JP2011068807A - Biaxially oriented polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film which can be made into an excellent high-density magnetic recording medium small in a dimensional change and also few in an error rate due to a use environment when being made into a magnetic recording medium and a change in environment during storage. <P>SOLUTION: The biaxially oriented polyester film is provided which has at least one layer A containing 1 to 10 mass% of a crystalline thermoplastic resin (A) other than a polyester the melting point of which is 280 to 400°C, and a haze of 10% or lower. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a biaxially oriented laminated polyester film excellent in transparency, heat resistance and dimensional stability, and is suitable for magnetic recording media, electrical insulation, capacitors, circuit materials, solar cell materials, etc. The present invention relates to a biaxially oriented polyester film that can be used.

  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, the aromatic polyamide may become too rigid and 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.

  There has been proposed a biaxially oriented polyester film in which a heat-resistant thermoplastic resin having good affinity between polyester and polyester is mixed and excellent in running property and scratch resistance (for example, Patent Document 1). However, since the heat-resistant thermoplastic resin decreases the crystallization speed of the polyester, the degree of crystallinity of the film decreases, resulting in insufficient dimensional stability, or a film made of the polyester alone used. There is a problem that the elastic modulus and the breaking strength are reduced as compared with the above, and further improvement is eagerly desired. In addition, a film comprising polyester and polyimide and polyimide and a nano-compatible polymer, and having improved heat resistance, rigidity, and thermal dimensional stability by using an aromatic polyether ketone as the polymer C that is nano-compatible with polyimide. Has been proposed (for example, Patent Document 2). However, when the three-component kneading is performed, especially the shear stress of the second-stage kneading is insufficient, the dispersion diameter of the polymer C in the film after melt extrusion is not uniform, or foreign matter due to the unmelted polymer C In addition, foreign matters due to thermal degradation of the polyester are likely to be generated in the film, and there are problems such as a decrease in transparency and stretchability of the film. In particular, since the dispersion domain in the polymer C film is large and coarse protrusions are formed, the error rate may be poor when used for magnetic recording media, for example. Furthermore, although a resin composition made of PEEK as a thermoplastic resin other than polyimide has been proposed (for example, Patent Document 3), there is no disclosure about a specific method for applying it to a polyester film.

JP 2001-323146 A JP 2004-123863 A JP 2002-249660 A

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

  The present invention for solving the above-described problems is characterized by the following (1) to (7).

  (1) Biaxial having at least one layer A containing 1 to 10% by mass of a crystalline thermoplastic resin (A) other than polyester having a melting point of 280 ° C. to 400 ° C. and having a haze of 10% or less Oriented polyester film.

  (2) The above-mentioned B layer having a melting point of 280 ° C. to 400 ° C. and containing a crystalline thermoplastic resin (A) other than polyester of 0.1% by mass or more and less than 1% by mass on at least one side of the A layer The biaxially oriented polyester film according to (1).

  (3) The S layer containing 1 to 30% by mass of an amorphous thermoplastic resin (B) other than polyester having a glass transition temperature of 100 to 250 ° C. is provided on at least one outermost layer. The biaxially oriented polyester film according to (1) or (2).

  (4) The above-mentioned (1) to (3), wherein the A layer and the B layer contain 1 to 50% by mass of an amorphous thermoplastic resin (B) other than polyester having a glass transition temperature of 100 to 250 ° C. The biaxially oriented polyester film according to any one of the above.

  (5) The biaxially oriented polyester film according to any one of the above (1) to (4), which has at least one layer having a crystallization index ΔTcg of 25 to 75 ° C.

  (6) The biaxially oriented polyester film according to any one of the above (1) to (5), wherein a peak temperature of loss tangent (tan δ) in dynamic viscoelasticity measurement in the longitudinal direction is 125 to 180 ° C.

  (7) The biaxially oriented polyester film according to any one of (1) to (6), wherein the crystalline thermoplastic resin (A) is an aromatic polyether ketone or polyimide.

  (8) The amorphous thermoplastic resin (B) contains at least one resin selected from the group consisting of polyetherimide, polyethersulfone, and polysulfone, and is in any one of the above (3) to (7) The biaxially oriented polyester film described.

  According to the present invention, it is possible to obtain a biaxially oriented polyester film that is transparent and excellent in rigidity and dimensional stability, and is suitable for magnetic recording media, electrical insulation, capacitors, circuit materials, solar cell materials, and the like. Can be used. Above all, when it is used as a magnetic recording medium, it is possible to reduce the environmental change of temperature and humidity and the dimensional change due to storage, and it is possible to obtain a biaxially oriented polyester film that can be used as a high-density magnetic recording medium with a low error rate. .

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

  The crystalline thermoplastic resin (A) other than polyester used in the present invention has a melting point of 280 to 400 ° C. By setting the melting point of the crystalline thermoplastic resin (A) within a specific range, it becomes easy to form a restraint point due to the microcrystal of the crystalline thermoplastic resin (A) in the biaxially oriented polyester film, and in the stretching step It becomes easy to increase molecular chain orientation. When the molecular chain orientation is increased, strengthening and dimensional stability can be improved. The crystalline thermoplastic resin (A) is a resin different from polyester. Further, in the biaxially oriented polyester film containing the amorphous thermoplastic resin (B) described later without using the crystalline thermoplastic resin (A), the amorphous thermoplastic resin (B) is more than the polyester. Even if the glass transition temperature is high, sufficient restraint points may not be formed in the polyester unless the miscibility with the polyester and the difference in melt viscosity are controlled.

  A preferable melting point of the crystalline thermoplastic resin (A) is 300 to 370 ° C, and a more preferable melting point is 320 to 360 ° C. Here, the crystallinity is a characteristic in which a melting point and a melting peak are detected when a sample is measured using differential scanning calorimetry (DSC) or the like. Further, the crystalline thermoplastic resin (A) is a resin having a ketone group, an imide group, or an amide group, and the restriction point due to the crystallites of the crystalline thermoplastic resin (A) in the biaxially oriented polyester film is efficiently It is preferable at the point which can be formed, and it is especially preferable that it is resin which has a ketone group or an imide group. Among these, aromatic polyether ketone or polyimide is preferable from the viewpoint of transparency of the biaxially oriented polyester film.

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

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

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

  The content of the crystalline thermoplastic resin (A) is preferably 1 to 10% by mass, more preferably 1 to 5% by mass, from the viewpoints of transparency, heat resistance, and dimensional stability. When the content of the crystalline thermoplastic resin (A) is less than 1% by mass, the number of domains and the domain diameter that are restraining points in the film become inappropriate, and it is difficult to improve the dimensional stability. If the amount exceeds 10% by mass, an unmelted product due to the crystalline thermoplastic resin (A) is generated, the dispersion diameter becomes uneven, the stretchability is remarkably lowered, and the transparency of the film is lowered. There is. The content of the crystalline thermoplastic resin (A) can be examined using a microscopic FT-IR method (Fourier transform microinfrared spectroscopy).

  The biaxially oriented polyester film of the present invention has at least one layer A containing 1 to 10% by mass of a crystalline thermoplastic resin (A) other than polyester having a melting point of 280 ° C. to 400 ° C. . A functional layer such as an easy adhesion layer or a release layer may be coated on one side of the A layer as long as the transparency and dimensional stability are not impaired. Moreover, you may be the laminated structure of two or more layers which laminated | stacked the other polyester layer.

  The haze of the biaxially oriented polyester film of the present invention is preferably 10% or less. Preferably it is 1.5 to 6%, More preferably, it is 1.5 to 4%. If the haze of the film exceeds 10%, the dispersion state of the crystalline thermoplastic resin (A) in the film becomes non-uniform and the surface properties and smoothness may be impaired. It becomes difficult to expand to.

  The total light transmittance of the biaxially oriented polyester film of the present invention is not particularly limited, but is preferably 85% or more, and more preferably 88% or more. If the total light transmittance is less than 85%, the dispersion diameter of the crystalline thermoplastic resin (A) in the film may be non-uniform or there may be a coarse dispersion diameter connected in a string shape. In some cases, the dimensional stability may be lowered, and the quality of the film, particularly the appearance, may be poor. In addition, the surface property may be deteriorated.

  The biaxially oriented polyester film of the present invention may have a B layer on at least one side of the A layer. The layer B contains 0.1 to less than 1% by mass of a crystalline thermoplastic resin (A) other than polyester having a melting point of 280 to 400 ° C., transparency, dimensional stability, electromagnetic conversion characteristics From the point of view, it is preferable. The B layer can be laminated on one side or both sides of the A layer, and the surface of the B layer is coated with a functional layer such as an easy adhesion layer or a release layer as long as the transparency and dimensional stability are not impaired. You can set it up. The lamination thickness of the B layer is not particularly limited, but the total thickness ratio of the B layer is 10 to 80%, preferably 15 to 60% with respect to the total film thickness, and the dimensional stability and the crystalline thermoplastic resin ( This is preferable because the height and the number of protrusions resulting from A) can be easily controlled. The crystalline thermoplastic resin (A) may be the same or different between the A layer and the B layer. In addition, fine particles having an average particle diameter of 10 to 800 nm can be contained in a proportion of 0.5% by mass or less as long as the purpose of the present application is not impaired.

  The outermost layer on at least one surface of the biaxially oriented polyester film of the present invention includes an S layer containing 1 to 30% by mass of an amorphous thermoplastic resin (B) having a glass transition temperature of 100 to 250 ° C. other than polyester. It is preferable to provide it. When the content of the amorphous thermoplastic resin (B) is 1 to 30% by mass, the dimensional stability is improved.

