JPH03165344A - Draw type optical disk - Google Patents

Abstract

PURPOSE:To obtain the DRAW type optical disk which has a high reflectivity and high CN and sensitivity and can decrease the jitters at the time of reproduction by having the structure successively formed with a transparent substrate, org. dyestuff recording layer and reflecting layer consisting of silver. CONSTITUTION:This optical disk is constituted by forming the transparent substrate 1 and the thin-film recording layer 3 consisting of indocyanine thereon, and providing the reflecting layer 4 consisting of the silver (Ag) for reflecting a laser beam thereon. Eye patterns are unified and the C/N is improved by using the silver as the reflecting layer in place of gold in this constitution. Further, the generation of bumps at the ends of long bit parts is obviated and the jitters of reproduction signals are decreased. The silver reflecting layer acts as a heat sink and rapidly cools the bit parts at the time of irradiation with the laser when the silver is used as the reflecting layer and, therefore, the rapid curing of the molten parts of the dyestuff layer and the substrate is accelerated in contrast with the long-term irradiation with the laser. The steep foremost ends A are thus formed even at the final ends thereof without forming the gentle terminals.

Description

[Detailed description of the invention] Technical field The present invention relates to a write-once optical disc.

BACKGROUND ART As write-once optical discs, a so-called air sandwich type disc in which a gap is provided inside a pair is known. This air sandwich type write-once optical disk is heated by irradiating a reflective organic dye recording layer toward the gap with a laser beam, causing spot-like evaporation or sublimation of the recording layer, forming pits, and changing the presence or absence of pits. This is an optical disc that takes advantage of the accompanying change in reflectance.

Furthermore, a stacked write-once type optical disc that does not have any gaps inside the optical disc has also been developed. The structure of such a stacked write-once optical disc is shown in FIG. In the figure, a substrate 1 is made of a transparent resin such as polycarbonate (PC) or polymethyl methacrylate (PMMA). A laser beam for recording information is guided on the transparent substrate 1 (
A pregroove (guide groove) for tracking is formed in advance. An organic dye recording layer 3 is formed on a transparent substrate 1, and a reflective layer 4 made of gold (Au) for optically enhancing the reproduction output level is provided on top of the organic dye recording layer 3. A protective layer 5 such as the above is provided.

In this optical disc, a laser beam for writing and recording is irradiated from the transparent substrate 1 side toward the recording layer 3,
It is reflected by the u-reflection layer 4. At this time, since the organic dye recording layer 3 has the property of absorbing light of a specific wavelength, as the organic dye recording layer 3 is heated and melted by irradiation with a laser beam of a specific wavelength, the recording layer 3 The substrate 1 in close contact is also heated. Here, the substrate 1 reaches a glass transition and becomes soft. At this time, the dye decomposes and pressure is applied to the interface between the substrate 1 and the recording layer 3. The materials of the dye and the substrate mix at the interface, eventually deforming the interface.

The pit portion 8 formed by the cooling of the deformed portion has a lower reflectance than the Au reflective layer portion of the apparent pond due to the phase difference of the laser beam. In this way, additional writing on the recording layer 3 is completed. By utilizing this change in reflectance, the presence or absence of this pit portion corresponds to a binary value of 1 or 0, thereby performing recording and reproduction on the optical disc.

However, as shown in FIG. 2, if writing is continued using continuous laser irradiation signals, a bump 9 will occur at the rearmost end of the corresponding long pit portion 8. This disturbs the reproduced signal, especially the eye pattern, and lowers the C/N ratio. Furthermore, even in the individual short pit portions 8, the shapes thereof, especially the shapes of the leading and trailing ends thereof, are not uniform, and there is a problem in that jitter during signal reproduction becomes large.

Summary of the Invention [Object of the Invention] Therefore, an object of the present invention is to provide a write-once optical disc with reduced jitter.

[Structure of the Invention] A write-once optical disc according to the present invention is a write-once optical disc having a transparent substrate, an organic dye recording layer formed on the substrate, and a reflective layer formed on the organic dye recording layer, The reflective layer is characterized by being made of silver.

[Action of the invention]

The above configuration reduces jitter during signal reproduction.

Example Hereinafter, embodiments according to the present invention will be described based on the drawings.

The write-once optical disc of the present invention has the same structure as the optical disc shown in FIG.

The board 1 is made of a PC. PC is PhIMA
PMMA is used as a substrate because it has lower hygroscopicity, but PMMA, which has less birefringence, may also be used as a substrate. A pregroove for tracking is formed on this substrate 1 in advance,
A thin film recording layer 3 of indocyanine is formed on it,
Reflects the laser beam. Furthermore, a protective layer 5 made of ultraviolet curing resin or the like is formed thereon.

In this way, conventionally gold was used as the reflective layer, but by using silver as the reflective layer, the eye pattern was improved and the C/N ratio was improved. Furthermore, bumps at the ends of long pits no longer occur, and the jitter of the reproduced signal is reduced.

This long bump at the end of the pit is caused by the fact that when irradiation is carried out for a long period of time, the melted part between the dye layer and the substrate that forms the bit becomes longer, and the expansion of the melted part appears at the rear end of the bit. As a result of experiments, it was found that this occurs.

As shown in the table below, silver has a high reflectance and exhibits high thermal conductivity. For this reason, when silver is used as the reflective layer instead of the conventional total reflection layer, the silver reflective layer acts as a heat sink during laser irradiation and rapidly cools the bit area, so it can be used for long periods of laser irradiation. On the other hand, the molten portion between the dye layer and the substrate is rapidly hardened, and even the rearmost end thereof does not have a smooth end, but instead becomes a steep rearmost end A of the pit, as shown in FIG. As a result of experiments, we were able to learn this fact, which led us to the present invention.

*Thermal conductivity unit: (k/Wm-' at 30
0-400, the present invention has a structure in which a transparent substrate, an organic dye recording layer of indocyanine, and a reflective layer of silver are sequentially formed. A write-once optical disc with high ratio and sensitivity can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged sectional view of a stacked write-once optical disc according to the present invention, and FIG. 2 is a partially enlarged sectional view of a conventional stacked write-once optical disc. Explanation of symbols of main parts 1...Substrate 3...Organic dye recording layer 4...Reflection layer

Claims (3)

[Claims] (1) A recordable optical disc having a transparent substrate, an organic dye recording layer formed on the substrate, and a reflective layer formed on the organic dye recording layer, wherein the reflective layer is made of silver. A write-once optical disc. (2) The write-once optical disc according to claim 1, wherein the substrate is made of a light-transmitting material selected from the group consisting of polycarbonate and polymethyl methacrylate. (3) The write-once optical disc according to claim 1 or 2, wherein a pre-address and a pre-groove are formed in advance on the substrate.