JP2003064206A - Polyester film for magnetic recording medium and magnetic recording tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester film for magnetic recording medium which can be used suitably not only for a video tape few in the drop-out but also for a vapor deposition-type magnetic tape for data backup which is low in the error rate. SOLUTION: The polyester film for magnetic recording medium is characterized in that, on the one surface A of the polyester film there exist fine surface protrusions due to fine particles, the particle size of the above fine particles is 5-50 nm, in the one surface A the number of the fine surface protrusions is 3-100 millions/mm<2> , the number of the 50-120 nm high surface protrusions is <=1000/mm<2> , the number of the >120 nm high surface protrusions is <=400/100 cm<2> , and the number of the aggregated, surface-attached substances is <=30/mm<2> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention manufactures a polyester film for a magnetic recording medium, in particular, a ferromagnetic metal thin film type magnetic recording medium for recording digital data for a digital video cassette tape, a data storage tape, etc. with high quality. The present invention relates to a polyester film suitable for magnetic recording media.

[0002]

2. Description of the Related Art A digital video tape for consumer use which was put into practical use in 1995 has a metal magnetic thin film of Co provided on a base film having a thickness of 6 to 7 μm by vacuum deposition, and a diamond-like carbon film coated on the surface thereof. Becomes D
In the case of a camera-integrated video using a V mini cassette, the basic specification (SD specification) has a recording time of 1 hour.

This digital video cassette (DVC)
Is the world's first digital video cassette for home use. Even though it is a small body, it can record a huge amount of information,
b. Image quality and sound quality do not deteriorate even after years because the signal does not deteriorate. C. Enjoy high image quality and high sound quality because it is not disturbed by noise. D. It has advantages such as that the image does not deteriorate even after repeated dubbing, and is highly evaluated in the market.

Also, this vapor deposition type digital video tape,
The use of DVC for data backup of computers started in 1996, and data of 8 mm tape width 8 mm (Mammoth Exabyte, Sony AI)
T system) A computer data backup device has been put into practical use, and it is popular because of its compact size, large capacity, and fast data transfer rate.

The base film is a polyester film, a polymer blend adhered to at least one side of the polyester film, and a particle size of 50 to 500.
Å consisting of a discontinuous film mainly composed of fine particles, the discontinuous film contains a water-soluble polyester copolymer,
A polyester film (for example, Japanese Patent Publication No. 63-57238) in which fine protrusions are formed on a discontinuous film by fine particles, a layer A made of a thermoplastic resin, and a layer B made of a thermoplastic resin containing fine particles are provided. A laminated composite film (for example, Japanese Examined Patent Publication No. 1-263338), and the like are used.

However, such a base film is apt to have surface defects due to foreign substances existing in the polyester used, surface scratches introduced during the film formation process, surface contaminants adhered during the film formation process, and the like. Yes, the dropout of tapes made from the base film tended to increase.

For the purpose of providing a polyester film for a magnetic recording medium, which is a DVC tape with less dropout, Japanese Patent Laid-Open No. 2000-25105 discloses that
The height A of the polyester film on one surface A on one side is 10
3 to 90 million pieces / m of fine surface protrusions of 50 nm
m ² is a polyester film having a height of 50 on one surface A of the polyester film.
~ 120nm surface protrusions 40,000 pieces / mm ² or less, height 1
A polyester film for a magnetic recording medium characterized by having 400 defects / 100 cm ² or less in surface defects of 20 nm or more and a magnetic recording tape comprising a ferromagnetic metal thin film layer provided on the surface of the polyester film have been proposed.

[0008]

However, the magnetic tape made from such a base film has a dropout sufficiently reduced for a video tape, but has an error rate (data It has been found that the decrease in the ratio of data that could not be recorded accurately) is still insufficient, and that the error rate tends to be high especially during data compression.

Therefore, an object of the present invention is to provide a polyester film for a magnetic recording medium which can be a vapor-deposited magnetic tape for data backup having a low error rate as well as for a video tape having a small dropout.

