JPH03268248A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To increase the Kerr rotation angle and to improve C/N and recording density by using an amorphous material comprising B and containing H to form a dielectric layer on a transparent substrate. CONSTITUTION:The magneto-optical recording medium consists of a transparent substrate 1, dielectric film 2, magnetic film 3, dielectric film 4 of the same quality as the film 2, and reflecting film 5 successively laminated. The film 2 and/or film 4 is made of an amorphous material comprising B and containing H. Since the material of this film contains H, an amorphous state can be easily obtained, and the film thus formed has a uniform composition and surface smoothness compared to a material without containing H. Moreover, with H incorporated, the film is hardly peeled and has excellent mechanical strength and durability. The refractive index of the film is >=2.0 which gives large enhancement effect and good transmittance for light.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a magneto-optical recording medium, particularly a magneto-optical recording medium which has excellent chemical stability, a large Kerr rotation angle, excellent optical transparency and a low C/N. This invention generally relates to magneto-optical recording media that can improve recording density.

[Prior Art] In recent years, with the advancement of the information society, rewritable magneto-optical memory has attracted attention, and rare earth element-transition metal element thin films such as TbFeCo are used as magnetic films for this magneto-optical memory. However, this method has the disadvantage that the obtained Kerr rotation angle is not very large, so that the C/N of the reproduced signal is not sufficient.

[Problems to be Solved by the Invention] Therefore, in this type of magneto-optical recording medium, the surface of a conventionally known amorphous magnetic film is coated with Sin or SiN.

A dielectric layer (film) such as AAN is formed, and its thickness is set to λ/
4n (λ is the laser wavelength, n is the refractive index) to increase the apparent Kerr rotation angle and increase the C/N (enhancement effect), but the improvement in characteristics by this is still unresolved. This is sufficient, and this dielectric layer is required to have an even higher refractive index and better transparency.

Additionally, the amorphous magnetic film used here contains rare earth metals, but since these rare earth metals are extremely easily oxidized, their magnetic properties can easily be lost under high temperature and high humidity conditions. There is a problem that it deteriorates, and there is a proposal to give the above dielectric layer the role of a protective film, but Si
On the other hand, with oxides such as O, the rare earth elements are reduced with St, so the effect is not sufficient, and with SiN
Although nitrides such as AfN have low reactivity and are suitable for the purpose of improving corrosion resistance, they tend to produce cranks when deposited on resin substrates and are mechanically unstable. There is a problem with strength.

Note that it has also been proposed to use BN for this dielectric film [M, Asano et al, IE
EETrans, Magn, MAG-23,262
0, (1987)], this film has a high refractive index, is transparent, and has excellent properties as a dielectric film, but even if it is formed by sputtering, it cannot be formed in a completely amorphous state. The composition is non-uniform, causing unevenness on the surface, and there are problems with durability.

[Means for Solving the Problems] The present invention relates to a magneto-optical recording medium that can solve the above problems, and includes a dielectric layer and a magnetic film on a transparent substrate placed on the light incident side. , a magneto-optical recording medium provided with a reflective film, characterized in that the dielectric layer is made of an amorphous material made of B containing H.

That is, as a result of various studies aimed at developing a magneto-optical recording medium that has a large Kerr rotation angle, excellent optical transparency, good C/N ratio, and improved recording density, the present inventors have developed a magneto-optical recording medium that can be provided on a substrate. When the electric layer is made of an amorphous material made of B containing H (hereinafter abbreviated as amorphous BAH film material), l
2) Since this film material contains H, it is easier to become amorphous than the B film which does not contain H, and a film with a uniform composition and a smooth surface can be obtained.2) This film material contains H. 3) Traditionally used materials such as Sin, SiN, and 8i'N have a refractive index of 1.
．． 4 to 1.8, this amorphous BA
Since the H film has a refractive index of 2.0 or more, it has a great enhancement effect, and it also has good light transmittance, especially in the visible to infrared region, so it
4) Amorphous BH[ has low thermal conductivity, so the thermal diffusion of the irradiated laser is small, and the expansion of the recording bit diameter can be suppressed, so the recording density can be reduced. can improve,
They discovered that the above effect can be obtained, and conducted research on the method of forming this amorphous BAH film, and completed the present invention.

