JPH061557B2 - Optical recording medium - Google Patents

Description

The present invention relates to an optical recording medium capable of recording and reproducing information with a laser beam.

[Prior Art] An optical disk memory that records and reproduces information on a medium with a laser beam has an excellent feature as a large-capacity recording device because of its high recording density. A chalcogen element such as tellurium (Te) or a compound thereof is used as the material for the optical recording medium (Japanese Patent Publication No. 47-26897).
In particular, tellurium-selenium alloys are often used (Japanese Patent Publication No. 54-41902, Japanese Patent Publication No. 57-7919, Japanese Patent Publication No. 57-).
56058 publication).

In recent years, a semiconductor laser has been used as a laser light source in order to miniaturize a recording device. A semiconductor laser has an oscillation wavelength of around 8000 Å, but a tellurium-selenium alloy is relatively well suited to this wavelength band, and can obtain an appropriate reflectance and an appropriate absorptivity {Physical Status Solidide, 7 ,, 189,1964 (phys.stat.sol. 7 , 189,1964)}.

An optical recording medium using this tellurium-selenium alloy as an optical recording layer has a structure as shown in FIG. That is, a recording layer 21 made of tellurium-selenium alloy is provided adjacent to the substrate 1. The recording laser light is focused onto the recording layer 21 through the substrate 1 to form pits 22. As the substrate 1, synthetic resin such as polycarbonate, polyolefin, polymethylpentene, acryl, epoxy resin, or glass is used, and the substrate 1 is usually guided so that pits can be accurately recorded in a concentric or spiral pattern at regular intervals. A groove is provided.

When light is incident on a groove with a width of about the laser beam diameter, the light is diffracted and the spatial distribution of the diffracted light intensity changes as the beam center shifts from the groove, so this is detected and the laser beam is incident on the center of the groove. The servo system is configured as follows. The width of the groove is usually 0.3 to 1.3 μm, and the depth of the groove is set in the range of 1/12 to 1/4 of the laser wavelength used. A similar servo system is configured for focusing. Information is read by irradiating a laser beam having a weaker power than that at the time of recording so as to pass over the pit, and detecting a change in reflectance due to the presence or absence of the pit.

[Problems to be Solved by the Invention] However, the signal quality was not sufficiently good in the optical recording medium using the tellurium-selenium alloy layer as the recording layer.

On the other hand, the inventors of the present invention have found that the recording layer containing tellurium, selenium, and nitrogen as main components improves the signal quality, and have already proposed. The present invention is a further improvement of the above, and an object thereof is to provide an optical recording medium having good weather resistance, high sensitivity, and good signal quality.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a substrate and a recording layer formed on the substrate on which information is partially removed by laser light to record information. In the optical recording medium consisting of, the recording layer comprises a layer formed on the side of the substrate containing silicon carbide as a main component, and tellurium, selenium, and nitrogen formed outside the substrate adjacent to this layer. It has at least a layer as a main component.

In the present invention, for example, as shown in FIG. 1, a layer containing sulfide as a main component (hereinafter abbreviated as a carbide layer) 2 and a layer containing tellurium, selenium, and nitrogen as main components (hereinafter tellurium-selenium) on a substrate 1. -Nitrogen layer) 3 is sequentially laminated to form a recording layer. Providing the carbide layer 2 between the substrate 1 and the tellurium-selenium-nitrogen layer 3 prevents the pits formed by recording from greatly expanding. Therefore, since the pits can be filled and recorded, high density recording becomes possible. In addition, since the margin for recording power fluctuation becomes large, it becomes a practical optical recording medium. Furthermore, since a large pit is not formed, tracking and focus servo do not become unstable, so that the optical recording medium becomes a practical one.

Various kinds of carbides can be used for the carbide layer, of which zirconium carbide, silicon carbide, chromium carbide, titanium carbide and the like are particularly desirable. In the case of non-absorbed carbide, the film thickness is preferably in the range of 5Å to 2000Å.
When absorbing carbides, the film thickness is preferably in the range of 2Å to 1000Å. The recording pits when the absorbing carbide is used are formed by the holes of the tellurium-selenium-nitrogen layer and the deformation of the carbide layer (holes, recesses, etc.).

