JPH0836738A - Polyester film for magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a film which excels in a dropout characteristic and travelling durability by using a polyester film which contains a specific quantity of spherical silica particles having a particle diameter within a specific range to make the surface orientation index satisfy a specific formula. CONSTITUTION:This polyester film contains 0.005 to 5.0wt.% spherical silica particles in which the volume average particle diameter is 0.1 to 2.0mum, the relative standard deviation is 0.3 to 1.5 and the particle size distribution curve at the predetermined grade width shows single peak distribution. The surface orientation index F and DELTAN are set to simultaneously satisfy DELTAN<1250-8000XF, -40<DELTAN<0 and 0.1500<F<0.1600. Thereby, even when the film travels at a high speed, the film is hard to be scratched, and can deal with the increase of a processing speed in every application.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyester film for a magnetic recording medium and a laminated polyester film for a magnetic recording medium. Specifically, 1/2 inch video tape, 8mm video tape, audio cassette tape, digital compact cassette (DCC) tape, digital audio tape deck (DAT) tape, digital data storage (DDS), quarter inch cartridge The present invention relates to a polyester film for a magnetic recording medium and a laminated polyester film for a magnetic recording medium, which are suitable for a tape for data storage such as (QIC), a tape for high definition video, a tape for double track video (W-VHS) and the like.

[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 that comes into contact with the magnetic material coating / calendering process in the manufacturing process. It has been a problem recently. Furthermore, with regard to video tapes, video tape recorders (V
(TR) Repeated reproduction and recording are often repeated, and the film surface is scratched due to contact friction with guide pins in the tape cassette, or powdery substances generated from the film due to contact friction. Problems such as deterioration of images due to dropouts are occurring. Further, when a reel-shaped video tape pancake on which an image is recorded by a sprinter or the like is incorporated into a cassette by a loader or the like, there is a problem that dropouts increase as the incorporation speed increases. In order to solve these problems, while making it difficult to scratch the film surface,
It is necessary to improve the runnability of the film by roughening the film surface and reducing the friction coefficient, but on the other hand, due to the demand for high image quality, the film surface is smoothed to produce a film with excellent electromagnetic conversion characteristics. The demand is increasing.

Many studies have been made on these dilemmas of film surface characteristics and their various characteristics, which have been contradictory to each other. For example, JP-A-59-171623 and JP-A-63-24038 disclose spherical silica. The inclusion of particles is proposed in Japanese Patent Laid-Open No. 61-5431 by the inclusion of inert inorganic particles such as colloidal silica. However, in reality, it is difficult to satisfy all the above problems even with such a known method.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves these problems, has excellent dropout characteristics, and has excellent running durability during repeated use in a high temperature and high humidity atmosphere.
It is another object of the present invention to provide a polyester film for a magnetic recording medium and a laminated polyester film for a magnetic recording medium which meet the demands for improving the slit characteristics in the manufacturing process of the magnetic recording medium and further improving the image quality.

[0005]

The object of the present invention is to have a volume average particle diameter of 0.1 to 2.0 μm, and the following (1)
Spherical silica particles in which the relative standard deviation defined by the formula is 0.3 to 1.5 and the particle size distribution curve H (μm) represented by the following formula (2) shows a single peak distribution. To 0.005
To 5.0 wt% of the polyester film, wherein the plane orientation indexes F and ΔN simultaneously satisfy the following expressions (3) to (5), and a polyester film for a magnetic recording medium and magnetic recording. This can be achieved by a laminated polyester film for media. Relative standard deviation = (Σ _{i = 1 → n} (Di −DN) ² / n) ^0.5 / DN (1) where Di: equivalent area circle diameter (μm) obtained from the projected area of each particle DN: The number average value of the area equivalent circle diameters [DN = (Σ _{i = 1 → n} Di) / n] (μm) n: The number of particles measured. H = 1 / TRUNC (n) 0.5 ‥‥‥‥‥‥‥‥‥‥‥ (2) [ where n is the measurement number of particles, TRUNC (n) ^0.5
Is an integer value when the decimal part of the value obtained by the square root of n is truncated. ] ΔN <1250-8000 × F ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (3) −40 <∆N <0 ‥‥‥‥‥‥‥ (4) 0.1500 <F <0.1600 ‥‥‥‥‥‥‥‥‥ (5) [Here, ΔN = (N _MD −N _TD ) × 1000, F = (N _MD +
N _TD ) / 2−nz, where N _MD is the refractive index in the film longitudinal direction, N _TD is the refractive index in the film width direction, and nz is the refractive index in the film thickness direction. ]

The polyester applied in the present invention is produced by a polycondensation reaction as a glycol component with 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. Such polyester may be obtained by copolymerizing a small amount of the third component as long as it does not impair the basic properties of the polyester film and the laminated polyester film of the present invention,
Also, a mixture of these polyesters may be used. Examples of the copolymerization component include dicarboxylic acid components such as 2,6-naphthalenedicarboxylic acid and isophthalic acid, P-
Oxycarboxylic acid components such as oxyethoxybenzoic acid, tetramethylene glycol, propylene glycol, neopentyl glycol, polyoxyalkylene glycol, P-xylylene glycol, 1,4-cyclohexanedimethanol, polyethylene glycol, 5-
Examples include diol components such as sodium sulforesordin. 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 or the like 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 a water glass method or the like, and can be synthesized by, for example, an ion exchange method using water glass (sodium silicate aqueous solution) as a starting material. In particular, in order to improve the slit property, which is one of the objects of the present invention, the refractive index of the spherical silica particles of 20 wt% ethylene glycol slurry at 25 ° C is 1.430 or more, preferably 1.435 to 1 A value of 0.450 is more desirable because 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.

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 surface 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 a recorded commercial soft tape.

The relative standard deviation, which is a measure of the spread of the particle size distribution of the spherical silica particles, must be 0.3 or more, preferably more than 0.6, and even 0.7. It is preferable to exceed. Further, it is necessary to be within 1.5, preferably 1.3 or less. The relative standard deviation referred to herein is the ratio of the standard deviation obtained in number unit from the area-equivalent diameter of particles and the number average diameter, and is represented by the following equation (1). Relative standard deviation = ((Σ _{i = 1 → n} Di −DN) ² / n) ^0.5 / DN (1) where Di: equivalent circle diameter (μm) obtained from the projected area of each particle DN: The number average value of the area equivalent circle diameters [DN = (Σ _{i = 1 → n} Di) / n] (μm) n: the number of particles measured

When the relative standard deviation of the spherical silica particles is within the above range, the slitting property, particularly the continuous slitting property is improved, and a long-time slit blade is used at the time of slitting which is the final step of the magnetic tape manufacturing process such as video tape. Even if it is not changed, the amount of cutting chips or shavings generated from the film cut end is extremely small, and the swelling of the end cross section of the film cut end 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 particular, the relative standard deviation is 1.
When it exceeds 5, the waviness of the film surface is deteriorated and the color S / N ratio of the magnetic recording medium is deteriorated, which is not preferable.

