JP2003025526A - Polyester film for magnetic recording medium and magnetic recording tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for a magnetic recording medium suitable for manufacturing a tape for DVC reduced in DO and enabling long-time recording. SOLUTION: In the polyester film for the magnetic recording medium constituted by forming a film containing fine particles with a particle size of 5-30 nm and an organic compound on the single surface of a polyester film, fine surface projections due to fine particles are present on the surface of the film and the number of the fine surface projections is 1,000,000-100,000,000/mm<2> , the number of the surface projections with a height of 50-120 nm is 1,500/100 cm<2> or less, the number of the surface projections with a height of 120 nm or more is 90/100 cm<2> or less, the Ra value of the surface of the film is 1-5 nm and the heat shrinkage factor of the film at 100 deg.C for 30 min is 0.5% or less in both longitudinal and lateral directions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for a magnetic recording medium, and more particularly to a polyester film for a magnetic recording medium suitable for a magnetic recording medium in which a large amount of image data such as VTR of a DVC system is digitally recorded.

[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. Tena,
In the case of a camera-integrated video using a DV mini cassette, the basic specification (SP mode) 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.

In 1998, one hour and two in SP mode
DV mini cassette tape (DVC) with a recording time of 0 minutes
-LP tape) has been put to practical use, and a polyethylene-2,6-naphthalate film having a thickness of 4 to 5 μm (for example, JP-A-5-185507) or a digital data storage (DDS-) is used as a base film.
Aromatic polyamide film known as a base for 2,3,4) tapes (for example, JP-A-10-16234).
9, JP-A-10-114038, etc.) is used, and this tape also has a long recording time and is highly evaluated in the market.

In order to lengthen the recording time, the tape running speed is reduced to 2/3 to narrow the track pitch of the basic specification from 10 μm to 6.7 μm, and the long time mode (LP mode) is set. That is, the DV mini-cassettes have now realized recording times of 90 minutes and 120 minutes.

[0006]

However, a longer recording time is desired. In order to realize this, there is a method of further thinning the magnetic tape, that is, a method of further thinning the base film of the magnetic tape. However, if the magnetic tape is made thinner, the stiffness of the magnetic tape will decrease, so contact between the magnetic tape and the magnetic head (head touch)
Results in poor magnetic transfer characteristics of the magnetic tape. Therefore, with this conventional method, it was considered difficult to realize a system having a recording time of 150 minutes or more with a DV mini cassette tape.

Therefore, according to the present invention, the recording time for a further longer time can be extended by a DV mini cassette tape (DVC-SLP tape,
An object of the present invention is to provide a polyester film for a magnetic recording medium that can be realized with a recording time of 150 minutes or more) and a magnetic tape suitable for the DVC magnetic recording system.

[0008]

In order to achieve the above object, the present invention has the following constitution.

That is, the polyester film for magnetic recording media of the present invention is a film having a coating film containing fine particles having a particle size of 5 to 30 nm and an organic compound formed on one surface of the polyester film. The surface of the coating has fine surface protrusions formed by the fine particles, the number of the fine surface protrusions is 1 million to 100 million / mm ² , and the number of surface protrusions having a height of 50 to 120 nm is 1500.
Pieces / mm ² or less, surface protrusions number of more height 120nm is 90 pieces / 100 cm ² or less, the surface of the coating film Ra
The value is 1 to 5 nm, and the thermal shrinkage at 100 ° C. for 30 minutes is 0.5% or less in both the longitudinal direction and the width direction.

Further, the polyester film is preferably composed of a blend of polyethylene terephthalate or polyethylene-2,6-naphthalate and a heat resistant polymer, and the heat resistant polymer has a glass transition temperature of 450 K or higher. It is preferably a polymer, particularly polyimide or polyetherimide.
Content of the heat-resistant polymer in the blend is 5 to 40
It is preferably in the weight%. Track pitch is 7 μm
It is preferably a polyester film for a magnetic recording medium used for the following magnetic tape of digital recording system.

The magnetic recording tape of the present invention is one in which a ferromagnetic metal thin film layer is provided on the coating side surface of the above polyester film for magnetic recording media. Further, the magnetic recording tape of the present invention has a ferromagnetic metal thin film layer on the surface of the coating side of a polyester film having a coating containing fine particles having a particle size of 5 to 30 nm and an organic compound formed on one surface. A magnetic recording tape provided, wherein the number of fine surface protrusions on the surface of the ferromagnetic metal thin film layer is 1 million to 100 million / mm ² , and the number of surface protrusions having a height of 50 to 120 nm is 1500. / Mm ² or less, the number of surface protrusions having a height of 120 nm or more is 90/100 cm ² or less, the Ra value of the surface is 1 to 5 nm, and the heat shrinkage rate at 100 ° C. for 30 minutes is the longitudinal direction and the width. It is characterized by being 0.5% or less in both directions.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester film used in the present invention is a film containing polyester as a main constituent material, and among them, a film containing a heat resistant polymer as a constituent material in addition to polyester is preferable.

