JPH02121132A - Information recording medium - Google Patents

Abstract

PURPOSE:To improve oxidation resistance without lowering the optical absorptivity of the recording medium by forming an AgTe-C film at a specified flow rate ratio. CONSTITUTION:This recording medium has a substrate 13 and a recording film 14 in an amorphous state which contains the AgxTe100-x(2<=x<=50atom%) alloy formed of an AgTe alloy at <={5<=Q<=50%} flow rate ratio Q={X/X+Y}X100% in an atmosphere mixture composed of gaseous hydrocarbon of a flow rate X and a rare gas of a flow rate Y as well as carbon and hydrogen and in which the carbon content of the part in contact with the substrate 13 is higher than the carbon content in the film. The degradation of the optical absorptivity is obviated in this way and the degree of a change in the reflectivity under high humidity is small. In addition, the life is long and the carbon content in the part in contact with the substrate is larger than in the inside and, therefore, the oxidation of the boundary between the substrate and the recording film is obviated.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Application Field) The present invention is directed to writing information by agglomerating recording film components by, for example, irradiation with a laser beam, and reducing the amplitude of the laser beam due to the aggregation of the components. The present invention relates to an information recording medium from which information is read through changes in information.

(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 T
It is known that it contains C and H, and that at least C and H form a chemical bond.

In addition, AgTe, C and H obtained by sputtering an AgTe alloy in an atmosphere containing hydrocarbons and a rare gas
(hereinafter referred to as AgTe-C film) has been developed as a recording film that has a long life even under high temperature and high humidity conditions.

(Problem to be solved by the invention) However, in order to increase the oxidation resistance performance of the AgTe-C film due to carbon and hydrogen, the flow rate ratio Q where the flow rate of hydrocarbon gas is X1 and the flow rate of rare gas is Y (Q-(X/ (
When X+Y)}×100%) is increased, the transmittance of the film increases and the optical absorption rate A (A-1-R-T, where R is reflectance and T is transmittance) decreases. The laser power must be increased. Furthermore, even if the recording film contains C and H and has excellent oxidation resistance, there is a problem in that oxidation (interfacial oxidation) cannot be avoided, for example, at the portion in contact with the organic resin substrate.

Therefore, an object of the present invention is to provide an information recording medium having a recording film containing an AgTe alloy, C, and H, which has improved oxidation resistance without reducing optical absorption.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides a substrate and an AgTe alloy on the substrate in a mixed atmosphere of a hydrocarbon gas at a flow rate of X and a rare gas at a flow rate of Y. Inside, the flow rate ratio Q-(X/ (X+Y))
Agx formed under x100% 5≦Q≦50%
'reloO-1 (2≦x≦50 atomic %) alloy and an amorphous recording film containing carbon and hydrogen, in which the amount of carbon in the portion in contact with the substrate is greater than the amount of carbon inside the film. Provides an information recording medium with characteristics.

(Function) The AgTe-C film of the present invention has a flow rate ratio Q of 5≦Q≦50%.
Since the film is formed below, the optical absorption rate does not decrease due to too much C and H.

Also, if it is within the above Q value range, AgT that does not contain C and H
The degree of change in reflectance under high humidity is smaller than that of a single e-alloy film, and it has a longer life.

Furthermore, since the recording film of the present invention has a higher carbon content in the portion in contact with the substrate than in the interior, oxidation does not occur at the substrate/recording film interface.

(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 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 hydrogen.

If there is a difference in the reflectance of the cluster components dispersed in the C-H matrix between aggregation and dispersion, it is possible to record information by, for example, making cluster dispersion correspond to no information and aggregation to presence. Can be done. Aggregation of clusters can be caused by heat generation due to laser irradiation. When Te is used as a single substance, the difference in reflectance between aggregation and dispersion is not so large. but,
Differences may be observed when a component that can form an alloy with this is added. In the present invention, it has been found that this effect is significant when 2 to 50 atomic % of Ag is added.

