JPH10138355A - Biaxially oriented polyester film for magnetic recording medium and video-soft tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film of high quality having excellent winding properties, cutting resistance and scratch resistance to be applied to acceleration of a manufacturing line of the film and a tape and to simultaneously provide a video-soft tape having excellent durability with small decrease in image quality at the time of fast dubbing. SOLUTION: This video-soft tape comprises a biaxially oriented polyester film for a magnetic recording medium which has 20,000 pieces/mm<2> or more of maximum number of protrusions (PC-H) of at least one surface of the film measured by a non-contact threedimensional surface roughness meter and 4 to 10 of maximum protrusion number ratio [α: (PC-H)/(PC-S)] of the maximum number (PC-H) measured by the meter to maximum number of protrusions (PC-S) measured by a contact three-dimensional surface roughness meter, and a biaxially oriented polyester film layer, a magnetic layer.

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 magnetic recording media and a tape for video software using the same. A biaxially oriented polyester film for a magnetic recording medium having a specific film surface, particularly excellent in abrasion resistance, scratch resistance, winding property, and the like required for video tape, and electromagnetic conversion characteristics and durability using the film. The present invention relates to a tape for video software having excellent properties and the like.

[0002]

2. Description of the Related Art In order to improve the flatness, slipperiness and abrasion resistance of a film, conventionally, inorganic particles such as silicon oxide, titanium dioxide, calcium carbonate, talc, clay and calcinable kaolin have been added to polyester. (For example, Japanese Patent Laid-Open No. 54
It is known to precipitate fine particles containing calcium, lithium or phosphorus in a polymerization system (for example, Japanese Patent Publication No. 52-32914).

In recent years, there has been a particularly strong demand for cost reduction, and the processing speed of the polyester film for magnetic recording medium manufacturing process (the film or tape feed speed in each process).
In addition to speeding up, the magnetic tape coated with a magnetic paint on the surface of the film, that is, also in the manufacturing process of a magnetic recording medium, a magnetic layer coating process, a calendar process, a slit process,
The biggest challenge is to increase the process speed, such as the process of incorporating a magnetic tape into a cassette, and the process of dubbing the resulting video tape, etc. to produce a soft tape. It has become.

[0004] The conventional film has the disadvantage that the film surface is scratched by the contacting rolls and guides as the process speed increases, and white powder is generated due to the film surface being scraped. In addition, due to the increase in the process speed in the calendering process, there is a problem that the frequency of cleaning the white powder attached to the calender roll increases, and the productivity decreases.
Further, in the step of winding the magnetic tape raw material into a pancake shape at a high speed, there is a problem that the product yield is reduced due to turbulence. In addition, with the spread of rental videos,
Since the video soft tape is repeatedly played back at high speed in a video recorder (VTR), the surface of the tape may be scratched due to friction with the guide pins in the tape cassette, or the image quality may be degraded due to the scraping of the magnetic layer. There is a problem with the durability of the tape.

[0005] In order to solve these problems, it is necessary to make the film surface hard to be damaged, to make the film surface rough, to reduce the friction coefficient, and to improve the winding property and running property. However, on the other hand, higher image quality is required, and improvement in the electromagnetic conversion characteristics of a film or tape is required. For this purpose, it is necessary to smooth the entire film surface. In the prior art, a film satisfying these conflicting film surface characteristics has not been obtained. Further, a tape for video software using a film satisfying the film characteristics as a support has not been obtained.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the problems that have been caused by increasing the processing speed in the film or tape manufacturing process and by repeatedly using video soft tapes, and to achieve smooth and smooth sliding. An object of the present invention is to provide a high-quality biaxially oriented polyester film for a magnetic recording medium which is excellent in properties, abrasion resistance, scratch resistance, winding property and the like. Another object of the present invention is to provide a tape for video software having excellent electromagnetic conversion characteristics and durability using the above-mentioned film as a nonmagnetic support.

[0007]

The objects of the present invention are as follows: (1) The maximum number of projections (PC-H) measured on at least one surface of a film by a non-contact three-dimensional surface roughness meter is 20;
000 / mm ² or more, and the maximum number of protrusions (PC-H) of the surface measured with a non-contact three-dimensional surface roughness meter and the maximum number of protrusions (PC-H) measured with a stylus type three-dimensional surface roughness meter The maximum ratio of the number of protrusions to (S) [α: (PC-H) / (PC-S)] is 4 to 10 and can be achieved by a biaxially oriented polyester film for a magnetic recording medium. Another object of the present invention is to provide (2) a video software tape having a biaxially oriented polyester film layer and a magnetic layer, wherein the non-contact three-dimensional film is formed on the film surface opposite to the magnetic layer of the film layer. The maximum number of protrusions (PC
-H) is 20000 / mm ² or more, and the maximum number of protrusions (PC-
H) and the maximum number of projections (PC-S) measured by the stylus type three-dimensional surface roughness meter [α: (PC-H) /
(PC-S)] is 4 to 10, which can be achieved by a tape for video software.

A more preferred embodiment of the present invention is (3)
The film has an average secondary particle diameter of 50 to 200 nm, an average primary particle diameter ratio (major axis / minor axis) of 1.25 to 3.0, and an average primary particle diameter / standard deviation of primary particle diameter (d / σ). Is 0.5 ~
5.0 to 0.5 of inorganic oxide fine particles (A).
% Of inert particles (B) having an average particle diameter of 300 to 1500 nm, and defined by the following formulas of the inorganic oxide fine particles (A) and the inert particles (B) on the surface. The polyester film of (1) or the tape for video software of (2), wherein the particle number parameter (β) is 20 to 80.

[0009]

(Equation 3)

[Wherein r (A), d (A) and c
(A) shows the average secondary particle diameter (nm), specific gravity (g / cm ³ ) and content (% by weight) in polyester of the inorganic oxide fine particles (A), respectively, and r (Bi), d ( Bi)
And c (Bi) are the average particle size (nm), specific gravity (g / cm ³ ) and content (% by weight) in polyester of the inert particles (B), respectively, and n is the inert particles ( B) is the number of types)

[0011] In a further preferred embodiment of the present invention,
(4) The polyester film or video software tape according to (3), wherein the inorganic oxide particles (A) are silica particles.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION As the polyester used in the present invention, a polyester whose main repeating unit is ethylene terephthalate and / or ethylene 2,6-naphthalate is preferred from the viewpoint of abrasion resistance and scratch resistance.