The polyester may be any polyester capable of forming a high-strength film by molecular orientation. Among them, polyethylene terephthalate and polyethylene-
2,6-naphthalate is preferred. 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. Examples of the polyester copolymerization component other than ethylene terephthalate and ethylene naphthalate include diethylene glycol,
Propylene glycol, neopentyl glycol, polyethylene glycol, p-xylylene glycol, 1,
A diol component such as 4-cyclohexanedimethanol,
Adipic acid, sebacic acid, phthalic acid, isophthalic acid, 5
-Dicarboxylic acid components such as sodium sulfoisophthalic acid, polyfunctional dicarboxylic acid components such as trimellitic acid and pyromellitic acid, and p-oxyethoxybenzoic acid. Further, the above-mentioned polyester is an alkali metal salt derivative of sulfonic acid which is non-reactive with polyester,
At least one such as polyalkylene glycol which is substantially insoluble in the polyester may be mixed in an amount not exceeding 5% by weight.

The heat-resistant polymer is not particularly limited as long as it is a heat-resistant polymer compatible with polyethylene terephthalate, but one having a glass transition temperature (Tg) of 450 K or more is preferable. Polysulfone (around Tg 463K), polyimide (around Tg 683K), polyetherimide (around Tg 490K) and the like can be used. Polyimide, polyetherimide, especially 2,2-bis [4-
A condensate of (2,3-dicarboxyphenoxy) phenyl] propane dianhydride and m-phenylenediamine is preferable because of good compatibility with the polyester. Addition of this heat-resistant polymer is preferable because the heat shrinkage of the polyester is lowered and the dimensional stability is improved. This effect is exhibited even when the strength of the base film is increased, and is also preferable from the viewpoint of preventing deterioration of heat shrinkage ratio and deterioration of dimensional stability due to increase in strength of the base film when thinned.

In the present invention, a coating containing fine particles and an organic compound is formed on one surface of the polyester film. The surface of the coating (hereinafter referred to as surface A) has fine surface protrusions due to the fine particles, the number of the fine surface protrusions is 1 million to 100 million / mm ² , and the particle diameter of the fine particles is 5 to 30 nm. Is. The fine surface protrusions reduce wear of the ferromagnetic metal thin film layer formed by vacuum deposition on the surface A by the video head during recording and reproduction. And grain size of the fine particles is 5nm less than or the number of fine surface protrusions is less than 1,000,000 / mm ^2, the fine surface protrusions number present on the surface of the magnetic layer of the magnetic tape is less than 1 million / mm ^2, The ferromagnetic metal thin film layer is not suitable because it is worn by the video head during recording and reproduction. When the particle size of the fine particles is larger than 30 nm, the height of fine surface protrusions appearing on the magnetic layer surface of the magnetic tape becomes high, and high surface protrusions tend to be scattered on the ferromagnetic metal thin film layer, resulting in a rough surface of the magnetic layer. And the output characteristics of the magnetic tape deteriorate, which is not preferable. Or when fine surface protrusions number is more than 100 million / mm ^2, too fine surface protrusions number present on the surface of the magnetic layer of the magnetic tape 100 million / mm ² and greater than the ferromagnetic metal thin film layer is rough, the magnetic tape It is not suitable because the output characteristics of are degraded.

The fine surface protrusions are provided by forming a coating layer containing fine particles in an organic compound on the surface of the polyester film. The average particle size of the fine particles is 5 to 30 nm, more preferably 8 to 25 nm. As the particle species, inorganic compounds such as silica, calcium carbonate and alumina, organic compounds such as polyacrylic acid spheres and polystyrene spheres, and inorganic particles such as silica, alumina and calcium carbonate as cores are coated with an organic polymer. Particles and the like can be used, but are not limited to these. 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 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 1500 / mm ² or less. If there are more surface protrusions in the above height range than the above number, the number of surface protrusions having a height of 50 to 120 nm on the surface of the magnetic layer of the magnetic tape exceeds 1500 / mm ^2, which is suitable because the error rate increases. Absent.

The number of surface protrusions having a height of 120 nm or more on one surface A of the polyester film of the present invention is 9
0/100 cm ² or less. When the number of surface protrusions having the above height is larger than the above number, the number of surface protrusions having a height of 120 nm or more present on the surface of the magnetic layer of the magnetic tape is 9 or more.
It is not suitable because the number of drops exceeds 0/100 cm ² and the dropout increases.

