JPH01241041A - Optical recording method - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium which can repeatedly record and reproduce information at high sensitivity, high speed, high S/N, and low error rate by providing a 1st thin film consisting of at least one kind of group Ib elements and the 2nd thin film consisting of at least one kind of group IVb elements on a base. CONSTITUTION:The 1st thin film 2 consisting of the group Ib elements and the 2nd thin film 3 consisting of the group IVb element are provided on the base. The 1st thin film and the 2nd thin film are melted and mixed when a light beam for recording is projected on the recording medium. The light reflectivity of the mixed part is thereby largely changed from the original state before the mixing. The light beam for reproducing of such a small output which does not affect the properties of both the 1st and 2nd thin films is, therefore, projected on this recording medium and the change rate of the light reflectivity of the above-mentioned mixed part is detected at the time of reproduction. The light beam of about the middle output to separate the mixed elements of the group Ib and the group IVb is projected on the mixed part to heat said part to a low temp. and to separate the mixed elements of the mixed part at the time of erasing. The information is thereby repeatedly recorded and reproduced at the high sensitivity, high speed, high S/N and low error rate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording method capable of repeatedly recording, reproducing and erasing information using a light beam.

Japanese Unexamined Patent Publication No. 183042/1989, directed by Atsushi Takebei, discloses an optical recording method in which a light beam such as a laser beam is incident on an optical information recording medium having an AuGe alloy thin film to repeatedly record, reproduce, and erase information. There is. During recording, this method injects a high-power recording light beam into the recording medium and heats it at a high temperature to melt the alloy thin film in that area and form an AuGe eutectic at 356°C.
This changes the light reflectance of the molten part (reproduction is performed by detecting this change with a low-power light beam), and when erasing, a medium-power light beam for erasing is applied to the recording medium. The molten part is heated at a low temperature by injecting Au.
and Ge phases. With this method, the change in light reflectance in the alloy thin film increases as the amount of Au increases.
Since this is a significant amount of Au, this thin film contains as much as 35 to 92 atm % of Au. However, since Au has a high light reflectance and therefore poor light absorption, optical information recording media using such alloy thin films have low thermal sensitivity and small changes in light reflectance during recording, so they can be used at high speeds. It is difficult to record and reproduce information with high S/N and low error rate. Furthermore, when 02 comes into contact with a molten layer containing Au like in this recording medium, irreversible Ge02 (which does not return to Ge) is likely to be formed, so the alloy thin film needs to be covered with a protective film etc. is chemically stable up to about 600°C in the absence of Au).

Furthermore, it is an object of the present invention to provide an optical recording method capable of repeatedly recording and reproducing information with high sensitivity, high speed, high S, and low error rate.

In the recording method of the present invention, a first thin film comprising at least one group 1b element and at least one rVb group element are formed on a support.
For an optical information recording medium having a second thin film consisting of a seed,
During recording, a recording light beam is incident and heated to a high temperature to melt and mix the first thin film and second thin film in that area, and during playback, a reproduction light beam is incident and the light reflectance of the mixed area changes. The present invention is characterized in that the amount of the mixed elements in the mixed portion is detected, and when erasing, an erasing light beam is incident and heated at a low temperature to separate the mixed elements in the mixed portion.

Since the optical reflectance of Au is significantly different from that of Ge (
(Au has a much higher semiconductor laser light reflectance)
The light reflectance of a single layer of Ge and a eutectic layer of AuGe (a mixed layer of Au and Ge may also be used) differs widely. For example, the light reflectance for light with a wavelength of 780 nm is 43% for a Ge single layer, while for an AuGe eutectic layer it is 780 nm.
It is 0%. Furthermore, as described in the above-mentioned publication, the AuGe eutectic layer is easily separated into Au and Ge layers by low-temperature heating. The present inventors have developed a sample A in which an AuGe layer with a high Ge content and an AuGe layer with a high Au content were sequentially provided on a support, and a sample A in which an AuGe layer with a high Ge content and an AuGe layer with a high Au content were sequentially provided on a support.
Sample B is prepared in which an AuGe layer with a high content of Ge and an AuGe layer with a high Ge content are sequentially provided, and when these samples are heated at a low temperature by entering an erasing (medium power) laser beam, in the case of sample A, the surface side Au gathers on the side, and Ge gathers on the support side (
On the other hand, in the case of sample B, Ge is on the surface side,
It was also found that Au gathers on the support side. Therefore, when erasing, a uniform Au+Ge mixed layer (alloy layer) is used as before.
It is easier to separate the Au layer and the Ge layer from the beginning if they are separated from each other.In this case, the order in which the Au layer and the Ge layer are formed is as follows: Ga
It is better to use a layered type, which is made of Au as mentioned above.
This is because if the molten layer containing Ge touches 0□, irreversible GeO□ is likely to be formed in the case of Ge. However, if the molten part is enlarged and Ge is formed on the entire surface, irreversible recording is possible. ), and other Group 1b materials other than Au, such as Cu and Ag.

The optical information recording medium used in the method of the present invention basically consists of a support 1 (which may be transparent or opaque) as shown in FIG.
A first thin film 2 of a group 1b element and a second thin film 3 of an rVb group element are provided on the top, but if the support is transparent, the order of forming these thin films can be reversed as shown in FIG. You may also do so.

