JPH04366424A - Method for initializing optical disk - Google Patents

Abstract

PURPOSE:To achieve an improved and uniform initialization by forming a crystal particle with a same particle diameter as that at an annular crystal portion around a recording bit which is formed at the time of recording at an entire phase-change type optical disk. CONSTITUTION:A focusing laser beam 2 is sent in radius direction in synchronization with rotation of a disk and is emitted to a disk. At this time, a power level of the laser beam 2 is set so that a recording layer of the disk is melted. A molten crystallization region 22 is formed at one portion of a pregroove in a state where the disk is turned in one revolution. By feeding the laser beam in radius direction in synchronization with the revolution and forming the molten crystallization region 22 continuously in concentrical shape or spiral shape, a molten crystallization region 22 is formed uniformly at a projecting portion 11 of the pregroove portion and a recessed portion 12 and a crystal with a same particle diameter as that around a recording point can be formed over an entire optical disk.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an optical disc that records information using a reversible phase change caused by laser beam irradiation. The present invention relates to an optical disc initialization method for initializing the state of a film.

0002

2. Description of the Related Art Optical disk recording systems using laser light are capable of large-capacity recording and non-contact high-speed access, and are now being put to practical use as large-capacity memories. Optical discs are classified into read-only types known as compact discs and laser discs, write-once types that allow users to record on their own, and rewritable types that allow users to repeatedly record and erase information. Write-once and rewritable optical discs are being used as external memory for computers and for document and image files.

[0003] Rewritable optical disks include phase-change optical disks that utilize phase changes in a recording film and magneto-optical disks that utilize changes in the magnetization direction of a perpendicularly magnetized 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.

So-called phase-change optical disks, which are rewritable and use a recording film that undergoes a phase change between crystal and amorphous upon irradiation with laser light, have been known. In phase-change optical discs, a high-power laser beam spot is irradiated on the recording film according to the information to be recorded, and the temperature of the recording film is locally raised to cause a phase change between crystal and amorphous. Reproduction is performed by recording and reading the accompanying change in optical constants as a difference in reflected light intensity using a low-power laser beam. For example, a phase-change optical disk using a recording film with a relatively slow crystallization time rotates the disk and irradiates the recording film formed on the disk with laser light to raise the temperature of the recording film above its melting point. After the light passes through
The area is made amorphous by rapid cooling and recorded. During erasing, the temperature of the recording film is maintained within the crystallization temperature range of not less than the crystallization temperature and not more than the melting point for a sufficient period of time to allow crystallization to proceed, thereby crystallizing the recording film. As a method for this purpose, a method of irradiating a long oval laser beam in the direction in which the laser beam travels is known. When performing a pseudo overwrite using two beams that records new information while erasing already recorded data, the elliptical laser beam for erasing is irradiated in advance of the circular laser beam for recording. .

On the other hand, a disk using an information recording film capable of high-speed crystallization uses a single laser beam focused in a circular shape. The conventionally known method is to reduce the power of laser light by 2
Crystallization or amorphization is achieved by changing between two levels. In other words, by irradiating the recording film with a laser beam of power capable of raising the temperature of the recording film above its melting point, most parts of the recording film become amorphous when cooled, while the temperature of the recording film becomes crystallized. The part that is irradiated with a laser beam with a power that reaches a temperature above the melting point and below the melting point becomes a crystalline state.

[0006]

When using a phase change optical disk, it is necessary to initialize the recording film prior to erasing information. The recording film of a phase change optical disc has
Chalcogenide materials such as GeSbTe and InSb
Te series, InSe series, InTe series, AsTeGe series, T
eOx-GeSn-based, TeSeSn-based, SbSeBi-based, BiSeGe-based, etc. are used, and all of them are formed by film forming methods such as resistance heating vacuum evaporation, electron beam vacuum evaporation, and sputtering. The state of the recording film immediately after film formation is a kind of amorphous state, and in order to form an amorphous recording part in this recording film, an initialization process is required to make the entire recording film crystalline. .

