JPS601627A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent jitter and to obtain a tape having a long life by coating a lubricant on a ferromagnetic metallic thin film formed on a support while keeping the electric potential of the thin film constant so as to prevent the thickness of a lubricant layer from being made ununiform owing to a change in electric charge on the surface of the thin film. CONSTITUTION:A ferromagnetic metallic thin film 2 is formed on a support 1 such as a polyethylene terephthalate film by vacuum deposition or other method, and a soln. 6 of a lubricant such as stearic acid is coated on the film 2. The thickness of the soln. 6 is regulated by rotating a metaling roll 7 in the direction of an arrow C while rotating an applicator roll 5 in the direction of an arrow B, and the resulting material having a formed lubricant soln. layer 8 is sent to a drying stage A. In order to keep the surface electric potential of the magnetic layer 2 constant before coating the lubricant, the base tape 4 is sent after holding between a backup roller 13 and a potential regulating roller 11 with high electric conductivity grounded through a brush 12. The adhesion of a lubricant layer 3 is prevented from being made ununiform owing to ununiformity in electrostatic charge during stripping when the base tape 4 is rewound, and a magnetic recording medium having superior durability is obtd.

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.

2. Description of the Related Art Structures of Conventional Examples and Their Problems In recent years, with the increasing demand for higher density magnetic recording, development of magnetic recording media having a magnetic recording layer made of a ferromagnetic metal thin film has been progressing in various fields.

The basic structure of the magnetic recording medium, as shown in the cross-sectional view in FIG. It consists of a lubricant coating layer 3 disposed for the purpose of improving the wear resistance of the metal thin film 2, and as necessary, a non-magnetic thin film, a soft magnetic thin film, a ferromagnetic metal thin film on the support 10, although not shown in the drawings. However, in such a magnetic recording medium, the thickness of the ferromagnetic metal thin film 2 used is 0.3 μm or less. Because the support 1 is so thin, the surface roughness of the support 1 becomes the surface roughness of the ferromagnetic metal thin film 2, so an extremely smooth support 1 must be used.

Therefore, the magnetic recording medium having the configuration shown in FIG. 1 is a helical scanning type video recorder 11. Even if a lubricant is selected to receive large friction when used in V, T, and R (lower V, Taa), repeated use at V, T, and R will cause the running to become unstable and the reproduction signal to fluctuate in the time direction. There was an inconvenience that the playback screen would shake or bend due to the generation of ginotarga.

In particular, as a result of pursuing the fact 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 to a ferromagnetic metal thin film formed on a support, the ferromagnetic metal thin film is held at a constant potential.

The number of crystal grains constituting the ferromagnetic metal thin film is 108 to 20.
Since it normally has an oxidized layer in the range of about 0.0%, when applying lubricant, when it is unwound from the wound state, it is detached and charged in the atmosphere, and a charge remains on the surface and the amount of charge is constant. Not yet.

Also, since magnetic recording media are produced in large quantities, the number of units that are continuously processed and processed is 5. Since the area is as large as ooo yd, the lubricant solution is also circulated and pumped.

At this time, the lubricant solution also becomes charged by friction with the components such as piping, pumps, container walls, and coke 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 investigation, it was confirmed that the same effect could be obtained by holding the potential at a constant level without relying on grounding.

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

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

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;
A lubricating layer 8 is formed.

At this time, measurement is performed to obtain an even thickness of the lubricating layer 8, and in this case, adjustment is mainly made by the gap between the applicator roll 5 rotating in the direction of arrow B and the metering roll 7 rotating in the opposite direction C. It is something that will be done.

The substrate 4 provided with the 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 liquid 6 carried in excess by the applicator roll 6 is transferred to the metering roll 7, scraped off by the doctor blade 9, and returned to the container 10 of the lubricant solution 6.

Reference numeral 11 denotes a potential regulating roller whose surface is made of a highly conductive material.
It is grounded by 2.

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

Reference numeral 14 denotes a free roller which 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 wise to configure the potential regulating roller 11 so that it is 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 direct current, not by grounding. Exceeding this range is not desirable 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 manner using other coating machines other than the coating machines shown in the above embodiments, and the types of the slender lubricant solution, the type of support 1 and the type of ferromagnetic metal thin film are as follows. The specific embodiments 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 6 is 20 holes, and the distance between the position where the applicator roll 5 and the substrate 4 contact and the potential regulating roller 11 with a diameter of 6Cr is 1 d 10 an. The surface potential of the substrate 4 was measured by bringing a voltage meter close.

