JPH0814888B2 - Magnetic recording media - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a magnetic recording medium having a ferromagnetic metal thin film as a high-density magnetic recording layer.

2. Description of the Related Art In recent years, as a high-density magnetic recording layer, a ferromagnetic metal thin film such as a Co—Ni oblique deposition film or a Co—Cr sputtered film that can be magnetized in the vertical direction has been studied for practical use.

In particular, the perpendicular magnetic recording system has been attracting attention as an important technology for high density recording in the future [foreign papers; IE Transactions on Magnetics (IE
EE TRANSACTIONS ON MAGNETICS) vol.MGA-13, No.5 PP
1272-1277 (1977)].

In perpendicular recording, since an antiparallel magnetization transition perpendicular to the medium surface is formed, the magnetization transition becomes extremely narrow and high-density recording is possible. It can be said that the key is to obtain a medium with a large signal output-to-noise ratio (hereinafter referred to as C / N) that is indispensable for use on a mass production scale [Applied Magnetic Seminar, "Perpendicular Magnetic Recording Method" (60 December 2012)].

At present, from the viewpoint of electromagnetic conversion, it was obtained by the sputtering method.
The Co-Cr film is the most excellent as a perpendicular magnetic film, and various protective films are placed on this magnetic recording layer to improve durability [eg, applied magnetic seminar, "perpendicular magnetic recording method"]. "Pages 67-76 (1985)].

For example, JP-A-57-116771 discloses a method of sputtering a polymer having an imide group to form a protective film on a magnetic recording layer, and JP-A-60-126627 discloses a hard carbon. A method of laminating a layer and a fluorine-containing lubricating oil layer is shown. A large number of in-plane magnetized films have also been proposed and disclosed for vacuum-deposited films, plasma-polymerized films, etc. [eg, JP-A-61-151837, JP-A-61-16026, and JP-A-58-6042].
No. 7].

Problems to be Solved by the Invention However, in the above-mentioned configuration, in order to ensure sufficient durability, the thickness of the protective film becomes as large as 300Å to 500Å,
When the recording wavelength is 0.5 μm or less, there is a problem that C / N is lowered by a few dB space loss, and improvement is desired.

The present invention has been made in view of the above circumstances, and provides a magnetic recording medium suitable for perpendicular magnetic recording with improved space loss.

Means for Solving the Problems In order to solve the above-mentioned problems, the magnetic recording medium of the present invention comprises an undercoat layer obliquely deposited on the fine particle coating layer, and a perpendicular magnetization film on the underlayer. is there.

With the magnetic recording medium of the present invention having the above-described structure, the underlayer forms a sharp projection shape due to the shadowing effect of the fine particles, and the perpendicular magnetization film formed thereon also has a projection shape close to this. Since the contact area is reduced and the cleaning effect on the head surface is improved, the durability of the perpendicular magnetization film itself is improved. Therefore, the thickness of the protective film is set to a thickness at which the space loss can be ignored. Therefore, a good C / N can be given even in short wavelength recording / reproducing.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an enlarged sectional view of a magnetic tape according to the first embodiment of the present invention. In FIG. 1, 1 is a polymer film made of an aromatic polyamide film having a thickness of 10 μm, and 2 is an average particle size.
The silica fine 150Å polyimide resin, average 10 ⁹ / c
This is a fine particle coating layer with m ² dispersed and fixed. 3 is 80 with a diameter of 50 cm
Titanium was deposited along the rotating drum kept at ℃ at 300Å and the minimum incident angle was 53 degrees.
0.14μm perpendicular magnetization film formed by electron beam evaporation of Co-Cr (Cr20wt%) along the rotating drum kept at 160 ° C within an incident angle of 10 degrees, and 5 was formed by vacuum evaporation method. did
A lubricating protective film made of 75 Å stearic acid, and 6 is a 0.5 μm back coat layer containing carbon and calcium carbide in a ratio of 1: 1 to 20% by weight with respect to the polyurethane resin.
The 8 mm wide magnetic tape having such a structure was evaluated by modifying an 8 mm video deck.

