JP2009221277A - Biaxially oriented polyester film and magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film can give a high density magnetic recording medium having a low error rate, scarcely causing the shaving of magnetic heads and magnetic tapes, and having excellent running durability. <P>SOLUTION: Provided is the biaxially oriented polyester film characterized by comprising 70 to 99 pts.mass of a polyester (A) having a melting point of ≥200°C and <280°C, 1 to 30 pts.mass of an amorphous thermoplastic resin (B) having a glass transition temperature of 100 to 250°C, and 0.1 to 4 pts.mass of a crystalline thermoplastic resin (C) having a melting point of 280 to 400°C, and having a Wc/Wb ratio of 0.05 to 0.3, wherein Wb is the content of the amorphous thermoplastic resin (B) and Wc is the content of the crystalline thermoplastic resin (C). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a biaxially oriented polyester film having excellent rigidity and dimensional stability, and can be suitably used for magnetic recording media, electrical insulation, capacitors, circuit materials, solar cell materials, and the like. Especially, when it is used as a magnetic recording medium, it is possible to reduce the environmental change of temperature and humidity and the dimensional change due to storage, the error rate is low, the magnetic head and magnetic tape are less scraped, and the running durability is high. The present invention relates to a biaxially oriented polyester film that can be used as a density magnetic recording medium.

  Biaxially stretched polyester film is used for various applications because of its excellent thermal properties, dimensional stability, mechanical properties, and ease of control of surface morphology, and is particularly useful as a support for magnetic recording media. Are known. In recent years, a magnetic recording medium such as a magnetic tape has been required to have a thin base film and a high density recording in order to reduce the weight, size, and capacity of the 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 due to 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 magnetic tape is used. 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 shaving of the head and tape.

  From this point of view, the support may be made of an aromatic polyamide having high rigidity superior to the biaxially stretched polyester film in terms of strength and dimensional stability. However, aromatic polyamides are too rigid and may cause head scraping. Furthermore, it is expensive and expensive, and is not practical as a support for general-purpose recording media. Also for polyester films using polyethylene terephthalate, polyethylene naphthalate, etc., a support for a magnetic recording medium that has been strengthened by using a stretching technique has been developed. However, it is still difficult to satisfy strict requirements such as dimensional stability with respect to temperature and humidity.

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

As for a biaxially oriented polyester film in which a polyester and a thermoplastic resin other than polyester are mixed, a film excellent in running property and scratch resistance has been proposed (for example, Patent Document 1). However, there is no disclosure of a method for mixing polyester and a thermoplastic resin having a melting point of 280 to 400 ° C., or a specific method or technical idea using a three-component resin such as polyimide and aromatic polyether ketone. In addition, in films consisting of polyester and polyimide and polyimide and nano-compatible polymer, a film with improved heat resistance and thermal dimensional stability has been proposed using aromatic polyether ketone as a polymer compatible with polyimide and nano-compatibility. (For example, Patent Document 2). However, the amount of the polymer mixed with polyimide or polyimide that is nano-compatible with polyester is large and may not be sufficient for effective molecular chain orientation by stretching or the like. For example, it is used for high-density magnetic recording media. In order to meet strict requirements such as dimensional stability against temperature and humidity, it may not always be sufficient, and in addition, foreign matter due to unmelted material is likely to be generated in the film, and the surface is likely to be rough, for example, magnetic recording When used for a medium or the like, electromagnetic conversion characteristics may be poor. 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.
JP 2001-323146 A JP 2004-123863 A JP 2002-249660 A

  An object of the present invention is to solve the above problems and obtain a biaxially oriented polyester film having excellent rigidity and dimensional stability. For magnetic recording media, for electrical insulation, for capacitors, for circuit materials, and for solar cells. It can be used suitably for materials, etc. Especially when it is used as a magnetic recording medium, it can reduce the environmental change of temperature and humidity and the dimensional change due to storage, the error rate is small, and the magnetic head and magnetic tape are scraped. It is an object of the present invention to provide a biaxially oriented polyester film that can be used as a high-density magnetic recording medium with less running durability.

  In order to solve the above problems, the present invention is characterized by the following (1) to (8).

  (1) 70 to 99 parts by mass of a polyester (A) having a melting point of 200 ° C. or higher and lower than 280 ° C., 1 to 30 parts by mass of an amorphous thermoplastic resin (B) having a glass transition temperature of 100 to 250 ° C., and The crystalline thermoplastic resin (C) having a melting point of 280 ° C. to 400 ° C. is contained at a ratio of 0.1 to 4 parts by mass, respectively, and the content (Wb) and crystal of the amorphous thermoplastic resin (B) Biaxially oriented polyester film in which the ratio (Wc / Wb) of the content (Wc) of the thermoplastic resin (C) is from 0.05 to 0.3.

  (2) The biaxially oriented polyester film according to the above (1), wherein the amorphous thermoplastic resin (B) contains at least one selected from the group consisting of polyetherimide, polyethersulfone and polysulfone.

  (3) The biaxially oriented polyester film according to the above (1) or (2), wherein the crystalline thermoplastic resin (C) is an aromatic polyether ketone or a thermoplastic crystalline polyimide.

  (4) The polyester (A) includes at least one selected from the group consisting of polyethylene terephthalate, polyethylene-2,6-naphthalate, and modified products thereof, according to any one of (1) to (3) above. Biaxially oriented polyester film.

  (5) The amorphous thermoplastic resin (B) and the crystalline thermoplastic resin (C) each form a dispersed phase in the polyester (A), and the average dispersed diameter of the amorphous thermoplastic resin (B) is 1. The biaxially oriented polyester film according to any one of the above (1) to (4), which is in the range of ˜50 nm and the average dispersion diameter of the crystalline thermoplastic resin (C) is in the range of 50 to 500 nm.

  (6) The biaxially oriented polyester film according to any one of the above (1) to (5), wherein the temperature expansion coefficient in the film width direction is −5.0 to 8.0 ppm / ° C.

  (7) The biaxially oriented polyester film according to any one of (1) to (6), wherein the humidity expansion coefficient in the film width direction is 0 to 6.0 ppm /% RH.

  (8) A magnetic recording medium using the biaxially oriented polyester film according to any one of (1) to (7).

  According to the present invention, a biaxially oriented polyester film having excellent rigidity and dimensional stability can be obtained, and it can be suitably used for magnetic recording media, electrical insulation, capacitors, circuit materials, solar cell materials, and the like. A biaxially oriented polyester film can be obtained. Above all, when it is used as a magnetic recording medium, it can reduce the environmental change of temperature and humidity and the dimensional change due to storage, the error rate is low, the magnetic head and magnetic tape are less scraped, and the running density is excellent. A biaxially oriented polyester film that can be used as a magnetic recording medium can be obtained.

  In the present invention, the polyester (A) is composed of, for example, a polymer having an acid component such as aromatic dicarboxylic acid, alicyclic dicarboxylic acid or aliphatic dicarboxylic acid or a diol component as a structural unit (polymerization unit). Can be used.

  Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-diphenyldicarboxylic acid. Acid, 4,4′-diphenyl ether dicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, and the like can be used. Among them, terephthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid can be preferably used. . As the alicyclic dicarboxylic acid component, for example, cyclohexane dicarboxylic acid or the like can be used. As the aliphatic dicarboxylic acid component, for example, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like can be used. These acid components may be used alone or in combination of two or more.

  Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, , 6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2'-bis (4'- β-hydroxyethoxyphenyl) propane and the like can be used, and among them, ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol and the like can be preferably used, and ethylene glycol is particularly preferable. etc It can be used. These diol components may be used alone or in combination of two or more.

  Polyester (A) may be copolymerized with a monofunctional compound such as lauryl alcohol or phenyl isocyanate, trimellitic acid, pyromellitic acid, glycerol, pentaerythritol, 2,4-dioxybenzoic acid, etc. These trifunctional compounds may be copolymerized within a range in which the polymer is substantially linear without excessive branching or crosslinking. In addition to the acid component and diol component, the present invention includes aromatic hydroxycarboxylic acids such as p-hydroxybenzoic acid, m-hydroxybenzoic acid, and 2,6-hydroxynaphthoic acid, p-aminophenol, and p-aminobenzoic acid. As long as the effect is not impaired, the copolymerization can be further carried out.

  The polyester (A) has a melting point of 200 ° C. or higher and lower than 280 ° C. in order to perform biaxial stretching and to exhibit the effects of the present invention such as dimensional stability. A preferable melting point is 230 ° C. or higher and 270 ° C. or lower.

  Polyester (A) is preferably polyethylene terephthalate or polyethylene naphthalate (polyethylene-2,6-naphthalate). Further, these copolymers and modified products may be used, and polymer alloys with other thermoplastic resins may be used. The polymer alloy here refers to a polymer multi-component system, which may be a block copolymer by copolymerization or a polymer blend by mixing. In this invention, it is preferable that at least 1 sort (s) of these polymers is included.

  The amorphous thermoplastic resin (B) having a glass transition temperature of 100 to 250 ° C. according to the present invention can be controlled in heat resistance (glass transition temperature) depending on its mixing ratio by using a polymer alloy with the polyester (A). It is preferably used because the polymer can be designed according to the use conditions. The mixing ratio of the polymer can be examined using a microscopic FT-IR method (Fourier transform microscopic infrared spectroscopy) or an NMR method. A preferable range of the glass transition temperature of the amorphous thermoplastic resin (B) is 150 to 250 ° C, and a more preferable range is 200 to 250 ° C.

  The amorphous thermoplastic resin (B) is a resin different from the polyester (A). Here, the term “amorphous” 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. Further, the amorphous thermoplastic resin (B) is preferably a resin having an imide group or a sulfone group for compatibility with the polyester (A), and is selected from the group consisting of polyetherimide, polyethersulfone and polysulfone. It is preferable to contain at least one selected from the above. In particular, a polyetherimide having an imide group is preferable because compatibility with the polyester (A) is likely to increase. Polyetherimide is a resin containing an ether bond in a polyimide constituent component composed of an imide group, and is represented by the following general formula.

(Wherein R ¹ is a divalent aromatic or aliphatic residue having 6 to 30 carbon atoms, R ² is a divalent aromatic residue having 6 to 30 carbon atoms, From the group consisting of alkylene groups having 2 to 20 carbon atoms, cycloalkylene groups having 2 to 20 carbon atoms, and polydiorganosiloxane groups chain-terminated with alkylene groups having 2 to 8 carbon atoms Selected divalent organic group.)
As said R < ¹ >, R < ² >, the aromatic residue shown by the following formula group can be mentioned, for example.

  In the present invention, 2,2-bis [4- (2,3-dicarboxyphenoxy) is used from the viewpoints of affinity with polyester (A) and a crystalline thermoplastic resin (C) described later, cost, melt moldability, and the like. A polymer having a repeating unit represented by the following formula, which is a condensate of phenyl) propane dianhydride and m-phenylenediamine or p-phenylenediamine, is preferred.

Or

(N is an integer of 2 or more, preferably an integer of 20 to 50)
This polyetherimide is available from SABIC Innovative Plastics under the trade name “Ultem” (registered trademark), and is “Ultem 1000”, “Ultem 1010”, “Ultem 1040”, “Ultem 5000”, “Ultem 6000” and “Ultem XH6050”. ”Series,“ Extreme XH ”, and“ Extreme UH ”registered trademark names.

