JPH02147389A - Information recording medium - Google Patents

Abstract

PURPOSE:To obtain an information recording medium which maintains recorded information stably and has excellent recording sensitivity by providing a recording film comprising an Au-Te alloy, carbon and hydrogen, on a substrate, and a dielectric film on the recording film. CONSTITUTION:An information recording medium 18 comprises a substrate 13 and a recording film 14 provided thereon. The recording film 14 comprises an Au-Te alloy, carbon and hydrogen. When Au is contained in an amount of 2-50atom%, recording of information is achieved by utilizing a phase change between an aggregated state and a dispersed state of clusters caused by heat generation upon irradiation with a laser light. When a writing laser power for the recording film reaches or exceeds 10mW, the aggregation of cluster components is accompanied by formation of a pit, which hinders accurate reproduction of information. To prevent the pit formation, a dielectric film 20 is provided on the recording film 14.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to writing information by a phase change caused by irradiation with a laser beam, for example, and to change the amplitude of the laser beam due to the phase change of the component. The present invention relates to an information recording medium in which the information is read through changes in the information.

(Prior Art) As a type of information recording medium, information is recorded by irradiation with laser light and the recorded information is reproduced.
A device equipped with a recording film containing Te as a main component has been developed. Furthermore, a recording film containing carbon and hydrogen in addition to the Te-based recording film has been developed and put into practical use (see Japanese Patent Laid-Open No. 58-9234).

When creating this recording film, Te is sputtered in an atmosphere containing hydrocarbon gas. Then, a film of simple Te (T
A recording film (
A Te-C film (hereinafter referred to as Te-C film) is obtained. This recording film is
It is known that it is an amorphous film and contains Te, C, and H, and that at least C and H are chemically bonded.

This recording film cannot be formed by vapor deposition using Te and hydrocarbon as sources (without using plasma), as in the case of the Te film. This is because a film is formed by a chemical reaction between C and H after the hydrocarbon gas is once decomposed in the plasma, and this is a major feature when forming an optical recording film.

(Problems to be Solved by the Invention) When a recording film made of Te and hydrocarbons as described above is compared with a recording film made of Te at a high temperature and high humidity of 65° C. and 90% (accelerated conditions), Te The film oxidizes within just one week and optical recording performance is impaired, whereas Te-C
The membrane remained stable without being oxidized even after one month.

However, the recording film of the Te-C film also crystallizes at high temperatures (above about 75 degrees Celsius), resulting in a rough surface that increases noise and has a greater effect on the reproduced signal. .

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide an information recording medium that has a long life even in a high temperature and high humidity environment.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes a substrate and a device on which information is recorded by undergoing a phase change by irradiation with a laser beam. Au x Te roo
-x (2≦x≦50 atomic %) alloy and a recording film containing carbon and hydrogen.

Further, in a second aspect of the invention, there is provided a substrate, and an AuxTel formed on the substrate, in which information is recorded by undergoing a phase change by irradiation with a laser beam. ox(2≦x
The present invention provides an information recording medium characterized by comprising a recording film containing a carbon and hydrogen (≦50 atomic %) alloy, and a dielectric film formed on the recording film.

(Function) In the present invention, the optical recording film of the present invention uses an AuTe alloy and can maintain a stable surface state even under high temperatures. , it is possible to provide an information recording medium that stably maintains recorded information and has excellent recording sensitivity even under high temperature and high humidity conditions.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing an information recording medium 18 having a two-layer structure, which is an embodiment of the present invention. The information recording medium 18 of the present invention includes a substrate 13 and this substrate 13.
It is composed of a recording film 14 laminated thereon.

The substrate 13 is made of a material that is transparent to the laser beam irradiated onto the information recording medium 18 for recording and reproducing information. For example, when using a laser beam with an oscillation wavelength near infrared, polycarbonate (PC),
Polymethyl methacrylate (PMMA), glass, polyolefin, epoxy resin, etc. are used.

The recording film 14 is made of an Au-Te alloy containing carbon and hydrogen.

If there is a difference in the reflectance of the cluster components dispersed in the C-H matrix between agglomeration and dispersion, for example, cluster dispersion can be considered as an information-free state, and cluster aggregation can be considered as an information-recorded state. By making them correspond, information can be recorded. Aggregation of clusters can be caused by heat generation due to laser irradiation. When Te is used as a single substance, the difference in reflectance between aggregation and dispersion is not so large. but,
A difference may be observed when a component capable of forming an alloy with this is added. In the present invention, it has been found that this effect is remarkable when 2 to 50 atomic % of Au is added.

