JPH0256746A - information carrier disk - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to the structure of an information carrier disk (hereinafter simply referred to as a disk) that can record, reproduce, and erase information with high density and large capacity using a laser beam or the like. be.

Conventional technology Conventionally, a recording medium layer is formed on one side of a disc substrate made of a disc-shaped transparent substrate, and minute holes are formed in the recording medium layer by irradiating laser light from the disc substrate side, or optically. Discs in which recording and reproduction are performed by forming bits with varying densities have been put into practical use. Furthermore, erasing disks that allow repeated recording and erasing by reversibly changing the optical density of the recording medium layer are being put into practical use.

This erasing disk uses laser light to heat a thin film.
By melting, cooling, it becomes amorphous and records information, and by heating and rapidly cooling it crystallizes and erases information. This material includes Nis R. Opsinski (S.

The chalcogen material Gel5TeHSI)232 etc. of Mr. R, 0vshlnsky, ) is known,
Chalcogen elements such as As2 S, As2 Se3 or 5b2se3 and group V of the periodic table or group ■ such as Ge
Thin films made of combinations of group elements, etc. are widely known. In order to record information on these thin films with laser light and erase that information, the thin film is crystallized in advance, and the intensity of the laser light focused to about 1 μm is modulated in accordance with the information, for example. A disc-shaped recording disk is rotated and irradiated, and the area irradiated with the laser beam is heated to a temperature higher than the melting point of the thin film and rapidly cooled, so that information can be recorded as an amorphous mark. A known method for erasing this information is to irradiate a long spotlight in the direction of the rotating trunk of the disk to heat the thin film to raise its temperature, and then crystallize it again by the slow cooling effect of the long spotlight. In this way, the erase disk becomes hot, albeit in a small area of around 1 μm. For example, if a resin substrate is used as the disk substrate and a recording medium layer is directly formed, this heat deforms the disk substrate, causing recording and erasure. cannot be repeated. For this reason, a dielectric layer is generally formed between the disk substrate and the recording medium layer or between the recording medium layer and a protective layer that protects the recording medium layer as a heat insulating layer to prevent thermal deformation. It is something that exists. In addition, this dielectric layer can be used as an optical layer that utilizes multiple interference of laser light for recording and erasing by providing a reflective layer on top of the dielectric layer on the protective layer side to improve the sensitivity of recording and erasing. There is also.

Problems to be Solved by the Invention The problem with information recording and erasable recording media using means of heating giM, melting and quenching it into amorphous form, and heating and temperature-raising crystallization is to improve signal quality in response to heating cycles. It is to fluctuate. The cause of this variation is thermal damage to the disk substrate or dielectric layer due to rapid heating to 400° C. or higher and repeated cooling many times by the recording spot light and the erasing spot light. If the disk substrate or dielectric layer is thermally damaged, recording, playback,
In the erase cycle, there is a problem in that noise increases and cycle characteristics deteriorate. Furthermore, since the dielectric layer serving as the heat insulating layer needs to have an appropriate thickness, there is also a production problem in that it takes time to form the film. An object of the present invention is to provide a disk with excellent cycle characteristics and excellent productivity.

Means for Solving the Problems In the present invention, a first dielectric layer, a recording medium layer, a second dielectric layer, and a reflective layer are sequentially formed on one surface of a transparent substrate. The thickness of the first dielectric layer is thinner than that of the first dielectric layer.

In other words, if a dielectric material also functions as an optical layer, for example, if a dielectric material with a refractive index of about 2.0 is used, the thickness of the first dielectric layer is about 1,000 layers, and the thickness of the second dielectric layer is about 1,000 layers. Generally, the dielectric layer is optically set to a film thickness of about λ/2.2000, but the thermal shock of the dielectric layer caused by the laser light is caused by the first layer on the disk substrate side that is irradiated with the laser light. A large amount of thermal shock is applied to the first dielectric layer, and a relatively small thermal shock is applied to the second dielectric layer. Therefore, even if the second dielectric layer is made thin, there is no problem as a heat insulating layer, and by making the second dielectric layer thinner, the time required for film formation can be shortened. In phase-change disks that utilize change, the thermal conductivity of the dielectric layer has a major influence on recording and erasing characteristics, and this thermal conductivity is determined by the thermal conductivity and thickness of the dielectric layer. For example, if the thermal conductivity of the dielectric layer is high, the heated recording medium layer will be easily cooled down, and since the second dielectric layer is in contact with the reflective layer, if it becomes thinner, the recording medium layer will also be cooled down quickly. This is advantageous in making the recording medium layer amorphous.

