JPH1053656A - Biaxially oriented polyester film for magnetic recording media - Google Patents

Abstract

(57) [Abstract] [Problem] Excellent in winding property, abrasion resistance, running durability,
In particular, a biaxially oriented polyester film of a magnetic recording medium useful as a base film of a magnetic recording medium for a high-speed duplicator is provided. An average particle diameter d _A is 0.8~1.6μm crosslinked polymer particles A 0.001 to 0.03 wt%, average particle diameter d _B is a 0.4~0.8μm 0.1 to 0.8% by weight of the inert particles B and an average particle diameter d _C of 0.01
Containing 0.05 to 1.0% by weight of inert inorganic particles C having a Mohs hardness of 7 or more and a mean particle size ratio of the crosslinked polymer particles A and the inert inorganic particles B ( d _A /
d _B ) is a biaxially oriented polyester film satisfying the following formula (1), wherein the ratio of the three-dimensional ten-point average roughness SRz to the three-dimensional center plane average roughness SRa (SRz /
SRa) satisfying the following formula (2): a biaxially oriented polyester film for a magnetic recording medium. 1.5 ≦ d _A / d _B ≦ 3 (1) SRz / SRa ≧ 20 (2)

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 for a magnetic recording medium, and more particularly, to a base film of a magnetic recording medium for a high-speed duplicator which is excellent in winding property, abrasion resistance and running durability. The present invention relates to a biaxially oriented polyester film for a magnetic recording medium.

[0002]

2. Description of the Related Art Biaxially oriented polyester films typified by polyethylene terephthalate films are widely used as base films for magnetic recording media such as magnetic tapes because of their excellent physical and chemical properties.

[0003] Among the uses of magnetic tapes, in recent years, the production of tapes prerecorded with software such as movies has greatly increased. Conventionally, a method of high-speed duplication from a master VTR to thousands of VTRs has been adopted. However, recently, a magnetic tape that has not been recorded is superimposed on a mirror master tape that has recorded software, and a magnetic field and temperature are applied,
A method of transferring a record has been adopted. In this case, the duplicating speed is very high, and the required characteristics of the magnetic tape have been changed, and the required characteristics of the base film for the high-speed duplicator have been newly developed. For example, the winding property when winding at high speed, the close contact with the master tape, the flattening of the surface to improve the electromagnetic conversion characteristics, and the improvement of the shaving property with the guide roll that comes in contact during duplication And so on.

Heretofore, in a base film of a magnetic recording medium, large particles of inert particles have been added to improve the winding property, thereby improving the air squeezing property. However, when a large amount of such inert particles having a large particle diameter is contained, the magnetic layer surface may be pushed up by protrusions, or the protrusions due to the inert particles having a large particle diameter may be transferred to the magnetic layer surface when the layers are wound up. This significantly deteriorates the surface properties of the magnetic layer of the magnetic tape. In addition, there is a problem that the large-sized inert particles are scraped off by contact with the guide rolls, generate white powder, and cause dropout.

Further, recently, the use of cassette halves, guide pins, or plastic guide pins with a surface finish to reduce costs has made the environment for the sharpness and running durability of magnetic tapes severe. Improvements are even more strongly desired than before.

[0006]

SUMMARY OF THE INVENTION The present inventor has developed a new characteristic required as a base film of the above-described magnetic tape for a high-speed duplicator, namely, a high-speed winding property.
We are keen to solve the issues of improving the flatness and abrasion resistance of the base surface, and how to achieve the improvement of the abrasion resistance and running durability that can cope with poor cassette halves and guide pins. As a result of repeated studies, the particles to be contained in the base film were made into three components,
The above-mentioned problems can be solved by specifying the particle size and content, and by satisfying the particle size ratio of the contained particles and the surface roughness of the film surface in a specific range, a biaxially oriented polyester film having excellent total performance can be obtained. The inventors have found that the present invention can be obtained, and reached the present invention.