  The S layer preferably contains substantially no crystalline thermoplastic resin (A) from the viewpoint of reducing the error rate. By laminating the S layer on the surface of the A layer or the B layer, the influence of the surface roughness of the lower layer is less likely to appear on the surface of the S layer, and the smoothing effect of the surface is manifested to produce an electromagnetic wave when used as a magnetic recording medium. Since it becomes a polyester film excellent in conversion characteristics and an error rate, it is preferable. The thickness of the S layer is not particularly limited, but is preferably 40 nm or more, preferably in the range of 100 to 1,000 nm from the viewpoint of achieving both dimensional stability and smoothing of the surface. If the thickness of the S layer is less than 40 nm, the smoothing of the surface roughness of the lower layer is insufficient, and the error rate when the magnetic recording medium is obtained may deteriorate. Further, when the thickness of the S layer exceeds 1,000 nm, the dimensional stability may be lowered.

  The S layer may contain fine particles having an average particle diameter of 10 to 100 nm, preferably 10 to 60 nm, as long as the purpose of the present application is not impaired. Preferable particles include inert particles such as inorganic particles and organic particles, and are not particularly limited. However, aggregated particles such as titanium oxide, colloidal silica, aluminum silicate particles, carbon black, alumina and zirconia, crosslinked polystyrene, silicone However, it is not limited to such as crosslinked organic particles such as polyimide. Further, the contained particles may be one type, but two or more types may be used in combination.

  When said A layer and B layer contain 1-50 mass% of amorphous thermoplastic resins (B) other than polyester whose glass transition temperature is 100-250 degreeC, it is crystalline thermoplasticity to a biaxially-oriented polyester film. This is preferable because the constraining points due to the fine crystals of the resin (A) can be formed efficiently. A preferable range of the glass transition temperature of the amorphous thermoplastic resin (B) is 150 to 250 ° C, and a more preferable range is 200 to 250 ° C. A preferable range of the content of the amorphous thermoplastic resin (B) in each layer is 3 to 40% by mass. If the content is out of the above range, the dispersibility of the crystalline thermoplastic resin (A) in the biaxially oriented polyester film becomes poor, resulting in poor stretching in the film forming process, transparency, dimensional stability, and error rate. It may be difficult to improve.

  The amorphous thermoplastic resin (B) is a resin different from polyester. Here, the term “amorphous” refers to a property in which, when a sample is measured using differential scanning calorimetry (DSC) or the like, only the glass transition temperature is detected and the melting point and melting peak are not detected.

  The amorphous thermoplastic resin (B) is preferably a resin having an imide group or a sulfone group in order to be compatible with the crystalline thermoplastic resin (A), and a group consisting of polyetherimide, polyethersulfone and polysulfone It is preferable that at least one resin selected from the group consisting of: In particular, a polyetherimide having an imide group is preferable because compatibility with the polyester and the crystalline thermoplastic resin (A) is likely to increase. Polyetherimide is a resin containing an ether bond in a polyimide constituent component composed of an imide group, and is represented by the following general formula.

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

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

Or

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

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

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

  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.

  The polyester may be copolymerized with a monofunctional compound such as lauryl alcohol or phenyl isocyanate, or a trifunctional compound such as trimellitic acid, pyromellitic acid, glycerol, pentaerythritol, or 2,4-dioxybenzoic acid. A compound or the like 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 having a melting point of 200 ° C. or higher and lower than 280 ° C. can be suitably used in order to perform biaxial stretching and to exhibit the effects of the present invention such as dimensional stability. A preferable melting point is 230 ° C. or higher and 270 ° C. or lower. In the present invention, polyethylene terephthalate, polyethylene naphthalate (polyethylene-2,6) can be used as the polyester in that a restraint point caused by microcrystals of the crystalline thermoplastic resin (A) having a specific melting point is formed in the film. -Naphthalate) is preferred. Further, these copolymers and modified products may be used, and polymer alloys with other thermoplastic resins may be used. The polymer alloy here refers to a polymer multi-component system, which may be a block copolymer by copolymerization or a polymer blend by mixing. In this invention, it is preferable that at least 1 sort (s) of these polymers is included.

  The biaxially oriented polyester film of the present invention preferably has at least one layer having a crystallization index ΔTcg of 25 to 75 ° C. The crystallization index ΔTcg is an indicator of whether or not the constraining points due to the microcrystals of the crystalline thermoplastic resin (A) are efficiently formed in the biaxially oriented polyester film. Preferably, the crystallization index ΔTcg is 40 to 70 ° C. In addition, it is preferable that the layer having ΔTcg in the above range is the A layer because dimensional stability is improved.

  The peak temperature of the loss tangent (tan δ) in the longitudinal direction of the biaxially oriented polyester film of the present invention is preferably 125 to 180 ° C. More preferably, it is 130-170 degreeC, More preferably, it is 133-160 degreeC. When the peak temperature of tan δ in the longitudinal direction is lower than 125 ° C., there is a possibility that the restraint points due to the crystalline thermoplastic resin (A) in the film are not efficiently formed. Further, the peak temperature of tan δ in the longitudinal direction of 180 ° C. is considered to be a limit on the production method of the polyester film.

  In the present invention, in order to efficiently form a restraint point of the crystalline thermoplastic resin (A) in the biaxially oriented polyester film, a crystalline thermoplastic resin (A It is important to uniformly disperse). However, when a small amount of a crystalline thermoplastic resin (A) having a higher melting point than that of polyester and having a different melt viscosity is contained in the polyester, the melting temperature is low in the normal polyester melt extrusion method, so that the crystalline heat Unmelted foreign matter due to the plastic resin (A) is likely to occur. Moreover, since the melt viscosity of the crystalline thermoplastic resin (A) at the melt extrusion temperature of the polyester is too high, there is usually a tendency not to uniformly disperse in the polyester.

  In order to solve this, in the present invention, before mixing with the polyester, (1) the crystalline thermoplastic resin (A) and the amorphous thermoplastic resin (B) having good affinity with the polyester are premixed in advance. Then, a two-component composition is prepared. Next, (2) the two-component composition obtained in the above (1) and the polyester containing the amorphous thermoplastic resin (B) are melt-kneaded to prepare a three-component composition. A two-stage kneading method is preferably employed. By using two-stage pre-melt kneading, a crystalline thermoplastic resin (A) other than polyester having a melting point of 280 to 400 ° C., which is originally difficult to uniformly mix with polyester, is converted into an amorphous thermoplastic resin (B ) Can be uniformly mixed in the polyester.

  Hereinafter, an example of the pre-melt kneading will be briefly described.

  First, the crystalline thermoplastic resin (A) and the amorphous thermoplastic resin (B) are mixed by the first stage pre-melt kneading. It is preferable to prepare a master chip (mixture 1) in which the amorphous thermoplastic resin (B) is mixed at a high concentration in the melting temperature range of 300 to 400 ° C, preferably in the range of 320 to 380 ° C. At this time, the blending ratio (mass ratio) of the amorphous thermoplastic resin (B) / crystalline thermoplastic resin (A) is preferably 50/50 to 90/10. A more preferable range is a range of 60/40 to 85/15.

  In the second stage pre-melt kneading, a mixture 1 of the crystalline thermoplastic resin (A) and the amorphous thermoplastic resin (B) obtained by the first stage kneading is prepared in advance using a polyester / non- Performing the second stage pre-melt kneading using the mixture 2 (mixing ratio (mass ratio): 60/40 to 30/70) with the crystalline thermoplastic resin (B) can increase the total light transmittance of the film. It is extremely important to be within the scope of the present invention. In this method, the melt viscosity of the mixture 2 is higher than the method in which the second stage pre-melt kneading is performed using the polyester alone or the high-viscosity polyester alone that does not contain the amorphous thermoplastic resin (B). In addition to increasing the shear stress during the second stage pre-kneading, it is possible to increase the mixing force, and because both the mixtures 1 and 2 each contain an amorphous thermoplastic resin (B). The three components are mixed efficiently, and the high-melting crystalline thermoplastic resin (A) is uniformly dispersed in the polyester. Furthermore, since the kneading temperature of the second stage is set to be equal to or higher than the melting point of the polyester, the amount of the polyester that is easily damaged by heat is reduced by using the mixture 2 containing a specific amount of the amorphous thermoplastic resin (B). There are also merits such as being able to be made, which is preferable in terms of transparency and dimensional stability of the biaxially oriented polyester film. The blending ratio of the mixture 1 and the mixture 2 is preferably in the range of 10/90 to 60/40, more preferably in the range of 20/80 to 50/50 by mass ratio.

  The melting temperature of the second stage pre-melt kneading is preferably exemplified by the range of [melting point of polyester + 60 ° C.] to [melting point of polyester + 100 ° C.]. In particular, it is preferable to carry out the second stage of kneading in the range of 300 to 330 ° C. from the viewpoint of the transparency and dimensional stability of the biaxially oriented film.

  When pre-melting and kneading with a twin screw extruder, it is also effective to appropriately adjust the screw rotation speed and the ratio of L / D (screw shaft length L / screw shaft diameter D) of the twin screw extruder. Furthermore, in a twin screw, in order to increase the kneading force, a screw shape provided with a kneading part such as a kneading paddle may be used. At this time, the mixing order of the raw materials is not particularly limited, and a method in which all raw materials are blended and then melt-kneaded by the above method, a part of the raw materials are blended and then melt-kneaded by the above method, and the remaining raw materials are blended. Any method such as a method of melt kneading or a method of mixing a part of raw materials and mixing the remaining raw materials using a side feeder during melt kneading by a single-screw or biaxial extruder may be used. Further, a method using a supercritical fluid described in Journal of Plastics Processing Society of Japan, “Molding”, Vol. 15, No. 6, pp. 382 to 385 (2003) can be preferably exemplified.

  The mixing ratio of the polymer can be examined using a microscopic FT-IR method (Fourier transform microscopic infrared spectroscopy) or an NMR method. Moreover, the presence of the restraint point in the film described above (during stretching) can be confirmed by molecular chain orientation analysis by laser Raman spectroscopy or crystal orientation by wide-angle X-rays. Moreover, the presence can also be confirmed by analysis of relaxation time by solid state NMR or solid state viscoelasticity analysis.

