JPH02167784A - Information recording medium - Google Patents

Abstract

PURPOSE:To make it possible to increase amorphous stability, crystallization speed, the stability of an amorphous recording mark and perform initialization, recording and deletion at high speed by forming a recording layer of an alloy of composition such as expressed by InxSbyTez. CONSTITUTION:An information recording medium consists of a protective layer 3, a recording layer 2, a protective layer 4 and a protective layer 5 formed on a substrate 1 in that order. The recording layer 2 is composed of an alloy expressed by InxSeyTez (x,y,z are atomic %, x+y+z=100). These x,y,z are set so that the crystallization temperature of this alloy is higher than 130 deg.C. The alloy of this composition is a material which changes between a crystal phase and an amorphous phase due to the change of conditions for a projected light beam, and is characteristic of significant crystallization speed. Consequently, it is possible to accelerate initialization, recording and deletion. The protective layers 3,4 protect the recording layer 2 against any adverse effect of moisture in the air and the protective layer 5 protects the information recording medium against possible damage or dust settlement on the surface.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) This invention provides information by irradiating a recording layer with a light beam such as a laser beam and inducing a phase change in the irradiated area depending on the irradiation conditions. The present invention relates to an information recording medium that reproduces information by recording and erasing information and detecting changes in optical properties such as reflectance and transmittance accompanying this phase change. Examples of such information recording media include optical discs and optical cards.

(Prior Art and Problems to be Solved by the Invention) Phase change type media have been widely known as information recording media from which information can be erased, such as so-called erasable optical discs. This phase change type information recording medium includes, for example, a substrate made of glass or plastic (polycarbonate resin, polymethyl methacrylate resin, etc.) and a recording layer formed on the substrate. Chalcogenide alloys such as GeTe are known as materials for forming this recording layer, and these alloys can be used for light beams under different conditions (
By irradiating it with a laser beam (for example, a laser beam), the phase changes reversibly between crystal and amorphous, so this phase change is used to record and erase information, and the reflectance associated with these phase changes is Alternatively, information can be read using changes in optical characteristics such as transmittance.

As such a recording layer, a material having a eutectic composition or a material forming an intermetallic compound that easily undergoes a phase change depending on the irradiation conditions of the light beam is suitable.

However, although alloys such as GeTe that have been conventionally used as the recording layer of phase change information recording media satisfy the above conditions, it cannot be said that they still have sufficient properties as information recording media. . In particular, it is desired to speed up initialization, recording, and erasing. Also, crystal-
When recording or erasing information through a phase change between amorphous states, the recorded portion usually becomes amorphous, but since amorphous states generally have relatively low stability, it is necessary to make the amorphous state more stable. It is also required to do so.

This invention was made in view of such circumstances, and
An object of the present invention is to provide an information recording medium that has excellent stability and can perform initialization, recording, and erasing at high speed.

[Structure of the Invention] (Means for Solving the Problems) An information recording medium according to the present invention comprises a substrate and a light beam irradiated by the irradiated portion (where the irradiated portion changes phase between a crystalline phase and an amorphous phase). An information recording medium having a recording layer, the recording layer being formed of an alloy having a composition represented by InxSbyTez (where x, y, and z are atomic percent, and x, 10, y + z - 100). , these x, y, and z are set so that the crystallization temperature of the alloy is higher than 130°C.

(Function) The In x S by T e z alloy is a material that satisfies the conditions for the recording layer of the phase change recording medium as described above, and has a high crystallization rate. By adjusting the alloy composition so that the crystallization temperature is higher than 130° C., the amorphous portion stably exists. Therefore, it has excellent stability and can speed up initialization, recording, and erasing.

(Example) Hereinafter, the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a sectional view showing an information recording medium according to an embodiment of the invention. The substrate 1 is made of a material commonly used in this technical field, such as a plastic such as polyolefin, epoxy, polycarbonate (PC), polymethyl methacrylate (PMMA), or glass. On this substrate 1, a protective layer 3, a recording layer 2, a protective layer 4, and a protective layer 5 are formed in this order.

The protective layer 3 and the protective layer 4 are disposed to sandwich the recording layer 2, and are made of an organic polymer material, such as a thermoplastic resin such as PMMA or polystyrene, or an ultraviolet curing resin (see 17).
2P resin) or 5i02, A1203, AIN, Zn
It is formed of a dielectric material such as S or ZrO2. These protective layers 3 and 4 serve to prevent the recording WI 2 from being affected by moisture in the air, and to prevent the irradiated portion of the recording layer 2 from being scattered by a light beam such as a laser beam during recording or erasing. It has the effect of preventing holes from being formed. These protective layers 3 and 4 can be suitably formed by a spin coating method, a vapor deposition method, a sputtering method, or the like. Note that the thickness of these protective layers 3.4 is preferably 10 to several tens of μm.

