JP3076083B2 - Optical disk initialization method and optical disk recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk for recording information using a reversible phase change by irradiating a laser beam, and more particularly to a method for recording information before using a prepared phase change optical disk. The present invention relates to an optical disk initialization method and an initialization device for initializing the state of a film, and a so-called one-beam overwrite recording method and a recording device for recording / erasing by changing a laser beam irradiation method.

[0002]

2. Description of the Related Art An optical disk recording system using a laser beam is capable of large-capacity recording and non-contact high-speed access.
Optical disks are classified into a read-only type known as a compact disk or a laser disk, a write-once type that can be recorded by the user himself, and a rewritable type that can be repeatedly recorded and erased by the user. Write-once / rewritable optical disks are about to be used as an external memory of a computer or as a document / image file.

[0003] As rewritable optical disks, there are a phase change optical disk using a phase change of a recording film and a magneto-optical disk using a change in the magnetization direction of a perpendicular magnetization film. this house,
Since phase change optical disks do not require an external magnetic field and can be easily overwritten, they are expected to become the mainstream of rewritable optical disks in the future.

Conventionally, a rewritable, so-called phase-change type optical disk using a recording film which causes a phase change between a crystal and an amorphous by irradiation with a laser beam has been known. A phase-change optical disk irradiates a high-power laser beam spot according to the information to be recorded on the recording film, and locally raises the recording film temperature to cause a phase change between the crystal and the amorphous. Recording is performed, and reproduction is performed by reading a change in the optical constant accompanying this as a reflected light intensity difference using a low power laser beam. For example, in the case of a phase change optical disk using a recording film having a relatively slow crystallization time, the disk is rotated, and the recording film formed on the disk is irradiated with laser light.
Raise the temperature of the recording film above the melting point, after the laser beam passes, quenched to make that part amorphous state,
Record. When erasing, keep the recording film temperature above the crystallization temperature,
The recording film is crystallized by keeping the recording film for a sufficient time to allow crystallization to proceed in the crystallization temperature range below the melting point. As a method for this, there is known a method of irradiating a long oval laser beam in a laser beam traveling direction. In the case of performing pseudo overwriting by two beams for recording new information while erasing already recorded data, the erasing elliptical laser light is arranged to be irradiated prior to the recording circular laser light. .

On the other hand, a disk using an information recording film capable of high-speed crystallization uses one laser beam condensed in a circular shape. A conventionally known method is to reduce the power of laser light by two.
By changing between two levels, crystallization or amorphization is performed. That is, by irradiating the recording film with a laser beam having a power capable of raising the temperature of the recording film to a temperature equal to or higher than the melting point, most of the recording film becomes amorphous when cooled, while the recording film temperature is crystallized. Above temperature,
The portion irradiated with the power laser beam that reaches a temperature equal to or lower than the melting point becomes a crystalline state.

[0006]

When a phase-change disk is used, it is necessary to initialize a recording film prior to recording / erasing. The recording film of the phase-change optical disk is made of a chalcogenide-based material such as GeSbTe-based or InSbT-based material.
e system, InSe system, InTe system, AsTeGe system, Te
Ox-GeSn system, TeSeSn system, SbSeBi system,
A BiSeGe system or the like is used, and all are formed by a film forming method such as a resistance heating vacuum evaporation method, an electron beam vacuum evaporation method, and a sputtering method. The state of the recording film immediately after film formation is a kind of amorphous state, and in order to perform recording on this recording film and form an amorphous recording portion, an initialization process for making the entire recording film crystalline. is necessary.

Conventionally, as a means for this initialization processing, a laser beam condensed to a diameter of 1 to 2 μm is recorded on an optical disk by using an optical head while rotating the disk using an ordinary optical disk device. The method of irradiating upward is adopted. However, in the case of initialization using such a normal optical head, there is a disadvantage that the pre-group portion of the disc cannot be initialized uniformly because the intensity distribution of the irradiation laser beam is a Gaussian distribution and the intensity distribution is not uniform. Was. That is, reflecting the intensity distribution of the irradiation laser light, the vicinity of the center of the irradiation of the laser light is heated to a temperature higher than the crystallization temperature and crystallized, but the surrounding area is not changed due to insufficient heating. There was a problem that it would be.

