JPH06183154A - Optical recording material - Google Patents

Abstract

PURPOSE:To enhance practicality by compounding a thimine compd. with a copolymer of unsaturated hydrocarbon and unsaturated carboxylic acid or a salt thereof. CONSTITUTION:An optical recording material is constituted by compounding thimine represented by the specific formula or a derivative thereof with a copolymer of unsaturated hydrocarbon such as ethylene and unsaturated carboxylic acid such as acrylic acid or a salt thereof. In the specific formula, R is an aminoalkyl group, a hydroxyalkyl group or an amoniated aminoalkyl group. The copolymer is used as a base material as it is, but a salt thereof, that is, an ionomer obtained by neutralizing the copolymer with a metal ion or amine is pref. used. The copolymer or a salt thereof is dispersed in a solvent such as methanol and a thimine compd. is added to and dispersed in the obtained dispersion to prepare a solution which is, in turn, cast and the formed layer is dried to remove solvent to form a thin film.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical recording material. More specifically, it relates to an optical recording material in which a thymine compound is mixed and dispersed in a specific copolymer.

[0002]

2. Description of the Related Art In recent years, as an information processing medium, a new optical recording material having a storage capacity dramatically increased as compared with a magnetic disk or an optical disk has been attracting attention and its research / development has been widely conducted.

The following equation (1)

[Chemical 1] (In the formula, R represents hydrogen or a substituent.)

The thymine represented by the formula (1) and its derivatives (hereinafter collectively referred to as thymine compounds) are reversibly subjected to the formation reaction of a cyclobutane type photodimer and its cleavage reaction by irradiation with light of a specific wavelength as shown in the following formula (2). It is known that this reversible photodimerization reaction is applied as an optical recording material.

[0005]

[Chemical 2]

The light absorption characteristics of the respective compounds produced by the above reversible reaction are as shown in FIG. 1, and the absorption peak disappears in the vicinity of 260 nm in the dimer.

A method of applying the photodimerization of a thymine compound and its cleavage reaction as an optical recording material is to disperse a thymine compound in an appropriate medium and form a thin film such as a film together with the medium. It is recorded by fixing the thymine compound in a dimerized state or a cleaved state by irradiating a minute portion of the thin film with ultraviolet rays of a specific wavelength, and whether the thymine compound is in a dimerized or cleaved state. Is performed by reading the record by reading at the specific portion of the light absorption rate of 270 nm.

[Problems to be Solved by the Invention]

In order to improve the practicality of the optical recording material, it is necessary to prevent the thymine compound from being uniformly dispersed in the medium by repeating the photoreaction, thereby reducing the reaction efficiency of the dimerization reaction. And high reactivity of the dimerization and its cleavage reaction. When a thymine compound is dispersed in a matrix such as a solvent or a polymer, the thymine compound is usually dissolved and uniformly dispersed in the matrix, or if the solubility is insufficient, it becomes a large aggregate and agglomerates, resulting in a dimerization reaction. It causes a decrease in reactivity or a reaction efficiency at the time of repeated reaction, resulting in poor practicability as an optical recording material.

In order to carry out the photodimerization reaction of a thymine compound efficiently and with good durability, it is necessary to find a method for solving the following two problems. 1) Increasing the local concentration of the thymine compound by uniformly dispersing the molecules of the thymine compound in the reaction medium as aggregates in a minute state in the medium. 2) To make the molecules of the thymine-based compound have an orientation suitable for the dimerization reaction in the medium.

[0010]

Means for Solving the Problems In view of the above points, the inventors of the present invention have conducted extensive studies and as a result, have focused on a polymer compound having a microphase-separated structure of a solid hydrophilic part and a hydrophobic part, and Is used as a reaction medium, a thymine derivative having a functional group capable of interacting with the hydrophilic part of the polymer compound introduced into thymine is dispersed in the matrix of the above polymer to obtain the thymine derivative in the hydrophilic part of the polymer. The present invention has been completed by discovering that the thymine derivative can be collected in the micro-aggregated portion of the thymine derivative to increase the local concentration of the thymine derivative and have an appropriate orientation.