[0007]

That SUMMARY OF THE INVENTION The present invention is an average particle diameter d _A is 0.8~1.6μm crosslinked polymer particles A 0.001 to 0.03 wt%, average particle diameter d _B is 0.
0.1 to 0.8% by weight of inert particles B having a particle size of 4 to 0.8 μm, and inert inorganic particles C having an average particle size d _C of 0.01 to 0.3 μm and a Mohs hardness of 7 or more. 0.0
5 to 1.0 and containing by weight%, and the ratio of the average particle size of the crosslinked polymer particles A and the inert inorganic particles B (d _A / d _B) is biaxially oriented polyester film satisfying the following formulas (1) And a ratio (SRz / SRa) between the three-dimensional ten-point average roughness SRz and the three-dimensional center plane average roughness SRa of the film surface satisfies the following expression (2). It is an axially oriented polyester film.

[0008]

1.5 ≦ d _A / d _B ≦ 3 (1) SRz / SRa ≧ 20 (2)

The polyester in the present invention is a polyester containing an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. The polyester is substantially linear and has film-forming properties, especially by melt-forming. Examples of the aromatic dicarboxylic acid include terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and anthracene dicarboxylic acid. it can. As the aliphatic glycol, for example, a polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol or the like, or an alicyclic group such as cyclohexanedimethanol. Diols and the like can be mentioned.

In the present invention, it is preferable that the polyester contains alkylene terephthalate and / or alkylene naphthalate as a main component.

Among these polyesters, in particular, polyethylene terephthalate and polyethylene-2,6-naphthalate, for example, terephthalic acid and / or 2,6-naphthalenedicarboxylic acid account for at least 80 mol% of all dicarboxylic acid components, and A copolymer in which 80% by mole or more of the component is ethylene glycol is preferred. At that time, not more than 20 mol% of the total acid components can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. Acid: It can be an alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid. In addition, 2 of all glycol components
0 mol% or less can be the above-mentioned glycols other than ethylene glycol. For example, aromatic diols such as hydroquinone, resorcinol and 2,2-bis (4-hydroxyphenyl) propane: 1,4-dihydroxydimethylenebenzene Aliphatic diols having an aromatic ring as described above; polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like.

The polyester of the present invention includes:
For example, aromatic oxyacids such as hydroxybenzoic acid, ω-
Also included are those which copolymerize or combine a component derived from an oxycarboxylic acid such as an aliphatic oxyacid such as hydroxycaproic acid at 20 mol% or less based on the total amount of the dicarboxylic acid component and the oxycarboxylic acid component.

Further, the polyester in the present invention includes:
An amount in the range that is substantially linear, for example, 2 for the total acid component
Also included are those obtained by copolymerizing a tri- or higher functional polycarboxylic acid or polyhydroxy compound such as trimellitic acid or pentaerythritol in an amount of not more than mol%.

The polyester is known per se and can be produced by a method known per se.

The biaxially oriented polyester film of the present invention simultaneously contains three types of inert particles A, B and C having different average particle sizes.

The inert particles A have an average particle size d _A is 0.8
It is a crosslinked polymer particle in the range of 1.6 μm, and its content is in the range of 0.001 to 0.03% by weight.
When the average particle diameter d _A and the content of the particles A are smaller than the above ranges, the effect of improving the winding property is insufficient, which is not preferable. On the other hand, when the average particle diameter d _A and the content are each larger than the above ranges, the electromagnetic conversion characteristics of the magnetic tape are deteriorated, and the abrasion resistance is also deteriorated. The average particle diameter d _A of the particles _A is 0.9.
１．５1.5 μm, preferably 1.0-1.5 μm.
More preferably, it is in the range of 1.4 μm. Also,
The content of the particles A is preferably in the range of 0.003 to 0.025% by weight, and 0.005 to 0.02% by weight.
Is more preferably within the range.

The crosslinked polymer particles A are preferably at least one selected from crosslinked silicone resin particles and crosslinked polystyrene particles. This is because the particles have a high affinity for polyester and the particles are soft, so that the impact applied to the projections is easily absorbed, and the projections do not easily fall off at high-speed collision.

