JPS62132254A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To remarkably improve the corrosion resistance of a recording layer of a photomagnetic recording medium, to simplify a production process of the spectral magnetic recording medium and to reduce the production cost thereof by adding hardly corrosive elements to an alloy of a rare earth metal and transition metal to form said recording layer so that the hardly corrosive elements are concd. on the surface of the recording layer. CONSTITUTION:The hardly corrosive elements are concd. on the surface of the alloy of the rare earth metal and transition metal and the secure corrosion- resistant film is formed when the recording layer of the photomagnetic recording medium is formed by adding the elements having the hardly corrosive characteristic to said alloy. The hardly corrosive elements contained in the alloy are successively deposited onto the surface of the alloy and the corrosion resistant effect is sustained even if the hardly corrosive elements on the surface are removed by certain reason. At least one kind of the elements selected from titanium, chromium, aluminum, platinum, zirconium, vanadium, tantalum, molybdenum, tangusten, copper, ruthenium, rhodium, palladium, niobium, iridium, and hafnium are preferably used for the additive elements.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical recording medium on which information can be repeatedly erased and rewritten.

[Conventional technology]

Magneto-optical disks, on which information can be erased and rewritten any number of times, are about to be put into practical use, similar to magnetic tapes or magnetic disks. As a recording material applied to the recording layer of such a magneto-optical disk, a uniform recording layer can be formed over a large area by a sputtering method or a vapor deposition method. ■Since there are no grain boundaries, a large S/N ratio can be obtained.
Traditionally, rare earth metals such as gadolinium, terbium, and dysprosium and iron have been used.

Amorphous alloys with transition metals such as cobalt are attracting attention (Nikkei Electronics, March 25, 1985, pages 167 to 188).

However, the above-mentioned amorphous alloy of rare earth metals and transition metals has the disadvantage that it is a highly oxidizable substance and easily corrodes in the air, so it is difficult to apply it as a recording layer of a magneto-optical recording medium. In some cases, the required service life cannot be satisfied unless some corrosion prevention means are added.

Conventionally, it has been used, for example, between the disk substrate and the recording layer made of the above-mentioned alloy, and on the surface side of the recording layer.

The corrosion resistance of the recording layer is improved by coating it with a protective film made of SiO, SiO2, 51gN4, or the like.

[Problem that the invention seeks to solve]

As mentioned above, if a method is adopted in which both the front and back sides of the recording layer are coated with protective films, the manufacturing process of the magneto-optical disk becomes longer due to the coating process, and the manufacturing cost of the magneto-optical recording medium increases. . In addition, with the above method, if defects such as pinholes and hair cracks occur in the protective film, corrosion of the recording layer will progress from there, so
! Advanced technology and quality control are required to form the layer, but on the other hand, there is a problem in that it is unreliable as a means of preventing corrosion of the recording layer. Furthermore, if a protective film of a type that is compatible with the composition of the recording material constituting the recording layer is not used, corrosion of the recording layer will be accelerated, so there is a problem in that it is difficult to select an optimal protective film.

[Means for solving problems]

As a result of experiments, the inventor of the present application has found that: (1) When a non-corrosive element is added to an alloy of rare earth metals and transition metals, the non-corrosive element is concentrated on the surface of the alloy, forming a strong corrosion-resistant film. , and ■ In addition to the above-mentioned non-corrosive elements, adding an element that promotes corrosion of the alloy further promotes this concentration phenomenon and forms a corrosion-resistant film in a short time, and furthermore, ■ protects corrosion resistance. Unlike the case of coating with a film, even if the non-corrosive elements on the surface of 1 are removed for some reason, the above-mentioned non-corrosive elements contained in the 9 alloys will be deposited one after another on the alloy surface, and the corrosion-resistant effect will continue. learned.

The present invention has been made based on the above-mentioned findings, and is capable of producing a recording layer of a magneto-optical recording medium using a recording material made of an alloy of a rare earth metal, a transition metal, and an element that is difficult to corrode. formed, and rare earth metal;
A transition metal, a first element that is difficult to corrode in itself, and a second additive element that promotes corrosion of the easily corrosive element in the alloy and promotes concentration of the first additive element in the alloy surface layer ( The present invention is characterized in that the recording layer of the magneto-optical recording medium is formed using a recording material made of an alloy of a concentration-promoting element (hereinafter referred to as a concentration-promoting element).

