JPH11242811A - Magnetic record medium and its support body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital video tape excellent in preservation of data and in running durability by providing a ferromagnetic metallic thin film layer on one side surface of a support body of a magnetic record medium. SOLUTION: An SRa value of one side surface A of a polyester film is 2-5 nm, and an SRz value is 10-40 nm, and a vapor deposition film of aluminum or aluminum oxide of thickness 50-200 nm is formed on the other side surface B. The SRa value of such a one side surface A is preferred to be made 2-4 nm because of remarkably reducing wear due to a video head at a recording/ reproducing time of time ferromagnetic metallic thin film formed by vacuum vapor deposition on the surface A and keeping an output characteristic of a DVC tape excellent, and the SRz value is preferred to be made 20-40 nm because of keeping the durability of the ferromagnetic thin film of the DVC tape in repeated recording/reproducing over many times and remarkably reducing a small dropout.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a support for a magnetic recording medium, and more particularly to a ferromagnetic metal thin film type magnetic recording medium for recording digital data, such as a digital video cassette tape and a data storage tape, which has improved data preservability. The present invention relates to a support for a magnetic recording medium suitable for performing the above.

[0002]

2. Description of the Related Art Consumer digital video tapes put into practical use in 1995 are provided with a metal magnetic thin film of Co on a base film by vacuum evaporation and coating the surface with a diamond-like carbon film. It has good running durability despite its surface property being smoother than that of the (evaporation) tape. Examples of the base film include (1) a polyester film, a polyester film comprising a discontinuous film adhered to at least one surface of the film and fine particles present in the film and on the film surface (for example, Japanese Patent Publication No. Sho 62-30105); (2) A polyester film in which a layer A made of a thermoplastic resin and a layer B made of a thermoplastic resin containing fine particles are laminated, and a polyester film having a lubricant-easy slip layer formed outside the layer B (for example, (JP-B 1-226337), (3) A composite film in which a layer A made of a thermoplastic resin and a layer B made of a thermoplastic resin containing fine particles are laminated (for example, JP-B 1-226338). (4) A polyester film having a discontinuous film mainly composed of a polymer blend containing an easily adhesive resin and fine particles (for example, Japanese Patent Publication No.
No. 57238), and (5) a polyester film in which a continuous thin film having fine projections is formed on one surface and a continuous thin film forming a smooth surface is formed on the other surface (for example, JP-A-6-297662).
And the like, and a base film having a smaller surface roughness for forming a metal magnetic film than a base film for a Hi8ME tape is used.

[0003]

However, the digital surface of such a consumer digital video tape has good running durability with respect to a magnetic head and running guide with respect to a magnetic head, but the data storage performance of the digital video tape is low. It turned out that they were not always satisfied.

That is, as a base film for forming a ferromagnetic metal thin film for a digital video tape by vacuum evaporation, (1) to (5) show good running durability with respect to a magnetic head and running guide with respect to a running guide. The DLC film is provided on the magnetic surface and a protective film is further provided on the magnetic surface to improve the durability of the outer surface of the magnetic surface. It has become clear that the ferromagnetic metal thin film is corroded from the interface side of the base film due to the permeation of moisture in the air from the side.

In the base films of (1) to (5), even if a back coat layer is provided on the running surface side, if the digital video tape is stored for a long time under high temperature and high humidity, the moisture permeating through the base film causes the ferromagnetic metal thin film. Is corroded.

[0006]

In order to solve such a problem, the present invention has the following arrangement.

That is, according to the present invention, one side A of the polyester film has an SRa value of 2 to 5 nm and an SRz value of 10 to 40 nm, and the other side B has a thickness of 50 nm.
A support for a magnetic recording medium, on which a deposited film of aluminum or aluminum oxide having a thickness of about 200 nm is formed, and a magnetic recording medium comprising a ferromagnetic metal thin film layer provided outside one surface A of the support. It is assumed that.

[0008]

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

The above-mentioned polyester may further comprise 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. May be mixed.

