JPH06101149B2 - Crystallization method of optical information recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for obtaining a crystalline state in an optical information recording medium, and particularly to crystallization suitable for bringing the entire medium into a crystalline state at once. Regarding the method.

[Conventional technology]

In order to record information on an optical information recording medium, for example, light beam energy such as laser light is applied to the medium to physically change one structural state of the medium to another structural state. You can A chalcogenide is known as such an information recording medium, and the chalcogenide can have two structural states, for example, an amorphous state and a crystalline state. For example, when the medium is irradiated with a light beam, heated, heated, and gradually cooled, the medium is crystallized, and when the medium is irradiated with a light beam having a short pulse width and rapidly cooled, the medium becomes an amorphous state.

As a recording method using the recording medium, there are a method of recording by changing from an amorphous state to a crystalline state and a method of changing by changing from a crystalline state to an amorphous state. For example, when recording at a short wavelength of 1 μm or less, the latter method of performing recording by changing to an amorphous state obtained by rapid heating and quenching is advantageous because thermal interference between pits during recording is small. However, when the information recording medium is manufactured, the medium is usually in an amorphous state. Therefore, when the above recording method is used, the medium needs to be in a crystalline state in advance.

As a method of producing the above structural change, Japanese Patent Publication No. 47-
As disclosed in Japanese Patent No. 26897, there is a method of using various forms of energy, for example, electromagnetic energy in the form of electric energy, radiant heat, light of a flash lamp for photography, energy of laser beam, and the like. There are beam-like energy, particle beam energy such as electron beam and proton beam.

As a specific method of applying the energy, for example, a method of leaving the information recording medium in a constant temperature bath and heating the entire medium, or as described in JP-A-61-208648, simultaneously with the heating A method of applying electric energy has been proposed.

[Problems to be solved by the invention]

However, the above method is applied to the entire information recording medium at 100 ° C to 150 ° C.
Since it is necessary to expose it to the above high temperature, it is difficult to apply it to an information recording medium using a plastic substrate such as an acrylic resin or a polycarbonate resin from the viewpoint of deformation.

Further, also in other methods, an effective method for collectively preliminarily crystallizing the entire information recording medium has not been sufficiently studied, and a method with good productivity has not been found.

An object of the present invention is to provide a method for collectively obtaining a crystalline state in an information recording medium.

[Means for solving problems]

In order to solve the above-mentioned object, the present inventors have studied methods of using various energies, and by irradiating the information recording medium with a high-power flash lamp, desired crystal states can be collectively obtained. I found a thing.

[Action]

As the above method, the present inventors next examined the methods (1) to (5).

(1) Oven heating method (2) Infrared heating method (3) High frequency induction heating method (4) Laser beam irradiation method (5) Photographic flash lamp irradiation method Hereinafter, the respective examination results will be described. FIG. 2 shows a cross-sectional view of the main part of the optical information recording medium used for the examination. The optical information recording medium has a disk shape with a diameter of 130 mm, and will be generically referred to as an optical disk hereinafter. Reference numeral 11 is a polycarbonate resin substrate, 12 is an Sb-Se-Bi recording film, 13 is an ultraviolet curable resin protective film, and 14 is an adhesive.

(1) Oven heating method Since the crystallization temperature of the Sb-Se-Bi recording film is 150 ° C, it is necessary to heat at 170 ° C for about 10 minutes to obtain a good crystal state. When glass is used as the substrate, 170
By leaving the recording film in an oven at 10 ° C. for 10 minutes, the recording film became in a good crystalline state. On the other hand, when an optical disk using a polycarbonate substrate was heated at 170 ° C. for 10 minutes, the substrate was deformed and became unusable. Further, when a similar experiment was conducted with an optical disk using a polyolefin resin substrate having a higher heat resistance than a polycarbonate resin, the substrate was not deformed but many bubbles were generated inside the substrate, which made it unusable.

As described above, the oven heating method is suitable for an optical disk using a substrate having high heat resistance such as a glass substrate, but is not suitable for practical use because the current plastic substrate has low heat resistance. To use the oven heating method, a heat resistant temperature of 200 ° C
The above resin substrate is required.

