JPH0451897B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical information recording medium in which information is recorded by forming holes or recesses in a recording layer by irradiation with an energy beam such as light or heat. The present invention relates to an optical information recording medium with improved performance and a longer service life.

Tellurium (Te) has traditionally been used as a recording thin film in optical information recording media in which a thin film layer formed on a substrate is irradiated with an energy beam to form a pit row corresponding to the signal to be recorded. It has been known. Te thin film is one of the materials that can form desired pits with the lowest energy and is extremely promising as a highly sensitive material for this type of coating. Sensitivity here refers to the energy required to form pits per unit area (mJ/
^cm2 ).

However, if Te is left in the atmosphere,
It is easily oxidized by oxygen and moisture, and oxides are formed on the film surface, degrading sensitivity. For example, when left in an atmosphere of 70° C. and 85% relative humidity, the sensitivity decreases by about 20% in about 5 hours, and by about 50% in about 15 hours. In addition, to prevent oxidation of the Te film, Te
Measures such as coating the film with an organic protective film have been taken, but sufficient longevity has not yet been achieved.

The present invention was made in view of these problems, and an object of the present invention is to provide an optical information recording medium that is highly sensitive and has a long life.

The optical information recording medium of the present invention is characterized in that the recording layer is formed of a film containing Te as a main component and 5 to 40 atomic percent of carbon C, thereby achieving high sensitivity and long life. It combines the following.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a cross-sectional configuration diagram showing an embodiment of the present invention.

In the figure, 1 is a substrate, and in this embodiment, an acrylic plate, which is one of synthetic resins, is used. However, other materials such as plastic or glass substrates may also be used, and may be selected as appropriate depending on the method of reading out the information recording. 2 is a Te thin film for information recording containing C, and its thickness must be thick enough to obtain sufficient light reflectance and thin enough not to impair sensitivity;
Approximately Å to 1 μm is appropriate. For recording information including C
The Te thin film 2 is obtained by sputtering Te as a target in a mixed gas of Ar and an organic gas containing C, such as CH ₄ or C ₂ H ₂ gas. here
The C content in the Te film can be freely controlled by the mixing ratio of Ar and CH ₄ (or C ₂ H ₂ ), for example, Ar/CH 4 (or C 2 H 2 ).
When CH ₄ =1, approximately 40 atomic % of C can be contained when expressed as Te1−xCx(H), but the C content in the optical information recording medium of the present invention is determined by the reason described below. It is preferable that the amount is in the range of 5 to 40 atomic %.

In Figures 2 a to c, CH ₄ is used as the organic gas containing C, and the gas mixture ratio, that is, Ar/CH ₄ is 0 to 1.0 (0
~100%) and 1.5mm thick acrylic substrate 1
A Te thin film containing C is formed by sputtering,
This figure shows various characteristics of the obtained recording film of about 700 Å.

In the figure, the horizontal axis is the gas mixture ratio in the sputtering, the vertical axis is the light absorption, the film formation rate (film formation rate ratio) normalized by the characteristic value of the thin film obtained with 100% CH ₄ and the reciprocal ratio of sensitivity (sensitivity ratio) are shown respectively. Here, the light energy absorbed by a unit volume of film is proportional to 2nk. As can be seen in Figure 2, optical absorption (2nk) increases as Ar in the mixed gas increases, but
Both film formation rate and sensitivity are within a 10% change. Focusing on the sensitivity, as shown in Figure 2c, it has approximately the same value over a wide range of gas mixture ratios, and this value is
This corresponds to the sensitivity when a pure Te thin film of about 400 Å is formed on an acrylic substrate, indicating that the recording medium of the present invention has high sensitivity.

However, when Ar/CH ₄ is less than 0.1 (10%), that is, when the C content in the Te film increases, the decrease in light absorption gradually increases as shown in Figure 2 a. As a result, the sensitivity decreases as shown in FIG. 2c. Furthermore, if the C content is too high, the intensity of the laser beam must be increased because the Te--C film becomes nearly transparent. From this perspective, Te
The content of C in the film is preferably 40 atomic % or less.

In addition, as mentioned above, the thin film formed by the sputtering method is amorphous, and the shape of the concave portion in the recorded state is smoother than that of polycrystalline Te, making it possible to keep the noise level low when reading information. can.

Figure 3 is a diagram comparing the deterioration of sensitivity over time in an atmosphere of 70°C and 85% relative humidity between a conventional Te unit and a recording film containing 10 to 35 atomic percent C in Te. It is. The deterioration in sensitivity in this figure is expressed as a change in the reciprocal of the energy required for recording relative to the initial value, and shows the case where both the conventional recording film made of Te alone and the recording film according to the present invention are formed on an acrylic substrate. . As can be seen from this figure, in the case of a recording film made of Te alone, the sensitivity deteriorates over time as shown by A in the figure. This is because local transparent areas (stains) develop over time, and after about 170 hours, the entire surface deteriorates.

On the other hand, in the case of a Te thin film containing 10 to 35 at% of C, as shown by B in the figure, the Te
There are no stains like those seen in thin films, and the sensitivity is always maintained at a constant level, indicating that a long service life has been achieved.

As is clear from the results shown in FIGS. 2a to 2c, when the C content was 10 to 35 at %, satisfactory results were obtained in both sensitivity and life. However, as mentioned above, when the C content exceeds 40 atomic percent, the decrease in sensitivity gradually increases, while when the C content falls below 5 atomic percent, there is no significant difference in lifetime compared to a film containing only Te. .

In the above example, a method of sputtering CH ₄ mixed with Ar was shown as a method for forming a Te thin film containing C. However, sputtering in Ar gas using Te containing an appropriate amount of C as a target can also be used in the same way. A thin film can be formed.

