JPH03181029A - information carrier disk - Google Patents

Abstract

PURPOSE:To improve cycle characteristics by using Ta2O5 as dielectric layers and confining the film thickness of the dielectric layer between a recording medium layer and a reflecting layer to <=50nm. CONSTITUTION:A disk substrate 1 consists of a transparent resin material, such as polycarbonate, and the 1st dielectric layer 2 is provided on this disk substrate 1. The 1st dielectric layer 2 consists of the Ta2O5 having excellent heat resistance and the recording medium layer 3 is provided on the 1st dielectric layer 2. The recording medium layer 3 is a mixed thin film consisting of Ge, Te and Sb and the 2nd dielectric layer 4 is provided on this recording medium layer 3. The 2nd recording medium layer 4 is formed of the same material as the material of the 1st dielectric layer 2 and the film thickness thereof is confined to <=50nm. The reflecting layer 5 is provided on this 2nd dielectric layer 4. The recording and erasing characteristics as well as the cycle characteristics are improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to information carrier disks (hereinafter referred to as
(simply referred to as a disk).

Conventional technology Conventionally, a recording medium layer is formed on one side of a disk-shaped disk substrate made of a transparent material, and minute holes are formed in the recording medium layer by irradiating laser light from the disk substrate side, or optical Discs that perform recording and reproduction by forming bits with varying order of density 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 records information by applying a laser beam to the recording medium layer, melting it, and rapidly cooling it to become amorphous, and then crystallizing it by heating and rapidly cooling it. It is to be erased. This material includes S, R
Chalcogen material RGe15Te81 by Mr. , 0vshinsky (Niss A/L'-Opshinsky) et al.
Sb2S2 and the like are known. Further, thin films made of a combination of As2S3 and the like are widely known.

A method of recording information on these recording medium layers with laser light and erasing the information is to crystallize the recording medium layer in advance, and then apply a laser beam focused to approximately 1 μm in r+-V to correspond to the information. For example, the intensity is modulated by rotating a disk-shaped recording disk and irradiation is performed. At this time,
The temperature of the laser beam irradiated area rises above the melting point of the recording medium layer,
Information is recorded in the form of marks that are rapidly cooled and turned into amorphous forms. 7 (2) In addition, when erasing information, a long spot light is irradiated in the direction of the rotating track of the disk. A method is known in which the medium layer is heated to a high temperature and re-crystallized by the slow cooling effect of a long spotlight.In this way, the erase disk becomes high temperature in a minute area of about 1 pm, and for example, the disk substrate If a resin substrate is used to form a direct recording M medium M5r, the disk substrate will be deformed by the laser beam and recording and erasing cannot be repeated.For this reason, the disk substrate and recording medium must be A dielectric layer is formed between the layers or between the recording medium layer and the protective layer that protects the recording medium layer as a heat insulator to prevent ripening. It functions as an optical layer that utilizes multiple interference of laser light, and in some cases, a reflective layer is provided on the dielectric layer on the protective layer side to improve recording/erasing sensitivity.

Problems to be Solved by the Invention Problems faced by information recording buttons and erasable disks that use means of heating the recording medium layer, melting and rapidly cooling it into amorphous form, and heating and temperature-raising crystallization are compatible with heating cycles. The problem is that the signal quality fluctuates. This variation factor is as follows.
Thermal damage to the disk substrate or dielectric layer due to repeated rapid heating and cooling of 400°C or more by recording spot light and erasing spot light.Thermal damage to the disk substrate or dielectric layer. In the case of a recording/reproducing/erasing cycle, noise increases and cycle characteristics deteriorate. Another reason is that, as mentioned above, erasing disks that utilize phase change are thermally recorded, so the cooling rate during recording or erasing determines the characteristics. In other words, the cooling rate is affected by the disk configuration, such as the material of the dielectric layer or the thickness of the dielectric layer, and if a dielectric with low thermal conductivity is used, or if the configuration is such that heat escapes easily, the temperature will increase. Another problem was that the recording medium layer was slowly cooled, making it difficult to write amorphous recording marks.

The present invention is intended to solve these problems, and it is an object of the present invention to provide an information carrier disk with excellent recording/erasing characteristics and excellent cycle characteristics.

