JPS6310337A - Optical information recording and erasing device - Google Patents

Abstract

PURPOSE:To surely erase information with a low power and less thermal damage without leaving information unerased by continuously projecting a first elliptic erasing light spot, whose lengthwise direction is approximately orthogonal to a recording track, and a second elliptic erasing light spot, whose lengthwise direction coincides with the direction of the recording track, in order. CONSTITUTION:The first elliptic erasing light spot a1 is so arranged that its lengthwise direction is orthogonal to a recording track 1, and the second elliptic erasing light spot a2 is so arranged that its lengthwise direction is on the same line as the recording track 1. When two erasing light spots a1 and a2 are projected to the same track and a disc is rotated, the temperature of an irradiated part quickly rises by the first erasing light spot a1 to melt the irradiated part and this part is cooled and solidified, but cooling is retarded by the second erasing light spot a2 and the irradiated part is kept at a temperature higher than the crystallization temperature for a long time, and therefore, the amorphous part is set to the crystalline state to complete erasing. Thus, information is erased with a low power and less thermal damage without being left unerased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus for erasing the information recording portion of an optical disc using a photosensitive recording material whose optical properties are reversibly changed by irradiation with a laser beam. It is.

2. Correction of conventional technical information: As a rewritable optical disc, a photosensitive material is formed in the form of a thin film on a disc substrate made of polymeric resin such as acrylic, and this optical disc is irradiated with a laser. Generally used are devices in which recording and erasing are performed by heating the recording medium and changing its optical properties, that is, 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 made by adding germanium, antimony, etc. to tellurium 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, the recording track 1 is irradiated with three pages of well-focused circular laser light with a high power density of about 1 μm in half-width, as shown by light b1 in FIG. As shown in the temperature change diagram of FIG. 6(A), it is necessary to melt the recording material and rapidly cool it. On the other hand, when erasing, perhaps slow cooling is necessary for crystallization, and elongated light with a relatively long light spot length, such as light b2 in Fig. 4, for example, about 20 μm in half width, is irradiated. Conventionally, it has been common practice to slowly cool and crystallize as shown in the temperature change diagram of FIG. 6(B).

In this way, the crystalline state that is generated is caused by the generation of crystal nuclei in the solid state, and the optical constants differ slightly from those of the crystal in the unrecorded area, leaving behind the recording signal and erasing it. In order to avoid this problem, as shown in Fig. 6, a circular light beam with a relatively high power density (hereinafter referred to as melt light) is inserted before the oblong erase beam C2, as shown in Fig. 6. ) C1 to uniformly melt the information recording part 2 and unrecorded part 3 on the recording trunk 1, and then slowly cooling it with the elliptical light (hereinafter referred to as annealing light) C2 to ensure erasing. There is (Japanese Unexamined Patent Publication No. 60-23192
Publication No. 8).

Figure 7 (5) shows the laser intensity distribution of the circular melt light C1 used for erasing in the direction perpendicular to the recording track, and Figure 7 (B) shows the temperature distribution of the recording material thin film. This is what is shown. The melting light has a laser power of 16 to 20 mW, in order to melt the information recording part with a width almost equal to the trunk width.
The corresponding half-width is required to be 2 to 3 μm, and if the power is small, for example, about 10 mW, the recording track width cannot be reliably melted, and on the contrary, the half-width is too small.
In order to melt more than the width of the recording track, a large laser power is required as described above. at the same time,
When a laser beam with such a shape is used, the temperature at the center of the recording track, which indicates the highest temperature in the recording material film, is raised to a temperature considerably higher than the melting temperature (Tm), which may result in thermal damage to the optical disk. Occasionally, this may occur.

Problems to be Solved by the Invention The present invention solves the above-mentioned problems caused by conventionally used melt light for erasing, namely: (1) the required laser power becomes large; (2) the recording track portion is heated more than necessary, and the optical disk This solves the problem of lowering the heat resistance of the eraser, and provides an erasing device that reliably melts recording tracks with a small amount of power, leaves no erased residue, and causes little thermal damage.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides an elliptical first track arranged so that its longitudinal direction is substantially orthogonal to the recording track.
The information recording section is erased by successively irradiating the recording track with a second erasing light having an oval shape whose longitudinal direction is in the same direction as the recording track.

The elliptical first erasing light whose longitudinal direction is approximately perpendicular to the recording track illuminates the recording track width with approximately uniform intensity, and the laser intensity does not spread in the recording track direction. With smaller power and suppressing excessive temperature rise of the recording film, the recording track portion is almost uniformly raised to the melting temperature and melted by 6B, and the laser intensity spread in the track direction of the second oval erasing light. Alternatively, by slowly cooling the heated recording film, reliable erasure can be performed by melting and slow cooling.

EXAMPLE Hereinafter, an example of the present invention will be described in detail with reference to the drawings. The recording medium may be one whose optical constants change before and after recording, as described above, such as a chalcogen compound, which is made into an amorphous state with low reflectivity by heating and rapidly cooling, and which produces a crystalline state with high reflectance by heating and slowly cooling, or Metal oxides using tellurium, germanium, antimony, etc. are used. The crystal-amorphous phase transformation of these recording media differs slightly depending on the composition of the material, but is not directly related to the method of the present invention and does not affect the present invention. Furthermore, although the recorded state is defined as amorphous and the erased state as crystalline, the reverse is of course possible, and in the present invention, for convenience, the recorded state is defined as amorphous and the erased state as crystalline.