In the information recording medium according to the present invention, information is recorded using the difference in reflectance before and after the phase change, but the difference in reflectance before and after recording is generally caused by the thickness of the recording film being at an extreme value due to interference. It becomes large when it is near the object to be given, which is convenient. Therefore, the thickness of the recording film according to the present invention is determined by considering that the interference effect decreases as the film thickness increases and converges to a certain reflectance, and that the laser power during recording increases as the film thickness increases. The thickness should be 5000 Å or less.

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

FIG. 2 is a schematic diagram of a sputtering apparatus for forming the recording film of the present invention. First, the valve 2 of this sputtering device is opened to the rotary pump 3 side, and the inside of the chamber 1 is heated to 0.2To.
Exhausted to rr. Then valve 2 is connected to cryopump 5.
It was opened to the side and 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 IO5CCM 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,
Alloy target 9 (5 inches in diameter: composition is A g aq
DC power supply 10 to T e <5; at%)
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.

A: After stopping the gas supply and DC power supply, use the cryopump 5 to temporarily pump the inside of the chamber 1 to I
' Exhaust to below Torr. Thereafter, valves 6 and 17 are opened, and Ar and CH4 gases are introduced into chamber 1 through Ar gas line 7 and CH4 gas line 8 while being controlled by a mass flow controller (not shown) at 5SCC each.
M and 1105CC were introduced. Then, using the conductance valve 4, the pressure inside the chamber 1 is reduced to 5 x 10-3T.
It was controlled to orr. After confirming that there was no pressure fluctuation, 100 W was applied to the AgTe target 9 from the DC power supply 10 to cause sputter discharge. After confirming that the discharge is stable, open the shutter 11 and remove the polycarbonate (PC) that was previously set on the rotor 12.
) A recording film 14 containing an AgTe alloy and carbon and hydrogen was laminated on the substrate 13. The rotor was rotated at 60 rpll.

Next, once the discharge is stopped and the gas is exhausted, the CH
4 and Ar gas were introduced in an amount of IO8CCM each. 1
After confirming that the pressure was maintained at 5×1 O −3 Torr for minutes, discharge was performed. When the film thickness reached 1,000 people, the shutter was closed and the power supply was stopped.

Next, the conductance valve 4 was fully opened, and the inside of the chamber 1 was evacuated to below 1X10-5 Torr using the cryopump 5. 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.

A g 33T e 67 obtained by the above method,
When the film thickness of a recording film containing C and H is 1000, as shown in Figure 3, the reflectance reaches a minimum value due to the multiple interference effect, so the film changes from amorphous (dispersed state) to crystalline state at this film thickness. When the phase changes to (agglomerated state), a significant increase in reflectance can be observed, indicating that information has been recorded.

By the way, in the above embodiment, the flow rate of methane gas was increased at the final stage of sputtering discharge to increase the flow rate ratio Q. However, when sputtering is normally performed in a mixed atmosphere of hydrocarbon gas and rare gas, the carbon generated in the chamber It may also be possible to utilize the fact that the amount of gas becomes larger at the end of the discharge than at the beginning of the discharge without increasing the flow rate of the hydrocarbon gas.

Example 2 By the method shown in Example 1, A g 33T e 6
7. A recording film containing C and H was formed on a PC board by 250 people at a rotation speed of 1800 rpi and a recording frequency of 3.7 MH.
z, recording pulse width 5 n5ec, linear velocity 5
, 7 m at points corresponding to 5 m/see
When writing with a laser power of W, a good C/N (Carrier/Noise) ratio of 30 dB was obtained.

In the recording film according to the present invention with a thickness of 250 mm, when the writing laser power exceeds 10 mW, not only cluster components agglomerate but also bits are formed, causing confusion when reading information. Therefore, in order to prevent the formation of bits, a fourth
As shown in the figure, an information recording medium 21 can be obtained in which a dielectric film 20 with a thickness of 300 to 1000 layers is laminated on a recording film 14 formed on a substrate 13. As the dielectric film, S t02 , S [OSA, 1'SS LN, etc. can be used. If the dielectric film is thinner than 300 mm, pinholes may occur;
If you exceed the number of people, the film formation time will be longer.