Further, as another optical disk initialization method,
A method of irradiating an optical disc with a high-power laser beam having a beam diameter of several tens of microns or more has also been proposed, but in this case, the beam diameter is large, so that it is quite difficult to raise the temperature of the recording film above the crystallization temperature. High power is required. Therefore, the light source that can be used here is a high-output gas laser or a high-output solid-state laser, and there is a disadvantage that a peripheral device is newly required and the initialization device itself becomes large.

In such an initialization method, the temperature is raised to a temperature higher than the crystallization temperature in order to crystallize the information recording film.
The recording film is not melted. For this reason, the formed initialized portion and the melt-crystallized portion (rim) formed around the recording point at the time of recording have different crystal states such as grain size, and a difference occurs in the reflectance between the two. There is a drawback, which causes a change in recording / erasing characteristics at the beginning of overwriting.

In a disk using an information recording film capable of high-speed crystallization, after initialization is completed, as described above, overwriting by one-beam overwriting using a single laser beam condensed in a circle, that is, The information is rewritten. Conventionally, crystallization or amorphization is performed by changing the power of laser light between two levels. The recording point is an amorphous region formed with high power, and the erasing point is a crystalline region formed with low power.However, recording and erasing are performed only by changing the power level of one laser beam. The temperature distribution of the recording film is not uniform due to the use of the condensed laser light. Therefore, there is a defect that the formation of the crystal region is not uniform particularly at the time of erasing, and an incomplete crystallization region is generated on both sides of the group portion. This results in unerased data when overwriting is performed, resulting in a reduced erasing rate and increased errors. Also, as in the initialization, the crystal state such as the grain size differs between the erased portion and the melt-crystallized portion (rim) formed around the recording point at the time of recording, resulting in a difference in the reflectance between the two. There was a drawback, and it was a cause that a sufficient erasing rate could not be obtained.

An object of the present invention is to solve the above-mentioned drawbacks and to perform a good initialization process of a phase change optical disk with a small device configuration by a simple method utilizing circuit technology adopted in a conventional optical disk device. An object of the present invention is to provide an optical disk initialization method and an initialization device, and further provide a novel recording method and a recording device which can improve an erasing rate and reduce errors when recording information by overwriting.

[0012]

[0013]

[0014]

The present invention uses a reversible phase change, records information by changing the phase state of an information recording film by laser light irradiation, and changes the recording method by changing the laser light irradiation method. A recording method for an overwrite phase-change optical disc for performing erasing, wherein a continuous pulse laser beam is applied during initialization to either a concave portion or a convex portion of the optical disc pre-groove portion including a concave portion and a convex portion.
By melting the information recording film and cooling
By continuously forming a molten recrystallized region formed in the above, by irradiating a laser beam of constant intensity at the time of the recording to form an amorphous region, at the time of the erasing, by irradiating a continuous pulsed laser beam The information recording film is melted, and a melt recrystallization region formed at the time of cooling is continuously formed. .

The present invention uses a reversible phase change and a laser
Information is recorded by the phase change of the information recording film due to light irradiation.
Record and erase by changing the laser beam irradiation method
Recording device for overwrite phase change optical disk
An optical head, and incorporated in the optical head
A semiconductor laser drive circuit for driving a semiconductor laser,
A collection for driving a condenser lens incorporated in the optical head
Optical lens servo circuit and optical disk rotation motor
Driving the optical head in the radial direction of the optical disc.
Optical head positioner and disk linear velocity control circuit,
Recording that generates a timing signal in response to a recording erase signal
A semiconductor laser having a signal control circuit and a reproduction amplifier;
The drive circuit includes a laser power control circuit and a pulse drive circuit.
Circuit and a pulse transmission circuit are provided, and the laser power control circuit is provided.
The path is where the recording timing signal from the recording signal control circuit is
When supplied, the phase change optical disc has a constant strength.
Irradiation of laser light to form an amorphous region
The erase drive circuit is configured to erase from the recording signal control circuit.
A phase change type optical disk when a
To a continuous pulsed laser beam.
Melting the recording film on the phase-change optical disc,
Continuous formation of the molten recrystallized region formed during cooling
Characterized in that that.

