JP2001030350A - Biaxially oriented polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film having excellent dimensional stability and high rigidity, hard to generate a dimentional change in use environment when used especially as a base film for a magnetic recording tape and suitable as a base film for a high density magnetic recording tape. SOLUTION: A biaxially oriented polyester film consists of polyester (A) based on an ethylene terephthalate unit and polyetherimide (B) and has single glass transition temp. (Tg). In this case, the crystal size of the (-105) surface, (100) surface and (010) surface thereof is set to 30-60Å.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester film having excellent dimensional stability and high rigidity. More specifically, the present invention relates to a high-density magnetic recording which has improved storage stability in a tape use environment. The present invention relates to a biaxially oriented polyester film particularly useful as a base film for media.

[0002]

2. Description of the Related Art Polyester films, for example, polyethylene terephthalate films, are widely used in various applications including magnetic recording applications and electric applications because of their excellent mechanical, thermal and electrical properties.

Magnetic recording tapes, which are one of the fields of application of such polyester films, are being made thinner and higher in density for miniaturization and long-time recording, and dimensional changes and tension in the use environment are being promoted. There is an increasing demand for improvement in elongation and deformation of the tape due to this.

[0004] In the case of a polyethylene terephthalate film, in order to meet the above requirements, the film is stretched in two directions, a longitudinal direction (hereinafter, referred to as a longitudinal direction) and a width direction (hereinafter, referred to as a lateral direction), and then, again in a longitudinal direction or / and a longitudinal direction. In addition, a method of stretching in the transverse direction to increase the strength is mainly used.
However, when the film is stretched to increase its strength,
At the same time, there has been a problem that a dimensional change due to heat shrinkage also increases. This dimensional change lowers the yield in the tape processing process, or causes a shift in the recording track when used as a tape to increase the error rate at the time of reproduction, so the polyethylene terephthalate film on the high-density magnetic recording tape is used. It is a major challenge for application.

[0005] The technical disclosure of polyethylene terephthalate (PET) and polyetherimide (PEI) compositions involved in the present invention has been made in the past (for example, "JOURNAL OF APPLIED POL").
YMER SCIENCE 48 935-937 (19
93) ", Macromolecules 2828
45-2851 (1995), POLYMER 38
4043-4048 "(1997). However, no report has been made on a biaxially oriented film formed by a compatible blend of PET and PEI, and even more, the dimensional stability of the film has not been known at all and has not been studied.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a biaxially oriented polyester film having excellent dimensional stability and high rigidity, particularly when used as a base film for a magnetic recording tape. An object of the present invention is to provide a biaxially oriented polyester film which is less likely to undergo dimensional change in the environment and is suitable as a base film for a high density magnetic recording tape.

[0007]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a polyester film comprising a polyester (A) containing ethylene terephthalate unit as a main component and a polyetherimide (B). In, to give orientation to the film by a stretching and heat treatment process,
The inventors have found that the above problems can be solved by setting the crystal size to a specific range, and have completed the present invention.

That is, the present invention provides a single glass transition temperature (T) comprising a polyester (A) containing ethylene terephthalate units as a main component and a polyetherimide (B).
g), a (-105) plane, (1)
The main feature is a biaxially oriented polyester film characterized in that the crystal size of the (00) plane and the (010) plane is 30 to 60 angstroms.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester (A) referred to in the present invention comprises an ethylene terephthalate unit, and preferably comprises at least 70 mol% of the unit.
The polymer is more preferably 80% by mole or more. The acid component is mainly terephthalic acid, but a small amount of other dicarboxylic acid components may be copolymerized.The glycol component is mainly ethylene glycol, but the other glycol components are copolymerized components. May be added. Examples of dicarboxylic acids other than terephthalic acid include aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, isophthalic acid, diphenylsulfonedicarboxylic acid, benzophenonedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, and 3,3′-diphenyldicarboxylic acid. Examples include aliphatic dicarboxylic acids such as acid, adipic acid, succinic acid, azelaic acid, sebacic acid and dodecandioic acid, and alicyclic dicarboxylic acids such as hexahydroterephthalic acid and 1,3-adamantanedicarboxylic acid. Further, as the glycol component other than ethylene glycol, for example, chlorohydroquinone, methylhydroquinone,
Aromatic diols such as 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfide, 4,4'-dihydroxybenzophenone, p-xylene glycol, and 1,3-propanediol 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, etc.
Aliphatic and alicyclic diols such as -butanediol, 1,6-hexanediol and neopentyl glycol. Further, besides the acid component and the glycol component, p-hydroxybenzoic acid, m-hydroxybenzoic acid, aromatic hydroxycarboxylic acids such as 2,6-hydroxynaphthoic acid and p-aminophenol, p-aminobenzoic acid, etc. If the amount is small enough not to impair the object of the present invention, it can be further copolymerized.