  In addition, the amorphous thermoplastic resin (B) in the present invention preferably has a melt viscosity of 100 to 600 (Pa · S) at a temperature of 350 ° C. and a shear rate of 100 (1 / second). It is preferable that the melt viscosity of the polyimide (B) is 100 to 600 (Pa · S) in terms of miscibility with the polyester (A) and the crystalline thermoplastic resin (C).

  The crystalline thermoplastic resin (C) of the present invention has a melting point of 280 to 400 ° C. By making the melting point of the crystalline thermoplastic resin (C) higher than the melting point of the polyester (A), it becomes easier to form constraining points due to the microcrystals of the crystalline thermoplastic resin (C) on the biaxially oriented polyester film. It becomes easy to increase the molecular chain orientation in the process. When the molecular chain orientation is increased, it becomes easier to obtain the effect of the present application by strengthening and improving dimensional stability. A preferable melting point of the crystalline thermoplastic resin (C) is 300 to 370 ° C, and a more preferable melting point is 320 to 360 ° C. The crystalline thermoplastic resin (C) is a resin different from the polyester (A). Here, the crystallinity is a characteristic in which a melting point and a melting peak are detected when a sample is measured using differential scanning calorimetry (DSC) or the like. Furthermore, the crystalline thermoplastic resin (C) is preferably a resin having a ketone group, an imide group, and an amide group, when mixed with the amorphous thermoplastic resin (B) or the polyester (A). A resin having a ketone group and an imide group is preferable. Among these, aromatic polyether ketone or thermoplastic crystalline polyimide is preferable.

  Aromatic polyether ketone is a thermoplastic resin having an aromatic bond, an ether bond and a ketone bond in its structural unit, and representative examples thereof include polyether ketone, polyether ether ketone, and polyether ketone ketone. In the present invention, polyetheretherketone (melting point 343 ° C.) represented by the following formula is particularly preferred. Polyetheretherketone is available from Victrex, Degussa, and Solvay Advanced Polymers.

  The thermoplastic crystalline polyimide contains a structural unit having an imide group and has crystallinity.

  In the present invention, it is particularly preferable to use polyimide represented by the following formula (melting point: 380 ° C.). A polyimide represented by the following formula is available from Mitsui Chemicals as “Aurum” (registered trademark).

  The present invention is a biaxially oriented polyester film comprising a polyester (A), the above-described amorphous thermoplastic resin (B), and the above-described crystalline thermoplastic resin (C). The polyester (A), amorphous The content ratio of the thermoplastic resin (B) and the crystalline thermoplastic resin (C) is 70 to 99 parts by mass of the polyester (A), 1 to 30 parts by mass of the amorphous thermoplastic resin (B), and the crystalline thermoplastic resin. (C) 0.1 to 4 parts by mass. The more preferable content of the polyester (A) is 80 to 97 parts by mass, and the particularly preferable range is 85 to 95 parts by mass. Moreover, the more preferable content of the amorphous thermoplastic resin (B) is 3 to 20 parts by mass, and the particularly preferable content is 5 to 15 parts by mass. If the content of the amorphous thermoplastic resin (B) is less than 1 part by mass, the glass transition temperature of the film is not sufficiently increased, so that the heat resistance, moist heat resistance and dimensional stability may not be sufficient. On the other hand, if it exceeds 30 parts by mass, the film-forming property of the film deteriorates and the production cost increases, and the average dispersion diameter of the amorphous thermoplastic resin (B) in the polyester (A) is preferred in the present invention. It tends to be difficult to control the range. Moreover, preferable content of crystalline thermoplastic resin (C) is 0.2-3 mass parts, and more preferable content is 0.5-1.5 mass parts. If the content of the crystalline thermoplastic resin (C) is less than 0.1 parts by mass, the portion that becomes a restraint point in the polyester film is reduced, so that it is not sufficient to obtain the effect of high orientation of the present invention. In addition, when the content of the crystalline thermoplastic resin (C) exceeds 4 parts by mass, the biaxial stretching of the polyester film cannot provide sufficient molecular chain orientation, For example, when the magnetic recording medium is used for a magnetic recording medium, the electromagnetic conversion characteristics are likely to be lowered, and the effect of the present invention may not be obtained.

  Further, the ratio Wc / Wb of the content Wb of the amorphous thermoplastic resin (B) to the content Wc of the crystalline thermoplastic resin (C) in the biaxially oriented polyester film of the present invention is 0.05 or more and 0.3. The following is preferable. As described above, the melting point of the crystalline thermoplastic resin (C) is preferably higher than the melting point of the polyester (A) in forming a constraining point in the film, but when the melting point is higher than that of the polyester (A), In the melt extrusion method, unmelted foreign matter is likely to be generated. Therefore, it is preferable to mix the amorphous thermoplastic resin (B) and the crystalline thermoplastic resin (C) in advance before mixing with the polyester (A). In the biaxially oriented polyester film of the present invention, when the ratio Wc / Wb of the content of the amorphous thermoplastic resin (B) and the crystalline thermoplastic resin (C) is less than 0.05, the crystalline thermoplastic resin When the content of (C) decreases, it becomes difficult to form a restraint point in the film, and when the content ratio Wc / Wb exceeds 0.3, the content of the crystalline thermoplastic resin (C) is In some cases, the molecular chain orientation due to stretching is hindered, or the film surface tends to become rough, making it difficult to obtain the effects of the present invention. In the biaxially oriented polyester film of the present invention, the more preferable range of the content ratio Wc / Wb of the amorphous thermoplastic resin (B) and the crystalline thermoplastic resin (C) is 0.05 to 0.25. There is a particularly preferred range of 0.08 to 0.18.

  In the biaxially stretched polyester film of the present invention, the crystalline thermoplastic resin (C) is dispersed in the polyester (A) through the amorphous thermoplastic resin (B), and the crystalline thermoplastic resin (C) Therefore, the molecular chain orientation of the polyester (A) can be easily increased. By setting the content ratio Wc / Wb of the amorphous thermoplastic resin (B) and the crystalline thermoplastic resin (C) within the above-described preferable range, molecular chain orientation can be effectively provided. The presence of the nodal point can be confirmed by molecular chain orientation analysis by laser Raman spectroscopy or crystal orientation by wide-angle X-rays. Moreover, the presence can be confirmed by analysis of relaxation time by solid state NMR or solid state viscoelasticity analysis.

  In the biaxially oriented polyester film of the present invention, the amorphous thermoplastic resin (B) and the crystalline thermoplastic resin (C) each form a dispersed phase in the polyester (A). The average dispersion diameter of the amorphous thermoplastic resin (B) in the polyester (A) is preferably in the range of 1 to 50 nm. When the average dispersion diameter of the amorphous thermoplastic resin (B) is less than the above range lower limit or greater than the above range upper limit, the glass transition temperature (Tg) of the polyester film of the present invention cannot be sufficiently increased, and the film In some cases, it is impossible to impart excellent heat resistance and moist heat resistance. The average dispersion diameter of the amorphous thermoplastic resin (B) is more preferably 40 nm or less. More preferably, it is 30 nm or less. Most preferably, it is 20 nm or less. The average dispersion diameter of the amorphous thermoplastic resin (B) is more preferably 3 nm or more. More preferably, it is 5 nm or more. Most preferably, it is 8 nm or more. The average dispersion diameter of the amorphous thermoplastic resin (B) is more preferably 3 to 40 nm. More preferably, it is 5-30 nm. Most preferably, it is 8-20 nm. When the average dispersion diameter of the amorphous thermoplastic resin (B) is within the above range, the film forming property is more stable.

  Moreover, it is preferable that the average dispersion diameter of crystalline thermoplastic resin (C) whose melting | fusing point in polyester (A) is 280-400 degreeC is the range of 50-500 nm. When the average dispersion diameter of the crystalline thermoplastic resin (C) is less than the lower limit of the range or larger than the upper limit of the range, an effective restraint point cannot be formed in the polyester film of the present invention, and the film has excellent dimensional stability. And surface properties may not be imparted. The average dispersion diameter of the crystalline thermoplastic resin (C) is more preferably 400 nm or less. More preferably, it is 300 nm or less. Most preferably, it is 200 nm or less. The average dispersion diameter of the crystalline thermoplastic resin (C) is more preferably 50 to 400 nm. More preferably, it is 50-300 nm. Most preferably, it is 50-200 nm. When the average dispersion diameter of the crystalline thermoplastic resin (C) is within the above range, a restraint point for expressing the effect of the present invention is formed in the film and the film forming property is more stable.

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

  The average dispersion diameter in the polyester (A) of the amorphous thermoplastic resin (B) and the crystalline thermoplastic resin (C) is determined under the condition that the cut surface of the film is applied with a transmission voltage of 100 kV using a transmission electron microscope. By observing underneath and taking a photograph taken at a magnification of 20,000 times as an image into an image analyzer, selecting any 100 dispersed phases, and performing image processing as necessary Then, the dispersion diameter is obtained and calculated as the number average.

  The average dispersion diameter was determined as follows. Cut the film in (a) a direction parallel to the longitudinal direction and perpendicular to the film surface, (b) a direction parallel to the width direction and perpendicular to the film surface, and (c) a direction parallel to the film surface. Prepared by thin section method. In order to clarify the contrast of the dispersed phase, it may be stained with osmic acid or ruthenic acid. The cut surface is observed using a transmission electron microscope (H-7100FA, manufactured by Hitachi) under a condition of a pressurization voltage of 100 kV, and a photograph is taken at 20,000 times. 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, whereby the size of the dispersed phase was determined as follows. The maximum thickness (la) and the maximum length (lb) in the film thickness direction of each dispersed phase appearing on the cut surface of (a), and the maximum thickness (lb) in the longitudinal direction of each disperse phase appearing on the cut surface of (a). The maximum length (lc), the maximum length (ld) in the width direction, the maximum length (le) in the film longitudinal direction and the maximum length (lf) in the width direction 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 (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.

  In the present invention, the amorphous thermoplastic resin (B) has a temperature of 350 ° C. and a shear rate of 100 (1 / second), the melt viscosity (ηb) and the crystalline thermoplastic resin (C) has a temperature of 350 ° C. and a shear rate of 100 (1). The ratio (ηb / ηc) of the melt viscosity (ηc) is preferably 1/3 or more and 3 or less. When the ratio of the melt viscosity is controlled within the above range, the average dispersion diameter in the polyester film (A) of the amorphous thermoplastic resin (B) and the crystalline thermoplastic resin (C) is controlled within the preferable range of the present invention. It becomes easy, the foreign material in a film is reduced, and it becomes possible to provide the film with the outstanding dimensional stability and surface characteristic.

  In the present invention, the method of mixing the polyester (A) with the crystalline thermoplastic resin (C) and the amorphous thermoplastic resin (B) is as follows: (1) Amorphous thermoplastic resin (B ) And the crystalline thermoplastic resin (C) are pre-melt kneaded (pelletized), and then the mixture of the composition obtained in (2) (1) and polyester (A) is pre-melt kneaded (pelletized). A two-stage melt-kneading process is preferably exemplified.

