JPS6344331A - Recording method for optical memory - Google Patents

Abstract

PURPOSE:To permit recording of a ternary coded signal and to improve recording density by projecting a high power laser and lower power laser in two stages onto an optical information recording medium formed with a thin alloy film composed of Au and Si on a substrate. CONSTITUTION:The Au-Si alloy is in the amorphous state and the reflectivity thereof is Ra from a room temp. to temp. T1 or below when the laser luminous flux having a prescribed temp. distribution is projected to the thin Au-Si alloy film. The phase transfer from the amorphous to crystal arises and the reflectivity Rb decreases at the temp. T1. Au precipitates and the reflectivity Rc increases to make Rb<Ra<Rc at T2 higher than the temp. T1. The Au is precipitated to increase the reflectivity Rc by projecting the high power laser to the optical information recording medium formed with the thin Au-Si alloy film on the substrate. The phase transfer to the crystal is induced to increase the reflectivity Rc by projecting the low power laser thereto. The ternary coded writing is thus permitted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an optical memory recording method using an optical information recording medium, and particularly to an optical memory recording method capable of increasing recording density.

(Prior art) Optical information recording media used in conventional optical memory recording methods form a focus by irradiating a laser beam that turns on and off according to a binary information signal, or change reflectance due to phase transition. is used to record information signals. In any case, the optical information recording medium used in the conventional optical memory recording method records a binary signal depending on the presence or absence of bits or the presence or absence of a change in reflectance.

Here, if it were possible to record ternary signals on an optical information recording medium, it would be possible to significantly improve the recording density of the optical information recording medium.

(Objective) An object of the present invention is to provide an optical memory recording method that makes it possible to significantly improve recording density by making it possible to record ternary signals on an optical information recording medium. It is in.

(Structure) The present invention uses an optical information recording medium in which an alloy thin film of Au and Si is formed on a substrate, and the power of a laser for information writing on the optical information recording medium is set to two levels, and a high-power laser is irradiated. By precipitating Au to increase the reflectance, and by irradiating it with a low-power laser, a phase transition from amorphous to crystal occurs and the reflectance decreases, thereby making three-value writing possible. shall be.

FIG. 1 shows the change in light reflectance with respect to temperature of the AuSi alloy. However, the change in reflectance corresponding to the temperature distribution when the sample is irradiated with a laser beam having a predetermined temperature distribution is shown, not the phenomenon when the entire sample is heat-treated. Also, the reflectance of each state is A with a known reflectance.
The I MW was irradiated with a laser beam having a predetermined temperature distribution as described above, the reflectance was read out, and the reflectance was compared with this.

As shown in Figure 1, the Au-Si alloy is in an amorphous state from room temperature to below a certain temperature T1, and at the temperature T1, a phase transition from amorphous to crystal occurs and the reflectance decreases. .

Furthermore, when the temperature reaches a predetermined temperature T2 higher than the temperature T1, Au
is precipitated and the reflectance increases. The reflectance in the amorphous state is Ra, the reflectance in the crystalline state is Rb,
If the reflectance in the Au precipitation state is Rc, then Rb
<Ra<Rc.

Figures 2 and 3 show the reflectance distribution of the irradiated area when an alloy of U and Si is irradiated with a laser beam for writing. FIG. 3 shows the case of irradiation with a low power laser beam. In the case of a high-power laser beam, as shown in Fig. 2 (a) and (b), a portion 2 whose temperature is lower than T2 and higher than Tl is distributed around a central portion 1 whose temperature is higher than T2. However, the temperature of the outer peripheral portion is lower than T1. On the other hand, in the case of a low-power laser beam, the temperature T
A portion 3 having a temperature lower than 2 and higher than temperature T1 is distributed, and the outer peripheral portion thereof is lower than temperature T1.

Figure 2 (C) shows the change in reflectance when an alloy of Au and Si is irradiated with a high-power laser beam as shown in Figures 2 (a) and (b). The part corresponding to the part l higher than T2 is A as explained in FIG.
u precipitates and the reflectance becomes high (and the temperature is lower than T2 and higher than Tl, corresponding to part 2, as explained in FIG. 1, a phase transition from amorphous to crystal occurs,
A region with low reflectance is formed around the above-mentioned region with high reflectance. On the other hand, when irradiating with a low-power laser beam as shown in Figures 3(a) and (b), the temperature is lower than the temperature T2 as shown in Figure 3(c). T
The reflectance of the portion corresponding to the portion 3, which is higher than 1, is low (it just becomes low), and the reflectance does not become high because there is no Au precipitation.

Based on the above, if we use an optical information recording medium in which a thin alloy film of Au and Si is formed on a substrate and switch the power of the laser for writing information to this medium in two stages, it is possible to It is possible to form a portion with low reflectance and an intermediate portion where reflectance does not change,
Therefore, it is possible to record a ternary information signal.

As a result of checking with an optical microscope, in the case of the high power laser beam shown in Figure 2, the writing diameter including the low power part 2 around the high power part 1 is as shown in Figure 3. The bit pitch is approximately 1.3 times that of the low-power laser beam that is used, and the bit pitch must be increased accordingly, but the pitch is not expanded that drastically. By being able to record encoded signals, it is possible to significantly expand the recording density.

Next, examples of the present invention will be described.

Au was deposited on a 1 mm thick glass substrate by dual electron beam evaporation.
An Au--Si alloy thin film with a composition of 70 atomic % and 30 atomic % Si was provided to a thickness of 200 mm, and this was used as a sample of an optical information recording medium. This sample was fixed, and a He-Ne laser with a beam diameter of 2 μm was applied to it.
Writing was performed by irradiating with m- and 51 for 100 m5ec, and then reading was performed with a laser beam of 1 mW. The read voltage of the non-written part in the amorphous state is Va,
The readout voltage of the 8 mwM deposited part, which is the Au deposited part, is ν
b. The read voltage of 5I write error in the crystal state is V
c, a signal ratio of νa:Vb nijic=5:2:8 was obtained.

As described above, according to the above embodiment, it is possible to record a ternary information signal by switching the power of the writing laser in two stages, thereby greatly improving the recording density. can.

(Effects) According to the present invention, an optical information recording medium in which an alloy thin film of Au and Si is formed on a substrate is used, and ternary value writing is performed by switching the power of a laser for writing information signals to the recording medium in two stages. This made it possible to significantly improve recording density.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the reflectance change with respect to temperature of Au-Si alloy for explaining the present invention in detail, and Fig. 2 is a diagram showing the temperature and power distribution of a high-power laser beam and the Au-Si alloy due to irradiation with this laser beam. FIG. 3 is a diagram showing the reflectance distribution of the -Si alloy. FIG. 3 is a diagram showing the temperature and power distribution of a low-power laser beam and the reflectance distribution of the Au-Si alloy due to irradiation with this laser beam.

Claims (1)

[Claims] An optical memory recording method using an optical information recording medium in which a thin alloy film of Au and Si is formed on a substrate, in which the power of a laser for writing information on the optical information recording medium is set to two levels, and a high-power laser is irradiated. In some cases, Au
Optical memory recording that increases the reflectance by precipitating it, and then irradiating it with a low-power laser causes a phase transition from amorphous to crystal to lower the reflectance, making it possible to perform three-value writing. Method.