That is, a recording film containing 2 to 50 atomic percent of Au records information by utilizing phase changes such as the agglomerated state and the dispersed state of clusters.

In the information recording medium according to the present invention, information is recorded using the difference in reflectance before and after the phase change, but the difference in reflectance before and after recording is generally caused by the thickness of the recording film being at an extreme value due to interference. It becomes larger when it is near the given object. Therefore, the film thickness of the recording film 14 according to the present invention is determined considering that the interference effect becomes smaller as the film thickness increases and converges to a constant reflectance, and that the laser power during recording increases as the film thickness increases. 5,000 or less.

Example 1 First, a method for forming the information recording medium shown in FIG. 1 will be described.

FIG. 2 is a schematic diagram of a sputtering apparatus for forming the recording film 14 of the present invention. First, open the valve 2 of this sputtering device to the rotary pump 3 side and apply 0.2T inside the chamber 1.
Exhausted to orr. Next, the valve 2 was opened to the cryopump 5 side, and the temperature was evacuated to 1×10 −′ Torr or less.

At this time, since there was no need to control the displacement, the conductance valve 4 was left fully open.

Next, valve 6 was opened, and IO8CCM was introduced into chamber 1 while adjusting Ar gas from A gas line 7 using a mass flow controller (not shown).Then, the pressure inside chamber 1 was measured using an ion gauge (not shown). 5 x 10-' with conductance valve 4 while monitoring with
Adjusted to Torr.

After confirming that this pressure does not fluctuate,
Alloy target 9 (5 inches in diameter: composition is Au IIT
O6? ; atomic%) to DC power supply 10 to 100
Sputter cleaning was performed by applying W and performing sputter discharge for 5 minutes with the shutter 11 closed.

After stopping the supply of Ar gas and the supply of DC power, the inside of the chamber 1 was once
-'Torr or less. Thereafter, valves 6 and 17 are opened, and Ar gas and CH4 gas are introduced into chamber 1 through Ar gas line 7 and CH4 gas line 8 while being controlled by a mass flow controller (not shown).
introduced one by one. Next, the pressure inside the chamber 1 was controlled to 5×10-'Torr using the conductance valve 4. After confirming that there is no pressure fluctuation, Au Te
100 W was applied to the target 9 from the DC power supply 10 to cause sputter discharge. After confirming that the discharge is stable, open the shutter 11 and close the rotor 12 in advance.
A recording film 14 containing an AuTe alloy and carbon and hydrogen was laminated on a PC board 13 that had been set in a PC board. The rotor was rotated at 60 rpm.

When the film thickness reached 1000 angstroms, the shutter was closed and power supply was stopped.

Next, the conductance valve 4 was fully opened, and the inside of the chamber 1 was evacuated to 1×10 −′ Torr or less using the cryopump 5 . Next, the valve 15 was opened, N2 gas was introduced into the chamber 1 from the N2 gas line 16, the pressure was returned to atmospheric pressure, and the medium 18 was taken out, thereby forming the information recording medium shown in FIG. 1.

As a result of X-ray diffraction analysis, it was confirmed that the recording film 14 thus obtained was an amorphous film in which no diffraction peak was observed from a specific diffraction angle.

Unlike polycrystalline films, amorphous films do not have grain boundaries, so
The reproduced laser beam is not modulated at the grain boundary portion and no grain boundary noise is generated.

When the recording film 14 containing Au Te s C and H obtained by the above method has a film thickness of 1000 Å, the reflectance reaches a minimum value due to the multiple interference effect, as shown in FIG. 3. Therefore, by changing the phase from an amorphous state (dispersed state) to a crystalline state (agglomerated state!B) at this film thickness, a significant increase in reflectance can be observed, and information can be recorded. Become.

In the above embodiments, a transparent organic resin substrate was used, but the substrate may be opaque if the writing and reproducing laser beams do not pass through the substrate and are incident on the recording film side.

Example 2 By the method shown in Example 1, A 1137T e b
A recording film containing S, C and H of 250 angstroms,
A film was formed on a PC substrate, and the linear velocity was 5.5 nm under the conditions of a rotational speed of 180 rpm, a recording frequency of 3.7 MHz, and a recording pulse width of 5 n5ee. When writing with a laser power of 7mW at a location corresponding to 5s/sec, 30dB
Good C/N (Carr1er/Nolse
) obtained the ratio.