The thickness of the tellurium-selenium-nitrogen layer is preferably in the range of 100Å to 1000Å from the viewpoint of recording / reproducing characteristics. Further, the content of nitrogen in the tellurium-selenium-nitrogen layer is 2% or more and less than 20% in terms of the number of atoms, and the recording / reproducing characteristics,
It is desirable from the viewpoint of weather resistance, and the content of selenium is preferably in the range of 2% to 50% in terms of atomic number from the viewpoint of weather resistance.

The tellurium-selenium-nitrogen layer contains lead, arsenic, tin, germanium, cadmium, thallium, antimony, sulfur, phosphorus, indium, gallium, zinc, bismuth, aluminum, copper, silver, magnesium, tantalum, gold, palladium, and cobalt. At least one element selected from the group may be added. In this case, the shape of the pit may be properly adjusted. However, it is desirable that the added amount is less than 20% in terms of the number of atoms.

The film forming method may be a vapor deposition method, a reactive vapor deposition method, an ion plating method, an ion beam deposition method, or the like, in addition to the sputtering method.

As the substrate, a commonly used one such as glass, synthetic resin such as polycarbonate, polyolefin, polymethylpentene, acryl, epoxy resin or the like is used.

[Function] By interposing the carbide layer between the substrate and the tellurium-selenium-nitrogen layer, the pits are not greatly expanded, and an excellent optical recording medium can be obtained. It is considered that this is because the difference in surface energy due to the presence or absence of the tellurium-selenium-nitrogen layer changes due to the formation of the carbide layer.

[Examples] Examples of the present invention will be described below.

15mm inner diameter, 130mm outer diameter, annealed at 100 ℃ for 2 hours,
On a polycarbonate resin disk substrate with a thickness of 1.2 mm, silicon carbide is formed to a thickness of about 60 Å, and subsequently, on this,
A tellurium-selenium alloy target was magnetron sputtered with a mixed gas of argon and nitrogen to form a tellurium-selenium-nitrogen layer having a tellurium-selenium-nitrogen ratio of 90: 4: 6 at an atomic percentage of about 240Å. This optical disk 95
After annealing in nitrogen atmosphere at ℃ for 1 hour, wavelength 8300
The substrate incident reflectance at Å was measured and found to be 32%. A semiconductor laser beam with a wavelength of 8300Å is incident through the substrate and focused on the recording layer to a diameter of about 1.6 μmφ, and the medium linear velocity is 5.6 m / se.
c, recording frequency was 3.77 MHz, recording pulse width was 70 nsec, recording power was 6.5 mW, and recording was performed at 0.7 mW. Band width 30
The carrier-to-noise ratio (C / N) at 50 kHz was as good as 50 db. After the optical disc was stored in an environment of high temperature and high humidity of 70 ° C. and 80% for 60 hours, the above characteristics were examined, but it was confirmed that the optical recording medium showed no change and was excellent in weather resistance.

It was confirmed that the recording power range in which a C / N of 45 dB or more was obtained was about twice as large as that of an optical disk having no silicon carbide layer for comparison, and a large margin for recording power fluctuation. Moreover, the tracking and focus servos were not unstable.

[Advantages of the Invention] As described above, the optical recording medium of the present invention has good weather resistance, high sensitivity, and good signal quality.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an embodiment of an optical recording medium of the present invention, and FIG. 2 is a partial sectional view showing a conventional optical recording medium. 1 ... Substrate 2 ... Carbide Layer 3 ... Tellurium-Selenium-Nitrogen Layer 21 ... Recording Layer 22 ... Pit

Claims (1)

[Claims] 1. An optical recording medium comprising a substrate and a recording layer formed on the substrate for partially recording information by selective removal by a laser beam, wherein the recording layer contains silicon carbide as a main component. And a layer formed on the substrate side,
Tellurium formed on the outside of the substrate adjacent to this layer,
An optical recording medium comprising at least a layer containing selenium and nitrogen as main components.