KR100186525B1 - Structure for phase change type optical disk - Google Patents

Abstract

A phase change type optical disk structure, comprising: Cr-Te (chromium-tellurium) added to an AgInSbTe alloy, which is a recording layer formed between a first dielectric layer and a second dielectric layer, formed on a polycarbonate substrate, and the like This is to prevent the repetitive recording and other characteristics.

Description

Phase change optical disk structure

The present invention relates to a high density phase change type optical disc, and more particularly, to a phase change type optical disc structure which prevents the flow of a recording layer.

In general, a phase change type optical disc concentrates laser light on a recording layer and rapidly cools the recording layer when its temperature rises above the melting point in response to its pulse output and pulse width, thereby making the recording layer amorphous and using it as a recording bit. At the time of erasing, unlike at the time of the above recording, the laser is irradiated with a low pulse output and a pulse width on the recording layer again to raise the temperature near the crystallization temperature, and then cool it to bring it to a crystallization state.

In the phase change type recording material, since the conversion of the crystalline and amorphous states occurs reversibly, it is attracting attention as a rewritable optical disc material.

In the phase change type optical disc, the information reproducing method uses information different in reflectance in such a phase, for example, in which the reflectance of the crystal state (erased state) is higher than that of the amorphous state (recording state). Play it.

Then, the laser beam is irradiated from the polycarbonate substrate side and initialized by applying a predetermined power so that the recording layer can be crystallized. Then, the information irradiance is melted and quenched to form an amorphous spot. .

Again, overwriting is repeated by irradiating a laser with a lower intensity on the spot in the amorphous state and returning it to the crystalline state.

As shown in FIG. 1, a conventional phase change type recording medium has a phase change type on a first dielectric layer (ZnS-SiO 2) 20 and a first dielectric layer 20 formed on a polycarbonate substrate 10. A recording layer (AgInSbTe) 30 formed of a recording material, a second dielectric layer (ZnS-SiO ₂ ) 40 sequentially formed on the recording layer 30, a metal reflective layer (Al alloy) 50, and an ultraviolet curable resin It consists of a protective layer 60 of (UV resin).

The first and second dielectric layers 20 and 30 above and below the recording layer 30 directly heat the recording layer 30 by the irradiation of laser light to prevent damage and to prevent the recording layer ( 30) is intended to prevent scattering by oxidation and heating.

In particular, the second dielectric layer 40 effectively absorbs laser light into the recording layer 30 to exhibit an Enhance effect of increasing the change in reflectance of the recording layer 30, thereby improving the sensitivity of the phase change fluorescent recording medium. It plays a role to improve.

ZnS-SiO _{2, which} is used as the first and second dielectric layers 20 and 40 in the phase change type optical recording medium having such a structure, is capable of obtaining an amorphous uniform film and having a relatively smaller coefficient of thermal expansion than other dielectric layers. Since it has an optically high refractive index and can be designed at the intermediate value of the recording layer 30 with the polycarbonate substrate 10, the incident laser light can be designed under antireflection conditions.

Therefore, the phase change optical recording medium can be erased even by a low power laser and the thermal stress applied to the phase change recording medium is reduced.

In addition, it is a feature of phase change optical discs to read out the difference of optical constants due to the structural change (crystalline-amorphous) of the recording material as the change in reflectivity. Currently, many materials have been developed and the representative recording material is GeTeSb alloy.

This material has been used steadily for a long time in computer-assisted storage in high speed environments of 10-20 ^m / _s . It is important that the crystallization rate is high in order to be able to record and erase at high speeds. The crystallization rate of the composition on the line of Sb2Te3 virtual binary system reaches 30-100ns, but it is already commercialized to satisfy the reversible change of crystalline and amorphous.

The water furnace recording layer is not the only core technology for constituting a disk because it is influenced by the composition, the holy land, the thickness, and the like of the dielectric film, which also includes the unique properties of the recording medium.

This is because, in the case of the phase change type disc, the recording mode uses thermal energy to use the reversible reaction of the phase, and thus the optical, thermal and mechanical effects must be considered in combination.

Today, high density, long and dense technologies including DVD (Digital Video Disc) are steadily evolving, and the rewritable type of magneto-optical discs, due to their excellent data stability despite the complex configuration, and the simple recording and reproducing technology of phase change discs. In order to increase the recording density on the substrate while competing with each other, a situation in which a short wavelength light source is employed is used to increase the density.

Therefore, the shortest way to take advantage of the advantages of the phase change type optical disc and overcome the disadvantages is to develop a recording material capable of stable recording and reproduction.

Recently, Ricoh and Osaka University in Japan are making efforts to apply CD-E (Cumpact Disc-Eraseable) application mainly to AgInSbTe of the employee industry.

In addition, AgInSbTe, a phase change type optical disk, is a material whose structure is fine and reversible phase change is particularly small and precisely jitter during mark edge recording, which modulates the mark length and achieves high density. It has all the advantages of controlling the length, and the elimination ratio is much higher than that of GeSbTe.

