JPS60111344A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To enable mass production of a magnetic recording medium for vertical magnetic recording with good reproducibility and to obtain the medium having high coercive force by using a high polymer base plate having high versatility by maintaining the temp. in the stage of depositing a thin ''Permalloy'' film by evaporation higher than the temp. in the stage of depositing a vertically magnetized film by evaporation. CONSTITUTION:Polyamide imide having about 10mum thickness is preliminarily subjected to a glow discharge treatment to form a thin Ni-Fe alloy film to about 0.5mum and in succession a thin Co-Cr alloy film is formed at about 0.15mum. The base plate is masked to keep the incident angle of Co-Cr within 6 deg. and said alloy is deposited by evaporation under the conditions under which vertical orientation is easy. The alloy is deposited by evaporation while the relation at which the base plate temp. in the stage of vapor deposition of Ni-Fe is higher by 55 deg.C than the base plate temp. in the stage of vapor deposition of Co-Cr is maintained. The vertical coercive force of the Co-Cr film obtd. in such a way is as shown in the figure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium suitable for perpendicular recording.

Conventional Structures and Their Problems In recent years, in order to increase the density of magnetic recording, the use of magnetic recording media having a magnetic recording layer made of a metal thin film has been considered. Among these, a perpendicular recording medium in which a permalloy thin film and a perpendicular magnetization film of, for example, C0-Cr are laminated on a polymer substrate has currently achieved the highest recording density.

However, this perpendicular recording medium is formed using a high-frequency sputtering method and is not suitable for mass production. Attempts have been made to manufacture such a medium using a vacuum evaporation method. There are high expectations for mass production.

However, the perpendicularly magnetized film produced by the conventionally known vacuum evaporation method is
There was a problem with reproducibility, which is thought to be caused by the fact that the dependence of coercive force on substrate temperature is too strong, so it is not always easy to maintain a constant substrate temperature in vacuum. It was wanted.

OBJECTS OF THE INVENTION The present invention was made in view of the above circumstances, and it is an object of the present invention to provide a complete method for manufacturing a magnetic recording medium for perpendicular recording with good reproducibility.

Structure of the Invention The present invention provides a method for forming a thin film having a two-layer structure of a permalloy thin film and a perpendicular magnetization film on a substrate by a vacuum evaporation method. It is characterized by being higher, has good reproduction,
All magnetic recording media for perpendicular recording with high coercive force can be manufactured.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an enlarged sectional view of a magnetic recording medium obtained by the manufacturing method of the present invention.

Permalloy thin film 2 which is a soft magnetic layer thin film on a polymer substrate 1
and secondly, Co -M (M is Cr.

M o + W + T i + V r Mn + Ru
You can choose from. ) A perpendicularly magnetized film 3 made of a thin alloy film is disposed, and a protective layer 4 is further disposed thereon, and may be in the form of a tape, disk, or sheet.

Polymer substrates that can be used in the present invention include polyethylene terephthalate, polyethylene 2-6 naphthalate,
These include polyamideimide, polyhydantoin, polybalapic acid polyimide, and the like.

The protective layer that can be used in the present invention is a wet method.

Regardless of the soft-forming method, the material is appropriately selected from organic and inorganic materials, but it is a matter of course that the thickness of the protective layer is o, iμ? If it does not have a protection ability suitable for the purpose at a thickness of n or less, preferably o, 03 μm or less, the space loss will be large and it will not be suitable for high-density recording, so there are restrictions from this point of view.

Next, the manufacturing part of the two-layer magnetic recording medium by the vacuum evaporation method, which is the gist of the present invention, will be described in detail.

The evaporation equipment used consisted of two cylindrical cans with a diameter of 50 m, and a cylindrical can with a diameter of 25111 cm directly below each cylindrical can. ? It is a winding evaporation device with an electron beam evaporation source placed on the + side.The cylindrical can has a built-in heater and uses a heating medium circulation system to fully control the surface temperature, and can be controlled in the range of 10℃ to 390℃. The surface temperature of the two cylindrical cans can be controlled independently.

The evaporation sources for the co-M alloy were binary, the distance between the centers of the evaporation sources was 7.6 crn, and the Ni-Fe evaporation source was used as a single evaporation source.

[Example-1] Polyamideimide with a thickness of 1000 m was treated with glow discharge in advance using a discharge gas of Ar 3x10-3 Torr.
.