Note that 1' in FIG. 2 is a transparent support.

In the case of the type shown in Figure 1, plastics and ceramics are used to make such optical information recording media.

A first thin film of a group 1b element is formed on a support such as glass using a PvD method (physical vapor deposition method) such as a vacuum evaporation method or a sputtering method; The second thin film of the group IVb element may be formed by the method,
In the case of the type shown in FIG. 2, the second thin film and the first thin film may be sequentially formed on the transparent support by the same method. In addition, in the case of the type shown in Fig. 1, silicon dioxide is added as a protective film on the second thin film, and in the case of the type shown in Fig. 2, on the first thin film.
A transparent dielectric film of titanium dioxide, silicon nitride, aluminum nitride, or the like may be provided. In any case, the thickness of the first thin film and the second thin film is 10 to 500 nm, preferably l(
It is about 1 to 50 nm.

To carry out the method of the present invention using the optical information recording medium as described above, first, during recording, a recording light beam of high power is incident on the recording medium (the first thin film and the second thin film are melted).
In the case of the type shown in the figure, the light enters from the second thin film side, and in the case of the type shown in Figure 2, it enters from the support side), and is heated at high temperature to melt and mix the first thin film and the second thin film in that part. As a result, the light reflectance of the mixed portion changes significantly compared to the original state before mixing. Therefore, during reproduction, a low-output reproduction light beam that does not affect the physical properties of both the first and second thin films is incident on the recording medium, and the amount of change in the light reflectance of the mixing portion is detected. Also, during erasing, the group 1b and group IVb of the mixed section
A medium-power light beam is applied, which is sufficient to separate the mixed elements of the group, and is heated at a low temperature to separate the mixed elements in the mixed part.

The present invention will be explained below by way of examples.

Example 1 ・5 sheets were placed on a glass plate (manufactured by Corning, USA, $7059).
After vacuum-depositing Au at room temperature under a reduced pressure of By doing so, we created an optical information recording medium. When the state of each thin film was examined by X-ray diffraction, it was found that the first thin film was a crystalline film and the second thin film was an amorphous film.

Next, a laser beam with a diameter of about 1 m was applied to this recording medium from the second thin film side using a semiconductor laser with an output of 20 mw, and the temperature of that part was raised to 450°C. When we measured the reflectance to laser light (wavelength 780 nm) before and after heating up, it was 45% before heating up, but 77% after heating up.
Met. Furthermore, when the state of the heated section was examined by X-ray diffraction, the γ phase of AuGe was confirmed. Next, the output of the laser light was lowered to 174 to 5 mW, and this was similarly applied from the second thin film side, the surface temperature was raised to 70°C, and after cooling, the light reflectance was measured again, and it was 48%. Ta. In addition, when the temperature rising part at this time was examined by X-ray diffraction method, it was found that AuGe
The γ phase (eutectic) had almost disappeared. The laser beam incident area had a Ge metallic color before the temperature was raised, but after the temperature was raised to 450°C, it became a slightly gold-like color of Au, and after the temperature was raised to 70°C, this golden color disappeared. It returned to the metallic color of Ge.

Even if the above heating-cooling operation was repeated, the light reflectance of the laser beam incidence part remained almost the same as above.

Comparative Example 1 5 x 10-'Torr on the same glass plate as Example 1
Au(27at+++%) Ge(7
An optical information recording medium was produced by vacuum-depositing a 3 atm% alloy to form a thin film with a thickness of 1000 nm. The reflectance of this material for laser light (wavelength 780 nm) is 63
%Met. Hereinafter, when the temperature was raised to 450°C by laser beam incidence as in Example 1, the reflectance after cooling was 7.
It became 0%. When the temperature was subsequently raised to 70° C., the reflectance after cooling was 67%.

Comparative Example 2 Au (50 atm%) Ge (50 atm%) was used as the vapor deposition source.
%) An optical information recording medium was produced in the same manner as in Comparative Example 1 except that the alloy was used. This laser light (wavelength 780nn)
+) reflectance was 66%. Thereafter, as in Example 1, the temperature was raised to 450° C. by laser beam incidence, and the reflectance after cooling was 72%. When the temperature was subsequently raised to 70° C., the reflectance after cooling was 67%.

Effect-1-1 Since the method of the present invention uses an optical information recording medium in which the thin film is separated into a group 1b element system and a group IVb element system, information can be recorded with high sensitivity, high speed, high S/N, and low error rate. can be recorded and played repeatedly.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of an optical information recording medium used in the method of the present invention.

Claims (1)

[Claims] 1. For an optical information recording medium having a first thin film made of at least one group Ib element and a second thin film made of at least one group IVb element on a support, recording light is applied during recording. The beam is incident and heated at a high temperature to melt and mix the first thin film and the second thin film in that part, and at the time of reproduction, a reproduction light beam is made incident and the amount of change in light reflectance of the mixed part is detected, and further An optical recording method characterized in that during erasing, an erasing light beam is incident and heated at a low temperature to separate the mixed elements in the mixed portion.