JPS61117537A - Light recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium long in life by forming a photochromic compd. dependent on cis-trans isomerization and having affinities to polar and nonpolar solvents balanced between hydrophilic parts and hydrophobic pats and forming built-up 2-dimensionally oriented monomolecular films on a substrate. CONSTITUTION:The photochromic compd. exhibiting photochromism dependent on cis-trans isomerization and having affinities to polar and nonpolar solvents is formed into built-up 2-dimensionally oriented monomolecular films 2a-2c to form the recording layer 2 on the substrate 1. As the photochromic compd., azobenzene having an -N=N- structure and indigo and thioindigo having a -C=C- structure each having affinities to both type solvents and the like are preferably used. The irradiation of laser beams causes the information recording layer 2 of the information recording medium to react so as to irreversibly bring absorption spectra different from those before the irradiation, thus permitting the information to be retained without naturally returning to the initial state, and the recording medium long in record life to be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called optical recording medium in which information obtained by physical or chemical changes in an information recording layer is optically read out.

Page 2 Conventional Technology Among the information recording layers of organic materials used in optical recording media are dyes, dye-polymer composites, photopolymers, diazo photosensitive materials, photochromics, and the like.

Dyes and dye-polymer composites are selectively melted and evaporated by irradiating the information recording layer with laser light.

Recording is performed by deforming the medium to form irregularities on the medium, which is called heat mode recording, and is used in the same way as chalcogenide semiconductor materials that are already in practical use.

On the other hand, organic photochromic materials have attracted attention for their reversibility and are being studied as rewritable photon mode recording. For example, it has been reported in L. M. Raston SPIE Journal 186 (1983). Many photochromic materials are soluble in solvents, and are expected to enable the formation of thin films using spin cords to manufacture disks, but they have not been put to practical use.

Problems to be Solved by the Invention When an organic photochromic material is irradiated with light, the photochromic compound reacts and has a spectrum different from the light absorption spectrum before irradiation. - Photochromic compounds based on trans isomerization exhibit photochromism in solution, but not at all in solid thin films.

The present invention aims to provide an optical recording medium using a thin film that is made of a photochromic material based on cis-trans isomerization and is stable in both states. photochromic compounds by isomerization,
The recording thin film is formed as a monomolecular film that is amphiphilic with a balance between hydrophilic and hydrophobic parts and oriented in a two-dimensional plane in the molecular dimension, and is accumulated on the substrate.

For production When the recording medium of the present invention is irradiated with a laser beam, the following occurs.

At this time, the recording medium of the present invention can maintain recording without returning naturally to the state before irradiation.

This is thought to be due to the fact that photochromism is maintained within the molecular bath and thin film of amphiphilic photochromic 1, and the thermal reverse reaction is stopped, resulting in a longer record-keeping life.

Examples The amphiphilic photochromic material used in the present invention is -N=
In compounds based on cis-trans isomerization of unsaturated double bonds, such as azobenzene having an N-skeleton and indigo and thioindigo having a -C=C- skeleton, at least one alkyl chain is added to an unsaturated double bond. It is synthesized so that it is added to a place other than the backbone of the heavy bond.

In order to form a recording layer by accumulating the above materials as a monomolecular film oriented in a two-dimensional plane in the molecular dimension, a monomolecular accumulation method called the so-called Langmuir-Prodgett method or horizontal deposition method is used to form a six-page substrate. Perform film formation on top. First, the amphiphilic photochromic material is dissolved in an optimal solvent and developed on the air-water interface formed by the so-called sub-phase of distilled water with optimally adjusted pH and metal ions, and after the solvent evaporates. The surface pressure created by the spreading material is controlled by the barrier. When the optimum surface pressure has been reached, the so-called cumulative pressure, gently move the smooth support substrate, such as glass, metal or semiconductor material, either perpendicular to the subphase or horizontally, and remove the substrate. A monomolecular film is transferred onto the top and a cumulative film is formed by repeating this process. Example 1 4-monostearoylaminoazobenzene is added to IX10
-Dissolved in benzene at a concentration of 3M. After irradiating this solution 1 with approximately 360 nm light, 250 μl of the sample was
18℃, pH=7 subphase, 1own/
The monolayer was compressed at a barrier speed of minutes. Approximately 20 d
When a cumulative pressure of , yn/cIn was generated, the disk substrate was moved up and down perpendicularly to the monomolecular film on the air-water interface to form a cumulative film. As a result of 6 pages of 16 round trips, 30 layers of monomolecular film were accumulated on the substrate, resulting in a recording layer as thick as about 750 layers as shown in FIG. 1 is a substrate, and 2 is a recording layer formed thereon.◇A protective film 3 is formed on the recording layer 2. The inside of the circle is an enlarged view of the recording layer 2, and 2a to 2C schematically show monomolecular layers.

The recording medium thus obtained was irradiated with light of approximately 440 nm, focused to a spot size of 1 μm, and recorded. Before irradiation, it absorbed approximately 440 nm light, but after irradiation, it was transmitted, and a change in the optical density of the recording layer 2 was clearly observed before and after irradiation, indicating that it has the function of an optical recording medium. Recognize. Moreover, photochromism has a long maintenance life and does not return to its original state like a solution.

Example 2 6.6'-dihexoxythioindigo as lX10-'
O dissolved in chloroform at a concentration of M to this solution approximately 5
After irradiating with 40 nm light, it was accumulated over 7 pages on the Or plated plate at a cumulative pressure of 15 dyn/- in the same manner as in Example 1. The Cr plated plate was used after being hydrophobically treated with Cd arachinate. Twelve layers of cumulative film were formed to obtain a recording layer approximately 300 times thick.

Spot size 1 of approximately 480 nm light is applied to this recording medium.
Irradiation was performed and recorded with a focus on μm.

Figure 2 shows the absorption characteristics before and after irradiation. As is clear from this figure, before irradiation, the reflected light is strong because it does not absorb 11540 nm light, but after irradiation, it absorbs light and the reflected light is weak. A change in optical density was observed, indicating that it had a function as an optical recording medium. Moreover, photochromism has a long shelf life and does not return to its original state like a solution.

Effects of the Invention As described above, according to the present invention, a thin film of a photochromic compound based on cis-trans isomerization, which could not be used conventionally, can be used as a recording layer with an extremely simple structure. , and can provide a recording medium with a long recording life.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of an optical recording medium according to an embodiment of the present invention, and FIG. 2 is a graph showing absorption spectra of the recording layer before and after irradiation in an embodiment of the present invention. 1...Substrate, 2...Recording layer.

Claims (3)

[Claims] (1) Optical recording medium that exhibits photochromism due to cis-trans isomerization and has a recording layer accumulated on a substrate as a monomolecular film in which an amphipathic photochromic compound is oriented in a two-dimensional plane in the molecular dimension. . (2) Claim 1 using amphiphilic azobenzene having a -N=N- skeleton as a photochromic compound
Optical recording medium described in Section 1. (3) The optical recording medium according to claim 1, which uses amphiphilic indigo or thioindigo having a -C=C- skeleton as a photochromic compound.