JPH01277341A - Optical recording medium - Google Patents

Abstract

PURPOSE:To provide the recording medium which allows both high-sensitivity recording and rewriting by forming a recording layer contg. one or two elements selected from Si, Ge and Sn and one element selected from halogen elements. CONSTITUTION:The one element or two elements selected from the three elements; Si, Ge and Sn and the one element selected from the halogen elements are incorporated as the essential components into the optical recording film of the optical recording medium so that recording and erasing are executed by the phase transition between the amorphous state and the crystalline state which takes place when the recording layer is irradiated by light. The optical properties of the amorphous alloy can be controlled by controlling the content of the halogen to be incorporated and the content of the halogen is preferably >=10<-3>% and <=10% by carbon atomic %. The recording medium having the sufficiently high recording sensitivity is obtd. and the stabler recording and reproducing characteristics are obtd. by using the recording material of a tetrahedral system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium on which information is recorded and reproduced by irradiation with laser light.

[Conventional technology]

Optical recording media, which record and reproduce information using laser light, have recently been rapidly put into practical use due to improvements in basic technologies such as semiconductor lasers, recording materials, and film formation methods, as well as the ability to record large amounts of data. The path has been opened. The above-mentioned recording medium recording methods include (1) forming pits or bubbles in the recording film, (2) changing optical properties such as reflectance of the recording film, etc. using thermal energy from laser beam irradiation. is proposed.

As conventional optical recording materials, those containing chalcogenide elements such as Te, Se, and 8 are in practical use. However, many chalcogenide-based elements are chemically unstable and there are concerns about their durability, and attempts have been made to improve them by adding various additives or providing protective films.

Some tetrahedral materials such as sGe and St are
It is chemically stable and less toxic than chalcogenide materials, and attempts have been made to use this material in optical recording media. For example, JP-A-58-1754
No. 5 discloses a technique using phase change between amorphous and crystalline silicon layers. Also, JP-A-60
No. 87443 discloses a technique in which amorphous silicon partially contains 5i-0-H bonds and recording is performed by switching the bond state.

[Problem to be solved by the invention]

However, with the above-mentioned conventional techniques, the recording sensitivity was insufficient, and writing and erasing in the semiconductor laser wavelength region was difficult. Furthermore, the technology disclosed in 45F No. 87443/1987 had poor thermal stability due to hydrogen desorption, etc.

The present invention has been made in view of the above problems, and provides an optical recording medium that uses a tetrahedral recording material, has sufficiently high recording sensitivity, and provides stable recording and reproducing characteristics. The purpose is to

[Means for Solving the Problems] In order to achieve the above object, the present invention forms an optical recording film on a substrate, strongly absorbs laser light in a predetermined wavelength range, and absorbs the laser light in a predetermined wavelength range. An optical recording medium in which data is written by changing the energy band structure and causing a change in optical properties as a result of phase change due to
1 element selected from the 3 elements of It is characterized by changes, recording, and erasure.

Amorphous alloys generally have a large number of dangling bonds that determine their optical properties. The number can be controlled by controlling the amount of halogen contained. The content of I-logen in the recording material according to the present invention is 10-3% or more in terms of atomic percent.
% or less, and if this range is exceeded, the sensitivity in the wavelength region of the semiconductor laser will drop significantly. Furthermore, if it is too small, the number of tank ring bonds will be large, and if it is too large, the crystal lattice will be distorted and the film will become brittle. Furthermore, among the fluorine atoms, fluorine has the least distortion of the crystal lattice and is suitable as an ingredient in the recording material. Further, by containing fluorine, the crystallinity of the recording material can be controlled, and stable recording and reproduction characteristics can be obtained. Generally, 5t-F bond (or Go-F, 5n-F bond) is
It has a larger bonding force than a 5i-H bond (or a Go-H, 5n-H bond), has excellent thermal stability, and can withstand continuous regeneration.

From the perspective of controlling optical properties, for example, phosphorus.

It is known to add small amounts of elements such as boron;
It is also effective for the material concerned. Further, this recording material may contain hydrogen in addition to the above-mentioned essential components.

The thickness of the recording film of the optical recording medium is not particularly limited, but
It is preferable that the reflectance before recording with respect to the wavelength of the laser beam used for recording etc. is set in the range of 5% or more and 60% or less. If it exceeds this range or is too low, tracking will not be sufficient during recording, reproduction, and erasing, making stable recording, reproduction, and erasing difficult. Also, if it is too high, it will not be able to absorb the recording laser beam sufficiently, and recording may not be possible at all.
This is not preferable because it requires high power for recording.

