JPH0530391B2 - - 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 semiconductor 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 Publication No. 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, but tellurium selenium alloys are relatively well suited to this wavelength range, and can provide moderate reflectance and moderate absorption (Physica Status Solidi).
stat・sol・7, 189, 1964)).

(Problems to be Solved by the Invention) However, none of these media has sufficiently good signal quality and is suitable for semiconductor laser recording.

An object of the present invention is to provide an optical recording medium suitable for semiconductor laser recording that has good weather resistance, sufficiently good signal quality, and a large recording power margin.

(Means for solving the problem) The optical recording medium of the present invention is an optical recording medium in which information is recorded and read by semiconductor laser light, and includes:
A layer mainly composed of silicon nitride, zirconium nitride, chromium nitride or titanium nitride,
An optical recording medium comprising at least two layers containing tellurium, selenium, and nitrogen as main components.

(Function) Optical recording media have conventionally had a configuration as shown in FIG. That is, the recording layer 21 is provided on 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, polymethylpentyl, acrylic, and epoxy resins, and glass are used. Guide grooves are provided on the substrate so that pits are recorded concentrically or spirally at regular intervals with high precision. When light enters a groove with the diameter of a laser beam, the light is diffracted, and as the beam center shifts from the groove, the spatial distribution of the diffracted light intensity changes.
A servo system is configured to detect this and direct the laser beam to the center of the groove. 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 servo system is similarly configured for condensing light.
Information is read by irradiating a laser beam with a power weaker than that used during recording so as to pass over the pits, and detecting changes in reflectance caused by the presence or absence of pits.

Although various materials can be used for the recording layer 21, a tellurium selenium alloy film is preferable in consideration of weather resistance. However, the signal quality was not sufficiently good with only the tellurium selenium alloy layer. The inventors of the present invention have found that by making the recording layer mainly composed of tellurium, selenium, and nitrogen, a medium with good signal quality and suitable for semiconductor laser recording can be obtained, and has already proposed this method. The present invention further improves these, and as shown in FIG.
By providing this, the pits formed by recording can be prevented from expanding significantly. Therefore,
High-density recording is possible because the pits can be packed together for recording. Furthermore, since the margin against fluctuations in recording power is increased, the optical recording medium becomes a practical optical recording medium. Furthermore, since no large pits are formed, tracking and focus servo do not become unstable, making it a practical optical recording medium. The reason why the pits do not expand significantly is not clear, but it is thought to be because the difference in surface energy depending on the presence or absence of the tellurium selenium nitrogen layer changes due to the formation of a layer mainly composed of nitride.

(Example) Examples of the present invention will be described below.

Silicon nitride is formed to a thickness of about 100 Å on a polycarbonate resin disk substrate with an inner diameter of 15 mm, outer diameter of 130 mm, and thickness of 1.2 mm that has been annealed at 100°C for 2 hours.
Subsequently, a tellurium selenium alloy target is magnetron sputtered with a mixed gas of argon and nitrogen to form a tellurium selenium nitrogen layer with an atomic percent ratio of tellurium to selenium to nitrogen of about 90:4:6.
A thickness of 240 Å was formed. After annealing this optical disk in a nitrogen atmosphere at 95°C for 1 hour, it was
When the incident reflectance of the substrate was measured, it was 32%. Semiconductor laser light with a wavelength of 8300 Å is incident through the substrate, focused to about 1.6 μmφ on the recording layer, and recorded under conditions of medium linear velocity of 5.6 m/sec, recording frequency of 3.77 MHz, recording pulse width of 70 nsec, and recording power of 6.5 mW. Regeneration was performed at 0.7mW. The carrier-to-noise ratio (C/N) with a bandwidth of 30 KHz was as good as 50 dB. After this optical disk was stored in a high temperature and high humidity environment of 70°C and 80% 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.

Compared to a comparative optical disk without a silicon nitride layer, the recording power range in which a C/N of 45 dB or more can be obtained is approximately twice as wide, and it was confirmed that there is a large margin against recording power fluctuations. Also, the tracking and focus servos did not become unstable.

Various nitrides can be used as the nitride layer, but silicon nitride, zirconium nitride, chromium nitride, and titanium nitride are particularly preferred. The film thickness for non-absorbing nitrides is from 5 Å.
A range of 2000 Å is desirable. In the case of absorbing nitride, the film thickness is preferably in the range of 2 Å to 1000 Å. When absorbing nitride is used, recording pits are formed by holes in the tellurium selenium nitrogen layer and deformations (holes, recesses, etc.) in the nitride layer. Further, the nitride layer may contain other components within a range that does not impair the effect of suppressing the enlargement of the pit diameter.

The thickness of the tellurium selenium nitrogen layer is preferably in the range of 180 Å to 400 Å from the viewpoint of recording/reproducing characteristics, and the nitrogen content is preferably 2% or more and 10% or less in atomic percent from the viewpoint of recording/reproducing characteristics and weather resistance. The amount is atomic percent 2
A range of 10% to 30%, particularly 10% to 30%, is desirable from the viewpoint of weather resistance.

The tellurium selenium nitrogen layer contains lead, arsenic, tin, germanium, cadmium, thallium, phosphorus, indium, gallium, zinc, aluminum, copper,
silver, magnesium, tantalum, gold, paladium,
Addition of at least one element selected from the group of cobalt may improve the shape of the pit. However, the amount added is preferably less than 20% in atomic percent.

In addition to the sputtering method, the film forming method may be an evaporation method, a reactive vapor deposition method, an ion, plate-tening method, an ion beam deposition method, or the like.

(Effects of the Invention) As is clear from the above embodiments, the present invention provides an optical recording medium that has good weather resistance, sufficiently good signal quality, a large recording power margin, and is suitable for semiconductor laser recording.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of the optical recording medium of the present invention, and FIG. 2 is a sectional view of a conventional optical recording medium. In the figure, 1 is a substrate, 2 is a layer mainly composed of nitride, 3 is a layer mainly composed of tellurium selenium nitrogen, 21 is a recording layer, and 22 is a pit.

Claims (1)

[Claims] 1. Optical recording media in which information is recorded and read by semiconductor laser light include a layer containing silicon nitride, zirconium nitride, chromium nitride, or titanium nitride as a main component, and a layer containing tellurium, selenium, and nitrogen as main components. An optical recording medium comprising at least two layers.