[0010]

In order to achieve the above object, the polyester film for a magnetic recording medium of the present invention comprises a polyester film having fine particles having a particle size of 5 to 50 nm and an organic compound on one surface A on one side. A polyester film for a magnetic recording medium, which comprises a coating film containing: wherein the surface of the coating film has fine surface protrusions due to the fine particles, and the number of the fine surface protrusions is 3,000,000 to 100,000,000 units / mm. ² , the number of surface protrusions with a height of 50 to 120 nm is 1000 / mm ² or less, the number of surface protrusions with a height of 120 nm is 400/100 cm ² or less, and the number of aggregated surface deposits is 30. / Mm ² or less.

As described above, according to the present invention, in the magnetic tape for data backup, the problem that the error rate becomes high especially at the time of data compression is caused by the aggregated adhered matter adhered on the surface of the polyester film. ,
That is, it has been made clear that it is difficult to cause a problem for video tapes because it has a low height, but it becomes an error rate for data backups.

Further, it is based on the finding that it is suitable for the purpose of achieving the purpose to contain an appropriate amount of the silicone compound in the coating.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester used in the present invention may be any polyester that can be formed into a high strength film by molecular orientation, but polyethylene terephthalate and polyethylene-2,6-naphthalate are preferable. That is, polyethylene terephthalate and polyethylene-2,6-naphthalate in which 80% or more of the constituents are ethylene terephthalate or ethylene naphthalate are preferable. Ethylene terephthalate, polyester copolymer components other than ethylene naphthalate, for example, diethylene glycol, propylene glycol, neopentyl glycol,
Polyethylene glycol, p-xylylene glycol,
Diol components such as 1,4-cyclohexanedimethanol, dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, and polyfunctional dicarboxylic acid components such as trimellitic acid and pyromellitic acid , P-oxyethoxybenzoic acid and the like.

Further, the above-mentioned polyester contains at least one of an alkali metal salt derivative of sulfonic acid which is non-reactive with the polyester and a polyalkylene glycol which is substantially insoluble in the polyester in an amount not exceeding 5% by weight. You may mix in.

A coating containing fine particles and an organic compound is formed on one surface of the polyester film of the present invention, and the surface A of the coating has fine surface projections due to the fine particles. Is 3 to 100 million / mm ² , and the particle size of the fine particles is 5 to 50 nm.
The fine surface protrusions reduce wear of the ferromagnetic metal thin film layer formed on the surface A coating film by vacuum deposition by the magnetic head during recording and reproduction. Fine particle size is 5n
If it is smaller than m, or the number of fine surface protrusions is 300
If the number is less than 10,000 / mm ^{2, the} number of fine surface protrusions with a particle size of 5 nm or more present on the magnetic layer surface of the magnetic tape will be less than 3 million / mm ² , and the ferromagnetic metal thin film layer during recording / reproduction will have a video head. It is not suitable because it is worn out.
If the particle size of the fine surface protrusions is larger than 50 nm, the height of the fine surface protrusions formed on the surface of the magnetic layer of the magnetic tape increases and the output characteristics of the magnetic tape deteriorate, which is not suitable. Or, if the number of fine surface protrusions is more than 100 million / mm ^{2, the} number of fine surface protrusions existing on the magnetic layer surface of the magnetic tape exceeds 100 million / mm ² , and the ferromagnetic metal thin film layer is too rough, and It is not suitable because the output characteristics of the tape will deteriorate.

The fine surface protrusions are provided by forming a coating layer containing fine particles in an organic compound on the polyester surface. The average particle size of the fine particles is 5 to 50 n
m, more preferably 8 to 30 nm, and as its particle species, particles of inorganic compounds such as silica, calcium carbonate and alumina, particles of organic compounds such as polyacrylic acid spheres and polystyrene spheres, silica, alumina and carbonic acid. Particles in which inorganic particles such as calcium are used as cores and coated with an organic polymer can be used, but are not limited thereto. The organic compound used in the coating layer is polyvinyl alcohol, tragacanth gum, casein, gelatin, cellulose derivative,
Polar polymers such as water-soluble polyester, polyurethane, acrylic resin, acrylic-polyester resin, and the like can be used, but are not limited thereto.

