JPH0676378A - Protecting film of magneto-optical recording medium - Google Patents

Abstract

PURPOSE: To obtain a protective film having two excellent effects; a light interference effect and an antioxidation effect for a magneto-optical recording medium. CONSTITUTION: The protective film of the magneto-optical recording medium contains hydrogenated amorphous silicon added with carbon. The hydrogenated amorphous silicon added with carbon has the following compsn.: a-(C11-x Cx )1-x :Hy (where, the values of x and y are x<=0.5, 0.4<=y<=0.5).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film for a magneto-optical recording medium, which has excellent optical interference effect and anti-oxidation effect.

[0002]

2. Description of the Related Art A magneto-optical recording medium is a recording medium for magnetically recording and optically reading information that has been input optically, and its basic structure is a substrate of polycarbonate or the like and a laminated layer on the substrate. It was composed of a recording film and a protective film. Here, the recording film is conventionally made of TbF.
Rare earth-transition metal alloy (RE-TM alloy) such as eCo,
Oxides such as garnet, or platinum was used as a laminated material such as cobalt. However, RE-
The TM alloy film generally has a problem that it cannot be used for a long time and lacks reliability because it is easily oxidized and has poor chemical stability.

Further, in general, the recording film material alone cannot obtain sufficient reflected light and has a low information reproducing sensitivity, so that the reproducibility of information is poor and there is a problem in practical use. Therefore, in order to solve such a problem, it has been proposed to provide a protective film or an optical interference film for improving the reproduction sensitivity. Here, the optical interference film is a film having an optical interference effect of amplifying reflected light with respect to incident light in an optical recording medium, and is closely related to the complex refractive index of the film material. That is, when the complex refractive index of a material is represented by n-ik, it is known that the larger the value of the real part n or the smaller the value of the imaginary part k, the higher the optical interference effect. Specifically, if n is 2.0 or more and k is 0.01 or less, it can be said that an excellent optical interference effect is obtained.

As a conventional technique relating to a protective film, for example, it is disclosed in US Pat. No. 4,661,420, and a protective film in which any one of hydrogen, carbon, nitrogen or oxygen is added to silicon is known. However, such a protective film not only has a poor protective effect but also has almost no optical interference effect, and in practice, it was necessary to separately provide an optical interference film.
Further, Japanese Patent Application Laid-Open No. 63-195840 discloses a hydrogenated amorphous silicon carbide material, but its purpose is to improve the adhesion between the substrate and the protective film, and to obtain the effect as the protective film and the light interference effect. Does not mention anything. Furthermore, JP-A-3-6
No. 6049 proposes a magneto-optical recording medium using hydrogenated amorphous silicon carbide as a protective film. However, such a material has an excellent protective effect but has a poor optical interference effect, and is therefore a separate optical interference film. Had to be installed in.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to solve these problems and to provide a protective film for a magneto-optical recording medium which has both excellent optical interference effect and excellent protective effect. I am trying.

[0006]

As a result of various studies to solve the above problems, the present inventor has set the ratio of the number of atoms of carbonized hydrogenated amorphous silicon within a specific range. As a result, it was found that a protective film for a magneto-optical recording medium having both excellent optical interference effect and protective effect can be obtained.

That is, the present invention is a protective film for a magneto-optical recording medium, comprising hydrogenated amorphous silicon carbide.
The carbonized hydrogenated amorphous silicon has the following composition: a- (Si _1-x C _x ) _{1 -y} : H _y (where x and y have values of x ≦ 0.5 and 0.4 ≦ y ≦
It is 0.5. ) Is included.

Here, the value of x is specified to be 0.5 or less because the Si content is low and the protective effect is poor.
This is because the real part n in the complex refractive index becomes small and the optical interference effect is reduced. Further, the value of y is specified to be 0.4 or more and 0.5 or less, that is, if the value is less than 0.4, the value of k becomes large, and if it exceeds 0.5, the value of n becomes small. Even so, the optical interference effect is reduced.

In the present invention, the method for producing the protective film of the hydrocarbonated amorphous silicon film is not particularly limited, but a silicon or hydrocarbon target is used and one or both of hydrogen gas is mixed. A film can be formed by performing sputtering in an argon gas atmosphere.
Alternatively, a mixed gas of silane gas and methane gas, or one or both of argon gas and hydrogen gas may be used to form a film by a chemical vapor deposition (CVD) method. Further, for the magneto-optical recording medium, a carbonized hydrogenated amorphous silicon film is formed by a CVD method on a polycarbonate or glass substrate or the like according to a conventional method, and then a RE-TM alloy film and an AI film or the like is formed by sputtering. It can be manufactured by forming a reflective film.

[0010]

EXAMPLES Next, the present invention will be described more specifically by way of examples. Sample preparation In Examples 1 to 3 and Comparative Examples 1 to 5, carbon-added hydrogenated amorphous silicon films were prepared by chemical vapor deposition (CVD) in silane gas, methane gas and hydrogen gas diluted to 20% in argon gas. It was formed on a glass substrate. In Comparative Examples 6 to 8, a film was formed by a sputtering method using a SiC target. Then, in Comparative Example 9, a film was formed by sputtering from a Si target using amorphous silicon. The results are shown in Table 1. In this case, the composition analysis shows that RBS (R
otherford Back Scatterin
g) method, for hydrogen, HFS (Hidroge
n Forward Scattering Anal
ysis) method.

