JPH0827932B2 - Magnetic recording media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having improved corrosion resistance and running characteristics, low noise, and high reliability.

[Conventional technology]

Fe, Co, Ni, or an alloy containing them as a main component, or an oxide thin film thereof is formed by a method such as a vacuum deposition method, a sputtering method, an ion plating method, or a plating method on a polyester film, a polyimide film, or the like. A ferromagnetic thin film type magnetic recording medium formed on a substrate made of a polymer film or a non-magnetic metal thin plate can dramatically improve the recording density as compared with the conventional coating type magnetic recording medium. , For this densification,
It is necessary to reduce the gap of the magnetic head and also smooth the surface of the magnetic recording medium to reduce the spacing loss as much as possible. However, if the surface is excessively flattened, the head touch and the running property will be hindered, and it becomes necessary to control the fine shape of the surface. In order to solve this problem and obtain stable running characteristics, for example, a particulate projection layer having a predetermined size and number is formed on the substrate by using fine particles such as silicon, carbon, and metal on the substrate. As a base layer, a ferromagnetic thin film layer is formed thereon to form fine projections on the surface of the ferromagnetic thin film layer.
59-48825, 59-48826 and 59-65928). However, although the running characteristics of the magnetic recording medium are stabilized by such a method, defects (voids) are generated in the ferromagnetic thin film layer due to the particle-like protrusions of the underlayer, which deteriorates the corrosion resistance of the magnetic layer. There was a problem. Further, there is a drawback that noise is increased as a magnetic recording medium because a considerably large unevenness is formed on the surface of the magnetic layer.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and drawbacks of the prior art, and to provide a magnetic recording medium having excellent running property and corrosion resistance, low noise, high performance and high reliability.

[Means for solving problems]

The object of the present invention is to determine the surface average roughness (Ra) of the substrate,
Ra ≦ 0.01 μm and maximum surface roughness (Rmax) is Rmax
By setting ≦ 0.05 μm, defects (voids) in the ferromagnetic thin film layer formed on the substrate can be reduced, corrosion resistance can be improved, and the spacing between the ferromagnetic thin film layer and the magnetic head can be changed. This can be achieved by reducing the noise of the magnetic recording medium by making the size smaller, and by further forming the particle-shaped projections having fine particles as nuclei on the surface of the ferromagnetic thin film layer to improve the running property.

As the substrate used for the magnetic recording medium of the present invention, plastic films such as polyester, polyimide, polyamide, polyvinyl chloride, and polycarbonate, and composite films in which carbon fiber, Cu, etc. are mixed in these plastic films, Cu, Zu Any of those conventionally used such as a non-magnetic metal film, an aluminum plate and a glass plate are preferably used. The surface average roughness (Ra) of these substrates is 0.01
Exceeds μm or maximum surface roughness (Rmax) is 0.05 μm
When it exceeds, the crevice corrosion due to defects in the ferromagnetic thin film layer is significantly deteriorated, and the roughness of the surface of the ferromagnetic thin film layer is increased, which causes an increase in noise.

In the magnetic recording medium of the present invention, on the ferromagnetic thin film layer,
The fine particles used for forming the particulate projections having the fine particles as the nucleus include metals such as Fe, Co, Ni, Mg, Mn, Al, Cr, and Ti, or oxides thereof, or hydroxides thereof. Examples thereof include fine particles made of graphite, silica, silicon carbide, molybdenum disulfide, barium carbonate, barium sulfate, and the like. In addition to these, fine particles of an inorganic compound or fine particles of an organic polymer compound that do not deteriorate magnetic properties are also preferable. Can be used for A means for forming particulate projections on a ferromagnetic thin film using these fine particles is to form a paint by adding a suitable amount of the fine particles, a resin component as a binder, and an organic solvent, and form a coating on the ferromagnetic thin film. It is performed by applying. And
As the binder, a vinyl chloride-vinyl acetate copolymer,
Conventionally widely used binder resins such as polyvinyl butyral resin, fibrin resin, polyurethane resin, and isocyanate compound are widely used, and as the organic solvent, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, ethyl acetate, tetrahydrofuran,
Conventionally widely used organic solvents such as dimethylformamide can be used alone or in combination of two or more.

If the height of the particle-shaped projections formed by cores of fine particles formed on the ferromagnetic thin film is less than 30Å, the running performance will not be stable, and
When it exceeds 500Å, the spacing becomes large and the output is lowered, so the range of 30 to 500Å is preferable. Also,
If the number of particulate projections is less than 1000 / mm ^2, it may cause noise during reproduction by the magnetic head and no improvement in running property is observed, and the number exceeds 1 million / mm ² . Therefore, the number of the particulate projections formed on the ferromagnetic thin film layer is preferably in the range of 1000 / mm ^{2 to} 1 million / mm ² .

As the material for forming the ferromagnetic thin film layer in the magnetic recording medium of the present invention, Co, Fe, elemental metals such as Ni, Co-Ni, Co-
Alloys such as Cr, Fe-Co, Fe-Co-Cr, Co-Pt, Co-Ti,
Alternatively, oxides of these metals and alloys, and Co-
P, Co-Ni-P, Fe-Si, Fe-Rh, Fe-V, Fe-Ti, Co
-B, Co-Si, Co-V, Co-Y, Co-Sm, Co-Mn, Co-
Ni-B, Co-Ni-Cr, Co-Ni-Ag, Co-Ni-Pd, Co-Ni
-Zn, Co-Cu, Co-Ni-Cu, Co-W, Co-Ni-W, Co-
Ferromagnetic materials such as Mn-P, Co-Sm-Cu, Co-Ni-Zn-P, and Co-V-Cr can be used, and the ferromagnetic metal thin film layer made of these ferromagnetic materials is vacuum-deposited. Method, sputtering method, ion plating method, ion beam deposition method, chemical vapor deposition method, electroplating method or electroless plating method.