The additive elements that have resistance to corrosion when used alone are as follows:
Titanium, chromium, aluminum, platinum.

Zirconium, vanadium, tantalum, molybdenum, tungsten, copper, ruthenium, rhodium.

It is preferable to use at least one element selected from palladium, niobium, iridium, and hafnium.
Further, as the concentration-promoting additive element, an element selected from semiconductors, nonmetals, and semimetals can be used. Among these elements.

Particular preference is given to using elements selected from silicon, germanium, boron, carbon and phosphorus.

〔Example〕

Hereinafter, specific examples will be given, and the corrosion resistance ratio flfi with a conventional recording layer to which no special element is added will be shown.

1st Example to 32nd Example T b z. Fes. A recording material made by adding 5% each of titanium, chromium, aluminum, platinum, zirconium, vanadium, tantalum, molybdenum, tungsten, copper, ruthenium, rhodium, palladium, niobium, iridium, and hafnium as non-corrosive elements to an alloy; A recording layer having a thickness of approximately 1,000 layers was formed on the surface of a glass substrate using recording materials to which 10% of each of the above elements was added, thereby forming 32 examples of magneto-optical recording media.

The recording layer was formed by RF sputtering, and the sputtering conditions were as follows: argon gas pressure 5×
10-3 Torr, sputter power 200-400
W, the distance between the substrate and the target was 55 mm, and the number of rotations of the substrate was 3 Q r p rn .

In addition, the target is on an alloy disk of Tb2゜Fe5o,
It was formed by placing a platelet of the additive element with a predetermined area determined from the sputtering rate.

33rd to 38th Examples T b zo F e so Gold alloy A recording material prepared by adding titanium as a non-corrosive element and phosphorus as a concentration promoting element, and Tb2°Fes. A recording material obtained by adding chromium as a corrosive element and phosphorus as a concentration promoting element to an alloy, and "l"b. Using a recording material made by adding aluminum as a non-corrosive element and phosphorus as a concentration promoting element to a F eaa alloy, a layer with a thickness of about 1,000 layers was formed on the surface of a glass substrate, and six cases were recorded. A magneto-optical recording medium was formed. Table 1 shows the composition of the recording layer of each example.
As shown.

Table 1 Note that the means for forming the recording layer, the film thickness, and the sputtering conditions are exactly the same as in the first to 32nd embodiments.

39th Example to 44th Example T b 2° Few. A recording material formed by adding titanium as a non-corrosive element and carbon as a concentration promoting element to an alloy, and Tb2°Few. A recording material obtained by adding chromium as a non-corrosive element and carbon as a concentration promoting element to an alloy, and TbzoFes. Approximately 1,000 particles were recorded on the surface of a glass substrate using a recording material made by adding aluminum as a non-corrosive element and carbon as a concentration promoting element to an alloy.
Six examples of magneto-optical recording media were formed by forming a recording layer with the thickness of a human being. The composition of the recording layer of each example is as shown in Table-2.

Table 2 The means for forming the recording layer, the film thickness, and the sputtering conditions are exactly the same as in the first to 32nd embodiments.

The target is a Tb, ヮFee*Cu+ alloy disk.

It was formed by placing a small plate of a non-corrosive element with a predetermined area determined from the sputtering rate.

45th Example to 50th Example Tb. A recording material made by adding titanium as a non-corrosive element and boron as a concentration promoting element to a Feoo alloy,
and Tb2°Fee. A recording material obtained by adding chromium as a layer corrosive element and boron as a concentration promoting element to an alloy, and Tbz. Fe,. Approximately 100% of
Six examples of magneto-optical recording media were formed by forming a recording layer having a thickness of 0.05 mm. The composition of the recording layer of each example is as shown in Table-3.

Table 3 The means for forming the recording layer, the film thickness, and the sputtering conditions are exactly the same as in the first to 32nd embodiments, and the target is T b + Fe@@ B +
It was formed by placing a small plate of a non-corrosive element with a predetermined area determined from the sputtering rate on an alloy disk of s.

51st Example to 56th Example T b z. Fes. A recording material made by adding titanium as a non-corrosive element and silicon as a condensation promoting element to an alloy, and a recording material made by adding chromium as a non-corrosive element and silicon as a condensation promoting element to an 'rb2゜Fello alloy. and TbzoF6m. Difficult to alloy
A recording layer with a thickness of approximately 100 mm was formed on the surface of a glass substrate using a recording material to which aluminum as an Il corrosive element and silicon as a concentration promoting element were added, and six examples of magneto-optical recording media were prepared. Formed. The composition of the recording layer of each example is as shown in Table-4.

