JP5098719B2 - Biaxially oriented polyester film and magnetic recording medium - Google Patents

Description

  The present invention relates to a biaxially oriented polyester film excellent in rigidity and dimensional stability. In particular, it can be suitably used for magnetic recording media, electrical insulation, capacitors, circuit materials, solar cell materials, etc., but especially when it is used as a magnetic recording medium, environmental changes in temperature and humidity and dimensional changes due to storage In particular, the present invention relates to a biaxially oriented polyester film that can be made to be a high-density magnetic recording medium that has a low error rate, a low error rate, and a low magnetic head or magnetic tape wear and excellent running durability.

  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 caused by heat during tape running or temperature and humidity changes during tape storage. Accordingly, there is an increasing demand for improvement in characteristics such as dimensional stability in the usage environment and storage environment of the tape. On the other hand, there is an increasing demand for improvement in running durability when 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 head and tape scraping.

  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.

For example, a biaxially oriented polyester film made of polyester and polyetherimide is disclosed (for example, Patent Documents 1 and 2). However, a specific method or technical idea of a biaxially stretched film using a crystal nucleating agent or using a resin composition having a melt crystallization temperature of 200 to 240 ° C. and a high crystallization rate is not disclosed. Further, as a polyester film using a resin composition having a high crystallization rate, a polyester film containing a crystal nucleating agent composed of alkali metal montanate or alkaline earth metal salt is disclosed (for example, Patent Document 3). . However, mechanical properties such as Young's modulus are low, and a specific method for controlling temperature expansion and humidity expansion is not disclosed.
JP 2000-309650 A JP 2000-141475 A JP-A-61-85468

  An object of the present invention is to solve the above problems and provide a biaxially oriented polyester film having excellent rigidity and dimensional stability, and in particular, for magnetic recording media, for electrical insulation, for capacitors, for circuit materials, It can be suitably used for solar cell materials, etc., but in particular when it is used as a magnetic recording medium, it can reduce environmental changes in temperature and humidity and dimensional changes due to storage, has a low error rate, and has a magnetic head and 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 wear of the magnetic tape and excellent running durability.

  The present invention for solving the above-described problems is characterized by the following.

(1) 70 to 99 parts by mass of polyester (A), 1 to 30 parts by mass of polyimide (B), the humidity expansion coefficient in the film width direction is 0 to 8.2 ppm /% RH, and A biaxially oriented polyester film having a melt crystallization peak temperature of 200 to 240 ° C.

  (2) The biaxially oriented polyester film according to (1) above, containing 0.2 to 1% by mass of a crystal nucleating agent.

  (3) The biaxially oriented polyester film according to (2) above, wherein the crystal nucleating agent is an alkali metal salt or alkaline earth metal salt of montanic acid.

  (4) Any of the above (1) to (3), wherein the polyester (A) contains at least one polymer selected from the group consisting of polyethylene terephthalate, polyethylene-2,6-naphthalate and modified products thereof. 2. A biaxially oriented polyester film described in 1.

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

  (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 ) A magnetic recording medium comprising the biaxially oriented polyester film according to any one of (1) to ( 6 ).

  According to the present invention, a biaxially oriented polyester film excellent in rigidity and dimensional stability can be obtained, and particularly suitable for magnetic recording media, electrical insulation, capacitors, circuit materials, solar cell materials, and the like. Although it can be used, especially when it is used as a magnetic recording medium, it can reduce environmental changes in temperature and humidity and dimensional change due to storage, has a low error rate, and has less wear and tear on the magnetic head and magnetic tape. A biaxially oriented polyester film that can be used as a high-density magnetic recording medium having excellent properties 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.

  Polyester (A) is preferably polyethylene terephthalate or polyethylene 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.

  In particular, the polymer alloy of the polyester resin and the polyimide resin is preferable because the heat resistance (glass transition temperature) can be controlled by the mixing ratio, and the polymer can be designed according to the use conditions. The mixing ratio of the polymer can be examined using a micro FT-IR method (Fourier transform micro infrared spectroscopy).

For example, in the case of polyester and polyimide, it is dissolved in a mixed solution of 70 parts by mass of hexafluoroisopropanol (HFIP) / 30 parts by mass of deuterated chloroform, and the NMR spectrum of ¹ H nucleus is measured. In the obtained spectrum, the peak area intensity of absorption specific to polyester and polyimide (for example, aromatic proton of terephthalic acid if polyester is polyethylene terephthalate, aromatic proton of bisphenol A if polyimide is polyetherimide) The molar ratio of the blend is calculated from the ratio and the number of protons. Further, the mass ratio is calculated from the formula amount corresponding to the unit unit of the polymer. In this way, the mixing ratio of the polyester component and the polyimide component can be specified.

