JPH07114726A - Polyester film for magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a polyester film excellent in running performance, running durability against repeated use, winding characteristics like a pancake and slitting characteristics and useful as a base film for a magnetic recording medium satisfying even the requirement of high image quality. CONSTITUTION:This polyester film contains 0.005-5.0wt.% spherical silica particles having 0.1-2.0mum volume average particle diameter and a relative standard deviation of >0.5 in polyester and further contains 0.005-5.0wt.% org. polymer particles having 0.1-2.0mum volume average particle diameter.

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 magnetic recording media, and more particularly to a polyester film suitable for a video tape which is excellent in running durability, slit property and film winding 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 necessary to impart the film sharpness at the time of slitting to the film characteristics and to make the pancake winding shape good. Many studies have been made in the past against these dilemmas of contradictory film surface characteristics, and for example, JP-A-59-17162.
No. 3, JP-A-63-234038, it is disclosed in JP-A-61-5431 that spherical silica particles are contained.
The publication discloses that inert inorganic particles such as colloidal silica are contained.

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, has excellent running durability by repeated use, has improved slit characteristics in the magnetic recording medium manufacturing process, and has an excellent pancake winding shape. It is an object of the present invention to provide a polyester film for a magnetic recording medium that meets the demand for 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.
0.005 to 5.0% by weight of spherical silica particles exceeding 5
This can be achieved by a polyester film for a magnetic recording medium, which contains 0.005 to 5.0% by weight of organic polymer particles having a volume average particle diameter of 0.1 to 2.0 μm.

[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 not particularly defined, but it is preferably 3 or less in order to keep the waviness of the film surface well.

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.

The organic polymer particles in the present invention include, for example, polystyrene particles or crosslinked polystyrene particles, vinyl particles such as styrene / acrylic and methacrylic crosslinked particles, benzoguanamine / formaldehyde resin particles,
Examples include, but are not limited to, silicone resin particles, polytetrafluoroethylene particles, polyphenyl ester particles, and phenol resin particles. At least a part of the particle-constituting portion is insoluble in polyester. Any particles may be used as long as they are polymer particles.

Preferably, a monovinyl compound (A) generally having only one aliphatic unsaturated bond in the molecule and a compound (B) having two or more aliphatic unsaturated bonds in the molecule as a crosslinking agent. And a copolymer thereof.

Specific examples of the compound (A) in the above copolymer include aromatic monovinyl compounds such as styrene, p-methylstyrene, m-methylstyrene, p-ethylstyrene and m-ethylstyrene, acrylonitrile and methacryloyl. Vinyl cyanide compounds such as nitrile, acrylic ester monomers such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate,
Butyl methacrylate Methacrylic acid ester monomers such as glycidyl methacrylate, acid anhydrides of mono- or dicarboxylic acids and dicarboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and amide monomers such as acrylamide and methacrylamide. Can be mentioned. Of these, styrene and p-ethylstyrene and m-ethylstyrene are particularly preferable from the viewpoint of heat resistance.

Further, specific examples of the compound (B) include divinylbenzene, trimethylolpropane triacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate and the like. Of these, divinylbenzene is particularly preferable from the viewpoint of crosslinking reactivity.

These compounds (A) and (B) may be used as a mixture of two or more kinds. Also,
In order to improve running durability which is one of the objects of the present invention, the proportion of the compound (B) in the organic polymer particles is 10 to 95% by weight, preferably 50 to 95% by weight in terms of monomer. More preferably, the amount is 80 to 95% by weight.

Preferred examples of the composition of the organic polymer particles of the present invention include "styrene / divinylbenzene copolymer", "divinylbenzene / p- and m-ethylstyrene copolymer", and "styrene / divinylbenzene / copolymer".
p- and m-ethylstyrene copolymer ".