The polyester is known per se and can be produced by a known method such as a condensation reaction of an ester oligomer obtained by a direct esterification method or a transesterification method.

The limiting viscosity of the polyester film is 0.5
When adjusted to ~ 0.6, the abrasion resistance of the resulting film,
Not only scratch resistance, but also heat shrinkage properties and slit properties are further improved. A video soft tape using the polyester film as a non-magnetic support has sufficient durability. Here, the intrinsic viscosity is defined as phenol /
It refers to the intrinsic viscosity obtained by dissolving a polyester film in a tetrachloroethane mixed solvent (weight ratio: 3/2) and measuring at 30 ° C. The intrinsic viscosity of the polyester film is more preferably from 0.52 to 0.58, and particularly preferably from 0.54 to 0.56. In order to adjust the intrinsic viscosity of the polyester film to this range, the intrinsic viscosity of the polyester polymer is set to be 0.01 to 0.5 times higher than that of the film.
02 must be kept high.

The polyester film of the present invention has a maximum number of protrusions (PC-H) of at least one surface measured by a non-contact three-dimensional surface roughness meter of not less than 20,000 / mm ² , preferably 21,000 / mm ^{2. It is 2} or more, more preferably 22000 pieces / mm ² or more. In the case of a tape for video software using the film as a support, the PC on the film surface opposite to the side on which the magnetic layer is provided
-H is 20,000 / mm ² or more, preferably 2
The number is at least 1,000 / mm ² , more preferably at least 22,000 / mm ² . Here, the maximum number of protrusions (PC-H) measured with a non-contact three-dimensional surface roughness meter is a non-contact three-dimensional surface roughness meter (ET-30HK) manufactured by Kosaka Laboratory Co., Ltd. and a three-dimensional roughness analyzer ( SPA-11), where the number of cuts on the cut surface is the largest (the film surface is sliced in parallel from above,
The number of cutouts of the projection is the largest). The measurement conditions and the like will be described later. 20,000 PC-H / mm ²
If it is less than 3, the film has insufficient abrasion resistance and scratch resistance. In addition, the tape for video software having the film surface has insufficient durability, and the electromagnetic exchange characteristics are deteriorated when dubbing at a high speed. On the other hand, PC-
The upper limit of H is 30,000 pieces / mm ² from a practical point of view.
Even if PC-H is increased to exceed 30,000 pieces / mm ² , little improvement in the abrasion resistance and scratch resistance is observed. The PC-H of the film side of the video software tape using the film was 35,000 to
50,000 pieces / mm ² is preferable because the tape durability is further improved.

Further, the polyester film of the present invention comprises:
The ratio of the maximum number of protrusions [α: (PC-H) / (PC-S) of at least one surface of the surface between PC-H and the maximum number of protrusions (PC-S) measured by a stylus type three-dimensional surface roughness meter. )] Is 4-1
0, preferably 4.1 to 6.
0, more preferably 4.2 to 5.8. When the film is used as a support for video software tape,
It is necessary that α of the film surface on the side opposite to the side on which the magnetic layer is provided is 4 to 10, preferably 5.
It is 0-9.0, more preferably 5.5-8.5. Here, PC-H is as defined above, and the maximum number of protrusions (PC-S) measured by a stylus type three-dimensional surface roughness meter is:
Contact type three-dimensional surface roughness meter (SE-3A) manufactured by Kosaka Laboratory Co., Ltd.
K) and the number measured using a three-dimensional roughness analyzer (SPA-11), where the number of cut edges on the cut surface is the largest (the film surface is sliced in parallel from the top, The number of cutouts of the projection is the largest). The measurement conditions and the like will be described later. If α is less than 4, especially the surface of the film surface without protrusions is easily shaved, and the abrasion resistance of the film surface and the tape surface opposite to the magnetic layer side of the video software tape become insufficient, and Electromagnetic exchange characteristics decrease when high-speed dubbing is performed on tape. Conversely, if α exceeds 10, the winding property becomes insufficient and the product yield decreases. In addition, a tape for video software using such a film has insufficient durability.

There are various methods for obtaining a film having the above-mentioned characteristics. For example, there is a method for adding a particle having certain physical properties during the production of polyester to obtain a polyester film. Specific methods include, for example, an internal precipitation particle method-a method of reacting a catalyst residue with an ester oligomer to precipitate particles in a polymerization reaction system, a method of blending a polyester and an incompatible polymer to form a sea-island structure, and a method of casting. There is a method of forming a spherulite by heating.

That is, in the film and the non-magnetic support film of the tape for video software, the inorganic oxide fine particles (A) having certain physical properties are contained in an amount of 0.1 to 0.5% by weight with respect to the polyester film, A particle number parameter (β) of the fine particles (A) and the inert particles (B) containing at least one active particle (B);

[0019]

(Equation 4)

[In the formula, r (A) is the average secondary particle size (nm) of the inorganic oxide fine particles (A), and d (A) is the specific gravity (g / cm ³ ) of the inorganic oxide fine particles (A). , C (A) represents the content (% by weight) of the inorganic oxide fine particles (A) in the polyester, and r (Bi) represents the average particle size (n) of the inert particles (B).
m) and d (Bi) is the specific gravity (g / c) of the inert particles (B).
m ³ ), c (Bi) indicates the content (% by weight) of the inert particles (B) in the polyester, and n is the number of types of the inert particles (B) used]. , PC-H on at least one side is 20,000 pieces / mm ²
Thus, a film having α of 4 to 10 is obtained. The particle number parameter (β) of the fine particles (A) and the inert particles (B) is more preferably adjusted to 25 to 75, and particularly preferably 30 to 70.

The inorganic oxide fine particles (A) have an average secondary particle size of 50 to 200 nm, preferably 60 to 180 n.
m, particularly preferably 70 to 160 nm, and an average primary particle diameter ratio (average value of (primary particle major axis / primary particle minor axis)) of 1.25 to 3.0, preferably 1.27 to 2.5, Particularly preferably, the average primary particle size / the standard deviation of the primary particle size (d / σ) is 0.5 to 5.0, preferably 1.0 to 4.0, and particularly preferably 1.0 to 4.0. Inorganic oxide fine particles of 1.2 to 3.0 are used.