  In that case, a method of pre-kneading into a master chip using a high-shear mixer with high shear stress such as a twin screw extruder is preferred. In the case of mixing with a twin screw extruder, from the viewpoint of reducing defective dispersion, a screw provided with a triple twin screw type or a double twin screw type is preferable. By using two-stage melt-kneading, the crystalline thermoplastic resin (C) having a melting point of 280 to 400 ° C., which cannot be mixed with the polyester (A), is introduced into the present invention via the amorphous thermoplastic resin (B). It becomes easy to mix in the biaxially oriented polyester film. When mixing the amorphous thermoplastic resin (B) and the crystalline thermoplastic resin (C), the amorphous thermoplastic resin (with a melting temperature in the range of 300 to 400 ° C., preferably in the range of 340 to 400 ° C.) It is preferable to prepare a master chip in which B) is mixed at a high concentration, and in particular, the mixed mass ratio of amorphous thermoplastic resin (B) / crystalline thermoplastic resin (C) is 50/50 to 90/10. The more preferable range is 60/40 to 80/20. Further, when the obtained composition is mixed with polyester, a high viscosity polyester having IV of 0.8 or more, preferably 1.0 or more is used, and polyester / (amorphous thermoplastic resin (B) and crystals are used. The mixing mass ratio of the mixture with the thermoplastic resin (C) is preferably 50/50 to 90/10, and more preferably 60/40 to 80/20. In this method, the shear stress is increased by high-viscosity polyester to increase the mixing force, and the mixing amount of the crystalline thermoplastic resin (C) is adjusted so that the melt viscosity does not become extremely high. Is preferable.

  On the other hand, a composition raw material prepared by pre-melting and kneading (pelletizing) a mixture of polyester (A) and amorphous thermoplastic resin (B) into a master chip is prepared, and the content of polyetherimide is adjusted appropriately. can do. In addition, when the polyester (A) and the amorphous thermoplastic resin (B) are mixed, there is a difference in melt viscosity. Therefore, a master chip in which the amorphous thermoplastic resin (B) is mixed at a high concentration is prepared. In particular, the mixing mass ratio of polyester (A) / amorphous thermoplastic resin (B) is preferably 10/90 to 70/30, more preferably 30/70 to 60/40. It is a range.

  When forming into a film, the mixed master chip raw material may be put into a normal single-screw extruder to form a melt, or may be directly sheeted without being converted into a master chip in a state where high shear is applied. Good.

  Moreover, when pelletizing with a twin-screw extruder, it is preferable to make screw rotation into 100-500 rotation / min, More preferably, it is the range of 200-400 rotation / min. Even when the screw rotation speed is set within a preferable range, high shear stress is easily applied, and defective dispersion is easily reduced. Further, 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, in order to increase the kneading force, it is preferable to provide a kneading part by a kneading paddle or the like, 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 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 by a single-screw or biaxial extruder may be used. Further, a method using a supercritical fluid described in Journal of Plastics Processing Society of Japan, “Molding”, Vol. 15, No. 6, pp. 382 to 385 (2003) can be preferably exemplified.

  The biaxially oriented polyester film of the present invention preferably has a temperature expansion coefficient in the width direction of −5.0 to 8.0 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 7.0 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 −5.0 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. is there. A more preferable range is −3.0 to 7.0 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 preferable range is 0 to 5.5 ppm /% RH, and a further preferable 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 12 to 20 GPa. A preferable range of the sum of Young's modulus is 13 to 20 GPa, and a more preferable range is 14 to 18 GPa. When the sum of Young's moduli is less than 12 GPa, for example, when used for a magnetic recording medium, 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, it is necessary to increase the stretch ratio and make it extremely oriented, resulting in frequent film breakage and poor productivity, and the break elongation becomes small and breaks easily. There is.

  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 5 to 12 GPa. When the Young's modulus in the longitudinal direction is smaller than 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 5.5 GPa, still more preferably 6 GPa. On the other hand, when the Young's modulus in the longitudinal direction is greater 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 5.5 to 11 GPa, and a further preferable range is 6 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 0.60. More preferably, it is in the range of ˜0.90, and further 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 6 to 12 GPa. If the Young's modulus in the width direction is smaller than 6 GPa, edge damage may be caused. The lower limit of the Young's modulus in the width direction is more preferably 7 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 7 to 11 GPa, and a further preferable range is 7 to 10 GPa.

  In the present invention, the polyester film preferably has a laminated structure of two or more layers. In particular, since the support of the present invention is used for a magnetic recording medium, one surface is required to have smoothness for obtaining excellent electromagnetic conversion characteristics, and the other surface is subjected to film formation / processing steps. Roughness is required for imparting transportability, running performance and running durability of the magnetic tape. Therefore, it is preferable that the polyester film has a laminated structure of two or more layers.

  When the biaxially oriented polyester film of the present invention is used for a magnetic recording medium, the center line average roughness RaA of the surface (A) on the side where the magnetic layer is provided is preferably 0.5 nm to 10 nm. If RaA on the surface (A) on the side where the magnetic layer is provided is smaller than 0.5 nm, the friction coefficient with the transport rolls, etc. may increase in the film production and processing process, which may cause process trouble, and magnetic tape. When used as a magnetic head, the friction with the magnetic head increases and the magnetic tape characteristics tend to deteriorate. When RaA is larger than 10 nm, electromagnetic conversion characteristics may be deteriorated when used as a magnetic tape for high-density recording. The lower limit of RaA on the surface (A) on the side where the magnetic layer is provided is more preferably 1 nm, still more preferably 2 nm, and the upper limit is 8 nm, more preferably 6 nm. A more preferable range is 1 to 8 nm, and a further preferable range is 2 to 6 nm.

  On the other hand, the center line average roughness RaB of the surface (B) on the back coat layer side is preferably 3 to 30 nm. When RaB on the surface (B) on the backcoat layer side is smaller than 3 nm, the friction coefficient with the transport roll, etc. becomes large in film production and processing processes, etc., which may cause process troubles and when used as a magnetic tape In addition, the friction with the guide roll is increased, and the tape running property may be lowered. Moreover, when RaB is larger than 30 nm, when storing as a film roll or pancake, the surface protrusion tends to be transferred to the opposite surface, and the electromagnetic conversion characteristics tend to deteriorate. The lower limit of RaB on the surface (B) on the backcoat layer side is more preferably 5 nm, still 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 polyester film is provided with inorganic and organic particles such as clay, mica, titanium oxide, calcium carbonate, carion, talc, wet silica, and the like in order to impart slipperiness, abrasion resistance, scratch resistance and the like to the surface. Inorganic particles such as dry silica, colloidal silica, calcium phosphate, barium sulfate, alumina, zirconia, organic particles containing acrylic acid, styrene resin, thermosetting resin, silicone, imide compound, etc., added during polyester polymerization reaction Particles (so-called internal particles) that are precipitated by the catalyst or the like may be added. The particle size of the particles can be examined by TEM or the like, and the addition amount of the particles can be examined by an X-ray microanalyzer or pyrolysis gas chromatography mass spectrometry.

  Moreover, it is preferable that the thickness of the biaxially oriented polyester film of this invention is 2-6 micrometers. When this thickness is smaller than 2 μm, the magnetic conversion characteristics may be deteriorated because the tape becomes stiff when it is formed into a magnetic tape. The lower limit of the thickness of the polyester film is more preferably 3 μm, and even more preferably 4 μm. On the other hand, when the thickness of the polyester film is larger than 6 μm, since the tape length per one tape is shortened, it may be difficult to reduce the size and increase the capacity of the magnetic tape. The upper limit of the thickness of the polyester film is more preferably 5.8 μm, still more preferably 5.6 μm. A more preferable range is 3 to 5.8 μm, and a further preferable range is 4 to 5.6 μm.

  The biaxially oriented polyester film of the present invention as described above is produced, for example, as follows.

  In order to produce a biaxially oriented polyester film, for example, polyester pellets are melted using an extruder, discharged from a die, cooled and solidified, and formed into a sheet. At this time, it is preferable to filter the polymer with a fiber-sintered stainless metal filter in order to remove unmelted material in the polymer. In addition, in order to impart easy slipping, abrasion resistance, scratch resistance, etc. to the surface of the polyester film, inorganic particles and organic particles such as clay, mica, titanium oxide, calcium carbonate, carion, talc, wet silica, dry type Inorganic particles such as silica, colloidal silica, calcium phosphate, barium sulfate, alumina, zirconia, organic particles containing acrylic acid, styrene resin, thermosetting resin, silicone, imide compound, etc., added during polyester polymerization reaction It is also preferable to add particles precipitated by a catalyst or the like (so-called internal particles). Furthermore, various additives such as compatibilizers, plasticizers, weathering agents, antioxidants, heat stabilizers, lubricants, antistatic agents, whitening agents, colorants, and the like, provided that they do not inhibit the present invention. Conductive agents, crystal nucleating agents, ultraviolet absorbers, flame retardants, flame retardant aids, pigments, dyes, and the like may be added.

  Subsequently, the sheet is biaxially stretched. The film is stretched biaxially in the longitudinal direction and the width direction and heat-treated. The stretching process is preferably divided into two or more stages in each direction. That is, the method of performing re-longitudinal and re-lateral stretching is preferable because a high-strength film optimum for a magnetic tape for high-density recording can be easily obtained.

  As the stretching method, a sequential biaxial stretching method such as stretching in the width direction after stretching in the longitudinal direction, a simultaneous biaxial stretching method in which the longitudinal direction and the width direction are simultaneously stretched using a simultaneous biaxial tenter, etc. Further, a method of combining a sequential biaxial stretching method and a simultaneous biaxial stretching method is included.

  It is particularly preferable to use a simultaneous biaxial stretching method. Compared with the sequential biaxial stretching method, the simultaneous biaxial stretching method is easy to stretch stably at a high magnification because crystals grow uniformly in the longitudinal direction and the width direction in the film forming process. That is, in the present invention, it is important to form a knot consisting mainly of the crystalline thermoplastic resin (C) in the polyester film, and in order to increase molecular chain tension using its performance in the stretching process. It is particularly effective to make molecular chain tension uniformly in the longitudinal direction and width direction by using simultaneous biaxial stretching, rather than gradually grading molecular chain tension in each step of sequential biaxial stretching. is there. Here, the simultaneous biaxial stretching is a stretching method including a step in which stretching in the longitudinal direction and the width direction is performed simultaneously. The longitudinal direction and the width direction do not necessarily have to be stretched at the same time in all sections, the longitudinal stretching starts first, and the stretching is performed in the width direction from the middle (simultaneous stretching). A method may be adopted in which the process is terminated first and the rest is stretched only in the width direction. As the stretching apparatus, for example, a simultaneous biaxial stretching tenter is preferably exemplified, and among them, a linear motor driven simultaneous biaxial tenter is particularly preferable as a method of stretching a film without breaking.

  The heat treatment after the stretching process may be carried out in one stage, but it is effective to control the temperature expansion coefficient and humidity expansion coefficient within the scope of the present invention without causing relaxation of molecular chain orientation by excessive heat treatment. Therefore, it is preferable to carry out the heat treatment in multiple stages by controlling the heat treatment temperature. Multi-stage means that the heat treatment temperature is changed and the process is carried out in two or more stages.