The Ra value of the surface A on one side of the polyester film of the present invention is such that the wear of the ferromagnetic metal thin film formed on the surface A by vacuum deposition by the magnetic head during recording / reproduction is minimized, and that of the magnetic tape. The thickness is 1 to 5 nm, preferably 2 to 4 nm, in order to maintain good output characteristics. R
When the a value is less than 1 nm, Ra of the ferromagnetic metal thin film layer formed by vacuum deposition on the surface A is less than 1 nm, which is too smooth, and the magnetic head causes the magnetic tape of the magnetic tape to be recorded and reproduced in the DVC video camera. The ferromagnetic metal thin film is worn out, which is not preferable. When the Ra value exceeds 5 nm, the Ra of the ferromagnetic metal thin film layer exceeds 5 nm and the surface is too rough, so that the output characteristics of the magnetic tape are deteriorated, which is not preferable.

100 of the polyester film of the present invention
The heat shrinkage rate at 30 ° C. for 30 minutes was 0.
It is 5% or less, more preferably -0.1 to 0.3%.
As a result, the heat shrinkability of the magnetic tape made from the polyester film of the present invention at 100 ° C. for 30 minutes is 0.5% or less in both the longitudinal direction and the width direction, and the heat shrinkability becomes small. As a result, the dimensional stability of the magnetic tape becomes very good, and the recording density for recording an image on the DVC tape can be made higher than the existing recording density. That is, the track pitch can be narrowed from the current 10 μm to 5 μm or less.

One of polyester films for magnetic recording media
Heat shrinkage at 00 ° C for 30 minutes is 0.5 in the longitudinal and width directions
%, The heat shrinkage rate of the magnetic tape made from this polyester film at 100 ° C. for 30 minutes exceeds 0.5% in both the longitudinal direction and the width direction, and the heat shrinkability becomes large.
Since the dimensional stability of the magnetic tape becomes poor, the recorded track is easily deformed with time. Therefore, in this case, if the track pitch is narrowed to 5 μm or less, the recorded tape track and the track on which the magnetic head runs tend to be inconsistent with each other during reproduction, which makes it difficult to reproduce the record.

100 of the polyester film of the present invention
The heat shrinkage at 30 ° C. for 30 minutes is −0.
If it is less than 1%, the curl of the Co metal vapor deposition film after vapor deposition of Co metal will not return and the magnetic tape produced will curl, which is not preferable.

In the case of a polyester film containing a heat resistant polymer, the content of the heat resistant polymer in the film is preferably 5 to 40% by weight, more preferably 7 to 30% by weight, It is preferably 10 to 20% by weight. If the content of the heat-resistant polymer is less than 5% by weight, the effect of the heat-resistant polymer will not be sufficiently exhibited, so that the heat shrinkage ratio of the film at 100 ° C. for 30 minutes is 0. It is difficult to set it to 5% or less, which is not preferable. When the content of the heat resistant polymer exceeds 40 weight,
The Young's modulus in the longitudinal direction of the film tends to fall below 4000 MPa, and the Young's modulus in the width direction tends to fall below 5500 MPa, which is not preferable.

In order to further increase the durability of the magnetic layer, the average particle size is 30 to 150 nm, preferably 40 to 1 in the polyester layer forming the surface on which the coating is formed.
It is preferable to add 0.01 to 1.0% by weight, preferably 0.02 to 0.8% by weight, of fine particles of 00 nm so as to have surface protrusions on the film surface.

The Ra value of the surface opposite to the surface A of the polyester film of the present invention (hereinafter referred to as the surface B) is a value of the winding shape when the polyester film is formed and then slit into a predetermined width. A good product can be easily collected, and a ferromagnetic thin film is provided on one side surface A of the polyester film, and then one side surface B is formed by winding in a roll shape.
The thickness is preferably 8 to 35 nm, more preferably 10 to 25 nm in order to minimize the transfer of the roughness of the film and the wavy deformation of the ferromagnetic thin film layer.

