JPH0334130B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a magnetic recording medium having a ferromagnetic metal thin film as a recording layer.

Until now, demands for higher density magnetic recording have been met by increasing the coercive force of magnetic recording media, but as wavelengths continue to get shorter, magnetization occurs closer to the surface of the media. Therefore, it is not possible to increase the output by increasing the coercive force alone, and materials with a high saturation magnetic flux density are being used. One of these is an extension of the conventional coating type,
A magnetic recording medium that uses fine particles of a ferromagnetic metal such as iron or an alloy, which is diluted with a non-magnetic material such as a binder but has essentially a high saturation magnetic flux density, instead of iron oxide. A medium whose magnetic recording layer is a ferromagnetic metal thin film that does not use a binder.
Since vacuum evaporation is used to form the thin film, some tapes have come into practical use under the name evaporation tape.

This vapor-deposited tape has a short history, and there are many issues that need to be investigated and improved on an industrial scale.

One of them is the control of coercive force. In particular, the development of technology to stably control large coercive forces is an important theme.

The so-called oblique evaporation method disclosed in Japanese Patent Publication No. 19389/1989 has the possibility of stably controlling the coercive force using a evaporation method.

However, the difficulties in implementing this method are that the deposition efficiency is low and that the coercive force changes as the incident angle changes, and this phenomenon becomes more pronounced as the coercive force increases. It is.

The present invention provides a method that can suppress changes in coercive force caused by changes in incident angle to a practical level, and will be described in detail below with reference to the drawings.

FIG. 1 shows a cross-section of essential parts of a vapor deposition apparatus for carrying out the method of the present invention. Although an example of a two-chamber configuration is shown here, the method of the present invention is not limited to this, and any device that satisfies the requirements described below can be used.

A polymer molded substrate (hereinafter simply referred to as a substrate) 1 is configured to move from a feed shaft 2 along a rotation can 3 and be wound up on a winding shaft 4. In this figure, other elements of the winding system, such as a flow roller and an expander roller, are omitted, but it goes without saying that they may be included as necessary.

The rotary can 3 also functions as cooling support, and instead of it, an endless belt made of a thin stainless steel plate, such as SUS304, may be used. Of course, this belt is also cooled before use.
Also, multiple cans can be used to perform repeated depositions.

An evaporation source 5 disposed opposite the rotary can 3
Although any known method can be used, according to experiments conducted by the inventors, electron beam heating is preferred. In the figure, the evaporation source 5 is schematically shown as a container 6 and the evaporation material 7, and the illustration of the electron source is omitted.

The inside of the vacuum chamber 8 is divided into an upper chamber 10 and a lower chamber 11 by a partition plate 9. Upper chamber 10 and lower chamber 11
are normally exhausted by independent exhaust devices 12 and 13, respectively. The mask 14 is used to limit the angle of incidence of vapor onto the substrate 1. When the center of the evaporation source 5 is P and the tip of the mask 14 is M,
The angle θ ₁ between the extension of the PM and the normal line drawn to the point where it intersects with the substrate 1 on the circumferential side of the can 3 represents the incident angle of the vapor.

Further, the angle θ _M formed between the normal line and the point M at the tip of the mask 14 is the incident angle of the vapor deposited onto the mask 14 . It is a requirement of the present invention that θ ₁ and θ _M have a relationship of θ ₁ < θ _M , and if this is satisfied,
There are no particular restrictions on the shape of the mask 14, and it may be a part of a circular arc or a combination of straight lines.

Examples of the present invention will be described in detail below.

Example 1 A polyethylene terephthalate film with a width of 500 mm and a thickness of 10.5 μm was used as a substrate, and the incident angles θ ₁ = 70° and θ _M = 80° (see Figure 1) were measured using the apparatus shown in Figure 1.
Co 80%-Ni 20% alloy layer 0.1 μm thick on the substrate
It was formed to a thickness of . The degree of vacuum in the lower chamber is 2×
It was 10 ^-5 Torr. The coercive force of the obtained magnetic layer is
At 1050 oersted, the squareness ratio of the B-H curve is 0.96
It was hot.

And, except for setting θ _M = 30° for comparison,
A magnetic layer was formed under the same conditions as in this example.

FIG. 2 shows sampling in the longitudinal direction of the sample prepared in this example and the sample prepared in the comparative example, and the coercive force distribution in the width direction is shown in the form of error bars.

As is clear from this, according to the method of the present invention, the coercive force is constant, and the variation in the width direction is also very small. However, according to the comparative example,
As the coercive force increases, its widthwise variation also increases.

Similar comparisons were made for the following examples, but
It is shown by comparing the coercive force at the time of 1000m deposition and immediately after the start.