  The heat treatment temperature can be determined based on the melting point of the polyester. The heat treatment temperature is preferably [melting point of polyester (A) (Tm) -100] to (Tm-50) ° C., and the heat treatment time is preferably in the range of 0.5 to 10 seconds. In particular, the heat treatment temperature for the first stage is preferably set to (Tm-75) to (Tm-50) ° C., more preferably (Tm-75) to (Tm-60) ° C. May be set to a lower temperature than the first stage. Preferably it is set to (Tm-100)-(Tm-75) degreeC, More preferably, it is set to (Tm-100)-(Tm-85) degreeC. Further, it is more preferable to perform a relaxation treatment at a relaxation rate of 1 to 5% in the width direction in the first-stage and / or second-stage heat treatment step.

  And the polyester film manufactured in this way is wound up by a roll. Furthermore, in order to improve the dimensional stability and storage stability which are the effects of the present invention, it is also preferable to heat-treat the wound film together with the rolls under a certain temperature condition. “Constant temperature condition” means that the film is placed together with a roll in a hot air oven or zone set to a certain temperature condition. By heat-treating the film while being in a roll, distortion of the internal structure of the film is easily removed, and dimensional stability such as creep characteristics is easily improved. For example, when the film is wound and stored, when used for a magnetic recording medium such as a magnetic tape, the film is stored in a wound state, or when the tape is run and used, the length of the film Although tension is applied in the direction and creep deformation may occur in the longitudinal direction, storage stability is likely to be significantly improved if dimensional stability such as creep characteristics is improved.

  In the present invention, the polyester film and the polyester film are optionally subjected to any processing such as heat treatment, microwave heating, molding, surface treatment, lamination, coating, printing, embossing, etching, etc. Also good.

  Hereinafter, regarding the method for producing a biaxially oriented polyester film of the present invention, polyethylene terephthalate (PET) is used as the polyester (A), polyetherimide is used as the amorphous thermoplastic resin (B), and aromatic is used as the crystalline thermoplastic resin (C). An example using an aromatic polyether ketone will be described as a representative example. Of course, the present application is not limited to a support using PET as a constituent component, and may be one using another polymer. For example, when a polyester film is formed using polyethylene-2,6-naphthalene dicarboxylate (polyethylene-2,6-naphthalate) having a high glass transition temperature or a melting point, it can be extruded at a temperature higher than the temperature shown below. What is necessary is just to extend | stretch.

  First, polyethylene terephthalate is prepared. Polyethylene terephthalate is manufactured by one of the following processes. (1) Using terephthalic acid and ethylene glycol as raw materials, a low molecular weight polyethylene terephthalate or oligomer is obtained by direct esterification reaction, and then a polymer is obtained by polycondensation reaction using antimony trioxide or titanium compound as a catalyst. Process (2) A process in which dimethyl terephthalate and ethylene glycol are used as raw materials, a low molecular weight product is obtained by transesterification, and then a polymer is obtained by polycondensation reaction using antimony trioxide or a titanium compound as a catalyst. Here, the reaction proceeds even without a catalyst, but the transesterification usually proceeds using a compound such as manganese, calcium, magnesium, zinc, lithium, titanium as a catalyst, and the transesterification reaction is carried out. After the completion of the reaction, a phosphorus compound may be added for the purpose of inactivating the catalyst used in the reaction.

  When the polyester constituting the film contains inert particles, it is preferable to disperse the inert particles in a predetermined proportion in the form of a slurry in ethylene glycol and add this ethylene glycol during polymerization. When adding inert particles, for example, water sol or alcohol sol particles obtained at the time of synthesis of the inert particles are added without drying once, the dispersibility of the particles is good. It is also effective to mix an aqueous slurry of inert particles directly with PET pellets and knead them into PET using a vented biaxial kneading extruder. As a method for adjusting the content of the inert particles, a master pellet of a high concentration of inert particles is prepared by the above method, and this is diluted with PET that does not substantially contain inert particles during film formation. A method for adjusting the content of the active particles is effective.

  As a method of mixing PET, aromatic polyetherketone (C) and polyetherimide (B), before melt extrusion, (1) polyetherimide (B) and melting point of aromatic polyetherketone (C) Preferred is a two-stage melt kneading in which the mixture is pre-melt kneaded (pelletized), and then the mixture of the composition obtained in (2) and (1) and PET is pre-melt kneaded (pelletized) into a master chip. Is done. In that case, a method of pre-kneading into a master chip using a high-shear mixer with high shear stress such as a twin screw extruder is preferred. When mixing with a twin screw extruder, from the viewpoint of reducing poor dispersion, a screw equipped with a triple twin screw type or a double twin screw type is preferable. By using two-stage melt kneading, it becomes easy to mix the aromatic polyether ketone (C), which cannot be mixed with PET, into the biaxially oriented polyester film of the present invention via the polyetherimide (B). In the present invention, polyetherimide (B) and aromatic polyetherketone (C) are mixed in the first kneading. It is preferable to prepare a master chip in which polyetherimide (B) is mixed at a high concentration in the melting temperature range of 300 to 400 ° C, preferably in the range of 340 to 400 ° C, and in particular, polyetherimide (B) / The mixing mass ratio of the aromatic polyether ketone (C) is preferably 50/50 to 90/10, and more preferably 60/40 to 80/20. Further, the composition obtained by the first stage kneading is mixed with PET by the second stage kneading. The blend chip obtained by the first stage kneading is dried under reduced pressure at 150 ° C. for 3 hours to carry out the second stage kneading. As the polyester used in the second stage of kneading, PET / (polyetherimide (B) and aromatic polyetherketone (C The blending mass ratio of the blend composition) is preferably 60/40 to 90/10, more preferably 70/30 to 80/20. In this method, the shear stress is increased by high-viscosity PET to increase the mixing force, and the mixing amount of the aromatic polyether ketone (C) is adjusted to prevent the melt viscosity from becoming extremely high. This is important because it can reduce the coarse foreign matter and can prevent a decrease in stretchability and can prevent the surface roughness from becoming extremely large.

  On the other hand, a composition raw material in which a mixture of PET and polyetherimide (B) is premelted and kneaded (pelletized) into a master chip is also prepared, and the content of polyetherimide can be adjusted as appropriate. In addition, when mixing PET and polyetherimide (B), there is a difference in melt viscosity. Therefore, it is preferable to prepare a master chip in which polyimide resin is mixed at a high concentration. In particular, PET / polyetherimide (B) ) Is preferably 10/90 to 70/30, more preferably 30/70 to 60/40.

  When forming into a film, the mixed master chip raw material may be put into a normal single-screw extruder to form a melt, or may be directly sheeted without being converted into a master chip in a state where high shear is applied. Good.

  Moreover, when pelletizing with a twin-screw extruder, it is preferable to make screw rotation into 100-500 rotation / min, More preferably, it is the range of 200-400 rotation / min. Even when the screw rotation speed is set within a preferable range, high shear stress is easily applied, and defective dispersion is easily reduced. Further, 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, in order to increase the kneading force, it is preferable to provide a kneading part by a kneading paddle or the like, 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 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 by a single-screw or biaxial extruder may be used. Further, a method using a supercritical fluid described in Journal of Plastics Processing Society of Japan, “Molding”, Vol. 15, No. 6, pp. 382 to 385 (2003) can be preferably exemplified.

  Next, the obtained PET pellets are dried under reduced pressure at 180 ° C. for 3 hours or more, and then supplied to an extruder heated to 270 to 320 ° C. under a nitrogen stream or under reduced pressure so that the intrinsic viscosity does not decrease. The film is extruded from a slit-shaped die and cooled on a casting roll to obtain an unstretched film. At this time, 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 altered polymers. Moreover, you may provide a gear pump as needed in order to improve fixed_quantity | feed_rate supply property. When laminating films, a plurality of different polymers are melt laminated using two or more extruders and manifolds or merging blocks.

  Next, for example, it leads to a simultaneous biaxial stretching tenter and biaxial stretching is performed simultaneously in the longitudinal and width directions. The stretching speed is preferably 100 to 20,000% / min in both the longitudinal and width directions. More preferably, it is 500-10,000% / min, More preferably, it is 2,000-7,000% / min. When the stretching speed is less than 100% / min, the film is exposed to heat for a long time. In particular, the edge portion is crystallized to cause stretching breakage, and the film-forming property is lowered. However, the Young's modulus of the produced film may be lowered. On the other hand, if it is higher than 20,000% / min, entanglement between molecules is likely to occur at the time of stretching, and the stretchability may be lowered, making it difficult to stretch at a high magnification.

  The stretching temperature varies depending on the type of polymer used, but can be determined using the glass transition temperature Tg of the unstretched film as a guide. The temperature in the first stretching step in each of the longitudinal direction and the width direction is preferably in the range of Tg to Tg + 30 ° C, more preferably Tg + 5 ° C to Tg + 20 ° C. When the stretching temperature is lower than the above range, film tearing frequently occurs and the productivity is lowered, or the redrawing property is lowered, and it may be difficult to stably stretch at a high magnification. In addition, when the stretching temperature is higher than the above range, particularly the edge portion is crystallized to cause stretching breakage, the film forming property is lowered, or the Young's modulus of the produced film is lowered without sufficient molecular orientation. Sometimes.

  And when the manufacturing process of a polyester film includes multistage stretching, that is, a re-stretching process, the first stage stretching temperature is as described above, but the second stage stretching temperature is preferably Tg + 40 ° C. to Tg + 120 ° C., more preferably. Is Tg + 60 ° C. to Tg + 100 ° C. When the stretching temperature is out of the above range, the film is frequently broken due to insufficient heat or crystallization, resulting in a decrease in productivity or a decrease in strength due to insufficient orientation. There is.

  On the other hand, the stretching ratio varies depending on the type of polymer used and the stretching temperature, and also in the case of multistage stretching, but the total area stretching ratio (total longitudinal stretching ratio × total transverse stretching ratio) is in the range of 20 to 40 times. It is preferable to do so. More preferably, it is 25 to 35 times. The total draw ratio in one direction of the longitudinal direction and the width direction is preferably 2.5 to 8 times, and more preferably 3 to 7 times. If the draw ratio is smaller than the above range, uneven drawing or the like may occur and the processability of the film may be reduced. Moreover, when a draw ratio is larger than the said range, stretch breaks occur frequently and productivity may fall.

  When extending | stretching by multiple steps | paragraphs regarding each direction, 2-4 times are preferable, and, as for the draw ratio in each of the 1st step | paragraph's longitudinal direction and the width direction, More preferably, it is 2.5-3 times. Moreover, the preferable area draw ratio in the first stage is 4 to 16 times, and more preferably 6 to 10 times. These stretch ratio values are particularly suitable when the simultaneous biaxial stretching method is employed, but can also be applied to the sequential biaxial stretching method. In the film structure of the present invention, there are knots mainly composed of the crystalline thermoplastic resin (C), so that stress rises easily at a low magnification in the stress strain curve. Therefore, if the first stage draw ratio is too high, the tension and crystallization of the molecular chain may proceed excessively and the second stage stretch may not be performed. It is preferable to set to.

  Moreover, 1.05-2.5 times are preferable and, as for the draw ratio in one direction in the case of performing redrawing, More preferably, it is 1.2-1.8 times. The area stretching ratio for re-stretching is preferably 1.4 to 4 times, more preferably 1.9 to 3 times.