The polyetherimide (B) referred to in the present invention is a polymer containing an aliphatic, alicyclic or aromatic ether unit and a cyclic imide group as a repeating unit, and is a polymer having melt moldability. There is no particular limitation as long as it exists. For example, U.S. Pat. Nos. 4,141,927, 26,2678, and 2606.
No. 912, Japanese Patent No. 2606914, Japanese Patent No.
596565, Japanese Patent No. 2596566, Polyetherimide such as Japanese Patent No. 2598478,
Japanese Patent No. 2598536, Japanese Patent No. 2599171, Japanese Patent Application Laid-Open No. 9-48852, Japanese Patent No. 25655
No. 6, Japanese Patent No. 25656436, Japanese Patent No. 256
No. 4637, Japanese Patent No. 25653548, Japanese Patent No. 25663547, Japanese Patent No. 2558341,
It is a polymer described in Japanese Patent No. 2558339 and Japanese Patent No. 2834580. As long as the effects of the present invention are not impaired, structural units other than cyclic imide and ether units, for example, aromatic, aliphatic and alicyclic ester units, and oxycarbonyl units are included in the main chain of the polyetherimide (B). It is a matter of course that may be contained.

Specifically, for example, a polymer containing a unit having an ether bond represented by the following general formula (I) can be mentioned.

[0012]

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In the above formula, R ₁ is a divalent aromatic or aliphatic residue having 6 to 30 carbon atoms; R ₂ is 6 to 30
Aromatic residue having 2 carbon atoms, alkylene group having 2 to 20 carbon atoms, cycloalkylene group having 2 to 20 carbon atoms, and alkylene having 2 to 8 carbon atoms It is a divalent organic group selected from the group consisting of polydiorganosiloxane groups chain-terminated with groups. As the above R ₁ and R ₂ , for example, the following formula group (I
Aromatic residue shown in I)

[0014]

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The following can be mentioned.

In the present invention, it is preferable to use a polyetherimide having a glass transition temperature of 350 ° C. or lower, more preferably 250 ° C. or lower. Further, the polyetherimide (B) must be compatible with the polyester (A). Compatible means that the two polymer blends have a single glass transition temperature (Tg) and are transparent. In addition, the Tg when these are compatible with each other is as follows.
Is generally known to exist between the Tg of polyethylene terephthalate (A) and the Tg of polyetherimide pellets (B). Note that having a single glass transition temperature (Tg) ideally means that T
g is found only once, and no other Tg or its equivalent is found at all.
Even if a gap similar to the heat flux other than the gap of the Tg is recognized, if the gap of the heat flux is 1/10 or less of the Tg, the gap is ignored and a single glass is used. It is considered to have a dislocation point temperature (Tg).
Further, even if there is a shoulder of 5 mJ / mg or less near the glass transition temperature, it is regarded as having a single Tg.

In the present invention, from the viewpoint of compatibility with the polyester (A), cost, melt moldability, etc., the following formula (II)
A polymer containing the structural unit represented by I) or (IV) and sold by General Electric Company of the United States under the trade name "ULTEM".

[0018]

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[0019]

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Is most preferred.

The biaxially oriented polyester film of the present invention contains a plasticizer, a weathering agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent as long as the effects of the present invention are not impaired. Compounds such as whitening agents, coloring agents, and conductive agents, inorganic particles, organic particles, and other kinds of polymers may be added.

The biaxially oriented polyester film of the present invention needs to have a single glass transition temperature (Tg). A single glass transition temperature means that there is only one glass transition temperature between the glass transition temperature of the polyester (A) and the glass transition temperature of the polyetherimide (B) in the differential scanning calorimetry (DSC) measurement. It is to be. When two or more glass transition temperatures are observed between the glass transition temperature of the polyester (A) and the glass transition temperature of the polyetherimide (B), the compatibility between the polyester (A) and the polyetherimide (B) becomes poor. Insufficiently, the film breaks at the time of film formation, or the surface property is deteriorated.

