

(Reference Example 2)
The PET pellets obtained in Reference Example 1 were dried under reduced pressure at 160 ° C. for 4 hours, and then subjected to a solid-phase polymerization reaction at 220 ° C., 8 hours and a reduced pressure of 133 Pa or less, and an intrinsic viscosity [η] = 1.1 PET (X -2) pellets were obtained. The melt viscosity of the resulting PET is, 300 ℃, 800Pa · S, 315 ℃ in 300 sec ^-1, was 560Pa · S at 300 sec ^-1.

(Reference Example 3)
Production of polyethylene-2,6-naphthalate (PEN) polymer pellets:
Add 0.03 parts of manganese acetate tetrahydrate salt to a mixture of 100 parts by weight of dimethyl 2,6-naphthalenedicarboxylate and 60 parts by weight of ethylene glycol, and gradually raise the temperature from 150 ° C to 240 ° C. The transesterification reaction was carried out. On the way, when the reaction temperature reached 170 ° C., 0.024 parts by mass of antimony trioxide was added. When the reaction temperature reached 220 ° C., 0.042 parts by mass of 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt (corresponding to 2 mmol%) was added. Thereafter, a transesterification reaction was carried out. After the transesterification reaction, 0.023 parts by mass of trimethyl phosphate was added. Next, the reaction product was transferred to a polymerization reactor, heated to a temperature of 290 ° C., and subjected to a polycondensation reaction under a high vacuum of 0.2 mmHg or less to obtain PEN pellets having an intrinsic viscosity of 0.65 dl / g.

(Reference Example 5)
After the PET pellets obtained in Reference Example 1 were dried under reduced pressure at 160 ° C. for 2.5 hours, a solid-phase polymerization reaction was performed at 220 ° C. for 8 hours at a reduced pressure of 133 Pa or less, and the melt viscosity at 300 ° C. and 300 sec ⁻¹ was 400 Pa. -PET pellets (X-3) of S were obtained.

Example 1
PET was used as polyester A, PEI was used as polyimide B, and PAR was used as amorphous resin C.

50 parts by mass of PET with an intrinsic viscosity of 0.65 obtained in Reference Example 1 and 50 parts by mass of PEI “Ultem 1010-1000” (355 ° C., melt viscosity 750 Pa · S at 300 sec ⁻¹ ) manufactured by SABIC Innovative Plastics, Dehumidified and dried at 150 ° C for 5 hours, then heated to 320 to 290 ° C (screw zone, temperature gradient set at the extrusion head), twin-screw, three-stage type screw (PET and PEI kneading plasticization zone / Dalmage kneading Supplyed to a vent type twin screw extruder (L / D = 40, vent hole pressure reduced to 200 Pa) equipped with a zone / fine dispersion compatibilization zone by reverse screw dalgege), and melt extrusion with a residence time of 3 minutes A PET / PEI blend pellet containing 50% by mass of PEI was obtained. This pellet was designated as blend pellet A.

Next, 83 parts by mass of PEI “Ultem 1040A-1000” (melting viscosity 250 Pa · S at 355 ° C., 300 sec ⁻¹ ) manufactured by SABIC Innovative Plastics, and PAR “U polymer U-100” manufactured by Unitika 17 parts by mass and 1.0 part by mass of γ-isocyanatopropyltriethoxysilane “KBE9007” manufactured by Shin-Etsu Chemical Co., Ltd. as a chain linking agent were heated to 320 to 380 ° C. (temperature gradient in the screw zone and extrusion head part) Vent type twin screw extruder (L / D = 40, vented) equipped with a twin-screw, three-stage screw (PEI and PAR kneading plasticization zone / Dalmage kneading zone / Fine dispersion compatibilizing zone by reverse screw dalmage) The pressure was reduced to 200 Pa), and melt extrusion was performed at a residence time of 3 minutes to obtain a PEI / PAR / chain linking agent blend pellet containing 17% by mass of a PAR resin. The resulting pellet was designated as blend pellet B.

  Next, 10 parts by mass of blend pellet B and 90 parts by mass of PET (X-2) having an intrinsic viscosity [η] = 1.1 obtained in Reference Example 2 were supplied to a twin screw extruder heated to 200 to 350 ° C. and melted. Extruded.

  Here, a vent type twin screw extruder (L / D = 40) consisting of 15 zones of cylinders was used for melt extrusion. In order to suppress thermal degradation of PET, blend pellet B is put into cylinder No.1 and melted sufficiently at 310-350 ° C in cylinder No.2-5, then PET (X-2) in cylinder No.6 Was added and blended pellet B and PET (X-2) were mixed at 200 to 300 ° C. in cylinders Nos. 7 to 15. PET / PEI / PAR blend pellets were obtained. The resulting blend pellet was designated as blend pellet C.

  Next, 0.2 parts by mass of the obtained PET / PEI blend pellet A, 58.8 parts by mass of the PET / PEI / PAR blend pellet C, and 41 parts by mass of PET pellets having an intrinsic viscosity of 0.65 obtained in Reference Example 1 are shown in Tables 1-2. After mixing at a content (mass%) and drying under reduced pressure at 180 ° C. for 3 hours, the mixture was put into an extruder, melt extruded at 300 ° C., and passed through a fiber sintered stainless metal filter (14 μm cut). Thereafter, the sheet was discharged from a T die into a sheet shape, and the sheet was solidified and cooled by an electrostatic application method on a cooling drum having a surface temperature of 25 ° C. to obtain an unstretched film.

