JPS61160836A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To eliminate the generation of projections owing to oligomer on the surface of a polyethylene terephthalate film by heating said film within a specific temp. range for specific time or below and forming a thin magnetic film consisting essentially of Co-Cr on the film under said conditions. CONSTITUTION:The polyester (PET) film 2 is brought into contact with a roll 1 heated to 100-140 deg.C and is guided in the course by auxiliary rolls 5, 6, 7, 8. The rolls 6, 7 are made vertically movable as shown by an arrow to permit the adjustment of the contact angle theta of the film 2 with the roll 1. The contact time of the film 2 with the roll is set at a few minutes or below. The magnetic material consisting essentially of Co-Cr is sputtered onto the film 2 through an aperture of a mask 9 from a target 10 under the roll to form the magnetic layer. The magnetic layer is thus formed at and for the temp. and time at and for which the oligomer in the PET film forms the projections on the film 2 surface or below. The spacing loss is decreased and the defect such as the easy tendency to the exfoliation of the magnetic layer is eliminated.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a C
The present invention relates to a method of manufacturing a magnetic recording medium having a magnetic layer thin film containing o-Cr as a main component.

[Technical background of the invention and its problems]

Recently, a so-called perpendicular magnetic recording system, in which the magnetic layer of a magnetic recording medium is magnetized in the perpendicular direction, has been attracting attention as a method for performing high-density recording.

Conventionally, magnetic recording media used in such perpendicular magnetic recording systems use a Co-0r sputtered thin film having an axis of easy magnetization in a direction perpendicular to the film surface as a magnetic layer, and various polymer films are used as a substrate for this. However, in particular, such polymeric films include polyethylene terephthalate (
Hereinafter, it will be abbreviated as PET. -) The film has good surface properties, flexibility and strength of 1, excellent per head, and is easy to mass-produce and has stable bill quality.Furthermore, the price is about 1/2 that of polyimide heat-resistant film. It is widely used because it has superior properties compared to other polymer films, such as a rating of 10.

Incidentally, in such a perpendicular magnetic recording medium, as magnetic properties, the saturation magnetization Ms determined by the film composition and the magnetic anisotropy energy Ku perpendicular to the film surface are large, and the coercive force HC-L perpendicular to the film surface is large. is required to be large.

Among these, it is particularly important that the coercive force He is sufficiently large because it affects the magnitude of the reproduction output, and for this reason, it is necessary to raise the temperature of the substrate surface to a certain degree during film formation.

Therefore, in the conventional manufacturing method of such a Co-Cr perpendicular magnetic recording medium, in a continuous forming method using a preheated cylindrical roll, the main component is Co-Cr which satisfies the magnetic properties required for a magnetic recording medium. In order to form a thin film, the roll temperature during sputtering is raised to a range of 100 to 140°C.

However, when the roll temperature is in the range of 100 to 140°C, when a PET film is used as the substrate of a magnetic recording medium, the oligomer components inherent in the PET film are exposed to the surface of the film due to contact between the heating roll and the PET film. , and are formed as minute protrusion-like precipitates on the film surface. For this reason, the surface properties of the film are significantly deteriorated by these precipitates, and in particular, microprotrusions caused by oligomers not only cause a simple increase in the spacing between the magnetic recording medium and the head that slides on it, but also cause the magnetic layer to deteriorate. This significantly reduces the adhesion strength of the magnetic layer, making it more likely to peel off from the substrate. Further, among the minute protrusions formed by the oligomer, those that have become coarse adhere to the head surface as the head surface of the magnetic recording medium runs, causing scratches on the magnetic recording medium and the head surface, and having an adverse effect on durability. Furthermore, the oligomers attached to the surface of the head act to further increase the spacing between the head and the magnetic recording medium, which may lead to a reduction in reproduction output. It is an object of the present invention to provide a method for manufacturing a magnetic recording medium that suppresses the generation of protruding precipitates due to oligomer components inherent in a PET film and provides a high-quality perpendicular magnetic recording medium.

[Summary of the invention]

First, to describe the concept of this invention, we first investigated the thermal behavior of PET film in detail and found that the average height y of oligomers precipitated on the surface of PET film by heating the PET film is determined by the heating temperature of the film and the heating temperature. It has been confirmed through experiments that it is related to time and can be approximately expressed by the following formula if the heating temperature is constant.

y = ni/1t-)-c where t is the heating time, and C and C are constant values determined by the heating temperature and the amount of residual oligomer in the film. Here, when we calculated the values of k and C for several types of PET films currently on the market that have relatively good surface properties, we found that k > O, C (0. In other words, due to excessive precipitation of oligomers, There is a latent period Δt, and oligomers hardly precipitate when heated within Δ, but oligomers rapidly precipitate when the heating time exceeds Δt.Therefore, in the step of forming a thin magnetic layer on a PET film substrate. In this case, if the heating time of the PET film is set to about Δ at the maximum, property deterioration due to oligomer precipitation can be suppressed as much as possible.
The relationship between heating time and average oligomer height in the case of ℃ is shown in FIG. From the figure, it can be seen that when the heating temperature is 140° C., Δt is 2 to 3 minutes S degrees. It was also found that Δt tends to increase as the heating temperature decreases.