  As the polyimide, for example, those containing a structural unit represented by the following general formula are preferable.

However, R ¹ in the formula is

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

Represents one or two or more groups selected from an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group.

  From the viewpoints of melt moldability and affinity with polyester, a polyetherimide containing an ether bond in the polyimide component as shown by the following general formula is particularly preferred. The polyetherimide (B) 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 ³ is a divalent aromatic or aliphatic residue having 6 to 30 carbon atoms, R ⁴ 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 < ³ >, R < ⁴ >, 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) phenyl] propane dianhydride and m-phenylene are used from the viewpoints of affinity with polyester (A), cost, melt moldability and the like. A polymer having a repeating unit represented by the following formula, which is a condensate with diamine 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.

  The film of the present invention contains polyester (A) and polyimide (B), and the total amount of polyester (A) and polyimide (B) is 70 to 99% by mass of polyester (A) and polyimide (B). It is preferable to contain 1-30 mass%. The more preferable content of the polyester (A) is 80 to 97% by mass, and the particularly preferable range is 85 to 95% by mass. Moreover, the more preferable content of polyimide (B) is 3 to 20% by mass, and the particularly preferable content is 5 to 15% by mass. When the content of the polyimide (B) is less than 1% 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% by mass, the film formability deteriorates and the production cost increases, and the average dispersion diameter of the polyimide (B) in the polyester (A) is as described below. It is likely to be difficult to control within the preferable range.

  In the biaxially oriented polyester film of the present invention, polyimide (B) forms a dispersed phase in polyester (A). The average dispersion diameter of the polyimide (B) in the polyester (A) is preferably in the range of 1 to 50 nm. When the average dispersion diameter of the polyimide (B) is less than the above range or larger than the above range, the glass transition temperature (Tg) of the polyester film of the present invention cannot be sufficiently increased, and the film has excellent heat resistance and moisture resistance. Thermal properties may not be imparted. The average dispersion diameter of the polyimide (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 polyimide (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 polyimide (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 polyimide (B) is within the above range, the film forming property may be more stable.

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

  The average dispersion diameter of the polyimide (B) in the polyester (A) is as follows. First, the cut surface of the film is observed using a transmission electron microscope under a condition of a pressurized voltage of 100 kV, and a photograph is taken at a magnification of 20,000 times. . Next, the obtained photograph is taken into an image analyzer as an image, 100 arbitrary dispersed phases are selected, image processing is performed as necessary, the dispersion diameter is obtained, and the average dispersion is obtained with the number average. The diameter.

  More specifically, the average dispersion diameter is 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. Prepare 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 (Hitachi H-7100FA type) under a condition of a pressurization voltage of 100 kV, and a photograph is taken at a magnification of 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. . 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). Ask. 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, and the average dispersion diameter of the dispersed phase is (I + J + K) / 3. Further, from I, J, and K, the maximum value is determined as the average major axis L, and the minimum value is 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)
Further, among the dispersed domains formed in the polyester, nitrogen atoms (N) are formed by energy dispersive X-ray spectroscopy using a field emission electron microscope (TEM-EDX method). The detected domain is defined as a polyimide (B) domain.

  In the present invention, for example, as a method of mixing polyester and polyimide, before melt extrusion, a mixture of polyester and polyimide is pre-melted and kneaded (pelletized) into a master chip, or mixed and melted during melt extrusion. There is a method of kneading. Of these, 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 preferably exemplified. In that case, the mixed master chip raw material may be put into an ordinary single-screw extruder to form a melt film, or may be directly sheeted without forming a master chip in a state where high shear is applied. 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. Moreover, when mixing polyester and a polyimide, since there is a difference in melt viscosity, it is preferable to prepare a master chip in which a polyimide resin is mixed at a high concentration. In particular, the mixing mass ratio of polyester / polyimide is 10/90 to 70/30 is preferable, and a more preferable range is 30/70 to 60/40.