  Both ends of the unstretched film were gripped by clips and led to a linear motor type simultaneous biaxial stretching tenter to form a film. The film temperature is heated to 95 ° C., and the film is simultaneously biaxially stretched at an area stretch ratio of 12.25 times (longitudinal magnification: 3.5 times, lateral magnification: 3.5 times). Subsequently, the film temperature was changed to 160 ° C., the film was stretched again at an area draw ratio of 2.16 times (longitudinal magnification: 1.2 times, lateral magnification: 1.8 times), heat-fixed at a heat-fixing temperature of 210 ° C. for 2 seconds, and then heat-fixed 2% relaxation heat treatment I in the longitudinal direction and the width direction, and then the relaxation heat treatment II of 4% in the longitudinal direction and 2% in the width direction is performed in two stages of 150 ° C and 100 ° C, and the thickness is 5 µm. A biaxially stretched polyester film was obtained. The composition and characteristics of this biaxially oriented polyester film were as shown in Tables 1 to 4, and had excellent characteristics as a base film for magnetic recording media.

(Examples 2 to 5)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the resin described in Table 1 was used as the amorphous resin C instead of PAR.

  Example 2 A biaxially oriented film using PSU “UDEL P-3900” manufactured by Solvay Advanced Polymers as amorphous resin C, PPE “PX100F” manufactured by Mitsubishi Engineering Plastics as amorphous resin The biaxially oriented film used was Example 3, the biaxially oriented film using PC “Caliver 301-4” manufactured by Sumitomo Dow as an amorphous resin was Example 4, and the JC COC “ A biaxially oriented film using JSR ARTON F4520 ”was taken as Example 5.

(Example 6)
In the same manner as in Example 1, 5.1 parts by mass of PET / PEI blend pellet A, 29.4 parts by mass of PET / PEI / PAR blend pellet C, and 65.5 parts by mass of PET pellets having an intrinsic viscosity of 0.65 (contents shown in Tables 1 and 2) %), Dried under reduced pressure at 180 ° C for 3 hours, put into an extruder, melt extruded at 300 ° C, passed through a fiber sintered stainless steel filter (14 µm cut), then T-die Then, the sheet was discharged in the form of a sheet, and the sheet was solidified and cooled by an electrostatic application method on a cooling drum having a surface temperature of 25 ° C. to obtain an unstretched film.

  In the same manner as in Example 1, biaxial stretching to heat treatment were performed to obtain a biaxially stretched polyester film having a thickness of 5 μm. The composition and characteristics of this biaxially oriented polyester film were as shown in Tables 1 to 4, and had excellent characteristics.

(Example 7)
90 parts by mass of PEI “Ultem 1040A-1000” manufactured by SABIC Innovative Plastics, 10 parts by mass of PAR “U polymer U-100” manufactured by Unitika, and a chain linking agent manufactured by Shin-Etsu Chemical Co., Ltd. 1.0 part by mass of γ-isocyanatopropyltriethoxysilane “KBE9007” heated to 320-380 ° C (temperature gradient set in screw zone and extrusion head), twin-screw, three-stage type screw (PEI and PAR kneading) Supply time to a vent type twin screw extruder (L / D = 40, vent hole pressure reduced to 200 Pa) equipped with a plasticizing zone / dull mage kneading zone / inverted screw dull mage). It was melt-extruded in 3 minutes to obtain a PEI / PAR / chain linking agent blend pellet containing 10% by mass of PAR resin. Further, a mixture of 100 parts by mass of the obtained PEI / PAR / chain linking agent blend pellets and 3 parts by mass of ion-exchanged water was melt-extruded by a twin screw extruder heated to 320 to 380 ° C. The resulting pellet was designated as blend pellet D.

  Next, 10 parts by mass of blended pellets D and 90 parts by mass of PET (X-2) were supplied to a twin screw extruder heated to 200 to 350 ° C. and melt extruded.

  Here, a vent type twin screw extruder (L / D = 40) consisting of 15 zones of cylinders was used for melt extrusion. In order to suppress thermal deterioration of PET, blend pellet D is put into cylinder No.1, and melted sufficiently at 310-350 ° C in cylinder No.2-5, then PET (X-2) in cylinder No.6 And blended pellet D and PET (X-2) were mixed at 200 to 300 ° C. with cylinders No. 7 to 15. PET / PEI / PAR blend pellets were obtained. The resulting blend pellet was designated as blend pellet E.

  Next, PET / PEI / PAR blend pellet E was dried under reduced pressure at 180 ° C. for 3 hours, then charged into an extruder, melt extruded at 300 ° C., and passed through a fiber sintered stainless steel filter (14 μm cut). The sheet was discharged from a T die into a sheet, and the sheet was solidified and cooled by an electrostatic application method on a cooling drum having a surface temperature of 25 ° C. to obtain an unstretched film.