The volume average particle size of the organic polymer particles of the present invention is required to be 0.1 to 2.0 μm, preferably 0.15 to 1.0 μm. If the volume average particle size of the particles is smaller than 0.1 μm, friction increases,
When it is used as a video tape, the running characteristics deteriorate. vice versa,
If it is larger than 2.0 μm, the electromagnetic conversion characteristics of a magnetic recording medium represented by a video tape will be poor. Further, the content of the organic polymer particles is required to be 0.005 to 5.0% by weight, preferably 0.01 to 2.0% by weight, and more preferably 0. 02 ~
It is preferably 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. Conversely, 5.
If it is more than 0% by weight, the electromagnetic conversion characteristics of a magnetic recording medium represented by a video tape will be poor.

Next, a method for producing the organic polymer particles will be described.
Explaining the method for producing the crosslinked polymer particles as an example, for example, there is a method in which a predetermined amount of the compound (A) and the compound (B) are mixed and the following emulsion polymerization is performed. (A) Soap-free polymerization method: a method in which an emulsifier is not used or an extremely small amount of emulsifier is used for polymerization. (B) A seed polymerization method in which fine polymer particles are added to the polymerization system prior to emulsion polymerization and emulsion polymerization is performed. (C) A core-shell polymerization method in which a part of a monomer (monomer) is emulsion-polymerized and the remaining monomer is polymerized in the polymerization system. The production method is not particularly limited, but the seed polymerization method (b) is preferable in order to obtain organic polymer particles having a sharper and more uniform particle size distribution.

In the present invention, the method of incorporating the spherical silica particles and the organic polymer particles into the polyester is not particularly limited, but in general, it is preferable to add the slurry of the spherical silica particles and the organic polymer particles during the production of the polyester. . As the addition method and the addition timing, conventionally known methods and times are used, but in the addition method,
A method of adding it as a slurry of glycol, which is a raw material for synthesizing the polyester, is particularly preferable. The slurry concentration at this time is 0.5 to 40% by weight, more preferably 1 to 20% by weight for spherical silica particles, and 0.5 for organic polymer particles.
It is preferably in the range of 25 to 25% by weight, more preferably 1 to 15% by weight because the particle dispersibility in polyester is improved.
Further, the content of water in the glycol of the slurry at the time of addition is preferably 1% by weight or less, more preferably 0.5% by weight or less, because the particle dispersibility in the 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.

In the present invention, it is necessary to use the spherical silica particles of the present invention in combination with the organic polymer particles in order to satisfy all the running properties, film winding properties, electromagnetic conversion properties and slit properties. With only spherical silica particles,
If the content of particles is such that the running property and film winding form are good, the electromagnetic conversion characteristics cannot be satisfied, and further dropout increases due to repeated running when used as a VTR tape. In addition, if the organic polymer particles alone are used, the winding shape of the film is deteriorated when the content of the particles is such that the running property and the electromagnetic conversion characteristics are good, and the scraping is increased in the calendering process during the production of the VTR tape. In the present application, the content ratio of spherical silica particles and organic polymer particles (weight of spherical silica particles / weight of organic polymer particles) is 0.1.
-10, and more preferably 0.2 to 6 are particularly preferable because all the above-mentioned characteristics are good.

Further, other inert particles such as calcium carbonate, aluminum oxide, zirconium oxide, antioxidants, heat stabilizers, etc. within the range that does not impair the effects of the present invention.
An inorganic or organic additive such as an ultraviolet absorber may be contained to the extent that it is usually added.