  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 within the above range is preferable from the viewpoint of dimensional stability due to a temperature change during recording / reproduction of the magnetic recording medium, for example, when used for a magnetic recording medium. The upper limit of the temperature expansion coefficient in the width direction is preferably 7.0 ppm / ° C., more preferably 5.0 ppm / ° C., and the lower limit is preferably −3.0 ppm / ° C., more preferably 0 ppm / ° C. In order to make the lower limit of the temperature expansion coefficient in the width direction smaller than −5.0 ppm / ° C., it is necessary to considerably increase the orientation in the width direction, and it may be difficult to obtain a biaxially oriented polyester film substantially. is there. A more preferable range is −3.0 to 7.0 ppm / ° C., and a further preferable range is 0 to 5.0 ppm / ° C.

  The biaxially oriented polyester film of the present invention preferably has a humidity expansion coefficient in the width direction of 0 to 6.0 ppm /% RH. A humidity expansion coefficient within the above range is preferable from the viewpoint of dimensional stability due to a change in humidity during recording / reproduction of the magnetic recording medium, for example, when used for a magnetic recording medium. 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 11 to 20 GPa. A preferable range of the sum of Young's modulus is 12 to 20 GPa, and a more preferable range is 13 to 18 GPa. When the sum of Young's moduli is less than 11 GPa, for example, when used for a magnetic recording medium, the Young's modulus in the longitudinal direction and the width direction is insufficient, as will be described later. Dimensional stability in the width direction tends to be reduced. 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 the dimensional stability in the width direction tends to be lowered. 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. When the Young's modulus in the width direction is smaller than 6 GPa, the dimensional stability in the width direction tends to be lowered. The lower limit of the Young's modulus in the width direction is more preferably 6.5 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.

  When the biaxially oriented polyester film of the present invention is used for a magnetic recording medium, the center line average roughness Ra on the surface on which the magnetic layer is provided is preferably 0.3 nm to 6 nm. When Ra on the surface on which the magnetic layer is provided is smaller than 0.3 nm, the friction coefficient with the transport roll, etc. may increase during film production and processing, etc., which may cause process troubles. In addition, the friction with the magnetic head is increased, and the magnetic tape characteristics are liable to deteriorate. On the other hand, when Ra is larger than 6 nm, electromagnetic conversion characteristics may deteriorate when used as a magnetic tape for high-density recording. The lower limit of Ra on the surface on which the magnetic layer is provided is more preferably 0.5 nm, still more preferably 1 nm, and the upper limit of Ra is 5 nm.

  On the other hand, the center line average roughness Ra of the surface on the back coat layer side (the surface opposite to the side on which the magnetic layer is provided) is preferably 5 to 15 nm. If Ra on the surface of the backcoat layer side is smaller than 5 nm, the friction coefficient with the transport rolls, etc. may increase in film production and processing processes, etc., which may cause process troubles. Friction with the roll increases, and tape running performance may be reduced. On the other hand, when Ra is larger than 15 nm, when the film is stored as a film roll or pancake, the surface protrusion tends to be transferred to the opposite surface and the elalate tends to increase.

  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) precipitated by a catalyst or the like added during the polyester polymerization reaction may be added. The particle size of the particles can be examined by TEM or the like, and the addition amount of the particles can be examined by an X-ray microanalyzer or pyrolysis gas chromatography mass spectrometry.

  Moreover, it is preferable that the thickness of the biaxially-oriented polyester film of this invention is 3-6 micrometers. When the thickness is smaller than 3 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 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, resin (polymer) pellets as raw materials 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. Also, various additives such as compatibilizers, plasticizers, weathering agents, antioxidants, thermal stabilizers, lubricants, antistatic agents, whitening agents, colorants, and the like, as long as they do not inhibit the present invention. Conductive agents, crystal nucleating agents, ultraviolet absorbers, flame retardants, flame retardant aids, pigments, dyes, and the like may be added.

  Subsequently, the sheet is 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 particular, in the present invention, it is preferable to use a simultaneous biaxial stretching method. Compared to the sequential biaxial stretching method, the simultaneous biaxial stretching method makes it easy to stably stretch at a high magnification because crystals grow uniformly in the longitudinal direction and the width direction in the film forming process. That is, in the present invention, it is necessary to form a large number of restraint points formed in the polyester film for the purpose of suppressing local stress concentration during stretching by the crystalline thermoplastic resin (A). Dispersing the stress at this restraint point is important for high-magnification drawing. In order to increase the molecular chain tension by making use of these characteristics in the stretching process, the molecular chain tension is gradually increased in each step of sequential biaxial stretching, and the uniform biaxial stretching is used in the longitudinal and width directions. It is particularly effective to make the molecular chain tension easy to 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 used. The heat treatment temperature is preferably [melting point of polyester (Tm) −80 ° C.] to (Tm−20 ° C.), and the heat treatment time is preferably in the range of 0.5 to 10 seconds. In particular, the heat treatment temperature of the first stage is preferably set to (Tm−75 ° C.) to (Tm−20 ° C.), more preferably (Tm−60 ° C.) to (Tm−30 ° C.). The heat treatment temperature may be set lower than the first stage. Preferably it sets to (Tm-100 degreeC)-(Tm-75 degreeC), More preferably, it sets to (Tm-100 degreeC)-(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 biaxially-oriented polyester film manufactured in this way is wound up on a core, and becomes a film 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 roll together with the core under a certain temperature condition. The constant temperature condition means that the film roll is installed together with the core in a hot air oven or zone set to a certain temperature condition. By directly heat-treating the film roll including the core, distortion of the internal structure of the film is easily removed, and dimensional stability such as creep characteristics is easily improved. For example, when the film is wound and stored, when used for a magnetic recording medium such as a magnetic tape, the film is stored in a wound state, or when the tape is run and used, the length of the film Although tension is applied in the direction and creep deformation may occur in the longitudinal direction, storage stability is likely to be significantly improved if dimensional stability such as creep characteristics is improved.

  In addition, you may perform arbitrary processes, such as heat processing, microwave heating, shaping | molding, surface treatment, lamination, coating, printing, embossing, an etching, as needed to the biaxially stretched polyester film of this invention.

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

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

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

  As a method of mixing PET with aromatic polyetherketone and polyetherimide, before melt extrusion, (1) pre-melt kneading (pelletizing) of aromatic polyetherketone and polyetherimide is carried out. Make a composition. Next, (2) two-stage melt kneading in which the composition obtained in (1) and polyester are pre-melt kneaded (pelletized) to prepare a three-component composition is preferably exemplified. In that case, a method of pre-kneading into a master chip using a high-shear mixer with high shear stress such as a twin screw extruder is preferred. When mixing with a twin screw extruder, from the viewpoint of reducing poor dispersion, a screw equipped with a triple twin screw type or a double twin screw type is preferable. By using two-stage melt-kneading, it becomes easy to mix the aromatic polyether ketone, which cannot be mixed with PET, into the biaxially oriented polyester film of the present invention via the polyetherimide.

  First, the first stage pre-kneading will be described. The polyetherimide pellets and the aromatic polyetherketone pellets are supplied to a bent twin-screw kneading extruder heated to a melting temperature in the range of 300 to 400 ° C., preferably in the range of 320 to 380 ° C., and melt extruded. A two-component blend composition is made. At this time, it is preferable to prepare a master chip in which polyetherimide is mixed at a high concentration, and it is particularly preferable that the mixing mass ratio of polyetherimide / aromatic polyetherketone is 50/50 to 90/10. More preferably, it is the range of 60 / 40-85 / 15.

  Next, the second stage pre-kneading will be described. The master chip obtained by the above first stage kneading is dried under reduced pressure at 150 ° C. for 3 hours to carry out the second stage kneading. A three-component blend composition is prepared using a PET composition having a single glass transition containing a polyetherimide prepared in advance as the polyester used in the second stage kneading. The mixing mass ratio of (PET / polyetherimide blend composition) and (aromatic polyetherketone and polyetherimide blend composition) is preferably 40/60 to 90/10, and more preferably the range is It is in the range of 50/50 to 80/20. Examples of the kneading temperature in the second stage include (melting point of polyester + 60 ° C.) to (melting point of crystalline thermoplastic resin (A) −20 ° C.). Preferably, it is the range of 300-360 degreeC. When the mixing mass ratio (PET / polyetherimide) of the PET composition having a single glass transition containing polyetherimide used here is 30/70 to 60/40, the fragrance cannot be mixed with PET. It is extremely important to uniformly disperse the group polyetherketone in the biaxially oriented polyester film and bring the total light transmittance of the film to a desired range. In addition, since the melt viscosity of the PET composition containing polyetherimide is higher than that of PET alone, the kneading force is increased. Can be mixed and dispersed. Furthermore, since the kneading temperature in the second stage is not lower than the melting point of PET, it is preferable to use a PET composition containing a specific amount of polyetherimide because there is a merit that the amount of PET subjected to thermal damage can be reduced.

Here, a method for producing a polyetherimide-containing PET composition used for the second-stage kneading will be described. Vent-type biaxial kneading in which PET pellets and polyetherimide pellets are blended so that the mixed mass ratio of PET / polyetherimide is in the range of 30/70 to 60/40 and heated to 270 to 300 ° C. Supply to an extruder and melt extrusion. The shear rate at this time is preferably 50 to 300 sec ⁻¹ , more preferably 100 to 200 sec ⁻¹ , and the residence time is preferably 0.5 to 10 minutes, more preferably 1 to 5 minutes. By kneading by the above method, PET and polyetherimide are compatible, and a pellet of polyetherimide-containing PET composition having a single glass transition temperature can be obtained.

  Here, having a single glass transition temperature (Tg) means that, ideally, only one Tg is literally recognized and no other Tg or equivalent is recognized at all. Even if a heat flux gap other than the Tg heat flux gap is recognized, it is ignored if the heat flux gap is 1/10 or less of the Tg, and it is regarded as having a single glass transition temperature. Moreover, even if there is a shoulder of 5 mJ / mg or less in the vicinity of Tg, it is regarded as having a single Tg.