The crosslinked polymer particles A preferably have an apparent Young's modulus of 10 to 100 kgf / mm ² , more preferably 10 to 50 kgf / mm ² . When the apparent Young's modulus is less than 10 kgf / mm ² , when particles are added to the film, the particles cannot withstand the stress at the time of stretching and are deformed, so that high projections necessary for imparting winding property are formed. It becomes difficult. On the other hand, if the apparent Young's modulus exceeds 100 kgf / mm ² , the particles become too hard, the impact resistance becomes poor, and the particles easily fall off.

The inert particles B is an average particle diameter d _B 0.4 to
The particles are in the range of 0.8 μm, the content of which is in the range of 0.1-0.8% by weight. When the average particle diameter d _B and the content of the inert particles B is less than the above range, respectively, poor slipperiness of the film, winding becomes difficult, traveling in VTR it becomes unstable. On the other hand, if it is larger than the above range, the abrasion resistance deteriorates. It is preferred that the average particle diameter d _B of the inert particles B is within the range of 0.4～0.7Myuemu, it is more preferably in the range of 0.4-0.6. The content of the inert particles B is preferably in the range of 0.15 to 0.7% by weight, and more preferably in the range of 0.2 to 0.6% by weight.

The type of the inert particles B is not particularly limited, but includes, for example, (1) silicon dioxide (including hydrate, silica sand, quartz, etc.); (2) alumina of various crystal forms;
(3) Silicates containing 30% by weight or more of SiO ₂ (eg, amorphous or crystalline clay minerals, aluminosilicates (including calcined products and hydrates), hot asbestos, zircon, fly ash, etc.) (4) oxides of Mg, Zn, Zr, and Ti; (5) sulfates of Ca and Ba;
(6) Phosphates of Li, Ba and Ca (e.g.
(Including hydrogen salts): (7) Benzoates of Li, Na, and K; (8) Terephthalates of Ca, Ba, Zn, and Mn; (9) Mg, Ca, Ba, Zn, Cd, Pb , S
r, Mn, Fe, Co, and Ni titanates; (1
0) chromates of Ba and Pb; (11) carbon (eg, carbon black, graphite, etc.); (12) glass (eg, glass powder, glass beads, etc.); (13) C
a and Mg carbonates; (14) fluorite; (15) Z
n and the like are preferred. Among them, calcium carbonate is most preferable.

The inert particles C are inert inorganic particles having a Mohs hardness of 7 or more, and have an average particle diameter d _C of 0.0
The content is in the range of 1 to 0.3 μm, and the content is 0.1 μm.
In the range of 0.5 to 1.0% by weight. Inert inorganic particles C
If the Mohs' hardness is less than 7, the scratch resistance is insufficient, which is not preferable. The inert inorganic particles having a Mohs' hardness of 7 or more are preferably aggregated particles made of aluminum oxide (alumina) and a spinel oxide, and have an average degree of aggregation in the range of 2 to 20. If the average agglomeration degree is too large or too small, the scratch resistance is insufficient. This average agglomeration degree is preferably in the range of 2 to 15, more preferably in the range of 2 to 10, and more preferably in the range of 2 or more and less than 5 from the viewpoint of the scratch resistance improving effect. Most preferred.

In the case where the inert inorganic particles C are agglomerated particles composed of aluminum oxide (alumina), it is preferable that the particles be a θ-type crystal because the effect of improving scratch resistance is greater. In the case where the inert inorganic particles C are aggregated particles made of a spinel-type oxide, MgAl ₂ O ₄ is preferable because the effect of improving scratch resistance is greater.

If the average particle diameter d _C and the content of the inert inorganic particles C are smaller than the above ranges, the effect of improving the scratch resistance is insufficient, which is not preferable. On the other hand, if it is larger than the above range, the effect of improving the scratch resistance is insufficient or the abrasion resistance deteriorates, which is not preferable. It is preferred that the average particle diameter d _C of the inert inorganic particles C is in the range of 0.03～0.25Myuemu, it is more preferably in the range of 0.05 to 0.2 [mu] m. The content is 0.1
０．７0.7% by weight, preferably 0.1-0.7% by weight.
More preferably in the range of 5 to 0.4% by weight,
Most preferably, it is in the range of 0.2% by weight or more and less than 0.25% by weight.

