JPS62250533A - Initial crystallization method for optical disk - Google Patents

Abstract

PURPOSE:To enable the initial crystallization of only the recording film without increasing the temp. of a substrate consisting of an org. material by subjecting the recording film, the initial state of which is in an amorphous state, to flash exposing by a prescribed light source. CONSTITUTION:Optical disks 40A, 40B of a phase change type constituted by preliminarily forming the recording films 32, 32B consisting of the material having large light absorption to a laser beam such as Te, Ge or InSb on transparent substrates 31A, 31B are imposed on a belt conveyor 30 driven in an X-direction. Flash light 36A is irradiated for the prescribed time from a xenon lamp 33 to the optical disk 40B arriving at the position below a reflection mirror 34 of said two disks. The recording film 32B of the disk 40B is thus exposed by the flash light 36A and the temp. thereof is increased up to the crystallization temp., by which the initial crystallization is effected. The flash light 36A having the wavelength in an IR region is mostly absorbed by the recording film 32B and the flash light 36B which is not absorbed by the recording film 32B is not absorbed by the transparent substrate 31B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for initial crystallization of an optical disk capable of heat mode recording using, for example, a laser beam.

(Prior Art) The recording format of conventionally used optical discs can be classified into three types shown in FIGS. 3 to 5.

In the type shown in FIG. 3, a laser beam is spot-irradiated onto a thin layer 11!2 of a low melting point material formed on a substrate 1 to melt and evaporate that portion, thereby recording information as minute holes 3.

The type shown in FIG. 4 has a base layer 6 on the substrate 4. A multilayer film IIu5 consisting of a film 7 is formed, and bubbles are generated from the base layer 6 whose temperature has increased when spot irradiation with a laser beam is performed, and the bulges 8 formed in specific parts of the upper thin film 7 are used as information. It is used as a recording section.

Roughly speaking, the type shown in FIG. 5 forms a thin film 10 whose structure changes with temperature changes on a substrate 9, and changes the local part 11 of 1vi10 into a structure with a different reflectance by spot irradiation with a laser beam. This type records information.

Since each of these types of recording parts (3, 8, 11>) produces phase A in the light transmission or reflection characteristics with respect to the non-recording part, each of the recording parts (3, 8, 11) is
, 11>, the recorded information can be read out.

However, among the recording parts (3, 8, 11), the types shown in Figures 3 and 4 cause irreversible changes to the recording parts (3, 8>), so even if recording is possible, erasure is impossible. I can't.

On the other hand, the type shown in FIG. 5 allows both recording and erasing by using a material whose optical properties can be reversibly changed thermally as the recording film material.

+J By the way, it is well known that semiconductors such as Ge, Te, and InSb can have two states, a stable crystalline phase and an amorphous phase, and the complex refractive index N=n- in each state.
The difference in ik is J, OF, N by J, 5 TUKE.
0N-crysta 11 ine Solid
41 (1970).

Furthermore, the idea of obtaining an optical memory by reversibly changing the two states of a semiconductor, crystallized and amorphous, by heat treatment with a laser beam is the idea of S and R.

Metallurgical 1ranscatio by 0VSHINSKY etc.
ns 2641 (1971).

In other words, when semiconductors such as Ge, Te, and InSb are heated to a molten state and cooled rapidly, they become amorphous, and when they are heated to a lower temperature and cooled slowly, they become crystalline. The phase and crystalline layer are each n”-1
Although they exist stably with optical properties characterized by complex refractive indices of k- and n-1k, these semiconductors have poor chemical stability when made into thin films and gradually corrode and deteriorate in the atmosphere, so they are not suitable for memory. It was not practical as an optical disc for

Attempts have also been made to make these semiconductors more durable by making them into compounds or sandwiching them between durable protective films. For example, as shown in FIG. 6, an S
i 02 protective film 21 (1000A>, TeGe recording film 22 (700A>).

It is known that a S i 02 protective film 23 (100 OA>) is formed and a UV resin film 24 is applied to roughly improve durability.