Table 4 The means for forming the recording layer, the film thickness, and the sputtering conditions are exactly the same as in the first to 32nd embodiments, and the target is T b 1? F esssi
It was formed by placing a small plate of a non-corrosive element with a predetermined area determined from the sputtering rate on a +a alloy disk.

Below, the effects of the magneto-optical recording media of each of the above examples will be described.

This will be explained based on FIGS. 1 to 10.

FIG. 1 shows the magneto-optical layout of the first to 32nd embodiments.
Figure 2 is a graph showing the rate of change in the Kerr angle when the medium is subjected to heating for 25 hours in an atmosphere of 80''C and 85% RH. This is a graph showing the rate of change in coercive force when aged under the same conditions as above, where the white circles are those with 5% of the non-corrosive element added, and the black circles are those with 10% of the N corrosive element added. Indicates what is added.

As shown in FIG. 1, the magneto-optical recording media of the first to 32nd embodiments each have a higher ratio of Kerr rotation angles before and after aging than those to which no non-corrosive elements are added. It can be seen that (θ to /θko) is small and the corrosion resistance is excellent. The degree of the effect increases as the proportion of the non-corrosive element increases; when 5% of the non-corrosive element is added,
The ratio of Kerr rotation angle before and after aging is 1/3.5 to 1/7
．． On the other hand, when 10% of the non-corrosive element is added, the ratio of the change in Kerr rotation angle before and after aging decreases to 1/6.5 to 1/9.

In addition, as shown in FIG.
The magneto-optical recording medium of the example has a lower coercive force ratio (He/Hco
) is small, which also shows that it has excellent corrosion resistance. Products with 5% platinum added as a non-corrosive element:
The ratio of coercive force before and after aging was almost the same as that of the sample without the addition of the non-corrosive element. however,.

When 10% of platinum is added, the ratio of the coercive force before and after the knee song is reduced to about 172 compared to the case where the non-corrosive element is not added, which is effective in improving corrosion resistance. The ratio of coercive force before and after aging due to the addition of a non-corrosive element increases as the proportion of the non-corrosive element added increases;
When adding 5% of the fiff element, the ratio of coercive force before and after aging decreases to 1/1.2 to 1/2.1, whereas when adding 10% of the non-corrosive element, It decreases to 1/1.9 to 1/2.3.

Figure 3 shows a magneto-optical recording medium with an
A graph showing the rate of change in the Kerr rotation angle when knee-singing for 25 hours in an atmosphere of 185% RH at °C. Figure 4 shows the magneto-optical recording medium of the above example aged under the same conditions as above. This is a graph showing the rate of change in coercive force when 5% of the non-corrosive element is added, and the black circle shows the product with 10% of the non-corrosive element added. . Also, for comparison, an alloy with no added phosphorus and a 5% non-corrosive element.
What is added is shiratama-kaku.

Black triangles indicate alloys to which phosphorus is not added and 10% of non-corrosive elements are added, Tb, oFes.
. Those consisting only of an alloy and no other elements added are indicated by an X mark.

As shown in FIG. 3, the magneto-optical recording media of the 33rd to 38th embodiments, to which phosphorus was added as a concentration promoting element, had a higher retention rate before and after aging than those to which phosphorus was not added. It can be seen that the rotation angle ratio (θ to /θho) is small, and the corrosion resistance is improved.

Further, as shown in FIG. 4, the 33rd embodiment to the 3rd embodiment
The magneto-optical recording medium of Example 8 has a higher ratio of coercive force before and after aging (H
c/Hco) is smaller, and it can be seen from this point that the corrosion resistance is also improved.

Figure 5 shows T b 2°Fee. Magneto-optical recording media obtained by adding carbon as a concentration-promoting element to the alloy and further adding a non-corrosive element (Examples 39 to 44) were heated for 25 minutes in an atmosphere of 80°C and 85% RH. A graph showing the rate of change in the Kerr rotation angle when aging is performed over time. Figure 6 is a graph showing the rate of change in coercive force when the magneto-optical recording medium of each of the above examples is aged under the same conditions as above. This is a graph showing 5% of non-corrosive elements in white circles.
The added items, and the black circles indicate 10 tM erosive root cords.
% added. For comparison, an alloy to which no carbon is added and 5% of a corrosive element is added to Shiratama-Kaku, and an alloy to which no carbon is added to which an element that is a separative corrosive is added. The one with 10% addition is shown as a black triangle, and the one consisting only of Tb2*Feea alloy with no other elements added is shown with an X mark.