The biaxially oriented polyester film of the present invention simultaneously contains the three types of particles of the inert particles A, B, and C. The ratio of the average particle size of the crosslinked polymer particles A and the inert particles B ( d _A / d _B ) must satisfy the following expression (1).

[0025]

## EQU3 ## 1.5 ≦ d _A / d _B ≦ 3 (1)

[0026] When the value of d _A / d _B is smaller than 1.5, is insufficient improvement effect of the winding resistance, but improvement is observed for the larger the winding resistance than the other 3, the magnetic tape In this case, the electromagnetic conversion characteristics deteriorate, and the abrasion resistance also deteriorates. The value of d _A / d _B is from 1.7 to 2.
7, and more preferably 1.9 to 2.4.

Further, in the biaxially oriented polyester film of the present invention, the ratio (SRz / SRa) of the three-dimensional ten-point average roughness SRz and the three-dimensional center plane average roughness SRa of the film surface is expressed by the following formula (2). Need to be satisfied.

[0028]

## EQU4 ## SRz / SRa ≧ 20 (2)

When the value of SRz / SRa is less than 20,
The effect of improving the winding property is insufficient. SRz /
SRa is preferably at least 24, more preferably at least 28.

The surface roughness of the biaxially oriented polyester film of the present invention is such that the center line average roughness Ra is 10 to 2
It is preferably 5 nm, more preferably 12 to 24 nm, particularly preferably 14 to 23 nm. The center line average roughness Ra is 10n.
If it is less than m, the surface is too flat, and the effect of improving the winding property and running durability is small. On the other hand, if it is more than 25 nm, the surface is too rough, so that the electromagnetic conversion characteristics of a magnetic tape deteriorate.

The longitudinal Young's modulus of the film is 400 kgf / mm ² or more, and more preferably 450 kgf / mm ^2.
mm ² or more, and the Young's modulus in the lateral direction is 500 kgf / mm ² or more, and more preferably 600 kgf / mm ² or more.
mm ² or more. When the Young's modulus in the vertical and horizontal directions is in the above range, it is preferable because it can cope with thinning for long-time tape use.

Further, the thickness of the film is 5 to 25 μm.
m, more preferably 10 to 20 μm.

The biaxially oriented polyester film of the present invention preferably has a winding index of 100 or less at a winding speed of 200 m / min. When the winding property index is 100 or less, the effect of improving the winding property is remarkable when used as a base film for a high-speed duplicator.

On the other hand, when the winding index is larger than 100, the winding shape is deteriorated due to irregular end faces when the film is wound at a high speed. Absent. Winding speed 200
The winding index at m / min is more preferably 85
And particularly preferably 70 or less.

The biaxially oriented polyester film of the present invention can be obtained by a method basically known in the art or accumulated in the art. For example, it can be obtained by first producing an unstretched film and then biaxially orienting the film. The unstretched film is
For example, polyester can be melt-extruded into a film at a temperature of melting point (Tm: ° C.) to (Tm + 70) ° C. and solidified by quenching to obtain an unstretched film having an intrinsic viscosity of 0.35 to 0.9 dl / g.

The unstretched film can be further made into a biaxially oriented film in accordance with a conventionally accumulated method for producing a biaxially oriented film. For example, the unstretched film is uniaxially (longitudinal or transverse) (Tg-10) to (Tg-10).
g + 70) ° C. (Tg: glass transition temperature of polyester) at a magnification of 2.5 to 7.0 times, and then in a direction perpendicular to the above stretching direction (when the first stage stretching is a longitudinal direction, Tg (° C.) to (T
It can be produced by stretching at a temperature of (g + 70) ° C. at a magnification of 2.5 to 7.0 times. In this case, the area stretching ratio is 9 to 3.
It is preferably doubled, more preferably 12 to 32 times. The stretching means may be either simultaneous biaxial stretching or sequential biaxial stretching. Further, the biaxially oriented film is (Tg + 70) ° C. to Tm
It can be heat-set at a temperature of (° C). For example, 190 to 23 for polyethylene terephthalate film
It is preferable to heat set at 0 ° C. The heat setting time is, for example, 1 to 60 seconds.