In the biaxially oriented polyester film of the present invention, the crystal size of the (-105) plane, the (100) plane, and the (010) plane needs to be 30 to 60 angstroms. It is preferable that all three surfaces be within the range of the crystal size. By setting the crystal size within the above range, heat shrinkage is unlikely to occur, and deformation with respect to load is small,
A highly rigid biaxially oriented polyester film having excellent dimensional stability can be obtained. Furthermore, as a result of intensive studies, it has been found that the dimensional stability can be improved when the crystal size is preferably 35 to 58 angstroms, and more preferably 40 to 55 angstroms.

The biaxially oriented polyester film of the present invention is not particularly limited.
A value of 08 to 0.18 is preferable because heat shrinkage is reduced because the structure is stabilized by the presence of crystals and the orientation of molecules is advanced. The plane orientation coefficient is preferably in the range of 0.09 to 0.175, more preferably 0.1 to 0.17.

The biaxially oriented polyester film of the present invention is not particularly limited, but preferably has an endothermic peak temperature (Tmeta) at a temperature lower than the melting point of the film from 180 ° C. to 220 ° C. From the viewpoint of crystal growth, the endothermic peak temperature (Tmeta) is preferably 180 ° C or higher, and from the viewpoint of maintaining the molecular orientation, it is preferably 220 ° C or lower. The endothermic peak temperature (Tmeta) is preferably 185 ° C to 215 ° C,
More preferably, the temperature is 190 ° C to 210 ° C.

In the biaxially oriented polyester film of the present invention, the content of the polyetherimide (B) is not particularly limited, but is preferably 1 to 50% by weight.
More preferably 5 to 30% by weight, further preferably 10
２５25% by weight. Since the melt viscosities of the polyester (A) and the polyetherimide (B) are greatly different, the content of the polyetherimide (B) is set to 1% by weight or more in order to knead with an extruder and make them compatible with each other. Is preferred. In order to sufficiently exhibit the effect of dimensional stability by the polyetherimide (B), the content of the polyetherimide (B) is preferably 1% by weight or more. On the other hand, the content of the polyetherimide (B) is preferably 50% by weight or less in order to biaxially stretch the obtained polyester film to develop a desired strength.

The intrinsic viscosity (IV) of the polyester film of the present invention is not particularly limited, but is preferably 0.6 to 1.0 dl / g from the viewpoints of film formability and dimensional stability.
Is more preferable, and the range of 0.65 to 0.80 dl / g is more preferable.

The sum (Y _MD + Y _TD ) of the Young's modulus (Y _MD ) in the longitudinal direction and the Young's modulus (Y _TD ) in the width direction of the biaxially oriented polyester film of the present invention is not particularly limited.
The range is preferably 8 to 25 GPa, more preferably 10 to 20 GPa, and particularly preferably 12 to 18 GPa.
Pa. This is because if the sum of the Young's moduli is 8 GPa or more, the elongation deformation due to stress is reduced. From the viewpoint of tear resistance and heat shrinkage properties of the film, the sum of Young's modulus is preferably 25 GPa or less.

The biaxially oriented polyester film of the present invention is not particularly limited from the viewpoints of dimensional stability of the base and workability in various film applications, but the heat shrinkage at a temperature of 100 ° C. is 2% or less. Is preferred. Temperature 100
The heat shrinkage at 0 ° C. is more preferably 1.0% or less, and 0.5%
The following are most preferred.

Although the polyester film of the present invention is not particularly limited, the temperature is 49 ° C., the humidity is 90% RH, and the load is 32.
It is preferable that the dimensional change rate (C) in the width direction after the treatment in MPa (longitudinal direction) for 72 hours is in the range of -0.3% or more to 0% or less. Here, the minus sign indicates contraction. More preferably, from -0.25% to 0%, and most preferably, from -0.2% to 0%.
% Or less. From the viewpoint of suppressing wrinkles during tape processing, the dimensional change (C) is preferably 0% or less. In addition, from the viewpoint of suppressing the shrinkage in the width direction at the time of processing the tape and improving the dimensional stability, the running durability of the tape, and the tape storability by suppressing dropout, the dimensional change rate (C)
Is preferably −0.3% or more.