As shown in FIG. 5, the magneto-optical recording media of the 39th to 44th embodiments to which carbon is added as a concentration promoting element are more aged before and after aging than those to which carbon is not added. It can be seen that the ratio of the Kerr rotation angle (θ to /θko) is smaller, indicating that the corrosion resistance is improved.

Further, as shown in FIG. 6, the 39th embodiment to the 4th embodiment
The magneto-optical recording medium of Example 4 has a higher ratio of coercive force before and after aging (H
e/Hco) has become smaller, which also shows that the corrosion resistance has been improved.

Figure 7 shows T b 2°Fe. Magneto-optical recording media obtained by adding boron as a concentration promoting element to the alloy and further adding a non-corrosive element (Examples 44 to 50) were heated for 25 minutes in an atmosphere of 80° C. and 85% RH. A graph showing the rate of change in the Kerr rotation angle when time-aged. Figure 8 is a graph showing the rate of change in coercive force when the magneto-optical recording medium of each of the above examples is aged under the same conditions as above. The white circles indicate those to which 5% of the slightly corrosive element is added, and the black circles indicate those to which 10% of the corrosive element is added. For comparison, an alloy to which boron is not added but which has 5% of a non-corrosive element added is Shiratama-Kaku, and an alloy to which boron is not added but which has a non-corrosive element to which 5% is added. The one with 10% addition is shown as a black triangle, and the one consisting only of T b 2° Feao alloy with no other elements added is shown with an x mark.

As shown in FIG. 7, the magneto-optical recording media of the forty-fourth to fiftieth examples to which boron was added as a concentration-promoting element had a higher retention rate before and after aging than those to which boron was not added. It can be seen that the rotation angle ratio has become smaller, indicating that corrosion resistance has been improved.

Further, as shown in FIG. 8, the forty-fourth embodiment to the fifth embodiment
In the magneto-optical recording medium of Example 0, the ratio of the coercive force before and after the 21-ging is smaller than that of the one to which boron is not added, and from this point as well, it can be seen that the corrosion resistance is improved. .

FIG. 9 shows T b 2°Fe. Magneto-optical recording media prepared by adding silicon as a concentration-promoting element to the alloy and further adding a non-corrosive element (Examples 51 to 56) were heated in an atmosphere of 80°C and 185% RH for 25 hours. A graph showing the rate of change in Kerr rotation angle when
FIG. 10 is a graph showing the rate of change in coercive force when the magneto-optical recording media of each of the above-mentioned examples are aged under the same conditions as above, and white circles indicate the percentage of change in coercive force when 5% of the non-corrosive element is added. The black circles indicate those containing 10% of the corrosive element. Also for comparison.

The white triangle indicates an alloy to which silicon is not added and 5% of a non-corrosive element is added, and an alloy to which silicon is not added but to which 10% of a non-corrosive element is added. Objects are black triangles, Tb2oFeg. Items consisting only of alloys with no other elements added are indicated by an X mark.

As shown in FIG. 9, the magneto-optical recording media of the 51st to 56th embodiments to which silicon is added as a concentration-promoting element have a higher curvature before and after aging than those to which silicon is not added. It can be seen that the rotation angle ratio has become smaller, indicating that corrosion resistance has been improved.

Furthermore, as shown in FIG. 10, the magneto-optical recording media of the 51st to 56th embodiments have a smaller coercive force ratio before and after aging than those to which silicon is not added. From this point as well, it can be seen that the corrosion resistance is improved.

Incidentally, as is clear from FIGS. 3 to 1O.

It can be seen that among the recording materials to which concentration-promoting elements are added, those to which phosphorus is added are most effective in reducing the ratio of Kerr rotation angles before and after aging and the ratio of coercive force.

1. The gist of the present invention is that the recording layer of the magneto-optical recording medium is formed of a recording material made of an alloy of a rare earth metal, a transition metal, and an additive element that is difficult to corrode when used alone;
And, it is formed using a recording material made of an alloy in which a concentration-promoting element is added to the above-mentioned alloy, and the additive element having a non-corrosive property and the concentration-promoting element are limited to those exemplified in the above example. It is not something that will be done.