The coating film contains 0.0% of a silicone compound.
It is more preferable that the content is 01 to 0.1% by weight. The silicone compound is preferable because it eliminates unevenness in the width direction of the coating layer. If there is unevenness in the thickness of the coating layer, the number of fine projections tends to increase at a thick portion, and if the thickness is thin, the number of fine projections tends to decrease, which is not preferable. The silicone compound is not particularly limited as long as the main chain is a polymer with a Si-O bond, but polydimethylsiloxane, methylhydrogenpolysiloxane, polymethylphenylsiloxane, cyclic dimethylsiloxane, polyether modified silicone, fluorine modified Silicone, amino-modified silicone and the like can be used, but are not limited thereto. When the content of the silicone compound is less than 0.001% by weight, the thickness of the coating layer tends to be uneven and the number of fine surface protrusions tends to be large, which is not preferable. When the content of the silicone compound exceeds 0.1% by weight, the adhesion of the coating film to the ferromagnetic metal vapor deposition film becomes poor, which is not preferable.

The number of surface protrusions having a height of 50 to 120 nm on one surface A of the polyester film of the present invention is 1000 / mm ² or less. If there are more surface protrusions in the above height range than the above number, the error rate of the magnetic tape increases, which is not suitable.

The number of surface protrusions having a height of more than 120 nm on one surface A of the polyester film of the present invention is 400/100 cm ² or less. If there are more surface protrusions of the above height than the above number, the dropout of the magnetic tape increases, which is not suitable.

Here, "height 5 present on the surface of the film
The surface protrusions in the “0 to 120 nm surface protrusion” and the “surface protrusion exceeding 120 nm in height” are not only surface protrusions formed by fine particles contained in the polyester polymer but also scratches, contaminants, and adhered substances existing on the surface. The defect-like protrusions due to the above are also included, and the defect-like protrusions have a different morphology from the surface protrusions due to the fine particles contained in the polymer and are identifiable.

The number of aggregated surface deposits on one surface A of the polyester film of the present invention is 30 / mm ^2.
It is the following. This aggregated surface deposit has a height of 120 nm
Even if it does not exceed the above range, the presence of more than the above number is not suitable because the error rate of the magnetic tape increases. Incidentally, the aggregated surface deposits, when providing the fine surface protrusions, that is, when forming a coating layer containing fine particles in an organic compound on the polyester surface, oligomers already present on the polyester surface, foreign matter such as dirt,
In addition, it is derived from foreign substances such as coating liquid aggregates and coating liquid modified substances existing in the coating layer. The form and shape are not limited. One lump, flat one, agglomerate, multiple alien substances that are not in a lump but are gathered together, like sand is scattered, archipelago-like connections There are various types, such as existing ones. It refers to a foreign substance adhering to the surface of a size whose existence can be confirmed at a magnification of about 100 times by observation with an optical microscope. It is a foreign substance that peels off from the surface when a solvent such as chloroform is dropped onto the adhered substance.

S on one surface B of the polyester film of the present invention (which is the surface opposite to the above-mentioned one surface A).
The Ra value is such that after the polyester film is formed, when the polyester film is slit into a predetermined width, a product with a good winding shape can be easily collected, and a ferromagnetic thin film is provided on one surface A of the polyester film before rolling. In order to minimize the occurrence of waviness-like deformation of the ferromagnetic thin film layer due to the roughness of the one side surface B being transferred to the one side surface A side due to the winding of the strip shape, it is more preferable that the thickness be 8 to 35 nm.
m is desirable. The SRz value of the one-side surface B was such that after the polyester film was formed, the rolled product after slitting the polyester film was kept good, and a ferromagnetic thin film was provided on the one-side surface A of the polyester film. In order to minimize the occurrence of waviness-like deformation of the ferromagnetic thin film layer due to the roughness of the one-side surface B being transferred to the one-side surface A side by roll-shaped winding later, 100 to 700 n
m, more preferably 140 to 550 nm is desirable.

On one surface B side of the polyester film of the present invention, a rougher coating layer containing a lubricant such as silicone is provided, or a polyester film layer containing larger fine particles is laminated. Those having the above-mentioned coating layer provided thereon are preferably used, but the invention is not particularly limited thereto. Examples of the fine particles used here include calcium carbonate, silica, alumina, polystyrene and the like. The average particle size of the fine particles is preferably 1
00-1000 nm, more preferably 150-900 n
m is used, and the addition amount thereof is preferably 0.05 to 1.0% by weight, more preferably 0.08 to
0.8% by weight is desirable.

The polyester film of the present invention preferably has a film thickness of less than 10 μm, more preferably 3.5 to 9.0 μm.

