JPH02167780A - Information recording medium - Google Patents

Abstract

PURPOSE:To make possible the manufacture of a highly oxidation resistant, long-lived and highly sensitive recording film even under circumstances of high temperature and high humidity by forming a recording film containing (Au, Te100-x)ySez(2<=x<=47 atomic %, 80<=y<=95 atomic %, 5<=z<=20 atomic %) alloy as well as carbon and hydrogen on a substrate. CONSTITUTION:An information recording medium 18 consists of a substrate 13 and recording films 14 laminated on the substrate 13. The substrate 13 used is made of a transparent material, to which a laser beam is projected on the information recording medium 18. The recording film 14 is an Au-Te alloy to which carbon, or carbon and hydrogen are added. The percentage of Au in (Au, Te100-x)ySez alloy should be 2<=x<=47 atomic % so that bits are formed at a lower melting point than Te, according to a heat mode recording system. The size of bits becomes uniform and the part of a rim formed outside of the bits is reduced by adding Au. Thus a recording density can be increased. The recommendable range of Se composition is 5<=z<=20 atomic %.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an information recording medium on which information is recorded and reproduced by, for example, irradiation with laser light.

(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, tellurium (Te) is sputtered in an atmosphere containing hydrocarbon gas.

As a result, a recording film (hereinafter referred to as a Te-C film) having higher sensitivity and superior oxidation resistance than a film containing only Te (Te film) is obtained. This recording film is an amorphous film, and is tellurium (T).
e) contains carbon (C) and hydrogen (H), and it is known that at least carbon (C) and hydrogen (H) are chemically bonded. This recording film cannot be formed even if it is attempted to be formed by vapor deposition using tellurium (Te) and hydrocarbons as sources (without using plasma), following the Te film, and can only be obtained by using plasma. This is because after the hydrocarbon gas is decomposed in the plasma, carbon (C) and hydrogen (H) undergo a chemical reaction to form a film, and this is a major feature when forming an optical recording film. There is.

(Problems to be Solved by the Invention) A recording film made of Te and hydrocarbons as described above and a recording film made of tellurium (Te) were heated at 65°C and 90% high temperature and high humidity (under accelerated conditions). In comparison, the Te film was oxidized within just one week and the optical recording performance was impaired, whereas the Te--C film was stable without being oxidized to the inside of the film even after one month had passed. However, Te −
The C film also has the problem that at high temperatures (about 75° C. or higher), the recording film crystallizes and the surface becomes rough, increasing noise and increasing the influence on reproduced signals.

In order to solve the above-mentioned problems, the present invention provides an information recording medium that does not easily become rough even under high temperature and high humidity environments, has a long lifespan, and can obtain accurate reproduction signals. The purpose is to

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes a substrate, and a (Au*Te) film formed on the substrate and on which information is recorded by irradiation with a laser beam. roo-3) 5ex(2≦x
The present invention provides an information recording medium comprising a recording film containing an alloy (≦47 atom %, 80≦y≦95 atom %, 5≦2≦20 atom %) and a recording film containing carbon and hydrogen.

(Function) The recording film included in the information recording medium of the present invention stably maintains recorded information even under high temperature and high humidity conditions by containing Au Te Se alloy, carbon and hydrogen. , and an information recording medium with excellent recording sensitivity can be obtained.

(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 the structure of the information recording medium of the present invention. The information recording medium of the present invention is composed of a substrate 13 and a recording film 14 laminated on the substrate 13.

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,
Polyolefins, epoxy resins, etc. are used.

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

This recording film contains (Au, Te 100-
m) The composition range of Au in the Sea alloy is 2≦x≦47 atomic % so that bits are formed with a melting point lower than that of Te in the heat mode recording method. This A
By adding u, the pits are uniform in size and the rim portion formed on the outside of the pits is reduced, so that effects such as increased recording density can be obtained. Further, the composition range of Se is 5≦2≦20 atomic %. This means that, for example, the composition range of Se is 5 atomic%.
If it is less than 20 at %, the effect of improving oxidation resistance cannot be sufficiently obtained, and if it exceeds 20 at %, the optical absorption rate will decrease.

Furthermore, if the thickness of the recording film 14 is 1000 angstroms or more, it is not preferable because the writing sensitivity will decrease, and it is necessary to be 1000 angstroms or less, but preferably 500 angstroms or less, and more preferably 500 angstroms or less. The preferred range is 100 to 300 angstroms. As shown in FIG. 2, this means that the pulse width is 60 n5ecs and the linear velocity is 5. This is also clear from the writing sensitivity characteristics when the laser is incident from the PC board 12 side under the condition of 5 m 2 /see. Further, if the thickness is less than 100 angstroms, the recording film 14 itself becomes discontinuous and the probability of pinhole formation increases, which is not preferable. In the case of heat mode recording, this pinhole may not only be mistakenly detected as a bit when reading information, but also trigger oxidation of the recording film 14.