This will be explained in further detail below.

[Function] The magneto-optical recording medium of the present invention is a magneto-optical recording medium in which a dielectric layer, a magnetic film, and a reflective film are provided on a transparent substrate, in which the dielectric layer is an amorphous BAH film.

The structure of this magneto-optical recording medium is known, and as shown in FIG. A dielectric film 2, a magnetic film 3, a dielectric film 4 of the same quality as the dielectric film 2, and a reflective film 5 are sequentially laminated on a substrate 1, and as shown in FIG. A dielectric film 8, a magnetic film 9, and a dielectric film 10 are sequentially laminated on 7.
It may also have a layered structure, and in these, when light 6.11 enters from the light incident side of the transparent substrate 1.7, the light 6 is reflected by the reflective film 5, and the thickness of the magnetic film is increased. In the one in FIG. 2, the incident light 11 is magnetic II! It is reflected at 9.

In the magneto-optical recording medium of the present invention, the dielectric film 2.8 and/or 4.8. The dielectric layer is formed using boron halides such as boron trichloride (BCA'3) and boron trifluoride (BF3). A boron source consisting of hydrogenated boron, such as diborane (32H8) or diborane (32H8), may be introduced into the reactor and the chemical vapor deposition method (hereinafter abbreviated as CVD method) may be used. If we use the plasma CVD method, which introduces a reactive gas into a vacuum device and excites the plasma to decompose it and form a film on the substrate, it is possible to form a film even at a low temperature of 400°C or less, so it is heat resistant. This provides an advantage in the case of resin substrates, which are problematic in the case of plastic substrates. In this case, if the above-mentioned boron source does not have hydrogen atoms, it is necessary to use N2 gas or hydrogen-containing gas as the fourth component, but from the viewpoint of manpower and ease of handling of the raw material gas. This source gas is preferably BJa.

The dielectric film can also be formed by a sputtering method. In this case, B is used as a target, a mixed gas atmosphere of Ar-82 is created in the vacuum apparatus, and a high frequency is applied to the substrate by reactive sputtering. A dielectric film may be formed on the substrate.

The dielectric film thus obtained is made of amorphous BAH and is said to be 500 to 1,000 thick, but this film has a refractive index of 1.75 and is due to multiple reflections of light on the surface of the medium. An apparent increase in θ (enhancement effect) cannot be expected, and on the other hand, if you try to make it larger than 2.30, the film quality will deteriorate and mechanical strength and durability will be adversely affected. It is desirable to set it as 1.75-2.30. This composition has a weight ratio of 100 boron elements.
It is preferable that the number of hydrogen atoms is in the range of 2 to 30, and this can be done by adjusting the composition ratio of each element depending on the film forming conditions.

In addition, in the magneto-optical recording medium of the present invention, a magnetic film and a reflective film are formed on the dielectric layer formed on the substrate, and both of these may be of known type. consisting of a rare earth element-transition metal element film, therefore T
b, rare earth elements such as Dy, Gd, and Nd and Fa,
Made of transition metal elements such as Co and Ni, for example T
bFe, TbFeCo, GdTbFe, GdDy
An amorphous metal film made of FeCo or the like with the structure shown in Figure 1 requires 200 to 500 people, and with the structure shown in Figure 2 it requires 80 people.
It may be formed by sputtering to a thickness of about 0 to 1,000 mm, and this reflective layer can be made of AJ, Cu, Au, A.
It is sufficient to provide a metal film such as G with a thickness of about 200 to 1,000.

[Example code] Next, examples of the present invention and comparative examples will be given.

Examples 1-3. Comparative Examples 1-2 A glass substrate was set in a plasma CVD device and heated to 100°C.
82H as a source gas and N2 as a carrier gas are introduced into the device, the pressure inside the device is maintained at 2.5 Torr, and a high frequency of 200 W is applied to generate plasma CV.
An amorphous BH film was formed on a substrate using the D method, and the composition of this film was measured using RBS-NFS, and the refractive index and transmittance of this film were measured, and the results shown in Table 1 were obtained. (Example 1).

