JPS62299394A - Optical recording medium - Google Patents

Abstract

PURPOSE:To contrive higher mass-productivity, weatherability and signal quality and enable reproduction to be achieved for a long time with sufficiently high laser power, by providing a layer comprising selenium as a main constituent, a layer comprising tellurium and nitrogen as main constituents and a layer comprising selenium as a main constituent in a laminated form in a recording layer of an optical recording medium capable of recording and reproducing information by laser light. CONSTITUTION:A recording layer provided on a base 1 comprises a selenium layer 2 comprising selenium as a main constituent, a tellurium-nitrogen layer 3 comprising tellurium and nitrogen as main constituents and a selenium layer 4, which are sequentially provided in a laminated form. With this construction, an excellent optical recording medium free of deterioration of reproduction characteristics even after reproduction for a long time with high laser power can be obtained. The thickness of each of the layers 2, 4 is preferably 5-100Angstrom while that of the layer 3 is preferably 100-1,000Angstrom , from the viewpoints of recording and reproduction characteristics and weatherability. The content of nitrogen in the layer 3 is preferably at least 2atom% and less than 20atom%, from the viewpoints of recording and reproduction characteristics and weatherability.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical recording medium on which information can be recorded and reproduced using laser light.

[Prior Art] Optical disk memories, which record and reproduce information on a medium using laser light, have excellent features as large-capacity recording devices because of their high recording density. Chalcogen elements such as tellurium (Te>) or compounds thereof are used as materials for this optical recording medium (Japanese Patent Publication No. 47-2689).
7@Publication). In particular, tellurium-selenium alloys are often used (Japanese Patent Publication No. 41902/1983, Japanese Patent Publication No. 57/1983).
-7919, Japanese Patent Publication No. 57-56058).

In recent years, in order to downsize recording devices, semiconductor lasers have been used as laser light sources. Semiconductor lasers have an oscillation wavelength of around 8,000 nm, and tellurium-selenium alloys are relatively well suited to this wavelength range, and can provide moderate reflectance and moderate absorption. , 7,189.1964 (phys, 5ta
t, 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 a tellurium-selenium alloy is provided adjacent to the substrate 1. The recording laser beam is focused and irradiated onto the recording layer 21 through the substrate 1, and pits 22 are formed. The substrate 1 is made of synthetic resin such as polycarbonate, polyolefin, polymethylpentene, acrylic, epoxy resin, etc., or glass. Usually, the substrate 1 is guided so that pits are recorded concentrically or spirally at regular intervals. A groove is provided.

When light enters a groove with a width similar to the diameter of the laser beam, the light is diffracted, and as the beam center shifts from the groove, the spatial distribution of the intensity of the diffracted light changes.This is detected and the laser beam is directed to the center of the groove. The servo system is configured as follows. The width of the groove is usually 0.3 to 1.31 JM, and the depth of the groove is set within the range of 1712 to 174 of the laser wavelength used. A servo system is similarly configured for condensing light. Information is read by irradiating a laser beam with a weaker power than during recording so as to pass over the pits, and detecting changes in reflectance due to the presence or absence of pits. It is desirable that the power of this reproducing laser beam be large, since this allows the reproduction signal and servo signal to be increased and is less susceptible to external noise.

[Problems to be Solved by the Invention] However, in the conventional optical recording media as described above, it is not easy to control the composition of the tellurium-selenium alloy used as the recording layer, and therefore mass production is difficult. There was a problem. Furthermore, sufficiently good recording and reproducing characteristics were not obtained.

On the other hand, the present inventors formed a selenium layer, a tellurium layer on the substrate,
We have already found and proposed that by sequentially laminating selenium layers to form a recording layer, an optical recording medium can be obtained that is mass-producible, weather resistant, highly sensitive, and has good recording and reproducing characteristics.

The present invention is a rough improvement on this, and provides an optical recording medium that is excellent in mass production and weather resistance, has high sensitivity and good signal quality, and can be reproduced for a long time with a sufficiently large laser power. With the goal.

[Means for Solving the Problems] The present invention provides an optical recording medium comprising a substrate and a recording layer formed on the substrate, a portion of which is selectively removed by laser light to record information. An optical recording medium characterized in that the recording layer has at least a layer mainly composed of selenium, a layer mainly composed of tellurium and nitrogen, and a layer mainly composed of selenium, which are laminated in sequence. .