  Subsequently, this stretched film is heat-treated under tension or while relaxing in the width direction. Of the heat treatment conditions, the heat treatment temperature is preferably 155 to 205 ° C., and the heat treatment time is preferably 0.5 to 10 seconds. It is preferable to perform the heat treatment process in two or more stages. In particular, the heat treatment temperature of the first stage is preferably set to 180 to 205 ° C., more preferably 180 to 195 ° C. The temperature is lower than that of the first stage, preferably 155 to 180 ° C, more preferably 155 to 170 ° C. Further, it is more preferable that only the second heat treatment step is relaxed at a relaxation rate of 1 to 5% in the width direction. According to the multi-step heat treatment process described above, molecular chain relaxation effectively proceeds while increasing dimensional stability against changes in Young's modulus and temperature / humidity, so that it is stored under a load that is an effect of the present invention. It becomes easy to improve the storage stability showing the dimensional change when doing.

  Thereafter, the film edge is removed and wound on a roll. In order to further enhance the effects of dimensional stability and storage stability of the present invention, it is also preferable to heat-treat in a hot air oven or the like in a state where the film is wound around a core (roll film). The atmospheric temperature of the heat treatment can be determined based on the glass transition temperature (Tg) of the biaxially stretched film, and is in the range of (Tg-80) to (Tg-30) ° C., more preferably (Tg-75). ) To (Tg-35) ° C., more preferably (Tg-70) to (Tg-40) ° C. A preferable treatment time is in the range of 10 to 360 hours, more preferably in the range of 24 to 240 hours, and still more preferably in the range of 72 to 168 hours. It is preferable that the total time of the heat treatment of the roll film performed in multiple stages is within the above range.

  Next, a method for manufacturing a magnetic recording medium will be described. The magnetic recording medium support (biaxially oriented polyester film) obtained as described above is slit into, for example, a width of 0.1 to 3 m, and conveyed at a speed of 20 to 300 m / min and a tension of 50 to 300 N / m. On the other hand, a magnetic coating and a non-magnetic coating are applied on one surface (A) by an extrusion coater. A magnetic paint is applied to the upper layer with a thickness of 0.1 to 0.3 μm, and a nonmagnetic paint is applied to the lower layer with a thickness of 0.5 to 1.5 μm. Thereafter, the support coated with the magnetic coating material and the nonmagnetic coating material is magnetically oriented and dried at a temperature of 80 to 130 ° C. Next, a back coat is applied to the opposite surface (B) with a thickness of 0.3 to 0.8 μm, and after calendar treatment, it is wound up. The calendering is performed using a small test calender (steel / nylon roll, 5 stages) at a temperature of 70 to 120 ° C. and a linear pressure of 0.5 to 5 kN / cm. Thereafter, the film is aged at 60 to 80 ° C. for 24 to 72 hours, slit to a width of 1/2 inch (1.27 cm), and a pancake is produced. Next, a specific length from this pancake is incorporated into a cassette to obtain a cassette tape type magnetic recording medium.

Here, examples of the composition of the magnetic paint include the following compositions.
(Composition of magnetic paint)
Ferromagnetic metal powder: 100 parts by weight Modified vinyl chloride copolymer: 10 parts by weight Modified polyurethane: 10 parts by weight Polyisocyanate: 5 parts by weight 2-ethylhexyl oleate: 1.5 parts by weight Palmitic acid: 1 Mass parts-Carbon black: 1 part by mass-Alumina: 10 parts by mass-Methyl ethyl ketone: 75 parts by mass-Cyclohexanone: 75 parts by mass-Toluene: 75 parts by mass (composition of back coat)
Carbon black (average particle size 20 nm): 95 parts by mass Carbon black (average particle size 280 nm): 10 parts by mass Alumina: 0.1 parts by mass Modified polyurethane: 20 parts by mass Modified vinyl chloride copolymer: 30 Mass parts: Cyclohexanone: 200 parts by mass Methyl ethyl ketone: 300 parts by mass Toluene: 100 parts by mass Magnetic recording media are, for example, data recording applications, specifically computer data backup applications (for example, linear tape recording media (LTO4 And LTO5))) and digital image recording applications such as video.

(Methods for measuring physical properties and methods for evaluating effects)
The characteristic value measurement method and effect evaluation method in the present invention are as follows.

(1) Average dispersion diameter of dispersed phase The film is (a) parallel to the longitudinal direction and perpendicular to the film surface, (b) parallel to the width direction and perpendicular to the film surface, and (c) parallel to the film surface. The sample was cut in various directions, 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 type, 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 thickness (la) and the maximum length (lb) in the film thickness direction of each dispersed phase appearing on the cut surface of (a), and the maximum thickness (lb) in the longitudinal direction of each disperse phase appearing on the cut surface of (a). The maximum length (lc), the maximum length (ld) in the width direction, the maximum length (le) in the film longitudinal direction and the maximum length (lf) in the width direction 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 (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). By manipulating the tone curve, brightness and contrast are adjusted, and then 100 points of the equivalent circle diameter of the high contrast component of the image obtained using a Gaussian filter are randomly observed, and the average value is taken as the average dispersion diameter. did. Here, when using a negative photograph of a transmission electron microscope photograph, Leafscan 45 Plug-In manufactured by Nippon Cytex Co., Ltd. is used as the scanner, and when using a positive transmission electron microscope, the scanner is used as the scanner. GT-7600S manufactured by Seiko Epson is used, and any of them can obtain an equivalent value. 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)
(2) Temperature expansion coefficient It measures on the following conditions with respect to the width direction of a film, and let the average value of three measurement results be the temperature expansion coefficient in this 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 a temperature of 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)}
(3) Humidity expansion coefficient It measures on the following conditions with respect to the width direction of a film, and makes the average value of three measurement results the humidity expansion coefficient in this 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)}
(4) Young's modulus The Young's modulus of the film 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.

(5) Centerline average roughness Ra
The centerline average roughness Ra of the film is measured under the following conditions using a stylus type surface roughness meter. Measurement is performed by scanning 20 times in the film width direction, and the average value of the obtained results is defined as the centerline average roughness Ra in the present invention.

・ Measuring device: High precision thin film level difference measuring device ET-10 manufactured by Kosaka Laboratory
・ Tip tip radius: 0.5μm
-Stylus load: 5mg
・ Measurement length: 1mm
・ Cutoff value: 0.08mm
・ Measurement environment: Temperature 23 ℃ Humidity 65% RH
(6) Glass transition temperature (Tg)
Specific heat is measured with the following equipment and conditions, and determined according to JIS K7121 (1987).

・ Device: 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 (22 mg)
Reference container: Aluminum open container (18mg)
The glass transition temperature is calculated by the following formula.

Glass transition temperature = (extrapolated glass transition start temperature + extrapolated glass transition end temperature) / 2
(7) Melting point (Tm)
Using a DSC (RDC220) manufactured by Seiko Instruments Inc. as a differential scanning calorimeter and a disk station (SSC / 5200) manufactured by Seiko Instruments Inc. as a data analysis device, about 5 mg of a sample is melted and held at 300 ° C. for 5 minutes on an aluminum tray, and rapidly cooled and solidified. After that, 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 the polyester (A) can be detected by the above method.

  As a method for detecting the melting point of the crystalline thermoplastic resin (C), a micro thermal analysis apparatus (“μ-TA apparatus” manufactured by TA 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. The measurement is performed by exposing the base film by an oblique cutting method, etc., contacting the V-shaped detection part of the sensor, and increasing from a normal temperature to a temperature of 400 ° C. under conditions of a heating rate of 10 ° C./second and an indentation strength of 20 nA. I did it.

(8) Width Dimension Measurement A film slit to a width of 1 m is conveyed with a tension of 200 N, and a magnetic coating and a non-magnetic coating having the following composition are applied to one surface (A) of the support with 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 at a temperature of 85 ° C. and a linear pressure of 2.0 × 10 ⁵ N / m with a small test calender device (steel / nylon roll, 5 steps). Wind up after calendaring. 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 nonmagnetic 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 (composition of back coat)
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 (l _A , l _B ) 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.

By measuring the lapse of 24 hours after _{l A} in A conditions, measuring the _{l B} after a lapse of 24 hours then B conditions. 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 dimensional change rate (ppm) = 10 ⁶ × ((l _B -l _A ) / l _A )
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. (9) Storage stability As in (8) above, the tape is taken out from the produced cassette tape cartridge, and the following two conditions are satisfied. Measure the width dimensions (l _C , l _D ) respectively, and calculate the dimensional change rate by the following equation.

  Specifically, dimensional stability is evaluated according to the following criteria.

After 24 hours at 23 ° C. and 65% RH, 1 _C is measured. After storing the cartridge for 10 days in an environment of 40 ° C. and 20% RH, 1 _D 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 × (| l _C −l _D | / l _C )
○: 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 (10) Running durability A cassette tape is prepared in the same manner as in (8) 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 0.0 × 10 ⁻⁴ ×: Error rate is 1.0 × 10 ⁻⁴ or more (11) Electromagnetic conversion characteristics A cassette tape is produced in the same manner as in (8) above, and a reel-to-reel tester is used for C / N measurement. And a commercially available MR head was 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.

  Based on the following examples, embodiments of the present invention will be described. Here, polyethylene terephthalate is referred to as PET, and poly (ethylene-2,6-naphthalenedicarboxylate (polyethylene-2,6-naphthalate)) is referred to as PEN.

Example 1
194 parts by mass of dimethyl terephthalate and 124 parts by mass of ethylene glycol were charged into a transesterification reactor, and the contents were heated to 140 ° C. and dissolved. Thereafter, 0.3 parts by mass of magnesium acetate tetrahydrate and 0.05 parts by mass of antimony trioxide were added while stirring the contents, and a transesterification reaction was performed while distilling methanol at 140 to 230 ° C. Next, 1 part by mass of a 5% by mass ethylene glycol solution of trimethyl phosphate (0.05 parts by mass as trimethyl phosphate) was added.

  Addition of trimethyl phosphoric acid in ethylene glycol reduces the temperature of the reaction contents. Therefore, stirring was continued until the temperature of the reaction contents returned to 230 ° C. while distilling excess ethylene glycol. In this way, after the temperature of the reaction contents in the transesterification reactor reached 230 ° C., the reaction contents were transferred to the polymerization apparatus.

  After the transition, the reaction system was gradually heated from 230 ° C. to 290 ° C. and the pressure was reduced to 0.1 kPa. The time to reach the final temperature and final pressure was both 60 minutes. After reaching the final temperature and the final pressure, the reaction was carried out for 2 hours (3 hours after the start of polymerization), and the agitation torque of the polymerization apparatus was a predetermined value (specific values differ depending on the specifications of the polymerization apparatus. The value indicated by polyethylene terephthalate having an intrinsic viscosity of 0.62 was a predetermined value). Therefore, the reaction system was purged with nitrogen and returned to normal pressure to stop the polycondensation reaction, discharged into cold water in a strand form, and immediately cut to obtain polyethylene terephthalate PET pellets (X) having an intrinsic viscosity of 0.62.