[Example] An example of the present invention will be described below in more detail.

Example 1 Commercially available polyethylene terephthalate film (thickness 9
μm, surface roughness Ra = 0.003 μm, Rmax = 0.01 μm) while introducing oxygen gas at a rate of 100 ml / min by a vacuum oblique incident vapor deposition method in an atmosphere of 8 × 10 ⁻⁵ Torr and Co− 20
A 1500 Å thick ferromagnetic thin film layer made of at% Ni was formed.
Then, nickel fine particles are mixed with a binder VAGH (manufactured by UCC, USA, vinyl chloride-vinyl acetate-vinyl alcohol copolymer) and methyl ethyl ketone which is a solvent, and continuously coated and dried on the ferromagnetic thin film layer to obtain nickel. About 100,000 protrusions with a height of 50Å centered on fine particles were formed / mm ² . After that, it was cut into a predetermined width to produce a magnetic tape having a sectional structure shown in FIG.

(Example 2) In the same manner as in Example 1 except that the nickel fine particles in Example 1 were used in place of the iron oxide fine particles, about 500,000 particle-shaped protrusions having a height of 200Å with the iron oxide fine particles as the cores were used. / Mm ² formed. Then, it was cut into a predetermined width to produce a magnetic tape.

(Example 3) In the same manner as in Example 1 except that silica fine particles were used in place of the nickel fine particles in Example 1, about 100,000 particle-shaped protrusions having a height of 150Å and having silica fine particles as a nucleus were formed. ² formed. Then, it was cut into a predetermined width to produce a magnetic tape.

(Example 4) In the same manner as in Example 1 except that the nickel fine particles in Example 1 were used in place of the nickel fine particles, approximately 350 Å-height particulate projections having graphite fine particles as cores were used.
10,000 pieces / mm ^{2 were} formed. Then, it was cut into a predetermined width to produce a magnetic tape.

The same procedure as Comparative Example 1 Example 1 was polyethylene terephthalate film on the Co particles ten thousand to about 10 particulate high protrusions 50Å to as the core pieces / mm ² to form a ferromagnetic thin film thereon Layers were formed. Then, it was cut into a predetermined width to produce a magnetic tape.

(Comparative Example 2) Instead of the Co fine particles in Comparative Example 1, about 50,000 particulate projections having a height of 350 Å centered on graphite fine particles / mm ^{2 were used.}
A magnetic tape was produced in the same manner as in Comparative Example 1 except that the magnetic tape was formed.

Comparative Example 3 A magnetic tape was produced in the same manner as in Example 1 except that the formation of the particulate projections in Example 1 was omitted.

(Comparative Example 4) Instead of the polyethylene terephthalate having the surface roughness in Example 1, the surface roughness Ra = 0.01 μm and Rmax = 0.1 μm.
Polyethylene terephthalate film (thickness 9 μm)
A magnetic tape was produced in the same manner as in Example 1 except that was used.

For each of the magnetic tapes produced in the above-mentioned examples and comparative examples, using a prototype VTR deck, 40 ° C, 80% R
Under the H environment, the squealing condition and the still life of the rotary head cylinder were measured, and the noise when the 5MHz signal was recorded and reproduced was measured. The noise of the magnetic tape obtained in Comparative Example 1 was designated as ObB. It was evaluated by the comparative value based on this. In addition, in the environment of SO ₂ = 0.1ppm, 35 ℃, 75% RH, 10h
r Corrosion resistance was evaluated by observing the corrosion resistance on the surface of the magnetic tape when exposed by an optical microscope. The result is first
It is summarized in the table.

As is clear from Table 1, all of the magnetic tapes obtained in the examples of the present invention have good running property and corrosion resistance, and further have excellent magnetic characteristics that noise is not increased.

〔The invention's effect〕

As described in detail above, a magnetic recording medium in which a ferromagnetic thin film layer is formed on a substrate having a smooth surface roughness according to the present invention, and a particulate projection layer is further provided on the ferromagnetic thin film layer,
It has good corrosion resistance and runnability, and has low noise.
A highly reliable magnetic recording medium having excellent durability and magnetic properties can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a magnetic tape according to an embodiment of the present invention. 1 ... Substrate, 2 ... Ferromagnetic thin film layer 3 ... Fine particles, 4 ... Binder 5 ... Particulate projection layer

Claims (5)

[Claims] 1. A magnetic recording medium comprising a magnetic recording layer made of a ferromagnetic thin film formed on a non-magnetic substrate, and a particulate projection layer having fine particles as nuclei provided on the magnetic recording layer. 2. The height of the particulate projections in the particulate projection layer is
30 ~ 500Å and the number of particulate projections is 1000 ~ 100,000
The magnetic recording medium according to claim 1, wherein the number is 1 / mm ² . 3. The surface roughness of the non-magnetic substrate is the average surface roughness Ra.
Is 0.01 μm or less, and the maximum surface roughness Rmax is 0.05 μm or less. 3. The magnetic recording medium according to claim 1, wherein 4. Fine particles are Fe, Co, Ni, Mg, Mn, Al, Cr or Ti, or oxides thereof, or hydroxides thereof, graphite, silica, silicon carbide, molybdenum disulfide, barium carbonate. At least one selected from
The magnetic recording medium according to any one of claims 1 to 3, wherein the magnetic recording medium is fine particles composed of seeds. 5. The particulate projection layer according to any one of claims 1 to 4, wherein the particulate projection layer is composed of fine particles and a binder containing a resin as a main component. Magnetic recording medium.