JP2574885B2 - Method and apparatus for crystallizing optical information recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for crystallizing an optical information recording medium for guiding a recording film formed on a substrate to a crystalline state at a time.

[Conventional technology]

Optical information recording medium (hereinafter abbreviated as recording medium)
For example, information can be recorded by applying light beam energy such as laser light to the recording medium and physically changing one structural state of the recording medium to another structural state.

As such a recording medium, a chalcogenide is known, and the chalcogenide can have, for example, two different structures in an amorphous state and a crystalline state.

Therefore, the recording medium is crystallized by irradiating the recording medium with a light beam to increase the temperature of the recording medium and then slowly cooled, and becomes amorphous when irradiated with a light beam having a short pulse width and rapidly heated and quenched.

As a recording method using the recording medium, there are a method of performing recording by changing from an amorphous state to a crystalline state, and a method of performing recording by changing from a crystalline state to an amorphous state.

For example, when performing short-wavelength recording of 1 μm or less, the latter method of performing recording by changing to an amorphous state obtained by rapid thermal quenching is advantageous because thermal interference between pits during recording is small.

However, when a recording medium is manufactured, the recording medium is usually in an amorphous state. Therefore, when the above recording method is used, the recording medium needs to be in an amorphous state in advance.

As a method of causing the above-mentioned structural change, for example, as shown in Japanese Patent Publication No. 47-26897, a method using various forms of energy is mentioned.

For example, electrical energy, heat radiation, flash lamp light,
There are beam energy such as electromagnetic energy in the form of laser beam energy, and particle beam energy such as electron beam and proton beam.

As a specific method of applying the energy to the recording medium, for example, a method in which the recording medium is left in a thermostat and the entire recording medium is heated, or as described in JP-A-61-208648. A method of applying electric energy to a recording medium simultaneously with the above-mentioned heating has been proposed.

However, the above method requires exposing the recording medium to a high temperature of 100 ° C. to 150 ° C. or higher, and is difficult to apply to a recording medium using a plastic substrate such as an acrylic resin or a polycarbonate resin in terms of deformation. .

Also, as described in JP-A-62-250533,
There is a method in which flash exposure is performed on a recording film formed on a substrate by a predetermined light source, and the recording film is crystallized by beam energy by the flash exposure.

When a recording film on a plastic substrate such as acrylic or polycarbonate is crystallized by this method, if the recording film is not sufficiently crystallized due to the crystallization temperature and the crystallization speed of the recording film formed on the substrate. Even if the recording film is crystallized, the substrate may be deformed and information may not be recorded or reproduced. In order for the above-mentioned recording film to crystallize, it is necessary to set the temperature above the crystallization temperature and hold it for a specific time or more.

Therefore, a xenon lamp as a light source, versus time recording film temperature characteristic shown in Figure 14 is, when the light at the input power P ₀ such that the characteristic 8, the recording film temperature be maintained above the crystallization temperature T _X short retention time and Delta] t _1, can not be sufficiently crystallize the holding time Delta] t ₁ the recording film.

Therefore, when light is emitted by the input power P ₁ such that the xenon lamp characteristics 9, the retention time becomes longer as Delta] t _2, it is possible to sufficiently crystallize the recording film.

However, when a substrate made of an organic resin such as polycarbonate or acrylic is used, the thermal deformation temperature of this substrate is about 130 ° C., which is one time lower than the crystallization temperature T _X formed on the substrate.
Lowers by nearly 00 ° C. Thus, in light emitting of the input power P _1, it will give thermal damage to the substrate.

This phenomenon occurs as the crystallization temperature T _X of the recording film increases or as the crystallization speed decreases, so that thermal damage to the substrate when the recording film is crystallized cannot be ignored.

[Problems to be solved by the invention]

The conventional crystallization method of a recording medium is performed as described above, and no consideration is given to crystallization of various recording films having different crystallization temperatures and crystallization speeds.
There is a problem that it is difficult to achieve both prevention of substrate deformation and crystallization of the recording film.

