JPS6222231A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To assure the good contact state with a rotary head and to stabilize an SN ratio in a short wavelength region by disposing a magnetic recording layer consisting of a thin ferromagnetic metallic film on a high-polymer film and using the high-polymer film of which the hardness continuously changes from the boundary between the high-polymer film and the magnetic recording layer to 1/3. CONSTITUTION:A hardened layer 2, a pulverous particle layer 3, the magnetic recording layer 4 formed by diagonal vapor deposition of Co-Ni-O and a protective lubricating layer 5 are formed on the high-polymer film 1. The hardened layer 2 of which the hardness changes from the surface to 1/3 depth is formed by irradiating 14keV electron beam for 5 seconds at 120muA/cm<2> to the high- polymer film 1 from the front side thereof. The good contact with the rotary head is thereby assured and the reproduction SN ratio in the short wavelength region is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium whose magnetic recording layer is a ferromagnetic metal thin film that can be used for high-density magnetic recording.

Conventional technology The magnetic recording layer that has been widely used in practical use is γ-layer doped with r Fe20s I Co .
Fe2o3. Ferromagnetic metal or alloy fine powder magnetic material such as Cro2 or iron is combined with vinyl chloride/vinyl acetate copolymer,
This is a coated magnetic layer that is dispersed in an organic binder such as a styrene-butadiene copolymer or an epoxy resin, and then coated and dried on a substrate such as a polymer film.

In recent years, with the increasing demand for high-density recording, it has become necessary to use a ferromagnetic metal thin film as a magnetic recording layer, which has the potential to provide an excellent signal-to-noise ratio (hereinafter referred to as S/N) in a high-density region. So-called metal thin film magnetic recording media have attracted attention, and efforts are being made to put them into practical use. [For example, the journal ``IEE Transaction on Magnetics''
Magnetics).

Vow, MAG-10, Mei 2. PP368-373
(1974)].

In particular, in order to take advantage of the high output characteristics in the short wavelength region, many proposals have been made with a focus on improving durability in applications where recording and reproducing are performed by sliding directly on a magnetic head.

For example, improvements in protective films [e.g., JP-A-63-88704, JP-A-59-171-026, etc.] and improvements in base films [JP-A-69-84928, JP-A-59-121631] etc.] have been proposed to improve the friction coefficient and scratch resistance.

Problems to be Solved by the Invention However, with the above configuration, when the thickness of the polymer film becomes thinner and the volume recording density is increased, it becomes difficult to obtain a good contact state with the rotating magnetic head. /N was unstable.

In view of the above-mentioned problems, the present invention provides a magnetic recording medium that ensures good contact with a rotating head and stabilizes reproduction S/N in a short wavelength range.

Means for Solving the Problems In order to solve the above problems, the magnetic recording medium of the present invention comprises:
A magnetic recording layer made of a ferromagnetic metal film is disposed on a polymer film whose hardness changes continuously from the interface between the polymer film and the magnetic recording layer to at least 1/3 of the depth of the polymer film. According to the present invention, the dynamic stiffness of the magnetic recording medium is increased in response to the pressure of the rotating magnetic head, and the entire thickness of the polymer film is increased. This is thought to be because the stiffness, which is said to decrease in proportion to the cube of the thickness due to thinning, does not have to be considered in effect.As a result, a stable contact condition with the head can be obtained. This means that the playback S/N can be stabilized, and because the hardness changes continuously,
Conversely, playback S/ caused by head wear due to contact with the magnetic head.
The N reduction phenomenon is also improved because the sudden impact effect of dynamic pressure is also alleviated.

EXAMPLES Below, magnetic recording media according to examples of the present invention will be described with reference to the drawings.

FIG. 1 is an enlarged sectional view of a magnetic recording medium according to a first embodiment of the present invention. In Figure 1, 1 is a polymer film, 2
is a hardened layer. 3 is a fine particle coating layer, 4 is Co-Ni
-0 is a magnetic recording layer consisting of an obliquely deposited film, and 5 is a protective lubricating layer.

The polymer film 1 is made of polyethylene naphthalate with a thickness of 6 μm and a Young's modulus in the longitudinal direction of 11o.

Ky-/-, but 14KeV from the surface side in the thickness direction
irradiated with an electron beam of 120 μA/d for 6 seconds.

A hardened layer 2 is formed thereon.

The hardened layer means that the radius of the tip is 1o.

100 m 1m1n using μm diamond needle
When measuring the displacement when a load was applied from the film surface, the film of the present invention was 1 oM/sec, and the displacement was 1 oM/sec compared to the blank polyethylene naphthalate film ij 1, 2 m
Since the hardness is based on electron injection, it is predicted that the hardness will be distributed in the depth direction, and by selecting the energy and irradiation amount, the hardness can be continuously distributed up to 1/3 of the depth. It is thought that changes can be made.

If the hardness changes by more than % in the depth direction, the head wear will be large, and if it is less than %, the contact stability will be lost.
A polymeric film having a hardness variation in the range from % to 1/3, preferably from Z to % is preferred.

Since the penetration depth is estimated to be 1.6 μm from the energy of the electrons, it is more likely that the hardened layer has a value closer to 1.6 μm.

Moreover, as Comparative Example A, a polyethylene naphthalate film without a hardened layer was prepared.

These two films were connected by 1 ooom, and fine particles were applied, vapor deposited, and heat treated to form a surface protection lubricant layer.
Magnetic tapes each having a width of 8 cm were produced.