S on the surface A on one side of the polyester film
The Ra value is preferably 2 to 5 nm, in order to minimize abrasion by the video head during recording / reproduction of the ferromagnetic metal thin film formed by vacuum deposition on the surface A, and to keep the output characteristics of the DVC tape good. Is 2 to 4 nm, and S
The Rz value is 10 to 40 nm, preferably 20 to 40 nm, in order to maintain the durability of the ferromagnetic thin film of the DVC tape and minimize the small dropout of the DVC tape during repeated recording and reproduction in a digital video tape recorder many times.
４０40 nm.

If the SRa value is less than 2 nm, the ferromagnetic metal thin film layer formed by vacuum evaporation on the surface A is too smooth, and the recording and reproduction in the digital video tape recorder is performed by the video head by the video head. The metal thin film is undesirably worn. When the SRa value exceeds 5 nm, the ferromagnetic metal thin film layer is too rough, and the output characteristics of the video tape deteriorate, which is not preferable.

When the SRz value is less than 10 nm, the ferromagnetic metal thin film layer is too smooth, and the durability of the ferromagnetic thin film of the video tape is reduced by repeated recording and reproduction in a digital video tape recorder many times. Absent. SR
If the z value exceeds 40 nm, the ferromagnetic metal thin film layer becomes too rough, and the number of small DOs on the video tape increases, which is not preferable.

The polyester film surface A has an average particle size of preferably 5 to 30 nm, more preferably 8 to 30 nm.
It is desirable that a coating layer made of an organic compound containing 0.5 nm to 12.0% by weight, more preferably 0.6 to 10.0% by weight of fine particles of nm is formed. Fine particles include silica, calcium carbonate, alumina, polyacrylic acid spheres, polystyrene spheres, and organic compounds such as polyvinyl alcohol, tragacanth rubber, casein, gelatin, cellulose derivatives, water-soluble polyesters, and polar polymers such as polyurethanes. Can be used, but is not limited thereto.

In order to further increase the durability of the magnetic layer,
The average particle size in the polyester layer forming the surface A is preferably 30 to 150 nm, more preferably 40 to 100 nm.
nm fine particles, preferably 0.01-1.0% by weight,
More preferably, it is contained in an amount of 0.02 to 0.8% by weight to have surface projections on surface A.

On one surface B of the polyester film, a deposited film of aluminum or aluminum oxide having a thickness of preferably 50 to 200 nm, more preferably 50 to 170 nm is formed. The vapor deposition of aluminum or aluminum oxide can make it difficult for moisture in the air to pass through the base film.
If the thickness of the deposited film of aluminum or aluminum oxide is less than 50 nm, the amount of permeation of moisture may increase, and the thickness of the ferromagnetic metal thin film layer provided outside the one surface A of the present support from the running surface side may be reduced. Corrosion to moisture may be reduced. If the thickness of the deposited film of aluminum or aluminum oxide exceeds 200 nm, the deposited film tends to be too thick and is easily peeled from the present support, which is not preferable.

On one surface B of the polyester film, surface projections are formed by fine particles having an average particle diameter of preferably 100 to 500 nm existing in the polyester film. Examples of the fine particles include, but are not limited to, inorganic compound particles such as silica, alumina, calcium carbonate, polystyrene spheres, and aluminum silicate particles, and organic compound particles. SRa of one side surface B of this support
The value is such that when the polyester film is formed and then slit into a predetermined width, a product having a good winding shape can be easily collected, and the surface A on one side of the polyester film can be obtained.
After the ferromagnetic thin film is provided thereon, it is preferable that the thickness of the ferromagnetic thin film layer be reduced to 8 to 20 in order to minimize the transfer of the roughness of one surface B due to the roll-shaped winding and the occurrence of undulating deformation in the ferromagnetic thin film layer.
nm, more preferably 10 to 18 nm. SR
After the polyester film is formed, the z-value is maintained in a good roll form after slitting the polyester film, and after the ferromagnetic thin film is provided on one surface A of the polyester film, the roll-shaped winding is performed. In order to minimize the transfer of the roughness of the surface B on one side and the occurrence of undulating deformation in the ferromagnetic thin film layer, it is preferably 100 to 500 n.
m, more preferably 140 to 360 nm. When the average particle diameter of the fine particles is less than 100 nm, the surface B of the present support is likely to be smooth, and the friction coefficient of the film is likely to be large when a ferromagnetic metal is vacuum-deposited on the surface A of the present support, Vacuum deposition may not be possible, which is not preferable. When the average particle diameter of the fine particles exceeds 500 nm, the surface B on one side of the support tends to be insufficiently adhered to the cooling can when the ferromagnetic metal is vacuum-deposited, so that the support is difficult to cool and the polyester film loses heat. It may happen, which is not preferable.