In other words, when the recording film on the substrate is crystallized by flash exposure, in order to prevent deformation of the substrate as much as possible, it is better to set the maximum temperature of the recording film by flash exposure higher than its crystallization temperature and approach it as close as possible. Is good.

However, in order to crystallize the recording film, the crystallization is not completed unless the recording film is kept at a temperature higher than the crystallization temperature for a specific time or longer. In order to extend the holding time, it is necessary to increase the output power of the lamp in the case of single emission exposure, which means that the maximum temperature of the recording film is increased.
There is a problem that the deformation of the substrate is involved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to prevent deformation of a substrate and to crystallize various recording films having different crystallization temperatures and speeds. A crystallization method and an apparatus therefor.

[Means for solving the problem]

To achieve the above object, the present invention of claim 1 is
The light beam energy of the flash lamp for irradiating the recording film formed on the substrate is controlled so that the recording film is heated to a temperature slightly higher than the crystallization temperature and the heated state is maintained for the crystallization time or longer. There is a feature in the point.

The inventions of claims 2 to 4 are inventions of an apparatus for performing the crystallization method of claim 1. A second aspect of the present invention is an apparatus for causing a plurality of flash lamps to emit light by shifting the time, a third aspect of the present invention is an apparatus in which a filter having a reduced transmittance is disposed in front of the flash lamp, and a fourth aspect of the invention. Is an apparatus obtained by applying an uncured ultraviolet curable resin on a substrate.

[Action]

In the crystallization method according to the first aspect of the present invention, the recording film is heated to a temperature slightly higher than the crystallization temperature, and the heated state is maintained for a crystallization time or longer, thereby ensuring the crystallization of the recording film. To prevent thermal damage to the substrate.

Further, the invention of claim 2 is a configuration in which the light emission of the plurality of flash lamps is shifted in time, the invention of claim 3 is a configuration in which a filter is provided in front of the flash lamp, and According to the invention, the uncured ultraviolet curable resin is applied to the substrate, and the crystallization method of claim 1 can be performed with a simple structure.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a cross-sectional view showing an apparatus for performing a crystallization method according to one embodiment of the present invention.

In FIG. 1, reference numerals 3 and 13 denote xenon lamps as flash lamps, 14 denotes a reflection mirror surrounding the xenon lamps 3 and 13, and 15 denotes a reflection mirror.
Is a quartz plate provided at the opening of the reflection mirror 14, and 16 is
A polycarbonate substrate on which a recording film having a composition of Sb47Se45Bi8 (atomic percent) having a thickness of about 110 nm is formed, and a UV-curable resin (SD-301) as a protective film is applied and cured by about 20 μm.

The light energy W (J) of the xenon lamps 3, 13 is
It is given by W = η × 1 / 2CV ² by the lamp luminous efficiency η, the capacitance C (F) of the main capacitor connected to the xenon lamp, and the charging voltage V (V). Since the luminous efficiency η varies depending on the lamp, the input energy 1 / xenon of the xenon lamps 3 and 13 in this embodiment.
2CV ² is a guide.

FIG. 2 is a diagram showing an example of a drive circuit for flashing the xenon lamp. FIG. 2 shows a xenon lamp 3
Only the drive circuit of FIG.

In FIG. 2, a xenon lamp 3 has anodes 4 at both ends.
And a cathode 5, and a trigger electrode 6 in the center. Between the power supply connection terminals O ₁ and O ₂ , the main capacitor C ₁ and the resistors R ₁ and R ₂
Are connected in parallel. The main capacitor C ₁ by the charging circuit (not shown), and is charged to a predetermined voltage.

Transformer T _r connects the primary winding in parallel with the resistor R ₂ via the capacitor C _2, connects the secondary winding between the trigger electrodes 6 and the power connection terminal O _2. Thyristor S is connected in parallel with the resistor R _2, the switch circuit 7 is connected to its gate terminal.

Now, given an ON signal from the switch circuit 7 to the gate terminal of the thyristor S, a discharge current flows in the capacitor C ₂ to the primary winding of the transformer T _r, generated in the secondary winding by the boost action of transformer T _r A high voltage is applied to the trigger electrode 6 of the xenon lamp 3.

