JPH02105332A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To increase reproduced output and recording density and to facilitate the production of a desired low-coercive force layer by providing the low- coercive force layer to the lower layer part of a perpendicular magnetic anisotropy film and providing a high-coercive force layer to the upper layer part. CONSTITUTION:Electric discharge is generated in gaseous Ar contg. a small amt. of an additive gas and the film having the low coercive force in a perpendicular direction is formed in an initial period at the time of forming the perpendicular anisotropy film by a sputtering method on a base film 3. The discharge is generated only in the gaseous Ar and the film having the high coercive force in the perpendicular direction is formed. The magnetic recording medium which is lower in coercive force in the lower layer part than in the upper layer part is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing magnetic recording media such as magnetic tapes and magnetic disks.

[Prior Art] In the area of magnetic recording technology, in recent years, perpendicular magnetic recording has been proposed as a high-density recording technology that exceeds the longitudinal magnetic recording that has been put into practical use, and research and development has been carried out vigorously. ing.

In order to realize this perpendicular magnetic recording, the magnetic recording medium must stably have magnetization recorded in a direction perpendicular to the surface of the magnetic film formed on the base material. Therefore, in order to maintain stable magnetization, the magnetic recording medium must have high perpendicular magnetic anisotropy and must have as high a coercive force in the perpendicular direction as possible.

[Explanation or Problem to be Solved] On the other hand, the intensity of the recording magnetic field generated by the magnetic head decreases from the surface of the magnetic recording medium in the direction of the film thickness.

Therefore, when the perpendicular coercive force varies in the film thickness direction as in conventional magnetic recording media, the reproduction output increases as the coercive force increases, but reaches a maximum value at a certain coercive force. Then there is a reduction in covering (metal surface technology, p. 28-37).
．． VOl, 35°1984). This is because, as mentioned above, the strength of the recording magnetic field generated by the magnetic head decreases from the surface of the magnetic recording medium in the film thickness direction, so the entire film can be recorded up to a certain coercive force, but even higher This is because when the coercive force is reached, sufficient recording is not possible in the lower layer of the magnetic recording medium because the recording magnetic field is low.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a magnetic recording medium that solves the conventional problems as described above, increases reproduction output, and improves recording density.

[Means for Solving the Problems] The present invention provides a method for manufacturing a magnetic recording medium comprising forming a perpendicular magnetic anisotropic film on a base material by sputtering, in which the perpendicular magnetic anisotropic film is formed at an early stage. is a method for producing a magnetic recording medium characterized by forming the perpendicular magnetic anisotropic film by causing discharge in Ar gas containing a small amount of additive gas, and then in Ar gas alone.

In the present invention, the perpendicular magnetic anisotropy film is preferably a CO-based alloy film, and the additive gas is preferably nitrogen or oxygen.

[Function] When forming and covering a vertically anisotropic film on a substrate by sputtering, if discharge is performed in Ar gas containing a small amount of added gas at the initial stage, a film with low coercive force in the vertical direction is formed. Ru. Thereafter, by discharging only in Ar scum, a film with high coercive force in the vertical direction is formed. From the above, it is easy to manufacture a magnetic recording medium that has a lower coercive force than the lower or upper layer of the magnetic recording medium.

[Example] Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a sputtering apparatus for continuous film formation used in this example. In the figure, 1 is a vacuum chamber;
2 is a take-up reel, 3 is a base material (base film), 4 is a running direction of the substrate, 5 is an intermediate []1-ru, 6 is an unwinding reel, 7 is a mask, and 8 is a taget. There is.

First, in order to obtain the manufacturing conditions for low coercive force in the vertical direction, we investigated the dependence of the vertical coercive force on the added gas. Oxygen (02) and nitrogen (N2) were used as additive gases, and the film formation method was as follows.

Target 8 is φ8 inch CoCr (Cr 18wt
%) A Ta chip is placed on an alloy target. The base film 3 uses a polyimide film, and after setting it in the vacuum chamber 1, the ultimate vacuum degree is 1XIO-4pa.
Exhausted to below. Next, set the temperature of intermediate roll 5 to approximately 100°C.
The base film 3 was rewound back and forth once using the take-up reel 2 and the unwind reel 6, and residual gas (such as H20) adsorbed on the film was vented.

After that, again at a vacuum level of 1XIO-4Pa or less,
Ar gas and various additive amounts of gases (nitrogen, oxygen) were introduced, and the intermediate roll 5 was rotated under sputtering conditions of input power 1 kW and total gas pressure 1 mrorr, and the film was continuously run while running in the direction of arrow 4. A film was formed at a film thickness of 0.1 stage. The temperature of the intermediate roll 5 during film formation was kept constant at about 100° C. The magnetic properties of the film thus produced were examined using a moving sample magnetometer.

The results are shown in FIG. The figure shows vertical coercive force H6
This figure shows the dependence of soil added residue (nitrogen, oxygen) partial pressure PN2 and Po2. From the present results, it was found that the vertical coercive force of the nitrogen valve 1) and the oxygen valve IA- decreased at 2 x 10-6 rorr or more and 6 x 10-6' rorr or more, respectively. Therefore, by determining the amount of additive gas to be added with reference to FIG. 2, it is possible to fabricate a material with an arbitrary low coercive force.

Next, a method for manufacturing the magnetic recording medium of the present invention will be described. First, an example using nitrogen as the additive residue will be described. The film formation method is as follows.

Note that the process up to gas release from the film is the same as above, so it is omitted here.