In the kneading part, the temperature range of the melting point of the polyester resin +10 to 65 ° C. is preferable. A more preferable temperature range is the melting point of the polyester resin +15 to 55 ° C., and a more preferable temperature range is the melting point of the polyester resin +20 to 45 ° C. Setting the temperature range of the kneading part to a preferable range facilitates increasing the shear stress and contributes to the reduction of defective dispersion. The residence time at that time is preferably in the range of 1 to 5 minutes. Moreover, it is preferable that screw rotation speed shall be 100-500 rotation / min, More preferably, it is the range of 200-400 rotation / min. 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.

  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.

  The melt crystallization peak temperature of the biaxially oriented polyester film of the present invention is 200 to 240 ° C. Preferably, it is 205-240 degreeC, More preferably, it is 210-230 degreeC. When the melt crystallization peak temperature is less than 200 ° C., the high Young's modulus, which is the effect of the present application, and the temperature expansion coefficient and the humidity expansion coefficient may be drastically reduced, making it difficult to control the dimensional stability. Sometimes. In addition, when the melt crystallization peak temperature exceeds 240 ° C., crystallization may proceed in the melt extrusion process of the film, and the filtration pressure may increase and coarse foreign matter may be generated or the film may be broken. is there. For example, when used for a magnetic recording medium, electromagnetic conversion characteristics may be poor. The melt crystallization peak temperature is an index of ease of crystallization in sheeting cooled from the molten state of the polyester.

  In order to control the preferable melt crystallization peak temperature of the present invention, it is preferable to contain 0.2 to 1% by mass of a crystal nucleating agent. A more preferable content is 0.2 to 0.7% by mass, and a more preferable content is 0.3 to 0.5% by mass. If the content of the crystal nucleating agent is less than 0.1% by mass, it is not sufficient to control the melt crystallization peak. On the other hand, if it exceeds 1% by mass, crystallization proceeds excessively and the film stretchability is poor. And surface characteristics may be poor. Here, the crystal nucleating agent is an additive having an effect of promoting crystallization from a molten state by increasing the temperature of the melt crystallization peak of the resin composition used for the polyester film.

  Examples of the crystal nucleating agent include alkali metal salts and alkaline earth metal salts of montanic acid. In addition, 4-carboxylic acid metal salts such as 4-tert-butylbenzoic acid aluminum salt and sodium adipate, sodium bis (4-tert-butylphenyl) phosphate, sodium-2,2′-methylenebis (4,6-ditertiary Preferred examples include acidic phosphate metal salts such as butylphenyl) phosphate, polyhydric alcohol derivatives such as dibenzylsorbitol, bis (4-methylbenzylidene) sorbide, and the like. When applied to the polyester of the present invention, among them, an alkali metal salt or alkaline earth metal salt of montanic acid is preferable, and sodium montanate is particularly preferable in terms of achieving compatibility and the effects of the present invention.

  Polyesters that do not contain polyimide are susceptible to melt crystallization in the unstretched sheeting process due to the inclusion of the crystal nucleating agent, and orientation crystallization also occurs in the stretching process. There are cases where film breakage occurs, and it is difficult to increase the Young's modulus and improve the dimensional stability by stretching at a high magnification. In the biaxially oriented polyester film of the present invention, the crystal nucleating agent has the effect of effectively suppressing molecular crystallization and enhancing the molecular chain orientation in the stretching step. That is, in the polyester containing the polyimide of the present invention, the degree of crystallinity tends to be high in a low-magnification region from an unstretched sheet to a stretch ratio of about 2 times, but no polyimide is added in a higher-magnification stretch region. Compared to the case, orientation crystallization in stretching tends to be suppressed. Therefore, it is easy to increase the tension of the amorphous molecular chain while suppressing the progress of orientation crystallization, and it is possible to control the characteristics depending on the molecular chain tension such as the temperature expansion coefficient and the humidity expansion coefficient.

  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 coefficient of humidity expansion 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.

  The biaxially oriented polyester film of the present invention preferably has a laminated structure of two or more layers. In particular, when the film of the present invention is used as a support for a magnetic recording medium, one surface is required to have smoothness for obtaining excellent electromagnetic characteristics, and the other surface is subjected to a film forming / processing step. And the roughness for imparting the running property and running durability of the magnetic tape is required. Therefore, it is preferable that the polyester film has a laminated structure of two or more layers.