The “average secondary particle size” of the fine particles (A) is determined by the laser diffraction / scattering method by calculating the total volume of the particle population by 100%.
Is the particle size at the point where the cumulative curve becomes 50% when the cumulative curve is obtained. First, the major axis and minor axis of the primary particle when calculating the “average primary particle size ratio” are defined as the maximum length (absolute maximum length) of the distance between any two points on the circumference of the image of the primary particle. The distance (width) of the primary particles in a direction perpendicular to this is defined as the minor axis. D for obtaining “d / σ” is
The projected area circle equivalent diameter of primary particles (Haywood diameter),
σ is the standard deviation of the projected circle equivalent diameter of the primary particle. The major axis, minor axis, and average primary particle diameter (d) of the primary particles of the fine particles (A) are determined by microscopy. That is, using a scanning electron microscope, at a magnification of 10,000 to 50,000, particles 30
Image analysis is performed for 00 to 5000 pieces.

The inorganic oxide fine particles (A) are used in an amount of 0.1 to 0.5% by weight, preferably 0.2 to 0.5% by weight, based on the polyester.
The content is preferably 0.4% by weight.

The inorganic oxide fine particles (A) were obtained by a method of hydrolyzing a vapor of silicon tetrachloride with an oxyhydrogen flame (flame hydrolysis method) from the viewpoint of improving the abrasion resistance and scratch resistance. Preferable examples include silica, alumina of δ, γ, θ, and η types, and spherical monodispersed silica obtained by a method of removing alkali from sodium silicate or a method of hydrolyzing alkoxysilane. Among them, silica obtained by the flame hydrolysis method is particularly preferable because the slit property can be further improved.

The fine particles (A) are silica obtained by a flame hydrolysis method and have an average primary particle size ratio of 1.25 to 3.0.
And average primary particle size / standard deviation of primary particle size (d /
When the silica particles having σ) of 0.5 to 5.0 are used,
The resulting film has further improved effects on abrasion resistance, scratch resistance, and slitting property. Further, the durability of a video software tape using the polyester film thus obtained as a nonmagnetic support is further improved.

The at least one inert particle (B) added together with the inorganic oxide fine particles (A) has an average particle diameter of 3
00 to 1500 nm, preferably 350 to 1400 n
m, more preferably 400 to 1400 nm. If the average particle diameter of the particles (B) is 300 to 1500 nm,
The effect of improving the winding property of the film is sufficient, the surface flatness is also sufficient, and the abrasion resistance is good. Tapes for video software using such a film have good electromagnetic exchange characteristics and little dropout. The average particle size of the particles (B) can be determined in the same manner as the fine particles (A).

By using the inert particles (B) in addition to the inorganic oxide fine particles (A), the coefficient of friction of the film against various guides is reduced, and only good scratch resistance and abrasion resistance can be obtained. In addition, the winding property is remarkably improved, so that the product yield in the film slitting step and the slitting step in the production of the magnetic tape is extremely improved. Furthermore, when this is used as a non-magnetic support of a video software tape, the tape durability is good.

The amount of the inert particles (B) is from 0.01 to 1% by weight, preferably from 0.1 to 0.5%, based on the polyester.
% By weight.

Examples of the inert particles (B) include synthetic calcium carbonate particles, heat-resistant organic polymer particles, spherical silica, kaolin particles, zeolite particles, calcium phosphate particles, titanium oxide particles and the like. Among them, at least one selected from synthetic calcium carbonate and heat-resistant organic polymer particles is preferable from the viewpoint of winding property, abrasion resistance and tape durability of the film.

As a method for producing synthetic calcium carbonate particles, for example, JP-A-5-117443 or JP-A-6-117443
JP-A-1908 discloses a method of blowing carbon dioxide into an aqueous suspension of calcium hydroxide for synthesis.

The heat-resistant organic polymer particles have a thermal decomposition temperature of 360 ° C. or more, preferably 38 ° C., when the weight is reduced by 10% by weight.
Organic polymer particles having good heat resistance of 0 ° C. or higher. Examples of such heat-resistant particles include cross-linked polystyrene particles, silicon resin particles, polyimide particles, and PTFE resin [poly (tetrafluoroethylene)] particles. As the crosslinked polystyrene particles satisfying the above heat resistance, for example, those obtained by a production method described in JP-A-7-238105 are preferable.

As the inert particles (B), the inert particles (B1) having an average particle diameter of 300 to 650 nm and the inert particles (B1) having an average particle diameter of 750 to 1300 nm
The mixture of 2) was subjected to a particle number parameter (β ′)

[0033]

(Equation 5)

[Wherein, r (A) is the average secondary particle size (nm) of the inorganic oxide fine particles (A), and d (A) is the specific gravity (g / cm ³ ) of the inorganic oxide fine particles (A). , C (A) represents the content (% by weight) of the inorganic oxide fine particles (A) in the polyester, and r (Bi) represents the average particle size (n) of the inert particles (B).
m) and d (Bi) is the specific gravity (g / c) of the inert particles (B).
m ³⁾ and, c (Bi) is the inclusion in the film to indicate the content in the polyester of the inert particles (B) (wt%)] is 300 to 1,300, chipping resistance is better In addition, the winding property under high-speed running is further improved. The average particle size of the inert particles (B1) is 350 to 600.
nm is preferable, and 400 to 550 nm is particularly preferable.
The average particle size of the inert particles (B2) is 800 to 1200.
nm, particularly preferably 850 to 1100 nm. Further, the particle number parameter (β) is preferably from 25 to 75, and particularly preferably from 30 to 70.

Inert particles (B2) and inert particles (B1)
Is preferably from 200 to 600 nm from the viewpoint of improving winding property under high speed, and particularly preferably from 250 to 500 nm.

The form of the inert particles (B) is preferably close to lumpy, cubic, or spherical from the viewpoint of winding properties and tape durability. Specifically, the “area ratio of the particles to the circumscribed circle” defined by the following formula (I) is preferably 60% or more from the viewpoint of abrasion resistance and winding property. It is particularly preferably at least 70%.

[0037]

(Equation 6)

The particle size of the inert particles (B) is preferably close to uniform from the viewpoint of preventing the formation of coarse projections due to the coarse particles and the deterioration of the abrasion resistance. Specifically, the following (I
It is preferable that the “degree of variation in particle size” defined by the formula I) is 50% or less. It is particularly preferably at most 30%.

[0039]

(Equation 7)

When synthetic calcium carbonate particles are used as the inert particles (B), polyethers described in, for example, JP-A-2-178333 are used to further increase the affinity between the polyester and the synthetic calcium carbonate. It is preferable to treat the surface of the synthetic calcium carbonate particles used in the present invention with a compound such as a system acrylic copolymer salt.

The addition of the inorganic oxide fine particles (A) and the inert particles (B) to the polyester polymerization system is preferably carried out by dispersing them in a slurry form from the viewpoint of preventing scattering of particles, supply accuracy and particle dispersibility. It is particularly preferable to add as a slurry of ethylene glycol. The slurry concentration is 5
20% by weight is suitable.

In the case of dispersing in the form of a slurry, in order to reduce coarse projections on the film surface, it is preferable to use a combination of a crushing treatment by a media dispersion method, centrifugal separation and filtration.

The method of adding the glycol slurry of the particles to the polyester in the present invention is different depending on the type of the silica particles (A) and other types of inorganic oxide fine particles (A) and inert particles (B). In the case of inorganic oxide fine particles other than silica and inert particles, it is particularly preferable to add them after the transesterification reaction or the esterification reaction and before the initial polycondensation reaction ends, from the viewpoint of particle dispersibility. The end of the initial condensation reaction means the time when the intrinsic viscosity reaches about 0.2.After this point, the viscosity of the reaction system is too high, so that the mixing of the added components becomes uneven and a homogeneous product is obtained. Can not be. Further, it is not preferable because depolymerization of the oligomer occurs, causing a decrease in productivity and an increase in the amount of diethylene glycol (DEG) by-produced. On the other hand, in the case of silica particles, it is preferable to add them at the stage before the start of the transesterification reaction or before the start of the esterification reaction from the viewpoint of particle dispersibility. Particularly preferably, when added at a stage where the temperature of the reaction vessel is 100 ° C. or lower, the particle dispersibility in the polymer is further improved.

Further, when a specific amount of a compound containing an atom belonging to Group II of the periodic table and a phosphorus compound are contained in the film, the dispersibility of the particles in the polyester is improved and the melting specific resistance of the polyester is reduced. Can be reduced. By lowering the melting specific resistance of the polyester, when the polyester sheet melt-extruded from the die using the electrostatic application cooling method is brought into close contact with the cooling drum, the adhesion between them is further improved, and confined bubbles called pinner bubbles , The speed of the rotating cooling drum can be increased, and the productivity of the film can be improved.

Examples of the compound containing an atom belonging to Group II of the periodic table include magnesium acetate and calcium acetate. Examples of the phosphorus compound include phosphoric acid, phosphoric acid triester, acidic phosphoric acid ester, phosphorous acid, phosphite and the like. The molar ratio (P / metal atom) of a metal atom belonging to Group II of the Periodic Table in the compound containing an atom belonging to Group II of the Periodic Table to P in the phosphorus compound is 0.5 to 1.0, preferably 0.1 to 1.0. When the content is adjusted to 55 to 0.90 and the P atom content in the phosphorus compound is adjusted to 10 to 200 ppm, a polyester having a melting specific resistance of 0.5 × 10 ⁸ Ω · cm or less can be obtained.

Further, master chips each containing at least one to three types of fine particles at a high concentration are manufactured, and
These master chips may be appropriately mixed and diluted with each other or with a polyester (bright resin) containing no particles to adjust to a required particle concentration.

Although the film of the present invention may be a single film,
If the film surface layer (biaxially oriented polyester film layer) is within the range regulated by the present invention, the film obtained from the recovered product was used (the layer of the biaxially oriented polyester film of the present invention) / (obtained from the recovered product). It is preferable from the viewpoint of cost reduction that the film is a laminated film composed of three layers of (film layer obtained) / (layer of biaxially oriented polyester film of the present invention). Furthermore, when manufacturing tape for video software,
On the surface of the film on which the magnetic layer is to be provided, a coating agent containing an aqueous polymer as a film-forming component described in JP-A-4-253737 is thinly coated to improve the adhesiveness with the magnetic layer. No problem.

The polyester film of the present invention is obtained, for example, by extruding polyester from a die at a temperature of melting point (Tm; ° C.) to (Tm + 50) ° C., and obtaining an unstretched film by an electrostatic cooling method. In a uniaxial direction (vertical or horizontal) from (Tg + 20) ° C. to (T
g + 70) ° C. (however, Tg; glass transition temperature of polyester) at a magnification of 2.5 to 5.0 times at least 2 times.
Stretching in more than one step, and then in a direction perpendicular to the above stretching direction (if the first stretching is longitudinal, the second stretching is transverse) at a temperature of (Tg + 30) ° C to (Tg + 70) ° C. The film is stretched in at least two stages at a magnification of 5 to 5.0 times. In this case, the area stretching ratio is preferably 12 to 22 times, more preferably 15 to 20 times. The stretching means may be either simultaneous biaxial stretching or sequential biaxial stretching.

Further, the obtained film was (Tg + 7
0) It can be heat-set at a temperature of from 0 ° C. to Tm (° C.).
For example, a polyethylene terephthalate film is preferably heat-set at 190 to 230 ° C. The heat fixing time is, for example, 1 to 60 seconds. In addition, in order to improve the heat shrinkage characteristics, it is effective to perform relaxation treatment in the horizontal and vertical directions.

The tape for video software of the present invention is prepared by applying a known method, for example, a magnetic paint having a composition described in JP-A-6-91751 to one surface of the biaxially oriented polyester film obtained as described above. Coating with a roll, magnetic orientation and drying. Furthermore, after calendering at 70 ° C. and a linear pressure of 200 kg / cm using a small calender, curing is performed at 70 ° C. for 48 hours. 1
Obtained by slitting to 1/2 inch.