Means for Solving the Problems In order to solve the problems, the present invention provides a first dielectric layer, a recording medium layer, a second dielectric layer, and a reflective layer on one side of a transparent disk substrate. The first dielectric layer and the second dielectric layer are made of Ta2O5, and the thickness of the second dielectric layer is 50 nm or less.

Function: With this structure, by using Ta2O5 as the dielectric layer and making the thickness of the second #electric layer 50 nm or less, the cooling rate during recording and erasing can be increased. be. By speeding up this cooling rate, recording and
Thermal shock caused by repeated erasing can be reduced, and cycle characteristics can be greatly improved. Furthermore, amorphous recording marks obtained by heating and rapidly cooling the recording medium layer can be reliably written, and recording marks with excellent signal quality can be obtained.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings.

In the figure, a first dielectric M2 is provided on an IFi disk substrate 1 made of a transparent St resin material such as polycarbonate. This first dielectric layer 2 is made of Ta02O5, which has excellent heat resistance, and has a thickness of about 150 nm.

A recording medium layer 3 is provided on the dielectric material 71i112 of '$1. This recording medium layer 3 contains Ge, Te,
The mixed thin film is made of Sb and has a thickness of about 30 nm. A second dielectric layer 4 is provided on the recording medium N3. This second dielectric layer 4Fi is made of the same material as the first dielectric layer 2, and has a thickness of 50 nm or less.

A reflective layer 5 is provided on the second dielectric layer 4, and the thickness of the reflective layer 5 is about 50 nm.

These thin films can be formed by vacuum evaporation or sputtering. A protective plate 6 is made of the same material as the disk substrate 1 and is pasted on the reflective layer 5 with an adhesive 7.

In the configuration shown in the drawings, recording and erasing are performed by irradiating a laser beam whose intensity is modulated in accordance with the information in the direction of arrow A.

Here, the thickness of the second dielectric layer 4 is made as thin as 50 nm or less, which is made of a metal layer such as AI, Au, or Cr, and includes a reflective layer 5 serving as a heat diffusion layer and a recording medium layer 3. As a result, the heat of the recording medium layer 3 during recording and erasing is rapidly transferred to the reflective layer 5.
This provides a great effect in rapidly cooling the recording medium NRR. Although the second dielectric layer 4 is thin, since the laser beam is irradiated from the side of the disk substrate 1 for recording and erasing, the second dielectric layer 4 is thin. The thermal shock was small and there was no problem even after repeated many cycles. Also, as mentioned above, the factor that influences the cooling rate is the material of the dielectric layer, i.e., f? , ＋
The Fxm ratio or the material of the reflective layer are also important factors, but the dielectric material of this example, Ta2O5, has appropriate thermal conductivity and is excellent in heat resistance and chemical stability. However, with the disk configuration of this example, C/N50
dB, erasure rate of 30 dB or more, recording/erasing repetition is 1
It was stable for more than 0.06 cycles.

Effects of the Invention As described above, according to the present invention, Ta2O is used as the dielectric layer.
5, and by setting the film thickness of the dielectric layer between the recording medium layer and the reflective layer to 50 nm or less, the cooling rate during recording and erasing can be increased, which reduces thermal shock during multiple cycles. and can improve cycle characteristics,
It is possible to easily write amorphous recording marks.

[Brief explanation of drawings]

The drawing is a sectional view of an information carrier disk according to an embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Disk substrate, 2... First [E body layer, 3...
... Recording medium layer, 4... Second dielectric layer, 5... Reflective layer, 6... Protective plate, 7... Adhesive. Yoshihiro Morimoto - Reflective layer

Claims (1)

[Claims] 1. On one side of the transparent disk substrate, there is a first dielectric layer, a layer with a property of absorbing the energy by laser light irradiation, heating up, melting, rapidly cooling, and becoming amorphous; An information carrier disk comprising a recording medium layer having a property of being crystallized by raising the temperature of a crystalline state, a second dielectric layer, and a reflective layer, wherein the first and second layers are sequentially formed. An information carrier disk characterized in that Ta_2O_5 is used as the dielectric layer, and the thickness of the second dielectric layer is 50 nm or less.