The Young's modulus in the longitudinal direction of the polyester film of the present invention is 4000 to 9000 MPa, more preferably 4200 to 8000 MPa, and the Young's modulus in the width direction is 50.
00 to 18000 MPa, more preferably 5500 to 1
It is 4000 MPa. Young's modulus in the longitudinal direction is 4000
When it is less than MPa, the magnetic tape made of this polyester film is undesirably stretched in the DVC video camera. Young's modulus in the longitudinal direction is 9000MP
When it exceeds a, the heat shrinkability of the magnetic tape produced from this polyester film tends to be large, and the dimensional stability of the magnetic tape tends to be poor, which is not preferable. When the Young's modulus in the width direction is less than 5000 MPa, the DVC of the magnetic tape produced from this polyester film
During recording and reproduction in the video camera, running of the magnetic head causes damage to the tape edge, particularly by repeatedly hitting the tape when the rotating magnetic head enters the magnetic surface from the tape edge, which is not preferable. If the Young's modulus in the width direction exceeds 18,000 MPa, the heat shrinkability of the magnetic tape made from this polyester film tends to be large, and the dimensional stability of the magnetic tape tends to be poor, such being undesirable.

One surface B of the polyester film of the present invention is constituted by a rougher coating layer containing a lubricant such as silicone, or a polyester film layer (laminated film layer) containing larger fine particles. However, it is not particularly limited thereto. Examples of the fine particles used here include calcium carbonate, silica, alumina, polystyrene and the like. The fine particles have an average particle diameter of preferably 100 to 1000 nm, more preferably 150 to 9 nm.
00 nm is used, and the addition amount is preferably 0.05 to 1.0% by weight, more preferably 0.08 to
It is 0.8% by weight.

The magnetic recording tape of the present invention comprises a polyester metal film of the present invention and a ferromagnetic metal thin film layer formed by vacuum deposition on the surface A of the polyester film. It can be used, but is not particularly limited, and a ferromagnetic material of iron, cobalt, nickel, or an alloy thereof is preferable. The thickness of the metal thin film layer is 1
It may be from 00 to 300 nm. 1 on this metal thin film layer
It is preferable that a diamond-like carbon film having a thickness of about 0 nm is coated, and a lubricant treatment is further applied thereon.

In the magnetic recording tape of the present invention, a back coat layer is provided on the surface B of the film, which is formed by applying a solution containing solid fine particles and a binder, and various additives as required. The solid fine particles, the binder, and the additives may be known ones, and are not particularly limited. The back coat layer may have a thickness of about 0.3 to 1.5 μm.

Next, a method for producing the polyester film and the magnetic recording tape of the present invention will be described.

The polyester film of the present invention comprises, for example, melting polyester, molding, biaxial stretching, heat setting,
In the usual plastic film manufacturing process, which is heat-fixed and then wound up, a polyester raw material prepared by blending a heat-resistant polymer at a blending ratio of 5 to 40% by weight is used as the polyester to be melted. 1
It can be produced by stretching at 80 ° C. at 2.9 to 5.7 times, 3.7 to 7.2 times, and heat setting at a temperature of 190 to 220 ° C.

Specifically, the use of coextrusion technology
The raw material for layer A in which the contained particles are removed as much as possible and the raw material for layer B in which the fine particles are positively contained are laminated to form an A / B laminated film, which is extruded and stretched in one direction, and then smoothed. The average particle size is 5 to 30 on the A side of the polyester film.
nm, preferably 8-20 nm fine particles 0.5-1
A coating liquid A made of an organic compound containing 2.0% by weight, preferably 0.6 to 10.0% by weight, is applied to form a coating layer on the surface A side.

The layer A may be a layer in which fine particles are contained in order to further increase the durability of the magnetic head of the magnetic tape. For example, the average particle diameter in the polyester layer forming the A layer is 30 to 150 nm, preferably 40 to 10 nm.
0.01 to 1.0% by weight, preferably 0.02 to 0.8% by weight, of 0 nm fine particles may be contained, and surface protrusions may be provided on the surface thereof.

In the case of a monolayer film in which the layer B is not laminated, a lubricant is applied to the surface B side of the smooth polyester film which has been stretched in one direction, that is, the surface opposite to the surface coated with the coating liquid A. You may perform the easy slip process which applies the coating liquid containing.

After stretching in one direction and applying the coating liquid A,
The polyester film of the present invention can be obtained by stretching the film in the other direction and then heat-setting and winding.

In the obtained polyester film,
The Ra value of the surface A can be adjusted to a desired level by adjusting the fine particles and components in the formed coating layer and the fine particles inside the A layer.

100 of the polyester film of the present invention
The heat shrinkage ratio at 30 ° C for 30 minutes was 0.
In order to reduce the content to 5% or less, the content of the heat resistant polymer is 5
It may be blended with polyester so as to be 40% by weight, and the stretching ratio and temperature at the time of producing the polyester film may be adjusted.

The polyester film of the present invention is used as a base film of a magnetic recording medium. In particular, it is suitable for use in DVC tape applications in which the track width is narrower than the existing track width, and in large-capacity data tape applications, because excellent results can be obtained.