Thereby, the gas in the xenon lamp 3 is ionized, and the internal resistance is reduced. And, between the two electrodes 4 and 5 of the xenon lamp 3, the charging voltage of the main capacitor C ₁ is discharged in a moment, the light emitting operation is performed.

Therefore, after the xenon lamp 3 shown in FIG. 1 is made to emit light at an input power of 1000 (J) using the drive circuit shown in FIG. 2, the xenon lamp 13 is input with a delay of, for example, Δtp (about 0.3 msec). When light is emitted at a power of 1000 (J), the characteristic of time-emission intensity shown in FIG. 3 is obtained.

Due to this emission intensity, the recording film has a xenon lamp 3,13
Are superimposed on each other, and the characteristic of time vs. recording film temperature as shown in FIG. 4 is obtained. Therefore, the recording film temperature is maintained at the temperature equal to or higher than the liquid crystallizing temperature T _X for the time Δtq. And since this time Δtq is longer than the crystallization time Delta] t _2, sufficient crystallization is carried out in recording film. Further, since the recording film temperature is maintained at a level slightly higher than the crystallization temperature T _X , thermal damage to the substrate can be reduced as much as possible.

In the present embodiment, the number of times of light emission is two, but the same effect can be obtained even when the number of times is two or more.

Second Embodiment In the first embodiment, the first light emission by the xenon lamp 3 and the second light emission by the xenon lamp 13 are performed with the same input power. Even when the first light emission is set to 1000 (J) and the second light emission is set to 800 (J), the same effect as in the first embodiment can be obtained.

(Embodiment 3) In the embodiment 1, the flash irradiation is performed by dividing into two times, but in the present embodiment, the irradiation is performed by dividing into three times.
The device is shown in FIG.

In FIG. 5, in which the same parts as those in FIG. 1 are denoted by the same reference numerals, reference numerals 18 to 20 denote xenon lamps. The basic drive circuits of these xenon lamps 18 to 20 are the same as in the first embodiment.
The drive circuit shown in FIG. 2 can be used.

Next, a processing algorithm will be described. First, the same substrate 16 as in the first embodiment is exposed by two xenon lamps 18 having an input power of 600 (J) with a total input power of 1200 (J).

Next, input power 900 (J) by the xenon lamp 20
, And finally with two xenon lamps 19 having an input power of 600 (J) with an input power of 1200 (J) in total.

In this embodiment, exposure is performed in three parts in consideration of the temperature distribution of the substrate. According to this embodiment,
The same effect as that of the first embodiment can be obtained.

(Example 4) FIG. 6 is a view showing another apparatus for performing the crystallization method of the present invention. In FIG. 6, 3 is a xenon lamp, 14
Is a reflection mirror, 15 is a quartz plate, 16 is Sb47Se45Bi8 on it
This is a polycarbonate substrate on which a recording film having a composition of (atomic percentage) of about 110 nm is formed, and a UV-curable resin (SD-301) is applied and cured as a protective film on the surface by about 20 μm. Reference numeral 17 denotes a filter disposed between the quartz plate 15 and the substrate 16, and the filter 17 is Sb48Se48Bi4 (atomic percent) having a higher crystallization temperature than the recording film. The operation of the xenon lamp 3 of this device is the same as that shown in FIG. 1, and the output energy of this xenon lamp 3 is set to 1/2 CV ² as in the first embodiment.

Next, a crystallization method using this apparatus will be described. Now, when a single light emission exposure is performed with the lamp input power set to 3000 (J), as shown in FIG. 7, the relationship between the time and the recording film temperature without the filter 17 is as shown by a characteristic 10 in FIG. Becomes extremely high, causing thermal damage to the substrate 16.

However, if the filter 17 is crystallized for _a heating time Δtb at _a temperature Ta, for example, the relationship between the time and the recording film temperature is as shown by a characteristic 12.

As a result, the maximum temperature of the recording film is lowered while maintaining the retention time Δtc equal to or higher than the crystallization temperature T _X. That is, due to the decrease in light transmittance by the crystallized filter 17, the energy applied to the recording film is reduced by the amount of the hatched portion, thereby suppressing thermal damage to the substrate 16 and ensuring sufficient crystallization of the recording film. It can be carried out.