[0016]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an optical disk initialization method according to the present invention. In the figure, a condensed laser beam 2 for initializing a disc is irradiated to either a pre-group protrusion 11 or a recess 12 of the disc 1. The condensed laser beam 2 is usually radiated with a diameter of 1 to 2 μm.
Further, the width of the pre-group convex portion 11 or concave portion 12 is 0.3 to 1.3 μm, and is formed on a spiral in the disk circumferential direction. For recording information, the wider one of the pre-groups is often used. For example, when the pre-group convex portion 11 having a width of 1.3 μm is used, even if an attempt is made to initialize the region with the condensed laser light 2 having a diameter of 1 to 2 μm, since the intensity distribution of the laser light is a Gaussian type, the convex portion is projected. It is difficult to make the entire part 11 into a uniform crystalline state. There is also a method in which the irradiation laser beam is initialized while being sent at a submicron level in the radial direction of the disk. However, as described above, the crystal grain size of the initialized portion formed below the melting point and above the crystallization temperature is molten. Since the crystal grain size is different from the crystal grain size formed at the time of crystallization, a difference occurs in the reflectance between the two, which causes a change in recording / erasing characteristics at the beginning of overwriting. In the present invention, the disk is irradiated with the laser beam 2 in the form of a continuous pulse. At this time, the power level of the laser beam 2 is
It is set so that the recording layer 63 of the disc is melted with the same width as the pre-group protrusion 11. In one pulse irradiation, a circular molten amorphous portion 21 and a molten recrystallization ring 22 are formed around the circular amorphous portion 21 as shown in FIG. 2A. 23 is an unchanged portion before laser irradiation.
The next laser light irradiation is executed when the center of the laser light beam moves by a distance corresponding to the width of the melt recrystallization ring 22. Thus, a molten amorphous portion 21 and a molten recrystallized portion 22 shown in FIG. 2B are formed. At this timing, by continuously irradiating a laser beam in a pulse shape as shown in FIG. 2C, a continuous melt-recrystallized portion can be formed as shown in FIG. 2D.

In the optical disk recording method according to the present invention, a method based on the same principle as that of FIG. In the present invention, a continuous pulse laser beam similar to that shown in FIG. At this time, the power level of the laser beam 2 is such that the recording layer 63 of the disc is
It is set to melt at a width equivalent to 1. In one pulse irradiation, a circular molten amorphous portion 21 and a molten recrystallization ring 22 are formed around the circular amorphous portion 21 as shown in FIG. 2A. The next laser light irradiation is executed when the center of the laser light beam moves by a distance corresponding to the width of the melt recrystallization ring 22. By doing this, FIG.
The molten amorphous portion 21 and the molten recrystallized portion 2 shown in FIG.
2 are formed. At this timing, by continuously irradiating a pulsed laser beam as shown in FIG. 2 (c), a continuous molten recrystallization portion, ie, an erased portion is formed as shown in FIG. 2 (d). Can be.

FIG. 3 is a diagram showing an information sequence to be recorded, a laser driving pulse at the time of recording, and a bit shape formed on the recording film. Here, the information sequence of FIG. 3A is recorded by NRZI modulation. FIG. 3B shows an NRZI modulated signal. Since the “1” level of the NRZI modulation signal corresponds to the recording bit and the “0” level corresponds to the erased portion, the laser driving pulse is generated by using the recording method of the present invention in FIG.
It will be modulated in the form of (c). That is, "1"
At the level, high-power laser light is irradiated at a constant value so that a molten amorphous portion can be formed. On the other hand, when the level is "0", continuous pulsed laser light is applied to form a molten recrystallized portion. FIG. 3D schematically shows the bit shape formed at this time. A molten amorphous portion 21 is formed in the recording region, and a molten recrystallized portion 22 is formed in the erased region.

FIG. 4 is a diagram showing the configuration of an initialization device according to the present invention. This optical disk initialization apparatus includes an optical head 41, a semiconductor laser drive circuit 42, an optical head condenser lens driving servo circuit 43, an optical disk rotation motor 44, an optical head positioner 45, and a disk linear velocity control circuit 46. 2 also shows the optical disc 1. The semiconductor laser drive circuit 42 includes a laser power control circuit 421, a pulse drive circuit 422, and a pulse oscillation circuit 423. The sensitivity of the optical disk 1 to be initialized and the disk linear velocity control circuit 46
The irradiation power and pulse width for melting the recording film are set according to the linear velocity at the time of laser irradiation set by
Further, the pulse interval is determined so that a melt-recrystallized portion can be continuously formed.