That is, the present invention relates to an optical recording material obtained by mixing and dispersing a thymine compound in a copolymer of unsaturated hydrocarbon and unsaturated carboxylic acid or a salt thereof.

As the unsaturated hydrocarbon component which is one component of the copolymer, ethylene, propylene, 1-butene,
Examples thereof include aliphatic olefins such as 1-hexene and 4-methyl-1-pentene, aromatic olefins such as styrene, α-methylstyrene, vinyltoluene, and isopropenyltoluene. Among these unsaturated hydrocarbon components, ethylene and styrene are preferable.

The unsaturated carboxylic acid component which is the other component of the copolymer includes monocarboxylic acids such as acrylic acid and methacrylic acid, dicarboxylic acids such as maleic acid and fumaric acid, and maleic anhydride. Examples thereof include dicarboxylic acid anhydrides and dicarboxylic acid half-esters such as maleic acid monomethyl ester. Of these, acrylic acid or methacrylic acid is preferably used.

Examples of the copolymer include unsaturated hydrocarbons and unsaturated carboxylic acids, and other polymerization components such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate and methyl methacrylate. It may be a copolymer of such an unsaturated carboxylic acid ester and a vinyl ester such as vinyl acetate.

As the copolymer, the unsaturated hydrocarbon is 50% by weight or more, preferably 60% by weight or more, and the unsaturated carboxylic acid is 1-40% by weight, preferably 5-30%.
It is preferable to use a copolymer which is copolymerized in a weight percentage. In particular, when it is used in the form of an ionomer as described later, it is preferable to use a copolymer having an unsaturated carboxylic acid content of 5% by weight or more in order to have a microphase-separated structure of ions.

Such a copolymer can be obtained by randomly copolymerizing raw material monomers using a radical initiator.

In the present invention, the above-mentioned copolymer of unsaturated hydrocarbon and unsaturated carboxylic acid can be used as a base material as it is, but it is more preferable to use a salt thereof, that is, an ionomer. The ionomer can be obtained by neutralizing the copolymer with metal ions, amines or the like. Examples of the metal ions include alkali metals such as Li, Na and K, alkaline earth metals such as Ca and Mg, and Z.
Monovalent to divalent metals such as transition metals such as n, Co and Mn are preferable. As amines, ammonia, monoamines such as ethylamine, diamines such as 1,3-bisaminocyclohexane, and derivatives of thymine with an amino compound can be used. Furthermore, complex salts of amines and transition metals can also be used. Neutralization degree is usually 10-100
Mol% is preferred.

In the present invention, as the thymine compound, the thymine represented by the above formula (1) or a derivative thereof is used, and in particular, it has affinity with the carboxyl group or salt thereof in the copolymer or salt thereof used as a reaction medium. It is preferable to use a thymine derivative having a functional substituent. Specifically, it is preferable to use a thymine derivative in which R in the formula (1) is an aminoalkyl group, a hydroxyalkyl group, an ammonium chloride aminoalkyl group, or the like. For example, in the combination of an unsaturated hydrocarbon-unsaturated carboxylic acid copolymer and a thymine derivative into which an aminoalkyl group having a primary or secondary amino group is introduced, the aminoalkyl group provides an appropriate coordination for dimerization. It will be easier.
Further, in the combination with an ionomer, the presence of the above-mentioned substituent makes it easy to collect in the ion-aggregated portion of the ionomer, increases the local concentration of the thymine derivative, and facilitates the orientation suitable for the dimerization reaction.

The ratio of the thymine compound to the unsaturated hydrocarbon-unsaturated carboxylic acid copolymer or its salt in the optical recording material is such that the thymine derivative per 100 monomer units of the polymer chain of the copolymer or its salt. A ratio of 15 to 60 molecules is suitable. If the proportion of the thymine compound is less than this range, the local concentration of the thymine compound does not increase, and if it is more than this range, the amount of thymine liberated without aggregating to the ionic aggregation part increases, and the thymine compound dimerization reaction occurs. It is not good because it reduces efficiency.