Although the biaxially oriented polyester film of the present invention may be a single film, another polymer layer, for example, polyester, polyolefin, polyamide, polyvinylidene chloride, acrylic polymer or the like may be laminated thereon. In particular, when the polyester layer is thinly laminated on the surface layer, the thickness (M) of the laminated portion is set to be smaller than the average diameter (N) of the particles contained in the laminated portion (M <N).
1/1000 to 1/2 of M, more preferably 1/1
By setting the ratio to 00/10, it is possible to obtain a film having excellent running properties, slipperiness, and smoothness, and is particularly preferable as a base film for magnetic recording, which emphasizes surface characteristics. Further, in the case of a laminated film of three or more layers made of polyester, productivity can be improved by mixing a recovered material and the like in the central layer. The particles that can be contained in the laminated portion include silicon oxide, magnesium oxide, calcium carbonate, titanium oxide, aluminum oxide, crosslinked polyester, crosslinked polystyrene, mica,
Examples include, but are not limited to, talc and kaolin.

The biaxially oriented polyester film of the present invention is not particularly limited, but can be suitably used for magnetic recording media, electric capacitors, thermal transfer ribbons and the like. Among them, magnetic recording medium applications are particularly preferred.

The thickness of the biaxially oriented polyester film of the present invention can be appropriately determined according to the use and purpose.
The range of -200 µm is preferred. In particular, for magnetic recording media, it is suitable for high-density magnetic recording tapes, especially base films for data storage, and has a linear recording density of preferably 25 KB / cm or more, more preferably 34 KB / cm. cm or more, even more preferably 39 kilobytes / cm or more. The film thickness is preferably in the range of 1 μm or more to 15 μm or less for magnetic recording material applications, 2 μm or more to 10 μm or less for data application type magnetic recording media, and 3 μm or more to 9 μm or less for data deposition type magnetic recording media. .

The biaxially oriented polyester film of the present invention is preferably used for an electric capacitor for 0.5 to 1 hour.
A film having a thickness of 5 μm is applied, and the dielectric breakdown voltage and the dielectric characteristics are excellent in stability.

The biaxially oriented polyester film of the present invention can be produced by a conventional biaxial stretching method, and the production method is not particularly limited.

For example, as a preferable method for producing the film of the present invention, the polyester (A) and the polyetherimide (B) are made compatible by melt extrusion, discharged from a die, and the molten polymer is cooled and solidified to form a sheet. Then, the sheet-like molded product is stretched in the machine direction and the transverse direction, and the total area ratio (the product of the stretch ratio in the longitudinal direction and the stretch ratio in the transverse direction) is stretched to 9 to 100 times. ~ 260
A method of heat-setting at a temperature of ° C. for 0.3 seconds to 100 seconds may be used. Here, the stretching in the longitudinal direction and the transverse direction may be any of the sequential biaxial stretching method and the simultaneous biaxial stretching method. Also,
In order to make the polyester (A) and the polyetherimide (B) compatible in the melt extrusion step, it is preferable to prepare a blend chip in advance. From the viewpoint of dimensional stability, thickness unevenness, and film breaking frequency, the total area magnification is 10
The ratio is more preferably from 70 to 70 times, and most preferably from 30 to 50 times. Further, the temperature of the heat treatment is preferably 180 ° C. to 245 ° C., and more preferably 190 ° C. to 2 ° C., although it depends on the use of the film.
30 ° C. is most preferred. The heat treatment time is more preferably 0.5 second to 10 seconds, and most preferably 1 second to 5 seconds, from the viewpoints of dimensional stability and productivity of the film.

Next, specific examples of the method for producing a biaxially oriented polyester film of the present invention will be described, but it goes without saying that the present invention is not limited to the following description.

The polyethylene terephthalate pellets (A) and the polyetherimide pellets (B) obtained by a usual method are mixed at a predetermined ratio to form 270 to 3
The mixture is supplied to a vent-type twin-screw kneading extruder heated to 00 ° C. and melt-extruded. The shear rate at this time is 50 to 300 s
ec ^-1 is preferable, and more preferably 100 to 200 sec.
The c ^-1 and the residence time are preferably from 0.5 to 10 minutes, more preferably from 1 to 5 minutes.