Further, as shown in FIG. 5, when the information recording medium 18 consisting of the substrate 13 and the recording film 14 according to the present invention is bonded to each other via the adhesive layer 19, the dielectric film 20 covers the surface of the recording film 14 with the adhesive layer 19. It also serves as a protector.

In the present invention, since information is recorded using phase change, there is no need for air to exist on the recording film.
It is possible to directly bond two pieces of information recording media together. Furthermore, since the information recording according to the present invention is not based on the formation of pits, the information recording location can accurately correspond to the marking portion on the recording film without producing a rim. Therefore, it is possible to narrow the bit interval and perform high-density recording.

Example 3 An Ag33Te6 film was formed according to the method of Example 1 at a flow rate ratio of Q-5 and 50%. As shown in FIG.
Even in an atmosphere (65°C - 90%) where the reflectance of the single film (Q-0) decreases due to rapid oxidation, the
It was extremely stable with no major changes for 00 hours. The reflectance is normalized by setting the reflectance immediately after film formation to 1. This means that it can be formed on organic resin substrates such as PC and PMMA that are relatively permeable to oxygen and water without using a dielectric protective film. The optical recording sensitivity is better when the film is formed on an organic resin substrate with low thermal conductivity than when it is formed on a glass substrate. Therefore, according to the present invention, it is possible to obtain an information recording medium with high optical recording sensitivity.

FIG. 7(a) shows Auger electron spectroscopy (AES) in the film thickness direction of the recording film according to the present invention formed under the above-mentioned Q-50% condition.
) showed the results. FIG. 7(b) shows the results of a recording film, which is the same as the recording film of the present invention, as a comparative example, except that there is no difference in carbon content between the inside of the film and the interface between the substrate and the film. The recording film contains C%TeS.
Although H is included in addition to Ag, H cannot be detected based on the principle of generation of Auger electrons, so C5Te and Ag components as well as oxygen absorbed by oxidation are shown. A.E.
Measurement of S was started from the surface of the film, and was performed while sputtering with Ar+ ions until the organic resin substrate (in this case, PC) appeared. Looking at this, it can be seen that in the recording film of the present invention, compared to the recording film of the comparative example, in the region in contact with the substrate, the amount of C is greater than the amount in the film, and on the other hand, the amount of oxygen is small, so oxidation does not progress. I understand.

In the above embodiments, a transparent organic resin substrate was used, but the substrate may be opaque when the writing and reproducing laser beams are incident from the recording film side without passing through the substrate.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an information recording medium that is free from oxidation even at the interface with the substrate 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, and FIG. 2 is an optical recording film forming apparatus according to an embodiment of the present invention.
FIG. 3 is a diagram showing changes in reflectance due to multiple interference effects, FIG. 4 is a cross-sectional view of a dielectric film laminated on the recording film of the information recording medium of the present invention, and FIG. 5 is a diagram showing the information recording medium of the present invention. Figure 6 is a cross-sectional view of an air sandwich type media, Figure 6 is a diagram showing changes in playback time and reflection level, and Figure 7 (a)
) and FIG. 7(b) are AES diagrams of the recording film. 1...Chamber, 9...AgTe alloy target, 13...PC board, 14...
...AgTe-C film. Applicant's representative Patent attorney Takehiko Suzue Figure 4 (λ) Figure 7 (a) Figure 7 (b)

Claims (1)

[Claims] (1) Substrate and AgTe alloy on this substrate in a mixed atmosphere of a hydrocarbon gas at a flow rate of X and a rare gas at a flow rate of Y at a flow rate ratio Q={X/(X+
Y)}×100% is Ag formed under 5≦Q≦50%
_xTe_1_0_0_-_x (2≦x≦50 atomic%)
An information recording medium comprising: an amorphous recording film containing an alloy, carbon and hydrogen, and in which the amount of carbon in a portion in contact with the substrate is greater than the amount of carbon inside the film.