Further, when the particle size distribution curve of the spherical silica particles of the present invention expresses the class width H (μm) of particle diameter by the following formula (2), it is necessary that the maximum point be one peak. When the maximum points in the particle size distribution curve of the spherical silica particles are 2 or more, the projection distribution controllability of the projections on the film surface is significantly lowered, and the desired film surface roughness can be reproducibly obtained by adjusting the addition amount of the particles. This is difficult to do, which is not preferable. H = 1 / TRUNC (n) ^0.5 ‥‥‥‥‥‥‥‥‥‥ (2) [where n is the number of particles measured, TRUNC (n) ^0.5
Is an integer value when the decimal part of the value obtained by the square root of n is truncated. ]

Further, the spherical silica particles of the present invention have a relative standard deviation defined by the above formula (1) of 0.3 to 1.5.
In order to make the particle size distribution curve H (μm) expressed by the formula (2) have a single peak distribution, the spherical colloidal particles having a predetermined particle size are formed from the water glass. 0.0% until the growth reaction is completed when synthesizing silica.
It is effective to add fine silica fine particles of 1 μm or less at least three times or more while shifting the addition timing. In this case, the total amount of fine silica added is preferably 0.01 to 5% by weight of the final spherical silica particle amount.

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 0.05 to 2.0% by weight, and further 0.1 to the polyester. It is preferably about 1.2% 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 the spherical silica particles at the time of polyester production. As the addition method and the addition timing, conventionally known methods and timings can be used, but the addition method is preferably a method of adding as a slurry of ethylene glycol which is a raw material for synthesizing the polyester. At this time, the slurry concentration is preferably in the range of 0.5 to 40% by weight, more preferably 1 to 20% by weight because the particle dispersibility in the polyester is improved. The water content in the glycol of the slurry at the time of addition was 1% by weight.
It is preferable that the amount is 0.5% by weight or less, because the particle dispersibility in the polyester is improved. It may be added at any time, and may be added at the time of charging the monomer, at the time of transesterification reaction, or before and after it, but it is particularly preferably added immediately before the transesterification reaction and before the start of the decompression of the polycondensation reaction. Further, the slurry of the particles may be added and dispersed by using a uniaxial or biaxial vent type extruder or the like after polymer production.

Further, other inert particles such as titanium dioxide, titanium monoxide, titanium nitride, kaolin, talc, calcium carbonate, and other inorganic particles, as well as organic particles, and internal particles may be used as long as the effects of the present invention are not impaired. Deposited particles,
Additives such as antioxidants, heat stabilizers, and ultraviolet absorbers may be contained to the extent that they are usually added.

Here, examples of the internally deposited particles include particles produced by combining at least one compound selected from the group consisting of a calcium compound, a magnesium compound, a manganese compound, and a lithium compound added at the time of polyester synthesis with a 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.

Specific examples of the calcium carbonate particles include heavy calcium carbonate, light calcium carbonate and colloidal calcium carbonate. Examples of the crystal type of calcium carbonate include calcite, aragonite, vaterite, and the like, but any of these may be used. Further, these calcium carbonate particles may be surface-treated. Further, a dispersion aid or an aggregation preventive agent may be used.

The calcium carbonate particles can be produced by a known method. For example, when using natural calcium carbonate, limestone is crushed, pulverized, classified, etc. to reduce coarse particles and sharpen the particle size distribution.Also, as a method for producing synthetic calcium carbonate particles, lime is used. Examples include those synthesized by the carbonation reaction of milk.
In particular, the pore volume of the calcium carbonate particles is 1.0 cm ³
/ G or less, more preferably 0.8 cm ³ / g or less, the calcium carbonate particles are dense and strong, and void formation due to the breakage of the particles during stretching is extremely reduced, so that the particles fall off during calendering. Is improved and the generation and adhesion of white powder are reduced. Further, by using together with the spherical silica of the present invention, not only the abrasion resistance of the film becomes good, but also the winding property of the film becomes good, which is more preferable.

Here, the pore volume (Vp) is the mercury-
It is obtained by the helium method, and specifically, using a mercury horosimeter under a pressure of 1.1 atm.
The specific volume (Vm) was obtained, and then the specific volume (V was measured by a constant pressure volumetric dead volume measurement using a gas adsorption device (using helium).
n) is obtained and Vn is subtracted from this Vm to calculate the pore volume (Vp).

Next, specific examples of the organic particles include polystyrene or crosslinked polystyrene particles and styrene.
Examples include vinyl particles such as acrylic or methacrylic crosslinked particles, benzoguanamine / formaldehyde resin particles, silicone resin particles, polytetrafluoroethylene particles, polyphenyl ester particles, and phenol resin particles, but are not limited to these. Without
Any particles may be used as long as at least a part of the constituent parts of the particles is an organic particle insoluble in polyester.

Preferably, a monovinyl compound (A) generally having 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. These compounds (A) and (B) may be used as a mixture of two or more kinds. 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 particles is 10 to 95% by weight, preferably 50 to 95% by weight in terms of monomer. More preferably 80-95
It is desirable that the content is wt%.

Particularly preferred examples of the composition of the organic particles include "styrene / divinylbenzene copolymer", "divinylbenzene / p- and / or m-ethylstyrene copolymer", and "styrene / divinylbenzene / copolymer". p- and / or m-ethylstyrene copolymer "
Is mentioned. In particular, when the organic particles are used in combination with the spherical silica of the present invention, not only the abrasion resistance of the film becomes good, but also scratches on the surface of the magnetic layer of the magnetic recording medium are extremely unlikely to occur, which is more preferable.

In addition to the inert particles of the present invention, fine agglomerated fine particles may be contained in combination for the purpose of imparting scratch resistance to the film surface, that is, scratch resistance. Such aggregated fine particles are aggregates composed of a large number of particles having a primary particle diameter of 5 to 50 nm, and examples thereof include those containing zirconium oxide, aluminum oxide, etc. as a component, and the specific surface area by the BET method is 10 m ² /
It is preferably at least g, more preferably at least 40 m ² / g.

