JPS62298947A - Information carrier disk - Google Patents

Abstract

PURPOSE:To well record and erase information in all areas from an inner peripheral part to a outer peripheral part by setting the layer thickness of a dielectric layer provided between a recording film and a reflective layer so that it is thicker in the outer peripheral part than the inner peripheral part. CONSTITUTION:The layer thickness of the dielectric layer is made thicker in the outer peripheral part than the inner peripheral part. A dielectric layer 2 which consists of an SiO2 and has about 150nm thickness, a recording film 3 which consists of materials where 5% Ge and 10% Sn are added to a TeOx (x 1.1) and has about 50nm thickness, a dielectric layer 4 consisting of an SiO2, and a reflective layer 5 which consists of an Al thin film and has about 50nm thickness are formed on a polycarbonate disk-shaped transparent substrate 1 having a guide groove 8, and a protective substrate 7 is provided on the reflective layer 5 with an adhesive between them. The layer thickness of the dielectric layer 4 is so continuously changed that it is thinner in the inner peripheral part and is thicker in the outer peripheral part and this thickness is about 80nm in the position of 60mm diameter and is about 150nm in the position of 110mm diameter.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to an information carrier disk on which information is recorded, reproduced, and erased by irradiation with laser light.

Conventional technology Currently, information carrier disks called write-once type, which can record documents, image files, etc. only once, have been put into practical use as large-capacity, high-density memories, but recently it has become difficult to erase recorded information.・Development of information carrier disks called erasable type that allows re-recording is underway.

This erasable information carrier disk uses a Te-based metal thin film as a recording film, as shown in Figure 2, and changes the phase between an amorphous state and a crystalline state using thermal energy from laser beam irradiation, thereby allowing information to be stored. There is a phase change type information carrier disk that performs recording and erasing. This is done by depositing a dielectric layer 10 such as SiO2, a To-based recording film 11 such as TeOxGeSn, a dielectric layer 12, and a reflective layer 13 such as A1 in this order on a disc-shaped transparent substrate 9 having a guide groove 16. A protective substrate 15 is provided thereon via an adhesive 14. When recording, the recording film is rapidly heated and cooled by irradiation with a well-focused laser beam of high power density, becoming an amorphous state with low reflectance, and an information focus is formed.

When erasing, the recording film is heated and removed by irradiating it with an elliptical shaped laser beam with low power density.
It is slowly cooled to a crystalline state with high reflectance, and the information is out of focus.

Problems to be Solved by the Invention Figure 3 shows a disk having the configuration shown in Figure 2 at a rotational speed of 12.
This graph shows the relationship between the recording nozzle and the C/N at a position between the diameter of Own and the diameter of 110 when recording is performed at 0 rpm. At the position of 60 mm in diameter, the recording power e
The highest C/N value of 54 dB was obtained with a diameter of 110 mw.
At the mm position, the highest C/N value of 56 dB was obtained with a recording power of 8 mw. Also, Figure 4 shows the highest C at the position of 60 mm diameter and the position of 110 rran diameter.
This figure shows the relationship between the erasure power and the erasure rate when erasing is performed after recording with a recording power that yields the /N value.

At a position with a diameter of 60WrIn, the highest erasure rate of 45 dB is obtained with an erasure power of 12 mw, and at a position with a diameter of 110rrvn, the highest erasure rate is 47 d with an erasure power of 15 mw.
B was obtained.

In this way, when recording and erasing is performed while keeping the disk rotation speed constant, the optimum laser power for recording and erasing differs between the inner and outer circumferences. This is because the linear velocity at the outer circumference is faster than at the inner circumference. Therefore, in order to perform optimal recording/erasing in all areas from the inner circumference to the outer circumference, the recording/erasing puff should be increased from the inner circumference to the outer circumference, or the linear velocity should be constant from the inner circumference to the outer circumference. It is necessary to change the rotation speed so that Therefore, a mechanism for changing the recording/erasing power or the disk rotation speed depending on the recording/erasing position is required9, resulting in a problem that the recording/reproducing apparatus becomes complicated and expensive.

