JPH03169588A - Write-once optical disk - Google Patents

Abstract

PURPOSE:To obtain a postscript type optical disc with an organic dye-stuff recording layer having the high reflectivity of a non-pit section and an absorption wavelength range by composing the organic dye-stuff recording layer of specific indolenine pentamethine. CONSTITUTION:A substrate 1 for a write-once optical disc is composed of PC or PMMA, a pre-group 2 for tracking is formed previously onto the substrate 1, the thin-film recording layer 3 of indolenine pentamethine is shaped onto the pre-group 2, and a reflecting layer 4 consisting of gold Au for reflecting laser beams is formed R<1> im formula represents hydrogen or a methyl group and R<2> the organic dyestuff recording layer of indolenine pentamethine shown by argin in the recording layer 3. A protective layer 5 made up of an ultraviolet radiation curing type resin, etc., may also be shaped onto the reflecting layer 4. Accordingly, the write-once optical disc having high reflectively and high C/N ratio and sensitivity is acquired.

Description

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

BACKGROUND ART As write-once type 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 to form bits 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 pregroove 2 (guiding groove) for tracking that guides a laser beam when recording information is formed in advance on the transparent substrate 1. An organic dye recording layer 3 is formed on the pregroove 2, a reflective layer 4 is provided on top of the organic dye recording layer 3 to optically enhance the amount of reflected light, and an ultraviolet curing resin, etc. A protective layer 5 is provided.

In this optical disc, a laser beam for recording and reproducing is irradiated from the transparent substrate 1 side toward the recording layer 3 and reflected by the reflective layer 4. 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 decomposed by irradiation with a laser beam of a specific wavelength, the organic dye recording layer 3 adheres closely to the recording layer 3. The substrate 1 is also heated. At this time, although the recording layer 3 should originally scatter toward the reflective layer 4 side, it is suppressed by the reflective layer 4 and decomposes on the spot, and no longer exhibits the characteristics of a dye. Exactly, only the light-irradiated portion remains as a black spot in the dye recording layer 3. At this time, it is possible to push the pregroove slightly and widen it, and to push the board again. The pit portions apparently have lower reflectance than other portions, and the transmittance is almost equal to zero. In this way, recording on the recording layer 3 is completed. This change in transmittance is used to reproduce the optical disc.

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 an amount of light of 1 is incident on the dye recording layer.

In addition, R is the amount of light reflected on the surface of the organic dye recording layer, and A
If T 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, then R+A+T- 1 (1) Here, a reflective layer is provided. This means that T is returned as it is via the dye recording layer.

If the absorption rate is a, then a - (1 - (R + T) l / (1 - R)
-(2), the amount of TXa is reabsorbed by the dye recording layer, and the amount of light TX(1-a) exits from the dye recording layer to the outside as external reflected light. Equation (1) is R+
Since it can be expressed as A0TXa+TX (1-a)-1-'<3), the amount of light that goes outside as external reflected light is r
Then, r-R+TX (1-a), so from equation (2), r-R+T2 / (1-R) -(4) Therefore, r-A2 / (1-R) -2A+1 -(5)
Therefore, qualitatively speaking, an increase in the externally reflected light fir cannot be expected unless the amount of passing light T is set to a certain large value.

A dye recording layer is required in which the transmitted light ffiT is large, the reflected light ffiR is small, and the absorbed light ffiA is moderate.

In this way, in such a laminated write-once optical disc, the organic dye recording layer exhibits high absorption and responds to a specific laser wavelength for writing, and the reflectivity, absorption, and transparency of the non-bit area decrease. Something appropriate is desired.

Summary of the Invention [Object of the Invention] Accordingly, an object of the present invention is to provide a write-once optical disc including an organic dye recording layer having a high reflectance in non-pit portions and an absorption wavelength band.

[Structure and operation 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 organic dye recording layer is characterized in that it consists of indolenine pentamethine, CLO4 5 l, represented by the following formula (A), where R1 is hydrogen or a methyl group and R2 is an alkyl group.