In addition, aggregate fine particles made of aluminum oxide are known to have various types of crystal structures such as alpha type, gamma type, delta type and theta type.
Excellent scratch resistance is obtained by containing aluminum oxide having a delta type crystal structure. Although the reason for this is unknown, it is considered that the aluminum oxide particles having a theta-type or delta-type crystal structure have a high affinity with polyester and have a function of increasing the abrasion resistance of the film surface.

Aluminum oxide having a theta-type crystal structure can be produced by, for example, a method in which alum is neutralized with a carbonate and then pyrolyzed, or a pyrolysis method from an aluminum alkoxide method, and in particular, conditions such as heat treatment time and temperature are controlled. It is obtained by doing.

Aluminum oxide having a delta type crystal structure can be produced by, for example, a method of hydrolyzing aluminum chloride. When the agglomerate fine particles are used in combination, the agglomerate fine particles having an agglomerate secondary particle diameter of 0.5 μm or less, preferably 0.3 μm or less, are used in an amount of 0.5% by weight or less, preferably in order not to impair the effects of the present invention. It is desirable to add 0.3 wt% or less, more preferably 0.2 wt% or less.

The aggregate fine particles are, for example, 1 to 20.
It can be obtained by combining, if necessary, a dispersion treatment using a sand grinder, a classification treatment such as a centrifugal classification treatment, and a filtration treatment after the ethylene glycol slurry having a weight percentage is obtained. Further, a dispersant such as a surfactant may be used together.

In order to achieve the object of the present invention, the plane orientation indexes F and ΔN are within a range that simultaneously satisfies the following expressions (3) to (5), preferably the following expressions (8) to (10). Need to be in. If the polyester film and the laminated polyester film do not satisfy the above-mentioned ranges of the plane orientation index F and ΔN, it is difficult to simultaneously satisfy the slit property and the abrasion property at the time of repeated running, and the film surface is likely to have minute waviness. The video tape's electromagnetic conversion characteristics deteriorate. ΔN <1250-8000 × F (3) -40 <ΔN <0 ‥‥‥‥‥‥ (4) 0.1500 <F <0.1600 ‥‥‥‥‥‥‥‥ (5) 1125 −7495 × F <ΔN <1250−8000 × F (8) −40 <ΔN <−5 ‥‥‥‥‥ (9) 0.1540 <F <0.1600 ‥‥‥‥‥ (10) ) [Where ΔN = (N _MD −N _TD ) × 1000, F = (N _MD +
N _TD ) / 2−nz, where N _MD is the refractive index in the film longitudinal direction, N _TD is the refractive index in the film width direction, and nz is the refractive index in the film thickness direction. ]

In the polyester film for a magnetic recording medium and the laminated polyester film for a magnetic recording medium of the present invention, the plane orientation index F and the refractive index nz in the thickness direction are within the range where the following expressions (7) and (8) are simultaneously satisfied. It is preferable that it has a good slitting property and a good scraping property in the calendering process, and also improves the adhesiveness between the magnetic recording binder layer of the video tape and the film. nz ≤ 1.603-0.6407xF ... (7) nz ≥ 1.595-0.6407xF ... (8)

Here, the ΔN can be raised by lowering N _MD and lowered by raising it. N _MD can be raised by increasing the stretching ratio in the longitudinal direction, and conversely can be lowered by lowering it. N _TD can be raised by increasing the stretching ratio in the width direction, and conversely can be lowered by lowering it. Further, N _MD can be raised by lowering the stretching temperature in the longitudinal direction, and conversely, can be lowered by raising it. N _TD can be raised by lowering the stretching temperature in the width direction, and conversely, it can be lowered.

The surface 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, it can be lowered 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.

The polyester film of the present invention is produced by appropriately adjusting the stretching ratio in the longitudinal and width directions, the stretching temperature and the heat treatment temperature.

In particular, the above (3) to (5) in the present invention.
In order to satisfy all the formulas, when stretching the unstretched film in the longitudinal direction, a method of stretching while heating with a high capacity infrared heater in a stretching zone, or a method of stretching at a high temperature using a Teflon roll and a ceramic roll, etc. Is effective. The stretching temperature in this case is preferably 125 to 145 ° C. in order to satisfy the above range.

The polyester film for magnetic recording media and the laminated polyester film for magnetic recording media of the present invention are preferably biaxially oriented by a conventional method and have a thickness of 3 to 30 μm, more preferably 5 to 13 μm. Are more preferably used for the purpose of the present invention.

The scraping index K in the present invention means a thickness of 15
A μm film is slit by a shear cutter type slitter at a slit speed of 50 m / min to 1/2 inch, and then 1 m after slitting at 1/2 inch is placed in a container containing 50 cc of pure water. The number of particles having a particle size of 3 to 20 μm when the film sample was removed and the immersion liquid was measured with a particle counter after installation so that only the cut surface was immersed and ultrasonic treatment was performed Is defined. 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.

At least one surface of the polyester film and the laminated polyester film of the present invention preferably has a center line average surface roughness (Ra) of 8 to 30 nm and a three-dimensional average surface roughness (SRa) of 13 to 50 nm. Furthermore, Ra is 12 to 25 nm and SRa is 17 to
It is preferably 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 height is 200
The number of protrusions of 400 nm is 1200 per 0.1 mm ^2.
The number is 100 or more, further 1,350 or more, particularly 1,500 or more, and the number of protrusions having a height of 400 nm to 800 nm is 400 or less per 0.1 mm ² , further 300 or less, particularly 200 or less. It is preferable. The number of protrusions having a height of 200 to 400 nm and the height of 400 n
When the number of protrusions of m to 800 nm is within the above range, the durability in use is particularly good and the image quality characteristics are good.

The following combinations are desirable as the specific constitution of the laminated polyester film of the present invention. 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 portion. )

A to C may include the polyester and spherical silica particles described above. It is also possible to utilize recovered polyester for the A layer. The recovered polyester preferably has a terminal carbonyl group of 30 to 50 equivalents / ton, further preferably 30 to 40 equivalents / ton. Here, the polyester film A of the base layer portion may be a polyester film which does not substantially contain particles, or may contain particles. The particle species is not particularly limited, for example, calcium carbonate as an inorganic particle, silica, kaolin, alumina, zirconia, barium sulfate, may be fine particles insoluble in polyester such as titanium oxide, also, organic such as cross-linked polystyrene. Particles 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 laminating 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 other than the present invention It may be contained. 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 and the laminated 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 by dispersing is effective for obtaining the relative standard deviation and particle size distribution in the present invention. Also,
As a method of adjusting the content of particles, a method of diluting a master pellet having a high concentration, preferably 1.0 to 5.0% by weight of particle content during film formation is preferable. Further, the ethylene glycol slurry is heated to 140 to 200 ° C., especially 18
The method of heat treatment at a temperature of 0 to 200 ° C. for 30 minutes to 5 hours, particularly 1 to 3 hours is effective for obtaining the desired range of the relative standard deviation and the abrasion index K in the present invention.