  When forming into a film, the master chip raw material mixed as described above may be put into a normal single screw extruder to form a melt, or it may be directly sheeted without forming a master chip in a state where high shear is added. May be.

Moreover, 50-500 sec- ¹ can illustrate preferably the shear rate at the time of the preliminary kneading of the 1st stage and the 2nd stage. The residence time is preferably 0.5 to 10 minutes, more preferably 1 to 5 minutes. In particular, it is preferable to set the shear rate during the second stage pre-kneading to 80 to 200 sec ⁻¹ because the three components can be efficiently mixed and dispersed. Further, the ratio of (screw shaft length / screw shaft diameter) of the twin screw extruder is preferably in the range of 20 to 60, more preferably in the range of 30 to 50.

  Further, in the twin screw, in order to increase the kneading force, it is preferable to provide a kneading part by a kneading paddle or the like, and the kneading part is preferably formed in a screw shape having two or more, more preferably three or more. At this time, the mixing order of the raw materials is not particularly limited, and a method in which all raw materials are blended and then melt-kneaded by the above method, a part of the raw materials are blended and then melt-kneaded by the above method, and the remaining raw materials are blended. Any method such as a method of melt kneading or a method of mixing a part of raw materials and mixing the remaining raw materials using a side feeder during melt kneading by a single-screw or biaxial extruder may be used. Further, a method using a supercritical fluid described in Journal of Plastics Processing Society of Japan, “Molding”, Vol. 15, No. 6, pp. 382 to 385 (2003) can be preferably exemplified.

  Next, the resulting pellets of the three-component blend composition and the PET pellets are each dried under reduced pressure at 180 ° C. for 3 hours or more, and then diluted with the PET pellets so as to obtain the desired polymerization ratio of the aromatic polyether ketone. To do. This blended pellet is supplied to an extruder heated to 270 to 300 ° C. under a nitrogen stream or under reduced pressure so that the intrinsic viscosity does not decrease, extruded from a slit die, cooled on a casting roll, and unstretched. Get a film. At this time, it is preferable to use various types of filters, for example, filters made of materials such as sintered metal, porous ceramics, sand, and wire mesh, in order to remove foreign substances and altered polymers. Moreover, you may provide a gear pump as needed in order to improve fixed_quantity | feed_rate supply property. When laminating films, it is also possible to melt laminate a plurality of different polymers using two or more extruders and manifolds or merge 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 may be appropriately set depending on the type of blend polymer used, and 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.

  When the polyester film production process includes multi-stage 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. Preferably it is Tg + 60 degreeC-Tg + 100 degreeC. 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 draw ratio may be appropriately set depending on the type of blend polymer to be used, the draw temperature, and the presence / absence of multistage drawing, but the total area draw ratio (total longitudinal draw ratio × total transverse draw ratio) is 20 to 40 times. It is preferable from the viewpoint of dimensional stability to be in the range. More preferably, it is 25 to 35 times. The total draw ratio in one direction of the longitudinal direction and the width direction is preferably 2.5 to 8 times, and more preferably 3 to 7 times. If the draw ratio is smaller than the above range, uneven drawing or the like may occur and the processability of the film may be reduced. Moreover, when a draw ratio is larger than the said range, stretch breaks occur frequently and productivity may fall.

  When extending | stretching by multiple steps | paragraphs regarding each direction, 2-4 times are preferable, and, as for the draw ratio in each of the 1st step | paragraph's longitudinal direction and width direction, More preferably, it is 2.5-3 times. Moreover, the preferable area draw ratio in the first stage is 4 to 16 times, and more preferably 6 to 10 times. These stretch ratio values are particularly suitable when the simultaneous biaxial stretching method is employed, but can also be applied to the sequential biaxial stretching method.

  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 ° C. to 215 ° C., and the heat treatment time is preferably in the range of 0.5 to 10 seconds. The heat treatment process is preferably performed in two or more stages. In particular, the first stage heat treatment temperature is preferably set to 180 to 215 ° C., more preferably 190 to 210 ° 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 above-described multi-stage heat treatment process, the dimensional stability against changes in Young's modulus and temperature / humidity can be easily improved.

  Thereafter, the film edge is removed and wound on a core. In order to further enhance the dimensional stability effect 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, film roll). The atmospheric temperature of the heat treatment can be determined based on the glass transition temperature (Tg) of the biaxially stretched film, and is preferably in the range of (Tg-80 ° C) to (Tg-30 ° C), more preferably (Tg- 75 ° C) to (Tg-35 ° C), more preferably (Tg-70 ° C) 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. When performing the heat treatment in multiple stages, it is preferable that the total time of the heat treatment of the roll film is within the above range.

  Next, a method for manufacturing a magnetic recording medium will be described.

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

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

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

(1) Total light transmittance, haze, and appearance Based on JIS-K 7361-1 (1997) and JIS-K 7136 (2000), measurement is performed using the following measuring device. The transmittance at five points is measured in the longitudinal direction with respect to the center of the support, and the average value of the measurement results is defined as the total light transmittance in the present invention.

Measuring device: Turbidimeter (NDH-5000) manufactured by Nippon Denshoku Industries Co., Ltd. Measuring environment: Temperature 23 ° C. Humidity 65% RH
Number of measurements: Measure 5 times.

  The appearance was judged according to the following criteria.

◎: Total light transmittance is 88% or more ○: Total light transmittance is less than 85 to 88% ×: Total light transmittance is less than 85% (2) Temperature expansion coefficient Under the following conditions with respect to the width direction of the film Measurement is performed, and an average value of three measurement results is defined as a temperature expansion coefficient in the present invention.

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

・ Temperature expansion coefficient (ppm / ° C.) = 10 ⁶ × {(ΔL / 12.6) / (40-30)}
(3) Humidity expansion coefficient It measures on the following conditions with respect to the width direction of a film, and makes the average value of three measurement results the humidity expansion coefficient in this invention.

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

Humidity expansion coefficient (ppm /% RH) = 10 ⁶ × {(ΔL / 12.6) / (80-40)}
(4) Young's modulus The Young's modulus of the film is measured according to ASTM-D882 (1997). Instron type tensile tester is used and the conditions are as follows. The average value of the five measurement results is defined as the Young's modulus in the present invention.

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

(5) Centerline average roughness Ra
Using an atomic force microscope, 20 fields of view were measured at different locations. About the obtained image, three-dimensional surface roughness was computed by Roughness Analysis of Off-Line function, and centerline average roughness Ra was measured. The conditions are as follows.

Measuring device: NanoScope III AFM (manufactured by Digital Instruments)
Cantilever: Silicon single crystal Scanning mode: Tapping mode Scanning range: 30μm
Scanning speed: 0.5Hz
Flatten Auto: Order 3
(6) Glass transition temperature (Tg)
Specific heat was measured with the following equipment and conditions, and determined according to JIS K7121 (1987).

・ Device: Temperature modulation DSC manufactured by TA Instrument
·Measurement condition:
・ Heating temperature: 270-570K (RCS cooling method)
・ Temperature calibration: Melting point of high purity indium and tin ・ Temperature modulation amplitude: ± 1K
・ Temperature modulation period: 60 seconds ・ Temperature increase step: 5K
・ Sample weight: 5mg
Sample container: Aluminum open container (22 mg)
Reference container: Aluminum open container (18mg)
The glass transition temperature is calculated by the following formula.

Glass transition temperature = (extrapolated glass transition start temperature + extrapolated glass transition end temperature) / 2
(7) Melting point (Tm)
Using a DSC (RDC220) manufactured by Seiko Instruments Inc. as a differential scanning calorimeter and a disk station (SSC / 5200) manufactured by Seiko Instruments Inc. as a data analysis device, about 5 mg of a sample is melted and held at 300 ° C. for 5 minutes on an aluminum pan, and then rapidly solidified. After that, the temperature is raised from room temperature at a heating rate of 10 ° C./min. At that time, the peak temperature of the endothermic peak of melting observed is defined as the melting point (Tm). The melting point of the polyester can be detected by the above method.

  In addition, as a method for detecting the melting point of the crystalline thermoplastic resin (A), a micro thermal analyzer (“μ-TA apparatus” manufactured by TA Instruments) was used. The sensor of this device is provided with a detection unit made of a wire whose tip is folded back in a V shape. The measurement is performed by exposing the base film by an oblique cutting method, etc., contacting the V-shaped detection part of the sensor, and increasing from a normal temperature to a temperature of 400 ° C. under conditions of a heating rate of 10 ° C./second and an indentation strength of 20 nA. I did it.

(8) Crystallization index (ΔTcg)
Using a film slit in the shape of a tape with a width of 1/2 inch, a single blade is pressed vertically against the surface on which the A layer is laminated, and the film is further driven by 0.5 cm (running tension: 500 g, travel speed: 6.7 cm / second). At this time, 10 mg of the scraped material on the film surface adhering to the tip of the single blade was collected and used as a sample. When the scraped material was less than 10 mg in one run, the same operation was performed using another film, and 10 mg of the sample was collected.

  It measured using the apparatus of said (7). 10 mg of a sample is set in a DSC apparatus, melted at a temperature of 300 ° C. for 5 minutes, and then rapidly cooled in liquid nitrogen. The sample is heated at 10 ° C./min, and the glass transition point Tg is detected. The temperature is further raised, the crystallization exothermic peak temperature from the glassy state is the cold crystallization temperature Tcc, the endothermic peak temperature based on crystal melting is the melting temperature Tm, and the crystallization exothermic peak temperature at the time of temperature drop is the temperature lowering crystallization temperature. Tmc. The difference between Tcc and Tg (Tcc−Tg) is defined as the crystallization index ΔTcg.