Conventionally, this initialization process has been carried out using an optical head while rotating the disk.
A method has been adopted in which a pregroove portion of an optical disc is irradiated with a laser beam focused to a diameter of 2 (μm). However, in this case, the intensity distribution of the irradiated laser beam is a Gaussian distribution and is not uniform, so there is a drawback that the pregroove portion of the disk cannot be uniformly initialized. In other words, reflecting the intensity distribution of the irradiated laser beam, the temperature near the center of laser beam irradiation is raised above the crystallization temperature and crystallized, but the surrounding area remains unchanged because the temperature is insufficiently raised. There was a problem with this.

[0008] Also, as another optical disc initialization method,
A method has also been proposed in which an optical disc is irradiated with a high-power laser beam with a beam diameter of several tens of microns or more, but in this case, because the beam diameter is large, it takes a considerable amount of time to heat 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, which has the disadvantage that new peripheral equipment is required and the initialization device itself becomes large.

Furthermore, in the conventional initialization method, as shown in FIG.
The grain size is different from that of the crystal 32 of the annular melt crystallized portion (rim) formed around the crystal 3, and as a result, the reflectance of the two is different, so that a sufficient erasing rate cannot be obtained, or
There was a drawback that the recording/erasing characteristics fluctuated at the initial stage of overwriting.

An object of the present invention is to solve the above-mentioned drawbacks and to provide an optical disk initialization method that can perform good initialization of a phase change type optical disk using a simple technique that utilizes the technology employed in conventional optical disk devices. It is about providing.

[0011]

[Means for Solving the Problems] In order to solve the above problems, the present invention uses reversible phase change to record, reproduce, and erase information by changing the phase state of an information recording film by laser beam irradiation. A method for initializing a phase change optical disk, characterized in that crystal grains having the same grain size as crystal grains in an annular crystal part around a recording bit formed during recording are formed over the entire phase change optical disk. .

Further, in the present invention, as the initialization method, the irradiation position of the focused laser beam is set to one of the phase change optical discs.
The focused laser beam is irradiated onto the phase change optical disk while being sent a certain amount in the radial direction of the phase change optical disk per rotation, and the laser beam is made of crystals having the same grain size as the crystal grains of the annular crystal part around the recording bit. It is characterized in that the crystallized regions are continuously formed in a concentric or spiral shape.

[0013]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an optical disc initialization method according to the present invention. In FIG. 1, the focused laser beam 2 for initializing the disk is 0.5 (μm) to 2 (μm)
m) is focused on the diameter and irradiated onto the disk. The width of the pregroove convex portion 11 or the concave portion 12 is 0.3 (μm) to 1
．． 3 (μm), and is formed in a spiral shape in the circumferential direction of the disk. The wider pregroove is often used for recording information. For example, 1
．． When using a pregroove convex portion 11 with a width of 3 (μm), even if you try to initialize that area with a condensed laser beam 2 with a diameter of 0.5 (μm) to 2 (μm), the intensity distribution of the laser beam will be Since it is a Gaussian type, it is difficult to make the entire convex portion 11 in a uniform crystalline state.

In the present invention, the focused laser beam 2 shown in FIG.
While feeding in the radial direction in synchronization with the rotation of the disk,
Irradiate onto the disc. The power level of the laser beam 2 at this time is set so as to melt the recording layer of the disk. When the disk rotates once, a molten crystallized region 22 is formed in a portion of the pregroove portion. By sending the laser beam in the radial direction in synchronization with the rotation and continuously forming the melted crystallized region 22 in a concentric or spiral shape,
The melted crystallized region 22 can be uniformly formed in the pregroove convex part 11 and the concave part 12, and at the time of initialization, crystals with the same grain size as the crystals 32 around the recording point (see FIG. 2) are formed over the entire optical disc. can do. In the figure, numeral 21 indicates a molten amorphous region.