  Moreover, when using the biaxially oriented polyester film of this invention as a support body for magnetic recording media, it is preferable that centerline average roughness RaA of the surface (A) at the side which provides a magnetic layer is 0.5 nm-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 biaxially oriented polyester film of the present invention is provided with inorganic particles, organic particles such as clay, mica, titanium oxide, calcium carbonate, carillon in order to impart slipperiness, abrasion resistance, scratch resistance, etc. to the surface. Organic particles containing inorganic particles such as talc, wet silica, dry silica, colloidal silica, calcium phosphate, barium sulfate, alumina, zirconia, acrylic acid, styrene resin, thermosetting resin, silicone, imide compound, etc. Further, particles (so-called internal particles) that are precipitated by a catalyst or the like added during the polyester polymerization reaction may be included. 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, ultraviolet absorbers, flame retardants, flame retardant aids, pigments, dyes, and the like may be added.

  Subsequently, the sheet 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.

  In the present invention, it is particularly preferable to use the simultaneous biaxial stretching method. In the present invention, in an unstretched film composed of a polyester-polyimide composition containing a crystal nucleating agent, crystallization is enhanced as compared with a normal polyester film. Therefore, in sequential biaxial stretching, in the first longitudinal direction or transverse direction stretching. Crystallization is likely to proceed, and stretching in the subsequent stretching step, and as a result, it may be difficult to achieve high magnification and high orientation as a total stretching ratio. Simultaneous biaxial stretching is preferred because it facilitates orientation crystallization and molecular orientation at once in the longitudinal and width directions. Furthermore, compared with the sequential biaxial stretching method, in the simultaneous biaxial stretching method, crystals are uniformly grown in the longitudinal direction and the width direction in the film forming process, and therefore, it is easy to stably stretch at a high magnification. 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 it is 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, the production method of the biaxially oriented polyester film of the present invention will be described as a representative example using polyethylene terephthalate (PET) as a polyester. Of course, the present application is not limited to a support using a PET film, but may be one using another polymer. For example, when a polyester film is formed using polyethylene-2,6-naphthalenedicarboxylate having a high glass transition temperature or a high melting point, it may be extruded or stretched at a temperature higher than the following temperature.

  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.

  When mixing PET and polyimide, since there is a difference in melt viscosity, it is preferable to prepare a master chip in which a polyimide resin is mixed at a high concentration. In particular, the mixing mass ratio of PET / polyimide is 10/90 to 70 / 30 is preferable, and a more preferable range is 30/70 to 60/40.

  In the kneading part, the temperature range of the melting point of PET resin +10 to 65 ° C. is preferable. A more preferable temperature range is the melting point of the PET resin +15 to 55 ° C., and a more preferable temperature range is the melting point of the PET resin +20 to 45 ° C. Setting the temperature range of the kneading part to a preferable range facilitates increasing the shear stress and contributes to the reduction of defective dispersion. The residence time at that time is preferably in the range of 1 to 5 minutes. Moreover, it is preferable that screw rotation speed shall be 100-500 rotation / min, More preferably, it is the range of 200-400 rotation / min. 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.

  Next, the obtained PET and pellets of the PET and polyimide composition were dried at 180 ° C. under reduced pressure for 3 hours or more, and then heated to 270 to 320 ° C. under a nitrogen stream or under reduced pressure so as not to lower the intrinsic viscosity. The unextruded film is obtained by feeding the extruded extruder, extruding from a slit-shaped die, and cooling on a casting roll. 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 stretching is performed in multiple stages in each direction, the stretching ratio in each of the first stage in the longitudinal direction and the width direction is preferably 2.5 to 4 times, more preferably 3 to 4 times. Moreover, the preferable area draw ratio in the 1st step is 6.25-16 times, More preferably, it is 9-16 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.

  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 obtained as described above is slit, for example, into a width of 0.1 to 3 m, and conveyed on one side (A) while being conveyed at a speed of 20 to 300 m / min and a tension of 50 to 300 N / m. A magnetic coating and a non-magnetic coating are applied to each other 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) 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)}
(2) Humidity 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 a 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)}
(3) 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.

(4) 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
(5) 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 mass: 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
(6) Melting point (Tm), melt crystallization peak temperature Using a Seiko Instruments DSC (RDC220) as a differential scanning calorimeter and a disk station (SSC / 5200) as a data analyzer, about 5 mg of a sample is made of aluminum. After melting and holding at 300 ° C. for 5 minutes on the saucer and rapidly solidifying, 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).

  Subsequently, after melting and holding at 300 ° C. for 5 minutes, the temperature is lowered at a rate of 20 ° C./min. At that time, the observed exothermic peak is the melt crystallization peak, and the peak temperature is taken as the melt crystallization peak temperature.

