JPS60257291A - Optical information recording member - Google Patents

Abstract

PURPOSE:To contrive enhancement of recording sensitivity, erasing sensitivity or the like and durability in repeated use, by a method wherein a germanium oxide layer is provided on a base, and a recording layer capable of being heated by irradiating with light with the result of a change in an optical constant thereof is provided thereon. CONSTITUTION:The layer 2 of germanium oxide GeOx (x=2) is provided on the base 1 by vapor deposition, sputtering or other similar method. In this case, germanium oxide may have the composition of GeOx (xapprox.=2), depending on the condition. The recording layer 3 the optical constant of which is changed upon irradiation with light is provided on the layer 2. Accordingly, the intensity of reflected light reaches a minium, is then increased to a maximum, is reduced to a minimum, is increased to a maximum, and such increase and decrease are repeated to converge to a fixed value. In this case, all of the maxima, minima and the limit can be made to be small. Accordingly, by providing the germanium oxide layer 2 between the base 1 and the recording layer 3, it is possible to enhance the efficiency of incidence of light, and to enhance the overall recording sensitivity.

Description

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

Conventional configurations and their problems The technology of recording and reproducing high-density information on a rotating disk at high speed using a laser beam has already been used in many research results and product development examples as an optical disk device. There are two types of reports that are essential to constructing an information system.

The recording materials used for these optical discs include those that change the reflectance and transmittance of light by creating shapes such as holes and bubbles, and those that change the reflectance and transmittance of light (refractive index n, extinction coefficient k).
) to change the reflectance.

Although there are devices that change the transmittance, the latter type is advantageous in that it can be provided with a protective layer that adheres tightly, and that changes are reversible in principle and rewritable. It is thought that it will become mainstream.

A typical optical disc of this type is [Te
0x (0 (X < 2):] ◇This method involves forming a trunk groove for light guide using ultraviolet curing resin on a resin base material such as PMMA, and then forming a trunk groove for light guide on the resin base material such as PMMA.
] It has a structure in which a thin film is installed by a method such as vapor deposition, and then a resin base material similar to the base material is glued together. This optical disc already contains still image files.

It is applied to system equipment such as documents and files, but
Several problems remain if this [Te0X] is to be used as the main material in a more advanced form, such as larger size and rewritability.

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 the use of combs, and the quality of the recorded signal deteriorates. 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 disc to improve recording sensitivity, erasing sensitivity, etc., and to provide an optical disc that is less susceptible to damage even after repeated use.

Structure of the Invention The optical information recording member according to the present invention provides a germanium oxide layer on a base material, heats the layer on the germanium oxide layer by irradiating it with light,
It is characterized in that a recording layer number having a property of changing its optical constant is laminated.

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 Examples' 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 a base material, P
Plastics such as MMA, vinyl chloride, polycarbonate, glass, etc. can be used depending on the purpose of use. 2 is germanium oxide Ge, which forms the basis of the present invention.
It is a layer of 0x (x-2 or x = 2) and is formed using a method such as vapor deposition or sputtering. When forming the film, germanium dioxide Ge2 is used as a source material for vapor deposition or as a target material for sputtering. Depending on the conditions of vapor deposition or sputtering, the circle may deviate slightly and become Ge0x (xyu2), but in the present invention, it is possible to obtain the same effect.

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, JP-A-59-17
Figure 2 shows the film thickness and reflection from the substrate side when a germanium oxide thin film was deposited using the method described above. This shows the relationship with the rate. The reflected light intensity is
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, as shown in the figure, it increases as the film thickness increases, reaches a maximum value, and then decreases. I found out that it does. In the case of a transparent material such as germanium oxide that absorbs almost no light, the relationship between the film thickness d, the refractive index n, and the wavelength λ at its maximum value is nd-λ/
4 is established, and the refractive index of the germanium oxide thin film is n=1.6. Assuming that the wavelength of the light source is λ=840 nm,
Film thickness d at which the reflected light intensity is maximum. is approximately 130 nm.

In FIG. 1, numeral 3 indicates a recording layer. When depositing the recording layer 3 on the germanium oxide layer 2 designed as described above, if the refractive index of the recording film 3 is higher than the refractive index of the germanium oxide 2, the whole including the recording layer 3 will be deposited. As a system of
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.

