JP2001043577A - Information recording medium initialization method and initialization apparatus - Google Patents

Abstract

(57) [Problem] In a conventional initial crystallization method for a rewritable phase-change optical recording medium, when the retention time of the crystallization temperature is to be increased, the power may be insufficient and the crystallization temperature may not be reached. There is a problem that a high quality recording / reproducing signal cannot be obtained. SOLUTION: A high-power semiconductor laser is used, the beam is divided into three, and the three beams are arranged so as to overlap on the recording film surface. As a result, the width of the beam spot in the short direction is widened, and the holding time of the crystallization temperature is lengthened even at the longitudinal end of the beam spot. As a result, initial crystallization of a high-quality information recording medium has become possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for initializing an information recording medium on which information can be recorded by a recording beam such as a laser beam.

[0002]

2. Description of the Related Art In a phase change type optical disk in which information is recorded by utilizing a phase change between a crystal and an amorphous phase, the crystallization takes about the same time as the laser irradiation time for recording by amorphization. When a recording film capable of high-speed erasing is used, the power of one energy beam is read out.
Level and read power level, two levels higher than
That is, by changing between a high power level and an intermediate power level, it is possible to perform so-called overwriting (rewriting by overwriting) in which new information is recorded while erasing existing information. Immediately after such a recording film is formed by a vacuum deposition method, a sputtering method or the like (as depo. State), at least a part thereof is in an amorphous state or in a metastable crystalline state. In such an as depo. State, the reflectance is usually low, and autofocusing and tracking tend to be unstable. Therefore, for example, a high-power laser beam having an output of 1 to 2 W is irradiated as an oval light spot so that the longitudinal direction thereof substantially coincides with the radial direction of the recording medium, and the recording film is heated to a temperature higher than the crystallization temperature and lower than the melting point. (Initial crystallization) in advance so that the temperature is within the above range. At this time, for example, in the invention by the present inventor (Japanese Patent Application No. 10-67955), in order to reduce the overlapping reflectance unevenness of the beam spot, the beam is divided into two and the two beam spots are divided on the recording film surface. The beam spots are arranged so as to at least partially overlap each other, and the width of the beam spot in the lateral direction is widened.

[0003]

In order to prevent the occurrence of defects due to damage to the information recording medium, a speed higher than the moving speed of the beam spot when the information recording medium is used in the optical disk apparatus (linear velocity in the case of a disk). It is desirable to perform initialization. However, in the crystallization from the as depo. State, since the atomic arrangement is largely disordered, the crystallization temperature holding time is five times as long as the crystallization temperature holding time when erasing a recording mark in an optical disc device. is there. In this case, irradiation may be performed with the beam spot in a defocused state, but it largely depends on the spread of the output beam from the high-power semiconductor laser and the autofocus state. Become. Therefore, in order to increase the crystallization temperature holding time by using the conventional technique, it was necessary to divide the beam spot into two in the rotation direction of the disk and to separate the distance between the two peaks. However, if the distance between the peaks is too large, the central portion between the peaks may have insufficient power and may not reach the crystallization temperature, and the initial crystallization under the optimum conditions may not be performed, and a high-quality recording / reproducing signal may be obtained. There was no problem.

An object of the present invention is to solve the above-mentioned problems in the prior art and to provide an apparatus for initializing an information recording medium for performing higher quality initial crystallization than in the prior art.

[0005]

In order to solve the above-mentioned problems in the prior art, in the initialization method of the present invention, a high-power semiconductor laser having a predetermined wavelength is used. The initialization is performed while the beam spot is moved in a direction substantially perpendicular to the recording track direction in this state. For example, when the linear velocity of the disk to be initialized is constant irrespective of location, initialization is performed by arranging the angle at which the longitudinal direction of the beam spot and the recording track direction intersect at approximately 90 degrees, thereby performing initialization.
Can be done in the shortest time. Furthermore, in the present invention, as a method for extending the holding time of the crystallization temperature, a beam spot having three intensity peaks in the short direction of the beam spot was used.
In this case, it is more effective to increase the peak power at which the power of the beam spot is applied to the recording medium earlier in time, because the temperature reaches a predetermined temperature, is maintained, and gradually decreases. At this time, the three intensity peaks can be obtained by using beams emitted from three separate lasers, dividing one beam into three beams and superimposing them, or changing the intensity distribution of one beam. May be formed. If the number of intensity peaks is reduced to three as described above, a crystallization temperature holding time that is five times longer than that of the optical disk device can be obtained even at the longitudinal end of the beam spot.