(9) The loss tangent (tan δ) was also determined using a dynamic viscoelasticity measuring device “DMS6100” manufactured by Seiko Instruments Inc. according to the peak temperature JIS-K7244 (1999). The sample size was 4 mm wide × 50 mm long, the sample was prepared so that the longitudinal direction of the film was 50 mm, and the distance between chucks was set to 20 mm, and the film protruding from the chuck was removed. The temperature dependence of the viscoelastic properties of each film was measured under the measurement conditions of a tensile mode, a drive frequency of 1 Hz, a distance between chucks of 20 mm, and a heating rate of 2 ° C./min. From this measurement result, the temperature at which tan δ was maximized was defined as tan δ of the film.

(10) Thickness of laminated layers Using a transmission electron microscope (H-600 type manufactured by Hitachi), the cross section of the film was observed by an ultrathin section method (RuO ₄ staining) at an acceleration voltage of 100 kV, and the interface was observed. And the thickness of the laminated portion is determined. The magnification may be selected depending on the thickness of the laminated portion to be determined, and is not particularly limited, but 10,000 to 100,000 times is appropriate.

(11) Error rate A film slit to a width of 1 m is conveyed with a tension of 200 N, and a magnetic paint and a non-magnetic paint having the following composition are applied on one surface (A) of the support by an extrusion coater (the upper layer is magnetic). The coating thickness is 0.2 μm, the lower layer is a nonmagnetic coating and the coating thickness is 0.9 μm), magnetically oriented, and dried at a drying temperature of 100 ° C. Next, a back coat having the following composition was applied to the opposite surface (B), and then at a temperature of 85 ° C. and a linear pressure of 2.0 × 10 ⁵ N / m with a small test calender device (steel / nylon roll, 5 steps). Wind up after calendaring. The original tape is slit to a width of 1/2 inch (12.65 mm) to make a pancake. Next, a length of 200 m from this pancake is incorporated into a cassette to form a cassette tape.

(Composition of magnetic paint)
Ferromagnetic metal powder: 100 parts by mass [Fe: Co: Ni: Al: Y: Ca = 70: 24: 1: 2: 2: 1 (mass ratio)]
[Long axis length: 0.09 μm, axial ratio: 6, coercive force: 153 kA / m (1,922 Oe), saturation magnetization: 146 Am ² / kg (146 emu / g), BET specific surface area: 53 m ² / g, X-ray Particle size: 15 nm]
Modified vinyl chloride copolymer (binder): 10 parts by mass (average polymerization degree: 280, epoxy group content: 3.1% by mass, sulfonic acid group content: 8 × 10 ⁻⁵ equivalent / g)
Modified polyurethane (binder): 10 parts by mass (number average molecular weight: 25,000, sulfonic acid group content: 1.2 × 10 ⁻⁴ equivalent / g, glass transition point: 45 ° C.)
Polyisocyanate (curing agent): 5 parts by mass (Coronate L (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd.)
2-ethylhexyl oleate (lubricant): 1.5 parts by mass Palmitic acid (lubricant): 1 part by mass Carbon black (antistatic agent): 1 part by mass (average primary particle size: 0.018 μm)
Alumina (abrasive): 10 parts by mass (α alumina, average particle size: 0.18 μm)
-Methyl ethyl ketone: 75 parts by mass-Cyclohexanone: 75 parts by mass-Toluene: 75 parts by mass (composition of nonmagnetic paint)
Modified polyurethane: 10 parts by mass (number average molecular weight: 25,000, sulfonic acid group content: 1.2 × 10 ⁻⁴ equivalent / g, glass transition point: 45 ° C.)
-Modified vinyl chloride copolymer: 10 parts by mass (average polymerization degree: 280, epoxy group content: 3.1% by mass, sulfonic acid group content: 8 × 10 ⁻⁵ equivalent / g)
-Methyl ethyl ketone: 75 parts by mass-Cyclohexanone: 75 parts by mass-Toluene: 75 parts by mass-Polyisocyanate: 5 parts by mass (Coronate L (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd.)
・ 2-ethylhexyl oleate (lubricant): 1.5 parts by mass Palmitic acid (lubricant): 1 part by mass (composition of back coat)
Carbon black: 95 parts by mass (antistatic agent, average primary particle size 0.018 μm)
Carbon black: 10 parts by mass (antistatic agent, average primary particle size 0.3 μm)
Alumina: 0.1 part by mass (α alumina, average particle size: 0.18 μm)
Modified polyurethane: 20 parts by mass (number average molecular weight: 25,000, sulfonic acid group content: 1.2 × 10 ⁻⁴ equivalent / g, glass transition point: 45 ° C.)
-Modified vinyl chloride copolymer: 30 parts by mass (average polymerization degree: 280, epoxy group content: 3.1% by mass, sulfonic acid group content: 8 × 10 ⁻⁵ equivalent / g)
• Cyclohexanone: 200 parts by mass • Methyl ethyl ketone: 300 parts by mass • Toluene: 100 parts by mass Recording / reproducing the recording cassette tape in a 29 ° C. and 65% RH environment using a commercially available LTO drive 3580-L11 manufactured by IBM (Wavelength 0.55 μm) is repeated 300 times and then evaluated according to the following criteria. The error rate is calculated from the error information (number of error bits) output from the drive by the following formula. Evaluation is based on the following criteria.

Error rate = (number of error bits) / (number of write bits)
Excellent: Error rate is less than 1.0 × 10 ⁻⁶ Good: Error rate is 1.0 × 10 ⁻⁶ or more, less than 1.0 × 10 ⁻⁴ Defect: Error rate is 1.0 × 10 ⁻⁴ or more (12 ) Electromagnetic conversion characteristics A cassette tape was prepared in the same manner as in (11) 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: 2m / sec
Recording track width: 18 μm
Playback track width: 10μm
Distance between shields: 0.27 μm
Recording signal generator: HP 8118A
Reproduction signal processing: spectrum analyzer This C / N was compared with a commercially available LTO4 tape (manufactured by Fuji Film Co., Ltd.), and 0 dB or more was judged as ◯, -2 or more and less than 0 dB was judged as Δ, and less than -2 dB was judged as ×. ○ is desirable, but Δ can be used practically.

(13) Width Dimension Measurement Take out the tape from the cassette tape cartridge prepared in the same manner as in (11) above, put the sheet width measuring device prepared as shown in FIG. 1 into the following constant temperature and humidity chamber, and measure the width dimension. Do. 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 the laser beam 10 is oscillated on the magnetic tape 9, the laser beam 10 oscillated linearly in the width direction from the laser oscillator 1 is blocked only at the portion of the magnetic tape 9 and enters the light receiving unit 2. 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 Co., Ltd.
Load 4: Weight (longitudinal direction)
Sample size: width 1/2 inch x length 250 mm
Holding time: 5 hours Number of measurements: Measured 3 times.
(Width dimensional 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. X is rejected.

A condition: 10 ° C, 10% RH, tension 1.0N
B condition: 29 ° C, 80% RH, tension 0.6N
Width change rate [ppm] = 10 ⁶ × ((l _B -l _A ) / l _A )
Excellent: width dimensional change rate of 0 [ppm] or more and less than 500 [ppm] Good: width dimensional change rate of 500 [ppm] or more and less than 800 [ppm] Poor: width dimensional change rate of 800 [ppm] or more

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

Example 1
(1) Preparation of PET pellets: 194 parts by mass of dimethyl terephthalate and 124 parts by mass of ethylene glycol were charged into a transesterification reaction apparatus, 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 having an intrinsic viscosity of 0.62 (raw material-1).

  (2) Production of high-viscosity PET pellets: PET pellets (raw material-1) obtained in (1) above were dried under reduced pressure at 160 ° C. for 4 hours, and then solid-phased at 220 ° C. for 8 hours at a reduced pressure of 133 Pa or less. A polymerization reaction was performed to obtain PET pellets having an intrinsic viscosity of 1.0 (raw material-2).

(3) Preparation of PET / polyetherimide pellets: Bent-type twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading sections heated to a temperature of 280 ° C. (manufactured by Nippon Steel Works, screw diameter 30 mm) , Screw length / screw diameter = 45.5), PET pellets obtained by the above method and polyetherimide (PEI) “Ultem 1010” pellets manufactured by SABIC Innovative Plastics Co., Ltd. were supplied with a shear rate of 100 sec ^−1. Then, melt extrusion was performed at a residence time of 1 minute to obtain polyester pellets containing 50% by weight of polyetherimide. In addition, the glass transition temperature of the produced polyester pellet was 150 degreeC (raw material-3).

(4) Preparation of two-component composition (first stage pre-kneading): Bent twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading sections heated to 350 ° C. (Nippon Steel) Made by SABIC Innovative Plastics, polyetherimide (PEI) "Ultem 1040" pellets 80 mass% and Victrex polyetheretherketone (screw diameter 30mm, screw length / screw diameter = 45.5) (PEEK) 20% by weight of “Victrex 90G” pellets are supplied, melt extruded at a shear rate of 300 sec ⁻¹ , discharged into a strand, cooled with water at a temperature of 10 ° C., and immediately cut to form a two-component composition pellet. (Raw material-4).

  (5) Preparation of three-component composition (preliminary kneading in the second stage): a co-rotating bent type twin-screw kneading extruder provided with three kneading paddle kneading parts heated to a temperature of 315 ° C. (Nippon Steel) To the manufactured product, screw diameter 30 mm, screw length / screw diameter = 45.5), 50% by mass of the raw material-3 obtained in the above (3) and the two-component composition pellet obtained in the above (4) ( 50% by mass of the raw material 4) is supplied, melt extruded at a screw speed of 300 revolutions / minute, discharged into a strand, cooled with water at a temperature of 25 ° C., and immediately cut to contain 10% by mass of PEEK. A three-component composition pellet was prepared (raw material-5).

