JPH061556B2 - 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 is used, and the substrate 1 is usually provided with guide grooves so that pits can be accurately recorded at concentric circles or spirals at regular intervals. It 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 only 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 includes a layer formed on the side of the substrate containing zinc sulfide as a main component, and tellurium, selenium and nitrogen formed outside the substrate adjacent to the 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 sulfide layer) 2 on a substrate 1,
A layer containing tellurium, selenium and nitrogen as main components (hereinafter abbreviated as tellurium-selenium-nitrogen layer) 3 is sequentially laminated to form a recording layer. Providing the sulfide layer 2 between the substrate 1 and the tellurium-selenium-nitrogen layer 3 prevents the pits formed by recording from greatly expanding. Therefore,
High-density recording is possible because pits can be filled and recorded. 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 sulfides can be used as the sulfide layer, of which zinc sulfide is particularly desirable. In the case of non-absorbing sulfide, the film thickness is preferably in the range of 5Å to 1800Å. In the case of absorbing sulfide, the film thickness is preferably in the range of 2Å to 900Å. The recording pits when the absorbing sulfide is used are formed by the holes of the tellurium-selenium-nitrogen layer and the deformation (holes, recesses, etc.) of the sulfide layer.

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.

[Operation] By interposing the sulfide layer between the substrate and the tellurium-selenium-nitrogen layer, the pits do not greatly expand, 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 sulfide layer.

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

Example Inner diameter 15 mm, outer diameter 130 mm, annealed at 100 ° C. for 2 hours,
Approximately 100 Å of zinc sulfide is formed on a 1.2 mm thick polycarbonate resin disk substrate, and then a tellurium-selenium alloy target is magnetron sputtered with a mixed gas of argon and nitrogen to give a tellurium-selenium-nitrogen ratio. A 90: 4: 6 tellurium-selenium-nitrogen layer was formed in a thickness of about 240 Å with a number of atomic percent.

After annealing this optical disk for 1 hour in a nitrogen atmosphere at 95 ° C., the substrate incident reflectance at a wavelength of 8300Å was measured and found to be 32%. A semiconductor laser beam with a wavelength of 8300Å enters through the substrate and is focused on the recording layer to about 1.6 μmφ.
Recording was performed at a medium linear velocity of 5.6 m / sec, a recording frequency of 3.77 MHz, a recording pulse width of 70 nsec, and a recording power of 6.5 mW, and the recording was performed at 0.7 mW. Bandwidth 30kHz carrier to noise ratio (C
/ N) was as good as 50db. This optical disc at 60 ℃, 80
After storing in an environment of high temperature and high humidity of 60% for 60 hours, the above characteristics were examined, but it was confirmed that the optical recording medium had 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 zinc sulfide layer for comparison, and that there was a large margin for recording power fluctuations. 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 ... Sulfide 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 recording information by selectively removing a part by laser light, wherein the recording layer contains zinc sulfide as a main component. And a layer mainly composed of tellurium, selenium, and nitrogen, which is formed adjacent to the substrate and outside the substrate. Optical recording medium.