When the polyester film of the present invention is used for a magnetic recording medium to manufacture a magnetic recording tape, a ferromagnetic metal thin film layer is provided on the coating on the surface A, and solid fine particles are further provided on the surface B. And it is preferable to provide a backcoat layer formed by applying a solution consisting of a binder and various additives as necessary, and the solid fine particles, the binder and the additive may be known ones, and particularly Not limited. The thickness of the back coat layer is 0.3 to 1.5
About μm is preferable.

Next, an example of the method for producing the polyester film of the present invention will be described.

The polyester film of the present invention has A
Using polyester from which contained particles have been removed as much as possible as the surface side raw material, it is produced in a usual plastic film manufacturing process consisting of melting, molding, biaxial stretching, and heat setting. 2.7 in the vertical and horizontal directions
~ 5.5 times, 3.5 ~ 7.0 times stretched, 190 ~ 2
Heat set at a temperature of 20 ° C. And it can manufacture by performing the following operations.

(1) 0.5 to 12.0 fine particles having an average particle size of 10 to 50 nm, preferably 10 to 30 nm are provided on the A-side of the smooth polyester film after stretching in one direction.
A coating liquid containing an organic compound in an amount of 0.6% by weight, preferably 0.6 to 10.0% by weight, is applied to form a coating layer on the surface A side, and fine surface protrusions are formed on the surface A side. The organic compound used in the coating layer is polyvinyl alcohol, tragacanth gum, casein, gelatin, cellulose derivative,
Polar polymers such as water-soluble polyester and polyurethane,
Blends of these can be used, but are not limited to. The number of the fine surface protrusions can be adjusted by adjusting the type of the fine particles, the average particle diameter, and the solid content coating concentration. It is more preferable that the coating liquid contains 0.001 to 0.1% by weight of the silicone compound in the solid content of the coating liquid. The main chain of the silicone compound is Si
The polymer is not particularly limited as long as it is a polymer with a -O bond, but polydimethylsiloxane, methylhydrogenpolysiloxane, polymethylphenylsiloxane, cyclic dimethylsiloxane, polyether modified silicone, fluorine modified silicone, amino modified silicone, etc. are used. Yes, but not limited to.

When it is desired to further increase the durability of the magnetic layer of the magnetic tape, fine particles having an average particle size of 30 to 150 nm, preferably 40 to 100 nm are added to the polyester film layer forming the surface A side. Surface A by including less than 0.0% by weight, preferably less than 0.8% by weight
It is preferred to have surface protrusions on top. As the fine particles, silica, calcium carbonate, alumina, polyacrylic acid spheres, polystyrene spheres and the like can be used, but are not limited thereto.

(2) In order to set the number of surface protrusions having a height of 50 to 120 nm to a level of 1000 / mm ² or less,
In the drying before melting the A-side raw material, it is effective to dry after drying the dryer in advance so as not to be contaminated by other raw materials.

(3) In order to set the number of surface protrusions having a height of 120 nm or more to 400/100 cm ² or less, 1) 0.6 μm (95%) of the layer A side melt was melt-extruded. (Cut diameter) Reduces foreign matters in the film by passing it through a high-precision filter having a performance of 2 or more. 2) If scratches are present on the surface of the stretching roll, control the height of scratches to not exceed 0.3 μm. It is effective to reduce surface scratches and surface deposits by controlling the surface stain so that the height from the surface of the stretching roll does not exceed 0.3 μm.

(4) The number of aggregated surface deposits is 30 /
To a mm ² or less, it is desirable that the number of surface foreign substance existing on the A side of the smooth polyester film at the time after stretching in one direction and 30 × transverse draw ratio / mm ² or less. That is, the main components of the surface-existing foreign matter are those deposited and deposited on the surface of the longitudinal stretching roll over time during the polyester film production, and the foreign matter adhered to the surface of the stretching roll that has been transferred to the surface of the film during longitudinal stretching. Therefore, it is desirable to periodically wipe off the surface of the longitudinal stretching roll with a dust-free cloth soaked in clean water. Further, it is desirable that the temperature of the coating liquid is set to 30 ° C. or lower so that the coating liquid does not aggregate, and the coating liquid is filtered and coated using a coating liquid filter having a filtration accuracy of 1 μm or more. in this way,
The number of aggregated surface deposits is reduced to 30 pieces / mm ² or less by regularly cleaning the longitudinal stretching rolls, keeping the coating solution temperature below 30 ° C., and filtering the coating solution with an accuracy of 1 μm or more. be able to.

