JPS63138530A - Optical disk device - Google Patents

Abstract

PURPOSE:To surely erase recorded optical information without causing performance deterioration of an optical disk by constituting the device of an extinction part applying temperature-rising and annealing to an extinction light and of a heat buffer part buffering an adrupt temperature gradient caused by the extinction part. CONSTITUTION:The extinction part is constituted by arranging a melt light 2 and an anneal light 3 on a recording track 1 and the heat buffer part 4 is constituted by a light with a large half value but a small beam power in a way covering the lights 2 and 3. The extinction light (the light 2 is moved forward and the light 3 is moved backward) is moved on the track 1 while annealing gradually and crystallizing the recording material film by the light 2. In this case, the heat buffer part 4 is moved while buffering the temperature gradient caused by the extinction part at the same time. According to the method above, all the extinction processes are finished and the moment the extinction light is extinguished, especially in the front of light 2, an adrupt temperature gradient is buffered and it is possible to erase optical information while suppressing the production of thermal damage and not deteriorating the performance of the optical disk.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical disc device using a photosensitive recording material whose optical properties can be reversibly changed by irradiation with a laser beam.

Conventional technology Conventionally, in order to create an optical disc that allows information to be corrected and rewritten, a photosensitive material is formed in the form of a thin film on a disc substrate made of polymeric resin such as acrylic, and the optical disc is heated by irradiating it with a laser. Generally used are devices in which recording and erasure are performed by changing the optical properties, ie, reflectance and transmittance, by rapid cooling and slow cooling.

As a recording material exhibiting the above characteristics, for example, a chalcogen compound or a metal compound containing tellurium with germanium, antimony, etc. as an additive is used, and by using these, recording is made into a state generally called amorphous with low reflectance.
For erasing, optical information can be recorded and erased in real time by heating and slowly cooling it to a crystalline state with high reflectance.

As a light source, a semiconductor laser that satisfies high aperture performance, is small, and can be directly modulated is generally used.

For amorphous recording, a well-focused circular laser beam with a large beam density (al It is necessary to irradiate track 1, melt the recording material, and rapidly cool it as shown in the temperature change diagram in Figure 4B.On the other hand, when erasing, it is necessary to slowly cool it for crystallization. Therefore, when the optical spot length is relatively long, such as b2 (beam diameter b2x in the disk rotational direction, beam diameter b2a in the disk radial direction) in FIG. 2μm
Conventionally, it has been common practice to irradiate a material with elliptical light of a certain degree, and to slowly cool it and crystallize it as shown in the temperature change diagram of FIG. 6B.

The crystalline state created in this way is caused by the generation of crystal nuclei in the solid state, and the crystals in the unrecorded area are
There has been a problem in that the optical constants are slightly shifted, leaving traces of the recorded signal, and the erasing rate is poor. In order to avoid this inconvenience, in front of the elliptical erasing beam C2 (beam diameter C2 in the disk rotational direction, C2A in the disk radial direction) as shown in FIG. 6A, a circular beam with relatively high power density (hereafter Melt light (referred to as melt light) C1 (beam diameter C1r) is irradiated to uniformly melt the information-unrecorded areas and recorded parts on the recording track, and then slowly cooled by elliptical light C2 (hereinafter referred to as annealing light). There is an attempt to ensure erasure using
1928).

FIG. 6B shows the circular melt light C1 used for the erasing,
It shows the laser intensity of the oval annealing light C2 in the disk rotation direction, and FIG. 6C shows the temperature change of the recording material thin film. The melting light has a laser power of 15~15 to melt the information recording area with a width 9 that is almost the same as the recording track width.
20 mW, and the corresponding half-width, '1r is 2
~3 μm is required, and if the power is small, for example, about 10 mW, it will not be possible to reliably melt the recording track width.On the contrary, in order to increase the half width and melt more than the width of the recording track, a large power as described above is required. You will need a laser. At the same time, when a laser source with such a shape is used, the temperature at the center of the recording track, which indicates the highest temperature of the recording material film, is raised to a temperature considerably higher than the melting temperature (Tm), which in turn increases the thermal stability of the optical disc. Damage could occur. Further, the thermal damage was particularly observed at a location (sector end) where the temperature gradient in front of the melt light at the time when the erasing light disappeared was the steepest.