In the magnetic tape of the present invention, a ferromagnetic metal thin film such as Co is formed on one surface A of the polyester film of the present invention by vacuum vapor deposition to have a film thickness of 100 to 300 nm,
This metal thin film is coated with a diamond-like carbon film having a thickness of about 10 nm, and a lubricant treatment is further applied on the thin metal film to form solid fine particles and a binder on one surface B, and various additives are added if necessary. It can be prepared by applying a solution added with and forming a back coat layer.

The thus-obtained magnetic tape of the present invention comprises a polyester film having a coating film containing fine particles having a particle size of 5 to 30 nm and an organic compound formed on one surface thereof. A magnetic recording tape provided with a ferromagnetic metal thin film layer, wherein the number of fine surface protrusions on the surface of the ferromagnetic metal thin film layer is 1 million to 100 million / mm ² , and the surface has a height of 50 to 120 nm. The number of protrusions is 150
0 pieces / mm ² or less, the number of surface protrusions having a height of 120 nm or more is 90 pieces / 100 cm ² or less, the Ra value of the surface is 1 to 5 nm, and the heat shrinkage rate at 100 ° C. for 30 minutes is in the longitudinal direction. It is 0.5% or less in both width directions, and the object of the present invention can be achieved by satisfying these characteristics.

[0041]

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.

When the particle size is obtained from the film, it is obtained by the method a) described below. a) A gold thin film vapor-deposited layer is provided on the coating surface A of the film at a thickness of 20 to 30 nm (χ nm) by a gold sputtering device, and a magnification of 10 is obtained by an electron microscope (preferably a scanning electron microscope).
The area circle equivalent diameter is obtained for at least 100 particles by observing at about 10,000 times, and the value obtained by subtracting 2χnm from this number average value is taken as the particle diameter.

(2) Number of fine surface protrusions The number of fine protrusions formed on the surface of the film is a protrusion that is observed by observing the film surface for 10 fields or more with a scanning electron microscope at a magnification of about 30,000 times. Was measured by determining how many are per 1 mm ² . The number of fine surface protrusions on the magnetic tape was also measured in the same manner as above.

(3) Surface projection number having a height of 50 to 120 nm Silver is vapor-deposited (shadowed) at an angle of 5 ° with respect to the surface of the film, 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 shadows on the surface (formed by fine particles present in the polyester polymer) ), And let the height of the surface protrusion be h and the shadow length H be tan 5 °
= H / H relationship is used to estimate height from shadow length,
The number of surface protrusions having a height of 50 to 120 nm was determined. 1m
Converted to the number per m ² , the height is 50 to 120 nm
And the number of surface protrusions. Also, the height on the magnetic tape is 50
The number of surface protrusions of 120 nm was also measured in the same manner as above.

(4) Number of surface protrusions with a height of 120 nm or more The film surface is observed using an optical microscope (observation magnification: 100 times), and what appears to be protrusions is marked. The height of the marked protrusions is the laser microscope manufactured by Keyence Corporation (surface shape measuring microscope VF-7500).
Is used to confirm whether the thickness is 120 nm or more. The number of surface projections having a height of 120 nm or more was calculated by converting the observed area into an area per 100 cm ² . In the case of the surface of the magnetic tape, after magnetic recording, the magnetic colloid is applied to the surface of the magnetic tape, and the applied surface is observed 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 surface protrusions having a height of 120 nm or more was converted into the area per 00 cm ² .

(5) Ra value The surface roughness Ra value of the surface of the polyester film was measured using an atomic force microscope (scanning probe microscope). Using a scanning probe microscope (SPI3800 series) manufactured by Seiko Instruments Inc., the surface of the film is subjected to atomic force microscope measurement scanning in a range of 30 μm square in a dynamic force mode. -It was calculated from the arithmetic average roughness corresponding to Ra. In-plane magnification is 10,000 to 5
The magnification is 10,000 times and the magnification in the height direction is about one million times. The surface roughness Ra value of the surface on the magnetic tape was also measured in the same manner as above.

(6) From the rising slope of the starting point in the stress-strain curve obtained by Young's modulus tensile test measurement, ASTM D-882
Calculated according to -67 and expressed in MPa. The sample width and effective length were 10 mm and 100 mm. Tensile speed is 100
mm / min. (7) Heat shrinkage rate at 100 ° C. for 30 minutes in an oven at a temperature of 100 ° C., width 10 mm, length 10
A sample of .about.30 cm was heat-treated for 30 minutes, and the difference between the original length and the length after the heat treatment was taken, divided by the original length, and multiplied by 100 to obtain a heat shrinkage ratio value. The sample was heat-treated by applying a load of 3 gr per 10 mm width.