The protective layer 5 is provided to prevent scratches, dust, etc. on the surface when handling the information recording medium, and is coated with an ultraviolet curing resin using a spin code method or the like, and then cured by irradiating it with ultraviolet light. It is formed by such things as This protective layer 5
The layer thickness is preferably 100λ to several tens of μm.

Although it is preferable to provide the protective layer 3°4.5, it is not necessary to provide it.

The recording layer 2 is made of InxSbyTez (X.

Vr" is atomic % and is x+y+z-100), and this X.

Vr z is set such that the crystallization temperature of this alloy is greater than 130°C. Note that this crystallization temperature is measured, for example, by setting the heating temperature to 10° C./min. An alloy having such a composition is a material that can undergo a phase change between crystalline and amorphous by changing the conditions of the irradiated light beam, and is characterized by a high crystallization rate. Therefore, initialization, recording, and erasing can be performed at high speed.

Furthermore, since the crystallization temperature is 130° C. or higher as described above, the amorphous state is highly stable.

This recording layer 2 can be suitably formed by a vapor deposition method, a sputtering method, or the like. Note that when performing vapor deposition or sputtering using an alloy target, it is necessary to take into account that there is a difference between the target composition and the composition of the film actually formed. Further, the film can also be formed by multi-source simultaneous vapor deposition, multi-source simultaneous sputtering, or the like. The thickness of the recording layer 2 is preferably 100 to 3000 Å.

Next, an example of a method for forming the recording layer of the information recording medium according to this embodiment will be explained with reference to FIGS. 2 and 3. FIG. 2 is a longitudinal cross-sectional view showing a schematic configuration of a sputtering apparatus used to form the recording layer of this embodiment, and FIG. 3 is a cross-sectional view thereof. In the figure, 10 indicates a vacuum vessel, and this vacuum vessel 10 has a gas introduction boat 1 on its bottom surface.
1 and a gas discharge boat 12. The gas exhaust boat 12 is connected to an exhaust device 13, and the inside of the vacuum container 10 is evacuated by the exhaust device 13 via the exhaust boat 12. Further, the gas introduction boat 11 is connected to an argon gas cylinder 14, and argon gas as a sputtering gas is introduced from the cylinder 14 into the vacuum vessel 10 via the gas introduction boat 11. Vacuum container 10
A disk-shaped rotating base 15 for supporting a substrate is placed in the upper part thereof with its surface horizontally, and the substrate 1 is supported on the lower surface thereof and is rotated by a motor (not shown). ing. Furthermore, near the bottom of the vacuum chamber 10, sputtering sources 21, 22, and 23 made of In, Sb, and Te, respectively, are arranged so as to face the base 15. A high frequency power source (not shown) is connected. These sputtering sources 21.22
The information at ゜23 is provided with monitor devices 24, 25゜26, respectively, and these monitor devices monitor the amount of sputtering from each sputtering source, and adjust the amount of sputtering to each sputtering source so that the recording layer has a predetermined composition. The amount of electricity input is adjusted.

In such a sputtering apparatus, first, the inside of the vacuum container 10 is evacuated to, for example, 10-6 Torr using an exhaust device. Next, while introducing argon gas into the container 10 through the gas introduction bow 111, the exhaust amount of the exhaust device 13 is adjusted to maintain the inside of the vacuum container 10 in an argon gas atmosphere at a predetermined pressure. In this state, while rotating the substrate 1, a predetermined power is applied to the sputtering sources 21, 22, and 23 for a predetermined time. As a result, sputtering is performed, and a recording layer having a predetermined composition is formed on the substrate 1. In addition,
When forming a protective layer, prior to forming the recording layer 2,
Similar to the case of forming the protective layer 3 on the substrate 1 by sputtering as described above using a sputtering source adjusted to the composition of the protective layer, then forming the recording layer 2, and then forming the protective layer 3. The protective layer 4 can be formed on the recording layer 2 under the following conditions.

Next, initialization, recording, erasing, and reproduction of information in the information recording medium of the present invention will be explained.

The initialization recording layer 2 is normally amorphous immediately after film formation, but it needs to be crystalline in order to record information, so the recording layer 2 is heated and slowed by irradiating the entire surface of the recording layer 2 with a light beam such as a laser beam. Cool and crystallize the recording layer 2.