Power 550W, frequency 13.56MHz, processing time 2
Second) A Ni--Fe alloy thin film of 80% Ni was formed to a thickness of 0.6 pm, and then a Co--Cr alloy thin film of 0.15 .mu.m was formed under conditions such that the Co5o ratio was Cr2O%.

Co-Cr was deposited under conditions that facilitated vertical alignment by masking so that the incident angle was within 6°. N i −F e
Figure 2 shows the vertical coercivity of a CO--Cr film obtained by continuously depositing the substrate temperature such that the substrate temperature during the deposition of Go--Cr is 56 DEG C. higher than the substrate temperature during the deposition of Go--Cr. straight line A
In the example of the present invention, the straight line B is the Ni-Fe film f0.6 at room temperature.
This is a case where a Co--Cr film is formed on a .mu.m film.

When comparing the two, I noticed two distinctive points. One is that a large coercive force can be obtained even at a low temperature during the deposition of CO-Cr, and the other is that The dependence of Go-Cr on the substrate temperature during vapor deposition is small.

Both of these features provide an excellent effect in mass-producing the entire Co--Cr perpendicular magnetization film. In other words, fluctuations in the substrate temperature during Co-Cr deposition have almost no effect on the coercive force.
Since a large coercive force can be obtained even at a low temperature, it is possible to obtain a perpendicularly magnetized film with a large coercive force with good reproducibility.

On the other hand, the influence of fluctuations in substrate temperature when obtaining a Ni--Fe film can be ignored. That is, the data shown by straight line A in FIG. 2 is obtained when Ni-Fe was deposited under conditions that the substrate temperature was 55°C higher than the substrate temperature during the deposition of CO-Cr, but the temperature difference between the two, f, ( It has been confirmed that even when the temperature is changed from 20°C to 30°C, the temperature falls on the straight line A within a range of ±10 [Oersted].

If the temperature is below 20°C, the effect of the present invention will become unstable due to fluctuations in the substrate temperature, so it is preferable to carry out the process with a gap of 20°C or more.

One difference from the conventional example shown in FIG. 2 is that N i
In addition to the good crystal orientation of -Fe, Co -Cr
This is thought to be due to the effect that impurities, especially the gas emitted from the substrate, do not participate in the crystal growth of the Co-Cr film because the substrate temperature during the deposition of Co-Cr is lower than that of Ni-Fe. This effect is achieved by using a 2511m polyimide substrate (manufactured by DuPont, trade name: Kabu l-/) 2
The same is true for the 2 μm polyhydantoin substrate (manufactured by Bayer AG, trade name RESISFOL), and Co-Cr
In addition, Co-Mo, Co-V, etc. were similarly confirmed.

[Example 2] Example on polyethylene terephthalate with a thickness of 10 μm
The same glow treatment as in 1 was applied to 80%N'i of Ni-Fe.
Alloy k 0.5 μm, deposited at a substrate temperature of 120°C,
Subsequently, Cr2O% Co-Cr'io was deposited to a thickness of 16 μm at a substrate temperature of 40° C.

The perpendicular coercive force of this Co--Cr film was 9061: Oersted.

This experiment was repeated nine times in total, with three types of substrates and 30 samples each, using different manufacturers of substrates.

This lot-to-lot reproducibility is extremely good, and the vertical coercive force is
It was in the range of 900-92o [Oersted].

The other noteworthy point of this example is 1. It has been proven that it is possible to remove the wall, which was previously thought to be impossible to create as a medium using polyethylene terephthalate, which is highly versatile, in the vacuum evaporation method.

Effects of the Invention The present invention is an improved vapor deposition method in which a permalloy thin film and a perpendicularly magnetized film are fully laminated on a substrate. The present invention has great practical value because magnetic recording media for perpendicular magnetic recording can be mass-produced with good reproducibility, and a highly coercive force medium can be obtained using a highly versatile polymer substrate.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of a magnetic recording medium that is a target of the magnetic recording medium manufacturing method of the present invention, and FIG. 2 shows the dependence of perpendicular coercive force on substrate temperature during the formation of a perpendicularly magnetized film in comparison with a conventional example. It is a diagram. 1... Substrate, 2... Permalloy thin film,
3... Perpendicular magnetization film.

Claims (1)

[Claims] When forming a thin film with a two-layer structure of a permalloy thin film and a perpendicularly magnetized film on a substrate using the vacuum evaporation method, the substrate temperature when the entire permalloy thin film is evaporated is higher than the substrate temperature when the perpendicularly magnetized film is evaporated. A method for manufacturing a magnetic recording medium.