Dispersion of the thymine compound in the unsaturated hydrocarbon-unsaturated carboxylic acid copolymer or its salt is carried out by the following method. 1) An unsaturated hydrocarbon-unsaturated carboxylic acid copolymer or a salt thereof is dispersed in a suitable solvent such as methanol, and a thymine compound is added and dispersed therein. The solution is cast and the solvent is removed by drying to give a thin film. 2) A thymine compound is added and dispersed in an aqueous dispersion of an unsaturated hydrocarbon-unsaturated carboxylic acid copolymer or a salt thereof, and then dried to form a thin film. 3) An unsaturated hydrocarbon-unsaturated carboxylic acid copolymer and a thymine-based compound are stirred in pressurized hot water to form an ammonium salt type ionomer aqueous dispersion, which is dried to form a thin film.

When an unsaturated hydrocarbon-unsaturated carboxylic acid copolymer or a salt thereof is dispersed in an aqueous medium, in order to accelerate the photodimerization reaction of the thymine derivative, the concentration of the polymer in the aqueous solution (the monomer unit in the polymer is It is necessary to increase the concentration) of the ionomer.
It is preferably set to 01 mol / l or more.

When the above thymine derivative is dispersed in the unsaturated hydrocarbon-unsaturated carboxylic acid copolymer or its salt, a dispersant such as a surfactant and other stabilizers may be used, if necessary. it can.

[0023]

The present invention will be described in more detail with reference to the following examples. The raw materials used in the examples and comparative examples are as follows.

1. Thymine-based compound 1-aminoethylthymine (molecular weight 169.2) having the following structural formula (3) was used.

[Chemical 3]

2. Polymer Material (1) Aqueous Dispersion of Ionomer (i) Aqueous Dispersion of 40% Potassium Neutralized Ionomer of Ethylene-Methacrylic Acid Copolymer (Methacrylic Acid Content 20% by Weight = 7.5 mol%) Solid Content: 18% %

(Ii) Same as above Aqueous dispersion of 90% potassium-neutralized ionomer of copolymer Solid content: 25% by weight

(2) Water-soluble polymer (i) Sodium polyacrylate (ii) Polyvinyl alcohol

Example 1 0.0203 g of 1-aminoethylthymine in 1 liter of a 5% aqueous methanol solution.
(1.2 × 10 ⁻⁴ mol / l) and 5.0 g of ionomer aqueous dispersion (i) (0.9 g as ionomer, concentration in aqueous solution (concentration of monomer unit in polymer) 0.027 mol / l) Mixed. This mixed solution was irradiated with ultraviolet rays having a wavelength of 280 nm to cause a photodimerization reaction of 1-aminoethylthymine. When the progress of the photodimerization reaction was traced by the change in the absorbance at a wavelength of 270 nm with an ultraviolet spectrometer, it was confirmed that the dimerization reaction proceeded as the ultraviolet irradiation energy increased. The results are shown in Figure 2. In FIG. 2, A ₀ : absorbance before irradiation A _f : final absorbance A : Absorbance at a point corresponding to the irradiation dose.

Example 2 In Example 1, the addition amount of the ionomer aqueous dispersion (i) was 9.5 g.
The concentration was changed to 0.051 mol / l in the aqueous solution, and the photodimerization reaction of the thymine derivative was measured. It was confirmed that the dimerization reaction proceeded as in Example 1. The results are shown in Figure 2.

Comparative Example 1 In Example 1, the photodimerization reaction was carried out by dissolving only 3-aminomethylthymine in a 5% methanol aqueous solution without using the ionomer aqueous dispersion. Little change in absorbance at 270 nm,
The progress of the dimerization reaction was extremely slow as compared with Examples 1 and 2. The results are shown in Figure 2.

[Example 3] In Example 1, the ionomer aqueous dispersion (ii) was used, and this was added to 5%.
2.23 g (0.56 g as ionomer, concentration 0.016 mol in aqueous solution) in 1 liter of aqueous methanol solution
/ L) was added. Ultraviolet rays (280 nm) as in Example 1.
It was confirmed that the dimerization reaction of 1-aminoethylthymine proceeded by the irradiation. The results are shown in Figure 2.

