JPH05238149A - Draw-type optical disc - Google Patents

Abstract

PURPOSE:To obtain a DRAW-type optical disc having long-term stability high reflection factor and high absorptive wavelength band by forming an organic color recording layer containing specific pentamethinecyanine and a reflective layer sequentially on a transparent substrate. CONSTITUTION:Pentamethinecyanine expressed by formula I (R is an alkyl group; W is hydrogen, an aryl group, an aromatic group and halogen; and X is iodine) is dissolved in diacetone alcohol. This solution of the dissolved pentamethinecyanine is applied to the surface of a transparent substrate such as polycarbonate or polymethylmethacrylate using a spin coating technique, then the applied coat is dried to form an organic color recording layer. After that, a reflective layer for laser beam reflection is formed on the organic color recording layer using a sputtering technique with a laser beam, thus to obtain a DRAW-type optical disc. The typical material for the formation of the reflective layer is Al, Au, Cu or Ag. The obtained DRAW-type optical disc has a long stable C/N ratio and high sensitivity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a write-once optical disc.

[0002]

2. Description of the Related Art As a write-once type optical disc, there is known a so-called air-sandwich type optical disc having a pair of internal gaps. In this air-sandwich write-once optical disc, the reflective organic dye recording layer toward the gap is heated by irradiation with a laser beam to cause evaporation or sublimation of the spot-shaped recording layer to form pits, and the presence or absence of pits. It is an optical disc that utilizes the change in reflectance due to.

Further, a laminated write-once type optical disk has been developed which does not carry a gap inside the optical disk. The structure of such a layered write-once optical disc is shown in FIG. In the figure, the substrate 1 is made of transparent resin such as polycarbonate (PC) or polymethylmethacrylate (PMMA). On the transparent substrate 1, a pre-groove 2 (guide groove) for tracking a laser beam for recording information is formed in advance. An organic dye recording layer 3 is formed on the pre-groove 2 and a reflective layer 4 is further provided on the organic dye recording layer 3 to optically enhance the amount of reflected light, and an ultraviolet curable resin is further formed on the reflective layer 4. Protective layer 5
Is provided.

In this optical disc, a laser beam for recording / reproducing is emitted from the transparent substrate 1 side toward the recording layer 3 and reflected by the reflecting layer 4. Organic dye recording layer 3
Has a property of absorbing light of a specific wavelength, the organic dye recording layer 3 is heated by irradiation with a laser beam of a specific wavelength and is decomposed, so that the substrate 1 in close contact with the recording layer 3 is also heated. To do. At this time, the recording layer 3 should originally be scattered toward the reflective layer 4, but it is pressed by the reflective layer 4 and decomposed on the spot, and the characteristic of the dye is no longer exhibited. Exactly, only the light-irradiated portion remains as a black dot in the dye recording layer 3.
At this time, although slightly, the pre-groove is expanded and the substrate is pressed again. The pit portion apparently has a lower reflectance than other portions, and the transmittance is almost equal to zero. Recording is thus completed on the recording layer 3. The optical disc is reproduced by utilizing this change in the transmittance.

In the case of such a laminated write-once optical disc,
The characteristics of the organic dye recording layer are as follows. That is,
It is assumed that a light amount of 1 is incident on the dye recording layer. R + A + T, where R is the amount of light reflected on the surface of the organic dye recording layer, A is the amount of light absorbed in the organic dye recording layer, and T is the amount of light passing through the organic dye recording layer. = 1 (1) Here, the provision of the reflection layer is nothing but the return of T directly through the dye recording layer. In addition, the absorption rate is a
Then, since a = {1- (R + T)} / (1-R) (2), the amount of T × a is reabsorbed by the dye recording layer and T × a.
The amount of light (1-a) is emitted from the dye recording layer as externally reflected light. Since the equation (1) can be expressed as R + A + T * a + T * (1-a) = 1 (3), r = R + T * (1 because it is -a), (2) from the ^{equation, r = R + T 2 /} (1-R) ... (4) ^{Therefore, r = a 2 / (1} -R) -2A + 1 ... (5) Thus, qualitatively Cannot be expected to increase the externally reflected light amount r unless the transmitted light amount T is set to a relatively large value. A dye recording layer having a large amount of transmitted light T, a small amount of reflected light R, and an appropriate amount of absorbed light A is required.

As described above, in such a layered write-once type optical disk, the organic dye recording layer reacts with high absorption at a specific laser wavelength for writing, and at the same time, the reflectivity, absorptivity and transmissivity of the non-pit portion. However, a suitable one is desired. A write-once optical disc has been proposed in which a cyanine dye such as an indolenine type dye is used as a dye satisfying such conditions as a recording layer together with a reflective layer.

However, in such a write-once type optical disc using a cyanine dye as a recording layer, many of the cyanine dyes have high photosensitivity, and the characteristics of the dye are deteriorated only by exposing the disc to ordinary light. There's a problem.

