JP2596473B2 - 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 a phase change between an amorphous phase and a crystalline phase is performed reversibly is performed by using a laser having an amorphous phase and a 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 by forming a thin film of a predetermined thickness directly or via an underlayer, and a protective layer and, in some cases, a reflective layer are laminated thereon. This is the basic configuration of the optical recording medium. The underlayer and the protective layer used here are SiO 2
₂ , a dielectric film such as ZnS, Si ₃ N ₄ , AlN, and Al ₂ O ₃ and a mixture thereof, such as a combination of ZnS and SiO ₂ . Au, Al, Ni-
Metals and alloys such as Cr are used. As these film forming methods, an evaporation method, an EB evaporation 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. The higher the crystallization temperature of the amorphous phase of the recording layer, the better the retention durability of the information on the recording medium. Here, the above Ge-Sb-
The crystallization temperature of each of the Te amorphous films is not more than 180 ° C., which is not always sufficient. So Ge-Sb-
Te ₁₅ ternary eutectic composition Ge ₁₅ Sb _61.5 Te _23.5 is 200
It has been found to have a crystallization temperature of at least ℃. However, an erase time of about 400 ns is not always sufficient for high-speed erase. 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
A ternary eutectic composition of b-Te Ge ₁₅ Sb _61.5 Te _23.5 contains at least one element of Ga and Pb. The base composition of the recording film may deviate by about ± 2 at% due to an error such as a film forming condition. In such a case, the above object can be achieved.

[0005]

[Action] Ge-Sb-Te ternary eutectic composition Ge ₁₅ S
It is considered that when Ga or Pb is doped into b _61.5 Te _23.5 , they become crystal nuclei to increase the crystallization speed. When the amount of the additive is less than the range of the present invention, there is no effect of shortening the erasing time, and when the amount is larger than the range, it becomes difficult to erase the recording.

[0006]

Embodiment 1 An embodiment of the present invention will be described below. The formation of the recording film, the protective film, and the like was performed by RF magnetron sputtering. Ge ₁₅ Sb _61.5 Te was added to the washed glass piece.
_Using a sputtering target containing 0.5 to 12.3 at% of Ga + Pb in _23.5 , introducing Ar = 3 mTorr and RF
The protective film according to film thickness ZnS-SiO ₂ mixture of about 0.99 nm were laminated to form a film with power -50 W. Place this sample in a nitrogen atmosphere.
It was heated at a temperature of 240 ° C for about 30 minutes for initial crystallization. Alternatively, the initial crystallization was performed by laser annealing of the recording / erasing characteristics evaluation region with continuous light or 1 KHz pulse light. For each sample, a recording pit having a diameter of about 0.6 μm was formed with laser light having a pulse width of 30 ns and a wavelength of 830 nm, and the erasing pulse width (erasing time) capable of erasing the recording pit was examined. The results are shown in Table 1. As is clear from these results, the Ge ₁₅ Sb _61.5 Te _23.5 recording film containing at least one element of Ga and Pb of the present invention was erasable in 150 ns or less.

Next, the crystallization onset temperature is determined by thermal analysis (DSC).
Investigated by. The rate of temperature rise during thermal analysis is 10 ° C. per minute. The results are shown in Table 1. As is clear from these results, the crystallization onset temperature of the Ge ₁₅ Sb _61.5 Te _23.5 thin film containing at least one element of Ga and Pb of the present invention _exceeded 180 ° C. By the way, the base composition of the recording film may be deviated by about ± 2 at% due to experimental errors such as film forming conditions. In such a case, (Ge15 ± 2Sb61.5 ± 2Te2
3.5 ± 2) gave similar results. Table 1 Additives Addition amount Erasure time Crystallization start temperature at% ns ° C None 0 400 225 Ga 1.8 150 233 Ga 3.8 100 247 Ga 6.2 Recording / erasing difficult Pb 0.5 150 227 Pb 1.0 130 225 Pb 5.0 100 200 Pb 8.5 100 187 Pb 9.5 Recording / erasing difficult

[0008]

Comparative Example As a comparative example of the erasing time and the crystallization start temperature, data of a Ge ₁₅ Sb _61.5 Te _23.5 (eutectic composition) recording film is shown in Table 1, and the evaluation conditions are the same as those of the example. is there. In the case of adding 6.2 at% of Ga and 9.5 at% of Pb, recording and erasing were difficult.

[0009]

As described above, the Ge-Sb according to the present invention has been described.
-Te3-element eutectic composition Ge ₁₅ Sb _{61 .5} Te _23.5 in G
An optical information recording medium having a recording layer doped with at least one element of a and Pb has a sufficiently short erasing time.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-76120 (JP, A) JP-A-5-116455 (JP, A) JP-A-63-225934 (JP, A) JP-A-1- 118229 (JP, A)

Claims (4)

(57) [Claims] 1. A ternary eutectic composition G of Ge, Sb and Te
G to e15 (± 2) Sb61.5 (± 2) Te23.5 (± 2)
An optical information recording medium having a recording thin film containing at least one of a and Pb. 2. Ge15 (± 2) Sb61.5 (± 2) Te2
Ga + Pb is 0.5 to 12.3a with 3.5 (± 2) being 100 at%.
2. The optical information recording medium according to claim 1, wherein the optical information recording medium contains t%. 3. Ge15 (± 2) Sb61.5 (± 2) Te2
2. The optical information recording medium according to claim 1, wherein Ga is contained at 1.8 to 3.8 at%, where 3.5 (± 2) is 100 at%. 4. Ge15 (± 2) Sb61.5 (± 2) Te2
2. The optical information recording medium according to claim 1, wherein Pb is contained in an amount of 0.5 to 8.5 at%, where 3.5 (± 2) is 100 at%.