Figure 3 shows a case where a Te-Tea2-based thin film is used as the recording layer material and a germanium oxide layer 2 is present (
, ), and (b) without the reflected light intensity are shown. In case (b) without the germanium oxide layer 2, the reflected light intensity increases as the film thickness increases, reaching a maximum value of 4.
After taking , it decreases and then reaches a minimum of 5. It converges to a constant value while repeating increases and decreases to a maximum of 6. On the other hand, in the case where the germanium oxide layer 2 is present, the reflected light intensity takes a small minimum value 7, increases to a maximum value 8, and then decreases to a minimum value 4z9. It converges to a constant value while repeating increases and decreases from a maximum of 1o. 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, between the base material 1 and the recording film 3, there is a germanium oxide layer 2.
By providing this, it is possible to increase the light incidence efficiency, and it is possible to improve the recording sensitivity as a whole.

The thickness of the germanium oxide layer 2 can be selected to maximize the reflected light intensity using the approximation formula described above, so that the effect of reducing the reflectance described above can be maximized. It is possible to obtain a similar effect even when the
The reflectance of light, including , takes a value between a and b in FIG.

As the recording layer 3, in addition to the above, Sb2Te3 may be used.

, Sb 2 S e 3, etc., which also change optical characteristics before and after recording, 'f e-C thin film, Pb
Materials that form holes, such as -To-5e thin films, can also be applied as they are.

Next, an example will be described in which a Te-Ge-5n-0 thin film (described in Japanese Patent Application No. 58-58-158) is used as the recording layer 3 and recording and erasing are performed repeatedly. 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.

Furthermore, 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. be. Patent application 58-581
T e o S n 1s G e s described in 58
Using an O2° thin film, optical discs with and without germanium oxide/IDI were prototyped, and repeated recording erasure experiments were conducted using the recording erasing method described in Japanese Patent Application No. 58-58158. Ta.

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 graph 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 extremely thick, and on top of that, Te6o S, n 1s Ge 5020 is used.
The thin film layer 13 is also formed by vapor deposition so that its reflectance is minimal. Furthermore, in this case, in order to avoid the influence of dust, scratches, etc. during repeated use, one more germanium oxide layer 14 is vapor-deposited on top of the recording film so that the reflectance is minimal, and an ultraviolet curing resin is applied. 1.1tr
The rIn-thick PMMA base material 16 is glued together to form an optical disc.

Figure 6 shows the recording power,
This figure shows the change in C/H when recording and erasing is repeatedly performed on the same track with the erasing power being 8 mW and 12 mW, respectively, and the erasing laser beam length being 15 μm at half-width. The recording frequency was 5 MHz, and the circumferential speed of the disk was 15 ml B. At this time, the optical disc AVC equipped with a germanium oxide layer had a high initial C/N due to its high light absorption efficiency, and at the same time, there was only a slight deterioration in the C/N even when it was used repeatedly. . In comparison, in optical disc b without a germanium oxide layer, aJC/N was somewhat low, and when used repeatedly, a decrease in C/N was observed as the noise level increased.

Effects of the Invention According to the present invention, by providing a germanium oxide layer between the base material and the recording layer, the reflectance is reduced, the recording sensitivity is high as a whole system, and the effect of protecting the base material is achieved. Accordingly, it is possible to provide an optical information recording member with excellent durability during repeated use.

[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. A graph showing the difference in reflectance of recording materials in the absence of
Fig. 4 is a cross-sectional view of an optical information recording member according to an embodiment of the present invention, which has a structure in which rewritable materials are bonded together, and Fig. 5 shows the continuation of the reflectance of the disc at each step during disc production. Figure 6 is a graph showing changes in C/N during repeated use with and without a germanium oxide layer.
It is a graph showing the difference in the change. 1...Base material, 2...Germanium oxide layer, 3...Recording layer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Discipline Thickness d (Ty Island Figure 3 (Cl) Moon 4 d (npn) (b) Discipline 4 d (n River Figure 4 Figure 5 CE et al. n'tn

Claims (3)

[Claims] (1) Germanium oxide Gemx (x = 2
or x = 2) layer, and a recording layer having a property of changing its optical constants when heated by light irradiation is laminated thereon. (2) The recording layer is characterized by using a thin film whose optical constant decreases when the temperature is raised by light irradiation and then rapidly cools, and whose optical constant increases when slowly cooled. An optical information recording member according to claim 1. (3) The thickness of the first germanium oxide layer is selected so that when light is incident from the base material side, the reflectance is maximized according to the wavelength of the light, and the reflectance is minimized. The optical information recording member according to claim 1, characterized in that the thickness of the recording layer is selected.