JPH01248322A - Optical recorder for phase change type information recording medium - Google Patents

Abstract

PURPOSE:To prolong the repetitive life or recording and erasing by repeating the recording and erasing at a prescribed number of times, then annealing the recording layer of the information recording medium by a laser beam of the lower output and lower scanning speed than at the time of the recording and erasing. CONSTITUTION:The information is recorded on the recording layer by scanning the 1st light beam 3mW at 0.1musec 1st scanning speed and the information is erased by scanning the 2nd light beam 8mW to the recorded part at 0.1musec 1st speed. If the recording characteristics of the recording layer are degraded after repeating these operations, for example, 10<4> times, the recording characteristics of the recording layer 3 can be recovered if the recording layer is annealed by scanning the 3rd light beam 3mW of the output lower than the outputs of the 1st and 2nd light beams on the recording layer at the 2nd speed 15musec smaller than the 1st speed. The repetitive life of the recording and erasing is thereby prolonged.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) This invention provides a recording layer that reversibly changes phase between two different phases by changing the irradiation conditions of a light beam. Record information on an information recording medium such as an optical disk equipped with
The present invention relates to an optical recording device for a phase change type information recording medium that erases this information.

(Prior Art) Phase change type optical discs, so-called erasable discs, on which information can be erased have been known. In this phase-change optical disk, by changing the conditions of the laser beam irradiated to the recording layer, the irradiated portion reversibly changes phase between one structural state and another structural state. . These two states each have a birefringence N=
Since n-tk are different, information can be optically read by irradiating a laser beam onto an optical disk in which these two phases have been formed according to the information signal (S, R,
0vshinsky MetallurgicalT
transactions 2 641 (1971
) ).

There are two types of phase change recording methods: one in which the recording layer is reversibly changed between crystalline and amorphous states by changing the irradiation conditions of the laser beam, and the other in which the recording layer is made into a single crystalline state. Some crystals can be reversibly changed between other crystals (e.g., equilibrium crystal phase and metastable crystal phase). Examples of the former recording layer include semiconductors such as Te, Ge, and Se, and TeGe.

Semiconductor compounds such as rnse, 5bse, 5bTe, and rnsbre are known. Furthermore, InSb is known as a typical recording layer for the latter.

The recording layer of such a phase change type erasable disk is
The following basic skills are required.

(1> The recording layer itself has good environmental resistance, and is stable under an environmental resistance test at a temperature of 70° C. and a humidity of 85%, for example.

(2) The phase change region formed in the recording layer, that is, the recording mark, has good environmental resistance and the information does not disappear.

(3) High-speed deletion of information is possible.

(4) Recording characteristics should not deteriorate even if information is recorded and erased ideally 106 times.

Among these, (3) is due to the recent increase in the capacity of optical discs and the increase in data transfer speeds, and as the rotational speed of optical discs is becoming faster, information must be recorded and erased using as short a laser pulse as possible. It is based on the market demand that

Recently, among the above functions as a phase change recording layer, (3)
Improvement of (4) is required, and technological development is mainly focused on this point.

Among these, in order to realize the high-speed erasing shown in (3),
It is necessary to use short pulses for both recording and erasing, and to perform recording and erasing only by varying the power of the laser beam.

In order to achieve such high-speed erasing on an actual disk, a so-called overwrite 1 method is essential, in which information is recorded while being erased by modulating the power of a laser beam while rotating the disk at a high speed. If this override method is used, there is an advantage that in addition to high-speed erasing, it is also possible to record while erasing.

(Problem to be Solved by the Invention) However, if recording and erasing are performed only by varying the power of the laser beam as described above, the recording layer may be
When made of sbTe, recording and erasing
After repeating this process about four times, the contrast between the recorded portion and the erased portion becomes extremely small, resulting in a situation where it is virtually impossible to record. This is an extremely small value compared to the required value of (71) above, and poses a practical problem.

The present invention has been made in view of the above circumstances, and is an optical device for phase change information recording media that can extend the repeated recording and erasing life of the recording layer when speeding up erasing. The purpose is to provide a recording device.