As a comparative example, one in which titanium was not deposited was prepared.
Recording was performed at a recording wavelength of 0.45 μm, and C / N was compared in each environment. The head used was a ferrite head with a gap length of 0.14 μm, and relative comparison was performed with the initial C / N at 23 ° C. and 55% RH set to 0 (dB). When it is repeatedly regenerated, at 23 ℃ 55% RH
At 130 passes, the example improved the C / N to +1.1 (dB) due to familiarity, while the comparative example decreased to -2.4 (dB). At 40 [deg.] C. and 5% RH, the value was -1.1 (dB) in 160 passes in the example, whereas it was -4.9 (dB) in the comparative example.

Further, the C / N of the product of the present invention was stable for 30 minutes under the above-mentioned two environmental conditions even in still reproduction, but in the comparative example, the noise started to increase from 10 minutes and decreased by 3 (dB) in 22 minutes. .

FIG. 2 is an enlarged sectional view of a magnetic disk according to the second embodiment of the present invention. In FIG. 2, 7 is a polymer film made of a polyethylene terephthalate film having a thickness of 26 μm, 8 is a fine particle coating layer in which carbon fine particles having an average particle diameter of 180 Å are polyester resin and are dispersed and fixed on an average of 2 × 10 ⁹ particles / cm ² .
9 is Cr along with the rotating drum kept at 80 ° C with a diameter of 50 cm.
Of 400 Å was obliquely vapor-deposited at a minimum incident angle of 50 degrees, and 10 was 13.56 (MH) along a rotating drum with a diameter of 50 cm and a temperature of 80 ° C.
z) 2.15 (KW) 0.16 formed by high frequency sputtering method
μm Co-Cr (Cr20.6wt%) perpendicular magnetic film, 11 is a lubrication protective film consisting of 85Å perchlorooctanoic acid vapor deposition film.

A 3.5-inch floppy disk with this structure is
Along with the comparative example manufactured without oblique deposition, the gap length is 0.15
Recording was performed with a ferrite head of μm, and C / N was evaluated. 40
At ℃ 30% RH, the example was stable within 1 (dB) even at the time of 7.9 million passes, but the comparative example was 3 (dB) at 4.3 million passes, C / N
Has deteriorated.

Although aromatic polyamide and polyethylene terephthalate are used as the polymer film in the above-described examples, polysulfone, polyphenylene sulfide, polyimide or the like may be used instead.

The fine particle coating layer is made of CaCO ₃ , BaSO in addition to silica and carbon.
₄ , TiO ₂ , CaO, Al ₂ O ₃ , polyester spheres, etc. are used.
The size is 100 Å ~ 200 Å and the density is 5 because of the balance between the cleaning effect of the head surface due to the protrusions and the output reduction
The range of × 10 ⁸ pieces / cm ^{2 to} 5 × 10 ⁹ pieces / cm ² is desirable.

In addition to Ti, Cr, permalloy may be used for oblique vapor deposition, and permalloy may be used, but Mo, W, Ta, etc. are not particularly limited, but Ti, Cr, Mo, etc. that help the orientation of Co-Cr are preferable.

Perpendicular magnetic films are Co-Cr, Co-Ti, Co-Ta, Co-Mo, Co-W,
Co-Cr-Nb, Co-Ni-Mn-P, etc. may be used.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to obtain an excellent effect that a magnetic recording medium having sufficient durability can be obtained even with a protective film having a film thickness of 100 Å or less, which does not affect the space loss.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of a magnetic tape according to the first embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a magnetic disk according to the second embodiment of the present invention. 1,7 ... Polymer film, 2,8 ... Particle coating layer, 3,9 ...
… Diagonal evaporation base layer, 4,10 …… Perpendicular magnetization film.

Claims (1)

[Claims] 1. A magnetic recording medium comprising an undercoat layer obliquely deposited on a fine particle coating layer, and a perpendicular magnetization film formed on the underlayer.