(2) Infrared heating method Fig. 3 shows a schematic sectional view of an infrared heating device. Reference numeral 15 is an infrared heating lamp (a quartz glass tube with a tungsten filament sealed therein), 16 is a lamp house, 17 is an outer wall of the apparatus, and 1 is an optical disk. The apparatus can heat and raise the temperature at a rate of 50 ° C./SeC using an infrared lamp, and can heat the recording film in a single hour. A crystallization experiment of the optical disk 1 was conducted using this apparatus, but even in this case, the deformation of the disk substrate could not be prevented.

(3) High-frequency induction heating method Using a frequency of 2MHz, 500V input and a ferrite magnetic pole,
A high frequency electromagnetic field was applied to the optical disc. However, since the chalcogenide recording film is a semiconductor / metalloid, it has almost no high frequency loss. Therefore, effective heating could not be performed and a good crystalline state could not be obtained.

(4) Laser Beam Irradiation Method FIG. 4 shows a laser beam irradiation device. 20 is output 400mW
Argon laser, 21 shutter, 22 NA 0.1 lens,
Reference numeral 23 is a disk rotation motor, which is structured to move in the direction of the arrow in the figure while rotating. In the apparatus, while the optical disc 1 is rotated by the motor 23, the laser beam is applied to the disc and the stage is moved to move the laser beam in the disc radial direction. Only by directly irradiating the laser of 400 mW, the temperature rise of the recording film is small, and it is not possible to bring it into a sufficient crystalline state. Therefore, the laser beam spot is narrowed to about 20 μmφ by using the lens 22 with NA 0.1. According to this method, since the laser beam is applied only to a part of the disk, the disk substrate is not deformed at all and there is no problem. However, since the laser beam spot diameter is small, it takes 10 to 30 minutes to crystallize the entire surface of the disk, which is a problem in terms of productivity.

(5) Method of irradiating photographic flash lamp As a photographic flash lamp, a commercially available strobe light (guide number 25) was used to irradiate the optical disk. When I made it close to the optical disk, it was 10 mm × 20
It was possible to crystallize in a narrow range of about mm. But,
It was difficult to crystallize the entire disc by this method, because almost no crystallization was possible at a distance of 5 mm or more from the optical disc.

As described above, the methods (1) to (5) have been examined, but there has been no method for crystallizing the optical disk in a short time.

However, the present inventors have paid attention to the fact that a portion of the optical disk can be crystallized in a short time with a small area by irradiating the flash lamp for photography, and considered to increase the output of the flash lamp.

In order to crystallize the entire 130 mm diameter optical disk, it is necessary to irradiate 100 times more energy than the output of a flash lamp for photography. The present inventors have found that over a large area, 2000
A flash lamp capable of irradiating energy of about Joule was manufactured as a prototype, and it was confirmed that the entire optical disk could be crystallized at once by the irradiation of the lamp. As a result, the entire optical disk could be crystallized in a short time with good productivity.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 5.

Embodiment 1 FIG. 1 shows a cross-sectional view of a main part of a flash lamp device used in this embodiment and a state in which an optical disc 1 is irradiated with a light beam. A flash discharge tube 2 uses a xenon lamp. Since the optical disk recording medium mainly obtains large energy absorption in the semiconductor laser wavelength region, it is necessary for the flash lamp to have a spectral energy distribution extending to around 800 nm which is the semiconductor laser wavelength. The xenon lamp not only has a spectral energy distribution close to that of natural daylight, but its energy distribution is sufficiently extended to the semiconductor laser wavelength range. Therefore, a xenon lamp is a suitable lamp for carrying out the present invention. Reference numeral 4 denotes a concave reflecting mirror, which is provided to irradiate the optical disc 1 with the light rays 3 from the flash discharge tube 2 effectively and uniformly. Reference numeral 5 is a transparent plate made of glass or the like.
FIG. 5 is a circuit showing an example of a circuit for discharging the flash discharge tube shown in FIG. 30 is a xenon lamp,
C ₁ and C ₂ are capacitors, Tr is a transformer, R ₁ and R ₂ are resistors, S is a thyristor, and 34 is a switch circuit. C ₁ is a main capacitor, which is charged to a predetermined voltage by a charging circuit (not shown). Main capacitor C ₁
One electrode is connected to the anode 31 of the xenon lamp 30,
The other electrode is connected to the cathode 32. Switch circuit 34
If an ON signal is given to the gate terminal of the thyristor S,
The current due to the discharge of the capacitor C ₂ flows in the transformer Tr,
A high voltage is applied to the trigger electrode 33 of the xenon lamp 30 by the boosting action of. As a result, the gas in the xenon lamp 30 is ionized, the internal resistance is reduced, and a discharge is instantaneously generated between both electrodes of the xenon lamp 30 to emit light. The light emission time at this time is 0.5 msec to 2 msec.

