JPH0334132B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium such as a vapor-deposited tape having a metal ferromagnetic layer as a magnetic recording layer on a polymer molded substrate. The purpose is to provide a method suitable for manufacturing recording media.

Vapor-deposited tape is a medium suitable for short wavelength recording.
Although it has been expected since the early 1970s, it took a lot of time to overcome issues such as durability and corrosion resistance, and it has only recently been put into practical use for some audio applications.

Attempts to use vapor-deposited tape for video applications are also progressing, and although a practical level of accuracy has been achieved in controlling the magnetic properties in order to obtain uniform properties in the longitudinal and width directions, there are still problems in terms of practical performance. There are still issues that require improvement.

One of these is that when comparing long tapes, even if the magnetic properties are exactly the same, the output fluctuations are different, and the other is that the noise is different.

The present inventor found that there is a significant difference in the surface properties of the media, and completed the present invention by examining in detail where the cause of the significant difference is at the time of manufacturing. The present invention will be explained below.

FIG. 1 shows the main parts of a manufacturing apparatus for carrying out the present invention, and FIG. 2 shows other main parts.

As shown in the figure, the substrate 1 is partially covered by the mask 6 due to the vapor flow of the ferromagnetic material emitted from the evaporation source 5 as it moves along the rotating support 2 from the delivery shaft 3 to the take-up shaft 4. It is deposited under a limited angle of incidence.

The rotating support 2 also has a function of circulating a medium therein to maintain a constant surface temperature and to perform a cooling effect to reduce the thermal influence on the substrate. Note that the rotating support may be a cooled endless metal thin plate.

After the vapor deposition is limited to the mask 6, the substrates are cooled down, but when moving at high speeds on a practical scale, the substrates are at room temperature or higher. The metal roller that is touched is heated up by the heat transfer effect and reaches a certain equilibrium temperature.

Therefore, when the temperature of the first and second rollers 7 and 8 (7' and 8' in Figure 2) is controlled, the controlled temperature has a strong correlation with the stability of the characteristics at the glass transition point Tg of the substrate. I discovered that. 1st
In the figure, the first roller 7 is in contact with the vapor deposition surface and the second roller 8 is in contact with the vapor deposition surface. In FIG. 2, on the contrary, the first roller 7' is in contact with the vapor deposition surface, and the second roller 8' is in contact with the surface opposite to the vapor deposition surface.

In an actual winding system, the number of metal rollers will increase further due to the introduction of expander rubber rollers, etc., but it is sufficient to control the temperature of the two rollers (depending on the roller diameter, only one may be sufficient) immediately after vapor deposition. Get results.

However, it goes without saying that this does not prevent the temperature of three or more rollers from being controlled.

The surface roughness of the roller is also preferably smooth, but in view of actual control standards, the surface roughness may be about 0.1S to 0.3S.

The most important thing is to control the temperature to below Tg, and at that time, even if the roller surface is scratched and the maximum roughness exceeds 0.5 μm and reaches 1 μm, the tape surface will not be damaged. It is noteworthy.

Next, examples of the present invention will be specifically described.

Example 1 A rotating support with a diameter of 1000 mm was maintained at 25°C,
Polyethylene terephthalate film (Tg=68.5℃) (thickness 9.5μm) moving at a speed of 35m/min
A ferromagnetic layer of 85% Co and 15% Ni was formed on the top by electron beam evaporation in an oxygen atmosphere of 2.5×10 ^-5 Torr to a thickness of 0.13 μm at an incident angle of 40° or more. Wind it up after controlling it to ℃±5℃,
A 1/2 inch tape was made.

The reproduction output fluctuations of this tape were investigated over a total length of 3000 m. The recording wavelength at this time is
It is 0.7 μm.

The resulting output fluctuation was ±0.6 dB. On the other hand, with the manufacturing method not based on the present invention, the output fluctuation is ±0.6 dB from the beginning of evaporation to 900 m.
However, from 1,000 m to 3,000 m, a region with large output fluctuations due to repeating phenomena without periodicity was observed. The maximum fluctuation range was ±3.2 dB, which was an order of magnitude larger.

Example 2 A rotating support with a diameter of 1000 mm was maintained at 5°C,
On a substrate (thickness: 11.5 μm) that has a coating layer with minute protrusions on both sides of a polyethylene terephthalate film (Tg = 70°C) that moves at a speed of 40 m/min.
A ferromagnetic layer of 80% Co and 20% Ni was deposited by electron beam evaporation in an oxygen atmosphere of 3×10 ^-5 Torr at an angle of incidence of
The tape was formed to a thickness of 0.1 μm at an angle of 43° or more, and wound with the roller on the winding side controlled at 30° ± 3°C to produce a 1/2 inch tape.

The reproduction output fluctuation of this tape at a recording wavelength of 0.7 μm was ±0.5 dB over the entire length of 4000 m.

On the other hand, for tapes manufactured using the conventional method, output fluctuations suddenly became large after 1800 m, with a maximum of ±5.2 dB.
It became. There was also a noticeable increase in noise.

In addition, an epoxy layer in which graphite was dispersed was placed on the opposite side of the vapor deposition surface of the film used in Examples 1 and 2.
It was confirmed that performance was similarly improved when a 1/2-inch tape was coated with a thickness of 0.1 μm.

It was also confirmed that the above-mentioned effect does not depend on the type and thickness of the substrate such as polyacetate, polyimide, polyamide, etc., nor does it depend on the type and thickness of the magnetic layer.

As is clear from the above description, according to the present invention, it is possible to stably produce a high-performance magnetic recording medium with uniform characteristics such as small output fluctuation in the longitudinal direction, and its industrial value is great.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are diagrams showing the main parts of a manufacturing apparatus used when carrying out the manufacturing method according to the present invention, respectively. 1... Substrate, 2... Rotating support, 5... Evaporation source, 7, 7', 8, 8'... Roller.

Claims (1)

[Claims] 1 After forming a ferromagnetic layer by vapor deposition on a polymer molded substrate that moves along a support, it is heated using a roller whose surface temperature is controlled to be below Tg, where the glass transition point of the substrate is Tg. A method for manufacturing a magnetic recording medium, comprising winding up the substrate.