The characteristic values of the present invention are based on the following measuring methods and evaluation criteria. (1) Stylus type three-dimensional average surface roughness (SRa) and maximum number of protrusions (PC-S) on the film surface and on the surface opposite to the magnetic layer of the tape Using a three-dimensional surface roughness meter (SE-3AK) and a three-dimensional roughness analyzer (SPA-11), the three-dimensional surface roughness (SR
Measure a). In addition, the number of cutouts with the largest number of cuts (the number of cutouts with the largest number of cutouts of the film surface sliced in parallel from the top) is defined as the maximum number of protrusions (PC-S). . The conditions are as follows. In Examples and Comparative Examples, the measured value was an average value of two measurements. • Detector (tip radius: 2 µm, load: 30 mg) • Cutoff: 0.25 mm • Magnification in X direction (longitudinal direction of film): × 200 • Magnification in Y direction (horizontal direction of film): × 500 • Z Magnification in the direction (height direction of the film): × 20,000 ・ Measuring area: 0.3 mm ²・ Pitch in the Y direction (lateral direction of the film): 2 μm ・ Number of scans in the Y direction: 500 times ・ Count mode: SIMPLE ・ Z Standard: UPPER

(2) Maximum number of protrusions on the film surface and the surface on the side opposite to the magnetic layer of the tape by a non-contact three-dimensional surface roughness meter (PC-H). Non-contact three-dimensional surface roughness meter (ET-
30HK) and three-dimensional roughness analyzer (SPA-11)
Is used to measure the three-dimensional surface roughness. The number of cuts with the largest number of cuts due to the cut surface (the number of cuts of the protrusions where the film surface is sliced in parallel from the top and the number of cuts of the protrusion is the largest) is defined as the maximum number of protrusions (PC-H). The conditions are as follows. In Examples and Comparative Examples, the measured value was an average value of three measurements. Detector: Optical stylus Hypos (spot diameter: 1.6 μm) Cutoff: 0.08 mm Magnification in X direction (longitudinal direction of film): × 1000 Magnification in Y direction (horizontal direction of film): × 2000 Magnification in the Z direction (height direction of the film): × 20000 ・ Measuring area: 0.01875 mm ²・ Measurement length in the X direction: 250 μm ・ Measuring speed in the X direction: 20 μm / s ・ Feed pitch in the Y direction (lateral direction of the film): 0.5 μm ・ Number of scans in the Y direction: 150 ・ Count mode: SIMPLE ・ Z reference: LOWER

(3) Average primary particle diameter ratio (major axis / minor axis), average primary particle diameter (d) and standard deviation of primary particle diameter (σ) of inorganic oxide fine particles (A) It is fixed on a sample stage, subjected to platinum sputtering, and subjected to a scanning electron microscope at 10,000 to 500
Observation was carried out at a magnification of × 00, and image analysis of 3000 to 5000 particles was performed with Luzex 2D manufactured by Nireco Co., Ltd., and the average primary particle diameter ratio (major axis / minor axis), average primary particle diameter (d), and primary particle diameter Is calculated.

When calculating from the inside of the film, a small piece of the sample film is fixed on a sample stage for a scanning electron microscope, and the film surface is applied to the film surface using a sputtering device (JFC-1100 type ion etching device) manufactured by JEOL Ltd. An ion etching process is performed under the following conditions. The conditions were as follows: a sample was placed in a bell jar, the degree of vacuum was raised to a vacuum of about 10 ⁻³ Torr, and ion etching was performed at a voltage of 0.25 KV and a current of 1.25 mA for about 10 minutes. Further, the same device was used to perform platinum sputtering on the film surface, and at a magnification of 10,000 to 50,000 with a scanning electron microscope, an observation place was selected so that the inert particles (B) did not enter the same field of view. At 3000-500
The above-mentioned image analysis is performed on 0 particles to determine each parameter.

(4) Average Particle Size Using a laser diffraction / scattering type particle size distribution analyzer (Microtrac HRA: manufactured by Leeds & Northlap Co.) until the ethylene glycol slurry of the particles becomes an appropriate concentration in ion-exchanged water. In addition, the particle size distribution is measured. When a cumulative curve is determined with the total volume of the particle means being 100%, the particle diameter at which the cumulative curve becomes 50% is determined by the average secondary particle diameter of the inorganic oxide fine particles (A) and the inert particles (B ) Is the average particle size (nm).

(5) Area ratio of particles to circumscribed circle At least 100 particles were observed and photographed with a scanning electron microscope (Hitachi S-510 type), and then converted to an image analyzer (Luzex 2D manufactured by Nireco Co., Ltd.). ) Is used to determine the projected cross-sectional area (μm ² ) of each particle and the area (μm ² ) of a circle circumscribing each particle, and the ratio of their average values is defined as the area ratio (%) of the particle to the circumscribed circle.

[0057]

(Equation 8)

(6) Variation of Particle Size At least 100 or more particles were measured for the Feret diameter in the horizontal direction using the apparatus described in (6) above, and the ratio of the standard deviation to the average value was used to determine the particle size. The degree of variation (%) is used.

[0059]

(Equation 9)

(7) Rolling property in slitter The winding appearance (wrinkles and winding disorder) when the film is wound in the slitter process is ranked as follows.

<Judgment of winding appearance> ◎: Even at 400 m / min, no wrinkles or turbulence occurs.: At 350 m / min, no wrinkles or turbulence occurs. Or winding disturbance occurs. XX: Wrinkles or winding disturbance occurs even if the speed is reduced to 300 m / min.

(8) Scuffing Resistance Using the film running tester shown in FIG. 1, the scuffing resistance is evaluated. In FIG. 1, 1 is a film, 2 is a capstan, 3 is a tension detector, 4 is a fixed guide pin (commercially available VT).
R fixed guide pin: the maximum protrusion height measured by a stylus type surface roughness meter is 0.15 μm, and the center line average surface roughness is 0.0
08 μm).

A polyester film slit to a 1/2 inch width was brought into contact with the fixed guide pin 4 at an angle of 135 ° at an atmosphere of 23 ° C. and 65 RH%, and a tension of 50 g was applied.
And run for 90 m at a speed of 200 cm / min. After running, the amount of white powder adhering to the surface of the fixed guide pin 4 is observed with an actual microscope and ranked as follows.

<Judgment of White Powder Amount>: No white powder adhered or partial and small even if white powder was present ：: White powder adhered thinly ×: Partly large amount of white powder adhered XX: Large amount of white powder adhered over the entire surface Adhesion 以上 or more causes no practical problem.

(9) Scratch Resistance In the running test machine shown in FIG. 1 used for evaluation of the abrasion resistance, a polyester film slit to a half inch width was fixed at 23 ° C. and 65 RH% atmosphere. As the guide pin 4, instead of the fixed guide pin 4 for a commercial VTR used in the evaluation of the abrasion resistance, a fixed pin obtained by bending a SUS sintered plate into a cylindrical shape and having an insufficient surface finish (a center line surface roughness of 0) is used. .15 μm) and run at 127 cm / sec for 90 m while applying a tension of 100 g while making contact at an angle of 90 °. After vapor deposition of the film after traveling with aluminum, the entire width of the film surface without vapor deposition was observed with an actual microscope while irradiating light obliquely, and the number of scratches on the film surface was ranked as follows. The number of scratches shallow and those having a half or more of the total width of the film were also included in the number.

