JP2560152B2 - Optical information recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium for recording an information signal by irradiating an optical pulse of laser light.

[0002]

2. Description of the Related Art A recording material in which an amorphous phase and a crystalline phase are reversibly changed is known as a laser between the amorphous phase and the crystalline phase.
Information is recorded using the fact that the light reflectances are different.
That is, when a recording layer that is in a crystalline state as an initial state is irradiated with laser light, the corresponding irradiated part is rapidly heated and rapidly cooled to change to an amorphous state, and the non-irradiated part has a reflectance. Are formed (recorded). Further, when the pits formed in the recording layer are irradiated with laser light weaker than at the time of recording, the corresponding irradiated portion is gently heated and cooled, and the pits in the amorphous state return to the crystalline state as the initial state ( Erase). These rewritable recording materials capable of reversibly performing a phase transition between an amorphous phase and a crystalline phase, in other words, reversibly recording and erasing, include, for example, Ge-S
b-Te (for example, JP-A-63-228433) has been reported. These recording materials are formed on a plastic substrate or a glass substrate to form a thin film having a predetermined thickness directly or through an underlayer, and a protective layer and, if necessary, a reflective layer are laminated thereon. The basic structure of the optical storage medium. The underlayer and protective layer used here are S
There are dielectric films such as iO ₂ , ZnS, Si ₃ N ₄ , AlN, Al ₂ O ₃ and mixtures thereof, such as a combination of ZnS and SiO ₂ . Further, as the reflective layer, Au, Al, N
Metals and alloys such as i-Cr are used. As these film forming methods, a vapor deposition method, an EB vapor deposition method, a sputtering method and the like are used.

[0003]

With the development of the information society, there has been an increasing demand for faster information transmission and reliability in holding recorded information. Here, the eutectic composition Ge ₁₅ Sb of the ternary system of Ge—Sb—Te
_61.5 Te _23.5 has a crystallization temperature of 200 ° C. or higher, and the recording / erasing cycle life of the composition is 10 ⁶ or more. However, the erasing time of about 400 ns is not always sufficient for high-speed erasing. An object of the present invention is to provide an optical information recording medium that can be erased at high speed.

[0004]

In order to achieve the above object, a rewritable optical information recording medium of the present invention has a Ge-S
In the eutectic composition Ge ₁₅ Sb _61.5 Te _23.5 of the ternary system of b-Te, a part of Sb is replaced with Bi. The composition of the recording film is ± due to experimental errors such as film forming conditions.
Although there may be a deviation of about 2 at%, the above object can be achieved in that case as well.

[0005]

[Action] Ge-Sb-Te ternary eutectic composition Ge ₁₅ S
In b _61.5 Te _23.5 , when a part of Sb was replaced with Bi, the ratio of Sb whose rate of crystallization was rate-determining in this system decreased, and the phase that separated the crystal of Sb increased, resulting in crystallization. It is thought that the speed has increased. Bi <
At 3 at%, there is no effect of shortening the erase time, and Bi> 10.5
At at%, the crystallization initiation temperature is less than 150 ° C, which is not sufficient for the durability of record storage.

[0006]

Embodiment 1 An embodiment of the present invention will be described below. The recording film, the protective film and the like were formed by RF magnetro sputtering. On the cleaned glass pieces, Ge ₁₅ Te _23.5 (Sb
/ Bi) Using a sputtering target having a composition of _61.5 , Ar = 3 mTorr was introduced and the film thickness was about 50 W at RF power.
A 80 nm recording film was formed. Next, Zn with a thickness of about 150 nm
A protective film made of an S-SiO2 mixture was laminated. This sample was heated in a nitrogen atmosphere at a temperature of 240 ° C for about 30 minutes to perform initial crystallization. Alternatively, the recording / erasing characteristic evaluation region was laser-annealed with continuous light or 1 KHz pulsed light to perform initial crystallization. For each sample, pulse width 30 ns, wavelength 830
A recording pit having a diameter of about 0.6 μm was formed by laser light of nm, and the erasing pulse width (erasing time) capable of erasing the recording pit and the repetitive life of recording and erasing were examined. The results are shown in Table 1. As is clear from this result, a part of Sb of Ge ₁₅ Sb _61.5 Te _23.5 is Bi
The replaced recording film was erasable in 350 ns or less, and the erasing time was obviously shortened.

Next, the crystallization onset temperature is determined by thermal analysis (DSC).
Investigated by. The rate of temperature rise during thermal analysis is 10 ° C / min. The results are shown in Table 1. As is clear from this result, the crystallization initiation temperature of the thin film of the present invention in which a part of Sb of Ge ₁₅ Sb _61.5 Te _23.5 is replaced with Bi is Bi = 3-10.5.
At at%, it exceeded 150 ° C. By the way, the composition of the recording film may deviate by about ± 2 at% due to an experimental error such as film forming conditions. In that case (Ge15 ± 2 (Sb / Bi)
Similar results were obtained with 61.5 ± 2 Te23.5 ± 2). Table 1 Recording film composition (at%) Erase time (ns) Repeated life (times) Crystallization start temperature (° C) Bi content 0 400 10 ⁶ 225 3.0 350 350 10 ⁶ 213 5.5 5.5 300 10 ⁶ 185 5 0.7 250 10 ⁶ 192 8.0 8.0 250 10 ⁶ 172 10.5 250 10 ⁵ 150 15.0 250 10 ⁴ 115

[0008]

[Comparative Example] As the erase time and the crystallization starting TEMPERATURE COMPARISON example, Ge ₁₅ Sb _{61 .5} Te _23.5 and Bi content excluding Bi substitution of the recording film of Ge ₁₅ Sb _46.5 Bi ₁₅ Te _23.5 of 15 at% de - The data are shown in Table 1. The evaluation conditions are the same as in the example.

[0009]

As described above, the Ge-Sb according to the present invention has been described.
-Te3-element of amorphous composition Ge ₁₅ Sb _{61 .5} Te _23.5 Sb,
The erasing time is sufficiently fast in the optical information recording medium having the recording layer in which a part of B is replaced with Bi.

Continuation of the front page (72) Inventor Shuji Yoshida 470-169 Renjoji, Odawara-shi, Kanagawa Nishiyama Mansion 101 (72) Inventor Takashi Yamagishi 1006-25 Minaminobita, Itami-shi, Hyogo (56) References JP 63 -244422 (JP, A) JP 63-225934 (JP, A) JP 1-118229 (JP, A) JP 3-10886 (JP, A)

Claims (2)

(57) [Claims] 1. A eutectic composition G of a ternary system of Ge, Sb, and Te.
An optical information recording medium having a recording thin film in which a part of Sb is replaced with Bi in e15 (± 2) Sb61.5 (± 2) Te23.5 (± 2). 2. The optical information recording medium according to claim 1, wherein Bi is contained in an amount of 3 to 10.5 at%.