JPH02169293A - Information recording medium - Google Patents

Abstract

PURPOSE:To provide an information recording medium having a high-sensitivity recording film capable of satisfactory optical recording even upon an increase in rotating frequency by providing a recording film which comprises a Cu-Te alloy, carbon and hydogen and which has specified composition ratios. CONSTITUTION:A recording film comprises a Cu-Te alloy, carbon and hydrogen, and has a structure in which Cu-Te alloy clusters are dispersed in a C-H matrix formed by chemical bonds of carbon and hydrogen. The recording film can be obtained by sputtering an alloy target by electric discharge in a stream of a mixed gas of a hydrocarbon gas and a rare gas in a vacuum vessel. The Cu content is preferably 2-50 atomic %. With Cu thus added, the size of pits becomes uniform, and the amount of rim parts is reduced, so that recording density is enhanced. The composition ratio, in atomic %, of carbon and hydrogen is preferably 25 atomic % <=C+H<=38 atomic %, whereas the composition ratio, in atomic %, of Cu and Te is preferably 62 atomic % <=Cu+Te<=75 atomic %. Since the recording film comprises the Cu-Te alloy, C and H, the recording film is hardly oxidized even when being left under hot and humid conditions.

Description

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

(Prior art) As a type of self-recording medium, information is recorded by irradiation with laser light and the recorded information is reproduced. something is being 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 manufacturing this recording film, tellurium (Te) is sputtered in an atmosphere containing hydrocarbon gas.

As a result, a recording film (hereinafter referred to as rTe-C film) which has higher sensitivity and better oxidation resistance than a single Te film (Tell!) is obtained. , C and H, and at least C and H
It is known that there are chemical bonds.

This recording film cannot be formed even if it is attempted to be formed by vapor deposition using Te and hydrocarbon as sources (without using plasma), following the Te film, and can only be obtained by using plasma. This is because a film is formed by a chemical reaction between C and H after the hydrocarbon gas is once decomposed in plasma, and this is a major feature when forming an optical recording film.

According to Japanese Patent Application Laid-Open No. 58-9234, Te-C
It is said that the film has both good optical properties and corrosion resistance when the composition ratio of C and H is 5 to 40 at%. In addition, the Tokuko Showa 6
According to Publication No. 3-42594, Te-Cl1! is formed by sputtering in a mixed atmosphere of rare gas and hydrocarbon gas, and when the flow rates of both gases are set as X and Y, respectively, under conditions that satisfy X/Y-1/4 to 4/1. It is said that when formed into a film, it has good optical properties and oxidation resistance.

(Problem to be solved by the invention) By the way, what about at high speed using an information recording medium? When recording +9 information, it is necessary to increase the rotational speed of the medium, but in this case, the contact time between the laser beam and the recording film becomes shorter, and sufficient recording may not be possible.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to provide an information recording medium equipped with a highly sensitive recording film that allows sufficient optical recording even when the rotational speed is increased.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention includes a substrate, Cu, Te, which is formed on the substrate, and on which information is recorded by irradiation with a laser beam. 100 -
An information recording medium characterized by comprising a recording film of 8at96, a substrate, and a Cu, Te+oo film formed on the substrate and on which information is recorded by irradiation with a laser beam.
-t (2≦x≦50 atoms 06) alloy and contains carbon and hydrogen, and the composition ratio in terms of atomic percent of carbon and hydrogen is 25 at%≦C1H≦38 at%, and the number of atoms of Cu and Te is 96 The composition ratio is 62at%≦Cu+T
Provided is an information recording medium characterized by comprising a recording film of e≦758 t %.

(Function) According to the present invention, by adding Cu, the conventional T
It can record with higher sensitivity than e-C film.

Furthermore, since the recording film contains Cu-Te alloy, C and H, compared to a Te-C film consisting only of Te, C and H,
It is less susceptible to oxidation even if left in high temperature and high humidity conditions.

(Example) Embodiments of the present invention will be described below 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 9 report recording medium 18 of the present invention has a substrate 1
3 and a recording film 14 laminated on this substrate 13.

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

However, when the writing and reproducing laser beams are made incident from the recording film surface side without passing through the substrate, the substrate may be opaque.

On the other hand, the recording film 14 contains a Cu--Te alloy, carbon, and hydrogen, and has a structure in which Cu--Te alloy clusters are dispersed in a C--H matrix in which carbon and hydrogen are chemically bonded.

Phase diagram of the already known Cu-Te binary system (Figure 2)
According to
Because it is much higher than that of a single unit (450℃),
A heat mode recording method in which bits are formed by melting a recording film is not very practical. Furthermore, if the Cu content is less than 2 at %, the effect of preventing crystallization due to oxidation of the recording film will hardly be obtained. Therefore, the content ratio of Cu is preferably 2 to 50 at%. Addition of Cu also has the effect of making the bits uniform in size and reducing the rim portion, thereby increasing the recording density.