(7) 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 nonmagnetic 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 weight (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: 3 times (width dimension change rate)
The width dimension (l _A , l _B ) is measured under two conditions, and the dimensional change rate is calculated by the following equation. The 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. (8) Storage stability As in (7) 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. The 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 (9) Electromagnetic conversion characteristics A cassette tape was prepared in the same manner as in (7) above, and a C / N measurement was performed using a reel-to-reel tester and a commercially available MR head mounted under the following conditions.

Relative speed: 2 m / sec, recording track width: 18 μm, playback track width: 10 μm
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 expressed as PET, and poly (ethylene-2,6-naphthalenedicarboxylate) is expressed 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.

  On the other hand, a vent-type twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading sections heated to a temperature of 290 ° 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. 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 (I).

  Bent-type twin-screw kneading extruder of the same direction rotation type provided with one kneading paddle kneading part heated to 290 ° C (manufactured by Nippon Steel, screw diameter 30 mm, screw length / screw diameter = 45.5) Is supplied with 98.5% by mass of the obtained PET pellet (X) and 1.5% by mass of a crystal nucleating agent “Recommon NaV101” made of sodium montanate manufactured by Kleint Japan Co., Ltd. After being melt-extruded in minutes, discharged into a strand, cooled with water at a temperature of 25 ° C., and immediately cut to produce a blend chip (II).

  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 68.5 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( I) 10 parts by weight and 20 parts by weight of blended chip (II) 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 was supplied with 62 parts by weight of PET pellets (X), PET Pellets (Z-1) 7 parts by mass, PET pellets (Z-2) 1 part by mass, blend chip (I) 10 parts by mass and blend chip (II) 20 parts by mass were dried at 180 ° C. for 3 hours under reduced pressure 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. After cooling and solidification, a laminated unstretched film was produced. 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.

  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 (I), and blend chip (II) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 48.5 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( I) 10 parts by weight and 40 parts by weight of blended chips (II) 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., to 42 parts by weight of PET pellets (X), PET 7 parts by mass of pellet (Z-1), 1 part by mass of PET pellet (Z-2), 10 parts by mass of blend chip (I) and 40 parts by mass of blend chip (II) were 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 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 (I), and blend chip (II) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 75.2 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( I) 10 parts by weight and 13.3 parts by weight of blended chip (II) 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 was supplied to PET pellet (X) 68.7. 3 parts by weight at 180 ° C. for 3 parts by weight, 7 parts by weight of PET pellets (Z-1), 1 part by weight of PET pellets (Z-2), 10 parts by weight of blend chip (I) and 13.3 parts by weight of blend chip (II) It supplied after drying under reduced pressure. 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 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 4
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (I), and blend chip (II) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 35.2 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( I) 10 parts by weight and 53.3 parts by weight of blended chip (II) 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. 3 parts by mass at 180 ° C., 7 parts by mass of PET pellets (Z-1), 1 part by mass of PET pellets (Z-2), 10 parts by mass of blend chip (I) and 53.3 parts by mass of blend chip (II) It supplied after drying under reduced pressure. 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 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 5)
Example 1 except that “ADEKA STAB NA-11” manufactured by ADEKA of sodium 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate was used in place of “RECOMMONT NaV101” as the crystal nucleating agent In the same manner as above, a biaxially stretched polyester film was obtained. 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 6)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (I), and blend chip (II) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. had 38.5 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( I) 40 parts by weight and 20 parts by weight of blended chips (II) were dried after drying at 180 ° C. under reduced pressure for 3 hours and supplied to the extruder E2, which was also heated to 295 ° C., to 32 parts by weight of PET pellets (X), PET 7 parts by mass of pellet (Z-1), 1 part by mass of PET pellet (Z-2), 40 parts by mass of blend chip (I) and 20 parts by mass of blend chip (II) were 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 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 x 3.1 times at a temperature of 125 ° 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 the same time 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 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 7)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (I), and blend chip (II) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. had 28.5 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( I) 50 parts by weight and 20 parts by weight of blended chips (II) 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., to which 22 parts by weight of PET pellets (X), PET Pellets (Z-1) 7 parts by mass, PET pellets (Z-2) 1 part by mass, blend chip (I) 50 parts by mass and blend chip (II) 20 parts by mass 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. After cooling and solidification, a laminated unstretched film was produced. 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 130 ° 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 the same time 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 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 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 re-stretched at 1.5 × 1.5 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, it had sufficient characteristics for dimensional stability, storage stability, and electromagnetic conversion characteristics when used as a magnetic tape. .