(8) Evaluation of characteristics of magnetic tape (number of DOs) The running speed of a commercially available camera-integrated digital video tape recorder (DVC video camera) was reduced to 1 / 2.5 and the normal mode (SP mode) was set to 2 Set the mode (super LP, SLP) mode that has 5 times longer recording time, and
The track pitch recorded on the VC tape was reduced to 1 / 2.5 (1 / 2.5). A magnetic tape was created by recording in a quiet room using an SLP mode DVC video camera, playing it back for 1 minute, and counting the number of block mosaics (dropouts (DO)) that appeared on the screen. The characteristics of the DVC-SLP tape) were evaluated.

The number of DOs was initially examined at room temperature (25 ° C.) for initial characteristics after tape production. Next, run the tape 100 times.
The number of DOs after repeating was measured to evaluate the running durability of the magnetic tape. In addition, the tape 1 at high temperature (60 ℃)
The number of DOs after standing for 0 days was measured to evaluate the image storage performance of the magnetic tape.

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

Example 1 Polyethylene terephthalate substantially free of inert particles was condensed with 2,2-bis [4- (2,3-dicarboxyphenoxy) phenyl] propane dianhydride and m-phenylenediamine. 10% by weight of a polyether imide composed of a material, and 10% by weight of the above polyetherimide in polyethylene terephthalate containing substantially no inactive particles.
Raw material B containing 0.30% by weight of 0 nm calcium carbonate was co-extruded at a thickness ratio of 5: 1 and longitudinally stretched 3.9 times at 125 ° C. by a roll stretching method.

In the step after the longitudinal stretching, the following aqueous solution was applied on the surface of the layer of the raw material A so that the solid content concentration was 30 mg / m ² . Outside surface A: 0.18% by weight of methyl cellulose Water-soluble polyester (70% by mole of terephthalic acid, 30% by mole of 5-sodium sulfoisophthalic acid: 1: 1 copolymer of ethylene glycol and an acid component) 0.35% by weight Aminoethylsilane coupling agent 0.02% by weight Ultrafine silica with an average particle size of 12 nm 0.05% by weight After that, it was stretched in a transverse direction at a temperature of 125 ° C. by 4.0 times and heat treated at 215 ° C. It was wound on a spool, slitted in a small width with a slitter, and wound in a roll on a cylindrical core to obtain a polyester film having a thickness of 6.3 μm.

A cobalt-oxygen thin film was formed on the surface A of this polyester film by vacuum vapor deposition to a thickness of 80 nm.
Formed in layers. Next, a diamond-like carbon film having a thickness of 10 nm is formed on the cobalt-oxygen thin film layer by a sputtering method.
And a fluorine-containing fatty acid ester lubricant was applied to a thickness of 3 nm. Then, on the opposite surface,
A back coat layer consisting of carbon black, polyurethane, and silicone is provided to a thickness of 500 nm, slitted to a width of 6.35 mm by a slitter, wound on a reel, and incorporated in a mini DVC cassette.
50 minutes).

The characteristics of the obtained polyester film and magnetic tape are shown in Tables 1 and 2. The Ra value on the B side of the polyester film was 20 nm.

Example 2 In the production of the polyester film of Example 1, raw material A was used.
A polyester film was produced in the same manner as in Example 1 except that silica having an average particle diameter of 60 nm was added to prepare a magnetic tape having a width of 6.35 mm (recording time: 150 minutes). The characteristics of the obtained polyester film and magnetic tape are shown in Tables 1 and 2. In addition, B of polyester film
The Ra value of the surface was 20 nm.

Example 3 In the production of the polyester film of Example 1, polyethylene terephthalate was changed to polyethylene-2,6-naphthalate, polyetherimide was changed to polyimide, and the content of calcium carbonate in raw material B was 1. 5. Change to 1% by weight, change the longitudinal stretching temperature and magnification to 5.0 times at 135 ° C., change the solid content concentration at coating to 54 mg / m ² , and set the transverse stretching temperature and magnification to 135 ° C., 6. Change to 5 times,
A polyester film having a thickness of 4.4 μm was manufactured in the same manner as in Example 1 except that the heat treatment was performed at 200 ° C. A magnetic tape having a width of 6.35 mm (recording time 21
0 minutes) was created. The characteristics of the obtained polyester film and magnetic tape are shown in Tables 1 and 2. The Ra value on the B side of the polyester film was 22 nm.

