JP3413906B2 - Polyester film for magnetic recording media - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for a magnetic recording medium, and more particularly to a polyester film suitable for a video tape having excellent running durability and slitting property.

[0002]

2. Description of the Related Art A magnetic recording medium using a polyester film has a drawback that the surface of the polyester film is scratched by a roll or the like which is in contact with the magnetic material coating / calendering process in the magnetic medium manufacturing process due to an increase in process speed. Has become a problem recently. Furthermore, with regard to video tapes, due to the increased frequency of use in ordinary households and the prevalence of pre-recorded commercially available tapes, video recorders (VTRs)
The number of repeated playbacks and recordings within
There are problems such as scratches on the film surface due to contact friction with guide pins in the tape cassette, and deterioration of images due to falling of powdery substances generated from the film due to contact friction. Further, at the time of slitting, which is the final step in the manufacturing process of magnetic recording media, particularly video tapes and the like, chips are generated from the cross section of the film, which causes an increase in dropout during magnetic recording. In order to solve these problems, it is necessary to prevent scratches on the film surface and to improve the runnability of the film by roughening the film surface to reduce the coefficient of friction. In order to improve the image quality, it is also necessary to smooth the film surface to improve the electromagnetic conversion characteristics. Furthermore, it is also necessary to impart the sharpness at the time of slitting to the film characteristics.
Many studies have been made in the past against these dilemmas of contradictory film surface characteristics. For example, JP-A-59-171623 and JP-A-63-234038.
Japanese Patent Laid-Open No. 61-5431 proposes to contain spherical silica particles, and Japanese Patent Laid-Open No. 61-5431 proposes to contain inert inorganic particles such as colloidal silica.

However, in reality, it is difficult to satisfy all of the above problems even with such a known method.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves these problems, the surface is less likely to be scratched (hereinafter referred to as scratch resistance), is excellent in running durability by repeated use, and has a slit in a magnetic recording medium manufacturing process. It is an object of the present invention to provide a polyester film for a magnetic recording medium which meets the demands for improved characteristics and higher image quality.

[0005]

The above object of the present invention is to provide a polyester having a volume average particle diameter of 0.1 to 2.0 μm and a relative standard deviation defined by the following formula (1) of 0.
5 to 3 spherical silica particles of 0.005 to 5.
It is achieved by a polyester film for a magnetic recording medium, characterized by containing 0% by weight and containing aluminum oxide particles and / or zirconium oxide particles.

[0006]

[Equation 2] The polyester applied in the present invention is produced by a polycondensation reaction as a glycol component and a bifunctional component such as an aromatic dicarboxylic acid or its alkyl ester. Of these, those containing polyethylene terephthalate as a main component are preferable.

Further, a small amount of copolyester which does not impair the basic properties of the polyester film of the present invention may be mixed. Examples of the copolymerization component of the copolyester include dicarboxylic acid components such as 2,6-naphthalenedicarboxylic acid and isophthalic acid, oxycarboxylic acid components such as P-oxyethoxybenzoic acid, and tetramethylene glycol, propylene glycol, neopentyl. Examples include diol components such as glycol, polyoxyalkylene glycol, P-xylylene glycol, 1,4-cyclohexanedimethanol, polyethylene glycol, and 5-sodium sulforesorzine. Of these, a copolyester obtained by copolymerizing a diol component such as polyethylene glycol is preferable in order to improve the adhesiveness of the film to the magnetic binder and to keep the chargeability due to static electricity low.

Further, the polyester film of the present invention may contain recovered polyester mainly composed of non-product parts generated in the production stage. Furthermore, these polyesters preferably have an intrinsic viscosity of 0.5 or more, more preferably 0.55 or more.

The spherical silica particles in the present invention are synthetic silica produced by an alkoxide method, a water glass method or the like, for example, an ion exchange method using water glass (sodium silicate aqueous solution) as a starting material or an alkoxy silicate as a starting material. Can be synthesized by a hydrolysis method or the like. In particular, in order to improve the slitting property, which is one of the objects of the present invention, synthetic silica starting from water glass is more preferable, and further, 25% by weight of a 20 wt% ethylene glycol slurry of the spherical silica particles. The refractive index at
When it is 1.430 or more, preferably 1.435 or more, not only the occurrence of voids around the particles in the polyester is reduced, but also the effect of improving the slit property becomes remarkable, which is more desirable.

The term "spherical" as used in the present invention means the particle size ratio of the maximum diameter and the minimum diameter on the projection plane of the particles (maximum diameter / minimum diameter).
Is preferably 1.0 to 1.3, more preferably 1.
It is preferably 0 to 1.1. Here, it is shown that the particle diameter ratio of 1.0 is a true sphere. When the particle size is out of the range, friction between the metal guide and the film becomes large, and the running property is apt to deteriorate when the video tape is repeatedly used in the VTR, causing tape squeaking and running in the VTR. It may stop.
Therefore, it is preferable that the particles are in the above range particularly for a video tape application requiring durability during running, for example, a base film for recorded commercial tapes for movies and the like.

The relative standard deviation, which is a measure of the spread of the particle size distribution of the spherical silica particles, needs to exceed 0.5, preferably exceeds 0.6, and further exceeds 0.7. It is preferable. Further, the upper limit is within 3 is 必 in keeping the waviness of the film surface good
It is important .

The relative standard deviation referred to here is represented by the following equation (1) as the ratio of the standard deviation obtained in number unit from the area-equivalent diameter of particles and the number average diameter.

[0013]

[Equation 3] When spherical silica particles with a relative standard deviation of more than 0.5 are used, the slitting property, especially the continuous slitting property is improved, and the slit blade is changed for a long time at the time of the final step of the magnetic tape manufacturing process such as video tape. Even if not, the amount of cutting chips or shavings generated from the film cut edge is extremely small, and the swelling of the end cross section of the film cut edge is reduced. It is considered that the manifestation of this effect is brought about by the extremely small wear of the slit blade in the step.

In the present invention, the volume average particle diameter of the spherical silica particles is required to be 0.1 to 2.0 μm, preferably 0.15 to 1.0 μm. When the volume average particle diameter of the particles is smaller than 0.1 μm, friction increases, and running characteristics when a video tape is used deteriorates. On the other hand, if it is larger than 2.0 μm, the electromagnetic conversion characteristics of the magnetic recording medium represented by the video tape will be poor. Further, the content of the spherical silica particles is required to be 0.005 to 5.0% by weight, preferably 0.01 to 2.0% by weight, and more preferably 0.05 to the polyester. It is preferably about 1.0% by weight. If the content of the particles is less than 0.005% by weight, friction increases and the running characteristics of a video tape deteriorate.
On the other hand, if it is more than 5.0% by weight, the electromagnetic conversion characteristics of the magnetic recording medium represented by the video tape will be poor.