The polyester film for a magnetic recording medium of the present invention is biaxially oriented by a conventional method and has a thickness of 3 to 50 μm, preferably 5 to 25 μm. The abrasion index K in the present invention means that a film having a thickness of 10 to 15 μm is slit into 1/2 inch at a slit speed of 50 m / min by a shear cutter type slitter, and then 1 mm after slitting the film into 1 inch. After placing in a container containing 50 cc of pure water so that only one cut surface is immersed and performing ultrasonic treatment,
It is defined as the number of particles having a particle size of 3 to 20 μm when the film sample is removed and the immersion liquid is measured with a particle counter. 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 slitting property is good and the calendering step is performed. It is preferable that 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-nz, 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 thickness direction of the film is shown. Further, in the polyester film of the present invention, when the plane orientation index F and ΔN are within the ranges that simultaneously satisfy the following formulas (4) to (6), not only the wear characteristics during repeated running become good, but also It is preferable that whiskers are less likely to be generated on the end surface of the film during slitting, and that abrasion powder is less likely to be generated in the calendering process performed during video tape processing. ΔN ≦ 1413-8327 × F ‥‥‥‥‥‥‥‥‥ (4) ΔN ≥ 1340-8627 × F ‥‥‥‥‥‥‥ (5) -60 ≤ ΔN ≤ -20 ‥‥‥‥‥‥‥‥‥‥ (6 ) [Where ΔN is ΔN = (NMD-NTD) × 1000,
F = (NMD + NTD) / 2-nz, NMD
Indicates the refractive index in the film longitudinal direction, and NTD indicates the refractive index in the film width direction. Here, the ΔN can be raised by lowering the NMD and lowered by raising it. 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. The NMD can be raised by lowering the stretching temperature in the longitudinal direction, and conversely, can be lowered by raising it. 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 (stretching ratio in the longitudinal direction × drawing ratio in the width direction) during stretching, and conversely, can be decreased by lowering it. be able to. When the area ratio is the same, it can be increased by decreasing the stretching temperature in the longitudinal direction or the width direction, and conversely, it can be decreased by increasing 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 8.
30 nm and a three-dimensional average surface roughness (SRa) of 13 to
50 nm is preferable, and Ra is 12 to.
At 25 nm, SRa is preferably 17-40 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. Further, the number of protrusions having a height of 200 to 400 nm is 1200 or more per 0.1 mm ² , and further 1350.
More than 1, especially more than 1,500 and height is 400n
The number of m-800 nm protrusions is 400 per 0.1 mm ^2.
The number is preferably not more than 300, more preferably not more than 300, and particularly preferably not more than 200. 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.

Further, the polyester films B and C of 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, the 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.

1 part of ethylene glycol slurry
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 a relative standard deviation in the present invention, a specific particle diameter ratio of volume average diameter and number average diameter, and abrasion. This is effective in obtaining the desired range of the index K.

Next, as a method for incorporating the organic polymer particles into a predetermined polyester, for example, a slurry obtained by subjecting the organic polymer particles to a wet dispersion treatment in the presence of a solvent such as ethylene glycol is added to the polyester polymerization reaction system. There is a method of doing. In addition, as the treatment method at this time, ultrasonic waves may be used together with the stirring, and a medium type mill such as sand grind 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. In addition, it may be kneaded into the polyester in a molten state by a method other than this, for example, in a powder state or a slurry state using a biaxial vent type extruder or the like.

Thus, the pellets containing a predetermined amount of spherical silica particles and organic polymer particles are sufficiently dried and then fed to a known melt extruder and extruded into a sheet from a slit die at 270 to 330 ° C. An unstretched film is prepared by cooling and solidifying on a casting roll. 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 it is formed into a film. The high-precision two-stage filtration filter referred to here means that the first stage has a 95% cutoff particle size of 4 to 10 μm, and 2
The stage is one in which filters having a 95% cutoff particle size of 1.5 to 5 μm are arranged in series, and the 95% cutoff particle size is the first stage> the second stage.

In the laminated polyester film, an unstretched film is prepared by laminating at least one surface of the polyester A of the base layer portion with at least one of the polyesters B and C of the laminated portion by coextrusion.

