JPS61217287A - Optical information-recording medium - Google Patents

Abstract

PURPOSE:To stabilize the state inside pits of a thin germanium telluride (GeTe) film and enable a reduction of noise at the time of reproduction, by adding Pb or Sn to GeTe in a ratio of not higher than a specified value, thereby reducing the volume change associated with a phase change. CONSTITUTION:A glass sheet, a polymethyl methacrylate resin or the like is used as a base 2, and a recording film 1 comprising Pb or Sn added to GeTe in a ratio of not higher than 15at.% is provided on the base 2 by vapor deposition. In recording or reproducing, the recording material is irradiated with laser beams 3 from the base 2 side. When the recording material is irradiated with intense laser beams, the exposed part undergoes a phase change from an amorphous phase to a crystalline phase under the heat generated by the irradiation, whereby the reflectance at the exposed part is increased, resulting in recording. In reproduction, signals are read by detecting the differences in reflectance. The recording medium, comprising a thin film of GeTePb or GeTeSn, is superior to a thin GeTe film with respect to pit stability, and therefore shows little noise.

Description

[Detailed Description of the Invention] (Industrial Application Field) The invention is a recording film that changes optical properties by F4 transformation due to the thermal energy of laser light and is deposited on a recording film substrate for recording information. (Prior art) Conventionally, as optical H information recording media, chalcogenization+m
tN film, Te low oxide thin film, SbtSeg + B11
In addition to Te++ two-layer thin films, there are GeTe thin films, which change from amorphous to crystalline (
Or vice versa) to cause a phase change, optical! 1'1
Recording is performed by changing the properties (refractive index, reflectance).

(The invention has been trying to solve the problem for a while.) However, among these, GeTe thin film has the following problems during recording.
Phase change from amorphous to crystal ゛J-4 Body/l blue shrinkage may cause cracks in the bit. The purpose is to stabilize the noise and reduce the noise during playback.4゜pbt or Sn? A: Cooled at a ratio of 15% or less to suppress volume change during phase change.

(English Example) Hereinafter, an embodiment of the present invention will be explained by 1.
The figure shows an embodiment of the invention, in which the substrate 2 includes a glass plate, polymethyl methacrylate resin, polyvinyl chloride resin,
Using polycarbonate resin, etc., as a recording film,
'GeTe with pb or Sn added is deposited. In this case, GeTe and Pb or Sn are completely mixed and deposited.
-4, or by depositing GeTe and PB or Sn by a binary evaporation method to form the recording film 1. To perform recording and reproduction on the optical information recording medium thus made,
As shown in FIG. 1, three laser beams are irradiated from the substrate 2 side. In this case, after the intense laser beam is fully irradiated, the exposed portion undergoes a phase change from amorphous to crystal due to the heat of the laser source irradiation, the reflectance increases, and recording is performed at t'LZ. For reproduction, read the signal by immersing it in reflectance. Note that this material has a low reflectance in a film thickness range of fd 800 A to 1200 A before recording, so the greatest contrast can be obtained in this range of film thickness.

Here, let's compare the state corresponding to (pi) fJ with the conventional example. First, PbXSn'fr: A thin film of only GeTe (film thickness 1050A) with no additives applied to a polymethyl methacrylate plate. , urine rate 2. Rotate at Om/s, use a semiconductor laser, 2.0 to 7.5 m
When recording in 0.5 mw steps in the range of w,
At a power of 3.0 mw or more, cracks appear in the formed pits. However, Pb'i for example 1
When recording in the same way for a thin film with 0% added, the result is 4.5
Stable pits without cracks can be obtained up to a power of rmy7 (at higher powers, holes will be formed due to melting and evaporation).6 Also, if a thin film to which Sn is added, for example, 5 T, is recorded in the same way, A stable 1-pit was obtained up to the power of 5.0 mw. By adding Pb or Snk, the volume change during the phase change from amorphous to crystal is reduced, and cracks are less likely to occur, making the state inside the pit more stable than when GeTe is used alone, and reducing noise during playback. Figure 2 shows that approximately 10 tb of pb'4 was added to GeTe (G
eTe),. For Pb1o deposited on a glass substrate with a film thickness of 105OA, the original wavelength was 830nrn.
The heat treatment temperature dependence of reflectance and transmittance on the substrate side is shown. The heat treatment time at each measurement point was approximately 10 minutes. Looking at this figure, you can see that both the reflectance and transmittance of my Z change between 160°C and 220°C. On the other hand, the reflectance change temperature range of GeTe-only mixture is 1600C to 1700C.
From this, it can be seen that by adding pb'2, the range of change in reflectance becomes wider4.

Figure 3 shows the result of adding about 5 tin of Sn to GeTe (GeTe
e,) 1ssna 1ssna 105 OA film deposited on a glass substrate in the same manner as in the case of PB. 4゜By heat-treating the above-mentioned recording medium as follows, an erasable record can be created. I can get the medium. That is, first, the change in reflectance (crystallization) is completely achieved at around 200°C, and in the case of Figure 3, it is around 190°C. Recording is performed when the entire light is irradiated.

In this case, since the cooling is rapid, the phase of the exposed area changes from crystal to amorphous, and the reflectance decreases by 4°, that is, recording occurs. Next, by lowering the original intensity of the 17-layer, increasing the exposure time and applying heat to the previously exposed area, a state of heating and slow cooling is created, causing a phase change from amorphous to crystal.
The reflectance can be increased again. In other words, erasing is possible.2゜(Effects) As mentioned above, due to non-invention, the A source information recording medium is GeTe.
Since # films of Pb and GeTeSn were used, GeTe
Compared to thin films, the pits are more stable and therefore there is less noise, which is an excellent effect.

[Brief explanation of drawings]

The eleventh figure is a cross-sectional view showing an embodiment of the recording medium according to the invention, and FIGS. 2 and 3 are two-line diagrams respectively illustrating all the characteristics of the recording medium according to the invention.

Claims (1)

[Claims] In an optical information recording medium in which a thin film is formed on a substrate and information is recorded by forming a portion with changing optical characteristics in the thin film using energy such as light or heat, the main component of the thin film is germanium telluride. , tin or lead in a ratio of 15% or less (atomic %).