FIG. 5 is a diagram showing a configuration of an optical disk recording apparatus according to the present invention. This optical disk recording apparatus comprises an optical head 41, a semiconductor laser drive circuit 42,
An optical head condenser lens driving servo circuit 43, an optical disk rotation motor 44, an optical head positioner 45, a disk linear velocity control circuit 46, a recording signal control circuit 48, and a reproduction amplifier 49 are shown in FIG. It is shown. The semiconductor laser drive circuit 42 includes a laser power control circuit 421, a pulse drive circuit 422, and a pulse oscillation circuit 423. The recording signal 47 enters the recording signal control circuit 48. Semiconductor laser drive circuit 4
2, a recording timing signal 481 and an erasing timing control signal 482 are sent from the recording signal control circuit 48 according to the timing of the recording signal 47. Timing signal 481
In response to the above, a constant recording current necessary for forming a molten amorphous recording bit is supplied from the drive circuit 42 to the semiconductor laser. Further, in response to the timing signal 482, the drive circuit 42 supplies a continuous pulse current necessary for forming a continuous melt-recrystallization portion to the semiconductor laser. At the time of recording signal reproduction, a low power, constant intensity laser beam is irradiated so as not to cause a change in the recording film, and a reproduction amplifier 49 amplifies and demodulates a light amount change from the disc received by the signal detector of the optical head and reproduces. A signal 491 is obtained.

As shown in FIG. 6, a phase-change type optical disk to be subjected to an initialization process has a first dielectric layer 62, a recording layer 63, and a second dielectric layer 62 on a disk-shaped substrate 61 made of glass or plastic. A first dielectric layer 62, a recording layer 63, and a second dielectric layer 64 are sequentially formed on a substrate 61 formed of a dielectric layer 64 and a metal reflective layer 65 in order, or a disk-shaped substrate 61 made of glass or plastic. It is a formed configuration. Here, the first dielectric layer 62 and the second dielectric layer 6
4 includes SiO ₂ , Si ₃ N ₄ , AlN, TiO ₂ , SiO
Materials such as are used. As the recording layer 63, a chalcogenide-based material such as GeSbTe-based, InSbTe-based,
InSe-based, InTe-based, AsTeGe-based, TeOx-
GeSn system, TeSeSn system, SbSeBi system, BiS
An eGe type or the like is used. Al,
Metals such as Au, Cu, Ag, and Ti are used.

Next, the operation of the optical disk initialization method of the present invention was confirmed using a single phase-change optical disk (130 mm in diameter) with a GeSbTe recording film formed on a polycarbonate substrate with a pre-group by sputtering. The optical disk used here was made of Si ₃ as a dielectric layer.
N ₄ and Al are used as the metal reflection layer. Pre-groups are formed in advance on the substrate at a 1.6 μm pitch. Here, the pre-group protrusions (lands) having a width of 1.0 μm were initialized. This disk was mounted on an initialization device having the configuration shown in FIG. 4, and initialization was attempted while rotating the disk at a constant linear speed of 11.3 m / s. Wavelength 8 for laser light source of optical head
A semiconductor laser having an output of 30 nm and an output of 40 mW was used. The laser spot diameter on the disk surface was about 1.5 μm.
Initialization was performed by setting the laser power on the disk surface to 20 mW and irradiating continuous pulses under the conditions of a frequency of 38 MHz and a pulse width of 15 ns. This processing increased the amount of reflected light. When the initialization track was observed using a transmission electron microscope, it was confirmed that a molten recrystallization region was uniformly formed over the entire 1.0 μm land portion. In the repeated overwriting after the initialization, the reproduction signal C / N and the erasure rate did not change, and a good reproduction signal C / N and the erasure rate were obtained.

Subsequently, in order to confirm the operation of the recording method of the present invention, the same disk as the disk used for confirming the above-mentioned initialization method, that is, GeSbT formed on a polycarbonate substrate with a pre-group by sputtering is used.
Single-layer phase-change optical disk with e-recording film (130 m diameter
m) was used for overwriting recording. Pre-groups are formed on the substrate at a pitch of 1.6 μm in advance. Here, the pre-group protrusions (lands) having a width of 1.0 μm are recorded after being initialized by the initialization method according to the present invention. . This disk was mounted on a drive device having the configuration shown in FIG. 5, and recording was attempted while rotating the disk at a constant linear speed of 11.3 m / s. A semiconductor laser having a wavelength of 830 nm and an output of 40 mW was used as a laser light source of the optical head. The laser beam spot diameter on the disk surface was about 1.5 μm. The recording power is 15 mW, the erasing condition is a pulse drive of 20 mW peak power, a frequency of 38 MHz, and a pulse width of 15 ns.
When the signal of Hz was overwritten, a C / N of 48 dB or more and an erasing rate of 40 dB or more were obtained. This method has been subjected to repeated overwriting up to 10 ⁵ times, variations in the initial recording and erasing characteristics are not, also 10
^No deterioration of the characteristics was observed up to ⁵ times. Further, when this recording track was observed using a transmission electron microscope, it was found that in the erased region, the entire land portion having a width of 1.0 μm was melt-crystallized uniformly, and a good amorphous bit was formed in the recorded region. It was confirmed that.