A method other than this, for example, a powder form,
Alternatively, in a slurry state, it 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 are sufficiently dried, then supplied to a known melt extruder, extruded into a sheet form from a slit die at 270 to 330 ° C., and cooled on a casting roll. An unstretched film is made by solidifying. 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 2-stage filtration filter referred to here is 95% of the first stage.
The cutoff particle size is 4 to 10 μm, and the second stage is a filter with 95% cutoff particle size of 1.5 to 5 μm arranged in series. The 95% cutoff particle size is the first stage> the second stage. It is what

Here, in the production of 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 polyester B and C of the laminated portion by coextrusion.
More specifically, it can be obtained by extruding the polyesters A, B and C by different extruding devices and co-extruding them before discharging the laminated sheet from the die. This lamination may be performed in a die for molding 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 a polymer pipe before being introduced into the die. . Especially when the laminated part in the polymer tube is formed in a rectangular shape,
It is particularly preferable because it 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, since the laminated portion polymer is laminated with a considerable thickness in the polymer tube rectangular laminated portion, it can be laminated easily and accurately. B / A / B, B / A / C, and B / A / B, B / A / C, B /
A, B / A / B / A / B, B / A / C / A / B laminated sheet 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 polyesters B and C, a particle type slurry and a particle-free polyester are melted while being kneaded by using a vent type twin-screw extruder, and the mixture is melted under vacuum from a vent hole arranged in the extruder. The polyester containing the particles of the present invention may be produced by dispersing while distilling off the solvent in the slurry.

The unstretched film thus obtained is then 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 to perform stretching in the longitudinal direction by 2
Stretching in the width direction after stretching 2.5 to 3.5 times in a range of (polymer glass transition point + 55 ° C) to (polymer glass transition point + 75 ° C) in stages, particularly three or more stages. 1
A method of stretching at 30 to 170 ° C. and a stretching ratio of 4 to 5 times is preferably used. 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 200 to 220 ° 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 film was thoroughly washed with methanol to remove surface deposits, washed with water, and dried to 300 g of a sample, and 2.7 kg of o-chlorophenol was added, 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, if the polyester part does not dissolve due to high crystallization,
The above melting operation is carried out 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 to remove,
Subtract the weight of this item from the sample weight. Hitachi's separation ultracentrifuge 40p type equipped with rotor RP30,
Solution 30 after filtering the glass filter per cell
After injecting cc, the rotor is rotated at 4500 rpm, and after confirming that there is no abnormal rotation, the inside of the rotor is evacuated, the rotation speed is increased to 30000 rpm, and the particles are centrifuged at this rotation speed. The completion of the separation is about 40 minutes later, but this confirmation should be confirmed if necessary.
The light transmittance at is higher than that before separation and becomes a constant value. 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, ο-chlorophenol at room temperature is added to the collected particles, the particles are almost uniformly suspended, and then the ultracentrifuge treatment is performed again. . This operation needs to be repeated until the particles to be described later are dried and then the particles are subjected to a differential scanning calorimetry analysis until a melting peak corresponding to the polymer cannot be detected. Finally, the thus obtained separated particles are vacuum-dried at 120 ° C. for 16 hours and weighed.
When the separated particles A obtained by the above operation contain silica particles and internally precipitated particles, it is necessary to separately obtain the amount of internal particles and the amount of spherical silica particles. First, the separated particles A are quantitatively analyzed for metal content, and C
The contents of a and Li and the contents of metals other than Ca and Li are determined in advance. Then, the separated particles A are heated under reflux in a 3-fold molar amount of ethylene glycol for 6 hours or more, and then heated to 200 ° C.
When ethylene glycol is distilled off and depolymerized as described above, only the internally precipitated particles are dissolved. Separated particles B obtained by centrifuging the remaining particles are dried and weighed to determine the amount of spherical silica particles. Further, the remaining weight obtained by subtracting the spherical silica particle amount from the initial total separated particle amount is defined as the internally precipitated particle amount. Here, when the separated particles B contain calcium carbonate in addition to the spherical silica particles, when the separated particles B are stirred in a 1N nitric acid solution for 6 hours or more, only the calcium carbonate particles are dissolved. Separated particles C obtained by centrifuging the remaining particles
Is dried and weighed to obtain the content of spherical silica particles. Also,
The weight of the separated particles C is subtracted from the weight of the separated particles B to obtain the content of calcium carbonate particles. When the above-mentioned separated particles C contain other inert particles such as aluminum oxide in addition to the spherical silica particles, the separated particles C are heated under reflux in a 20% aqueous solution of sodium hydroxide for 6 hours or more to give only spherical silica particles. Dissolve. Separated particles D obtained by centrifuging the remaining particles are dried and weighed to obtain the content of other inert particles (for example, aluminum oxide). Also,
The weight of the separated particles D is subtracted from the weight of the separated particles C to obtain the content of the spherical silica particles. In addition, in order to confirm whether the separation operation of the particles has been completely performed, quantitative analysis of the metal content is performed on the separated particles after each of the above separation operations, and the accuracy of particle amount measurement can be improved by repeating these operations.

(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 was obtained, and the particle size ratio "average value of major axis / minor axis" was calculated from these values.
To calculate. However, only those particles having a particle size ratio of 1.3 or less were counted as spherical silica particles 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 _{i = 1 → n} (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 For each particle counted in the measurement in (2) above, the area equivalent circle diameter is obtained, and the number of particles is changed to 5000 or more and the following numerical processing is performed. By doing so, the number average diameter DN is obtained by the following formula. DN = Σ _{i = 1 → n} Di / N Here, Di is the equivalent circle diameter of the particles, and N is the number of counted particles. Next, Di, number average diameter DN, number of particles N
Standard deviation σ (= {Σ _{i = 1 → n} (Di −D
N) ² / N} ^0.5 ) divided by the number average diameter DN (σ / D
N) was taken as the relative standard deviation.

(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 = (Σ _{i = 1 → n} Di ³ / N) ^1/3 Here, Di is the area equivalent circle diameter of particles, and N is the number of counted particles.

(5) Volume average diameter of inert particles other than spherical silica particles The inert particles separated in the above (1) are dispersed in methanol, and a centrifugal sedimentation type particle size distribution measuring device (manufactured by Horiba Ltd. The median cumulative value (50% by volume) in the cumulative distribution curve of the Stokes diameter obtained by measurement with CAPA500) was defined as the volume average diameter.