  Both ends of the unstretched film were gripped by clips and led to a linear motor type simultaneous biaxial stretching tenter to form a film. The film temperature is heated to 95 ° C., and the film is simultaneously biaxially stretched at an area stretch ratio of 12.25 times (longitudinal magnification: 3.5 times, lateral magnification: 3.5 times). Subsequently, the film temperature was changed to 160 ° C., the film was stretched again at an area draw ratio of 2.25 times (longitudinal magnification: 1.5 times, lateral magnification: 1.5 times), heat-fixed at a heat-fixing temperature of 210 ° C. for 2 seconds, and then heat-fixed 2% relaxation heat treatment I in the longitudinal direction and the width direction, and then the relaxation heat treatment II of 4% in the longitudinal direction and 2% in the width direction is performed in two stages of 150 ° C and 100 ° C, and the thickness is 5 µm. A biaxially stretched polyester film was obtained. The composition and characteristics of this biaxially oriented polyester film were as shown in Tables 1 to 4, and had excellent characteristics as a base film for magnetic recording media.

(Example 8)
In the same manner as in Example 7, the content (mass%) of PET / PEI blend pellet A1 part, PET / PEI / PAR blend pellet E50 part and 49 parts by weight of PET pellets having an intrinsic viscosity of 0.65 are shown in Tables 1-2. After being dried under reduced pressure at 180 ° C for 3 hours, put into an extruder, melt extruded at 300 ° C, passed through a fiber sintered stainless steel metal filter (14 μm cut), and then sheeted from the T die The sheet was tightly solidified by an electrostatic application method on a cooling drum having a surface temperature of 25 ° C. and cooled to obtain an unstretched film.

  In the same manner as in Example 1, biaxial stretching to heat treatment were performed to obtain a biaxially stretched polyester film having a thickness of 5 μm. The composition and characteristics of this biaxially oriented polyester film were as shown in Tables 1 to 4, and had excellent characteristics.

(Example 9)
The PET / PEI blend pellet A 0.2 part by mass obtained in Example 1 and the PET / PEI / PAR blend pellet C 58.8 part by mass and the melt viscosity at 300 ° C. and 300 sec ⁻¹ obtained in Reference Example 5 are 400 Pa · S. 41 parts by weight of PET pellets (X-3) were mixed so that the content (mass%) shown in Tables 1 and 2 was reached, dried under reduced pressure at 180 ° C. for 3 hours, then put into an extruder, and kept at 300 ° C. Extruded, passed through a fiber sintered stainless steel metal filter (14 μm cut), then discharged from the T-die into a sheet, and the sheet was solidified by cooling by electrostatic application on a cooling drum with a surface temperature of 25 ° C. And an unstretched film was obtained.

  Both ends of the unstretched film were gripped by clips and led to a linear motor type simultaneous biaxial stretching tenter to form a film. The film temperature is heated to 95 ° C., and the film is simultaneously biaxially stretched at an area stretch ratio of 12.25 times (longitudinal magnification: 3.5 times, lateral magnification: 3.5 times). Subsequently, the film temperature was set to 160 ° C., and the film was stretched again at an area draw ratio of 2.24 times (longitudinal magnification: 1.4 times, lateral magnification: 1.6 times), heat-fixed at a heat setting temperature of 210 ° C. for 2 seconds, and then heat-set temperature 2% relaxation heat treatment I in the longitudinal direction and the width direction, and then the relaxation heat treatment II of 4% in the longitudinal direction and 2% in the width direction is performed in two stages of 150 ° C and 100 ° C, and the thickness is 5 µm. A biaxially stretched polyester film was obtained. The composition and characteristics of this biaxially oriented polyester film were as shown in Tables 1 to 4, and had excellent characteristics.

(Example 10)
6 parts by mass of blend pellet B obtained in Example 1 and 94 parts by mass of PET (X-2) obtained in Reference Example 2 were supplied to a twin-screw extruder heated to 200 to 350 ° C. and melt extruded.

  Here, a vent type twin screw extruder (L / D = 40) consisting of 15 zones of cylinders was used for melt extrusion. In order to suppress thermal degradation of PET, blend pellet D is put into cylinder No.1, and melted sufficiently at 310-350 ° C with cylinder No.2-5, then PET (X-2) with cylinder No.6 And blended pellet D and PET (X-2) were mixed at 200 to 300 ° C. with cylinders No. 7 to 15. PET / PEI / PAR blend pellets were obtained. The resulting blend pellet was designated as blend pellet F.

  Next, PET / PEI / PAR blend pellet F was dried under reduced pressure at 180 ° C. for 3 hours, then put into an extruder, melt extruded at 300 ° C., and passed through a fiber sintered stainless metal filter (14 μm cut). Then, the sheet was discharged from a T die into a sheet, and the sheet was solidified and cooled by an electrostatic application method on a cooling drum having a surface temperature of 25 ° C. to obtain an unstretched film.

  Both ends of the unstretched film were gripped by clips and led to a linear motor type simultaneous biaxial stretching tenter to form a film. The film temperature is heated to 95 ° C., and the film is simultaneously biaxially stretched at an area stretch ratio of 12.25 times (longitudinal magnification: 3.5 times, lateral magnification: 3.5 times). Subsequently, the film temperature was set to 160 ° C., and the film was stretched again at an area draw ratio of 2.24 times (longitudinal magnification: 1.4 times, lateral magnification: 1.6 times), heat-fixed at a heat setting temperature of 210 ° C. for 2 seconds, and then heat-set temperature 2% relaxation heat treatment I in the longitudinal direction and the width direction, and then the relaxation heat treatment II of 4% in the longitudinal direction and 2% in the width direction is performed in two stages of 150 ° C and 100 ° C, and the thickness is 5 µm. A biaxially stretched polyester film was obtained. The composition and characteristics of this biaxially oriented polyester film were as shown in Tables 1 to 4, and had excellent characteristics.