In the present invention, we focus on the incubation period Δt of oligomer precipitation, and when forming a thin magnetic layer while heating a PET film substrate, the time during which the PET film substrate is heated to a predetermined temperature is adjusted to at most Δt. This makes it possible to suppress property deterioration due to oligomer precipitation as much as possible while ensuring necessary magnetic properties. In other words, since the value of Δt at the substrate temperature necessary to satisfy the magnetic properties required in the present invention is about the same at 140°C, the time for heating the PET film substrate is set within a few minutes. By doing so, deterioration of properties due to oligomer precipitation can be suppressed as much as possible.

〔Effect of the invention〕

According to this invention, PET heated to 100-140°C
Since a thin magnetic layer mainly composed of Co--Cr is formed on a film substrate by a method such as sputtering, a perpendicular magnetic recording medium satisfying magnetic properties can be obtained.

Moreover, since the total heating time of the PET film substrate in the medium obtained in this manner is set to be less than 2 to 3 minutes, the formation of protruding precipitates on the surface of the film and the lumen due to oligomer components is almost non-existent. Therefore, it is possible to suppress a decrease in reproduction output due to spacing loss, and to ensure sufficient durability of the magnetic layer.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows an example in which the present invention is applied to an apparatus for a continuous forming method using a cylindrical heating roll.

In the figure, 1 is the main roll, and this roll 1 is always 100.
Heated to ~140°C. PET film 2. is run. This film 2 is sent out from an unwinding roll 3, wound up by a take-up roll 4, and guided along a running path by auxiliary rolls 5, 6, 7, and 8.

Here, the auxiliary roll 6.7 can be moved up and down in the direction of the arrow shown in the figure, so that the contact angle θ of the film 2 with the main roll 1 can be adjusted.

On the other hand, the mask 9 corresponds to the contact part of the main roll 1 with the film 2.
A Co-C:r target 10 is provided via the . This target 10 is placed on the second side of the film.

This is for forming a magnetic layer thin film containing -Cr as a main component by sputtering.

In such a device, the PET film 2 fed out from the unwinding roll 3 is guided to the main roll 1 via the auxiliary roll 5.
It is set to less than 1 minute.

In this way, the roll l heated to 100-140℃
Since a magnetic layer thin film is formed by sputtering with the PET film 2 in contact with the PET film 2, a magnetic recording medium whose magnetic properties are sufficiently titrated can be obtained. In addition, by keeping the contact time between the roll 1 and the PET film 2 to 2 to 3 minutes or less, it is possible to suppress the formation of protruding precipitates on the film surface due to oligomer components, thereby minimizing the reduction in playback output due to spacing loss. At the same time, sufficient durability of the magnetic layer can be ensured without deterioration of the adhesion strength of the magnetic layer to the PUT film surface, and furthermore, a better head touch can be obtained.

Incidentally, in the apparatus for the continuous forming method described in FIG. The contact time between the film 2 and the film 2, that is, the heating time of the film 2, is 2 to 3 minutes or less, centered around 43 minutes.
A plurality of settings of 2 to 3 minutes or more were made, and under each of these setting times, media with a thin film of 0 to 5 μm formed by sputtering on the film 2 were obtained, and these media were subjected to perpendicular recording and reproduction using a ring head. When the state of the reproduced output was investigated, the results shown in FIG. 3 were obtained.

In the figure, the reproduction output when the film heating time is 1 minute is set to 100%.

As a result, as is clear from Fig. f43, it was confirmed that if the heating time of the PET film was set to 2 to 3 minutes or less, the reduction in reproduction output due to spacing loss could be suppressed. At the same time, we also investigated the state of the thin film formed on the PET film for each medium.
When the time was 3 minutes or less, good results were obtained in terms of durability and head touch.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications without changing the gist.

For example, although the continuous forming method using a cylindrical heating roll has been described above, it is also possible to apply other methods. Furthermore, in the above, we have described the case where the PET film is heated only once, but if, for example, sputtering is performed multiple times and the film is heated each time, the total time for these heating steps should be 2 to 3 minutes or less. Just do it.

Further, when heating is performed as a post-treatment after forming a thin film on the film surface by sputtering, it goes without saying that the heating time at this time should also be within a range of 2 to 3 minutes or less.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram for explaining the invention in detail, Figure 2 is a characteristic diagram for explaining the invention in detail.
The figure is a schematic configuration diagram showing one embodiment of the present invention, and the figure $3 is a characteristic diagram for explaining the embodiment. 1... Main roll 2.++ PET film 3
．． 4, 5, 6, 7, 8...Roll 9...Mask 10...Target

Claims (3)

[Claims] (1) A step of supplying a substrate made of polyethylene terephthalate film, heating the surface of the substrate supplied in this step to 100 to 140°C, and heating for 2
, 3 minutes or less, and forming a magnetic layer thin film containing Co--Cr as a main component on the heated substrate surface. (2) The step of heating the substrate surface to 100 to 140°C and setting the heating time to 2 to 3 minutes or less is 100°C.
The magnetic recording medium according to claim 1, wherein the substrate is brought into contact with the circumferential surface of a cylindrical roll heated to ~140°C, and the contact time is set to be 2 to 3 minutes or less. manufacturing method. (3) The method for manufacturing a magnetic recording medium according to claim 1 or 2, wherein the step of forming a thin magnetic layer on the substrate uses a sputtering method.