JPS63161547A - Initializing method for information recording medium and erasing method for information in information recording medium - Google Patents

Abstract

PURPOSE:To eliminate defective initialization or recording left unerased by radiating a 1st light beam being an output having an energy of a degree to melt a recording layer to the amorphous recording layer at film forming and radiating a 2nd light beam being a lower output than that of the 1st light beam so as to crystalize and initialize the recording layer. CONSTITUTION:Part of a recorded part or a part of a recording layer 3 is molten by the 1st light beam, and the molten part is a crystallized to obtain a molten/solidified structure and the recorded part or the recording layer 3 is formed to be nearly unified crystal structure by the 2nd light beam entirely, when initializing the recording layer through the crystalization by radiating a light beam to the amorphous recording layer 3 at film forming via a base 1 and a protection layer 2, and erasing the information by radiating a light beam 6 to the recorded part 7 of the recording layer through which the informa tion recording is erased through the reversible phase change between different crystals. Thus, unerased part and initial defect is suppressed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to, for example, initializing a recording layer in an amorphous state during film formation by irradiating a light beam to crystallize it. The present invention relates to a method for initializing an information recording medium, and a method for erasing information in an information recording medium, which erases recorded information by irradiating a recording layer of an optical disc with a light beam.

(Prior Art) It has been known that semiconductor materials such as TeGe and TeGe can exist as two stable crystalline and amorphous phases with different complex refractive indices N5sn-ik (J,
5tuke J, of, Non-CrySta
llineSOIidl, 1 1970) The idea of creating an optical memory by reversibly changing these semiconductor materials into two states, crystalline and amorphous, by heat treatment with a laser beam is well known (S.

R,0vshinsky et al, Met
alluolcal Transaction L,
641, 1971) a Based on these, phase-change type optical disks in which information can be erased have been developed using the above-mentioned semiconductor materials in the recording layer.

Thin films of semiconductor materials such as Te, Ge, and TeGe described above become amorphous when heated to a molten state and cooled at high speed, and become crystalline when heated to a lower concentration and slowly cooled. The amorphous state and the crystalline state have different optical properties because of the complex refractive index expressed by n-1k. Therefore, in these materials, information is recorded and erased by utilizing differences in optical properties such as differences in reflectance or transmittance between crystalline and amorphous materials.

On the other hand, optical discs have also been proposed in which information is recorded and erased through phase changes between different crystals. In such an optical disc, a recording layer made of, for example, lnsb formed by vapor deposition is used.

Such a recording layer is amorphous when it is formed, but by irradiating the recording layer with a laser beam that has a high output and a relatively large pulse width, the irradiated area is melted and then slowly cooled. This results in fine crystallization. Next, the irradiated portion is coarsened by irradiating the microcrystalline portion with a laser beam having a large output and a relatively small pulse width. In this case, since the complex refractive index of each crystal phase is different,
By causing a phase change between these crystals, information can be recorded and erased. This InSb crystal is chemically stable, and has the advantage that, for example, the recording layer will not deteriorate even if it is left in an environment at a temperature of 70° C. and a relative humidity of 85% for one month.

(Problems to be Solved by the Invention) However, in the information recording/erasing method based on a phase change between crystalline and amorphous states, there is a problem that the stability of the amorphous state is low. That is, when the crystallization temperature of the material is low, the amorphous recording pits gradually crystallize, making it impossible to distinguish between the recorded portion and the non-recorded portion.

In addition, when recording and erasing information due to a phase change between crystalline and crystalline materials, the information is recorded and erased when the amorphous is initially crystallized at al1 and due to the phase change between the crystalline and crystalline materials. In this case, the recording layer is first melted and then solidified. For this reason, it is necessary to initialize the optical disk and erase information by irradiating it with a laser beam having a relatively large output of, for example, 9 to 11 mW and a relatively long pulse width of 6 μS. In particular, since the amorphous film immediately after deposition is extremely stable in terms of energy, for example, if the linear velocity of the disk is 1. If the linear velocity is 3.0 m/s, initialization can be performed by irradiating the laser beam once under the conditions described above, but if the linear velocity is 3.0 m/s, 3 to 4 irradiations are required. If the four-strand speed is 5.0 m/s, it is not possible to completely melt the material even after 8 to 10 irradiations, causing a so-called initialization failure. It may be possible to resolve this by increasing the size, but
In this case, the recording layer is partially melted and other parts are not melted, so that the laser reflection intensity differs locally, resulting in initialization failure.

