JPS63227389A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium requiring low recording power, having high reliability and enabling a recording layer to be easily provided, by incorporating at least two metals, i.e., In and Sb and an Sn oxide in a mixed state in the recording layer. CONSTITUTION:A recording layer comprises two metals, i.e., In and Sb and an Sn oxide in a mixed state. Before recording, the recording layer is amorphous. Before recording, In and Sb in the recording layer are mainly present as an In-Sb amorphous alloy in an oxide comprising the Sn oxide as a main constituent. The In-Sb amorphous alloy is heated by absorbing recording light at the time of recording, and partially reduces Sn in the Sn oxide. The reduced metallic Sn is alloyed with In and Sb to form an In-Sb-Sn ternary alloy crystal having a reflectance higher than that of the In-Sb alloy in a crystalline state, in a matrix comprising the Sn oxide as a main constituent. Therefore, recording marks having favorable contrast as compared with that in recording by utilizing only the crystallization of an In-Sb amorphous film are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to optical recording media such as optical discs and laser COMs (COM) in which information is recorded and reproduced using light.

[Prior Art] Conventional optical recording media include write-once optical recording media and erasable optical recording media. Write-once recording media are protected against falsification of records.
Since it is not possible to store data such as documents, it has excellent storage security, and has different uses from rewritable magnetic recording media and erasable optical recording media.

As this write-once optical recording medium, optical recording media in which recording is made by making holes called pits in the recording layer, such as Te-C film (Japanese Patent Publication No. 59-33320), have been used. If this structure is used, the recording sensitivity will be significantly lowered, so in order to obtain practical recording sensitivity, the disk must have a hollow structure, which has the drawback of low productivity due to the complicated structure. Therefore, recently,
Phase-change type write-once optical recording media are attracting attention because they have a structure in which disks are closely laminated together, or a single-plate structure in which a protective layer is simply laminated on a recording layer, resulting in less decrease in recording sensitivity.

As a phase change type write-once optical recording medium, one in which a low oxide thin film recording layer of Te is formed on a substrate (Japanese Patent Laid-Open No. 50-46
317>, JP-A-59-35988) in which a recording layer in which a 5b-3e amorphous alloy and a 1e-3i amorphous alloy are alternately laminated in multiple layers is formed on a substrate.

[Problems to be Solved by the Invention] However, with this prior art, there are the following problems.

In other words, in the case of an optical recording medium having a low Te oxide layer as a recording layer, the crystallization temperature is as low as about 110'C, and the thermal stability of recording is low. Also 5b-3e and Te-[3
When the multilayer film of i is used as a recording layer, there is a problem that productivity is low because the process of forming the recording layer is complicated.

The present invention improves these problems, has low recording power,
An object of the present invention is to provide an optical recording medium that is highly reliable and in which a recording layer is easily formed.

[Means for Solving the Problems] The present invention provides an optical recording medium in which information is recorded and reproduced by irradiating a recording layer formed on a substrate with light. At least In,
The optical recording medium is characterized in that it contains the two metals No. 3b and Sn oxide in a mixed state.

The recording of information in the optical recording medium of the present invention is performed by the grooves, which combine the phase change from the amorphous phase to the crystalline phase, the alloying of the crystals in the recording layer, and the redox reaction, and this recording mechanism is as follows: It is estimated as follows.

The recording layer of the present invention includes at least inl, 5b as components.
It contains two types of metals and a Snl compound in a mixed state. In the state before recording, the recording layer is amorphous.

In and sb in the recording layer are mainly I before recording.
It exists as an n-3b amorphous alloy in an oxide whose main component is Snv oxide. The In-3b amorphous alloy absorbs recording light during recording and is heated, thereby partially reducing Sn in the Sn oxide. Reduced metal Sn and in
, 3b are alloyed, an In-8b-Sn ternary alloy crystal having a higher reflectance than a crystalline In-3b alloy is formed in a matrix mainly composed of Sn oxide. Therefore, good recording marks of 1 to 1 last are formed compared to recording using only the crystallization of the n-3b amorphous film. Furthermore, the Sn atoms in the recording layer of the present invention are
Before recording, Sn is bonded to oxygen, and alloying due to solid-phase diffusion of Sn is difficult to proceed at relatively low temperatures, which has the advantage of high thermal stability for recording near room temperature.

Further, the crystallization temperature of the amorphous state before recording is approximately 160° C. to 240° C., although it depends on the composition, and the amorphous state is stable near room temperature.

In the recording layer of the present invention, the preferred composition range for obtaining good recording sensitivity and high carrier-to-noise ratio is defined by the amount charged at the time of forming the recording film, and is shown below.

That is, when the atomic percent of the two metals In and 3b and the 3n oxide (denoted as 3nQx in the formula) are expressed as α, β, and γ, respectively, and X is expressed as the atomic ratio of oxygen atoms to Sn, Formula I na S bB (S n OX ) r
In, 30≦α≦40 30≦β≦40 20≦T≦40 1.0≦X≦2.0 and α+β+γ−100.

If in is less than 30 atomic % or Sb is less than 30 atomic %, the recording sensitivity will decrease and the applications will be limited. Also i
If n is 40 atomic % or more, or if Sb is 40 atomic % or more, the contrast of the recording/reproduction signal is reduced and the applications are limited. Also, if X of 5nOx is less than 1.0,
Thermal stability of the recording layer decreases, limiting its uses.