The biaxially oriented polyester film of the present invention is poor in terms of improvement in winding property at high speed, flatness of base surface, and abrasion resistance required for a base film of a magnetic recording medium for a high-speed duplicator. It has excellent performance in improving abrasion resistance and running durability against a simple cassette half, a guide pin, and the like, and is extremely useful for a magnetic recording medium.

The various physical properties and properties in the present invention are measured and defined as follows.

(1) Average particle size (DP) of particles CP-50 type centrifugal particle size analyzer (Centrifugal Particle S) manufactured by Shimadzu Corporation
ize Analyzer). The particle size corresponding to 50% by mass is read from the integrated curve of the particles of each particle size and its abundance calculated on the basis of the obtained centrifugal sedimentation curve, and this value is defined as the above average particle size (see Book “Particle Size Measurement Technology, Published by Nikkan Kogyo Shimbun, 1975, pp. 242-24
7).

(2) Apparent Young's Modulus of Particles Ultra-micro compression tester MCTM-201 manufactured by Shimadzu Corporation
Using a diamond indenter at a constant load speed (29 mgf
/ Second) and apply an external force to one particle. And
The load P (kgf) when the particles are broken, the displacement Z (mm) of the indenter when the particles are broken, and the particle size d (m
From m), the apparent Young's modulus Y is calculated according to the following formula, and the same operation is performed 10 times, and the average value of 10 times is used as the apparent Young's modulus of the particles.

[0041]

## EQU5 ## Y = 2.8P / πdZ

(3) Average Cohesion of Particles The film containing the particles was formed into an ultra-thin section having a thickness of 100 nm in the cross-sectional direction, and the transmission electron microscope (for example, JEOL JE)
When the particles are observed at a magnification of about 100,000 times using M-1200EX), the smallest particles (primary particles) that cannot be further divided can be observed. 100 from this observation
The number of primary particles of the individual particles, particularly the aggregated particles (secondary particles), is counted, and the value obtained by dividing the total of the primary particles by the number of measured particles is defined as the average degree of aggregation.

(4) Three-dimensional center plane average roughness (SRa),
Three-dimensional ten-point average roughness (SRz) Using a three-dimensional roughness measuring instrument (SE-3CK manufactured by Kosaka Laboratory), needle diameter 2 μmR, needle pressure 30 mg, measurement length 1 mm, sampling pitch 2 μm, cutoff 0.25 mm , Vertical magnification 20,000 times, horizontal magnification 200 times, number of scanning 10
The three-dimensional surface profile of the film surface is imaged under zero conditions. A portion having an area S _M is extracted from the obtained profile on the center plane, and orthogonal coordinate axes, X-axis, and Y-axis are placed on the center plane of the extracted part, and an axis orthogonal to the center plane is given by the following equation as a Z-axis. Let the value be SRa.

[0044]

(Equation 6)

Here, S _M = L _X × M _Y.

Regarding SRz, the average of the first to fifth peaks and the first to fifth peaks of the plane parallel to the average line of the portion extracted from the profile by the reference area are shown. The distance from the average of the valley depth is SRz.

(5) Surface roughness of film (Ra) This is a value defined by JIS B0601 as a center line average roughness (Ra). In the present invention, a stylus type surface roughness meter manufactured by Kosaka Laboratory Co., Ltd. (SURFCORDER SE-30C). The measurement conditions and the like are as follows. (A) Tip radius of the stylus: 2 μm (b) Measurement pressure: 30 mg (c) Cutoff: 0.25 mm (d) Measurement length: 2.5 mm (e) How to summarize data: Repeated measurement of the same sample six times Excluding one of the largest values, the average value of the remaining five data is displayed.

