JPS612593A - Optical information-recording member - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical information recording member that uses a laser beam to record and reproduce information signals at high density and high speed, and that allows information to be rewritten.

Conventional configurations and their problems The technology for recording and reproducing high-density information using laser beams is already well known and is currently being actively applied to document file systems, still image file systems, etc. . In addition, research and development cases are being reported regarding rewritable recording systems.

Regarding recording media in which information is repeatedly recorded and erased by reversibly increasing and decreasing the optical properties of the recording thin film, such as refractive index and extinction coefficient, using a laser beam, for example, Japanese Patent Publication No. 47
T @ 51Gfil 1sS found in -26897
Amorphous thin films based on chalcogen elements other than oxygen, such as b2S2, have been known, but they have not been put into practical use due to the problem of being sensitive to moisture.

An oxide thin film based on Te and O has improved moisture resistance.

These erase records by irradiating relatively strong and short pulsed light to rapidly cool the irradiated area from a heated state to decrease its optical constant, and by irradiating relatively weak and long pulsed light to increase the optical constant. The idea is to generally use the direction in which the optical constant decreases during recording and the direction in which it increases during erasing.

The Te-Tea2 thin film conventionally used as a recording material has, for example, a state in which small To particles (~20 particles) are scattered in an amorphous TeO2 matrix, or a state in which Te and TeO2 have no peak in X-ray diffraction. It is thought that T is mixed in an almost amorphous state that cannot be detected, but in any case, it is T that changes its structure significantly upon irradiation with light and contributes to the recording of information signals.
e particles. Therefore, by combining these Te particles with an appropriate substance, the thermal conditions necessary for the reversible structural change of To can be controlled, and the irradiation power and irradiation time required for erasing records with a laser beam, etc., can be controlled to some extent. It is possible.

For example, Japanese Patent Application Laid-Open No. 55-28530 describes a method for increasing the reversibility of structural changes in Te-Teo2 thin films using Se and S, and Japanese Patent Application No. 58-58158 describes a method for increasing the reversibility of structural changes in Te-Teo2 thin films using Se and S. , In, Sb, B
Due to the addition of elements such as i, burnt #)To TeO2
There have been proposals for methods to increase the structural reversibility of thin films, and at the same time to improve film stability and reproducibility during manufacturing. Subsequent detailed research revealed that, for example, when Ge is added, the Te particle size increases and the energy required to restore order increases rapidly, making it possible to control the thermal stability of recorded signal bits even in small amounts ( (1983, Proceedings of the 30th Applied Physics Association Conference, P87~), and due to its semimetallic nature, during recording, when Sn solidifies from a molten state by irradiation with a laser beam, it combines with 're and its particle size increases. It has become clear that in addition to the effect of suppressing growth, it also has the effect of acting as a nucleus for crystalline recovery during erasing, and that recording sensitivity and erasing sensitivity can be controlled by selecting the concentration of addition. An optical disc was prototyped using a recording thin film doped with (
1983 JAPAN DISPLAY Proceedings P46~
). This disk had the excellent characteristics of being able to record and erase data simultaneously in real time, and the recorded signal bits were also stable, but the sensitivity, especially the erase sensitivity, was not sufficient, and current semiconductor lasers, for example, are not capable of Since this was at the upper limit, further improvement in sensitivity was required.

OBJECTS OF THE INVENTION The object of the present invention is to improve the conventional To--TeO3 oxide thin film and provide a highly sensitive optical information recording medium that can be recorded and erased with low power.

Structure of the Invention In order to achieve the above-mentioned object, the present invention uses a thin film formed by simultaneously adding at least Bi, Ge, and Au to a Te T@102-based material having a relatively large Te component. By appropriately selecting the composition ratio of each additive, it is possible to improve the recording/erasing sensitivity without impairing the stability of the recording thin film.

DESCRIPTION OF EMBODIMENTS The present invention will now be described in detail with reference to the drawings. Figure 1 shows
FIG. 1 is a sectional view of an optical information recording member of the present invention. In the present invention, a recording thin film 2 is formed on a substrate 1 by a method such as vapor deposition or sputtering. The base material may be any material used for ordinary optical discs, such as PMMA, vinyl chloride,
A transparent resin such as polycarbonate, a glass plate, etc. can be used.