Comparative Example 1 In the production of the polyester film of Example 1, the particle size of ultrafine silica in the aqueous solution was changed to 4 nm. Otherwise, in the same manner as in Example 1, a polyester film having a thickness of 6.3 μm and a magnetic tape having a width of 6.35 mm (recording time 15
0 minutes) was created. The characteristics of the obtained polyester film and magnetic tape are shown in Tables 1 and 2. The Ra value on the B side of the polyester film was 20 nm.

Comparative Example 2 In the production of the polyester film of Example 1, the particle size of the ultrafine silica in the aqueous solution was changed to 40 nm. Otherwise in the same manner as in Example 1, a polyester film having a thickness of 6.3 μm and a magnetic tape having a width of 6.35 mm were prepared.
The characteristics of the obtained polyester film and magnetic tape (recording time: 150 minutes) are shown in Tables 1 and 2. The Ra value on the B side of the polyester film was 20 nm.

Comparative Example 3 In the production of the polyester film of Example 1, the concentration of ultrafine silica in the coating solution was changed to 0.01% by weight. Otherwise, in the same manner as in Example 1, a 6.3 μm-thick polyester film was manufactured to prepare a magnetic tape having a width of 6.3 mm. The characteristics of the obtained polyester film and magnetic tape (recording time: 150 minutes) are shown in Tables 1 and 2.
The Ra value on the B side of the polyester film was 20 nm.

Comparative Example 4 In the production of the polyester film of Example 1, the concentration of ultrafine silica in the coating solution was changed to 0.24% by weight. Otherwise, in the same manner as in Example 1, a 6.3 μm-thick polyester film was manufactured to prepare a magnetic tape having a width of 6.3 mm. The characteristics of the obtained polyester film and magnetic tape (recording time: 150 minutes) are shown in Tables 1 and 2.
The Ra value on the B side of the polyester film was 20 nm.

Comparative Example 5 In the production of the polyester film of Example 1, the polyetherimide was changed to polyether ether ketone.
Otherwise, in the same manner as in Example 1, a 6.3 μm-thick polyester film was manufactured to prepare a magnetic tape having a width of 6.3 mm. The characteristics of the obtained polyester film and magnetic tape (recording time: 150 minutes) are shown in Tables 1 and 2. The Ra value on the B side of the polyester film was 25 nm.

Comparative Example 6 In the production of the polyester film of Example 1, the polyetherimide was changed to polyether sulfone. Otherwise, in the same manner as in Example 1, a 6.3 μm-thick polyester film was manufactured to prepare a magnetic tape having a width of 6.3 mm. The characteristics of the obtained polyester film and magnetic tape (recording time: 150 minutes) are shown in Tables 1 and 2. The Ra value on the B side of the polyester film was 20 nm.

Comparative Example 7 In the production of the polyester film of Example 1, the ultrafine silica in the aqueous solution was changed to the ultrafine silica having a particle size of 8 nm. In addition, the concentration of methyl cellulose in the aqueous solution is 0.08
Changed to% by weight. Otherwise, in the same manner as in Example 1, a polyester film having a thickness of 6.3 μm was produced, and a width of 6.
A 35 mm magnetic tape (150 minutes recording time) was created. The characteristics of the obtained polyester film and magnetic tape are shown in Tables 1 and 2. The Ra value on the B side of the polyester film was 20 nm.

Comparative Example 8 In the production of the polyester film of Example 1, the ultrafine silica in the aqueous solution was changed to the ultrafine silica having a particle size of 18 nm. The concentration of methyl cellulose in the aqueous solution should be 0.2.
Changed to 5% by weight. Others are the same as in Example 1,
A polyester film having a thickness of 6.3 μm was manufactured, and a magnetic tape having a width of 6.35 mm (recording time 150 minutes) was prepared. The characteristics of the obtained polyester film and magnetic tape are shown in Tables 1 and 2. In addition, B of polyester film
The Ra value of the surface was 20 nm.

Comparative Example 9 In the production of the polyester film of Example 1, the longitudinal stretching ratio was changed to 4.5 times. Otherwise, in the same manner as in Example 1, a polyester film having a thickness of 6.3 μm was manufactured to prepare a magnetic tape having a width of 6.3 mm. Obtained polyester film and magnetic tape (recording time 150
Min) is shown in Tables 1 and 2. The Ra value on the B side of the polyester film was 22 nm.

Comparative Example 10 In the production of the polyester film of Example 1, the transverse stretching ratio was changed to 4.5. Otherwise, in the same manner as in Example 1, a polyester film having a thickness of 6.3 μm was manufactured to prepare a magnetic tape having a width of 6.3 mm. Obtained polyester film and magnetic tape (recording time 150
Min) is shown in Tables 1 and 2. The Ra value on the B side of the polyester film was 22 nm.