Table 1 Conditions and results for producing hydrogenated amorphous silicon containing carbon ───────────────────────────────── ─── Gas flow rate Compositional breakdown rate (ccm) (atm.%) (N, k) ───────────────────────────── ─ Silane Methane Hydrogen Carbon Hydrogen Wavelength (850nm) Gas ^* Gas Gas xy Real part n> 2.0 Imaginary part k <0.01 ──────────────────────── ──────────── Example 1 5.0 1.0 80 8 43 〇 〇 Example 2 2.0 1.0 80 25 47 〇 〇 Example 3 1.0 1.0 80 50 45 〇 〇 Comparative Example 1 1.0 2.0 80 57 42 △ ○ Comparative example 2 1.0 5.0 80 69 41 × ○ Comparative example 3 2.0 1.0 100 30 67 × ○ Comparative example 4 1.0 5.0 100 75 67 × ○ Comparative example 5 0.0 10 100 100 67 × ○ Comparative example 6 ---- ---- 61 15 △ × Comparative Example 7 --- --- --- 61 0 ○ × Comparative Example 8 --- --- --- 30 20 ○ × Comparative 9 --- --- --- 0 0 〇 × ───────────────────────────────────

Measurement of Complex Refractive Index FIGS. 1 and 2 show the results of measuring the values of n and k of the complex refractive index at a wavelength of 830 nm when the values of x and y are variously changed. In FIG. 1, ◯ means an n value of 2.0 or more, Δ means 1.5 or more and x is less than 1.5, and ◯ means a k value of 0.01 or less and x is 0. It means that it exceeds .01.

Measurement of effect of protective film The effect of protecting the magnetic recording medium against oxidation was confirmed by a heat resistance test and a holding force Hc measurement. Specifically, the heat resistance test was performed in an atmosphere of 115 ° C., and the oxygen distribution was evaluated using Auger electron spectroscopy. The results are shown in Figures 3 and 4.

FIG. 4 shows the results of analyzing the composition of the TbFe film without the protective film after 1000 hours of the weather resistance test in the depth direction using Auger electron spectroscopy. The vertical axis of the figure is proportional to the amount of each element, the horizontal axis of the sputter time is proportional to the depth from the surface, the TbFe film is formed up to a depth of 30 minutes, and the deeper portion is formed on the substrate. Corresponds to the glass used. Although the amount of oxygen decreases as it enters the TbFe film from the surface, since it exists deep inside the TbFe film, oxidation occurs from the surface of the TbFe film over time, and the oxidation gradually occurs in the TbFe film. It is thought that it progressed into the membrane.

FIG. 3 shows the composition of the TbFe film provided with the protective film of the carbon-doped hydrogenated amorphous silicon film of Example 1 after 1000 hours of the weather resistance test, analyzed in the depth direction by Auger electron spectroscopy. This is the result. In the figure, a carbon-doped hydrogenated amorphous silicon film is formed up to a depth of 18 minutes, a TbFe film is formed up to a depth of 42 minutes, and a deeper portion is a glass substrate. There is. Oxygen exists only at the boundary between the carbon-doped hydrogenated amorphous silicon film and the TbFe film, and the TbFe film and the glass.
e was not observed in the film.

From this, the oxygen at the boundary between the TbFe film and the glass is the oxygen adhering to the glass substrate before attaching the TbFe film, and the carbon-doped hydrogenated amorphous silicon film and the TbFe film.
The oxygen at the boundary with the Fe film is the oxygen attached to the surface of the TbFe film when the TbFe film is transferred to another device for forming a carbon-doped hydrogenated amorphous silicon film after forming the film. Conceivable. Further, it can be seen that the carbon-added hydrogenated amorphous silicon film sufficiently suppresses the invasion of oxygen from the surface and protects the TbFe film from oxidation. Further, the holding power Hc was measured and evaluated by a curl measuring device. Results are shown in FIG. Even after 1000 hours of the heat resistance test, the sample using the protective film of the present invention showed almost no change in the holding force Hc.

[0017]

According to the present invention, in a magneto-optical recording medium, a protective film having two excellent effects of a light interference effect and an antioxidant effect can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a region where a material composition ratio has a real part n value of complex elastic modulus of 2.0 or more.

FIG. 2 is a diagram showing a region in which a material composition ratio has an imaginary part k value of a complex elastic modulus of 0.01 or less.

FIG. 3 is a heat resistance test 100 using Example 1.
It is an Auger electron spectroscopy chart after 0 hour.

FIG. 4 is a heat resistance test 1000 using Comparative Example 1.
It is an Auger electron spectroscopy chart after time.

FIG. 5 is a diagram showing changes in holding force Hc using Example 1 and Comparative Example 1 up to 1000 hours in a heat resistance test.

Claims (2)

[Claims] 1. A protective film for a magneto-optical recording medium, comprising carbon-doped hydrogenated amorphous silicon, said carbon-doped hydrogenated amorphous silicon having the following composition: a- (S _{11- x} C _X ) _1-y : H _y (where x and y have values of x ≦ 0.5, 0.4 ≦ y ≦ 0.
The protective film is characterized in that it has 5). 2. A magneto-optical recording medium having the protective film according to claim 1.