(Example 11)
SABIC Innovative Plastics PEI “Ultem 1040A-1000” and “Ultem 1010-1000” used in Example 1 SABIC Innovative Plastics polyimide (PI) resin “Extem” A biaxially oriented polyester film was prepared in the same manner as in Example 1 except that EXTEM) XH1015 ″ was used. The composition and characteristics of this biaxially oriented polyester film were as shown in Tables 1 to 4, and had excellent characteristics.

(Example 12)
2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane manufactured by Shin-Etsu Chemical Co., Ltd. instead of γ-isocyanatopropyltriethoxysilane “KBE9007” manufactured by Shin-Etsu Chemical Co., Ltd. used as the chain linking agent in Example 1 A biaxially oriented polyester film was prepared in the same manner as in Example 1 except that “KBM303” was used. The composition and characteristics of this biaxially oriented polyester film were as shown in Tables 1 to 4, and had excellent characteristics.

(Example 13)
The blend pellet A obtained in Example 1 was obtained.

  Next, 83 parts by mass of PEI “Ultem 1040A-1000” manufactured by SABIC Innovative Plastics and 17 parts by mass of PAR “U polymer U-100” manufactured by Unitika were heated to 320 to 380 ° C. ( Vented twin-screw extrusion equipped with twin-screw, three-stage type screw (PEI and PEEK kneading plasticizing zone / Dalmage kneading zone / inverted screw dull mage-compensating zone) Was supplied to a machine (L / D = 40, the degree of pressure reduction of the vent hole was 200 Pa), and melt-extruded with a residence time of 3 minutes to obtain PEI / PAR blend pellets containing 17% by mass of PEEK resin. A biaxially oriented polyester film was prepared in the same manner as in Example 1 except that this PEI / PAR blend pellet was used in place of the PEI / PAR / compatibilizer blend pellet B used in Example 1. The composition and characteristics of this biaxially oriented polyester film were as shown in Tables 1 to 4, and had excellent characteristics.

(Example 14)
50 parts by weight of PEN having an intrinsic viscosity of 0.65 obtained in Reference Example 3 and 50 parts by weight of PEI “Ultem 1010-1000” manufactured by SABIC Innovative Plastics, dehumidified and dried at 175 ° C. for 5 hours, and then 320 to 290 ° C. (Screw zone, set temperature gradient at the extrusion head), equipped with a twin-screw, three-stage type screw (PEN and PEI kneading plasticization zone / Dalmage kneading zone / Fine dispersion compatibilizing zone by reverse screw dull mage) Supply to vent type twin screw extruder (L / D = 40, vent hole pressure reduction degree is 200Pa), melt extrude in residence time 3 minutes, PEN / PEI blend pellets containing 50% PEI Obtained. This pellet was designated as blend pellet G.

  Next, 10 parts by mass of the blended pellet B obtained in Example 1 and 90 parts by mass of PEN obtained in Reference Example 3 were supplied to a twin screw extruder heated to 200 to 350 ° C. and melt extruded.

  Here, a vent type twin screw extruder (L / D = 40) consisting of 15 zones of cylinders was used for melt extrusion. In order to suppress the thermal deterioration of PEN, blend pellet B is put into cylinder No.1, and melted sufficiently at 310-350 ° C with cylinder No.2-5, then PEN is put into cylinder No.6, and cylinder Blend pellets B and PEN were mixed at 200-300 ° C in Nos. 7-15. PEN / PEI / PAR blend pellets were obtained. The resulting blend pellet was designated as blend pellet H.

  Subsequently, 0.2 parts by mass of the obtained PEN / PEI blend pellet G, 58.8 parts by mass of the PEN / PEI / PAR blend pellet H, and 41 parts by mass of the PEN pellet obtained in Reference Example 3 are shown in Tables 1-2. %), Dried under reduced pressure at 175 ° C. for 5 hours, put into an extruder, melt extruded at 300 ° C., passed through a fiber sintered stainless steel filter (14 μm cut), then T-die Then, the sheet was discharged in the form of a sheet, and the sheet was solidified and cooled by an electrostatic application method on a cooling drum having a surface temperature of 55 ° C. to obtain an unstretched film.

  Both ends of the unstretched film were gripped by clips and led to a linear motor type simultaneous biaxial stretching tenter to form a film. The film temperature is heated to 140 ° C., and the film is simultaneously biaxially stretched at an area stretch ratio of 12.25 times (longitudinal magnification: 3.5 times, lateral magnification: 3.5 times). Subsequently, the film temperature was changed to 180 ° C., and the film was stretched again at an area draw ratio of 2.16 times (longitudinal magnification: 1.2 times, lateral magnification: 1.8 times), heat-fixed at a heat-fixing temperature of 210 ° C. for 2 seconds, and then heat-fixed. 2% relaxation heat treatment I in the longitudinal direction and the width direction, and then the relaxation heat treatment II of 4% in the longitudinal direction and 2% in the width direction is performed in two stages of 150 ° C and 100 ° C, and the thickness is 5 µm. A biaxially stretched polyester film was obtained. The composition and characteristics of this biaxially oriented polyester film were as shown in Tables 1 to 4, and had excellent characteristics as a base film for magnetic recording media.