As shown in FIG. 3, the phase change optical disk to be subjected to initialization processing has a first dielectric layer 62, a recording layer 63, a second dielectric layer 63, and a second dielectric layer 62 on a disk-shaped substrate 61 made of glass or plastic. A structure in which a dielectric layer 64 and a metal reflective layer 65 are sequentially formed, or a first dielectric layer 62, a recording layer 63, and a second dielectric layer 64 are sequentially formed on a disk-shaped substrate 61 made of glass or plastic. This is the formed configuration. Here, the first dielectric layer 62 and the second dielectric layer 6
4 contains SiO2, Si3 N4, AlN, TiO2
, SiO, etc. are used. The recording layer 63 is made of a chalcogenide material such as GeSbTe or InS.
bTe series, InSe series, InTe series, AsTeGe series,
TeOx-GeSn system, TeSeSn system, SbSeBi
BiSeGe type, BiSeGe type, etc. are used. Metal reflective layer 65
Metals such as Al, Au, Cu, Ag, and Ti are used for the material.

Next, the operation of the optical disk initialization method was confirmed using a single-plate phase change optical disk (diameter 130 mm) with a GeSbTe recording film formed by sputtering on a pregrooved polycarbonate substrate. The optical disc used here employs SiO2 as the dielectric layer and Al as the metal reflective layer. Initialization was attempted while rotating this disk at a constant linear velocity of 11.3 (m/s).

The laser light source of the optical head has a wavelength of 830 (n
m), a semiconductor laser with an output of 20 (mW) was used. The laser spot diameter on the disk surface was approximately 1.5 (μm). With only the focus servo applied without the tracking servo, the laser beam is
Initialization was performed while feeding the disk by 0.1 (μm) to 2 (μm) in the radial direction. At this time, the output of the laser beam on the disk surface was set to 13 (mW). As shown in Figure 4, when the laser beam is sent in the radial direction of the disk in units of 0.1 (μm) to 0.6 (μm), the amount of reflected light increases the most, and repeated overwriting after initialization increases. Good reproduced signal C/N and erasure rate were obtained. In addition, after initializing the disk by sending a laser beam in the radial direction of the disk in units of 0.1 (μm) to 0.6 (μm), we observed the recorded tracks using a transmission electron microscope, and found that the initialization area was It was confirmed that the grain size of the crystal and the grain size of the crystal around the recording bit were the same.

[0018]

[Effects of the Invention] As explained above, in the present invention, since the melt recrystallized region is used as the initialization part, good and uniform initialization can be performed, and there is no change in recording/erasing characteristics after initialization. It has the advantage of being recordable. In addition, during overwrite recording, since the erased part is a melted recrystallized part, the melted recrystallized part (
It has the same crystal structure as the rim), which improves the erasure rate. A device to which the initialization method according to the present invention is applied can utilize existing optical head technology, and has the advantage of being able to have a compact device configuration.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of initializing an optical disc according to the present invention.

FIG. 2 is a diagram showing a crystal in an initialization part and a crystal around a recording point in conventional initialization.

FIG. 3 is a cross-sectional view showing one configuration of a phase change optical disc.

FIG. 4 is a diagram showing the results of initialization of an embodiment in which initialization was performed using the present invention.

[Explanation of symbols]

2 Focused laser beam 11 Pregroove convex part 12 Pregroove recess 21 Molten amorphous region 22 Melt crystallization region 31 Crystal of initialization part 32 Crystals around the recording point 33 Record points 61　Substrate 62 First dielectric layer 63 Recording layer 64 Second dielectric layer 65 Metal reflective layer

Claims (2)

[Claims] [Claim 1] Using reversible phase change, information can be recorded, reproduced, and
A method for initializing a phase change optical disc for erasing, the method comprising:
An optical disk initialization method characterized in that crystal grains having the same grain size as the crystal grains of the annular crystal portion around the recording bit formed during recording are formed on the entire phase change optical disk. 2. The optical disc initialization method according to claim 1, wherein the irradiation position of the focused laser beam is moved by a certain amount in the radial direction of the phase change optical disc per one revolution of the phase change optical disc. A method for initializing an optical disc, comprising irradiating the phase change optical disc with a focused laser beam to continuously form crystallized regions made of crystals having the grain size in a concentric or spiral shape.