(6) Calender Sharpness The sharpness of the running surface of the base film is evaluated using a three-stage mini super calender. The calender is a three-stage calender consisting of a nylon roll and a steel roll. The processing temperature is 80 ° C, and the linear pressure applied to the film is 200 kg / c.
m, film speed is run at 100 m / min. When the running film has traveled a total length of 4000 m, the dirt attached to the top roller of the calendar is used to evaluate the sharpness of the base film. <Five-level judgment> Grade 1: No dirt on nylon rolls. Grade 2: Almost no dirt on nylon rolls. Grade 3: Some dirt on nylon rolls, but can be easily removed by dusting. Grade 4: Dirt on nylon rolls. Difficult to remove by spraying,
It can be wiped off with a solvent such as acetone. Grade 5: Nylon rolls are very dirty and difficult to remove even with solvents.

(7) Blade Sharpness In a temperature of 20 ° C. and a humidity of 60%, the edge of a blade (a blade for an industrial razor testing machine manufactured by GKI USA) was vertically applied to a film cut to a width of 1/2 inch. 2 mm more
It is pushed in and brought into contact, and is run (friction) at a speed of 100 m / min and an inlet tension T ₁ = 50 g. 1 film
After traveling 00 m, the amount of shavings attached to the blade is evaluated. <Judgment> ：: The width of the shaving powder adhering to the blade tip is 0.5 mm
Less than ○: The width of the shaving powder adhering to the blade edge is 0.5 mm
Or more and less than 1.0 mm △: The width of the shaving powder adhering to the blade tip is 1.0 mm
Not more than 2.0 mm ×: The width of the shaving powder adhering to the blade tip is 2.0 mm
that's all.

(8) High-speed running scratching property and scraping property Measured as follows using the apparatus shown in FIG.
In FIG. 1, 1 is an unwinding reel, 2 is a tension controller, 3, 5, 6, 8, 9 and 11 are free rollers, 4 is a tension detector (entrance), 7 is a fixed rod, 10
Is a tension detector (exit), 12 is a guide roller,
Reference numeral 13 denotes a take-up reel.

In an environment at a temperature of 20 ° C. and a humidity of 60%, the width 1 /
The film cut into 2 inches is fixed to the 7 fixed rods at an angle θ = 6
The vehicle is run at a speed of 300 m / min at a speed of 300 m / min so that the inlet tension becomes 50 g, and the vehicle travels 200 m. The shavings attached to the fixed bar 7 after running and the scratches of the film after running are evaluated.

At this time, a 6φ tape guide (surface roughness R) made of SUS304 and having a sufficiently finished surface was used as a fixing rod.
a = 0.015 μm) when using the A method, and using a 6φ tape guide (surface roughness Ra = 0.15 μm) obtained by bending a SUS sintered plate into a cylindrical shape and having an insufficient surface finish. The method C is a method using a carbon black-containing polyacetal tape guide of 6φ.

<Determination of shaved powder> A: No shaved powder is observed at all. O: Sharp powder is slightly observed. Δ: Existence of shaved powder is recognized at a glance. > ：: No scratches are observed. ○: 1 to 5 scratches are observed. Δ: 6 to 15 scratches are observed. X: 16 or more scratches are observed.

(9) Low-speed repeated running friction coefficient (μ
k), Scratch property It is measured as follows using the apparatus shown in FIG.
In an environment of a temperature of 20 ° C. and a humidity of 60%, the non-magnetic surface of the magnetic tape is brought into contact with the fixing rod 7 at an angle θ = (152/180) π radian (152 °) and moved at a speed of 200 cm per minute ( Friction). Outlet tension when the inlet tension T ₁ is to adjust the tension controller 2 such that 50g (T _2: g) the film is detected by the outlet tension detector to After 50 round trip, the traveling friction coefficient μk by: Is calculated.