The obtained polyetherimide-containing chip is vacuum-dried at 180 ° C. for 3 hours or more, then put into an extruder, melt-extruded at 280 to 320 ° C., and passed through a fiber sintered stainless steel metal filter. After that, the sheet is discharged from the T die in a sheet shape. Further, the sheet is subjected to a surface temperature of 2
The film is brought into close contact with a cooling drum at 5 to 30 ° C. to be cooled and solidified to obtain a substantially non-oriented film.

Next, this unstretched film is biaxially stretched,
Biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. here,
Using a longitudinal stretching machine in which several rolls are arranged, stretching is performed in the machine direction using the peripheral speed difference of the rolls (MD stretching 1), and then transverse stretching is performed by a stenter (TD stretching 1). A biaxial stretching method in which longitudinal stretching is performed again by a roll longitudinal stretching machine (MD stretching 2) and transverse stretching is again performed by a stenter (TD stretching 2) will be described.

First, the unstretched film was treated with (Tg-100)
To (Tg + 100) (° C.), preferably (Tg−
50) to (Tg + 50) (° C.), more preferably (Tg−30) to (Tg + 30) (° C.).
Preferably 1.5 to 4.0 times, more preferably 2.0 times.
The film is stretched to 3.5 times and cooled by a group of cooling rolls at 20 to 50 ° C (MD stretching 1). Next, stretching in the width direction is performed using a stenter. The stretching ratio is 2.0 to 6.0 times, preferably 3.0 to 5.5 times, and more preferably 4.0 to 5.5 times.
5.0 times, temperature is (Tg-100)-(Tg + 100)
(C), preferably (Tg-50) to (Tg + 5).
0) (° C.), more preferably (Tg-30) to
It is performed in the range of (Tg + 30) (° C.) (TD stretching 1).

Further, the film was treated with (Tg-100)
(Tg + 100) (° C.), preferably (Tg−5)
0) to (Tg + 50) (° C.), more preferably in the range of (Tg−30) to (Tg + 30) (° C.), and heated in the longitudinal direction by 1.1 to 4.0 times. Preferably it is 1.4 to 3.0 times, more preferably 1.6 to 3.0 times.
The film is stretched again by a factor of 2.5 and cooled by a group of cooling rolls at 20 to 50 ° C (MD stretching 2). Next, stretching in the width direction is performed again using a stenter.

The stretching ratio is 1.1 to 3.0 times, preferably 1.2 to 2.5 times, and more preferably 1.3 to 2.0 times.
The temperature is in the range of Tg to 250 (° C.), preferably (T
g + 20) to 240 (° C.), more preferably (Tg + 40) to 220 (° C.) (TD stretching 2). If necessary, while stretching this stretched film under tension or in the width direction, 150 to 250 ° C, preferably 170 to 240 ° C, more preferably 160 to 220 ° C.
Heat treatment in the range of

Thereafter, after cooling to room temperature, the film edge is removed, and the biaxially stretched film of the present invention can be obtained.

[Method of measuring physical properties and method of evaluating effects]
The method of measuring characteristic values and the method of evaluating effects are as follows.

(1) Refractive index In accordance with the method specified in JIS-K7105, the refractive index was measured using an Abbe refractometer with sodium D line as a light source. The mounting liquid used was methylene iodide,
It measured at 65 degreeC and 65% RH.

The plane orientation coefficient fn is expressed as (1) when the refractive indices in the longitudinal direction, the width direction, and the thickness direction are na, nb, and nc.
/ 2) × (na + nb) −nc.

(2) Crystal Size (Angstrom) Sample Preparation Samples were superposed with their directions aligned, solidified with a collodion-ethanol solution, and used for measurement.・ Measuring device X-ray generator 4036A2 type manufactured by Rigaku Denki Co., Ltd. X-ray source: CuKα ray (using Ni filter) Output: 40 kv 20 mA Goniometer Rigaku Denki Co., Ltd. Slit diameter ： Detector ： Scintillation counter Count recording device RAD-C type manufactured by Rigaku Denki Co., Ltd. ・ Analysis method 2θ / θ intensity data is measured by wide-angle X-ray diffraction, and each direction is measured. It was calculated from the half width of the surface using the following Scherrer equation.