(6) Particle Size Distribution Curve of Spherical Silica Particles With respect to the particles counted in the measurement of the above (3), the class width (μm) is obtained by the following formula (2), and the particles represented by the class width are represented on the horizontal axis. The particle size distribution curve is obtained by taking the diameter, taking the number of particles having a particle size represented by the median value of the class width on the vertical axis, and connecting the vertices of the median values of the classes. H = 1 / TRUNC (n) ^0.5 ‥‥‥‥‥‥‥‥‥‥ (2) [where n is the number of particles measured, TRUNC (n) ^0.5
Is an integer value when the decimal part of the value obtained by the square root of n is truncated. ]

(7) 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.

(8) 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.

(9) 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 ΔN sodium D line (wavelength 589 nm) as the light source. , From the refractive index N _TD in the film width direction, ΔN = (N _MD −N _TD ) × 1000, F
= (N _MD + N _TD ) / 2-nz. Methylene iodide was used as the mount solution, and measurement was performed at 25 ° C. and 65% RH.

(10) Number of projections on film surface and three-dimensional surface roughness (SRa) The film measurement surface is made of aluminum and has a thickness of 0.10 ± 0.
After being vapor-deposited to a thickness of 05 μm, the three-dimensional roughness was measured using a non-contact surface roughness meter HIPOSS (Model ET-30HK) and a three-dimensional roughness analyzer (Model SPA-11) from Kosaka Laboratory. The conditions are as follows, and the average value of 5 measurements was taken as the value.・ Detector ： Optical stylus hypoth ・ Vertical magnification ： 20,000 times ・ Horizontal magnification ： 500 times ・ Cutoff ： 0.08mm ・ Feeding pitch ： 0.5μm ・ Measurement length ： 500μm ・ Measurement area ： 0.0199mm ²・ Measurement Speed: 100 μm / sec HYST: ± 6.25 nm COUNT MODE: SIMPLE Z reference: UPPER The projection height was calculated based on 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 to 800 nm measured under the above conditions was converted into each number / 0.1 mm ² .
SRa is the three-dimensional average surface roughness (center plane average roughness).

(11) Center line average surface roughness (Ra) The center line average surface roughness (R) was measured according to JIS-B-0601 using a probe type surface roughness meter SE-3FA manufactured by Kosaka Laboratory.
a) was measured. The conditions are as follows, and the average value of 20 measurements was used as the value.・ Detector: PUDA5 ・ Vertical magnification: 50,000 times ・ Cutoff: 0.25 mm ・ Measuring length: 4 mm ・ Measuring speed: 500 μm / sec

(12) Image quality, scratch resistance, dropout characteristics, running durability A magnetic paint of the following composition was applied to a film having a thickness of 15 μ by a gravure roll so that the coating thickness after drying was 4 μ, Orient and dry. Further, 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 steps), 6
A raw sheet was prepared by curing at 0 ° C. for 48 hours. This raw sheet was slit into 1/2 inch to prepare a pancake. VT this pancake with a loader
The tape was incorporated into an R 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-Coronate L (Japan 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 This tape is used for household VTR (Panasonic NV-FS8).
00) using the Shiba Soku TV test waveform generator (T
G7 / U706) records 100% chroma signal,
Shiba Soku color noise measuring instrument (92
The chroma S / N was measured at 5D / 1) to determine the image quality. Furthermore, this tape is used for household VTR (Panasonic NV-
FS800) is used to record color bar signals with a Shiba Soku TV test waveform generator (TG7 / U703).
From the reproduced signal, a dropout counter (VH01CZ, manufactured by Shibasoku) having a value larger than 5 μsec−16 dB was counted as a dropout.

Next, this VTR cassette is used as a home VTR.
Built in (Panasonic NV-FS800), repeated running (playback / high-speed rewinding) was repeated 100 times, and in the same way, chroma S / N was measured from the playback signal with a color noise measuring machine (925D / 1) made by Shiba Soku to obtain the image quality. Judgment, Shiba Soku dropout counter (VH
01CZ), a value larger than 5 μsec−16 dB was counted as a dropout. Further, scratch resistance was judged by the amount of scraping of white powder on the VTR cassette guide pin and the amount of scraping of the film after the repeated running.

Here, the dropout characteristic was judged by the dropout increase rate defined by the following equation. Dropout increase rate = (Number of dropouts after repeated running-Number of dropouts before repeated running) / (Number of dropouts before repeated running) x 100 (%)

Next, the VTR cassette produced above was incorporated into a domestic VTR (Panasonic NV-FS800), and running (reproduction / high-speed rewinding) was repeated 100 times under the conditions of a temperature of 40 ° C. and a relative humidity of 70%. After removing the video tape from the VTR cassette, the running tester TBT-
After being mounted on 300 (manufactured by Yokohama System Laboratory Co., Ltd.), it was run once under an atmosphere of a temperature of 20 ° C. and a relative humidity of 60%, and the entrance side tension T0 and the exit side tension T1 of the metal guide post were set as starting points. From the end point to the end point are divided into 10 equal parts, and the friction coefficient μk value is calculated by the following equation (11).
The number average value was used as the friction coefficient μka after the running test.
Similarly, take out the video tape from the VTR cassette before the running test and perform the friction coefficient μ before the running test in the same manner as above.
I calculated kb. Here, the value obtained by subtracting the friction coefficient μkb before the running test from the friction coefficient μka after the running was defined as the running durability in a high temperature and high humidity atmosphere. μk = 0.733 log (T1 / T0) (11) Here, the inlet tension T0 was set to be constant at 50 g. The video tape was attached at a wrap angle of 180 ° so that the running surface of the video tape was in contact with the guide post made of metal. The metal guide post has a diameter of 8 mmφ and is made of SUS27 (maximum surface roughness Rmax = 0.15 μm,
The average surface roughness Ra = 0.02 μm) was used. The running speed was 3.3 cm / sec.

These judgment criteria are as follows, and if all of the image quality, scratch resistance, dropout increase rate, and running durability are rank 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.

Judgment Rank Dropout increase rate Running durability Less than 55% Less than 0.05 45-20% 0.05 or more but less than 0.10 3 21-50% 0.10 or more but less than 0.15 2 51 -100% 0.15 or more and less than 0.20 1 Over 100% 0.20 or more

(13) Evaluation of Slitting Property The sheet obtained in (12) above was 1
Slit to 1/2 inch width to make a video tape. Visually observe the slit area with this shear cutter,
The degree of beard and powder generation is classified into the following 5 grades and evaluated. Here, if the rank is 4 or higher, there is no practical problem. (Note) Most of the biaxially oriented polyester films for video tapes currently on the market have a slit property level of 2 or 3.

