JPH02121888A - Data recording medium - Google Patents

Abstract

PURPOSE:To provide a data recording medium capable of obtaining a high C/N ratio by forming a recording film containing a specific alloy as well as carbon, nitrogen, fluorine and hydrogen on a substrate. CONSTITUTION:A data recording medium 18 is constituted of a substrate 13 and the recording film 14 laminated to said substrate 13. The substrate 13 is formed using a material transparent to laser beam applied to the data recording medium for the purpose of the recording and regeneration of data. The recording film 14 is composed of a material wherein carbon, nitrogen, fluorine and hydrogen are contained in an Ag-Te alloy. The composition of this AgxTe100-x alloy is set to 2<=x<=55atomic% so that a pit is formed at temp. lower than the m.p. of Te in a heat mode recording system. This optical recording film is excellent in oxidation resistance because of the sputtering in a hydrocarbon atmosphere. Since the laser beam absorbing substance in a C-H matrix is converted from Te to AgTe, a m.p. is lowered from 450 deg.C to 350 deg.C and high sensitivity recording becomes possible even in low power. Since this recording film has pits reduced in a caliber and aligned uniformly, a high C/N ratio is obtained.

Description

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

(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 made of Te.
It is known that it contains 5C and H, and at least C and H form a chemical bond.

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.

(Problem to be Solved by the Invention) However, in the Te-C film, at a writing laser power that exceeds the recording threshold, the bits become wide open and the shape becomes irregular.
There was a problem in that the se) ratio suddenly decreased.

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 can obtain a high C/N ratio.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes a substrate, and an Agx Te,oo which is formed on the substrate and on which information is recorded by irradiation with a laser beam. The present invention provides an information recording medium characterized by comprising a -1 (2≦x≦55 atomic %) alloy and a recording film containing carbon, nitrogen, fluorine, and hydrogen.

(Function) Since the optical recording film of the present invention is sputtered in a hydrocarbon atmosphere, it has excellent oxidation resistance. Furthermore, compared to the Te--C film, since the laser light absorbing substance in the C--H matrix is changed from Te to AgTe, the melting point is lowered from 450° C. to 350° C., making it possible to record with high sensitivity even at low power. In addition, since the recording film of the present invention has small and uniform pit diameters, it has a high C.
/N ratio is obtained. Hereinafter, the recording film of the present invention will be described for convenience.
The film also contains H.

(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 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.

Further, the recording film 14 is an Ag-re gold alloy containing carbon, nitrogen, fluorine, and hydrogen.

The composition of the Ag x Te 100-x alloy in the present invention is 2≦x≦55 atomic % so that pits are formed at a melting point lower than that of Te in the heat mode recording method.
shall be. Adding Ag can have effects such as making the bit sizes uniform and reducing the rim portion, increasing the recording density.

The thickness of the AgTe-C-N-F recording film 14 is 1000 Å.
If it is more than 50, the writing sensitivity will decrease, so preferably 50
0 Å or less, more preferably 100 to 300 people.

As shown in Figure 2, this is a pulse width of 50 n5ee%.
This is also clear from the writing sensitivity characteristics when a laser is incident on the PCC substrate opening under the condition of a linear velocity of 5.5 m/see.

Furthermore, if the thickness is less than 100 Å, the recording film becomes discontinuous and the probability of pinhole formation increases, which is not preferable. In the case of heat mode recording, these pinholes are not only undesirable because they may be mistaken for original bits during readout, but they also trigger oxidation of the recording film, so they must be minimized as much as possible.

Next, the tolerance of the reproduction laser power (the power level at which reproduction can be performed without causing deterioration of the recording film) of the information recording medium shown in FIG. 1 will be explained. The reproduction laser beam used to read out the information recorded in the pits is normally continuously oscillated. In order to read out information with a good S/N ratio in this state, it is necessary to increase the reproduction laser power.
If a certain threshold is exceeded, pits (information) may be destroyed and the level of reproduced reflected light may decrease. Therefore, the linear velocity is 5,
Continuously hold on the track of 5 m/see,
Changes in the reflected light level were observed using a synchroscope while changing the reproduction laser power. The observation results are shown in Figure 3.

According to this observation result, what film thickness of AgTe-C-N-
For the F film, if the laser power is 0.6 or 0.8 mW,
The level of reflected light did not change for 3 hours. However, when the power was increased 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 level of reflected light is normalized with the level immediately after reproduction set at 1.

The allowable playback power of the write-once recording film, which is currently being standardized, is a linear velocity of 5.5 m/sec at a rotational speed of 180 Orpm.
In this case, the maximum power is determined to be 0.5 mW. The maximum allowable reproduction laser power P,, m (mW) is P,,, -
It is given by 0.2+0.055V. Here, V is the linear velocity (m/5ee) of the recording medium. Also P east
It is required that there be no change in the reflected light level even after 105 cycles of continuous playback, which is required at a rotation speed of 1800.
rp11 - at least 1 for linear speed 5.5 m/see
This means that it should not change over time. 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 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 set the inside of the chamber 1 to 0.2 Torr.
Exhausted to r. Next, the valve 2 was opened to the cryopump 5 side, and the temperature was evacuated to below 1X10-5T Orr. 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 Ar gas was introduced into the chamber 1 as IO3CCM from the Ar gas line 7 using a mass flow controller (not shown) while turning g. Next, while monitoring the pressure inside the chamber 1 with an ion gauge (not shown), the conductance valve 4 measures 5 x 10=
Adjusted to Torr. After confirming that this pressure does not fluctuate, a D
Sputter cleaning was performed by applying 100 W from the C power supply 10 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
' Exhaust to below Torr. After that, open valves 6, 17, and 25 to fill chamber 1 with Ar gas, CH4 gas, and N gas.
F3 gas was introduced through Ar gas line 7, CH4 gas line 8, and NF3 gas line 26 at 10.10 SCCM and 5 SCCM, respectively, while being controlled by a mass flow controller (not shown). 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 AgTe
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, the shutter 11 is opened and the polycarbonate (PC) substrate 13 set in advance on the rotor 12 is opened.
A recording film 1 containing an AgTe alloy and carbon and hydrogen thereon.
4 were laminated. The rotor was rotated at 60 rpm.