(Example 15)
SABIC Innovative Plastics Co. PEI "Ultem (Ultem) 1040A-1000" and 60 parts by mass (355 ° C., a melt viscosity 250 Pa · S at 300 sec ^-1), manufactured by Unitika Ltd. of PAR "U Polymer U-100" (355 ° C., a melt viscosity 410Pa · S) 40 parts by weight and the at 300 sec ^-1, as a chain linking agent, Shin-Etsu chemical Co., Ltd. of γ- isocyanate - DOO triethoxysilane "KBE9007" 1.0 part by weight to 320-380 ° C. heating Vent type equipped with a twin-screw, three-stage type screw (PEI and PAR kneading plasticization zone / Dalmage kneading zone / inverted screw dalmage fine dispersion compatibilization zone) PEI / PAR / chain linking agent containing 30% by mass of PAR resin, fed to a twin screw extruder (L / D = 40, vent hole pressure reduced to 200 Pa), melt extruded with a residence time of 3 minutes Of blended pellets were obtained. Further, a mixture of 100 parts by mass of the obtained PEI / PAR / chain linking agent blend pellets and 3 parts by mass of ion-exchanged water was melt-extruded by a twin screw extruder heated to 320 to 380 ° C. The obtained pellets were designated as blend pellet H.

Next, 10 parts by mass of blended pellet H and 90 parts by mass of PET (X-2) (melt viscosity 600 Pa · S at 300 ° C., 300 sec ⁻¹ ) of intrinsic viscosity [η] = 1.1 obtained in Reference Example 2 were 200 to 350. The mixture was supplied to a twin screw extruder heated to ° C and melt extruded.

Here, a vent type twin screw extruder (L / D = 40) consisting of 15 zones of cylinders was used for melt extrusion. In order to suppress thermal degradation of PET, blend pellet H is put into cylinder No.1, and melted sufficiently at 310-350 ° C with cylinder No.2-5, then PET (X-2) with cylinder No.6 Was added and blended pellet B and PET (X-2) were mixed at 200 to 300 ° C. in cylinders Nos. 7 to 15. PET / PEI / PAR blend pellets were obtained. The resulting blended pellets were designated as blended pellet I (melt viscosity of 300 Pa · S at 315 ° C., 300 sec ⁻¹ ).

  Next, 7 parts by mass of the PET / PEI blend pellet A obtained in Example 1 and 25 parts by mass of the PET / PEI / PAR blend pellet I and 68 parts by mass of PET pellets having an intrinsic viscosity of 0.65 obtained in Reference Example 1 After mixing to the content (mass%) shown in 2 and drying under reduced pressure at 180 ° C for 3 hours, it was put into an extruder, melt extruded at 300 ° C, and a fiber sintered stainless steel metal filter (14 µm cut) Then, the sheet was discharged in a sheet form from a T die, and the sheet was adhered and solidified by a static electricity application method on a cooling drum having a surface temperature of 25 ° C. to obtain an unstretched film.

  Both ends of the unstretched film were gripped by clips and led to a linear motor type simultaneous biaxial stretching tenter to form a film. The film temperature is heated to 95 ° C., and the film is simultaneously biaxially stretched at an area stretch ratio of 12.25 times (longitudinal magnification: 3.5 times, lateral magnification: 3.5 times). Subsequently, the film temperature was changed to 160 ° C., the film was stretched again at an area draw ratio of 2.16 times (longitudinal magnification: 1.2 times, lateral magnification: 1.8 times), heat-fixed at a heat-fixing temperature of 210 ° C. for 2 seconds, and then heat-fixed 2% relaxation heat treatment I in the longitudinal direction and the width direction, and then the relaxation heat treatment II of 4% in the longitudinal direction and 2% in the width direction is performed in two stages of 150 ° C and 100 ° C, and the thickness is 5 µm. A biaxially stretched polyester film was obtained. The composition and characteristics of this biaxially oriented polyester film were as shown in Tables 1 to 4, and had excellent characteristics as a base film for magnetic recording media.

(Comparative Example 1)
PET of intrinsic viscosity 0.65 obtained in Reference Example 1 was dried under reduced pressure at 180 ° C. for 3 hours, then put into an extruder, melt extruded at 285 ° C., and passed through a fiber sintered stainless steel metal filter (14 μm cut). Thereafter, the sheet was discharged from a T die into a sheet shape, and the sheet was solidified and cooled by an electrostatic application method on a cooling drum having a surface temperature of 25 ° C. to obtain an unstretched film.

  Both ends of the unstretched film were gripped by clips and led to a linear motor type simultaneous biaxial stretching tenter to form a film. The film temperature is heated to 95 ° C., and the film is simultaneously biaxially stretched at an area stretch ratio of 12.25 times (longitudinal magnification: 3.5 times, lateral magnification: 3.5 times). Subsequently, the film temperature was changed to 160 ° C., the film was stretched again at an area draw ratio of 2.16 times (longitudinal magnification: 1.2 times, lateral magnification: 1.8 times), heat-fixed at a heat-fixing temperature of 210 ° C. for 2 seconds, and then heat-fixed 2% relaxation heat treatment I in the longitudinal direction and the width direction, and then the relaxation heat treatment II of 4% in the longitudinal direction and 2% in the width direction is performed in two stages of 150 ° C and 100 ° C, and the thickness is 5 µm. A biaxially stretched polyester film was obtained. The composition and characteristics of this biaxially oriented polyester film are as shown in Tables 1 to 4.

