JPH0284383A - Optical recording medium - Google Patents

Abstract

PURPOSE:To enhance light resistance, productivity, optical characteristics or the like by using a chroconium coloring matter having a t-butyl-substd. nitrogen- containing heterocyclic ring at either end of its molecule as a recording material. CONSTITUTION:A recording layer comprises a chroconium coloring matter of formula I, wherein the heterocyclic ring at either end is a t-butyl-substd. nitrogen-containing heterocyclic ring, and each of R1 and R2 is a substd. or unsubstd. alkyl, cycloalkyl, allyl, substd. or unsubstd. aralkyl or substd. or unsubstd. aryl. The chroconium coloring matter, having a 5-membered ring at a central linking portion thereof, is structurally stable, and expansion of a delocalization region of pi-electrons causes a shift of absorption to the longer wavelength side, thereby enabling application of the coloring matter to a semiconductor laser with a wavelength of, for example, about 830nm. The solubility of the chroconium coloring matter depends heavily on substituent groups on the heterocyclic rings (nitrogen-containing heterocyclic rings) at both ends, and, particularly, introduction of t-butyl groups contributes effectively to enhancement of solubility of the coloring matter in general-purpose solvents.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium typified by an optical disk, and particularly to an optical recording medium using an organic dye as a recording material.

[Summary of the invention]

[Prior art] Optical recording systems have the characteristics of being able to record and reproduce without contact, being easy to handle, and being resistant to scratches and dust.
Since it has the advantage of a much larger storage capacity than current magnetic recording methods, it is expected to be used for large-capacity files such as code information and image information.

In particular, there is a lot of interest in so-called write-once optical recording media that users can directly read after writing, and research into recording materials is progressing in order to meet the demands for high sensitivity, high stability (chemical and mechanical), and high quality. It is being

In recent years, there has been active research into organic thin films that can cause optical property changes with light energy of relatively long wavelengths (e.g., 700 nm or more). It is expected that this method will be put to practical use because pits can be formed using a semiconductor laser. It takes! Thin films can be formed by a general-purpose method such as a spin code, so
It is also attracting attention from the viewpoints of mass productivity, manufacturing cost, etc.

[Problem to be solved by the invention]

By the way, the aforementioned Yu8! ! Optical recording media with a thin film recording layer must have good solubility for the organic dye used as the recording material, have an absorption band in a long wavelength range like a semiconductor laser, and have sufficient molecular absorption. It is required to have a number of properties such as having a high reflectance coefficient, exhibiting high reflectance when formed into a film, and having excellent light resistance and heat resistance.

Cyanine dyes have large absorption in the near-infrared region, which is the wavelength range of semiconductor lasers, for example, and also have high reflectance in the near-infrared region, so they are considered to be viable recording materials for this type of optical recording medium. ing.

However, cyanine dyes generally have poor light resistance, and there remains concern about their reliability when long-term storage of information is assumed.

Therefore, the present invention was proposed in view of the above-mentioned conventional situation, and provides an organic dye material with excellent properties such as light resistance, solubility, bimolecular extinction coefficient, 1 reflectance, etc., and thereby improves confidence. The purpose of the present invention is to provide an optical recording medium with excellent performance and productivity.

[Means to solve the problem]

The present inventors significantly improved solubility, molecular extinction coefficient 1 reflectance, etc. by introducing a monobutyl group into the heterocycle of the croconium dye, which has a pentagonal ring at the central connection site of the petero ring. We have come to the conclusion that this is the case.

The present invention was completed based on this knowledge, and the recording layer is a nitrogen-containing heterocycle substituted with a butyl group of the following formula, R,
, R represents a substituted or unsubstituted alkyl group, a cyclic alkyl group, an allyl group, a substituted or unsubstituted aralkyl group, or a substituted or unsubstituted aryl group. ) It is characterized by containing a croconium pigment represented by:

In the present invention, the central connecting part of the croconium dye used as a recording material is a five-membered ring, and it is expected that the dye will be stabilized by reducing ring strain and the absorption wavelength will be extended by expanding the delocalized region of π electrons. Ru.

On the other hand, the nitrogen-containing heterocycle bonded to both ends of the five-membered ring is
Any type of substituent may be used as long as a t-butyl group is introduced as a substituent, but particularly quinoline rings, benzothiazole rings, and indolenine rings substituted with L-butyl groups provide good optical performance. Show characteristics.

Therefore, the nitrogen-containing heterocycle but, It is preferable that it is either.

Groups R,,R introduced in addition to the t-butyl group.

Examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, 5ee-butyl group, t-butyl group, n-pentyl group, and n-hexyl group.