The 5i02 protective films 21 and 23 function to prevent holes from being formed due to laser power during recording and erasing.

It is known that a phase change optical disk formed using such a recording film 22 is chemically stable and has stable recording/erasing repeatability.

However, this optical disc also has the following drawbacks. That is, apart from cases where the recording film exists in a crystalline state immediately after deposition, such as in a phase change semiconductor formed of Te, in ordinary phase change semiconductors such as Ge, TeGe, and InSb, the recording film does not exist immediately after deposition. Since it exists in an amorphous state, it cannot be written to as it is.

Generally, when recording information using the phase change between crystal and amorphous, writing (amorphousization) is performed by irradiating a short pulse of laser light with high power, and writing is performed using a relatively low power. Erasing (crystallization) is then performed by irradiating a long pulse of laser light.

Therefore, if the initial state is amorphous, the recording film must first be crystallized over the entire surface of the optical disk. Such initial crystallization may also be carried out by continuous irradiation of a laser beam of relatively low power in the circumferential direction of the optical disk, but this has the problem of increasing the time required for initial crystallization.

In addition, two laser beam sources are provided in the disk device,
It is also possible to use one of these laser beams for both initial crystallization and erase crystallization, thereby performing initial crystallization while writing with the other laser beam, but in this case, the laser beam source There is a problem that the cost of the device increases due to the presence of two layers.1 This problem can be solved by changing the recording layer from amorphous to crystalline before shipping the manufactured optical disk from the factory. be done.

In order to crystallize an amorphous substance, it is generally necessary to heat the substance to a temperature higher than the crystallization temperature (usually 150° C. or higher).

However, substrates for optical disks on which the above-mentioned recording film is deposited are usually made of organic materials such as acrylic and polycarbonate due to cost considerations, so if such substrates are heated above their crystallization temperature, However, there is a problem that this substrate may be deformed or melted.

In this case, if the substrate is made of an inorganic material such as glass, the above-mentioned problems will disappear, but on the other hand, it will increase the cost and make it difficult to form pregrapes (laser beam guide grooves). This will cause inconvenience.

(Problems to be Solved by the Invention) As described above, in the past, for various reasons, there have been many difficulties in initial crystallization of the recording film of a commercialized optical disk at the stage of shipment from a factory or the like.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an initial crystallization method that can perform initial crystallization of only a recording film without increasing the temperature of a substrate made of an organic material.

[Structure of the Invention] (Means for Solving the Problems) The method of the present invention provides a recording film that changes phase between crystalline and amorphous on a substrate made of an organic material, and A method for initial crystallization of an optical disk capable of recording and reproducing information by irradiation with a laser beam, in which when the recording film is in an amorphous state, the recording film is exposed to flash light from a predetermined light source. It is something.

(Function) When performing initial crystallization of the recording film on an optical disc configured by providing a recording film that changes phase between crystalline and amorphous on a substrate made of an organic material, If this recording film is in an amorphous state, flash exposure is performed for a predetermined time using a predetermined light source. This flash exposure causes the temperature of the recording film to rise rapidly, thereby changing the recording film from an amorphous state to a crystalline state.

At this time, the irradiation time of the light beam to the recording film is extremely short since it is a flash exposure, and therefore, no deformation of the substrate occurs due to the flash exposure.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows an outline of a flash exposure device for agglomerating according to the method of this embodiment, and this device consists of a transparent belt conveyor 3o driven in the direction of the arrow A concave reflecting mirror 34 is disposed at a predetermined position in the movement area of the belt conveyor 30 with its opening facing downward and is spaced apart from the belt conveyor 30 by a certain distance; a xenon flash lamp 33 which is a light source for flash exposure; and a dish-shaped reflecting mirror 35 disposed opposite to the reflecting mirror 34 with the belt conveyor 30 in between.
It is composed of:

The xenon flash lamp 33 is energized by a power supply device (not shown) for a predetermined period of time (1 μSeC).
~1m5ec) and emit flash light.

Next, a method for performing initial crystallization of a phase change optical disk using the flash exposure apparatus having the above configuration will be described.