[0055]

Equation 7] μk = (2.303 / θ) log (T 2 / T 1) = 0.868log (T 2/35)

If the running friction coefficient (μk) is 0.25 or more, the running becomes unstable when repeatedly running in a VTR. Therefore, if the running friction coefficient (μk) is more than this value, it is determined that the running durability is poor.

At this time, a 6φ tape guide (surface roughness R) made of SUS304 and having a sufficiently finished surface was used as a fixing rod.
a = 0.015 μm) when using the A method, and using a 6φ tape guide (surface roughness Ra = 0.15 μm) obtained by bending a SUS sintered plate into a cylindrical shape and having an insufficient surface finish. The method C is a method using a carbon black-containing polyacetal tape guide of 6φ.

The scratching property is determined for the non-magnetic surface scratch of the tape after running according to the following criteria. <Scratch judgment> ：: No scratches are observed at all ○: 1 to 5 scratches are observed Δ: 6 to 15 scratches are observed ×: 16 or more scratches are observed

The magnetic tape is manufactured as follows. 100 parts by weight of γ-Fe ₂ O ₃ (hereinafter simply referred to as “parts”)
And the following composition were kneaded and dispersed in a ball mill for 12 hours. Polyester urethane 12 parts Vinyl chloride-vinyl acetate-maleic anhydride copolymer 10 parts α-alumina 5 parts Carbon black 1 part Butyl acetate 70 parts Methyl ethyl ketone 35 parts Cyclohexanone 100 parts After dispersion, further fatty acid: oleic acid 1 part Fatty acid: palmitic acid 1 part of a fatty acid ester (amyl stearate) was added and kneaded for 10 to 30 minutes. Further, 7 parts of a 25% ethyl acetate solution of a triisocyanate compound was added,
The magnetic coating solution is prepared by high-speed shearing dispersion for one hour.

The obtained coating solution is applied on a polyester film so that the dry film thickness becomes 3.5 μm. Next, after performing an orientation treatment in a DC magnetic field, the resultant is dried at 100 ° C. After drying, it is subjected to a calendering treatment and slit to a width of 1/2 inch to obtain a magnetic tape.

(10) Winding property index In the apparatus shown in FIG. 1, a film having a width of 1/2 inch is passed through the film without passing through the fixing rod 7, and at a temperature of 20 ° C. and a humidity of 60%, 200 m / min. 200m at the speed of
The vehicle is caused to run, and the end face position is detected by the CCD camera at a position immediately before being taken up by the take-up reel 13.

The amount of change in the end face position is represented as a waveform with respect to the time axis, and the waveform is calculated as a winding index by the following equation.

[0063]

(Equation 8)

Here, t: measurement time (second) x: end face variation (μm)

(11) Winding property In the apparatus shown in FIG.
The tape is run for 500 m at a speed of one minute, and evaluation is made based on whether or not winding on the winding reel side is possible and the roll shape of the wound magnetic tape. <Judgment> ：: The end face deviation of the wound roll is 1 mm or less. Δ: The end face deviation of the wound roll exceeds 1 mm.

(12) Electromagnetic conversion characteristics VHS type VTR (BR640 manufactured by Victor Company of Japan, Ltd.)
0) was modified, and a 4 MHz sine wave was input to the recording / reproducing head through an amplifier, and recorded on a magnetic tape and reproduced.
The reproduced signal is input to a spectrum analyzer.
The noise generated at a distance of 0.1 MHz from the carrier signal 4 MHz was measured, and the ratio of the carrier to the noise (C /
N) is expressed in dB. The magnetic tape was measured using this method, and the magnetic tape obtained in Comparative Example 8 was used as a reference (± 0).
The difference from this magnetic tape is defined as the electromagnetic conversion characteristic as dB).

[0067]

EXAMPLES The present invention will be further described below with reference to examples.

Examples 1 to 8, Comparative Examples 1 to 14 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and a lubricant as a lubricant Addition particles shown in Tables 1 and 3 were added, polymerization was carried out by a conventional method, and intrinsic viscosity (orthochlorophenol, 35 ° C.)
56 polyethylene terephthalates were obtained.