By using the coextrusion technique, the above A
B containing the raw material for the layer and positively larger particles
The A / B laminated film may be melt-extruded to form a film using the raw material for the layer, or a coating liquid containing a lubricant may be applied to the surface B side opposite to the surface A side without using the B layer. The surface B side may be slippery treated. The layer B may be used, and a coating liquid containing a lubricant may be further applied to the surface B for easy slipping treatment.

The biaxial stretching can be carried out, for example, by a sequential biaxial stretching method or a simultaneous biaxial stretching method, but if desired, it is further stretched in the longitudinal direction or the transverse direction or the longitudinal and transverse directions before heat setting to obtain mechanical strength. It is also possible to use a so-called enhanced type, which has a higher

The polyester film of the present invention is suitable as a base film for a magnetic recording medium, particularly when used in digital video tape applications and data storage tape applications, because it gives excellent results.

The magnetic recording tape of the present invention is a tape in which a ferromagnetic metal thin film layer formed by vacuum deposition is provided on the surface A of the polyester film of the present invention and formed into a tape. A known thin film can be used as the thin film, and the thin film is not particularly limited, but a thin film made of a ferromagnetic material of iron, cobalt, nickel, or an alloy thereof is preferable. The thickness of the metal thin film layer is preferably 20 to 300 nm.

That is, the magnetic recording tape of the present invention comprises Co film on one surface A of the polyester film of the present invention.
The ferromagnetic metal thin film made of
It is formed with a thickness of 0 to 300 nm, and 10 n
A diamond-like carbon film having a thickness of about m is coated, and a lubricant is further coated thereon, and on the other hand, one side surface B is coated with a solution containing solid fine particles and a binder, to which various additives are added if necessary. By doing so, a back coat layer is provided, and the tape is cut into a predetermined tape width, whereby it can be manufactured.

[0038]

EXAMPLES The measurement methods used in this example are shown below. (1) Particle size of fine particles Electron microscope (electron microscope) Fine particle powders are scattered on a test table so that the particles do not overlap as much as possible, and the magnification is 1,000,000 times with an electron microscope (preferably a transmission electron microscope). The area-equivalent diameter was determined for at least 100 particles, and the number average value was used as the particle diameter. In addition,
When the particle size is obtained from the film, it is obtained by the method a) described below. a) A gold thin film deposition layer having a thickness of 20 to 30 nm (χn
m) and observed with an electron microscope (preferably a scanning electron microscope) at a magnification of about 100,000, and at least 10
The area circle equivalent diameter is obtained for 0 particles, and the value obtained by subtracting 2χnm from this number average value is taken as the particle diameter.

(2) Number of fine surface protrusions on the film The number of fine surface protrusions formed on the surface of the film was observed by a scanning electron microscope at a magnification of about 30,000 to observe the film surface for 10 or more visual fields and 1mm visible surface protrusion
It was measured by determining how many per ² there are. (3) Silver is vapor-deposited (shadowed) at an angle of 5 ° with respect to the surface of the film having the number of surface protrusions having a height of 50 to 120 nm, and then platinum is coated by sputtering. The shadowed film surface is observed from directly above with a scanning electron microscope at a magnification of about 5,000 times for about 10 fields of view, and surface projections having a shadow on the surface (formed by fine particles existing in the polyester polymer are formed. Other than the projections, including surface defects such as surface defects due to scratches, contaminants, and deposits, and let the height of the projection be h, the length of the shadow be H, and use the relationship of tan5 ° = h / H. The projection height was estimated from the length of the shadow, and the number of surface projections having a height of 50 to 120 nm was determined. Converted to the number of pieces per 1 mm ² , the height is 5
The number of surface protrusions was 0 to 120 nm.