As the recording thin film, a six-element thin film is used, in which Au is further added to the quaternary To-0-B i -Ge. As mentioned above, a recording thin film formed using a quaternary thin film of To-0-5n-Ge is capable of recording and erasing data simultaneously in real time, but it is not sensitive enough. 0
The sensitivity limit in the -8n-Ge four-element system is thought to be due to the fact that Sn serves two functions as described above. In other words, by changing the additive concentration of Sn, for example, if the additive concentration of Sn is increased, the effect as a nucleus for recovering crystallinity, which is one of the two functions, becomes greater, but on the other hand, the melting point of the entire system increases. It becomes difficult to melt and recording becomes difficult. On the other hand, if it decreases, the melting point will drop and it will become easier to melt, but on the other hand, the number of crystal nuclei during erasing will decrease and it will become difficult to erase.Of course, if it decreases extremely, the effect of suppressing the grain size growth of To will be lost. We lose reversibility. '1. ! 7. Recording sensitivity and erasing sensitivity both depend on the Sn concentration at the same time, so in an actual system, a concentration that satisfies both of them must be selected, and there is a compositional sensitivity limit. be.

Therefore, in the present invention, the role of Sn is divided into two,
The degree of freedom in material design is expanded and sensitivity is further improved by separately allowing Bi to play the role of suppressing the grain growth of To during recording, and letting Au play the role of nucleation during erasing.

Due to its semimetallic nature, Bi is easily included in the film like Sn and combines with To to form an amorphous state.
Compound B 12T es has a lower melting point than Sn-, and can be expected to improve recording sensitivity.

The effect of adding Au to a TeTeO2 thin film has already been disclosed in Japanese Patent Application No. 59-61463.

Tsumari, Au is Te T@! In the 02 series, Au −
It forms a certain compound called Te, which is easily crystallized, so it acts as a crystal nucleus during erasing and increases the erasing sensitivity.Also, since it is a property of Au that it does not undergo oxidation, even a small amount of addition is sufficient. , the effect on other properties of the entire system is small. Furthermore, a noticeable decrease in the melting point was observed in the system to which Au was added, suggesting that by appropriately selecting other additives, a recording thin film with excellent recording and erasing properties can be obtained.

In the present invention, as mentioned above, ae is applied as a thermal stability control element, Bi is applied as a recording characteristic control element, and Au is applied as an erasure characteristic control element to the To-Tea2-based material, and the composition ratio of each element is changed. The optimum composition was extracted.

Hereinafter, the present invention will be explained in more detail using specific examples.

First, a method for manufacturing the Te-0-Ge-Bi-Au recording material of the present invention will be explained.

FIG. 2 shows the inside of a Pelger of a quaternary vapor deposition apparatus used for manufacturing the recording member of the present invention. In the figure, 1
4 to 17 are To-TeO2, Ge, respectively.

Sources corresponding to Bi and Au, 10 to 13 are shutters, and 8 to 9 are heads of a thickness monitoring device. After the vacuum system 18 is evacuated to approximately 1σ5 Torr, each of the four sources is separately heated with an electron beam using four electron beam guns (not shown) provided in the vacuum system. K Te -0-Ge -8n-A is heated on a rotary plate 6 supported by a shaft 4 connected to an external motor 3 while monitoring the deposition rate and feeding back to the power source.
Synthesize a 6-element thin film of u.

At this time, the sintered pellet described in Japanese Patent Application No. 58-116317 can be used, for example, as the Te Te0) source, and it is possible to precisely control the five elements using four sources. The film composition is AES.

Methods such as XPS, XMA, SIMS, etc. can be determined.

As for the vapor deposition method, it is of course possible to use five sources, and it is also possible to reduce the number of sources by using the mixture pellets described in Japanese Patent Application No. 58-233009. Furthermore, it is also possible to form by sputtering.

Next, a method for evaluating the characteristics of the recording thin film formed by the above method will be explained.

Since the recording member of the present invention utilizes repeated and reversible changes, it has a characteristic in the direction in which the optical constant increases (called blackening because the optical density increases), that is, an erasing characteristic, and a characteristic in the direction in which the optical constant decreases (optical density In other words, it is necessary to evaluate the recording characteristics at the same time.

FIG. 3 simply shows an evaluation system for the recording member of the present invention. The light emitted from the semiconductor laser 19 is made into parallel light by the first lens 2o, then shaped into a circular beam by the second lens system 21, and then passed through the beam fritters to 22. N4 board 23
The light is focused through the third lens 24 into a circular spot with a half-width of approximately 0.9 μm, and is irradiated onto the recording medium 26 . The reflected light follows the opposite path to the incident light and passes through the beam splitter.
The light is bent by a fourth lens 27, and enters a photodetector 28, where the recording state is checked.

In the present invention, the semiconductor laser is modulated, and the irradiation power is set to a relatively small value, for example, 1 mW/
Measure the irradiation time at which blackening starts by fixing the power density to approximately 1μ and changing the irradiation time, or
A method is applied, such as fixing the irradiation light at a certain level, varying the irradiation light power, and measuring the irradiation light power at which blackening begins. Similarly, to evaluate the whitening characteristics, the recording member is blackened in advance, the irradiation light power is fixed at a relatively high level, for example, 7 mW/μ, and the shortest irradiation time required for whitening is measured, or the irradiation time is set to about 5 onsec, for example. Apply a method such as fixing the irradiation light power to 100% and measuring the irradiation light power at which whitening starts by changing the irradiation light power.

Next, the results of evaluating recording members of various compositions formed by the above-described method using the above-described method will be described.

Example 1 As the evaluation material composition, the composition was controlled so that the ratio of the number of atoms of Te-0-Ge-Bi was 75:10:15, and at the same time, this Te7. Recording members with various compositions were obtained by controlling the compositions of Au and O in three systems: Ge1°Bil, Au, and 0.

Figure 4a shows (Te0.76G80.1B) among the above compositions.
io, 16) 02゜That is, T @eoG@sB 1
1 mW/μ by changing the amount of Au added to 12020
This figure shows the change in the irradiation time required to start blackening when irradiated with the power of This figure shows that the addition of Au greatly shortens the irradiation time to start blackening, but a sufficient effect can be obtained even when the amount added is about 2%. For example, b is irradiation time of 60μ to a blackened area by irradiating 6μ with a power of 1mW/μba, for example.
It shows the change in the irradiation power required to start whitening when irradiation is performed with changing the irradiation power as nSeC. From this, it can be seen that although adding d to Au increases the irradiation light power required to start whitening, there is no practical problem up to about 15%, and that whitening is extremely difficult to occur at 20%. From these two figures, the basic characteristics of the Te -0-B i -Ge 7 Au system can be obtained, and the addition amount of Au can be selected in the range of 2 to 16 times without impairing the recording characteristics. It was found that it is possible to erase data several times faster than At this time, it was confirmed that when the irradiation power density was increased to 8 degrees, each curve shifted in the other direction.

Next, the results of similar experiments conducted on systems in which the composition ratio of Te-Ge-B i was changed will be explained.

Example 2 Te-Ge-Bi, Au as evaluation material compositions
, O was controlled to have a composition ratio of 70:10:20, and recording members with various compositions were obtained by changing the composition ratios of the three components To--Ge--Bi.

FIG. 5a shows G in which the composition ratio of Bi in the three-component system of To-Bi-Ge in the above composition is 15%.

Te-Ge-Bi-Au when changing the composition ratio of
For example, the temperature at which blackening starts for a -0 series thin film is
The results of the investigation using the method described in No. 229 are shown below. From this figure, G
.

It can be seen that as the additive concentration increases, the blackening start temperature increases and the thermal stability of the white state increases. When these recording films were left in a clean open at 60°C, the change in transmittance was investigated. It was confirmed that the transmittance decreased after about 24 hours in the case where the change start temperature was 100'C or less, but in the case where the change start temperature was lower than 100'C, the transmittance decreased by at most 1% of the absolute amount after about 1 month.
%, and if the Ge concentration is 3% or more, the thermal stability is considered to be sufficient. If the Ge concentration is further increased, the film will be able to withstand higher temperature conditions, but the film's transmittance will greatly increase (absorption will decrease), and the blackening sensitivity will tend to decrease. G.

Sufficient erasure sensitivity was obtained when the addition concentration was in the range of 3% to 16%.