In the present invention, the method of incorporating the spherical silica particles into polyester is not particularly limited,
Generally, it is preferable to add a slurry of spherical silica particles during the production of polyester. How and when to add
Conventionally known methods and times are used, but as the addition method, a method of adding as a slurry of ethylene glycol which is a raw material for synthesizing the polyester is particularly preferable. At this time, the slurry concentration was SiO ₂ weight% of 0.
It is preferably 5 to 40% by weight, more preferably 1 to 20%
It is preferable that the content is in the range of wt% because the particle dispersibility in polyester is improved. Further, the water content in the glycol of the slurry at the time of addition is 1% by weight or less, more preferably 0.
The amount of 5% by weight or less is preferable because the particle dispersibility in polyester is improved. The addition time may be arbitrary, and it may be added at the time of charging the monomer, at the time of transesterification reaction, or before and after it. Further, the slurry of the particles may be dispersed by adding and kneading using a uniaxial or biaxial vent type extruder after the production of the polymer.

The aluminum oxide particles in the present invention are conventionally known as α-type aluminum oxide particles having a crystal structure, γ-type, δ-type, η-type and θ.
-Type, κ-type, χ-type, etc. active aluminum oxide particles and amorphous aluminum oxide particles.

Various synthetic methods are known. For example, δ-type aluminum oxide is obtained by blowing hydrogen or oxygen into aluminum chloride and hydrolyzing it in the gas phase.
Similarly, when steam is blown into aluminum chloride to hydrolyze it in the gas phase, amorphous aluminum oxide is obtained, and when alum is neutralized with carbonate and then hydrolyzed, γ-type and θ-type aluminum oxide is obtained by hydrolyzing aluminum alkoxide. Γ type by firing the obtained aluminum hydroxide,
δ-type and θ-type aluminum oxide can be converted into η-type and θ-type aluminum oxide by firing aluminum hydroxide obtained by spark discharge of metallic aluminum in water. In addition, in the usual method called the Bayer method, α-type aluminum oxide is produced, and mainly the determination of such a crystal structure depends on the selection of these synthesis methods and the firing temperature and the firing time. At this time, depending on the selection of the firing temperature and the firing time, two or more kinds of crystal structures may coexist when the firing is completed, but in the present invention, such particles or a single crystal structure, or a mixed crystal structure was used. It can be one.

Among such aluminum oxide particles, γ-type, δ-type, η-type, θ-type, κ-type, and χ-type active aluminum oxide particles are preferable. In addition, such a crystal structure of various aluminum oxides can be identified by usual X-ray diffraction. The primary particle size of the particles is 10 m ² /
It is preferably at least g, and more preferably in the range of 30 to 600 m ² / g.

Further, the aluminum oxide particles of the present invention are
Dispersion treatment in the presence of glycol components such as polyester main raw materials and copolymerization components, specifically ethylene glycol, tetramethylene glycol, diethylene glycol, propylene glycol, 1,4-cyclohexanedimethanol, 5-sodium sulforesorcin The secondary particle size is preferably 3.0 μm or less, more preferably 0.005 to 1.0 μm.

The content of aluminum oxide particles in the polyester is preferably 0.001 to 5% by weight, more preferably 0.05 to 1% by weight.

Next, the zirconium oxide particles of the present invention can usually be obtained from naturally occurring zirconium ores, that is, zircon sand, badderite, and the like. Examples of the production method include a method in which the above-mentioned zircon sand is melted and obtained by firing zirconium hydroxide through zirconium oxychloride, and a method in which hydrogen and oxygen are blown into zirconium chloride and hydrolysis is performed in a gas phase. To be The zirconium oxide particles thus obtained have various forms depending on the production conditions, and are known to have monoclinic crystals, tetragonal crystals, cubic crystals, rhombohedral crystals, orthorhombic crystals, and a mixture of these crystal phases. ing. Further, in general, stabilizers include those containing calcium oxide, magnesium oxide, yttrium oxide and the like. In the present invention, such particles or a single crystal structure or a mixture thereof may be used, but monoclinic or tetragonal crystals are preferable. The crystal structure of such various zirconium oxide particles can be identified by ordinary X-ray diffraction.

The volume average diameter of the zirconium oxide particles used in the present invention is 0.005-3.0 μm, preferably 0.005-O. It is 5 μm.

The content of zirconium oxide particles in the polyester is preferably 0.001 to 5% by weight, more preferably 0.05 to 1% by weight.

In the present invention, the combination of the spherical silica particles defined in the present invention with the above-mentioned aluminum oxide particles and / or zirconium oxide particles is excellent in scratch resistance, running durability by repeated use, and slit characteristics, and It is necessary to reduce the generation of white powder in the VTR cassette after being made into a video tape.

Further, other inert particles such as calcium carbonate, titanium dioxide, titanium monoxide, titanium nitride, kaolin, talc and other inorganic particles, cross-linked polystyrene and other organic particles may be used as long as they do not impair the effects of the present invention. Particles, internally precipitated particles, additives such as antioxidants, heat stabilizers, and ultraviolet absorbers may be contained to the extent that they are usually added.

Examples of the internally deposited particles include particles produced by binding at least one compound selected from the group consisting of calcium compound, magnesium compound, manganese compound, and lithium compound added at the time of polyester synthesis with the polyester constituent component. . Further, the internally precipitated particles may contain elemental phosphorus and a trace amount of other metal components such as zinc, cobalt, antimony, germanium and titanium within a range that does not impair the effects of the present invention.

The polyester film for a magnetic recording medium of the present invention is biaxially oriented by a conventional method, and preferably has a thickness of 3 to 50 μm, more preferably 5 to 25.
It is preferably in the range of μm.

The scraping index K in the present invention means a thickness of 10
Film 1 after being slit to 1/2 inch at a slit speed of 50 m / min with a shear cutter type slitter, and then slit to 1/2 inch
m was placed in a container containing 50 cc of pure water so that only one cut surface was immersed, and after ultrasonic treatment, the film sample was removed, and the immersion liquid was measured with a particle counter. It is defined as the number of particles having a particle size of ˜20 μm. In the present invention, it is preferable that the scraping index K is 60 or less, preferably 40 or less, because the audio characteristics during reproduction of the video tape are particularly good.

