JPH08235588A - Recording method of information - Google Patents

Abstract

PURPOSE: To record information by a single laser beam by biasing the beam power to an erasing level and increasing the recording level of the beam for a specific time when overwriting the information using a single energy beam. CONSTITUTION: The power is raised to an amorphous level for a short time at the place where the recording medium is to be made amorphous in accordance with the information signal. When the information including a laser beam pulses of length more than twice a shortest pulse length is recorded, the laser beam is divided into original recording waveforms and plural short pulses and are radiated as shown in the center section of the waveforms in a figure. When the laser beam is divided into plural short pulses as mentioned above, it is desirable to make the power lower than a crystallization power level between pulses. By dividing the laser beam into plural pulses to be radiated, a recording pattern is formed on a disk to provide regerative signals which are faithful to original signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording method using an information recording member capable of rewriting information by irradiating an energy beam such as light or an atomic beam, and particularly recording with a single laser beam. The present invention relates to a method of recording effective information on a rewritable phase change type optical disc that is erased.

[0002]

2. Description of the Related Art A conventional recording / erasing method for a phase change type optical disk recording medium is disclosed in, for example, Japanese Patent Laid-Open No. 59-71140. In this method, when erasing the already recorded information by crystallizing the recording film, an elliptical light spot long in the track direction is used to maintain a temperature at which crystallization is possible for a relatively long time. After that, to record new information, the power of a sufficiently condensed circular light spot was modulated by an information signal. However, recently, the inventors of the present invention have improved the material used for the recording film so that a well-focused circular light spot crystallizes while passing over one point on the disc. Made possible Therefore, the circular light spot makes it possible to perform recording by erasing first with one rotation of the disk and then modulating and irradiating the laser power with the next one rotation. Further, by modulating the laser power between the crystallization power level and the amorphization power level according to the information signal, it becomes possible to rewrite the information with one rotation of the disk.

[0003]

However, in the above-mentioned prior art, when the rotational speed of the disk is increased in order to increase the information transfer rate, it is necessary to further increase the rate of atomic arrangement change (for example, crystallization) of the recording film. Even if the crystal is melted by irradiation with an energy beam (eg, laser beam), the atomic arrangement returns to its original state (eg, recrystallization) during cooling after irradiation, and the atomic arrangement changes in the opposite direction (eg, amorphous). Qualification) cannot be performed.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to use a recording film having a large phase change speed,
It is to provide a method capable of reliably causing a reversible phase change.

[0005]

The above object is achieved by forming a recording point with a single pulse or a plurality of pulses having a panel width shorter than the time taken for the center of an energy beam spot to pass from end to end of the recording point. To be done. It is more preferable to use a pulse having a pulse width narrower than 3/4 of the time required to pass from one end to the other, more preferably a pulse width having a pulse width narrower than 1/2, and a pulse width narrower than 1/4. A pulse is particularly preferable.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION By narrowing the pulse width as described above, it is possible to prevent thermal diffusion due to transfer conduction from the irradiated portion to the periphery thereof and to relatively reduce the irradiation beam energy. Therefore, the cooling rate after irradiation can be increased.

The present invention has a problem that, when information is overwritten with a single laser beam (rewriting is performed by overwriting without erasing in advance), the cooling rate after laser light irradiation tends to be low. Will be solved,
Especially effective.

The recording medium to which the present invention is applied may be one that causes a phase change between a crystal and an amorphous state and another that causes a change in atomic arrangement. For example, one atomic arrangement change is also effective for crystal-to-crystal atomic arrangement change that requires rapid cooling or amorphous-to-amorphous atomic arrangement change.

The present invention is effective regardless of the type of energy beam, and light, electron beam, ion beam or the like can be used. However, in the case of electron beams and ion beams, the thickness of the protective film on the recording film of the recording medium is preferably 1 μm or less, more preferably 1000 or less.

The present invention will be described below with reference to examples.

Both sides of a recording film containing In and Se as a main component, which performs recording / erasing by reversible phase change between a crystalline state and a nearly amorphous state, are sandwiched by SiO ₂ protective films. The structure was formed on a disk-shaped glass substrate having an ultraviolet curable resin layer on the surface. Bits representing tracking grooves and addresses are transferred to the surface of the ultraviolet curable resin layer. Next, an ultraviolet curable resin was applied onto the above protective film, and it was attached to another glass substrate and cured by ultraviolet rays.