Example 4 In Example 1, the ionomer concentration in a 5% aqueous methanol solution was 0.006 mol.
/ L to 0.051 mol / l by changing the concentration at several points,
A photodimerization reaction of 1-aminoethylthymine was performed. 27
From the rate of change in absorbance at 0 nm wavelength, the reaction rate constant of the photodimerization reaction of 1-aminoethylthymine was determined, and the relationship between this and the ionomer concentration was determined, showing the reaction rate constant when the ionomer concentration was higher than 0.012 mol,
It was found that above this concentration, the ionomer has a large effect of promoting the photodimerization reaction of the thymine derivative. This was considered to be because the ionomer produced micelles in a 5% aqueous methanol solution at a concentration above this concentration (limit micelle concentration). The results are shown in Fig. 3.

[Comparative Example 2] In Example 4, the ionomer component was changed to sodium polyacrylate, and the sodium polyacrylate concentration (0.001 to 0.021 mol) was used.
/ L), the photodimerization reaction rate constant of 3-aminothymine was determined. Although the effect of accelerating the photodimerization reaction of 3-aminothymine by adding sodium polyacrylate was slightly recognized, the effect was inferior to that of the ionomer, and the phenomenon that the effect of accelerating the dimerization reaction was large at a specific polymer concentration was recognized. There wasn't. The results are shown in Fig. 3.

[Comparative Example 3] In Example 4, the ionomer component was changed to polyvinyl alcohol, and the photodimerization reaction rate constant of 3-aminothymine was determined within a polyvinyl alcohol concentration range of 0.001 to 0.040 mol / l. . At any concentration of polyvinyl alcohol, the effect of accelerating the photodimerization reaction of 3-aminothymine by adding polyvinyl alcohol was not recognized at all. The results are shown in Fig. 3.

Example 5 1-aminoethylthymine was added to the ionomer aqueous dispersion (i) at a ratio of 9 molecules of 1-aminoethylthymine per 100 units of the ionomer monomer and mixed. The mixed solution was cast on quartz glass and dried to form a thin film in which 1-aminoethylthymine was dispersed in an ionomer matrix. 280 from above this thin film
Ultraviolet rays having wavelengths of nm and 240 nm were repeatedly irradiated to cause a dimerization reaction and a cleavage reaction of the thymine derivative. The progress of the reaction is shown by the thin film 270 nm.
Followed by the absorbance of. It was confirmed that 1-aminoethylthymine efficiently performs a reversible dimerization reaction in an ionomer matrix by irradiation with ultraviolet rays, and it was confirmed that it exhibits performance as an optical recording material. The results are shown in Fig. 4.

[0036]

According to the present invention, an optical recording material utilizing the photoreaction of a thymine compound can be provided. In the present invention, by using an unsaturated hydrocarbon-unsaturated carboxylic acid copolymer or a salt thereof as a medium, the photodimerization reaction of the thymine derivative is promoted, and the reversible dimerization reaction is efficiently performed by repeated irradiation of ultraviolet rays. Therefore, it can be used as a rewritable recording material.

[Brief description of drawings]

FIG. 1 is a diagram showing light absorption characteristics of a compound produced by a reversible photodimerization reaction of a thymine-based compound.

FIG. 2 is a diagram showing the relationship between ultraviolet irradiation energy and the progress of 1-aminoethylthymine dimerization reaction in the presence and absence of various concentrations of ionomer aqueous dispersion.

FIG. 3 is a diagram showing the relationship between the polymer concentration and the reaction rate constant of the dimerization reaction of 1-aminoethylthymine when each polymer of ionomer aqueous dispersion, sodium polyacrylate and polyvinyl alcohol is used as a reaction medium. .

FIG. 4 is a graph of 1 when a thin film in which 1-aminoethylthymine is dispersed in an ionomer matrix is repeatedly irradiated with ultraviolet rays having wavelengths of 280 nm and 240 nm.
-Progress of reversible dimerization of aminoethylthymine
It is the figure shown by the light absorbency of 70 nm.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C08L 23/00 KFB 7107-4J

Claims (1)

[Claims] 1. An optical recording material comprising a copolymer of unsaturated hydrocarbon and unsaturated carboxylic acid or a salt thereof in which a thymine compound is mixed and dispersed.