  The obtained PET pellet (X) was 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 to obtain PET pellets with an intrinsic viscosity of 1.0 (Y )

  Bent type twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading parts heated to 350 ° C. (Nippon Steel Works, screw diameter 30 mm, screw length / screw diameter = 45.5) Supplied with 70% by mass of pellets of polyetherimide (PEI) “Utem 1040” manufactured by SABIC Innovative Plastics and 30% by mass of pellets of polyether ether ketone (PEEK) “Victrex 90G” manufactured by Victrex After melt extrusion at several 300 revolutions / minute and discharging into a strand shape, cooling with water at a temperature of 10 ° C., cutting was performed immediately to prepare a blend chip (I).

  Next, a co-rotating vent type twin-screw kneading extruder provided with three kneading paddle kneading sections heated to a temperature of 300 ° C. (manufactured by Nippon Steel Works, screw diameter 30 mm, screw length / screw diameter = 45 5) is supplied with 70% by mass of the obtained PET pellet (Y) and 30% by mass of the blended chip (I), melt-extruded at a screw rotation speed of 300 revolutions / minute, and discharged into a strand shape at a temperature of 25 After cooling with water at 0 ° C., it was immediately cut to produce a blend chip (II).

  On the other hand, a vented twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading sections heated to a temperature of 300 ° C. (manufactured by Nippon Steel Works, screw diameter 30 mm, screw length / screw diameter = 45. 5) 50% by mass of the obtained PET pellet (X) and 50% by mass of polyetherimide “Ultem 1010” pellets manufactured by SABIC Innovative Plastics Co., Ltd. are melt-extruded at a screw rotation speed of 300 revolutions / min. Then, after cooling with water at a temperature of 25 ° C., it was immediately cut to produce a blend chip (III).

  Further, in the same direction rotation type bent type biaxial kneading extruder heated to 280 ° C., 98 mass parts of PET pellets (X) and 20 mass% water slurry of spherical crosslinked polystyrene particles having an average diameter of 0.3 μm were added. Mass parts (2 parts by mass as spherical cross-linked polystyrene) are supplied, the vent hole is maintained at a reduced pressure of 1 kPa or less, moisture is removed, and the intrinsic viscosity of 0.2 mass% of spherical cross-linked polystyrene particles having an average diameter of 0.3 μm is contained. 62 PET pellets (Z-1) were obtained.

  Further, the average diameter was determined in the same manner as the method for producing PET pellets (Z-1) except that spherical crosslinked polystyrene particles having an average diameter of 0.8 μm were used instead of spherical crosslinked polystyrene particles having an average diameter of 0.3 μm. An PET pellet (Z-2) having an intrinsic viscosity of 0.62 containing 2% by mass of 0.8 μm spherical crosslinked polystyrene particles was obtained.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 85.3 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), and blended chips ( II) 5.6 parts by mass of blend chip (III) and 7.6 parts by mass of blended chip (III) were supplied after drying under reduced pressure at 180 ° C. for 3 hours and the same was heated to 295 ° C. 8 parts by mass, 7 parts by mass of PET pellets (Z-1), 1 part by mass of PET pellets (Z-2), 5.6 parts by mass of blend chip (II) and 7.6 parts by mass of blend chip (III) It supplied after drying under reduced pressure at 3 degreeC for 3 hours. In order to stack two layers, they are merged in a T-die (lamination ratio E1 (A side) / E2 (B side) = 5/1) and adhered while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. The mixture was cooled and solidified to produce a laminated unstretched film containing 5% by mass of PEI and 0.5% by mass of PEEK. In addition, the glass transition temperature (Tg) of the unstretched film was 90 degreeC.

  This laminated unstretched film was biaxially stretched using a simultaneous biaxial tenter having a linear motor clip. Simultaneously in the longitudinal direction and the width direction, the film was stretched 2.8 times × 2.8 times at a temperature of 105 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was re-stretched 1.5 × 1.8 times at the same time in the longitudinal direction and the width direction at a temperature of 180 ° C. Thereafter, after heat treatment at 200 ° C. for 5 seconds, a relaxation treatment of 2% in the width direction was performed at 160 ° C. to produce a biaxially oriented polyester film having a thickness of 5 μm. The biaxially stretched film had a glass transition temperature (Tg) of 115 ° C. and a melting point (Tm) of 255 ° C.

  When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, it had excellent dimensional stability, storage stability, and electromagnetic conversion characteristics when used as a magnetic tape. .

(Example 2)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (II) and blend chip (III) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 82.1 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( II) 11.1 parts by mass and 5.3 parts by mass of the blended chip (III) were dried after drying under reduced pressure at 180 ° C. for 3 hours and supplied to the extruder E2, which was also heated to 295 ° C., and the PET pellet (X) 75 .6 parts by mass, 7 parts by mass of PET pellets (Z-1), 1 part by mass of PET pellets (Z-2), 11.1 parts by mass of blend chip (II) and 5.3 parts by mass of blend chip (III) 180 It supplied after drying under reduced pressure at 3 degreeC for 3 hours. In order to stack two layers, they are merged in a T-die (lamination ratio E1 (A side) / E2 (B side) = 5/1) and adhered while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. The mixture was cooled and solidified to produce a laminated unstretched film containing 5% by mass of PEI and 1% by mass of PEEK. In addition, the glass transition temperature (Tg) of the unstretched film was 90 degreeC.

  The obtained unstretched film was stretched in the same manner as in Example 1 to obtain a biaxially stretched polyester film. When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, it had excellent dimensional stability, storage stability, and electromagnetic conversion characteristics when used as a magnetic tape. .

(Example 3)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (II) and blend chip (III) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 72.1 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( II) 11.1 parts by mass and 15.3 parts by mass of blended chip (III) were dried at 180 ° C. under reduced pressure for 3 hours and then supplied to the extruder E2, which was also heated to 295 ° C., and the PET pellet (X) 65 .6 parts by mass, 7 parts by mass of PET pellets (Z-1), 1 part by mass of PET pellets (Z-2), 11.1 parts by mass of blend chip (II) and 15.3 parts by mass of blend chip (III) 180 It supplied after drying under reduced pressure at 3 degreeC for 3 hours. In order to stack two layers, they are merged in a T-die (lamination ratio E1 (A side) / E2 (B side) = 5/1) and adhered while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. The mixture was cooled and solidified to produce a laminated unstretched film containing 10% by mass of PEI and 1% by mass of PEEK. The glass transition temperature (Tg) of the unstretched film was 95 ° C.

  This laminated unstretched film was biaxially stretched using a simultaneous biaxial tenter having a linear motor clip. Simultaneously in the longitudinal direction and the width direction, the film was stretched 2.8 times × 2.8 times at a temperature of 110 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was re-stretched 1.5 × 1.8 times at the same time in the longitudinal direction and the width direction at a temperature of 180 ° C. Thereafter, after heat treatment at 200 ° C. for 5 seconds, a relaxation treatment of 2% in the width direction was performed at 160 ° C. to produce a biaxially oriented polyester film having a thickness of 5 μm. The biaxially stretched film had a glass transition temperature (Tg) of 120 ° C. and a melting point (Tm) of 255 ° C.

  When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, it had excellent dimensional stability, storage stability, and electromagnetic conversion characteristics when used as a magnetic tape. .

Example 4
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (II) and blend chip (III) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 65.6 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( II) 22.2 parts by mass and 10.7 parts by mass of blended chip (III) were dried at 180 ° C. under reduced pressure for 3 hours and then supplied to the extruder E2, which was also heated to 295 ° C., and the PET pellet (X) 59 1 part by weight, 7 parts by weight of PET pellets (Z-1), 1 part by weight of PET pellets (Z-2), 22.2 parts by weight of blend chip (II) and 10.7 parts by weight of blend chip (III) It supplied after drying under reduced pressure at 3 degreeC for 3 hours. In order to stack two layers, they are merged in a T-die (lamination ratio E1 (A side) / E2 (B side) = 5/1) and adhered while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. The mixture was cooled and solidified to produce a laminated unstretched film containing 10% by mass of PEI and 2% by mass of PEEK. The glass transition temperature (Tg) of the unstretched film was 95 ° C.

  The obtained unstretched film was stretched in the same manner as in Example 3 to obtain a biaxially stretched polyester film. When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, it had excellent dimensional stability, storage stability, and electromagnetic conversion characteristics when used as a magnetic tape. .

(Example 5)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (II) and blend chip (III) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 62.4 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( II) 27.8 parts by mass of blend chip (III) and 8.3 parts by mass of blended chip (III) were dried at 180 ° C. for 3 hours after drying under reduced pressure and supplied to the extruder E2 which was also heated to 295 ° C. 0.9 parts by weight, 7 parts by weight of PET pellets (Z-1), 1 part by weight of PET pellets (Z-2), 27.8 parts by weight of blend chip (II) and 8.3 parts by weight of blend chip (III) are 180 parts. It supplied after drying under reduced pressure at 3 degreeC for 3 hours. In order to stack two layers, they are merged in a T-die (lamination ratio E1 (A side) / E2 (B side) = 5/1) and adhered while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. The mixture was cooled and solidified to produce a laminated unstretched film containing 10% by mass of PEI and 2.5% by mass of PEEK. The glass transition temperature (Tg) of the unstretched film was 95 ° C.

  The obtained unstretched film was stretched in the same manner as in Example 3 to obtain a biaxially stretched polyester film. When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, it had excellent dimensional stability, storage stability, and electromagnetic conversion characteristics when used as a magnetic tape. .

(Example 6)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (II) and blend chip (III) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 42.7 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( II) 44.4 parts by mass and 11.4 parts by mass of blended chip (III) were dried at 180 ° C. under reduced pressure for 3 hours and then supplied to the extruder E2, which was also heated to 295 ° C., and the PET pellet (X) 36 2 parts by weight, 7 parts by weight of PET pellets (Z-1), 1 part by weight of PET pellets (Z-2), 44.4 parts by weight of blend chip (II) and 11.4 parts by weight of blend chip (III) 180 It supplied after drying under reduced pressure at 3 degreeC for 3 hours. In order to stack two layers, they are merged in a T-die (lamination ratio E1 (A side) / E2 (B side) = 5/1) and adhered while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. The solution was solidified by cooling to prepare a laminated unstretched film containing 15% by mass of PEI and 4% by mass of PEEK. In addition, the glass transition temperature (Tg) of the unstretched film was 100 degreeC.

  This laminated unstretched film was biaxially stretched using a simultaneous biaxial tenter having a linear motor clip. Simultaneously in the longitudinal direction and the width direction, the film was stretched 2.8 times × 2.8 times at a temperature of 115 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was redrawn at a temperature of 190 ° C. at 1.5 × 1.8 times in the longitudinal direction and the width direction simultaneously. Thereafter, after heat treatment at 200 ° C. for 5 seconds, a relaxation treatment of 2% in the width direction was performed at 160 ° C. to produce a biaxially oriented polyester film having a thickness of 5 μm. The biaxially stretched film had a glass transition temperature (Tg) of 125 ° C. and a melting point (Tm) of 255 ° C.

  When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, it had excellent dimensional stability, storage stability, and electromagnetic conversion characteristics when used as a magnetic tape. .