[Structure of the invention] (Means for solving the problem) =5- The optical recording device for a phase change type information recording medium according to the present invention has the following features:
Phase change technology that records information on a phase change information recording medium that has a recording layer that reversibly changes between two different phases by changing the irradiation conditions of a light beam, and erases this information. An optical recording device for a type information recording medium, comprising a recording means for recording information by scanning a first light beam on the recording layer at a first speed, and a recording means for recording information by scanning a first light beam on the recording layer, and a second light beam on the recording layer. an erasing means for erasing recorded information by scanning at a first speed; and a third light beam having a lower output than the first and second light beams on the recording layer at a third speed lower than the first speed. an annealing means for annealing the recording layer by scanning at a speed of 2, and after repeating recording and erasing a predetermined number of times by the recording means and erasing means, the recording layer is annealed by the annealing means. do.

(Function) A first light beam is scanned over the recording layer at a first speed to record information, and a second light beam is scanned over the recorded area at a first speed to erase the information. , 6- Even if the recording characteristics of the recording layer deteriorate after repeating these operations a predetermined number of times (for example, 104 times), a third light beam with a lower output than the first and second light beams is then applied. When the recording layer is annealed by scanning at a second speed lower than the first speed, the recording characteristics of the recording layer can be restored, and recording and erasing can be repeated a predetermined number of times.

This annealing can be repeated many times. Therefore, the repeated recording and erasing life can be significantly extended compared to the conventional technology.

(Example) This example will be explained in detail below.

First, we will explain the general basic principles of recording and erasing methods for information recording media equipped with a phase-change recording layer.
The case where 5bTe is used will be explained as an example. I n5b
When Te is irradiated with a laser beam with a relatively small output of 3 to 11 mW and a relatively long pulse width of 2 to 3 μsec, the irradiated area becomes an equilibrium crystal phase with fine crystal grains, and the output in the same area is 10 mW. When irradiated with a relatively large laser beam of 18 mW and a relatively short pulse width of 041 μsec, it becomes amorphous. This phase change can be performed reversibly, and by making each phase correspond to a recording state and an erasing state, it is possible to repeatedly record and erase information.

This phase change can be repeated about 108 times, but if recording and erasing are repeated using short pulses for both recording and erasing and only changing the power level, the contrast between the variable recorded part and the erased part will be reduced about 104 times. It's gone.

This will be explained more specifically. FIG. 3 is a sectional view showing a phase change optical disc. The substrate 1 has a disk shape and is made of polycarbonate. On this substrate 1 is SiO2
A dielectric protective layer 2, an In5bTe recording layer 3.5i02 dielectric protective layer 4, and an ultraviolet curing resin layer 5 are laminated in this order to constitute a recording section 6. The protective layer 2.4 has a function of preventing the recording layer 3 from melting and forming holes during laser beam irradiation, and the ultraviolet curing resin layer 15 has a function of preventing scratches on the disk during handling. are doing.

FIG. 4 is a block diagram showing a static evaluation device for optical discs. In FIG. 4, reference numeral 7 is an optical head, and 8 is an objective lens for condensing a laser beam. The optical disc is placed on a seismic stand 9, and a laser beam is applied from the substrate 1 side. An example of the light emission pattern is shown below.

(1) The InSbTe recording layer 3 is usually deposited by vacuum sputtering, and since it is amorphous immediately after deposition, it is first irradiated with a laser with an output of 3 mW for 15 μsec to make the recording layer 3 completely crystalline in an equilibrium phase ( initial crystallization).

(2) Information is recorded by irradiating the initially crystallized portion with a laser pulse having an output of 13 mW and a pulse width of 0.1 μsec. Then, the recorded portion is irradiated with a weak laser beam with an output of 0.4 mW, and the reflectance at this time is read.

(3) The output is 5 mW and the pulse width is 5 μs in the recorded part.
The information is erased by irradiation with an ec laser pulse. Then, the erased portion is irradiated with a laser beam with an output of 0.4 mW, and the reflectance at this time is read.

Recording and erasing in (2) and (3) were repeated, and the reflectance was plotted every time recording and erasing was performed 20 times, and the results are shown in FIG. According to this figure, the reflectance Rw of the recorded portion
The contrast between R6 and the reflectance of the erased part is 10
It has not decreased even after repeating recording and erasing six times.

On the other hand, the erasure shown in (3) above is performed with an output of 8 mW and a pulse width of 0.
．． FIG. 6 shows the contrast of reflectance when recording and erasing are repeated using a laser pulse of 1 μsec. As is clear from this figure, in this case, by repeating recording and erasing about 104 times, Con1 to Last disappear. That is, the laser pulse width for recording and erasing information is both Q, 1', czsec, and the power is 13
When recording and erasing is repeated by modulating between mW and 8mW, the number of times that recording and erasing can be repeated is approximately 1/100 compared to when the erasing pulse is set to a low output and a long pulse width. found.