Alkyl groups such as n-octyl groups, substituted alkyl groups such as 2-hydroxyethyl groups and 2-carboxyethyl groups, cyclic alkyl groups such as cyclohexyl groups, aralkyl groups such as allyl groups and benzyl groups, carboxybenzyl groups, and sulfonate groups. Examples include substituted aralkyl groups such as benzyl groups, aryl groups such as phenyl groups, and substituted aryl groups such as carboxyethyl groups.

The substituents Rs and R4 introduced into the quinoline ring may be hydrogen, or may be an alkyl group, a substituted alkyl group, a cyclic alkyl group, etc. as in the above R, ,R.

The above-mentioned croconium dye can be synthesized by subjecting croconic acid to a condensation reaction with a nitrogen-containing heterocyclic compound (quinaldine, benzothiazoleindolenine, etc.).

The method for synthesizing croconic acid is shown by the following reaction formula (A).

A nitrogen-containing heterocycle into which a t-butyl group has been introduced may be synthesized according to a conventional method. For example, the 1-butyl-substituted quinaldine shown above can be synthesized by (a) cyclization reaction for synthesizing quinoline having a t-butyl group. , (b) Introduction of Rs, Rn, (c) R
It is synthesized through a three-step reaction consisting of addition of + and Rz to the N position. The reaction at each stage is shown below.

・・・ ・(a) ・ ・ ・(b) ・ ・ ・ ・(C) The above-mentioned croconium dye may be used as a recording layer by forming a film alone on a substrate, or may be formed into a film together with some kind of binder. It may also be used as a recording layer. As a film forming method, thin film forming techniques such as vapor deposition, coating techniques such as spin cord, blade coating, roller coating, etc. can be employed.

Note that as the substrate and the binder, any material used in conventional optical recording media can be used, and as the solvent when the coating technique is employed, any general-purpose solvent can be used.

Furthermore, a base film, a protective film 1 reflective film, etc. may be formed as necessary.

[Effect]

Croconium dye is structurally stable because it has a five-membered ring in the central linkage, and the delocalized region of π electrons is expanded, so the absorption shifts to longer wavelengths, making it suitable for semiconductor lasers with a wavelength of about 830 nm, for example. be done.

The solubility of such croconium dyes largely depends on the substituents on the heterocycles (nitrogen-containing heterocycles) at both ends, and the introduction of -butyl groups is particularly effective in improving solubility in general-purpose solvents.

〔Example〕

The present invention will be explained below using specific experimental results.

First, a croconium dye was synthesized according to the following method.

7 g of sodium rhodizonate was dissolved in 350 g of water, and 30 g of calcium carbonate and 20 g of activated manganese dioxide were added thereto. This cloudy liquid was stirred for 1 hour and refluxed, then immediately filtered and washed several times with hot water). When the filtrate was cooled, potassium croconate crystals were precipitated. After cooling down sufficiently,
Hydrochloric acid was added until the crystals disappeared, and then an aqueous barium chloride solution was added to obtain golden barium croconate. Sufficient amount of barium croconate (55g) 'c sulfuric acid aqueous solution (H, 30, 20mf/HtO180m
1) and stirred for about 1 hour (55-60°
C) The produced barium sulfate was filtered off, washed with hot water, and then dried under reduced pressure (~40'C).

The residue was heated with ethanol (251d) + dioxane (
150d) and treated with a small amount of activated carbon. After filtration, the filtrate was condensed at 40° C. under reduced pressure, and when crystallization started, it was diluted with benzene and cooled until it became cloudy. After standing for several hours, the crystals were filtered out and washed with benzene.
Croconic acid was obtained by vacuum drying.

Next, the synthesized croconic acid (0,00845 mol) was also -
Quinaldine ethiosite (0,01
After heating a mixed solution consisting of 69 mol) and 50 ml of n-butanol to 110°C, pyridine 4rd was added, stirred at the same temperature for 5 minutes, and then left to cool. The solvent was removed in 7 distillations under reduced pressure, and this was transferred to an open column (filling material; Kie
seIgeI 60. Merck, developing solvent: ethanol/chloroform-178) to trap the produced dye. After the solvent was evaporated, the solid was recrystallized with ethanol, and the filtered crystals were washed several times with ethanol and n-hexane and then dried.

The obtained dye has the following structural formula (i). (Hereinafter, referred to as dye i.) (i) The obtained croconium dye (i) had excellent solubility.

In other words, unsubstituted croconium dyes are only soluble in halogenated solvents such as dimethylformamide (DMF), benzonitrile, chloroform, and dichloromethane, but the croconium dye (i) obtained by the above-mentioned synthesis method is is an alcohol-based solvent, a ketone-based solvent,
It also showed good solubility in general-purpose solvents such as ether solvents.

Next, the optical properties of the synthesized croconium dye (i) were investigated.

That is, 1.0% by weight of this croconium dye (i)
A chloroform solution (not specifically containing a binder) was spin-coated on a glass substrate to form a coating film with a thickness of 670 mm, and the wavelength dependence of the transmittance and reflectance of the obtained thin film was investigated. The results are shown in Figure 1.