When the film thickness reached 250 people, the shutter was closed and power supply was stopped. Then conductance valve 4
is fully opened, and the inside of chamber 1 is pumped using cryopump 5.
It was evacuated to below X 10-5 Torr. 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 a polycrystalline film, an amorphous film does not have grain boundaries, so that reproduction laser light is not modulated at the grain boundaries and does not generate grain boundary noise.

Example 2 Information recording medium 1 manufactured by the method shown in Example 1
In No. 8, the ratio of read errors (error rate) occurring as a result of surface roughness due to oxidation, which is an index of oxidation resistance, was analyzed. After leaving the information recording medium 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 for a certain period of time under accelerated conditions of 75° C. and 90%. , and measured the error rate. The results are shown in FIG. The error rate was normalized with the value before being placed under acceleration conditions as 1.

According to this figure, the error rate of the Te film increases in just a few days. The Te-C film also gradually increases after 100 hours. On the other hand, the AgTe-C-N-F film of the present invention showed almost no change even after being left for 1000 hours. Therefore, it can be seen that the AgTe-C-N-F film has good oxidation resistance even under high temperature and high humidity, and has a long life. Note that AgTe-
The C-N-F film was also found to be an amorphous film when subjected to X-ray diffraction analysis after this measurement.

FIG. 6 shows a pulse width of 50 n5ec and a writing frequency of 3.
Using a GaAs semiconductor laser with a frequency of 7 MHz and a wavelength of 830 nm, the numerical aperture (NA) of the objective lens is 0.52, and the linear velocity is 5.
．． Te-C film and AgTe-C under the condition of 5m/see.
-C/N when written on N-F film (Carrle
r/Noisc). From this, the AgTe-C-N-F film of the present invention is different from the conventional Te-C
It can be seen that the sensitivity is even higher than that of a membrane.

In this example, hydrocarbon gas (methane) and N
AgT in a mixed atmosphere of F3 gas and rare gas (argon)
Although the e-target was sputter-discharged, the discharge may be performed in an atmosphere that does not contain a rare gas.

Further, in this embodiment, a transparent organic resin substrate is used, but the substrate may be opaque when the writing and reproducing laser beams are made incident from the recording film side without passing through the substrate.

Example 3 A film was formed using the apparatus shown in FIG. 4 using the same procedure as in Example 1, except that benzene gas was used instead of CH4 gas and NF3 gas was not used. As shown in FIG.
T e 6. Recording film containing alloy, C and H 1] 4 to 250
An information recording medium 118 with multiple layers was obtained.

The writing sensitivity characteristics, reproduction laser power tolerance, error rate, and C/N ratio of this recording film were determined in the second, third, and third stages, respectively.
When examined under the same conditions as in Figures 5 and 6, it was found that
Results similar to those shown in FIGS. 9, 10 and 11 were obtained. Therefore, even if AgTe alloy is sputtered in an atmosphere containing hydrocarbon gas having benzene rings, AgTe-
It can be seen that a recording film having good recording characteristics similar to that of the C-N-F film can be obtained.

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

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an information recording medium according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the film thickness of the A gT e-C-N-F film and writing sensitivity, and FIG. FIG. 4 is a diagram showing the change in reflection level with time. FIG. 4 is an optical recording film forming apparatus according to an embodiment of the present invention. FIG. 5 is a diagram showing the error rate of the recording film under acceleration conditions. FIG. -C film and AgTe-C-N
- A diagram showing the recording sensitivity of the F film, FIG. 7 is a cross-sectional view of an information recording medium according to another embodiment of the present invention, and FIG. 8 is a diagram showing the thickness and writing of the recording film according to another embodiment of the present invention. Figure 9 shows the relationship between sensitivity. Figure 9 shows changes in playback time and reflection level.
Figure 0 shows the error rate of the recording film under acceleration conditions.
and FIG. 11 is a diagram showing the recording sensitivity of a Te-C film and a recording film according to another embodiment of the present invention. 1...Chamber, 9...AgTeTe alloy target layer 3...PC board,...AT-〇N-F film.

Claims (2)

[Claims] (1) A substrate, Ag_xTe_1_0_0_-_x(2≦x
≦55 atomic %) alloy, and a recording film containing carbon, nitrogen, fluorine, and hydrogen. (2) A substrate, Ag_xT, which is formed by sputtering an AgTe alloy on this substrate in a mixed atmosphere of a hydrocarbon gas having a benzene ring and a rare gas, and information is recorded by irradiation with laser light.
An information recording medium comprising: a recording film containing an e_1_0_0_-_x (2≦x≦55 atomic %) alloy, carbon and hydrogen, and having a thickness of 1000 Å or less.