Further, in the polyester film of the present invention, when the plane orientation index F and the refractive index nz in the thickness direction are within the ranges satisfying the following expressions (2) and (3) at the same time, the slit property is good and the calendering step is performed. It is preferable because not only the abrasion resistance of the magnetic recording medium becomes good but also the adhesiveness between the magnetic layer binder of the magnetic recording medium and the polyester film is improved. nz ≤ 1.603-0.6407 × F (2) nz ≧ 1.595-0.6407 × F (3) [Here, the plane orientation index F is F = ( NMD + NTD) / 2
Defined by -nz, NMD represents the refractive index in the longitudinal direction of the film, NTD represents the refractive index in the width direction of the film, and nz represents the refractive index in the thickness direction of the film. ] Further, in the polyester film of the present invention, the plane orientation index F and ΔN
Is preferably within the range where the following expressions (4) to (6) are simultaneously satisfied, because the wear characteristics during repeated running are good. ΔN ≤ 1413-8327 × F ‥‥‥‥‥‥‥‥‥‥ (4) ΔN ≥ 1340-8627 × F ‥‥‥‥‥‥‥‥‥ (5) -60 ≤ ΔN ≤ 30 ‥‥‥‥‥‥‥‥‥‥‥‥‥ (6) [Where ΔN is ΔN = (NMD−NTD) × 1000, F =
It is defined by (NMD + NTD) / 2-nz, where NMD represents the refractive index in the longitudinal direction of the film, and NTD represents the refractive index in the width direction of the film. ] Further, in the polyester film of the present invention, the above-mentioned plane orientation index F and ΔN have the following (7) to
When it is within the range that simultaneously satisfies the expression (9), not only the wear characteristics during repeated running become good, but also the beard-like material is less likely to be generated on the end surface of the film at the time of slitting,
It is preferable because abrasion powder is less likely to be generated in the calendering process performed when processing the video tape. ΔN ≤ 1413-8327 × F ‥‥‥‥‥‥‥‥‥ (7) ΔN ≥ 1340-8627 × F ‥‥‥‥‥‥‥ (8) -60 ≤ ΔN ≤ -20 ‥‥‥‥‥‥‥‥ (9) ) here, the ΔN is, NMD can cause lowered is <br/> by lowering the, it can be increased by raising. NMD can be raised by increasing the stretching ratio in the longitudinal direction, and can be lowered by lowering it. NTD can be raised by increasing the draw ratio in the width direction and can be lowered by lowering it. Further, NMD can be raised by lowering the stretching temperature in the longitudinal direction, and can be lowered by raising it conversely. NTD can be raised by lowering the stretching temperature in the width direction, and conversely it can be lowered.

The plane orientation degree F can be raised by increasing the area ratio (stretching ratio in the longitudinal direction × stretching ratio in the width direction) during stretching, and conversely can be decreased by lowering it. it can. When the area ratio is the same, it can be raised by lowering the stretching temperature in the longitudinal direction or the width direction, and conversely, it can be lowered by raising the temperature.

The refractive index nz in the thickness direction can be increased by increasing the area ratio (stretch ratio in the longitudinal direction × stretch ratio in the width direction) during stretching, and conversely can be decreased by lowering it. be able to. Further, if the area ratio is the same, can be reduced by lowering the stretching temperature in the longitudinal direction or width direction, conversely, it can be increased by raising the temperature. Further, it can be increased by increasing the heat treatment temperature, and conversely can be decreased by decreasing the heat treatment temperature.

At least one side of the polyester film of the present invention has a center line average surface roughness (Ra) of 8 to 30 n.
m, and the three-dimensional average surface roughness (SRa) is 13 to 50 n
m is preferable, and Ra is 12 to 25 n.
m, SRa is preferably from 17 to 40 nm. When the surface roughness is in the above range, the coefficient of friction is small, the abrasion resistance is good, and the image quality characteristics are good, which is preferable.
Furthermore, the number of protrusions having a height of 200 to 400 nm is 0.1 m.
More than 1200 pieces, and even more than 1350 pieces per m ² ,
Particularly, the number is 1500 or more and the height is 400 nm to 80
The number of protrusions of 0 nm is 400 or less per 0.1 mm ² ,
Further, it is preferably 300 or less, and particularly preferably 200 or less. When the number of protrusions having a height of 200 to 400 nm and the number of protrusions having a height of 400 nm to 800 nm are within the above ranges, the use durability is particularly good and the image quality characteristics are good.

The polyester film of the present invention comprises a single layer,
Although it can be applied to both laminated films, from the viewpoint of surface flatness and the like, it is preferable to use a laminated film in which at least one layer of the polyester film of the present invention is arranged. The following combinations are desirable as the specific constitution when the laminated polyester film is formed. B / A / B B / A / C B / A where A: base layer polyester film B, C; laminated polyester film B / A is one side of the base layer polyester film A, B
/ A / B indicates that the polyester B is laminated on both sides of the polyester film A of the base layer.

Further, although A to C may contain the above-mentioned polyester and spherical silica particles, it is possible to utilize the above-mentioned recovered polyester in at least the A layer, and as the recovered polyester, , The terminal carbonyl group is 30 to 50 equivalents / ton, and further 30 to 4
It is preferably 0 equivalent / ton.

Here, the polyester film A of the base layer portion
May be a polyester film containing substantially no particles, or may contain particles. The type of particles is not particularly limited, for example, calcium carbonate as an inorganic particle, silica, kaolin, alumina, barium sulfate, may be fine particles unnecessary for polyester such as titanium oxide, also, organic particles such as cross-linked polystyrene. May be included.

The polyester films B and C in the laminated portion form a surface, and in order to realize the effect of the present invention, the polyester film containing the particles of the present invention is used for at least one laminated polyester film. It is preferable to laminate films. When laminated on both sides, the opposite surface is not limited to the polyester film containing the particles of the present invention, may be substantially free of particles, particles outside the present invention May be included. further,
A coating layer such as an antistatic agent may be provided in order to improve the adhesiveness with the magnetic agent and prevent static electricity.

The thickness ratio of the polyester film in the laminated portion containing the spherical silica particles of the present invention to the polyester film A in the base layer portion is preferably 40% or less, and the volume average diameter of the spherical silica particles is preferably 40% or less. However, it is more effective when the laminated thickness is 0.2 to 5 times.

Next, a method for producing the polyester film of the present invention will be described. First, as a method for incorporating the spherical silica particles of the present invention into a predetermined polyester, it may be added before the polymerization, during the polymerization, or after the polymerization, but is mixed as a slurry with ethylene glycol which is a diol component of the polyester. The method of adding after dispersion is effective for obtaining the volume average diameter and the relative standard deviation in the present invention. Further, as a method for controlling the content of particles, a method of diluting a master pellet having a high concentration, preferably a particle content of 1.0 to 5.0% by weight during film formation, has a relative standard deviation of the present invention, It is effective for obtaining the volume average as well as the height distribution of the surface protrusions in a desired range.