This recording film is an amorphous film in which no diffraction peaks from specific diffraction angles are observed even by X-ray diffraction analysis.

Information is recorded by forming bits on this recording film. The thickness of the recording film is preferably 100 to 1000. If the film thickness exceeds 1,000 layers, a large amount of energy is required to form the bits, and writing sensitivity decreases. More preferably, it is 300λ or less. This is also clear from the writing sensitivity characteristics shown in FIG. 3 when the laser is incident through the PCM board under the conditions of a pulse width of 60 n5 ec and a linear velocity of 5.5 m/see. On the other hand, if it is thinner than 100 mm, the recording film becomes discontinuous and the probability of pinhole formation increases, which is not preferable. These pinholes not only pose a risk of being mistaken for original bits during readout, but also trigger oxidation of the recording film, so they must be minimized as much as possible.

The recording film of the present invention can be obtained, for example, by sputtering an alloy target by electric discharge while flowing a mixed gas of a hydrocarbon gas and a rare gas into a vacuum container containing a Cu--Te alloy target.

By the way, the so-called magnetron sputtering method in which a magnet is disposed under a backing plate of a target is preferable for sputtering. This is because a magnetic field is formed and electrons in the plasma can be confined near the target, thereby preventing the electrons in the plasma from entering the substrate and increasing the temperature. This is particularly effective when using a substrate material with poor heat resistance such as PCSPMMA. Furthermore, when the plasma on the target is confined within a magnetic field, the plasma polymer on the target is decomposed and no longer deposited on the target, making it easier to sputter the AgTe target and stabilizing the film formation rate.

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

FIG. 4 is a schematic diagram of a sputtering apparatus for forming the recording film of the present invention. First, open the valve 2 of this sputtering device to the rotary pump 3 side and adjust the inside of the chamber 1 to 0°2 To
Exhausted to rr. Then valve 2 is connected to cryopump 5.
It was opened to the side and exhausted to below Ix10=Torr.

After that, open valves 6 and 17 to introduce Ar and C into chamber 1.
H4 gas was introduced through Ar gas line 7 and CH4 gas line 8 at a rate of 5 SCCM each while being controlled by a mass flow controller (not shown). When the flow rate of hydrocarbon gas is W and the flow rate of rare gas is Q-W/ (
W+Z), in this case it is 9 to 50%.

Next, the pressure inside the chamber 1 was controlled to 5×10 −3 Torr using the conductance valve 4 . After confirming that there is no pressure fluctuation, the Cu-Te alloy (composition is Cu
2sT e 72 ; at%) DC to target 9
70 W was applied from the power supply 1o to cause sputter discharge. After confirming that the discharge is stable, the shutter 11 is opened, and a plate containing Cu-Te alloy and carbon and hydrogen is placed on the PC board 13, which has been set in advance on the rotor 12 with a rotational speed of 6°rpH. The recording film 14 was laminated by 300 people.

Then, the shutter 1] was closed, and the power supply was stopped.

Furthermore, the supply of CH4 gas and Ar gas was also stopped.

Next, the conductance valve 4 is fully opened, and the cryopump 5 is used to pump the inside of the chamber 1 to IX], 0-5T.
It was exhausted to below orr. Then open the valve 15 and
After introducing N2 gas into the chamber 1 from the N2 gas line 16 and returning it to atmospheric pressure, the medium 18 was taken out, thereby forming the information recording medium shown in FIG. 1.

A recording film made of Cu-Te alloy, C and H is conveniently coated with r
CuTe-C film. In Figure 5, CuTe-C
ij) The difference in sensitivity between the film and the Te-c film at the same film thickness is shown. The vertical axis shows C/N (Carrier/No.1s).
e) Take the ratio and record it on the horizontal axis. The recording condition was a rotation speed of 180 rpm.

Recording radius r = 30 IIIm s Recording frequency 3.7
These are the results when the frequency is MHz and the numerical aperture (NA) of the objective lens is −0.50. Overall, the CuTe-C film has a higher C/
The N value indicates that highly sensitive recording is possible.

Using the same procedure, increase the flow rates of CH4 gas and Ar gas to 2
Recording films were manufactured under various Q values using Iriti.

FIG. 6 shows the optical recording sensitivity characteristics of these recording films. In the figure, the vertical axis indicates the modulation amplitude ratio of the reproduced reflected light after optical recording shown in FIG. The vertical axis is the laser power during writing (a semiconductor laser with a wavelength of 830 nm was used).

The pulse width was 80n5ec.

Looking at this, the optical recording film formed under Q-20% shows the highest writing sensitivity. followed by Q-40%, 80
The sensitivity decreases in the order of %, and in the case of Q-100%, that is, when sputtering with only CH gas, the sensitivity becomes even lower. Furthermore, in the case of Q-O1, that is, a film made only of Cu-Te alloy, the sensitivity is low.

