JPH02117886A - Information recording medium - Google Patents

Abstract

PURPOSE:To obtain excellent oxidation resistance under hot and humid conditions and contrive a longer useful life and a higher sensitivity by providing on a substrate a recording film for recording information by irradiation with laser light, the recording film comprising a specified alloy, carbon and hydrogen. CONSTITUTION:An information recording medium comprises a substrate 13 and a recording film 14 provided on the substrate 13. The substrate 13 is made of a material transparent to laser light with which the recording medium is irradiated for recording and reproduction of information. The recording film 4 comprises an Ag-Te alloy, carbon and hydrogen. The alloy has a composition off (AgxTe100-x)ySez, wherein 2<=x<=55atom% so that bits can be formed at a melting point lower than the melting point of Te. The addition of Ag has the effect of uniformizing the size of the bits, reducing the amount of rim parts, enhancing recording density, and the like. The value of z is in the range of 5<=z<=20atom%. If the thickness of the recording film 4 is 1000Angstrom or more, writing sensitivity is lowered. Therefore, the thickness of the film 4 is preferably 100-300Angstrom .

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention is directed to, for example, writing information by forming pits by irradiating the laser beam, and writing the information through changes in the amplitude of the laser beam caused by the bits. 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) Comparing the recording film made of Te and hydrocarbon as described above and the recording film made of Te at a high temperature and high humidity of 65° C. and 90% (under accelerated conditions), Te film oxidizes within just one week and optical recording performance is impaired, whereas Te film
The C film remained stable without being oxidized even after one month.

However, the recording film of the Te-C film also crystallizes at high temperatures (above about 75 degrees Celsius), resulting in a rough surface that increases noise and has a greater effect on the reproduced signal. .

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide a long-life information recording medium that does not have a rough surface even under high temperature and high humidity environments.

[Structure of the Invention (Means for Solving the Problems)] In order to achieve the above object, the present invention includes a substrate, a substrate formed on the substrate, and information recorded by irradiation with a laser beam (Agx Te100- x ) y S ez (2≦
x≦55 atom%, 80≦y≦95 atom%, 5≦2≦20
The present invention provides an information recording medium characterized by comprising a recording film containing a atomic %) alloy, carbon, and hydrogen.

(Function) The optical recording film of the present invention is produced by sputtering an AgTe alloy in a mixed atmosphere of hydrocarbon gas and alkyl selenium gas or a mixed atmosphere in which a rare gas is added, so that the surface condition can be maintained stably even at high temperatures. did.

The present invention provides an information recording medium that stably maintains recorded information and has excellent recording sensitivity even under high temperature and high humidity conditions by providing a recording film containing an AgTeSe alloy and carbon and hydrogen. It is something that can be provided. Hereinafter, the recording film of the present invention will be described as rAgTe for convenience.
Se-C 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 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.

(Agx Te, oo-x) y S in the present invention
In the heat mode recording method, the ez gold alloy composition is
2≦x so that bits are formed with a melting point lower than Te.
≦55 at%. Adding Ag can have effects such as making the bit sizes uniform and reducing the rim portion, increasing the recording density.

Further, 2 is 5≦2≦20 atomic %. If 2 is less than 5 atomic percent, the effect of improving oxidation resistance will not be sufficiently exhibited;
This is because when the amount exceeds atomic %, the optical absorption rate decreases.

The thickness of the AgTe5e-C recording film 14 is preferably 500 Å because 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 the laser is incident through the PC board under the conditions of a pulse width of 60 n5ecs 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 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 light used to read information recorded in bits 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 speed is 5.5m
/see track continuously, the reproducing laser power was changed, and changes in the reflected light level were observed using a synchroscope. 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 AgTe5e-C 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 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/see 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□8 (mW) is PIla
It is given by x-0,2+0.055V. Here, V is the linear velocity (m/see) of the recording medium. Also P, ax
It is required that there be no change in the level of reflected light even after 105 cycles of continuous playback, which is required at a rotation speed of 180.
Orpm - If the linear velocity is 5.5 m/see, it must not change for at least 1 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 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 I.times.10-5 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 IOSCCM 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, 100 W is applied from the DC power supply 10 to the Ag-Te alloy target 9 (diameter 5 inches, composition is Ag 45T e 55 ; at%), and the shutter 11
Sputter cleaning was performed by performing sputter discharge for 5 minutes with the chamber closed.