Also, 1 part of ethylene glycol slurry is used.
The method of heat treatment at a temperature of 40 to 200 ° C., particularly 180 to 200 ° C. for 30 minutes to 5 hours, especially 1 to 3 hours is effective for obtaining the desired range of the relative standard deviation and the scraping index K in the present invention.

Next, as a method for incorporating the aluminum oxide particles and / or zirconium oxide particles of the present invention into a predetermined polyester, for example, the aluminum oxide particles and / or zirconium oxide particles are wet in the presence of a solvent such as glycol. A method of adding the dispersion-treated slurry to a polyester polymerization reaction system can be mentioned. As a treatment method at this time, ultrasonic waves may be used in combination with stirring, and a medium type mill such as a sand grinder may be used. The time of addition may be any time before the completion of the polymerization reaction, but is preferably from before the transesterification reaction to before the start of the reduced pressure of the polymerization reaction. It is to be noted that a method other than this, for example, a powdery state or a slurry state may be kneaded into the polyester in a molten state using a melt extruder or the like.

Thus, the pellets containing a predetermined amount of spherical silica particles, aluminum oxide particles and / or zirconium oxide particles were sufficiently dried and then fed to a known melt extruder, which was fed from a slit die at 270 to 330 ° C. It is extruded into a sheet and cooled and solidified on a casting roll to produce an unstretched film. At this time, it is effective to install a high-precision two-stage filtration filter in the polymer channel in order to reduce coarse protrusions when the film is formed. The high-precision two-stage filtration filter mentioned here means that the first stage has a 95% cutoff particle size of 4 to 10 μm and the second stage has 95%.
A filter having a% cut-off particle diameter of 1.5 to 5 μm is arranged in series, and a 95% cut-off particle diameter is a first step> second step.

Here, in the laminated polyester film, at least one of polyesters B and C in the laminated portion is laminated on at least one surface of the polyester A in the base layer portion by coextrusion to form an unstretched film.

The laminated film in the present invention can be obtained by extruding the polyesters A, B and C by different extruders and by coextruding them before discharging the laminated sheet from the die. This lamination may be performed in a die for forming and discharging into a sheet (for example, a manifold), but since the lamination thickness is thin as described above, it is preferable to perform it in the polymer pipe before being introduced into the die. . Particularly, it is particularly preferable that the laminated portion in the polymer tube is formed in a rectangular shape because the laminated portion can be uniformly laminated in the width direction. The molten polymer laminated at the rectangular laminated portion in the polymer tube is widened to a predetermined width in the sheet width direction by the manifold in the die to obtain a sheet-shaped unstretched film from the die.

Therefore, even if the laminated polyester film after biaxial orientation is extremely thin, in the polymer tube rectangular laminated portion, since the laminated portion polymer is laminated with a considerable thickness, it is easy and accurate. Can be stacked. By using two or three melt extruders, a confluent block or a die for two, three or five layers, B / A /
B, B / A / C, B / A, B / A / B / A / B, B / A
A laminated sheet of / C / A / B can be obtained. When the confluence block is used, it is effective to make the laminated portion rectangular as described above in order to stably produce the laminated polyester film of the present invention industrially without unevenness in the width direction.

In the production of the above polyesters B and C, the particle slurry and the particle-free polyester are kneaded and melted by using a twin-screw extruder, and the mixture is melted under a vacuum through a vent hole arranged in the extruder. A polyester containing the particles of the present invention may be produced by dispersing the solvent in the slurry while distilling it off.

Next, this unstretched film is biaxially stretched to be biaxially oriented. As a stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, the sequential biaxial stretching method of first stretching in the longitudinal direction and then in the width direction is used, and the stretching in the longitudinal direction is divided into two stages, particularly three or more stages (polymer glass transition point + 20 ° C.) to In the range of (glass transition point of polymer + 60 ° C.), the film is stretched 3 to 4.5 times and then stretched in the width direction at a stretching temperature of 100 to 160 ° C. and a stretching ratio of 3 to 5 times. Next, this stretched film is heat-treated. The heat treatment conditions in this case are 150 to 230.
0.5 to 60 ° C., preferably in the range of 180 to 210 ° C.
Seconds are preferred. The running direction in this heat treatment process,
It can be performed in any state of relaxation, fine stretching, and under constant length in both width directions.

The characteristic values in the present invention are as follows:
According to evaluation criteria. (1) Particle content sample was sufficiently washed with methanol to remove surface deposits, washed with water, and dried to add 300 kg of sample to 2.7 g of o-chlorophenol. After warming, it is left as it is for 1 hour to dissolve the polyester part. However, in the case where the polyester portion is not dissolved due to a high degree of crystallization, the above melting operation is performed after once melting and quenching.

Then, coarse insoluble matter such as dust contained in the polyester is filtered off with a G-1 glass filter and removed, and the weight of the above-mentioned filter is subtracted from the weight of the sample.

Hitachi's separation ultracentrifuge 40p type was equipped with a rotor RP30, and after injecting 30 cc of the solution after the glass filter filtration into one cell, the rotor was rotated to 45
After confirming that there is no abnormal rotation, the rotor is evacuated, the rotation speed is increased to 30,000 rpm, and the particles are centrifuged at this rotation speed.

The separation is completed after about 40 minutes, but this confirmation is made if necessary by making the light transmittance of the liquid after the separation at 375 mμ higher than that before the separation. After separation, the supernatant is removed by a gradient method to obtain separated particles.

Since polyester particles may be mixed in the separated particles due to insufficient separation, normal temperature o-chlorophenol is added to the collected particles, and the particles are almost uniformly suspended, and then the ultracentrifuge is again used. Perform processing.

This operation must be repeated until the particles to be described later are dried and subjected to a differential scanning calorimetric analysis to detect no melting peak corresponding to the polymer. Finally, the separated particles A thus obtained are vacuum dried at 120 ° C. for 16 hours and weighed.

The separated particles A obtained by the above operation contain both spherical silica particles and aluminum oxide particles and / or zirconium oxide particles. Therefore, it is necessary to separately determine the amount of spherical silica particles and the amount of aluminum oxide particles and / or zirconium oxide particles. First, the separated particles are quantitatively analyzed for the metal content,
The contents of Si, Zn and Al and the contents of metals other than Si, Zn and Al are obtained. Then, when the separated particles are heated under reflux in a 20% aqueous solution of sodium hydroxide for 6 hours or more, only spherical silica particles are dissolved. The separated particles B obtained by centrifuging the remaining particles are dried and weighed to obtain the content of aluminum oxide particles and / or zirconium oxide particles. Further, the weight of the separated particles B is subtracted from the weight of the first separated particles A to obtain the content of the spherical silica particles. At this time, the accuracy can be improved by quantifying the metal content of the separated particles and repeating the above operation.