As long as the above-mentioned SRa and SRz values of the surface B are satisfied, the surface protrusions of fine particles having an average particle diameter of 500 to 1000 nm existing in the polyester film may be slightly used on one side surface B. Also 100nm
Surface projections of fine particles in which less than a few particles are aggregated may be used together.

The polyester film of the present invention has a thickness of 7 μm.
m is preferable, and the thickness is more preferably 3.5 to 3.5.
6.9 μm is desirable.

The magnetic recording medium of the present invention has a surface A of the support of the present invention.
(If a coating layer is formed on the surface A, the coating layer is provided). A ferromagnetic metal thin film layer formed by vacuum deposition is provided on the coating layer. Although what is used is not particularly limited, one made of a ferromagnetic material of iron, cobalt, nickel, or an alloy thereof is preferable. Metal thin film layer thickness is 100-300n
m is preferred.

The magnetic recording medium of the present invention is characterized in that a back coat layer formed by applying a solution containing solid fine particles and a binder and, if necessary, various additives is provided on the surface B. However, solid fine particles, binder,
Known additives can be used and are not particularly limited. The thickness of the back coat layer is about 0.3 to 1.5 μm.

Next, an example of the production method of the present invention will be described.

[0022] The polyester film of the present invention can be used in an ordinary plastic film production process consisting of melting, molding, biaxial stretching and heat setting, by using a co-extrusion technique to remove the contained particles as much as possible with the raw material for the layer A. Particle size is 1
An A / B laminated film using the raw material for the layer B containing 0.05 to 1.5% by weight of particles having a particle size of 00 to 500 nm is extruded, and 2.7 to 3.degree. 2 times,
It can be manufactured by stretching 3.5 to 7.0 times and heat setting at a temperature of 180 to 220 ° C.

On the side A of the smooth polyester film stretched in one direction, fine particles having an average particle size of 5 to 30 nm, preferably 8 to 30 nm are contained in an amount of 0.5 to 12.0% by weight, preferably 0.1 to 1% by weight. It is preferable to form a coating layer on the surface A by applying a coating liquid composed of an organic compound containing 6 to 10.0% by weight.

The layer A may contain fine particles in order to further increase the durability of the magnetic tape by the magnetic head.

The SRa and SRz of the surface A can be adjusted by adjusting the fine particles and components in the coating layer formed on the surface A and the fine particles inside the A layer.

Aluminum oxide is vacuum-deposited on one surface B of the polyester film, and oxygen is introduced at the time of vacuum deposition so that aluminum oxide has a thickness of 5 mm.
The support of the present invention can be prepared by providing the support at 0 to 200 nm.

The support of the present invention is preferably used as a support for a magnetic recording medium, particularly when used for digital video tape applications, because excellent results can be obtained. It is also preferable that excellent results can be obtained even when used for data storage tape applications.

In the magnetic tape of the present invention, a ferromagnetic metal thin film of Co or the like is formed on one surface A of the support of the present invention to a thickness of 100 to 300 nm by vacuum evaporation, and a film of about 10 nm thickness is formed on the metal thin film. The back coat layer is formed by coating a diamond-like carbon film, further performing a lubricant treatment thereon, and applying a solution containing one or more solid fine particles and a binder, and various additives as necessary. And create it.

[0029]

EXAMPLE The measuring method used in this example is shown below.

(1) SRa and SRz values Optical stylus type (critical angle focus error detection system) manufactured by Kosaka Laboratory
Was measured using a three-dimensional roughness meter (ET-30HK).

SRa value: center line average surface roughness corresponding to the center line average roughness (Ra) specified in JIS B0601.

SRz value Ten-point average surface roughness corresponding to ten-point average roughness (Rz) specified in JIS B 0601.
Enter the distance between the average of the highest to fifth peak elevations and the average of the deepest to fifth valley bottoms, using the average surface of the part extracted by the reference area from the roughness surface as the reference surface. What was converted.

The test piece was subjected to Al evaporation on the measurement surface.

