JPS62282979A - Optical recording medium - Google Patents

Abstract

PURPOSE:To enhance mass productivity and weatherability, by successively laminating a selenium layer, a tellurium layer and selenium layer to a substrate to provide a recording layer and setting the thickness of the selenium layer to 5-20Angstrom and the tellurium layer to 275-400Angstrom . CONSTITUTION:A selenium layer 2 with a thickness of 5-20Angstrom , a tellurium layer with a thickness of 275-400Angstrom and a selenium layer 4 with a thickness of 5-20Angstrom are successively formed to a substrate 1 by vacuum vapor deposition to form a recording layer to obtain an optical recording medium. As the substrate, a synthetic resin such as polycarbonate, polyolefin, polymethylpentene an acrylic resin or an epoxy resin or glass is used. Further, a layer formed of a separate substance, for example, a lead layer, a palladium layer or a magnesium layer can be inserted between the above-mentioned layers.

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 or compounds thereof are used as materials for this optical recording medium (Japanese Patent Publication No. 47-2689).
Publication No. 7). 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 excavation wavelength of around 8000A, but tellurium-selenium alloys are relatively well suited to this wavelength range, and can provide moderate reflectance and moderate absorption.7. 189.1964 (phys, 5tat
, sol, 7.189.1964)).

An optical recording medium using this tellurium-selenium alloy as an optical recording layer has a groove 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. As the substrate 1, synthetic resins such as polycarbonate, polyolefin, polymethylpentene, acrylic, epoxy resin, etc., and glass are used. Guide grooves are provided on the substrate so that the bits are recorded concentrically or spirally at regular intervals with high precision. 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 1.3 mm, 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 focusing light. Information is read by irradiating a laser beam with a weaker power than that used during recording so as to pass over the bit, and detecting changes in reflectance caused by 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, since it is difficult to form bits uniformly over one track, sufficiently good recording and reproducing characteristics cannot be obtained.

On the other hand, by sequentially laminating a selenium layer, a tellurium layer, and a selenium layer on a substrate, the present inventors achieved excellent mass productivity and weather resistance, and were able to form pits uniformly over one track circumference, resulting in high sensitivity and good performance. We have already proposed an optical recording medium with excellent recording and reproducing characteristics. However, even in this case, there was still room for improvement in terms of reproduction characteristics when reproduced for a long time with high laser power.

An object of the present invention is to provide an optical recording medium that can be easily mass-produced, has good weather resistance, high sensitivity, and good signal quality, and can be reproduced for a long time with a sufficiently large laser power.

[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. The recording layer has at least a selenium layer, a tellurium layer, and a selenium layer in this order, and each of the selenium layers has a thickness of 5 to 20. A, and the thickness of the tellurium layer is in the range of 275 to 400 mm.

In the present invention, for example, as shown in FIG.
A recording layer is formed by sequentially laminating the tellurium layer 3 of A and the selenium layer 4 having a thickness of 5 to 20 layers. Further, a layer formed of another material, such as a lead layer, a palladium layer, a magnesium layer, etc., may be inserted between each layer.

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

The optical recording medium of the present invention can be manufactured by, for example, sequentially vacuum-depositing selenium, tellurium, and selenium onto a substrate.

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

Example 1 A polycarbonate resin disk substrate with an inner diameter of 15 m, an outer diameter of 130 IN r1, and a thickness of 1.2 #, which had been annealed at 100"C for 2 hours, was placed in a vacuum device and was heated to a size of 5 x 1O-6T.
It was evacuated to below orr. As evaporation sources, tellurium (Te) was placed in the first resistance heating boat, and selenium (Se) was placed in the second resistance heating boat. First, Se was deposited to a thickness of 13 layers, then Te was deposited to a thickness of 350 layers, and finally Se was deposited to a thickness of 1 layer.
Three layers were deposited. After annealing this optical disk in a nitrogen atmosphere at 95° C. for 1 hour, the substrate incident reflectance at a wavelength of 8300 was measured and found to be 41%. Semiconductor laser light with a wavelength of 8300 is incident through the substrate and focused on the recording layer to about 1.5IIInφ, and the medium linear velocity is 5.
．． Recording was performed at a speed of 6 m/sec, a recording frequency of 3.77 IHz, a recording pulse width of 7 on sec, and a recording power of 6.5 mW, and reproduction was performed at 0.7 mW. Band width 30kHz2
The carrier-to-noise ratio (C/N) of 51 dB was good, and it was also good even after 106 times of reproduction at 1.0 mWF.

Next, after storing the disk of this example in a high temperature and high humidity environment of 70°C and 80% for 60 hours, the above characteristics were examined, but there was no change, confirming that it was an optical recording medium with excellent weather resistance. It was done.

Examples 2 to 21 Optical recording media were produced in the same manner as in Example 1, except that the film thicknesses of the se layer and the Te layer were as shown in Table 1.

The same table shows the results of a deterioration test and a weather resistance test using reproducing power in the same manner as in Example 1.

Comparative Examples 1 to 4 Optical recording media were produced in the same manner as in Example 1, except that the thicknesses of the Se layer and Te layer were as shown in Table 1.

The same table shows the results of a deterioration test and a weather resistance test using reproducing power in the same manner as in Example 1.

Table 1 shows the amount of decrease in C/H when regenerating 10'' times at 1.0 mW.

As can be seen from Table 1, excellent effects are exhibited when the thickness of the tellurium layer ranges from 2 to 40 OA and the thickness of the selenium layer ranges from 5 Å to 20 OA.

[Effects of the Invention] As explained above, the present invention 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. can get.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing an 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 layer 21...Recording layer 22...Pit 22 pits

Claims (1)

[Claims] (1) An optical recording medium comprising a substrate and a recording layer formed on the substrate, a portion of which is selectively removed by a laser beam to record information, wherein the recording layer includes at least a selenium layer, a tellurium layer and 1. An optical recording medium comprising selenium layers in sequence, each of the selenium layers having a thickness in the range of 5 to 20 Å, and the tellurium layer having a thickness in the range of 275 to 400 Å.