(2) Particle size ratio of spherical silica particles Polyester is removed from the film by a plasma low temperature ashing method to expose the particles. The processing conditions are selected such that polyester is incinerated but particles are not damaged.
Scanning electron microscope (ESM32 manufactured by Elionix Co., Ltd.)
00) and the image of the particles is processed with an image analyzer (IBAS2000 manufactured by Carl Zeiss).

In this measurement, the major axis / minor axis ratio of the individual particles shown in the following formula is obtained, and the particle size ratio "average value of major axis / minor axis" is calculated from these values. However, only the particle diameter ratio of individual particles of 1.3 or less was counted as spherical silica and subjected to numerical processing. Ratio of major axis to minor axis of individual particles = D1 / D2 where D1 is major axis (maximum diameter) and D2 is minor axis (shortest diameter). Particle size ratio = Σ (D1i / D2i) / N D1i, D2i is the long diameter (maximum diameter) of each individual particle,
Minor diameter (shortest diameter), N is the number of counted particles.

(3) Relative Standard Deviation of Spherical Silica Particles The area equivalent circle diameters of the particles counted in the measurement of (2) above are determined, and the following numerical processing is performed when the number of observed particles is changed to 5,000 or more. What to do Here, Di is the equivalent circle diameter of the particles, and N is the number of counted particles. And

(4) Volume average diameter of spherical silica particles The volume average diameter V of the particles counted in the measurement of the above (3) is calculated by the following formula. V = (ΣDi ³ / N) ^1/3 Here, Di is the equivalent circle diameter of the particles, and N is the number of counted particles.

(5) Volume average diameter of aluminum oxide particles and / or zirconium oxide particles Aluminum oxide particles and / or separated in the above (1)
Or disperse the zirconium oxide particles in methanol,
Centrifugal sedimentation type particle size distribution measuring instrument (Horiba Seisakusho CAPA5
The central cumulative value (50% by volume) in the cumulative distribution curve of the Stokes diameter measured in 00) was defined as the volume average diameter.

(6) Scraping index K A film sample having a thickness of 15 μm was slit with a shear cutter manufactured by Nishimura Seisakusho at a slit speed of 50 m / min into 1/2 inch, and then slit into 1/2 inch to obtain a film sample 1 m. Was placed in a container containing 50 cc of pure water so that only one cut surface of the film sample was immersed, and after ultrasonic treatment, the film sample was removed and the immersion liquid was removed by a particle counter (HIAC / ROYCO). CL-
The number of particles having a size of 3 to 20 μm measured in 5) was defined as the abrasion index K.

(7) Refractive index nz in the thickness direction The refractive index nz in the thickness direction of the biaxially oriented film is set by using an Abbe refractometer as a light source of sodium D line (wavelength 589 nm). Methylene iodide is used for the mount solution,
It was measured at 25 ° C. and 65% RH.

(8) Refractive index nz in the thickness direction of the biaxially oriented film and refractive index NMD in the longitudinal direction of the film using an Abebe refractometer with the plane orientation index F and the ΔN sodium D line (wavelength 589 nm) as the light source. , Refractive index NTD in the film width direction, ΔN = (NMD-NTD) × 1000, F
= (NMD + NTD) / 2-nz. Methylene iodide was used as the mount solution, and measurement was performed at 25 ° C. and 65% RH.

(9) Number of projections on film surface and three-dimensional surface roughness (SRa) Non-contact surface roughness meter HIPOSS (model ET of Kosaka Laboratory)
-30HK) and three-dimensional roughness analyzer (model SPA-
11) was used to measure the three-dimensional roughness. The conditions are as follows, and the average value of 20 measurements was taken as the value.・ Vertical magnification: 20,000 times ・ Horizontal magnification: 500 times ・ Cutoff: 0.08 mm ・ Feeding pitch: 0.5 μm ・ Measuring length: 500 μm ・ Measuring area: 0.0194 mm ²・ Measuring speed: 100 μm / sec ・ HYST: ± 6.25 nm-COUNT MODE: SIMPLE-Z standard: UPPER The protrusion height was calculated with reference to the cut surface at which the area ratio of the cut surface was 70%. The number of protrusions having a height of 200 to 400 nm and 400 nm or more measured under the above conditions was converted into each number / 0.1 mm ² . SR
a is three-dimensional surface roughness (center plane average roughness).

(10) Center line average surface roughness (Ra) According to JIS-B-0601, a contact point type surface roughness meter BE-3E manufactured by Kosaka Laboratory was used, and the center line was measured at a cutoff of 0.25 mm and a measurement length of 4 mm. The average surface roughness (Ra) was measured.

(11) Image Quality, Scratch Resistance, Use Durability A magnetic coating composition having the following composition is applied to a film by a gravure roll, magnetically oriented and dried. Furthermore, after calendering at a temperature of 70 ° C and a linear pressure of 200 kg / cm with a small calendar device (styrene roll, nylon roll, 5 stages),
Cure at 70 ° C. for 48 hours. 1/2 of this material
Slit into inches to make a pancake. This pancake was incorporated into a VTR cassette to obtain a VTR cassette tape.

(Composition of magnetic paint) Co-containing iron oxide (BET value 50 m ² / g): 100 parts by weight S-REC A (Sekisui chemical vinyl chloride / vinyl acetate copolymer): 10 parts by weight Nopollan 2304 ( Nippon Urethane Polyurethane Elastomer): 10 parts by weight Cotonate L (Japan Urethane Polyisocyanate): 5 parts by weight Lecithin: 1 part by weight Methylethylketone: 75 parts by weight Methylisobutylketone: 75 parts by weight Toluene: 75 parts by weight, carbon black: 2 parts by weight, lauric acid: 1.5 parts by weight This tape was recorded with a 100% chroma signal by a TV test waveform generator (TG7 / U706) manufactured by Shibasoku using a home VTR. Shiba Soku color from the playback signal
The image quality was judged by measuring the chroma S / N with a noise measuring machine (925D / 1).