(Comparative Example 2)
50 parts by mass of PET with an intrinsic viscosity of 0.65 obtained in Reference Example 1 and 50 parts by mass of PEI “Ultem 1010-1000” manufactured by SABIC Innovative Plastics Co., Ltd. were dehumidified and dried at 150 ° C. for 5 hours. Equipped with a twin-screw, three-stage type screw (PET and PEI kneading plasticization zone / Dalmerization kneading zone / Fine dispersion compatibilizing zone by reverse screwing dalmage) heated to ℃ (screw zone, setting temperature gradient at extrusion head) PET / PEI blend chip containing 50% by mass of PEI fed to a vented twin screw extruder (L / D = 40, vent hole pressure reduced to 200 Pa), melt extruded with a residence time of 3 minutes Got.

  Next, the obtained PET / PEI blend chip and the above-mentioned PET chip having an intrinsic viscosity of 0.65 were mixed so as to have the contents (mass%) shown in Tables 1 and 2, and dried under reduced pressure at 180 ° C. for 3 hours. It is put into an extruder, melt extruded at 285 ° C., passed through a fiber sintered stainless steel metal filter (14 μm cut), then discharged into a sheet form from a T die, and the sheet is placed on a cooling drum having a surface temperature of 25 ° C. It was solidified by an electrostatic application method and cooled to obtain an unstretched film.

  Both ends of the unstretched film were gripped by clips and led to a linear motor type simultaneous biaxial stretching tenter to form a film. The film temperature is heated to 95 ° C., and the film is simultaneously biaxially stretched at an area stretch ratio of 12.25 times (longitudinal magnification: 3.5 times, lateral magnification: 3.5 times). Subsequently, the film temperature was changed to 160 ° C., the film was stretched again at an area draw ratio of 2.16 times (longitudinal magnification: 1.2 times, lateral magnification: 1.8 times), heat-fixed at a heat-fixing temperature of 210 ° C. for 2 seconds, and then heat-fixed 2% relaxation heat treatment I in the longitudinal direction and the width direction, and then the relaxation heat treatment II of 4% in the longitudinal direction and 2% in the width direction is performed in two stages of 150 ° C and 100 ° C, and the thickness is 5 µm. A biaxially stretched polyester film was obtained. The composition and characteristics of this biaxially oriented polyester film are as shown in Tables 1 to 4.

(Comparative Example 3)
50 parts by mass of PET with an intrinsic viscosity of 0.65 obtained in Reference Example 1 and 50 parts by mass of PAR “U polymer U-100” manufactured by Unitika Co., Ltd. were dehumidified and dried at 150 ° C. for 5 hours, and then heated to 320 to 290 ° C. (Screw zone, temperature gradient is set at the extrusion head) Bent type two equipped with twin-screw three-stage type screw (PET and PAR kneading plasticization zone / Dalmage kneading zone / Reverse screwing dull mage) The mixture was supplied to a shaft extruder (L / D = 40, the degree of vacuum at the vent hole was 200 Pa), and melt-extruded with a residence time of 3 minutes to obtain a PET / PAR blend pellet containing 50% by mass of PAR. The PET / PAR blend pellets and the above PET pellets with an intrinsic viscosity of 0.65 were mixed so as to have the content (mass%) shown in Tables 1-2, dried under reduced pressure at 180 ° C for 3 hours, and then put into an extruder. , Melt extruded at 300 ° C, passed through a fiber sintered stainless metal filter (14 µm cut), discharged from a T-die into a sheet, and the sheet was applied to a cooling drum having a surface temperature of 25 ° C by electrostatic application. It was solidified and cooled, and an unstretched film was obtained.

  The both ends of this unstretched film are gripped with clips and guided to a linear motor type simultaneous biaxial stretching tenter, the film temperature is heated to 95 ° C, and the area stretching ratio is 12.25 times (vertical magnification: 3.5 times, lateral magnification: 3.5 times), biaxially stretched at a film temperature of 160 ° C, and when trying to stretch again at an area stretch ratio of 2.16 times (longitudinal magnification: 1.2 times, lateral magnification: 1.8 times), film breaks frequently. A biaxially oriented polyester film was not obtained.

(Comparative Example 4)
In the same manner as in Comparative Example 2, PET / PEI blend pellets containing 50% by mass of PEI were obtained. Further, PET / PAR blend pellets containing 50 mass% PAR were obtained in the same manner as in Comparative Example 3.

  Subsequently, the obtained PET / PEI blend pellet, the PET / PAR blend pellet and the PET pellet having the intrinsic viscosity of 0.65 were mixed so as to have the content (% by mass) shown in Tables 1-2, After drying under reduced pressure for a period of time, it was put into an extruder, melt extruded at 300 ° C., passed through a fiber sintered stainless steel metal filter (14 μm cut), and then discharged into a sheet form from a T-die. An unstretched film was obtained by solidifying and cooling on a cooling drum at 0 ° C. by electrostatic application.

