JPH02201734A - Optical disk recording method - Google Patents

Abstract

PURPOSE:To expand an erasing power margin, and to record a signal at a high quality on a recording film by irradiating an optical disk by means of laser power >=1.5 times of the laser power, which is obtained when the optical disk is irradiated with a light beam and an amorphous phase emerges. CONSTITUTION:The laser power is assumed as P0 which makes amorphous phase emerge when the optical disk is irradiated with the laser power directly and continuously, the optical disk is irradiated with the power P1>=1.5XP0. In such a way, erasing can be made to correspond to the intermediate state between a crystal state and an amorphous state. Thus an erasing characteristic can be improved, the erasing power margin is expanded, and a phase changing medium can be recorded and erased at a high quality and at high efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for efficiently and high quality recording information on a recording film of an optical disk that causes a crystalline/amorphous phase change phenomenon.

[Conventional technology]

To record information on the recording film of an optical disk that causes a crystalline/amorphous phase change phenomenon, the recording film is irradiated with a laser beam to heat the recording film material above its melting point and then rapidly cooled. This is done by forming an amorphous mark.

On the other hand, information can be erased by irradiating the recording film with a laser beam with a lower power than during recording to raise the temperature of the recording film to below its melting point, thereby changing the phase of the amorphous marks on the recording film to a crystalline state. ing.

By the way, since a recording film is generally in a mixed crystal/non-quality state when it is manufactured, when it is actually supplied as a recording disk, the entire recording film is brought into a crystalline state in advance. This is called initialization.

FIG. 3 is an explanatory diagram of the conventional recording process (crystallization, initialization, amorphization, erasure, etc.).

First, (al is an explanatory diagram about the crystallization process.

The vertical axis of the figure is reflectance, and the horizontal axis is recording power.

Here, the one with a higher reflectance is in a crystalline state, and the one with a lower reflectance is in an amorphous state. There are recording film configurations in which this relationship is reversed, but in that case, the change in reflectance between crystallization and amorphization may be reversed.

The reflectance of the optical disc after film formation is the value F1 at the point indicated by 21. When this optical disk is irradiated with a laser beam in a direct current manner, the reflectance begins to change from point 21, passes through point 22 (reflectance F3), and reaches point 23 (reflectance F2) as shown by the curve. The process from point 21 to point 22 is a crystallization process, and after point 22 an amorphous phase appears and the reflectance tends to decrease. The power at which the amorphous phase appears at this time is PO, and the point 21.23
Let Q1 and Q2 be the corresponding recording powers, respectively.

Now, before recording information, it is first brought into a crystalline state. There are two ways to do this. One method is to irradiate with power PO to bring the reflectance to F3, and the other is to first irradiate with power Q2 and then irradiate with power PO to bring the reflectance to F4. In both methods, point 22 in the crystallized state
The reflectance ranges from 25 to 25 in the crystalline state. If a high-power laser beam is irradiated to the part in this state (crystal), the irradiated area will become amorphous and the reflectance will be less than the value normally indicated by F1, and information will be transmitted. is recorded.

When new information is to be recorded in this previously recorded area, the information is first erased by applying the power PO to crystallize the area. This erasing process is shown in FIG. 3(b). The vertical axis is the erasure rate, and the horizontal axis is the erasure power. The erase characteristic near the erase power PO is as shown by a curve 26. In this case, the erasing rate is maximum at point 27 (the PO point).

[Problem to be solved by the invention]

However, in the region where the erasing power is lower than point 27, erasing is insufficient, and in the region where the erasing power is higher than point 27, the amorphous phase is They appear and cannot be erased.As described above, this erasing method has a problem in that the power margin for erasing is extremely narrow.

The present invention has been made in view of the above circumstances, and its purpose is to provide an optical disc recording method that widens the power margin for erasure and enables high-quality signals to be recorded on a recording film. That's true.

[Means to solve the problem]

To this end, the present invention provides an optical disc recording method for recording information by irradiating a light beam onto an optical disc having a rewritable recording film that utilizes a crystal/amorphous phase transition phenomenon. The optical disc is irradiated with a first laser power that is 1.5 times or more higher than the laser power at which an amorphous phase appears when the optical disc is heated.

After the irradiation with the first laser power, a second laser power greater than the first laser power may be irradiated, and then a third laser power smaller than the first laser power may be irradiated.

Further, each of the first, second, and third laser powers may be configured by an envelope of an optical pulse train.

〔Example〕

An embodiment of the optical disc recording method of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is an explanatory diagram of the power of a laser beam irradiated onto an optical disc recording film. First, in (a), the peak power P1 of the laser beam is PO(
3 is a diagram showing a driving characteristic 2 of a laser beam when a value is set to a value 1.5 times or more of the power (common with the power PO shown in FIG. 3). FIG. Here, this power P1 is used as the power corresponding to "0" in the information array (or the power for erasing).

In the same figure (b), while erasing with the power P1 described above, a laser beam with a power P2 higher than that power P1 is irradiated to the part corresponding to 'IJ of the information string 3, and then that beam is irradiated with a laser beam with a power P2 higher than the power P1. FIG. 4 is a diagram showing a driving characteristic 4 in which the power is changed to a lower power P3 and then returned to Pl. In this method, an amorphous mark is formed immediately after changing the laser beam to the power P3.