(14) Thickness of Laminated Portion and Base Layer of Laminated Polyester Film (a) Thickness of Laminated Portion Using a secondary ion mass spectrometer (SIMS: A-DIDA 3000 manufactured by ATOMIKA) under the following conditions. The concentration ratio (M ⁺ / C ⁺ ) of the element due to the highest concentration of particles and the carbon element of polyester is defined as the particle concentration, and the depth (thickness) direction from the surface of the laminated polyester film is analyzed. To do. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the laminated film of the present invention, the particle concentration which once reached the maximum value [MAX] at the depth [I] decreases again and converges to a constant value [M]. Here, the particle concentration is ([M
AX] + [M]) / 2 depth [J] (where J>
I) is the thickness of the laminated portion. Primary ion species: O ₂ ⁺ Primary ion accelerating voltage: 12 KV Primary ion current: 120 nA Tester area: 400 μm Analysis area: Gate 30% Measuring vacuum degree: 1.0 × 10 ^-8 torr E-GUN: 0.4 KV -3.0A

(B) Thickness of Base Layer Part The total thickness of the film is determined by a known method such as a dial gauge method, an optical interference method, or a gravimetric method. The base layer thickness was obtained by subtracting the laminated thickness from the total thickness of this film.

[0069]

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. 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 diameter of 0.18 μm
m, particle size ratio of 1.1, relative standard deviation of 0.68, and 2.4 parts by weight of spherical silica particles synthesized by the water glass method having a maximum value of the particle size distribution curve of 1 mountain were added as an ethylene glycol slurry, and the usual method was used. The polycondensation reaction was carried out according to. 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 2.0% by weight of spherical silica particles. The refractive index of the spherical silica particles in the ethylene glycol slurry was 1.441 (polyester A).

In the same manner as for the polyester A, a particle-free polymer was obtained without adding spherical silica particles. The intrinsic viscosity of the obtained polymer was 0.619 (polyester B).

Further, instead of spherical silica particles, 2.4 parts by weight of calcium carbonate particles having a volume average particle size of 0.65 μm and a pore volume of 0.66 cc / g were added as an ethylene glycol slurry, and the above polyester A was used. A polymer was obtained by the same method. The polymer thus obtained has an intrinsic viscosity of 0.615 and a calcium carbonate particle content of 2.0.
% By weight (polyester C).

10.0 parts by weight of dimethyl terephthalate, 62 parts by weight of ethylene glycol and 0.06 of calcium acetate
A transesterification reaction is carried out by a conventional method using 1 part by weight of a catalyst, and the product is 0.04 part by weight of antimony trioxide, 0.08 part by weight of lithium acetate and 0.0
After adding 4 parts by weight, 0.02 parts by weight of phosphorous acid and 0.1 parts by weight of trimethyl phosphate, polycondensation was carried out to obtain an intrinsic viscosity of 0.618 and an internally precipitated particle of 0.38 parts by weight. A polymer containing 1 part (100 parts by weight of polyester) was obtained. 1.2% by weight of calcium element in the internally precipitated particles,
It contained 2.0% by weight of lithium element and 4.9% by weight of phosphorus element. Further, the volume average diameter of the internally precipitated particles is
It was 0.65 μm (polyester D).

Example 1 Pellets E obtained by mixing the polyester A and the polyester B thus obtained in a predetermined amount so that the spherical silica particle content in the final polyester film is 0.60% by weight are 180 ° C. Then, it was dried under reduced pressure (3 Torr) 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 depressurized (3 Torr) at 180 ° C. for 3 hours like the laminated portion raw material.
r) dried. The base layer raw material is supplied to the extruder 1 and 310
C., and the raw material for the laminated portion was supplied to the extruder 2 and melted at 280.degree. 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.

The unstretched film was subjected to the roll temperature of FIG. 1 at 80 ° C. for rolls 1 and 2, 122 ° C. for rolls 3 and 4, 135 ° C. for roll 5, and 13 for roll 6.
5 ° C., 117 ° C. for roll 7, and 1.15 times between rolls 5 and 6, 1.50 times between rolls 6 and 7, and 1.95 times between rolls 7 and 8 The peripheral speed difference of the roll was adjusted and the film was stretched in the machine direction. This uniaxially stretched film was stretched 4.1 times in the transverse direction in the first stenter under hot air at 140 ° C., and further re-stretched in the longitudinal direction at a stretching temperature of 125 ° C. and a stretching ratio of 1.10, and then secondly. 5 in hot air of 210 ℃ under slight stretching 1.03 times in the transverse direction in the stenter
Heat treatment for 2 seconds, total thickness 15μm, laminated thickness on one side 1μm
A biaxially oriented laminated polyester film of was obtained. The final running speed of the biaxially oriented laminated polyester film at this time was 150 m / min.

The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film are shown in Tables 1 and 2. In Tables 1 and 2, ΔN is -25 and the plane orientation index F is 0.1.
560, the refractive index nz in the thickness direction was 1.499, and the average surface roughness Ra was 15 nm, which were all within the range of the present invention. Further, as is clear from the results of Tables 1 and 2, it is found that the dropout characteristics and the S / N ratio (image quality) characteristics are excellent, and other characteristics are also good.

Examples 2 to 3 Examples except that the content of the spherical silica particle laminated portion in the polyester film was 0.90% by weight (Example 2) and 1.5% by weight (Example 3), respectively. A biaxially oriented laminated polyester film was obtained in the same manner as in 1. The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film are shown in Tables 1 and 2. As is clear from the results of Tables 1 and 2, it is understood that the films of Examples 2 to 3 are excellent in S / N ratio (image quality) characteristics and other characteristics are also good.

Examples 4 to 5 Spherical silica particles synthesized by the water glass method having a volume average particle size of 0.55 μm, a particle size ratio of 1.1, and a relative standard deviation of 0.76 are used, and the content in the polyester film of the laminated portion is 0.30
A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that the weight% (Example 4) and 0.60% (Example 5) were used. The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film are shown in Tables 1 and 2. As is clear from the results of Table 1 and Table 2, Example 4
It can be seen that each of the films Nos. 5 to 5 is excellent in dropout characteristics and S / N ratio (image quality) characteristics, and is also excellent in other characteristics.