Example 3 In the recording film having a thickness of 250 angstroms according to the present invention, when the writing laser power is 101 W or more, not only cluster components but also bits may be formed. This bit formation hinders accurate information reproduction during information reproduction. Therefore, in order to prevent this bit formation, as shown in FIG. 4, a multilayered information recording medium is formed in which a dielectric film 20 having a thickness of 300 to 1000 angstroms is laminated on a recording film 14. As this dielectric film 20, 8102, SI O, Al5SI
N etc. can be used. In addition, this dielectric film 2
It is desirable that the film thickness of 0 is in the range of 300 angstroms to 1000 angstroms. for example,
If the film thickness is less than 300 angstroms, pinholes may occur. This is also because when the thickness exceeds 1000 angstroms, the film forming time becomes longer.

In an information recording medium with such a three-layer structure,
The minimum value of the reflectance due to the multiple interference effect changes depending on the refractive index and film thickness of each dielectric.

Further, as shown in FIG. 5, this dielectric film 20
3 and the recording film 14 are bonded together via the adhesive layer 19, the back surface of the recording film 14 is bonded to the adhesive layer 1.
It also plays a role of protection from 9.

In the present invention, since information is recorded using phase change, two media provided with recording films can be directly bonded to each other. Furthermore, since information is recorded using phase change, the melted portion that is irradiated with laser light does not form a rim (bulge) due to interfacial tension at the substrate interface. That is, only a difference in reflectance occurs in the recording film, and so-called marking portions and non-marking portions are clearly formed, so that scattering of the read laser beam by the rim, which occurs in the case of bit formation, does not occur. Furthermore, since no rim is generated, it is possible to record high-density information by narrowing the bit interval.

Example 4 In Example 1, the flow rate ratio Q (Q-(X/(X0Y))X100%) was 50%, where the flow rate of hydrocarbon gas was X1 and the flow rate of rare gas was Y. however,
When Q is increased, the transmittance of the film increases, resulting in optical absorption A (A-1-R-T; R is reflectance, T is transmittance)
As a result, the laser power during recording must be increased.

Therefore, if the flow rate ratio Q is set to 5≦Q≦50%, the optical absorption rate will not decrease due to too much C and H. Also, if it is within the above Q value range, A that does not include C and H
The degree of change in reflectance under high humidity is smaller than that of a film made of a single u Te alloy, and it has a longer lifespan.

Therefore, according to the method of Example 1, the flow rate ratios Q-5 and 5
FIG. 6 shows the reflectance of a 250 mm thick recording film containing AuTe formed under 0.096. That is, in the atmosphere (6
At 5°C - 90%), the reflectance of the Te single film and the Au Te single film (Q-0) immediately decreases due to oxidation, but the records formed under the flow rate ratios Q-5 and 50% The film was extremely stable even in this atmosphere (65° C.-90%) with no significant change for 1000 hours.

The reflectance is normalized by setting the reflectance immediately after film formation to 1.

This means that it can be formed on organic resin substrates such as PC and PMMA that are relatively permeable to oxygen and water without using a dielectric protective film. The optical recording sensitivity is better when the film is formed on an organic resin substrate with low thermal conductivity than when it is formed on a glass substrate. Therefore, according to the present invention, it is possible to obtain an information recording medium with high optical recording sensitivity.

Example 5 Next, as shown in FIG. 8, an information recording medium 7° having a structure in which a dielectric film 71 was provided above and below a recording film 64 was manufactured.

FIG. 7 is a schematic diagram of a sputtering apparatus for forming this information recording medium 70. First, the valve 52 of this sputtering device is opened to the rotary pump 53 side, and the chamber 5 is opened.
1 was evacuated to 0.2 Torr. Then valve 52
Open it to the cryopump 55 side and attach IX10-'To
Exhausted to below rr.

At this time, since there was no need to control the displacement, the conductance valve 54 was left fully open.

Next, open the valve 56 and use Ar from the Ar gas line 57.
IO8CCM was introduced into the chamber 51 while controlling the gas with a mass flow controller (not shown). Next, while monitoring the press-fit inside the chamber 51 with an ion gauge (not shown), the conductance valve 54
It was adjusted to 10-3 Torr. After confirming that this pressure does not fluctuate, the RF power supply 78
300 W was supplied to the O2 target 79. The shutter 80 was closed for 5 minutes to perform sputter cleaning on the surface of the 8102, and then the shutter 80 was opened and the St 02 film 71 was laminated on the PC board 63 that had been set on the rotor 62 in advance. The rotation speed of the rotor 62 was maintained at 60 rpm during film formation.