L = Kλ / (β ₀ cos θ _B ) L: crystal size (angstrom) K: constant (= 1.0) λ: wavelength of X-ray (= 1.5418 angstroms) θ _B : Bragg angle β ₀ = (Β _E −β _I ) ^1/2 β _E : Apparent half width β _I : Instrument constant (= 1.046 × 10 ⁻² ).

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

(4) Heat shrinkage rate Measured according to JIS-C2318. Sample size: width 10 mm, mark interval 200 mm Measurement conditions: temperature 100 ° C., processing time 30 minutes, no load 100 ° C. The heat shrinkage was determined by the following formula.

Heat shrinkage (%) = [(L ₀ -L) / L ₀ ]
× 100 L ₀ : Mark line interval before heat treatment L: Mark line interval after heat treatment

(5) Dimensional change rate (C) (%) Sample size: 100 mm in longitudinal direction, 30 in width direction
mm The above sample was subjected to 2 ° C at 23 ° C and 65% RH.
After humidity control for 4 hours, the sample is stuck on a chrome mask manufactured by Dai Nippon Printing Co., Ltd., and the length (L0) in the width direction is measured using an optical microscope. Then, at 49 ° C, 90
% RH, with a load of 32 MPa applied in the longitudinal direction,
Leave for 72 hours. After leaving for 72 hours, release the load and
After controlling the humidity and humidity for 24 hours under the conditions of 3 ° C. and 65% RH, the length (L1) in the width direction was measured. The dimensional change rate in the width direction (TD) is expressed by the following formula: dimensional change rate (C) (%) = [(L1−L0) / L0] ×
100.

(6) Glass transition temperature Tg, Tmeta A robot DSC “RDC220” manufactured by Seiko Denshi Kogyo Co., Ltd. was used as a differential scanning calorimeter (DSC), and a disk station “SS” manufactured by the company was used as a data analyzer.
5 mg in an aluminum saucer using “C / 5200”
Is melted at a temperature of 300 ° C. for 5 minutes, and then quenched in liquid nitrogen. This sample is heated from room temperature to 2
The temperature was raised at a temperature rising rate of 0 ° C./min to obtain a temperature rising DSC curve. The glass transition temperature was determined from the chart according to JIS K-7121. In the case where a shoulder is observed near the glass transition temperature in the DSC curve, after determining the glass transition temperature, the area (unit mJ / mg) of the portion deviated from the baseline is determined, and if the value is 5 mJ / mg or less. , And a single Tg.

Tmeta is obtained by raising the temperature of a biaxially oriented polyester film at a rate of 20 ° C./min to obtain a DSC curve with a temperature rise, obtaining an endothermic peak accompanying melting, and observing the endothermic peak at a lower temperature than the endothermic peak. The endothermic peak was designated as Tmeta.

(7) Intrinsic viscosity: Measured at a concentration of 0.1 g / ml in orthochlorophenol at 25 ° C. The unit is indicated by [dl / g].

(8) Electromagnetic conversion characteristics of magnetic tape (S /
N) A 200 nm-thick vapor-deposited layer of a cobalt-nickel alloy (Ni 20% by weight) was provided on the film of the present invention using a continuous vacuum vapor deposition apparatus in the presence of a trace amount of oxygen. Further, after forming a carbon protective film on the surface of the vapor deposition layer by a known means,
It was slit to a width of 8 mm to prepare a pancake. Next, a length of 200 m from this pancake was incorporated into a cassette to form a cassette tape.

Using a commercially available Hi8 VTR, video S /
The N ratio was determined. For the measurement of the S / N ratio, a signal was supplied from a TV test signal generator, and a commercially available standard Hi8ME tape was attached to a 0 dB (d) using a video noise meter.
Comparative measurement was performed as B). The running conditions were 25 ° C, 6
0% RH.

If the electromagnetic conversion characteristics are 0 dB or more compared to a commercially available Hi8ME tape, the digital recording VT
This is a level that can be sufficiently used as an R tape. Evaluation was made according to the following criteria. (+3 dB or more) ：: A level that can be sufficiently used as a magnetic recording medium for data storage. (0 dB or more, less than +3 dB) Δ: This is a level that can be sufficiently used as a digital recording type VTR tape. (Less than 0 dB) x: Insufficient level as a recording type VTR tape.

(9) Dropout The number of dropouts (DO) was determined by using the above-deposited cassette tape and a commercially available digital video tape recorder (DVC) with a built-in camera.

