JPS60155496A - Information-recording medium - Google Patents

Abstract

PURPOSE:To obtain an information-recording medium in which a recording layer can be securely brought into a crystalline state and an amorphous state even in a disk system, by constituting a thin-film recording layer of an SbSe compound comprising Ge in a specified percentage, in an erasable optical recording medium. CONSTITUTION:An SiO2 film is vapor deposited, if required, on an acrylic resin base, and then a Ge-containing SbSe film is provided thereon as a thin-film recording layer. The SbSe film is provided by using an SbSe vapor source and a Ge vapor source and vapor-depositing the two substances while controlling the ratio of the amounts thereof. The film thickness is set to be about 900Angstrom , and the Ge content is set to be 1-10atom%, preferably, 3-8atom%. The SbSe compound may be Sb2Se3 or an SbSe compound comprising 10-90atom% of Sb. After vapor-depositing an SiO2 film on the recording layer, the resultant material is adhered to an acrylic resin plate by a UV-curing type resin, followed by curing the resin to obtain the recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a recording medium for optically recording information such as a laser beam, and particularly to an erasable recording medium.

BACKGROUND ART AND PROBLEMS Erasable optical recording materials include magneto-optical materials such as T.
bPθ+ GdCo etc. are known. However, in an information recording medium made of such a magneto-optical material, the optical system is complicated because the recorded information, that is, the direction of magnetization, is read out using polarized light. Also,
Since the erasure is performed using an external magnetic field, the device becomes complicated.

In contrast, by utilizing reversible phase transitions from amorphous to crystalline and from crystalline to amorphous, phase transition from crystalline to amorphous is performed by rapid heating and cooling, for example, information record;
A method has been proposed in which a phase transition from amorphous to crystalline occurs by removing heat, for example, erasure is performed, and the ζ signal is reproduced by changing the reflectance R1 transmittance τ between the amorphous state and the crystalline state. It was done. This method has the advantage that the optical system is simplified because recording and erasing are performed by causing a crystalline-5-amorphous phase transition depending on the amount of laser light and the irradiation time. Further, this recording method using phase transition has the advantage that the amount of reproduced signals is much larger than the amount of reproduced signals using the above-mentioned magneto-optical material, and recording with a large ζ contrast ratio can be performed.

As a recording material that undergoes such a phase transition, S
E-based materials, lower oxides of Te, etc. are known. Since Sb2Ses undergoes a phase transition from amorphous to crystalline at about 170° C., an information recording medium that utilizes the reversibility of this material from crystalline to amorphous is attracting attention. In this recording material made of Sbz Ses, the transition from amorphous to crystalline state can be achieved by locally irradiating laser light and heating this area to 170° C. or higher. In this case, the transition from amorphous to crystalline must be maintained at a temperature of 170° C. or more for a period of time or more, and heat removal conditions such as slow heating with laser light are required. On the other hand, the transition from crystalline to amorphous is achieved by increasing the irradiated laser beam and heating it to its melting temperature of about 600°C;
Rapid cooling is required for amorphization. That is, information is erased and recorded by causing a transition from amorphous to crystalline by removing heat and slow cooling, and by causing a transition from crystalline to amorphous by rapid cooling.

However, in reality, recording materials that utilize this phase transition are
Depending on the film thickness, thermal conductivity, crystallization time, etc., it is not always possible to record and erase the 'ζ information as described in -. For example, although the transition from an amorphous state to a crystalline state can be performed relatively easily, the transition from a crystalline state to an amorphous state may not be performed satisfactorily. The reason is that even if the crystalline portion is melted by laser beam irradiation, it will recrystallize during the cooling process. In order to avoid such recrystallization during the cooling process, it is possible to increase the Se content in the 5bSe compound of the recording material, or to prolong the crystallization time by adding a small amount of A3 etc. to the 5bSe compound. By making the crystallization time longer than one cooling time of the molten part, it is ensured that recrystallization does not occur during cooling.

However, when the crystallization time is increased in this manner, crystallization becomes difficult when using a so-called disk method in which crystallization is performed by irradiating a laser beam while rotating a recording medium.

Purpose of the Invention The present invention avoids the above-mentioned drawbacks and makes it possible to reliably perform recording and erasing, that is, to reliably crystallize and amorphize recording 1-, even when using a disk method. The purpose of this invention is to provide an information recording medium that enables the following.

That is, in the present invention, the above-mentioned disadvantages due to recrystallization in 5h2S83 are solved when its melting temperature is 60°C.
Compared to about 0℃, the crystallization temperature is about 170℃,
Since the temperature difference between the two is large, recrystallization is likely to occur during cooling, and based on this, we aim to increase the crystallization temperature of the recording material using this 5bSe compound. .

Summary of the Invention In the present invention, "ζ" is 1 to 10 atomic % in the 5bSe compound.
It has a thin film recording layer containing Ge, and information is recorded on this by light irradiation.