Even when erasing information, if information is recorded using a laser beam with a short pulse width of 100 to 200 ns,
There is a problem in that the recorded pits cannot be completely melted and unerased portions remain.

This invention has been made in view of the above circumstances, and is an information recording medium that does not cause initialization failures or unerased data, and can always maintain a recording layer in a state where sound recording can be performed. The object of the present invention is to provide a method for initializing information on an information recording medium and a method for erasing information from an information recording medium.

[Structure of the Invention] ′ (Means for Solving the Problems) The method for initializing an information recording medium according to the present invention is such that the recording layer can be melted into an amorphous state at the time of film formation. The method is characterized in that the recording layer is crystallized and initialized by irradiating it with a first light beam having an output of , and then by irradiating a second light beam with a lower output than the first light beam.

Furthermore, the method for recording information in an information recording medium according to the present invention includes a recording portion of a recording layer where information is recorded and erased by a reversible phase change between different crystal phases by irradiation with a light beam. Erasing information by irradiating a first light beam with a power sufficient to melt the recording layer, and then irradiating this portion with a second light beam having a lower power than the first light beam. It is characterized by

(Function) When the amorphous recording layer is crystallized by irradiating a light beam during film formation and initializing the recording layer, information is recorded and erased through a reversible phase change between different crystal phases. When erasing information by irradiating the recording part of the recording layer with a light beam, a part of the recording part or part of the recording layer is melted by the first light beam, and the part becomes a melt-solidified structure. The second light beam causes the recording portion or the recording layer to have a substantially uniform crystal structure as a whole. Therefore, unerased portions or initialization defects can be suppressed.

(Example) Examples of the present invention will be described in detail below.

The information recording medium used in this embodiment is configured as shown in FIG. 1, for example. The substrate 1 is made of a material that is transparent and shows little change over time, such as glass or polycarbonate resin. A protective layer 2, a recording layer 3, and a protective layer 4 are formed on the substrate 1 in this order. Ho II! 12.degree. 4 is arranged so as to sandwich the recording layer 3, and prevents the recording layer 3 from melting. This protective layer 2.4 is made of SiO2. A protective layer 5 is formed on the protective layer 4 to prevent damage to the optical disc. This protective layer 5 is formed, for example, by applying an ultraviolet curing resin onto the protective layer 4 and curing the applied layer by irradiating it with ultraviolet rays.

Further, the recording layer 3 is made of an In-8b alloy, and can be formed by a sputtering method or a vapor deposition method. This 1n-8b alloy can have two different crystal forms depending on the irradiation conditions of the light beam.

Since the recording layer 3 is in an amorphous state immediately after film formation, the recording layer 3
The recording layer 3 is initialized by being irradiated with a laser beam under predetermined conditions through the substrate 1 and the protective layer 2 to crystallize the entire recording layer 3. Next, a laser beam under different conditions is irradiated to change the phase of the irradiated portion to another form of crystal, thereby forming information recording bits 7. Furthermore, the recording bit 7 is irradiated with a laser beam 6 to change the phase of that portion to the original crystalline state and erase the information. Information is also reproduced by irradiating the recording 113 with a weak laser beam and detecting the reflectance.

As a result of intensive studies by the inventor of the present invention regarding the laser beam irradiation for initializing the optical disk and erasing the recorded bits as described above, for example, after first irradiating the laser beam with a relatively large output of 9 to 14 mW, then By irradiating a laser beam with a relatively small output of 3 to 7 mW, initialization and erasure can be performed without causing initialization failure or erasing residue even when the linear velocity is as high as 5.0 m/s or more. We found that it is possible to stably implement the method. An example of such laser beam irradiation conditions is shown in FIG.

The reason why the optical disc can be initialized and the recorded bits can be almost completely erased through such a process is as follows.

