JPH0545434B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical information recording member, particularly an optical disk, that optically records and reproduces high-density information at high speed using a laser beam or the like.

Conventional configuration and its problems The technology for recording and reproducing high-density information on a rotating disk at high speed using a laser beam is
There are already many examples of research results as optical disk devices.
There have been reports of product development examples, and it is becoming indispensable for configuring information systems.

The recording materials used for these optical discs include:
There are those that change the reflectance and transmittance of light by changing the shape of holes and bubbles, and those that change the reflectance and transmittance by changing the optical properties (refractive index n, extinction coefficient k).
There are devices that change the transmittance, but the latter type is advantageous in that it can provide a protective layer that adheres to it, and that changes can be reversibly rewritable in principle. It is thought that this will become the mainstream.

A typical optical disk of this type is one using [TeO _x (O<x<2)].

This involves forming track grooves for light guides on a resin base material such as PMMA using ultraviolet curing resin.
It has a structure in which a [TeO _x ] thin film is placed on top of it by a method such as vapor deposition, and then a resin base material similar to the base material is laminated. This optical disk has already been applied to system equipment such as still image files and document files, but using this [ _TeO Several problems remain.

In other words, with the current structure, the base material is easily damaged near the interface between the base material and the recording layer due to repeated use, and the quality of the recorded signal deteriorates.In order to further increase the capacity, the disk shape Attempts to increase the rotation speed in order to increase the transfer rate or to increase the transfer rate require some kind of countermeasure, as there is a concern that the recording sensitivity may be insufficient with the current output of semiconductor lasers. do.

OBJECTS OF THE INVENTION An object of the present invention is to improve the structure of an optical disk to improve recording sensitivity, erasing sensitivity, etc., and to provide an optical disk that is less susceptible to damage even after repeated use.

Structure of the Invention The optical information recording member according to the present invention includes, on a base material,
It is characterized by sequentially laminating two layers: a germanium oxide layer and a recording layer made of a thin film of a material whose reflectance changes when irradiated with light.

The germanium oxide layer increases the incidence efficiency of laser light and increases the apparent recording sensitivity, and also acts as a protective layer for the base material to prevent damage to the base material due to repeated use.

DESCRIPTION OF EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 shows a sectional view of the basic structure of the optical information recording member of the present invention. 1 in the figure is
As the base material, plastics such as PMMA, vinyl chloride, polycarbonate, glass, etc. can be used depending on the purpose of use. Reference numeral 2 denotes a layer of germanium oxide GeO _x (x=2 or x2), which forms the basis of the present invention, and is formed using a method such as vapor deposition or sputtering. When forming the film, germanium dioxide GeO ₂ is used as a source material for vapor deposition or as a target material for sputtering.
In the present invention, substantially the same effect can be obtained in some cases where O is slightly removed depending on the conditions of vapor deposition or sputtering to become GeO _x (x2).

The film thickness can be set to a film thickness at which the amount of reflected light when light is incident from the base material 1 side shows a maximum value as an interference effect. As a setting method, for example, the reflectance measurement method proposed in Japanese Patent Laid-Open No. 59-17139 can be used.

FIG. 2 shows the relationship between the thickness of a germanium oxide thin film deposited using the method described above and the reflectance from the substrate side. As a result of multiple interference between the reflected light from the substrate surface and the reflected light from the interface between the substrate and the germanium oxide layer, the reflected light intensity increases as the film thickness increases, reaching a maximum as shown in the figure. It was found that after taking the value, it decreases. In the case of a transparent material such as germanium oxide, which absorbs almost no light, an approximate formula such as nd = λ/4 can be found between the film thickness d, the refractive index n, and the wavelength λ at the maximum value. If the refractive index of the germanium oxide thin film is n = 1.6 and the wavelength of the light source is λ = 840 nm, then
The film thickness d _O at which the reflected light intensity reaches its maximum is approximately 130 nm.

In FIG. 1, 3 indicates a recording layer. A recording layer 3 is formed on the germanium oxide layer 2 designed as described above.
When depositing the recording layer 3, if the refractive index of the recording film 3 is higher than the refractive index of the germanium oxide 2, the recording layer 3
As a whole system including this, the intensity of reflected light from the base material side 1 can be made much smaller than in the case without the germanium oxide layer 2, and the light incidence efficiency can be increased.

FIG. 3 shows the difference in reflected light intensity between the case (a) with the gemmanium oxide layer 2 and the case (b) without it when a Te-TeO ₂ -based thin film is used as the recording layer material. In case (b) without the germanium oxide layer 2, the reflected light intensity increases as the film thickness increases, reaches a maximum value of 4, then decreases, and then
It converges to a constant value while repeating increases and decreases from a minimum of 5 to a maximum of 6. On the other hand, germanium oxide layer 2
, the reflected light intensity takes a small minimum value of 7, then increases and reaches a maximum of 8, and then decreases to a minimum of 9 and a maximum of 10, repeating increases and decreases and converges to a constant value. At this time, it has been found that when the germanium oxide layer 2 is present, the overall maximum value, minimum value, and convergence value can be made lower than when there is no convergence value. Therefore, by providing the germanium oxide layer 2 between the base material 1 and the recording film 3, it is possible to increase the light incidence efficiency, and the overall recording sensitivity can be improved.