Next, the tolerance of the reproduction laser power (the power level at which reproduction can be performed without causing deterioration of the recording film 14) in the information recording medium 18 shown in FIG. 1 will be explained. The reproducing laser beam for reading information recorded as pits is usually a continuously oscillated laser beam. In this state,
In order to obtain a good S/N ratio and reproduce information, it is also necessary to increase the reproduction laser power. However, if this reproducing laser power exceeds a certain threshold, the pits may be destroyed and the level of the reproduced reflected light may decrease. Therefore, linear velocity 5. The information recording medium 18 rotating at 5 m/see is continuously held on the track formed on the information recording medium 18, the laser power of the reproduction laser beam is changed, and changes in the reflected light level are observed using a synchroscope. I observed it. The observation results are shown in Figure 3. Incidentally, the level of reflected light shown in FIG. 3 is normalized with the level immediately after reproduction as 1.

According to this observation result, even for a recording film with a film thickness of
With a laser power of 0.6 or 0.8 mW, the level of reflected light did not change for 3 hours.

However, when the laser power was set to 1 mW, the level of reflected light decreased within several hours. In this case, the smaller the film thickness, the greater the degree of decrease.

The allowable reproduction power of the write-once recording film, which is currently being standardized, is a rotational speed of 180 Orpm and a linear speed of 5.5a+/see.
In the case of
wax -0, 2+ O', 55 V. Here, V is the linear velocity of the information recording medium (m/5ee
) is shown. Furthermore, it is required that there should be no change in the level of reflected light even after 10 consecutive cycles of reproduction with P wax, but the rotation speed is 180 Orpm and the linear velocity is 5.
In the case of 51/see.

This means that it should not change for at least one hour. Therefore, under these conditions, the recording film 14 of the present invention, which does not change for up to 3 hours even with a power of 0.8 mW, satisfies these requirements.

Example 1 First, a method for forming the information recording medium 18 shown in FIG. 1 will be described.

FIG. 4 is a schematic diagram of a sputtering apparatus for forming the information recording medium 18 of the present invention. First, open the valve 2 of this sputtering device to the rotary pump 3 side, and make the inside of the chamber 1 zero.
．． It was evacuated to 2 Torr.

Next, open valve 2 to the cryopump 5 side and
It was evacuated to below 10-'Torr. At this time, since there was no need to control the displacement, the conductance valve 4 was left fully open.

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

After confirming that this pressure does not fluctuate,
Alloy target 9 (diameter 5 inches, two compositions A u +2
T ess ; atomic%), DC power supply 10
A power of 100 W was applied from 100 W to 100 W, and sputter discharge was performed for 5 minutes with the shutter 11 closed to perform sputter cleaning.

After stopping the supply of Ar gas and the supply of DC power, the inside of the chamber 1 is temporarily heated to I
The exhaust was evacuated to below Torr. After that, open the valves 6.17 and 25, and introduce Ar gas, CH4 gas, and Se (CH3)2 gas into the chamber 1 through the A gas line 7, the CH4 gas line 8, and the 5e (CHi)2 gas line 26, through the mass flow controller. (not shown), 10, 10 and 5 SCCM were introduced respectively. Next, the pressure inside the chamber 1 was controlled to 5XIO-Torr using the conductance valve 4. Thereafter, it was confirmed that there was no pressure fluctuation. After checking, add DC to Au Te target 9.
A power of 100 W was applied from the power supply 10 to cause sputter discharge. After confirming that the discharge is stable, open the shutter 11 and place the Au Te
A recording film 14 containing an alloy, carbon, and hydrogen was laminated. Rotor 12 was rotated at 60 rpIll. When the thickness of the recording film 14 reached 250 angstroms, the shutter was closed and power supply was stopped. Next, the conductance valve 4 is fully opened, and the cryopump 5 is opened.
The inside of the chamber 1 was evacuated to below I.times.10-' Torr. Thereafter, the valve 15 was opened and N2 gas was introduced into the chamber 1 from the N2 gas line 16 to return the pressure to atmospheric pressure, and then the information recording medium 18 was taken out.