Comparative Example 11 In the production of the polyester film of Example 1, the content of polyetherimide was changed to 3% by weight. Otherwise, in the same manner as in Example 1, a 6.3 μm-thick polyester film was manufactured to prepare a magnetic tape having a width of 6.3 mm. The characteristics of the obtained polyester film and magnetic tape (recording time: 150 minutes) are shown in Tables 1 and 2. The Ra value on the B side of the polyester film was 20 nm.

Comparative Example 12 A polyester film having a thickness of 6.3 mm and a thickness of 6.3 mm was produced in the same manner as in Example 1 except that the polyetherimide was not used in the production of the polyester film of Example 1. I made a magnetic tape. Obtained polyester film and magnetic tape (recording time 150
Min) is shown in Tables 1 and 2. The Ra value on the B side of the polyester film was 19 nm.

[0069]

[Table 1]

[0070]

[Table 2]

As is clear from the results shown in Tables 1 and 2, the DVC tape produced by providing the ferromagnetic metal thin film layer on the surface A on one side of the polyester film of the present invention was recorded with a significantly narrowed track pitch. Even when it was played back, it exhibited excellent recording and playback performance. On the other hand, in the case of using the film other than the present invention, the recording / reproducing performance was inferior because the dropout occurred at the time of reproducing, particularly after reproducing after being left at a high temperature.

[0072]

The magnetic tape manufactured by using the polyester film for magnetic recording medium of the present invention as the base film and providing the ferromagnetic metal thin film layer on the surface A can significantly reduce the track pitch. The DV mini-cassette tape (DVC-SLP tape, recording time of 150 minutes or more) can realize a longer recording time. Therefore, according to the present invention, it is possible to obtain a magnetic tape suitable for the DVC magnetic recording system and capable of further lengthening the recording time, and a polyester film for a magnetic recording medium, which makes it possible.

Continued front page    F-term (reference) 4F100 AA08 AA37 AB01C AB15                       AJ06 AK01B AK41A AK42                       AK49A AK51 AK52 AL05A                       BA02 BA03 BA07 BA10A                       BA10B BA10C DD07B DD07C                       DE01B EH20 EH66 EJ37                       GB41 JG06C JJ03A JL04B                       JM02C YY00B                 5D006 CB01 CB02 CB06 CB07 CB08                       FA00

Claims (8)

[Claims] 1. On one surface of a polyester film,
A film formed by forming a coating containing fine particles having a particle size of 5 to 30 nm and an organic compound, wherein the surface of the coating has fine surface protrusions due to the fine particles, and the number of the fine surface protrusions is 1 million to 100 million pieces / mm ² , and the number of surface protrusions with a height of 50 to 120 nm is 1500 pieces / m.
The number of surface protrusions having a height of m ² or less and a height of 120 nm or more is 90/100 cm ² or less, and the Ra value of the surface of the coating film is 1
A polyester film for a magnetic recording medium, which has a heat shrinkage of 0.5 to 5 nm at 100 ° C. for 30 minutes in both the longitudinal and width directions of 0.5% or less. 2. The polyester film for a magnetic recording medium according to claim 1, wherein the polyester film comprises a blend of polyethylene terephthalate or polyethylene-2,6-naphthalate and a heat resistant polymer. 3. The polyester film for a magnetic recording medium according to claim 2, wherein the heat resistant polymer is a polymer having a glass transition temperature of 450 K or higher. 4. The polyester film for a magnetic recording medium according to claim 3, wherein the heat-resistant polymer is polyimide or polyetherimide. 5. The content of the heat resistant polymer in the blend is 5 to 40% by weight.
5. A polyester film for a magnetic recording medium according to any one of items 4 to 4. 6. The polyester film for a magnetic recording medium according to claim 1, which is used for a magnetic tape of a digital recording system having a track pitch of 7 μm or less. 7. A magnetic recording tape comprising a ferromagnetic metal thin film layer provided on the coating side surface of the polyester film for a magnetic recording medium according to claim 1. 8. A magnetic film in which a ferromagnetic metal thin film layer is provided on the surface of a polyester film having a film containing fine particles having a particle size of 5 to 30 nm and an organic compound formed on one surface thereof. A recording tape, wherein the number of fine surface protrusions on the surface of the ferromagnetic metal thin film layer is 1 million to 100 million /
mm ² , the number of surface protrusions with a height of 50 to 120 nm is 1500 / mm ² or less, the number of surface protrusions with a height of 120 nm or more is 90/100 cm ² or less, and the Ra value of the surface is 1 to 5 nm. The magnetic recording tape is characterized in that the heat shrinkage at 100 ° C. for 30 minutes is 0.5% or less in both the longitudinal direction and the width direction.