JPH01137436A - optical recording medium - Google Patents

Abstract

PURPOSE:To enable the writing of information with small energy and to prolong the life of the title medium by incorporating at least tellurium, antimony, carbon, and hydrogen into a recording film. CONSTITUTION:This optical recording medium 10 is constituted by forming the recording film 12 on the surface on one side of a substrate 11. The recording film 12 consists of the thin film contg. at least the tellurium, antimony, carbon, and hydrogen. Pits are formed to the irradiated parts of the recording film when the film is irradiated with the energy beam such as laser beam modulated according to the information to be recorded. The writing sensitivity of the recording medium 10 is improved. In addition, the durability thereof is improved and the longer life is obtd.

Description

[Detailed Description of the Invention] The present invention relates to a physical change such as a hole or a four-part or optical characteristic change in a recording film provided on a substrate by irradiation with an energy beam such as light or heat. The present invention relates to an optical recording medium in which information is recorded in accordance with the arrangement of the changed portions, and in particular to an optical recording medium with improved susceptibility and longer life.

- U4 north t and 1Jlt゛There are two types of optical recording media, one in which a physically changed part such as a hole or four parts is formed in a part of the recording film by irradiating the optical recording medium with an energy beam, and the other in which a physically changed part such as a hole or four parts is formed in a part of the recording film. There is a method of forming an optical property changing section whose optical properties (refractive index, reflectance) are changed.

As a recording film in any type of optical recording medium, a recording film containing tellurium (Te) as a main component has been known for a long time (Japanese Patent Laid-Open Nos. 58-71195, 1983-9).
Publication No. 234). A recording film containing Te as a main component can form a desired physical change part or optical property change part (hereinafter collectively referred to as a "bit") with very low energy, and is extremely promising as a high-sensitivity material. be. Sensitivity here refers to the energy required to form bits per unit area (mJ
/cJ).

However, when Te is left in the atmosphere, it is oxidized by oxygen or moisture, increasing its light transmittance and becoming transparent. When such Te is used as a recording film, the film thickness is extremely thin, on the order of several hundred layers, so if the light transmittance increases due to oxidation of the film, the sensitivity will drop significantly. That is, when the film is oxidized, the melting and evaporation temperature increases, and the absorption of energy such as light decreases due to transparency, so the energy required for bit formation increases, resulting in a significant decrease in sensitivity. For example, if a Te film is left in an atmosphere with a temperature of 70°C and a relative humidity of 85%,
Sensitivity decreases by about 20% in about 5 hours, and about 50% in about 15 hours.
% decrease.

In order to solve these problems, various measures have been taken to prevent oxidation of the Te film. One known method is to coat Tefi with a stable inorganic substance, but although this method is effective in preventing the oxidation of Te1i, it reduces the sensitivity and is expensive, so it has not been put to practical use. Not yet.

On the other hand, a method of coating the Te film with plastic is also known, but this method is advantageous in that the degree of deterioration of sensitivity is small due to the low thermal conductivity of plastic, but it allows oxygen and water to permeate relatively easily. Therefore, it is not very useful in preventing oxidation of TeM.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide an optical information recording medium that can write information with low energy and has a long life.

Big brother example taka! In order to achieve such an object, the present invention forms a recording film on a substrate, irradiates the recording film with an energy beam to physically or optically change a part of the recording film, and changes this change. An optical recording medium in which information is recorded in accordance with the arrangement of parts, characterized in that the recording film is made of a thin film containing at least tellurium, antimony, carbon, and hydrogen.

According to such an optical recording medium according to the present invention, since antimony, carbon, and hydrogen are contained in tellurium, the writing sensitivity of the recording medium is improved, the durability is improved, and the service life can be extended. Become.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail based on embodiments shown in the drawings.

FIG. 1 is a schematic cross-sectional view of an optical recording medium according to an embodiment of the present invention.

As shown in FIG. 1, in the optical recording medium 10 according to the present invention, a recording film 12 is formed on one surface of a substrate 11.

In addition to inorganic materials such as glass and aluminum, the substrate 11 may be made of polymethyl methacrylate, polycarbonate, a polymer alloy of polycarbonate and polystyrene, an amorphous polyolefin as shown in U.S. Pat. No. 4,614,778, or poly(4-4). Organic materials such as methyl-1-pentene, epoxy resin, polyethersulfophone, polysulfone, polyetherimide, etc. can be used. The thickness of this substrate 11 is preferably 0.
5 to 2.5 mm, particularly preferably 1.0 to 1.5 m.

The recording film 12 according to the present invention is made of a thin film containing at least tellurium (Te), antimony (Sb), carbon (C), and hydrogen (H), and is modulated (on/off) depending on the information to be recorded. By irradiating an energy beam such as a laser beam, a bit is formed in the irradiated portion. This bit may be a physically changed part such as a hole or a recess, or it may be a part that changes optical properties such as refractive index or reflectance. The film thickness of [12] needs to be thick enough to obtain sufficient light reflectance and thin enough not to impair sensitivity; specifically, about 100 μm to 1 μm is appropriate.

Such a record r! The content of sb in A12 is preferably 1 to 40,000 atomic %, particularly 1 to 30 atomic %, based on the entire recording film. When the content of sb is 1 atomic % or less, the change in transmittance of the recording film 12 over time becomes large, and the performance of the recording film 12 deteriorates over time.
This is not preferable because it does not extend the service life. Furthermore, if the sb content is 40 atomic % or more, the recording sensitivity will be insufficient, which is not preferable.

It is preferable that the C content in the recording film 12 is 5 to 40 atomic % based on the whole. If the C content is 5 atomic % or less, the recording film formed using a single low-melting point metal will have a longer lifespan. This is not preferable because no significant difference with the membrane can be seen;
If it exceeds atomic %, the recording sensitivity will be insufficient, which is not preferable.