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 the valves 6, 17, and 25 to fill the chamber 1 with Ar gas, CH4 gas, and 5
e(CH3)2 gas was introduced through Ar gas line 7, CH4 gas line 8, and Se (CH3)2 gas line 26 at 10.10 and 5 SCCM, respectively, while being controlled by a mass flow controller (not shown). Next, the pressure inside the chamber 1 is increased by 5X using the conductance valve 4.
The pressure was controlled at 10-3 Torr. 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, the shutter 11 is opened and a recording film 14 containing an AgTe alloy and carbon and hydrogen is deposited on a polycarbonate (PC) substrate 13 that has been set on the rotor 12 in advance. were laminated. rotor is 60 rp
Rotated with IIl. When the film thickness reached 250 people, the shutter was closed and power supply was stopped. Next, the conductance valve 4 was fully opened, and the inside of the chamber 1 was evacuated to below I.times.10@-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.

In order to include the AgTeSe ternary alloy and C and H in the recording film of the present invention, instead of sputtering an AgTeSe alloy target in a hydrocarbon gas or sputtering an AgTe alloy target in an alkyl selenium gas,
An alloy target is sputtered in an atmosphere containing hydrocarbon gas and alkyl selenium gas. In this way, the amount of selenium in the recording film can be easily controlled by adjusting the flow rate of the selenium-containing gas, and the amount of C and H in the recording film does not depend only on the decomposition of alkyl selenium gas. It can be easily controlled by adjusting the hydrocarbon gas flow rate.

In addition, it is not necessary to use a fragile and difficult-to-manufacture target consisting of the three components of Ag5TeSSe, and it is possible to prevent compositional deviations in the recording film due to continuous sputtering of the target.

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 AgTe5e-C 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 AgTe5e-C film has good oxidation resistance even under high temperature and high humidity, and has a long life. Note that the AgTe5e-C film was an amorphous film even when subjected to X-ray diffraction analysis after this nJ determination.

FIG. 6 shows a pulse width of 50 n5eas and a writing frequency of 3.
A GaAs semiconductor laser with a frequency of 7 MHz and a wavelength of 830 nn+ was used, and the numerical aperture (NA) of the objective lens was 0.52.
, under the condition of linear velocity 5.5 m/see, Te-C film and Ag
C/N (Carr
ier/No.1se) ratio.

From this, it can be seen that the AgTe5e-C film of the present invention is different from the conventional Te5e-C film.
It can be seen that the sensitivity is even higher than that of the -C film.

In this example, the AgTe target was sputter-discharged in a mixed atmosphere of hydrocarbon gas (methane), alkyl selenium gas (S e (CH3) 2 ), and rare gas (argon); The discharge may be performed in an atmosphere.

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.

[Effects of the Invention] As explained 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]

Figure 1 is a cross-sectional view of an information recording medium according to an embodiment of the present invention, Figure 2 is a diagram showing the relationship between AgTe5e-C film thickness and writing sensitivity, and Figure 3 is a diagram showing changes in playback time and reflection level. FIG. 4 is a diagram showing 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, and FIG. 6 is a diagram showing the error rate of the recording film after undergoing acceleration conditions. - It is a figure which shows the recording sensitivity of C film|membrane. 1... Chamber, 9... AgTe alloy target,
13-PC board, 14-A g T e S e -
C membrane. Applicant's agent Patent attorney Takehiko Suzue Book 1 - Including laser power

Claims (1)

[Claims] (1) A substrate, (Ag_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≦55 atomic%, 80≦y≦95 atomic%
, 5≦z≦20 atomic %) alloy, and a recording film containing carbon and hydrogen.