The number of DOs was measured by recording the produced DVC tape with a commercially available digital video tape recorder with a built-in camera, playing it back for one minute, and counting the number of block mosaics that appeared on the screen. The running conditions were 25 ° C. and 60% RH. (30 or less) ○: This is a level that can be sufficiently used as a magnetic recording medium for data storage. (50 or less) Δ: This is a level that can be sufficiently used as a digital recording type VTR tape. (51 or more) ×: Insufficient level as a digital recording type VTR tape.

(10) Running Durability of Magnetic Tape After running the magnetic tape 200 times at 25 ° C. and 60% RH, the S / N ratio and the number of DOs were measured and evaluated according to the following criteria. ：: The decrease in S / N ratio is 1 dB or less, and the increase in dropout is 30 or less. Δ: S / N ratio is 2 dB or less, and dropout is 50 or less. X: The reduction of the S / N ratio is more than 2 dB, or the increase of the dropout is more than 50.

(11) Film Lamination Thickness Using a transmission electron microscope (H-600, manufactured by Hitachi), the cross section of the film was examined by an ultra-thin section method (R) at an accelerating voltage of 100 kV.
(UO ₄ staining), the interface is captured, and the layer thickness is determined. The magnification is usually selected according to the thickness of the laminate to be determined, and is not particularly limited, but 10,000 to 100,000 times is appropriate.

[0064]

EXAMPLES The present invention will be described based on examples and comparative examples.

Example 1 Polyethylene terephthalate obtained by a conventional method (unique
Pellets (50% by weight) having a viscosity of 0.85) and polyether
Luimide pellets ("Ultem 1010" (Gen
eral Electric (registered trademark)) (50
%)) To a vented biaxial kneading press heated to 280 ° C.
Feed to the output machine, shear rate 100 sec ^-1, Residence time 1
Extruded at 50 minutes, containing 50% by weight of polyetherimide.
The obtained chip (I) was obtained.

The obtained polyetherimide-containing chip (I) and polyethylene terephthalate (intrinsic viscosity 0.6
5) was dry blended at a weight ratio of 40:60. 18
After vacuum drying at 0 ° C. for 3 hours, the mixture was put into an extruder, and 285
The mixture was melt-extruded at ℃, passed through a fiber sintered stainless metal filter (5 μm cut) at a shear rate of 10 sec ⁻¹ , and discharged from a T-die into a sheet. Further, this sheet was closely adhered to a cooling drum having a surface temperature of 25 ° C. and solidified by cooling to obtain a film containing 20% by weight of a polyetherimide in a substantially non-oriented state.

The obtained film was stretched under the conditions shown in Table 1. First, using a longitudinal stretching machine in which several rolls are arranged, stretching is performed in the longitudinal direction (MD stretching 1) using the peripheral speed difference of the rolls, and then, transverse stretching (T) is performed by a stenter.
D stretching 1), further longitudinal stretching (MD stretching 2) with a roll longitudinal stretching machine, transverse stretching (TD stretching 2) with a stenter, heat treatment, cooling to room temperature, removal of film edge, thickness A 7.2 μm biaxially stretched film was obtained.

The properties of the obtained film are as shown in Table 2. The crystal size was within the range of the present invention, and it was a high quality film having excellent dimensional stability.

Examples 2 and 3 In the same manner as in Example 1, 50
The chip (I) containing the weight% was obtained. The same chip (I) and polyethylene terephthalate (intrinsic viscosity: 0.65) were mixed at an arbitrary ratio, and melt-extrusion and biaxial stretching were performed in the same manner as in Example 1 to obtain 43% by weight of polyetherimide.
The obtained biaxially oriented polyester film was obtained. The obtained film was a high quality film having excellent dimensional stability. Further, as shown in Example 3, the dimensional stability was good even when the addition amount of the polyetherimide was 3% by weight.

Example 4 A film was formed in the same manner as in Example 1 except that stretching and heat treatment were performed under the conditions shown in Table 1. The crystal size was within the range of the present invention, and was a high quality film with excellent dimensional stability.

Example 5: Except that biaxial stretching was performed only in MD stretching 1 and TD stretching 1,
A film was formed in the same manner as in Example 1. Also in this case, the crystal size was within the range of the present invention, and it was a high quality film having excellent dimensional stability.