The fine particle coating layer is made of silica fine particles with a diameter of 200 mm and a thickness of 3
The magnetic recording layer was fixed at a density of 100 pieces/(μm)2 with 0-layer epoxy resin, and the magnetic recording layer was 7 x 10 (T
Co-N1(Ni; 2
Coercive force 1200 obtained by depositing 0.2 μm of 5 wt%)
The protective lubricating layer is a thin film of 1×1σ4(Towτ
) was formed using a vacuum evaporation method in a film of 1,1-stinic acid (S
O people).

The recording/reproducing head is C with a gap length of 0.22 μm.

-A signal with a recording wavelength of 0.66 μm was recorded using a B-based amorphous head, and the reproduction S/N was compared. 1. We also compared head wear. The results are shown in Table 1 below.

In addition, a thicker tape, that is, a tape with greater stiffness, was also prepared as comparative tape B. The polymer film used here was a polyethylene terephthalate film with a thickness of 16 μm and a Young's modulus of 7eoKP/-.

Table 1 *1. The average value and stability were measured for 100 arbitrary tape rolls. The environment is 25℃ and 76%RH.
As described above, according to the present invention, the reproduction S/N is 6.
・Despite being as thin as 4 μm, it is equivalent to or better than a tape with a total thickness of 15.4 μm, and because there is less head wear, the S/N decrease due to repeated use is much better than a tape with a total thickness of 16.4 μm. It can be seen that the value is shown.

A second embodiment of the present invention will be described below with reference to FIG. In Figure 2, 6 is a polyamide film with a thickness of 5 μm, and the Young's modulus is 1200 Kp/- in the longitudinal direction and 11
KeV electron beam at 130aA/CIIK.

In addition to the irradiation for 6.5 seconds, irradiation with 105 KeV OAr"i,t7 at 1oμA/i for 1 minute was performed to remove 10% from the surface.
．． The hardened layer 7 was formed up to the range of 6-.

Comparative Example A used a 6 μm polyamide film without a hardened layer, and Comparative Example B used a 13 μm thick polyamide film (Young's modulus: 900 K9/ma).

The fine particle coating layer 8 is made of titania particles with a diameter of 150 particles fixed with a polyimide resin (thickness of 36 particles) at a density of 136 particles/(μm)2, and the base layer 9 is made of titania particles with a thickness of 0 and formed by electron beam evaporation. .03 μm germanium-silicon layer (Go:Si = 88:12 wt%), 1o is a Co-Cr (Cr; 20 wt%) perpendicular magnetization film, and the surface temperature of the holder during formation of this film was 126 °C.
The vapor deposition was carried out by electron beam evaporation, using a vapor flow containing only near-vertical components with an incident angle of 3 degrees or less.

The thickness and perpendicular coercive force of the Co-Cr film are as follows:
μm).

It is 5oo (oe).

The protective film 11 is a perfluorooctanoic acid vapor-deposited film having a thickness of 70 mm formed by a vacuum evaporation method.

Both the Example and the Comparative Example were processed into tapes with a width of 8 mm and a ring-shaped magnetic head (gap length of 0.18 μm).

Recording and reproduction are performed at a recording wavelength of 0.6 μm using a Co-Nb-B amorphous alloy head, and the reproduction S
/N'+ head wear was compared. The results are shown in Table 2 below.

(>1,000 9. White) Table 2 As described above, according to the present invention, although the total thickness is as thin as 5.5 μm, the head It can be seen that the wear is extremely small. In addition, the change in the block error rate, which is one of the indicators of digital recording performance, is small and the value after 500 buses is also good. Error rate is also 2
In contrast, in Comparative Example B, the block error rate increased by 6 to 8 times even though the S/N ratio was good due to the large amount of head wear. The advantages over density digital recording are understood.

Note that the polymer film may also be made of polyethylene terephthalate, polyphenylene sulfide, polyimide, or the like. Furthermore, particle injection is suitable as a means for forming the hardened layer. The fine particle coating layer may be provided as necessary, and is not an essential requirement of the invention (In addition to 5102-TiO, CaCo3
．． In addition to polyester balls, resins can be selected from a wide range of other materials such as polyester, polyamide, urethane, etc.

The magnetic recording layer can be formed by electron beam evaporation, sputtering,
Perpendicular magnetization film formed by wet plating method etc.

In-plane magnetized film made of Co-Cr, Go-Ni
-0, Co-0, Co+Ti, Co-B1. C
o-Mn.

Co-Mg, Co-Ag, Co-Rh, Co-
Ru, Fe-Bi, Co-P, Go-8m
, Go-Mo, Co-W, etc. may be used.

Effects of the Invention As described above, according to the present invention, even a thin tape can be reproduced by S/
It is possible to obtain a magnetic recording medium for high-density magnetic recording that has good N, stable S/N even after repeated use, low head wear, and stable block error rate.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a magnetic recording medium according to a first embodiment of the invention, and FIG. 2 is an enlarged sectional view of a magnetic recording medium according to a second embodiment of the invention. 1.6...Polymer film, 2,7...
- Hardened layer, 4.10... Magnetic recording layer. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure 1...Ki 1 or poly film 2...Stone fAIL, Tatami 4...Ishimori ki 14 Green layer Fig. 2 6..., Polymer film 7...1446 layer 9...Down C1 10 ... 1 is also Naomine iotome

Claims (1)

[Claims] A magnetic recording layer made of a ferromagnetic metal thin film is arranged on a polymer film, and the hardness of the polymer film changes continuously from the interface of the magnetic recording layer to at least 1/3 in the depth direction. magnetic recording media.