For the substrate, a light-transmitting material such as polycarbonate or polymethyl methacrylate can be used.

The reflective layer is made of aluminum AI, gold Au, copper Cu, silver Ag.
Metals such as can be used.

Indolenine pentamethine has a high reflectance and a narrow absorption wavelength band.

Hereinafter, the present invention will be explained 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 PC or PM
It is made up of MA. PC is used as a substrate because it has lower hygroscopicity than PMMA, but PM has less birefringence.
MA may be used as a substrate. A pregroove 2 for tracking is formed in advance on this substrate 1, and a thin film recording layer 3 of indolenine bentamethine is formed thereon.
A reflective layer 4 made of gold (Au) is provided to reflect the laser beam. Furthermore, a protective layer 5 such as an ultraviolet curing resin may be formed thereon.

The present invention was achieved based on the knowledge that indolenine pentamethine is a substance that has the characteristics of such a dye recording layer 3 as having broadband reflectivity and a sharp absorption wavelength band at a specific wavelength.

Effects of the Invention As explained above, the present invention has a structure in which a transparent substrate, an organic dye recording layer of indolenine pentamethine, and a reflective layer are sequentially formed on a reflective layer, so that C. A write-once optical disc with high /N ratio and high sensitivity can be obtained.

Examples As Example 1, the transparent substrate is PMMA, and on this substrate is recorded an organic dye of indolenine bentamethine shown in the following (A1) in which Rl is a methyl group and R2 is also a methyl group in the above formula (A). A write-once optical disk was fabricated by forming a layer using a diacetone alcohol solvent by a subin coating method, and then forming an Au reflective layer on this organic dye recording layer by a sputtering method.

FIG. 2 is a graph showing the reflectance wavelength characteristics of the write-once disk of Example 1, in which the reflectance decreases at a wavelength of 700 nm, and at around 780 nm and 830 nm (the reversal rate becomes higher). to show that

FIG. 3 is a graph showing the absorption wavelength characteristics of an organic dye solution forming the recording layer of such an optical disc, with 65
It showed a high absorption peak at one wavelength of 8n.

In Example 2, the transparent substrate was made of PMMA, and spin coating was applied on this substrate in the same manner as in Example 1.
), where Rl is hydrogen and R2 is {n-butyl group. An organic dye recording layer of indolenine pentamethine shown in (A2) below is formed, and a vapor deposition method (this method is applied) on this organic dye recording layer. Therefore, a write-once optical disc with an Au reflective layer was formed.

FIG. 4 is a graph showing the reflectance wavelength characteristics of the write-once optical disc of Example 1, showing that the reflectance decreased at a wavelength of 700 nm and was high near 780 nm and 830 nI1. show.

FIG. 5 is a graph showing the absorption wavelength characteristics of an organic dye solution forming the recording layer of such an optical disc,
It showed a high absorption peak at a wavelength of 5 1 na+.

[Brief explanation of the drawing]

Figure 1 is a partially enlarged sectional view of a stacked write-once optical disc.
2 and 4 are graphs showing the reflectance wavelength characteristics of the write-once optical disk according to the present invention, and FIGS. 3 and 5 are graphs showing the absorption coefficient of an organic dye solution forming the recording layer of the write-once optical disk according to the present invention. It is a graph showing wavelength retention. Explanation of symbols of main parts 1... Substrate 3... Recording layer 4... Reflective layer 5... Protective layer

Claims (4)

[Claims] (1) A write-once optical disc comprising 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 comprising:
Indolenine pentamethine represented by the following formula (A), where R^1 is hydrogen or a methyl group and R^2 is an alkyl group, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (A) 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) Claim 1 or 2, characterized in that a pre-address and/or a pre-groove is formed in advance on the substrate.
Write-once optical disc as described. (4) The write-once optical disc according to any one of claims 1 to 3, wherein the reflective layer is made of a metal thin film selected from the group consisting of aluminum, gold, copper, and silver.