In a disk-shaped recording medium, when the rotation speed is constant, the larger the radius to be initialized is,
If the laser beam power is increased, the angle at which the longitudinal direction of the beam spot intersects the recording track direction is reduced, or both the power and the angle are changed, good initialization can be performed regardless of the radius. In some cases, it is also effective to reduce the feed pitch.

The initialization apparatus used in the present invention is equipped with a high-power semiconductor laser, means for converging a beam emitted from the laser near a recording film to form a beam spot, means for rotating a recording medium, At least means for moving the laser beam relative to the recording medium, and in addition to the above means, means for giving three light intensity peaks in the short direction of the beam spot. Furthermore, when three light intensity peaks are given in the short direction of the beam spot,
The recording medium may have a means for increasing the peak power irradiated before the recording medium in time, make it possible to change the intensity ratio of the peaks of the three light intensities, or set the peak intensity of each of the three light intensities. The distance between them may be made variable. Further, four or more light intensity peaks may be provided.

As the recording film used in the present invention, a crystal-amorphous phase-change optical recording film capable of high-speed crystallization, a recording film utilizing an amorphous-amorphous change, a crystal system and a crystal grain are used. Although a crystal-to-crystal phase change recording film such as a change in diameter is preferable, another recording film may be used. In particular, a recording film utilizing a phase change such as a Ge-Sb-Te recording film or an Ag-In-Sb-Te recording film may be used. Further, if a recording film in which a high melting point material such as Ag2Te having a higher melting point than the main component material is added to the recording film or a recording medium having two reflective layers is used, the thickness of the recording film due to the flow of the recording film is increased. It is preferable because the change can be suppressed.

When the recording film is to be initially crystallized, it is preferable to form each layer such as a recording film on a substrate and at least apply a protective coat of, for example, an ultraviolet curable resin, since the damage to the recording film is small. In particular, it is preferable to perform the process after the optical recording medium having the structure in which the protective layer of the ultraviolet curable resin is applied and the protective plate are closely adhered to each other by an adhesive such as an ultraviolet curable resin or a hot melt method. Alternatively, irradiation may be performed on both surfaces after the optical recording media are adhered to each other to form a double-sided recording medium.

The operation of initializing the recording film is performed simultaneously with the certification (defect inspection by reading) of the recording medium.
Alternatively, it may be performed before or after that. The above operation of initializing the recording film or raising the temperature to just below the melting point may be performed at the stage when the maker manufactures the recording medium (related to the manufacturing method). In addition, the present invention is applicable not only to disk-shaped recording media but also to other forms of recording media such as card-shaped recording media.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below using embodiments.

FIG. 1 is a structural sectional view of a rewritable optical disk having a guide groove used in this embodiment. First, a ZnS-SiO2 protective layer 2 having a thickness of about 100 nm was formed on a polycarbonate substrate 1 having a guide groove (track pitch: 1.48 μm, U-shaped groove) having a diameter of 120 mm and a thickness of 0.6 mm by magnetron sputtering. . Next, a recording film 3 having a composition of Ge2Sb2Te5 was formed to a thickness of about 20 nm. Next, ZnS-Si
The O2 intermediate layer 4 was formed to a thickness of about 18 nm. And
Further, the Al-Ti layer (first reflection layer) 5 is
A Ti layer (second reflective layer) 6 was formed to a thickness of about 50 nm. These films were formed sequentially in the same sputtering apparatus. Thereafter, an ultraviolet curable resin layer 7 was applied and cured thereon, and then adhered to another disk having the same structure with a two-liquid mixed room temperature curable adhesive 8.