FIG. 4 shows another embodiment of the present invention,
A Te thin film containing 5 to 40 atomic % of C is used as both a recording thin film and a protective film. That is, in the figure, 1 is a 1.5 mm thick acrylic plate, 3 is a Te film, and 2 is a Te thin film containing 5 to 40 atomic % of C. The thickness of the C-containing Te thin film 2 can be selected within the range of 100 Å to 1 μm, but it is preferably thick enough to protect from outside air such as water and oxygen, and thin enough not to impair sensitivity. Therefore, in this embodiment, the thickness is set to about 300 Å. In addition, since the Te film 2 containing C is a brown semi-transparent material, the Te film 3 needs to be thick enough to obtain sufficient light reflectance and not impair sensitivity. It can be selected in the range of 100 Å to 0.5 μm.
In this embodiment, the thickness of the Te film 3 is 400 Å.

The sensitivity of the C-containing Te film 2 with a film thickness of 300 Å obtained by sputtering in a mixed gas of CH 4 :Ar=1:4 is almost equal to the sensitivity _of the 400 Å Te film 3 on the acrylic substrate. Further, when recording is performed using optical energy on a recording medium having the structure shown in this embodiment, the C-containing Te film 2 and the underlying Te film 3 are evaporated at the same time, forming holes or recesses.

5 to 40 atom % according to the invention as explained above
Since the Te film 2 containing C is extremely less oxidized by water, oxygen, etc. than a film of pure Te, the Te film 2 containing C in this example also effectively acts as a protective film for the Te film 3. . Therefore, compared to conventional devices, the lifetime can be significantly extended without deterioration in sensitivity.

FIGS. 5a and 5b show still another embodiment of the present invention, in which when the substrate is a synthetic resin substrate made of plastic such as acrylic, moisture penetrating from the substrate side For the purpose of preventing deterioration of the recording film caused by deterioration or unreacted monomers, impurities, additives, etc. in the plastic reacting with the recording film on the substrate, a film containing mainly Te and containing C is placed between the substrate and the recording film. This is an example of forming a film.

That is, in FIG. 5, 1 is a plastic substrate with a thickness of 1.5 mm, 2 is a film mainly composed of Te and containing 5 to 40 atomic % of C, and 3 is a composite thin film of Te, Bi, etc. Here, the thickness of the Te film 2 containing C is several hundred Å.
Although it can be selected in the range of 1000 Å to several 1000 Å, it is preferably 1000 Å or less.

The configuration shown in this figure can be used in a system in which an energy beam is irradiated from the substrate side to a recording medium whose recording layer side is not exposed to the atmosphere. In addition to being usable as a recording film, this film 2 has a strong adhesion to the substrate 1 and is physically very stable, so it will not absorb water, oxygen, etc. that permeate the substrate 1, or any particles inside the substrate 1. It is also effectively used as a protective film against foreign substances such as reactive monomers, impurities, additives, and adhesives left on the substrate.

FIG. 6 shows still another embodiment of the present invention. In the figure, 1 is a 1.5mm thick acrylic board,
2 is a Te film containing 5 to 40 atom% of C, 3 is Te film
The membrane 4 is a layer of low thermal conductivity material. Here, the film thicknesses of the C-containing Te films 2 and 3 are the same as those shown in FIG. 5, and the film thickness of the low thermal conductive material layer 4 is 100
It can be appropriately selected within the range of Å to 10 μm.
The low thermal conductivity material layer 4 is provided to prevent moisture from penetrating from the outside air through the acrylic substrate 1, and is made of physically and chemically stable material, such as tellurium oxide (Te-O) film. I can do it.
However, as mentioned above, Te films containing C also have low thermal conductivity and are physicochemically stable.
A Te-C film can also be used as the low thermal conductivity material layer. In other words, in this case, the Te film 3 is Te-C
The structure is sandwiched between the films 2 and 4, and these three layers form a recording layer, and the Te-C films 2 and 4 also form a recording layer.
acts effectively as a protective film.

FIGS. 7a, b, and c show still another embodiment of the present invention, in which an organic protective layer is provided to prevent dust and scratches. In other words, in Figure 7 a, b, and c, 1 is a substrate, and 2 contains 5 to 40 atomic percent of C.
3 is a Te film, 4 is a low thermal conductive material layer,
5 is an organic protective film. This organic protective film 5 is 1μm
It has a film thickness of ~10 mm and can be formed by coating, and its material can be, for example, an ultraviolet curing resin.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram showing one embodiment of the present invention;
Figures 2 a to c are diagrams showing various characteristics of the recording medium shown in Figure 1 relative to the gas mixture ratio, where a represents light absorption, and b
3 shows the film formation rate ratio, c shows the sensitivity ratio, FIG. 3 is a comparison diagram of the lifespan of the recording medium shown in FIG. 6 and 7 a to 7 c each show other embodiments of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Te-C film, 3... Te film, 4... Low thermal conductivity material layer, 5... Organic protective film.

Claims (1)

[Claims] 1. Using tellurium as a target, sputtering is performed on a substrate in a hydrocarbon gas or a mixed gas of a hydrocarbon gas and a rare gas, with tellurium as the main component and containing 5 to 45 atomic percent carbon. A method for manufacturing an optical information recording medium, which comprises forming a film and irradiating the film with an energy beam to form holes or deformed parts. 2. The method for manufacturing an optical information recording medium according to claim 1, wherein the substrate is made of glass or synthetic resin. 3. The method for manufacturing an optical information recording medium according to claim 1, wherein the film is amorphous. 4. The method for manufacturing an optical information recording medium according to claim 1, wherein the film has a thickness of 200 Å to 1 μm.