Examples FIG. 1 and FIG. 2 show 5b2Sea doped with Ge, respectively.
2 shows the measurement results of the transition temperature and reflectance R when the Ge content is changed. The reflectance R in this case is for semiconductor laser light (wavelength = 8300), and the curves (11 and (2) in Figure 2 measure the reflectance before and after the transition occurs, respectively. As is clear from Figure 1, by doping only about 3 atomic percent of Ge, the transition temperature increases to 170.
℃ to 260℃. As is clear from Fig. 2, the change in reflectance caused by crystallization, that is, the difference in value between curves 11) and (2), is maintained unimpaired by the Ge doping. The film thickness of the sample was approximately 1000.The film was produced at °C1 by placing Sb2Se3 in one of two boats and Ge in the other in a vacuum evaporation apparatus (vacuum bell jar). Other metal atoms were added to 5b2SI33 above the glass substrate by controlling the amount of evaporation of each source.
Snt Pbt Tet Bit Zn+ Cat
In the case of ML Cr+Ni+Mrt+Si, etc., not only did the change in reflectance due to crystal a become small, but also the effect of increasing the transition temperature, that is, the crystallization temperature did not occur.

In addition, the effect of increasing the transition temperature by adding Ge is not limited to the above-mentioned Sb2Se3, but also when sb is 10 at% to 9
A similar effect was seen with 0 at% 5bSe compound.

And, the G'e content of 5bSe has a transition temperature of 250
It is desirable to select 3 to 8 atomic % within the range of ~350°C. In other words, if the Ge content exceeds 8 at%, the temperature at which the amorphous state changes to crystalline state becomes too high.
Not only does the sensitivity decrease, but even if the laser power is slightly higher than the appropriate power, the recording layer reaches its melting temperature, resulting in a disadvantage that its optimum power range becomes narrower. Further, if the Ge content is less than 3 at % and the transition temperature is less than 250° C., it becomes difficult to substantially obtain the effect of avoiding recrystallization during the cooling process.

Example 1 5i0211* was deposited to a thickness of 1,500 mm by electron beam evaporation on an acrylic substrate with a guide groove having a thickness of 1.2 u+ formed by an injection method, and a 68-containing 5bSe film was deposited on top of this by electron beam evaporation. A 1B film recording layer was formed.

Co-evaporation from this SbSeg deposition source and a Ge deposition source was performed to a thickness of approximately 900 mm. After that, 5i0211Q was further coated on this 5bSeGe thin recording layer for 2000 minutes.
The film was vapor-deposited to a human thickness, and then an ultraviolet curing resin was used on top of this to adhere to an acrylic plate with a thickness of 1.2 cm and cured. The composition of the 5bSeGe thin film recording layer in this case is (S
ba 5e2) ss Ges. In this case, the reason why the 5i02 film was formed sandwiching the thin film recording layer was to prevent thermal deformation of the acrylic substrate when the thin film recording layer was locally heated by condensed laser beam irradiation. This is to avoid adverse reactions caused by this thermal deformation. Recording and erasing were performed on the 20 l diameter disk thus produced by irradiating semiconductor laser light from the acrylic base side. That is, first, a portion of the thin film recording layer formed in an amorphous state that would become a recording track was crystallized at a disk rotation speed of 45 rpm. At this time, the power of the semiconductor laser on the disk surface is 1oII
It was IW. Next, the thus crystallized track was changed from crystalline to amorphous at a disk rotation speed of 180 rpm and a laser power modulation frequency of 2 MHz, and recording was performed. The peak power at this time was 151 on the disk surface.
Met. The optical recording pits amorphized by this recording took on an elliptical shape, as shown in an enlarged plan view of FIG.

FIG. 4 is an enlarged plan view of a similar recording pit of 5bsSb2 not according to the present invention, that is, not doped with Ge; in this case, the shape is asymmetric, and such an asymmetrical recording pit When information is optically reproduced from
is not obtained. The reason why such asymmetric recording pits occur is as follows. In other words, when the laser beam moves on the disk, the cooling rate of heat is fast in the part B at the moment when the laser beam is turned off, but at the other end part A, even after the laser beam has passed, the heat cools down in the neighboring part C. Depending on the laser beam irradiation, this part C
°ζ does not cool down rapidly due to the supply of heat from Therefore, the quenching conditions are not sufficiently satisfied on this part A side, and during the cooling process, a portion of the part recrystallizes, so that the optical information pit becomes substantially smaller on the A side.

In contrast, in the recording medium according to the present invention described above, the 5bSe recording layer is doped with Ge, so that the transition temperature is substantially raised, so that the recording pits shown in FIG. As such, the quenching conditions are substantially equivalently satisfied on the part A side, and recrystallization is less likely to occur, resulting in excellent symmetry.

In addition, although the above-mentioned case is mainly a case where recording is performed from crystal to amorphous and erasing is performed by °C from amorphous to crystal, recording and erasing can also be performed in the opposite manner. .

Effects of the Invention As described above, according to the present invention, by incorporating Ge in the recording layer made of a 5bSe compound, the transition temperature can be increased, and the optical properties can be changed by the transition of the crystal 5 amorphous state. Since there is no inferiority, as mentioned in 111, reliable erasure of records, excellent symmetry, optical recording pits, and therefore small distortion of reproduction output can be achieved.
/N or even better S/N playback,
It is suitable for use as a video disc or audio disc.

[Brief explanation of the drawing]

FIGS. 1 and 2 are measurement curves of the transition temperature and optical characteristics of 5bSeGe with respect to Ge content, and FIGS. 3 and 4 are explanatory diagrams of recording pits. 46 content (I!!+%) 66 content (S No. %) Figure 3 CB Lace family! h direction figure 4 leh - bell vJθ helmet

Claims (1)

[Claims] An optical information recording medium comprising a thin film recording layer made of a 5bSe compound containing 1 to 10 atomic % of Ge, and information is recorded on the thin film recording layer by light irradiation.