JPH02121887A - Data recording medium - Google Patents

Abstract

PURPOSE:To obtain a high C/N ratio by reducing and uniformly aligning the calibers of pits by mounting a recording film containing a specific alloy as well as carbon and fluorine, on which data is recorded by the irradiation with laser beam, 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 material quality transparent to the laser beam applied to the data recording medium for the purpose of the recording and regeneration of data. The recording film 14 is formed from a material wherein carbon and fluorine are contained in an Ag-Te alloy and the composition of an AgxTe100-x alloy is set to 2<=x<=55 atomic % so that a pit is formed at temp. lower than the m.p. of Te in a heat mode recording system. When Ag is added, effect such that the sizes of pits are aligned and rim parts are reduced and recording density is enhanced is obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) 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 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.
%C and H, and it is known that at least C and H form a chemical bond.

This recording film cannot be formed even if an attempt is made to form it in pale blue (without using plasma) using Te and hydrocarbon as sources, following the Te film, and it 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, the pits open widely and become irregular in shape when the writing laser power exceeds the recording threshold.
) There was a problem in that the 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 Ag too-1 (2≦x≦55 atomic%
) An information recording medium characterized by comprising an alloy and a recording film containing carbon and fluorine.

(Function) According to the present invention, since it is possible to change the recording film/substrate interfacial tension compared to the conventional C-H recording film, it is possible to make the pit diameter small and uniform.
A high C/N ratio can be obtained.

Hereinafter, the recording film of the present invention will be conveniently referred to as "rAgTe-C-F film".

(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 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.

The recording film 14 is made of an Ag-Te alloy containing carbon and fluorine.

Ag, Te, in the present invention. . The composition of the -0 alloy is set to 2≦x≦55 atomic % so that pits are formed at a melting point lower than that of Te in the heat mode recording method. A
Adding g can have effects such as making the pits uniform in size and reducing the rim portion, increasing the recording density.

The thickness of the AgTe-C-F recording film 14 is preferably 500 Å since writing sensitivity decreases if it is 1000 Å or more.
The number of participants is preferably 100 to 300 people. This is also clear from the writing sensitivity characteristics when a laser is incident on the PCC substrate opening under conditions of a pulse width of 60 n5ec and a linear velocity of 5.5 m/see, as shown in FIG. 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 pits 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 light used to read out information recorded in the pits is usually 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 the observation results, the level of reflected light did not change for 3 hours with a laser power of 0.6 or 0.8 mW for any thickness of the AgTe-C-F film. 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 standardized with the level immediately after reproduction being 1.

The allowable playback power of the write-once recording film, which is currently being standardized, is a linear velocity of 5.5 m/s at a rotational speed of 1800 rpm.
In the case of ee, the maximum power is determined to be 0.5 mW.

The maximum allowable reproduction laser power P, , (mW) is P, ,
, −0,2+0.055V.

Here, V is the linear velocity (m/5ec) of the recording medium.

Furthermore, it is required that there be no change in the reflected light level even after 105 cycles of continuous playback at Pl, 8, which is required for at least 1 hour at a rotation speed of 1800 PLL and a linear speed of 5.5 m/See. 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 this requirement.

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 1X10-5 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 IO3CCM 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 orr. After confirming that this pressure does not fluctuate, Ag-Te alloy target 9 (5 inch diameter:
The composition is A g 45 T e 55 : at%) and DC
Apply 100W from power supply 10, shutter 1
1 was closed and sputter discharge was performed for 5 minutes to perform sputter cleaning.

After stopping the supply of Ar gas and the supply of DC power, the inside of the chamber 1 was once
It was evacuated to -5 Torr or less. After that, open valves 6 and 17 to introduce Ar gas and 03F8 gas into chamber 1.
IO5C through gas line 7 and C3F8 gas line 8 while adjusting with a mass flow controller (not shown).
We introduced commercials one by one. Next, the pressure inside the chamber 1 was controlled to 5×10 −3 Torr using the conductance valve 4 .

After confirming that there was no pressure fluctuation, 100 W was applied from the DC power supply 10 to the AgTe target 91;l: to cause sputter discharge. After confirming that the discharge is stable, the shutter 11 is opened and the recording film 1 containing AgTe alloy, carbon and fluorine is placed on the polycarbonate (PC) substrate 13 that has been set in advance on the rotor 12.
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. Next, the conductance valve 4 is fully opened, and the inside of the chamber 1 is pumped with I using the cryopump 5.
It was evacuated to below X 10' 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-F film of the present invention has 1
There was almost no change even after leaving it for 000 hours. Therefore, it can be seen that the AgTe-C-F film has good oxidation resistance even under high temperature and high humidity, and has a long life. Note that the AgTe-C-F film was also an amorphous film when X-ray diffraction analysis was performed after this measurement.