First, information is recorded by irradiating a narrowed beam of circular light with high power density onto a 7B unrecorded optical disk that has been rendered into a highly reflective crystalline state through heat treatment.

For example, in the case of an optical disc rotating at 1000 rpm, the light intensity is around 10 mW, and the half width is 1
When circular light of a little less than μm is irradiated onto the trunk of a disk with a radius of 10 crn, the recording material film is rapidly heated due to the well-focused light, and in a short time of about 100 nSeC.
As the laser beam passes through it, it is rapidly cooled, and a width equivalent to the width of the recording track (generally about 7000 A) becomes amorphous, thereby creating an information recording section (bit).

FIG. 1 shows the arrangement and shape of the erasing light on the optical disk according to the present invention.
1 and a second erasing light a2 whose longitudinal direction is arranged on the same line as the recording track 1. Figure 2 (8) shows the above 2
This is the change in light intensity at one point on the track when two erasing beams a1 and a2 are irradiated onto the same track and the disk is rotated. It is something. The temperature of the irradiated part rises rapidly due to the first erasing light a1, reaches the melting point Tm, melts, and then cools and solidifies; however, due to the second erasing light a2,
It is gradually cooled and held at a temperature higher than the crystallization temperature Ta for a sufficiently long time to be crystallized.

When the recording trunk was observed by X-ray diffraction, the first erasure light a
1, when the track is heated and cooled, the area near the center of the track is in an amorphous state, similar to the recording state, but the cooling is suppressed by the second erasing light that passes through the track, and the crystallization occurs before it reaches the vitrification temperature Tq. Since the amorphous portion is kept at a temperature higher than the oxidizing temperature for a long time, the amorphous portion becomes a crystalline state, and erasing is completed. Both the information recording area (amorphous state) and the non-information recording area (crystalline state) on the recording track are melted by the first erasing light and become a liquid state, so they are sufficiently diffused and a change in composition occurs between them. etc., there is no distinction between the two.

FIG. 3 (the ladle shows the light intensity distribution of the first erasing light in the direction perpendicular to the recording track 1 (track width direction), and FIG. 3 (6) shows the light intensity distribution of the first erasing light 9 The maximum temperature reached by the recording material when heated by the paper is also shown in the track width direction.

The results shown in FIGS. 2 and 3 show that the recording member was Te6oG.
An optical disk made of e1゜5n16Au16 was rotated, the linear velocity was 10 m/sec, the power of the first erasing light was 10 mW, and the half-width was 3 in the direction orthogonal to the recording track.
μm, which was obtained when elliptical light with a diameter of 1 μm in the track direction was irradiated. As shown in Figure 3 (B),
The maximum temperature of the recording material remains at a relatively small temperature difference with respect to the tart temperature, and the melting area is sufficiently wider than the width of the information recording section, that is, the track width, so that it melts reliably and does not remain unerased. There was no melting residue that would cause this.

The shorter the half-width of the first erasing light in the recording track direction, the smaller the optical power will be. The half width in the direction perpendicular to the track is 1.6 to 4.
μm, and the optical power of the first erasing light was in the range of 7 to 16 rIM, melting the recording track 10" width and effectively exerting the above function. As the second erasing light, for slow cooling, It is desirable that the long axis is an elliptical beam in the direction of the recording trunk.To explain in detail, an amorphous portion having a width of approximately % to 1 times the track width generated by the first erasing beam is heated to a crystallization temperature for a long time. In order to hold and crystallize, the half-width of the short axis is about 1 μm, and the half-width of the long sleeve is 1 μm.
If the distance between the centers of the first erasing light and the second erasing light is about 2 to 16 μm, the power of the second erasing light is a weak power of 6 to 10 mW. was also successfully crystallized.

Effects of the Invention As shown above, in the erasing method according to the present invention, the first erasing light is made wide in the direction orthogonal to the recording track, and narrow in the track direction, so that the erasing method reliably erases the recording track. Since the width is melted and then slowly cooled and crystallized by the second erasing light that is continuously irradiated, erasing can be achieved with low power, without leaving any unerased material, and with little heat loss.

[Brief explanation of the drawing]

11 Vane FIG. 1 is an explanatory diagram showing the shape and arrangement of the erasing light according to an embodiment of the present invention, and FIG. 3(c) is a light intensity distribution diagram of the first erasing light, (b) is a temperature distribution diagram, and FIG. 4 is a shape diagram of the conventional recording light erasing light. Fig. 6 (5) is a temperature change characteristic diagram during recording, (B) is a temperature change characteristic diagram during erasing, and Fig. 6 shows the shape of erasing light in another conventional example.
An explanatory diagram of the arrangement, FIG. 7(8) is a light intensity distribution diagram of the first erasing light of the conventional example, and FIG. 7(B) is a temperature distribution diagram. 1... Recording track, 2... Information recording section, 3... Information unrecorded section. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Time Opening Time Opening 3 Figure 4 Figure 5 Time Time Figure 6

Claims (1)

[Claims] In an optical disk whose recording material is a substance whose optical properties change depending on the state of light irradiation, the information recording section is created by increasing the light irradiation power and heating and rapidly cooling the information recording section, which is an ellipse arranged so that the longitudinal direction is perpendicular to the recording track. The information recording section is irradiated with a first light beam and heated to melt the information recording section, and then a second elliptical light beam whose longitudinal direction is arranged in the same direction as the recording track is irradiated to gradually remove the information from the melted state. An optical information recording/erasing device characterized by erasing information by cooling it.