In addition, we decided to form this amorphous BAH film by the sputtering method, and put a glass substrate and B as a target in a vacuum device, and the inside of the device was filled with 80% Ar gas and N gas.
A gas atmosphere consisting of 20% of two gases was created, the pressure was set to 10 torr, and a high frequency wave with an output of 300 W was applied to form an amorphous BAH film on the substrate by sputtering.The composition, refractive index, and transmission of this film were determined. When the ratio was examined, the results shown in Table 1 were obtained (Example 2.3). For comparison, the target in the sputtering method was BN or SiO, and the introduced gas was A'-
When calculated as N2/15% or total, the refractive index and transmittance of the obtained dielectric film were inferior to those of the examples as shown in Table 1.

Table 1 Next, an amorphous B:H dielectric film, a TbFe magnetic film, an amorphous B;H dielectric film, and an aluminum reflective film were formed on a glass substrate by sputtering under the conditions of an argon gas pressure of 7 m Torr and a high frequency output of 200 W. When we created a magneto-optical recording medium using the above dielectric film and examined the changes in the Kerr rotation angle for a laser beam with a wavelength of B33 nm when the thickness of this dielectric film was changed, we obtained the results shown in Figure 3. The film thickness d is 80n, where d=λ/4n.
θk reached a maximum value of 2.01 near m, indicating a sufficient enhancement effect. In order to examine the durability of this product, we examined the relationship between the holding time and coercive force under conditions of 85° C. and 85% RH, and the results shown in FIG. 4 were obtained.

For comparison, this experiment was also conducted using a dielectric layer made of BN or SiO, and the results shown in FIGS. 3 and 4 were obtained. As mentioned above, it has been shown that there is a sufficient enhancement effect, but BN and SiO are inferior to this, and furthermore, the coercive force of Example 1 hardly decreases even after 500 hours have passed. It was confirmed that this decreases considerably for BN and SiO.

[Effects of the Invention] The present invention relates to a magneto-optical recording medium in which a dielectric film, a magnetic film, and a reflective 1 2 film are provided on a substrate as described above. It is an amorphous material consisting of B containing
According to this, this dielectric film has a refractive index of 1.75 to 2.30.
This amorphous film has a large enhancement effect, increasing the Kerr rotation angle, and has excellent light transmittance, which increases C/N. This makes the film surface smooth, and it also has excellent mechanical strength and durability, and its low thermal conductivity reduces the thermal diffusion of the laser and increases the diameter of the recording bit. This provides an advantage in that the recording density is improved.

[Brief explanation of drawings]

Figures 1 and 2 are configuration diagrams of magneto-optical recording media, Figure 3 is a graph of the relationship between dielectric film thickness and Kerr rotation angle in Examples and Comparative Examples, and Figure 'i44 is a diagram of Examples and Comparative Examples. This is a graph showing the relationship between retention time and coercive force. Codes in the figure: 1.7...Transparent substrate 2.4, 8.10...Dielectric film (layer) 9...Magnetic film 5...Reflection film

Claims (1)

[Claims] 1. A magneto-optical recording medium comprising a dielectric layer, a magnetic film, and a reflective film on a transparent substrate placed on the light incident side, in which the dielectric layer is made of B containing H. A magneto-optical recording medium characterized by being made of a crystalline material. 2. The amorphous material has a weight composition ratio of B:H of 100:2 to 3.
2. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium consists of 0. 3. The magneto-optical recording medium according to claim 1, wherein the amorphous material has a refractive index (n) of 1.75 to 2.30. 4. The magneto-optical recording medium according to claim 1, wherein the dielectric layer is formed by a plasma CVD method or a sputtering method. 5. Claim 1, wherein the dielectric layer is formed by a plasma CVD method using B_2H_6 as a raw material and H_2 as a carrier gas.
The magneto-optical recording medium described in . 6. The magneto-optical recording medium according to claim 1, wherein the dielectric layer is formed by sputtering using B as a target in an Ar-H_2 mixed gas atmosphere.