The measurement direction was the width direction, the cutoff value was 0.08 mm, the measurement length was 0.1 to 0.25 mm, the feed pitch was 0.2 μm, the measurement speed was 20 μm / s, and the number of measurement was 100. . The unit was nm.

(2) The evaluation of the characteristics of the magnetic tape (DVC tape) of the present invention in which a ferromagnetic thin film is provided on the film of the present invention is as follows.
Recording and playback were performed in a quiet room using the LP mode of a commercially available digital video tape recorder with a camera, and the number of dropouts (DO) was determined. DO
The number was measured by recording the produced DVC tape with a commercially available digital video tape recorder with a built-in camera, playing it back for one minute, and counting the number of block mosaics appearing on the screen.

The number of DOs is room temperature and normal humidity (25 ° C., 60% R
In H), the initial characteristics after the tape production were first examined. The number of DO after leaving the tape at high temperature and high humidity (60 ° C., 80% RH) for 7 days, the initial characteristics after leaving the tape at normal temperature and normal humidity (25 ° C., 60% RH), and 100 runs of the left tape The number of DOs after the repetition was measured. The storage performance of the data was evaluated by leaving it under high temperature and high humidity.

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

Example 1 Material A containing polyethylene terephthalate substantially free of inert particles and 0.03% by weight of silica having an average particle size of 60 nm, polyethylene terephthalate substantially free of inert particles and average particle Raw material B containing 0.50% by weight of aluminum silicate having a diameter of 190 nm was co-extruded at a thickness ratio of 5: 1 and roll-extended to 110
The film was longitudinally stretched at 3.0 ° C. to 3.0 times.

In the step after the longitudinal stretching, the following aqueous solution was applied to the outside of the surface A on one side.

Outer surface A: 0.10% by weight of methylcellulose 0.30% by weight of water-soluble polyester (70% by mole of terephthalic acid, 30% by mole of 5-sodium sulfoisophthalic acid: 1: 1 copolymer of acid component and ethylene glycol) Polymer) Aminoethylsilane coupling agent 0.01% by weight Ultrafine silica having an average particle size of 12 nm 0.03% by weight Solid content concentration 20 mg / m2 Then, it is stretched 4.2 times in a transverse direction at 102 ° C. by a stenter. Then, it was heat-treated at 215 ° C., wound around an intermediate spool, slit into a small width with a slitter, and wound up in a roll shape on a cylindrical core to obtain a roll-shaped polyester film having a thickness of 6.3 μm.

A support having a thickness of 100 nm was formed of aluminum on the polyester surface B by vacuum evaporation.

A cobalt-oxygen thin film having a thickness of 1100 nm was formed on the surface A of the support by vacuum evaporation. 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. Subsequently, a back coat layer made of carbon black, polyurethane, and silicone was provided to a thickness of 500 nm, slit to a width of 6.35 mm by a slitter, and wound around a reel to produce a magnetic tape (DVC video tape, LP mode).

Table 1 shows the properties of the obtained support and magnetic tape. The SR of side B of the composite polyester film
The a value and SRz value were 14,225 nm.

Example 2 In the production of the support of Example 1, a small amount of oxygen was injected and aluminum oxide was deposited to a thickness of 100 nm during vacuum deposition of aluminum.
A magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1 except that the magnetic tape was formed to have a thickness of. Table 1 shows the properties of the obtained support and magnetic tape.

The S on the B side of the composite polyester film
Ra value and SRz value were 14,225 nm.

Example 3 In the production of the base film of Example 1, the polyethylene terephthalate was changed to polyethylene-2,6-naphthalate, the content of aluminum silicate in the raw material B was set to 1.1% by weight, and the longitudinal stretching temperature was changed. 4. Magnification at 135 ° C.
0 times, the transverse stretching temperature and the magnification were 135 ° C and 6.5 times, and the heat treatment was changed at 200 ° C.
A composite polyester film roll having a thickness of 4.2 μm was obtained. Otherwise, a magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1. Table 1 shows the properties of the obtained support and magnetic tape.

The S on the B side of the composite polyester film
Ra value and SRz value were 14,225 nm.