  The both ends of this unstretched film are gripped with clips and guided to a linear motor type simultaneous biaxial stretching tenter, the film temperature is heated to 95 ° C, and the area stretching ratio is 12.25 times (vertical magnification: 3.5 times, lateral magnification: 3.5 times), biaxially stretched at a film temperature of 160 ° C, and when trying to stretch again at an area stretch ratio of 2.16 times (longitudinal magnification: 1.2 times, lateral magnification: 1.8 times), film breaks frequently. A biaxially oriented polyester film was not obtained.

(Comparative Example 5)
In the same manner as in Comparative Example 2, PET / PEI blend pellets containing 50% by mass of PEI were obtained.

  Furthermore, 50 parts by mass of PAR “U polymer U-100” manufactured by Unitika Ltd., 50 parts by mass of PET with an intrinsic viscosity of 0.65 obtained in Reference Example 1, and γ-isocyanate manufactured by Shin-Etsu Chemical Co., Ltd. as a compatibilizer. Biaxial 3-stage type screw (PET and PAR kneading plasticization zone) 0.5 parts by mass of topropyltriethoxysilane “KBE9007” heated to 320-290 ° C (screw zone, temperature gradient set at extrusion head) / Dalmage kneading zone / fine dispersion compatibilization zone by reverse screw dalmage) fed to a vent type twin screw extruder (L / D = 40, vent hole pressure reduced to 200 Pa), with a residence time of 3 minutes To obtain PET / PAR / compatibilizer blend pellets containing 50 mass% PAR.

  Next, the obtained PET / PEI blend pellets and the PET / PAR / compatibilizer blend pellets and the PET pellets having the intrinsic viscosity of 0.65 were mixed so as to have the contents (mass%) shown in Tables 1-2. After drying under reduced pressure at 180 ° C. for 3 hours, it is put into an extruder, melt extruded at 300 ° C., passed through a fiber sintered stainless steel metal filter (14 μm cut), and then discharged into a sheet form from a T die. Was solidified and cooled on a cooling drum having a surface temperature of 25 ° C. by an electrostatic application method to obtain an unstretched film.

  The both ends of this unstretched film are gripped with clips and guided to a linear motor type simultaneous biaxial stretching tenter, the film temperature is heated to 95 ° C, and the area stretching ratio is 12.25 times (vertical magnification: 3.5 times, lateral magnification: 3.5 times), biaxially stretched at a film temperature of 160 ° C, and when trying to stretch again at an area stretch ratio of 2.16 times (longitudinal magnification: 1.2 times, lateral magnification: 1.8 times), film breaks frequently. A biaxially oriented polyester film was not obtained.

(Comparative Example 6)
94 parts by weight of PET with an intrinsic viscosity of 0.65 obtained in Reference Example 1, 5 parts by weight of PEI “Ultem 1010-1000” manufactured by SABIC Innovative Plastics, and 1 part by weight of PAR “U polymer U-100” manufactured by Unitika The part was dried under reduced pressure at 180 ° C. for 3 hours, put into an extruder, melt extruded at 300 ° C., passed through a fiber sintered stainless steel metal filter (14 μm cut), and then discharged from the T die into a sheet. The sheet was solidified and cooled on a cooling drum having a surface temperature of 25 ° C. by an electrostatic application method to obtain an unstretched film.

  The both ends of this unstretched film are gripped with clips and guided to a linear motor type simultaneous biaxial stretching tenter, the film temperature is heated to 95 ° C, and the area stretching ratio is 12.25 times (vertical magnification: 3.5 times, lateral magnification: 3.5 times), biaxially stretched at a film temperature of 160 ° C, and when trying to stretch again at an area stretch ratio of 2.16 times (longitudinal magnification: 1.2 times, lateral magnification: 1.8 times), film breaks frequently. A biaxially oriented polyester film was not obtained.

(Comparative Example 7)
94 parts by weight of PET with an intrinsic viscosity of 1.1 obtained in Reference Example 2, 1 part by weight of PAR “U polymer U-100” manufactured by Unitika, and PEI “Ultem 1040A-1000” manufactured by SABIC Innovative Plastics After 5 parts by weight, dry blend of 1 part by weight of bisphenol A type epoxy resin having an epoxy equivalent of 875 to 975 and a molecular weight of 1,600, it is melt-kneaded with a TEX30 type twin screw extruder manufactured by Nippon Steel, Ltd. Pelletized. Pellets that have been dehumidified and dried at 120 ° C overnight are put into an extruder, melt extruded at 300 ° C, passed through a fiber sintered stainless steel metal filter (14 µm cut), and then discharged into a sheet form from a T die. Was solidified and cooled on a cooling drum having a surface temperature of 25 ° C. by an electrostatic application method to obtain an unstretched film.
The both ends of this unstretched film are gripped with clips and guided to a linear motor type simultaneous biaxial stretching tenter, the film temperature is heated to 95 ° C, and the area stretching ratio is 12.25 times (vertical magnification: 3.5 times, lateral magnification: 3.5 times), biaxially stretched at a film temperature of 160 ° C, and when trying to stretch again at an area stretch ratio of 2.16 times (longitudinal magnification: 1.2 times, lateral magnification: 1.8 times), film breaks frequently. A biaxially oriented polyester film was not obtained.