More specific examples will be shown below.

(Example 1) A polyethylene terephthalate film (hereinafter referred to as Film 8) having a thickness of 9 μm was circulated around a 80'C medium, and a film A was formed along the outer periphery of a cylindrical can (not shown).
Heating the electron beam using a binary evaporation source while moving at 22 nL/mm at 70 K for each co
0.19 ferromagnetic metal thin film with 19 wt% Cr by controlling the input of 36 KVil for W, Cr
A substrate formed with a thickness of μm was obtained.

The degree of vacuum during the vapor deposition is 8×10 TORR,
The obtained ferromagnetic metal thin film is a perpendicularly magnetized film.

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

The lubricant solution used was one in which myristic acid was dissolved in n-hexane, and the coating speed was (r: i 60 m/mjn).

5, 00 771 Divide the board into 5 equal parts and apply the lubricant solution in 1. The magnetic tape was run in units of ○○○m, and the tape was repeatedly run in V, T, and R directions.

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 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 It appeared as a fluctuating jitter, and the length was 100 meters.
60 volumes of the invention product and 60 volumes of the comparative example at 25°C.
, 6o%R,H', 30''C'+ 85.%R,H-
' , (7J) Environmentally friendly, 100 each
After repeated use, the products of the present invention had no jitter that could be clearly seen on the screen, whereas the comparative example had 25°C, 260% R, H, Te 30%, 30°C, 85°C.
% R, Hof 60% (D 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 locations corresponded to the locations where the potential suddenly changed, ie, the locations indicated by arrows E and F, as shown in FIG.

(Example 2) A 7 μm thick aromatic polyamide film (hereinafter referred to as film B) was held insulated from a vacuum container by a cylindrical can around which a medium at 200°C was circulated, and a film was placed along the outer periphery of the cylindrical can. While moving the film B at a rate of 30@/mm, heating electron beams were applied to each co-heater using a binary evaporation source.
For KW.

A perpendicular magnetization film, which is a ferromagnetic metal thin film with a Cr content of 20% by weight, was heated to zero by controlling the input power of 40 KW to Cr.
．． A substrate formed with a thickness of 2 μm was obtained.

Prior to vapor deposition, the inside of the vacuum chamber was heated to 2 x 10' TORR.
After evacuating to
When the ferromagnetic metal thin film was formed using RR, a high frequency voltage of 13.56 μm was applied to the cylindrical can.

This high frequency voltage has an anode voltage of 3.5 KV and an incident wave of 515 KV.
0 CW] Reflected wave 50 [W':] The matching state 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%.

The lubricant solution used for coating was prepared by dissolving stearic acid, a lubricant, in methyl ethyl ketone. The coating speed was 76 m/mM, and 500077
Each of the H substrates was divided into 5 equal parts and the coating was repeated in units of 1000 m, and a magnetic tape with a width of 8111A was used to run repeatedly in V, T, and R directions.

30'C, 90% R, H, respectively 17) When the tape was used repeatedly 100 times, there were no tape rolls in which jitter clearly appeared on the screen with the inventive product, but out of 60 tape rolls with the comparative example. It was 50%.

To examine durability from a different angle, operate V, T, and R in still frame mode, select 10 arbitrary positions on each tape at 30'C, 90%, RH, and time until the playback output drops by 3 dB. With respect to 500 measurement points for all tapes, all of the products of the present invention took more than 30 minutes, while the comparative example took 50 minutes.
There were 34 points for less than 1 minute, 21 points for 5 to 10 minutes, and 131 points for 10 to 30 minutes, and the durability was clearly inferior.

Effects of the Invention As described above, the method of the present invention can be used simply by arranging, for example, a potential regulating roller in a part of an existing coating machine, and can be used to produce metal thin film magnetic recording media, which has traditionally been labor-intensive. Sequentiality: In particular, there is no deterioration in image quality caused by sick problems caused by running instability caused by repeated use of V, T, and R.
Magnetic tape with long methyl life can be obtained in large quantities with good reproducibility0

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

Claims (1)

[Claims] A method for manufacturing 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.