Comparative Example 1 In the production of the base film of Example 1, the solid content concentration in the application of the aqueous solution was 10 mg / m 2. Others are Example 1.
A 6.3 μm-thick composite polyester film roll and a support were obtained in the same manner as described above to prepare a magnetic tape having a width of 6.35 mm. Table 1 shows the properties of the obtained support and magnetic tape.
Shown in

The S on the B side of the composite polyester film
Ra value and SRz value were 14,225 nm.

Comparative Example 2 In the production of the base film of Example 1, the concentration of methylcellulose in the aqueous coating solution was set to 0.15% by weight. Otherwise in the same manner as in Example 1, a composite polyester film roll having a thickness of 6.3 μm and a support were obtained, and a magnetic tape having a width of 6.35 mm was prepared. Table 1 shows the properties of the obtained support and magnetic tape.

The S on the B side of the composite polyester film
Ra value and SRz value were 14,225 nm.

Comparative Example 3 In the production of the base film of Example 1, the concentration of the ultrafine silica in the aqueous coating solution was set to 0.02% by weight. Otherwise in the same manner as in Example 1, a composite polyester film roll having a thickness of 6.3 μm and a support were obtained, and a magnetic tape having a width of 6.35 mm was prepared. Table 1 shows the properties of the obtained support and magnetic tape.

The S on the B side of the composite polyester film
Ra value and SRz value were 14,225 nm.

Comparative Example 4 In the production of the base film of Example 1, the average particle diameter of silica contained in the raw material A was changed to 90 nm. Otherwise in the same manner as in Example 1, a composite polyester film roll having a thickness of 6.3 μm and a support were obtained, and a magnetic tape having a width of 6.35 mm was prepared. Table 1 shows the properties of the obtained support and magnetic tape.

The S on the B side of the composite polyester film
Ra value and SRz value were 14,225 nm.

Comparative Example 5 A support was obtained in the same manner as in Example 1, except that the thickness of the vapor-deposited aluminum film on the polyester surface B was 30 nm. Otherwise, a magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1. Table 1 shows the properties of the obtained support and magnetic tape.

The S on the B side of the composite polyester film
Ra value and SRz value were 14,225 nm. Observation of the magnetic tape after storage at high temperature and high humidity revealed that the magnetic layer surface had stains visible to the naked eye on the entire surface.

Comparative Example 6 A support was obtained in the same manner as in Example 1 except that the thickness of the vapor-deposited aluminum film on the polyester surface B was 300 nm. Otherwise, a magnetic tape having a width of 6.35 mm was prepared in the same manner as in Example 1. Table 1 shows the properties of the obtained support and magnetic tape.

The S on the B side of the composite polyester film
Ra value and SRz value were 14,225 nm. After storage at high temperature and high humidity, a part of the back coat layer of the magnetic tape that was run 100 times was visually observed.

Comparative Example 7 In the production of the base film of Example 2, the formation of aluminum oxide on the polyester surface B was stopped, and the polyester film itself was used as a support. Others are Example 1.
A magnetic tape having a width of 6.35 mm was prepared in the same manner as described above.
Table 1 shows the properties of the obtained support and magnetic tape.

The S on the B side of the composite polyester film
Ra value and SRz value were 14,225 nm. Observation of the magnetic tape after storage at high temperature and high humidity revealed that the magnetic layer surface had stains visible to the naked eye on the entire surface.

[0062]

[Table 1]

[0063]

As is clear from the characteristics shown in Table 1, the magnetic tape in which the ferromagnetic metal thin film layer is provided on one surface A of the support of the present invention has a small number of DOs and is excellent in data storage performance.
It can be a digital video tape with excellent running durability.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08G 63/189 C08G 63/189 C08L 67/02 C08L 67/02

Claims (4)

[Claims] 1. One surface A of one side of a polyester film
Wherein the SRa value is 2 to 5 nm and the SRz value is 10 to 40 nm, and a deposited film of aluminum or aluminum oxide having a thickness of 50 to 200 nm is formed on one surface B of the other side of the magnetic recording medium. Support. 2. A support for a magnetic recording medium according to claim 1, wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate. 3. The support for a magnetic recording medium according to claim 1, wherein the support is used for a magnetic recording medium of a digital recording system. 4. A magnetic recording medium comprising a polyester film according to claim 1 and a ferromagnetic metal thin film layer provided outside one surface A of the polyester film.