A light beam with high recording power and short pulse width is irradiated onto the recording layer 2,
The irradiated area is heated and rapidly cooled to change its phase to an amorphous state, thereby forming a recording mark.

A light beam having a lower output and a longer pulse width than that used during recording is irradiated onto the recording mark portion formed on the erasing recording layer 2 to change the phase of the recording mark portion into a crystal, thereby erasing information.

A relatively weak light beam is irradiated onto the recording layer 2 on which reproduced information has been recorded, and the information is read by detecting the difference in optical characteristics, such as reflectance, between the recorded mark portion and the non-recorded portion.

In addition, since the information recording medium according to the present invention has a high crystallization speed, overriding is possible. Oval light is a light beam such as a laser beam emitted from a single light source, which is power-modulated between two power levels PE (erase) and Pw (record) as shown in Figure 4. This method involves superimposing pulses at a recording power level on a light beam at an erasing power level to overwrite new information while erasing previously recorded information.

Next, in In x S b y T e z,
The results of understanding compositions with crystallization temperatures exceeding 130°C will be explained.

In-5b-Te alloys of various compositions were formed on glass substrates using the apparatus shown in FIGS. 2 and 3, and the structures of the films were confirmed by X-ray diffraction. As a result, in the In-3b-TeB original composition shown in FIG. 5, an amorphous thin film can be obtained in the region indicated by monoclinic lines, and can be used as a phase-change recording layer. was confirmed.

The crystallization temperature of the amorphous sample in the above test was measured using a high-sensitivity differential scanning calorimeter (DSC). Since the crystallization temperature varies slightly depending on the temperature increase rate during measurement, this temperature increase rate was fixed at 10° C./min. As a result, the crystallization temperature is 130° C. or higher in the double hatched region in FIG. 5, that is, in a limited composition range of about 70 at % or less Te, 80 at % or less sb, and 60 atomic % or less in,
It was confirmed that the stability of the amorphous state is high.

Next, test examples of the present invention will be explained.

In-3b- was deposited on a glass substrate in the same manner as the above test.
Five samples A to H were prepared with Te alloy thin films formed thereon. The thin film compositions of these samples are shown in Table 1.

Table 1 For these samples, laser beams of various pulse widths were focused and irradiated onto the alloy thin film from the substrate side at a constant intensity using an objective lens, and the relationship between the pulse width and the change in reflectance of the irradiated area was determined. The results are shown in FIG. Figure 6 is a graph showing the relationship between the pulse width of the irradiated laser beam on the horizontal axis and the change in reflectance on the vertical axis, and is shown for the case where the laser beam power is 3 mW. be. As confirmed from this figure, it was confirmed that the change in reflectance occurred in 1 μsec or less in all samples. Since the change in reflectance corresponds to a phase change from amorphous to crystalline, this result indicates that the rate of crystallization of these samples is extremely high.

Such a tendency was similarly confirmed in other In-8b-Te alloys having compositions in which the heating rate during measurement was within the range of 10° C./min.

As explained above, In-5b-Te alloys with a composition range in which the crystallization temperature is 130°C or higher are capable of phase change between crystalline and amorphous states, and are stable in the amorphous state. Furthermore, it was confirmed that the crystallization rate was high.

[Effects of the Invention] According to the present invention, since the B layer is formed of an In-8b-Te alloy having a crystallization temperature of 130° C. or higher, the amorphous stability is high and the crystallization rate is high. . Therefore, it is possible to obtain an information recording medium with extremely excellent properties such as excellent stability of amorphous recording marks and the ability to perform initialization, recording, and erasing at high speed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an information recording medium according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view showing a schematic configuration of an apparatus for forming a recording layer, and FIG. Figure 4 shows the power of the laser beam during override, Figure 5
The figure shows the composition range in which the In-5b-Te ternary alloy can become amorphous and the composition range in which the crystallization temperature is higher than 130°C. Figure 6 shows the pulse width of the irradiated laser beam and the amount of change in reflectance. It is a graph diagram showing the relationship between. 1; Substrate, 2; Recording layer, 3, 4, 5. protective layer.

Claims (1)

[Claims] An information recording medium comprising a substrate and a recording layer whose irradiated portion changes phase between a crystalline phase and an amorphous phase by irradiation with a light beam, the recording layer comprising In_xSb_yTe_z
(However, x, y, z are atomic %, x+y+z=1
00), and x, y, and z are set such that the crystallization temperature of the alloy is higher than 130°C.