Example 6 Spherical silica particles having a volume average particle size of 1.2 μm, a particle size ratio of 1.1 and a relative standard deviation of 0.78 were synthesized by a water glass method. 0.1
A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that the amount was 4% by weight. The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film are shown in Tables 1 and 2. As is clear from the results of Tables 1 and 2, the film of Example 6 had a dropout characteristic, S /
It can be seen that all of the N ratio (image quality) characteristics, scraping property, slit property, and running durability are good.

Example 7 The same method as in Example 1 was carried out except that spherical silica particles having a volume average particle diameter of 0.19 μm, a particle diameter ratio of 1.1 and a relative standard deviation of 0.36 were used. A biaxially oriented laminated polyester film was obtained. The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film are shown in Tables 1 and 2.
It was shown to. As is clear from the results of Table 1 and Table 2, the film of Example 7 has excellent S / N ratio (image quality) characteristics,
It can be seen that the other characteristics are also good.

Example 8 In the first stenter, the stretching ratio in the horizontal direction was 4.4 times, the stretching temperature in the horizontal direction was 135 ° C., and the stretching ratio in the re-longitudinal stretching was 1.
A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that the adjustment was made to be 05 times.
The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film are shown in Tables 1 and 2. As is clear from the results shown in Tables 1 and 2, it can be seen that the film of Example 8 is excellent in S / N ratio (image quality) characteristics and is also excellent in other characteristics.

Example 9 Polyester so that the content of calcium carbonate particles in the laminated portion of the polyester film was 0.10% by weight and the content of spherical silica particles in the laminated portion of the polyester film was 0.30% by weight. A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that A, polyester B and polyester C were mixed and adjusted. The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film 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 the dropout characteristics and the S / N ratio (image quality) characteristics, and is also excellent in other characteristics.

Example 10 Polyester so that the content of internally deposited particles in the laminated portion of the polyester film was 0.30% by weight and the content of spherical silica particles in the laminated portion of the polyester film was 0.20% by weight. A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that A, polyester B and polyester E were mixed and adjusted. The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film are shown in Tables 1 and 2. As is clear from the results of Tables 1 and 2, the film of Example 10 had dropout characteristics, S
It can be seen that the / N ratio (image quality) characteristics, the sharpness, and the slit property are all excellent, and the running durability is also good.

Example 11 Polyester A and polyester B were contained in the final polyester film having a spherical silica particle content of 0.60% by weight.
The mixture is mixed in a predetermined amount so that it will be dried at 180 ° C for 3 hours under reduced pressure (3 Torr), and this is fed to a single-screw main extruder and melted at 310 ° C. 15 μm in thickness in the same manner as in Example 1 except that an unstretched film having a single-layer structure was produced by extruding the film, winding it around a casting drum having a surface temperature of 45 ° C. by an electrostatically applied casting method, and cooling and solidifying the film. A biaxially oriented polyester film of was obtained. The measurement and evaluation results of the properties of the obtained biaxially oriented film are shown in Tables 1 and 2. Table 1, Table 2
As is clear from the above results, the film of Example 11 is excellent in dropout characteristics and is also excellent in other characteristics.

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 0.18 μm, a particle diameter ratio of 1.03 and a relative standard deviation of 0.17 were used. A biaxially oriented laminated polyester film was obtained. The refractive index of the spherical silica particles in the ethylene glycol slurry is
It was 1.423. The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film are shown in Tables 3 and 4. As is clear from the results of Tables 3 and 4, the film of Comparative Example 1 is inferior in slit property.

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 laminated polyester film was obtained. The refractive index of the spherical silica particles in the ethylene glycol slurry is 1.
It was 425. The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film 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 slit property.

Comparative Example 3 Spherical silica particles having a volume average particle diameter of 2.3 μm, a particle diameter ratio of 1.05 and a relative standard deviation of 0.69 were synthesized by a water glass method, and the content in the laminated portion of the polyester film was adjusted. 0.2
A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that the content was 0% by weight. The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film are shown in Tables 3 and 4. As is clear from the results of Tables 3 and 4, the film of Comparative Example 3 had dropout characteristics, S /
It can be seen that the N ratio (image quality) characteristic, film scraping (scratch resistance), and slit property are inferior.

Comparative Example 4 The spherical silica particles synthesized by the water glass method having a volume average particle diameter of 0.08 μm, a particle diameter ratio of 1.1 and a relative standard deviation of 0.58 were used. 1.2
A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that the content was 0% by weight. The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester 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 Using spherical silica particles synthesized by the water glass method having a volume average particle size of 0.55 μm, a particle size ratio of 1.1 and a relative standard deviation of 0.68, the content in the polyester film in the laminated portion was adjusted. 5.5
A biaxially oriented laminated 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 7.0 parts by weight.

The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester 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 dropout characteristics, S / N (image quality) characteristics, film abrasion (scratch resistance), and slit characteristics.

Comparative Example 6 Using spherical silica particles synthesized by the water glass method having a volume average particle size of 0.55 μm, a particle size ratio of 1.1 and a relative standard deviation of 0.68, the content in the polyester film at the laminated portion was adjusted. 0.0
A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that the content was 04% by weight. The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film 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 dropout characteristics, film scraping (scratch resistance), and running durability.

Comparative Example 7 Calcium carbonate particles having a volume average particle size of 0.65 μm were used in place of the spherical silica particles, and polyester A and polyester B were used so that the content in the polyester film in the laminated portion was 0.50% by weight. A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1, except that the polyester C was mixed and adjusted. The measurement and evaluation results of the properties of the obtained biaxially oriented laminated polyester film are shown in Tables 3 and 4.
It was shown to. As is clear from the results of Tables 3 and 4, the film of Comparative Example 7 is inferior in dropout characteristics and film scraping (scratch resistance).

Comparative Example 8 The temperature of the rolls 5 and 6 in FIG. 1 was set to 119 ° C.,
Except that the draw ratio in the horizontal direction in the first stenter is 4.6 times and the draw ratio in the re-longitudinal stretching is 1.05,
A biaxially oriented laminated 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 laminated polyester film are shown in Tables 3 and 4. As is clear from the results of Tables 3 and 4, the film of Comparative Example 8 is inferior in running durability.

Comparative Example 9 A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the magnification during re-vertical stretching was adjusted to 1.40 times. 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 9 is inferior in running durability. Further, it is difficult to stably produce a film because the film is frequently broken during the production of the film.