(Comparative Example 1) In Example 4, when the filter 17 was removed and the input power of the xenon lamp 3 was made to emit light at 3000 (J), which is the same as Example 4, the recording film was sufficiently crystallized. The thermal damage to the substrate increased, resulting in a large warpage of the substrate.

(Embodiment 5) Fig. 8 shows another apparatus for carrying out the crystallization method of the present invention, wherein 3 is a high-output xenon lamp, 14 is a reflection mirror, 15 is a quartz plate, and 16 is a top plate. This is a polycarbonate substrate on which a recording film having a composition of Sb47Se45Bi8 (atomic percent) is formed. An ultraviolet curing resin (SD-301) having a thickness of about 20 μm is formed on the substrate 16 as a protective film, and the substrate is irradiated with ultraviolet rays for 5 seconds by an ultraviolet curing device. This protective film is completely cured by irradiation with ultraviolet rays for 30 seconds, and has an uncured layer after irradiation for 5 seconds.

Therefore, using the apparatus shown in FIG. 1, the xenon lamp 3 is caused to flash with an input power of 1500 (J), and a light beam energy having a characteristic of time-emission intensity shown in FIG. 9 is given.
The protection film is cured by receiving the light beam energy. For this reason, the characteristics of time vs. recording film temperature are as shown in FIG.
The temperature gradient after reaching the crystallization temperature T _X can be kept low. As a result, the recording film can be sufficiently crystallized, and thermal damage to the substrate can be reliably prevented.

The temperature gradient after reaching the above crystallization temperature T _X is:
It can be determined by the specific heat and thermal conductivity of the recording film and the thermal conductivity and specific heat of the material in contact with the recording film.

(Comparative Example 2) When the ultraviolet-curable resin as the protective film in Example 5 was completely cured by irradiating ultraviolet rays for 30 seconds, and the flash light was irradiated at an input power of 1500 (J), the recording film was sufficient. Crystallization failed.

(Example 6) The crystallization apparatus used in this example is the same as that in Example 5. However, on a polycarbonate substrate on which a recording film having a composition of Sb47Se45Bi8 (atomic percent) was formed, an ultraviolet curable resin (SD-301, manufactured by Dainippon Ink) was applied and cured by about 20 μm as a protective film.

FIG. 11 shows a driving circuit of the xenon lamp in the crystallization apparatus according to the sixth embodiment. The operation of the driving circuit is basically the same as that of the driving circuit shown in FIG. Cd switches SW1 ~
4 is connected between the power supply connection terminals O ₁ and O _{2 in} parallel with each other.

First, the switches SW1 to SW4 are all turned on, and the main capacitors Ca, Cb, Cc, and Cd are charged by a charging circuit (not shown). After the charging is completed, all the switches SW1 to SW4 are turned off.

Next, a signal is sent from the switch circuit 7 to the gate circuit,
To turn on the thyristor S, to discharge the capacitor C _2, to induce a high voltage to the trigger electrode 6. Thereby, the resistance value in the lamp decreases.

At this time, first, the switch SW1 is closed to release the charging voltage of the main capacitor Ca. Next, the switch SW1 is opened and at the same time the switch SW2 is closed, the charging voltage of the main capacitor Cb is opened.Then, the switch SW2 is opened and the switch SW3 is closed at the same time, and the charging voltage of the main capacitor Cc is turned on. At the same time as opening, the switch SW4 is closed to release the charging voltage of the main capacitor Cd, and the xenon lamp is issued.

This is shown in FIG. In FIG. 12, the vertical axis is the emission intensity, and the horizontal axis is time. Reference numerals 21 to 24 denote light emission times due to the discharge of the main capacitors Ca to Cd.

FIG. 13 shows the recording film temperature when flash light having such a light emission profile was irradiated. As shown in FIG. 13, at the same time as the maximum temperature is suppressed, the width of the waveform is widened, and favorable crystallization can be performed.

In this embodiment, the capacities of the main capacitors Ca to Cd were set to Ca = Cb = Cc = Cd = 12.5 mF, the applied voltage was set to 537 V, and the main capacitors Ca, Cb, and Cc were each discharged in 0.05 msec. Crystallization was sufficiently performed under these conditions, and no thermal damage to the substrate occurred.

(Example 7) Example 6, the energy E to store each capacitor (1 / 2CV ^2, C = capacitance, V = applied voltage) the By doing so, the same effect as in the sixth embodiment can be obtained.

That is, using the same xenon lamp driving circuit as shown in FIG.
= 12.5mF, Cb = 10mF, Cc = 7.5mF, Cd = 5mF, Example 6
After crystallization by the same algorithm as
The same effect as that of Example 6 was obtained.

As described above, the seven embodiments according to the present invention have been described with respect to the write-once phase change disk. However, it is needless to say that these embodiments can be applied to a rewritable phase change disk.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, the maximum temperature of the recording film due to flash irradiation can be suppressed, and
Since the holding time at a temperature higher than the crystallization temperature of the recording film can be lengthened, the crystallization of the recording film can be satisfactorily performed, and the thermal damage to the substrate can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an apparatus for carrying out the crystallization method of the present invention, FIG. 2 is a driving circuit diagram of a xenon lamp, and FIG. 3 is a characteristic of a time-emission intensity of a xenon lamp by the apparatus shown in FIG. FIG. 4, FIG. 4 is a characteristic diagram of time vs. recording film temperature by the apparatus of FIG. 1, FIG. 5 is a cross-sectional view showing an apparatus for implementing the crystallization method of the present invention, and FIG. FIG. 7 is a cross-sectional view showing another example of an apparatus for performing the method, FIG. 7 is a characteristic diagram of a time-emission intensity of a xenon lamp by the apparatus of FIG. 6, and FIG.
FIG. 9 is a cross-sectional view showing an apparatus for performing the crystallization method of the present invention. FIG. 9 is a characteristic diagram of time versus recording film temperature by the apparatus of FIG. 8, and FIG. 10 is time versus recording by the apparatus of FIG. Characteristic diagram of film temperature, FIG. 11 is a driving circuit diagram of a xenon lamp, FIG. 12 is a characteristic diagram of time-emission intensity of a xenon lamp flashed by the driving circuit shown in FIG. 11, and FIG. 13 is FIG. FIG. 14 is a characteristic diagram of time vs. recording film temperature due to a flash of a xenon lamp for explaining a conventional crystallization method. 3,13,18-20: Xenon lamp, 16: Recording medium, 17: Filter.

Claims (3)

(57) [Claims] 1. A method for crystallizing an optical information recording medium in which a recording film formed on a substrate of an optical information recording medium is crystallized at once, wherein the substrate is deformed to a temperature higher than a crystallization temperature. An optical information recording medium, characterized in that a plurality of flash lamps are sequentially emitted to irradiate the recording film with light beam energy so that the recording film is maintained at a temperature lower than the temperature for a time equal to or longer than the crystallization time of the recording film. Crystallization method. 2. An apparatus for crystallizing an optical information recording medium which collectively crystallizes a recording film formed on a substrate of an optical information recording medium, comprising: a plurality of light sources for irradiating the recording film with light beam energy; A flash lamp, and each of the flash lamps is sequentially illuminated at a time interval capable of holding the recording film at a temperature higher than its crystallization temperature and lower than a temperature at which the substrate is deformed for a time equal to or longer than the crystallization time of the recording film. An apparatus for crystallizing an optical information recording medium, comprising: a lamp driving circuit. 3. A method for crystallizing an optical information recording medium, wherein a recording film formed on a substrate of an optical information recording medium is collectively crystallized, comprising: applying an uncured ultraviolet curable resin onto the recording film; A flash lamp for irradiating the recording film with light beam energy emits light to simultaneously cure the ultraviolet curable resin and crystallize the recording film, and deform the recording film above the crystallization temperature to deform the substrate. A crystallization time of the optical information recording medium, wherein the crystallization time of the recording film is maintained at a temperature lower than a temperature at which the recording film is formed.