A method of initializing the disk manufactured as described above will be described with reference to FIG. In this embodiment, a high-output semiconductor laser having a wavelength of 810 nm (maximum output 2 W) 10
The collimated lens 11 converts the beam emitted from the laser beam into collimated light, splits the beam into three beams by two prisms 13, and forms three beam spots 9 by the objective lens 12.
Get. First, the disk was rotated at a constant speed of 8 m / s (constant linear velocity) and controlled so that the recording film was focused, and the beam spot 9 was irradiated (irradiation power: 1700 mW). At this time, the length (half width of peak power) of the beam spot 9 is about 75 [μm]. Further, as shown in FIG. 3, the major axis direction of the beam spot 9 is substantially orthogonal (90 degrees) to the recording track 14 direction. Thus, the largest number of areas can be initialized in one rotation of the disk, so that the entire disk can be initialized in a short time. Here, the distance between the first and second peaks and the distance between the second and third peaks were set to about 3 μm. In this embodiment, as shown in FIG. 4, the power of the peak irradiated earlier in time is increased. This is preferable because the temperature of the recording film quickly rises and can be kept at the optimum temperature. next,
The relationship between the peak intensity number (in this case, the number of beam spots) and the state after initialization was examined.

Number of peak intensities Jitter (σ / TW) Number of peeling defects 1 peak 12% 20 beams / track 2 peaks 10% 5 beams / track 3 peaks 8% None From these results, three peak intensities of beam spot 9 were obtained. As a result of initialization, high-quality initialization could be performed over the entire surface of the disk without defects. 2 peaks, 3 peaks
The peak power of each peak was equal.

The height of the first irradiated peak intensity is H1, the height of the second irradiated peak intensity is H2, and the height of the third irradiated peak intensity is H3. The relationship between the peak intensity ratio and the state after the initialization was examined.

Peak intensity ratio Jitter (σ / TW) Number of peel defects (H1: H2: H3) 1: 2: 3 12% 10 / track 1: 1.5: 2 11% 3 / track 1: 1: 18% None 2: 1.8: 1.5 7% None 2: 1.5: 1 7% None 3: 2: 1 10% 2 tracks / track From these results, a particularly preferable range of the peak power ratio is as follows. , H1: H2 in the range of 2: 1.8 to 2: 1.5, H
2: H3 ranges from 1: 1 to 1.5: 1.

The relationship between the power ratio when the power at the longitudinal end of the beam spot is H4 and the power inside the beam spot is H5 using a 20-element laser array and the state after the initialization are shown. Examined.

[0018] From these results, a high-quality initialization state was obtained when the power ratio between the longitudinal end and the inside of the beam spot was in the range of 1.2: 1 to 1.1: 1.

Here, the beam spot 9 is arranged so that the major axis direction is substantially orthogonal (90 degrees) to the recording track 14 direction, but it is not necessarily required to be 90 degrees.

In this embodiment, a beam spot having three peak intensities is formed, but a beam spot having four or more peak intensities may be formed. Also in this case, it is more effective to increase the power of the peak at which the beam spot is irradiated on the recording medium earlier in time, since the optimum temperature can be quickly raised and maintained.

Also, in the present embodiment, the first and second,
Although the distance between the second and third peaks is set to about 3 μm, the distance may be varied within a range of three times or less the width of the beam spot in the short direction.

In a disk-shaped recording medium, when the rotation speed is constant, the larger the radius to be initialized is,
If the laser beam power is increased, the angle at which the longitudinal direction of the beam spot intersects the recording track direction is reduced, or both the power and the angle are changed, good initialization can be performed regardless of the radius. In some cases, it is also effective to reduce the feed pitch.

The initialization apparatus used in the present embodiment is equipped with a high-power semiconductor laser, means for converging a beam emitted from the laser near a recording film to form a beam spot, means for rotating a recording medium, It has at least means for moving the initialization beam relative to the recording medium, and in addition to the means, means for giving three light intensity peaks in the short direction of the beam spot. Furthermore, when three light intensity peaks are given in the short direction of the beam spot,
The recording medium may have means for increasing the peak power that is irradiated before the recording medium in time, make it possible to change the ratio of the peaks of the three light intensities, or change the ratio between the peaks of the three light intensities. The distance may be made variable. Further, four or more light intensity peaks may be provided.

[0024]

According to the present invention, the retention time of the crystallization temperature is lengthened by superimposing a plurality of peaks using a high-power semiconductor laser, so that a higher quality initial crystallization than before can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a disk structure.

FIG. 2 shows an embodiment of an initialization device.