Next, this optical disk is rotated at a rotation speed of 600 rpm.
I searched for a place to record while rotating with and tracking and auto-focusing. Where it should be recorded,
After the laser light power was raised from the read power level to the crystallization power level, the power was varied as shown in FIG. The upper part of FIG. 1 shows an array of amorphization points formed on the recording track. The other parts on the tracks are crystallized, and the as-depo state (as-deposited state) is maintained between the tracks. Actually the position of the light spot does not move,
The points on the disk move to the left, but in the figure, the points on the disk stand still and the light spot moves to the right. In the lower diagram of FIG. 1, the horizontal axis corresponds to the horizontal position of the light spot center in the upper diagram, and shows the laser power irradiated to each point when the light spot moves to the right. There is. The power is raised to the amorphization level for a short time at the place where the amorphization is to be performed according to the information signal. The time width during which the laser power rises to the amorphization level is about 3/4 of the time taken for the center of the light spot to pass from end to end of the corresponding amorphization point (range where the crystallinity is worse than the surroundings). ing. However, the definition of the time width in which the power rises was defined as the width of the half value point of the pulse height from the crystallization level. Irradiation with laser light at the amorphization power level melts the irradiated portion on the disk and quenches it to become amorphous. When recording information including a pulse having a length twice or more the length of the shortest pulse, the original recording waveform is divided into a plurality of short pulses as shown in the central portion of the waveform in FIG. Irradiate. In the example of FIG. 1, the irradiated portion forms a long amorphized portion in which three amorphized portions stick to each other. When divided into such short pulses, the power is preferably lower than the crystallization power level between the pulses, and the power is preferably 0 or the read power level. However, depending on the composition of the recording film and the material of the protective film, the crystallization power level may be lowered to a level slightly higher. It is particularly preferable that the narrower the interval between the pulses is, the more the power of that portion is reduced. FIG. 1 shows a case where the read power level is lowered. Even if the information to be recorded has a portion with a long pulse width, it is possible to form a recording pattern on the disc that gives a reproduction signal that is faithful to the original signal by dividing the pulse into multiple pulses for irradiation. You can When the information to be recorded has only a short pulse width portion, of course, the above division into a plurality of pulses is not necessary. The laser power waveform of this embodiment is a waveform capable of rewriting information by overwriting, that is, overwriting, which does not need to be erased in advance.

It is more preferable to set the time width for the laser power to reach the amorphization level to be 1/2 or less of the time taken for the center of the light spot to pass from the end to the end of the corresponding amorphization point. When it is 4 or less, the amorphization can be completed completely, which is particularly preferable.

Similarly, when the entire track is crystallized and erased by continuous laser light irradiation and then recording is performed by the laser light whose power is modulated between the read power level and the amorphization power level, the same pulse is used. It is preferable to narrow the width. However, in this case, the cooling rate is always high because the power is always lowered to the read power level between the pulses. Therefore, the effect is not so remarkable as in the case of single beam overwrite.

In the case of single beam overwrite, the crystallization power level is 30 to 9 with respect to the amorphization power level.
If adjusted within a range of 5%, a reproduction signal can be obtained regardless of the time width of the amorphization power level. 5
A range of 5 to 90% is a more preferable range.

In this embodiment, the recording is considered to be amorphous, but the viewpoint may be changed so that crystallization is considered to be recording.

[0017]

According to the present invention, since the atomic arrangement can be changed in the opposite direction even if a recording film capable of changing the atomic arrangement at a high speed is used, it is possible to increase the transfer rate of information, and moreover, a single transfer can be made. Since it is possible to overwrite with a laser beam, it is extremely advantageous for recording and reading a large amount of information.

[Brief description of drawings]

FIG. 1 is a diagram showing the operating principle of an embodiment.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keikichi Ando 1-280, Higashi Koikekubo, Kokubunji, Tokyo Stock Company, Central Research Laboratory, Hitachi Ltd. (72) Inventor, Norio Ohta 1-280 Higashi Koikeku, Kokubunji, Tokyo Central Research Laboratory of Hitachi, Ltd.

Claims (4)

[Claims] 1. Energy of light, electron beam, ion beam, etc.
In an information recording method for recording information by changing the atomic arrangement of a recording film using a beam, when the information is overwritten by a single energy beam, the beam power is set to an erasing level. A method of recording information, characterized in that the recording level is raised to a recording level for a time shorter than the pulse width of the information signal to be recorded or reproduced. 2. The pulse width according to claim 1, which is 3/4 of the pulse width.
A method of recording information, characterized by increasing the recording level only for the following times. 3. In claim 1 and 2, to be recorded,
Alternatively, a plurality of pulses for raising the power to a recording level are made to correspond to a pulse shorter than the shortest of the information signal to be reproduced, and the sum of the widths of the plurality of pulses is to be recorded or reproduced. A method of recording information, characterized in that the pulse width is shorter than the pulse width of the information signal to be reproduced. 4. The power level between a plurality of pulses according to claim 3, wherein the power level between the plurality of pulses is changed from an information read level to an erase power level.
A method of recording information characterized by being in a range up to the level.