The optical recording film described above can be formed by a conventional method such as a sputtering method, a vacuum evaporation method, or a CVD method, and the film forming method is not particularly limited.

Any substrate can be used as long as it is transparent enough to transmit laser light. Examples of these include substrate materials with excellent transparency such as glass, polyester resin, polyolefin resin, polyamide resin, polycarbonate resin, and polymethacrylic resin. Alternatively, a recording film may be formed on an opaque substrate, and an arbitrary transparent protective layer may be laminated thereon. It is also possible to form an arbitrary intermediate layer on the substrate and form a recording film on the intermediate layer. Furthermore, it is also possible to control the optical properties by laminating known Vb, Vlb, group Ⅰ elements, Mg, Au, etc. on the optical recording layer according to the present invention. It is also possible to provide a light reflecting layer. Further, the shape of the recording medium may be circular, rectangular, etc., or may be disk-shaped, card-shaped, etc. It goes without saying that the substrate of the present invention may be a substrate having irregularities such as guide grooves for tracking, etc., similarly to known recording media.

The wavelength of the laser beam used for recording etc. is not particularly limited, but one of 11000 nm or less is suitable for use. Therefore, the wavelength of current semiconductor lasers is 750
~850 nm range is effectively used. In this case, the recording power is generally in the range of about 1 to 15 mW.

The present invention will be explained in more detail with reference to Examples below.

〔Example〕

Thickness: 1.2fi, inner diameter: 15cm, outer diameter: 13mm
A recording film consisting of Sl, Sn, and fluorine was formed on a transparent disc made of polycarbonate using a binary reactive sputtering method.

The film forming conditions are shown below. First, look inside the chamber 5X
Evacuate to 10 Torr, then add argon gas and fluorine gas at a ratio of 1=1 to a gas pressure of 5X10.
It was introduced to become Torr. High frequency power was applied to the Si and Sn targets to form a recording film having a Si to Sn atomic ratio of 5i4oSnso to a film thickness of 50 nm. When the above recording film was analyzed by ESCA, it was found that fluorine was present in the film at an atomic percent of 5XIO.
To was included. Furthermore, crystal structure analysis was performed using thin film X-ray diffraction method. As a result, the recording film has an amorphous structure after being formed, and is crystallized by heat treatment at 180° C. or higher. Therefore, after film formation, the land portion is irradiated with a laser whose power is lower than the recording laser power to anneal the land portion and crystallize the recording thin film. During recording, it can be used as a rewritable optical recording medium by irradiating it with a strong laser beam to cause a phase change that turns it into an amorphous state, and by reading the resulting changes in optical properties such as reflectance. there were.

When we measured the recording and reproducing characteristics of this optical recording medium, we found that
Good recording and reproducing characteristics could be obtained.

A maximum CNR of 45 dB and a recording laser power of 6 mW or more achieved 4 Q'dB or more. Although writing and erasing were performed 100 times, the recording and reproducing characteristics did not change. An accelerated deterioration test was conducted in which the sample was held at 75°C and 85°C for 1000 hours, and the archival life and shelf life were measured, but no signs of deterioration were observed.

In addition, SiH4 gas and fluorine gas were introduced, and Sn
A recording thin film is formed by the CVL (resistance heating) method,
When evaluated, an optical recording medium with similarly good recording sensitivity was obtained.

〔Effect of the invention〕

As explained above, based on this invention, St, Ge
High-sensitivity recording using chemically stable tetrahedral materials can be achieved by forming a recording layer containing as essential components one or two elements selected from SnO and at least one element selected from halogen elements. A rewritable optical recording medium can be obtained.

Claims (3)

[Claims] (1) An optical recording medium on which recording is performed by irradiation with light, in which one element selected from the three elements Si, Ge, and Sn is used.
An optical recording medium characterized by having a recording layer containing as an essential component at least one element selected from an element or two elements and a halogen element. (2) The recording layer contains at least one element selected from halogen elements in an amount of 10^-^3% or more in terms of atomic percentage.
The optical recording medium according to claim 1, characterized in that the optical recording medium contains 0% or less. (3) The optical recording medium according to claim 1 or 2, wherein the halogen element is fluorine.