<Judgment of Scratch Property> ：: 10 or less / total width: 11 to 30 / total width ×: 31 to 60 / total width ×: 61 or more / total width ○ .

(10) Slitting property The polyester film is slit by a shear cutter to a width of 1/2 inch and a length of 1000 m. Observation of the degree of beard generation at the slit portion of the film was performed using an electron microscope (5000 to 10
000 times). Further, the degree of generation of the powder adhering to the shear cutter is visually observed. The degree of mustache and powder generation was ranked as follows.

<Judgment of slitting property> A: Very little generation of whiskers and powder ○: 〃 little ×: 〃 slightly more XX: 多 い more ○: Above ○, no practical problem.

(11) Electromagnetic conversion characteristics of video tapes
A magnetic paint having a composition described in JP-A No. 1 is applied by a gravure roll, magnetically oriented, and dried. Furthermore, a small calender (steel roll / nylon roll, 5
After performing a calendering process at 70 ° C. and a linear pressure of 200 kg / cm in step (2), curing is performed at 70 ° C. for 48 hours. 1
/ 2 inch was slit to make a pancake. This pancake was incorporated into a VTR cassette to form a VTR cassette tape.

Using a tape for home use, a 100% chromatographic signal was recorded by a television test waveform generator (TG7 / U706: Shibasoku), and a color noise measuring device (925D / 1: Shibasoku) was obtained from the reproduced signal. )) And the chroma S / N was measured, and the result was defined as A. In addition, the same sample tape as that in which A was measured using a magnetic tape transfer type video software high-speed printing system (Sprinter manufactured by Sony Magnescale Co., Ltd.) was recorded on the pancake of the master tape on which the same signal was recorded (not shown). The chroma S / N of the tape after dubbing onto the pancake was measured in the same manner as above, and was designated as B. The reduction in chroma S / N (AB) due to the dubbing was ranked as follows.

<Determination of Decrease in Image Quality (Chroma S / N) Due to Dubbing> ：: Less than 3 dB ○: 3 dB or more and less than 5 dB: 5 dB or more and less than 7 dB ×: 7 dB or more ○: Practical problem Absent.

(12) Durability of Video Tape A video test tape generator (TG) using the video software high-speed printing system (Sprinter manufactured by Sony Magnescale Co., Ltd.) prepared in (11) above by using a home VTR. -7/1: Shiva-Soku), a color bar signal is recorded, and a large drop-out number of 20 μB or more is measured from the reproduced signal by a drop-out counter (TDA-100: Micro Systems Laboratory) for 15 μsec and C. And Next, the video soft tape is repeatedly run on a home VTR (fast forward, rewind).
Was performed 100 times. After that, the tape is played back, and the signal is used as a dropout counter ((TG-7 / 1)).
A large dropout number of 15 μsec, 20 dB or more was measured, and was set as D. Increase rate of dropout due to repeated running of this video soft tape [(D-C) / C
× 100;%] was defined as durability, and ranked as follows.

<Durability (increase in dropout)> ：: less than 10%: 10% or more and less than 20% ×: 20% or more and less than 50% XX: 50% or more There is no level.

[0074]

EXAMPLES The present invention will be described in detail based on examples and comparative examples. All parts in Examples and Comparative Examples are parts by weight unless otherwise specified.

Example 1 A polyester containing silica particles as the inorganic oxide fine particles (A) was obtained by the following method. While cooling the esterification reactor, 86.4 parts of terephthalic acid and 64.4 parts of ethylene glycol were charged, and while stirring, 0.03 part of antimony trioxide and 0% of magnesium acetate tetrahydrate were used as a catalyst. 0.088 parts and 0.16 parts of triethylamine were charged, and the mixture was waited until the temperature of the reactor was cooled to 80 ° C. On the other hand, average primary particle size ratio (major axis / minor axis)
Is 1.35 and the standard deviation of average primary particle diameter / primary particle diameter is 2.35.
5. Silica particles (A) obtained by flame hydrolysis of silicon tetrachloride (5) are mixed in ethylene glycol, and the slurry is wet-crushed by a dyno mill, centrifuged by a super decanter, and a high-precision filter having a pore size of 1 μm. To obtain an ethylene glycol slurry containing 12% by weight of silica particles (A) having an average secondary particle diameter of 110 nm. After the temperature in the can of the esterification reactor reaches 80 ° C., the slurry (particle content: produced polymer 10
2.0 parts per 0 parts) to the esterification reactor,
After 5 minutes, the pressure was increased and the gauge pressure was 3.5 kg / cm ² ,
The pressure esterification reaction was performed at 240 ° C. Thereafter, the inside of the esterification reactor was returned to normal pressure, and 0.043 part of trimethyl phosphate was added. Five minutes after the addition of trimethyl phosphate, the esterification reaction product was transferred to a polycondensation reaction vessel, and a polycondensation reaction was performed at 280 ° C. under reduced pressure to obtain a polyester having an intrinsic viscosity of 0.58. This is designated as polyester (A).

The polyester containing the inert particles (B) was obtained by the following method. Raise the temperature of the esterification reactor to 200
When the temperature reached ° C, 86.4 parts of terephthalic acid and 64.4 parts of ethylene glycol were charged, and while stirring, 0.017 part of antimony trioxide and 0.071 part of magnesium acetate tetrahydrate were used as a catalyst. And 0.16 parts of triethylamine. Next, the temperature was increased under pressure, and the esterification reaction was performed under the conditions of a gauge pressure of 3.5 kg / cm ² and 240 ° C. Thereafter, the pressure in the esterification reactor was returned to normal pressure, and 0.026 parts of trimethyl phosphate was added. Fifteen minutes after the temperature was further raised to 260 ° C. and trimethyl phosphate was added, centrifugation treatment with a superdecanter and filtration treatment with a filter having a pore size of 5 μm were performed, and an aqueous solution of sodium tripolyphosphate was added as a dispersant to calcium carbonate with Na atoms. As 0.1% by weight. An average particle size of 570 nm with an area ratio to the circumscribed circle of 80% and a degree of variation of the particle size of 28%.
Glycol calcite-type synthetic calcium carbonate particles (B1) in ethylene glycol (particle content: produced polymer 1)
2.0 parts per 100 parts). After 15 minutes, the resulting esterification reaction product was transferred to a polycondensation reactor and
A polycondensation reaction was carried out at 80 ° C. under reduced pressure to obtain a polyester having an intrinsic viscosity of 0.58. This is designated as polyester (B1).

