JPH0379776B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method of manufacturing an optical recording medium that can record and reproduce information using laser light. (Prior Art) Optical disk memories, which record and reproduce information on a medium using laser light, have excellent characteristics as large-capacity recording devices because of their high recording density. As materials for this optical recording medium, chalcogen elements such as Te or compounds thereof are used (Japanese Patent Publication No. 47-26897). In particular, tellurium selenium alloys are often used (Japanese Patent Application Laid-Open No. 47-4832, JP-A No. 50-42849, JP-A No. 50-43947). 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 8000 Å, and tellurium selenium alloys are relatively well suited to this wavelength range, and can provide moderate reflectance and moderate absorption (phys.stat. sol.7, 189,
1964)). (Problems to be Solved by the Invention) However, it is not easy to control the composition of tellurium selenium alloys. There was a problem with mass production. An object of the present invention is to provide a method for manufacturing an optical recording medium that is easy to mass-produce, has good signal quality, and has good weather resistance. (Means for solving the problem) The method for manufacturing an optical recording medium of the present invention is a method for manufacturing an optical recording medium in which information is recorded by selectively removing a part of a recording layer formed on a substrate using a laser beam. The method is characterized in that a selenium layer is formed on the substrate, a tellurium layer is formed thereon, a selenium layer is formed thereon, and then annealing is performed. (Function) Optical recording media have conventionally had a configuration as shown in FIG. That is, a recording layer 5 is formed on the substrate 1. The recording laser beam is focused and irradiated onto the recording layer 5 through the substrate 1, and pits 6 are formed. As the substrate 1, polycarbonate, polymethylpentene,
Synthetic resins such as acrylic resins and glass are used. Although various materials can be used for the recording layer 5, a tellurium selenium alloy is preferable in view of weather resistance. However, since it is not easy to control the composition of the tellurium selenium alloy film, there has been a problem in mass production. The present inventors formed a selenium layer 2, a tellurium layer 3, and a selenium layer 4 individually as shown in FIG. The inventors have discovered that an optical recording medium can be obtained which has better recording and reproducing characteristics than a recording medium and has weather resistance as good as that of an optical recording medium having a tellurium selenium alloy recording layer, leading to the present invention. Example 1 An example of the present invention will be described below. A polycarbonate resin disk substrate with a guide groove having an inner diameter of 15 mm, an outer diameter of 130 mm, and a thickness of 1.2 mm was placed in a vacuum evaporation apparatus, and the atmosphere was evacuated to 2×10 ^-5 Torr or less. As evaporation sources, Te was placed in the first resistance heating boat (made of molybdenum), and Se was placed in the second resistance heating boat (made of molybdenum). First, Se is deposited to a thickness of 25 Å, then Te is deposited to a thickness of 225 Å, and finally Se is deposited to a thickness of 25 Å.
The film was deposited to a thickness of Å. At this point, the substrate incident reflectance of the flat section at a wavelength of 8300 Å was measured and was 31%.
The absorption rate was 44%. Next, after annealing this optical disk in a nitrogen atmosphere at 80°C for 1 hour, the substrate incidence reflectance was measured again, and it was found to be 34%.
The absorption rate was 44%. Wavelength 8300Å
Using AlGaAs semiconductor laser, medium linear velocity 5.6
m/sec, recording frequency 0.625MHz (duty 50
When recording at 3.5 mW and playing back at 0.7 mW under conditions of 30kHz signal-to-noise ratio (C/
N) is 56dB, 2nd high frequency to signal ratio (2ndH/C)
A signal of good quality was obtained at -33dB. For comparison, a disk in which no Se layer was provided between the substrate and the tellurium layer had the same optical properties after annealing, but the recording and reproducing properties were significantly different.
The recording power at which 2ndH/C is minimum is 4.0mW, and 2ndH/C at that time is -31dB.
The C/N decreased to 38dB. This is because the noise after recording has increased significantly. Next, the optical recording medium of this example was placed in a high temperature and high humidity environment of 70°C and 80%.
After storage for 120 hours, the above characteristics were examined and there were no changes, confirming that the optical recording medium had excellent weather resistance. For comparison, disks with only a tellurium layer and disks with a selenium layer on a substrate and a tellurium layer thereon were unable to perform good recording and reproduction due to tellurium oxidation. Furthermore, for comparison, a disk that was not annealed had a problem in that the optical properties and recording/reproducing properties changed due to the high temperature and high humidity test. In the production of the optical recording medium of this example, a single element is deposited only three times, so there is no variation in film composition that is associated with the production of compounds. Therefore, film thickness control is the only factor that causes variations in medium characteristics. The film thickness variation of the vapor deposition apparatus is 1% or less, which is three times the standard deviation, within one run, and is not more than 3%, which is three times the standard deviation, between runs. This level of film thickness variation had no significant effect on the recording/reproducing characteristics and weather resistance of the optical recording medium of this example, and mass production was possible. Further, in this example, the annealing condition was set at 80° C. for 1 hour in nitrogen, but almost the same effect was obtained even in air atmosphere. I also tried varying the annealing time up to 24 hours, but the same effect was still obtained. Moreover, almost the same effect was obtained at 90°C. However, when the annealing temperature is lowered to 70°C or 60°C, it is desirable that the annealing temperature is 1 hour or more. Example 2 Optical recording media as shown in the table below were prepared and recorded and reproduced in the same manner as in Example 1. All annealing conditions were 80°C for 1 hour. All samples had a C/N of 54 dB or more and a 2ndH/C of -26 dB or less, and the characteristics did not change even after a high temperature and high humidity test at 70°C and 80% for 120 hours. Although the recording power at which 2ndH/C becomes the minimum increases slightly when the Te layer is thicker, recording was still possible at a low power of 5 mW or less. In the above embodiment, the thickness of the selenium layer is the same on both the upper and lower sides, but it is also possible to have different thicknesses. However, the thickness is preferably in the range of 5 to 60 Å from the viewpoint of high weather resistance.

【table】

【table】

[Table] (Effects of the Invention) As is clear from the above examples, the present invention makes it possible to mass-produce optical recording media with good signal quality and good weather resistance.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an optical recording medium, and FIG. 2 is a schematic cross-sectional view of a conventional optical recording medium. In the figure, 1 is a substrate, 2 and 4 are selenium layers, 3 is a tellurium layer, 5 is a recording layer, and 6 is a pit.

Claims (1)

[Claims] 1. A method for manufacturing an optical recording medium in which information is recorded by selectively removing a part of a recording layer formed on a substrate with a laser beam, in which a selenium layer is formed on the substrate, and a tellurium layer is formed on the selenium layer. A method for producing an optical recording medium, which further comprises forming a selenium layer thereon, and then annealing the selenium layer.