The recording layer material of the phase change type optical disc according to the prior art is considered to have a disadvantage in that it is extremely difficult to make a mixed phase, and the repetitive recording characteristics are bad.

In addition, since the difference in reflectivity required for CD-E is large, the sensitivity is high, which is advantageous for recording information, but the light absorption of the medium is high, resulting in severe media flow during overwriting, which is a disadvantage in repeated use of recorded data.

The present invention has been made to solve the problems of the prior art, by adding a high melting point material Cr-Te in the recording layer to prevent the media flow during overwriting to improve the characteristics such as repeat recording It is to provide a changeable optical disk structure.

1 is a cross-sectional view of an image development type optical disk according to the prior art,

2 is a cross-sectional view of a phase change type optical disk according to the present invention.

* Explanation of symbols for main parts of the drawings

10 polycarbonate substrate 20 first dielectric layer

30: recording layer 40: second dielectric layer

50: reflective layer 60: protective layer

A feature of the phase change type optical disc structure according to the present invention is that Cr-Te, which is a high melting point material, is added to the recording layer by about 2wt% to 15wt% to prevent the flow of the recording film.

Hereinafter, a preferred embodiment of a phase change type optical disk structure according to the present invention will be described with reference to the accompanying drawings.

2 is a cross-sectional view of a phase change type optical disk according to the present invention.

As shown in FIG. 2, after the polycarbonate substrate 10 is mounted on the sputtering apparatus, ZnS-SiO ₂ is coated with a thickness of about 1000 kPa to about 3000 kPa as the first dielectric layer 20.

Subsequently, a recording layer 30 having Cr-Te (chromium-tellurium) added to AgInSbTe is applied to a thickness of about 100 kPa to 300 kPa.

At this time, the amount of Cr-Te added to the recording layer 30 is 2wt% to 15wt%.

If the amount of Cr-Te added to the recording layer 30 is less than or equal to 2%, it is difficult to exert an effect of suppressing the medium flow, and if it is more than 15%, the recording layer itself is deteriorated and the sensitivity of the recording layer is reduced.

Here, the material of the recording layer 30 is added with B, C, N (boron, carbon, nitrogen) for controlling the microstructure of AgInSbTe, Ti, V (titanium, vanadium), etc. for controlling the crystallization rate.

Therefore, a disk made of such a material can be suitably combined with a recording technique such as controlling the length of a mark using a high density pulse width recording method and a compound pulse, so that a disk suitable for high speed and high density recording can be produced.

Next, the second dielectric layer 40 is coated with the same ZnS-SiO ₂ as the first dielectric layer 20 to a thickness of about 100 kPa to about 300 kPa.

Subsequently, an Al-Ti metal layer is applied to the reflective layer 50 at a thickness of about 500 kPa to 1000 kPa.

Finally, a protective layer 60 made of UV resin for protection of the substrate.

In the case of the recording layer 30 added with Cr-Te according to the present invention, since the melting point of Cr-Te is much higher than that of AgInSbTe, and the particle size is very fine, AgInSbTe can be easily mixed to prevent deterioration of sensitivity during recording. However, even in the case of repeated thermal cycles, there is an advantage that the flow of the medium does not occur.

In addition, the material of the recording layer 30 consisting purely of AgInSbTe repeats a continuous process of melting and cooling again by a thermal cycle which is continuously repeated when recording is performed.

Receiving such a thermal cycle causes a phenomenon in which the material of the recording layer 30 moves to one side in a molten state.

However, in the case of the recording layer 30 to which Cr-Te is added, such flow phenomenon can be prevented.

In the case of Cr-Te, the melting point is about 1200 ° C, while AgInSbTe is about 600 ° C.

That is, when the recording layer is melted to 600 ° C. or higher for the recording of information, AgInSbTe is completely melted, but in the case of Cr-Te, the melting point is about 1200 ° C., so that the solid remains without melting.

As a result, they remain solid during many long and erase processes, and when AgInSbTe melts and flow occurs, it inhibits their movement and inhibits flow, resulting in an improvement in the disc's repeatability. Bring it.

The phase change type optical disc structure according to the present invention has the effect of improving the characteristics of repetitive recording and the like by adding Cr-Te, which is a high melting point material, into the recording layer to prevent the medium flow during overwriting.

Claims (3)

In a phase change type optical disk having a polycarbonate substrate, A first dielectric layer formed on the polycarbonate substrate; A recording layer formed of a material in which Ct-Te, which is a high melting point material, is added to the first dielectric image; A second dielectric layer formed on the recording layer; Phase change type optical disk structure, characterized in that consisting of the ultraviolet curable resin layer formed on the reflective layer. The method of claim 1, A phase change type optical disc structure, characterized in that the melting point of the Cr-Te material added to the recording layer is 1200 ℃. The method of claim 1, Phase change type optical disk structure, characterized in that the amount of Cr-Te material added to the recording layer is 2 ~ 15wt%.