Example 2 On a polyethylene terephthalate film with a length of 2050 m, a width of 500 mm, and a thickness of 15 μm, the incident angle of vapor θ ₁
= 73°, a magnetic layer made of 100% Co was formed to a thickness of 0.2 μm. The angle of the tip of the mask was θ _M =80°, and the degree of vacuum in the lower chamber was 1.7×10 ⁻⁵ Torr. The obtained coercive force is at the initial stage, at 1000m, and at 2000m, respectively.
1200 oersted, and the squareness ratio of the B-H curve is
At 0.97, the uniformity in the width direction did not change either.

On the other hand, for comparison, when formed at θ _M = 20°,
At 1000 m, the coercive force varied between 1220 and 1410 oersted. At this time, the deposited on the tip of the mask
The Co thickness was now 19 mm, and the angle of incidence had changed substantially.

Example 3 85% Co was deposited on a polyethylene terephthalate film with a width of 500 mm and a thickness of 11.5 μm at an incident angle θ ₁ = 60°.
A magnetic layer consisting of 15% Cr was formed. Vacuum degree 1
×10 ^-5 Torr, and the cases of θ _M =85° and θ _M =75° were compared and studied. The initial value at 1000m is coercive force.
980 Oersted, the squareness ratio of the B-H curve is 0.98,
The coercive force distribution in the width direction was uniform in all cases.

After examining these two examples in more detail, we found that as the length increases to 2000m and 3000m, θ _M =
There was a tendency for the coercive force to change slightly in the case of θ _M =75° compared to the case of 85°. From this point of view, it is of course necessary to maintain the relationship θ ₁ <θ _M , but it is also preferable to make θ _M as large as possible. However, if the evaporation position shifts due to a drop in the evaporation level, the angle of incidence tends to change, so θ ₁ = 75
It is practical to set the angle to ~85°. However, this is not the case if a feeder is provided to replenish the evaporation material to the evaporation source to accommodate the lengthening of the substrate, thereby keeping the level of the molten metal at the evaporation source constant.

Example 4 80% Co on a polyamide substrate with a thickness of 8.5 μm
A magnetic layer consisting of 20% Ni was formed to a thickness of 0.15 μm. Oxygen is introduced into the lower chamber, and the vacuum level is 4.5×.
Vapor deposition was performed while maintaining a vacuum level of 10 ^-5 Torr. In addition,
θ ₁ =45° and θ _M =80°.

The coercive force of the obtained magnetic layer was 920, and the squareness ratio of the BH curve was 0.88. And 4000m of substrate
The values were substantially uniform in both the width direction and the longitudinal direction over the length. For comparison, when θ _M =20°, the coercive force increased by about 15% at 1000 m and by 34% at 2000 m. At 3000m, to control the deposited film thickness, we need to reduce the film movement speed by 40%.
It became necessary to increase the power of the electron beam input by 30%. It can be seen from this that the present invention can maintain the set conditions and has excellent film thickness controllability.

In addition to the first apparatus used in these Examples, the effects of the present invention can be obtained even if a high frequency electrode is disposed between the film as a substrate and the evaporation source, and ion plating is performed at a high frequency of 13.56 MHz. I confirmed that I can get it. Then, as the evaporation material, Fe,
Co-V, Co-W, Co-Mn, Co-Ti, Co-Si,
It was confirmed that the effects of the present invention can be obtained even when Co-Ni-Cr, Co-Pt, etc. are used.

As described above, the method of the present invention sets the vapor incident angle to the part of the mask that regulates the vapor incident angle for magnetic layer formation to be larger than the vapor incident angle to the substrate. To provide a vapor-deposited tape for magnetic recording and reproducing, which can keep the coercive force of a magnetic layer and the squareness ratio of a B-H curve constant even when a magnetic material is continuously vapor-deposited on a substrate, and thus has stable quality. Can be done.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a diagram comparing and showing the characteristics and variations of magnetic tapes manufactured by the method of the present invention and a comparative example. . 1... Polymer molded substrate, 3... Rotating can, 5
... Evaporation source, 9 ... Partition plate, 8 ... Vacuum chamber, 10
...Upper chamber, 11...Lower chamber, 12,13...Exhaust device, 14...Mask.

Claims (1)

[Claims] 1. When ferromagnetic material is continuously deposited on a polymer molded substrate moving along a cooling support, the incidence of vapor near the part of the mask that limits the angle of vapor incidence for magnetic layer formation is related to angle limitation. A method for manufacturing a magnetic recording medium, characterized in that the angle is larger than the incident angle for forming the magnetic layer.