Comparative Examples 1 and 2 In the same manner as in Example 1, a substantially non-oriented polyester film containing polyetherimide was obtained. The obtained film was formed under the stretching and heat treatment conditions shown in Table 1. The crystal size was out of the range of the present invention, and the dimensional stability was poor.

Example 6 In the same manner as in Example 1, a chip containing 50% by weight of polyetherimide was obtained.

Next, using two extruders, extruder A heated to 290 ° C. was charged with 40 parts by weight of the blended chips obtained by the above pelletizing operation and PET having an intrinsic viscosity of 0.65.
60 parts by weight of chips (I) were supplied after being vacuum-dried at 180 ° C. for 3 hours, and supplied to an extruder B heated to 280 ° C.
0.3% by weight of spherical silica particles having an average particle size of 0.17 μm
And polyethylene terephthalate (PET) (I) containing 0.05% by weight of spherical silica particles having an average particle diameter of 0.3 μm.
The pellets of I) were supplied after being vacuum-dried at 180 ° C. for 3 hours. Thereafter, they are merged in a T-die (stacking ratio I / II =
10/1), while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C., solidified and cooled and solidified to prepare a laminated unstretched film.

This unstretched film is stretched 3.5 times at a temperature of 115 ° C. in one step in the longitudinal direction by a roll-type stretching machine, and further, at a temperature of 120 ° C. in a width direction using a tenter.
The film was stretched three times. Subsequently, a roll-type stretching machine is used to remove 2
In the step, the film was re-stretched 1.6 times at a temperature of 155 ° C. and re-stretched 1.5 times at a temperature of 190 ° C. in the width direction using a tenter. After a heat treatment at 205 ° C. for 3 seconds under constant length, a 3% relaxation treatment was performed in the width direction to obtain a biaxially oriented polyester film having a thickness of 5 μm.

As shown in Table 3, the properties of this biaxially oriented polyester film were low in dropout, and had excellent characteristics such as electromagnetic conversion characteristics and running durability as base films for magnetic recording media.

Comparative Example 3 A laminated unstretched film was prepared in the same manner as in Example 6.

This unstretched film is stretched 2.9 times at a temperature of 127 ° C. in one step in the longitudinal direction by a roll-type stretching machine, and is further stretched in a width direction at a temperature of 127 ° C. using a tenter.
The film was stretched 5 times and heat-treated at a constant temperature of 145 ° C. for 0.2 seconds to obtain a biaxially oriented polyester film having a thickness of 5 μm.

As shown in Table 3, the properties of this biaxially oriented polyester film were inferior to films for magnetic recording media.

[0080]

[Table 1]

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[Table 2]

[0082]

[Table 3]

[0083]

According to the present invention, a biaxially oriented polyester film having excellent dimensional stability and high rigidity can be obtained. The film of the present invention greatly improves running durability and storage stability when used as a base film of a magnetic tape. It can also be widely used for various applications such as ribbons and condensers.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (reference) // B32B 27/36 B32B 27/36 B29K 67:00 79:00 B29L 7:00 F term (reference) 4F071 AA46 AA60 AA84 AA86 AA89 AH14 BB08 BC01 4F100 AA37 AB15 AB16 AB31 AK42A AK49A AK54A AL05A AR00B BA02 BA03 BA05 BA06 BA10B BA13 EH66 EJ38A GB41 JA04A JA05A JA11A JA20A JG06 QA04G01 QA04A01 5D006 CB01 CB07

Claims (5)

[Claims] 1. A film having a single glass transition temperature (Tg) comprising a polyester (A) having an ethylene terephthalate unit as a main component and a polyetherimide (B), wherein a (-105) plane, (100) The biaxially oriented polyester film, wherein the (010) plane and the (010) plane have a crystal size of 30 to 60 angstroms. 2. A film having a plane orientation coefficient of 0.08 to 0.1.
8. The biaxially oriented polyester film according to claim 1. 3. The biaxially oriented polyester film according to claim 1, wherein an endothermic peak temperature (Tmeta) at a temperature lower than the melting point of the film is from 180 ° C. to 220 ° C. 4. A polyetherimide (B) having a content of 1
The biaxially oriented polyester film according to any one of claims 1 to 3, wherein the amount is from 50 to 50% by weight. 5. A magnetic recording medium comprising a biaxially oriented polyester film according to any one of claims 1 to 4, wherein a magnetic layer is provided on at least one surface.