JPH02178086A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium easy to form a single phase by crystallization, performing a phase change between a crystalline state and an amorphous state stably and suitable for the recording, reproduction and erasure of data by forming a recording layer whose optical characteristics are changed by the application of optical energy on a substrate in a specific element compositional ratio. CONSTITUTION:A recording layer 3 whose optical characteristics are changed by the application of optical energy is formed on a substrate 1 composed of a polycarbonate resin or the like. This recording layer 3 is formed of three elements of Zn, Ge and Sb and the compositional ratio thereof is set to the vicinity of the composition of a ZnGeSb2 compound, that is, to a range of 10at.%-<Z<40at.%, 10 at.% <Ge<40at.% and 35at.%<Sb<65at.% to form an optical recording medium 6. This optical recording medium 6 is rotated at linear velocity of 2.0m/s and the recording layer 3 is irradiated with semiconductor laser beams of DC output of 5mW per one truck to be crystallized and the reflectivity of the crystallized part increases. The crystallized truck is irradiated with a laser beam spot modulated in its intensity by a data signal to be made amorphous and the reflectivity of the irradiated part is lowered to record the data signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium on which information can be optically recorded, reproduced, and erased.

[Conventional technology]

In recent years, optical properties (refractive index,
2. Description of the Related Art Information recording media (hereinafter simply referred to as "medium" or "optical disk") that record and reproduce information by changing extinction coefficient (extinction coefficient, reflectance, etc.) are being actively developed. Among these methods, a method of recording information by irradiating an amorphous medium with low reflectivity with a laser beam and locally heating it to cause a phase change, turning it into a crystalline state with high reflectance and recording information, has recently been in the spotlight. It is beginning to be put into practical use as a write-once optical disc.

Such write-once optical discs are capable of: - Once the original information is recorded, it cannot be completely erased; however, a chalcogenide thin film is used to reversibly cause a phase transition between an amorphous state and a crystalline state. Recording media that enable recording, erasing, and rewriting, such as Te-0-Ge-3n, 5n-Te-3
e, Te-Ge-3b, In-3b-Te, In-3e
etc. are known.

[Problem to be solved by the invention]

In the conventional technology, there are many examples of combinations of ternary systems, and it is difficult to determine the combination of elements and composition that can be used as an optical recording medium (optical disk) from among them. By the way, when a third element is added to a binary system that can generate intermetallic compounds, the crystallization temperature increases, the stability of the amorphous state improves, and the crystallization speed increases, so high-speed erasure is also possible.゛It can be achieved.

However, because the third element forms a compound with each element that makes up the binary system before creating the base binary intermetallic compound, if recording, playback, and erasing are repeated,
There was a drawback that the composition of the intermetallic compound gradually shifted, making it impossible to achieve single-phase crystallization, resulting in a decrease in erasing properties.

[Means to solve the problem]

The present invention forms a recording layer on a substrate whose optical characteristics change by applying optical energy, and this recording layer is made of Zn.
, Ge, and Sb, and the composition ratio is ZnG.
eSb2 compound composition vicinity, i.e. 10at, X< Z n
<40at,%, 10atJ<G e <40a
t,%.

35 at, %<S b <65 at. The above problems have been solved by providing an optical recording medium that is in the range of %.

〔Example〕

An embodiment of the optical disc of the present invention will be described. In order to stably change the phase between crystalline and amorphous states, rewritable optical discs are designed to have single-phase elements that make up the recording medium, and include Zn, a group 1V element that makes up the medium. Ge of
The composition ratio of sb of the same group V was set near the composition of the ZnGeSb2 compound.

As the composition ratio deviates from ZnGeSb2 (i.e. 1:1:2), compounds such as Zn and Ge and Zn and sb are more likely to be produced.
%<Z n<40at, %, 10at9%<Ge<
40at, χ, 35at. %<Sb<65at,%
As a result of measurement and evaluation, it has become clear that a range of .

By irradiating and heating the amorphous thin film made of Zn, Ge, and Sb, a ZnGeSb2 compound is generated and crystallized. On the other hand, the medium can be made amorphous by heating the medium to a temperature higher than the melting point of the produced compound and then rapidly cooling it. Recording and erasing of signals could be realized by utilizing changes in optical properties associated with these, such as changes in reflectance.

Hereinafter, specific examples of the optical recording medium of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged partial cross-sectional view of the medium of the present invention. Reference numeral 1 denotes a polycarbonate resin substrate (hereinafter also simply referred to as "substrate") on which groups for troughing have been formed in advance, for example, in a spiral shape, and this substrate 1
One side 6: ZnS (zinc sulfide) is vacuum-deposited as the first protective layer 2 to a thickness of about 100 nm. Next, the above 3
Z as a metallic element. , Ge, and Sb are evaporated from separate tungsten boats, and the recording layer 3 is formed (formed) by ternary co-evaporation. Therefore,
The recording layer 3 is a mixed film of Zn, Ge, and Sb, and
When analyzed using an <X-ray microanalysis) device, the composition ratio was Zn:Ge:5b=35:20:
It was 45. A second protective layer 4 is further formed on this recording layer 3.
After vacuum-depositing ZnS to a thickness of about 100 nm,
The ultraviolet curable resin layer is spin-coded to form an optical recording medium 6.
complete.

This optical recording medium 6 is rotated at a linear velocity of 2.0 ra/s,
A semiconductor laser beam (wavelength: 780 nm) with a DC output (recording power) of 6 mW is irradiated onto the disk surface (recording layer 3) for one track. This crystallized the recording layer 3 and increased the reflectance of that portion.

When this crystallized track is irradiated with a light spot of a laser beam whose intensity is modulated by an information signal or the like, it becomes amorphous, and an information signal can be recorded with the reflectance at that location reduced.

In fact, when a single frequency signal (700 KIIZ) was recorded with a laser output of 10 mW, the C/N was 40 dB. The reproduction laser output at this time is 1 mW.

When this recording track was irradiated three times with semiconductor laser light with a DC output of 6 mW, the reflectance returned to its initial crystallized state and the C/N decreased to 15 dB, giving good results.

〔effect〕

As described above, the optical recording medium of the present invention has the following excellent features.

An optical recording medium suitable for recording, reproducing, and erasing information can be provided by forming a recording layer having a composition near the 03-element intermetallic compound and applying optical energy.

■The composition ratio of element Zn of group ■ of the periodic table, element Ge of group IV, and element sb of group V of the periodic table, which is a recording medium, is
By setting the composition to be close to the two-compound composition, a single phase can be easily generated when crystallized, and a phase change between crystalline and amorphous can be stably performed.

[Brief explanation of the drawing]

FIG. 1 is an enlarged partial sectional view of the optical recording medium of the present invention. 1... Substrate, 2, 4... 1st. second protective layer, 3.
... Recording layer, 5... Ultraviolet curing resin layer, 6... Optical recording medium. Patent applicant: Kunio Umiki, representative of Victor Japan Co., Ltd.

Claims (1)

[Claims] An optical recording medium in which a recording layer whose optical characteristics change upon application of optical energy is formed on a substrate, the recording layer being composed of three elements of Zn, Ge, and Sb, the composition ratio of which is close to the ZnGeSb_2 compound composition. , that is, 10 at. %
<Zn<40at. %, 10at. %<Ge<40at
．． %, 35at. %<Sb<65at. % range.