(4) Number of surface protrusions with a height of 120 nm or more Film A was observed using an optical microscope (observation magnification: 100 times).
Observing the side surface, surface protrusions (including those that look like protrusions, as well as those that look like scratches and aggregated surface deposits. These aggregated surface deposits are single lumps, flat ones, and aggregates. Shape, multiple alien substances that are not in a lump but are gathered, sand is scattered, connected island-like, etc.
It is as if they are collectively attached to the surface with a diameter of about 2 μm or more. ) Is observed and marked. The height of the marked surface protrusions is measured by a Keyence laser microscope (surface shape measuring microscope).
It is confirmed using VF-7500) whether the thickness is 120 nm or more, and the number of those having a thickness of 120 nm or more is measured. The number of surface projections having a height of 120 nm or more was calculated from the observed area by converting the number into 100 cm ² . The judgment from the magnetic tape is performed by magnetically recording, coating the surface of the magnetic tape with a magnetic colloid, and observing the coated surface with an optical microscope (observation magnification: 100 times). A portion on the coated surface where the magnetic recording is missing is marked, and the height of the marked defects is 120 using a laser microscope (surface shape measuring microscope VF-7500) manufactured by Keyence Corporation.
Confirm whether or not it is nm or more. 1 from the observed area
The number of protrusions and defects having a height of 120 nm or more was converted into the number per 00 cm ² .

(5) Number of aggregated surface deposits Among the surface protrusions observed in the observation of (4), the number of aggregated surface deposits (the aggregated one is counted as one surface deposit) is counted. taking measurement. It was divided by the observed area and converted into the number per mm ^{2, which} was taken as the number of aggregated surface deposits. To make it easier to see, use a scanning electron microscope.
The same number may be obtained by observing at an observation magnification of about 000 times. (6) Characteristic evaluation of magnetic tape (data tape) The evaluation was performed by determining the error rate of the magnetic tape using a commercially available Exabyte data 8 mm device, mammoth. The error rate was measured by obtaining the ratio of write errors when back-up recording 2 GB of data from the hard disk to the tape and the ratio of read errors when reading. (The compression ratio was 2.5 times.) The error rate was determined at the time of first use after the tape was manufactured, and at the time of recording and storing 100 times and after reading.

Next, the present invention will be described based on examples.

[Example 1] A raw material A obtained by adding 0.03% by weight of silica having an average particle diameter of 60 nm to polyethylene terephthalate containing substantially no inert particles was dried in a dryer which was previously cleaned. Then, the same polyethylene terephthalate was mixed with a raw material B containing 0.20% by weight of aluminum silicate having an average particle diameter of 300 nm and a thickness ratio of 5: 1.
At the ratio of
The film was longitudinally stretched 3.0 times at 110 ° C. by a roll stretching method. The extrusion system for raw material A was provided with a high-precision filter having a performance of 0.6 μm cut (95% cut diameter).

In the step after the longitudinal stretching, an aqueous solution having the following composition was kept on the outside of the surface A on one side at a temperature of 25 ° C. and filtered with a filter having a filtration accuracy of 0.8 μm. ^It was applied so as to be ² . Aqueous solution applied to the outside of surface A: Methyl cellulose 0.10% by weight Water-soluble polyester (= 1: 1 copolymer of 70 mol% terephthalic acid, 30 mol% 5-sodium sulfoisophthalic acid acid component and ethylene glycol) 0.30% by weight Amino-modified silicone 0.004% by weight Ultrafine silica with an average particle size of 18 nm 0.008% by weight

After that, in a lateral direction at a temperature of 102 ° C.
4.2 times, was heat-treated at 215 ° C., wound on an intermediate spool, slitted with a slitter to have a small width, and wound into a roll on a cylindrical core to obtain a roll-shaped polyester film having a thickness of 6.3 μm. Surface scratches and surface stains on all rolls that touch the film during the film forming process have a scratch height of 0.
It was controlled so as not to exceed 3 μm, and the surface contamination should not exceed 0.3 μm as the height from the surface of the stretching roll. The surface of the longitudinal stretching roll was wound with a film having a specified length (17,000 m) and then cleaned with an exposed dustproof cloth soaked in clean water.

A cobalt-oxygen thin film having a thickness of 150 nm was formed on the surface A of this polyester film by vacuum vapor deposition. Next, a diamond-like carbon film having a thickness of 10 nm was formed on the cobalt-oxygen thin film layer by a sputtering method, and a fluorine-containing fatty acid ester-based lubricant was added to the thickness of 3 nm.
It was applied in a thickness of nm. Subsequently, a back coat layer made of carbon black, polyurethane, and silicone is provided on the surface B to a thickness of 500 nm, and a width of 8 is obtained by a slitter.
A magnetic tape (data tape) was prepared by slitting it into mm and winding it on a reel.