The irradiation light energy W (J) of the xenon lamp depends on the luminous efficiency η of the lamp, the capacity C (F) of the main capacitor connected to the xenon lamp and the charging pressure V (v). Given in. Since the luminous efficiency η varies depending on the lamp, the input energy of the lamp in this embodiment is Is used as a guide. According to this example, by setting the input energy to 2000 J, the entire optical disc having a diameter of 130 mm could be crystallized at once. The charging voltage at this time was about 800V. When the input energy was 1000 J, the entire optical disc could not be crystallized sufficiently by irradiating the xenon lamp once. However, complete crystallization could be achieved by repeating the irradiation several times. The relationship between the input energy W and the number of irradiations N for complete crystallization is about W, where W ₀ is the energy for complete crystallization in one irradiation.
× NW ₀ .

In the above embodiment, after the optical disc 1 was assembled, flash light irradiation was performed from the substrate side. The process of irradiating with flash light is not limited to this, and as shown in FIG. 6, it is also possible to irradiate with flash light after forming the recording film or after forming the protective film. That is, as shown in FIG. 6, the optical disk manufacturing process according to the present invention is performed after the substrate is manufactured and then Sb-Se
-A Bi recording film is formed, an ultraviolet-curable resin protective film is applied and cured, and then bonded with an adhesive to obtain an optical disc.
Therefore, the process of crystallizing by flash light irradiation can be inserted in the place shown by ,, in FIG.

When the glass substrate was used, there was no problem even if the flash irradiation was performed at any time of ,,, but when the plastic substrate was used, the method (FIG. 6) corresponding to the process shown in Example 1 ( If a method of irradiating with flash light after bonding the optical discs) is adopted, minute irregularities may occur on the substrate surface (recording film formation surface side). As a method of improving this, the above-mentioned method will be described below.

Example 2 A polycarbonate resin substrate was used as a substrate, and an Sb-Se-Bi recording film was formed to a thickness of 120 nm on the substrate by a sputtering method. The disk was irradiated with flash light by using the flash light generation device shown in Example 1. Crystallization could be performed with a low energy of 1000 J of flash irradiation energy, but cracks were generated in the recording film with this energy. It is considered that these are due to the difference in the coefficient of thermal expansion between the substrate and the recording film by about one digit. The cracks can be prevented by setting the irradiation energy to 500 J or less, but it is necessary to increase the number of irradiations because the energy for crystallization is too small. On the other hand, fine irregularities on the substrate surface did not occur. Crystallization is performed with irradiation energy of 600 J and irradiation frequency of 4 times, and an ultraviolet curing resin protective film is applied and cured,
An optical disk was obtained by bonding with an adhesive.

Example 3 A polycarbonate resin substrate was used as a substrate, and an Sb-Se-Bi recording film was formed on the substrate with a thickness of 120 nm by a sputtering method. Then, a UV-curable resin protective film was applied and formed to a thickness of 30 μm, and cured by UV irradiation. The disk was irradiated with flash light by using the flash light generation device shown in Example 1. There are two directions of irradiating the flash light, that is, the substrate side and the protective film side. By irradiating from the protective film side, a good crystal state and a substrate surface state were obtained. When the irradiation was performed from the substrate side, there were cases where minute unevenness was generated on the substrate surface, as in the case of irradiation after the disk bonding in Example 1. In addition, the formation of the protective film did not cause the recording film to crack as in Example 2. However,
When the thickness of the protective film is 2 μm or less, the protective film has a thickness of 2 because the protective film has wrinkle-like swelling during flash irradiation.
It should be at least μm, preferably at least 5 μm. The irradiation energy was set to 2000 J, and crystallization was performed by irradiating a flash light once from the protective film side, and the crystallization was performed to bond them together with an adhesive to obtain an optical disk.