Furthermore, this VTR cassette is used for home VT
It was incorporated into R and repeated running (reproduction / high-speed rewinding) was repeated 100 times, and similarly, the chroma S / N was measured from the reproduced signal with a Shiba Soku color noise measuring machine (925D / 1) to determine the image quality. V after repeated running
The scratch resistance was judged by the amount of white powder scraped on the TR cassette guide pin and the amount of scraped film. The criteria for these judgments are as follows, and if the rank is 4 or higher, there is no problem in practical use. Judgment rank S / N (image quality) Film scraping (scratch resistance) 5 Excellent, image quality is extremely good Guide pin stains almost none 4 Good, almost no problem 3 Slight white powder stains 3 Disturbance in image quality Scraped object stains 2 Image quality The image quality is poor. 1) Image quality is poor. Scrap is large and white powder adheres. (12) Evaluation of slitting property A magnetic coating liquid of the following composition is applied to one side of a polyester film with a thickness of 14.5 μm and the film thickness after drying is 3 μm. To be coated. After coating, it is oriented in a DC magnetic field, dried, and then calendered. This sheet is slit into 1/2 inch width with a shear cutter to make a video tape. The degree of occurrence of whiskers and powder is visually classified and evaluated by visually observing the slit portion by the shear cutter. Slitting property A: generation of whiskers and powder is extremely small. 〃 B: 〃 Little. 〃 C: 〃 Normal level. 〃 D: 〃 Somewhat large. 〃 E: There are many. (Note) Most of the biaxially oriented polyester films for video tapes currently on the market have a slit property level of C or D.

[0067]

EXAMPLES The present invention will be described based on examples. Reference Example Preparation of Polyester 100 parts by weight of terephthalic acid and 43 parts by weight of ethylene glycol were kneaded to prepare a slurry. The slurry is continuously added at a constant rate to a reaction product of 50 parts by weight of terephthalic acid and 21.5 parts by weight of ethylene glycol stored in a reactor at 245 ° C., and transesterification reaction is performed at 245 ° C. under normal pressure to produce a product. Water was continuously distilled out of the system from the rectification tower.
The slurry supply time was 3 hours and 30 minutes, and the transesterification reaction was 4 hours. From the obtained reaction product, an esterification reaction product corresponding to 100 parts by weight of terephthalic acid was transferred to a polymerization apparatus, and 0.045 parts by weight of phosphoric acid, 0.023 part by weight of antimony trioxide, and a volume average particle diameter of 0.16 μm.
2.4 parts by weight of spherical silica particles synthesized by the water glass method having m, a particle size ratio of 1.1 and a relative standard deviation of 0.71 were added as an ethylene glycol slurry, and a polycondensation reaction was carried out according to a conventional method. At this time, the ethylene glycol slurry containing the spherical silica particles was heat-treated at the boiling point of ethylene glycol for 10 minutes. The polymer thus obtained had an intrinsic viscosity of 0.615 and contained 2 parts by weight of spherical silica particles. The refractive index of the spherical silica particles in the ethylene glycol slurry was 1.440. (Polyester A) 100 parts by weight of terephthalic acid and ethylene glycol 4
A slurry was prepared by kneading 3 parts by weight. 245 in the reactor
The slurry was continuously added at a constant rate to a reaction product of terephthalic acid (50 parts by weight) and ethylene glycol (21.5 parts by weight) stored at 0 ° C., and transesterification reaction was carried out at 245 ° C. under normal pressure to rectify the produced water. It was continuously distilled out of the system from the tower. The slurry supply time was 3 hours and 30 minutes, and the transesterification reaction was 4 hours. An esterification reaction product corresponding to 100 parts by weight of terephthalic acid was transferred from the obtained reaction product to a polymerization apparatus, and 0.045 parts by weight of phosphoric acid, 0.023 part by weight of antimony trioxide, and a volume average particle size of 0.3 μm were used.
2.4 parts by weight of θ-type aluminum oxide particles of m were added as an ethylene glycol slurry, and polycondensation reaction was carried out according to a conventional method. At this time, the ethylene glycol slurry was treated with ultrasonic waves for 20 minutes. The polymer thus obtained has an intrinsic viscosity of 0.610 and contains aluminum oxide particles 2
It contained parts by weight. (Polyester B) Further, a zirconium oxide particle-containing polymer was obtained by adding zirconium oxide particles having a volume average diameter of 0.35 μm instead of the aluminum oxide particles in the same manner as in the polyester B. The obtained polymer has an intrinsic viscosity of 0.61
It was 3. (Polyester C) In the same manner as in the case of polyester A, a particle-free polymer was obtained without adding spherical silica particles. The intrinsic viscosity of the obtained polymer was 0.620. (Polyester D) Example 1 The polyester A, polyester B, polyester C and polyester D thus obtained had a spherical silica particle content of 0.6% by weight and an aluminum oxide particle content in the final polyester film. The pellet E mixed in a predetermined amount so that 0.1% by weight was dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours to obtain a raw material for the laminated portion. Separately, a polyethylene terephthalate raw material having an intrinsic viscosity of 0.63 was prepared as a raw material for the base layer, and 180
It dried under reduced pressure (3 Torr) at 3 degreeC for 3 hours.

The base layer portion was supplied to the extruder 1 at 310 ° C., and the raw material for the laminated portion was supplied to the extruder 2 and melted at 280 ° C.
These polymers are combined and laminated in a confluent block having a rectangular laminated part before entering the mouthpiece, and are wound around a casting drum having a surface temperature of 45 ° C. by an electrostatic applied casting method to be cooled and solidified, and both sides of the base layer polyester A An unstretched film having a three-layer structure was produced by laminating polyester B on the above. At this time, the discharge amount of each extruder was adjusted, and the total thickness and the laminated thickness were adjusted.

This unstretched film was subjected to the roll temperature of FIG. 1 at 75 ° C. for roll 1 and roll 2, 115 ° C. for roll 3 and roll 4, 126 ° C. for roll 5, and 12 for roll 6.
6 ° C., 118 ° C. for roll 7, 1.6 times between rolls 5 and 6, 1.3 times between rolls 6 and 7, 2.1 times between rolls 7 and 8 It was stretched in the vertical direction by adjusting the peripheral speed difference of the rolls.

This uniaxial film was heated at 120 ° C. in a stenter.
Stretched 4.6 times in the horizontal direction under hot air, and then 1.03
Under double stretching, heat treated with hot air at 205 ° C for 5 seconds,
A biaxially oriented film having a thickness of 15 μm was obtained. The final traveling speed of the biaxially oriented film at this time was 160 m / min.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 1 and 2. Δ in Tables 1 and 2
N is -42, plane orientation index F is 0.1687, refractive index nz in the thickness direction is 1.493, and F-5 value in the TD direction (direction perpendicular to the running direction of the film) is 14.3 kg / mm ^2.
And the abrasion index K is 32 and the average surface roughness Ra is
It was 15 nm, and all were within the scope of the present invention. Further, as is clear from the results of Tables 1 and 2, it is found that the S / N ratio (image quality) characteristics, film scraping, and slitting property are all excellent.