  (6) Production of particle-containing PET pellets: 98 parts by mass of the above PET pellets (raw material-1) and an average particle diameter of 0.06 μm were added to a bent biaxial kneading extruder of the same direction rotation type heated to 280 ° C. 20 parts by mass (2 parts by mass as colloidal silica particles) of 10% by mass water colloidal silica particles was supplied, the vent holes were kept at a reduced pressure of 1 kPa or less, moisture was removed, and the average particle size was 0.06 μm. A particle-containing pellet (raw material-6) having an intrinsic viscosity of 0.62 containing 2% by mass of colloidal silica particles was obtained.

  90 mass parts of PET pellets (raw material-1) and 10 mass parts of three-component composition pellets (raw material-5) were supplied to an extruder heated to 295 ° C. under reduced pressure at 180 ° C. for 3 hours. These were closely cooled and solidified while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C., and 6.5% by mass of amorphous thermoplastic resin B (hereinafter referred to as “resin B”) as a whole film and crystalline heat A laminated unstretched film containing 1% by mass of plastic resin A (hereinafter referred to as resin A) was produced.

  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 3.5 × 3.5 times at a temperature of 95 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was re-stretched 1.2 × 1.7 times at a temperature of 160 ° C. simultaneously in the longitudinal direction and the width direction. 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. Note that ΔTcg of the biaxially stretched film was 61 ° C.

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

(Example 2)
As the raw material used for the A layer, the PET pellet (raw material-1) used in Example 1 and the ternary composition pellet (raw material-5) were prepared. Furthermore, as a raw material used for the S layer, a raw material-1, a PET / polyetherimide pellet (raw material-3), and a particle-containing pellet (raw material-6) were prepared.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. was reduced to 80 parts by mass of raw material-1 and 20 parts by mass of raw material-5 at 180 ° C. for 3 hours as the A layer raw material. In the extruder E2 supplied after drying and also heated to 280 ° C., 75 parts by mass of the raw material-1 and 10 parts by mass of the raw material-3 so that the particle concentration becomes 0.3% by mass as the S layer raw material. And 15 parts by mass of raw material 6 were mixed and dried at 180 ° C. for 3 hours under reduced pressure, and then supplied. The two layers are joined together in a T-die (lamination thickness ratio E1 (A layer) / E2 (S layer) = 4/1), and close contact cooling while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. Solidified to produce a laminated unstretched film containing 11.4% by mass of resin B and 1.6% by mass of resin A as the entire film.

  The resulting unstretched film was obtained by changing the restretch ratio to 1.3 × 1.5 in the same manner as in Example 1 to obtain a biaxially stretched polyester film. In addition, ΔTcg on the A layer side of the biaxially stretched film was 65 ° C.

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

(Example 3)
As raw materials used for the A layer and the B layer, the PET pellets (raw material-1) obtained in Example 1 and the three-component composition (raw material-5) described in the above (5) were prepared.

  In the extruder E1 heated to 295 ° C. using two extruders E1 and E2, 40 parts by mass of raw material-1 and 60 parts by mass of raw material-5 were blended as PE layer contents. Was adjusted to 6% by mass, dried under reduced pressure at 180 ° C. for 3 hours, and then supplied. Similarly, in the extruder E2 heated to 295 ° C., as a layer B raw material, 97 parts by mass of raw material-1 and 3 parts by mass of raw material-5 were blended to adjust the PEEK content to 0.3% by mass, It was supplied after drying under reduced pressure at 180 ° C. for 3 hours. The two layers are joined together in a T-die (lamination thickness ratio E1 (A layer) / E2 (B layer) = 1/5), and close contact cooling while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. Solidified to produce a laminated unstretched film containing 8.13% by mass of resin B and 1.25% by mass of resin A as the entire film.

  This laminated unstretched film was biaxially stretched in the same manner as in Example 1 using a simultaneous biaxial tenter having a linear motor clip. The ΔTcg on the A layer side of the biaxially stretched film was 83 ° C.

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

Example 4
(7) Two-component composition (preliminary kneading of the first stage): a co-rotating bent type twin-screw kneading extruder provided with three kneading paddle kneading parts heated to 350 ° C. (manufactured by Nippon Steel Works) , Screw diameter / screw diameter = 45.5), 50% by mass of pellets of polyetherimide (PEI) “Ultem 1040” manufactured by SABIC Innovative Plastics and polyetheretherketone (PEEK manufactured by Victorx) ) Supply 50% by mass of “Victrex 90G” pellets, melt extrude at a shear rate of 300 sec ⁻¹ , discharge into strands, cool with water at a temperature of 10 ° C., and immediately cut to produce two-component composition pellets (Raw material-7).

  (8) Three-component composition (preliminary kneading of the second stage): Bent type twin-screw kneading extruder of the same direction type provided with three kneading paddle kneading sections heated to a temperature of 315 ° C. (manufactured by Nippon Steel Works) , Screw diameter 30 mm, screw length / screw diameter = 45.5), 50% by mass of the raw material-3 obtained in the above (3) and the two-component composition pellet obtained in the above (7) (raw material— 3) Supplying 50% by mass of 7), melt extruding at a screw speed of 300 revolutions / minute, discharging in a strand form, cooling with water at a temperature of 25 ° C., and immediately cutting to include 3 components containing 25% by mass of PEEK A composition pellet was produced (raw material-8).

  As a raw material used for the A layer, a PET pellet (raw material-1) and a three-component composition chip (raw material-8) were prepared. The raw material used for B layer prepared the B layer raw material used in Example 3. Furthermore, the S layer raw material used in Example 2 was prepared as the S layer raw material.

  In the extruder E1 heated to 295 ° C. using three extruders E1, E2, and E3, 90 parts by mass of the raw material-1 and 10 parts by mass of the raw material-8 were blended as PE layer raw material. The content was adjusted to 2.5% by mass and supplied after drying under reduced pressure at 180 ° C. for 3 hours. Similarly, in the extruder E2 heated to 295 ° C., as a layer B raw material, 97 parts by mass of raw material-1 and 3 parts by mass of raw material-5 were blended to adjust the PEEK content to 0.3% by mass, It was supplied after drying under reduced pressure at 180 ° C. for 3 hours. Furthermore, in the extruder E3 heated to 280 ° C., 75 parts by mass of the raw material-1 and 10 parts by mass of the raw material-3 so that the particle concentration becomes 0.3% by mass as the S layer raw material, and further the raw material 6 Was mixed with 15 parts by mass, dried at 180 ° C. under reduced pressure for 3 hours, and then supplied. In order to laminate these three layers, they are merged in a T-die (lamination thickness ratio E2 (B layer) / E1 (A layer) / E3 (S layer) = 1/2/2) to form a cast drum having a surface temperature of 25 ° C. A solid uncooled film containing 4.39% by mass of resin B and 1.06% by mass of resin A as a whole was produced by applying an electrostatic charge to solidify by cooling.

  This laminated unstretched film was biaxially stretched in the same manner as in Example 1 using a simultaneous biaxial tenter having a linear motor clip. The ΔTcg on the A layer side of the biaxially stretched film was 58 ° C.

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

(Example 5)
As a raw material used for the B layer, a blending amount of the two-component composition pellet (raw material-4) and the three-component composition (preliminary kneading in the second stage) described in (5) above is 40% by mass of the raw material-4. A three-component composition pellet containing 8% by mass of PEEK was prepared under the same conditions as in (5) above except that the raw material-3 was changed to 60% by mass (raw material-9).

  Then, the raw material-1 and the raw material-5 which were used in Example 1 were prepared as a raw material used for A layer.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. had 90 parts by mass of PET pellets (raw material-1) as a raw material for layer A, and a three-component composition chip (raw material-5). 10 parts by mass after drying at 180 ° C. for 3 hours under reduced pressure, and feeding to the extruder E2 similarly heated to 295 ° C., 90 mass of PET pellets (raw material-1) used in Example 1 as the B layer raw material Then, 10 parts by mass of a three-component composition chip (raw material-9) was dried at 180 ° C. for 3 hours under reduced pressure and then supplied.

  The two layers are joined together in a T-die (lamination thickness ratio E1 (A layer) / E2 (B layer) = 3/2), and close contact cooling while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. Solidified to produce a laminated unstretched film containing 0.92 mass% resin A and 6.38 mass% resin B as the entire film.

  This laminated unstretched film was biaxially stretched in the same manner as in Example 1 using a simultaneous biaxial tenter having a linear motor clip. The ΔTcg on the A layer side of the biaxially stretched film was 61 ° C.

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

(Example 6)
(9) Production of PEN pellets: 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 was added, and the temperature was 150 ° C. The ester exchange reaction was carried out while gradually raising the temperature to 240 ° C. 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 to obtain PEN pellets (raw material-10) having an intrinsic viscosity of 0.65.

(10) Production of PEN / polyethersulfone pellets: Bent type twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading parts heated to a temperature of 300 ° C. (manufactured by Nippon Steel Works, screw diameter 30 mm) , Screw length / screw diameter = 45.5), PEN pellets (raw material-10) and polyethersulfone (PES) “Sumika Excel 4100G” manufactured by Sumitomo Chemical Co., Ltd. It was melt-extruded at 100 sec ⁻¹ and a residence time of 1 minute to obtain polyester pellets containing 50% by mass of polyethersulfone (raw material-11).

  (11) Preparation of two-component composition (preliminary kneading of the first stage): a co-rotating vent type twin-screw kneading extruder provided with three kneading paddle kneading sections heated to 350 ° C. (Nippon Steel) Manufactured by Sumitomo Chemical Co., Ltd., polyethersulfone (PES) “Sumika Excel 4100G”, 85% by mass of pellets manufactured by Victrex Co., Ltd., with a screw diameter of 30 mm and a screw length / screw diameter of 45.5). Polyetheretherketone (PEEK) “Victrex 90G” pellets of 15% by mass are supplied, melt extruded at a screw speed of 300 rpm, discharged into a strand, cooled with water at a temperature of 10 ° C., and immediately cut. Two-component composition pellets (raw material-12) were prepared.