(Example 7)
The laminated unstretched film obtained in Example 1 was biaxially stretched using a simultaneous biaxial tenter having a linear motor clip. Simultaneously in the longitudinal direction and the width direction, the film was stretched 2.8 times × 2.8 times at a temperature of 105 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was re-stretched 1.6 × 1.6 times at the same time in the longitudinal direction and the width direction at a temperature of 180 ° C. Thereafter, after heat treatment at 200 ° C. for 5 seconds, a relaxation treatment of 2% in the width direction was performed at 160 ° C. to produce a biaxially oriented polyester film having a thickness of 5 μm. The biaxially stretched film had a glass transition temperature (Tg) of 115 ° C. and a melting point (Tm) of 255 ° C.

  When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, it had sufficient characteristics for dimensional stability, storage stability, and electromagnetic conversion characteristics when used as a magnetic tape. .

(Example 8)
The laminated unstretched film obtained in Example 1 was biaxially stretched using a simultaneous biaxial tenter having a linear motor clip. Simultaneously in the longitudinal direction and the width direction, the film was stretched 2.8 times × 2.8 times at a temperature of 105 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was redrawn at a temperature of 180 ° C. in the longitudinal direction and the width direction simultaneously at 1.8 × 1.5 times. Thereafter, after heat treatment at 200 ° C. for 5 seconds, a relaxation treatment of 2% in the width direction was performed at 160 ° C. to produce a biaxially oriented polyester film having a thickness of 5 μm. The biaxially stretched film had a glass transition temperature (Tg) of 115 ° C. and a melting point (Tm) of 255 ° C.

  When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, it had sufficient characteristics for dimensional stability, storage stability, and electromagnetic conversion characteristics when used as a magnetic tape. .

Example 9
Bent type twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading parts heated to a temperature of 380 ° C. (manufactured by Nippon Steel Works, screw diameter 30 mm, screw length / screw diameter = 45.5) 70 mass% of pellets of polyetherimide (PEI) “Ultem 1040” manufactured by SABIC Innovative Plastics Co., Ltd. and 30 mass% of pellets of thermoplastic polyimide (TPI) “Aurum PD450” manufactured by Mitsui Chemicals Co., Ltd. are supplied. After melt extrusion at 300 rpm, the strand was discharged, cooled with water at a temperature of 10 ° C., and immediately cut to prepare a blend chip. A biaxially stretched polyester film was obtained in the same manner as in Example 1 except that thermoplastic polyimide “Aurum” (manufactured by Mitsui Chemicals) was used in addition to polyether ether ketone (PEEK). When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, it had sufficient characteristics for dimensional stability, storage stability, and electromagnetic conversion characteristics when used as a magnetic tape. .

(Example 10)
To a mixture of 100 parts by mass of dimethyl 2,6-naphthalenedicarboxylate and 60 parts by mass of ethylene glycol, 0.03 parts by mass of manganese acetate tetrahydrate salt is added and gradually increased from a temperature of 150 ° C. to a temperature of 240 ° C. The transesterification was carried out while raising the temperature. In the middle, 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, and 0.023 parts by mass of trimethyl phosphoric acid was added. Next, the reaction product is transferred to a polymerization apparatus, heated to a temperature of 290 ° C., subjected to a polycondensation reaction under a high vacuum of 30 Pa, and the stirring torque of the polymerization apparatus is a predetermined value (specifically depending on the specifications of the polymerization apparatus). Although this value was different, the value indicated by polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.65 in this polymerization apparatus was a predetermined value). Therefore, the reaction system was purged with nitrogen and returned to normal pressure to stop the polycondensation reaction, discharged into cold water in the form of a strand, and immediately cut into PEN (polyethylene-2,6-naphthalate) pellets (P) with an intrinsic viscosity of 0.65. Got.

  The obtained PEN pellet (P) was dried under reduced pressure at 160 ° C. for 4 hours, and then subjected to a solid-phase polymerization reaction at 220 ° C. for 8 hours at a reduced pressure of 133 Pa or less to obtain PEN pellets (Q )

  Bent-type twin-screw kneading and extruding machine of the same direction rotation type provided with three kneading paddle kneading parts heated to a temperature of 300 ° C. (manufactured by Nippon Steel Works, screw diameter 30 mm, screw length / screw diameter = 45.5) 70 mass% of the obtained PEN pellet (Q) and 30 mass% of the blend chip (I) obtained in Example 1 are supplied, melt-extruded at a screw rotation speed of 300 revolutions / minute, and discharged in the form of a strand. After cooling with water at a temperature of 25 ° C., it was immediately cut to produce a blend chip (IV).

  On the other hand, a vented twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading sections heated to a temperature of 300 ° C. (manufactured by Nippon Steel Works, screw diameter 30 mm, screw length / screw diameter = 45. 5) 50% by mass of the obtained PEN pellets (P) and 50% by mass of pellets of polyetherimide “Ultem 1010” manufactured by SABIC Innovative Plastics Co., Ltd. are melt-extruded at a screw rotation speed of 300 revolutions / min. After being discharged in a shape and cooled with water at a temperature of 25 ° C., it was immediately cut to produce a blend chip (V).

  Further, a bent-type twin-screw kneading extruder of the same direction rotating type heated to 280 ° C. was charged with 98 parts by mass of PEN pellets (P) and 20% by mass of 10 mass% water slurry of spherical crosslinked polystyrene particles having an average diameter of 0.3 μm. Mass parts (2 parts by mass as spherical cross-linked polystyrene) are supplied, the vent hole is maintained at a reduced pressure of 1 kPa or less, moisture is removed, and the intrinsic viscosity of 2% by mass of spherical cross-linked polystyrene particles having an average diameter of 0.3 μm is contained. 62 PEN pellets (R-1) were obtained.

  Further, the average diameter was determined in the same manner as the method for producing the PEN pellet (R-1) except that spherical crosslinked polystyrene particles having an average diameter of 0.8 μm were used instead of spherical crosslinked polystyrene particles having an average diameter of 0.3 μm. A PEN pellet (R-2) having an intrinsic viscosity of 0.62 containing 2% by mass of 0.8 μm spherical crosslinked polystyrene particles was obtained.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 85.3 parts by mass of PEN pellets (P), 1.5 parts by mass of PEN pellets (R-1), blended chips ( IV) 5.6 parts by mass and 7.6 parts by mass of the blended chip (V) were dried at 180 ° C. under reduced pressure for 3 hours and then supplied to the extruder E2, which was also heated to 295 ° C., and the PEN pellet (P) 78 8 parts by mass, 7 parts by mass of PEN pellet (R-1), 1 part by mass of PEN pellet (R-2), 5.6 parts by mass of blend chip (IV) and 7.6 parts by mass of blend chip (V) It supplied after drying under reduced pressure at 3 degreeC for 3 hours. In order to stack two layers, they are merged in a T-die (lamination ratio E1 (A side) / E2 (B side) = 5/1) and adhered while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. The mixture was cooled and solidified to produce a laminated unstretched film containing 5% by mass of PEI and 0.5% by mass of PEEK. The glass transition temperature (Tg) of the unstretched film was 120 ° C.

  Moreover, it biaxially stretched with respect to the obtained unstretched film using the simultaneous biaxial tenter which has a linear motor type clip. Simultaneously in the longitudinal direction and the width direction, the film was stretched 2.8 times × 2.8 times at a temperature of 135 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was re-stretched 1.6 × 2.0 times simultaneously in the longitudinal direction and the width direction at a temperature of 180 ° C. Thereafter, after heat treatment at 200 ° C. for 5 seconds, a relaxation treatment of 2% in the width direction was performed at 170 ° C. to produce a biaxially oriented polyester film having a thickness of 5 μm. The biaxially stretched film had a glass transition temperature (Tg) of 135 ° C. and a melting point (Tm) of 265 ° C.

  When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, when used as a magnetic tape, it had sufficient characteristics for dimensional stability and storage stability.

(Example 11)
The laminated unstretched film obtained in Example 1 was biaxially stretched using a simultaneous biaxial tenter having a linear motor clip. Simultaneously in the longitudinal direction and the width direction, the film was stretched 3.3 times × 3.3 times at a temperature of 105 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was re-stretched at 1.2 × 1.4 times in the longitudinal direction and the width direction at a temperature of 180 ° C. at the same time. Thereafter, after heat treatment at 200 ° C. for 5 seconds, a relaxation treatment of 2% in the width direction was performed at 160 ° C. to produce a biaxially oriented polyester film having a thickness of 5 μm. The biaxially stretched film had a glass transition temperature (Tg) of 115 ° C. and a melting point (Tm) of 255 ° C.

  When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, when used as a magnetic tape, it had sufficient characteristics for dimensional stability and storage stability.

Example 12
The laminated unstretched film obtained in Example 1 was biaxially stretched using a simultaneous biaxial tenter having a linear motor clip. Simultaneously in the longitudinal direction and the width direction, the film was stretched 2.8 times × 2.8 times at a temperature of 105 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was re-stretched 1.5 × 1.8 times at the same time in the longitudinal direction and the width direction at a temperature of 180 ° C. Then, after heat-treating at a temperature of 200 ° C. for 5 seconds, a biaxially oriented polyester film having a thickness of 5 μm was produced. The biaxially stretched film had a glass transition temperature (Tg) of 115 ° C. and a melting point (Tm) of 255 ° C.

  When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, when used as a magnetic tape, it had sufficient characteristics for dimensional stability and storage stability.

(Example 13)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that polysulfone (UDEL P3703NT11 manufactured by Solvay Advanced Polymer Co., Ltd.) (PSF) (glass transition temperature 190 ° C.) was used as the amorphous thermoplastic resin (B). . When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, when used as a magnetic tape, it had sufficient characteristics for dimensional stability and storage stability.

(Example 14)
Biaxial orientation in the same manner as in Example 1 except that polyethersulfone (REDEL A A-300 manufactured by Solvay Advanced Polymer Co., Ltd.) (PES) (glass transition temperature 225 ° C.) is used as the amorphous thermoplastic resin (B). A polyester film was obtained. When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, when used as a magnetic tape, it had sufficient characteristics for dimensional stability and storage stability.
(Example 15)
A laminated unstretched film was obtained in the same manner as in Example 1. The obtained unstretched film is stretched 3.0 times at a temperature of 105 ° C. in a longitudinal direction using a roll stretching machine, and further stretched 2.8 times at a temperature of 110 ° C. in the width direction using a tenter. did. Subsequently, the film was re-stretched 1.5 times at a temperature of 150 ° C. in two stages using a roll-type stretching machine, and re-stretched 1.8 times at 190 ° C. in the width direction using a tenter. Further, after heat treatment at a temperature of 200 ° C. for 10 seconds under a constant length, a relaxation treatment of 1% in the width direction was performed to obtain a biaxially oriented polyester film having a thickness of 5 μm. When the obtained biaxially stretched polyester film was evaluated, as shown in Tables 1 and 2, when used as a magnetic tape, it had sufficient characteristics for dimensional stability and storage stability.