FIG. 8 shows changes in reflectance of optical recording films formed under various Q values in high temperature and high humidity state B (60° C.-90%). The reflectance is normalized by setting the reflectance immediately after film formation to 1. The decrease in reflectance is a parameter of the oxidation resistance of the recording film. According to the same figure, the film made only of the Cu--Te alloy of Q-0 has the worst oxidation resistance. As the Q value increases to 20, 40, and 80%, the decrease in reflectance is improved, and at Q-100%, the reflectance hardly decreases even after 10,000 hours.

FIG. 9 shows the maximum possible reproduction laser power value of the recording film formed under each Q value. The reproduction laser power value is Q-
The value of the recording film of 0 is standardized as 1. Looking at this, it is almost constant above Q-50%. On the other hand, in the case of Q-0 to 50%, high reproduction power can also be used. That is, it is possible to have a wide margin for the reproduction laser power, and the power of the reproduction laser beam can be easily adjusted.

Combining the various characteristics shown in Figures 6, 8, and 9, we get
It can be said that the optical recording film formed under Q-40 to 80% is superior in terms of sensitivity, oxidation resistance, and laser power margin.

FIG. 10 shows compositional analysis values of recording films formed under each Q value. The composition corresponding to Q-40-80% is 25 at%
It can be seen that ≦C+H≦38 at%. On the other hand, Cu and T
When we analyzed the composition of e, we found that the composition ratio of C and H was exactly 10.
The value subtracted from 0%, that is, 62at%≦Cu+Te≦
It was found to be 75 at%. In this example,
C and H were subjected to elemental analysis, and Cu and Te were subjected to atomic absorption spectrometry.

In addition, the H/C value corresponding to Q-40 to 8096 is 1.0
It can be seen that 0≦I(/C≦1.35.

Therefore, if the above composition is obtained as a result of composition analysis,
It can be seen that the recording film has excellent oxidation resistance even without being subjected to an accelerated test lasting more than 1000 hours. Furthermore, the recording sensitivity is good and the laser power margin is wide, which can be easily determined in a short period of about half a day.

Example 2 Cu-T in rare gas and hydrocarbon gas or hydrocarbon gas
When the e-alloy target is sputtered, the composition of the Cu-Te alloy in 1JIIa becomes no longer equal to the composition of the Cu-Te alloy target, and the amount of Cu may decrease in the recording film. Therefore, using the apparatus shown in Fig. 4, Cu-T
The film was formed under the same conditions as in Example 1 except that the composition of the e-alloy target was changed, and the relationship between the composition of the Cu-Te alloy target and the composition of the Cu-Te alloy in the recording film was determined using ICP (inductively coupled plasma). I investigated using the emission spectroscopy (Fr) method. The detection results are shown in FIG. From the same figure, the composition of the Cu-Te alloy of the recording film is 10% higher than that of the target.
%, it can be seen that there is a tendency for Cu to decrease. Therefore, in order to obtain a desired Cu composition, it is sufficient to increase Cu and Q in the target by about 10 at%.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an information recording medium provided with a recording film having excellent oxidation resistance and recording sensitivity.

[Brief Description of the Drawings] Fig. 1 is a cross-sectional view of an information recording medium according to an embodiment of the present invention, Fig. 2 is a Cu-Te state diagram, and Fig. 3 is a Cu-Te-CM state diagram.
FIG. 4 is an optical recording film forming apparatus according to an embodiment of the present invention, FIG. 5 is a diagram showing the recording amplitude of Te-C film and CuTe-C film, Figure 8 shows various Q
Figure 9 is a diagram showing the maximum reproduction laser power value of recording films deposited under various Q values, and Figure 10 is a diagram showing changes in reflectance of recording films deposited under various Q values. The figure below shows the composition ratio of the recording film formed, and FIG. 11 shows the relationship between the Cu composition of the Cu--Te alloy target and the CU composition in the recording film. 1...Chamber, 9...Cu-T e
Alloy target, 13...PC board, 14...
...CuTe-C film. Applicant's representative Patent attorney Takehiko Suzue Figure Q

Claims (2)

[Claims] (1) A substrate, Cu_xTe_1_0_0_-_x(2≦x
≦50 at%) alloy, carbon and hydrogen, and the composition ratio of the carbon and hydrogen by the number of atoms is 25 at%≦C
An information recording medium comprising: a recording film with +H≦38at%; (2) A substrate, Cu_xTe_1_0_0_-_x(2≦x
≦50 at%) alloy, carbon and hydrogen, and the composition ratio of the carbon and hydrogen by the number of atoms is 25 at%≦C
+H≦38 at% and a recording film having a composition ratio of Cu and Te in atomic percent of 62 at%≦Cu+Te≦75 at%.