Problems to be Solved by the Invention In the conventional erasing method, as mentioned in the conventional example, the temperature gradient becomes steep in front of the melt light (sector end) at the point when the erasing light disappears. Therefore, thermal damage occurs, which is a major cause of performance deterioration of the optical disk.

Therefore, the present invention provides a method for reliably erasing optical information recorded on an optical disk without causing performance deterioration of the optical disk due to thermal damage.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention is such that the erasing light is composed of an erasing section and a thermal buffer section whose beak power is lower than that of the erasing section.

Effects According to the present invention, with the above-described configuration, the conventional erasing mechanism of melting and slow cooling is carried out by the erasing section, and a region with a gentle temperature gradient is formed around the erasing section by the thermal buffer section.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings. As the recording medium, as mentioned above, the optical stability changes depending on the state before and after recording, i.e., the amorphous state with low reflectance is produced by heating and cooling rapidly, and the crystalline state with high reflectance is produced by heating and slowly cooling, for example, chalcogen compounds, Alternatively, a metal compound using tellurium, germanium, antimony, etc. is used.

The crystalline and amorphous phase transformations of these recording media differ slightly depending on the composition of the material, but are not directly related to the method of the present invention and do not affect the present invention. Also, the recorded state is defined as amorphous and the erased state is defined as crystalline.
The reverse is of course also possible, and in the present invention, for convenience, the recorded state is amorphous and the erased state is crystalline.

First, information is recorded on an unrecorded optical disk, which has been made into a highly reflective crystalline state through heat treatment or the like, by irradiating a focused circular beam with high power density.

For example, in the case of an optical disc rotating at 11000 rpm, the power is around 10 mW, and the half width is 1 μm.
When weak circular light is irradiated onto a track with a radius of 10α on the disk, the recording material film is rapidly heated due to the well focused light, and in a short time of approximately 100 nSeC, it is rapidly cooled due to the passage of the laser light, and almost no heat is generated. The same width as the recording track width (generally about 7000 degrees) is amorphized to generate an information recording portion (bit). In the embodiment, a method for erasing an information recording section will be explained.

FIG. 1A is a block diagram of the erasing beam of the present invention, in which melt light 2. The annealing light 3 was arranged to constitute an erasing section, and the thermal buffer section 4 was composed of light having a large half width and a small beam power so as to cover the melt light 2 and the annealing light 3. FIG. 1B shows the intensity distribution of the erasing light in the disk rotation direction, and the solid lines 5, 6.7 are melt light 2, annealing light 3, and 7, respectively. The dotted line 8 represents the individual intensity distribution of each of the thermal buffers 4. Anneal light 3,
This is the intensity distribution when the thermal buffer section 4 is combined.

The erasing light passes over the recording track with the melt light 2 in the front and the annealing light 3 in the rear, heating the recording material film by the melt light 2 to raise the temperature, and immediately thereafter slowly cooling the recording material film by the annealing light 3. It moves while crystallizing. At this time, the thermal buffer section 4 simultaneously moves while softening the temperature gradient caused by the erasing section. According to the above method, when the erasing process is completed and the erasing light disappears, the steep temperature gradient that occurs especially in front of the melt light can be made gentler, suppressing the occurrence of thermal damage and improving the performance of the optical disk. It becomes possible to erase optical information without deteriorating it.

