JPH051756B2 - - Google Patents

Description

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 an excellent feature as a large-capacity recording device because of their high recording density. The material for this optical recording medium is tellurium (Te).
Chalcogen elements such as or compounds thereof are used (Japanese Patent Publication No. 47-26897). In particular, tellurium-selenium alloys are often used (Tokuko Showa).
54-41902, Japanese Patent Publication No. 57-7919, 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 8000 Å, and tellurium-selenium alloys are relatively well suited to this wavelength range, and can provide moderate reflectance and moderate absorption {Fijica Status Solidai, 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 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, polymethylpentyl, acrylic, or epoxy resin, or glass, and the substrate 1 is usually guided so that pits are recorded concentrically or spirally at regular intervals. A groove is provided.

[Problems to be Solved by the Invention] However, in the conventional optical recording medium as described above, tellurium, which is used as a recording layer,
With selenium-based alloys, it is difficult to form pits uniformly over one circumference of the track, so that sufficiently good recording and reproducing characteristics cannot be obtained. Furthermore, since large pits are formed during recording, high-density recording is not possible, and there is little margin for fluctuations in recording power, which poses a practical problem.

An object of the present invention is to provide a practical optical recording medium that has good weather resistance, allows high-density recording, and has good signal quality.

[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 is a selenium layer, a palladium layer, and a tellurium-selenium alloy layer laminated in sequence on a substrate.

In the present invention, as shown in FIG. 1, a selenium layer 2, a palladium layer 3, and a tellurium-selenium alloy layer 4 are sequentially laminated on a substrate 1 to form a recording layer.

Here, the thickness of the selenium layer is in the range of 5 to 100 Å, the thickness of the palladium layer is in the range of 0.5 to 50 Å, and the thickness of the tellurium layer is in the range of 0.5 to 50 Å.
The thickness of the selenium alloy layer is preferably in the range of 100 to 500 Å from the viewpoint of recording/reproducing characteristics and weather resistance, and the composition ratio of the tellurium-selenium alloy is preferably in the range of 5 to 50 atomic % of selenium to improve recording/reproducing characteristics and weather resistance. Desirable from this point of view.
Note that the palladium layer having a thickness of 0.5 to 50 Å here corresponds to the weight average thickness, and is actually a discontinuous film.

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 sequentially forming a selenium layer, a palladium layer, and a tellurium-selenium alloy layer on a substrate by vacuum evaporation. The tellurium-selenium alloy layer may be formed by single-source deposition from a tellurium-selenium alloy material, or by dual-source deposition from a tellurium layer and selenium.

[Function] By interposing the selenium layer and the palladium layer between the substrate and the tellurium-selenium alloy layer, pits are prevented from expanding significantly, and an excellent optical recording medium can be obtained. This is because the initial formation of small holes in the tellurium-selenium alloy layer, which is the main cause of reflectance changes due to pit formation, has become easier and more reliable due to the formation of the selenium and palladium layers. -This seems to be because the difference in surface energy due to the presence or absence of the selenium alloy layer changed due to the formation of the selenium layer and palladium layer.

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

Example 1 A polycarbonate resin disk substrate with 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 vacuum was evacuated to 6×10 ^-6 Torr or less. First, a selenium layer is deposited to a thickness of 50 Å by resistance heating evaporation, then palladium is deposited to a thickness of 1 Å by electron beam heating evaporation at a value calculated from the frequency change of the crystal resonator, and finally a tellurium-selenium alloy is deposited by resistance heating evaporation. It was deposited to a thickness of 225 Å so that the ratio of atomic % was 79:21. After annealing this optical disk at 95℃ for 1 hour,
The substrate incident reflectance at a wavelength of 8300 Å was measured and was 35%. Semiconductor laser light with a wavelength of 8300 Å is incident through the substrate and focused to approximately 1.5 μmφ.
Recording was performed under the conditions of a medium linear velocity of 5.6 m/sec, a recording frequency of 3.77 MHz, and a recording pulse width of 70 nsec, and reproduction was performed at 0.7 mW. Bandwidth at recording power 6.0mW
The carrier to noise ratio (C/N) at 30kHz is
It was good at 49dB. Further, the recording power range in which a C/N of 45 dB or more was obtained was wide, from 5.5 mW to 8.5 mW.

For comparison, an optical disk with a recording layer made of a 225 Å thick tellurium-selenium alloy (composition ratio 79:21 at %) was evaluated in the same way, and the recording power was
No pit is formed at 8.0mW, 48dB at 8.5mW
However, at 9.0 mW, the pits became too large and the C/N decreased to 41 dB, and the usable recording power range was very narrow.

Also, for comparison, 50 Å thick selenium and 225 Å thick tellurium-selenium alloy (composition ratio is 79:21 in atomic percent).
When an optical disk in which the recording layer was made by sequentially laminating the following layers was similarly evaluated, the highest C/N was obtained at a recording power of 6.0 mW, but the value was as low as 44 dB. This is because the noise increases significantly after recording.

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

Example 2 In the same manner as in Example 1, a 40 Å thick selenium layer, 2
An optical disk having a recording layer formed by sequentially laminating a palladium layer with a thickness of Å and a tellurium-selenium alloy layer with a thickness of 250 Å (composition ratio: 79:21 in atomic %) was prepared and evaluated in the same manner as in Example 1. At a recording power of 6.0 mW, the C/N is good at 48 dB, and the recording power range where a C/N of 45 dB or more can be obtained is from 5.5 mW.
It had a wide range of 8.0mW.

[Effects of the Invention] As explained above, the optical recording medium of the present invention has excellent weather resistance, allows high-altitude recording, and has good signal quality, so it is practically useful.

[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... Selenium layer, 3... Palladium layer,
4... Tellurium-selenium alloy layer, 21... Recording layer, 22
...Pitsuto.

Claims (1)

[Claims] 1. An optical recording medium consisting of a substrate and a recording layer formed on the substrate, a portion of which is selectively removed by laser light to record information, wherein the recording layer is made of a selenium layer, a palladium layer, a tellurium layer, etc. - An optical recording medium characterized in that selenium alloy layers are sequentially laminated on a substrate.