That is, when the linear velocity is 5.0 m/s or more, even a laser beam with a large output of about 11 mW can cause In-8b
Since the irradiated area of the recording layer 3 formed by is only partially melted, a part of the irradiated area becomes a crystal with a melted-solidified structure, and the other part is not melted but has a different crystal phase that has grown as a crystal. However, by irradiating the laser beam with the next lower output power, the crystals in the melted-solidified structure described above are recrystallized, and the other crystal phases described above are further crystallized. As the crystal formation progresses, both of them are averaged out, resulting in a uniform crystal form.

Next, a test example in which initialization of an optical disk and erasing of recorded pits were carried out using this example will be specifically explained. On a substrate made of polycarbonate, a 700 8102 dielectric protective layer, summer n+oSbs, is applied by sputtering.
Recording layer of 900 people formed by a, 5in2 of 700 people
Dielectric protective layers were formed and laminated in this order. after that,
On top of the last formed protective layer, a 3μ
Overcoated with a milk UV resin layer. The optical disk sample manufactured in this way was evaluated for disk dynamic evaluation 1.
Evaluation was made by setting iii. First, the rotation speed is 900rl)
l, linear velocity5. While rotating om/sr, wavelength 83
The outputs of two 0 nm semiconductor lasers were set to 11 mW and 7 mW, respectively, and the semiconductor lasers were sequentially irradiated with continuous light to crystallize and initialize the entire recording layer. Next, the output of one of the semiconductor lasers was set to 0.5 mW, and as a result of continuous light irradiation with this laser and playback, the variation in reflected light over the entire surface of the disk was within ±5%, and the reflection level after initialization was was found to be stable. Next, the output of the same laser was set to 15 mW, and the pulse width was set to 200 ns.
The recording layer was irradiated with this laser with a duty value of 50%, and information was recorded by changing the phase of the irradiated portion. Then, as a result of reproducing with continuous light of 0.5 mW, an AC signal with an amplitude of about 120 mV could be obtained. after that,
The two semiconductor lasers mentioned above were again powered at 11 mW and 7 mW, respectively.
W, and first set the pulse width of 11mW to 1.5μ.
The recording pits were irradiated with a pulse of 7 mW, and then the same portion was irradiated with a pulse of 7 mW with a pulse width of 1.5 μs to cause a phase change and erase the recorded pits.

Then, when the output of one laser was set to 0.5 mW and the laser was used for continuous light reproduction, the AC signal was completely erased and returned to the exact same level as the DC component at the time of initialization. The variation in reflected light over the entire surface of the disk was within ±5%.

When the above recording and erasing was repeated 104 times or more, the magnitude of the AC signal and the reflectance of the DC component after erasing did not change at all.

Furthermore, as a result of more detailed experiments, the output of the laser beam irradiated first during initialization and erasing was 9 to 14.
It has been found that 3 to 8 mW is appropriate for the output of the laser beam irradiated onto the bales.

[Effects of the Invention] According to the present invention, when initializing an information recording medium and erasing information, a first light beam having an output sufficient to melt the recording layer is irradiated, and then a light beam higher than this output is irradiated. A second light beam having a lower power is applied. In this way, the irradiated area can be made into a uniform crystalline phase, and there is no initialization failure or erased residue, and the recording layer can always be maintained in a state in which information can be recorded in a healthy manner.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an information recording medium used for carrying out the present invention, and FIG. 2 is a diagram showing a timing chart of a laser beam for carrying out the present invention. 1; Substrate, 2.4.5: Protection III, 3: Recording layer, 7
;Record pit. Figure 1 Figure 42 One side closed

Claims (4)

[Claims] (1) During film formation, the recording layer in an amorphous state is irradiated with a first light beam having a power sufficient to melt the recording layer, and then a second light beam having a lower power than the first light beam is irradiated. 1. A method for initializing an information recording medium, comprising crystallizing and initializing a recording layer by irradiating it with a light beam. (2) The method for initializing an information recording medium according to claim 1, wherein the recording layer is formed of an indium-antimony alloy. (3) The recording portion of the recording layer where information is recorded and erased through a reversible phase change between different crystal phases when irradiated with a light beam has an output sufficient to melt the recording layer. 1. A method of erasing information in an information recording medium, which comprises irradiating a first light beam and then irradiating the area with a second light beam having a lower output than the first light beam to erase the information. (4) The method for erasing information in an information recording medium according to claim 3, wherein the recording layer is formed of an indium-antimony alloy.