  (12) Preparation of a three-component composition (preliminary kneading in the second stage): Bent-type twin-screw kneading extruder of the same direction type provided with three kneading paddle kneading sections heated to a temperature of 330 ° C. (Nippon Steel) 50% by mass of the raw material-11 obtained in the above (10) and 50% of the raw material-12 obtained in the above (11), manufactured by Tokoro, 30 mm in screw diameter, screw length / screw diameter = 45.5) 3 parts composition pellets containing 7.5% by mass of PEEK after being melt-extruded at a screw speed of 300 revolutions / minute, discharged into a strand, cooled with water at a temperature of 25 ° C., and immediately cut. (Raw material-13).

  In the extruder E1 heated to 310 ° C. using two extruders E1 and E2, 80 parts by mass of PEN pellets (raw material-10) and three-component composition pellets (raw material-13) 20 The mass part was supplied after drying under reduced pressure at 180 ° C. for 3 hours. In the extruder E2 heated to 295 ° C., 99 parts by mass of PET pellets (raw material-1) and 1 part by mass of ternary composition pellets (raw material-5) at 180 ° C. for 3 hours are used as the B layer raw material. It supplied after drying under reduced pressure. The two layers are joined together in a T-die (lamination thickness ratio E1 (A layer) / E2 (B layer) = 4/1), and cooled closely while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. Solidified to produce a laminated unstretched film containing 10.93% by mass of resin B and 1.22% by mass of resin A.

  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 4 × 4 times at a temperature of 135 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was redrawn at a temperature of 150 ° C. simultaneously in the longitudinal direction and the width direction by 1.4 × 1.6 times. 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 ΔTcg on the A layer side of the biaxially stretched film was 95 ° 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 in dimensional stability and error rate.

(Example 7)
(13) Preparation of PEN / polyetherimide pellets: Bent twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading sections heated to a temperature of 300 ° C. (manufactured by Nippon Steel Works, screw diameter 30 mm) , 50% by mass of PEN pellets (raw material-10) and 50% by mass of polyetherimide (PEI) “Ultem 1010” manufactured by SABIC Innovative Plastics Co., Ltd. Then, melt extrusion was performed at a shear rate of 100 sec ⁻¹ and a residence time of 1 minute to obtain polyester pellets containing 50% by mass of polyetherimide (raw material-14).

  (14) Preparation of two-component composition (first stage pre-kneading): Bent twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading sections heated to a temperature of 380 ° C. (Nippon Steel) Made by SABIC Innovative Plastics, polyetherimide (PEI) "Ultem 1010" pellets 85 mass% and Mitsui Chemicals thermoplastic polyimide ( TPI) Supply 15% by mass of pellets of “Aurum PD450”, melt extrude at a screw speed of 300 revolutions / minute, discharge in a strand, cool with water at a temperature of 10 ° C., and immediately cut to form a two-component composition A pellet (raw material-15) was produced.

  (15) Preparation of three-component composition (preliminary kneading in the second stage): Co-rotating bent type twin-screw kneading extruder provided with three kneading paddle kneading sections heated to a temperature of 330 ° C. (Nippon Steel) To the manufactured product, screw diameter 30 mm, screw length / screw diameter = 45.5), 40% by mass of the raw material-14 obtained in the above (13) and the two-component composition pellet obtained in the above (14) ( 60% by mass of the raw material-15) was melt-extruded at a screw speed of 300 rpm, discharged into a strand, cooled with water at a temperature of 25 ° C., and immediately cut to contain 9% by mass of TPI. A ternary composition pellet was prepared (raw material-16).

  Similarly, the raw material-10 and the raw material-16 were prepared as the raw material used for B layer, and it was set as the following mixing | blending.

  Two extruders E1 and E2 were used, and the extruder E1 heated to 310 ° C. had 88 parts by mass of PEN pellets (raw material-10) as a raw material for layer A, ternary composition chip (raw material-16). 12 parts by mass was dried under reduced pressure at 180 ° C. for 3 hours and then supplied to the extruder E2, which was also heated to 310 ° C., 99 parts by mass of PEN pellets (raw material-10) as a B layer material, and a three-component composition chip (Raw material-16) 1 part by mass was dried at 180 ° C. under reduced pressure for 3 hours and then supplied. The two layers are joined together in a T-die (lamination thickness ratio E1 (A layer) / E2 (B layer) = 4/1), and cooled closely while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. Solidified to produce a laminated unstretched film containing 6.94% by mass of resin B and 0.9% by mass of resin A as the entire film.

  This laminated unstretched film was biaxially stretched in the same manner as in Example 6 using a simultaneous biaxial tenter having a linear motor clip. ΔTcg on the A layer side of the biaxially stretched film was 93 ° C.

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

(Example 8)
(16) Preparation of a three-component composition (preliminary kneading in the second stage): Bent-type twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading sections heated to a temperature of 330 ° C. (Nippon Steel) To the manufactured product, screw diameter 30 mm, screw length / screw diameter = 45.5), 50% by mass of the raw material-4 obtained in the above (4) and the two-component composition pellet obtained in the above (14) ( 50% by mass of the raw material-14) is melt-extruded at a screw speed of 300 revolutions / minute, discharged into a strand, cooled with water at a temperature of 25 ° C., and immediately cut to contain 10% by mass of PEEK. A ternary composition pellet was prepared (raw material-17).

  As the A layer raw material, a three-component composition (raw material-17) and a PEN pellet (raw material-10) prepared in Example 6 were prepared. Raw material-1, PET / polyetherimide pellets (raw material-3), and particle-containing pellets (raw material-6) were prepared as S layer raw materials.

  In the extruder E1 heated to 310 ° C. using two extruders E1 and E2, 90 parts by mass of PEN pellets (raw material-10) and three-component composition pellets (raw material-17) 10 were used as the A layer raw material. In the extruder E2, which was supplied after being dried under reduced pressure at 180 ° C. for 3 hours and also heated to 310 ° C., 75 parts of raw material-1 was used as the S layer raw material so that the particle concentration would be 0.3% by mass. 10 parts by mass of material, raw material-3, and 15 parts by mass of raw material 6 were blended, dried at 180 ° C. for 3 hours under reduced pressure, and then supplied. In order to laminate these two layers, they are merged in a T-die (lamination thickness ratio E1 (A layer) / E2 (B layer) = 5/1), and close contact cooling while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. Solidified to produce a laminated unstretched film containing 6.25% by mass of resin B and 0.83% by mass of resin A.

  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 4 × 4 times at a temperature of 135 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was redrawn at a temperature of 150 ° C. simultaneously in the longitudinal direction and the width direction by 1.4 × 1.6 times. 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 ΔTcg on the A layer side of the biaxially stretched film was 98 ° 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 in dimensional stability and error rate.

(Comparative Example 1)
Polyester pellets (raw material-3) containing 50% by mass of the polyetherimide obtained in Example 1 as the raw material used for the A layer, and the raw material-6-containing particles produced in Example 1 as the particle-containing pellets. A particle pellet containing 2% by mass of alumina particles was prepared in the same manner except that the average particle size was changed to alumina particles having an average particle size of 0.04 μm (raw material-18). As raw materials used for the B layer, raw material-1, raw material-3, and particles containing pellets, except that the containing particles of raw material-6 prepared in Example 1 were changed to crosslinked polystyrene particles having an average particle diameter of 0.3 μm. Similarly, a particle pellet containing 2% by mass of crosslinked polystyrene particles was prepared (raw material-19).

  In the extruder E1 heated to 280 ° C. using two extruders E1 and E2, 80 parts by mass of the raw material-1 as a raw material for the A layer, 10 parts by mass of the raw material-3, and 10 parts by mass of the raw material-18 Was supplied after being dried under reduced pressure at 180 ° C. for 3 hours and similarly heated to 280 ° C., the B layer material was 65 parts by weight of raw material-1, 20 parts by weight of raw material-3, and raw material— 19 was blended in an amount of 15 parts by mass and dried at 180 ° C. for 3 hours under reduced pressure. The two layers are merged in a T-die (lamination thickness ratio E1 (A layer) / E2 (B layer) = 12/1), and cooled closely while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. Solidified to produce a laminated unstretched film.

  This laminated unstretched film was stretched 3.2 times in the longitudinal direction at a temperature of 97 ° C. and a stretching speed of 6,000% / min with a roll-type stretching machine, and then the temperature was increased to 103 ° C. in the width direction using a tenter. Stretched 4.5 times. Further, the film was re-stretched 1.6 times at a temperature of 155 ° C. in the longitudinal direction using a roll-type stretching machine, and re-stretched 1.1 times at a temperature of 195 ° C. using a tenter. Thereafter, after heat treatment at 210 ° C. for 10 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 6.5 μm. The ΔTcg of the A layer of the biaxially stretched film was 78 ° C. The results of evaluating the obtained biaxially stretched polyester film are shown in Tables 1 and 2.

(Comparative Example 2)
(17) Preparation of two-component composition (first stage pre-kneading): Bent twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading parts heated to 350 ° C. (Nippon Steel) Made by SABIC Innovative Plastics, polyetherimide (PEI) “Utem 1040” pellets 70 mass% and Victrex polyetheretherketone (screw diameter 30 mm, screw length / screw diameter = 45.5) (PEEK) 30% by mass of “Victrex 90G” pellets are supplied, melt extruded at a shear rate of 300 sec ⁻¹ , discharged into a strand, cooled with water at a temperature of 10 ° C., and immediately cut to form a two-component composition pellet. (Raw material-20).