The laminated film in the present invention can be obtained by extruding the polyesters A, B and C by different extruders and 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, the polymer in the rectangular laminated portion in the polymer tube is laminated with a considerable thickness, so that 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, a biaxial extruder is used to melt the particle slurry and the particle-free polyester while kneading, 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 and 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 The sample was thoroughly washed with methanol to remove surface deposits, washed with water, and dried. 300 g of the sample was added with 2.7 kg of o-chlorophenol, and the temperature was raised to 100 ° C with stirring, and the temperature was raised. 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 matters such as dust contained in the polyester are filtered off with a G-1 glass filter and removed, and the weight of the above-mentioned substance 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 glass filter-filtered solution into each cell, the rotor was rotated to 45
After rotating at 00 rpm and confirming that there is no abnormal rotation, the inside of the rotor is evacuated, the rotation speed is increased to 30,000 rpm, and the particles are centrifuged at this rotation speed. Although the completion of the separation is about 40 minutes later, this confirmation is performed if necessary by the light transmittance at 375 mμ of the liquid after the separation becoming a constant value 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. In this operation, after the particles described below are dried, the particles are subjected to a differential scanning calorimetric analysis,
It must be repeated until no melting peak corresponding to the polymer can be detected. 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 organic polymer particles. Therefore, it is necessary to separately determine the amount of spherical silica particles and the amount of organic polymer particles. First, the separated particles are quantitatively analyzed for the metal content to determine the Si content and the metal content other than Si. Then, the separated particles are heated under reflux in an aqueous solution of 20% by weight of sodium hydroxide for 6 hours or more to dissolve only the spherical silica particles. The remaining particles are further stirred in a 1N nitric acid solution for 6 hours and then centrifuged to obtain separated particles B, which are washed with water, dried and weighed to obtain the content of organic polymer 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 treatment conditions are selected such that polyester and organic polymer particles are incinerated but spherical silica particles are not damaged. This is observed with a scanning electron microscope (ESM3200 manufactured by Elionix), and the image of the particles is processed by 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 particles and numerically processed. 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. Here, Di is the equivalent circle diameter of the particles, and N is the number of counted particles. did.

(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 from 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 organic polymer particles The organic polymer particles separated in the above (1) are dispersed in methanol, and a centrifugal sedimentation type particle size distribution analyzer (manufactured by Horiba Ltd.)
The median cumulative value (50% by volume) in the cumulative distribution curve of Stokes diameter measured by CAPA500) was defined as the volume average diameter.

(6) Scraping Index K A film sample having a thickness of 15 μm was slit by 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. 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) The refractive index nz in the thickness direction of the biaxially oriented film and the refractive index NMD in the longitudinal direction of the film using an Atsube refractometer with the plane orientation index F and ΔN sodium D line (wavelength 589 nm) as the light source. From the refractive index NTD in the film width direction, ΔN = (NMD-NTD) ×
1000, F = (NMD + NTD) / 2-nz.
Methylene iodide is used as the mount solution at 25 ° C, 65%
It was measured by RH.

(9) Number of projections on film surface and three-dimensional surface roughness (SRa) Kosaka Laboratory's non-contact surface roughness meter HIPOSS (model ET)
-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 ・ Feed 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 . S
Ra is the 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 The film is coated with a magnetic coating composition having the following composition 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 ・ Contonate L (Nippon urethane polyisocyanate): 5 parts by weight Lecithin: 1 part by weight Methyl ethyl ketone: 75 parts by weight Methyl isobutyl ketone: 75 parts by weight Toluene: 75 parts by weight Carbon black: 2 parts by weight Lauric acid: 1.5 parts by weight Use this tape for household use A 100% chroma signal is recorded by a TV test waveform generator (TG7 / U706) made by Shibasoku using a VTR, and the chroma S / N is measured from the reproduced signal by a color noise measuring instrument made by Shibasoku (925D / 1). Was judged.

Furthermore, this VTR cassette is used for household 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 Distortion is large. There is a lot of dirt on shavings. 1 Poor image quality.

(12) Evaluation of Slitting Property A polyester coating having a thickness of 14.5 μm is coated on one side with a magnetic coating solution having the following composition so as to have a thickness of 3 μm after drying. 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 〃 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.

