JPS6076025A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To increase the coercive force of a vapor deposition film by applying the vacuum vapor deposition of an evaporation source to the surface of a substrate from an oblique direction and then applying the vacuum vapor deposition of the evaporation source continuously to said vapor deposition film at a smaller incident angle than the incident angle of said first vapor deposition. CONSTITUTION:In the first stage the vacuum vapor deposition of an evaporation source 5 is applied obliquely to the surface of a substrate 2 so that the incident angle theta of a line 5x of vapor deposition direction is preferably set at 45-90 deg. via an opening part 6a. In the second stage the sources 5 are continuously vapor deposited under vacuum on the vapor deposition film of the first stage so that the incident angle theta' of a line 5y of vapor deposition direction is set at <=30 deg. and preferably at 20-0 deg. via an opening part 6b. Thus the good results are obtained for the electromagnetic conversion characteristics of a vapor deposition film 10 owing to the oblique vapor deposition of the first stage. Furthermore the film surface density is improved with the vacuum vapor deposition of the second stage with a small incident angle. This improves greatly the corrosion resistance of the film 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium using a vacuum evaporation method.

Conventionally, in the method of manufacturing magnetic recording media such as magnetic tape by vacuum-depositing an evaporation source made of a ferromagnetic metal or its alloy onto a substrate such as a polyester film, the evaporation source is generally deposited obliquely to the surface of the substrate. Vacuum deposition increases the coercive force of the deposited film and yields good results in electromagnetic conversion characteristics.

However, the vapor deposited film formed by the above-mentioned oblique vapor deposition has a problem in that it has poor corrosion resistance and the saturation magnetic flux density tends to decrease over time. For this reason, a thin film of another metal, alloy, or oxide is further formed on the obliquely deposited film by ordinary vacuum deposition or sputtering.
The above corrosion resistance is improved. However, this method requires two types of evaporation sources and is troublesome to operate, so it is not necessarily an industrially desirable method.

From the above viewpoint, the inventors have completed this invention as a result of intensive study to find a method for easily forming a vapor deposited film with excellent electromagnetic conversion characteristics and corrosion resistance from one type of evaporation source. reached.

That is, in this invention, an evaporation source made of a ferromagnetic metal or an alloy thereof is vacuum-deposited on a substrate from an oblique direction to the substrate surface, and then the incident angle with respect to the substrate surface at the time of vapor deposition is further adjusted. The present invention relates to a method for manufacturing a magnetic recording medium, characterized in that the evaporation source is continuously vacuum-deposited at a smaller incident angle.

Hereinafter, a method for manufacturing a magnetic recording medium according to the present invention will be explained with reference to the drawings.

1 and 2, 1 is a supply roll for a substrate 2 such as a polyester film, 3 is a cylindrical cooling rotary can, 4 is a take-up roll, 5 is an evaporation source made of a ferromagnetic metal or its alloy, 6 7 is a control plate for regulating the evaporation direction of the evaporation source 5 with respect to the substrate surface, and 7 is each of the above elements 1 to 6.
This is a vacuum chamber formed by evacuating the interior of the chamber in which the chamber is disposed to a predetermined degree of vacuum by means of a vacuum pump 8.

In this apparatus, an evaporation source 5 is first evaporated by a heating source (not shown) such as an electron beam, and then evaporated onto a substrate 2 that is supplied from a supply roll 1 and runs once at a predetermined speed along a cooling rotary can 3. Vacuum evaporate. This vacuum evaporation consists of a first stage of evaporation in which the evaporation direction is oblique to the surface of the substrate 2, and a subsequent (second stage of evaporation). This is done through the sections 6a and 6b.

That is, in the first stage, the angle between the normal line 9X and the vapor deposition direction line 5x at the point where the vapor deposition direction line 5X passing through the opening 6a intersects with the substrate 2 traveling along the cooling rotation can, that is, the incident angle θ. is usually 30 to 90 degrees, preferably 45 to
The evaporation source 5 is vacuum-deposited from an oblique direction on the surface of the substrate 2 so that the angle is 90 degrees, and in the second stage, the evaporation source 5 is evaporated through the opening=B6b on the front side in the running direction of the substrate 2 after the evaporation. The incident angle l expressed by the angle between the vapor deposition direction line 5y and the same normal line 9y as described above is usually less than 30 degrees, preferably 20 degrees.
The evaporation source 5 is further vacuum-deposited continuously on the first-stage deposited film so that the angle of incidence is ~0 degrees, that is, the incident angle θ' is smaller than the incident angle θ of the first stage.