The characteristics of the obtained polyester film and magnetic tape are shown in Table 1. The SRa value and SRz value of the B surface of the polyester film were 20 nm and 270 nm.

Example 2 A magnetic tape having a width of 8 mm was prepared in the same manner as in Example 1 except that silica having an average particle size of 60 nm was removed from the raw material A in the production of the base film of Example 1. The properties of the obtained polyester film and magnetic tape are shown in Table 1. The SRa value and SRz value of the B surface of the polyester film are 20 nm and 270 nm.
Met.

Example 3 In the production of the base film of Example 2, polyethylene terephthalate was changed to polyethylene-2,6-naphthalate and the content of aluminum silicate in raw material B was changed to 1.1% by weight. The longitudinal stretching temperature and the magnification were changed to 5.0 times at 135 ° C, the solid coating amount at the time of applying the aqueous solution was changed to 50 mg / m ^2, and the transverse stretching temperature and the magnification were changed to 135 ° C and 6.5 times. Then, the heat treatment was changed to 200 ° C., and in the same manner as in Example 2 except for the above, a polyester film roll having a thickness of 4.2 μm was obtained. A magnetic tape having a width of 8 mm was prepared from the obtained polyester film in the same manner as in Example 1. The properties of the obtained polyester film and magnetic tape are shown in Table 1. The SRa value and SRz value of the B side of the polyester film are 2
It was 2 nm and 280 nm.

Example 4 A magnetic tape having a width of 8 mm was prepared in the same manner as in Example 1 except that the modified silicone was removed from the aqueous coating solution in the production of the base film of Example 1. The obtained polyester film had several coating irregularities extending in the longitudinal direction in the width direction, and a magnetic tape was collected from the film portion having no coating irregularity. Table 1 shows the characteristics of the polyester film and the magnetic tape in the area without coating unevenness. SRa on the B side of the polyester film
Value and SRz value were 20 nm and 270 nm.

[Example 5] In the production of the base film of Example 1, the concentration of the modified silicone in the coating solution was adjusted to 0.
Changed to 15% by weight. A magnetic tape having a width of 8 mm was prepared in the same manner as in Example 1 except for the above. The adhesive strength of the magnetic layer of the obtained magnetic tape was very weak, and the magnetic tape peeled off immediately and the error rate of the magnetic tape was poor. Table 1 shows the properties of the polyester film and the magnetic tape. The SRa value and SRz value of the B surface of the polyester film were 20 nm and 27
It was 0 nm.

[Comparative Example 1] In the production of the base film of Example 1, the coating amount of the solid content when the aqueous solution was coated was 5 mg / m 2.
Changed to ² . Others are the same as in Example 1 and the thickness is 6.
Obtain a roll of polyester film of 3μm, width 8mm
I made a magnetic tape. The properties of the obtained polyester film and magnetic tape are shown in Table 1. The SRa value and SRz value of the B side of the polyester film are 20 nm and 2
It was 70 nm.

[Comparative Example 2] In the production of the base film of Example 1, the concentration of the ultrafine silica in the coating solution was adjusted to 0.
09% by weight, the amount of solid content applied when applying an aqueous solution is 80 mg /
Changed to m ² . Others were made in the same manner as in Example 1 to obtain a polyester film roll having a thickness of 6.3 μm and a width of 8 μm.
mm magnetic tape was created. The properties of the obtained polyester film and magnetic tape are shown in Table 1. The SRa value and SRz value of the B side of the polyester film are 20n.
m, 270 nm.

[Comparative Example 3] In the production of the base film of Example 1, the particle size of the ultrafine silica in the coating aqueous solution was 4n.
m, the amount of solid content applied when the aqueous solution was applied was changed to 10 mg / m ² . Others are the same as in Example 1, and the thickness is 6.3 μm.
A roll of polyester film was obtained to prepare a magnetic tape having a width of 8 mm. The properties of the obtained polyester film and magnetic tape are shown in Table 1. The SRa value and SRz value of the B surface of the polyester film were 20 nm and 270 n.
It was m.