Te and Ge are deposited on transparent substrates 31A and 31B on a belt conveyor 30 driven in the direction of arrow X.

Phase-change optical disks 4OA and 40B each having a recording film 32, 32B made of a material that has high light absorption for a laser beam, such as InSb, formed in advance are mounted, and the disc 4OA and 40B are placed below the reflecting mirror 34. The optical disc 40B is exposed to the xenon flash lamp 33 for a predetermined period of time (1 μSeC to 1
m5eC) Irradiate with flash light 36A. As a result, the recording film 32B of the optical disc 40B is exposed to the flash light 36.
A is exposed to light, and the temperature is raised to the crystallization temperature to perform initial crystallization.

At this time, as shown in FIG. 2(a), the flash light 36
Of A, most of those whose wavelength is in the infrared region are the recording film 32B.
Further, the flash light 36B that is not absorbed by the recording film 32B is transmitted through the transparent substrate 31B without being absorbed and becomes transmitted light 36C. Therefore, the substrate 31B does not generate heat.

In addition, the effect of heat generation due to the temperature rise of the recording film 32B is also considered, but as mentioned above, the exposure time is extremely short;
Since the recording film 32B is instantly cooled, there is almost no effect thereof.

In this way, the optical disk 4 that has undergone initial crystallization
0B is transferred outward from the reflecting mirror 34 by the belt conveyor 30, and the next stage optical disk 40A is transferred below the reflecting mirror 34, whereupon initial crystallization is performed in the same manner as in the case described above.

The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the invention. For example, in the method of the embodiment described above, a case was explained in which initial crystallization is performed on an optical disc-wedge portion using a belt conveyor method, but it is also possible to perform initial crystallization on a large number of optical discs at once using a batch processing method. In some cases, productivity can be increased. Furthermore, a halogen lamp may be used as the light source.

Experimental Example: An optical disk similar to the type shown in FIG. 6 described above was manufactured by a reactive sputtering method using a 5-inch disk-shaped acrylic (PM'MA) substrate. That is, as shown in FIG. 2(b), S i 0 on the acrylic 114 board 60
2 (7) After forming the lower tt[61f1000A film, the recording film 62 of amorphous T 690 G e to is deposited at 700^
A protective film 63 of SiO2 was roughly formed on this recording film 62 to a thickness of 1000, and a UV resin film 64 was formed thereon.

The above film forming process is performed using the same reactive sputtering apparatus using three independent targets, and SiO2 is performed using a single target. This was carried out while controlling the RF (radio frequency) power applied to each of these targets so that the component ratio expressed as follows.

Next, the optical disc having the above configuration is transferred below the reflecting mirror 34 of the flash exposure device shown in FIG. Exposure was carried out.

Then, for the optical disc taken out from this installation,
As a result of measuring line diffraction, it was found that it was crystallized.

[Effects of the Invention] According to the present invention described above, it is possible to provide an initial crystallization method that can efficiently crystallize an amorphous recording film without affecting the substrate of an optical disc by deforming or the like. can.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an outline of a flash exposure device used to realize the embodiment method of the present invention, and FIG. 2 (a>
2(b) is an explanatory diagram showing the absorption state of flash light in the recording film and substrate of a phase-change optical disc, and FIG. 2(b) is a partial sectional view showing a conventional optical disc. , FIG. 6 is a partial cross-sectional view of a phase change optical disk. 30...Belt conveyor, 31A, 31B...Substrate, 32A, 32B...Recording film, 33...Xenon flash lamp, 40A,
40B...Optical disc.

Claims (2)

[Claims] (1) A method for initial crystallization of an optical disc in which a recording film that changes phase between crystalline and amorphous is provided on a substrate made of an organic material, and information can be recorded and reproduced by irradiating the recording film with a laser beam. A method for initial crystallization of an optical disc, characterized in that the recording film, which is initially in an amorphous state, is subjected to flash exposure using a predetermined light source. (2) The method for initial crystallization of an optical disk according to claim 1, wherein the light source is a xenon flash lamp.