(Comparative Example 1)
The PET pellet (X), PET pellet (Z-1), and PET pellet (Z-2) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 98.5 parts by mass of PET pellets (X) and 1.5 parts by mass of PET pellets (Z-1) at 180 ° C. In the extruder E2, which was supplied after drying under reduced pressure for 3 hours and heated to 295 ° C., 92 parts by mass of PET pellets (X), 7 parts by mass of PET pellets (Z-1), and PET pellets (Z-2) 1 The mass part was supplied after drying under reduced pressure at 180 ° C. for 3 hours. In order to stack two layers, they are merged in a T-die (lamination ratio E1 (A side) / E2 (B side) = 5/1) and adhered while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. After cooling and solidification, a laminated unstretched film was produced. In addition, the glass transition temperature (Tg) of the unstretched film was 80 degreeC.

  This laminated unstretched film was biaxially stretched using a simultaneous biaxial tenter having a linear motor clip. Simultaneously in the longitudinal direction and the width direction, the film was stretched 3.1 times 3.1 times at a temperature of 95 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was redrawn at a temperature of 160 ° C. simultaneously in the longitudinal direction and the width direction by 1.4 × 1.7 times. Thereafter, after heat treatment at 200 ° C. for 5 seconds, a relaxation treatment of 2% in the width direction was performed at 160 ° C. to produce a biaxially oriented polyester film having a thickness of 5 μm. The biaxially stretched film had a glass transition temperature (Tg) of 105 ° C. and a melting point (Tm) of 255 ° C. The results of evaluating the obtained biaxially stretched polyester film are shown in Tables 1 and 2.

(Comparative Example 2)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2) and blend chip (III) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 88.5 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1) and blended chips ( III) Extruder E2 that was supplied after drying 10 parts by weight at 180 ° C. under reduced pressure for 3 hours and also heated to 295 ° C. was supplied with 82 parts by weight of PET pellets (X) and 7 parts by weight of PET pellets (Z-1). Then, 1 part by mass of PET pellets (Z-2) and 10 parts by mass of blend chip (III) were dried at 180 ° C. under reduced pressure for 3 hours and then supplied. In order to stack two layers, they are merged in a T-die (lamination ratio E1 (A side) / E2 (B side) = 5/1) and adhered while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. It was cooled and solidified to produce a laminated unstretched film containing 5% by mass of PEI. In addition, the glass transition temperature (Tg) of the unstretched film was 90 degreeC.

  This laminated unstretched film was biaxially stretched using a simultaneous biaxial tenter having a linear motor clip. Simultaneously in the longitudinal direction and the width direction, the film was stretched 3.1 times by 3.1 times at a temperature of 105 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was redrawn at a temperature of 180 ° C. in the longitudinal direction and the width direction simultaneously by 1.4 × 1.7 times. Thereafter, after heat treatment at 200 ° C. for 5 seconds, a relaxation treatment of 2% in the width direction was performed at 160 ° C. to produce a biaxially oriented polyester film having a thickness of 5 μm. The biaxially stretched film had a glass transition temperature (Tg) of 115 ° C. and a melting point (Tm) of 255 ° C. The results of evaluating the obtained biaxially stretched polyester film are shown in Tables 1 and 2.

(Comparative Example 3)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (II) and blend chip (III) obtained in Example 1 are used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 29.8 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( II) 66.7 parts by mass and 2.0 parts by mass of blended chip (III) were dried after drying under reduced pressure at 180 ° C. for 3 hours and supplied to the extruder E2, which was also heated to 295 ° C., to PET pellet (X) 23 3 parts by mass, 7 parts by mass of PET pellets (Z-1), 1 part by mass of PET pellets (Z-2), 66.7 parts by mass of blend chip (II) and 2.0 parts by mass of blend chip (III) It supplied after drying under reduced pressure at 3 degreeC for 3 hours. In order to stack two layers, they are merged in a T-die (lamination ratio E1 (A side) / E2 (B side) = 5/1) and adhered while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. The mixture was cooled and solidified to produce a laminated unstretched film containing 15% by mass of PEI and 6% by mass of PEEK. In addition, the glass transition temperature (Tg) of the unstretched film was 100 degreeC.

  The obtained unstretched film was stretched in the same manner as in Example 4 to obtain a biaxially stretched polyester film. The results of evaluating the obtained biaxially stretched polyester film are shown in Tables 1 and 2.

(Comparative Example 4)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (II) and blend chip (III) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 88 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), and blended chips (II). 0.5 parts by weight and 10 parts by weight of the blended chip (III) were dried after drying at 180 ° C. for 3 hours under reduced pressure and supplied to the extruder E2, which was also heated to 295 ° C., and 81.5 parts by weight of PET pellets (X) , 7 parts by weight of PET pellets (Z-1), 1 part by weight of PET pellets (Z-2), 0.5 parts by weight of blend chip (II) and 10 parts by weight of blend chip (III) are dried under reduced pressure at 180 ° C. for 3 hours. It was supplied after. In order to stack two layers, they are merged in a T-die (lamination ratio E1 (A side) / E2 (B side) = 5/1) and adhered while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. The mixture was cooled and solidified to produce a laminated unstretched film containing 5% by mass of PEI and 0.05% by mass of PEEK. In addition, the glass transition temperature (Tg) of the unstretched film was 90 degreeC.

  The obtained unstretched film was stretched in the same manner as in Example 1 to obtain a biaxially stretched polyester film. The results of evaluating the obtained biaxially stretched polyester film are shown in Tables 1 and 2.

(Comparative Example 5)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (II) and blend chip (III) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 75.6 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( II) 22.2 parts by mass and 0.7 parts by mass of the blended chip (III) were dried at 180 ° C. for 3 hours under reduced pressure and supplied to the extruder E2 which was also heated to 295 ° C. 1 part by weight, 7 parts by weight of PET pellets (Z-1), 1 part by weight of PET pellets (Z-2), 22.2 parts by weight of blend chip (II) and 0.7 parts by weight of blend chip (III) It supplied after drying under reduced pressure at 3 degreeC for 3 hours. In order to stack two layers, they are merged in a T-die (lamination ratio E1 (A side) / E2 (B side) = 5/1) and adhered while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. The mixture was cooled and solidified to produce a laminated unstretched film containing 5% by mass of PEI and 2% by mass of PEEK. In addition, the glass transition temperature (Tg) of the unstretched film was 90 degreeC.

  The obtained unstretched film was stretched in the same manner as in Example 1 to obtain a biaxially stretched polyester film. The results of evaluating the obtained biaxially stretched polyester film are shown in Tables 1 and 2.

(Comparative Example 6)
Two-axis cubed type heated to 350 ° C by "Ultem 1010" (PEI) (75 mass%) manufactured by SABIC Innovative Plastics and polyether ether ketone (PEEK450P) (25 mass%) manufactured by Victrex The blend chip 1 was obtained by supplying to a vent type twin-screw kneading extruder equipped with a screw and melt-kneading with a residence time of 3 minutes. Thereafter, a polyethylene terephthalate (PET) chip (50% by mass) having an intrinsic viscosity of 0.85 in which the blend chip 1 (50% by mass) obtained here and 0.5% by mass of spherical silica particles having an average diameter of 0.07 μm were blended. The mixture was supplied to a twin-screw kneading extruder heated to 300 ° C., and melt-kneaded with a residence time of 2 minutes to produce a blend chip 2-1 (PET / PEI / PEEK blend chip). Similarly, the same method as described above, except that PET blended with 0.5% by mass of spherical crosslinked polystyrene particles having an average diameter of 0.3 μm and 0.025% by mass of spherical crosslinked polystyrene particles having an average diameter of 0.8 μm was used. The PET / PEI / PEEK blend chip 2-2 was prepared by the method described above.

  Next, using two extruders A and B, a laminated film was prepared so that the polymer of the extruder A formed the layer I on the magnetic surface side, and the polymer of the extruder B formed the layer II on the running surface side. To Extruder A heated to 280 ° C., 40 parts by mass of Blend Chip 2-1 and 60 parts by mass of PET having an intrinsic viscosity of 0.65 were supplied after drying under reduced pressure at 180 ° C. for 3 hours. The heated extruder B was fed with 40 parts by weight of blend chip 2-2 and 60 parts by weight of PET having an intrinsic viscosity of 0.65 after drying under reduced pressure at 180 ° C. for 3 hours, and after joining them in a T-die ( A lamination ratio I / II = 10/1) was adhered to a casting drum having a surface temperature of 25 ° C. by static electricity and cooled and solidified to obtain a laminated unstretched film.

  Subsequently, the laminated unstretched film obtained here was first used in a longitudinal direction at a temperature of 110 ° C. at a temperature of 110 ° C. using a longitudinal stretching machine in which several rolls were arranged, using a peripheral speed difference of the rolls. The film was stretched at a magnification of 5 times, and then stretched at 115 ° C. and 3.5 times using a stenter. Thereafter, the film was further longitudinally stretched by a roll longitudinal stretching machine at a stretching temperature of 140 ° C. and a stretching ratio of 1.8 times. Thereafter, the both ends of the film are again gripped with clips, guided to a stenter, stretched again in the width direction of the film at a stretching temperature of 180 ° C. and a stretching ratio of 1.4 times, and subsequently heat treated at a temperature of 200 ° C. Then, 4% and 1% relaxation treatments were applied laterally in two cooling zones controlled at 150 ° C. and 100 ° C., respectively, and after cooling to room temperature, the film edge was removed, An axially oriented film was obtained. The characteristics of the biaxially oriented film obtained here are shown in Tables 1 and 2.

It is a schematic diagram of the sheet | seat width measuring apparatus used when measuring 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)

70 to 99 parts by mass of polyester (A) having a melting point of 200 ° C. or higher and lower than 280 ° C., 1 to 30 parts by mass of amorphous thermoplastic resin (B) having a glass transition temperature of 100 to 250 ° C., and a melting point of 280 Each containing 0.1 to 4 parts by mass of a crystalline thermoplastic resin (C) at ℃ to 400 ° C., and the content (Wb) of the amorphous thermoplastic resin (B) and the crystalline thermoplasticity A biaxially oriented polyester film having a resin (C) content (Wc) ratio Wc / Wb of 0.05 or more and 0.3 or less. The biaxially oriented polyester film according to claim 1, wherein the amorphous thermoplastic resin (B) contains at least one selected from the group consisting of polyetherimide, polyethersulfone and polysulfone. The biaxially oriented polyester film according to claim 1 or 2, wherein the crystalline thermoplastic resin (C) is an aromatic polyether ketone or a thermoplastic crystalline polyimide. The biaxially oriented polyester film according to any one of claims 1 to 3, wherein the polyester (A) contains at least one selected from the group consisting of polyethylene terephthalate, polyethylene-2,6-naphthalate and modified products thereof. . The amorphous thermoplastic resin (B) and the crystalline thermoplastic resin (C) each form a dispersed phase in the polyester (A), and the average dispersed diameter of the amorphous thermoplastic resin (B) is 1 to 50 nm. The biaxially oriented polyester film according to any one of claims 1 to 4, wherein the biaxially oriented polyester film is in a range and an average dispersion diameter of the crystalline thermoplastic resin (C) is in a range of 50 to 500 nm. The biaxially oriented polyester film according to any one of claims 1 to 5, wherein a temperature expansion coefficient in the film width direction is -5.0 to 8.0 ppm / ° C. The biaxially oriented polyester film according to any one of claims 1 to 6, wherein a humidity expansion coefficient in the film width direction is 0 to 6.0 ppm /% RH. A magnetic recording medium comprising the biaxially oriented polyester film according to claim 1.

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