The film thickness of the germanium oxide layer 2 is such that the above-mentioned effect of reducing the reflectance can be obtained to the maximum when the thickness of the germanium oxide layer 2 is selected so as to maximize the reflected light intensity using the above-mentioned approximation formula. It is possible to obtain a similar effect even if it is not the maximum, and in this case, the reflectance of light including the recording layer 3 takes a value between a and b in FIG. 3.

In addition to the above, the recording layer 3 may include Sb ₂ Te ₃ ,
Sb ₂ Se ₃ , etc., which also change the optical characteristics before and after recording, or Te-C thin film, Pb-Te-Se
Materials that form holes, such as system thin films, can also be applied as they are.

Next, an embodiment will be described in which a Te--Ge--Sn--O thin film (described in Japanese Patent Application No. 58-58158) is used as the recording layer 3 to perform repeated recording and erasing. The method of using this type of recording thin film is to record by first setting the film in a high reflectance state and changing it to a low reflectance state by irradiating it with light. The reflectance reduction effect of the germanium oxide layer is very useful in terms of increasing the incidence efficiency of the light. Further, when used repeatedly, the resin base material 1 may be thermally deformed and the noise level may increase, but this deformation can be suppressed by interposing the inorganic material layer of germanium oxide. Using the Te ₆₀ Sn ₁₅ Ge ₅ O ₂₀ thin film described in Japanese Patent Application No. 58-58158, optical disks with and without a germanium oxide layer were produced as prototypes, and the records described in Japanese Patent Application No. 58-58185 were also produced. We conducted repeated record erasing trials using this record erasing method.

FIG. 4 is a cross-sectional view of an optical disk prototyped with a germanium oxide layer provided thereon, and FIG. 5 is a continuous view showing the reflectance of the disk at each step during the production of the optical disk.

The base material 11 is made of PMMA with a thickness of 1.2 mm, on which a germanium oxide layer 12 is vapor-deposited so that the reflectance is maximum, and on top of that, a Te ₆₀ Sn ₁₅ Ge ₅ O ₂₀ thin film layer 13 is deposited so that the reflectance is minimum. This is also formed by vapor deposition so that it becomes . Furthermore, in this case, one more germanium oxide layer 14 is added on top of the recording film to avoid the effects of dust, scratches, etc. during repeated use.
is vapor-deposited so that the reflectance is minimal, and a 1.1 mm thick PMMA base material 15 is glued together using an ultraviolet curing resin to form an optical disk.

Figure 6 shows that using these optical disks, the recording power and erasing power were 8 mW, 12 mW, respectively.
This figure shows how the C/N changes when recording and erasing is repeatedly performed on the same track with the erasing laser beam length set to 15 μm in half width. The recording frequency was 5 MHz, and the circumferential speed of the disk was 15 m/s.
At this time, in the optical disk a having the germanium oxide layer, the initial C/N was high due to good light absorption efficiency, and at the same time, the deterioration of the C/N was only slight even during repeated use. In comparison, optical disk b without germanium oxide layer
In this case, the initial C/N was rather low, and when used repeatedly, a decrease in the C/N was observed as the noise level increased.

Effects of the Invention By providing an inorganic material layer between the base material and the recording layer, the optical information recording member according to the present invention has the effect of protecting the base material and provides optical information with excellent durability during repeated use. A recording member can be provided.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the basic structure of the optical information recording member of the present invention, FIG. 2 is a graph showing the relationship between the thickness of the germanium oxide layer and the reflectance, and FIG. FIG. 4 is a graph showing the difference in reflectance of the recording material when no recording material is used, FIG. FIG. 6 is a graph showing continuous changes in reflectance of the disk during each process during disk production. FIG. 1...Base material, 2...Germanium oxide layer, 3...
...recording layer.

Claims (1)

[Claims] 1 Germanium oxide GeOx (x=2
An optical information recording member in which two layers are successively laminated: an inorganic material layer consisting of x≈2) and a recording layer consisting of a thin film of material that causes a change in reflectance upon irradiation with light, wherein the inorganic material layer is is transparent to light, and has a refractive index smaller than that of the thin film of material constituting the recording layer, and has a thickness that is equal to when the inorganic material layer and the recording layer are laminated. An optical information recording member, characterized in that the reflectance as viewed from the substrate side is selected to be lower than that when the recording layer is formed alone on the substrate. 2. The optical information recording member according to claim 1, which is composed of at least three layers in which one more inorganic material layer is laminated on the recording layer.