Further, the content of H in the recording film 12 is preferably 5 to 40 atomic % based on the entire recording film from the viewpoint of life span and the like. The content of each element contained in the recording film 12 is measured, for example, by ICP emission spectrometry (inductively coupled plasma emission spectrometry) for metal elements, and by organic elemental analysis for carbon and hydrogen. .

In order to provide such a recording film 12 on one surface of the substrate 11, it can be done, for example, as follows.

First, an alloy is made from Te and sb, and this alloy is used as a target in a mixed gas of an organic gas containing C and H, such as CH4 or C2H2 gas, and A gas.
A recording M12 made of a Te--Sb alloy thin film containing C and H is deposited on the substrate 11 by sputtering. Alternatively, without producing an alloy consisting of Te and sb, a 're-sb alloy thin film containing C and H is sputtered onto the substrate 11 in the above mixed gas using Te and sb as separate targets. CH may also be deposited without using sputtering method.
It is also possible to apply a recording layer W412 made of a 're-sb film containing C and H to the substrate by forming a plasma of 4 and TB-Sb vapor. Further, a similar recording film 12 can also be formed by vapor phase epitaxy or plasma vapor phase epitaxy. Still other methods include Te, St),
Part or all of the C and H atoms may be ionized and deposited on the substrate in the form of a beam.

The contents of C and H in the recording film 12 made of a Te-Sb alloy thin film containing C and (1) can be controlled by changing the mixing ratio of organic gas such as CH4 and Ar and the applied high-frequency power. can.

For example, at a mixing ratio of CH4/Ar = 1, it is approximately 0.3W/-
By applying high frequency (13.56 MH2) power between the Te-5b target and the substrate 11, a film containing C in an atomic ratio of 0.2 to Te can be formed.

're- containing C and H thus formed
The optical properties such as reflectance or attenuation coefficient of the recording film 12 made of the sb alloy thin film vary depending on the content of C and H, and in order to use it for information recording, the film thickness should be adjusted depending on the optical properties as described above. is determined. As a result of experiments, it was found that the thickness of the recording film 12 is suitably in the range of 100 λ to 1 μm, as described above, and is best when the number of participants is 200 to 1000 people. The film formed under the above conditions is amorphous, and when this recording film is used as an optical recording medium using the physical change part formation method, the film formed under the above conditions has a higher The etched area around the physical change area becomes smooth, and the noise level when reading information can be suppressed to a low level. Further, even when such a recording film is used as an optical recording medium of the optical characteristic change portion formation method, the noise level during information reading can be suppressed to a low level. That is, when used as a recording medium of this type, in principle, Te1l
There is no problem of an increase in noise level due to swelling around bits in a single recording film, and it is also possible to reduce noise.

Note that, according to the present invention, the recording film 12 as described above includes:
Low melting point metals other than Te can be included. Examples of low melting point metals other than Te include bismuth, zinc, cadmium, indium, lead, and tin.

[Examples] The present invention will be described below based on more specific examples.

Create a 're-sb alloy consisting of Te and sb, use this alloy as a target, and use it as a 1:2 mixture of CH4 gas and A gas.
．． Sputtering is performed on the substrate 11 in the mixed gas of No. 3, and the content of Te is 48 atomic % and the content of sb is 7 atomic %.
, the content of C is 20 at%, the content of () is 25 at%
A recording film 12 was obtained.

Comparison 1 Same as Example 1 except that sb is not included, but sb with Te content of 55 at%, C content of 20 at%, and To content of 25 at% is not included. A recording film was obtained.

[Comparison between Example 1 and Comparative Example 1] Table 1 shows the rate of change over time (%) in the transmittance of each recording film obtained as described above. For Example 1 and Comparative Example 1, the recording film was heated at a temperature of 70°C and a relative humidity of 90%.
It shows the rate of change (%) in transmittance when left for 1000 hours in an atmosphere of

As shown in Table 1, in Example 1, the transmittance did not change even after 1000 hours, whereas in Comparative Example 1, the transmittance decreased. Note that in Comparative Example 1, the reason why the transmittance decreased is considered to be because Te was oxidized and temporarily turned black. It is also undesirable that the transmittance decreases from the initial state as described above because it becomes necessary to finely adjust the amount of energy of the energy beam used for recording or reproduction.

As explained above, according to the present invention, since the recording film contains at least Te, Sb, C, and H, recording sensitivity is improved and recording is maintained even after a long period of time. The transparency of the film hardly changes, the durability of the recording film itself is improved, and an optical recording medium with a long life can be obtained. Moreover, since the durability of the recording film itself is improved, as a result,
Since it is possible to use an acrylic substrate, a plastic substrate, etc. that easily allows moisture and oxygen to pass through as the substrate, it is possible to obtain an optical recording medium that is inexpensive and excellent in mass production.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an optical recording medium according to an embodiment of the present invention. 10... Optical recording medium 11... Substrate 12...
Recording membrane agent Patent attorney Shunichi Suzuki Figure 1

Claims (1)

[Claims] 1) A recording film is formed on a substrate, and a part of the recording film is changed physically or optically by irradiating the recording film with an energy beam, and the arrangement of the changed portions is changed. An optical recording medium adapted to record information correspondingly, characterized in that the recording film is a thin film containing at least tellurium, antimony, carbon, and hydrogen. 2) The content of antimony contained in the recording film is 1
The optical recording medium according to claim 1, characterized in that the content is 40 at.%. 3) The optical recording medium according to claim 1 or 2, wherein the content of carbon contained in the recording film is 5 to 40 atomic %.