(13) Pancake winding state The sheet coated with the magnetic coating solution of (12) above, dried, and calendered is slit into 1/2 inch at a slit speed of 100 m / min with a shear cutter manufactured by Nishimura Seisakusho. Make a 3000m roll pancake. This pancake is a sprinter (HSP made by Sony Magnescale-
Wind up at 5000 m) at a speed of 500 m / min.

After visually observing the end face after winding,
Evaluation is made according to the following three grades according to the degree of unevenness. here,
Rank A was the best when the end surface was smooth and was close to a mirror surface. Judgment rank End face state A Smooth near mirror surface B Some unevenness C C The degree of unevenness is large and the end face is disturbed.

[0065]

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 part by weight of phosphoric acid, 0.023 part by weight of antimony trioxide, and a volume average particle size of 0.20
2.4 parts by weight of μm divinylbenzene / p-ethylstyrene copolymer particles (emulsion-polymerized at a composition ratio of divinylbenzene 55% by weight and p-ethylstyrene 45% by weight) were added as an ethylene glycol slurry, 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 had an intrinsic viscosity of 0.614 and contained 2 parts by weight of organic polymer particles. (Polyester B) In the same manner as the polyester A, a particle-free polymer was obtained without adding spherical silica particles. The intrinsic viscosity of the obtained polymer was 0.620. (Polyester C) Example 1 The polyester A, the polyester B, and the polyester C thus obtained had a spherical silica particle content of 0.30% by weight in the final polyester film, and a divinylbenzene / p-ethylstyrene copolymer was used. Polymer particle content is 0.
1 part of pellet D mixed in a predetermined amount so as to be 20% by weight
It was dried under reduced pressure (3 Torr) at 80 ° 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 base layer raw material, and dried at 180 ° C. for 3 hours under reduced pressure (3 Torr) in the same manner as the laminated portion raw material.

The base layer part was supplied to the extruder 1 at 310 ° C., and the raw material for the laminated part 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 shown in FIG. 1 at 75 ° C. for rolls 1 and 2, 115 ° C. for rolls 3 and 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 The peripheral speed difference of the roll was adjusted and the roll was stretched in the vertical direction.

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 -40, plane orientation index F is 0.1688, 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 14.0 kg / mm ^2.
Further, the abrasion index K defined in the present application was 25, and the average surface roughness Ra was 19 nm, both of which were within the range of the present application. Further, as is clear from the results of Tables 1 and 2, it is understood that the S / N ratio (image quality) characteristics, film scraping, slitting property, and pancake winding properties are all excellent.

Examples 2 to 3 The content of spherical silica in the polyester film was 0.6.
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the content was 0% by weight (Example 2) and 1.0% by weight (Example 3). 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 was
It can be seen that the S / N ratio (image quality) characteristic, film scraping, slitting property, and pancake winding characteristic are all excellent.

Examples 4 to 5 The content of divinylbenzene / p-ethylstyrene copolymer particles in the polyester film was 0.30% by weight (Example 4) and 0.60% by weight (Example 5). except,
A biaxially oriented polyester film was obtained in the same manner as in Example 1. 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 Tables 1 and 2, each of the films of Examples 4 to 5 is excellent in S / N ratio (image quality) characteristics, film scraping, slitability, and pancake winding characteristics. I understand.

Example 6 Divinylbenzene / p-ethylstyrene copolymer particles were used as divinylbenzene / p-ethylstyrene copolymer particles having a volume average particle diameter of 0.19 μm (divinylbenzene 85% by weight, p-ethylstyrene 15% by weight). %) To obtain a biaxially oriented polyester film in the same manner as in Example 1 except that it was emulsion polymerized at a composition ratio of. 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, the film of Example 6 is excellent in all of the S / N ratio (image quality) characteristics, film scraping, slitting property, and pancake winding property.