[0008]

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a write-once optical disc having an organic dye recording layer having long-term stability, high reflectance and absorption wavelength band.

[0009]

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 organic dye recording layer comprises a mixture of pentamethinecyanine, and at least pentamethinecyanine represented by the following chemical formula 1,

[0010]

[Chemical 1]

(In the chemical formula 1, R represents an alkyl group,
W represents hydrogen, an aryl group, an aromatic group or halogen, and X represents iodine). Here, the substrate may be made of a light transmissive material such as polycarbonate or polymethylmethacrylate. For the reflective layer, metals such as aluminum Al, gold Au, copper Cu, and silver Ag can be used.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. In the write-once read-many optical disc of the present embodiment, FIG.
It has the same structure as the optical disc shown in FIG. The substrate 1 is made of PC or PMMA. PC is used as a substrate because it has lower hygroscopicity than PMMA, but PMMA having a small birefringence may be used as the substrate. A pre-groove 2 for tracking is previously formed on the substrate 1, and a thin film recording layer 3 made of a mixture of pentamethinecyanine, which is an organic dye, is formed thereon. Further, a reflective layer 4 made of gold Au for reflecting the laser beam is provided on the thin film recording layer 3. Furthermore, a protective layer 5 made of an ultraviolet curable resin or the like is formed thereon.

As a specific example, the thin film recording layer 3 made of a pentamethinecyanine mixture on a PMMA transparent substrate is as follows:
A pentamethine cyanine represented by the following chemical formula 2 which is a kind of pentamethine cyanine represented by the above chemical formula 1, and

[0014]

[Chemical 2]

Naphthoindolenin pentamethine represented by chemical formula 3,

[0016]

[Chemical 3]

A mixture of was used. A write-once optical disc was prepared in which an organic dye recording layer was formed by a spin coating method using a diacetone alcohol solvent containing this mixture, and an Au reflective layer was formed on the organic dye recording layer by a sputtering method. The pentamethinecyanine mixture had a high reflectance and a narrow absorption wavelength band. In addition, as a comparative example, a transparent substrate is PMMA, and on this substrate, indolenin pentamethine represented by chemical formula 4 which is conventionally known,

[0018]

[Chemical 4]

An organic dye recording layer of a mixture of naphthoindolenin pentamethine represented by the above chemical formula 3 is formed by a spin coating method using a solvent of diacetone alcohol, and the organic dye recording layer is sputtered on the organic dye recording layer. , A write-once type optical disc having an Au reflective layer was prepared. FIG. 2 is a graph showing the block error rate with respect to the light exposure elapsed time of the write-once type optical disks of the above-mentioned example and the comparative example. In the graph, in the comparative example, the block error rate sharply increases during the light exposure elapsed time of 0 to 100 hours (plot: ◯), while in the present embodiment, the block error rate is blocked even when the light exposure elapsed time exceeds 100 hours. No increase in error rate is observed (plot:
◎).

[0020]

As described above, according to the present invention,
Transparent substrate, counter ion X represented by the above chemical formula 1
Has a structure in which an organic dye recording layer made of a mixture containing pentamethinecyanine, which is an iodine anion, and a reflective layer are sequentially formed, so that a write-once optical disc having long-term stability and high C / N ratio and high sensitivity can be obtained.

[Brief description of drawings]

FIG. 1 is a partially enlarged cross-sectional view of a laminated write-once optical disc.

FIG. 2 is a graph showing a block error rate with respect to a light exposure elapsed time of a write-once optical disc of an example and a comparative example.

[Explanation of symbols]

 1 ... Substrate 3 ... Recording layer 4 ... Reflective layer 5 ... Protective layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masaaki Hayami Inventor Masaaki Hayami 1-3 2-3 Shimoishii, Okayama-shi, Okayama Japan Institute of Photosensitive Dyes (72) Inventor Yoshiki Okazaki 1-chome, Shimoishii, Okayama-shi, Okayama No. 2 and No. 3 Stock Company Japan Photosensitive Dye Research Institute

Claims (4)

[Claims] 1. A write-once type 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 organic dye recording layer is a pentalayer. A pentamethinecyanine consisting of a methinecyanine mixture and represented by at least the following chemical formula 1, (In chemical formula 1, R represents an alkyl group, W represents hydrogen, an aryl group, an aromatic group or halogen, and X represents iodine.) A write-once type optical disc. 2. The write-once optical disc according to claim 1, wherein the substrate is made of a light transmissive material selected from the group consisting of polycarbonate and polymethylmethacrylate. 3. The write-once optical disc according to claim 1, wherein pre-addresses and / or pre-grooves are formed in advance on the substrate. 4. The write-once optical disc according to claim 1, wherein the reflective layer is made of a metal thin film selected from the group consisting of aluminum, gold, copper and silver.