As a result of the inventor's repeated efforts to investigate such problems, for example, after repeating recording and erasing 104 times using only power modulation, for example, similar to the case of initial crystallization shown in (1) above, 3mW.

It has been found that the functions of the recording layer can be regenerated by irradiation with a 15 μsec laser beam, that is, a laser beam with a smaller output and a longer pulse width than the laser beam used for erasing.

In other words, according to the inventor's experiments, power modulation alone can reduce
04 times recording (13mW, 0.1μ5ec) and erasing (
8mW, o, 1μ5ec), then 3mW, 15
When annealing is performed by irradiating a laser beam for μsec, and then recording and erasing are performed again under the same conditions, the same reflectance as the first time can be obtained in the recorded portion and the erased portion, and 104 times thereafter. It was possible to record and erase information.

Such an effect can also be obtained by annealing under similar conditions after repeating the second 104 times of recording and erasing.
It was possible. In other words, recording and erasing could be repeated 5×10” times.

This is about half the number of times erased when using a laser beam with a long pulse width and relatively low power.
This is sufficient for practical use.

Next, the results of dynamic evaluation of the optical disc based on the results of the above static evaluation will be explained.

This test was conducted using a performance evaluation device according to the following procedure.

(a) Rotate the optical disk at 10 rpm, 3 mW
The laser beam was continuously irradiated to initialize crystallization for one revolution.

(b) Next, the optical disk was rotated at 900 rl) m, and the initially crystallized portion was heated at 100 μsec with an output of 15 mW.
Recording was performed by irradiating pulsed light with a duty ratio of 50%. When the recorded portion was irradiated with a 0.8 mW reproducing laser beam, the signal amplitude was approximately LOOmV.

(C) Next, while maintaining the rotational speed of the optical disc at 90 Orpm, the recorded portion was continuously irradiated with a 9 mW laser beam to erase the recorded signal. In this case, o,
When the erased part is irradiated with the smw reproduction laser beam,
The amplitude of the signal was OmV.

Repeat operations (b) and (C), each time 0.8 mW.
The magnitude of the signal amplitude was measured using the reproducing beam. As a result, after repeating recording and erasing 103 times, residual signals began to appear during playback after erasing, and after 203
By repeating zero recording and erasing about 0 times, the contrast between the recorded portion and the erased portion disappeared. That is, while the signal amplitude after recording is 100 mV, the amplitude after erasing is also 10 mV.
0 mV remained. This result means that the number of repetitions of recording and erasing is smaller in the performance evaluation than in the static evaluation described above.

Next, with the contrast gone, the optical disc was returned to a low speed of 1 Qrpm, and the portion where recording and erasure had been repeated was again irradiated with a continuous laser beam with an output of 3 mW, similar to the initial crystallization in (a).

Thereafter, when the operations (b) and (C) were performed to reproduce the signal of the erased portion, the amplitude of the erased signal returned to OmV.

Furthermore, when the recording and erasing of (b) and (C) are repeated, and the signal amplitude of the erased portion is measured by irradiating the reproduction laser beam each time, the remaining erased area appears from around the 103rd repetition, and after the 1500th repetition. Grade 1: Contrast between the recorded portion and the erased portion has disappeared.

According to the results of this experiment, when a phase-change optical disk is used in an actual optical recording device, recording and erasing can be repeated approximately 1000 times before the contrast between the recorded and erased areas disappears. It was later found that if the optical disk is annealed under the conditions of initial crystallization, recording and erasing can be repeated approximately 1000 times.

Based on this result, after initial crystallization under the above-mentioned conditions, recording and erasing were repeated 1000 times and annealing was repeated, and it was possible to perform this operation 50 times. That is, 100
At 0x50 times, recording and erasing could be performed 5x104 times.