Example 7 Divinylbenzene / p-ethylstyrene copolymer particles having a volume average particle diameter of 0.55 μm (emulsion-polymerized at a composition ratio of 85% by weight of divinylbenzene and 15% by weight of p-ethylstyrene) A biaxially oriented polyester film was obtained in the same manner as in Example 1 except for the above. 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 Tables 1 and 2, the film of Example 7 is excellent in all of the S / N ratio (image quality) characteristics, film scraping, slitting property, and pancake winding 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. The refractive index of the spherical silica particles in the ethylene glycol slurry is 1.42.
It was 6. Measurement of the properties 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 Comparative Example 1 is inferior in the slit property specified in the present application.

Comparative Example 2 The same procedure as in Example 1 was carried out 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. The refractive index of the spherical silica particles in the ethylene glycol slurry is 1.42.
It was 7. Measurement of the properties 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 Comparative Example 2 is inferior in the slit property specified in the present application.

Comparative Example 3 The same procedure as in Example 1 was carried out except that spherical silica particles having a volume average particle size of 2.2 μm, a particle size ratio of 1.05 and a relative standard deviation of 0.69 were used. A biaxially oriented polyester film was obtained. The measurement and evaluation results of the properties of the obtained biaxially oriented film are shown in Tables 3 and 4. Table 3 and 4
As is clear from the results of Comparative Example 3, the film of Comparative Example 3 had electromagnetic conversion characteristics (S / N ratio) and film scraping (scratch resistance).
It can be seen that both are inferior.

Comparative Example 4 Spherical silica particles having a volume average particle size of 0.09 μm, a particle size ratio of 1.1, and a relative standard deviation of 0.78 were synthesized by the water glass method, and the content in the polyester film was 0.60. weight%
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that The measurement and evaluation results of the properties of the obtained biaxially oriented film are shown in Tables 3 and 4. As is clear from the results of Tables 3 and 4, the film of Comparative Example 4 is inferior in film abrasion (scratch resistance).

Comparative Example 5 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 the 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 1 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. The measurement and evaluation results of the properties of the obtained biaxially oriented film are shown in Tables 3 and 4. As is clear from the results of Tables 3 and 4, the film of Comparative Example 5 is inferior in both electromagnetic conversion characteristics (S / N ratio) and film scraping (scratch resistance).

Comparative Example 6 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 the 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 1 except that the weight percentage was changed.

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 Comparative Example 6 is inferior in film abrasion (scratch resistance).

Comparative Example 7 The content of spherical silica in the polyester film was 1.3.
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the content was wt% and the divinylbenzene / p-ethylstyrene copolymer particles were not included. The measurement and evaluation results of the properties of the obtained biaxially oriented film are shown in Tables 3 and 4. As is clear from the results of Tables 3 and 4, the film of Comparative Example 7 is inferior in film abrasion (scratch resistance) and electromagnetic conversion characteristics.

Comparative Example 8 The procedure of Example 1 was repeated except that the content of divinylbenzene / p-ethylstyrene copolymer particles in the polyester film was 0.9% by weight and spherical silica particles were not included. An axially oriented polyester film was obtained. The measurement and evaluation results of the properties of the obtained biaxially oriented film are shown in Tables 3 and 4. As is clear from the results of Tables 3 and 4, Comparative Example 8
It can be seen that the film of No. 1 is inferior in pancake winding property.

[0084]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[0085]

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 particularly problematic in terms of product performance. It is particularly useful as a base film for pancakes with the spread of video software.

[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 to 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: Silicone rubber-coated metal roll 10: the film.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C08L 67/02 KJS // B32B 27/36 7421-4F B29K 67:00 105: 16

Claims (3)

[Claims] 1. A polyester having a volume average particle diameter of 0.1 to 0.1.
A spherical silica particle having a diameter of 2.0 μm and a relative standard deviation defined by the following formula (1) exceeding 0.5 is 0.005
~ 5.0 wt%, and the volume average particle size is 0.1
A polyester film for a magnetic recording medium, comprising 0.005 to 5.0% by weight of 2.0 μm organic polymer particles. [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. A laminated polyester film for a magnetic recording medium, comprising at least one layer of the polyester film according to claim 1 or 2.