The magnetic recording medium 11 with the vapor deposited film 10 formed on the substrate 2 in this manner is then wound around the winding roll 4 while running on the cooling rotary can 3, and then undergoes necessary processes such as cutting. After that, it is made into a product.

As is clear from the above description, in the present invention, the same evaporation source 5 is vacuum-deposited on the substrate 2 at different incident angles θ and θ'. The oblique vapor deposition makes it possible to obtain good results in the electromagnetic conversion characteristics of the vapor deposited film 10, and the second stage of vacuum vapor deposition with a small incident angle densifies the film surface, thereby improving the corrosion resistance of the vapor deposited film 10. can be greatly improved.

Further, in this method, only one evaporation source 5 is required, and two openings 6a are provided at predetermined positions of the control board 6.

Since ordinary vapor deposition means can be used as is except for providing 6b, this method is extremely advantageous in terms of economy and manufacturing workability compared to the conventional method of forming thin films of other metals.

The ferromagnetic metal or alloy thereof used as the evaporation source 5 in the present invention includes Fe, Co, Ni, or an alloy thereof, or a combination thereof with Cu or Zn.

These evaporation sources 5 are used in the first stage and The thickness of the deposited film 10 when deposited on the substrate 2 by the second stage of vacuum evaporation is about 500 to 5,000 OOA.The traveling speed of the substrate 2 and the evaporation rate of the evaporation source 5 are as described above. It is set appropriately depending on the thickness of the vapor deposition layer 10.

It is preferable that the difference between the incident angle θ of the first stage and the incident angle θ' of the second stage be as large as possible. However, generally more than 10 degrees,
Particularly preferably, the difference is 30 degrees or more (this makes it possible to improve electromagnetic conversion characteristics and improve corrosion resistance).

EXAMPLES Below, examples of the present invention will be described in more detail.

20. As an example substrate. A polyester film with a thickness of I is set in a vacuum chamber as shown in Fig. 1, and an incident angle of 40 ~ A first stage deposition at an angle of incidence of 90 degrees followed by a second stage at an angle of incidence of 5 to 10 degrees.
Vacuum evaporated by step evaporation to a thickness of 2,000λ
coercive force 800 oersted, saturation magnetic flux density 8.000
A Gaussian vapor deposition film was formed. Details of the vapor deposition conditions are as follows.

Cylindrical cooling rotary can; diameter 300mm heating cylinder; shortest distance from electron beam gun evaporation source to substrate; 250τm atmosphere
; Oxygen/Argon = 1/10 degree of vacuum; 5 X 10-
5 Torr Running speed of the substrate: 0.5 tn 1 minute After the above vacuum deposition, the magnetic tape of the present invention was obtained by cutting into a predetermined width.

Comparative Example A control plate with only one opening was used instead of the control plate with two openings shown in Fig. 1, and only the first stage of vapor deposition was performed at an incident angle in the range of 40° to 9♂. was carried out in exactly the same manner as in the example except that the second stage of vapor deposition was not performed.
A conventional magnetic tape with a deposited film having a saturation magnetic flux density of 7,000 Gauss was prepared.

The results of examining the electromagnetic characteristics and corrosion resistance of the above Examples and Comparative Examples are as shown in the following table. In addition, the electromagnetic conversion characteristics are determined by measuring the reproduction output at the recording wavelength IP.
The comparative example was set as a reference (0) and expressed as a relative value. Further, the corrosion resistance was measured by measuring the saturation magnetic flux density after being left in an atmosphere of 60° C. and 90% RH for one week, and expressed as the rate of decrease (a) with respect to the initial value.

As is clear from the above table, the magnetic tape obtained by the method of this invention has electromagnetic conversion characteristics comparable to those of conventional tapes, and has highly improved corrosion resistance.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a vacuum evaporation apparatus for implementing the method of the present invention, and FIG. 2 is a schematic diagram for explaining the main part of the method of the present invention. 2 Substrate, 5... Evaporation source, θ... Incident angle during oblique evaporation, θ'... Incident angle smaller than the above angle.

Claims (1)

[Claims] (1) After vacuum-depositing an evaporation source made of a ferromagnetic metal or its alloy onto the substrate from an oblique direction to the substrate surface,
A method for producing a magnetic recording medium, characterized in that the evaporation source is further vacuum-deposited on the deposited film at an angle of incidence smaller than the angle of incidence with respect to the substrate surface during the deposition.