[Comparative Example 4] In the production of the base film of Example 1, the particle size of the ultrafine silica in the coating solution was adjusted to 60.
nm and silica addition concentration were changed to 0.01% by weight. Otherwise in the same manner as in Example 1, a polyester film roll having a thickness of 6.3 μm was obtained, and a magnetic tape having a width of 8 mm was prepared. The properties of the obtained polyester film and magnetic tape are shown in Table 1. The SRa value and SRz value of the B surface of the polyester film were 20 nm and 270 nm.

[Comparative Example 5] In Example 1, the raw material A was dried in a dryer without prior cleaning. Otherwise in the same manner as in Example 1, a polyester film roll having a thickness of 6.3 μm was obtained, and a magnetic tape having a width of 8 mm was prepared. The properties of the obtained polyester film and magnetic tape are shown in Table 1. The SRa value and SRz value of the B surface of the polyester film were 20 nm and 270 nm.

[Comparative Example 6] In Example 1, the foreign matter cutting performance of the high-precision filter provided in the extrusion system of the raw material A was changed to that of 2.0 μm cut (95% cut diameter). Others are the same as in Example 1 and the thickness is 6.3 μm.
A polyester film roll of m was obtained, and a magnetic tape having a width of 8 mm was prepared. The properties of the obtained polyester film and magnetic tape are shown in Table 1. The SRa value and SRz value of the B surface of the polyester film were 20 nm and 270.
was nm.

[Comparative Example 7]
100 cm scratch on the surface with a height of 0.4 μm ²I
A film was formed using a stretching roll containing about 50 rolls.
Otherwise, the same as in Example 1, except that the thickness of the polyethylene was 6.3 μm.
Obtain a roll of stell film and attach a magnetic tape with a width of 8 mm.
Created. The obtained polyester film and magnetic tape
Table 1 shows the characteristics of the cups. In addition, B of polyester film
The SRa value and SRz value of the surface are 20 nm and 270 nm.
It was

Comparative Example 8 In the production of the base film of Example 1, the longitudinal stretching roll was not cleaned at all. Further, the temperature of the coating solution was not controlled. Otherwise in the same manner as in Example 1, a roll of the composite polyester film having a thickness of 6.3 μm was obtained, and a magnetic tape having a width of 8 mm was prepared. The properties of the obtained polyester film and magnetic tape are shown in Table 1. The SRa value and SRz value of the B surface of the polyester film were 20 nm and 270 nm.

[0060]

[Table 1]

As is clear from the characteristics shown in Table 1, the magnetic tape produced using the polyester film of the present invention had a low error rate and was an excellent data tape.

[0062]

According to the present invention, a polyester film for a magnetic recording medium suitable for a video tape with less dropouts and a vapor-deposited magnetic tape for data backup with a low error rate can be obtained. The present invention is particularly effective for reducing the error rate of a vapor-deposited magnetic tape for data backup.

Continued front page    F-term (reference) 4F006 AA35 AB03 AB05 AB20 AB24                       AB35 AB37 AB56 AB74 BA02                       CA02 DA04                 4F100 AA03 AA37 AB10 AB15 AH00B                       AK01B AK41A AK42A AK51                       AK52 BA02 DD07B DE01B                       EH17 EH172 EH46 EH462                       EH66 EH662 EJ38 EJ382                       GB41 JM02B YY00B                 5D006 CB01 CB07 FA09

Claims (5)

[Claims] 1. A polyester film for a magnetic recording medium, comprising a polyester film and a coating film containing fine particles having a particle size of 5 to 50 nm and an organic compound formed on one surface A of the polyester film. There are fine surface protrusions due to the fine particles, and the number of the fine surface protrusions is 30.
00,000 to 100,000,000 units / mm ^2, the number of surface protrusions of height 50~120nm is 1000 / mm ² or less, the number of surface projections exceeding the height 120nm is 400/100 cm ² or less, and collectively form A polyester film for a magnetic recording medium, wherein the number of surface deposits is 30 / mm ² or less. 2. The silicone compound in the coating is 0.001.
The polyester film for a magnetic recording medium according to claim 1, wherein the polyester film contains 0.1 to 0.1% by weight. 3. The polyester film for a magnetic recording medium according to claim 1, wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate. 4. The polyester film for a magnetic recording medium according to claim 1, which is used for a digital recording type magnetic tape. 5. A magnetic recording tape comprising a ferromagnetic metal thin film layer provided on the coating film on one surface A of the polyester film according to claim 1.