FIG. 3 is an example of arrangement of an initialization beam.

FIG. 4 is a lateral spot intensity distribution according to an embodiment of the initialization apparatus.

FIG. 5 is a longitudinal spot intensity distribution according to an embodiment of the initialization apparatus.

[Explanation of symbols]

 1, 1 '... polycarbonate substrate 2, 2' ... ZnS-SiO2 dielectric layer 3, 3 '... recording film (Ge2Sb2Te5) 4, 4' ... ZnS-SiO2 dielectric layer 5, 5 '... Al -Ti (first reflection layer) 6, 6 '... Al-Ti (second reflection layer) 7, 7' ... UV-curable resin protective layer 8 ... hot melt adhesive layer 9 ... beam spot 10 ... semiconductor Laser 11: Collimating lens 12: Objective lens 13: Prism 14: Recording track.

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Motoyasu Terao 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Inventor Yasushi Yasushi 1-280 Higashi-Koikekubo, Kokubunji-shi, Tokyo Hitachi, Ltd. Within the Central Research Laboratory (72) Inventor Makoto Miyamoto 1-280 Higashi Koikekubo, Kokubunji City, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (72) Inventor Akemi Hirotane 1-280 Higashi Koikekubo, Kokubunji City, Tokyo Within the Central Research Laboratory, Hitachi, Ltd. (72) Inventor Eiji Sahoda 2880 Kozu, Odawara City, Kanagawa Prefecture Inside Hitachi Computer Equipment Co., Ltd. (72) Inventor Shin Matsumoto 2880 Kozu, Kokuzu, Odawara City, Kanagawa Prefecture Inside Hitachi Computer Equipment Co., Ltd. (72) Inventor Kazuhiro Soga Kanagawa 2880 Kozu, Odawara City, Prefecture Hitachi Computer Equipment Co., Ltd. (72) Inventor Yasumi Horiguchi 2880 Kozu, Odawara-shi, Kanagawa F-term within Hitachi Computer Equipment Co., Ltd. 5D090 CC11 FF36 HH01 KK03 KK12 KK14 5D119 AA23 BB04 DA01 DA08 EB04 EB14 FA02 FA08 HA36

Claims (7)

[Claims] 1. An initialization method for initially setting an optical recording medium on which information can be recorded by recording an energy beam into a recordable state, wherein a beam spot having a longitudinal direction and a lateral direction is formed. Are arranged so as to form an angle other than parallel to the recording track direction, and initialization is performed using a beam spot having three or more intensity peaks in the short direction of the beam spot. Information recording medium initialization method. 2. An information recording medium initialization method according to claim 1, wherein the beam spot irradiated first on the recording medium of the beam spot has the peak power of the other two beams. A method for initializing an information recording medium, wherein the method is higher than a peak power of a spot. 3. An initialization apparatus for initially setting an optical recording medium on which information can be recorded by irradiating an energy beam with a high-power semiconductor laser mounted thereon and recording a beam emitted from the laser. Means for condensing near the film to form a beam spot.
Initializing an information recording medium, comprising means for giving one or more light intensity peaks, means for rotating the recording medium, and means for moving the initialization beam relative to the recording medium. apparatus. 4. An apparatus for initializing an information recording medium according to claim 3, wherein 3 is set in the lateral direction of the beam spot.
Means for making the peak power of the beam spot irradiated first on the recording medium temporally higher than the peak powers of the other two beam spots when one light intensity peak is given. An information recording medium initialization device. 5. An apparatus for initializing an information recording medium according to claim 3, wherein 3 is set in the short direction of the beam spot.
An apparatus for initializing an information recording medium, comprising means for varying the ratio of the intensity of each peak when two light intensity peaks are provided. 6. An apparatus for initializing an information recording medium according to claim 3, wherein 3 is set in the short direction of the beam spot.
An apparatus for initializing an information recording medium, comprising: means for changing the distance between each peak when two light intensity peaks are given. 7. An apparatus for initializing an information recording medium according to claim 3, wherein a beam emitted from a high-power semiconductor laser is converted into collimated light by a collimating lens, and an objective lens is formed by using two prisms. An apparatus for initializing an information recording medium, comprising: means for obtaining three beam spots by means of: