JPS6357855B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic recording medium, and particularly to a magnetic recording medium having a magnetic recording layer made of a metal or alloy magnetic thin film. Ferromagnetic thin films are effective for magnetic recording media and have long been attracting attention. In order to improve the magnetic properties of this thin film, it is known that the coercive force in the longitudinal direction can be improved by so-called oblique deposition, in which the film is deposited obliquely with respect to the base surface (Japanese Patent Publication No. 41-197).
19389). This method is effective in increasing coercive force, but in cases where the substrate cannot be heated sufficiently, such as with polyethylene terephthalate bases, the adhesion area (the area where the ferromagnetic metal particles adhere to the base) is ) cannot be made large,
It was found that the main drawbacks were that the density of the thin film could not be increased and there were defects in the film structure, typified by weak adhesive strength, which hindered its practical use. On the other hand, thin films created by reducing the incident angle (the angle of incident particles measured from the normal to the base surface) have the expected protection from shape anisotropy because the length direction of the columnar shape is oriented in the thickness direction. It was found that the magnetic force is not effective along the length of the tape. However, this film reduces the shadow area caused by so-called shadowing, where part of the base or vapor deposited layer is shadowed when viewed from the evaporation source due to previously deposited particles, resulting in a structurally stable and strong film. There are features that can be used. Since the obliquely deposited magnetic thin film is structurally weak as described above, attempts have been made to compensate for this drawback by attaching some kind of protective film to its surface. However, this method not only increases the number of manufacturing steps, but also requires consideration of magnetic influences, so there are still problems with its practicality. In contrast, the present inventors have succeeded in obtaining a ferromagnetic thin film with excellent magnetic properties and adhesion strength by performing oblique vapor deposition followed by nearly perpendicular vapor deposition. The outline of the thin film obtained by the present invention is as follows.
As shown in the figure. As shown in the figure, a first ferromagnetic layer 2 is formed on a substrate 1 by oblique vapor deposition with an incident angle 7 of 45° or more as shown in FIG. It is formed at a lower angle of incidence (less than 30°) than the layer. The thicknesses of the ferromagnetic layers 2 and 3 do not need to be particularly limited, and can be determined in consideration of magnetic properties and the like. Examining the mechanism of the present invention, the density of the obliquely deposited first layer decreases due to shadowing, resulting in a structure that is so-called "full of gaps." Particles fly into the gap at a low angle of incidence and enter the gap. It is understood that in this way, the entire film has a strong structure. Examples are shown below to specifically explain the effects of the present invention. Example 1 FIG. 3 is a schematic diagram of the evaporation section of the vacuum evaporation apparatus used in the experiment of this example. The entire system shown is housed in a vacuum chamber (not shown), and a polyethylene terephthalate base B, which is the base of a magnetic recording medium or a tape-shaped substrate, is wound around a feed roll 8, and from there a guide roller 11 is wound. around,
Next, a large-diameter rotating drum 1 rotating clockwise
0, the sheet passes through a guide roller 11 and is wound onto a winding roll 9. A sample crucible 15 whose exterior is heated and contains an alloy M of cobalt and nickel in a weight ratio of 4:1 to be vapor-deposited is arranged below the lower surface side of the rotating drum 10 through which cold water is passed, that is, the side through which the base B passes. , and the rotating drum 10
A mask 14 is interposed between the melt and the crucible 15 . The mask is formed with elongated slits a and b (extending in the width direction of the base B), with slit a directing the alloy vapor to position 12 in the figure at an incident angle of 70 degrees, while slit b directing the alloy vapor to position 13 in the figure. The alloy vapor is directed at an angle of 20 degrees to the location. In this figure, the diameter of the rotating drum 10 was 25 cm, and the point 12 was located at a height of 30 cm from the crucible 15. The above system was operated to move the base B in the direction of the arrow at a speed of 40 cm/min, while the evaporation source 15 was heated with an electron beam so that the deposition rate was 2000 Å/min at the portion 12. Also, the pressure of the system is 5×10 ⁵ Torr
It was hot. Under these conditions, of the two slits a and b, the sample made by closing b is called sample 1, and the sample made by opening the two slits is called sample 2. The differences between the two are shown in Table 1. Among the magnetic properties, there is no significant difference in the coercive force Hc and the squareness ratio φr/φm, but it can be seen that the adhesive strength of Sample 2 is significantly improved. Example 2 FIG. 4 is a schematic diagram of a vacuum evaporation apparatus used in the experiment of this example. A vacuum chamber is not shown. The base B of polyethylene terephthalate, which serves as the base of the magnetic recording medium, that is, the tape-shaped substrate, is wound onto a take-up roll 18 via a delivery roll 17, guide rollers 19, 19, and as described in Example 1. A mask 22 having slits a and b similar to that and a magnetic alloy M similar to that in Example 1.
A crucible 23 containing . roll 1
By adjusting the positional relationship between 7, 18 and guide rollers 19, 19 and the position of the mask 22, the alloy vapor is deposited on the surface of the base B at 20 at an incident angle of 80 degrees, and at 21. Incidentally, it was determined that the film should be deposited at an incident angle of 20 degrees. A magnetic recording medium was produced by operating the above system at the same base drive speed, deposition rate, and pressure as in Example 1. At this time,
Sample 3 made by closing slit b, and sample a,
Table 1 also shows the differences in Sample 4, which was created by opening both B and B. In this case as well, a remarkable improvement in adhesive strength was observed without impairing the magnetic properties, confirming the effectiveness of the present invention.

[Table] Note that Hc, φr, and φr/φm were measured using VSM at a maximum applied magnetic field of 5000G. φr is length 20cm, width
This is the residual magnetic flux of a 3.8mm sample. The adhesive strength is a value measured using samples of the same width using Tensilon.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the magnetic thin film of the magnetic recording medium of the present invention, FIG. 2 is a diagram showing the relationship between the direction of the base and the incident direction of the magnetic metal particles, and FIG. 3 is the magnetic thin film according to the first embodiment of the present invention. FIG. 4 is a front view showing a recording medium manufacturing apparatus, and FIG. 4 is a front view showing a magnetic recording medium manufacturing apparatus according to a second embodiment of the present invention.

Claims (1)

[Claims] 1. In a horizontal recording type thin film magnetic recording medium consisting of a vapor deposited film of cobalt, nickel, iron, or an alloy thereof provided on a tape-shaped substrate, the vapor deposited film is such that the growth direction of the ferromagnetic metal or alloy particles is perpendicular to the substrate surface. The first magnetic layer has an angle of 45 degrees or more to the perpendicular to the substrate surface, and the second magnetic layer has a growth direction of ferromagnetic metal or alloy particles formed thereon that is 30 degrees or less to the perpendicular to the substrate surface. A horizontal recording type magnetic recording medium characterized by: