JPS612592A - Optical information-recording member - Google Patents

Abstract

PURPOSE:To enable to record and erase information with low energy, by using a thin film of a material based on a Te-TeO2 material containing a relatively large amount of component Te with at least, In, Ge and Au incorporated therein, in which the compositional ratios of the additives are specified. CONSTITUTION:The thin film is provided in which the relative values of the total number of atoms of Te-In-Ge and the numbers of atoms of Au and O lie in the shaded region A-E on the figure and the relative numbers of atoms of Te, Ge and In lie in the shaded region F-K on the figure. Accordingly, by using the thin film of the five-element oxide system Te-O-GE-In-Au, an optical information-recording member can be obtained which comprises Te as a main constituent for reversible change and has a combination of excellent characteristics owing to the respective effects of the constituents, namely, enhancement of thermal stability by Ge, enhancement of recording sensitivity by In, enhancement of erasing speed by Au, and enhancement of moisture resistance by O.

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.

``Recording media in which information is repeatedly recorded and erased by reversibly increasing or decreasing the optical properties of the recording thin film, such as the refractive index and extinction coefficient, using a laser beam, are described in Japanese Patent Publication No. 4, for example.
T 111 s 1G el found in 7-26897
Amorphous thin films based on chalcogen elements other than oxygen, such as s S b 2 S 2 , 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 TeTeO2 thin film conventionally used as a recording material has, for example, an amorphous TeO2 matrix in which small particles of Te (~20 particles) are scattered, or To and TeO2 formed by, for example, X-ray radiation. It is thought that the Te particles are mixed in an amorphous, near-d state with no peak detected in the analysis, but in any case, it is the Te particles that significantly change their structure upon irradiation with light and contribute to the recording of information signals. Therefore, by combining these Te particles with an appropriate substance, the thermal conditions necessary for reversible structural change of To can be controlled, and for example, the irradiation power and irradiation time required for erasing records with a laser beam can be controlled to some extent. is possible.

For example, Japanese Patent Application Laid-Open No. 55-28530 describes a method for increasing the reversibility of structural changes in Te Ter2 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 Ter2 thin films using Se and S. There are proposals for a method of increasing the structural reversibility of the Te-Tea2 thin film by adding elements such as Sb and Bi, and at the same time improving the stability of the film and the reproducibility during manufacturing. After detailed research, for example, G.

Adding Te increases the particle size and the energy required to restore order increases rapidly, making it possible to control the thermal stability of recorded signal pits even in small amounts (1983, 30th Applied Physics Union Lecture) In addition, due to its semimetallic nature, Sn combines with Te when it solidifies from a molten state by laser beam irradiation during recording, suppressing the grain size growth, and also forms a crystal during reverse erasing. It also has the effect of acting as a core for sexual recovery,
It became clear that recording sensitivity and erasing sensitivity could be controlled by selecting the doping concentration, and an optical disk was prototyped using a recording thin film to which Ge and Sn were added simultaneously (1983 Engineering APAND IS PLAY 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. This is the upper limit of laser performance, and further improvement in sensitivity is required.

OBJECTS OF THE INVENTION The object of the present invention is to improve the conventional Te T@02 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 made of a To T@102 material with a relatively large Te component and simultaneously adding at least In, Ge, and Au. By appropriately selecting the composition ratio of each of the additives, it is possible to improve the recording and erasing sensitivity without impairing the stability of the recording thin film.Description of Examples The present invention will be described in detail below with reference to the drawings. do. Figure 1 shows
FIG. 1 is a sectional view of an optical information recording member of the present invention. In the present invention, the recording thin film 2 is formed on the base material 1 by a method such as vapor deposition or sputtering. The base material may be one used for ordinary optical discs (PMMA, vinyl chloride,
Transparent resin such as polycarbonate, a glass plate, etc. can be used.

As the recording thin film, a quinary thin film in which Au is further added to the quaternary T e -0-I n -G e is used. As mentioned above, a recording thin film formed using a quaternary thin film of T o -0-8n -G e is capable of simultaneously recording and erasing data in real time, but the sensitivity is not sufficient.

The sensitivity limit in the To-0-8n-Ge four-element system is thought to be due to the fact that Sn serves two functions as described above. By changing the additive concentration of Sn, for example, if the additive concentration of Sn is increased, the effect as a nucleus for crystallinity recovery among the two functions becomes greater, but on the other hand, the melting point of the entire system increases. This makes recording difficult. On the other hand, when it decreases, the melting point decreases and it becomes easier to melt, but on the other hand, the number of crystal nuclei during erasing decreases and it becomes difficult to erase. Of course, if the amount decreases extremely, the effect of suppressing Te grain size growth will be lost and reversibility will be lost. In other words, recording sensitivity and erasing sensitivity both depend on the Sn concentration, so in an actual system, a concentration that satisfies both needs to be selected, and this is where a compositional sensitivity limit occurs. It is.

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

Due to its semimetallic properties, In has T in the film like Sn.
It is easy to combine with 5nTe to form an amorphous state, and compounds with Te, such as InTe and 5nTe3, have lower melting points than 5nTe 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. In other words, Au forms a compound called Au-Te in the TeTeO2 system, and since this substance is easily crystallized, it acts as a crystal nucleus during erasure and increases the erasure sensitivity. However, it is sufficiently effective even when added in small amounts, and has little effect on other properties of the entire system. Furthermore, in the system to which Au was added, the melting point was noticeably lowered, and it is believed 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, Ge is applied as a thermal stability control element, In as a recording characteristic control element, and Au as an erasing characteristic control element to the Te-Teo2-based material, and the composition ratio of each element is changed to optimize the The composition was extracted.

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

First, a method for manufacturing the T e -0-G e-I n-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
4-17 are T e T e O2, respectively.

A source compatible with Ge, In, and Au with 10 to 13
1 is a shutter, and 6 to 9 are heads of a film thickness monitoring device. After drawing the vacuum system 18 to a vacuum of about 10 Torr, the four sources were individually heated with electron beams using four electron beam guns (not shown) provided in the vacuum system to control the evaporation rate. T e -0 - G e -I n is placed on a rotary plate 5 supported by a shaft 4 connected to an external motor 3 while monitoring and feeding back to the power supply.
-Aut7) Synthesize a 5-element thin film. At this time Te
- For Teo2 source, for example, Japanese Patent Application No. 58-11631
The sintered pellets described in 7 can be used, and it is possible to precisely control the six elements using four sources.

The film composition is AES.

It can be determined using methods such as XPS, XMA, SIMS, etc.

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. 68-233009. Furthermore, it is also possible to form by sputtering.

Next, a method for evaluating the characteristics of the recording thin film formed by the two methods will be described.

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 by the semiconductor laser 19 is made into parallel light by the first lens 20, and then shaped into a circular beam by the second lens system 21. A circular spot 12 having a half width of about 0.9 μm is converged by the lens 24 and irradiated onto the recording medium 25 .

The reflected light follows a path opposite to that of the incident light, is bent by the beam splitter 22, is converged by the fourth lens 27, and enters the photodetector 28 to confirm the recording state.

In the present invention, the semiconductor laser is modulated, and the irradiation power is set to a relatively low value, for example, 1 mW/μ-, for evaluating the blackening characteristics.
Measure the irradiation time at which blackening starts by fixing the irradiation time at a certain power density and changing the irradiation time.For example, fix the irradiation time to about 1 μm and measure the irradiation light power at which blackening starts by changing the irradiation light power. Apply methods such as Similarly, to evaluate the whitening property, 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. Alternatively, a method may be applied in which the irradiation time is fixed to, for example, about 60 nsec, the irradiation light power is changed, and the irradiation light power at which whitening starts is measured.

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 for the evaluation material composition, the composition was controlled so that the ratio of the number of atoms of To-Ge-In was 75:10:15, and at the same time, the composition of Te76Ge1°In16, Au, and 0 was
The compositions of Au and O were controlled as one system, and recording members with various compositions were obtained.

Figure 4a shows ("eO, T5Ge0.
IIno, 15) 80020 That is, T e
Au for e o G e a I n 12o2°
This figure shows the changes in the irradiation time required for the start of blackening when the amount of addition was changed and irradiation was performed at a power of 1 mW/μ. This figure shows that adding Au greatly shortens the irradiation time to start blackening, but a sufficient effect can be obtained even when the amount added is about 2%. b represents the change in the irradiation power required to start whitening when a blackened area is irradiated with a power of 1 mW/μ- for a duration of 6μ, and the irradiation power is varied, for example, with an irradiation time of 5 On In2. It shows. It can be seen from this that although adding Au increases the irradiation light power required to start whitening, there is no practical problem up to about 16%, and that whitening is extremely difficult to occur at 20%.

From these two figures, the basic characteristics can be secured in the To-〇-I n-Ge-Au system, and by selecting the amount of Au added in the range of 2 to 16%, the recording characteristics will not be impaired. It turns out that it is possible to erase data several times faster. At this time, it was confirmed that each curve shifted to the left when the irradiation power density was increased.

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

Example 2 As the evaluation material composition, the composition ratio of To-Ge-In, Au, and O was controlled to be 70:10:20, and the composition ratio of the three components Te-Ge-In was changed. Recording members having various compositions were obtained in this manner.

Figure 6a shows, for example, the blackening start temperature when the composition ratio of In in the three-component system of To-In-Ge in the above composition is 15% and the composition ratio of Ge is changed. 59-70
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 addition concentration of e increases, the blackening start temperature increases and the thermal stability of the white state increases. When these recording films were left in a clean oven at 50°C and their transmittance changes were examined, it was confirmed that the transmittance decreased after about 24 hours for those whose change start temperature was below 100°C, but For example, after about a month, at most 1 of the absolute amount
% change was observed, and it is considered that thermal stability is sufficient if the Ge concentration is 3% or more. 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. Ge addition concentration is 3%~
Sufficient erasure sensitivity was obtained in the 16% range.

Figure 6 shows the Ge content in the Te-In-Ge three-component system.
The irradiation pulse width, which shows the change in recording sensitivity when the composition ratio of In is changed to 10%, is approximately 50 ng.
It is 52. From this figure, it can be seen that when the concentration of In added is about 3%, the sensitivity is slightly poor and the amount of change in reflectance is small, and when it is less than that, it is difficult to whiten, and when the concentration of In is about 10.20%, sufficient recording (whitening) sensitivity can be obtained. %, it can be seen that the sensitivity decreases slightly and the amount of change in reflectance decreases.

At this time, it was found that the erasing speed was several times higher than that of the conventional method due to the effect of Au. If the In concentration is further increased, the proportion of To, 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 of the thin film of the present invention with respect to its concentration will be shown.

Example 3 It has been known that the moisture resistance of TeTaO2-based oxide thin films changes depending on the oxygen concentration in the film. Therefore, as a typical composition, T @
Based on the composition 7oG @ 6I n 1s A u 1o, the composition was controlled so that the oxygen concentration varied within the range of 0 to 60%.

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 RH% 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 in the film to form Te.
Forms O2 or combines with Ge and In to form Ge
It is possible that O2゜I n 203 or the like or a composite oxide of these is formed.
It is thought that both of these work to increase the moisture resistance of the Te-based alloy, which is mainly composed of To, by intermingling with each other in a divided manner.

However, if the zero component is increased too much, the heat transfer coefficient of the system decreases, and the heat generated during light irradiation is likely to be accumulated, and as a result, the film becomes more likely to tear during repeated use. 0 component is 40%
It turns out that there is no problem with this point if the following is true.

To summarize the above evaluation results, T e −0−G e
-I n-Au S-based thin film has a composition ratio of the three components of Te-Ge-In that belongs to the region surrounded by F- in FIG. For example, in the area surrounded by A to E in FIG.
fil e 0020G @ s I n 1oAu
It was found that those represented by No. 6 had excellent recording/erasing characteristics and recording characteristics with excellent stability. The coordinates of each point are shown in the table below.

Effects of the Invention According to the present invention, Te-0-Ge-I n-Au (7
) Using a quinary 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 with Ge 2) Improvement in recording sensitivity with In 3) Erasing with Au Improvement in 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. 2 is a partially cutaway perspective view showing the configuration of an example of a vapor deposition apparatus for manufacturing the optical information recording medium of the present invention, and FIG.
The figure is a sectional view showing the 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 illustrating changes, FIGS. 5a and 5b, are Ge9 degrees, blackening start temperature, and I of the optical information recording member of the present invention, respectively.
FIG. 6 is a graph showing the relationship between the density of n and the whitening initiation power characteristic, FIG. 6 is a graph showing the relationship between the density of 0 and moisture resistance characteristics in an embodiment of the present invention, and FIGS. 7 and 8 are the optical information recording members of the present invention. 1 is a triangular diagram showing the composition range of an optical information recording film used for. 1... Base material, 2... Recording thin film. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 3 Figure 4 (αJ 118 shot n8P11f-voice 1; eC) (h) vI! , v /

Claims (1)

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