(Comparative Example 8)
SABIC Innovative Plastics PEI “Ultem 1010-1000” (75% by mass) and Unitika PAR “U Polymer U-100” (25% by mass) heated to 350 ° C. A PEI / PAR blend chip 1 was obtained by feeding to a vented twin-screw kneading extruder equipped with a screw of the type and melt-kneading with a residence time of 3 minutes. Thereafter, the blend chip 1 obtained here (50% by mass) and an intrinsic viscosity 0.85 polyethylene terephthalate (PET) chip (50% by mass) were supplied to a twin-screw kneading extruder heated to 300 ° C., and the residence time was 2 minutes. The blend chip 2 was obtained by melt-kneading with the above.

Next, PET chip (60% by mass) with an intrinsic viscosity of 0.65 and blend chip 2 (40% by mass) obtained by the above pelletizing operation were dried under reduced pressure at 180 ° C. for 3 hours, and then a screw having a diameter of 150 mm heated to 290 ° C. It is put into a single screw extruder equipped, melt extruded, passed through a fiber sintered stainless steel metal filter (5 μm cut) at a shear rate of 10 seconds ^-1 and then discharged into a sheet form from a T die, the sheet On a cooling drum having a surface temperature of 25 ° C., it was solidified at a draft ratio of 10 at a speed of 30 m / min and cooled to obtain a substantially unoriented unstretched film.

  Both ends of the unstretched film were gripped by clips and led to a linear motor type simultaneous biaxial stretching tenter to form a film. The film temperature is heated to 95 ° C., and the film is simultaneously biaxially stretched at an area stretch ratio of 12.25 times (longitudinal magnification: 3.5 times, lateral magnification: 3.5 times). Subsequently, the film temperature was changed to 160 ° C., the film was stretched again at an area draw ratio of 2.16 times (longitudinal magnification: 1.2 times, lateral magnification: 1.8 times), heat-fixed at a heat-fixing temperature of 210 ° C. for 2 seconds, and then heat-fixed 2% relaxation heat treatment I in the longitudinal direction and the width direction, and then the relaxation heat treatment II of 4% in the longitudinal direction and 2% in the width direction is performed in two stages of 150 ° C and 100 ° C, and the thickness is 5 µm. A biaxially stretched polyester film was obtained. The composition and characteristics of this biaxially oriented polyester film are as shown in Tables 1 to 4.

  Here, abbreviations in the table are shown below.

PET: Polyethylene terephthalate
PEN: Polyethylene-2,6-naphthalate
PI: Polyimide
PEI: Polyetherimide
PEEK: Polyetheretherketone

  The biaxially oriented film of the present invention has excellent moisture and heat resistance, dielectric breakdown characteristics, dimensional stability, and running durability. The use of the biaxially oriented film of the present invention is not particularly limited, but for printing materials such as process / release materials, electrical insulating materials, solar cell materials, circuit board materials, capacitors, packaging, ink ribbons, etc. It can be widely used as a high-density magnetic recording medium, and its industrial value is extremely high.

It is the schematic which shows the measuring apparatus of a width dimension.

Explanation of symbols

1: Laser oscillator 2: Light receiving unit 3: Load detector 4: Load 5: Free roll 6: Free roll 7: Free roll 8: Free roll 9: Magnetic tape 10: Laser light

Claims (8)

Polyester (A) having a glass transition temperature of 50 ° C. or more and less than 130 ° C., Amorphous polyimide (B) having a glass transition temperature of more than 210 ° C. and not more than 300 ° C., and Amorphous having a glass transition temperature of 130 ° C. or more and 210 ° C. or less Including the resin (C), the total content of the polyester (A), the amorphous polyimide (B) and the amorphous resin (C) is 80% by mass or more and 100% by mass or less of the total weight of the film. The mass ratio of the polyester (A), the amorphous polyimide (B), and the amorphous resin (C) is 70 to 99, 0.1 to 30, 0.01 to 20, respectively, and the film width direction A biaxially oriented polyester film having a humidity expansion coefficient of 0 to 6.0 ppm /% RH. The amorphous polyimide (B) weight W _B and the greater than the mass W ratio W _C / W _B are 0 _C of the amorphous resin (C) of less than 1/3, according to claim 1 Biaxially oriented polyester film. The biaxially oriented polyester film according to claim 1 or 2, wherein the internal haze of the film is 0 to 75%. The biaxially oriented polyester film according to any one of claims 1 to 3, wherein the polyester (A) is polyethylene terephthalate or polyethylene naphthalate. The biaxially oriented polyester film according to any one of claims 1 to 4, wherein the amorphous polyimide (B) is a polyetherimide. 6. The amorphous resin (C) according to claim 1, wherein the amorphous resin (C) is at least one amorphous resin selected from the group consisting of polysulfone, polyphenylene ether, polycarbonate, polyarylate, and cyclic olefin copolymer. Axial-oriented polyester film. In the film, the polyester (A) forms a continuous structure, and the amorphous polyimide (B) and the amorphous resin (C) together form a disperse phase with respect to the polyester (A) to form a discontinuous structure. The biaxially oriented polyester film according to any one of claims 1 to 6. The biaxially oriented polyester film according to any one of claims 1 to 7, which has a temperature expansion coefficient in the film width direction of -6.0 to 6.0 ppm / ° C.

Images