[0025]

As described above, according to the present invention, since the melting and recrystallization region is used as the initialization portion, good and uniform initialization can be performed, and the recording and erasing characteristics do not change after the initialization. There is an advantage that can be. Also, at the time of overwrite recording, since the erased portion is a melt-recrystallized portion, it has the same crystal structure as the melt-recrystallized portion (rim) formed around the recording bit, and the erasing rate can be improved. In the apparatus to which the initialization method and the recording method according to the present invention are applied, the existing optical head technology can be used, and a desired function can be obtained with a small addition of a circuit.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of an optical disk initialization method and a recording method according to the present invention.

FIG. 2 is a diagram showing the principle of initialization and erasure during overwriting of an optical disc according to the present invention.

FIG. 3 is a diagram showing a data recording method of the present invention.

FIG. 4 is a diagram showing a configuration of an optical disk initialization device according to the present invention.

FIG. 5 is a diagram showing a configuration of an optical disk recording device according to the present invention.

FIG. 6 is a cross-sectional view showing a configuration of a phase change optical disc.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical disk 2 Condensed laser beam 11 Pregroup convex part 12 Pregroup concave part 21 Melted amorphous part 22 Melted recrystallization part 23 Unchanged part 41 Optical head 42 Semiconductor laser drive circuit 421 Laser power control circuit 422 Pulse drive circuit 423 pulse Oscillation circuit 43 Optical head condenser lens driving servo circuit 44 Optical disk rotation motor 45 Optical head positioner 46 Disk linear velocity control circuit 47 Recording signal 48 Recording signal control circuit 481 Recording timing signal 482 Erase timing signal 49 Reproduction amplifier 491 Reproduction signal 61 Substrate 62 First dielectric layer 63 Recording layer 64 Second dielectric layer 65 Metal reflective layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 00-7/135

Claims (2)

(57) [Claims] 1. An overwrite phase change type in which information is recorded by a phase change of an information recording film by laser light irradiation using a reversible phase change, and recording and erasing are performed by changing the laser light irradiation method. A method for recording an optical disc, comprising: irradiating a continuous pulse laser beam during initialization to either the concave or convex portion of the optical disc pre-groove portion having a concave portion and a convex portion, thereby melting the information recording film. To continuously form a molten recrystallized region formed at the time of cooling, irradiate a laser beam of a constant intensity during the recording to form an amorphous region, and irradiate a continuous pulsed laser beam at the time of erasing. An optical disk recording method, wherein the information recording film is melted to continuously form a molten recrystallized region formed during cooling. 2. An overwrite phase change type in which information is recorded by a phase change of an information recording film by laser light irradiation using a reversible phase change, and recording and erasing are performed by changing the laser light irradiation method. An optical disk recording apparatus, comprising: an optical head; a semiconductor laser drive circuit that drives a semiconductor laser incorporated in the optical head; and a condenser lens servo circuit that drives a condenser lens incorporated in the optical head. An optical disk rotation motor, an optical head positioner for driving the optical head in a radial direction of the optical disk, a disk linear velocity control circuit, a recording signal control circuit for generating a timing signal corresponding to a recording / erasing signal, and a reproduction amplifier. The semiconductor laser drive circuit includes a laser power control circuit, a pulse drive circuit, and a pulse transmission circuit. The laser power control circuit, from the recording signal control circuit
When a recording timing signal is supplied, the phase change type
Irradiate the optical disk with laser light of a certain intensity to form an amorphous region
And the pulse drive circuit erases from the recording signal control circuit.
When a timing signal is supplied, the phase change optical data
Irradiating the disk with continuous pulsed laser light
Therefore, the recording film is melted on the phase-change optical disk.
And continuously form the molten recrystallized region formed during cooling.
Optical disc recording apparatus which is characterized in that formed.