Comparative Example 10 The temperature of the roll 4 in FIG. 1 was 125 ° C., the temperatures of the rolls 5 and 6 were 147 ° C., the draw ratio between the rolls 5 and 6 was 1.2 times, and between the rolls 6 and 7 was 1.2. The draw ratio is 1.1 times, and the draw ratio between the roll 7 and the roll 8 is 2.8.
A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1, except that the stretching ratio in the transverse direction and the stretching ratio in the transverse direction were adjusted to 4.5. 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 result, the film of Comparative Example 10 is inferior in slitting property. Further, it is difficult to stably produce a film because the film is frequently broken during the production of the film.

Comparative Example 11 The temperature of roll 5 and roll 6 in FIG.
Other than setting the draw ratio in the horizontal direction in the first stenter to 4.0 times and the draw ratio in re-longitudinal stretching to 1.05,
A biaxially oriented laminated 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 laminated polyester film are shown in Tables 3 and 4. As is clear from the results of Tables 3 and 4, the film of Comparative Example 11 is inferior in slit property.

Comparative Examples 12 to 13 Volume average particle size 0.18 μm, particle size ratio 1.2, relative standard deviation 0.77, particle size distribution curve of 0.22 μm and 0.
Spherical silica particles (Comparative Example 11) synthesized by the water glass method having a two-peak distribution having two peaks at 73 μm, a volume average particle diameter of 0.18 μm, a particle diameter ratio of 1.2, and a relative standard deviation of 0.1.
76, 0.13 μm, 0.22 μ in the particle size distribution curve
A biaxially oriented polyester film was obtained in the same manner as in Example 1, except that spherical silica particles (Comparative Example 12) synthesized by the water glass method with a three-peak distribution having three peaks at m and 0.82 μm were used. It was 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 apparent from the results of Comparative Examples 11 and 12, the average surface roughness Ra of the films of Comparative Examples 11 and 12 is almost the same even though the particle characteristics such as the volume average particle diameter, the particle diameter ratio, and the relative standard deviation of the particle diameters are almost the same. 24 nm (Comparative Example 11) and 11 nm (Comparative Example 12) are very different, and it is difficult to produce a film having a specific surface roughness with good reproducibility by adjusting the addition amount of the particles, etc. Becomes extremely difficult. Further, as is clear from the results of Tables 3 and 4, the balance of electromagnetic conversion characteristics, shaving characteristics, and slit characteristics deteriorates.

[0097]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[0098]

INDUSTRIAL APPLICABILITY According to the present invention, by using spherical silica particles in a specific range and by setting the plane orientation indexes F and ΔN in the specific ranges, both running durability in high temperature and high humidity atmosphere and slit resistance are excellent, and This is a polyester film that has an extremely small dropout increase during repeated running, and since the film is not easily scratched even at high speeds, it can respond to an increase in film processing speed for each application. . Further, when a video tape is used, an S / N, that is, a film in which the image quality is less likely to deteriorate even after repeated use is obtained. The use of the polyester film for magnetic recording media of the present invention is not particularly limited, but 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 longitudinal 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. The film runs from roll 1 to roll 9 and is stretched.

Claims (6)

[Claims] 1. A volume average particle size of 0.1 to 2.0 μm, a relative standard deviation defined by the following formula (1) of 0.3 to 1.5, and a particle size class width H ( μm) is represented by the following formula (2), and the particle size distribution curve is a polyester film containing 0.005 to 5.0% by weight of spherical silica particles exhibiting a one-peak distribution. Δ
A polyester film for a magnetic recording medium, wherein N simultaneously satisfies the following formulas (3) to (5). Relative standard deviation = (Σ _{i = 1 → n} (Di −DN) ² / n) ^0.5 / DN (1) where Di: equivalent area circle diameter (μm) obtained from the projected area of each particle DN: The number average value of the area equivalent circle diameters [DN = (Σ _{i = 1 → n} Di) / n] (μm) n: The number of particles measured. H = 1 / TRUNC (n) ^0.5 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (2) [where n is the number of particles measured, TRUNC (n) ^0.5
Is an integer value when the decimal part of the value obtained by the square root of n is truncated. ] ΔN <1250-8000 × F ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (3) −40 <∆N <0 ‥‥‥‥‥‥‥ (4) 0.1500 <F <0.1600 ‥‥‥‥‥‥‥‥‥ (5) [Here, ΔN = (N _MD −N _TD ) × 1000, F = (N _MD +
N _TD ) / 2−nz, where N _MD is the refractive index in the film longitudinal direction, N _TD is the refractive index in the film width direction, and nz is the refractive index in the film thickness direction. ] 2. 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 (6) and (7). nz ≦ 1.603-0.6407 × F (6) nz ≧ 1.595-0.6407 × F (7) 3. The volume average particle size is 0.1 to 2.0 μm, the relative standard deviation defined by the following formula (1) is 0.3 to 1.5, and the particle size class width H ( polyester film (B) containing spherical silica particles in an amount of 0.005 to 5.0% by weight, in which the particle size distribution curve shows one peak distribution when expressed by the following formula (2). One layer of (A) is laminated on at least one side, and the plane orientation index F and ΔN are (3) to
A laminated polyester film for a magnetic recording medium, which simultaneously satisfies the expression (5). Relative standard deviation = (Σ _{i = 1 → n} (Di −DN) ² / n) ^0.5 / DN (1) where Di: equivalent area circle diameter (μm) obtained from the projected area of each particle DN: The number average value of the area equivalent circle diameters [DN = (Σ _{i = 1 → n} Di) / n] (μm) n: The number of particles measured. H = 1 / TRUNC (n) 0.5 ‥‥‥‥‥‥‥‥‥‥ (2) [ where n is the measurement number of particles, TRUNC (n) ^0.5
Is an integer value when the decimal part of the value obtained by the square root of n is truncated. ] ΔN <1250-8000 × F ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (3) −40 <∆N <0 ‥‥‥‥‥‥‥ (4) 0.1500 <F <0.1600 ‥‥‥‥‥‥‥‥‥ (5) [Here, ΔN = (N _MD −N _TD ) × 1000, F = (N _MD +
N _TD ) / 2−nz, where N _MD is the refractive index in the film longitudinal direction, N _TD is the refractive index in the film width direction, and nz is the refractive index in the film thickness direction. ] 4. The laminated polyester film for a magnetic recording medium according to claim 3, wherein the refractive index nz in the thickness direction and the plane orientation index F satisfy the following formulas (6) and (7). nz ≤ 1.603-0.6407xF ... (6) nz ≥ 1.593-0.6407xF ... (7) 5. The polyester film for a magnetic recording medium according to claim 1, wherein the spherical silica particles have a refractive index of 1.430 or more in ethylene glycol. 6. The polyester film for a magnetic recording medium according to claim 1, wherein the abrasion index K is 60 or less.