The polyethylene terephthalate pellets were dried at 170 ° C. for 3 hours and supplied to an extruder hopper.
Melted at a melting temperature of 280-300 ° C., and the melted polymer was passed through a 1 mm slit die to finish the surface for 0.3 s.
Extruded on a rotating cooling drum having a surface temperature of 20 ° C. to obtain an unstretched film having a thickness of 200 μm.

The unstretched film thus obtained is preheated at 75 ° C., and is further moved between low-speed and high-speed rolls by 15 m.
m, and it was stretched 3.2 times by heating with three IR heaters having a surface temperature of 800 ° C. from above, rapidly cooled, then supplied to a stenter, and stretched 4.3 times in the transverse direction at 120 ° C. .
The obtained biaxially oriented film was heat-set at 205 ° C. for 5 seconds to obtain a 14 μm-thick heat-set biaxially oriented polyester film.

Tables 2 and 4 show the characteristics of the film thus obtained. As is clear from Tables 2 and 4, the one according to the present invention exhibits excellent electromagnetic conversion characteristics, is excellent in winding property and scraping property, and is also excellent in scratch property, scraping property and running durability against various tape guides. In addition, it shows extremely excellent characteristics.

[0072]

[Table 1]

[0073]

[Table 2]

[0074]

[Table 3]

[0075]

[Table 4]

[0076]

The biaxially oriented polyester film of the present invention is excellent in winding property, base surface flatness and abrasion resistance required as a base film for a magnetic tape for a high-speed duplicator. It also has excellent abrasion resistance against guide pins and the like and running durability, and has extremely excellent total performance for magnetic recording media.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a running friction coefficient measuring device.

[Explanation of symbols]

 Reference Signs List 1 unwinding reel 2 tension controller 3, 5, 6, 8, 9, 11 free roller 4 tension detector (entrance) 7 fixing rod 10 tension detector (exit) 12 guide roller 13 take-up reel

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location // B29K 67:00 105: 16 B29L 7:00

Claims (6)

[Claims] 1. A mean particle diameter d _A is 0.8~1.6μm crosslinked polymer particles A 0.001 to 0.03 wt%, average particle diameter d _B is in 0.4~0.8μm 0.1 to 0.8% by weight of certain inert particles B and an average particle diameter d _C of 0.01
Containing 0.05 to 1.0% by weight of inert inorganic particles C having a Mohs hardness of 7 or more and a mean particle size ratio of the crosslinked polymer particles A and the inert inorganic particles B ( d _A /
d _B ) is a biaxially oriented polyester film satisfying the following formula (1), wherein the ratio of the three-dimensional ten-point average roughness SRz to the three-dimensional center plane average roughness SRa (SRz /
SRa) satisfying the following formula (2): a biaxially oriented polyester film for a magnetic recording medium. 1.5 ≦ d _A / d _B ≦ 3 (1) SRz / SRa ≧ 20 (2) 2. The crosslinked polymer particles A are at least one selected from crosslinked silicone resin particles and crosslinked polystyrene particles, and the particles have an apparent Young's modulus of 10 to 10.
^{2. The} biaxially oriented polyester film for a magnetic recording medium according to claim 1, which has a weight of 0 kgf / mm ² . 3. The magnetic recording medium according to claim 1, wherein the inert inorganic particles C are at least one kind of aggregated particles selected from aluminum oxide particles and spinel-type oxide particles, and have an average degree of aggregation of 2 to 20. For biaxially oriented polyester film. 4. The center line average roughness Ra of the film surface is 1
The biaxially oriented polyester film for a magnetic recording medium according to claim 1, which has a thickness of 0 to 25 nm. 5. The biaxially oriented polyester film for a magnetic recording medium according to claim 1, wherein a winding index at a winding speed of 200 m / min is 100 or less. 6. The biaxially oriented polyester film for a magnetic recording medium according to claim 1, wherein the film has a thickness of 5 to 25 μm.