The thickness of the recording layer of the present invention is usually from 10 nm to 1100 nm.
It is 0n. In order to obtain high recording sensitivity and good recording characteristics, the thickness is preferably from 20 nm to 200 nm.

The recording layer of the present invention does not require deformation of the recording layer during recording, unlike a recording layer that performs recording by deformation of the recording layer or opening, so even if a protective layer is formed by laminating it on the recording layer, the recording sensitivity decreases. There are few. Therefore, by laminating the protective layer on the recording layer, the oxidation resistance and moist heat resistance of the recording layer can be significantly improved. Examples of the material for the protective layer include polymer compounds such as ultraviolet curing resins, and inorganic compounds such as 5i02. In particular, in order to significantly improve the oxidation resistance and heat resistance of the records, Si, Ge, Te, Zr, Ti
It is preferable to provide a protective layer of a metal oxide such as , AI, etc. on the recording layer.

As the substrate in the present invention, plastic, glass,
It may be made of materials similar to conventional recording media, such as aluminum.

For the purpose of avoiding the influence of dust by recording from the substrate side using convergent light, it is preferable to use a transparent material as the substrate. Preferred examples of the above-mentioned materials include polyethylene terephthalate-1, polymethyl methacrylate, polycarbonate, epoxy resin, polyolefin resin, and glass. More preferably, polymethyl methacrylate, polycarbonate, and epoxy resin are used because they have a low birefringence and are easy to mold. Although the thickness of the substrate is not particularly limited, it is practical to have a thickness of 10 microns or more and 5 mm or less. If it is less than 10 microns, it will be susceptible to dust III even when recording with convergent light from the substrate side, and if it exceeds 5 mm, if recording with convergent light,
It becomes impossible to increase the numerical aperture of the objective and the lens, and the pitch size becomes large, making it difficult to increase the recording density.

The substrate may be flexible or rigid. The flexible substrate can be used in the form of a tape or sheet. The rigid substrate can be used in the form of a card or a circular disk. Further, if necessary, two substrates may be used to form a closely bonded structure, an air sandwich structure, an air incident structure, or the like.

The light used for recording on the optical recording medium of the present invention is light such as a laser beam or a strobe light, and a semiconductor laser is particularly preferred because it is small and has a small consumption horn and can be easily modulated.

As a method for forming the recording layer of the optical recording medium of the present invention on a substrate, a thin film forming technique in vacuum can be used. - Examples include a method of co-evaporating a Sn, 3b or Insb alloy and a Snl oxide, or a method of co-sputtering the above-mentioned elements or compounds.

Since the recording layer of the present invention is a single layer, the recording layer can be formed easily and quickly and has excellent productivity.

[Example] Hereinafter, the present invention will be explained in detail based on examples.

Example 1 On a polycarbonate disk substrate with a groove size of 1.2 mm in thickness and 13 cm in diameter with a pitch of 1.6 μm, 11
After forming a 00n SiO2 protective layer by vacuum evaporation, I
n, Sb, and 5nOz were co-evaporated under vacuum condition of 1O-5torr while monitoring with a crystal oscillator film thickness meter.
A recording layer having a thickness of 1100 nm and having an atomic composition of n 40 S b 30 (S nO/, 7) 30 was formed. The atomic composition was analyzed by photoelectron spectroscopy (using VG Scientific's IJESCALAB-5) and elemental analysis.

Furthermore, a protective layer of 1100 nm was formed on the recording layer to constitute an optical recording medium of the present invention.

This recording medium was rotated at a linear velocity of 4 m/sec, and the numerical aperture was 0.5.
Recording was performed by irradiating the recording layer from the substrate side with a semiconductor laser beam having a wavelength of 830 nm focused by an objective lens. The laser power during recording was 4 mW, and the recording frequency was 1
MHz ~2.5M1-IZ (duty ratio 50%)
And so. After recording, when reproducing with a 0.8 mW semiconductor laser beam under the same linear velocity conditions, the reflectance of the recorded mark increased to 46% compared to 27% in the unrecorded area.
In addition, the carrier-to-noise ratio of the reproduced signal is 40 at a recording frequency of 1 MHz to 2.5 M1-fz, as shown in Table 1.
A value sufficient for digital recording of dB or higher was obtained by 1q.

Example 2 A recording layer having the same composition as in Example 1 was formed on a heat-resistant glass substrate. Changes in DC electrical resistance of this sample due to temperature were measured at a heating rate of 10°C/min, and the crystallization temperature of the Q layer was determined to be between 230°C and 250°C. This crystallization temperature is as high as →-min to ensure long-term thermal stability at room temperature.

Table 1 [Effects of the Invention] Since the optical recording medium of the present invention is constructed as described above, it exhibits the following excellent effects.

(1) An optical recording medium with high recording sensitivity and good signal quality can be obtained.

(2) The recording layer has high thermal stability, and an optical recording medium with good recording thermal stability can be obtained.

(3) Since the recording layer is a single layer, a recording medium with excellent productivity can be obtained.

Claims (1)

[Claims] (1) In an optical recording medium in which information is recorded and reproduced by irradiating a recording layer formed on a substrate with light, the recording layer is made of at least two metals, In and Sb, and Sn oxide. An optical recording medium characterized by containing a mixture of substances.