Therefore, if the power of the laser beam is changed from P1==)P2→P3→P1 at the timing corresponding to "1" according to the information sequence and driven, the previously recorded information will be erased while new information will be recorded. will be recorded.

Figure C1 is an example in which the drive waveform in Figure 3B is constituted by a pulse train 5. Note that such a pulse train formation of the laser beam can of course be applied to Figure 3A as well.

The 21st m+al is a diagram showing the relationship between erasing power and passivity (waveform 6) when a symbol with a wavelength of 2 μm is recorded after irradiation with a laser beam of power P1 and this recorded signal is erased. (b) is a diagram showing the relationship between erasing power and passivity (waveform 6). FIG. 7 is a diagram showing the relationship between reflectance and reflectance (waveform 7).

In the conventional method, as described in the explanation of Fig. 3, the power PO
Since erasing is performed using a laser beam near , the power margin for erasing was narrow. However, in this embodiment, erasing is performed using a power higher than that of the conventional method, specifically, a power P1 that is 1.5 times or more of PO. , there is no such thing.

According to an experimental example, when the value of the power P1 was set to be 1.5 times or more the power PO, the erasure rate was 130 dB or less. The power Pc in FIG. 2 (al, (kl)) is P c
= 1.5 x P O . In the case of even higher erase power, 40d
An erasure rate of B or less was obtained.

This means that when continuously irradiated with a high-power laser beam,
This is because even after the laser beam passes through the recording film, cooling is relatively slow due to the influence of the rear end of the laser beam. At this time, the reflectance of the optical disc recording film is in an intermediate state between the reflectance F1 after film formation and the reflectance F3 or F4 in the crystalline state, as shown by F2. In the case of recording, by momentarily interrupting (changing) the laser beam as shown in waveform 4.5 in FIG. 1, an amorphous mark can be formed and recording can be achieved.

Furthermore, it is possible to override previously recorded information by one beam, as shown in Figure 1.According to experiments, under the condition of PL>1.5xPO, the erasure rate is less than -30 dB, which is sufficient for practical use. A good erasing characteristic was obtained.

The method of this embodiment has a wide erase power margin as shown in FIG. The upper limit power is the power that causes permanent deformation of the recording film, and is usually 3 to 4 times the power po.

As described above, in the optical disc recording method of the present invention,
If the laser power at which an amorphous phase begins to appear when an optical disk is continuously irradiated with laser power (direct current) is PO, then the optical disk is irradiated with a power PI of 1.5 x P 0 or more. Also, while irradiating this power P1,
A power P2 larger than this power P1 is irradiated, and then a power P3 smaller than the power P1 is irradiated. Alternatively, the laser power for these recordings is configured by the envelope of the optical pulse train. As a result, the erasing characteristics can be significantly improved and the erasing power margin can be expanded. Therefore, it becomes possible to perform high quality and efficient recording/erasing on the phase change medium.

Note that the present invention is of course not limited to the embodiments described above.

〔Effect of the invention〕

As described above, according to the present invention, unlike the conventional method in which erasing corresponds to either a crystalline state or an amorphous state, it is possible to correspond to an intermediate state between them, so that stable erasing with a wide erasing margin can be realized.

The invention also has new signal processing advantages. In other words, the fact that the erased state is between the crystalline state and the amorphous state means that it is possible to record at a three-level level, which is the addition of another state to the crystalline state and the amorphous state.
Multi-value recording becomes possible.

Therefore, by level modulating the laser power,
A crystalline state can be recorded by applying a low level of laser power, an amorphous state can be recorded by applying a high power, and an intermediate state can be recorded by applying a medium power. These are suitable as efficient information processing methods.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of an optical disc recording method according to an embodiment of the present invention, and FIG. 3 is an explanatory diagram of a conventional optical disc recording method. DESCRIPTION OF SYMBOLS 1... Information string, 2... Power characteristic line, 3... Information string, 4... Power waveform, 5... Power waveform converted into a pulse train, 6... Waveform of erasure rate, 7... ...Reflectance waveform, PO1QIQ2, Pl, Pc...Laser power, 2
1 to 23... points, F1 to F4... reflectance. Agent Patent Attorney Tsune Akira Nagao LCL Tansanken

Claims (3)

[Claims] (1) In an optical disc recording method in which information is recorded by irradiating a light beam onto an optical disc having a rewritable recording film that utilizes a crystal/amorphous phase transition phenomenon, when the optical disc is irradiated with a light beam, An optical disc recording method characterized in that the optical disc is irradiated with a first laser power that is 1.5 times or more the laser power at which an amorphous phase begins to appear. (2) Next to the irradiation with the first laser power, the first
A second laser power greater than the laser power is irradiated, and then a third laser power smaller than the first laser power is irradiated to record new information while erasing the previous information. An optical disc recording method according to claim 1. (3) The optical disc recording method according to claim 1 or 2, wherein each of the first, second, and third laser powers is configured by an envelope of an optical pulse train.