JPH01165029A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To eliminate curling and to obtain a medium having both flat faces by changing the vapor deposition speed of a Co-Cr film for the 1st face and the vapor deposition speed for the 2nd face and setting the vapor deposition speed for the 1st face higher than the vapor deposition for the 2nd face. CONSTITUTION:The Co-Cr film having 0.3mum thickness is formed continuously on one face of a high-polymer film 11 by using a continuous take-up type vacuum deposition device. The surface temp. of a can is kept at 250 deg.C and the vapor deposition at 500nm/s at this time. This tape is further turned over and the Co-Cr film is formed to 0.3mum on the surface reverse from the first vapor deposition surface. The curl delta is generated if both the 1st face and 2nd face are produced at the same vapor deposition speed at this time. The curl decreases as the vapor deposition of the 2nd face is gradually lowered. The flat both-face medium is thus obtd. in a 180-250nm/s range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a perpendicular magnetic recording medium, and particularly to a method for producing a flat medium with little curl in a double-sided medium in which magnetic films are provided on both sides.

[Conventional technology]

The perpendicular magnetic recording method proposed by Iwasaki et al. of Tohoku University (Special Publication No. 58-1988) is essentially a method suitable for high-density recording because the demagnetizing field decreases as the recording density increases. In particular, when this perpendicular recording method is applied to the field of flexible disks, it is expected that the recording density will be improved by 5 to 10 times or more at once, and therefore its development is being actively carried out.

As a recording medium used for perpendicular recording, a Co--Cr film produced by a vacuum evaporation method or a sputtering method is usually used. Flexible disks are made of organic polymer film,
Co-C is heated to about 100 to 300°C and processed using the method described above.
It is made by depositing a r film. However, in this case, since a polymer film such as polyimide with low rigidity is used as a substrate, curls caused by differences in thermal expansion coefficients or large curls caused by the internal stress of Go-Crli itself occur. . Additionally, double-sided media with a magnetic thin film as a magnetic recording layer are already available.

This method is known from Japanese Patent Application Laid-open Nos. 52-112306 and 56-169220.

In order to eliminate the above curl, after forming a film on one side,
If a film is formed on the opposite side under the same conditions.

It is thought that the curls on both sides are canceled out and flattened. However, it is difficult to eliminate curls with this method, and in normal cases, the curls become large when the film is formed the first time, and the film cannot be completely flattened. Therefore, a method of intentionally changing the film thickness on the front and back sides is known as Japanese Patent Application Laid-Open No. 191424/1982, and there is also a method of intentionally changing the deposition temperature on the front and back sides.

[Problem that the invention sought to solve]

However, in any of the above methods, the front and back surfaces have different magnetic properties, so they are not preferred for double-sided flexible disks. The present invention was made to solve the above-mentioned problems, and both sides have the same magnetic properties,
Another object of the present invention is to provide a flexible disk with less curling.

[Means for Solving the Problems] The method of the present invention increases the rate of magnetic film formation on both sides of a polymer film serving as a carrier of a recording medium, such that the rate of magnetic film formation is high on one side and slow on the other side, and more preferably at the initial rate. It is characterized by a high film formation speed and a slow film formation speed on the back side.

[Effect]

In the present invention, the internal stress of the Co-Cr film etc. is tensile stress,
In addition, the stress increases as the deposition rate increases, and the stress caused by the difference in temperature expansion coefficient (bimetallic effect) is compressive stress, and the polarity of the stress is different, which suppresses the occurrence of curling. It is something.

[Embodiments of the invention]

The details of the present invention will be explained below using examples.

Example 1 Using the continuous winding type vacuum evaporation apparatus shown in FIG. 1, G was coated on one side of a polyimide tape (Kapton 200H; manufactured by Toshi-Dubon Co., Ltd.) to a thickness of 0.3 μm.

-Cr film was continuously formed. At this time, the can surface temperature was 250° C., and the deposition rate was 500 nm/s. Furthermore, this tape was turned over to form a Co--Cr film with a thickness of 0.3 μm on the opposite side to the first vapor-deposited side.

The can surface temperature at this time was 250°C, but the deposition rate was changed to 80,100°240.500 nm/s.
Four types of double-sided vapor deposited films were produced.

A disk-shaped sample with a diameter of 130+ua was punched out from the sample thus prepared.

The size of the curl of a sample is expressed by the distance δ between the plane and the vertex of the curl when the sample is placed on a plane, as shown in FIG. Further, at this time, when the first vapor deposition surface was turned upward, a case where the film curled in a convex manner was defined as a positive (plus) curl.

FIG. 3 shows the curls of the samples produced by changing the second deposition rate. As can be seen from the figure, in the sample prepared at the same deposition rate (500 nm/s) on the first and second surfaces,
While positive curl occurred, as the deposition rate was decreased, the curl decreased and a flat double-sided medium was obtained in the range of 180 to 250 nm/s.

Example 2 Thickness 30n between polyimide tape and Go-Cr film
After depositing a Ge layer of m at a can temperature of 250° C., a Co—Cr film was deposited at a deposition rate of 350 nm/s. This tape was further turned over to form a 30 nm Ga layer on the opposite side, and then the evaporation rate was 80, 150, 350, 5.
A G o -Cr film was formed at a speed of 00 nm/s. The curl of the Co--Cr film thus produced was measured in the same manner as in Example 1. The results are shown in FIG. 3 by broken lines.

As is clear from the figure, even when a M Ge layer is provided,
Conditions that are slower than the Co-Cr deposition rate on the first surface, about 100
It can be seen that a flat medium is obtained at nm/s.

Figure 4 shows the vertical coercive force (Ha
(above) and the deposition rate, but as is clear from the figure, there is no significant change in coercive force.

As is clear from the above examples, when producing a double-sided Co-Cr medium, a flat medium is created by slowing down the deposition rate on the second deposition surface compared to the deposition rate during the formation of the first deposition surface. It becomes possible to obtain.

Note that the relationship between the first and second evaporation rates varies depending on the evaporation temperature, Co-Cr film thickness, base film thickness, and mechanical properties, and is not included in this example. However, in any case, it is necessary to make the second deposition rate slower than the first deposition rate.

〔Effect of the invention〕

According to the present invention, the magnetic properties of each side of a double-sided flexible disk medium are not changed.

Since curl can be eliminated, it is effective in producing media that are flat on both sides.

Note that in this example, G o -Cr is used as the magnetic film.
Examples of films include Co-V and Co-Ni.

Similar effects can be obtained with films such as C0-0.

[Brief explanation of the drawing]

Figure 1 is a schematic side sectional view of the continuous evaporation device, Figure 2 is an explanatory diagram of the method for measuring curl, Figure 3 is a diagram of the relationship between curl size and deposition rate, and Figure 4 is the relationship between coercive force and deposition rate. FIG. 1... Supply roll, 2... Base film, 3...
・Heating can roll, 4... Winding roll, 5...E
/B electron gun, 6...co-Cr crucible, 7...G
Crucible for a. 8...Shutter, 9...Co-Cr double-sided medium, 1
゜...Co-Cr1li, 11...Base film.

Claims (1)

[Claims] 1. A magnetic film mainly composed of a Co-Cr alloy is formed directly on the surface of an organic polymer film, or via a high magnetic permeability layer or a non-magnetic layer, and is sequentially formed on one side at a time. A method for manufacturing a magnetic recording medium, characterized in that in the step of manufacturing a double-sided medium, the deposition rate of the Co--Cr film on the first side and the deposition rate on the second side are changed. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the deposition rate on the first surface is made faster than the deposition rate on the second surface.