Next, an optical recording device using such a principle will be explained. FIG. 1 is a schematic configuration diagram showing an optical recording apparatus according to the present invention. In FIG. 1, reference numeral 11 is a modulator, which outputs a predetermined signal to the laser light source 12 during initial crystallization, recording, erasing, or reproduction. The laser light source 12 is
When recording information, for example, a 13 mW laser beam L is output at a predetermined timing, and when erasing information, an 8 mW laser beam L is output. This laser beam L is made into parallel light by a collimator lens 13, and is condensed and irradiated by a polarizing beam splinter 14, a λ/4 plate 1 and a metal plate 5, and then a condensing lens 16 toward the recording layer of the optical disc 20. In this case, the optical disc 30 is rotated at a constant speed of, for example, 900 rl)m, and recording and erasing can be performed simply by irradiating the optical disc 20 with a power-modulated laser beam.

That is, recording and erasing are performed by scanning the optical disc with laser beams L having different outputs at the same speed. In this way, when recording and erasing is performed only by power modulation, that is, when the override method is adopted, the laser beam irradiation pattern during recording and erasing becomes as shown in FIG. That is, information is recorded and erased by power modulating between W and E in the figure.

When reproducing information, for example, 0.8 m from the light source 12.
A weak laser beam of W is output, and the collimator lens 13
The light is converted into parallel light by the recycle bag [
19, and the information is reproduced by this reproduction device 19.

After recording and erasing information is repeated, for example, 1000 times, a signal for outputting a laser beam for annealing is output from the modulator 11 to the light 8112, and a laser beam of lower power than that used for recording and erasing (for example, initial crystal The recording layer of the optical disk 20 is irradiated with an output of 3 mW, which is the same as that used in This annealing reproduces the recording layer whose contrast has begun to deteriorate.
Further, similar recording and erasing can be repeated.

In this way, by repeating recording and erasing at high speed and then annealing with a weak laser beam at low speed, the number of times recording and erasing can be repeated can be dramatically increased compared to the conventional method.

In addition, in this embodiment, In is used as the information recording medium.
Although the example using the 5bTe recording layer is shown, the present invention is not limited to this, and other recording layers such as InSe, 5bCe, 5bTe, etc.
It can also be applied to bSe, 'TeGe, etc., and similar effects can be obtained. In this case, the number of repetitions of recording and erasing until annealing is performed depends somewhat on the composition of the recording layer.

It goes without saying that the present invention can also be applied to an optical card device that uses an optical card as a phase change information recording medium.

Furthermore, in implementing the present invention, it is possible to record the number of repetitions of recording and erasing in a specific sector of the information recording medium, and to prepare software that performs annealing when the number of repetitions reaches a predetermined value. good.

[Effects of the Invention] According to the present invention, after repeating recording and erasing a predetermined number of times, the recording layer of the information recording medium is annealed using a laser beam with a lower output and a lower scanning speed than during recording and erasing. The recording properties of the layer can be reproduced.

Therefore, even if recording and erasing are repeated at high speeds, the life of the recording layer can be significantly extended compared to the conventional method. That is,
When a phase change type information recording medium is used, an extremely large advantage can be obtained in that an override method becomes possible.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an optical recording device according to an embodiment of the present invention, Fig. 2 is a graph showing laser beam output for recording and erasing in an override method, and Fig. 3 is a diagram showing a phase change type information recording medium. 4 is a schematic configuration diagram showing a static evaluation device for an optical disk. FIG. 5 is a graph showing changes in reflectance of the recorded portion and erased portion when erased using a low-output, long-pulse laser beam. 6 are graphs showing changes in the reflectance of recorded portions and erased portions when erasing is performed using a high-power, short-pulse laser beam. 11; Modulator, 12; Laser light source, 13°16.
17, 18; Lens, 14; Polarizing beam splitter, 1
5; λ/4 plate, 19; playback device, 20; optical disc. Applicant's agent Patent attorney Takehiko Suzue ♀ ■ ■
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Claims (1)

[Claims] A phase change type information storage medium that records information on a phase change information recording medium that has a recording layer that reversibly changes between two different phases by changing the irradiation conditions of the light beam, and erases this information. An optical recording device for an information recording medium, comprising a recording means for recording information by scanning a first light beam on the recording layer at a first speed, and a recording means for recording information by scanning a first light beam on the recording layer. an erasing means for erasing recorded information by scanning at a speed of 1; and a third light beam having a lower output than the first and second light beams on the recording layer; and an annealing means for annealing the recording layer by scanning at a speed of , and after repeating recording and erasing a predetermined number of times by the recording means and erasing means, the recording layer is annealed by the annealing means. Optical recording device for phase change type information recording media.