JPH0443323B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a metal thin film type magnetic recording medium with excellent durability.

Conventional Structures and Their Problems In recent years, with the increasing demand for higher density magnetic recording, development of magnetic recording media in which a ferromagnetic metal thin film is used as a magnetic recording layer is progressing in various fields.

The basic structure of the magnetic recording medium, as shown in the cross-sectional view in FIG. 2, and a lubricant coating layer 3 disposed for the purpose of improving the wear resistance of the support 1. If necessary, although not shown, a non-magnetic thin film, a soft magnetic thin film, and a ferromagnetic metal thin film 2 of the support 1 are coated. A coating layer or the like disposed on the surface opposite to the surface having the surface is added as a component.

However, in such a magnetic recording medium, since the thickness of the ferromagnetic metal thin film 2 used is as thin as 0.3 μm or less, the surface roughness of the support 1 becomes the surface roughness of the ferromagnetic metal thin film 2, resulting in an extremely smooth surface. Support 1 must be used.

Therefore, when the magnetic recording medium having the structure shown in Fig. 1 is used in a helical scanning type video tape recorder (hereinafter referred to as VTR), which has components such as a rotating cylinder and a rotating head, it is subject to large friction. Even if the lubricant was selected, repeated use in a VTR caused scanning to become unstable and the playback signal to fluctuate in the time direction, causing so-called jitter, which caused the playback screen to shake or distort.

In particular, as a result of our efforts to find out that there are parts where the above phenomenon appears more strongly in the longitudinal position of the magnetic recording medium and parts where jitter can be ignored by visual observation, we found that when applying lubricant using a coating machine, the surface of the ferromagnetic metal thin film It has been found that there is a strong correlation with the phenomenon that has a potential and that the potential changes with the longitudinal position.

OBJECTS OF THE INVENTION An object of the present invention is to provide a method for manufacturing a metal thin film type magnetic recording medium with excellent durability.

Structure of the Invention The present invention is characterized in that when a lubricant solution is applied onto a ferromagnetic metal thin film formed on a support, the ferromagnetic metal thin film is held at a constant potential.

The crystal grains that make up the ferromagnetic metal thin film usually have an oxidized layer in the range of 10 to 200, so they may peel off in the air when applying lubricant or when unwinding from the wound state. It is charged and a charge remains on the surface, and the amount of charge is not constant.

Furthermore, since magnetic recording media are produced in large quantities, the unit in which they are continuously processed and processed has a large area of about 5000 m ² , so the wetting and lubricant solution is also circulated and pumped.

At this time, the lubricant solution is also charged by friction with the components such as piping, pumps, container walls, and coater heads.

It is difficult to imagine that both the other side to be coated and the lubricant solution to be coated will be charged to the same polarity and the same potential, and for this reason, during the short period of time during which the ferromagnetic metal thin film and the lubricant solution are coated. A repulsion phenomenon occurs or a discharge phenomenon occurs, resulting in uneven formation of the lubricant layer.

In order to solve this problem, the present invention has succeeded in obtaining a uniform lubricant layer by carefully examining the configuration of the coating machine and grounding the ferromagnetic metal thin film when applying the lubricant solution. It is based on

As a result of further consideration, even if it does not depend on grounding,
A similar effect was confirmed by holding the potential at a constant level.

DESCRIPTION OF EMBODIMENTS FIG. 2 is a block diagram of the main parts of a coating machine used in carrying out the present invention.

A magnetic recording medium original plate 4 (hereinafter referred to as a substrate) consisting of a support 1 and a ferromagnetic metal thin film 2 moves in the direction of arrow A.

A lubricant solution 6 carried by an applicator roll 5 is applied to the surface of the substrate 4 on the side having the ferromagnetic metal thin film 2, thereby forming a lubricant layer 8.

At this time, metering is performed to obtain a uniform thickness of the lubricating layer 8, and in this case, it is mainly adjusted by the gap between the applicator roll 5, which rotates in the direction of arrow B, and the metering roll 7, which rotates in the direction of reaction C. It is something that

The substrate 4 coated with a lubricating layer 8 having a certain wet thickness is advanced to a drying oven (not shown) and then wound up.

A portion of the lubricant solution 6 carried in excess by the applicator roll 5 is transferred to the metering roll 7, scraped off by the doctor blade 9, and returned to the container 10 for the lubricant solution 6.

Reference numeral 11 denotes a potential regulating roller whose surface is made of a highly conductive material, and this potential regulating roller 11 is grounded by a brush 12 .

Reference numeral 13 denotes a back-up roller, and the back-up roller 13 holds the substrate 4 between the potential regulating roller 11 and the potential of the ferromagnetic metal thin film 2 at a constant level. The backup roll 13 is preferably made of rubber.

Reference numeral 14 denotes a free roller that contacts the surface of the substrate 4 on the side opposite to the lubricant layer 8 side until the lubricant solution 6 forming the lubricant layer 8 dries.

It is preferable that the potential regulating roller 11 is configured to be close to the position where the lubricant solution 6 is applied.

Further, the potential of the potential regulating roller 11 can be adjusted in the range of -300V to +300V by a DC power supply without being grounded. Exceeding this range is not preferable because pinholes may occur in the ferromagnetic metal thin film 2.

It should be noted that the present invention can be carried out in the same way with other coating machines other than the coating machines shown in the above embodiments, and the types of lubricant solutions, types of supports, and types of ferromagnetic metal thin films are as follows. The specific embodiments also have exactly the same effects.

The dimensions and configuration of the coating machine used in the implementation of the present invention and the comparative examples are as follows.