At a wavelength of 8300, the transmittance was 8.8% and the reflectance was 25.0%.

Furthermore, a coating solution consisting of 1 part by weight of croconium dye (i) and 100 parts by weight of 12-dichloroethane was applied to a glass disk using a spin code (rotation speed: 2000 rpm) L, and a semiconductor laser with a wavelength of 7B0nn+ was used to perform recording and reproduction. Ta. The thickness of the formed croconium dye thin film was measured at a linear velocity of 5 m/sec during recording and playback for 630 people.
c, recording power was 10 mW.

As a result, a CN ratio of 48 to 51 dB was obtained at 1 to 4 M7.

Next, following the same method as in the case of dye (i),
Penzothiazoleethiodide with a butyl group introduced, t
- Croconium dye (11) and croconium dye (i
ii) was synthesized. The structural formula of each dye is as follows.

Table 1 Table 1 shows the optical properties (optical properties in chloroform solution) of each of the synthesized dyes.

The optical properties measured were maximum absorption wavelength, single molecule extinction coefficient, and light resistance. The light resistance is measured by the filter transmitted light of a 500W xenon arc lamp light source (1.0X10S lux) (
It was expressed as the residual rate of absorbance (780 nm) when a filter (IRA-253+PC filter) was irradiated for 5 minutes. The optical properties of cyanine dyes are also described for comparison.

From Table 1, each dye showed a molecular extinction coefficient equal to or higher than that of the cyanine dye.

The maximum absorption wavelength largely depended on the type of nitrogen-containing heterocycle, with the shift to longer wavelengths being particularly large in the quinoline ring, and similar in the benzothiazole and indolenine rings. Regarding the light resistance in solution, a superior survival rate was obtained compared to cyanine dyes.

Next, the optical properties of each dye were evaluated in a single layer film. That is, a 1% by weight chloroform solution of each dye was spin-coded onto a glass substrate to form a thin film, and the maximum absorption wavelength, absorbance at 780 nm and 830 nm, transmittance, reflectance from the substrate side, and light resistance were measured. In addition, light resistance is measured using filter transmitted light (filter: IRA-2) of a 500W xenon arc lamp light source (1.0 x 10' lux).
53+PC filter) was irradiated for 1 hour, it was expressed as the residual rate of absorbance. The results are shown in Table 2.

Table 2 From Table 2, each dye has a long wavelength shift, so 830
It is suggested that it is also compatible with nm oscillation semiconductor lasers. In addition, the light resistance in the 'fi1m state is very excellent, surpassing that of cyanine dyes.

(Effects of the Invention) As is clear from the above explanation, in the optical recording medium of the present invention, since a croconium dye into which a t-butyl group is introduced is used as a recording material, optical properties such as reflectance etc. It is possible to provide an optical recording medium with excellent recording and reproducing characteristics.

In particular, when the nitrogen-containing heterocycles at both ends of the croconium dye are a quinoline ring, benzothiazole ring, or indolenine ring, excellent optical properties are exhibited, and this together with the fact that these dyes have excellent light resistance. Accordingly, it is possible to provide an optical recording medium having high reliability and page properties superior to those using a cyanine dye as a recording material.

In addition, a monobutyl group has been introduced into the croconium dye, and its solubility in general-purpose solvents has been greatly improved, resulting in improvements in workability, etc., and from a productivity perspective. expensive.

Therefore, it can be said that the optical recording medium of the present invention is very useful as a storage carrier for various information such as large capacity files.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the wavelength dependence of transmittance and reflectance of a single layer film of croconium dye (i).

Claims (4)

[Claims] (1) The recording layer has the following formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, there are ▲ mathematical formulas, chemical formulas, tables, etc. in the formula ▼, ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼ is a nitrogen-containing heterocycle substituted with a t-butyl group, and R_
1, R_2 represents a substituted or unsubstituted alkyl group, a cyclic alkyl group, an allyl group, a substituted or unsubstituted aralkyl group, or a substituted or unsubstituted aryl group. ) An optical recording medium characterized by containing a croconium dye represented by: (2) The croconium dye has the following formula ▲ Numerical formula, chemical formula, table, etc. or a substituted or unsubstituted aryl group, and R_3 and R_4 represent a substituted or unsubstituted alkyl group or cyclic alkyl group. recoding media. (3) The croconium dye has the following formula ▲ Numerical formula, chemical formula, table, etc. 2. The optical recording medium according to claim 1, wherein the optical recording medium is a croconium dye represented by: or a substituted or unsubstituted aryl group. (4) The croconium dye has the following formula ▲ Numerical formula, chemical formula, table, etc. 2. The optical recording medium according to claim 1, wherein the optical recording medium is a croconium dye represented by: or a substituted or unsubstituted aryl group.