Recording film 1 of information recording medium 18 formed in this way
As a result of X-ray diffraction analysis, Sample No. 4 was confirmed to be an amorphous film in which no diffraction peak was observed from a specific diffraction angle. Unlike a polycrystalline film, this amorphous film does not have grain boundaries, so that the reproduced laser light is not modulated at the grain boundaries and does not generate grain boundary noise.

In order to include the Au Te Se ternary alloy, carbon (C), and hydrogen (H) in the recording film 14, an Au Te Se alloy target is sputtered in a hydrocarbon gas, or an Au Te Se alloy target is sputtered in a hydrocarbon gas.
Rather than sputtering a Te alloy target in an alkyl selenium gas, an Au 2 Te alloy target is sputtered in an atmosphere containing a hydrocarbon gas and an alkyl selenium gas. According to this sputtering method, the amount of selenium (Se 2 ) in the recording film can be easily controlled by adjusting the flow rate of the selenium-containing gas, and the amount of carbon and hydrogen in the recording film 14 can also be controlled by controlling the amount of selenium (Se 2 ) in the recording film 14. This can be easily controlled by adjusting the hydrocarbon gas flow rate without relying solely on gas decomposition. Also, gold (Au), tellurium (Te)
It is not necessary to use a target consisting of the three components of selenium (Se) and selenium (Se), and it is also possible to prevent compositional deviation of the recording film due to continuous sputtering of the target.

Implementation flj 2 Information recording medium 1 manufactured by the method shown in Example 1
8, the ratio of read errors (error rate) resulting from surface roughness due to oxidation, which is an index of oxidation resistance, was analyzed. The information recording medium 18 containing the Te film and Te-C film having the same film thickness as shown in Example 1 and the recording film 14 of the present invention was left for a certain period of time under accelerated conditions of 75° C. and 90%. After that, information was written and the error rate was measured. The results are shown in FIG. The error rate shown in this figure was normalized by setting the value before the acceleration condition to 1. According to the measurement results, the error rate of the Te film increased in just a few days.

In the Te-C film as well, it gradually increased after 100 hours. On the other hand, the recording film 14 of the present invention showed almost no change even after being left for 1000 hours. Therefore, it can be seen that the recording film 14 of the present invention has good oxidation resistance even under high temperature and high humidity, and has a long life. Note that this recording film 14
was an amorphous film when X-ray diffraction analysis was performed after this measurement.

Next, pulse width 50n5ecs write frequency 37MH
2. Using a GaAs semiconductor laser with a wavelength of 830 ni,
Objective lens numerical aperture (NA) 0.52, linear velocity 5°5i/
Under the conditions of see, Te-C film and AuTe 5e-C
C/N (Carrler/N o
The size of the ise) was analyzed. The detection results are shown in FIG. According to the analysis results shown in FIG. 6, it can be seen that the recording film 14 of the present invention has higher sensitivity than the conventional Te--C film.

In addition, in the embodiment described above, the information recording medium 1
As a manufacturing method of No. 8, we have explained the case where the AuTe target is sputter-discharged in a mixed atmosphere of hydrocarbon gas (methane), alkyl selenium gas (Se (CHi) 2), and rare gas (argon), but this is not necessarily the case. For example, the discharge may be performed in an atmosphere that does not contain a rare gas.

Furthermore, in the information recording medium of the present invention, a transparent organic resin substrate was used as the substrate 13 in the explanation;
When the information writing and reproducing laser beam is made incident not from the substrate 13 side but from the recording film 14 side, the substrate 13 may be formed of an opaque material.

[Effects of the Invention] As described above, the present invention can provide an information recording medium having a recording film that has excellent oxidation resistance, long life, and high sensitivity even in a high temperature and high humidity environment.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an information recording medium that is an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between recording film thickness and writing sensitivity.
Fig. 3 is a diagram showing changes in playback time and reflection level, Fig. 4 is a diagram showing the configuration of an optical recording film forming apparatus for forming the information recording medium shown in Fig. 1, and Fig. 5 is a diagram showing recording after undergoing acceleration conditions. FIG. 6 is a diagram showing the error rate of the film, and FIG. 6 is a diagram showing the recording sensitivity of the recording film. 13...Substrate, 14...Recording film 18・
・・・ Information recording medium

Claims (1)

[Claims] (1) A substrate, (Au_xTe_1_0_0_-_x)_y formed on this substrate and on which information is recorded by irradiation with laser light.
Se_z (2≦x≦47 atomic%, 80≦y≦95 atomic%
, 5≦z≦20 atomic %) alloy, and a recording film containing carbon and hydrogen.