JPH0367249B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical recording material constituting a rewritable optical recording medium.

BACKGROUND ART Conventionally, photochromic compounds have been known as materials that produce reversible color changes when using two types of light sources with different wavelengths. Spiropyran and fulgide are representative examples. Optical recording media with binary storage have been proposed by taking advantage of these reversibilities, but no examples have been put into practical use.

Problems to be Solved by the Invention There are several problems in using photochromic materials as optical recording media.

Among these, the stability of the colored material (colorless material in the case of inverse photochromic materials) is important. However, many photochromic materials to date have
If you leave a colored object in a dark place, it will return to its colorless state. Therefore, the recorded information cannot be saved, and it can only be used as a temporary storage optical recording medium.

Another important issue is the method of thinning the film. The Langmuir Blossom (LB) method is excellent for forming uniform thin films. However, many conventional photochromic materials have molecular structures in which the hydrophobic functional portion within the molecule is weak. Therefore, it has been difficult to create a thin film using the LB method.

An object of the present invention is to provide an optical recording medium that can be formed into a film by the LB method and has extremely high thermal stability in a colored state, that is, has extremely high stability of recorded information.

Means for Solving the Problems The present invention provides an optical recording medium having a recording layer consisting of a photochromic compound represented by the following general formula and a hetero-LB film consisting of alternating long-chain carboxylic acids, long-chain alcohols, or long-chain esters. This is what we provide.

In addition, R here is a hydrocarbon from C=1 to C=31.

Effect When spread on water to form an LB film, the photochromic compound changes from a colorless substance to a colored substance without irradiation with light. Therefore, the thin film obtained by the LB method is characterized by being a colored body from the beginning. It gradually returns to a colorless body in the dark.

However, when a heterojunction is formed between the photochromic compound and a long-chain carboxylic acid, a long-chain alcohol, a long-chain ester, or a mixture thereof, the stability of the colored body is dramatically increased. When a photochromic compound forms a heterojunction with a long-chain carboxylic acid, etc., the interaction between these molecules becomes significant. It is thought that this is because, as a result, the Zwitter ion, which is a colored substance of the photochromic compound, is stabilized.

Moreover, by introducing a long-chain alkyl group into the above-mentioned photochromic compound, the balance between hydrophilicity and hydrophobicity of the molecule is improved, and it becomes possible to form an LB film by itself. Furthermore, by forming an LB film using a mixture with hydrocarbons, the filling rate of the long chain portion of the above compound is increased, resulting in a more stable film.
LB film is formed.

In addition, C = 31, whose raw materials are easily available industrially.
It is a hydrocarbon up to. Preferably, a hydrocarbon having C=13 to C=23 has a good balance between hydrophilicity and hydrophobicity, and it is easy to form an LB film by itself.
By mixing hydrocarbons, an even better LB film can be formed.

Examples Example 1 Spiropyran (hereinafter referred to as
SP1801) was used.

Sample solutions were prepared separately by dissolving SP1801 and stearic acid in benzene to a concentration of 1 mM. This was made into a thin film accumulated on a glass substrate by the LB method under normal conditions (subphase: PH7/phosphoric acid buffer, temperature 18° C., compression speed: 20 mm/min, cumulative pressure: 20 mN/m). In this case, first develop the stearic acid and accumulate three layers in a row, then
One layer of SP1801 was accumulated. This was followed by one layer of stearic acid, followed by one layer of SP18101, and so on. The cumulative number of layers was 10, and an alternating heterolayer membrane was obtained. The first two layers of stearic acid were provided to stabilize the hydrophobicity of the substrate.

This recording layer had a light blue color from the beginning and had a maximum absorption wavelength of 560 nm. When exposed to light at this wavelength, it quickly returned to its colorless form, and when exposed to ultraviolet light, it became a colored substance.
The colored body was extremely stable in the dark. It showed more than 1000 times more stability than spiropyran, which does not form a normal heterojunction. The absorption spectrum used for this binary recording is shown in the figure.

Example 2 A cleaned quartz substrate was immersed in a 10% toluene solution of trimethylchlorosilane for 10 minutes, and then washed with trichloroethane to make it hydrophobic in advance. A 1:2 mixture of SP1801 and octadecane and stearyl alcohol were separately dissolved in benzene to a concentration of 1 mM. Accumulation was carried out under the same conditions as in Example 1. First, add 1 stearyl alcohol
Layers were deposited and then one layer of a mixture of SP1801 and octadecane was deposited to obtain an alternating hetero-membrane.

This recording layer showed almost the same photochromic reaction as in Example 1. The maximum absorption wavelength of colored bodies is
It was 570nm.

Example 3 A sample solution was prepared by dissolving methyl stearate in benzene to a concentration of 1 mM. SP1801 used the sample solution of Example 1. Accumulation was carried out under the same accumulation conditions as in Example 1 and in the same substrate treatment as in Example 2.

First, accumulate one layer of methyl stearate, then
One layer of SP1801 was accumulated to obtain an alternating heterogeneous membrane.
This recording layer showed almost the same photochromic reaction as in Example 2. The maximum absorption wavelength of colored bodies is
It was 570nm.

Effects of the Invention According to the present invention, it is possible to provide an optical recording medium that has a long recording life and is capable of forming an ultra-thin film, and its ripple effects are large.

[Brief explanation of drawings]

The figure is an absorption spectrum diagram of a recording layer of an optical recording medium in one embodiment of the present invention. A...Colorless type, B...Colored type.

Claims (1)

[Scope of Claims] 1. An optical recording medium having a recording layer consisting of a photochromic compound represented by the following general formula and an alternating hetero-LB film of a long-chain carboxylic acid, a long-chain alcohol, or a long-chain ester. (However, R is C=
alkyl chain from 1 to 31) 2. The optical recording medium according to claim 1, having a recording layer consisting of an alternating hetero-LB film of a mixture of a photochromic compound and a hydrocarbon, and a long-chain carboxylic acid, a long-chain alcohol, or a long-chain ester.