Although an organic protective film is used as the protective film, it is possible to prevent the recording film from cracking by providing an inorganic protective film such as SiO _{2 having a} thickness of about 50 nm to 1 μm on the recording film. In addition, a composite of an inorganic protective film and an organic protective film may be used, and in this case, the thickness of the organic protective film may be 2 μm or less.

In the above-mentioned embodiment, the reason why minute irregularities may occur on the substrate surface when the flash light is irradiated from the substrate side is considered that the substrate itself absorbs a part of the flash spectrum. On the other hand, when the irradiation is performed from the protective film side, most of the irradiation energy is absorbed by the recording film and the damage to the substrate is small.

Fourth Embodiment In the third embodiment described above, flash light irradiation is applied to the entire disc, but as shown in FIG. 7, a part of the optical disc may be crystallized by providing a mask on the inner circumference and the outer circumference. it can. In FIG. 7, 41 is a polycarbonate resin substrate, 42 is an Sb-Se-Bi recording film, 42 is a UV-curable resin protective film having a thickness of 30 μm, 44 is an inner peripheral mask, and 45 is an outer peripheral mask. FIG. 8 shows a plan view of an optical disk obtained by the mask flash irradiation as shown in FIG. In FIG. 8, 47 is a portion where the flash is irradiated to crystallize the recording film, and 46 is a portion where the flash is cut by a mask and the recording film is kept in an amorphous state. Normally, when the recording film is provided on the substrate 41, the recording film is not provided on the innermost and outermost portions, but when flash light irradiation is performed on the boundary portion, cracks of the recording film or peeling of the protective film from the portion are performed. Could occur. It is considered that this is because heat is concentrated on the above-mentioned boundary portion during flash irradiation, and in order to prevent this, as shown in FIG.
It was effective to adopt an irradiation method such that the above-mentioned boundary portion was not irradiated with flash light. That is, it is considered that the above-mentioned mask prevented the heat of the irradiated portion from diffusing to the non-irradiated portion through the recording film, thereby preventing the thermal concentration as described above.

Although the mask is provided on the inner and outer circumferences in the above-described embodiments, the present invention is not limited to this, and it is possible to mix a crystalline state and an amorphous state by masking and irradiating an arbitrary portion of the optical disk. is there.

Although the method of crystallizing an optical disc at the optical disc manufacturing stage has been described so far, the present invention is not limited to this. After recording on the optical disc, a part or all of this data is crystallized by flash irradiation and erased. It goes without saying that the method can be applied.

Although a xenon lamp is used as a light emitting source in the above-mentioned embodiment, the present invention is not limited to this, and various lamps are used because the information recording medium causes wide energy absorption centering on the semiconductor laser wavelength range. be able to.

〔The invention's effect〕

According to the present invention, the entire optical disc can be brought into a crystallized state in a short time, so that the productivity of the optical disc can be improved.

Further, according to the present invention, since the entire optical disk is uniformly irradiated with flash light, there is an advantage that the entire optical disk can be crystallized without unevenness, as compared with laser light irradiation or the like.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a flash light generating apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view of an essential part of an optical disk used in the embodiment of the present invention, and FIG. 3 is used for a study in the present invention. FIG. 4 is a schematic sectional view of a laser beam irradiation apparatus used in the examination of the present invention in FIG. 4, FIG. 5 is a flash / generation circuit diagram used in an embodiment of the present invention, FIG. FIG. 6 is a block diagram showing an optical disk manufacturing process used in the present invention, FIG. 7 is a partial sectional view for explaining another embodiment of the present invention, and FIG. 8 is obtained by one embodiment of the present invention. It is a top view of an optical disc. DESCRIPTION OF SYMBOLS 1 ... Optical disc, 2 ... Flash discharge tube, 3 ... Light beam, 4 ... Reflecting mirror, 5 ... Transparent plate, 11 ... Polycarbonate resin substrate, 12 ... Recording film, 13 ... Protective film.

Claims (1)

[Claims] 1. A method of crystallizing an optical information recording medium comprising a recording medium formed on a substrate, wherein a high-power flash light beam is applied to the entire recording medium to collectively or partially form the medium. A method for crystallizing an optical information recording medium, characterized in that crystallization is caused in the film.