Example 9
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 3.1 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 re-stretched 1.7 × 1.4 times at a temperature of 180 ° C. 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 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 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.

  On the other hand, the same direction rotation type bent type twin screw kneading extruder provided with one kneading paddle kneading part 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. Then, after cooling with water at a temperature of 25 ° C., it was immediately cut to produce a blend chip (III).

  Bent-type twin-screw kneading extruder of the same direction rotation type provided with one kneading paddle kneading part heated to a temperature of 300 ° C. (manufactured by Nippon Steel Works, screw diameter 30 mm, screw length / screw diameter = 45.5) Are supplied with 98.5% by mass of the obtained PEN pellet (P) and 1.5% by mass of a crystal nucleating agent “Recommon NaV101” made of sodium montanate manufactured by Cleart Japan Co., Ltd. After being melt-extruded in minutes, discharged into a strand, cooled with water at a temperature of 25 ° C., and immediately cut to produce a blend chip (IV).

  In addition, in the same direction rotation type bent type twin-screw kneading extruder heated to 280 ° C., 98 parts by mass of PEN pellets (P) and 20% by mass of 10% by mass water slurry of spherical crosslinked polystyrene particles having an average diameter of 0.3 μm were obtained. 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 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.

    Using two extruders E1 and E2, the extruder E1 heated to 295 ° C. includes 68.5 parts by mass of PEN pellets (P), 1.5 parts by mass of PEN pellets (R-1), blended chips ( III) 10 parts by weight and 20 parts by weight of blended chips (IV) were dried after drying at 180 ° C. under reduced pressure for 3 hours and supplied to the extruder E2, which was also heated to 295 ° C., to PEN pellet (P) 62 parts by weight, PEN 7 parts by mass of pellet (R-1), 1 part by mass of PEN pellet (R-2), 10 parts by mass of blend chip (III) and 20 parts by mass of blend chip (IV) were 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. 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 3.3 times × 3.3 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 1.5 × 1.9 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 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.

(Comparative Example 1)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2) and blend chip (I) 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 ( I) After feeding 10 parts by weight at 180 ° C. under reduced pressure for 3 hours and supplying the same to an extruder E2 heated to 295 ° C., 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 (I) were 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 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 2)
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 3)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (I), and blend chip (II) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 81.9 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( I) 10 parts by weight and 6.6 parts by weight of blended chip (II) 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 the PET pellet (X) 75.4 3 parts by weight at 180 ° C. for 3 parts by weight, 7 parts by weight of PET pellets (Z-1), 1 part by weight of PET pellets (Z-2), 10 parts by weight of blend chip (I) and 6.6 parts by weight of blend chip (II) It supplied after drying under reduced pressure. 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 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 4)
The PET pellet (X), PET pellet (Z-1), PET pellet (Z-2), blend chip (I), and blend chip (II) obtained in Example 1 were used.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. contained 8.5 parts by mass of PET pellets (X), 1.5 parts by mass of PET pellets (Z-1), blended chips ( I) 10 parts by weight and 80 parts by weight of blended chip (II) 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 2 parts by weight of PET pellet (X), PET 7 parts by mass of pellet (Z-1), 1 part by mass of PET pellet (Z-2), 10 parts by mass of blend chip (I) and 80 parts by mass of blend chip (II) were 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 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.

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 (7)

70 to 99 parts by mass of polyester (A), 1 to 30 parts by mass of polyimide (B), a humidity expansion coefficient in the film width direction of 0 to 8.2 ppm /% RH, and melt crystallization A biaxially oriented polyester film having a peak temperature of 200 to 240 ° C. The biaxially oriented polyester film according to claim 1, comprising 0.2 to 1% by mass of a crystal nucleating agent. The biaxially oriented polyester film according to claim 2, wherein the crystal nucleating agent is an alkali metal salt or alkaline earth metal salt of montanic acid. The biaxial orientation according to any one of claims 1 to 3, wherein the polyester (A) contains at least one polymer selected from the group consisting of polyethylene terephthalate, polyethylene-2,6-naphthalate and modified products thereof. Polyester film. The biaxially oriented polyester film according to any one of claims 1 to 4, wherein the polyimide (B) is a polyetherimide. 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 magnetic recording medium obtained by using the biaxially oriented polyester film according to any one of claims 1-6.

Images