In the present invention, for example, as shown in FIG. 1, a layer 2 containing selenium as a main component (hereinafter referred to as a selenium layer) 2 and a layer containing tellurium and nitrogen as a main component (hereinafter referred to as a tellurium-nitrogen layer) are provided on a substrate 1. 3 and selenium layer 4 are sequentially laminated to form a recording layer. In addition, other layers may be present between the substrate 1 and the selenium layer 2 and/or outside the selenium layer 4. By providing at least the three layers of selenium layer 2, tellurium-nitrogen layer 3, and selenium layer 4 in sequence, the reproduction characteristics do not deteriorate even when reproduced for a long time with high laser power.
An excellent optical recording medium can be obtained.

The thickness of the upper and lower selenium layers is preferably in the range of 5 to 100 μm, and the thickness of the tellurium-nitrogen layer is preferably in the range of 100 to 1000 μm, from the viewpoint of recording/reproducing characteristics and weather resistance. tellurium
The content of nitrogen in the nitrogen layer is desirably 2% or more and less than 20% in terms of atomic percent from the viewpoint of recording/reproducing characteristics and weather resistance.

As the substrate, commonly used materials such as synthetic resins such as polycarbonate, polyolefin, polymethylpentene, acrylic and epoxy resins, and glass are used.

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

A polycarbonate resin disk substrate having an inner diameter of 15 ends, an outer diameter of 130 m, and a thickness of 1.2 m, which had been annealed for 2 hours in Example ioo'c, was placed in a vacuum apparatus and evacuated to 3 x 10' TOrr or less. As an evaporation source, tellurium (Te) was placed in the first resistance heating board, and selenium (Se) was placed in the second resistance heating port. By reactive vapor deposition in a nitrogen gas atmosphere, a layer containing Se as the main component was formed to a thickness of 40 mm, a layer of Te and nitrogen (N) was formed to a thickness of 260 mm (the content of N was 6% in terms of atomic percent), and a layer of Se The main component layers were sequentially laminated to a thickness of 40 layers. After this optical disk was annealed for 1 hour in a nitrogen atmosphere at 95° C., the substrate incident reflectance at a wavelength of 8300 was measured and found to be 38%. A semiconductor device with a wavelength of 8,300 people enters the light through the substrate and 1.6Jj! on the recording layer! Narrow down to about riφ, medium linear velocity 5
．． Recording was performed under the conditions of 6 m/Sec, recording frequency 3.77) IH2, recording pulse width 70 nsec, and recording power 5.5 mW, and reproduction was performed at 0.7 m-. Band width 30kHz2
The carrier-to-noise ratio (C/N) was good at 50 dB, and the same good result was obtained even after reproducing 106 times at 1.0 mW.

Next, after storing the disk of this example in a 70'C 180% high temperature and high humidity environment for 60 hours, the above characteristics were examined, but there were no changes, confirming that it was an optical recording medium with excellent weather resistance. Ta.

For comparison, 40-layer thick Se, 260
For a disk in which a Te layer with a thickness of 40 mm and a layer of Se with a thickness of 40 mm were sequentially laminated, the C/N deteriorated by approximately 1 dB after 106 times of playback at 1.0 mWF.

[Effects of the Invention] As explained above, the optical recording medium of the present invention is excellent in mass production and weather resistance, has high sensitivity and good signal quality, and can be reproduced for a long time with a sufficiently large laser power. It's Chino.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing one embodiment of the optical recording medium of the present invention, and FIG. 2 is a partial sectional view showing a conventional optical recording medium. 1...Substrate 2.4...Selenium layer 3...Tellurium-nitrogen layer 21...Recording layer 22...Pit

Claims (1)

[Claims] (1) In an optical recording medium consisting of a substrate and a recording layer formed on the substrate, a portion of which is selectively removed by a laser beam to record information, the recording layer includes selenium layered sequentially. 1. An optical recording medium comprising at least a layer containing tellurium as a main component, a layer containing tellurium and nitrogen as a main component, and a layer containing selenium as a main component.