Examples 2-3 The spherical silica content in the polyester film was 0.6.
0 wt% (Example 2), 1.30 wt% (Example 3),
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that zirconium oxide particles were used as the aluminum oxide particles. The measurement and evaluation results of the properties of the obtained biaxially oriented film are shown in Tables 1 and 2. As is clear from the results of Table 1 and Table 2, each of the films of Examples 2 to 3 had S
It can be seen that the / N ratio (image quality) characteristics, film scraping, and slitting property are all excellent.

Example 4 A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the stretching ratio between the roll 7 and the roll 8 in FIG. 1 was adjusted to be 2.4 times.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 1 and 2. As is clear from the results shown in Tables 1 and 2, it is understood that the film of Example 4 is excellent in S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 5 A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the stretching ratio between the roll 7 and the roll 8 in FIG. 1 was adjusted to 2.3 times.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 1 and 2. As is clear from the results in Tables 1 and 2, it is understood that the film of Example 5 is excellent in all of the S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 6 The temperature of the roll 5 and the roll 6 in FIG.
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the stretching ratio between the roll 7 and the roll 8 was adjusted to 2.3 times.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 1 and 2. As is clear from the results of Tables 1 and 2, the film of Example 6 is excellent in all of S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 7 The temperature of the rolls 5 and 6 in FIG.
Example 1 except that the stretching ratio in the horizontal direction was 4.8 times.
A biaxially oriented polyester film was obtained in the same manner as in.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 1 and 2. As is clear from the results in Tables 1 and 2, it is understood that the film of Example 7 is excellent in S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 8 A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the temperature of the rolls 5 and 6 in FIG. 1 was 123 ° C.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 1 and 2. As is clear from the results of Tables 1 and 2, it is understood that the film of Example 8 is excellent in S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 9 Example 1 was repeated except that the stretching ratio in the horizontal direction was 4.3 times.
A biaxially oriented polyester film was obtained in the same manner as in.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 1 and 2. As is clear from the results of Tables 1 and 2, it is understood that the film of Example 9 is excellent in S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 10 The same method as in Example 1 was carried out except that spherical silica particles having a volume average particle diameter of 0.17 μm, a particle diameter ratio of 1.1 and a relative standard deviation of 0.82 were used. A biaxially oriented polyester film was obtained.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 1 and 2. As is clear from the results of Tables 1 and 2, it is understood that the film of Example 10 is excellent in all of S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 11 Spherical silica particles having a volume average particle size of 0.50 μm, a particle size ratio of 1.05 and a relative standard deviation of 0.76, which were synthesized by the water glass method, were used, and the content in the polyester film was 0.20. A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the weight percentage was changed. Moreover, the refractive index at 25 ° C. of a 20 wt% ethylene glycol slurry of the spherical silica particles was 1.440.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 1 and 2. As is clear from the results of Tables 1 and 2, it is understood that the film of Example 11 is excellent in S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 12 Spherical silica particles having a volume average particle size of 0.89 μm, a particle size ratio of 1.05 and a relative standard deviation of 0.78, which were synthesized by the water glass method, were used, and the content in the polyester film was 0.20. A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the weight percentage was changed. Further, the refractive index at 25 ° C. of a 20 wt% ethylene glycol slurry of the spherical silica particles was 1.439.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 1 and 2. As is clear from the results of Tables 1 and 2, it is understood that the film of Example 12 is excellent in all of S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 13 A biaxially oriented polyester film was obtained in the same manner as in Example 11, except that the content of aluminum oxide particles in the polyester film was 0.06% by weight.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 1 and 2. As is clear from the results in Tables 1 and 2, it is understood that the film of Example 13 is excellent in S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 14 Spherical silica particles having a volume average particle size of 0.55 μm, a particle size ratio of 1.1, and a relative standard deviation of 0.58 were synthesized by an alkoxide method, and the content in a polyester film was 0.20% by weight. %, The temperature of roll 5 and roll 6 in FIG.
And a biaxially oriented polyester film in the same manner as in Example 2 except that the stretching ratio between the rolls 7 and 8 is adjusted to 1.9 times and the stretching ratio in the horizontal direction is 4.2 times. Got The refractive index at 25 ° C. of a 20 wt% ethylene glycol slurry of the spherical silica particles is
It was 1.426.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 3 and 4. As is clear from the results of Tables 3 and 4, it is understood that the film of Example 14 has good S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 15 The temperature of roll 5 and roll 6 in FIG.
A biaxially oriented polyester film was obtained in the same manner as in Example 14 except that the stretching ratio between the rolls 7 and 8 was adjusted to 2.5 times and the stretching ratio in the horizontal direction was adjusted to 4.2 times. It was

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 3 and 4. As is clear from the results of Tables 3 and 4, the film of Example 15 has good S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 16 The temperature of roll 5 and roll 6 in FIG.
A biaxially oriented polyester film was obtained in the same manner as in Example 14, except that the stretching ratio between the rolls 7 and 8 was 2.1 times and the stretching ratio in the horizontal direction was 4.6 times. It was

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 3 and 4. As is clear from the results of Tables 3 and 4, it is understood that the film of Example 16 has good S / N ratio (image quality) characteristics, film scraping, and slitting property.

Example 17 In the same manner as in Example 1, except that spherical silica particles having a volume average particle diameter of 0.51 μm, a particle diameter ratio of 1.05, and a relative standard deviation of 0.74 were synthesized by the alkoxide method. A biaxially oriented polyester film was obtained. Further, the refractive index at 25 ° C. of a 20% by weight ethylene glycol slurry of the spherical silica particles was 1.427.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 3 and 4. As is clear from the results of Tables 3 and 4, it is understood that the film of Example 17 has good S / N ratio (image quality) characteristics, film scraping, and slitting property.

Comparative Example 1 The same method as in Example 1 was carried out except that spherical silica particles having a volume average particle diameter of 0.16 μm, a particle diameter ratio of 1.1 and a relative standard deviation of 0.17 were used. A biaxially oriented polyester film was obtained. Further, the refractive index at 25 ° C. of a 20% by weight ethylene glycol slurry of the spherical silica particles was 1.427.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 5 and 6. As is clear from the results of Tables 5 and 6, the film of Comparative Example 1 is inferior in slit property.