On the other hand, in the production of the polyester (B1), instead of the calcite-type synthetic calcium carbonate particles (B1) having an average particle diameter of 570 nm, the area ratio to the circumscribed circle is 75%, and the degree of dispersion of the particle diameter is small. 25% slurry of calcite-type synthetic calcium carbonate particles (B2) having an average particle size of 850 nm (particle content: polymer 100
Of a polyester having an intrinsic viscosity of 0.58. This is designated as polyester (B2).

Further, in the production of the polyester (B1), the addition of calcite-type synthetic calcium carbonate particles (B1) having an average particle diameter of 570 nm was stopped, and a polyester having an intrinsic viscosity of 0.58 containing no added fine particles was obtained. .
This is designated as polyester (C).

Polyesters (A), (B1) and (B)
2) and (C) were mixed and dried at a weight ratio of 15: 15: 3.75: 66.25. Next, the extruded sheet was melt-extruded at 290 ° C., filtered through a prefilter having a pore size of 5 μm and a final filter having a pore size of 40 μm, and then the unstretched sheet was adhered to a cooling drum by an electrostatic application cooling method. Next, the peripheral speed difference of the roll was changed in the vertical direction, and the
The film was stretched at 127 ° C. in 6 steps and 3.23 times in two stages.
This uniaxially stretched film is horizontally stretched using a stenter.
It is divided into stages, 1.94 times at 118 ° C, and 1.4 at 123 ° C.
The film was stretched 1.3 times at 7 ° C. and 130 ° C., further heat-treated with hot air at 204 ° C. under fine stretching at 1.09 times, and subsequently relaxed 2.4% in the transverse direction at the same temperature. Once cooled, the rolls are cooled vertically at 125 ° C due to the peripheral speed difference of the rolls.
After giving 8% relaxation, the film was gradually cooled, cooled to room temperature, and wound up to obtain a biaxially oriented polyester film having a thickness of 14.5 μm and an intrinsic viscosity of 0.56.

A magnetic paint having a composition described in JP-A-6-91751 is applied to the biaxially oriented polyester film by a gravure roll, magnetically oriented, and dried. Furthermore, with a small calender (steel roll / nylon roll, 5 steps), 70 ° C, linear pressure 200 kg / cm
And then cure at 70 ° C. for 48 hours. This material was slit into 1/2 inch to make a pancake. This pancake was incorporated into a VTR cassette to obtain a video software tape.

Comparative Example 1 The procedure of Example 1 was repeated except that the polyesters (A), (B1), (B2) and (C) were mixed in a weight ratio of 5: 20: 7.5: 67.5. A film having the same thickness and intrinsic viscosity and a tape for video software using the film were obtained. In Comparative Example 1, the ratio (α) of the maximum number of protrusions described in claim 1 is outside the scope of the claims.

Comparative Example 2 Same as Example 1 except that the polyesters (A), (B1), (B2) and (C) were mixed in a weight ratio of 3.75: 5: 3.75: 87.5. To obtain a film having the same thickness and intrinsic viscosity and a tape for video software using the film. In Comparative Example 2, the maximum number of protrusions (PC-H) described in claim 1 is outside the scope of the claims.

Comparative Example 3 Polyesters (A), (B1), (B2) and (C)
Example 1 except for mixing at a weight ratio of 5: 5: 5: 65
A film having the same thickness and intrinsic viscosity as described above and a tape for video software using the film were obtained. In Comparative Example 3, the maximum projection number ratio (α) described in claim 1 is outside the scope of the claims.

Example 2 Instead of the calcite-type synthetic calcium carbonate particles (B1) having an average particle diameter of 570 nm in the polyester (B1) of Example 1, the area ratio to the circumscribed circle was 96.
%, The degree of variation in particle size is 12%, and the thermal decomposition temperature at the time of weight loss of 10% is 383 ° C, and the average particle size is 450 nm. Crosslinked polystyrene particles (S246 manufactured by Nippon Synthetic Rubber Co., Ltd.)
7) except that polyester (B)
Polyester (B1a) was obtained in the same manner as in 1). Polyester (A), (B1a), (B2), (C)
A film having the same thickness and intrinsic viscosity and a tape for video software using the film were obtained in the same manner as in Example 1 except for mixing at a weight ratio of 5: 10: 5: 70.

Practical Example 3 An average particle diameter of 160 nm and an average primary particle diameter ratio (major axis / minor axis) produced by a method of removing alkali (sodium) in a wet system from sodium silicate as a raw material were obtained. 1.0
5. Except that the ethylene glycol slurry of spherical monodisperse colloidal silica particles having an average primary particle diameter / standard deviation of primary particle diameter of 18 was used instead of the silica particles (A) used in Example 1, Example 1 polyester (A)
Polyester (A1) was obtained in the same manner as described above. A film having the same thickness and intrinsic viscosity and a tape for video software using the film were obtained in the same manner as in Example 2 except that the polyester (A1) was used instead of the polyester (A). Although the present practical example 3 satisfies the range described in claim 1, the average primary particle diameter ratio (major axis / minor axis) and the average primary particle diameter /
The standard deviation of the primary particle size is outside the scope of claim 2.

Tables 1 and 2 show the properties of the polyester films obtained in Examples 1 to 3 and Comparative Examples 1 to 3.

[0087]

[Table 1]

[0088]

[Table 2]

As is clear from the results shown in Tables 1 and 2, the film of the present invention was also excellent in properties such as winding property, abrasion resistance and scratch resistance. Also,
Video software tape using the film of the present invention,
There is little decrease in electromagnetic conversion characteristics when dubbing at high speed,
And it had excellent durability.

[0090]

The oriented polyester film of the present invention has
It has a surface having a specific maximum number of projections (PC-H) and a specific maximum number of projections (α). Therefore, it is a high-quality polyester film that is extremely excellent in winding property, abrasion resistance, scratch resistance, and slitting property and can be adapted to high-speed production lines of films and tapes. Furthermore, since the tape for video software using the polyester film has little deterioration in image quality at the time of high-speed dubbing and is also excellent in durability, it is preferably used as a tape for video software particularly for video rental having a high repetition frequency. it can.