After the film was formed to a thickness of 1000 angstroms, the shutter 80 was closed to stop the discharge. Furthermore, the gas supply is stopped and the inside of the chamber 51 is pumped with the cryopump 65.
It was evacuated to below 10-'Torr.

Next, a recording film 64 containing A u T e SC and H was formed as follows.

First, open the valve 56 and use Ar from the Ar gas line 57.
i105cC was introduced into the chamber 51 while adjusting the gas with a mass flow controller (not shown). Next, while monitoring the pressure inside the chamber 51 with an ion gauge (not shown), the conductance valve 54
It was adjusted to 10-' Torr. After confirming that this pressure does not fluctuate, 100 W is applied from the DC power supply 60 to the Au-Te alloy target 59 (diameter 5 inches, composition is Au 37 Te 63; atomic %),
Sputter cleaning was performed by performing sputter discharge for 5 minutes with the shutter 61 closed.

A: After stopping the gas supply and DC power supply, use the cryopump 55 to temporarily pump the inside of the chamber 1
It was evacuated to below 0-'Torr. Then valves 56 and 6
7 and put Ar gas and CH4 gas into the chamber 51.
Ar gas line 57 and CH.

IO5CCM was introduced at a time through gas line 58 while being controlled by a mass flow controller (not shown). Next, the chamber 51 is opened using the conductance valve 54.
The pressure inside was controlled at 5 x 10-'Torr. After confirming that there is no pressure fluctuation, the Au Te target 5
9 was applied with 100 W from a DC power supply 60 to cause sputter discharge.

After confirming that the discharge was stable, the shutter 61 was opened, and a recording film 64 containing a CuTe alloy, carbon, and hydrogen was laminated on the 5102 film 71 that had been laminated previously.

When the film thickness reached 1000 angstroms, the shutter was closed and power supply was stopped. Next, the conductance valve 54 was fully opened, and the inside of the chamber 51 was evacuated to below I.times.10-' Torr using the cryopump 55.

Next, in exactly the same manner as in the case of forming the 810□ film, RF power was supplied to the St02 target 80 in an Ar gas atmosphere to deposit the SIO□ film 71 on the recording film 64 to a thickness of 1000 angstroms. . After forming the SiO□ film,
Gas in chamber 1 is pumped by cryopump 55.
Evacuate to below 0-'Torr. Next, open the valve 65 and supply N/2 gas from the N2 gas line 66 to the chamber 5.
1 and returned to atmospheric pressure, the information recording medium 70 was taken out.

That is, as the structure is schematically shown in FIG.
An information recording medium 70 can be obtained, which is composed of a substrate 63, a dielectric film 71, a recording film 64, and a dielectric film 71 sequentially laminated on the substrate 63.

In the information recording medium 70 of this example, the dielectric film 71 was provided not only at the interface between the recording film 64 and the substrate 63 but also on the side in contact with air, so that it had extremely excellent oxidation resistance.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an information recording medium that has a long life even in a high temperature and high humidity environment and has a highly sensitive recording film.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the structure of an information recording medium according to an embodiment of the present invention, Fig. 2 is a sputtering apparatus for manufacturing the integrated information recording medium of the present invention, and Fig. 3 is a reflection due to multiple interference effect. Figures 4, 5 and 8 are cross-sectional views showing the structure of an information recording medium according to another embodiment of the present invention, and Figure 6 shows changes in information reproduction time and reflection level. FIG. 7, which is a diagram showing changes, is a sputtering apparatus for manufacturing an information recording medium according to another embodiment of the present invention. 13, 63... Substrate 14, 64... Recording film 20, 71... Dielectric film

Claims (2)

[Claims] (1) A substrate, Au_xTe_ which is formed on this substrate and on which information is recorded by undergoing a phase change by irradiation with laser light.
An information recording medium comprising: a recording film containing a 1_0_0_-_x (2≦x≦50 atomic %) alloy and carbon and hydrogen. (2) A substrate, Au_xTe_ which is formed on this substrate and on which information is recorded by undergoing a phase change by irradiation with laser light.
An information recording medium comprising: a recording film containing a 1_0_0_-_x (2≦x≦50 atomic %) alloy, carbon and hydrogen; and a dielectric film formed on the recording film.