Figure 6 shows the change in recording sensitivity when the composition ratio of Ge in the three-component system of Te-Bi-Ge is set to 10% and the composition ratio of Bi is changed.The irradiation pulse width is approximately 50 nS.
It is eC. From this figure, it can be seen that when the concentration of Bi added is about 3%, the sensitivity is somewhat poor and the amount of change in reflectance is small, and when it is less than that, whitening is difficult to occur.
It can be seen that sensitivity (whitening) can be obtained, and that when it reaches about 26%, the sensitivity decreases slightly and the amount of change in reflectance decreases. At this time, it has been found that the erasing speed is several times higher than that of the conventional method due to the effect of Au.If the OBi concentration is further increased, the proportion of Te, which is the main component, will eventually decrease and the reversibility itself will be lost.

As described above, the appropriate concentration of each component was found.

Next, the results of comparing the durability against humidity of the thin films of the present invention will be shown.

Example 3 It has been known that the moisture resistance of an oxide thin film based on p Te TaO2 base changes depending on the oxygen concentration in the film. Therefore, as a typical composition, TI
! The composition was set at 17oGesB 116Au 1°, and the composition was controlled so that the oxygen concentration varied within the range of 0 to 50%.

FIG. 6 shows the results of examining the change in transmittance when the thin film was left in a constant temperature and humidity chamber at 40° C. and 90 PH% for about one month. This figure shows that if the composition ratio of oxygen in the entire system is 10% or more, there is a decrease in transmittance at the initial stage, but there is almost no change after that.
If the above is the case, it can be seen that there is no change at all from the initial state.

Oxygen combines with To to form T e02 in the film, or with Ge and Bi to form GeO2°B.
It is possible that they form i2O3 or a composite oxide, but both of these work to increase the moisture resistance of the To-based alloy, which is mainly composed of Te, by being mixed in a way that separates it. It is considered that the However, if the zero component is increased too much, the heat transfer coefficient of the system decreases and heat due to light irradiation is likely to be accumulated, and as a result, the film is likely to be torn during repeated use. It was found that there is no problem in this respect as long as the zero component is 40 inches or less.

To summarize the above evaluation results, To-0-Ge-13i
-Is the Au 5-element thin film composed of the ternary To-Ge-8n? For example, in the region where the composition ratio of TeGeB1, Au, and O belongs to the region surrounded by F− in FIG. 8, and the composition ratio of TeGeB1, Au, and O belongs to the region surrounded by A to E in FIG.
It was found that materials represented by 0G@sB 1 and oAu6 have excellent recording/erasing characteristics and recording characteristics with excellent stability. The coordinates of each point are shown in the table below.0 Effects of the Invention According to the present invention, the 6
Using a base oxide thin film, Te is the main component for reversible changes, and the effects of each component are as follows: 1) Improvement in thermal stability due to Ge 2) Improvement in recording sensitivity due to Bi 3) Au
-Improvement in erasing speed 4) It is possible to obtain an optical information recording member with excellent characteristics that combines the multiple effects of improving moisture resistance due to O.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the optical information recording member of the present invention, FIG. FIG. 3 is a cross-sectional view showing an optical system of an apparatus for measuring the recording and erasing characteristics of the optical information recording member of the present invention, and FIG. Graphs showing the changes, FIGS. 6(a) and 6(b) are graphs showing the Ge concentration and blackening start temperature, and the Bi concentration and whitening start power characteristics of the optical information recording member of the present invention, respectively. Graphs showing the relationship between the concentration of 0 and moisture resistance properties in one embodiment of the present invention, FIGS. 7 and 8 are triangular diagrams representing the composition range of the optical information recording film used in the optical information recording member of the present invention. 1... Base material, 2... Recording thin film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 Figure 4 (a) B radiation time (MeJ1c) (L) Irradiation time (-to town, Figure 5<a) (b) if, radiation time (voice wm Fig. 6 Iron amount time (day) Fig. 7 1θθ Te-(re-84“

Claims (1)

[Claims] A thin film consisting of at least Te, O, Bi, Ge, and Au, with the sum of the number of Te-Bi-Ge atoms in the film and Au, O
The ratio of the number of atoms to the number of atoms is in the diagonally shaded area surrounded by A to E in Figure 7, and the ratio of the number of atoms of Te, Bi, and Ge is surrounded by F to J in Figure 8. An optical information recording member comprising a thin film present in a region.