[Brief description of the drawings]

FIG. 1 is a schematic view of a traveling tester for evaluating abrasion resistance and scratch resistance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Film 2 Capstan 3 Tension detector 4 Fixed guide pin

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] December 20, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 2

[Correction method] Change

[Correction contents]

(Equation 1) [Wherein, r (A) represents the average secondary particle size (nm) of the inorganic oxide fine particles (A), d (A) represents the specific gravity (g / cm ³ ) of the inorganic oxide fine particles (A), and c (A) shows the content (% by weight) of the inorganic oxide fine particles (A) in the polyester as r (B
i) is the average particle size (nm) of the inert particles (B), and d (B
i) is the specific gravity (g / cm ³ ) of the inert particles (B), c
(Bi) indicates the content (% by weight) of the inert particles (B) in the polyester, and n is the number of types of the inert particles (B) used.]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 5

[Correction method] Change

[Correction contents]

(Equation 2) [Wherein, r (A) represents the average secondary particle size (nm) of the inorganic oxide fine particles (A), d (A) represents the specific gravity (g / cm ³ ) of the inorganic oxide fine particles (A), and c (A) shows the content (% by weight) of the inorganic oxide fine particles (A) in the polyester as r (B
i) is the average particle size (nm) of the inert particles (B), and d (B
i) is at least one specific gravity (g / g) of the inert particles (B).
cm ³ ), c (Bi) indicates the content (% by weight) of the inert particles (B) in the polyester, and n is the number of types of the inert particles (B) used.]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009]

(Equation 3)

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

[0019]

(Equation 4)

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction contents]

[0033]

(Equation 5)

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0085

[Correction method] Change

[Correction contents]

[0085] The implementation example 3 sodium silicate as a raw material, was produced in a manner to continue to remove alkali (sodium) content in a wet system, the average particle size of 160 nm, an average primary particle size ratio (long diameter / short diameter) Is 1.0
5. Except that the ethylene glycol slurry of spherical monodisperse colloidal silica particles having an average primary particle diameter / standard deviation of primary particle diameter of 18 was used instead of the silica particles (A) used in Example 1, Example 1 polyester (A)
Polyester (A1) was obtained in the same manner as described above. A film having the same thickness and intrinsic viscosity and a tape for video software using the film were obtained in the same manner as in Example 2 except that the polyester (A1) was used instead of the polyester (A). This implementation example 3, but satisfy the scope of claim 1, the average primary particle size ratio of the silica particles according to claim 2 (long diameter / short diameter) and the average primary particle size /
The standard deviation of the primary particle size is outside the scope of claim 2.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B29K 67:00 105: 16 B29L 7:00 C08L 67:02

Claims (6)

[Claims] 1. A non-contact three-dimensional surface roughness of at least one film surface, wherein the maximum number of protrusions (PC-H) measured by a non-contact three-dimensional surface roughness meter is 20,000 / mm ² or more. The maximum number of protrusions (PC-H) measured with a stylus type and the maximum number of protrusions (PC-H
S) and the maximum projection number ratio [α: (PC-H) / (PC-
S)] is 4 to 10, wherein the polyester film is a biaxially oriented polyester film for a magnetic recording medium. 2. The polyester film has an average secondary particle size of 50 to 200 nm, an average primary particle size ratio (major axis / minor axis) of 1.25 to 3.0, and a standard deviation of average primary particle size / primary particle size. 0.1 to 0.5% by weight of the inorganic oxide fine particles (A) having (d / σ) of 0.5 to 5.0 and an average particle size of 30
A particle number parameter (β) defined by the following formula of the inorganic oxide fine particles (A) and the inert particles (B), which contains at least one kind of inert particles (B) having a particle size of 0 to 1500 nm.
2. The biaxially oriented polyester film for a magnetic recording medium according to claim 1, wherein the number is from 20 to 80. (Equation 1) [Wherein, r (A) represents the average secondary particle size (nm) of the inorganic oxide fine particles (A), d (A) represents the specific gravity (g / cm ³ ) of the inorganic oxide fine particles (A), c (A) shows the content (% by weight) of the inorganic oxide fine particles (A) in the polyester as r (B
i) is the average particle size (nm) of the inert particles (B), and d (B
i) is the specific gravity (g / cm ³ ) of the inert particles (B), c
(Bi) indicates the content (% by weight) of the inert particles (B) in the polyester, and n is the number of types of the inert particles (B) used.] 3. The biaxially oriented polyester film for a magnetic recording medium according to claim 2, wherein the inorganic oxide particles (A) are silica particles. 4. A biaxially oriented polyester film layer and magnetic properties
A tape for video software having a
Non-contact three-dimensional of the film surface opposite to the magnetic layer of the lum layer
The maximum number of protrusions (PC-H) measured with a surface roughness meter is 200
00 pieces / mm ^TwoNon-contact three-dimensional of the surface
Maximum number of protrusions (PC-H) measured by surface roughness meter and stylus type
The maximum number of protrusions (PC-S) measured with a three-dimensional surface roughness meter
Of the maximum number of protrusions [α: (PC-H) / (PC-S)]
4 to 10 tapes for video software
H. 5. The film layer having an average secondary particle size of 50 to 2
00 nm, average primary particle size ratio (major axis / minor axis) is 1.25 to
3.0, and average primary particle size / standard deviation of primary particle size (d /
0.1 to 0.5% by weight of the inorganic oxide fine particles (A) having σ) of 0.5 to 5.0 and an average particle size of 300 to 15
A particle number parameter (β) defined by the following formula of the inorganic oxide fine particles (A) and the inert particles (B) on the surface containing at least one inert particle (B) having a diameter of 00 nm
5. The tape for video software according to claim 4, wherein the number is from 20 to 80. 6. (Equation 2) [Wherein, r (A) represents the average secondary particle size (nm) of the inorganic oxide fine particles (A), d (A) represents the specific gravity (g / cm ³ ) of the inorganic oxide fine particles (A), c (A) shows the content (% by weight) of the inorganic oxide fine particles (A) in the polyester as r (B
i) is the average particle size (nm) of the inert particles (B), and d (B
i) is at least one specific gravity (g / g) of the inert particles (B).
cm ³ ), c (Bi) indicates the content (% by weight) of the inert particles (B) in the polyester, and n is the number of types of the inert particles (B) used.] 6. The biaxially oriented polyester film for a magnetic recording medium according to claim 5, wherein the inorganic oxide particles (A) are silica particles.