Comparative Example 2 In the same manner as in Example 11 except that spherical silica particles having a volume average particle size of 0.55 μm, a particle size ratio of 1.1 and a relative standard deviation of 0.19 were used. A biaxially oriented polyester film was obtained. Further, the refractive index at 25 ° C. of a 20 wt% ethylene glycol slurry of the spherical silica particles was 1.425.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 5 and 6. As is clear from the results of Tables 5 and 6, the film of Comparative Example 2 is inferior in slit property.

Comparative Example 3 The same procedure as in Example 11 was carried out except that spherical silica particles having a volume average particle diameter of 2.2 μm, a particle diameter ratio of 1.05 and a relative standard deviation of 0.69 were used. A biaxially oriented polyester film was obtained.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 5 and 6. As is clear from the results of Tables 5 and 6, the film of Comparative Example 3 is inferior in both electromagnetic conversion characteristics (S / N ratio) and film scraping (scratch resistance).

Comparative Example 4 Spherical silica particles having a volume average particle diameter of 0.09 μm, a particle diameter ratio of 1.1 and a relative standard deviation of 0.78 were synthesized by a water glass method, and the content in the polyester film was 0.90. weight%
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 5 and 6. As is clear from the results in Tables 5 and 6, it can be seen that the film of Comparative Example 4 is inferior in film abrasion (scratch resistance).

Comparative Example 5 Spherical silica particles having a volume average particle diameter of 0.55 μm, a particle diameter ratio of 1.1, and a relative standard deviation of 0.58 were synthesized by a water glass method, and the content in the polyester film was 5.2. A biaxially oriented polyester film was obtained in the same manner as in Example 11 except that the weight percentage was changed. However, the amount of spherical silica particles added in the reference example was 6.0 parts by weight.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 5 and 6. As is clear from the results of Tables 5 and 6, the film of Comparative Example 5 is inferior in both the electromagnetic conversion characteristics (S / N ratio) and the film abrasion (scratch resistance).

Comparative Example 6 Spherical silica particles having a volume average particle diameter of 0.55 μm, a particle diameter ratio of 1.1, and a relative standard deviation of 0.58 were synthesized by a water glass method, and the content in the polyester film was 0.004. A biaxially oriented polyester film was obtained in the same manner as in Example 11 except that the weight percentage was changed. The measurement and evaluation results of the properties of the obtained biaxially oriented film are shown in Tables 5 and 6. As is clear from the results of Tables 5 and 6, it can be seen that the film of Comparative Example 6 is inferior in film scraping (scratch resistance).

Comparative Example 7 A biaxially oriented polyester film was obtained in the same manner as in Example 11 except that aluminum oxide particles were not included.

Measurement of characteristics of the obtained biaxially oriented film
The evaluation results are shown in Tables 5 and 6. As is clear from the results in Tables 5 and 6, it can be seen that the film of Comparative Example 7 is inferior in film scraping (scratch resistance).

[0114]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[0115]

EFFECTS OF THE INVENTION The polyester film of the present invention is excellent in both scratching property and slitting property, and the film is not easily scratched even when running at high speed. It is possible. Also, when used as a video tape, S /
N, that is, a film in which the image quality is not easily degraded is obtained. The use of the polyester film for a magnetic recording medium of the present invention is not particularly limited, but scratches on the film surface in the processing step are a particular problem in terms of product performance. It is particularly useful as a base film for pancakes with the spread of

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an outline of a vertical stretching device.

[Explanation of symbols]

1: Hard chrome plated metal roll 2-6: Silicone rubber coated metal roll 7: Mirror-finished ceramic roll 8 and 9: hard chrome-plated metal roll 11 and 14: rubber roll 12 and 13: Metallic roll coated with silicone rubber 10: Film

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C08L 67/02 C08L 67/02 // B32B 27/36 B32B 27/36 B29K 67:00 B29K 67:00 105: 16 105: 16 (56) References JP-A-4-62137 (JP, A) JP-A-63-234038 (JP, A) JP-A-4-151231 (JP, A) JP-A-5-230237 (JP, A) Kaihei 5-84820 (JP, A) JP 3-137814 (JP, A) JP 2-108232 (JP, A) JP 4-238111 (JP, A) JP 5-54367 ( JP, A) JP 5-81644 (JP, A) JP 4-228502 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/68-5/718

Claims (6)

(57) [Claims] 1. A polyester having a volume average particle diameter of 0.1 to 0.1.
It has a relative standard deviation of 2.0 μm and a relative standard deviation defined by the following formula (1) of more than 0.5, and contains 0.005 to 5.0% by weight of spherical silica particles of 3 or less , and aluminum oxide particles and And / or zirconium oxide particles are contained in the polyester film for a magnetic recording medium. [Equation 1] 2. The polyester film for a magnetic recording medium according to claim 1, wherein the abrasion index K is 60 or less. 3. The polyester film for a magnetic recording medium according to claim 1, wherein the refractive index nz in the thickness direction and the plane orientation index F satisfy the following formulas (2) and (3). nz ≤ 1.603-0.6407 × F (2) nz ≧ 1.595-0.6407 × F (3) [Here, the plane orientation index F is F = ( NMD + NTD) / 2
Defined by -nz, NMD represents the refractive index in the longitudinal direction of the film, NTD represents the refractive index in the width direction of the film, and nz represents the refractive index in the thickness direction of the film. ] 4. The polyester film for a magnetic recording medium according to any one of claims 1 to 3, wherein the plane orientation index F and ΔN simultaneously satisfy the following expressions (4) to (6). . ΔN ≦ 1413-8327 × F ‥‥‥‥‥‥‥‥‥ (4) ΔN ≥ 1340-8627 × F ‥‥‥‥‥‥‥‥ (5) -60 ≤ ΔN ≤ 30 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (6) [Where ΔN is ΔN = (NMD−NTD) × 1000, F =
It is defined by (NMD + NTD) / 2-nz, where NMD represents the refractive index in the longitudinal direction of the film, and NTD represents the refractive index in the width direction of the film. ] 5. The polyester film for a magnetic recording medium according to claim 1, wherein the plane orientation index F and ΔN simultaneously satisfy the following formulas (7) to (9). . ΔN ≤ 1413-8327 × F ‥‥‥‥‥‥‥‥‥ (7) ΔN ≥ 1340-8627 × F ‥‥‥‥‥‥‥ (8) -60 ≤ ΔN ≤ -20 ‥‥‥‥‥‥‥‥ (9) ) [Where ΔN = (NMD−NTD) × 1000, F = (NMD +
NTD) / 2-nz, where NMD is the refractive index in the film longitudinal direction, NTD is the refractive index in the film width direction, and nz is the refractive index in the film thickness direction. ] 6. A laminated polyester film for a magnetic recording medium, which comprises at least one layer of the polyester film according to any one of claims 1 to 5.