FIG. 6 shows a pulse width of 50 n5ec and a writing frequency of 3.
Using a GaAs-based semiconductor laser with a frequency of 7 MHz and a wavelength of 830 ni, a Te-C film and an AgTe-
C/N (Carrier/
(Nolse). From this, it can be seen that the AgTe-C-F film of the present invention has higher sensitivity than the conventional Te-C film.

In this example, fluorocarbon gas (C3
AgTe under a mixed atmosphere of F8) and rare gas (argon)
Although the target was subjected to sputter discharge, 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 When sputtering an AgTe alloy target using only fluorocarbon gas, there are the following two drawbacks.

1) AgTe alloy target with fluorocanibone gas 1
The recording film made by sputtering in an atmosphere of 1) is
The optical absorption coefficient (absorption rate) becomes smaller.

For this reason, in the case of a heat mode recording method in which information is recorded by forming pits using heat generated when laser light is absorbed, a decrease in recording sensitivity is observed.

2) During sputtering of an AgTe alloy target, carbon powder, which is considered to be a decomposition product of fluorocarbon gas, adheres significantly to the target surface, so if sputtering is performed continuously for a long period of time, the sputtering film formation rate may decrease.

This is a major drawback in terms of production.

Here, the flow rate of fluorocarbon gas is X1, the flow rate of rare gas is Y, and the gas flow rate ratio is Q-(X/ (X+Y)IX1
Defined as 00%, Q-30, 50°60 and 100%
As a result of investigating the writing sensitivity characteristics of the AgTe-C film (film thickness 250, composition Ag33T e 67) formed according to each gas flow rate ratio (using C3H8 gas and argon gas), the results are as shown in Fig. 7. I was able to get good results.

When detecting this sensitivity characteristic, the rotation speed was 1850 rpm.

The pulse width was 60 n5ec. From this detection result,
It can be seen that in the case of Q-100%, the laser power required to obtain a constant reproduced signal amplitude is larger than in the case of other Q values, and the writing sensitivity is deteriorated.

Also, the condition of the target surface under each Q value is Q-100%.
In this case, there was the most black discoloration and a large amount of deposits.

As the Q value decreased, the percentage of deposits tended to decrease. FIG. 8 shows the results of measuring error rates under the same recording conditions as in FIG. 5 for recording films formed under various Q values under the same conditions as in FIG. 7. Therefore, from the results shown in FIGS. 7 and 8, the sputtering condition Q is 5≦Q≦5.
It turns out that 0% is preferable.

Example 4 FIG. 9 shows the effect of the gas flow rate ratio Q on the sputtering rate. If sputtering is continued under conditions where the gases are C3H8 gas and argon gas, and the flow rate of C3H8 gas exceeds 10105 CC, the sputtering rate will decrease. In Figures 9 and 10, the sputtering rate is The first value is normalized as 1.
Figure 0 shows the flow rate of fluorocarbon gas (C3H8 gas) at 10.20 and 1 while keeping the same flow rate ratio (Q -50%).
It shows the sputtering rate when it is 1005CC. As the flow rate increased, the amount of deposits on the target surface tended to increase. Therefore, it can be seen that the flow rate ratio of the fluorocarbon gas is preferably IOSCCM or less.

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide an information recording medium that can perform high-density recording with a high CZN ratio.

[Brief explanation of 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 diagram showing the relationship between AgTe-C-F film thickness and writing sensitivity, and FIG. 3 is a diagram showing playback time and reflection level. FIG. 4 is a diagram showing the change in the 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, and FIG. A diagram showing the recording sensitivity of the AgTe-C-F film. Figure 7 is a diagram showing the relationship between writing laser power and modulation degree for each gas flow rate ratio. Figure 8 is a diagram showing the acceleration time and error rate for each gas flow rate ratio. FIG. 9 is a diagram showing the change in sputter rate for each gas flow rate ratio, and FIG. 10 is a diagram showing the change in sputter rate for each fluorocarbon gas flow rate. 1...Chamber, 9...AgTe alloy target, 13...PC board, 14...
...AgTe-C-F film.

Claims (1)

[Claims] (1) A substrate, Ag_xTe_1_0_0_-_x(2≦x
≦55 atomic %) alloy, and a recording film containing carbon and fluorine.