〔Effect of the invention〕

As explained above, in the magneto-optical recording medium of the present invention, the recording layer is formed using a recording material made of an alloy of a rare earth metal and a transition metal to which a corrosive element is added. The corrosive elements are concentrated, and the corrosion resistance of the recording layer is significantly improved. especially.

When using a recording material in which a concentration-promoting element is added in addition to a non-corrosive element, the easily corrosive element in one alloy corrodes and falls off, and the non-corrosive element is quickly deposited on the surface of the recording layer. Since it is concentrated, the corrosion resistance of the recording layer is further significantly improved.

Furthermore, since there is no need to coat the surface of the recording layer with a protective film, the manufacturing process of the magneto-optical recording medium is simplified and the manufacturing cost can be reduced. Furthermore, unlike the case of coating with a protective film, even if the non-corrosive elements on one surface are removed for some reason, the non-corrosive elements contained in the alloy will be deposited one after another on the surface of the recording layer, reducing the corrosion resistance effect. It has the characteristic of being persistent.

[Brief explanation of drawings]

The accompanying drawings illustrate the advantages of the present invention. Figure 1, Figure 3, Figure 5, Figure 7, Figure 9 shows the test l.
FIG. 2 is a graph showing changes in Kerr rotation angle when aged for 25 hours in an atmosphere of 0° C. and 85% RH.
Figures 4, 6, 8, and 10 show samples heated at 80°C.
It is a graph showing the change in coercive force when subjected to 25 hours of heating in an atmosphere of 85% RH. Of these graphs, Figure 1 is a graph showing the rate of change in the Kerr rotation angle of a recording layer made of a recording material to which various refractory elements have been added, and Figure 2 is a graph showing the rate of change in the Kerr rotation angle of a recording layer made of a recording material to which various refractory elements have been added. Figure 3 is a graph showing the rate of change in the Kerr rotation angle of a recording layer made of a recording material doped with phosphorus and a non-corrosive element. , Fig. 4 is a graph showing the rate of change in coercive force of a recording layer made of a recording material to which phosphorus and a non-corrosive element are added, and Fig. 5 is a graph showing a rate of change in coercive force of a recording layer made of a recording material to which carbon and a non-corrosive element are added. ! FIG. 6 is a graph showing the rate of change in the Kerr rotation angle of the 2@ layer; FIG.
FIG. 7 is a graph showing the rate of change in the Kerr rotation angle of a recording layer made of a recording material doped with boron and a non-corrosive element;
Figure 8 is a graph showing the rate of change in coercive force of a recording layer made of a recording material doped with boron and a corrosive element.
The figure is a graph showing the rate of change in the Kerr rotation angle of a recording layer made of a recording material to which silicon and a non-corrosive element are added.
Figure 0 is a graph showing the rate of change in coercive force of a recording layer made of a recording material to which silicon and a non-corrosive element are added. Figure 3 Figure 4 Mim mouth rC, boiled
Deluxe Toka ARC Figure 5 Figure 6 Figure 7: Figure 8
Figure 9 Figure 10 Procedure-? [Tu official text (spontaneous) February 1986, Zo day

Claims (4)

[Claims] (1) A magneto-optical recording medium characterized in that a recording layer is formed of an alloy of a rare earth metal, a transition metal, and an additive element that is resistant to corrosion when used alone. (2) The additive element having a non-corrosive property in the vehicle body is at least selected from titanium, chromium, aluminum, platinum, zirconium, vanadium, tantalum, molybdenum, tungsten, copper, ruthenium, rhodium, palladium, niobium, iridium, and hafnium. 2. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is one type of element. (3) A rare earth metal, a transition metal, a first additive element that is corrosion resistant in its own form, and the first additive element in the surface layer.
1. A magneto-optical recording medium characterized in that a recording layer is formed of an alloy with a second additive element that promotes concentration of the additive element. (4) The first additive element, which is difficult to corrode in itself, is titanium, chromium, aluminum, platinum, zirconium, vanadium, tantalum, molybdenum, tungsten,
The second additive element group is at least one element selected from copper, ruthenium, rhodium, palladium, niobium, iridium, and hafnium, and promotes concentration of the first additive element in the surface layer, silicon, 4. The magneto-optical recording medium according to claim 3, characterized in that the material is germanium, boron, carbon, or phosphorus.