  (18) Preparation of three-component composition (preliminary kneading of the second stage): Bent-type twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading sections heated to a temperature of 300 ° C. (Nippon Steel) To the manufactured product, screw diameter 30 mm, screw length / screw diameter = 45.5), 70% by mass of the raw material-2 obtained in the above (2) and the two-component composition pellet obtained in the above (17) ( 30% by mass of the raw material-20) is melt-extruded at a screw speed of 300 revolutions / minute, discharged into a strand, cooled with water at a temperature of 25 ° C., and immediately cut to contain 9% by mass of PEEK. A three-component composition pellet was prepared (raw material-21).

  As raw materials used for the A layer, PET pellets (raw material-1), polyester pellets (raw material-3), particle pellets (raw material-19), two-component composition pellets (raw material-20) used in Example 1, Raw material-21 was prepared as a three-component composition pellet. The raw material used for the B layer is the same except that the raw material-1, raw material-3, raw material-6, and further the raw material-6 produced in Example 1 were changed to crosslinked polystyrene particles having an average particle diameter of 0.8 μm. A particle pellet containing 2% by mass of crosslinked polystyrene particles was prepared (raw material-22).

  Two extruders E1 and E2 were used, and the extruder E1 heated to 295 ° C. had 85.3 parts by mass of PET pellets (raw material-1) and 1.5 parts by mass of particle pellets (raw material-19). 5.6 parts by mass of three-component pellets (raw material-21) and 7.6 parts by weight of polyester pellets (raw material-3) were supplied after drying under reduced pressure at 180 ° C. for 3 hours, and also heated to 295 ° C. In the extruder E2, 78.8 parts by mass of raw material-1, 7 parts by mass of particle pellets (raw material-19), 1 part by mass of raw material-22, 5.6 parts by mass of ternary pellets (raw material-21) , And 7.6 parts by mass of raw material-3 were dried at 180 ° C. under reduced pressure for 3 hours and then supplied. In order to laminate these two layers, they are merged in a T-die (lamination thickness ratio E1 (A layer) / E2 (B layer) = 5/1), and close contact cooling while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C Solidified to produce a laminated unstretched film containing 0.5% by mass of PEEK.

  This laminated unstretched film was biaxially stretched using a simultaneous biaxial tenter having a linear motor clip. Simultaneously in the longitudinal direction and the width direction, the film was stretched 2.8 × 2.8 times at a temperature of 105 ° C. and a stretching speed of 6,000% / min, and cooled to 70 ° C. Subsequently, the film was re-stretched 1.5 × 1.8 times at the same time in the longitudinal direction and the width direction at a temperature of 180 ° C. Thereafter, after heat treatment at 200 ° C. for 5 seconds, a relaxation treatment of 2% in the width direction was performed at 160 ° C. to produce a biaxially oriented polyester film having a thickness of 5 μm. Note that ΔTcg of the A layer of the biaxially stretched film was 62 ° C.

  The evaluation results of the obtained biaxially stretched polyester film are shown in Tables 1 and 2.

(Comparative Example 3)
PET pellet (raw material-1) obtained in Example 1, high-viscosity PET pellet (raw material-2), and two-component composition pellet raw material-23 and three-component composition prepared in the following (19) and (20) Material pellet raw material-24 was prepared.

(19) Preparation of two-component composition (preliminary kneading in the first stage): Under the same conditions as raw material-4 prepared in Example 1, the polyetherimide was changed to 75% by mass of “Ultem 1010” pellets to obtain a polyether ether The pellet of ketone “Victrex90G” was changed to 25% by mass to prepare a two-component composition pellet (raw material-23)
(20) Preparation of a three-component composition (preliminary kneading in the second stage): Bent twin-screw kneading extruder of the same direction type provided with three kneading paddle kneading sections heated to a temperature of 300 ° C. (Nippon Steel) To the manufactured product, screw diameter 30 mm, screw length / screw diameter = 45.5), 50% by mass of the raw material-2 obtained in the above (2) and the two-component composition pellet obtained in the above (19) ( 50% by mass of the raw material-23) was melt-extruded at a screw speed of 300 revolutions / minute, discharged into a strand, cooled with water at a temperature of 25 ° C., and immediately cut to obtain 12.5% by mass of PEEK. A three-component composition pellet was prepared (raw material-24).

  60 mass parts of raw material-1 and 40 mass parts of raw material-24 were dried under reduced pressure at 180 ° C. for 3 hours to an extruder heated to 290 ° C. for 3 hours. These were closely cooled and solidified while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C., to prepare a laminated unstretched film containing 5% by mass of PEEK.

  The obtained unstretched film was stretched 3.5 times at a temperature of 110 ° C. and a stretching speed of 6,000% / min in a longitudinal direction using a roll stretching machine, and then a temperature of 115 ° C. in the width direction using a tenter. Stretched 3.5 times. Thereafter, the film was further stretched 1.8 times at a stretching temperature of 140 ° C. in the machine direction, then stretched 1.4 times at a stretching temperature of 180 ° C. again with a tenter, heat-treated at a temperature of 210 ° C. for 10 seconds, and then at a temperature of 160 ° C. A relaxation treatment of 3% in the width direction was performed to produce a 6.5 μm thick biaxially oriented polyester film. In addition, (DELTA) Tcg of the biaxially stretched film was 77 degreeC. The results of evaluating the obtained biaxially stretched polyester film are shown in Tables 1 and 2.

(Comparative Example 4)
As raw materials used for the A layer, PET pellets (raw material-1), polyester pellets (raw material-3), particle-containing pellets (raw material-19) and ternary composition pellets (raw material-5) used in Example 1 were prepared. Raw materials-1, raw material-3, raw material-5, and particle pellets (raw material-22) were prepared as raw materials used for the B layer.

  In the extruder E1 heated to 280 ° C. using two extruders E1 and E2, 82 parts by mass of the raw material-1, 3 parts by mass of the raw material-5, and 15 parts by mass of the raw material-19 are used as the A layer raw material. In the extruder E2, which was supplied after being dried under reduced pressure at 180 ° C. for 3 hours and heated to 280 ° C., 96.5 parts by mass of raw material-1 and 3 parts by mass of raw material-5 and 0 of raw material-22 were supplied. 0.5 parts by mass were dried at 180 ° C. under reduced pressure for 3 hours and then supplied. The two layers are joined together in a T-die (lamination thickness ratio E1 (A layer) / E2 (B layer) = 1/5), and close contact cooling while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. Solidified to produce a laminated unstretched film containing 0.3% by mass of PEEK.

  This laminated unstretched film was biaxially oriented in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 5 μm. In addition, (DELTA) Tcg of A layer of a biaxially stretched film was 76 degreeC.

  The evaluation results of the obtained biaxially stretched polyester film are shown in Tables 1 and 2.

(Comparative Example 5)
The raw materials used for the A layer were prepared as PET pellets (raw material-1) and ternary composition pellets (raw material-25) prepared in the following (21). As raw materials used for the B layer, raw material-1 and ternary composition pellets (raw material-5) were prepared.

  (21) Preparation of a three-component composition (preliminary kneading in the second stage): Bent twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading parts heated to a temperature of 315 ° C. (Nippon Steel) (Made in a factory, screw diameter 30 mm, screw length / screw diameter = 45.5), 40% by mass of the raw material-3 obtained in the above (3) and 60% by mass of the two-component composition pellet (raw material-7). , Melt-extruded at a screw speed of 300 revolutions / minute, discharged into a strand, cooled with water at a temperature of 25 ° C., and immediately cut to produce a ternary composition pellet containing 30% by mass of PEEK. (Raw material-25).

  In the extruder E1 heated to 280 ° C. using two extruders E1 and E2, 60 parts by mass of the raw material-1 and 40 parts by mass of the raw material-24 at 180 ° C. for 3 hours as the A layer raw material In the extruder E2 which was supplied after drying under reduced pressure and was also heated to 280 ° C., 99 parts by mass of raw material-1 and 1 part by mass of raw material-5 were dried under reduced pressure at 180 ° C. for 3 hours as B layer raw materials. Supplied. The two layers are joined together in a T-die (lamination thickness ratio E1 (A layer) / E2 (B layer) = 2/3), and cooled closely while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. Solidified to produce a laminated unstretched film containing 4.86% by mass of PEEK as the whole film.

  This laminated unstretched film was biaxially oriented in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 5 μm. The ΔTcg of the A layer of the biaxially stretched film was 48 ° C.

  The evaluation results of the obtained biaxially stretched polyester film are shown in Tables 1 and 2.

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

Claims (8)

A biaxially oriented polyester film having a melting point of 280 ° C. to 400 ° C., having at least one layer A containing 1 to 10% by mass of a crystalline thermoplastic resin (A) other than polyester, and having a haze of 10% or less . It has B layer which contains 0.1 to 1 mass% of crystalline thermoplastic resins (A) other than polyester whose melting | fusing point is 280 degreeC-400 degreeC on the at least single side | surface of A layer. The biaxially oriented polyester film described. The S layer containing 1 to 30% by mass of an amorphous thermoplastic resin (B) other than polyester having a glass transition temperature of 100 to 250 ° C. is provided on at least one outermost layer. 2. A biaxially oriented polyester film according to 2. A layer and B layer contain 1-50 mass% of amorphous thermoplastic resins (B) other than polyester whose glass transition temperature is 100-250 degreeC, They are in any one of Claims 1-3. Biaxially oriented polyester film. The biaxially oriented polyester film according to any one of claims 1 to 4, comprising at least one layer having a crystallization index ΔTcg of 25 to 75 ° C. The biaxially oriented polyester film according to any one of claims 1 to 5, wherein the peak temperature of loss tangent (tan δ) in the measurement of dynamic viscoelasticity in the longitudinal direction is 125 to 180 ° C. The biaxially oriented polyester film according to any one of claims 1 to 6, wherein the crystalline thermoplastic resin (A) is an aromatic polyether ketone or polyimide. The biaxially oriented polyester according to any one of claims 3 to 7, wherein the amorphous thermoplastic resin (B) contains at least one resin selected from the group consisting of polyetherimide, polyethersulfone and polysulfone. the film.

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