JPH02167778A - Information recording medium - Google Patents

Abstract

PURPOSE:To make possible the manufacture of a recording film which demonstrates high oxidation resistance, long life and high sensitivity even at high temperature and humidity by forming a recording film, containing (Cu, Te100-x)ySez(2<=x<=40 atomic %, 80<=y<=95 atomic %, 5<=z<=20 atomic %) alloy as well as carbon and hydrogen, where information is recorded by projecting laser beam to the surface of a substrate. CONSTITUTION:An information recording medium 18 consists of a substrate 13 and many recording films 14 laminated on the substrate 13. The substrate 13 used is made of a transparent material for a laser beam projected to an information recording medium 18 for recording and retrieving information. The recording film 14 containing (Cu, Te100-z)ySez(2<=x<=40 atomic %, 80<=y<=95 atomic %, 5<=z<=20 atomic %) alloy as well as carbon and hydrogen is a binary intermetallic compound of Cu-Te. Cu27 and Te73 showing an eutectic point fuse at less than 330 deg.C or a temperature lower than Te. The composition of Cu should range from 2 to 40atomic %, considering the fusion point. The composition of Se should range within the limits of 5<=z<=20.

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 (Cu 1oo-*) Sex(2
≦X≦40 atomic%, 80≦y≦95 atomic%, 5≦2≦2
0 atomic %) alloy 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 CuTeSe 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 WA 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 a Cu-Te alloy containing carbon and hydrogen.

This recording film contains (Cu*Te 100-
i) The composition range of Cu in the Set alloy will be explained. As already known, according to the phase diagram of the Cu-Te binary system, Cu 2 Te is an intermetallic compound.
, Cu<Te5, it is known that CuTe exists. However, the melting points of these compounds are 1125° C., 800° C., and 600° C., which are much higher than the melting point of Te alone. At least for heat mode recording in which pits are formed by melting the recording film 14, materials having a higher melting point than Te are not very attractive. However, Cu27Te exhibiting a eutectic point
73 melts at a temperature of 330° C. or lower, which is lower than Te. Considering this point, it is found that the Cu composition is preferably in the range of 2 to 4 atomic percent.

Further, the composition range of Se is 5≦2≦20 atomic %. This is because, for example, if the composition range of Se is less than 5 at%, the effect of improving oxidation resistance cannot be obtained sufficiently, and if it exceeds 20 at%, the optical absorption rate decreases. It is.

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. Preferably, the thickness is in the range of 100 to 300 angstroms. This is also clear from the writing sensitivity characteristics when the laser is incident from the PC board 12 side under conditions of a pulse width of 60 n5 ecs and a linear velocity of 5.5 m/see, as shown in FIG. 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. A reproduction laser beam for reading out information recorded as bits 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 the reproduction laser power exceeds a certain threshold, the bits may be destroyed and the level of the reproduction reflected light may decrease. Therefore, the information recording medium 18 rotating at a linear velocity of 5.5 m/see is continuously held on the track formed on the information recording medium 18, and the laser power of the reproduction laser beam is changed, so that the reflected light Changes in level were observed using a synchronoscope. 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 permissible reproducing power of the write-once recording film, which is currently being standardized, is determined to be a maximum of 0.5 mW at a rotation speed of 1800 rpm and a linear velocity of 5.5 m/see, and the maximum permissible reproducing laser power P max (llW) is Pma
It is given by x-0,2+0.55V. Here, V indicates the linear velocity (m/see) of the information recording medium. Also, it is required that there is no change in the level of reflected light even after 10 cycles of continuous reproduction at p max, but the rotation speed is 1800 rpm and the linear speed is 5.5a+/see.
In the case of.

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 08+nW, 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 let the inside of the chamber 1 pass through the Q
, and 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 the IOSCCM was introduced into the chamber 1 while adjusting the Ar gas from the A gas line 7 using a mass flow controller (not shown).Then, the pressure inside the chamber 1 was measured using an ion gauge (see the figure). 5 x 10- with conductance valve 4 while monitoring with
It was adjusted to 3 Torr.

After confirming that this pressure does not fluctuate, the Cu-Te
Alloy target 9 (5 inches in diameter; composition is Cu 27T)
e 73 ; at.

After stopping the supply of Ar gas and the supply of DC power, the inside of the chamber 1 is once IX10-
The exhaust was evacuated to 5 Torr or less. After that, open the valves 6.17 and 25 and fill the chamber 1 with A gas, CH4 gas and 5
e(CH*)2 gas is passed through the Ar gas line 7, CH4 gas line 8, and Se (CR2)2 gas line 26,
while adjusting with a mass flow controller (not shown).
10,110 and 5 SCCM were introduced, respectively. Next, the pressure inside the chamber 1 is reduced to 5 using the conductance valve 4.
The pressure was controlled at 10-3 Torr. Thereafter, after confirming that there was no pressure fluctuation, 100 W was applied to the CuTe target 9 from the DC power supply 10 to cause sputter discharge. After confirming that the discharge is stable, the shutter 11 is opened and a recording film containing CuTe alloy and carbon and hydrogen is placed on the polycarbonate (PC) substrate 13 that has been set in advance on the rotor 12. 14 were laminated.

Rotor 12 was rotated at 60 rpIll. Recording film 1
When the film thickness of No. 4 reached 250 angstroms, the shutter was closed and the power supply was stopped. Then,
The conductance valve 4 was fully opened, and the inside of the chamber 1 was evacuated to below I.times.10-' Torr using the cryopump 5. 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 CuTeSe ternary alloy, carbon (C) and hydrogen (H) in the recording film 14, an AuTeSe alloy target can be sputtered in a hydrocarbon gas, or a CuTeSe alloy target can be sputtered in a hydrocarbon gas.
Rather than sputtering an e-alloy target in an alkyl selenium gas, a CuTe alloy target is sputtered in an atmosphere containing a hydrocarbon gas and an alkyl selenium gas. According to this sputtering method, selenium (Se
) can be easily controlled by adjusting the flow rate of this selenium-containing gas, and the amount of carbon and hydrogen in the record 114 does not depend only on the decomposition of alkyl selenium gas, but can be easily controlled by adjusting the flow rate of the hydrocarbon gas. can be easily controlled. Furthermore, it is not necessary to use a target consisting of the three components of copper (Cu), tellurium (Te), and selenium (Se), and it is possible to prevent compositional deviation of the recording film due to continuous sputtering of the target.

Example 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 after just a few days of tS.

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
When X-ray diffraction analysis was performed after this measurement, it was found to be an amorphous film.

Next, pulse width 50n5ee% write frequency 37MH
z, a GaAs semiconductor laser with a wavelength of 830 na+ was used, the numerical aperture (NA) of the objective lens was 0.52, and the linear velocity was 5.
Under the condition of 5m/see, Te-C film and CuTe
C/N (Carr1er) when writing to 5e-C film
/N oise) 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
8, hydrocarbon gas (methane), alkyl selenium gas (Se (CH3) 2) and rare gas (
Although a case has been described in which the AuTe target is sputter-discharged in a mixed atmosphere of argon), the present invention is not necessarily limited to this, and 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 to enter from the side of the recording film 14, 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 high-temperature environments.

[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.

Claims (1)

[Claims] (1) A substrate, (Cu_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≦40 atom%, 80≦y≦95 atom%
, 5≦z≦20 atomic %) alloy, and a recording film containing carbon and hydrogen.