-Example Hereinafter, an example of the present invention will be described based on the drawings. In the figure, l is a disk substrate made of a resin substrate such as polycarbonate or a glass substrate, and 2 is a first dielectric layer made of ZnS or SiO□, which has excellent heat resistance, and the film thickness is about 1000. 3 is the recording medium layer, which is a mixed thin film made of GeTe alloy and sb, and has a thickness of approximately 500 mm.4 is the second dielectric layer, which is made of the same material as the first dielectric layer 2 and has a thickness of There are approximately 300 people.

5 is a reflective layer for utilizing multiple interference of laser light;
It is made of metals such as Cu and Al1, and the film thickness is approximately 500. As a method for forming these thin films, a vacuum evaporation method or a sputtering method can be used. Reference numeral 6 denotes a protection plate, which is the same as the disk substrate L and is bonded to the disk substrate L with an adhesive 7. In the configuration shown in Fig. 0, recording and erasing is performed by irradiating laser light from the direction of arrow B. It is something. Since recording and erasing is performed by irradiating laser light from the disk substrate 1 side and heating the recording medium layer 3, the thermal shock is strongly applied to the first dielectric layer 2, and the second dielectric layer 3 is heated. The thermal shock to the dielectric N4 is small. Therefore, the second dielectric N4 can be used as a heat insulating layer with a thickness of 19 mm, and only needs to function as an optical layer.

Further, the second dielectric layer 4 is in contact with the reflective layer 5, and since the reflective layer 5 is a metal layer, it also serves as a heat diffusion layer.

Therefore, the thickness of the second dielectric layer 4 is one of the factors that determines the cooling conditions for the recording medium layer 2. That is, if the second dielectric layer 4 is thin, the recording medium layer 2 heated by the laser beam will more easily lose heat, be rapidly cooled, and become amorphous. On the other hand, if it is thicker, the recording medium layer 2 will be more easily cooled down.

Optical discs require higher recording speeds and higher transfer rates, and this rapid cooling condition, that is, the conditions for making the recording medium layer amorphous, is important. For example, even if the recording medium layer is difficult to become amorphous, 2. By making the second dielectric layer 4 thinner, it can be cooled more easily.

In addition, in the example shown in the figure, the film thickness of the second dielectric 4 is set to approximately 300 mm, but this would be approximately 1/
This corresponds to 10λ or less, which can be almost ignored optically, and the thickness of the second dielectric layer is 1/2.
It was possible to obtain the same performance as when λ was set to 2000 people.

Effects of the Invention The present invention provides a disk substrate with a first dielectric layer, a recording medium layer,
By making the thickness of the second dielectric layer in contact with the reflective layer thinner than that of the first dielectric layer in a disk in which a second dielectric layer and a reflective layer are sequentially formed, the recording medium layer can be rapidly cooled. This makes it possible to record amorphous marks due to rapid cooling at high speed and with good S/N characteristics.

[Brief explanation of the drawing]

The figure is a partially omitted sectional view of an information carrier disk in one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Disc substrate, 2... First dielectric layer, 3... Recording medium layer, 4... Second dielectric layer, 5 ...Reflection layer. Name of agent Patent attorney Shigetaka Awano 1 person f--Hisu 2-s Honke 2・-¥-〇Words 辂Hoei 3--115Otsu@1shi1yo1yoil Outside-・- Second I71 shell I Robe color 5--10,000 layer

Claims (2)

[Claims] (1) A first dielectric layer is irradiated with laser light on one side of the transparent substrate, absorbing the energy and raising the temperature.
An information carrier in which a recording medium layer, a second dielectric layer, and a reflective layer are sequentially formed, which have the property of melting, rapidly cooling, and becoming amorphous, and of crystallizing by raising the temperature of the amorphous state. 1. An information carrier disk, characterized in that the second dielectric layer is thinner than the first dielectric layer. (2) The information carrier disk according to claim (1), wherein the second dielectric layer has a thickness of 300 Å or less.