FIG. 2A is a configuration diagram of an erasing beam according to another embodiment of the present invention, in which melt light 10° annealing light 1 is applied onto recording tracks 5 and 9.
1 is arranged to constitute an erasing section, and a thermal buffer section 12 is arranged in front of the melt light 1o to constitute an erasing light. Second
Figure B shows the intensity distribution of the erasing light in the disk rotation direction, and the solid lines 13.14°15 indicate the melt light 10.15°, respectively. This is the individual intensity distribution of the annealing light 11° and the thermal buffer section 12, and the dotted line 16 is the combined intensity distribution of the melt light, the annealing light, and the thermal buffer section. The erasing light is directed 1° in front of the melt light,
On the recording track 9 with the annealing light 11 at the rear,
The recording material film is heated and heated by the melt light 10, and immediately thereafter, the recording material is slowly cooled by the annealing light 11 and moved while being crystallized.

At this time, the thermal buffer section 12 simultaneously moves while making the temperature gradient caused by the melt light 10 gentle.

According to the above method, when the erasing process is completed and the erasing light disappears, the steep temperature gradient that occurs especially in front of the melt light can be made gentler, suppressing the occurrence of thermal damage and improving the performance of the optical disk. It becomes possible to erase optical information without deteriorating it.

In addition, since the thermal buffer section is formed relatively narrowly in front of the melt light, even if the power required for the thermal buffer section is small, it is possible to create a gentle temperature gradient from the high temperature section, and it is possible to create a gentle temperature gradient from the high temperature section to the erase section. The impact will be less.

Figure 3 shows a deflection prism 17 with a parallel part in the center and tapered parts at both ends, which splits the wavefront of a laser beam emitted from one light source into three parts, directs the light to the road side, and thermally buffers it onto the recording track. Spots are formed in the direction of rotation of the disk in order of the part 2o, the melt light 21, and the annealing light 22. With the above configuration, it is possible to provide a thermal buffer with one beam without increasing the number of light sources, and in addition to the above-mentioned effects, there are effects such as cost reduction and miniaturization.

Effects of the Invention The optical disk device of the present invention is composed of an erasing section that heats up and gradually cools the erasing light, and a thermal buffer section that softens the steep temperature gradient caused by the erasing section. This has great practical effects, such as softening the steep temperature gradient that occurs at the moment of erasing, eliminating thermal damage to the optical disk during erasing, and preventing performance deterioration of the optical disk.

[Brief explanation of the drawing]

FIG. 1 explains the operation of an optical disk device according to an embodiment of the present invention, in which A is a block diagram of an erasing light, B is a laser intensity distribution diagram, and FIG. 2 is a hard disk drive of an optical disk device according to a different embodiment of the present invention. 3 is a schematic diagram of an optical system of an optical disk device according to a different embodiment of the present invention, and FIG. 4 is a diagram illustrating a conventional recording operation. A is a beam shape diagram, B is a temperature change diagram on the recording film, and FIG. 5 is a diagram explaining the conventional erasing operation. 6 illustrates a different conventional erasing operation, in which A is a beam shape diagram, B is a laser intensity distribution diagram, and C is a temperature change diagram on the recording film. 1, 9...=-recording track, 2, 5, 10.13
...Melt light, 3.6, 11.14...
- Annealing light, 4,7.12.15...Thermal buffer section, 8.16...Erasing light intensity distribution. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 (A) tB> Distance Figure 4 (A> αtr (B'1 轡藺 - Figure 5 (A) Ff Figure 6

Claims (3)

[Claims] (1) An optical disc device characterized in that erasing is performed by irradiating the recording surface of an optical disc with an erasing beam consisting of an erasing section and a thermal buffer section whose beam power is lower than that of the erasing section. (2) The optical disc device according to claim 1, wherein the erasing beam is configured by an erasing section having two high and low beam power peaks and a thermal buffer section in front of the erasing section. (3) A deflection prism with a parallel part in the center and tapered parts on both sides of the parallel part is used to direct the laser beam emitted from one light source into the erasing part by the tapered part and the parallel part on one side, and into the erasing part by the tapered part and the parallel part on the other side. 3. The optical disc device according to claim 2, wherein the optical disc device is divided into a thermal buffering portion by a tapered portion, and the thermal buffering portion and the erasing portion are arranged in this order from the front to form an erasing beam.