The diameter of the applicator roll 5 is 20 cm, and the distance between the position where the applicator roll 5 and the substrate 4 touch and the potential regulating roller 11 with a diameter of 6 cm is 10 cm. The surface potential of the substrate 4 was measured by bringing the substrate 4 close to the substrate.

More specific examples will be shown below.

Example 1 A polyethylene terephthalate film (hereinafter referred to as film A) with a thickness of 9 μm was moved at 22 m/min along the outer periphery of a cylindrical can (not shown) around which a medium at 80°C was circulated. while heating the electron beam using a dual evaporation source, respectively.
By controlling the input power to be 70 KW for Co and 36 KW for Cr, a substrate was obtained in which a ferromagnetic metal thin film with a Cr content of 19% by weight was formed with a thickness of 0.19 μm.

The degree of vacuum during the vapor deposition was 8×10 ⁻⁷ _TORR , and the obtained ferromagnetic metal thin film was a perpendicularly magnetized film.

The substrate was taken out into the atmosphere, and 4 hours later, a lubricant solution was applied to the substrate using the above-mentioned coating machine so that the film thickness after drying was approximately 50 mm.

The lubricant solution used was myristic acid dissolved in n-hexane, and the coating speed was 60 m/min.

A 5000 m long board was divided into 5 equal parts, a lubricant solution was applied in 1000 m increments, and the tape was made into 8 mm wide magnetic tape and repeatedly run on a VTR.

As a comparative example, the potential regulating roll 11 was removed and the surface potential of the substrate was observed at that position.

An example is shown in Figure 3. In this way, the surface potential was unstable in the comparative example, but it was at the ground potential in the example, and the difference between the two appears as an increase in the coefficient of friction depending on the longitudinal position of the tape during repeated running, and as a result, the playback screen This appeared as a fluctuating jitter, and 50 rolls of the invention product and 50 rolls of the comparative example were rolled at 25°C, 60% RH 30°C, and each roll was 100 m long.
When tested in an environment of 85% RH, the products of the present invention had no jitter that could be discerned on the screen after repeated use 100 times, whereas the comparative example showed no jitter that could be discerned on the screen at 25°C and 60% RH. 30%, 30℃, 85%
At RH, 60% of the tape was clearly recognized as a jitter component. When we investigated the relationship between the locations where jitter occurred and the surface potential, it became clear that the potentials corresponded to the locations where the potential suddenly changed, that is, the locations indicated by arrows D, E, and F, as shown in FIG.

Example 2 A cylindrical can in which a 7 μm thick aromatic polyamide film (hereinafter referred to as film B) was circulated around a medium at 200°C was held insulated from a vacuum container, and the film was placed along the outer periphery of the cylindrical can. B
While moving at 30 m/min, heating electron beams were applied to Co and Cr using a dual evaporation source at 74 KW and 74 KW, respectively, for Co and Cr.
The perpendicular magnetization film, which is a ferromagnetic metal thin film with a Cr content of 20% by weight, is controlled so that 40KW is applied to the
A substrate formed with a thickness of 0.2 μm was obtained.

Prior to vapor deposition, the inside of the vacuum chamber was evacuated to 2×10 ^-7 T _ORR , and then oxygen was introduced to form the ferromagnetic metal thin film at 2×10 ^-6 T _ORR . high frequency voltage was applied.

This high frequency voltage is anode voltage 3.5KV and incident wave 550
[W] The matching state of the reflected wave 50 [W] was maintained.

The substrate was taken out into the atmosphere, and one day later, a lubricant solution was applied to the substrate using the above-mentioned coating machine so that the film thickness after drying was about 50 mm.

The lubricant solution used for coating was prepared by dissolving stearic acid, a lubricant, in methyl ethyl ketone. The coating speed was 75 m/min, and each board of 5000 m in length was divided into 5 equal parts and the coating was repeated in 1000 m increments as in the comparative example, and the V.
I drove the TR repeatedly.

When each tape was used 100 times in an environment of 30°C and 90% RH, there were no rolls of tape in which jitter appeared on the screen with the product of the present invention, but in 50% of the 50 rolls with the comparative example. It was hot.

To examine durability from a different angle, we operated the VTR in still frame mode, selected 10 arbitrary positions on each tape at 30°C and 90%RH, and measured the playback output.
The time it took for the tape to drop by 3 dB was over 30 minutes for all tapes with 500 measurement points, whereas for the comparative example, 34 points were under 5 minutes, and 21 points were between 5 and 10 minutes.
The points varied from 10 minutes to 30 minutes at 131 points, and the durability was clearly inferior.

Effects of the Invention As described above, according to the method of the present invention, the durability of metal thin film magnetic recording media, which had conventionally had difficulty in durability, can be improved by simply arranging, for example, a potential regulating roller in a part of an existing coating machine. In particular, it is possible to obtain a large quantity of magnetic tape with good reproducibility and a long still life without deterioration in image quality caused by jitter caused by running instability caused by repeated use in a VTR.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a magnetic recording medium, Fig. 2 is a diagram showing the main parts of an example of a coating machine used in the implementation of the present invention, and Fig. 3 is a longitudinal change in surface potential during coating on a substrate of a comparative example. FIG. 3 is a surface potential characteristic diagram showing an example. 1...Support, 2...Ferromagnetic metal thin film, 3...
Lubricant coating layer, 4...Substrate, 5...Applicator roll, 6...Lubricant solution, 11...Potential regulation roll.

Claims (1)

[Claims] 1. A method for producing a magnetic recording medium, which comprises maintaining the ferromagnetic metal thin film at a constant potential when applying a lubricant solution onto the ferromagnetic metal thin film formed on a support.