After releasing the film gas, reduce the final vacuum to 1xlO-4P again.
Evacuate to below a, add Ar gas and add amount 6 x 10-6
Torr of nitrogen gas was introduced, and a film of 0.1 μm thick was continuously formed while rotating the coal 5 and running the film 3 in the direction of arrow 4 under sputtering conditions of input power 1 kW and total gas pressure 1 mTorr. did.

The base film 3 is rewound using the take-up reel 2 and the unwind reel 6, and after being evacuated again to 1×10″4 Pa or less, a film of 0.2 cm is formed in the same manner using only Ar gas, and the entire film is The film thickness was set to 0.31 m.

The temperature of the intermediate roll 5 during film formation was kept constant at about 100°C, and the rotational speed of the intermediate roll 5 was varied to obtain the desired film thickness. The vertical coercive force of the CoCrTa film produced in this way is approximately 600Q up to a film thickness of 0.1/ffl.
The film thickness was approximately 1.3000 e, and a medium with a low coercive force was obtained in the desired lower layer portion. Also, for comparison, as in the conventional case, a C film with a thickness of 0.3 using only Ar gas
A 0CrTa film was also produced. This perpendicular coercive force was approximately L 3000 e, independent of film thickness.

C0Cr produced by the production method of the present invention as described above
- [a film and CoCrT prepared by the same method as before
The recording and reproducing characteristics of each of the a-films were investigated. The results are shown in FIG. The head used here has a gap length of 0.3, and the recording and playback characteristics are as follows: playback output V (
This figure shows the dependence of the relative value on the recording density. The results show that the CoCrTa film produced by the production method of the present invention has improved reproduction output and recording density compared to films produced by the conventional method.

Next, an example using oxygen as the additive gas will be described. In the case of oxygen, from Figure 2, the amount added to obtain the same low coercive force as nitrogen is 2X10-510 "r,"
The other sputtering conditions were the same.

As a result, it was found that the reproduction output and recording density were improved as shown in FIG.

In the above embodiment, the target 8 was a composite target in which Ta chips were placed on a C0Cr alloy target, but it may be any target such as a 000118 alloy target, and the Cr content may be other than 18 wt%. Although a polyimide film is used as the base film 3, it may be an organic film such as a polyamide film or a polyester film. During sputtering, the input power and total gas pressure are each 1. OKW, 1mTo
Although rr was used, other values may be used, and the temperature of the intermediate roll 5 was also set at approximately 100°C, but other temperatures may be used.

Roughly speaking, the low coercive force layer of the perpendicular magnetic anisotropic film was made to have a uniform coercive force in this example, but it was made to have a uniform coercive force in the perpendicular direction.
Alternatively, the coercive force may be decreased in stages,
For example, the structure may be such that the coercive force decreases sequentially from the surface of the film.

In the case of a coercive force like -, the film thickness was set to 0.1 μm in this example, but any thickness may be used as long as it is about 1/2 or less of the total film thickness. The coercive force in the direction perpendicular to the film surface can also take any value.

In addition, in this example, the nitrogen and oxygen gases added were 5 x 10-6 Torr and 2 x 1 Torr, respectively.
orr, but other pressures that reduce the coercive force in the vertical direction as shown in FIG. 1 may be used. Furthermore, although the medium was produced by a continuous film forming method in this example, a batch method may also be used, in which case the base material 3 may be a glass substrate, a plastic substrate, a metal substrate, etc. in addition to the above-mentioned organic film.

Furthermore, in this example, R
F magnetron sputtering method was used, but "<[varnish batter removal, DC sputtering method, ion beam sputtering method, electron beam evaporation method, resistance heating evaporation method, MBE method, CVD method,
Any conventionally known N film forming technique such as plating method can be used. In addition, in this example, a C0Cr1'-a film was used as the perpendicular magnetic recording medium, or other C0Cr films such as a C0Cr film were used.
An o-based alloy film or other metal film may be used.

[Effects of the Invention] As explained above, the magnetic recording medium manufactured by the manufacturing method of the present invention has a low coercive force layer in the lower layer of the perpendicular magnetic anisotropic film and a high coercive force layer in the upper layer. structure, the reproduction output and recording density are increased compared to the conventional technology. Further, as for the low coercive force layer, a desired low coercive force layer can be easily produced because a low coercive force in any perpendicular direction can be obtained depending on the amount of additive gas added.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the sputtering apparatus for continuous film formation used in an embodiment of the present invention, and Fig. 2 shows the dependence of the vertical coercive force of H6 soil on the partial pressure of added gas (oxygen, nitrogen) for a C0CrTa film. FIG. 3 is a diagram illustrating the dependence of the reproduction output V (relative value) on the recording density for the magnetic recording medium obtained by the method of the present invention in comparison with that by the conventional technique. 1... Vacuum chamber 2... Take-up reel 3
... Base material (base film) 4 ... Running direction 5 ... Intermediate roll 6
...Unwinding reel 7...Mask 8...Target

Claims (3)

[Claims] (1) A method for manufacturing a magnetic recording medium comprising forming a perpendicular magnetic anisotropic film on a base material by sputtering,
In the initial stage of forming the perpendicular magnetic anisotropic film, the perpendicular magnetic anisotropic film is formed by discharging in Ar gas containing a small amount of additive gas, and then discharging only in Ar gas. A method for manufacturing a magnetic recording medium. (2) The perpendicular magnetic anisotropy film is a Co-based alloy film (
1) The method for manufacturing the magnetic recording medium described above. (3) The method for manufacturing a magnetic recording medium according to claim (1), wherein the additive gas is nitrogen or oxygen.