The present invention has been made in view of this point, and is an information carrier disk that can perform good recording and erasing in all areas from the inner circumference to the outer circumference even if the disk rotation speed and recording/erasing power are constant. is intended to provide.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention makes the thickness of the dielectric layer provided between the recording film and the reflective layer thicker at the outer periphery than at the inner periphery. It is set to .

Operation According to the above-described structure of the present invention, the heat insulating effect of the dielectric layer provided between the recording film and the reflective layer is greater at the outer periphery than at the inner periphery. As a result, the amount of heat absorbed by the reflective layer during recording and erasing is smaller in the outer periphery than in the inner periphery, and the amount of heat that effectively acts on the recording film becomes smaller. Recording/erasing sensitivity increases. Therefore, by making up for the lack of recording/erasing power that occurs due to the increase in linear velocity at the outer periphery by increasing the sensitivity, a constant disk rotation speed and recording/erasing power can be achieved in all areas from the inner periphery to the outer periphery. Good recording and erasing can be performed with power.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 is a sectional view of an information carrier disk in one embodiment of the present invention. This is made of 5iO2 as a dielectric layer 2 on a polycarbonate disc-shaped transparent substrate 1 having guide grooves 8.
e about 150 nm, and TeaX (''~1.1
) with 5% Ge and 5nlO% added to approximately 50nm.
, 5102 as the dielectric material 4 + further A as the reflective layer 5
A thin film of I was formed to a thickness of about 5σl, and a protective substrate 7 was provided thereon with an adhesive 6 interposed therebetween. Here, the film thickness of the dielectric layer 4 changes continuously such that it is thinner at the inner circumferential part and thicker at the outer circumferential part, and is about 80 nm at a position of 60+++ m in diameter and 11 nm in diameter.
It is set to be approximately 150 nm at a position between 0 and 0.

When this information carrier disk was rotated at 120 rpm while recording and erasing signals with a frequency of I MHz, the recording power was 6 mw and the erasing power was 12 mw K! C/Ns, *dB, recorded at a diameter of 60-
Recorded at a position with an erasure rate of 4 sdB and a diameter of 110 mm C/N 5
Good recording and erasing of 6 dB and erasing rate of 47 dB was achieved.

The film thickness distribution of the dielectric layer 4 is determined by the optical properties, specific heat, thermal conductivity, density, etc. of each layer constituting the information carrier disk, and the material of each layer is not particularly limited. In addition, the dielectric layer 2 in this embodiment is an optical intermediate layer for improving C/Ni by utilizing optical interference, and also serves as an optical intermediate layer to prevent damage to the substrate 1 due to temperature rise of the iron film 3 during recording and erasing. Although this dielectric layer 2 is provided as a heat insulating layer for this purpose, it is also possible to omit this dielectric layer 2.

Effects of the Invention As described above, according to the present invention, good recording and erasing can be performed in all areas from the inner circumference to the outer circumference with a constant disk rotation speed and recording/erasing power with a simple configuration. be able to.

Therefore, there is no need to add complicated functions to the recording/reproducing device, and it is possible to provide an information carrier disk that is industrially extremely advantageous.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of an information carrier disk in an embodiment of the present invention, FIG. 2 is a sectional view showing the structure of a conventional information carrier disk, and FIGS. 3 and 4 are sectional views of a conventional information carrier disk. FIG. 3 is a characteristic diagram showing the relationship between recording power and C/N at the inner and outer peripheries of the disk, and between erasing power and erasing rate. 1.9...Transparent substrate, 2,4,10.12...
...Dielectric layer, 3, 11...Recording film, 5,
13...Reflection layer. Fig. 1 7 Protective substrate 7 Transparent substrate Fig. 2 15 #: Protective substrate 9 Clear substrate Fig. 3 246B Recording power (mW) 4th (!

Claims (1)

[Claims] A dielectric layer is provided between a recording film whose phase changes due to thermal energy of laser beam irradiation and a reflective layer made of a thin metal film, and the dielectric layer is thicker at the outer circumference than at the inner circumference. An information carrier disk characterized in that it is set as follows.